NOZZLE BODY FOR A LIQUID SPRAY GUN

Abstract

 Nozzle body (1) for a liquid spray gun for spraying a liquid, the nozzle body comprising a tubular nozzle tube, comprising
a) an elongated nozzle tube passage (58), extending between a nozzle tube inlet and a nozzle tube outlet (52),
b) a nozzle tube wall (71).
In an outlet cross section taken in a plane through the nozzle tube outlet (52) orthogonal to the spray axis (200), the nozzle tube outlet has a central portion (80) and two or more protrusions (82) protruding radially outward from the central portion.
Each protrusion (82) is located at a respective angular protrusion position as measured in the outlet cross section circumferentially around the spray axis (200). In the outlet cross section, the outer surface (75) of the nozzle tube wall (71) forms a recess (90) receding radially inward towards the spray axis (200), through which recess atomizing gas exits into outside air (93). The recess is located at an angular recess position as measured in the outlet cross section circumferentially around the spray axis (200).
In the outlet cross section, the angular recess position is located angularly between the respective angular protrusion positions of two protrusions (82), adjacent to each other, of the two or more protrusions.

Description

[0001] This disclosure relates to liquid spray guns in which a liquid to be sprayed is atomized by a pressurized gas. It relates more specifically to nozzle bodies for use in such spray guns, and to nozzle assemblies and spray guns comprising such nozzle bodies.

[0002] Spray guns according to the present disclosure are used, for example, in automotive repair shops to apply liquid paint to surfaces of a vehicle using pressurized air or another pressurized gas. Most of these spray guns have a spray gun body or a spray gun platform with a trigger and a handle for manual spraying operation, while others are used with robots and are equipped with mechanical or electrical interfaces to allow computer-controlled spraying operation by the robot.

[0003] Spray technology and environmental regulations are trending towards spray guns which utilize lower gas pressures or can be laboratory certified to produce certain levels of paint "transfer efficiency". A challenge with using lower gas pressures is that the amount of energy available to both draw-out and atomize the liquid paint is reduced. This situation can negatively impact the application speed and paint finish quality. The challenge is compounded by the fact that paint manufacturers are moving to liquid paint formulations which are water-based and have an increased solids content. These liquid paints tend to have higher viscosities which, at identical atomizing gas pressure and gas flow rates, can result in reduced paint flow rates and in the liquid paint being more difficult to atomize. A stronger flow of atomizing gas can provide for a finer atomization that generates a finer paint spray. However, increasing the pressure of the atomizing gas also increases the volume of undesirable high-frequency noises, generally results in lower transfer efficiency, increases consumption of pressurized atomizing gas, and causes higher operating costs.

[0004] Nozzle bodies are known from traditional liquid paint spray guns. A nozzle body generally comprises a nozzle having a nozzle opening through which the liquid to be sprayed exits the nozzle body into outside air. Specific traditional nozzle bodies are described in PCT patent applications WO 2012/109298 A1 or WO 2013/016474 A1, for example. The United States patent application published as US 2017/0348710 A1 is directed to a spray gun capable of setting a spray gas pressure at a relatively low pressure and performing good atomization without making auxiliary gas holes in a gas cap. Similarly, United States patent US 7,926,733 B2 aims at providing a system for improving atomization in a spray coating device.

[0005] It is desirable to further improve atomization of the liquid without increasing the flow rate or the pressure of the atomizing gas. Alternatively, it may be desirable to achieve acceptable atomization using a reduced gas flow rate which will improve transfer efficiency.

[0006] The present disclosure attempts to address this need. It provides a nozzle body for a liquid spray gun for spraying a liquid, the nozzle body comprising a tubular nozzle tube, comprising

a) an elongated nozzle tube passage, extending lengthwise between a nozzle tube inlet through which, in use, liquid enters the nozzle tube, and a nozzle tube outlet, through which, in use, the liquid exits the nozzle tube passage into outside air in a spray direction,

b) a nozzle tube wall having a radially outer surface being, in use, in contact with atomizing gas for atomizing the liquid after the liquid has exited the nozzle tube outlet, and an opposed radially inner surface delimiting the nozzle tube passage and being, in use, in contact with the liquid,

wherein the spray direction through a centroid of the cross section of the nozzle tube outlet defines a spray axis, wherein the spray axis defines axial directions and radial directions orthogonal to the axial directions, wherein the nozzle tube outlet is arranged around the spray axis, characterized in that, in an outlet cross section taken in a plane through the nozzle tube outlet orthogonal to the spray axis, the nozzle tube outlet has a central portion and two or more protrusions protruding radially outward from the central portion, wherein each protrusion is located at a respective angular protrusion position as measured in the outlet cross section circumferentially around the spray axis, and in that, in the outlet cross section, the outer surface of the nozzle tube wall forms a first recess receding radially inward towards the spray axis, through which recess, in use, atomizing gas exits into outside air, wherein the first recess is located at an angular recess position as measured in the outlet cross section circumferentially around the spray axis, wherein, in the outlet cross section, the angular recess position is located angularly between the respective angular protrusion positions of two protrusions, adjacent to each other, of the two or more protrusions.

[0007] The atomization process primarily occurs in regions where the high velocity atomizing gas meets the low velocity liquid and interacts with it. The fluid flow behaviour within this "interaction zone" is presumed to be very important to the overall atomization quality. The inventors of the present disclosure have found that increasing the size of the interaction zone by "folding" it into recesses and protrusions helps improve atomization. A larger interaction zone spreads out both the liquid flow and the atomizing gas flow over a larger surface area as the gas and the liquid exit the spray gun nozzle. The inventors believe that the increased length and volume of the zone of interaction between the pressurized atomizing gas and the liquid helps the atomizing gas to more effectively break up the liquid into minute droplets than in traditional nozzle bodies. An interdigitated, interleaved or intertwined arrangement, in which the recess is located angularly between two adjacent protrusions, increases the length of the interaction zone and enhances atomization, compared to a nozzle body without recess and without protrusions. In contrast to a nozzle body according to the present disclosure, an arrangement in which the recess is aligned with a protrusion (i.e. in which the recess is located angularly at a protrusion position) may not increase the interaction zone at all, or at least not to the same degree, and therefore provides less improvement of the atomization, if any at all.

[0008] According to the present disclosure, where the liquid exits the nozzle, the cross section of the nozzle tube outlet through which the liquid exits the nozzle comprises protrusions, and the gas-guiding outer surface of the nozzle tube wall forms one or more recesses in angular positions between the angular positions of the protrusions. The protrusions and the recess(es) result in the liquid outlet having a larger perimeter than a traditional circular liquid outlet and hence result in a longer and therefore a larger zone of interaction between the atomizing gas and the liquid. The larger interaction zone provides for improved atomization of the liquid without having to increase the flow rate or the pressure of the atomizing gas.

[0009] Including recesses and protrusions in a nozzle body as described herein helps improve atomization. One potential unintended consequence may be that this design may cause an increase in air pressure in front of the nozzle tube outlet, which in turn, could reduce the liquid flow rate. This is particularly true of gravity fed spray gun systems which rely on negative pressure in front of the nozzle tube outlet to extract liquid from the reservoir. The inventors believe that when a recess and a protrusion are aligned, i.e. arranged at the same angular position, the negative consequences (reducing the liquid flow rate) can outweigh the improvement in atomization. However, when the recess is positioned angularly between two protrusions (particularly when the recess is positioned centered between them) a designer has means to minimize the reduction in paint flow rate while still providing the improved atomization. A designer may provide the nozzle tube wall, for example, with a ramped outer surface at the nozzle tube outlet to increase the liquid flow rate to its typical levels or higher.

[0010] The noun "liquid" as used herein refers, inter alia, to liquid paints such as those comprising pigments or other suspended particles or dyes, to liquid primers, and to liquid clearcoats, liquid lacquers, liquid base coats, or liquid varnishes. A liquid may be coloured or colourless. Liquid paints are, for example, those liquid paints used in auto repair shops to coat surfaces of vehicle parts. Generally, as used herein, "liquid" refers to liquid coating materials that can be applied to a surface using a spray gun system, including (without limitation) paints, primers, base coats, lacquers, varnishes and similar paint-like materials as well as other materials such as adhesives, sealers, fillers, putties, abrasive slurries, mold release agents and foundry dressings which may be applied in atomized form depending on the properties and/or the intended application of the material. A liquid according to the present disclosure may comprise a carrier liquid and solid particles (pigments, powders, granules, etc.) suspended in the carrier liquid.

[0011] As used herein, a (non-gaseous) substance is considered liquid if its dynamic viscosity at 20 °C and atmospheric pressure is lower than about 20000 mPa.s, particularly if its dynamic viscosity at 20 °C and atmospheric pressure is lower than about 2000 mPa.s.

[0012] Most traditional spray guns use pressurized air for atomization of the liquid and shaping of the spray jet. However, other gases and gas mixtures are sometimes used for these purposes. The term "gas" as used herein refers to a gas, such as, for example, nitrogen, oxygen, argon, carbon dioxide, or helium, as well as to a mixture of gases, such as air. The use of "air" in conventional technical terms like "air cap" for a component of a spray gun is not meant to preclude the useability of this component with another gas mixture or with another gas.

[0013] Like in traditional nozzle bodies, when in use, a nozzle body according to the present disclosure is generally connected to a barrel (such as to a barrel holding a paint cup) or to the body of a spray gun. Liquid is supplied into the nozzle body through the barrel or through the spray gun body. A nozzle port on the barrel or on the spray gun body can be engaged with a corresponding matching barrel port on the nozzle body, so that the liquid to be sprayed can flow from the barrel or the spray gun body through the nozzle port and the barrel port into the nozzle body and - within the nozzle body - to the nozzle tube outlet where it exits the nozzle body and the spray gun.

[0014] A nozzle body according to the present disclosure comprises a nozzle tube having a wall, an inlet, an outlet, and a passage through which the liquid flows from the inlet to the outlet. At the nozzle tube outlet, the liquid exits the nozzle body in a spray direction. The liquid is then atomized close to the nozzle tube outlet by a flow of pressurized gas ("atomizing gas") to form a spray of minute liquid droplets which propagates through surrounding air to eventually hit the surface that is to be coated with the liquid.

[0015] The nozzle bodies according to the present disclosure are for use in spray guns which spray a liquid and atomize the liquid using pressurized gas. Nozzle bodies and nozzle body assemblies for other types of spraying devices, such as airless spray guns are outside the scope of this disclosure.

[0016] Nozzle bodies according to the present disclosure comprise a tubular nozzle tube having a wall ("nozzle tube wall"), an inlet ("nozzle tube inlet"), an outlet ("nozzle tube outlet") and a passage ("nozzle tube passage"). A nozzle tube may be a tubular element of any length. It may be, for example, a tubular element of a length of 2 millimeters (mm) or more, or of 5 mm or more, or of 10 mm or more.

[0017] The tubular nozzle tube extends in a length direction. The length direction of the nozzle tube defines axial directions of the nozzle tube and of the nozzle body. Radial directions of the nozzle tube are directions orthogonal to the axial directions of the nozzle tube.

[0018] In a certain position along its length, rearward from the nozzle tube outlet, the nozzle tube may have a cross section. The shape of the cross section is not particularly limited. At a certain longitudinal position, rearward from the nozzle tube outlet, the nozzle tube may have, for example, a circular cross section or an elliptical cross section. It may have an irregular (e.g. non-symmetric) cross section in at least a longitudinal section of the elongated nozzle tube. The nozzle tube may have, for example, a cross section which varies in size or shape along its length direction, such as from a circular to an elliptic cross section or from a larger circular cross section to a smaller circular cross section.

[0019] In certain embodiments the tubular nozzle tube is straight, i.e. it is a straight tubular element. In certain embodiments the nozzle tube is a straight tubular element of identical circular cross section along its length. In other embodiments the nozzle tube is bent or curved. In certain embodiments the nozzle tube comprises a straight axial section. In some of these embodiments the straight axial section comprises the nozzle tube outlet.

[0020] The nozzle tube is tubular. "Tubular" refers to the shape of a tube, as is common, such as, for example, a cylindrical tube such as a straight tube having a circular cross section, a curved tube such as an S-shaped tube, or a deformed tube. A tube is considered herein to be hollow and to comprise a tube wall. In a deformed tube, the tube wall has an irregular shape or an irregular cross section.

[0021] The nozzle tube may be connectable or connected, e.g. at the nozzle tube inlet, to a paint-conducting element for conducting the liquid into the nozzle tube.

[0022] The nozzle tube comprises a nozzle tube passage which extends lengthwise between the nozzle tube inlet and the nozzle tube outlet for conducting the liquid from the nozzle tube inlet to the nozzle tube outlet. The nozzle tube inlet is a first end of the nozzle tube passage. In use, liquid enters the nozzle tube through the nozzle tube inlet. The nozzle tube outlet is a second end of the nozzle tube passage, opposite to the first end. In use, the liquid exits the nozzle tube passage through the nozzle tube outlet into outside air.

[0023] In certain embodiments the nozzle tube passage is straight between the nozzle tube inlet and the nozzle tube outlet. In certain embodiments the nozzle tube passage is a straight cylindrical space of identical circular cross section along its length. In certain embodiments the nozzle tube passage comprises a straight axial section. In some of these embodiments the straight axial section comprises the nozzle tube outlet.

[0024] In other embodiments the nozzle tube passage is curved. In some of these embodiments the nozzle tube passage comprises a curved section and a straight section. The straight section may comprise the nozzle tube outlet.

[0025] The nozzle tube passage may have a cross section. The shape of the cross section may not be particularly limited. The nozzle tube passage may have, for example, a circular cross section or an elliptical cross section or an irregularly shaped cross section.

[0026] The axial position at which the liquid exits the nozzle tube passage into outside air is the axial position "at the nozzle tube outlet", as used herein. As the nozzle tube wall delimits the nozzle tube passage which ends at the nozzle tube outlet, this axial position is the axial position at which the nozzle tube wall (and the nozzle tube) ends. In other words, the nozzle tube wall extends axially up to the nozzle tube outlet. Also, the outer surface of the nozzle tube wall ends at the nozzle tube outlet.

[0027] The cross section of the nozzle tube passage at the nozzle tube outlet determines the cross section of the liquid flow in the specific axial position in which the liquid exits the nozzle body, i.e. at the nozzle tube outlet. This particular cross section is to be taken in a plane through the nozzle tube outlet orthogonal to the spray axis. This particular cross section is termed "outlet cross section" herein.

[0028] In the outlet cross section, a protrusion of the nozzle tube outlet protrudes radially outward from the central portion. A protrusion may protrude radially outward from the central portion by at least 0.2 millimeters (mm). A more pronounced protrusion may, in certain scenarios, provide for a larger interaction zone and an improved atomization, compared to a less pronounced protrusion. Hence, in certain embodiments, a protrusion may protrude radially outward from the central portion by at least 0.5 mm, by at least 1.0 mm, or by at least 1.5 mm.

[0029] A minimum radius of the central portion is the shortest radial distance of the inner surface of the nozzle tube wall from the spray axis, determined in the outlet cross section. The central portion may have a minimum size defined by the area of a circle having a radius equal to the minimum radius of the central portion.

[0030] A protrusion, or each protrusion, may protrude radially outward from the central portion by at least 20% of the minimum radius of the central portion. A more pronounced protrusion may, in certain scenarios, provide for a larger interaction zone and an improved atomization, compared to a less pronounced protrusion. Hence, in certain embodiments, a protrusion, or each protrusion, may protrude radially outward from the central portion by at least 50% of the minimum radius of the central portion, or by at least 80% of the minimum radius of the central portion.

[0031] According to the present disclosure, in the outlet cross section, the nozzle tube outlet has a central portion and two or more protrusions protruding radially outward from the central portion, wherein each protrusion is located at a respective angular protrusion position as measured circumferentially around the spray axis in the outlet cross section. The central portion may be of a circular shape, for example, or of a non-circular shape, such as of an elliptical shape, a square shape, a rectangular shape or an irregular shape.

[0032] The nozzle tube outlet may have more than two protrusions. A greater number of protrusions can help enlarge the interaction zone between liquid and atomizing gas further, and thereby contribute to an even more effective atomization of the liquid. Hence in certain embodiments the nozzle tube outlet has three protrusions or four protrusions or six protrusions or eight protrusions. More specifically, in certain embodiments, in an outlet cross section taken in a plane through the nozzle tube outlet orthogonal to the spray axis, the nozzle tube outlet has a central portion and three, four, six or eight protrusions protruding radially outward from the central portion, wherein each protrusion is located at a respective angular protrusion position as measured in the outlet cross section circumferentially around the spray axis.

[0033] Independent of the number of protrusions, the angular protrusion positions of the protrusions may be equally distributed about a 360° circle centered around the spray axis. Where the nozzle tube outlet has six protrusions, for example, their angular protrusion positions may be at angles of 60°, 120°, 180°, 240°, 300° and 360°, respectively.

[0034] The outer surface of the nozzle tube wall may form further recesses, such as a second recess, a third recess, etc. A greater number of recesses can help enlarge the interaction zone between liquid and atomizing gas, and thereby contribute to a more effective atomization of the liquid. In certain embodiments of the nozzle body according to the present disclosure, in the outlet cross section, the outer surface of the nozzle tube wall forms one or more further recesses each receding radially inward towards the spray axis, through which further recesses, in use, atomizing gas exits into outside air.

[0035] Intertwinement, interdigitation and interleaving between protrusions and recesses can be made easier if the number of recesses equals the number of protrusions.

[0036] This allows a recess to be located between each pair of protrusions adjacent to each other, which enlarges the interaction zone and helps improve atomization. Therefore, in certain embodiments of the nozzle body described herein the total number of recesses (first recess and further recesses) is equal to the total number of the two or more protrusions.

[0037] Specifically, in certain embodiments of the nozzle body according to the present disclosure, in the outlet cross section, the outer surface of the nozzle tube wall forms one or more further recesses each receding radially inward towards the spray axis, through which further recesses, in use, atomizing gas exits into outside air, wherein the total number of recesses (first recess and any further recesses) is equal to the total number of the two or more protrusions.

[0038] In nozzle bodies according to the present disclosure each protrusion and each recess may be of a different size and/or shape, as determined in the outlet cross section. Alternatively, all protrusions may be of an identical size and shape, as determined in the outlet cross section. Independent from the protrusions, all recesses may be of an identical size and shape, as determined in the outlet cross section.

[0039] To determine an angular protrusion position, the outlet cross section is inspected. It shows a closed curve which is the intersection of the inner surface of the nozzle tube wall with the plane of the outlet cross section and which represents the radially outer boundary of the nozzle tube outlet. It also shows an "axis point" which represents the intersection of the spray axis with the plane of the outlet cross section. In the plane of the outlet cross section, an arbitrarily chosen straight radial line ("zero-degree line") starting from that axis point marks a zero-degree (or 12 o'clock) angular position against which circumferential directions and angular positions around the spray axis can be measured in the outlet cross section.

[0040] For a given protrusion of the nozzle tube outlet in the outlet cross section, the point of the closed curve at greatest radial distance from the axis point is determined. Should there be more than one of these points, their middle point is used. In the outlet cross section, a dotted line is drawn from the axis point to that point of the protrusion and the angle between the zero-degree line and the dotted line is measured circumferentially in a clockwise direction centered around the axis point. This angle is the angular position of the protrusion, or the "angular protrusion position".

[0041] An angular position of a recess in the outer surface of the nozzle tube wall can be determined in a corresponding manner in the outlet cross section. The outlet cross sectional view shows a closed curve which is the intersection of the outer surface of the nozzle tube wall with the plane of the outlet cross section and which represents the radially inner boundary of the atomizing gas flow (an atomizing gas passage is formed when an air cap is arranged over the nozzle body). The closed curve has a recess receding radially inwardly towards the axis point. The point of the recess at smallest radial distance from the axis point is determined. Should there be more than one of these points, their middle point is used. In the outlet cross sectional view, a dashed line is drawn from the axis point to that point of the recess and the angle between the zero-degree line and the dashed line is measured circumferentially in a clockwise direction centered around the axis point. This angle is the angular position of the recess, or the "angular recess position".

[0042] Two protrusions are considered "adjacent" or "adjacent to each other" if no third protrusion exists such that the angular protrusion position of the third protrusion is angularly positioned in the smallest interval between the angular protrusion positions of the two protrusions.

[0043] As used herein, and in contrast to the term "located angularly between", a recess is considered "located between" two protrusions if a straight line between at least one point of a first protrusion to at least one point of a second protrusion intersects a portion of the recess.

[0044] It may be advantageous for the first recess and any further recesses, if present, to comprise a portion that is located between portions of two protrusions adjacent to each other. A recess that is angularly located between two protrusions may still have no portion that is located between these protrusions, as per the above definition of "located between". Interaction between the liquid and the atomization gas is deemed stronger - and atomization enhanced - where a protrusion and a recess are closer to each other. An intertwinement or interleaving of the first recess with the protrusions between which it is angularly positioned will thus provide a closer interaction between liquid and atomizing gas, and thereby help improve atomization. Therefore, in certain embodiments a portion of the recess is located between respective radially outermost portions of the two protrusions adjacent to each other.

[0045] Where the outer surface of the nozzle tube wall forms further recesses, it appears advantageous if each of the recesses is located angularly between two adjacent protrusions of the nozzle tube outlet, as this can contribute to enlarging the interaction zone and thus to obtaining better atomization. Typically, not more than one recess is positioned angularly between two protrusions adjacent to each other, but in certain embodiments two or more recesses may be positioned angularly between two protrusions adjacent to each other. Therefore, in certain embodiments of the nozzle body according to the present disclosure, in the outlet cross section, the outer surface of the nozzle tube wall forms one or more further recesses each receding radially inward towards the spray axis, through which further recesses, in use, atomizing gas exits into outside air, wherein each further recess is located at a respective further angular recess position as measured in the outlet cross section circumferentially around the spray axis, wherein, in the outlet cross section, each further angular recess position is located angularly between the respective angular protrusion positions of two protrusions, adjacent to each other, of the two or more protrusions.

[0046] In certain of these embodiments, each of the further angular recess positions is located angularly in the middle between the respective angular protrusion positions of two protrusions, adjacent to each other, of the two or more protrusions. The positioning in the middle can help obtain a more regular spray pattern.

[0047] In many scenarios it would appear as a waste of space if no recess were positioned angularly between two protrusions adjacent to each other. In other words, it is often advantageous that at least one recess is positioned angularly between two protrusions adjacent to each other, as this arrangement may help enlarge the interaction zone and thereby improve atomization. Therefore, in certain embodiments, in the outlet cross section, the outer surface of the nozzle tube wall forms one or more further recesses each receding radially inward towards the spray axis, through which further recesses, in use, atomizing gas exits into outside air, and wherein between the angular protrusion positions of any two protrusions, adjacent to each other, of the two or more protrusions, an angular recess position of at least one recess of the first recess and the further recesses is angularly located.

[0048] In certain of these embodiments, the angular recess position of at least one recess of the first recess and the further recesses is angularly located in the middle between the angular protrusion positions of any two protrusions, adjacent to each other, of the two or more protrusions, The positioning in the middle can help obtain a more regular spray pattern.

[0049] The tubular nozzle tube has a nozzle tube wall. The wall may extend generally lengthwise in axial directions. It may extend from the nozzle tube inlet to the nozzle tube outlet. The nozzle tube wall may separate the nozzle tube passage from a space outside the nozzle tube, such as from an atomizing gas passage.

[0050] The nozzle tube wall may have a thickness. The thickness may be defined by the extension of the nozzle tube wall in radial directions. The thickness of the nozzle tube wall may vary along the length of the nozzle tube. Alternatively, the thickness of the nozzle tube wall may be constant along the length of the nozzle tube.

[0051] Atomization of the liquid by pressurized atomizing gas can be more efficient where the apertures through which the liquid and the gas exit are geometrically closer together in the outlet cross section. In nozzle bodies according to the present disclosure apertures for atomizing gas (atomizing gas outlet) and for liquid (nozzle tube outlet) are separated by the nozzle tube wall. In nozzle bodies according to the present disclosure, atomizing gas exits through the recess(es), while liquid exits through the protrusions of the nozzle tube outlet. It will often be advantageous if at least a portion of the recess (or of each recess, if there are two or more) is spaced only a small distance from a respective portion of the protrusions between which it is angularly positioned. Therefore, in certain embodiments of the nozzle body described herein, the first recess comprises a portion which is spaced, as measured in the outlet cross section, less than one millimeter from a portion of any of the adjacent protrusions between which the first recess is angularly positioned.

[0052] In certain embodiments, all portions of the first recess and, if present, of all further recesses are spaced less than one millimeter from a closest portion of any of the protrusions, as measured in the outlet cross section. The recesses are thus located close to a close-by protrusion, which helps ensure a strong interaction between atomizing gas and the liquid, which generally translates into a strong atomization of the liquid.

[0053] More specifically, the radially innermost portion (i.e. the "bottom" portion, located closest to the spray axis) of the first recess - and optionally of each further recess, if present - is advantageously arranged geometrically close to one of the adjacent protrusions between which the recess is angularly positioned. A geometrical distance of two millimeters of less, measured in the outlet cross section, corresponds to a "close" position. In certain embodiments, therefore, a distance, as measured in the outlet cross section, between the radially innermost portion of the first recess and any portion of the adjacent protrusions between which the first recess is angularly located, is less than two millimeters.

[0054] The choice of material or materials of the nozzle tube wall is not particularly limited. In certain embodiments of the nozzle body according to the present disclosure the nozzle tube wall is made of, or comprises, a polymeric material or a metal. Polymeric material can generally be molded or cast or otherwise formed to a high degree of precision at reasonable cost to form the nozzle tube and the nozzle tube wall. Metals are versatile materials which can be machined, metal injection molded, cast or otherwise formed to a high degree of precision at reasonable cost to form the nozzle tube and the nozzle tube wall as well as the protrusions and any recess(es). Within the group of polymeric material and the group of metallic materials, a number of suitable materials are known that don't significantly react chemically with typical liquids and thereby can be used over extended periods of time, making polymeric and metal materials versatile substances for manufacturing nozzle bodies and nozzle tube walls according to the present disclosure.

[0055] Generally, nozzle bodies are typically machined from metal and installed on a spray gun platform or on a barrel using threads. However, machining nozzles from metal greatly limits design options and comes at a high cost. More recently nozzle bodies have been molded from plastic as part of large assemblies. Molding allows for increased feature complexity. The size of the molded part greatly affects the precision with which small features can be made. In general, small parts can be molded more precisely.

[0056] In many spray guns and nozzle assemblies, a single component called "atomizer" conducts atomizing gas towards the atomizing gas outlet and liquid to the nozzle tube outlet. An atomizer generally comprises a nozzle body and an atomizer base. The nozzle body is a front portion of the atomizer and comprises the nozzle tube outlet and the terminal part of the nozzle tube wall as described herein. The atomizer base is a rearward portion of the atomizer and comprises a barrel port as described above, and/or other means for attaching the atomizer to a barrel or to a spray gun platform.

[0057] The nozzle body and the atomizer base of certain atomizers can be manufactured separately and later be attached to each other to form the atomizer. Separate manufacturing may be advantageous, as large portions of a typical atomizer, and in particular the atomizer base, do not require extreme manufacturing precision to function properly. The performance of the nozzle body, however, is highly sensitive to mechanical tolerances and imperfections. By separating the manufacturing of the nozzle body from the manufacturing of the atomizer base, much tighter manufacturing controls can be applied to the manufacturing of the nozzle body than to the manufacturing of the atomizer base. Thereby, the nozzle body can be manufactured at a higher degree of precision in terms of its physical dimensions, surface smoothness, material homogeneity, etc. This can result in the nozzle bodies having a much higher degree of precision than the atomizer bases.

[0058] The high degree of mechanical precision also enables manufacturing of complex nozzle body designs, potentially even down to a microscopic scale.

[0059] The separate manufacturing of the nozzle body and the atomizer base and their subsequent attachment to each other at a later stage can bring other advantages. The nozzle body and the atomizer base may be manufactured from different materials, such as from different polymeric materials or different metal materials, which may allow to reduce raw material cost. The nozzle body and the atomizer base may be manufactured at the same time in simultaneous processes, thus saving time in manufacturing.

[0060] Another potential advantage is that a modular atomizer concept can be applied: a selected one out of various different types of nozzle bodies (each having a different nozzle tube outlet shape and thereby providing a different atomization characteristic, for example) can be attached to the same single type of atomizer base. Many different types of atomizers can thus be made using the same atomizer base, bringing down cost for stockkeeping and manufacturing of the atomizer base. A large variety of intricate and complex nozzle body designs may thus be manufactured quickly and cost effectively before being joined with a standardized atomizer base.

[0061] In an exemplary manufacturing process using the modular concept described in the preceding paragraphs, a small, intricate, nozzle body is micro-molded from a first polymeric material and is then attached to the atomizer base, molded from a second polymeric material, via one or more of a variety of means such as quick connect, threads, plastic welding, or adhesives.

[0062] As stated above, the modular atomizer concept may be used with nozzle bodies according to the present disclosure in which the nozzle tube outlet has protrusions and the outer surface of the nozzle tube wall forms a recess angularly between the protrusions, or with other types of nozzle bodies.

[0063] Returning to nozzle bodies according to the present disclosure, the nozzle tube wall comprises a radially inner surface and an opposed radially outer surface. The inner surface and the outer surface are separated by a thickness of the nozzle tube wall. The inner surface is oriented radially inward and faces the nozzle tube passage. It delimits the nozzle tube passage. In use, the liquid, conducted by the nozzle tube passage, is in contact with the inner surface of the nozzle tube wall.

[0064] The radially outer surface is generally arranged opposite to the radially inner surface and radially outward from the inner surface. The outer surface is oriented radially outward and faces radially away from the nozzle tube passage. In certain embodiments the outer surface is concentric with the inner surface.

[0065] In use, the outer surface is in contact with the atomizing gas as the atomizing gas flows forward towards an atomizing gas outlet for atomizing the liquid after the liquid has exited the nozzle tube outlet. The outer surface may be operable to guide pressurized atomizing gas, e.g. towards an atomizing gas outlet in the vicinity of the nozzle tube outlet. The outer surface may thus not only delimit the nozzle tube wall and the nozzle tube, but in certain embodiments also delimits, in conjunction with another element, e.g. with an element of an air cap as explained below, an atomizing gas passage in a nozzle assembly. In some of such embodiments, the outer surface is in contact with atomizing gas conducted through the atomizing gas passage towards an atomizing gas outlet, arranged circumferentially around the nozzle tube wall at the nozzle tube outlet.

[0066] Atomizing air exits the spray gun through the first recess (and each further recess, if present). In order to conduct the atomizing air from the spray gun platform to the recess(es), the outer surface of the nozzle tube wall can be provided with a channel or a groove which extends in its length direction from a frontmost axial portion of the nozzle tube wall where, in the outlet cross section, the groove forms the recess, to a rearward axial portion of the nozzle tube wall. A groove may follow a linear path or a curved path. If the path is linear, the path may be parallel to the spray axis, or it may form an angle with the spray axis. This latter arrangement may result in a helical groove formed in the outer surface of the nozzle tube wall. A groove may be generally beneficial in that it provides a well-defined direction to the portion of the pressurized atomizing gas which exits through the recess, allowing some of the atomizing gas to impinge on the ejected liquid at a desired angle and at a desired axial position. This may result in better atomization.

[0067] Thus generally, in certain embodiments the outer surface of the nozzle tube wall forms an elongated groove for conducting pressurized atomizing gas towards the recess, wherein the groove begins in the first recess and extends lengthwise rearward in axial directions.

[0068] Such a groove in the nozzle tube wall may have, at each longitudinal position along its length, a depth which is measured in radial directions from the outer surface of the nozzle tube wall towards the spray axis. The depth is determined in a cross section of the groove at each longitudinal position. The depth may be smaller - and the groove thus shallower - at a rearward length position than the depth at the recess. Alternatively, the depth of the groove may be the same at any length position of the groove. In rare scenarios the depth may be greater - and the groove thus deeper - at a rearward length position than the depth at the recess.

[0069] A width of the groove is measured, at each longitudinal position along the groove length, in circumferential directions on the outer surface of the nozzle tube wall. The width is determined in a cross section of the groove at each longitudinal position. The width may be smaller - and the groove thus narrower - at a rearward length position than the width at the recess. Alternatively, the width of the groove may be the same at any length position of the groove. In certain scenarios the width may be greater - and the groove thus wider - at a rearward length position than the width at the recess.

[0070] Radially inwards of the outer surface is the nozzle tube wall and the nozzle tube passage, while the atomizing gas passage is located radially outwards of the outer surface. In certain embodiments the nozzle tube wall is arranged radially between the nozzle tube passage and the atomizing gas passage. In certain nozzle assemblies the nozzle tube wall separates the nozzle tube passage from the atomizing gas passage.

[0071] In certain embodiments the outer surface of the nozzle tube wall is shaped to direct atomizing gas emanating from the atomizing gas outlet angularly away from the spray axis. Within this angularly-outward directed flow of atomizing gas the pressure in front of the nozzle tube outlet is lower than it is in traditional geometries in which atomizing gas flows in directions along the spray axis or towards the spray axis. The lower pressure before the nozzle tube outlet draws more liquid from the nozzle passage and increases the liquid (e.g. paint) flow rate, although the consumption of pressurized gas is unchanged with respect to traditional nozzle bodies. To obtain a liquid flow rate similar to those obtained with traditional nozzle bodies, the pressure and/or volume of the pressurized atomizing gas can be reduced in spray guns featuring such a nozzle body. This may result in energy and cost savings. A lower pressure of the atomizing gas may also result in less generation of high-frequency noise or in lower volume of high-frequency noise during spraying operations, which reduces occupational noise exposure and associated health risks for human operators.

[0072] In particular, a groove as described in the preceding paragraphs may be oriented or shaped to direct at least a portion of the pressurized atomizing gas, exiting through the recess into outside air, angularly away from the spray axis. Shaping or orienting the groove like this may provide a higher liquid flow rate, as the groove provides a well-defined direction to a considerable portion of the pressurized atomizing gas which exits through the recess. Directing at least some of the atomizing gas away from the spray axis is believed to create a larger zone of low pressure in front of the nozzle tube outlet, which may help extracting liquid more effectively and increasing liquid flow rates without having to increase the pressure of the atomizing gas.

[0073] Therefore, in certain embodiments, the groove is oriented or shaped to direct at least a portion of the pressurized atomizing gas, exiting into outside air through the first recess, angularly away from the spray axis.

[0074] In the context of these geometric considerations, it is noted that the forward end of the outer surface of the nozzle tube wall may not be a perfect edge. On a small scale, this forward end may have an inconsistent shape, recesses, protrusions (such as plastic flash or metal burrs), or chamfers, such as may be required for a reliable manufacturing process of the nozzle tube or unavoidable in industrial production processes. Such imperfections of axial extensions of 0.4 mm or less, whatever their orientation or shape, are generally not considered suitable to considerably affect the flow of atomizing gas in the desired way. Such unavoidable inconsistencies or indispensable chamfers at the forward end of the outer surface of the nozzle tube wall are thus not considered recesses of the outer surface of the nozzle tube wall at the nozzle tube outlet nor are they considered protrusions of the nozzle tube outlet in the outlet cross section.

[0075] The nozzle tube inlet may be shaped such as to be connectable, directly or indirectly, to a liquid nozzle port on a barrel of a nozzle assembly or of a spray gun body. A direct connection is a connection in which the nozzle tube inlet is in surface contact with the liquid nozzle port, whereas an indirect connection is a connection in which one or more intermediate elements connect the nozzle tube inlet with the liquid nozzle port. A connection of the nozzle tube inlet to a liquid nozzle port on a barrel would allow liquid to flow from the barrel or from the spray gun body, as the case may be, into the nozzle body and through the nozzle tube passage to the nozzle tube outlet where it exits the nozzle body into outside air and is atomized by atomizing gas.

[0076] The nozzle tube outlet is an aperture in the nozzle tube through which the liquid exits the nozzle tube passage (and the nozzle body) and enters the surrounding air. The nozzle tube outlet is one end of the nozzle tube passage and is delimited, in radial directions, by the nozzle tube wall which extends up to the nozzle tube outlet.

[0077] Viewed in the outlet cross section, the nozzle tube outlet has a central portion and two or more protrusions protruding radially outward from the central portion. The central portion may have, for example, a circular shape or a square shape. A protrusion, or each protrusion, may have, for example, an elongated shape, a rectangular shape, or a rounded shape. The elongated shape may define a protrusion length direction. The protrusion length direction may be a radial direction, i.e. a direction oriented radially away from the spray axis. A protrusion, or each protrusion, may have a rectangular shape, a square shape, a circular shape, an elliptic shape or a polygonal shape, for example. In certain embodiments, all protrusions have the same shape, whereas in other embodiments two or more protrusions have different respective shapes.

[0078] Viewed in the outlet cross section, the shape of the nozzle tube outlet determines the cross section of the flow of liquid as it exits the nozzle tube and enters surrounding air, before the liquid is atomized to form minute droplets. Viewed in the outlet cross section, the nozzle tube outlet may have, for example, an elliptic shape, a square shape, a rectangular shape, a polygonal shape, or a star shape. A star shape, for example, may comprise a central portion and three, four, five, six, seven, eight, or any higher number of protrusions. Viewed in the outlet cross section, the angular protrusion positions of the protrusions may be equally spaced from each other, as measured circumferentially around the spray axis.

[0079] Viewed in the outlet cross section, the shape of the nozzle tube outlet may be symmetric about a center point or about a center of the nozzle tube outlet. The cross section of the nozzle tube outlet may be rotationally symmetric or axially symmetric about a center point or a center of the nozzle tube outlet. Viewed in the outlet cross section, the shape of the nozzle tube outlet may be rotationally symmetric or axially symmetric about the spray axis. Viewed in the outlet cross section, the nozzle tube outlet may alternatively be of an irregular shape, e.g. a shape exhibiting no symmetry.

[0080] In order to define in a most general manner a center point or a center of the nozzle tube outlet as viewed in the outlet cross section, the commonly known notion of a "centroid" is applied. A centroid of a plane shape, such as of the nozzle tube outlet as viewed in the outlet cross section, is commonly known to be the arithmetic mean position of all the points in the surface of the shape. To illustrate the concept of a centroid: Assuming a uniform mass density, the center of mass of the plane shape coincides with the centroid. Informally, the centroid can be understood as the point at which a cutout of the shape of the plane shape (with uniformly distributed mass) would be perfectly balanced on the tip of a pin.

[0081] A larger zone of interaction between the liquid and the atomization gas can enhance mixing and helps improve atomization. In certain scenarios, for a given cross sectional area of the nozzle tube outlet, a larger interaction zone can be obtained by a increasing the length of the perimeter line delimiting the nozzle tube outlet in the outlet cross section. For a circular nozzle tube outlet of radius r (measured in the outlet cross section), i.e. one not having any protrusions, the cross-sectional area A of the nozzle tube outlet in the outlet cross section is A= π r², while the path length P of the perimeter of the circular outlet is P= 2π r. As a dimensionless ratio, referred to as "bulge ratio" B herein, B= P²/A is thus a representative measure for a length of the interaction zone, normalized to the area of the nozzle tube outlet. For a circular nozzle tube outlet without any protrusions, the bulge ratio is B= 4π = 12.6 approximately. In nozzle bodies according to the present disclosure, in which the nozzle tube outlet has protrusions, as viewed in the outlet cross section, B is larger than 12.6, and this larger bulge ratio B corresponds to a longer interaction zone, stronger interaction and generally better atomization. B may thus be larger than 12.6. Preferably, the bulge ratio B is larger than 40.0, resulting in an even longer interaction zone and stronger atomization. In certain embodiments nozzle bodies having values of B exceeding 100.0 have shown very good performance. In certain other scenarios nozzle bodies having values of B exceeding 100.0 or even 180.0 may result in too high pressures and a reduced amount of liquid being sprayed. B may thus be smaller than 180.0, or it may be smaller than 100.0.

[0082] Therefore, in certain embodiments of the nozzle body according to the present disclosure, the nozzle tube outlet is delimited, in the outlet cross section, by a perimeter line having a path length P, wherein the nozzle tube outlet has, in the outlet cross section, a geometric area A, and wherein a bulge ratio B= P²/A is larger than 13.0, and optionally wherein B is larger than 40.0, wherein P² and A are measured in the same units.

[0083] The liquid exits the nozzle tube at the nozzle tube outlet into outside air in a spray direction. The spray direction is thus the flow direction of the liquid flow at the very position where the liquid exits the nozzle tube passage. This position is a position at the nozzle tube outlet, i.e. in the most forward portion of the nozzle tube wall in the vicinity of the nozzle tube outlet. Depending on the circumstances, further downstream the liquid flow may not have a well-defined flight direction anymore. The definition of the "spray direction" herein is therefore based on the direction of the liquid flow at the very position where the liquid exits the nozzle tube passage into outside air.

[0084] The spray direction is generally determined by the orientation of a terminal portion of the nozzle tube passage, i.e. the portion closest to the nozzle tube outlet. The spray direction through the centroid of the shape of the nozzle tube outlet, viewed in the outlet cross section, defines a spray axis. The spray axis thus always passes through the centroid and is collinear with the spray direction at the position of the centroid.

[0085] The nozzle tube outlet is arranged around the spray axis. In certain embodiments the nozzle tube outlet has an annular shape as viewed in the outlet cross section. In certain embodiments the nozzle tube outlet comprises the spray axis. Liquid thus exits nozzle tube passage at the position of the spray axis. In certain of these embodiments, the central portion of the nozzle tube outlet comprises the spray axis. In such nozzle tube outlets liquid exits the nozzle tube passage through the nozzle tube outlet at the position of the spray axis. This geometry may help in obtaining a contiguous jet of liquid which may be altered or shaped further downstream into a consistent and balanced spray pattern.

[0086] The flow direction of the atomizing gas may be determined by the orientation and/or shape of the outer surface of the nozzle tube wall alone, or by the orientation and/or shape of the outer surface of the nozzle tube wall in conjunction with another surface of the nozzle body. In many known spray gun designs, however, such as in certain ones shown in the international patent application published as WO 2012/109298 A1, the flow direction of the atomizing gas is determined by the orientation and/or shape of the outer surface of the nozzle tube wall and an orientation and/or shape of a surface of an air cap. Air caps are generally known from many existing spray guns: an air cap is an element directly or indirectly attached to the barrel of a nozzle assembly or to the body of the spray gun and helps direct pressurized gas in suitable directions for atomizing the liquid jet and for shaping the jet of minute droplets of atomized liquid. Certain air caps are provided with air horns having shaping air apertures to direct so-called shaping gas from opposite directions towards a jet of atomized liquid in order to shape the spray jet into a desired pattern.

[0087] When an air cap is connected directly or indirectly with the nozzle body, the outer surface of the nozzle tube wall may be arranged to form, in conjunction with a surface of the air cap, an atomizing gas outlet arranged around the nozzle tube outlet in a generally circumferential direction. The outer surface of the nozzle tube wall, with its recess(es), may, for example, be arranged opposite to that surface, and/or parallel to that surface. The atomizing gas outlet may be formed between a surface of the air cap and the outer surface of the nozzle tube wall at the nozzle tube outlet, i.e. between a surface of the air cap and the outer surface of a terminal end of the nozzle tube wall. The first recess, and all further recesses if present, form portions of the atomizing gas outlet, as atomizing gas exits into outside air through the recess(es). Where the outer surface of the nozzle tube wall can form a portion of the atomizing gas outlet, this avoids the necessity to provide an additional element of a spray gun which would direct the atomizing gas into a desired direction in a desired pattern.

[0088] In certain embodiments of the nozzle body according to the present disclosure the outer surface of the nozzle tube wall is therefore arranged to form, in conjunction with a surface of an air cap when the air cap is connected directly or indirectly with the nozzle body, an atomizing gas outlet arranged circumferentially around the nozzle tube outlet, such that the pressurized atomizing gas exits into outside air through the atomizing gas outlet and atomizes the liquid after the liquid has exited the nozzle tube outlet, wherein the atomizing gas outlet comprises the first recess. The atomizing gas outlet may be arranged in the plane of the nozzle tube outlet orthogonal to the spray axis. The atomizing gas outlet may be arranged in the plane through the nozzle tube outlet orthogonal to the spray axis.

[0089] A generally circumferential arrangement of the atomizing gas outlet around the nozzle tube outlet is not limited to a circular circumferential arrangement, but includes, for example, elliptic circumferential arrangements, square or rectangular or other polygonal circumferential arrangements, star-shaped circumferential arrangements and circumferential arrangements of irregular shape. The atomizing gas outlet may have a generally annular shape, a generally circular shape, a generally elliptic shape, a generally square or a generally rectangular or another polygonal shape, a star shape or an irregular shape.

[0090] In preferred embodiments the atomizing gas outlet is shaped such as to form, in a plane of the atomizing gas outlet orthogonal to the spray axis, a radially outer ring portion and one or more recess portions protruding radially inwardly from the ring portion. The recess portion(s) may be the recess(es) formed by the outer surface of the nozzle tube wall. Through the ring portion and through the recess portion(s), in use, atomizing air exits into outside air. The ring portion is delimited - in radially outward directions - by a surface of the air cap, when the air cap is connected with the nozzle body.

[0091] The delimiting surface of the air cap may be referred to herein as nozzle aperture edge. The nozzle aperture edge forms an aperture for accommodating the nozzle body in a front wall of the air cap in which aperture the front terminal end of the nozzle tube wall is arranged. The nozzle aperture edge may be a circular edge or an elliptical edge, for example.

[0092] The recess portions are delimited - in radially inward directions - by the nozzle tube wall. Each recess portion is a recess as explained above, which, as viewed in the outlet cross section, is formed by the outer surface of the nozzle tube wall and recedes radially inward towards the spray axis, so that through the recess, in use, atomizing air exits into outside air. Each recess is located at an angular recess position as measured in the outlet cross sectional view circumferentially around the spray axis.

[0093] The shape of the atomizing gas outlet is a shape as it is viewed from the front, looking rearward along spray axis at the atomizing gas outlet. The shape of the atomizing gas outlet may be the shape of the atomizing gas outlet in the plane of the nozzle tube outlet or the shape of the atomizing gas outlet viewed in the outlet cross section.

[0094] Although the shape of the atomizing gas outlet is not particularly limited, it is preferred that the atomizing gas outlet forms essentially a full 360° circumference (of whatever shape) around the nozzle tube outlet. This helps ensure proper atomization of the liquid. In alternative scenarios, however, the atomizing gas outlet may form an incomplete circumference (of whatever shape) around the nozzle tube outlet. The atomizing gas outlet may, for example, be shaped such as to form only a plurality of recess portions protruding radially inwardly from the ring portion, but no radially outer ring portion. In such a shape, the recess portions may not be connected with each other in the outlet cross sectional view.

[0095] The width of the atomizing gas outlet is not particularly limited. "Width of the atomizing gas outlet", as used herein, is the extension of the atomizing gas outlet in radial directions in the plane of the atomizing gas outlet. In certain configurations, the width is the radial distance from the outer surface of the nozzle body to the nozzle aperture edge of the air cap. The atomizing gas outlet may have a width of between 0.01 millimetre (mm) and 5.00 mm, for example. Preferably, the atomizing gas outlet has a width of between 0.10 millimetre (mm) and 1.00 mm. At a given atomizing gas pressure a wider atomizing gas outlet will result in lower gas speed and hence a reduced shear stress/velocity gradient between the gas and the liquid to be atomized. In contrast, a narrower atomizing gas outlet lets less gas pass through but it may flow at a higher velocity and thereby increase the shear stress between the gas and the liquid. The preferred widths are chosen amongst a large set of design parameters (desired air consumption, desired liquid flow rate, atomization quality, etc.) to help obtain an acceptable balance between these effects.

[0096] The atomizing gas outlet may be concentrically circumferentially arranged around the nozzle tube outlet at a certain radial distance from the nozzle tube outlet. This radial distance may be the thickness of the nozzle tube wall at the terminal end of the nozzle tube, i.e. at the nozzle tube outlet. The radial distance, at the nozzle tube outlet, between the nozzle tube outlet and the atomizing gas outlet may be between 0.01 mm and 5 mm, preferably it is between 0.1 mm and 1 mm. Since the atomizing gas exit velocity is often highest at the atomizing gas outlet and decays moving downstream, there can be benefits to placing the nozzle tube outlet as close as practically possible to the gas outlet. One way to do so is by minimizing the radial distance between the nozzle tube outlet and the atomizing gas outlet. Generally, a greater radial distance may allow for a thicker and hence more stable nozzle tube wall. Conversely, a smaller radial distance may result in more efficient extraction and atomization of the liquid.

[0097] The nozzle tube outlet may be arranged in a geometrical plane, such as a plane orthogonal to the spray axis or orthogonal to the axial directions. The atomizing gas outlet may be arranged in the same geometric plane as the nozzle tube outlet, or it may be recessed or protruding from the plane of the nozzle tube outlet, e.g. by up to 5 mm.

[0098] The outer surface of the nozzle tube wall may also be arranged to form, in conjunction with a surface of an air cap when the air cap is connected directly or indirectly with the nozzle body, an atomizing gas passage for conducting a pressurized atomizing gas toward the atomizing gas outlet. The pressurized atomizing gas can thus exit the atomizing gas passage into outside air at the atomizing gas outlet and can atomize the liquid after the liquid has exited the nozzle tube outlet.

[0099] A first portion of the atomizing gas passage may thus be formed by a surface of the air cap, while a second portion of the atomizing gas passage may be formed by the outer surface of the nozzle tube wall. Before the air cap is connected with the nozzle body, the atomizing gas passage may thus not exist, or may be incomplete because it is not properly delimited so that pressurized atomizing gas is not conducted toward the atomizing gas outlet. However, in the absence of an air cap the outer surface of the nozzle tube wall is suitable (e.g. suitably shaped, and/or suitably arranged, and/or with a suitable surface structure) to form a portion of the atomizing gas passage, once a suitable air cap is connected.

[0100] A suitable air cap may be connected with the nozzle body according to the present disclosure directly or indirectly. Where two elements are connected without intermediate elements and in surface contact with each other, they are considered to be "directly connected" herein. Where two elements are connected with each other via one or more intermediate elements they are considered to be "indirectly connected" herein.

[0101] A nozzle body as described herein, in conjunction with an air cap, can form a nozzle assembly. In a nozzle assembly or otherwise, the air cap may be connected with the nozzle body in a fixed spatial relation. The fixed spatial relation can help keep the shape of an atomizing gas outlet formed between a portion of the air cap and the nozzle tube wall constant under external forces. The nozzle assembly may be attachable to a platform of a spray gun, such as by attachment of the nozzle body to the spray gun platform or by attachment of the air cap to the spray gun platform or both.

[0102] In certain of these nozzle assemblies the nozzle assembly comprises a nozzle body as described herein and an air cap, connected with the nozzle body in a fixed spatial relation, wherein the air cap includes a front wall facing generally in the spray direction and comprising a nozzle aperture delimited by a nozzle aperture edge, and wherein the nozzle tube is arranged in, or protrudes outwardly through, the nozzle aperture, such that the atomizing gas outlet is formed between the nozzle aperture edge and the nozzle tube wall.

[0103] Such a nozzle assembly may also be advantageous in that the radially inner delimitation of the atomizing gas outlet is formed by the nozzle tube wall and the radially outer delimitation of the atomizing gas outlet is formed by the nozzle aperture edge. A nozzle body as described herein can thereby be used with air caps of different geometries. This, in turn, allows for geometric variations of the atomizing gas outlet, e.g. of its shape, width or its orientation, just by utilizing different air caps, and without having to change the nozzle body.

[0104] The present disclosure therefore also provides a nozzle assembly comprising a nozzle body according to the present disclosure and an air cap, connected with the nozzle body in a fixed spatial relation, wherein the air cap comprises a front wall facing generally in the spray direction and comprising a nozzle aperture delimited by a nozzle aperture edge, and wherein the nozzle tube is arranged in, or protrudes outwardly through, the nozzle aperture, such that the atomizing gas outlet is formed between the nozzle aperture edge and the nozzle tube wall.

[0105] In certain embodiments of such a nozzle assembly the nozzle tube is arranged in the nozzle aperture such that the nozzle tube outlet is flush, or almost flush, with the front surface of the front wall of the air cap. The front surface of the front wall of an air cap faces generally in the spray direction. In other embodiments the nozzle tube protrudes outwardly through the nozzle aperture such that the nozzle tube outlet is located in a plane forward from a plane in which the nozzle aperture is located.

[0106] The front wall of the air cap is an outer wall of the air cap which comprises a front surface facing generally forward, i.e. facing generally in the spray direction. The front surface of the front wall is generally in contact with the outside air. The front wall may be a wall of the air cap of which a portion may be arranged between opposite air horns, comprised in the air cap, if such air horns are present.

[0107] The front wall may form a nozzle aperture in which the forward end of the nozzle tube may be arranged or through which the forward end of the nozzle tube protrudes outwardly. When in use, the air cap including its front wall is arranged centered about the spray axis. The nozzle aperture may be arranged centered about the spray axis, and concentric with the nozzle tube outlet. In the plane of the nozzle tube outlet, a gap between the nozzle tube and the nozzle aperture edge may exist. The gap may extend circumferentially around, and concentric with, the nozzle tube. A width of the gap extends in radial directions. The gap may form the atomizing gas outlet described herein. The atomizing gas outlet is arranged circumferentially around the nozzle tube outlet, such that the pressurized atomizing gas exits into outside air through the atomizing gas outlet and atomizes the liquid after the liquid has exited the nozzle tube outlet.

[0108] For an evenly covered target surface it is often desired to obtain a jet of liquid spray which is perfectly rotationally symmetric with respect to the spray axis. In order to get close to a symmetric jet of liquid, in certain embodiments of the nozzle bodies described herein the nozzle tube outlet and/or the nozzle tube wall are of rotationally symmetric shape and are arranged concentrically with each other, such as centered on the spray axis. Similarly, the entire air cap and/or the nozzle aperture edge may be of rotationally symmetric shape and may be arranged concentrically with each other, such as centered on a symmetry axis of the air cap.

[0109] In order to get closer to a symmetric jet of liquid, in certain embodiments of the nozzle assemblies described herein the nozzle tube outlet, the nozzle tube wall, the nozzle aperture edge, and the atomizing gas outlet are each of rotationally symmetric shape and are each arranged concentrically with respect to the spray axis.

[0110] Certain liquid spray guns have a barrel attached to the spray gun platform through which the to-be-sprayed liquid flows from an external container into the spray gun. After a spraying operation only the barrel and the nozzle body need to be cleaned from liquid, not the spray gun platform. A rear portion of the barrel is usually attached to the spray gun platform, while its front portion often serves to attach an air cap and a nozzle body. A further function of a barrel is to conduct pressurized gas from the spray gun platform to the atomizing gas outlet and potentially towards a shaping gas outlet (e.g. in air horns) at the front portion of the spray gun. A barrel may comprise separate ducts for conducting liquid, atomizing gas and shaping gas. In some embodiments, the barrel and the nozzle body are integrally formed as a single component.

[0111] Nozzle assemblies comprising an air cap and a nozzle body according to the present disclosure have been described above. Nozzle bodies according to the present disclosure can be, in use, connected to a spray gun body, but alternatively they can be attached to a barrel which is attached to the spray gun body. Also, an air cap can be connected to the spray gun body, but it can alternatively be connected to a barrel which is attached to the spray gun body. Where the air cap and the nozzle body are each connected to a barrel, these connections to the barrel may help establish and maintain a fixed spatial relation between the nozzle body and the air cap. This fixed spatial relation helps maintain a constant shape and orientation of the atomizing gas outlet, which is formed between a portion of the air cap (e.g. its nozzle aperture edge) and a portion of the nozzle body (its nozzle tube wall). Maintaining the shape and orientation of the atomizing gas outlet helps keep the jet of atomized liquid in a consistent, fixed geometry and contributes to an atomization which is more constant over time.

[0112] Therefore, in certain embodiments of the nozzle assemblies described herein the nozzle assembly further comprises a barrel having a liquid port connector for directly or indirectly connecting a liquid reservoir to the barrel, wherein the air cap is connected with the barrel, and the nozzle body is connected with the barrel, such that the air cap is connected with the nozzle body in a fixed spatial relation.

[0113] The nozzle bodies according to the present disclosure can be connected to a spray gun platform, directly or via their connection to a barrel connected to the spray gun platform, to form a liquid spray gun in which the nozzle tube outlet has protrusions and the outer surface of the nozzle tube wall forms one or more recesses in angular positions between the angular positions of the protrusions, as described herein. The protrusions and recesses help improve the atomization of the liquid and/or help consume less of the pressurized atomization gas while obtaining a comparable degree of atomization.

[0114] The present disclosure therefore also provides a liquid spray gun for spraying a liquid, comprising a nozzle body as described herein, or a nozzle assembly as described herein.

[0115] Nozzle bodies according to the present disclosure can be manufactured in traditional manufacturing processes like, for example, machining or molding. They may also be created via additive manufacturing processes using a 3D printer. Digital data describing the nozzle body may be stored on a machine-readable medium and may be sent to the 3D printer by digital processors such that the 3D printer "prints" the nozzle body.

[0116] The present disclosure thus also provides a non-transitory machine-readable medium having data stored thereon representing a three-dimensional model of a nozzle body as described herein or of a nozzle assembly as described herein, the data being formatted to be accessed by one or more digital processors interfacing with a 3D printer, wherein the one or more digital processor(s) is/are operable to cause the 3D printer to manufacture the nozzle body or the nozzle assembly, respectively.

[0117] Exemplary embodiments of nozzle bodies and nozzle assemblies according to the present disclosure will now be described in more detail with reference to the following Figures:

Fig. 1

Exploded perspective view of a spray gun comprising a first nozzle body according to the present disclosure;

Fig. 2

Perspective view of the first nozzle body, attached to a barrel;

Fig. 3

Perspective view of a spray head assembly comprising the first nozzle body and the barrel of Figure 2;

Fig. 4

Longitudinal sectional view of the spray head assembly of Figure 3;

Fig. 5

Longitudinal sectional view of a forward portion of the first nozzle body of Figures 1-4;

Fig. 6

Perspective view of the front portion of the first nozzle body;

Fig. 7

Side view of the front portion of the first nozzle body;

Fig. 8

Cross section of the nozzle tube outlet of the first nozzle body;

Fig. 9

Perspective view of a second nozzle body according to the present disclosure;

Fig. 10

Perspective sectional view of the second nozzle body and an air cap;

Fig. 11

Perspective view of a third nozzle body according to the present disclosure;

Fig. 12

Perspective view of a fourth nozzle body according to the present disclosure; and

Fig. 13

Perspective views of a fifth nozzle body, of an atomizer base, and of an assembled atomizer.

[0118] Figure 1 is an exploded perspective view of one illustrative embodiment of a liquid spray gun comprising a nozzle body according to the present disclosure. The liquid spray gun has a variety of components including a liquid spray gun platform 10 and a spray head assembly 20 that is - preferably releasably - attached to the liquid spray gun platform 10 at a barrel interface 11. The spray head assembly 20 provides features that control movement of both the liquid to be sprayed (a liquid paint, for example) and the atomizing gas (air, for example) used to atomize the liquid as described herein. In some embodiments, the spray head assembly 20 is disposable and can be thrown away after use (although in some instances it may be reused). If disposed after use, cleaning of the spray head assembly 20 in some embodiments can be avoided and the spray gun can be conveniently changed over by, e.g., attaching a different spray head assembly 20 connected to the same or a different liquid container. Connection of the spray head assembly 20 to the barrel interface 11 of the spray gun platform 10 may be achieved by any suitable technique. For example, connection structures on the spray head assembly 20 may cooperate (e.g., mechanically interlock) with openings 11a and 11b at the barrel interface 11 to retain the spray head assembly 20 on the spray gun platform 10.

[0119] The spray gun platform 10 depicted in Figure 1 defines a variety of cavities that, taken together, form the passages that deliver pressurized gas to the spray head assembly 20. Among other features, the spray gun platform 10 includes a fitting 12 such that the gas supply passages in the spray gun platform 10 can be connected to a gas source (not shown) that supplies gas to the spray gun platform 10 at greater than atmospheric pressure. A needle passage is also provided in the spray gun platform 10 to allow a needle 14 to pass into the spray head assembly 20 attached to the barrel interface 11. Control over both gas flow and liquid flow through the liquid spray gun is, in the depicted embodiment, provided by a trigger 15 that is pivotally engaged to the spray gun platform 10 by a retaining pin 16a and clip 16b. The needle 14 extends into the spray head assembly 20. The trigger 15 is preferably biased to the inoperative position in which needle 14 closes the liquid nozzle opening in the spray head assembly 20 and also closes a gas supply valve 17. When the trigger 15 is depressed, needle 14 is retracted to a position in which its tapered front end 14a allows liquid to flow through liquid nozzle tube outlet in the spray head assembly 20. At the same time, gas supply valve 17 also opens to deliver gas to the spray head assembly 20 from the passages in the spray gun platform 10. Gas and liquid flow may be further controlled by a fan gas control assembly 18a which controls gas delivered to a fan gas passage outlet 19a and to atomizing gas outlet 19b from the gas supply manifold in the platform 10, and atomizing gas control assembly 18b which restricts how far the trigger 15 may be depressed and thereby limits the total flow of gas and paint. In particular, the control assembly 18b controls the atomizing gas/liquid stream emanating from the spray head assembly 20, and control assembly 18a controls gas flow to the air horns (if provided) of the spray head assembly 20 to adjust the spray pattern geometry.

[0120] The spray head assembly 20 includes a barrel 30, an air cap 40 attached to the barrel 30, and a first nozzle body 1 according to the present disclosure, attached to a nozzle port on the barrel 30. The nozzle body 1 may be a separate element as shown in Figure 1, or may form, in conjunction with the air cap 40, an integrated air cap/nozzle body.

[0121] Figure 2 illustrates, in a perspective view, the first nozzle body 1 of Figure 1 as it is attached to the barrel 30, which in turn is to be attached at its rear portion 38 to the liquid spray gun platform 10 at the barrel interface 11. The barrel 30 has a liquid inlet 73 through which the liquid is conducted into the barrel 30 and toward the nozzle body 1. A liquid port connector 74 at the end of the liquid inlet 73 is formed as a connector structure via which a liquid container (not shown), such as a liquid paint cup, can be connected to the barrel 30. The liquid can flow from the liquid container through the liquid inlet 73 and a liquid passage in the barrel 30 into a nozzle tube passage of the nozzle body 1. The liquid is sprayed through a nozzle tube outlet 52 in the front of the nozzle body 1 and exits the nozzle tube passage into outside air in a spray direction 300 along a spray axis 200 which passes through the center of the nozzle tube outlet 52. The nozzle tube outlet 52 has a central portion and protrusions as explained below. For clarity, recesses in the outer surface 75 of the first nozzle body 1 are not shown. The shape of the nozzle body 1 is rotationally symmetric about the spray axis 200.

[0122] The barrel 30 and the nozzle body 1 are shown before an air cap 40 is arranged over the front portion 36 of the barrel 30, so that an atomizing gas passage 33 in the barrel 30 is visible through which, in use, pressurized atomizing gas flows through the barrel 30 toward the nozzle tube outlet 52.

[0123] Once a suitable air cap 40 is mounted over the front portion 36 and the nozzle body 1, an inner surface of the air cap 40 and the outer surface 75 of the nozzle body 1 cooperate to form an atomizing gas passage for conducting pressurized atomizing gas towards an atomizing gas outlet 54 (see Figure 3) arranged circumferentially around the nozzle tube outlet 52.

[0124] Figure 3 illustrates, in a perspective view, the barrel 30 and the first nozzle body 1 of Figures 1 and 2 with an air cap 40 mounted over them, together forming a spray head assembly 20. The outer surface 75 of the nozzle body 1 at the nozzle tube outlet 52 forms a first portion of a delimiting surface of the atomizing gas passage 33, shown in Figure 2, for conducting pressurized atomizing gas towards a generally annular atomizing gas outlet 54 arranged circumferentially around the nozzle tube outlet 52, such that the atomizing gas exits the atomizing gas passage 33 into outside air at the atomizing gas outlet 54 and atomizes liquid after the liquid has exited the nozzle tube outlet 52. The protrusions in the nozzle tube outlet 52 and the recesses in the outer surface of the nozzle tube wall are not shown for clarity.

[0125] The air cap 40 comprises two air horns 43a, 43b, arranged opposite to each other. So-called shaping gas exits the air horns 43a, 43b through two shaping gas apertures 46 on each of the air horns 43a, 43b. The shaping gas apertures 46 on the air horns 43a, 43b are located on opposite sides of the spray axis 200 such that shaping gas flowing through the barrel 30 under greater than atmospheric pressure is directed against opposite sides of a jet of atomized liquid exiting the nozzle tube outlet 52 into outside air in the spray direction 300. The forces exerted by the shaping gas can be used to change the shape of the jet of atomized liquid to form a desired spray pattern (e.g., circular, elliptical, etc.).

[0126] Figure 4 is a longitudinal sectional view of the spray head assembly 20 of Figure 3, which comprises the first nozzle body 1 according to the present disclosure. The nozzle body 1 comprises a nozzle tube 66 having a nozzle tube wall 71 which, in this embodiment, has the shape of a funnel narrowing towards the nozzle tube outlet 52. The liquid to be sprayed flows through the liquid inlet 73, through the barrel 30 and passes, from a nozzle tube inlet 57, through an elongated nozzle tube passage 58 to the nozzle tube outlet 52 through which, in use, the liquid exits the nozzle tube passage 58 into outside air in the spray direction 300 along the spray axis 200. The spray axis 200 defines axial directions 220 parallel to the spray axis 200, and radial directions 210 orthogonal to the axial directions 220. The spray direction 300 is an axial direction 220.

[0127] The rear portion 38 of barrel 30 can be attached to the liquid spray gun platform 10 at the barrel interface 11, as shown in Figure 1, so that the spray gun platform 10 and the spray head assembly 20 form a complete liquid spray gun.

[0128] Once connected with the nozzle body 1, the air cap 40 is rotationally symmetric about the spray axis 200. It has a front wall 60 which forms a circular nozzle aperture delimited by a nozzle aperture edge 65. In this embodiment the forward end of the nozzle tube 66 is arranged in the nozzle aperture delimited by the nozzle aperture edge 65 of the front wall 60 such that the nozzle tube outlet 52 is almost flush with the front surface 62 of the front wall 60 of the air cap 40 which faces generally in the spray direction 300.

[0129] The atomizing gas outlet 54 is formed between the nozzle aperture edge 65 of the front wall 60 of the air cap 40 and the radially outer surface 75 of the nozzle tube wall 71. The atomizing gas outlet 54 therefore has a generally annular shape and is arranged circumferentially around the nozzle tube outlet 52. The small-scale shape of the atomizing gas outlet 54 and of the nozzle tube outlet 52 is not shown in Figures 1-4, but will be explained in the context of Figure 6.

[0130] Figure 5 is a longitudinal sectional view of a forward portion of the first nozzle body 1 of Figures 1-4. The nozzle body 1 comprises the tubular nozzle tube 66, which in turn comprises the elongated nozzle tube passage 58, extending lengthwise between a nozzle tube inlet 57 (not visible in Figure 5) through which, in use, liquid enters the nozzle tube 66, and the nozzle tube outlet 52, through which, in use, the liquid exits the nozzle tube passage 58 into outside air 93 in the spray direction 300. The nozzle tube outlet 52 defines the precise axial position (indicated by a plane 330 of the nozzle tube outlet 52) at which the liquid exits the nozzle tube passage 58 into outside air 93. In the embodiment of Figure 5, the nozzle tube 66 is rotationally symmetric about a tube symmetry axis 230, so that the length direction of the nozzle tube passage 58 and the spray direction 300 are both parallel to the tube symmetry axis 230, and the spray axis 200 and the tube symmetry axis 230 are identical.

[0131] The nozzle tube 66 also comprises the nozzle tube wall 71 which comprises the radially outer surface 75 and the opposed radially inner surface 76. The inner surface 76 delimits the nozzle tube passage 58 and is in contact with the liquid when the nozzle body 1 and the spray gun to which it is mounted are in use.

[0132] The spray direction 300 through a centroid 310 of the cross section of the nozzle tube outlet 52 defines the spray axis 200. The cross section, taken in the nozzle tube outlet plane 330, of the nozzle tube outlet 52 has a central portion 80 and a plurality of protrusions 82, as illustrated in Figure 6. The nozzle tube outlet 52 is arranged around, and comprises, the spray axis 200. It comprises the spray axis 200, considering that at the centroid 310 liquid exits the nozzle tube outlet 52. The liquid exits the nozzle tube outlet 52 in a well-defined direction (the spray direction 300), as turbulence is introduced only further downstream. Turbulence introduces irregular velocities into the liquid after the liquid has exited the nozzle tube outlet 52 and only at positions somewhat downstream from the nozzle tube outlet plane 330.

[0133] The outer surface 75 of the nozzle tube wall 71 is operable to form, in conjunction with a surface of a suitable air cap 40 (not shown) when the air cap 40 is connected directly or indirectly with the nozzle body 1, an atomizing gas outlet 54 (see Figure 10) arranged circumferentially around the nozzle tube outlet 52, such that pressurized atomizing gas 110 exits into outside air 93 through the atomizing gas outlet 54 and atomizes the liquid after the liquid has exited the nozzle tube outlet 52. The atomizing gas 110 flows along, and is in contact with, the outer surface 75 of the nozzle tube wall 71.

[0134] In the embodiment of Figure 5 a terminal portion 77 of the outer surface 75 of the nozzle tube wall 71 at the nozzle tube outlet 52 (i.e. in the nozzle tube outlet plane 330) is oriented radially outwardly to direct at least a portion of the pressurized atomizing gas 110 exiting the atomizing gas outlet 54 angularly away from the spray axis 200. In the embodiment of Figure 5 the terminal portion 77 of the outer surface 75 of the nozzle tube wall 71 at the nozzle tube outlet 52 appears "ramped" in the longitudinal sectional view, i.e. inclined away from the spray axis 200 at an angle alpha (α). In alternative embodiments, not shown here, the terminal portion 77 of the outer surface 75 does not form a ramp and does not direct atomizing gas 110 angularly away from the spray axis 200 but directs the atomizing gas 110 parallel to the spray axis 200 or even towards the spray axis 200.

[0135] Figure 6 is a detailed perspective view of the nozzle tube outlet 52 of the first nozzle body 1 of Figures 1-5. Different from Figures 1-5, Figure 6 shows the small-scale structure of the nozzle tube outlet 52 and of the nozzle tube wall 71. In the plane 330 of the nozzle tube outlet 52, orthogonal to the spray axis 200, the nozzle tube outlet 52 has a central portion 80 and eight protrusions 82 protruding radially outward from the central portion 80. Each protrusion 82 is located at a respective angular protrusion position as measured circumferentially around the spray axis 200. The protrusions 82 are angularly evenly distributed about the spray axis 200, the difference in the angular position of two adjacent protrusions 82 being 45 degrees. The spray axis 200 passes through the centroid 310 of the cross section of the nozzle tube outlet 52. The centroid 310 is located in the nozzle tube outlet plane 330 (not shown in Figure 6).

[0136] The outer surface 75 of the nozzle tube wall 71 forms eight recesses 90 through which atomizing gas 110 can exit the nozzle assembly 20 when an air cap 40 is connected with the nozzle body 1 in a fixed spatial relation, as shown, for example, in Figure 4. Each recess 90 recedes radially inward towards the spray axis 200. In use, atomizing gas 110 exits the nozzle assembly 20 into outside air 93 through the recesses 90. Each recess 90 is located at an angular recess position as measured in the nozzle tube outlet plane 330 circumferentially around the spray axis 200. Each recess 90 is arranged such that its angular recess position is located between the respective angular protrusion positions of two adjacent protrusions 82 of the eight protrusions 82 of the nozzle tube outlet 52.

[0137] The recesses 92 are angularly evenly distributed about the spray axis 200, the difference in the angular position of two adjacent recesses 92 being 45 degrees.

[0138] Figure 7 is a side view of the front portion of the first nozzle body 1. In an outlet cross section taken in nozzle tube outlet plane 330 the outer surface 75 of the nozzle tube wall 71 forms the eight recesses 90, of which only three are visible in

[0139] Figure 7. These recesses 90 are located at the forward ends of respective grooves 92 which extend forward in axial direction 220 from a rearward position up to the recesses 90 in the nozzle tube outlet plane 330. When an air cap 40 is connected and the spray gun is used, pressurized atomizing gas 110 flows forward through the grooves 92 to the recesses 90 where it exits into outside air 93 and atomizes the liquid after the liquid has exited the nozzle tube outlet 52.

[0140] Figure 8 is a cross section taken in the nozzle tube outlet plane 330 orthogonal to the spray axis 200, also referred to as the "outlet cross section". The nozzle tube outlet plane 330 is the plane of the paper. In the outlet cross section, the nozzle tube outlet 52 has a central portion 80 and eight protrusions 82 protruding radially outward from the central portion 80. The central portion 80 is the portion inside a circle 81 around the spray axis 200, drawn only partially in a dashed style to enhance clarity.

[0141] Each protrusion 82 is located at a respective angular protrusion position 84 as measured in the outlet cross section circumferentially around the spray axis 200. The 12 o'clock position is arbitrarily chosen as a reference for all angular positions determined in the context of Figure 8. The protrusion 82a at the 6 o'clock position in the central dial of Figure 8, for example, is located at the angular protrusion position 84a, which is at an angle of 180° relative to the 12 o'clock position. The protrusion 82b at the 7h30 o'clock position in Figure 8, which is adjacent to the protrusion 82a, is located at the angular protrusion position 84b, which is at an angle of 225° relative to the 12 o'clock position. The protrusion 82c at the 9 o'clock position, which is adjacent to the protrusion 82b, is located at the angular protrusion position 84c, which is at an angle of 270° relative to the 12 o'clock position. The dial in the center is not part of the cross section but has been added to explain angular positions. Angular protrusion positions are determined using a symmetry line of a protrusion and determining its intersection with the central dial indicating the angular position in a clock-like manner. Where a protrusion is not sufficiently symmetric to define a radial or near-radial symmetry line, the angular protrusion position 84 may be determined by drawing a straight line from the radially outermost point of the protrusion 82 to the spray axis 200 and determining the angular position of its intersection with the circular dial.

[0142] In the outlet cross section of Figure 8, the outer surface 75 of the nozzle tube wall 71 forms eight recesses 90 each receding radially inward towards the spray axis 200. Each recess 90 is located at a respective angular recess position 94 as measured in the outlet cross section circumferentially around the spray axis 200. The angular recess position 94 of each recess 90 is located between the respective angular protrusion positions 84 of two adjacent protrusions 82 of the eight protrusions. For example, the angular recess position 94a of the recess 90a is located in the middle between the respective angular protrusion positions 84a, 84b of the two adjacent protrusions 82a, 82b, so that its angular recess position 94a is 202.5° relative to the 12 o'clock position.

[0143] Angular recess positions 94 are determined using the same geometric system as used for determination of the angular protrusion positions 84. The recess 90a to the left of the 6 o'clock position in Figure 8, for example, is located at the angular recess position 94a (202.5°), which is an angular position in the middle between the respective angular protrusion positions 84a (180°) and 84b (225°) of the two adjacent protrusions 82a and 82b. Similarly, the recess 90b just below the 9 o'clock position is located at the angular recess position 94b (247.5°), which is in the middle between the angular protrusion positions 84b (225°) and 84c (270°) of the two protrusions 82b and 82c which are adjacent to each other.

[0144] The angular position of a recess may be determined in different ways, depending on its geometry. Where, in the nozzle tube outlet plane 330, a recess 90 is generally symmetric with respect to a line through the spray axis 200, the angular position of that line on the (virtual) central dial may be used to determine the angular recess position 94. Where a recess 90 is not sufficiently symmetric to define a radial or near-radial symmetry line its angular recess position 94 may be determined by drawing a straight line from the radially innermost point of the recess 90 to the spray axis 200 and determining the angular position of its intersection with the central virtual dial.

[0145] Similarly, the angular position of a protrusion 82 may be determined in different ways, depending on its geometry. Where, in the nozzle tube outlet plane 330, a protrusion 82 is generally symmetric with respect to a line through the spray axis 200, the angular position of that line may be used to determine the angular protrusion position 84. Where a protrusion 82 is not sufficiently symmetric to define a radial or near-radial symmetry line, where the protrusion 82 is shaped such that a point of its contour in the nozzle tube outlet plane 330 is further away from the spray axis 200 than any other point of its contour, this point may be used to determine the angular protrusion position 84 by drawing a radial line through it and determining the angular position of that line on the dial.

[0146] Although the protrusions 82 and the recesses 90 are arranged symmetrically and distributed evenly about the circumference in the embodiment of Figure 8, this symmetry and even distribution is not a requirement, and in certain alternative embodiments, not shown here, arrangement, shape and distribution of protrusions 82 and recesses 90 may not be even and/or symmetric. The number of protrusions 82 and recesses 90 is not particularly limited. Nozzle bodies 1 having three or four protrusions 82 and the same number of recesses 90 are expected to provide the benefit of improved atomization, just as nozzle bodies 1 having five, six or more protrusions 82 and the same number of recesses 90, such as eight, ten or twelve protrusions 82 and recesses 90.

[0147] Increasing the size of the interaction zone between liquid and atomizing gas by "folding" the interaction zone into recesses 90 and protrusions 82 helps improve atomization of the liquid. A larger interaction zone spreads out both the liquid flow and the atomizing gas flow over a larger surface area as the gas and the liquid exit the spray gun.

[0148] Figure 9 shows a second nozzle body 2 according to the present disclosure, similar to the first nozzle body 1 of Figures 6-8, in a perspective view. The nozzle tube outlet 52 has a central portion and four protrusions 82, arranged to form the shape of a "plus" sign in the nozzle tube outlet plane 330. The protrusions 82 protrude radially outward from the central portion, and each protrusion 82 is located at a respective angular protrusion position 84 as measured in the nozzle tube outlet plane 330. Due to the "plus" sign shape; the angular protrusion positions 84 of the nozzle body 2 as oriented in Figure 9 are at the 12 o'clock (0°), 3 o'clock (90°), 6 o'clock (180°), and 9 o'clock (270°) positions respectively, relative to the arbitrarily chosen 12 o'clock (0°) reference position.

[0149] The outer surface 75 of the nozzle tube wall 71 forms four grooves 92 and, at the forward end of the respective grooves 92, four recesses 90 receding radially inward towards the spray axis 200, through which recesses 90, in use, atomizing gas 110 exits into outside air. Each recess 90 is located at an angular recess position 94 as measured in the nozzle tube outlet plane 330 circumferentially around the spray axis 200. Each angular recess position 94 is located between the respective angular protrusion positions 84 of two protrusions 82 adjacent to each other. In the embodiment of Figure 9 each recess 90 is "located between" (according to how this term is used herein) two protrusions 82 adjacent to each other, viewed in the nozzle tube outlet plane 330. This is because the recesses 90 extend radially inward closer to the spray axis 200 than the protrusions 82 extend radially outward away from the spray axis 200, so that a straight line connecting the respective radially outermost points of two adjacent protrusions 82 intersects the recess 90 between them. The angular recess positions are at 45°, 135°, 225°, and 315°, respectively, relative to the 12 o'clock (0°) reference position.

[0150] Figure 10 shows in a perspective partially-sectional view the second nozzle body 2 of Figure 9 and an air cap 40. The nozzle tube passage 58 extends lengthwise between a nozzle tube inlet 57 through which, in use, liquid enters the nozzle tube 66. The nozzle tube wall 71 has a radially outer surface 75 being, in use, in contact with atomizing gas for atomizing the liquid after the liquid has exited the nozzle tube outlet 52, and an opposed radially inner surface 76 delimiting the nozzle tube passage 58 and being, in use, in contact with the liquid.

[0151] The air cap 40 is connected with the nozzle body 2, the connection is not shown. The outer surface 75 of the nozzle tube wall 71 forms, in conjunction with a delimiting surface 64 of the air cap 40, an atomizing gas outlet 54 arranged circumferentially concentrically around the nozzle tube outlet 52, such that the pressurized atomizing gas 110 exits into outside air 93 through the atomizing gas outlet 54 and atomizes the liquid after the liquid has exited the nozzle tube outlet 52.

[0152] The delimiting surface 64 of the air cap 40 forms a circular edge 65 which may also be referred to herein as nozzle aperture edge 65. The nozzle aperture edge 65 forms an aperture for the nozzle body 2 in the front wall 60 of the air cap 40 in which aperture the front terminal end of the nozzle tube wall 71 is arranged. The nozzle aperture edge 65 may be a circular edge, as shown in Figure 10, or an elliptical edge, for example.

[0153] Figure 11 shows, in perspective view, a third nozzle body 3 according to the present disclosure having six protrusions 82 and six recesses 90 in the nozzle tube outlet plane 330. The recesses 90 are located at the forward end of corresponding grooves 92. The grooves 92 have a generally triangular profile which gets deeper and wider with decreasing distance going forward to the nozzle tube outlet plane 330.

[0154] Figure 12 shows, in a further perspective view, a fourth nozzle body 4 according to the present disclosure having eight protrusions 82 and eight recesses 90 in the nozzle tube outlet plane 330. The fourth nozzle body 4 is identical with the first nozzle body 1 of Figures 6-8 except that the protrusions 82 are narrower and longer so that the central portion 80 has a smaller radial extension. Such a geometry results generally in an even larger interaction zone between the liquid and the atomization gas and hence in a potentially better atomization of the liquid.

[0155] Figure 13 shows a series of three perspective views visualizing a process for assembling an atomizer 110 of a spray gun. A fifth nozzle body 5 in the leftmost frame may be a nozzle body like the first, second, third, or fourth nozzle body 1, 2, 3, 4 according to the present disclosure, having protrusions 82 and recesses 90 as described herein, or, as in Figure 13, a traditional nozzle body not featuring protrusions or recesses. The nozzle tube wall 71 of the fifth nozzle body 5 has no protrusions or recesses in the cross section of its nozzle tube outlet 52. It is manufactured from a transparent polymeric material at a very high degree of mechanical accuracy in a high-precision micro-molding process. Attachment elements 108 in the form of two opposed circumferential tongues 108 (of which only one is visible in Figure 13), arranged around the nozzle tube inlet, facilitate rotational attachment of the nozzle body 5 to an atomizer base 100 in a fluid-tight manner.

[0156] An atomizer base 100, shown in the frame in the middle of Figure 13, is manufactured from a polymeric material at a low degree of mechanical accuracy in a high-speed molding process. The atomizer base 100 has twelve atomizing gas channels 102, arranged in a circle, for conducting pressurized atomizing gas to the atomizing gas outlet 54, and a liquid aperture 104 for conducting liquid into a nozzle body 5. An attachment mechanism 106 comprising a plurality of recesses extending circumferentially around the liquid aperture 104 of the atomizer base 100 can be engaged with the tongues 108 of the nozzle body 5 to facilitate rotational attachment of the nozzle body 5 to the atomizer base 100 in a fluid-tight manner, such that the nozzle body 5 and the atomizer base 100, after assembly, form a complete atomizer 110.

[0157] The frame on the right of Figure 13 shows the atomizer 110 after assembly, with the nozzle body 5 secured to the atomizer base 100 via the tongues 108 on the nozzle body 5 and the attachment mechanism 106 on the atomizer base 100. This atomizer 110, assembled from the two elements 5, 100, is functionally equivalent to a single-piece atomizer and can be joined to a barrel 30 to form a nozzle assembly similar to the nozzle assembly 20 of Figure 4.

Claims

1. Nozzle body (1, 2, 3, 4) for a liquid spray gun for spraying a liquid, the nozzle body comprising a tubular nozzle tube (66), comprising

a) an elongated nozzle tube passage (58), extending lengthwise between a nozzle tube inlet (57) through which, in use, liquid enters the nozzle tube (66), and a nozzle tube outlet (52), through which, in use, the liquid exits the nozzle tube passage (58) into outside air (93) in a spray direction (300),

b) a nozzle tube wall (71) having

- a radially outer surface (75) being, in use, in contact with atomizing gas for atomizing the liquid after the liquid has exited the nozzle tube outlet (52), and

- an opposed radially inner surface (76) delimiting the nozzle tube passage (58) and being, in use, in contact with the liquid,

wherein the spray direction (300) through a centroid (310) of the cross section of the nozzle tube outlet (52) defines a spray axis (200), wherein the spray axis defines axial directions (220) and radial directions (210) orthogonal to the axial directions,

wherein the nozzle tube outlet (52) is arranged around the spray axis (200),
characterized in that, in an outlet cross section taken in a plane (330) through the nozzle tube outlet (52) orthogonal to the spray axis (200), the nozzle tube outlet (52) has a central portion (80) and two or more protrusions (82) protruding radially outward from the central portion (80), wherein each protrusion (82) is located at a respective angular protrusion position (84) as measured in the outlet cross section circumferentially around the spray axis (200), and

in that, in the outlet cross section, the outer surface (75) of the nozzle tube wall (71) forms a first recess (90) receding radially inward towards the spray axis (200), through which recess (90), in use, atomizing gas (110) exits into outside air (93), wherein the first recess (90) is located at an angular recess position (94) as measured in the outlet cross section circumferentially around the spray axis (200),

wherein, in the outlet cross section, the angular recess position (94a) is located angularly between the respective angular protrusion positions (84a, 84b) of two protrusions (82a, 82b), adjacent to each other, of the two or more protrusions (82).

2. Nozzle body (1, 2, 3, 4) according to claim 1, wherein the nozzle tube outlet (52) has three protrusions (82) or four protrusions (82) or six protrusions (82) or eight protrusions (82).

3. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein a portion of the first recess (90) is located between respective radially outermost portions of the two protrusions (82a, 82b) adjacent to each other.

4. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein, in the outlet cross section, the outer surface (75) of the nozzle tube wall (71) forms one or more further recesses (90) each receding radially inward towards the spray axis (200), through which further recesses (90), in use, atomizing gas (110) exits into outside air (93),
wherein the total number of recesses (first recess and further recesses) (90) is equal to the total number of the two or more protrusions (82).

5. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein, in the outlet cross section, the outer surface (75) of the nozzle tube wall (71) forms one or more further recesses (90) each receding radially inward towards the spray axis (200), through which further recesses (90), in use, atomizing gas (110) exits into outside air (93), wherein each further recess (90) is located at a respective further angular recess position (94) as measured in the outlet cross section circumferentially around the spray axis (200),
wherein, in the outlet cross section, each further angular recess position (94a) is located angularly between the respective angular protrusion positions (84a, 84b) of two protrusions (82a, 82b), adjacent to each other, of the two or more protrusions (82).

6. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein, in the outlet cross section, the outer surface (75) of the nozzle tube wall (71) forms one or more further recesses (90) each receding radially inward towards the spray axis (200), through which further recesses (90), in use, atomizing gas (110) exits into outside air (93),
and wherein between the angular protrusion positions (84) of any two protrusions (82), adjacent to each other, of the two or more protrusions (82), an angular recess position (94) of at least one recess (90) of the first recess and the further recesses is angularly located.

7. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein the first recess (90a) comprises a portion which is spaced, as measured in the outlet cross section, less than one millimeter from a portion of any of the adjacent protrusions (82a, 82b) between which the first recess is angularly located.

8. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein a distance, as measured in the outlet cross section, between the radially innermost portion of the first recess (90a) and any portion of the adjacent protrusions (82a, 82b) between which the first recess (90a) is angularly located, is less than two millimeters.

9. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein the nozzle tube outlet (52) is delimited, in the outlet cross section, by a perimeter line having a path length P, wherein the nozzle tube outlet (52) has, in the outlet cross section, a geometric area A, and wherein a bulge ratio B= P²/A is larger than 13.0, and optionally wherein B= P²/A is larger than 40.0, wherein P² and A are measured in the same units.

10. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein the outer surface (75) of the nozzle tube wall (71) forms an elongated groove (92) for conducting pressurized atomizing gas towards the first recess (90), wherein the groove (92) begins in the first recess (90) and extends lengthwise rearward in axial directions (220).

11. Nozzle body (1, 2, 3, 4) according to claim 10, wherein the groove (92) is oriented or shaped to direct at least a portion of the pressurized atomizing gas (110), exiting into outside air (93) through the first recess (90), angularly away from the spray axis (200).

12. Nozzle body (1, 2, 3, 4) according to any one of the preceding claims, wherein the outer surface (75) of the nozzle tube wall (71) is arranged to form, in conjunction with a surface (64) of an air cap (40, 41) when the air cap (40, 41) is connected directly or indirectly with the nozzle body (1), an atomizing gas outlet (54) arranged circumferentially around the nozzle tube outlet (52), such that the pressurized atomizing gas (110) exits into outside air (93) through the atomizing gas outlet (54) and atomizes the liquid after the liquid has exited the nozzle tube outlet (52), wherein the atomizing gas outlet (54) comprises the first recess (90) and, if present, the further recesses (90).

13. Nozzle assembly (20) comprising a nozzle body (1, 2, 3, 4) according to any one of the preceding claims and an air cap (40), connected with the nozzle body in a fixed spatial relation,

wherein the air cap (40) comprises a front wall (60) facing generally in the spray direction (300) and comprising a nozzle aperture delimited by a nozzle aperture edge (65),

and wherein the nozzle tube (66) is arranged in, or protrudes outwardly through, the nozzle aperture, such that the atomizing gas outlet (54) is formed between the nozzle aperture edge (65) and the nozzle tube wall (71).

14. Nozzle assembly (20) according to claim 13, further comprising a barrel (30) having a liquid port connector (74) for directly or indirectly connecting a liquid reservoir to the barrel (30), wherein the air cap (40) is connected with the barrel (30), and the nozzle body (1, 2, 3, 4) is connected with the barrel (30), such that the air cap (40) is connected with the nozzle body (1, 2, 3, 4) in a fixed spatial relation.

15. Liquid spray gun for spraying a liquid, comprising a nozzle body (1, 2, 3, 4) according to any one of claims 1-12, or a nozzle assembly (20) according to any one of claims 13-14.

Drawing