Abstract:
The invention concerns a device for stacking flat products, in particular, folding boxes, comprising a lower and upper transport unit, wherein the flat products are transported between the transport units in the direction of a stack shaft, each transport unit comprising at least one conveyor belt, wherein the position of the front end, facing the stack shaft, of at least one conveyor belt can be adjusted and changed.

Description:
BACKGROUND OF THE INVENTION 
   The invention concerns a device for stacking flat products, in particular, folding boxes, comprising a lower and an upper transport unit, wherein the flat products are transported between the transport units in the direction of a stack shaft, wherein each transport unit comprises at least one conveyor belt. 
   There are a plurality of conventional devices for stacking flat products. DE 38 08 799 C2 discloses e.g. a means for transferring flat objects and combining them into piles. DE 33 21 584 A1 discloses a device for stacking folding boxes. DE 28 27 540 C2 and DE 24 37 475 C3 each disclose a stacking device for folding boxes. DE 37 35 486 C2 discloses a device for turning and stacking folded box blank parts and DE 30 38 058 C2 discloses a means for forming packets of blanks. All of these devices have the disadvantage that they can form only one single type of stack. Depending on the design of the flat product, in particular, of the folding box, it is, however, necessary to form a stack through down-stacking or up-stacking to prevent the products being stacked from jamming during stacking. For this reason, in conventional devices for change-over between two different flat products, e.g. between two folding boxes, not only the entire supply unit has to be adjusted to a new folding box, but it may also be necessary to replace the device for stacking the folding boxes with another stacking device which permits stacking in the other stacking mode. In other words, one folding box blank e.g. can merely be down-stacked, whereas another folding box blank can exclusively be up-stacked and requires a different stacking device. Changing of the stacking device requires time during which the entire production plant is inoperative. 
   When changing over from one folding box to another, in particular, if they have different and irregular contours, e.g. are L-shaped, it is sometimes even necessary to use another stacking device for stacking the folding boxes of different geometry, even though the stacking direction is not changed. 
   It is therefore the underlying purpose of the invention to provide a device of the above-mentioned type which considerably reduces the change-over time between different products to be stacked compared to prior art. 
   SUMMARY OF THE INVENTION 
   This object is achieved in accordance with the invention with a device of the above-mentioned type in that the position of the front end, facing the stack shaft, of at least one conveyor belt can be adjusted and changed. 
   In particular, for folding boxes having a non-rectangular geometry, e.g. L-shaped folding boxes, having a long and a short longitudinal side, the conveyor belts can be adjusted such that their separation from the end of the stack shaft is larger for the longer longitudinal side of the folding box than for the short longitudinal side of the folding box. The separation from the impinging surface in the stack shaft which the front edge of the folding box hits upon entering the stack shaft thereby substantially corresponds to the length of the respective longitudinal edge of the folding box. This means that the folding box is accurately transported by the conveyor belts until it is completely or almost completely located in the stack shaft. The geometry of the folding box is thereby irrelevant since the position of the front ends of the conveyor belts can be adjusted to the different geometries of the folding boxes. 
   In an inventive further development, each conveyor belt can be moved, as viewed in the transport direction, away from the end of the stack shaft by at least the length of the product to be stacked and irrespective of the other conveyor belts. Due to the fact that the conveyor belt can be moved away from or towards the stack shaft by a length which changes with different folding boxes, adjustments required for a change of folding boxes can be effected within a minimum amount of time and, in particular, automatically if the folding box data is stored in a device control means. 
   In accordance with the invention, the front and one rear end of at least one conveyor belt are each guided around a deflecting roller and the deflecting rollers are mounted to a common carriage which can be moved in or opposite to the transport direction. The front end of the conveyor belt is adjusted in a simple manner by moving the carriage by the desired amount. The length of the conveyor belt does thereby not change, since the front deflecting roller is moved by the same amount and in the same direction as the rear deflecting roller. 
   The invention permits exact positioning of the carriage in that the carriage can be moved using a toothed rack. The toothed rack is directly mounted to the carriage and is moved by a stepping motor. It is, however, also feasible to mount the drive to the carriage, which can be moved on a stationary toothed rack. 
   In a particularly preferred embodiment, the front end of at least one conveyor belt of the lower transport unit can be adjusted in an upward direction beyond the transport plane. This measure facilitates up-stacking of the products to be stacked using the inventive device by lifting the front end of the folding box and thereby lifting the entire folding box such that the subsequent folding box can be pushed below the previous folding box. A stacking method of this type is generally used if the lower side of the folding box is relatively smooth and has no punching and folding edges. 
   The invention provides simple adjustment to this mode of stacking by guiding the front end of this conveyor belt around a deflecting roller, the deflecting roller being rotatably mounted to a shackle which can be upwardly tilted. 
   The stacking method can be changed from down-stacking to up-stacking, i.e. from stacking in a downward direction to stacking in an upward direction merely by turning the shackle, thereby lifting the front end of the conveyor belt. This can be effected either manually or preferably automatically. The lower transport unit is pulled forward and the upper transport unit is pushed back to release the upper stack shaft. 
   In its upwardly pivoted position, the shackle preferably forms a support for a section of the flat product. This is advantageous in that the flat product is supported on this support after being positioned in the stack shaft, and is lifted from the conveyor belt. This has the essential advantage that the conveyor belt does not slide along the surface of the folding box located in the stack shaft, thereby damaging it. 
   In a further development, a support roller which can be adjusted in a vertical upward direction beyond the transport plane is provided at a separation from the front end of at least one conveyor belt, wherein its separation from the end of the stack shaft is smaller than the length of the product to be stacked in the region of that conveyor belt. This support roller ensures that not only the front end of the product to be stacked is lifted from the transport plane, which is completely sufficient for short products, but also the rear end, which generally tends to hang downwards, and is suitable, in particular, for long products. In particular, for products having a low bending resistance, e.g. thin folding boxes, it is thereby ensured that the rear end is lifted to a sufficient degree to ensure that the subsequent folding box is safely pushed below the rear end of the previous folding box. 
   In accordance with the invention, the support roller is rotatably mounted to a second shackle which can be upwardly tilted. This shackle can also be upwardly tilted from its rest position into the operative position either manually or automatically. The shackle can also be adjusted in and opposite to the transport direction to adjust its position to the dimensions of the folding box. 
   A loop for the conveyor belt is provided for returning the conveyor belt opposite to the transport direction upstream of the support roller into the transport plane. This loop serves for exact positioning of the conveyor belt in the desired plane and can be positioned to be adjusted in and opposite to the transport direction and also in a vertical direction. 
   If the inventive stacking device is changed-over from up-stacking to down-stacking, the front end of at least one conveyor belt of the upper transport unit can preferably be adjusted in a downward direction below the transport plane of the lower transport unit. This ensures that the leading front edge of the flat product is disposed in a downward direction after entering the stack shaft. 
   In a further development, the front end of this conveyor belt is guided around a deflecting roller and the deflecting roller is rotatably mounted to a slider which is disposed to be displaceable and/or pivotable. When the stacking device is changed over from one stacking mode to the other, only the slider including deflecting roller, about which the conveyor belt is guided, need be downwardly displaced or pivoted. The front end of the upper conveyor belt is thereby adjusted such that a downward momentum is exerted on the front edge of the arriving product to be stacked. 
   This displacement or pivoting of the slider may also be effected manually or automatically when the upper transport unit has been pushed forward and the lower transport unit has been pushed backward to provide free entry into the lower stack shaft. 
   In a preferred embodiment, loops for the conveyor belt are provided adjacent to the deflecting roller. These loops lift the upper conveyor belt to such an extent that it does not collide with the front end of the lower conveyor belt and no narrowings are generated between the lower and upper conveyor belts, i.e. the transport gap has a substantially uniform size. 
   The position and extension of both the lower and upper conveyor belts are adjusted in accordance with the invention in that the loops are disposed to be adjustable in height and/or in the transport direction and opposite thereto. This permits exact adjustment of the extension of the conveyor belts to the shape of the folding box in the region of each conveyor belt. 
   In accordance with the invention, each conveyor belt has its own drive to precisely adjust the location and position of the folding box being transported as well as its orientation on the conveyor belts. The current position of the folding box is preferably detected by suitable sensors and in case of deviations from the desired position, the drives are correspondingly controlled to ensure optimum orientation of the folding boxes. Further advantages, features and details of the invention can be extracted from the dependent claims and the following detailed description of a particularly preferred embodiment with reference to the drawing. The features shown in the drawing and mentioned in the claims and in the description may be essential to the invention either individually or in arbitrary combination. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
       FIG. 1  shows a side view of the inventive stacking device for down-stacking; and 
       FIG. 2  shows a side view of the inventive stacking device for up-stacking. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a stacking device which is designated in total with  10  and substantially comprises a lower transport unit  12  and an upper transport unit  14 . The two transport units are mounted to a machine frame  16  and have circulating conveyor belts  18  and  20 . The conveyor belts  18  and  20  are each driven by their own drives  22  and  24 , independently of each other. The two conveyor belts  18  and  20  normally have the same transport speed, wherein, to correct the position of the flat products to be transported (not shown), the transport speeds may vary. 
   It is clear that the lower transport unit  12  comprises bearings  26  on stands  28  of the machine frame  16 , which are disposed to be displaceable in a horizontal direction, and has a toothed rack  30  on its lower side which mates with a drive  32 . The horizontal position of the lower transport unit  12  is adjusted via this drive  32 , i.e. the lower transport unit  12  can assume a rear position ( FIG. 1 ) or a forward position ( FIG. 2 ). The rear position is required for down-stacking, whereas the forward position is required for up-stacking. In correspondence thereto, the upper transport unit  14  comprises two bearings  34  which are disposed on the stands  28  to be displaceable in a horizontal direction, and also comprises a toothed rack  36  which mates with a drive. The upper transport unit  14  can also be displaced in a horizontal position between a front and rear position via this drive  38 , wherein the front position is required for down-stacking ( FIG. 1 ) and the rear position is required for up-stacking ( FIG. 2 ). 
   The conveyor belt  18  of the lower transport unit  12  surrounds a first front deflecting roller  40 , a second front deflecting roller  42  disposed therebelow, a rear deflecting roller  44 , the drive  22 , an inlet roller  45  and a loop  46 . The two front deflecting rollers  40  and  42  and the rear deflecting roller  44  are thereby located on a carriage  48  which can be displaced in the bearings  26 , wherein the loop  46  is mounted to a holder  50  which can be displaced on the carriage  48 , in particular, on a guiding rail  52 . The inlet roller  45  is mounted to the rear stand  28 . The guiding rail  52  comprises two further holders  54  and  56  to which a shackle  58  and  60 , respectively, are pivotably mounted. In the rest position of the shackles  58  and  60  ( FIG. 1 ), a support roller  62  which is rotatably mounted to the shackles  58  and  60  does not lift the conveyor belt  18  out of the transport plane  64 .  FIG. 2  shows the shackle  58  being pivoted through 90° such that the conveyor belt  18  is lifted upwards out of the transport plane  64 . The loop  46  serves to return the section  66  of the lower conveyor belt  18  located between the support roller  62  and the loop  46  back into the transport plane  64 . 
   The front first deflecting roller  40  is mounted to a pivotably disposed shackle  68 , and can be upwardly displaced by pivoting the shackle  68  ( FIG. 2 ) such that the entire section  70  of the lower conveyor belt  18  located between this first deflecting roller  40  and the support roller  62  is located above the transport plane  64 . The shackle  68  has a support  72  to support a section of a disposed flat product. 
   The upper conveyor belt  20  of the upper transport unit  14  surrounds a front first deflecting roller  74 , a loop  76 , a roller inlet  78 , the drive  24 , a deflecting roller  80  and a front upper deflecting roller  82 . The front first deflecting roller  74 , the upper deflecting roller  82  and the rear deflecting roller  80  are mounted to a second carriage  84  which bears the toothed rack  36  and can be horizontally displaced via the drive  38 . The loop  76  is displaceably mounted to the carriage  84  via a holder  86 . The front first deflecting roller  74  is located on a slider  88  which is mounted on the carriage  84  such that it can be adjusted substantially in a vertical direction, thereby moving the front first deflecting roller  74  into a lower position ( FIG. 1 ) which is below the transport plane  64 . The section  90  of the upper conveyor belt  20  which is thereby deflected extends to the loop  76 . It is located in front of the first deflecting roller  40  of the lower conveyor belt  18 . 
   When the stacking device  10  is adjusted as shown in  FIG. 1  and a flat product to be stacked is transported in the transport direction  92  on the lower conveyor belt  18 , the front end of the product is forced downwards by the section  90  of the upper conveyor belt  20  or a downward momentum is exerted on the front end. This ensures that the product to be stacked safely reaches the stack shaft located below the section  90 . The lower transport unit  12  is thereby sufficiently withdrawn to the right-hand side, i.e. opposite to the transport direction  92 , such that the product to be stacked is transported via the lower conveyor belt  18  to almost directly in front of the end of the stack shaft. If the cross-section of the folding box is not rectangular, the individual lower conveyor belts  18  can assume different positions such that the front ends of these conveyor belts  18  substantially follow the rear shape of the folding box. 
   In the setting of the stacking device  10  of  FIG. 2  for up-stacking, the upper transport unit  14  is withdrawn and the sections  66  and  70  of the lower conveyor belt  18  are displaced in an upward direction out of the transport plane  64 . The support roller  62  is thereby separated from a stop in the stack shaft by a distance which is shorter than the length of the product to be stacked. This means that the product to be stacked projects past the rear of the support roller  62 . The next product which is supplied via the lower conveyor belt  18  can therefore be pushed initially below the projecting end of the previous product and then completely below the product. The slider  88  is thereby sufficiently displaced opposite to the transport direction  92  such that it does not collide with the products supported on the section  66 . The product may additionally be held down by the deflecting roller  74 , if required. 
   The inventive stacking device  10  permits up-stacking and down-stacking, wherein the adjustments can be made either manually and/or mechanically, in particular, via a control unit of the stacking device  19 . Exchange of the stacking device in case of change of the product to be stacked is therefore avoided.