COMPLIANT SYSTEM WITH FIN

Abstract

 The invention relates to a system (1) for conveying a web (2). The system comprises a center element (11) extending along a longitudinal axis (AA'); and at least one fin (12) or a set of fins, arranged around the longitudinal axis.

Description

FIELD OF INVENTION

[0001] The present invention relates to a roller system for web handling. In particular, the present invention relates to a roller system designed to guide a web. The present invention also relates to a roller system to convey a web. The invention finally relates to a method to convey a web using such roller system.

BACKGROUND OF INVENTION

[0002] In various fields, there is a need to guide a web along a set of rollers. In particular, in the field of web converting, lateral shifting or web off-tracking may contribute to flaws at different stages. Web position correction may be vital to ensure the process of web converting, especially when high speeds and/or thin films are used.

[0003] To resolve this problem, US2989265 describes a web handling system comprising two tubes with a pivot driven by a bracket arm. One limitation of such solution is its encumbrance and the use of two guide members.

[0004] US3326435 B1 describes two cylinders free to rotate about a pivotal axis to correct the misalignment of the flat web. However, a first limitation of this solution is that it requires at least two cylinders and means to modify the axis of rotation of the two cylinders (piston, hydraulic cylinders, energy sources, slide connections, ...), increasing the volume and the complexity of the whole system.

[0005] US8554354 describes a method of adaptive guiding of a web on a roller. One limitation of this method is the use of electronics and computerized systems.

[0006] There is therefore a need for a new system allowing self-centering of a web in a high-speed converting or manufacturing process overcoming the cited limitation.

SUMMARY

[0007] The invention relates to system for conveying a web. The system comprises a center element extending along a longitudinal axis; and at least one fin or a set of fins, arranged around the longitudinal axis, preferably on the surface of the center element. The fin or each fin of the set of fins comprises a first lateral portion separated from a second lateral portion by a plane orthogonal to the longitudinal axis and comprises an outer surface, for supporting the web, along at least the first and second lateral portions.

[0008] In one embodiment, the fin or each fin of the set of fins is movable between three positions: a first position, a second position and a third position.

[0009] In one embodiment, in the first position, the profile of the outer surface is symmetric with respect to the plane.

[0010] In one embodiment, in the second position, a first distance between the outer surface of the first lateral portion of the fin and the longitudinal axis is less than a second distance between the outer surface of the second lateral portion and the longitudinal axis.

[0011] In one embodiment, in the third position, the second distance between the outer surface of the second lateral portion of the fin and the longitudinal axis is less than the first distance between the outer surface of the first lateral portion and the longitudinal axis.

[0012] The second or third position is obtained by tilting the fin according to the longitudinal axis along its degree of freedom in rotation.

[0013] The fin or each fin of the set of fins is arranged to move from the first position to the second position or to the third position when the distribution of the pressure exerted by the web on the outer surface is respectively higher on the first portion than on the second portion or higher on the second portion than on the first portion.

[0014] According to another aspect, the invention relates to a roller system for conveying a web comprising: a center roller for rotation along (or about) a longitudinal axis of the center roller; and a set of fins, arranged around the longitudinal axis.

[0015] Each fin of the set of fins comprises an outer surface for supporting the web, the outer surface delimiting a first lateral portion of the fin and a second lateral portion of the fin separated from the first lateral portion by a plane orthogonal to the longitudinal axis.

[0016] In one embodiment, each fin of the set of fins is movable between three positions:

• a first position, wherein the profile of the outer surface is symmetric (preferably in a radial plane) with respect to the plane orthogonal to the longitudinal axis; in said first position, in a radial plane,
• a second position wherein a first distance between the first lateral portion and the longitudinal axis is less than a second distance between the second lateral portion and the longitudinal axis;
• a third position wherein the second distance is less than the first distance.

[0017] In one embodiment, the fin is arranged to move from the first position to the second position or to the third position when the distribution of the pressure exerted by the web on the outer surface is respectively higher on the first portion than on the second portion or higher on the second portion than on the first portion. In other words, the fin is arranged to move from the first position to the second position or the third position, under the effect of a total force exerted by the web is higher on respectively the first lateral portion or the second lateral portion of the surface.

[0018] In one embodiment, each fin is mechanically connected to the center roller by a mechanical link and each fin is configured to tilted around the mechanical link to move from the first position to the second or the third position.

[0019] In one embodiment, the mechanical link comprises a pivot connection, preferably an axial pivot connection between the fin and the center roller.

[0020] In one embodiment, the mechanical link between a fin and the center roller comprises a junction comprising at least one tapered portion.

[0021] In one embodiment, the junction between the center roller and the fin comprises: a thin central portion; a first tapered portion having a thickness decreasing from the fin to the thin central portion and a second tapered portion having a thickness decreasing from the center roller to the thin central portion.

[0022] In one embodiment, in the second position or in the third position, a second axis perpendicular to the outer surface and passing through the mechanical connection is tilted with respect to the longitudinal axis by an angle strictly inferior to 90°.

[0023] In one embodiment, each fin is removably connected to the center roller.

[0024] In one embodiment, at least one fin comprises a perforated outer surface.

[0025] In one embodiment, each lateral portion of the fins being movable to reduce its distance with the longitudinal axis when a pressure is applied on its outer surface.

[0026] In one embodiment, the center roller and the plurality of fins are one unique monobloc element.

[0027] In one embodiment, the profile of the outer surface of the fin comprises a concave profile.

[0028] In one embodiment, the profile of the outer surface of the fin comprises a convex profile.

[0029] According to another aspect, the invention also relates to a system for conveying a web comprising a support element having a first face and at least one fin, arranged on the first face. Each fin comprises a first lateral portion separated from a second lateral portion by a plane perpendicular to the first face, and an outer surface, for supporting the web, along at least the first and second lateral portions.

[0030] In one embodiment, the support element is mechanically fixed to the frame with 0 degree in freedom in rotation and preferably 0 degree of freedom in translation. In one embodiment, the support element or the system is removable from the frame.

[0031] In one embodiment, the at least one fin is movable between at least three positions:

• a first position, wherein the profile of the outer surface is symmetric with respect to the plane;
• a second position wherein a first distance between the first lateral portion and the first face is less than a second distance between the second lateral portion and the first face;
• a third position wherein the second distance is less than the first distance.

[0032] The second or third position is obtained by tilting the fin according to the longitudinal axis along its degree of freedom in rotation.

[0033] The fin is arranged to move from the first position to the second position or to the third position when the distribution of the pressure exerted by the web on the outer surface is respectively higher on the first portion than on the second portion or higher on the second portion than on the first portion. In other words, the fin is arranged to move from the first position to the second position or the third position, under the effect of a total force exerted by the web is higher on respectively the first lateral portion or the second lateral portion of the surface.

[0034] According to another aspect, the invention also relates to a conveyor system comprising a plurality of rollers to transport a web along a predefined path and at least one roller system according to the invention and/or a system according to the invention.

[0035] According to another aspect, the invention relates to a method for conveying a web, comprising providing conveyor system according to the invention and a web, wherein the at least one roller of the conveyor system is rotated to move the web along its predefined path. The method further comprises using the fin to move the web along its predefined path and to automatically correct web misalignment.

BRIEF DESCRIPTION OF FIGURES

[0036] 

Fig. 1 is a schematic sectional view of a portion of a roller system according to one embodiment of the present invention.

Fig. 2A is a schematic sectional view of the roller system illustrated on figure 1 when the fin is in a first engaged position.

Fig. 2B is a schematic sectional view of the roller system illustrated on figure 1 when the fin is in a first engaged position.

Fig. 3 is a schematic sectional view of a roller system illustrated in figure 1 in respect with a plane perpendicular to the longitudinal axis of said roller system.

Fig. 4 is a schematic perspective view of the roller system according to one embodiment of the present invention.

Fig. 5 is a sectional view of the roller system illustrated on figure 4.

Fig. 6 is a sectional view of the connection between the center roller and a fin according to one embodiment of the present invention.

Fig. 7 is a schematic view of a conveyor system comprising a roller system according to one embodiment of the invention and conveying an endless ribbon.

Fig. 8 is a graph showing the edge position of the web on a roller system according to one embodiment of the invention over the time.

Fig. 9 is a schematic sectional view of a portion of a roller system according to one embodiment of the present invention wherein the section of the outer surface of the fin is concave.

Fig. 10 is a schematic sectional view of a portion of a system according to one embodiment of the present invention.

DETAILED DESCRIPTION

[0037] In a converting process, the flat web tends to align itself perpendicular to the next roller's axis of rotation. When at least one of the rollers' axes within a conveyor system is not perfectly aligned to the others, the web tends to move, and its width creates an angle with the machine direction, ("Web-roller misalignment angle" or "distortion angle"). The edges of the web are misaligned and a gradient in tension may arise across the web. This may result in winding or unwinding-induced flaws, vibrations, and premature wear. The invention takes advantage of variations in tension across the web: the edge of higher tension will trigger the retractation of the roller system on one side. As the web tension becomes balanced again, and the edges of the web retrieve an accurate alignment with the machine direction, and then, the roller system may recover its initial shape. The web is straightened again to feed the next roller with a balanced tension and web-roller misalignment is cancelled.

[0038] The invention relates to a roller system to convey and guide a flat web. The concept of the invention relates to a roller initially shaped as a cylinder with adaptative geometry. When the pressure applied to the roller is a little greater on one side, for example when a circulating web is about to be off-centered or tends to drift away, the geometry of the roller is modified. Web tension across the width is then regulated as to keep the web centered and edges aligned to the machine direction. The geometry is therefore compliant with the web tension disequilibrium. The switch in geometry is triggered by the tilt or the deformation of at least one fin arranged on a center roller. Industrially, the roller system could be installed anywhere a fine alignment or re-alignment of web is required, including in dryers.

[0039] The invention advantageously provides web tension control and a compact solution for guiding the web while avoiding the creation of a distortion angle between the web and the machine direction of said web. One advantage is to convey and align the web without the need of external energy. Another advantage is the possibility to use such roller system in explosive atmospheres environment. Another advantage lies in the phenomenon of double correction of the tension depending on the wrap angle over the roller system. The tilt of the fin is both dependent on the web tension induced by the up-stream roller as well as web tension induced by the down-stream roller. The roller system genuinely provides self-correction of tension imbalance between up- and downstream rollers.

[0040] The invention also provides a precise and reliable edge alignment during winding a web onto a spool, reel, beam, jumbo roll, rolls, core, mandrel as well as an unwinding guidance. In other words, the roller system according to the invention advantageously automatically laterally centers a web transported by said roller when the web is laterally displaced or misaligned.

[0041] Ultimately, the invention provides a solution to reduce downtime and waste in a converting process.

Definitions

[0042] In the present description, the following terms has to be understood according to their given definitions.

[0043] "Lateral portion" of a fin should be understood as a portion of the fin including one longitudinal end of said fin.

[0044] "Roller system" has to be understood as a roller system comprising at least one fin, preferably a plurality of fins placed on or around a center roller and intended to guide and/or support a flat web.

[0045] "Web" or "flat web" refers to as any film, foil, sheet or like wherein the length and/or the width dimension are at least 10 times or 100 times superior to the thickness dimension. The web may comprise any structure that is long, thin and flexible (paper, film, foil, nonwovens, textiles...).

[0046] "Machine direction" refers to the direction of transport of the web in contact with the outer surface of a fin.

[0047] The flat web could be a length-finite web or a closed loop such as a band or any kind of endless films, ribbons or like. The web could be a multilayer stack.

[0048] The term "sensibly" followed by an angular value should be understood at the value +/- 0,5° or +/- 1°. For example, "sensibly perpendicular" should be understood as "showing an angle ranging from 89,5° to 90,5°".

[0049] In the present description, the term "lateral" or "laterally" refers to as a dimension parallel to the longitudinal axis AA' of the roller system.

[0050] In the present description, the term "convey" or "conveyor" refers to as any type of process whereby a moving web could be in contact with a rotating roller, such as but not limited to web carrying or guiding during a converting or manufacturing process.

Flat web

[0051] Optionally, the web exhibits a flat and/or flexible surface. The flat web may comprise any kind of materials such as metal, glass, paper, fabric, leather, plastic, particles, etc., in plain, in a laminate or in a blend of any combination. The flat web may be plain, rough, smooth, or open such as a net. The flat web may comprise a polymer such as polyester or polyimide. The flat web may be an aluminum or copper foil. The flat web may be coated or printed.

[0052] Preferably, the flat web is designed and/or intended to be coated, printed, chemically treated, cut, slit, sliced, wound and/or unwound, cured or dried. The other face which is not coated is intended to be in contact with the outer face of the roller system. The flat web may also come from a shape-forming manufacturing process such as cast or blown film extrusion.

[0053] Optionally, the flat web is a band. The roller system according to the invention is particularly advantageous to manage the alignment of an endless ribbon running along a path forming a loop. The flat web may be a drive belt. The flat web may be used to carry objects or to drive elements in rotation. The roller system may be used to address misalignment of a web in manufacturing industries such as: food containers, automobile and aircrafts parts, furniture surfaces, bags, insulation, boxes, carpet, clothing, credit cards, flooring, magazines, currency, newspapers, siding, upholstery, wrapping, adhesive tapes, food wrap, tapes, tissue. The roller system may also be used for the printing industry and within printers (electrophotography, laser printing, thermal transfer printers...).

Roller system

[0054] The system according to the invention comprises one support and at least one fin movably connected to this support.

[0055] One embodiment of the present invention wherein the support is a roller is now described in reference to figures 1 to 6.

[0056] The system 1 comprises a roller system and the support comprises a center roller 11 (also called "center roller" or "center roller" in the following description) with a rotation axis AA'.

[0057] The center roller 11 preferably longitudinally extends along its rotation axis AA' (also called "longitudinal axis" in the present description).

[0058] A set of fins 12 is arranged around the longitudinal axis of the center roller, preferably on the center roller surface. The fins are radially distributed over the center roller's surface. Fins 12 are protruding upward from the center roller 11 to compensate misalignment and correct position when the web tends to shift away (lateral shift) or to stand at an angle from the center (angular distortion). Such roller aims at reducing off-tracking of the web.

[0059] In one embodiment, the roller system is free in rotation like an idler roller. One advantage is to guide the web after unwinding or before it is rewinding, acting as a displacement guide.

[0060] In another embodiment, the roller system is motorized. One advantage is to provide a web-to-roller traction.

[0061] The roller system comprises a plurality of fins 12 radially distributed around the center roller 11. The roller system may comprise at least one fin. The flat web is capable of moving over the outer surface 15 of the fins.

[0062] The roller system or parts of the roller system may comprise polymers, rubbers, ceramics, metals...

[0063] The roller system may withstand high temperatures, speeds, tensions, loads... One advantage is to use the roller system in any converting process, for example a process involving a drying or curing step.

Center roller

[0064] The center roller 11 is preferably a roller having a cylindrical shape such as a right circular cylinder. The cylinder may be plain or hollow. The longitudinal axis of said cylindrical shape is preferably the axis of rotation AA'.

[0065] The center roller is not limited to the shape of a right circular cylinder. The center roller may comprise a core, a mandrel, core chucks, or core center rollers. The center roller may be a dead of live center roller.

[0066] One advantage of the center roller 11 is to allow the radial display of fins 12, at a given and steady distance from the axis of rotation AA'.

[0067] In one embodiment, the stem of the fins may be radially and evenly spread around the center roller, preferably around the circumference of the center roller, halfway up its length. In another embodiment, the center roller may comprise at least one fin.

[0068] In one embodiment, said center roller 11 comprises at its longitudinal ends connecting means to cooperate with complementary connecting means of the frame of a conveyor system. These connecting means are well known by the skilled person. In one embodiment, the connecting means comprise a blind hole and complementary spindle and/or a couple stator / rotor.

[0069] The center roller is designed to insure both a rotation of the roller system around the rotation axis AA' and supporting the fins 12.

[0070] In one embodiment, the roller system comprises damping means to support fins along its length. One advantage is to prevent oscillations of the fin and the web at high speed. Preferably, the damping means comprises a foam or an elastic material. Preferably, the damping means are arranged between the fin and the center roller. In one embodiment, the damping means comprise a stop to limit the movement of the fin.

[0071] In one embodiment, the center roller is perforated, and air (or any other gaz) may be blown from its core toward the outside, in direction of the gap between the fins. One advantage is to support the web between each fin with a fluid. Air blow may also circulate within the fins through the mechanical link 13. Air blow may be transported using means such as a nozzle, hollow cables...

Fins

[0072] The fins 12 are arranged around the center roller 11. The outer surface 15 of each fin is intended to support part of the web. The web may be supported by a portion of the surface 15 of the fin. In other words, a portion of the outer surface 15 of the fin, or parts of the lateral portions of the fin may support the web. The actual contact between the web and the outer surface 15 of the fin is depending, among other features, on the profile of the fins, the aspect of the surface (rugosity, presence of dents, notch...), the stretch of the web... As a matter of fact, parts of the portions towards the center might not be in full contact with the web, especially when the fin are designed with a concave profile or when the fins are curved, skewed, or shaped along their circumference. The web may be supported by an equivalent portion of the surface 15 of the fin when the web runs over an air cushion.

[0073] In one embodiment illustrated in figure 3, the roller system comprises 8 fins.

[0074] Preferably, as illustrated, each fin extends longitudinally along a direction sensibly parallel to the longitudinal axis AA' to cover the outside surface of the center roller along its length dimension.

[0075] Preferably, each fin extends longitudinally from both part of the mechanical link 13.

[0076] Preferably, the fins 12 are regularly arranged around the center roller 11 with a space between each fin.

[0077] By "regularly arranged", is has to be understood that the angular space Z between each adjacent fins 12 is identical or sensibly identical around the longitudinal axis AA'. Preferably, the angular space Z between two adjacent fins 12 is equal or sensibly equal to 360°/n wherein n is the number of fins 12 arranged on the center roller 11.

[0078] The fins 12 extend longitudinally across the web's width (i.e., the length dimension is at least 5 times longer than its width dimension and its thickness dimension). Narrow fins advantageously modify the gap between fins to adjust the contact area with the web. Grip or slippage could therefore be promoted or reduced according to the type of web.

[0079] Furthermore, the narrower the fins are, the more the number of fins increases. One advantage is to provide a higher density of fins around the center roller and to increase the center of the web on the fins, especially when the web reaches high speeds. The density of the fins may also allow the increase in wrap angle (the overlap angle of the film over the roller), which advantageously may improve the center of the web on the fin. The density of fins also allows better management of mechanical tension differentials upstream and downstream of the roller system.

[0080] In one embodiment, the thickness of the fin is constant along a direction parallel to the AA' axis. In another alternative embodiment, their lateral portions are thicker than at the central portion. In one embodiment, the fins have a tapered portion along the AA' axis.

[0081] A sectional view of one fin connected to the center roller 11 according to a plane comprising the longitudinal axis AA' is illustrated in figure 1. In one embodiment, the profile of the outer surface 15 of the fin in a plane comprising the longitudinal axis AA' is straight or flat but other profiles may be implemented. Preferably, the profile of the outer surface 15 comprises an axial symmetry with respect to a second axis DD' passing through the barycenter of the fin.

[0082] Each fin is mechanically connected to the center roller 11, preferably by a mechanical link 13. Preferably, the profile of the outer surface of the fin comprises an axial symmetry with respect to a second axis DD' passing through the mechanical link 13.

[0083] In one embodiment illustrated in figure 9, the profile of the outer surface 15 of the fin in a plane comprising the longitudinal axis AA' is concave. The concave shape of the outer surface of the fins enables the roller system to macroscopically look like a concave roller. Preferably, the profile of the outer surface of the fins are symmetric according to a plane passing through the axis DD'. The concave profile may advantageously add other features to the roller system to handle the web. For instance, such concave profile may guide the web to spread across the roller as to prevent wrinkles. Web spreading may also be enhanced by the gaps between each fin exhibiting a flat or curved outer surface. Another advantage is to prevent the emergence of wrinkles within the web.

[0084] In another embodiment, the profile of the outer surface 15 of the fin in a plane comprising the longitudinal axis AA is convex. When located above a winding roller whereby the web could be stored, one advantage is to guide the web properly, to avoid air trapping within the coil and to reduce downtime and waste.

[0085] In one embodiment, the fin surface is perforated to allow air blow (or other gaz) underneath the web or to create air outflow. The perforations comprise through holes extending from the outer surface of the fin and the opposite surface. One advantage is to control the contact between the web and the roller such as to enhance and/or facilitate web guiding by reducing or increasing slippage. Another advantage is to increase web speed and reduce maintenance. Another advantage is to allow an air flow creating an air cushion between the web and the outer surface, curving the web to reduce the risk of wrinkling the web. In one embodiment, the system comprises means to adjust the air flow creating an air cushion between the web and the outer surface. For example, the surface with the perforation comprises a gate to partially close the perforation and means to control the position of said gate. In a preferred embodiment, a space gap is managed between two adjacent fins. This space gap advantageously avoids the fins to bump into each other and brings closer together the fins when in its engaged position. The space gap may advantageously allow to reduce air entrainment, air flotation or air entrapment between a web and a roller. It may be used to promote air out gassing during winding. Depending on the web's features or the type of process involved, the number of fins, their thickness or chemical composition may be adapted. The performance of the tilt may be improved when the fin material is isotropic and fins symmetrical with respect to a plane orthogonal to the longitudinal axis AA'.

[0086] Each fin of the set of fins, or preferably the outer surface of each fin of the set of fins comprises a first lateral portion separated from a second lateral portion by a plane. The plane is orthogonal to the longitudinal axis AA'. Preferably, the plane is passing through the mechanical link as described after when there is only one mechanical link connecting the fin to the center roller.

[0087] The outer surface of the fin extends at least along both the first lateral portion and the second lateral portion.

[0088] In one embodiment, the fin comprises a heater to heat the outer surface of the fin. One advantage is to heat the web.

Mechanical link

[0089] In one embodiment, the mechanical link is a joint and has a degree of freedom allowing the fin to tilt. The tilt may be induced under the action of the unbalanced web tension. One advantage is to correct the unbalance tension of the flat web in contact with the roller at the onset of misalignment occurring while the web is in contact with the roller system.

[0090] Preferably, the mechanical link 13 between the fin and the center roller 11 is located at the projection of the second axis DD' passing through the center point or the barycenter of the fin and perpendicular to AA'.

[0091] One advantage is to provide a web position correction while the web edges tend to drift to one direction (left or right). The mechanical link allows to retrieve an equilibrium in the tension across the web's width. The distance between the fin and the center roller in that direction dynamically decreases to counterbalance the web lateral displacement. Preferably, the second axis DD' defines a boundary between a first and a second lateral side of the outer surface 15 of the fin and the second side is preferably the symmetric of the first side with respect to the second axis DD'.

[0092] As illustrated in figure 2, the mechanical link 13 between the fin and the center roller 11 allows the tilt of the fin when the web is off-tracks and starts to drift away. In other words, the angle Y between the second axis DD' and the longitudinal axis AA' is strictly inferior to 90°. In one embodiment, the angle Y between the second axis DD' and the longitudinal axis AA' is strictly inferior to 90° and superior to 88°.

[0093] This range of angle advantageously allows to center the web on the fin.

[0094] For example, the roller system comprises means to limit the angle Y such as a stop arranged to limit the movement of the fin. The height and/or the position of the stop is configured to adjust the maximum tilt of the fin.

[0095] In a preferred embodiment, the mechanical link 13 is designed to allow the fin to tilt toward one extremity, according to a rotation axis EE' which is orthogonal or sensibly orthogonal to the longitudinal axis AA' of the center roller 11 and the second axis DD'. The mechanical link has one axis of rotation and may exhibit different levels of rotational stiffness.

[0096] In one preferred embodiment, the mechanical link 13 does not allow the rotation of the fin with respect to the center roller about an axis parallel to the longitudinal axis AA' and/ or to the second axis DD'. In other words, the mechanical link 13 between the fin 12 and the center roller 11 is an axial pivot link comprising a single degree of freedom in rotation around the rotation axis EE' and 0 degree of freedom in translation.

[0097] In one embodiment, the mechanical link is designed to reach an optimum between its geometry and its chemical composition. The roller system may be designed to withstand high load, high speeds, and vibrations. The design of the mechanical link may take into account the relationship between a complex of parameters, such as the film thickness, its width, its elastic, stiffness, bending or Young's modulus, its tension, the distortion angle between the longitudinal axis AA' and the machine direction... The number of fins may also be related to the center roller diameter, the friction coefficient of its outer surface, the web speed, the required alignment tolerances... For example, shape and materials may be defined by finite element analysis. The mechanical link may be welded, press fit, bolted.

[0098] In one embodiment, the mechanical link is designed to reduce vibrations during web transportation. The stiffness of the mechanical link may be tailored accordingly. One advantage is to damp vibrations when processing the web at high speeds. Damping means may comprise foam, rubber, or springs. One advantage is to regulate the tilt.

[0099] One embodiment of such mechanical link is now described in reference to figure 6 which does not limit the invention.

[0100] In said embodiment, the roller assembly comprising the center roller 11, the center roller, the mechanical link and the fins 12 may be made of one unique monobloc element. Preferably, the unique monobloc element is made of a material based on polymeric material such as polyamide, polystyrene or polyethylene. One advantage of the monobloc element is to advantageously facilitate the roller system 1 cleaning, e.g., when immersed in a solvent or cleaning bath.

[0101] In said embodiment, the section of the mechanical link 13 between the center roller 11 and the fin 12 according to a plane comprising the longitudinal axis AA' and the rotation axis EE' comprise a central portion 133. The central portion 133 may be narrowed. One advantage is to concentrate the strain from the unbalanced web tension and to allow the inclination of the fin 12 with respect to the center roller 11. The existence of this narrow section may act as a pivot with more or less stiffness, according to the material features and mechanical properties such as its elasticity.

[0102] In another embodiment, each part of the roller system is made out of a distinct material. In another embodiment, each part may be removable. One advantage is to separate each element and to clean each part independently, for instance with a solvent and/or using a specific washing machine or process.

[0103] The outer surface of fins may vary depending on the type of web, so that the film drift easily over it. The outer surface of fins may be coated, etched, mechanically or chemically treated. The outer surface may be smooth, rough or wavy, hollowed or plain. In one embodiment, the outer surface may be coated with a silicone-based or fluor-based layer. The outer surface may be covered with an elastomer, a rubber, a tape, a fabric, cork, such as nut not limited to acrylic, nitrile, butyl, EPDM, fluorocarbon, cotton, polymers such as polyurethane, neoprene, SBR, silicone. The outer surface may be coated with anodized aluminum oxide, ceramic, chromium, nickel, tungsten carbide. The outer surface may comprise beads, roughness, holes, balls such as chromium balls. Coating or chemical treatment of the surface may provide additional features to the roller system. The outer surface may be slippery, solvent resistant and easy to clean.

[0104] One advantage is to reduce the surface tension of the outer surface to promote web sliding. Another advantage is to avoid skewing tension distributions or other web handling problems.

[0105] In one embodiment, the fins have different surface properties. One advantage is to allocate to each fin a function for sliding or a grip to ensure its adjustment role.

[0106] In one embodiment, the dimension of the thin central portion 133 according to the EE' axis is the same as the width of the fin 12 according to the same EE' axis to advantageously block the rotation of the fin 12 according to another axis.

[0107] Preferably, the mechanical link further comprises a first tapered portion 131 between the center roller 11 and the thin central portion 133 and/or comprises a second tapered portion 132 between the fin 12 and the thin central portion 133.

[0108] These tapered portions advantageously reduce the risk of breakage of the mechanical link and increase the lifetime of the roller system.

[0109] In one alternative embodiment, the mechanical link 13 comprises hinge means between the fin and the center roller to provide a one degree of freedom connection in rotation.

[0110] In one alternative or cumulative embodiment, the fin is mechanically fixed to the center roller 11 and the fin 12 has an elasticity allowing both lateral sides of the fin to bend by action of a tension of the flat web from the relaxed position to the engaged position.

[0111] In a preferred embodiment, each fin 12 is movable with respect to the center roller 11 around the rotation axis EE' independently one from each other.

[0112] In one embodiment, the mechanical link may comprise several parts or may comprise several mechanical links. The pivot function provided by the mechanical link may be broken down into several pivot function. The mechanical link may comprise one pivot junction with the center roller and one pivot junction with the fin, each junction being connected by connecting means such as rod. The two pivot junctions may exhibit different stiffnesses. One advantage is to combine tilt and damp of the fin.

[0113] In one embodiment, the junction may comprise a compliant mechanism. One advantage is to adjust the position of the fin or each fin of the set of fins when the total torque with respect to the pivot point exerted by the web on the outer surface is respectively higher on the first portion than on the second portion or higher on the second portion than on the first portion. Another advantage is to allow a smooth, gradual and agile way to switch the fin from one position to another position.

[0114] In one embodiment, the fin or each fin of the set of fins is arranged to tilt or rotate continuously between the first position over the second position to the third position depending on the distribution of the pressure exerted by the web on the outer surface. When the torque, which is the pressure times the lever arm length with respect to the tilting axis, is respectively higher on the first portion than on the second portion the fin will tilt, thus reducing the pressure and the torque on the first side and increasing it on the second side until torques on either side are in equilibrium.

Lateral correction of the flat web

[0115] The execution of the invention to avoid and/or correct the lateral shift of the flat web is now described. The fin 12 in contact with the circulating web 2 passes from the relaxed to the engaged position to correct lateral shift. Once the fin is not in contact with the web anymore, it retrieves its relaxed position. During rotation, the roller system has successively at least one fin in contact with the web and at least one fin is prone to tilt. One advantage is to create a dynamic and compliant roller.

Relaxed (or idle) position

[0116] In the "relaxed position", a gap lies between each fin. The gap avoids direct contact of each fin with an adjacent one. The space gap is managed between two adjacent fins in the relaxed position. In the relaxed position, each gap dimension is sensibly steady and homogeneous as to avoid the fins to be overlapped or in contact. The roller system may therefore be circumscribed within a rectangular cylinder. This space gap advantageously allows to the launch of the "engaged position" upon unbalance of tensions across the web.

[0117] Figure 1 illustrates a fin of the roller system according to one embodiment of the invention in a relaxed position.

[0118] In this relaxed position, the flat web 2 may be sensibly centered on the second axis DD'. While the web is running over rollers, its width's center aligns with the machine direction crossing the second axis DD' defined by the mechanical link 13.

[0119] In one embodiment, each fin is symmetric relative to an axis perpendicular to the longitudinal axis AA'.

[0120] In the relaxed position, the profile of the outer surface 15 is symmetric with respect to a plane which is orthogonal to the longitudinal axis AA'. The "profile" of the outer surface 15 should be understood as the profile according to a plane passing through the AA' axis and the fin.

[0121] According to one embodiment, in the relaxed position, a first distance B between the outer surface of the first lateral portion and the longitudinal axis AA' is equal or sensibly equal to a second distance C between the outer surface of the second lateral portion and the longitudinal axis AA'. The first distance and the second distance are measured on equidistant points from the orthogonal plane of symmetry.

Engaged position

[0122] The engaged position (or "tilted position") may arise upon tensions differences across the film on one lateral side in contact with the fin 12. Such imbalance may lead to instabilities during the web transport. Tension asymmetry may intensify the web-roller misalignment angle between the web's edges and the machine direction and may initiate or accentuate the lateral shift of a web. In other words, the engaged position may be triggered by the onset of web lateral shift and/or when unbalanced tensions arise across the web's width, especially at their edges.

[0123] To cope with this phenomenon, the fins may tilt / bend in relation to the mechanical link. The fin 12 in contact with the web may lean toward the lateral side where the web's tension is higher. The fin in contact with the web is in the engaged position and may tilt and/or bend. The tension difference existing at one lateral extremity of the flat web in contact with the fin's outer surface induces the inclination of fins. Once the engaged position is triggered, the fin in contact with the web may bow toward one side.

[0124] The mechanical link allows the fin to rotate around the EE' axis to an engaged position (or "tilted position") wherein the second axis DD' shows an angle Y with the longitudinal axis AA' strictly inferior to 90° or inferior or equal to 89,5° or 89°. Once in the engaged position, the gaps between each fin may vary along the fin's length. The lateral side whereby the fins could be tilted is consequently reshaped. Therefore, a lateral shift of the flat web on the roller assembly leads to the tilt of the fin 12 and the tilt of the fin 12 leads to center again the flat web on the outer surface.

[0125] In the engaged position illustrated in figure 2A, the first distance B between a first lateral side of the roller system 1 and the longitudinal axis AA' is superior to a second distance C between a second lateral side of the roller system and the longitudinal axis AA'.

[0126] The distance C between the lateral side of the fin and the longitudinal axis AA' is shorter in the engaged position than in the relaxed position. This variation of distance advantageously allows the correction of a misalignment of the flat web conveyed by the roller system. Indeed, the more the distance between the flat web with the longitudinal axis is, the more the radial speed is. The radial speed difference along the width of the flat web allows the flat web to climb the slope and allow the flat web to re-center itself.

[0127] The second lateral side is the side wherein the fin has been tilted, i.e., the side of higher web's tension to offset.

[0128] Here, the first and second distances B and C refer to the distance between one point of the outer surface 15 of the fin 12 and the longitudinal axis AA' of the center roller. In the engaged position, because the first distance B is superior to the second distance C, the course of the web in contact with the roller system is different. In other words, the path taken by the web is modified and compensate the unbalanced tensions. For the web, the path of the lateral side with higher tension is shortened due to the tilt of the fin while the other side is increased. The dynamic adjustment of the web's path over the roller system allows the web's tensions to retrieve an equilibrium across its width. In the engaged position, the roller system acts as if one end is being swollen in comparison to the other end.

[0129] During the rotation of the roller system around its center roller axis AA', the fins are successively in contact with the web. When in contact with the web, the fin may operate in the engaged position and may recover its relaxed position as soon as it stops being in contact with the web.

[0130] The symmetry of the profile of the outer surface of the fin 12 advantageously allows stabilizing the position of the flat web in the center of the fin 12 in the relaxed position.

[0131] A second engaged position is illustrated in figure 2B wherein the fin is tilted on the other direction. In this second engaged position, the first distance B is inferior to the second distance C.

Conveyor System

[0132] The roller system may be inserted within a conveyor system 200 to hold and/or transport a flat web 2. The presence of such roller system advantageously avoids and/or eventually corrects the lateral shift of a flat web in autonomy. The conveyor system 200 may be implemented within a machine. The machine could be a printer, a coating line, a film extruding line...

[0133] One embodiment of the conveyor system 200 according to one aspect of the invention is now described in reference to figure 7.

[0134] The conveyor system 200 may comprise at least one roller 202, 203 to hold and transport the flat web. The conveyor system 200 may comprise a plurality of rollers 202, 203. The plurality of rollers is optionally mounted to a frame to rotate on themselves to transport the flat web 2 along their circumferential surface. The rollers may have a shape of a cylinder or be circumscribed in a cylinder. Additionally, conical, concave, convex, diablo or tapered rollers may be used in any arrangement. Rollers may be mounted to the frame to rotate around their longitudinal axis.

[0135] At least one roller among the plurality of rollers is a roller system 1 according to the invention.

[0136] The invention is initially intended to be used in a converting process but also may be used in any situation where webs rotation around rolls. One example is the distribution belt of an automotive engine.

[0137] The roller system may be inserted within a conveyor system comprising core, core center roller, line center roller, mandrels, drive belt, pulleys, spool, wound rolls. The roller system may be use in association or in place of spreaders, bowed rollers, crowned rollers, transport rollers, web drive (idler), accumulators, dancer rollers, edge guides, guide rollers, load cell tension rollers, spreader rollers (bowed, concave, dual, edge pull), squaring rollers, skewing roller, winder, winder lay-on rollers in converting but also in manufacturing webs.

[0138] One advantage of the roller system is to be inserted easily in existing system, with no need to change the whole or rebuilding a machine. Besides, there is no need to add cables or additional electronic or hydraulic means. Moreover, the insertion of the roller system is independent from the source of misalignment: There is no need to fully understand which roller is responsible for misalignment. Troubleshooting and cost related to realignment. becomes therefore unnecessary. The frequency of periodic realignment and/or roller change may be reduced (maintenance). Alignment and realignment tolerances adjustment may be facilitated. Web sagging and/or deflection due to gravity may also be reduced.

[0139] The presence of the roller system may correct in-plane misalignment and accurately re-align the web without tools (hand or optical transits). The roller system may also cope with plastic web relaxation or absorb creep of plastic films.

[0140] At least one of the rollers 202 is preferably a drive roller comprising a motor to control the rotation of said drive roller to transport the web 2.

[0141] The roller system may cope with machine vibration due to roller imbalance. As a matter of fact, misalignment can cause or can be caused by vibrations. Proper web alignment may therefore advantageously reduce web stress variations, reduce the emergence of wrinkle, improve machine component life and reduce premature machine part failure.

[0142] In one embodiment, the conveyor system, upstream and downstream of the system according to the invention, comprises means for controlling the mechanical tension of the web. In one example, such means comprises a spring-loaded tension roller. A controller can coordinate the motion of the tension roller 220 in response to an input detected by a band-path sensor. In addition, the web can be kept at constant tension, such as by looping the band around the spring-loaded tension roller, which is attached to a linear slide upstream and downstream the system according to the invention.

Example

[0143] A proof of concept has been carried out using an endless band moving in cycle around a driven roller (also called "speed roller") and an idler roller equipped with a spring to manage the web's tension. The idler has an adjustable axis of rotation to change its orientation during the experiment as to artificially create a web-roller misalignment angle between the web and the rollers. The experimental set-up is further equipped with a profile sensor to detect and measure the position of the web edges.

[0144] As a matter of fact, during the rotation of such endless band around the loop, lateral shift is exacerbated. The magnitude of lateral shift may build up after each cycle. Without any correcting means, the band accumulates lateral shift and deviation becomes more and more marked.

[0145] The experiment simulates lateral shift due for example to unperfect alignment of rotation axis of the rollers within a conveyor system. To mitigate this lateral shift, the correction of the web position has been demonstrated with a compliant roller with 8 fins. The current design of the compliant roller is produced with an additive manufacturing process, where the material is not isotropic (layering). The orientation of the layers was chosen in a way that the layers are parallel to the central plane, which is perpendicular to the axis AA' to achieve rotational symmetry.

[0146] The result of this experiment is illustrated in figure 8 showing the edge position S in mm (or lateral position) over the time T in second.

[0147] At the beginning of the experiment (T=0s) the web is centered on the roller system.

[0148] Then, a lateral shift is manually imposed to the web (between T= 0s and 50s).

[0149] When substituting the idler with an 8-fins polyamide roller, the compliant joint or mechanical link allows the fin to tilt or even bend under load. After 500 seconds, the band has recovered its initial position.

Support

[0150] In an alternative embodiment illustrated in figure 10, the support is a fixed support comprising a single fin. In this embodiment, the support is mechanically connected to the frame 100 of the conveyor system 200. A fin as described before is mechanically connected to the surface of the support with a mechanical link similar at the mechanical link a described before.

[0151] In this embodiment, the web, during its transport by a conveyor system, slides on the outer surface of the fin and the mechanical connection between the fin and the support advantageously allow the fin to tilt when a lateral shift of the web occurs, leading to recenter the web as described previously.

[0152] In this embodiment, the outer surface of the fin advantageously comprises a coating allowing a modification of the friction between the outer surface of the fin and the web to adjust sliding.

[0153] The support element is preferably a cylinder or a portion of a cylinder extending along a longitudinal axis AA'. Preferably, the cylinder comprises a non-circular hollow cylinder such as a parallelepiped or a rectangular cuboid.

Claims

1. Roller system (1) for conveying a web (2) comprising:

- a center roller (11) for rotation about a longitudinal axis (AA') of the center roller (11); and

- a set of fins (12), arranged around the longitudinal axis (AA'), each fin of the set of fins comprising an outer surface for supporting the web, the outer surface delimiting a first lateral portion of the fin and a second lateral portion of the fin separated from the first lateral portion by a plane orthogonal to the longitudinal axis (AA').

2. Roller system (1) according to claim 1, each fin being movable relative to the longitudinal axis (AA') between at least three positions:

- a first position, wherein the profile of the outer surface is symmetric with respect to the plane;

- a second position wherein a first distance between the first lateral portion and the longitudinal axis (AA') is less than a second distance between the second lateral portion and the longitudinal axis (AA');

- a third position wherein the second distance is less than the first distance.

3. Roller system (1) according to claim 2, the fin being arranged to move from the first position to the second position or the third position, under the effect of a total force exerted by the web is higher on respectively the first lateral portion or the second lateral portion of the surface.

4. Roller system (1) according to claim 2 or claim 3, wherein each fin is mechanically connected to the center roller (11) by a mechanical link (13) and each fin (12) is configured to tilt around the mechanical link (13) to move from the first position to the second or the third position.

5. Roller system (1) according to claim 4, wherein the mechanical link comprises a pivot connection, preferably an axial pivot connection between the fin (12) and the center roller (11).

6. Roller system (1) according to claim 4 or claim 5, wherein the mechanical link (13) between a fin (12) and the center roller (11) comprises a junction comprising at least one tapered portion (131, 132).

7. Roller system (1) according to claim 6, wherein the junction between the center roller (11) and the fin (12) comprises:

- a thin central portion (133);

- a first tapered portion (132) having a thickness decreasing from the fin (12) to the thin central portion (133), and

- a second tapered portion (131) having a thickness decreasing from the center roller (11) to the thin central portion (133).

8. Roller system (1) according to any of claims 4 to 7, wherein, in the second position or in the third position, a second axis (DD') perpendicular to the outer surface and passing through the mechanical connection (13) is tilted with respect to the longitudinal axis (AA') by an angle (Y) strictly inferior to 90°.

9. Roller system (1) according to any of claims 1 to 8 wherein the profile of the outer surface of the fin (12) comprises a concave profile.

10. Roller system (1) according to any of claims 1 to 8 wherein the profile of the outer surface of the fin (12) comprises a convex profile.

11. System (1) for conveying a web (2) comprising:

- a support element having a first face,

- at least one fin, arranged on the first face and comprising an outer surface for supporting the web, the outer surface delimiting a first lateral portion of the fin and a second lateral portion of the fin separated from the first lateral portion by a plane orthogonal to the first face.

12. System (1) according to claim 11, the at least one fin being movable between three positions:

- a first position, wherein the profile of the outer surface is symmetric with respect to the plane;

- a second position wherein a first distance between the first lateral portion and the first face is less than a second distance between the second lateral portion and the first face;

- a third position wherein the second distance is less than the first distance between.

13. System (1) according to claim 12, the fin being arranged to move from the first position to the second position or the third position, under the effect of a total force exerted by the web is higher on respectively the first lateral portion or the second lateral portion of the surface.

14. Conveyor system (200) comprising a plurality of rollers (1, 202, 203) to transport a web along a predefined path and at least one roller system (1) according to one of the claims 1 to 10 and/or a system according to one of the claims 11 to 13.

15. Method for conveying a web, comprising providing conveyor system according to claim 14 and a web, wherein the roller system according to one of the claims 1 to 10 and/or the system according to one of the claims 11 to 13 is used to move the web along its predefined path and to automatically correct web misalignment.

Drawing