Abstract:
The invention concerns a device for stacking flat products, in particular, folding boxes, comprising a stack shaft for receiving the flat products which comprises an inlet opening opposite to an impinging surface, and is provided with guiding element disposed in side flanks, which guide the flat products in the form of a stack, wherein each side flank comprises a transport means for upward and downward vertical movement of a tray which projects into the stack shaft and which carries the flat products.

Description:
BACKGROUND OF THE INVENTION 
   The invention concerns a device for stacking flat products, in particular, folding boxes, comprising a stack shaft for receiving the flat products, which has an inlet opening opposite to an impinging surface, and guiding elements disposed in side flanks, which guide the stack of flat products. 
   Folding box production plants conventionally terminate in a stack shaft in which the produced folding boxes are stacked into piles and from which the piles are removed. Due to great differences in shapes, sizes and folds of the folding boxes, the folding boxes must be stacked either in an upward or downward direction. Folding boxes with a relatively flat and smooth upper side are usually down-stacked. This is not possible if the upper side of the folding box is not flat or the blank has steps. A subsequent folding box could be arrested by one of these steps and become jammed. For this reason, folding boxes of this type are generally up-stacked, wherein the folding boxes are sequentially pushed below the previously deposited folding box (up-stacking). 
   In case of product change between two folding boxes, the stacking type may also have to be changed. Towards this end, the stack shaft must also be replaced to permit stacking in the other direction. This is time and labor consuming and therefore expensive. 
   It is the underlying purpose of the invention to design a device for stacking flat products of the above-mentioned type which is suited for both stacking directions. 
   SUMMARY OF THE INVENTION 
   This object is achieved in accordance with the invention with a device of the above-mentioned type in that a transport means is provided in at least one side flank for upward and downward vertical movement of a tray which projects into the stack shaft and carries flat products. 
   In the inventive stacking device, the tray for transporting the flat products can be moved in the upward and downward directions. For down-stacking, the stack is formed on the two trays, each provided at one side flank. The lowermost flat product of the stack is supported on these trays and the following products are disposed onto this stack, while the trays move downwards. For up-stacking, a flat product is pushed below the stack, and the product pile is lifted by the tray as soon as the required number of products has been stacked. 
   In a further development, the tray can be continuously and/or gradually moved, in particular, at different speeds. If the trays are continuously lowered, the stack can be formed by sequentially deposited flat products in correspondence with the lowering speed. In case of gradual lowering of the tray, the flat products may also be supplied discontinuously without disturbing the operation. As soon as the stack is completed, the trays can be moved at a higher speed to remove the stack from the stacking zone and to supply two new trays for forming a new stack. The supply of new flat products must therefore only be interrupted for a very short time. 
   The transport means preferably comprises two neighboring chains which drive a carriage which can be moved on a guiding rail. It is also feasible to use belts or other circulating transport means instead of the chains, which can be precisely controlled and can transfer supporting forces. The carriage connected to the chains bears one tray on which the stack is supported. 
   To also facilitate stacking of flat products, in particular, substantially wedge-shaped folding boxes, e.g. having a thicker front region and a thinner rear end, the tray is pivotably disposed on the carriage in accordance with the invention. In this fashion, the bottom of the stack can be inclined while the stack is being lowered to provide sufficient space for the thicker sections of the flat products. The flat products can still be disposed in a horizontal direction on top of the growing stack. 
   In a further development, a pivot lever is mounted to the tray via which the tray can be pivoted about a pivot bearing. This lever pivots the bottom either once or gradually to form a prisma-shaped shaft with inclined bottom for receiving the flat products. 
   For pivoting in accordance with the invention, the pivot lever comprises a feeler roller on its free end, wherein the feeler roller is deflected by a cam, a ramp, a forced guidance or the like. When the tray moves in a vertical direction, the feeler roller of the pivot lever moves along and is displaced out of its rest position by the cam or ramp to thereby pivot the pivot lever. The tray is thereby pivoted from its rest position into an inclined position and the bottom of the stack shaft is tilted. Pivoting can also be effected via a separate drive. 
   To prevent inadvertent tilting of the tray from its rest position, the tray is spring-loaded in the direction of its horizontal rest location. This spring ensures that the tray always assumes its horizontal rest position if the pivot lever is not deflected via the cam, ramp or the like, such that the product stack is located vertically above the tray. 
   To facilitate adjustment of the inventive device to wedge-shaped and also uniformly shaped products, the cam or ramp can be moved into or be at least partially retracted from the path of motion of the feeler roller. If uniform products are to be disposed, which do not require pivoting of the tray, the cam or ramp is displaced to such an extent that the feeler roller is not engaged. The pivot lever is thereby not pivoted and the trays remain in their horizontal rest position. If the cam or ramp is still more or less in the path of motion of the feeler roller, i.e. in the engagement region of the feeler roller, the pivot lever is more or less pivoted thereby inclining the trays. 
   The inclination of the cam or ramp can be adjusted to be able to stack products of different wedge shapes in a likewise proper fashion. This means that the trays can be tilted to a greater or lesser extent for a given advance. This permits depositing of both products with a slight wedge shape and products with a distinct wedge shape. 
   A sensor is preferably provided for detecting the stack height, wherein the sensor signal controls the transport means. The trays can thereby be gradually lowered by an amount which corresponds to the height of the product previously disposed onto the stack. 
   In one embodiment, the trays support the flat product in the region of its opposite side edges. The flat product and thereby the entire stack are not supported along the full surface but merely in the region of the right and left side edges. This support is dimensioned to safely hold the product such that it does not sag. The mere lateral support has the substantial advantage that the finished pile can be grasped on its lower side by a removal device without having to previously remove the pile from the trays. 
   The lower end of the stack shaft preferably comprises a disposal device for the product pile, wherein the trays pass the disposal device without colliding. The trays deposit the finished stack on the disposal device to be grasped and delivered by a gripper device. The stack is thereby always guided by corresponding guiding elements which secure it from being displaced until it is delivered. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     Further advantages, features and details of the invention can be extracted from the dependent claims and the following description which describes in detail a particularly preferred embodiment with reference to the drawing. The features shown in the drawing and mentioned in the description and claims may be essential to the invention either individually or in arbitrary combination. 
       FIG. 1  shows a side view of a removal unit comprising a stacking device; 
       FIG. 2  shows a view in the direction of the arrow II in accordance with  FIG. 1  onto a part of the stacking device; 
       FIGS. 3   a  to  3   d  schematically show the up-stacking process; 
       FIG. 4  schematically shows tilting of a tray, 
       FIG. 5  shows the tray in the tilted and horizontal positions; and 
       FIG. 6  shows a view in the direction of arrow VI in accordance with  FIG. 5 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a delivery belt designated with reference numeral  10  which circulates in a device (designated in total with  12 ) for transporting flat products  14 , in particular, folding boxes  16 . The individual folding boxes  16  are transported into a stack shaft  20  at high speed in the transport direction (arrow  18 ). The front edges  22  of the folding boxes  16  strike an impinging surface  24  and are thereby decelerated.  FIG. 1  shows a device  12  for down-stacking, i.e. a stack  26  is formed by down-stacking superposed folding boxes  16 . This stack  26  is laterally guided by guiding elements  28 , as is described in detail below. The stack  26  is formed on a tray  30  and is supported thereby. The tray  30  is located on a transport means  32 , schematically shown in  FIG. 1  and in detail in  FIG. 2 . This transport means  32  has a circulating chain  34  with carriage  36  and tray  30  mounted thereto.  FIG. 2  shows different positions of the carriage  36  which is guided by the chain  34  about a lower deflecting roller  38 . A total of three carriages  36  of this type are mounted to the chain  34  at regular intervals. The tray  30  is located on the carriage  36  and supports the stack  26 . The carriage  36  is held and guided on its longitudinal sides by two chains  34  which are housed in the guiding elements  28 . 
     FIG. 2  shows both stacking types, i.e. down-stacking  39  and up-stacking  41 . The lower stack  26  is formed by transporting folding boxes  16  through an inlet opening  40  into the stack shaft  20  and disposing them on top of the stack  26 . The stack  26  is then lowered by downward displacement of the carriage  34  by the thickness of the folding box  16  such that the next folding box  16  can again be deposited on top of the stack  26 . When the stack  26  has reached the maximum stack height and the pile  42  is finished, it is moved into its lowermost position by lowering the carriage  36  to permit removal of the pile  42  from the stack shaft. The pile  42  is thereby supported on a support  44  such that the carriage  36  can be moved further, and the pile  42  is removed from the tray  30 . The next carriage  36  arrives at an increased speed from above and is positioned in the region of the inlet opening such that the first folding box  16  of the new stack  26  can be disposed on its tray  30 . The carriage  36  then moves downwards with reduced speed, controlled by sensors of a light barrier. 
   During up-stacking  41 , the stack  26 ′ is formed without a tray  30  since the subsequent folding boxes  16  are always disposed at the bottom of the stack  26 ′. In contrast to  FIG. 1 , the delivery belt  10  delivering the folding box  16  thereby extends to the region of the impinging surface  24 . This ensures that the folding box  16  is safely pushed below the stack  26 ′. The two trays  30  are located on the side next to the delivery belt  10 , i.e. the delivery belt  20  is positioned between the trays  30 . The trays  30  are necessary for up-stacking  41  only for delivering the finished stack  26 ′ and not, as is the case for down-stacking  39 , for the stacking process itself. 
   The transport means  32  comprises a second chain (not shown) with a holding-down means  76  mounted thereto which is supported on the stack  26 ′ ( FIG. 3 ). As soon as a folding box  16  has been pushed below the pile  26 ′, the holding-down means  76  is lifted by the thickness of the folding box  16  through transport of the second chain (see  FIGS. 3   a  and  3   b ). 
   When the stack  26 ′ has reached its maximum stack height, the pile  42 ′ is moved upwards through movement of the carriage  36  with tray  30  from a lower, inoperative position up to the finished pile  42 ′ ( FIG. 3   c ) and lifts the stack at high speed until the stacks abuts against a stop  46  ( FIG. 3   d ). As soon as the pile  42 ′ has been removed from the stacking region, a new stack  26 ′ is formed. The next holding down means  76 ′ is previously moved, at high speed, from its inoperative position below the delivery belt  10  into a position above the delivery belt  10  such that the first folding box  16  can be pushed below this holding-down means  76 ′. The holding-down means  76 ′ is then gradually lifted by the thickness of the supplied folding boxes  16 , controlled by a sensor, and the next stack  26 ′ is formed. 
   In the meantime, the finished pile  42 ′ is fetched by a suitable gripper in the upper position such that the tray  30  is again free. The carriage  36  and the free tray are then moved into an initial position such that the next tray  30  is waiting at a separation below the forming stack  26 ′ ( FIGS. 3   a  and  3   b ). 
   The holding-down means can also be used for down-stacking  39  by moving it to the forming stack  26  at a separation therefrom, leaving a gap for pushing the folding box  16  between stack  26  and holding-down means. This may be advantageous for folding boxes with extremely irregular thickness. 
   In any event, the carriage  36  can be moved in a downward direction, i.e. for down-stacking  39 , and also in an upward direction for up-stacking  41 . When changing the folding box  16 , change of the stack shaft  20  which stacks the other folding box  16  in the other stacking mode is no longer required. Both stacking modes can be carried out in the same stack shaft  20 . 
     FIGS. 4 ,  5 , and  6  show the carriage  36  and the tray  30  in a horizontal position and also in a pivoted position  30 ″. Towards this end, the tray  30  is mounted to a bearing block  48  which can be pivoted about a pivot bearing  50 . A pivot lever  52  is moreover fixed to the bearing block  48 , and can also be pivoted together with the bearing block  48  about the pivot bearing  50 . Pivoting is effected by a shaft  54  which penetrates through the bearing block  48 . 
   The free end  56  of the pivot lever  52  has a hexagon bolt  58  with a feeler roller  60 , wherein the hexagon bolt  58  and feeler roller  60  penetrate through a kidney-shaped opening  62  in a side wall  64  of the carriage  36 .  FIGS. 4 ,  5 , and  6  also show that the carriage  36  is mounted to the chain  34 . 
   When the carriage  36  is gradually moved downwards ( FIG. 4 ), the feeler roller  60  abuts an inclined surface  66  of a ramp  68  and is gradually deflected to the left from this ramp  68  (shown by a plurality of feeler roller  60  positions). Deflection of the feeler roller  60  to the left pivots the pivot lever  52  in a counter-clockwise direction (see  FIGS. 4 and 5 ). The pivoted position is shown by reference numerals with double primes. Pivoting of the pivot lever  52 ″ also pivots the bearing block  48 ″ thereby tilting the tray  30 ″. Folding boxes  16  having a substantially wedge-shaped cross-section can thereby be disposed on the tray  30 ″. 
   The inclined surface  66  merges into a straight surface  70  after reaching the maximum inclination of the pivot lever  52  (15°). At the lower end of the ramp  68 , the pivot lever  52  is pivoted by a correspondingly receding inclined surface (not shown) back into its initial position in which the tray  30  re-assumes its horizontal position. 
   The horizontal position represents a stable rest position for the tray  30 . In this position, the tray  30  is held by a tension spring  72  which is mounted at one side to the side wall  64  and, on the other side, to a holder on the lower side of the tray  30 . The tray  30  is held in the horizontal rest position via the tension spring  72  and abuts a stop  74 . The tray  30  is lifted from this stop  74  only when the pivot lever  52  is deflected, i.e. is actively pivoted. Stacking of folding boxes  16  having a substantially wedge-shaped cross-section is thereby facilitated.