DEVICE FOR SPREADING AN ADHESIVE ON A FILM AND APPARATUS FOR PRODUCING A MULTI-LAYER FILM PROVIDED WITH SAID SPREADING DEVICE

Abstract

Disclosed is a device for spreading an adhesive on a film, including at least a first metering roller and at least a second metering roller, which rotates in contact with an adhesive, the surface of the first metering roller being spaced from the surface of the second metering roller by a gap so that a portion of the surface of the second metering roller is coated with a uniform layer of adhesive, and a regulating device for moving at least the first metering roller with respect to the second metering roller to vary the width of the gap, wherein the regulating device is controlled by a control unit, the control unit being configured to control the position of the first metering roller and to regulate the width of the gap as a function of geometric and/or dimensional parameters of the first metering roller.

Claims

1. Device for spreading an adhesive on a film comprising: at least a first metering roller (10); and at least a second metering roller (11), facing the first, that can rotate in contact with an adhesive; wherein the surface of the first metering roller (10) is spaced from the surface of the second metering roller (11) by a gap (G) such that, following rotation, a portion of the surface of the second metering roller (11) is coated with a uniform layer of adhesive, the device also comprising a regulating device (20) for moving at least the first metering roller (10) with respect to second metering roller (11) to vary the width of the gap (G), and consequently the thickness of the layer of adhesive on the surface of the second roller, wherein said regulating device (20) is controlled by a control unit, said control unit being configured to control the position of the first metering roller (10) and to regulate the width of the gap (G) as a function of geometric and/or dimensional parameters of said first metering roller (10).

2. Device according to claim 1, wherein the control unit is connected to a device for detecting the angular position of the first metering roller (10).

3. Device according to claim 2, wherein the first metering roller (10) is associated with a positioning system that allows the roller to be arranged in a discrete number of defined angular positions.

4. Device according to claim 1, wherein the control unit can access a database containing geometric and/or dimensional parameters of the first metering roller (10).

5. Device according to claim 1, wherein the regulating device (20) comprises a pair of eccentric supports (21), each adapted to support an end of the first metering roller, said eccentric supports comprising a fixed portion (22) and a moving portion (23), rotatable with respect to the fixed portion about a rotation axis (Xe), the first metering roller being housed rotatably in the moving portion so that its axis (X) is eccentric with respect to the rotation axis (Xe) of the moving portion (23).

6. Device according to claim 5, wherein the moving portion (23) is rotated with respect to the fixed portion by means of a motor (26) controlled by the control unit.

7. Device according to claim 6, wherein the moving portion (23) comprises a ring provided, externally, with teeth (24), meshed on which is a worm screw (25) connected to said motor (26).

8. Device according to claim 1, wherein the control unit is connected to sensors (27) adapted to detect a parameter correlated to the temperature of the surface of one or of both the metering rollers (10, 11).

9. Apparatus for producing a multi-layer film equipped with one or more spreading devices according to claim 1.

10. Apparatus according to claim 9, comprising: a first spreading device (120) for spreading a first component of a two-component adhesive on at least a first face (S1f) of a first layer of film (S1); a second spreading device (130) for spreading a second component of the two-component adhesive on at least a first face (S2f) of a second layer of film (S2); a coupling unit (110) for bringing the aforesaid faces of said first and second layers into mutual contact in a gluing point (I) to create a multi-layer film (M); a winder (160) for winding the coupled multi-layer film on a take-up reel (BM).

11. Apparatus according to claim 10, wherein the coupling unit (110) comprises a heated calender (111) and a presser roller (112), defined between which is the gluing point (I) in which the two faces of the film come into contact, the unit being configured so that after the gluing point the multi-layer film (M) is wound on the calender (111) on an arc of contact with an angle () from 18 to 23.

12. Apparatus according to claim 11, wherein before the gluing point (I), the first layer of film (S1) is wound on the calender (111) on an arc of contact with an angle (a) from 68 to 78.

13. Device according to claim 2, wherein the control unit can access a database containing geometric and/or dimensional parameters of the first metering roller (10).

14. Device according to claim 3, wherein the control unit can access a database containing geometric and/or dimensional parameters of the first metering roller (10).

15. Device according to claim 2, wherein the regulating device (20) comprises a pair of eccentric supports (21), each adapted to support an end of the first metering roller, said eccentric supports comprising a fixed portion (22) and a moving portion (23), rotatable with respect to the fixed portion about a rotation axis (Xe), the first metering roller being housed rotatably in the moving portion so that its axis (X) is eccentric with respect to the rotation axis (Xe) of the moving portion (23).

16. Device according to claim 3, wherein the regulating device (20) comprises a pair of eccentric supports (21), each adapted to support an end of the first metering roller, said eccentric supports comprising a fixed portion (22) and a moving portion (23), rotatable with respect to the fixed portion about a rotation axis (Xe), the first metering roller being housed rotatably in the moving portion so that its axis (X) is eccentric with respect to the rotation axis (Xe) of the moving portion (23).

17. Device according to claim 4, wherein the regulating device (20) comprises a pair of eccentric supports (21), each adapted to support an end of the first metering roller, said eccentric supports comprising a fixed portion (22) and a moving portion (23), rotatable with respect to the fixed portion about a rotation axis (Xe), the first metering roller being housed rotatably in the moving portion so that its axis (X) is eccentric with respect to the rotation axis (Xe) of the moving portion (23).

18. Device according to claim 2, wherein the control unit is connected to sensors (27) adapted to detect a parameter correlated to the temperature of the surface of one or of both the metering rollers (10, 11).

19. Device according to claim 3, wherein the control unit is connected to sensors (27) adapted to detect a parameter correlated to the temperature of the surface of one or of both the metering rollers (10, 11).

20. Device according to claim 4, wherein the control unit is connected to sensors (27) adapted to detect a parameter correlated to the temperature of the surface of one or of both the metering rollers (10, 11).

Description

[0055] Further characteristics and advantages of the present invention will become more apparent from the description of an example of a preferred, but not exclusive, embodiment of a spreading device and of an apparatus for producing a multilayer film, as illustrated in the accompanying drawings, wherein:

[0056] FIG. 1 is a schematic lateral view of a spreading device in accordance with the present invention;

[0057] FIGS. 2a and 2b are two perspective views of the regulating device of the position of the metering roller;

[0058] FIG. 2c is a sectional view along a plane perpendicular to the axis of the metering roller;

[0059] FIG. 2d is a sectional view along a plane passing through the axis of the metering roller;

[0060] FIG. 3 is a schematized representation of a part of the regulating device of FIG. 2;

[0061] FIG. 4 is a schematic lateral view of an apparatus for producing a multi-layer film equipped with the spreading unit of FIG. 1;

[0062] FIG. 5 is a schematic lateral view of the coupling unit of the apparatus of FIG. 4.

[0063] With reference to the accompanying FIG. 1, the number 1 indicates as a whole a device for spreading an adhesive on a moving film.

[0064] Within the context of the present invention, adhesive is meant as an adhesive composition with at least two components formulated as a kit, the components of which are prepared separately and kept separated from each other until the moment in which the layers of film to be joined are coupled and in which the components of the kit are in preferably in fluid or paste-like form.

[0065] The term film is meant as any structure, typically flexible, with a thickness of less than 1 mm and preferably less than 0.5 mm. Suitable materials are, for example, paper, polymers and metal coated polymers, metal sheets or nonwoven fabric.

[0066] The spreading device comprises a first metering roller 10 and a second metering roller 11, arranged parallel and facing each other. The first metering roller 10 is preferably maintained blocked in rotation during operation of the apparatus. The second metering roller 11 is instead rotated with respect to the first in a direction of rotation indicated by the arrow Rd. The outer surface of the metering rollers 10, 11 is preferably smooth and coated, or made of chromed steel.

[0067] In the space between the two metering rollers 10, 11, in the upper part there is defined a chamber 12 into which there can be deposited an adhesive in contact with a part of the outer surface of both rollers. To maintain the fluidity of the adhesive at a desired value, the metering rollers are preferably provided with heating means to heat the outer surface.

[0068] The surfaces of the two metering rollers 10, 11 are spaced by a gap of a few hundredths of millimetre so that, following rotation of the second metering roller with respect to the first, the adhesive is laminated through the gap and a thin and uniform layer remains adhering to the surface of the second metering roller 11. This layer of adhesive, by means of one or more rollers that rotate in contact with the second metering roller 11, is transferred to a moving film S.

[0069] In the variant illustrated, the spreading device comprises a further conveyor roller 13 that rotates in contact with the second metering roller 11 in an opposite direction of rotation Rt.

[0070] The conveyor roller 13 is preferably coated with a layer of vulcanized rubber. The task of the conveyor roller 13 is to pick up the layer of adhesive from the second metering roller 11 and transfer it to a spreading roller 14 that rotates in contact therewith in an opposite direction of rotation Rs.

[0071] The spreading roller 14 is, in turn, placed in contact with the layer of moving film S, on which the adhesive is spread in a continuous and uniform layer.

[0072] Advantageously, the rotation speed of the spreading roller 14 is greater with respect to that of the conveyor roller 13 which, in turn, is greater with respect to that of the second metering roller 11.

[0073] This increase in speed allows a gradual decrease in the thickness of the layer of adhesive deposited on the surface of the rollers and, subsequently, on the layer of film.

[0074] The gap, i.e. the minimum distance between surfaces of the metering rollers 10, 11, can be regulated by means of a regulation system so as to vary the thickness of the layer of adhesive picked up by the second metering roller 11 and, consequently, the thickness of the layer of adhesive applied to the film S.

[0075] FIGS. 2a to 2d illustrate a detail of the spreading device in which the aforesaid regulation system, indicated as a whole with 20, is visible. In accordance with a preferred variant of the invention, said regulation system acts on the first metering roller 10 moving it with respect to the second metering roller 11 whose axis of rotation is fixed.

[0076] The first metering roller 10 comprises an operating central portion 10a comprised between two support shafts 10b (FIG. 2d), by means of which the metering roller is supported by the frame of the spreading device (not illustrated in the figure). Each support shaft 10b is coupled with an eccentric support 21 comprising a fixed portion 22, integral with the frame of the device, and moving portion 23, connected to the fixed portion and rotatable with respect to it about an axis of rotation Xe (FIG. 3). Said fixed and moving portions are preferably in the form of concentric rings. More in detail, the moving portion 23, inner ring, is housed in the fixed portion 22, outer ring.

[0077] The support shaft 10b is, in turn, housed rotatingly in a seat produced in the moving portion 23 so that its axis of rotation X is decentred with respect to the axis of rotation Xe of the moving portion. FIG. 3 represents, schematically and in section, the fixed portion 22, the moving portion 23 and support shaft 10b. In the figure, the letter E indicates the eccentricity between the axis X of the first metering roller 10 and the axis of rotation Xe of the moving portion 23, which, to make the drawing clearer, is intentionally out of proportion. In actual fact, the value of the eccentricity E is preferably from 0.2 mm to 1 mm.

[0078] By observing FIG. 3, the operation of the regulating device 20 can be better understood. When the moving portion 23 is rotated about the axis Xe by an angle , the axis X of the first metering roller 10 performs a rotation along a circumference with a radius E moving, with respect to an initial position, by a length D. This movement causes the surface of the first metering roller 10 to move toward or away from the surface of the second metering roller 11 and, therefore, increase or decrease of the gap G (not indicated in the figure).

[0079] On the outer surface of the moving portion 23 there are produced teeth 24, preferably with a helical profile, meshed on which is a worm screw 25 (FIGS. 2c, 2d).

[0080] Rotation of the worm screw 25, in one or in the other direction, causes rotation of the moving portion 23 and therefore, as described above, an increase or decrease of the gap G.

[0081] The screw 25 is moved by a motor 26, optionally associated with an encoder 32 (FIG. 2d).

[0082] A regulation system of this type allows variations of the gap G to be obtained with a precision up to one micron where the extension of the gap is typically from 50 to 80 micron.

[0083] According to the invention, the regulation system is controlled by a control unit (not illustrated in the figure) configured to correct the position of the first metering roller 10 with respect to the second metering roller 11, as a function of the geometric and/or dimensional parameters of the surface of the first metering roller. In fact, as said first metering roller 10 is maintained in a fixed angular position during the spreading process, any defects (geometric and/or dimensional tolerances) cannot be averaged as instead occurs for the second metering roller 11.

[0084] For this purpose, according to a preferred aspect of the invention, the control unit is connected to a device for detecting the angular position of the first metering roller 10. By means of this device, the control unit detects which part of the surface of the first metering roller 10 is involved in the spreading process, and in particular the zone close to the gap G where the adhesive is laminated on the surface of the second metering roller 11.

[0085] In fact, this operating part is not always the same, but, on the contrary, the first metering roller 10 is used in different angular positions, at times even in the same production batch, for example to utilize a new clean zone or, in any case, to utilize its surface in a uniform manner.

[0086] Advantageously, the control unit can be connected to, or can contain, a database in which the aforesaid geometric and/or dimensional parameters of the first metering roller 10 such as eccentricity, cylindricity, rectilinearity, etc., are stored.

[0087] These parameters can be detected in advance by means of measurement instruments and stored in the aforesaid database.

[0088] As a function of the aforesaid parameters, the control unit can control, in a coordinated manner, operation of the motors 26 of the two eccentric supports 21 to position the first metering roller 10 so that the value of the gap G corresponds as closely as possible to the nominal process value constant along the length of the operating part of the metering rollers.

[0089] In this way, the regulating device 20 is able to compensate the operating tolerances of the metering rollers, maintaining constant and correct the amount and hence the thickness of the adhesive picked up by the second metering roller.

[0090] In a preferred variant, said system for detecting the angular position of the first metering roller comprises one or more sensors 27 (FIG. 2b), integral with the frame of the device, adapted to detect references 28 produced on the first metering roller 10 or on a part integral therewith.

[0091] In the variant illustrated, the sensor 27 comprises an optical sensor configured to detect the position of a plurality of holes 28 produced on a hub 29 integral with the first metering roller 10. Alternatively, the sensor 27 can comprise an inductive, capacitive or magnetic sensor, or other position sensors with or without contact.

[0092] As mentioned above, the first metering roller 10 can be arranged in different angular positions, which are then maintained while the spreading device is operating. According to a preferred variant, these positions are defined by a plurality of seats 30 (FIG. 2d) produced on the hub 29. A positioning mechanism 31 (FIG. 2c) can engage said seats 30 to maintain, during the process, a given selected angular position.

[0093] According to a preferred aspect of the invention, the control unit can be connected to sensors adapted to detect a parameter correlated with the temperature of the surface of one or of both the metering rollers 10, 11.

[0094] This parameter can comprise, for example, the temperature of a fluid by means of which the surface of the metering rollers is heated.

[0095] The control unit, processing the aforesaid temperature values, is able to calculate the thermal expansions of the rollers and, also as a function of the viscosity/fluidity of the adhesive used, can correct the position of the metering rollers to restore the ideal value of the gap G.

[0096] In order to regulate the thickness of the layer of adhesive deposited on the film S, the control unit can be configured to control the motor means that rotate the second metering roller 11 and the conveyor roller 13 and, in particular, to continuously regulate the rotation speed as a function of the translation speed of the film S and optionally of the temperature parameter of the metering rollers.

[0097] With reference to FIG. 4, the number 100 indicates as a whole an apparatus for producing a laminated multilayer film obtained by joining two layers of film.

[0098] The apparatus 100 comprises at least a coupling unit 110, a first spreading device 120 and a second spreading device 130 such as the one described above.

[0099] According to a preferred embodiment, said first and said second spreading unit 120, 130 are configured to each spread a component of a two-component adhesive respectively on a first layer of film S1 and on a second layer of film S2.

[0100] The two layers of film S1 and S2, are subsequently guided by a plurality of rollers toward the coupling unit in which they are made to adhere to each other to create a coupled multilayer film M.

[0101] The first and the second layer of film S1, S2 are unwound from two reels B1, B2 supported and rotated by a first unwinder 140 and by a second unwinder 150 that respectively serve the first spreading device 120 and the second spreading device 130.

[0102] The multilayer film M is instead wound on a reel BM by a winder 160.

[0103] FIG. 5 represents the coupling unit 110 of the apparatus. In the coupling unit 110, the first layer of film S1, on the face S if of which a first component of the adhesive is spread, and the second layer of film S2, on the face S2f of which a second component of the adhesive is spread, converge.

[0104] According to a preferred variant, the coupling unit 110 comprises a heated calender 111 and a presser roller 112, preferably rubber coated, that rotates in contact with the calender 111.

[0105] The presser roller 112 is mounted on a moving support 113 that, by means of actuators 114, can be rotated around a pivot point Ps to move the presser roller 112 away from the calender 111 or to regulate the contact pressure.

[0106] Between the calender 111 and the presser roller 112 there is defined a gluing point I, in which the two faces S if and S2f come into contact to start the chemical reaction of the two components of the adhesive.

[0107] The contact pressure exerted by the presser roller is sufficient to complete mixing of the two components A and B of the adhesive so that, after the gluing point, the two layers of film S1, S2 are joined and in a multilayer film M.

[0108] According to a preferred variant, the first layer of film S1 is partially wound around the surface of the calender 111 before the contact point I, while the second layer of film S2 is partially wound on the outer surface of the presser roller 112.

[0109] According to a preferred variant, the calender 111 is heatable with the aid of a fluid that circulates under the outer surface, for example in a network of coiled pipes.

[0110] The heat released from the calender 111 can be transferred to the first component of the adhesive on the first layer of film S1 to improve the efficiency of the hardening process.

[0111] For this purpose, the first layer of film S1 is conveyed toward the gluing point I so that the winding angle on the calender 111 is preferably from 68 to 78 and more preferably from 71 to 75. An ideal angle is of around 73.

[0112] The second layer of film S2 is instead conveyed toward the gluing point I so that the winding angle on the presser roller is preferably from 18 to 26 and more preferably from 20 to 24. An ideal angle is of around 22.

[0113] Again to improve the hardening process of the adhesive, after the gluing point I, the coupled multilayer film M is preferably maintained in contact with the calender 111 for an arc of contact of from 18 to 23.

[0114] A plurality of guide rollers 115 convey the coupled film M from the gluing point I toward the winder 160 in which it is wound onto a take-up reel BM.

[0115] Preferably, the coupling unit is provided with a further cooled calender 116, placed between the gluing point I and the winder 160.

[0116] As a function of the material of the layers of film S1, S1, the multilayer film M can be cooled, winding it partially on said calender 116 before it is wound.

[0117] The invention has been described purely for illustrative and non-limiting purposes, according to some preferred embodiments. Those skilled in the art may find numerous other embodiments and variants, all falling within the scope of protection of the claims below.