Abstract:
The machine has a heated plate, a conveyor for conveying the elements along a conveyor path leading across the heated plate, a top part vertically movable with respect to the heated plate, a membrane disposed on the top part and a separating film disposed between the membrane and the heated plate which can be moved synchronously with the conveyor. The separating film is divided into sections and every section is retained exclusively by a single edge oriented transversely to the conveying path by a retaining device. The sections therefore sit loosely on the elements free of tension. The membrane lies against a peripherally extending peripheral face of the top part facing the heated plate and can be moved directly onto the plane of the surface of the heated plate in order to form a closed chamber with it. Finally, the membrane is connected to a clamping device.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a divisional of and Applicant claims priority under 35 U.S.C. §§120 and 121 of parent U.S. patent application Ser. No. 11/921,488 filed on Aug. 31, 2009, which application is a national stage application under 35 U.S.C. §371 of PCT/EP2006/005221 filed on Jun. 1, 2006, which claims priority under 35 U.S.C. §119 of Swiss Application No. 0950/05 filed on Jun. 3, 2005, the disclosures of each of which are hereby incorporated by reference. The international application under PCT article 21(2) was not published in English. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The invention relates to a machine for producing board-shaped elements of composite material, with a heated plate, conveyor means for transporting the elements along a conveyor path running above the heated plate, a top part which can be moved vertically with respect to the heated plate, a membrane disposed on the top part and a separating film disposed between the membrane and the heated plate which can be moved synchronously with the conveyor means. 
         [0004]    2. The Prior Art 
         [0005]    When producing board-shaped elements made from composite material, for example photovoltaic elements, several layers, including glass amongst others, are assembled under the effect of pressure and heat. The machines needed for this process generally have a heatable laminating station, a cooling station and conveying means for intermittently conveying the elements. The laminating station has a heated plate and a top part which can be lowered onto the heated plate, and a membrane is provided which forms a closed chamber in conjunction with the heated plate in the lowered state. By evacuating this chamber, gas can be removed from around the elements and the membrane is applied to the heated plate due to the pressure acting on the side of the membrane facing away from the chamber so that the elements are pressed together. 
         [0006]    In terms of conveying means for the elements, known means comprise a conveyor belt, which simultaneously protects the heated plate against dirt, for example adhesive spilling out of the elements. In order to protect the vacuum membrane as well, a known approach is to provide a separating film for the elements, covering their top surface. Both the conveyor belt and the separating film may be used in the form of endless webs. The disadvantage of this is that control mechanisms have to be provided in order to ensure that the webs do not run sideways off the rollers conveying and turning the webs. Instead of using endless webs, a known way of avoiding this problem is to use sections which are conveyed by means of traction elements, for example chains, disposed to the side of the displacement path. This being the case, the sections are inter-connected by spring elements to form an endless loop. Due to the spring elements, the sections are subjected to tensile stress in the conveying direction, which causes the sections of separating film lying on top to lift off the elements as soon as the pressing force is removed. Any adhesive which leaks out between the separating film and the elements exerts a force directed upwards towards the elements, which is particularly problematic in the laminating station because the adhesive between the layers of elements has not yet set at this stage. 
         [0007]    In the case of many known machines, the membrane is clamped in a frame, which is in turn sealed with respect to the heated plate and its edge by means of a peripherally extending seal when the press is closed. Apart from the extra work needed to produce the frame and the seal, the disadvantage of this approach is the fact that the membrane is subjected to high tensile forces in the region of the frame during the pressing operation. Tearing of the membrane during the pressing operation can cause damage to the elements to be laminated. During operation, the membrane is exposed to high temperature fluctuations, as a result of which it expands and contracts again with every work cycle. If the membrane is retained in the frame too loosely, there is a tendency for creases to form and it has to be tautened again. The job of subsequent tautening takes time because the frame has to be dismantled and then screwed back down again after tautening. 
       SUMMARY OF THE INVENTION 
       [0008]    The underlying objective of the invention is to propose a laminating machine which does not have the disadvantages outlined above. 
         [0009]    This objective is achieved by the invention due to the fact that the separating film is divided into sections, every section is held by retaining means exclusively at a single edge oriented transversely to the conveying path, the sections are not connected to one another and the retaining means can be moved along the conveying path by drive means. 
         [0010]    The advantages of this solution reside in the fact that the separating film conforms efficiently to the shape of the elements to be laminated because it lies loosely on the elements and the separating film is not stretched when the press is opened, which means that no force is transmitted by the separating film to the elements. Also as a result of the invention, a saving is made on components and the work involved in inter-connecting the sections of separating film which has to be carried out in the case of known machines is dispensed with. 
         [0011]    In one embodiment of the invention, the drive means have peripherally extending traction means, in particular chains. These traction means may be guided next to the heated plate and can be easily synchronized with the conveyor means. 
         [0012]    In another embodiment, the sections are guided in a circle by pulley means, and in a region where the sections are guided essentially vertically in a downward direction, guides in the form of brushes are provided, with bristles oriented towards at least one of the two surfaces of the sections. Without these guides, the sections of the separating film at the rear as viewed in the conveying direction, which are effectively held by the retaining means at the front end only, drop downwards in this region and prevent the elements from getting into the machine. 
         [0013]    In another embodiment, the retaining means have a C-shaped section, into the lengthways orifice of which a closed loop of the section extends, in which an anchoring bar is accommodated, the diameter of which is bigger than the width of the orifice. These retaining means are particularly simple and inexpensive to manufacture and also ensure that the sections of separating film are secured without creases. 
         [0014]    By virtue of another aspect of the invention, the objective is achieved due to the fact that the membrane lies against a peripherally extending peripheral surface of the top part facing the heated plate, the membrane can be fitted on the surface of the heated place or its edge in an arrangement which provides a seal with the region of its surface lying opposite the peripheral surface to prevent excessive external pressure and the membrane is connected to clamping means disposed on the top part. 
         [0015]    A major advantage of this solution resides in the fact that the membrane itself provides the seal on the heated plate forming a closed chamber in conjunction with it, with the separating film and optionally the conveying means inserted in between but without a frame incorporating an additional seal. During the pressing operation, therefore, few tensile forces act on the membrane because the zone in which the membrane is clamped is disposed on a level with the heated plate and not above the heated plate, as is the case with the prior art. The maximum tensile force in the membrane does not therefore occur until the press is opened, so that any tearing of the membrane which might occur does not cause damage to the laminated elements. Furthermore, a pre-defined clamping action can be obtained and maintained in the membrane by the clamping means, thereby avoiding excessive strain and creases in the membrane. 
         [0016]    In one embodiment, the clamping means are connected to the membrane by means of clamp mechanisms. The clamp mechanisms enable the membrane to be held and clamped without having to provide holes in its edge, which can tear open in a known manner. 
         [0017]    In another embodiment, every clamp mechanism comprises two clamping jaws which can be clamped to one another by screws and which have longitudinally disposed recesses and clamp the membrane between them, and a section deflecting the membrane is placed in at least one of the recesses. These inexpensive features enable the membrane to be secured particularly reliably without excessive strain, due to a strong pinching action. 
         [0018]    In another embodiment, the clamping means contain a mechanism which generates at least one force. Other than a mechanism which stores a force, such as a spring, a device such as a servo-motor may be used to generate a force, which maintains a constant clamping action even in the event of big changes to the length of the membrane. 
         [0019]    In another embodiment, the device generating the force is piston-cylinder unit. Such a unit saves on space and is particularly easy to operate. 
         [0020]    In another embodiment, finally, the device generating the force is connected to the membrane via traction means. This feature enables the device generating the force to be positioned where space is left available on the machine. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0021]    The invention will be explained in more detail below with reference to examples of embodiments illustrated in the appended drawings. 
           [0022]    Of these: 
           [0023]      FIG. 1  is a schematically illustrated longitudinal section through an embodiment of the machine proposed by the invention, 
           [0024]      FIG. 2  shows a detail from  FIG. 1  on a larger scale than in  FIG. 1 , 
           [0025]      FIG. 3  shows the same detail as  FIG. 2  but in a different operating mode, 
           [0026]      FIG. 4  shows an embodiment of the retaining means for the separating film, 
           [0027]      FIG. 5  shows an embodiment of the clamping means for the membrane and 
           [0028]      FIG. 6  shows a detail from a machine of the type known from the prior art. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0029]    Firstly, it should be pointed out that the same parts described in the different embodiments are denoted by the same reference numbers and the same component names and the disclosures made throughout the description can be transposed in terms of meaning to same parts bearing the same reference numbers or same component names, Furthermore, the positions chosen for the purposes of the description, such as top, bottom, side, etc. relate to the drawing specifically being described and can be transposed in terms of meaning to a new position when another position is being described. 
         [0030]    The embodiments illustrated as examples represent possible design variants of the machine and it should be pointed out at this stage that the invention is not specifically limited to the design variants specifically illustrated, and instead the individual design variants may be used in different combinations with one another and these possible variations lie within the reach of the person skilled in this technical field given the disclosed technical teaching. Accordingly, all conceivable design variants which can be obtained by combining individual details of the design variants described and illustrated are possible and fall within the scope of the invention. 
         [0031]    For the sake of good order, finally, it should be pointed out that, in order to provide a clearer understanding of the structure of the machine, it and its constituent parts are illustrated to a certain extent out of scale and/or on an enlarged scale and/or on a reduced scale. 
         [0032]      FIG. 1  is a highly simplified schematic diagram showing a view in section through the longitudinal axis of one embodiment of a machine  1  proposed by the invention. The machine is naturally mounted in a frame, although this is not illustrated in order to retain clarity. In the machine, board-shaped elements  4 , such as photovoltaic elements, are conveyed by a conveyor means  6  into a laminating station  2 , where the elements  4  are laminated under the effect of pressure and heat. The elements  4  are then conveyed by the conveyor means  6  in the direction of arrow  31  to a cooling station  3 , where they remain under pressure for a certain period of time. The laminating station  2  essentially comprises a heated plate  5  and a top part  8  which can be moved vertically with respect to it. Reference  12  denotes lifting drives, by means of which the top part  8  can be lowered and raised relative to the heated plate  5 . On its bottom face, the top part  8  bears a membrane  9 , which forms a closed chamber with the heated plate  5  which can be evacuated when the top part  8  is in the lowered state. When the chamber is evacuated, the elements  4  to be laminated are pressed by the membrane  9  against the heated plate  5  and any air inclusions which might still exist between the layers of elements  4  are removed and adhesive disposed between the layers of elements  4  is activated due to the pressure and/or the heat. A chamber  16  is formed in the top part  8  between the membrane  9  and an intermediate wall  14 , to which a negative pressure or a positive pressure can be applied in order either to raise the membrane  9  or push it down. A cavity  13  provided in the top part communicates with the chamber  16  via orifices  15  disposed in the intermediate wall  14 . 
         [0033]    The cooling station  3  essentially comprises a cooling plate  21  and a top part  28  which can be moved relative to it by means of lifting drives  22  and which, like the top part  8  of the laminating station  2 , likewise bears a membrane  29 . 
         [0034]    The conveyor means  6  in this example are provided in the form of rectangular sections  7  of flat, flexible material, which are retained both by the front edge in the conveying direction  31  and at the rear edge in the conveying direction by retaining means  23 . The retaining means  23  of two adjacent sections  7  of the conveyor means  6  are connected to one another by springs  24  so that the conveyor means  6  forms an endless loop guided around pulley blocks  18 , the re-circulating strand of which is guided underneath the cooling plate  21  and the heated plate  5 . 
         [0035]    A separating film  10  is laid without any tension on every element  4  or group of elements  4  at the intake end  30  into the machine  1 , on the one hand in order to protect the membrane  9  from soiling, for example due to adhesive spilling out of the elements  4 , and on the other hand to prevent any force, which might occur in particular when opening the laminating station  2 , from causing a relative movement between the individual layers of elements  4 . Every section of the separating film  10  is retained at a leading edge in the conveying direction  31 , oriented perpendicular to the conveying direction by retaining means  32 , in the form of a section in the embodiment illustrated as an example here, which is moved along the conveyor path by a traction means drive, for example a chain, disposed at both ends of the conveyor path. The retaining means  32  will be described in more detail below with reference to  FIG. 4 . The other edges of the sections  11  of separating film  10  are free, so that every section lies loosely on the elements  4  as it is conveyed through the machine  1 . This is of particular advantage on the run leading away from the laminating station  2  to the cooling station  3  because the elements  4  are still hot here and the adhesive joining the individual layers has not yet set and is therefore sticky and has a tendency to flow. If the separating film were tensioned on this run, as is the case with the machines known from the prior art mentioned above, this could lead to an undesired relative movement between the layers. The other advantage which this arrangement has over that known from the prior art is that a retaining means can be dispensed with on one side for each section of the separating film  10  and the springs connecting the sections can be dispensed with altogether. The traction means drive moving the retaining means  32  runs in a circle and the sections  11  of separating film  10  are guided by means of pulley blocks  17 , as a result of which they are fed above the top parts  28  respectively  8  of the cooling station  3  and laminating station  2  back to the intake end  30  of the machine  1 , on the left-hand side in  FIG. 1 . Guides may be provided above the machine (not illustrated), across which the free end  19  of every section of the separating film  10  is dragged. In order to prevent the sections  11  from simply falling in the region in which they are fed back in an essentially vertical direction with respect to the intake end  30 , guides are provided there in the form of elongate brushes  20  oriented in the conveying direction  31 . Rigid guides disposed on both faces of the separating film  10  would be inappropriate because they would then have to be separated from one another by a space to enable the retaining means  32  to pass through between them. Depending on the stiffness of the separating film  10 , the latter would be able to fold backwards and forwards between the guides in this space, thereby undesirably leading to bending. By contrast, the brushes on the two sides of the separating film  10  may reach as far as its top surface, because their bristles flex, thereby enabling the retaining means  32  to pass by without any difficulty. 
         [0036]    Although these are not illustrated, cleaning mechanisms may be provided on the run on which the conveyor means  6  and the separating film  10  are directed on leaving the cooling station  3  back to the intake end  30  of the machine  1 , by means of which any soiling such as adhesive residues may be removed from the conveyor means  6  and separating film  10 . As clearly illustrated in  FIG. 1 , the conveyor means  6  and the separating film  10  do not have to be of the same length, For example, the separating film  10  may perfectly easily have one or more sections than the conveyor means  6 . 
         [0037]      FIG. 2  is a detail from  FIG. 1  on a larger scale illustrating the laminating station  2  in the opened position, in other words with the top part  8  raised. The element  4  to be laminated is positioned on the heated plate  5  with a section  7  of the conveyor means disposed in between and covered by means of a section  11  of the separating film. As may be seen from this drawing, the retaining means  32  of section  11 , the retaining means  23  of section  7  and the springs  24  which interconnect the sections  23  are positioned so that they are clamped by the top part  8  as it is moved downwards. The retaining means  32  of section  11  and the retaining means  23  of section  7  are offset from one another in the conveying direction so that they do not lie on top of one another. The membrane  9  is guided around the edges  46  of the top part  8 , and a seal  34  may be inserted between the membrane  9  and the top part  8 . The edges of the membrane  9  are held by means of a clamp mechanism  33  which co-operates with a clamp drive  25 . The clamp drive  25  is advantageously provided in the form of a hydraulically or pneumatically driven piston-cylinder unit. In order to save on space, it is of advantage if the clamp drive  25  is disposed above on the top part  8  and its force is transmitted to the clamp mechanisms  33  via traction means  26 , for example Bowden cables fed by pulley blocks  27 , for example. The clamp drive  25  enables a pre-defined tension to be maintained in the membrane  9 . To this end, it may be connected to the control system of the machine. 
         [0038]      FIG. 3  illustrates the laminating station closed, in other words the top part  8  has been lowered by means of the lifting drive  12  until the peripherally extending bottom edge  46  presses the seal  34 , the membrane  9 , the section  11  of separating film and the section  7  of the conveyor means  6  in a sealing arrangement against the heated plate  5  and its edge lying at the same level. As a result, a closed chamber  35  is formed between the heated plate  5  and the membrane  9 , in which the elements  4  to be laminated are disposed. This chamber  35  is now evacuated so that gas is removed from around the elements  4  and the membrane  9  lies tightly on the elements  4  whilst section  11  of the separating film  10  lies loosely on top of them. 
         [0039]      FIG. 4  illustrates an example of an embodiment of the retaining means  32  of section  11  of the separating film  10  on a larger scale than in the preceding drawings. Section  11  of the separating film  10  is provided with a loop  36  at a single edge, which may be formed by folding it over and welding, adhering or stitching. This loop  36  is retained in the lengthways orifice of a C-shaped section  37  by means of an anchoring bar  38 , the diameter of which is bigger than the width of said orifice. The anchoring bar is advantageously of a tubular shape. 
         [0040]      FIG. 5  illustrates the clamp mechanism for the membrane  9  on an even larger scale than illustrated in  FIGS. 2 and 3  above. The membrane  9  is clamped between two clamping jaws  39  and  40 , of which clamping jaw  39  is connected to the traction means  26 , although this is not illustrated. In order to improve the hold of the membrane  9  in the clamp mechanism  33 , the clamping jaw  40  is also provided with longitudinally extending recesses in which the fitting sections  42  fit. The clamping jaw  39  also has recesses in the region of the fitting sections, so that the membrane  9  is bent round on clamping, which significantly increases friction resistance to being torn out. Screws  41  are used to clamp the clamping jaws  39  and  40  together. 
         [0041]      FIG. 6  is a schematic diagram showing a detail of a laminating press of the type known from the prior art. The membrane  9  is secured by means of a clamping frame  43  attached to the top part  8 . The clamping frame  43  is fixedly screwed to a flange of the top part by means of screws  45  which are inserted through holes provided in the membrane  9 . In order to seal the frame  43  on the heated plate  5  and its edge, it is necessary to provide a seal  44  in the clamping frame  43 . 
         [0000]    
       
         
               
             
               
               
             
           
               
                   
               
               
                 List of reference numbers 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 Machine 
               
               
                 2 
                 Laminating station 
               
               
                 3 
                 Cooling station 
               
               
                 4 
                 Board-shaped element 
               
               
                 5 
                 Heated plate 
               
               
                 6 
                 Conveyor means 
               
               
                 7 
                 Section of 6 
               
               
                 8 
                 Top part of 2 
               
               
                 9 
                 Membrane 
               
               
                 10 
                 Separating film 
               
               
                 11 
                 Section of 10 
               
               
                 12 
                 Lifting drive for 8 
               
               
                 13 
                 Cavity in 8 
               
               
                 14 
                 Intermediate wall of 8 
               
               
                 15 
                 Orifice in 14 
               
               
                 16 
                 Chamber 
               
               
                 17 
                 Pulley block for 10 
               
               
                 18 
                 Pulley block for 6 
               
               
                 19 
                 Free end of 10 
               
               
                 20 
                 Brushes 
               
               
                 21 
                 Cooling plate 
               
               
                 22 
                 Lifting drive for 28 
               
               
                 23 
                 Retaining means for 6 
               
               
                 24 
                 Spring 
               
               
                 25 
                 Clamp drive 
               
               
                 26 
                 Traction means 
               
               
                 27 
                 Pulley block 
               
               
                 28 
                 Top part of 3 
               
               
                 29 
                 Membrane 
               
               
                 30 
                 Intake end 
               
               
                 31 
                 Conveyor mechanism 
               
               
                 32 
                 Retaining means for 11 
               
               
                 33 
                 Clamp mechanism 
               
               
                 34 
                 Seal 
               
               
                 35 
                 Chamber 
               
               
                 36 
                 Loop 
               
               
                 37 
                 C-section 
               
               
                 38 
                 Bar 
               
               
                 39 
                 Clamping jaw 
               
               
                 40 
                 Clamping jaw 
               
               
                 41 
                 Screw 
               
               
                 42 
                 Fitting section 
               
               
                 43 
                 Clamping frame 
               
               
                 44 
                 Seal 
               
               
                 45 
                 Screw 
               
               
                 46 
                 Peripheral surface