a method and unit for positioning a layer of material onto a sheet to be covered, preferably a sheet of glass

Abstract: A method and unit (1) for positioning a layer (2) of covering material onto a sheet (3) to be covered, in which an end portion of a strip (8) of covering material is held close to one edge (20) of the sheet (3) before exerting on a surface (41) of the strip (8), opposite that which is brought into contact with the sheet (3), a thrust action such as to curve the strip (8) and progressively bring an end portion (55) of the strip (8) into a position overlying and facing the sheet (3); during the progressive curving the strip (8) is cut transversely to form the covering layer (2) and, with the curving completed, the layer (2) is released and progressively settles onto the sheet (3) to be covered.

Description: The present invention relates to a unit for positioning a layer of material onto a sheet, preferably a sheet of glass. In particular, the present invention is advantageously, but not exclusively, applicable to the continuous production of laminated (multilayer) sheets, to which the following specification will make explicit reference without loss of generality thereby. US 3260143 shows an apparatus for storing bolts of cloths, which are spread horizontaly and lied one onto the other. For the production of sheets of laminated glass and, in particular, sheets having sheets of glass intercalated with one or more layers of thermoplastic material it is known to hold the glass sheet to be covered in a fixed position at a forming station, to grip one edge of the covering material normally wound on a coil, and to unwind it by progressively drawing it over the sheet thereby making it slide on the sheet itself. This mode of operation, although used, does not allow the production of products all having a high and constant quality and reliability. What is explained above essentially derives from the fact that during the sliding of the layer of material over the sheet, notwithstanding that positioning takes place in a controlled environment, the sheet material itself adheres locally to the glass sheet so that, inevitably, during advance along the sheet, waves, curls or wrinkles and/or pockets are created in some zones and consequent positioning in others. These wrinkles and stretches are difficult to eliminate, especially in an automatic continuous forming process, and translates ultimately into a loss of homogeneity in the deposited layer. The presence of trapped air bubbles, on the other hand, compromises both the reliability of the laminated sheet, in that the air bubbles generate localised delaminations of the layer of material from the sheet, and render the laminated sheet itself unacceptable and with a variable light permeability from region to region. The adherence of the layer material to the sheet, is moreover even more accentuated in the presence of electrostatic charges on the layer material, thus frequently involving significant deviations or "skidding" of the layer material from the theoretical direction of advance along the sheet with the consequence that some perimatral regions of the sheet can remain uncovered, and inevitably, the laminated sheet must be rejected. Alternatively, for positioning a layer of thermoplastics material onto sheets of glass it is known to advance both the glass sheet to be covered and the end of the layer of material which is unwound at the same velocity. Such a mode of production, although allowing the elimination of relative sliding and therefore localised adherence between the sheet and the layer of covering material is unsatisfactory in that it does not allow continuous superimposition of several layers onto the sheet. In fact, for the deposition of a new layer of thermoplastics material the sheet covered with the first layer must be stopped again and brought back into its initial position and again repositioned thereby first of all creating a discontinuity in the cycle of production and causing relative displacements between the sheet and the first covering layer itself. The object of the present invention is that of providing a method of positioning a layer of covering material over a sheet to be covered, which allows the above-explained problems to be solved in a simple and economic manner. According to the present invention there is provided a method for positioning a layer of covering material onto a sheet to be covered, preferably a sheet of glass, according to claim 1. The present invention also relates to a unit for positioning a layer of covering material over a sheet, preferably a glass sheet. According to the present invention there is provided a unit for the positioning of a layer of covering material onto a sheet to be covered, preferably a glass sheet, according to claim 10. The invention will now be described with reference to the attached drawings which illustrate a non-limitative embodiment thereof, in which, Figure 1 is a side view, in section, of a preferred embodiment of the unit for positioning a layer of covering material onto a sheet, formed according to the principles of the present invention; and Figure 2 is a drawing similar to Figure 1 and illustrates the unit of Figure 1 in a different operating condition. In the attached figures the reference numeral 1 generally indicates a unit for positioning a layer 2 of covering material, preferably a thermoplastic material known per se, over a sheet 3 to be covered, preferably a sheet of glass. The unit 1 comprises a support structure 4 in turn comprising a base 5 and a rigid portal frame 6 extending upwardly from the base 5. The frame 5 supports a motorised unwinding device 7, known per se, for a strip 8 of covering material wound in a coil 9 supported in a known manner not described in detail, by its own base 10 which is only partly illustrated. The device 7 comprises, in particular, a pair of rollers 11 and 12 rotatable about respective axes 13 parallel with one another, and of which the roller 11 is a common return roller over which the strip 8 unwound from the coil 9 passes, whilst the roller 12 is a presser roller rotatable under the thrust of an associated drive motor 14. At the output from the device 7 the strip 8 passes through a channel 15 of variable width, an inlet 16 of which faces the rollers 11 and 12 and an outlet 17 of which faces the base 5. The base 5 defines a horizontal support plane 18 for the sheet 3 to be covered, disposed in a position spaced from the region where the frame 6 is connected to the base 5, and a rectilinear guide 19 which extends parallel to the plane 18 from a perimetral edge 20 of the sheet 3 towards the frame 6, and has an intermediate portion facing the outlet 17. Along the guide 19 slides a carriage 21 which has its own frame 22 and supports a gripping and retaining device 23 for a free end portion of the strip 8 projecting beyond the outlet 17. In particular the device 23 includes a crossbeam 24 connected to the frame 22 and a plurality of mechanical pincer members 25, known per se, carried by the crossbeam 24 itself. The cross beam 24 is adjustable with respect to the frame 22 in a direction orthogonal to the plane 18, preferably by means of a lead screw device 26. Each pincer member 25 is, on the other hand hinged to the cross beam 24 to rotate about an horizontal axis 27 parallel to the axis 13 and the plane 18 under the thrust of an actuator unit, known and not illustrated, preferably of the cam type, between a grip position, illustrated in Figure 1, in which the pincer member 25 is able to engage the said end of the strip 8, and a lowered retention position, illustrated in Figure 2, in which the pincer member 25 is able to retain the end of the strip 8 in a predetermined fixed position. The carriage 21 is movable along the guide 19 under the thrust of a motion device 28, preferably of pneumatic type, between an advance position (Figure 2) in which the pincer members 25 extend close to the edge of the sheet 3 and raised with respect to the edge 20 itself, and a retracted position (Figure 1) in which the pincer members 25 extend beneath the outlet 17. Still with reference to Figures 1 and 2, the unit 1 further includes a thrust device 30 for progressively advancing an end portion of the strip 8 retained, in use, by the pincer members 25 above the sheet 3. The device 30 comprises a pair of C-shape rectilinear guides 31 only one of which is visible in the attached drawings, which extend parallel to the guide 19 on opposite lateral sides of the carriage 21 in a raised position with respect to the guide 19 itself and the plane 18 and a motorised slide 32. The slide 32 has its own frame 33 and a plurality of shoes 34 coupled to the guides 31 in an axially slidable manner. The slide 32 supports a thrust drum 35 which has its axis 36 orthogonal to the guide 31 and parallel to the plane 18, and is provided with a pair of outer radial flanges 38 only one of which is visible in the attached drawings, fixedly connected to opposite ends of the drum 35 to define, in use, respective axial abutments for the strip 8. The drum 35 is coupled to the frame 33 in an angularly fixed position with respect to the guides 31 to cooperate, in use, slidingly with the strip 8. Alternatively, the drum 35 is coupled to the frame 33 in a rotatable manner about its axis 36. The slide 32 is movable along the guides 31 under the thrust of a drive device 39 known per se, preferably of the sprocket type or, alternatively, of pneumatic type, to displace the thrust drum 35 along a rectilinear path P parallel to the plane 18 and raised with respect to the plane 18 itself between two end-of-stroke positions a retracted or rest position of which is illustrated in Figure 1, and an operative advance position. When disposed in its retracted position the drum 35 lies within the frame 6 in a position underlying the roller 11 in such a way that when the carriage 21 is disposed in its retracted position and the pincer members 25 grip the end of the strip 8 the drum 35 faces and is spaced from a surface 41 of the strip 8 opposite that which, in use, will then be brought into contact with the sheet 3. When, on the other hand, it is disposed in its advanced position, the drum 35 extends close to an edge 42 of the sheet 3 opposite the edge 20. Still with reference to the attached drawing, the unit 1 finally includes a device 43 for cutting the strip 8, known per se, for producing the covering layer 2. The device 43 is carried by the frame 6 and comprises fixed support walls 44 for the strip 8 and a pair of movable thrust walls 44 for locking the strip 8 against the fixed walls 44. The walls 44 are fixedly connected to the frame 6 in positions spaced from one another, and define a first wall of the channel 15, whilst the walls 45 are disposed one below the other in vertically spaced positions and define a second wall of the channel 15. The walls 45 are carried by respective slides 47 which are coupled to the frame 6 by respective slide and guide assemblies 48 which are known and not described in detail, and are movable with respect to the frame 6 in a direction parallel to the path P under the thrust of a linear actuator 49 for displacing the associated walls 45 between a retracted rest position (Figures 1 and 2) and an advanced closure position, in which the walls 45 themselves lock the strip 8 against the walls 44. Finally, the cutting device 43 comprises a cutting blade 50, known per se, which is movable together with one of the slides 47 in the direction parallel to the path P and is coupled to the slide 47 itself by means of a known guide and slide assembly 51 to displace with respect to the slide 47 along a cutting path substantially orthogonal to the path P under the thrust of its own actuator 52 of known type. The operation of the unit 1 will now be described starting from the condition in which the slides 47 are disposed in their retracted rest positions, the blade 50 is maintained outside the channel 15, the end portion of the strip 8 extends into the channel 15, the carriage 21 and the slide 32 are both maintained in their retracted positions, and the pincer members 25 are open in their gripping positions. Starting from this position, by means of the device 7, the strip 8 is progressively unwound from the coil 9 and advanced towards the retention device 23 upon reaching which the grip members 25 are activated and coupled to the end of the strip which, at this point, is stretched with its surface 41 facing the drum 35 (Figure 1). After this the device 28 is activated and the carriage 21 is progressively displaced towards its advanced position in which it retains the end of the strip 8 close to the edge 20 of the sheet 3. Simultaneously the device 39 is activated and the slide 32 is progressively displaced at a given velocity V1 towards its advanced position. During the displacement of the slide 32 the drum 35 comes into contact with the surface 41 of the strip 8 and exerts an unwinding thrust which simultaneously causes the strip 8 to contact both about guide roller 54 freely rotatable on the frame 6, and the drum 35 itself. During displacement of the drum 35 the strip 8 is thus bent into a V over the drum 35 which subdivides the strip 8 into two facing portions 55 and 56 of variable length, of which the portion 55 faces and overlies, but is spaced from, the sheet 3 and forms with the sheet 3 itself an acute angle different from zero, whilst the portion 56 extends in a position substantially parallel to the path P. At this point, as soon as the section of strip 8 lying between the pincer members and the cutting blade 50 assumes a value slightly in excess of the length of the sheet 3, that is to say the distance between the edges 20 and 42, the slide 32 is stopped and the actuator 49 is subsequently activated, which carries the walls 45 into their closure positions, and the actuator 52 is activated which carries the blade 50 transversely cutting the strip 8 and forming the layer 2. Following this cut, the portion 56 overlies in part a support casing or guard carried by the carriage 21 and in part the branch 55. At this point the device 39 is activated again and the slide 32 completes its stroke towards its advanced position at a speed V2 very much greater than the speed V1 and, preferably, equal to twice the speed V1. During this latter displacement of the drum 35, upon relative sliding of the two portions 55 and 56, the portion 55 progressively overlies the sheet 3 gradually expelling the air present between the portion 55 itself and the sheet 3, whilst the portion 56 continues to slide on the portion 55. When the slide 32 reaches its advanced position the latter portion of the layer 2 also overlies the sheet 3 with its edge projecting beyond the edge 42, after which the pincer members 25 are reopened releasing the layer 2 which thus progressively completes its settling down positioning onto the sheet 3 still expelling air. At this point the slides 32 and 47 and the carriage 21 can be brought back to their respective initial positions and another layer 2 can be superimposed on the layer 2 first deposited by following the same phases as has just been described. Alternatively, another sheet 3 of glass can be disposed, in a known manner, onto the layer 2, or possibly a further layer 2 again following the same phases as described. From what has been described it will be evident that the unit 1 described allows an automatic and continuous covering to be achieved of any sheet with any covering layer material and, in particular, to be achieved always continuously whatever the type of laminated sheet nevertheless achieving high and constant quality and reliability. In fact, as opposed to the known mode of operation, in procedures actuated by the unit 1 described, the covering material no longer slides on the sheet to be covered, in that it is progressively laid onto the sheet itself. Because of this, during the positioning of the layer, no type of localised adhesion is formed between the covering layer and the sheet and, when the covering is completed, there are no wrinkles, stretches and/or zones of exposed sheet due to positioning errors of the layer encountered. This essentially derives from the fact that during the positioning phase first the strip 8 and then the layer 2 are always unequivocally positioned with respect to the sheet in that, on one hand, they are retained in fixed positions by the pincer members 24 and, on the other hand are consequently guided by the outer flanges 38 of the thrust and unwinding drum 35. The progressive careful placing of the covering layer 2 on the sheet 3 encourages the expulsion of air from between the layer 2 and the sheet 3 avoiding the formation of air bubbles responsible for localised delaminations and imperfections of an aesthetic nature. From the above it will be evident that the unit 1 described can have modifications and variations introduced thereto which do not go beyond the scope of protection of the present invention. In particular a different retention device could be provided for retaining the end of the strip in fixed position with respect to the sheet, as well as a different thrust and unwinding device able to carry, first of all, the end portion of the strip into a position overlying and spaced from the sheet 3 without relative sliding movements, and then to allow a gradual settling of the layer over the sheet itself.

Claims: A method for positioning a layer (2) of covering material onto a sheet to be covered, preferably a sheet of glass, the method comprising the steps of maintaining a sheet (3) to be covered in a horizontal fixed position, progressively unwinding a strip (8) of covering material from a coil (9) thereof, and progressively displacing a portion of the said strip (8) of covering material over the sheet (3); a free end of the said strip (8) being retained in a releasable manner close to one edge (20) of the said sheet (3); the progressive displacement of the said strip portion being effected by exerting on a surface (41) of the said strip (8) opposite that which is disposed, in use, in contact with the said sheet (3) a thrust action in such a way as to curve the strip (8) and progressively carry an end portion (55) of the strip (8) itself into a position facing and overlying the said sheet (3) without relative sliding motion between the sheet (3) and the strip (8); the method further comprising the further steps of transversely cutting the strip (8) to form the said covering layer (2) and releasing the covering layer (2) allowing it to settle onto the sheet (3) to be covered; characterised in that the curving of the said strip (8) is effected in such a way that the said end portion (55) forms with the said sheet (3) an acute angle different from zero, in order to allow a gradual settling of said end portion (55) onto said sheet (3). A method according to Claim 1, characterised in that the said continuous thrust action is effected by advancing a thrust member (35) in contact with the surface (41) of the strip (8) opposite that disposed, in use, in contact with the said sheet (3), and at least partly winding the said strip (8) about the thrust member (35) itself. A method according to Claim 2, characterised in that the said thrust member (35) is advanced over the said sheet (3) along a rectilinear path (P) substantially parallel to the sheet (3) itself. A method according to Claim 3, characterised in that the said thrust member (35) is advanced along the said rectilinear path (P) at a variable speed. A method according to Claim 3 or Claim 4, characterised in that during at least part of the said rectilinear path (P) of advance the said strip (8) is wound substantially in a V about the said thrust member (35). A method according to any of Claims 3 to 5, characterised in that during at least part of the said rectilinear path (P) the strip (8) is wound about the said thrust member (35) in such a way that two portions (55, 56) of the strip (8) cooperate slidingly together. A method according to any of Claims from 3 to 6, characterised in that the said cutting step is effected when the said thrust member (35) passes a fixed intermediate point of its advancing path (P). A method according to Claim 7, characterised in that during the said cutting step the said thrust member (35) is maintained stationary at the said intermediate point. A method according to any of Claims from 3 to 8, characterised in that during advancement along the said path (P) the said thrust member (35) slidingly cooperates with the said strip (8). A unit (1) for positioning a layer (2) of covering material onto a sheet to be covered, preferably a sheet of glass, according to the method of anyone of the preceding claims; the unit (1) comprising: first (5) and second (10) support means for supporting a sheet (3) to be covered in a fixed horizontal position, and respectively, a coil (9) of strip (8) of covering material for said sheet (3); releasable retention means (25) for holding a free end of said strip (8) in a releasable manner close to one edge (20) of said sheet (3); advancing means (30) for progressively carrying a portion of said strip (8) over said sheet (3); said advancing means (30) including a thrust member (35), which is movable from a retracted position to an advanced position for exerting, on a surface (41) of said strip (8) opposite that disposed, in use, in contact with said sheet (3), a thrust action to curve said strip (8) and progressively carry an end portion (55) of the strip (8) into a position facing and overlying said sheet (3), without relative sliding between the sheet (3) and the strip (8); and cutting means (50) for transversely cutting the strip (8) and forming said covering layer (2); characterised in that said thrust member (35) is disposed higher than the retention means (25) with respect to said sheet (3), so that said strip (8) forms an acute angle different from zero with said sheet (3) during displacement from the retracted to the advanced positions, in order to allow a gradual settling of said end portion (55) onto said sheet (3); said thrust member (35) facing and being spaced from said surface (41) of the strip (8), when said thrust member (35) is disposed in its retracted position and said retention means (25) hold said free end of the strip (8). A unit according to Claim 10, characterised in that said cutting means (50) are carried by a fixed frame (6). A unit according to Claim 10 or 11, characterised in that said advancing means (30) further comprise guide means (31) for advancing said thrust member (35) along a path (P) above said sheet (3), and motion means (39) for displacing said thrust member (35) along said path (P) between said retracted and advanced positions, in each of which the thrust member (35) is always disposed on the same side of the strip (8) with respect to said retention means (25). A unit according to Claim 12, characterised in that said path (P) is a rectilinear path. A unit according to Claim 13, characterised in that said rectilinear path (P) is parallel to said sheet (3). A unit according to Claims from 12 to 14, characterised in that the said thrust member (35) comprises a drum (35) having an axis (36) substantially orthogonal to the said path (P). A unit according to Claim 15, characterised in that the said drum (35) is locked against rotation about its axis (36) with respect to the said sheet (3). A unit according to Claim 15, characterised in that the said drum (35) is rotatable about its axis (36) with respect to the said sheet (3). A unit according to any of Claims from 10 to 17, characterised in that the said thrust member (35) includes guide means (38) for the said strip (8) disposed, in use on opposite lateral edges of the said strip (8). A unit according to one of Claims from 10 to 18, characterised in that the said strip (8) is slidably engaged in an outlet passage (17), and in that the said retention means (25) are movable between a grip position in which they are disposed substantially facing the said outlet passage (17) and are able positively to connect with the end of the said strip (8), and a retention position in which they retain the end of the strip (8) close to the edge (20) of the said sheet (3). A unit according to any of Claims from 10 to 19, characterised in that it includes adjustment means (26) for adjusting the position of the said retention means with respect to the said sheet (3) in a direction substantially orthogonal to the sheet (3) itself.

Inventors: BERGIA ALESSANDRO, QUAGLIA TERESIO, BERGIA, ALESSANDRO, QUAGLIA, TERESIO
Applicants: BOTTERO SPA, BOTTERO S.P.A.
Application year: 1998
Main classification: B65H35
IPC codes: B65H35, B32B17