Abstract:
The intermediate store has an input station for loading and an output station for unloading transport racks circulating in buffer zones between these two stations. The two stations each have a vertical conveyor for the transport racks, each of the two vertical conveyors being equipped with two pairs of chains driven independently of one another. The two pairs of chains in the input station alternately transport one transport rack each stepwise past a loading device and subsequently, after being decoupled from synchronous operation, transport them further, with the result that loading of the transport racks without interruption is permitted. The output station is formed analogously so that there too there are no interruptions between the emptying of two successive transport racks.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates to an intermediate store serving for flexible decoupling of the product flow between a production facility and a further processing station and having a transport rack with equidistant shelves, 
        comprising an input station having a loading device and an output station having an unloading device, these two stations each being equipped with a vertical conveyor for the transport rack,     and comprising two buffer conveyors arranged between these two stations intended for buffer zones containing the transport racks, a first one for the full transport racks and the second one for the empty transport racks,     and comprising aids for transferring the transport racks from the first vertical conveyor to the first buffer zone, from this to the second vertical conveyor, from this to the second buffer zone and from this to the first vertical conveyor.        
 
         [0006]     2. Description of the Prior Art  
         [0007]     It is known that small products in the form of piece goods, such as, for example, bakery products or chocolate bars, are transported in rows when being transferred from the production facility to a further treatment station, for example a packing station, so that the transport direction thereof is transverse to the axis of these product rows. A problem which inevitably occurs in transporting such products arises from the fact that it is practically impossibly to enable production and packing to operate synchronously. In particular, there will constantly be interruptions in the production sequence, and in the packing of these delicate goods, too, unforeseen or planned breaks cannot be avoided.  
         [0008]     It was therefore at an early stage that the production facility was connected to the packing station by intermediate stores in which the goods produced can be temporarily stored and then called up when required by the packing personnel or the packing machine.  
         [0009]     For transport, the products are stored in transport racks which are provided with a number of shelves for holding the products.  
         [0010]     An intermediate store serving the above-mentioned purpose is disclosed in European Patent EP 0 732 279. The intermediate store described there has an input elevator which conveys the transport rack stepwise vertically past the infeed conveyor serving it and from there into a first buffer zone. An output elevator removes the full transport rack, as required, from the buffer zone and conveys it downward past a delivery device and, after emptying, into a second buffer zone. The planes defined by the chains of the two elevators are parallel to the direction of movement of the transport rack in the buffer zones.  
         [0011]     According to this proposal, both the input elevator and the output elevator are each equipped with a pair of chains passed over at least four stationary deflection wheels. Each of these two pairs of chains has one continuously revolving chain each on each side of the transport path and is provided with drivers for picking up the transport rack delivered to the chain region. These therefore serve for loading a transport rack in the working cycle, for accepting the next transport rack and moreover for the horizontal displacement adjacent to the vertical movement in the upper and lower region. Although this design makes it possible to ensure that the elevators include not only a vertical movement component but also two horizontal movement components, and the number of individual drives are therefore reduced, this multiple function of the elevators results in an undesired influence on the processes taking place in the upper or lower transport region, which adversely affects the dynamics and flexibility of the system. Since in fact a rapid passage of the transport rack through the store is very desirable in most cases and the transport racks should therefore follow one another in the two elevators as far as possible without spaces, the known solution proves to be insufficiently flexible for minimizing the spaces between adjacent transport racks during vertical transport and, particularly at high throughput speeds, for ensuring a stable position of the transport racks.  
         [0012]     Since it is impossible to avoid an undesired space between two successive transport racks in this arrangement, a further device has to be mounted to ensure continuous operation: the conveyor belt arranged at the entrance of the store is therefore formed to be pivotable in such a way that its free end is adjustable in height. However, this is associated with an additional constructional effort which moreover requires a further control to be derived from the movement of the transport racks.  
       SUMMARY OF THE INVENTION  
       [0013]     It is the object of the present invention to propose an intermediate store which permits uniform, continuous passage of the product without queues and hence creates the preconditions for maintaining a constant production speed. With a view to dynamic and independent control of the transport racks following one another during vertical transport, the elevator process should be controllable both in the input region and in the output region so that no spaces occur between vertically adjacent transport racks, ensuring a continuous production sequence.  
         [0014]     This object is achieved by an intermediate store serving for flexible decoupling of the product flow between a production facility and a further processing station and having a transport rack with equidistant shelves, 
        comprising an input station having a loading device and an output station having an unloading device, these two stations each being equipped with a vertical conveyor for the transport rack,     comprising two buffer conveyors arranged between these two stations intended for buffer zones containing the transport racks, a first one for the full transport racks and the second one for the empty transport racks,     and comprising aids for transferring the transport racks from the first vertical conveyor to the first buffer zone, from this to the second vertical conveyor, from this to the second buffer zone and from this to the first vertical conveyor,     wherein each of the two vertical conveyors has two pairs of chains which are provided with drives independent of one another and all of which are arranged so that the planes defined by the two sides of a chain are perpendicular to the transport direction of the transport racks in the buffer zones,     wherein the drives of the vertical conveyors are controlled so that an empty transport rack transferred to the input station is moved by the first pair of chains, initially in synchronous operation corresponding to the shelf spacing, past the loading device and is loaded there and, after the end of loading, is decoupled from the synchronous operation and fed to the first buffer zone ( 12 ),     wherein the subsequent empty transport rack transferred to the input station is accepted by the second pair of chains and follows the preceding transport rack without a gap in the same synchronous operation, is likewise decoupled from the synchronous operation after the end of loading and is fed to the first buffer zone, wherein the following transport rack is in turn accepted by the first pair of chains,     and wherein the full transport racks transferred to the output station are moved in an analogous manner, alternately by the two pairs of chains, in synchronous operation, past the unloading device, are unloaded there and are then decoupled from the synchronous operation and fed to the second buffer zone.        
 
         [0022]     The result of this design, according to the invention, of the intermediate store is that both at the input station and at the output station, each second transport rack following a first one can continuously accept the next product row arriving. This means that a product flow is possible with high cadence, continuously and without interruption, because an empty transport rack is always available. As soon as a transport rack has been loaded, it is immediately decoupled from the synchronous operation, moved upward and is placed into a first buffer zone, while at the same time, i.e. in a continuous procedure, an empty transport rack for synchronous filling is moved upward. Since the synchronous operation is therefore reduced to the straight-forward loading and unloading process, the products carried in the transport racks are accelerated only very slightly in the feed direction so that they cannot slip or fall down.  
         [0023]     Even at the outflow of the intermediate store, the product can be ejected continuously, i.e. without interruption, in the direction of the packing station, since a full transport rack is always standing ready here. While a transport rack is being unloaded, the previously emptied transport rack, which has been decoupled, is simultaneously moved downward, unloaded and then transferred in the empty state to the second buffer zone. While both the loading and the unloading process can therefore take place without a break in synchronous operation, the vertical movement following the loading and preceding the unloading takes place in the same way as the preceding or subsequent horizontal movement. This ensures a smooth and hence safe flow of material.  
         [0024]     The division of the complete vertical drive into two independently driven pairs of chains guarantees continuous conveying of the transport rack without queues and furthermore makes it possible, if required, to control the relative position of adjacent transport racks.  
         [0025]     According to a preferred embodiment of the inventive concept, to enable two adjacent product rows located one above the other to be ejected on the unloading side simultaneously from the transport rack onto a horizontal conveyor, a storage plate which temporarily receives the upper product row and then transfers it to the horizontal conveyor is arranged above the horizontal conveyor.  
         [0026]     In a preferred embodiment, a pusher bar which pushes the product rows placed on the conveyor belt, immediately after they have been set down, at the transport speed of the conveyor belt and thus prevents the individual rows from initially being transported at a speed which is lower than the conveyor belt speed, and hence also prevents a speed difference occurring between conveyor belt and conveyed goods and hence abrasion of the latter, which would result in soiling of the conveyor belt, is arranged closely above the horizontal conveyor leading to the packing station, which conveyor comprises substantially a conveyor belt. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0027]     An embodiment of an intermediate store according to the invention is described below with reference to the attached very schematic drawing. In the drawing,  
         [0028]      FIG. 1  shows a side view of the substantial parts of an intermediate store according to the invention,  
         [0029]      FIG. 2  shows an end view of the substantial parts in the direction of the arrow II of  FIG. 1 ,  
         [0030]      FIG. 3  shows an end view of the substantial parts in the direction of the arrow III of  FIG. 1 ,  
         [0031]      FIG. 4  shows a side view in a further phase of product movement,  
         [0032]      FIG. 5  shows an end view in the direction of the arrow V of  FIG. 4 ,  
         [0033]      FIG. 6  shows an end view in the direction of the arrow VI of  FIG. 4 ,  
         [0034]      FIG. 7  and  8  show a schematic diagram of a detail of the design of the unloading station. 
     
    
       [0035]     In order to be able to represent and describe the substantial features of the invention well, only the transport racks and—purely schematically—the various conveyors for the transport racks are shown in the drawing, not the guide rails and the other constructional details necessary for operating the store.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0036]     The intermediate store shown in the drawing contains eight transport racks, which are denoted by 1-8. Here, each of these transport racks is equipped with ten equidistant shelves  9 , the size of the shelves and their mutual spacing being adapted to the size and the weight of the products  10  to be transported. The intermediate store has an input station E and an output station A and, between these two stations, two buffer zones, a first denoted by  12  for the loaded transport racks in the upper part of the store and a second denoted by  13  for the empty transport racks in the lower part of the store. Of course, each of the two buffer zones  12  and  13  must be so large that they can hold all except two of the transport racks present in the entire intermediate store, i.e. six in the example shown, which cannot be seen exactly in  FIGS. 1 and 4 .  
         [0037]     The input station E contains a loading device which is indicated here only very schematically and is denoted by  11 . The input station furthermore includes a vertical conveyor, which is denoted here as a whole by  14  and serves for transporting the empty transport racks fed from the second buffer zone  13 , in synchronous operation, i.e. stepwise according to the spacing of the shelves  9 , past the loading device  11  so that the individual shelves  9  of each transport container can be loaded there with the products fed from a production facility, i.e. for example with one row each of chocolate bars or biscuits. This vertical conveyor  14  has two pairs  15  and  16  of chains which are provided with drives independent on one another and of which the chains  15   a  and  16   a  can be seen in  FIGS. 1 and 4  and the chains  15   a  and  15   b  of the pair  15  of chains in  FIGS. 2 and 5 , which for their part obscure the view of the chains  16   a  and  16   b  of the pair  16  of chains there.  
         [0038]     From the drawing, it is evident that all four chains are arranged in such a way that each plane defined by the two sides of a chain is perpendicular to the transport direction  17  of the transport racks in the buffer zones  12  and  13 .  
         [0039]     In  FIGS. 1 and 2 , as many as six of the ten shelves  9  of the transport rack  1  have now been loaded. After the next upward step of the conveyor, the following, i.e. the seventh, shelf is loaded. Each chain has a driver for transporting the individual transport racks upward, for example the chain  15   a  has the driver  25   a  and the chain  15   b  has the driver  25   b , both of which together transport the transport rack  1  upward. The chain  16   a  has the driver  26   a  and the chain  16   b , which is not visible, has the driver  26   b .  
         [0040]     As soon as the last shelf, i.e. the tenth shelf  9  of this transport rack  1 , has been loaded during the stepwise upward movement of the transport rack  1 , those chains of the second pair  16  of chains which are each provided with a driver ensure, as is evident from  FIGS. 4 and 5 , that a following transport rack, which is denoted here by  8  and has been removed from the lower, i.e. the second, buffer zone  13  shortly before the loading of the tenth shelf of the transport rack  1 , follows the transport rack  1  virtually without any space and is transported upward by this pair of chains in synchronous operation, i.e. stepwise, so that this transport rack  8  too can be loaded by the loading device  11 . At the same time, the two chains  15   a  and  15   b  of the first pair  15  of chains transport the transport rack  1  completely to the top, where it is transferred to the buffer space conveyor  20  in the upper, i.e. first, buffer zone  12  by an aid  19  serving as a pusher. This is formed in such a way that the individual transport racks reach a point as close as possible to the exit present on the right in  FIGS. 1 and 4  of the drawing, where they queue.  
         [0041]     When the second transport rack  8  has been filled, it is, after being decoupled from synchronous operation, transported completely to the top and from there to the buffer space conveyor  20  in the upper first buffer zone  12 .  
         [0042]     In the meantime, however, the first pair  15   a  and  15   b  of chains has already accepted the following, i.e. the third, transport rack  7  and transported it upward so that it is adjacent to the second transport rack  8  virtually without any space, so that, on the one hand, the loading device  11  can operate without interruption and, on the other hand, no speed changes giving rise to rocking occur during the horizontal movement of the transport rack.  
         [0043]     The output station A is designed analogously to the input station E: here, the vertical conveyor is denoted as a whole by  21 . It serves for transporting the individual transport racks from top to bottom past the unloading device denoted as a whole by  24 . It too has two pairs of chains denoted by  22  and  23  and provided with drives independent of one another, of which only the chains  22   b  and  23   b  can be seen in  FIGS. 1 and 4  but the chains  22   a  and  22   b  of the pair  22  of chains can be seen in  FIGS. 3 and 6 .  
         [0044]     The chain  22   a  has a driver  32   a , the chain  22   b  has a driver  32   b , the chain  23   b  has a driver  33   b  and the chain  23   a , which is not visible, has a driver  33   a . Here too, as can be seen in the drawing, all chains are arranged in such a way that the planes defined by the two sides are perpendicular to the displacement direction  17  of the transport racks in the buffer zones  12  and  13 .  
         [0045]     As shown in  FIGS. 1 and 3 , the pair  22   a / 22   b  of chains first transports the transport rack  5  stepwise downward past the unloading device  24  so that this unloading device can unload the individual shelves  9 . Before the last shelf has been unloaded, the aid  27  in the form of a pusher transfers a full transport rack, i.e. the transport rack  4  in this case, to the vertical conveyor  21 , in particular to its pair  23  of transport chains. Said pair of transport chains transports the transport rack downward so that it is adjacent to the transport rack  5  virtually without any space, so that the unloading device  24  can operate without interruption. The empty transport rack  5  is then transferred to the buffer space conveyor  28  in the lower, i.e. in the second, buffer zone  13 . This buffer space conveyor  28  serves for moving the empty transport racks as far as possible to the left in  FIGS. 1 and 4  so that they can be fed to the vertical conveyor  14  as required. Here too, the two pairs of chains which are independent of one another therefore ensure that there are no spaces between the individual transport racks in the vertical conveyor, i.e. there are no breaks during unloading.  
         [0046]     Here, the unloading device  24  shown in  FIGS. 1 and 4  has a dual pusher  29  which simultaneously pushes the product rows from two shelves  9  present one on top of the other onto a horizontal conveyor, namely from the lower shelf onto a conveyor belt  13  moving transversely to the output direction and from an upper shelf onto a storage plate  31  arranged above this conveyor belt  30 . Said storage plate is formed so as to be either retractable or tiltable so that the product row present on it can be transferred to the conveyor belt underneath as soon as the lower product row of the two product rows simultaneously ejected has been transported away.  
         [0047]     Depending on the type of product, it may be expedient to provide a scraper which pushes the product rows from the storage plate  31  onto the conveyor belt  30 .  
         [0048]     As shown in  FIGS. 7 and 8 , it is expedient to provide a motor-driven pusher bar  32  which pushes the product rows  10  placed on the conveyor belt, immediately after they have been set down, at the speed of the conveyor belt so that slipping of the conveyed goods on the conveyor belt is avoided.