MIXING MACHINE FOR THE PREPARATION OF MORTARS AND PLASTERS FOR THE CONSTRUCTION INDUSTRY

Abstract

 The present invention relates to a mixing machine (10) for the preparation of mortars and plasters for the construction industry, comprising:
- a loading tank (11);
- a tubular mixing chamber (15), comprising in turn an inlet opening (16) connected to the loading tank (11), an inner surface (22), and an unloading mouth (17);
- a feed screw (18), rotating about a feed axis (X1), configured to determine the movement of a material to be mixed from the bottom (14) of the loading tank (11) towards the tubular mixing chamber (15);
- a mixing tool (19), placed to operate inside the tubular mixing chamber (15) and operationally connected to the feed screw (18) so as to rotate with it;
- pumping means (20) for introducing a mixing liquid into said tubular mixing chamber (15);
- drive means (21) for driving the feed screw (18) and the mixing tool (19).
The mixing tool (19) comprises a rotating longitudinal body (25) placed to rotate about a longitudinal axis (X2) thereof, from which rotating longitudinal body (25) at least one flexible scraping element (26) develops, configured to be in contact with the inner surface (22) of the tubular mixing chamber (15) at least when said rotating longitudinal body (25) rotates about said longitudinal axis (X2) thereof.

Description

[0001] The invention relates to a mixing machine for the preparation of mortars and plasters for the construction industry.

[0002] Various types of mixing machines are now known and widespread in the construction industry field, such as plastering machines, with a vertical or inclined axis, for the application of coating glues, and continuous mixers for dry mortar in bags, in which mixing takes place in a substantially horizontal direction.

[0003] These mixing machines are configured to process sandy materials, aggregates in general, and other pre-mixed materials typical of the field, in order to mix them with water to form a fluid output material, which is made available to operators on site.

[0004] In general, such mixing machines include:

• a loading tank, in turn comprising a loading mouth, one or more inclined walls and a bottom towards which the one or more inclined walls converge;
• a tubular mixing chamber, which in turn comprises an inlet opening connected to the loading tank, and an unloading mouth, on the opposite side of the same tubular chamber with respect to the inlet opening;
• a feed screw, rotating about a feed axis, configured to determine the movement of the material to be mixed from the bottom of the loading tank towards the tubular mixing chamber;
• a mixing tool, placed to operate inside the tubular mixing chamber and operationally connected to the feed screw so as to rotate with it;
• pumping means for introducing a mixing liquid, normally water, into the tubular mixing chamber;
• drive means for driving the feed screw and the mixing tool.

[0005] By means of such mixing machines, a mixture is made which constitutes a plaster or mortar.

[0006] Typically, the mixing tool comprises a rotation shaft from which paddles develop radially; such paddles extend radially up to a predetermined distance from the inner surface of the tubular mixing chamber, e.g. about 1 cm, in order to prevent the paddles themselves from bending against a layer of material that may form on such inner surface.

[0007] Such paddles may consist, for example, of cantilevered radial bars, or of arched paddles comprising two or more radial bars and a longitudinal bar attached to the ends of the radial bars, whereby 'longitudinal' means that this bar develops in a direction parallel to the development direction of the rotating shaft.

[0008] The feed screw and the mixing tool are generally coaxial.

[0009] For mixing machines known as 'continuous mixers', with a horizontal axis, the feed screw and the mixing tool are coaxially connected by an intermediate joint, which also has an auxiliary feed propeller.

[0010] For mixing machines known as 'plastering machines', with a vertical axis or inclined axis, the feed screw and the mixing tool are joined together, so they either define a single piece, or the two pieces are welded together.

[0011] These known mixing machines, although widespread and appreciated today, have some limitations and some aspects of perfectibility.

[0012] A first limitation of the known mixing machines is linked to the fact that the mixture obtained using sandy materials, i.e. inert materials, mixed with water in the tubular mixing chamber, centrifuged by the movement of the mixing tool, adheres to the inner surface of the same mixing chamber in a mild way and is easily removable; on the other hand, when sticky materials are used, such as tile glues or coating glues, the resulting mixture adheres strongly to the inner surface of the tubular mixing chamber and tends to form a coating up to one centimetre thick, which is very difficult to remove due to the sticky material it is made of.

[0013] This coating of sticky material is very harmful to the integrity of the mixing machine, since if it develops over one centimetre in thickness, it can cause the paddles of the mixing tool to stop, resulting in the blocking of the latter and the feed screw which is connected to the mixing tool itself.

[0014] Furthermore, even if it does not become so thick as to be harmful to the integrity of the machine, this coating of sticky material nevertheless causes a reduction in the transit section inside the tubular mixing chamber, and at the same time subtracts material from the mixture formed in the mixing chamber, since this material instead of mixing with the water remains stuck in the coating; in this way, the mixture coming out of the mixing machine does not have the desired composition and density.

[0015] Another disadvantage of the formation of a coating of material inside the mixing chamber is that pieces of this coating come detached from the inner surface of the tubular mixing chamber in an uncontrolled and unpredictable manner, randomly and undesirably changing the predetermined density of the mixture being prepared.

[0016] Generally, cleaning the tubular mixing chamber requires stopping the mixing machine, opening the tubular mixing chamber, removing the mixing tool and cleaning to remove the coating of sticky material.

[0017] The removal of this coating of sticky material is very difficult, as it requires a jet of water and the simultaneous mechanical action of a specific scraping tool in order to be performed.

[0018] Particularly on construction sites set up inside private homes, the use of the large amount of water needed for effective cleaning can cause a lot of inconvenience.

[0019] Another drawback of continuous mixers of the known type is linked to the fact that, when the water is introduced into the tubular mixing chamber, it initially tends to go towards the area upstream of the mixing tool, instead of downstream, and towards the unloading mouth, and then reverses its motion at the intermediate joint with the auxiliary propeller; in the tubular compartment in which the intermediate joint is housed, the material entering from the loading tank and the water tend to partially mix and adhere to the inner surface of the tubular compartment, resulting in the formation of a layer of material with problems similar to those described above for the coating formed in the tubular mixing chamber.

[0020] Another limitation of known continuous mixers is linked to the fact that the sandy or granular materials, or other materials, which are introduced into the loading tank, often also contain more or less extensive pieces of fibre, for example hemp filaments, or metal fragments, which tend to group together and form agglomerates that tend to block the unloading mouth. The problem lies in the fact that, when the unloading mouth is partially blocked, the mixing uniformity is compromised, as the mixture of water and sandy or powdery material, which is being processed in the tubular mixing chamber, no longer advances smoothly.

[0021] All mixers of the known type described above have the disadvantage that the flow rate of mixed material flowing out the mixer is difficult to keep constant. The object of the present invention is to develop a mixing machine for the preparation of mortars and plasters for the construction industry, capable of obviating the aforementioned drawbacks and limitations of the known technique.

[0022] In particular, an object of the invention is to develop a mixing machine whose tubular mixing chamber is easy to clean.

[0023] A further object of the invention is to develop a mixing machine which makes it possible to obtain a more constant, i.e. less variable, output flow rate of mortar or plaster than similar machines of a known type.

[0024] A further object of the invention is to develop a mixing machine which makes it possible to obtain at the outlet a mortar or plaster with a more stable, i.e. less variable, density than similar machines of a known type.

[0025] A further object of the invention is to develop a mixing machine that is structurally simple and easy and cheap to maintain.

[0026] Again, an object of the invention is to develop a simple and safe-to-operate mixing machine.

[0027] Again, an object of the invention is to develop a mixing machine that can be set up in a number of different configurations according to needs and technical requirements.

[0028] The above-mentioned object and purposes are achieved by a mixing machine for the preparation of mortars and plasters for the construction industry, according to claim 1.

[0029] Further characteristics of the mixing machine according to claim 1 are described in the dependent claims.

[0030] The task and the aforesaid objects, together with the advantages that will be mentioned hereinafter, are indicated by the description of three embodiments of the invention, which are given by way of non-limiting example with reference to the attached drawings, where:

• figure 1 represents a perspective view of a mixing machine according to the invention in a first embodiment thereof;
• figure 2 represents a perspective view of a detail of the machine according to the invention in the first embodiment thereof;
• figure 3 represents a cross-sectional side view of the mixing machine in the first embodiment thereof, in a first operating step;
• figure 4 represents the same view as figure 3 with the machine in a second operating step;
• figure 5 represents the same view as figures 3 and 4 with the machine in a third operating step;
• figure 6 represents a schematic perspective view of the detail of figure 2 in a variant embodiment thereof;
• figure 7 represents a perspective view of a mixing machine according to the invention in a second embodiment thereof;
• figure 8 represents a perspective view of a detail of the machine of figure 7 according to the invention;
• figure 9 represents an exemplary perspective view of the detail of figure 8 inside a machine as in figure 7;
• figure 10 represents a partially cross-sectional schematic side view of a mixing machine according to the invention in a third embodiment thereof;
• figure 11 represents a perspective view of a detail of the machine of figure 10;
• figure 12 represents a perspective view of a variant embodiment of the details of figures 8 and 11;
• figure 13 represents a perspective view of another variant embodiment of the details of figures 8 and 11.

[0031] With reference to the above figures, a mixing machine for the preparation of mortars and plasters for the construction industry is indicated as a whole of a first embodiment thereof with the numeral 10.

[0032] A mixing machine 10 as shown in figures 1 to 5 is known in technical jargon as a 'continuous mixer', particularly suitable for dry bagged mortars.

[0033] Such a mixing machine 10 for preparing mortar comprises:

• a loading tank 11, in turn comprising a loading mouth 12, one or more inclined walls 13, and a bottom 14 towards which the one or more inclined walls 13 converge;
• a tubular mixing chamber 15, in turn comprising an inlet opening 16, clearly visible in figures 3 to 5, connected to the loading tank 11, an inner surface 22, and an unloading mouth 17 positioned on the opposite side of the tubular mixing chamber 15 with respect to the inlet opening 16;
• a feed screw 18, rotating about a feed axis X1, configured to determine the movement of a material to be mixed from the bottom 14 of the loading tank 11 towards the tubular mixing chamber 15;
• a mixing tool 19, well represented in figure 2, placed to operate inside the tubular mixing chamber 15 and operationally connected to the feed screw 18 so as to rotate with it;
• pumping means 20 for introducing a mixing liquid, normally water, into the tubular mixing chamber 15;
• drive means 21 for driving the feed screw 18 and the mixing tool 19.

[0034] The pumping means 20 and the drive means 21 are to be understood as being known per se.

[0035] The pumping means 20 may, for example, comprise a pump driven by the same drive means 21, or with an autonomous and independent drive; the pumping means 20 may also be other, technically equivalent, means.

[0036] The drive means 21 may for example comprise an electric motor configured to transmit rotation to the feed screw 18 via a belt system, or by other technically equivalent means known per se.

[0037] The peculiarity of the invention resides in the fact that the mixing tool 19 comprises a rotating longitudinal body 25 placed to rotate about a longitudinal axis X2 thereof, at least one flexible scraping element 26 developing from said rotating longitudinal body 25, configured to be arranged in contact with the inner surface 22 of the tubular mixing chamber 15 at least when the rotating longitudinal body 25 rotates about its longitudinal axis X2.

[0038] This flexible scraping element 26 develops in the direction of the longitudinal axis X2 between two connection points 28 and 29 with the rotating longitudinal body 25.

[0039] The mixing machine 10, belonging to the 'continuous mixer' type, has the tubular mixing chamber 15 positioned with a horizontal axis; consequently, the longitudinal axis of the rotating longitudinal body 25 is also substantially horizontal.

[0040] In this first embodiment of the invention, which is of course intended to be illustrative and not limiting of the invention itself, the rotating longitudinal body 25 comprises a rotation shaft 30.

[0041] Such rotation shaft 30 is of such a length that it longitudinally crosses the tubular mixing chamber 15 from the inlet opening 16 to the unloading mouth 17.

[0042] The unloading mouth 17 is open downwards.

[0043] Below the unloading mouth 17 there may be a collar 17a for directing the outlet jet and possibly a jet breaker grille 17b.

[0044] The rotating longitudinal body 25 comprises mixing paddles 23, radially developing from the rotation shaft 30; said mixing paddles 23 extend radially up to a predetermined distance from the inner surface 22 of the tubular mixing chamber 15, for example about 1 cm, in order to prevent the same paddles 23 from crashing against a layer, or coating, of material that may form on said inner surface 22.

[0045] The mixing paddles 23 are to be understood to be of a known type in themselves, and are to be understood to be of various shapes and sizes according to needs and technical requirements.

[0046] For example, in such a first embodiment of the invention, such mixing paddles 23 comprise:

• one or more radial cantilever bars 23a; for example, there is a radial cantilever bar 23a, positioned on the section of the rotation shaft 30 which is located at the unloading mouth 17;
• a plurality of arced paddles 23b, comprising two or more radial bars and a longitudinal bar attached to the ends of the radial bars, wherein 'longitudinal' means that this bar develops in a direction parallel to the development direction of the rotation shaft.

[0047] Advantageously, the flexible scraping element 26 comprises a cable made of metallic material 27, hereinafter also referred to as 'metal cable' for brevity; in particular, the flexible scraping element 26 comprises a metal cable 27.

[0048] The use of a metal cable 27 makes it possible to have a flexible scraping element 26 that is self-supporting when not in use, i.e. it does not bend downwards by gravity, and at the same time, thanks to its mass, when it is drawn in rotation it is pushed against the inner surface 22 of the tubular mixing chamber 15 by the centrifugal force.

[0049] The flexibility of the metal cable 27 allows easy removal of the mixing tool 19 from the tubular mixing chamber 15, for example for cleaning operations, or for replacement or maintenance of the mixing tool 19 itself.

[0050] In the example embodiment described herein, again by way of non-limiting example of the invention, the two connection points 28 and 29 to the rotation shaft 30 are positioned one in proximity to the inlet opening 16 and one in proximity to the unloading mouth 17, respectively.

[0051] The metal cable 27 is constrained to at least one of the two connection points in such a way that it does not translate in a radial direction in relation to said longitudinal axis X2.

[0052] For example, the metal cable 27 is constrained to the rotation shaft 30 at both connection points 28 and 29 in such a way that it does not translate in the radial direction with respect to the longitudinal axis X2, unless there is clearance; this clearance is understood to be comprised between 1 mm and 10 mm.

[0053] At a first connection point 28, a first end 27a of the metal cable 27 is inserted and fixed into a locking collar which is in turn fixed to a mixing paddle 23; in this way, the first end 27a is not able to move in a radial direction with respect to the longitudinal axis X2.

[0054] A second end 27b of the metal cable 27 is placed to cross the rotation shaft 30 in a corresponding through-hole diametrically defined on the same rotation shaft 30 at a second connection point 29.

[0055] This second end 27b is fixed to the rotation shaft 30 by means of two clamps 27c, opposite with respect to the diameter of the rotation shaft 30, which prevent the second end 27b from moving radially, except for physiological millimetre level clearance.

[0056] In an alternative embodiment, one or both of the ends 27a and 27b are constrained to the rotation shaft 30 by means which allow free translation in a radial direction; this free translation is intended to be able to take place over a length of, for example, between 2 cm and 10 cm, where the translation limits are imposed by corresponding mechanical limit switches.

[0057] Figure 3 clearly shows how the flexible scraping element 26 is arranged in contact with the inner surface 22 and is able, by rotating about the longitudinal axis X2, to remove the coating, or layer, of material from it, which would otherwise adhere to the inner surface 22 creating the undesired blocking of the space between the mixing paddles 23 and the same inner surface 22.

[0058] The mixing machine 10 may also comprise a mixing tool 19 in turn comprising an auxiliary flexible scraping element 31, as well exemplified in figures 2 to 5. This auxiliary flexible scraping element 31 also develops in the direction of the longitudinal axis X2 between two connection points 32 and 33 with the rotating longitudinal body 25, i.e., in particular, with the rotation shaft 30.

[0059] The auxiliary flexible scraping element 31 is positioned at the unloading mouth 17 and is of a size such that it passes through at least part of said unloading mouth 17 during rotation, as shown in the schematic section of figure 5.

[0060] Similarly to what is written above for the flexible scraping element 26, the auxiliary flexible scraping element 31 comprises an auxiliary metal cable 34, hereinafter referred to as 'auxiliary metal cable 34'; in particular, the auxiliary flexible scraping element 31 consists of an auxiliary metal cable 34.

[0061] Said auxiliary metal cable 34 is constrained with the rotation shaft 30 by a first end 34a thereof to at least one of the two connection points, for example to a first connection point 32, so as to translate in a radial direction with respect to said longitudinal axis X2.

[0062] For example, the first end 34a of the auxiliary metal cable 34 is positioned to pass through a diametrical through-hole defined on the rotation shaft 30.

[0063] The first end 34a has an anti-extraction head 34c, which is larger than the cross-section of the through-hole on the rotation shaft 30.

[0064] Thanks to this technical device, when the auxiliary metal cable 34 is in contact with the inner surface 22, the first end 34a moves radially away from the rotation shaft 30, as schematically shown in figure 4, whereas when the auxiliary metal cable 34 is at the unloading mouth 17, the first end 34a moves radially towards the rotation shaft 30 and the auxiliary cable 34 extends until it reaches the flow-breaker grille 17b, cooperating in the cleaning of the same flow-breaker grille 17b; the first end 34a is prevented from exiting the through hole in which it is inserted by the presence of the anti-extraction head 34c, clearly visible in figure 4.

[0065] A second end 34b of the auxiliary metal cable 34 is fixed to the rotation shaft 30 by means of two clamps 37, opposite with respect to the diameter of the rotation shaft 30, which prevent the second end 34b from moving radially, except for physiological millimetre level clearance.

[0066] The auxiliary metal cable 34 is therefore of such a length that, in the maximum radial extension arrangement between the two connection points 32 and 33, it touches the flow-breaker grille 17b.

[0067] The flexible scraping element 26 and the auxiliary flexible scraping element 31 are advantageously and suitably angularly offset from the longitudinal axis X2, of rotation; for example, the flexible scraping element 26 and the auxiliary flexible scraping element 31 are offset by 90°.

[0068] Furthermore, appropriately, the flexible scraping element 26 and the auxiliary flexible scraping element 31 are mounted on the rotation shaft 30 in such a way that they are not pinched between the mixing paddles 23 and the inner surface 22 of the tubular mixing chamber 15.

[0069] Then, the flexible scraping element 26 and the auxiliary flexible scraping element 31 are mounted on the rotation shaft so as to follow the mixing paddles 23 with respect to the direction of rotation of the mixing tool 19.

[0070] The feed screw 18 and the mixing tool 19 are generally coaxial.

[0071] The feed screw 18 and the mixing tool 19 are coaxially connected by an intermediate joint 38, clearly visible in figures 3, 4 and 5, provided with an auxiliary feed propeller 38b, the latter being shown in figure 5.

[0072] Said intermediate joint 38 has a scraping relief 38a, visible in figure 3, configured to rub against the inner surface in the tubular compartment 39 in which the intermediate joint 38 is housed.

[0073] In this embodiment, the scraping relief 38a comprises a piece of metal cable fixed to protrude from the auxiliary propeller 38b of the intermediate joint 38.

[0074] Thanks to such scraping relief 38a, the material adhering to the inner surface of the tubular compartment 39 is immediately removed, thereby preventing the formation of a coating or layer of material with drawbacks entirely similar to those described above for the coating, or layer, formed in the tubular mixing chamber.

[0075] A variant embodiment of a mixing tool 519 is schematically shown in figure 6.

[0076] In such a variant, the mixing tool 519 comprises a rotating longitudinal body 525 placed to rotate about a longitudinal axis X2 thereof, two flexible scraping elements 526a and 526b developing from such rotating longitudinal body 525, configured to arrange themselves in contact with the inner surface 22 of the tubular mixing chamber 15 at least when the rotating longitudinal body 525 rotates about its longitudinal axis X2.

[0077] Such flexible scraping elements 526a and 526b develop in the direction of the longitudinal axis X2 between two connection points 528 and 529 and 532 and 533 respectively, with the rotating longitudinal body 525.

[0078] The rotating longitudinal body 525 comprises a rotation shaft 530.

[0079] The flexible scraping elements 526a and 526b both consist of a respective metal cable 570 and 571.

[0080] Each metal cable 570 and 571 develops in an 'S'-shaped line from one end of a rotation shaft 530 to the other, diametrically crossing the same rotation shaft 530 in a central area thereof.

[0081] The two metal cables 570 and 571 are advantageously and appropriately offset at an angle with respect to the longitudinal axis X2, of rotation; for example, the two metal cables 570 and 571 are offset by 90°.

[0082] The ends of the cables are constrained to the rotation shaft 530 in the same way as described above for the cables 27 and 34 made of metallic material.

[0083] In this peculiar configuration, the mixing tool 519 has no mixing paddles, but the same flexible scraping elements 526a and 526b also have the mixing function.

[0084] Figures 7 to 9 show a second embodiment of a mixing machine according to the invention, referred to therein as number 110.

[0085] The mixing machine 110 in this second embodiment is known in technical jargon as a 'plastering machine', of the vertical axis type, particularly for glues for installing external coatings, and therefore in general for very sticky materials.

[0086] Such a mixing machine 110 comprises:

• a loading tank 111, in turn comprising a loading mouth 112, one or more inclined walls 113, and a bottom 114 towards which the one or more inclined walls 113 converge;
• a tubular mixing chamber 115, in turn comprising an inlet opening 116 connected to the loading tank 111, an inner surface 122, and an unloading mouth 117 positioned on the opposite side of said tubular mixing chamber 115 with respect to the inlet opening 116;
• a feed screw 118, rotating about a feed axis X1, configured to determine the movement of a material to be mixed from the bottom 114 of the loading tank 111 towards the tubular mixing chamber 115;
• a mixing tool 119, placed to operate inside said tubular mixing chamber 115 and operationally connected to the feed screw 118 so as to rotate with it;
• pumping means 120 for introducing a mixing liquid into the tubular mixing chamber 115;
• drive means 121 for driving said feed screw 118 and the mixing tool 119.

[0087] In such an embodiment, the feed screw 118 comprises a bent bar 118a, developing along a substantially helical line; such bent bar 118a is fixed to a rotation shaft 118b, also intended to be part of the feed screw 118.

[0088] The mixing tool 119 comprises a rotating longitudinal body 125 placed to rotate about a longitudinal axis X2 thereof.

[0089] From the rotating longitudinal body 125 a flexible scraping element 126 develops, configured to be in contact with the inner surface 122 of the tubular mixing chamber 115 at least when the rotating longitudinal body 125 rotates about its longitudinal axis X2.

[0090] The flexible scraping element 126 develops in the direction of said longitudinal axis X2 between two connection points 128 and 129 with said rotating longitudinal body 125.

[0091] In particular, in such a second embodiment of the invention, the mixing machine 110 has a tubular mixing chamber 115 positioned at a vertical axis X3.

[0092] The rotating longitudinal body 125 comprises a fork 130 whose two opposite symmetrical arms 130a, 130b develop in an axial direction parallel to the inner surface 122 of said tubular mixing chamber 115.

[0093] Said arms 130a and 130b develop between an upper crosspiece 135, connecting to said feed screw 118, and a lower crosspiece 136 placed between the lower ends of said arms 130a, 130b.

[0094] The flexible scraping element 126 comprises a cable made of metallic material 127, constrained to the rotating longitudinal body 125 between two connection points 128, 129, a first connection point 128 being defined at the upper crosspiece 135, a second connection point 129 being defined at the lower crosspiece 136.

[0095] The metal cable 127 also develops from the second connection point 129, which is lower, to a third connection point 128a, which is higher, located at the upper crosspiece 135 on the opposite side with respect to the first connection point 128.

[0096] The second connection point 129 is preferably, but not exclusively, defined at the centre of the lower crosspiece 136.

[0097] The metal cable 127 develops between said first 128 and second 129 connection points and between said second 129 and third 128b connection points according to a substantially helical line.

[0098] In this way, the metal cable 127 is configured to promote the advancement of the material being mixed.

[0099] The second connection point 129 is defined, for example, by an annular element fixed to the lower crosspiece 136.

[0100] The metal cable 127 can be tied to the connection points 128, 129, 128a in the same way as described above for the metal cables 27 and 34 relating to the first embodiment of the invention, i.e. such cable can be fixed at both ends, or have the possibility of sliding for at least one of the two ends.

[0101] The mixing machine 110 is to be understood to comprise, below the tubular mixing chamber 115, a spray pump 150, in a known manner per se, which spray pump is coaxially connected to the mixing tool 119, as exemplified in figure 9.

[0102] The rotation shaft 118b of the feed screw 118 is rigidly fixed in the axial direction to the fork 130 of the mixing tool 119, for example, but not exclusively, by welding.

[0103] Figures 10 and 11 show a third embodiment of a mixing machine according to the invention, which is indicated therein by the number 210.

[0104] The mixing machine 210 in this third embodiment is also known in technical jargon as the 'plastering machine'.

[0105] In such a mixing machine 210, the tubular mixing chamber 215 is positioned at an axis X4 inclined with respect to the ground by an angle comprised between 20° and 70°.

[0106] Also in said third embodiment, the rotating longitudinal body 225 of the mixing tool 219 comprises a fork 230 whose two opposite symmetrical arms 230a, 230b develop in an axial direction parallel to the inner surface of said tubular mixing chamber 215.

[0107] The arms 230a, 230b develop between an upper crosspiece 235, connecting with the feed screw 218, and a lower crosspiece 236 placed between the lower ends of said arms 230a, 230b.

[0108] The flexible scraping element 226 comprises a cable 227 made of metallic material, constrained to the rotating longitudinal body 225 between two connection points 228, 229, a first connection point 228 being defined at said upper crosspiece 235, and a second connection point 229 being defined at said lower crosspiece 236.

[0109] The cable 227 made of metallic material also develops from the second connection point 229, which is lower, to a third connection point 228a, which is higher, located at the upper crosspiece 235 on the opposite side with respect to the first connection point 228.

[0110] The metal cable 227 develops between said first 228 and second 229 connection points and between said second 229 and third 228b connection points according to a substantially helical line.

[0111] In this way, the metal cable 227 is configured to promote the advancement of the material being mixed.

[0112] The second connection point 229 is defined, for example, by an annular element fixed to the lower crosspiece 236.

[0113] This second point of connection 229 is preferably, but not exclusively, defined at the centre of the lower crosspiece 236.

[0114] Also in this embodiment, the mixing machine 210 comprises a spray pump 250 coaxially connected to the mixing tool 219.

[0115] In a variant embodiment of the mixing tool 319 according to the invention, exemplified in figure 12, the flexible scraping element 326 comprises:

• a cable 327 made of metallic material, constrained to the rotating longitudinal body 325 between two connection points 328, 329, a first connection point 328 being defined at said upper crosspiece 335, and a second connection point 329 being defined at said lower crosspiece 336;
• an anti-pinch terminal 340 fixed to a lower end 327a of said cable made of metallic material 327.

[0116] Such an anti-pinch terminal 340 may for example comprise a spherical body, which is larger than the distance between the inner surface of the tubular mixing chamber and the outer surface of the arms 330a and 330b of the fork 330.

[0117] Such an anti-pinch terminal 340 has the double function of preventing the end 327a of the metal cable 327 from being pinched between the fork 330 and the inner surface of the mixing chamber, and striking the same inner surface promoting the detachment of the material that may have adhered to it.

[0118] In such a peculiar embodiment, the metal cable 327 is constrained to the rotating longitudinal body 325 between two connection points 328, 329, where a first connection point 328 is defined at a lateral side of the upper crosspiece 335 with respect to the longitudinal axis X2 of the mixing tool 319, and the second connection point 329 is defined at the opposite side of the lower crosspiece 336 with respect to the same longitudinal axis X2.

[0119] Such a configuration is easier to make and easier to assemble than the embodiments of the invention described above.

[0120] In another variant embodiment of the mixing tool 419 according to the invention, exemplified in figure 13, comprising a fork 430 as described above for the third embodiment of the invention, the flexible scraping element 426 comprises a cable 427 made of metallic material, constrained to the rotating longitudinal body 425 between two connection points, a first connection point being defined at the upper crosspiece, not illustrated for simplicity and to be understood as analogous to what is represented in figure 12, and a second connection point 429 being defined at said lower crosspiece 436.

[0121] The lower end 427a of the metal cable 427 is fixed to a terminal 440 which is in turn fixed to the lower crosspiece 436.

[0122] The lower end 427a is fixed by means of a threaded element 490 which is designed to press in a radial direction on the lower end 427a through a corresponding radial threaded hole made on the terminal 440.

[0123] In this embodiment, the terminal 440 consists of a spherical body made of metallic material.

[0124] The fixing means of the lower end 427a to the rotating longitudinal body 425, and in particular to the fork 430, are to be understood to be also other, similar and technically equivalent means.

[0125] Advantageously, also in such a variant embodiment, the metal cable 427 is constrained to the rotating longitudinal body 425 between two connection points, where a first connection point is defined at a lateral side of the upper crosspiece with respect to the longitudinal axis X2 of the mixing tool 419, and the second connection point 429 is defined at the opposite side of the lower crosspiece 436 with respect to the same longitudinal axis X2.

[0126] The flexible scraping elements, described above as defined by a cable made of metallic material, are to be understood to be capable of being made with other technically equivalent flexible elements, for example with predominantly longitudinal developing bodies made of plastic.

[0127] The present invention therefore overcomes the described drawbacks. Advantageously, the mixer of the invention simplifies mortar and plaster mixing operations and has better reliability than known mixers which require frequent manual intervention during operation.

[0128] This reduced need for operator intervention also increases the efficiency of its use.

[0129] With the present invention a mixing machine has been thus developed for the preparation of mortars and plasters for the construction industry, capable of obviating the aforementioned drawbacks and limitations of the known technique.

[0130] In particular, the invention provides a mixing machine whose tubular mixing chamber is easy to clean, even when dry, thanks to the constant scraping work that one or more metal cables perform against the inner surface of the tubular mixing chamber at the same time as the mixing operation itself.

[0131] Furthermore, the invention provides a mixing machine which allows to obtain a more constant output flow rate of mortar or plaster than similar machines of the known type, by preventing the formation of a thick layer of material on the inner surface of the tubular mixing chamber, a layer of material which, by coming detached irregularly from the inner surface, would alter the flow rate and density of the output mixture.

[0132] Thus, with the invention, a mixing machine has been developed which makes it possible to obtain at the outlet a mortar or a plaster having a more stable density, i.e. less variable, than similar machines of the known type; thanks to the 'whip' effect of the scraping metal cable, when mixing the residual material which in known machines sticks to the inner surface, in the mixing machine according to the invention this residual material no longer sticks, and therefore it no longer happens that the material suddenly detaches, mixing with the material being mixed and thus overturning the predetermined density of the material being mixed.

[0133] Again, the invention provides a mixing machine that is structurally simple and easy and cheap to maintain.

[0134] The invention further provides a mixing machine that can be set up in a number of different configurations according to needs and technical requirements.

[0135] In particular, the aim of maintaining a constant flow rate of mixed material coming out of the mixing machine is achieved, reducing the need for operators to continuously intervene through manual operations.

[0136] The invention thus conceived is susceptible of numerous modifications and variants, all of which are within the scope of the inventive concept; moreover, all the details may be replaced by other technically equivalent elements.

[0137] In practice, the components and materials used, as well as the dimensions and shapes, as long as they are compatible with the specific use, can be any according to requirements and the state of the art.

[0138] If the characteristics and techniques mentioned in any claim are followed by reference signs, these reference signs are to be intended for the sole purpose of increasing the intelligibility of the claims and, consequently, such reference signs have no limiting effect on the interpretation of each element identified by way of example by these reference signs.

Claims

1. Mixing machine (10, 110, 210) for the preparation of mortars and plasters for the construction industry, comprising:

- a loading tank (11, 111), in turn comprising a loading mouth (12, 112), one or more inclined walls (13, 113), and a bottom (14, 114) towards which said one or more inclined walls (13, 113) converge;

- a tubular mixing chamber (15, 115, 215), in turn comprising an inlet opening (16, 116) connected to said loading tank (11, 111), an inner surface (22, 122, 222), and an unloading mouth (17, 117) positioned on the opposite side of said tubular mixing chamber (15, 115, 215) with respect to said inlet opening (16, 116);

- a feed screw (18, 118, 218), rotating about a feed axis (X1), configured to determine the movement of a material to be mixed from said bottom (14, 114) of said loading tank (11, 111) towards said tubular mixing chamber (15, 115, 215);

- a mixing tool (19, 119, 219, 319, 419, 519), placed to operate inside said tubular mixing chamber (15, 115, 215) and operationally connected to said feed screw (18, 118, 218) so as to rotate with it;

- pumping means (20, 120) for introducing a mixing liquid into said tubular mixing chamber (15, 115, 215);

- drive means (21, 121) for driving said feed screw (18, 118, 218) and said mixing tool (19, 119, 219, 319, 419, 519),

said mixing tool (19, 119, 219, 319, 419, 519) comprising a rotating longitudinal body (25, 125, 225, 325, 425, 525) placed to rotate about a longitudinal axis (X2) thereof, from said rotating longitudinal body (25, 125, 225, 325, 425, 525) at least one flexible scraping element (26, 126, 226, 326, 426, 526a, 526b) developing, configured to be in contact with said inner surface (22, 122, 222) of said tubular mixing chamber (15, 115, 215) at least when said rotating longitudinal body (25, 125, 225, 325, 425, 525) rotates about said longitudinal axis (X2) thereof, said at least one flexible scraping element (26, 126, 226, 326, 426, 526a, 526b) developing in the direction of said longitudinal axis (X2) between two connection points (28, 29; 128, 129; 228, 229; 328, 329) with said rotating longitudinal body (25, 125, 225, 325, 425, 525),

characterized in that said at least one flexible scraping element (26, 126, 226, 326, 426, 526a, 526b) comprises a cable made of metallic material (27, 127, 227, 327, 427).

2. Mixing machine according to claim 1, characterized in that said tubular mixing chamber (15) is positioned with a horizontal axis, said rotating longitudinal body (25) comprising a rotation shaft (30), said rotation shaft (30) being of a length such that it longitudinally crosses said tubular mixing chamber (15) from said inlet opening (16) to said unloading mouth (17).

3. Mixing machine according to one or more of the preceding claims, characterized in that said two connection points (28, 29) are respectively positioned one in proximity to said inlet opening (16) and one in proximity to said unloading mouth (17), said at least one cable made of metallic material (27) being constrained to at least one of the two connection points (28) so as not to translate in a radial direction with respect to said longitudinal axis (X2).

4. Mixing machine according to one or more of the preceding claims, characterized in that it comprises an auxiliary flexible scraping element (31) developing in the direction of said longitudinal axis (X2) between two connection points (32, 33) with said rotating longitudinal body (25), said auxiliary flexible scraping element (31) being positioned at said unloading mouth (17) and being of such dimensions as to cross at least partially said unloading mouth (17) during rotation.

5. Mixing machine according to claim 4, characterized in that said auxiliary flexible scraping element (31) comprises a cable made of metallic material (34), said cable made of metallic material (34) being constrained to at least one of the two connection points (32) so as to translate in a radial direction with respect to said longitudinal axis (X2).

6. Mixing machine according to claim 1, characterized in that said tubular mixing chamber (115) is positioned at a vertical axis (X3), said rotating longitudinal body (125) comprising a fork (130) whose two opposite symmetrical arms (130a, 130b) develop in an axial direction parallel to the inner surface (122) of said tubular mixing chamber (115), said arms (130a, 130b) developing between an upper crosspiece (135), connecting to said feed screw (118), and a lower crosspiece (136) placed between the lower ends of said arms (130a, 130b).

7. Mixing machine according to the preceding claim, characterized in that said at least one flexible scraping element (126) comprises a cable made of metallic material (127), constrained to said rotating longitudinal body (125) between two connection points (128, 129), a first connection point (128) being defined at said upper crosspiece (135), a second connection point (129) being defined at said lower crosspiece (136), said cable made of metallic material (127) developing between said connection points (128, 129) according to a substantially helical line.

8. Mixing machine according to claim 1, characterized in that said tubular mixing chamber (215) is positioned at an axis (X4) inclined with respect to the ground by an angle comprised between 20° and 70°, said rotating longitudinal body (225) comprising a fork (230) whose two opposite symmetrical arms (230a, 230b) develop in an axial direction parallel to the inner surface (222) of said tubular mixing chamber (215), said arms (230a, 230b) developing between an upper crosspiece (235), which is connected to said feed screw (218), and a lower crosspiece (236), placed between the lower ends of said arms (230a, 230b), said at least one flexible scraping element (226) comprising a cable made of metallic material (227), constrained to said rotating longitudinal body (225) between two connection points (228, 229), a first connection point (228) being defined at said upper crosspiece (235), a second connection point (229) being defined at said lower crosspiece (236), said cable made of metallic material (227) developing between said two connection points (228, 229) according to a substantially helical line.

9. Mixing machine according to one or more of the preceding claims, characterized in that said at least one flexible scraping element (326) comprises:

- a cable made of metallic material (327), constrained to said rotating longitudinal body (325) between two connection points (328, 329), a first connection point (328) being defined at said upper crosspiece (335), and a second connection point (329) being defined at said lower crosspiece (336);

- an anti-pinch terminal (340) fixed to a lower end (327a) of said cable made of metallic material (327).

Drawing