Abstract:
A device and a method produce multi-layered wafer blocks filled with a spreadable mixture such as a cream. A wafer base sheet coated with a spreadable mixture is transported along a first conveyor surface to a stacking area. A wafer cover sheet is transported along a second conveyor surface to the same stacking area. The wafer cover sheet is laid flat on the coated side of the wafer base sheet in the stacking area, and then the wafer base sheet and the wafer cover sheet are transported away together. The wafer cover sheet and wafer base sheet are moved respectively in the stacking area at a speed that is different from zero at all moments.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to an apparatus and a method for producing multilayer wafer blocks filled with a coating mass such as, for example, a cream in which a wafer base sheet coated with a coating mass is transported along a first conveying surface to a stacking area, a wafer cover sheet is transported along a second conveying surface to the same stacking area, in the stacking area the wafer cover sheet is supplied to the coated side of the wafer base sheet and placed flat thereon and then the wafer base sheet and the wafer cover sheet are removed jointly. 
     Such apparatuses have been known for a fairly long time and are used in various embodiments. 
     For example, apparatuses and methods are known in which wafer sheets, in particular crispy brittle flat wafers, are baked in tong automatic baking machines where the wafer sheets are baked at high pressure in closed and locked wafer tongs and then cooled. The wafer sheets are preferably thin-walled crispy brittle wafers having a size of up to 400×800 mm. Flat wafers are for example used to form wafer finger blocks which have a layered structure, for example, comprising alternate layers of wafer sheets and cream fillings. Wafer finger blocks can, for example, consist of two wafer sheets with an interposed cream layer, of two wafer sheets with a plurality of interposed cream layers but also can consist of a structure of more than two wafer sheet layers, where in each case one or more cream layers are disposed between two wafer sheets. In most cases the wafer finger blocks have respectively one wafer sheet on the two exterior surfaces. The terminating layers are therefore designed as wafer sheets. 
     For this purpose a wafer base sheet is transported on a conveying surface to a coating machine. The coating machine applies a layer of a coating mass, for example, a cream, and transports the coated wafer base sheet further. Parallel to this, flat wafers are removed from the wafer baking oven, which are transported along a second conveying surface but not coated. A so-called sandwich former is used for combining the wafer cover sheet and the coated wafer base sheet. For this purpose, sandwich formers corresponding to the prior art stop the base sheet at a stop, supply the wafer cover sheet in this rest position and place it flat on the cream layer or on the coated side of the wafer base sheet. As a result of the consistency of the cream, the wafer cover sheet adheres to the cream and subsequently to the wafer base sheet. The stop is then removed and the finished sandwich consisting of a wafer cover sheet, a cream layer and a wafer base sheet can be transported further. 
     A disadvantage with this design is that the wafer flow cannot be conveyed continuously but must be stopped briefly for joining and stacking the wafer sheets. Modern wafer baking ovens convey up to 80 wafer sheets per minute. In particular, when combining two wafer baking ovens which produce wafer sheets in parallel, it is accordingly necessary to provide a sandwich forming device which can process a high throughput. Due to the delay caused by the braking and restarting of the individual wafer sheets, sandwich formers corresponding to the prior art are restricted in their conveying capacity. This results from the fact that the crispy brittle wafers cannot be accelerated and retarded arbitrarily sharply since the wafer sheets could not withstand the higher acceleration forces due to the low mechanical resistance. The result of a too-severe acceleration would be broken wafers which must be discarded as rejects. 
     In order to minimise rejects, it is further necessary to keep the edge regions of the wafer blocks which have defects due to production tolerances as small as possible. For this reason it is important to place the wafer sheets, in particular the wafer base sheet and the wafer cover sheet as accurately as possible above one another. Wafer sheets which do not lie exactly congruently on one another but are slightly laterally displaced must be calibrated at the edge regions. This is accomplished by trimming the edge regions. Accordingly the more accurately the wafer sheets can be placed one above the other and the fewer defects the edges of the wafer sheets have as a result of any conveying and stop devices, the less they need to be trimmed and the fewer rejects are produced. 
     BRIEF SUMMARY OF THE INVENTION 
     It is now the object of the present invention to provide a method and an apparatus for producing multilayer wafer blocks filled with a coating mass, where a high throughput is achieved, at the same time the wafer sheets are positioned exactly above one another, the dimensional tolerances of the finished product are adhered to as exactly as possible, the wafer sheets are processed as gently as possible and where the apparatus is favourable to produce, favourable to maintain and easy to operate. 
     The object according to the invention is solved inter alia whereby the wafer cover sheet and the wafer base sheet in the stacking area are each moved at a speed which is non-zero at each time point. It is furthermore consistent with the inventive idea that the wafer cover sheet on contact with the coating mass of the wafer base sheet, and the wafer base sheet have substantially the same speed in the conveying direction, that the wafer cover sheet is stopped by a stopper mounted upstream of the stacking area in the conveying direction and is transported at the desired entry time by one or more transport devices along the second conveying surface in the direction of the stacking area and that the wafer cover sheet is transported by one or more positioning elements in the conveying direction in the direction of the stacking are, in particular is pushed. Furthermore, the invention is characterised in that the wafer base sheet is transported by a first transport device in the direction of the stacking area, wherein the transport speed of the first transport device in the conveying direction is lower than the transport speed of the positioning element, that the wafer base sheet is pushed by the positioning elements into the stacking area, that the wafer base sheet is transported along a first conveying surface and the wafer cover sheet is transported along a second conveying surface by the positioning elements into the stacking area and that the positioning elements grip behind the wafer cover sheet and behind the wafer base sheet and thereby centre the two wafer sheets above one another and push in the conveying direction. For solving the object according to the invention, the invention further relates to an apparatus for producing multilayer wafer blocks filled with a coating mass such as, for example, a cream, comprising a first conveying surface for transporting a wafer base sheet to the stacking area, a second conveying surface for transporting a wafer cover sheet to the stacking area, and at least one positioning element for the exact positioning of the wafer cover sheet above and/or on the wafer base sheet, wherein the positioning element is disposed movably in the conveying direction. The apparatus is positively characterised in that the positioning elements are movable at least in sections along the second conveying surface, that the positioning elements are movable at least in sections along the first conveying surface, that the positioning elements are driven by a belt running along a first contour and that the positioning elements are movable initially in the conveying direction along the second conveying surface and thereafter along the first conveying surface. Further features of the invention are that a run-in area is provided in which the first and the second conveying surface are configured to approach one another, that that the positioning elements in the run-in area are movable along the second conveying surface and in the stacking area along the first conveying surface and that the positioning elements in the stacking area are disposed to run substantially normal to the first conveying surface. It can further be provided according to the invention that a fourth transport device is provided along the second conveying surface which is preferably configured as a belt conveyor, that a first transport device is provided along the first conveying surface which is preferably configured as a belt conveyor, that the first and the second conveying surface are combined in the stacking area, that separating elements running along the second conveying surface and disposed in the run-in area are provided, which are configured to run asymptotically or in a wedge shape in the direction of the first conveying surface. In addition, further features of the invention can be that openings are disposed between the separating elements, that the positioning elements have extensions which project in the run-in area through the openings disposed between the separating elements in the direction of the first conveying surface and that the wafer base sheet is transported by a first transport device in the direction of the stacking area, where the transport speed of the first transport device in the conveying direction is greater than the speed of the positioning element and that the wafer cover sheet is transported by a fourth transport device in the direction of the stacking area, where the transport speed of the fourth transport device in the conveying direction is greater than the speed of the positioning element and that both wafer sheets are pushed towards the positioning element, where the speed of the wafer sheets is determined by the speed of the positioning element. 
     The invention will be explained in detail in the following with reference to selected exemplary embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         FIG. 1  is a diagrammatic, side view of an apparatus for producing multilayer blocks according to the invention; 
         FIG. 2  is a diagrammatic, side view of a second embodiment of the apparatus for producing multilayer blocks according to the invention; 
         FIG. 3  is a diagrammatic, perspective view of a part of the apparatus for producing multilayer blocks according to the invention; 
         FIG. 4  is a diagrammatic, side view of a link of the apparatus for producing multilayer blocks according to the invention; 
         FIG. 5  is a diagrammatic, side view of the link from the opposite side; and 
         FIG. 6  is a diagrammatic, perspective view of a third embodiment of the apparatus for producing multilayer blocks according to the invention. 
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG. 1  shows an apparatus according to the invention for producing multilayer wafer blocks filled with a coating mass such as, for example, a cream, comprising a first conveying surface  4  which in the present embodiment comprises a first transport device  11  and a second transport device  12 . Furthermore there is provided a second conveying surface  6  which comprises a third transport device  13  and a fourth transport device  14 . The second conveying surface comprises an elevated section running substantially parallel to the first conveying surface, a sloping section running substantially from the elevated section to the stacking area  5  and a run-in area  18  which approaches the first conveying surface running substantially asymptotically or in a wedge shape to the second conveying surface. Furthermore, a fifth transport device  15  is provided. This comprises positioning elements  10  which are disposed substantially movably along the second conveying surface. Further, a detector  16  is provided in the region of the first conveying surface  4 . This detects the time of entry of a wafer sheet, in particular of the wafer base sheet  2 , into the apparatus according to the invention and/or to the first transport device  11 . A stopper  9  is provided in the area of the second conveying surface  6 . This comprises a retaining element such as, for example, a brush which hinders the further movement of a wafer sheet, in particular a wafer cover sheet  3 . The stopper can be actuated by a signal coming from a control unit  17 . The retaining element is thereby moved and the movement of the wafer sheet released. Subsequently the wafer sheet is then conveyed further in the direction of the stacking area  5 . 
     Typically wafers coming from a wafer baking oven are transferred to a cooling device. The wafers are subsequently supplied to the first conveying surface  4  and the second conveying surface  6 . A device is provided along the first conveying surface  4  which applies a layer consisting of a coating mass, a cream or similar to wafer sheets which are conveyed past. Examples of such devices are contact coating devices in which viscous masses or a cream is applied by means of a roller device, film application devices or also pressure head devices in which the cream is sprayed on via nozzle heads. In order to make the application of the coating mass as efficient as possible, the application is carried out continuously. In order to minimise wastage here, the individual wafer sheets are arranged flat edge to edge. This substantially continuous band of coated wafer sheets which will subsequently be designated as wafer base sheets  2  is transferred via the second transport device  12  to the first transport device  11 . In this case, the first transport device  11  has a higher transport speed than the second transport device  12 . As a result, the individual wafer sheets are pulled apart and transported spaced apart from one another along the first conveying surface in the direction of the stacking area  5 . 
     Parallel to this, uncoated wafer sheets which are subsequently designated as wafer cover sheets  3  are transported along the second conveying surface  6  in the conveying direction  7 . In this case, the wafer cover sheets  3  are transferred from a third transport device  13  to a fourth transport device  14 . As mentioned initially, this has a stopper  9 . At a certain time, the stopper opens, with the result that the wafer cover sheet  3  is conveyed further in the direction of the stacking area  8 . Here the wafer sheet impacts against the nearest positioning element  10  which is moved along the second conveying surface  6 . However, the movement of the positioning element  10  is slower than the transport speed of the wafer cover sheet with the result that the sheet is stopped by the positioning element. If the wafer sheet is now in contact with the rear side of the positioning element  10 , the speed of the wafer cover sheet is determined by the speed of the positioning element. The positioning element  10  is accordingly disposed upstream of the wafer sheet in the conveying direction and retards the wafer sheet. 
     The positioning elements are guided and driven circumferentially by a fifth transport device  15 . The fifth transport device  15  has a plurality of positioning elements  10 . During further movement of the wafer cover sheet  3  along the second conveying surface  6 , the positioning elements  10  located along a belt also move further, with the result that after a certain distance a second positioning element follows behind the wafer cover sheet in the conveying direction. This is preferably disposed at a distance from the wafer sheet and moves at the same speed as the front positioning element. If the wafer sheet is conveyed further into the run-in region  18 , it comes in contact with a braking element  19 . This brakes the movement of the wafer sheet and consequently brings about a change of stop of the front edge of the wafer sheet on the front positioning element to a stop with the rear edge of the wafer cover sheet at the rear following positioning element in the conveying direction. Now the wafer cover sheet is pushed by the fifth transport device  15 , in particular by the positioning element  10  which follows the wafer sheet. 
     At the same time, a coated wafer base sheet is conveyed along the first conveying surface  4 . This has a layer of a coating mass which in the present configuration points upwards, i.e. in the direction of the second conveying surface  6 . On the underside the wafer base sheet  2  has no coating mass layer and thus lies directly on the first transport device  11 . The two wafer sheets (wafer base sheet  2  and wafer cover sheet  3 ) are transported in such a manner that they are supplied to the run-in area  18  and the stacking area  5  approximately at the same time. The synchronisation of the speeds or the positions on the respective transport device is accomplished by the detector  16  and the stopper  9 . If the wafer base sheet  2  is located in the run-in area  18 , the wafer cover sheet  3  lying thereabove is pushed by the positioning elements  10  of the fifth transport device. Separating elements  20  are provided in the run-in area which extend in a finger shape or in a strip shape running along the second conveying surface in the direction of the first conveying surface. The fingers have intermediate spaces which extend substantially along the conveying direction. The positioning elements  10  pushing the wafer cover sheet  3  have extensions  21  which are guided through between the separating elements  20  and during movement also move the wafer base sheet  2 . This movement is also accomplished as a pushing movement in which the extensions  21  of the positioning elements  10  are in contact with the rear edge of the wafer base sheet  2  and push the wafer base sheet in the direction of the stacking area  5 . In the run-in area the positioning elements are moved in such a manner that the wafer base sheet  2  and the wafer cover sheet  3  are pushed by a substantially perpendicular edge or perpendicular surface. As a result of this perpendicular straight guidance of the positioning elements  10 , the two moving wafer sheets  2 ,  3  are centered and positioned exactly above one another. The separating elements  20  end at the end of the run-in area  18 . The two superposed wafer sheets are no longer separated by the separating elements  20  during conveyance into the stacking area  15  and thus lie one on top of the other. The approach of the two sheets is accomplished on the one hand by the force of gravity and/or on the other hand by the wedge-shaped convergence of the first conveying surface  4  and the second conveying surface  6 . The sheets now lying one on top of the other form a wafer block which is formed from two wafer sheets with an interposed layer of a coating mass. 
       FIG. 2  shows a similar configuration to  FIG. 1  in which again a first transport device  11  is provided. This can be configured, for example, as a conveyor roller arrangement, belt or band conveyor. Also provided is the fourth transport device  14  in the course of which the stopper  9  is provided. The stopper  9  in the same way as the detector  16  is connected to a control unit  17  not shown and is used to synchronise the two incoming wafer sheets which should be supplied substantially temporally in parallel to the stacking area  5 . The positioning elements  10  are driven by a belt  23  and guided by a link  24 . The link controls the position of the positioning elements in various regions relative to the conveying surfaces and to the wafer sheets. In particular in the run-in area  18  the positioning elements are guided in such a manner that the wafer base sheet  2  and the wafer cover sheet  3  are moved exactly above one another. The individual wafer sheets  2 ,  3  and subsequently the combined wafer block  1  are pushed in the run-in area  18  and at the beginning of the stacking area  5 . This has the result that the positioning element  10  presses onto the rear edge of the wafer sheets. After or during the formation of the wafer block from the two wafer sheets  2 ,  3 , the positioning element  10  is withdrawn from the link control and thus loses contact with the wafer block. The wafer block itself is on the one hand conveyed further by inertia and on the other hand by the first transport device and a transport device located downstream of the first transport device. Subsequently the withdrawn positioning element is guided away substantially upwards via a deflecting roller in order to be guided to the second conveying surface again following the belt. 
     This withdrawal or backward folding of the positioning element is necessary since the rear edge of the wafer block is thereby protected from damage. 
       FIG. 3  shows an oblique view of a part of the apparatus according to the invention. Shown again are the first transport device  11 , the fourth transport device  14  and the fifth transport device  15 . This in turn has positioning elements  10  which are moved along a belt  23 . The positioning elements  10  further have extensions  21  which in the run-in area  18  grip through the openings  22  between the separating elements  20 . The separating elements  20  run substantially in a strip shape along the conveying direction and along the second conveying surface  6 . Furthermore, the link  24  is provided for controlling the movement of the positioning elements  10 . 
       FIG. 4  shows a detailed view of the guidance of the positioning elements  10  in the rigidly disposed link  24  with respect to the machine frame. The positioning elements  10  each have a cam  25  and a guide element  26 . The movement of the individual elements is accomplished by a driven belt or a driven band  23 . The guide element  26  is guided along this band  23  following the first contour  27 . 
     The respective positioning element is disposed rotatably on the guide element  26 . Further, the cam  25  which scans the second contour  28  is rigidly connected to the positioning element. During the movement of the positioning element  10  along the first contour  27 , the cam  25  now leaves the second contour  28 . Since the first contour and the second contour do not run parallel in all areas, a rotation of the positioning elements  10  with respect to the band  23  or the first contour  27  occurs. In the present form, the cam  25  is designed as a lever which has a roller  31  on the side located far from the connection to the positioning element  10 . This roller  31  engages in the leading form  29  which is configured to follow the second contour  28 . The lever is rigidly connected to the positioning element  10  and is disposed rotatably about the axis of rotation  30 . 
       FIG. 5  shows the same link but viewed from the other side. The positioning elements  10 , the cams  25 , the guide elements  26 , the first contour  27 , the second contour  28 , the leading form  29 , the axes of rotation  30  and the roller  31  can again be seen. 
       FIG. 6  shows an oblique view of one embodiment of the present apparatus according to the invention. The view shows the opposite side of the arrangement to that shown in  FIG. 3 . The stopper  9 , the positioning elements  10 , a first transport device  11 , a fourth transport device  14 , a fifth transport device  15 , the run-in area  18  with the strip-shaped separating elements  20  and the openings  22  disposed between the separating elements  20  are again shown. The separating elements  20  here have free ends which point in the direction of the stacking area  5 . The openings  22  are open in the direction of the stacking area  5 . The extensions of the positioning elements  10  move, guided by the link  24  and driven by the band  23 , at least partially along the second conveying surface  6 . The extensions  21  thereby engage in the openings  22  of the separating elements  20  and close them off similarly to a comb. To this end the extensions  21  project at least partially through the openings  22  in the direction of the first conveying surface  4 . Due to the projecting regions, the positioning elements  10  can also move the wafer base sheet transported on the first conveying surface. The bands  23  in this embodiment are designed as toothed belts, driven by a drive and deflected by a plurality of deflecting rollers. The band  23  is designed to be circumferentially closed. Furthermore, the fourth transport device  14  and the first transport device  11  comprise closed strip-shaped movement means. These are also driven and deflected around deflecting rollers. 
     As noted in the description to  FIGS. 1 to 6 , the apparatus according to the invention is adapted to place wafer sheets continuously on one another in order to thus form wafer blocks. For this purpose a plurality of wafer sheets are supplied one after the other, via a first conveying surface  4  and a second conveying surface  6  to the stacking area  5 . Apart from some short interruption of the movement by the stopper  9  along the second conveying surface  6  which serves to exactly synchronise the two wafer sheets to the combined, both the wafer cover sheet and the wafer base sheet are moved continuously. In particular the bringing together and the exact placement of the two wafer block components one on top of the other takes place in a continuous moving process. In order to improve the accuracy of fit of the two sheets to be placed one on top of the other, positioning elements  10  are provided. In the embodiments described these positioning elements  10  push a pair comprising a wafer cover sheet and a wafer base sheet and thus act as a co-moving pushing stop. 
     It is however completely consistent with the inventive idea that the positioning elements  10  in the stacking area  5  do not have a pushing but a braking effect. In this case, the speed of the positioning elements  10  is lower than the conveying speed of the two wafer sheets. In the run-in area  18  and moreover in the stacking area  5 , according to this embodiment not shown the wafer cover sheet and the wafer base sheet are pushed by the transport devices onto the moving stop, i.e. the positioning element  10 . Since the speed of the positioning element is lower, both sheets arrive with the front edge at the positioning elements  10 . The transport devices thus have a slippage with respect to the respective wafer sheets. In particular for conveyance of the wafer base sheet, the first transport device  11  is adapted to the positioning element  10  serving as a stop. In particular the fourth transport device  14  is provided for conveyance of the wafer cover sheet to the positioning element  10 . In the embodiment just described but not shown, the braking element  19  is omitted. 
     The braking element  19  in  FIG. 1  and  FIG. 2  is designed as a resiliently pre-stressed element which is pre-stressed with a certain spring force against at least one separating element  20 . If a wafer sheet is now pushed between the braking element and the separating element, the sheet is braked due to the friction. Other possibilities for braking the wafer sheet are braked rollers, rolls, friction surfaces etc. 
     The apparatus according to the invention and the method according to the invention enable the continuous combining and forming of wafer blocks at very high throughput. Thus, for example, up to 100 or more wafer blocks per minute can be formed. As a result of the continuous formation of the wafer blocks and the further advantages of the apparatus according to the invention, the quality achieved and the associated wastage is furthermore optimised. 
     At this point, it should be noted that the invention is not restricted to the exemplary embodiments listed. Further embodiments corresponding to the inventive idea are obtained from combinations of individual or several features which can be deduced from the entire description, the figures and/or the claims. Consequently embodiments are also disclosed which consist of combinations of features stemming from different exemplary embodiments. The figures are at least partially schematic views where the dimensions and proportions can deviation from other embodiment or features not depicted in the drawings and from real embodiments. 
     REFERENCE LIST 
     
         
           1  Wafer block 
           2  Wafer base sheet 
           3  Wafer cover sheet 
           4  First conveying surface 
           5  Stacking area 
           6  Second conveying surface 
           7  Conveying direction 
         
           8 
         
           9  Stopper 
           10  Positioning element 
           11  First transport device 
           12  Second transport device 
           13  Third transport device 
           14  Fourth transport device 
           15  Fifth transport device 
           16  Detector 
           17  Control unit 
           18  Run-in area 
           19  Braking element 
           20  Separating element 
           21  Extensions (of the positioning elements) 
           22  Openings (separating elements) 
           23  Band (positioning elements) 
           24  Link 
           25  Cam 
           26  Guide element 
           27  First contour 
           28  Second contour 
           29  Leading form 
           30  Axis of rotation of cam 
           31  Roller