Abstract:
A device is described for changing pallets in an automatic palletizer that arranges objects on the pallets. The object was to refine such a device in such a way that it not only minimizes the space occupied by the automatic palletizer, but also enables the length of interruptions in the palletizing process to be reduced. To solve this object, it is suggested to provide a transfer vehicle having a first pallet area for receiving a first pallet, and a second pallet area for receiving a second pallet, and a driving arrangement for moving the transfer vehicle between at least a first position and a second position, wherein when the transfer vehicle is in its first position the first pallet region of the transfer vehicle can be loaded with an empty pallet while the objects can be arranged on a pallet in the second pallet area.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   The present application claims priority from European Patent Application No. 04002815.1, filed Feb. 9, 2004. 
   FIELD OF THE INVENTION 
   The present invention relates to a device for changing pallets in an automatic palletizer, for positioning objects on the pallets, an automatic palletizer having such a device, and a method for changing the pallets in the automatic palletizer. According to the present invention, the objects to be positioned on the pallets may particularly be envelopes, hygiene products, such as diapers, feminine hygiene products, tissues, and the like, as well as labels for bottles packed in boxes or other containers. 
   BACKGROUND OF THE INVENTION 
   It is known to use automatic palletizing equipment, i.e., automatic palletizers, in conjunction with envelope manufacturing machines. In this process, the finished envelopes discharged at the end of the envelope manufacturing machine are first supplied to an automatic packaging device, an automatic packer, which deposits a given quantity of envelopes in a packaging box and packs them therein in a manner secure for transport. The automatic packer is followed by an automatic palletizer including a palletizing robot and a device for changing the pallets. The palletizing robot accepts the packaging boxes coming from the automatic packer and arranges them in a space-saving manner suitable for transport on a pallet that is prepared at a loading station provided for that purpose. 
   As soon as a pallet is completely filled with packaging boxes, it must be replaced by an empty pallet in order to be able to continue the palletizing process. Devices for changing pallets are known which transport the loaded pallet via a fixedly installed, conventional roller and/or chain conveyor from the loading station to a collection station, from which the pallet may be collected by a forklift, for example. Moreover, the known devices have a supply station, from which an empty pallet may be supplied, also via a fixedly installed, conventional roller and/or chain conveyor. 
   The known devices having roller and/or chain conveyors for changing the pallets have two essential disadvantages. Firstly, they have a relatively substantial space requirement since the roller and/or chain conveyors must be fixedly installed at the supply station, the loading station, and the collection station. This leads to space problems particularly when the space behind the envelope manufacturing machine is limited and/or a plurality of envelope manufacturing machines are set up next to one another and the passage between the machines must be just wide enough to allow operating and maintenance work to be performed appropriately at the machine. The width of the passage required for this is typically smaller than the width to be provided when a collection station or a supply station having conventional roller and/or chain conveyor equipment is to be provided between two neighboring machines. Secondly, in the case of the known devices, the palletizing process must also be interrupted for an unacceptably long time in order to change the palettes, both to convey full pallets from the loading station to the collection station and also for conveying the empty palette from the supply station to the loading station, which can only take place subsequently. 
   BRIEF SUMMARY OF THE INVENTION 
   Accordingly, the object of the present invention is to provide a device for changing pallets in an automatic palletizer for positioning objects on the pallets, an automatic palletizer equipped with such a device, and a method for changing the pallets in the automatic palletizer, which minimizes the space requirement of the automatic palletizer and also facilitates the shortest possible interruption periods of the palletizing process. 
   This object is achieved with a device, an automatic palletizer, and a method having the features of claims  1 ,  12 , and  13 , respectively. Further embodiments of the present invention are described in the dependent claims. 
   The present invention suggests a device for changing pallets using a movable transfer vehicle that is able to accommodate a first pallet in a first pallet region and a second pallet in a second pallet region. A drive unit via which the transfer vehicle is movable between at least a first station and a second station is provided on the transfer vehicle and/or at a stationary point of the device which does not move with the transfer vehicle. Thus, in a first position of the transfer vehicle the first pallet region is at a supply station of the automatic palletizer, at which an empty pallet may be placed in the first pallet region. At the same time, when the transfer vehicle is in its first position the second pallet region of the transfer vehicle is at a loading station of the automatic palletizer. Therefore, the objects to be palletized may be arranged or stacked on a pallet located in the second pallet region preferably using a palletizing robot. When the transfer vehicle has moved to its second position, the first pallet region including the empty pallet is located at the loading station while the full pallet located in the second pallet region is moved to a collection station from which it may be collected by a forklift, for example, for subsequent shipment. 
   Moving the transfer vehicle from the first position to the second position advantageously results in the full pallet being conveyed from the loading station to the collection station and the empty pallet moving from the supply station to the loading station at the same time. As a result, the period for which the palletizing process must be interrupted is minimized in the present invention compared with the consecutive conveying of the full pallet to the collection station and the empty pallet to the loading station. 
   The transfer vehicle preferably has a non-driven means for relative pallet movement which renders it possible to move the transfer vehicle, preferably without significant friction, under a pallet which remains stationary with respect to its surroundings while the pallet continues to rest on the transfer vehicle or to be carried by the vehicle, i.e., to be in contact with the transfer vehicle. The means for providing relative pallet movement extends over both the first pallet region and the second pallet region and may be mounted on the transfer vehicle around deflection pulleys in an endlessly rotating manner. Alternatively, it is possible to create the means for relative pallet movement from one or more sliding rails attached to the transfer vehicle. Such sliding rails are able to slide easily along the underside of a palette while in contact therewith. The means providing for relative pallet movement particularly enables the transfer vehicle to be moved from its second position back to its first position after collecting a full pallet at the collection station without moving the pallet at the loading station relative to its surroundings, i.e. in the second position of the transfer vehicle in the first pallet region. As a result, the pallet at the loading station is able to be loaded with the objects to be palletized as the transfer vehicle under it passes through while simultaneously contacting, carrying, and supporting the pallet. 
   The present invention achieves the advantage that the collection station for collecting the full pallet may be provided outside of a racking system of the automatic palletizer, and specifically without the need to provide permanent roller and/or chain conveyors that occupy substantial space as in the related art. The second pallet region of the transfer vehicle, bearing the full pallet, moves simply in the manner of a self-supporting cantilever arm out of the racking system of the automatic palletizer to a position provided for collection purposes and functioning only temporarily as a collection station. After the transfer vehicle returns to its first position, this collection station is again completely free and may be used for other purposes, for example as a passage between two adjacent machines, i.e., as another traffic surface which is not limited with respect to its use by objects of the device of the present invention protruding from the floor. 
   The endlessly circulating means for relative pallet movement may preferably be one or more roller chains, in particular multiple strand roller chains. In chains of this type, a plurality of rollers is rotatably mounted between the links of two link chains. Other means for relative pallet movement, such as plastic and/or rubber belts endlessly rotating about deflection pulleys or in the form of rotatably mounted rollers protruding slightly from the surface of the transfer vehicle, are also conceivable. 
   According to the present invention, the transfer vehicle may be guided in its movement between the first position and the second position by a guide device. This preferably has at least two guide rails with which guide rollers rotatably mounted on the transfer vehicle engage. Alternatively it is conceivable to mount the guide rails on the transfer vehicle and to rotatably mount the guide rollers engaging therewith in a fixed manner on the racking system. One or more wheels are preferably positioned in the center region of the transfer vehicle and may be motor-driven by the drive unit. The preferably self-supporting, second pallet region of the transfer vehicle may be supported by one or more support wheels as necessary. 
   If the empty pallets are not to be individually supplied to the supply station, according to the present invention an automatic pallet magazine for storing empty pallets may be provided above the supply station or above the first pallet region of the transfer vehicle in the first position. Since the pallet magazine has a frame, it is preferably positioned at a certain minimum distance from the loading station to ensure that there is sufficient space around the pallet to be loaded to enable the palletizing robot to carry out its function. Therefore, the embodiment including the pallet magazine provides for a third position of the transfer vehicle in which the objects to be palletized may be deposited on a pallet located in the second pallet region. In this third position, the first pallet region of the transfer vehicle is not able to be loaded with an empty pallet. The transfer vehicle must be moved to the first position for this purpose. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A number of embodiments of the present invention will be described for exemplary purposes with reference to the drawing. In the drawing: 
       FIG. 1  shows a plan view of two automatic packers and two automatic palletizers of the present invention of two adjacent envelope manufacturing machines (not shown), 
       FIG. 2  shows a side view of a device of the present invention having a transfer vehicle in the first position, 
       FIG. 3  shows a plan view of the device of the present invention according to  FIG. 2 , 
       FIG. 4  shows a front view of the device of the present invention in the viewing direction according to  FIG. 3  from below, 
       FIGS. 5-13  shows side views of various operating states of a first embodiment of the device of the present invention not including a pallet magazine, specifically: 
       FIG. 5  shows the transfer vehicle in its first position including an empty pallet in the first pallet region, 
       FIG. 6  shows the transfer vehicle in its second position, 
       FIG. 7  shows the transfer vehicle after returning to the first position, 
       FIG. 8  shows the transfer vehicle including an empty pallet in the first pallet region and an pallet being loaded in the second pallet region, 
       FIG. 9  shows the transfer vehicle in its second position including the loaded pallet in the second pallet region, 
       FIG. 10  shows the transfer vehicle according to  FIG. 9 , loading of the pallet located in the first pallet region having begun, 
       FIG. 11  shows the transfer vehicle according to  FIG. 10 , the loaded pallet having been collected and an empty pallet having been supplied, 
       FIG. 12  shows the transfer vehicle moved to the first position during the palletizing process, 
       FIG. 13  shows the pallet vehicle extended into the second position following completion of the palletizing process, 
       FIGS. 14-23  show side views of various operating states of a second device of the present invention including a pallet magazine, specifically: 
       FIG. 14  shows the transfer vehicle in its third position as well as the loaded pallet magazine, 
       FIG. 15  shows the transfer vehicle moved to the first position to collect an empty pallet, 
       FIG. 16  shows the transfer vehicle in the second position, including an empty pallet in the first pallet region, 
       FIG. 17  shows the transfer vehicle moved back to the third position, 
       FIG. 18  shows the transfer vehicle according to  FIG. 17  during the palletizing process, the next empty pallet already having been separated, 
       FIG. 19  shows the transfer vehicle including a loaded pallet in the first position, 
       FIG. 20  shows the transfer vehicle including an empty pallet and a loaded pallet in the second position, 
       FIG. 21  shows the transfer vehicle according to  FIG. 20  during the palletizing process as well as a further, separated, empty pallet, 
       FIG. 22  shows the transfer vehicle according to  FIG. 21 , the loaded pallet having been collected during the palletizing process, 
       FIG. 23  shows the transfer vehicle returned to the third position during the palletizing process, 
       FIG. 24  shows a plan view of a further embodiment of the device of the present invention similar to the one according to  FIG. 3 , and 
       FIG. 25  shows a view of another embodiment of the device of the present invention similar to the one according to  FIG. 3  or  24 . 
   

   DETAILED DESCRIPTION 
   The plan view according to  FIG. 1  shows two automatic packaging devices  16  and two automatic palletizers according to the present invention  17  with devices for changing pallets according to the invention. The rear ends  18  of two envelope manufacturing machines (not shown), which are adjacent  FIG. 1 , are also shown. The envelopes that are produced by the envelope manufacturing machines are fed to the respective automatic packaging device  16  at machine ends  18  in stacks, and the automatic packaging device packs the stacks of envelopes in packaging boxes. In the embodiment shown, the packaging boxes filled with finished envelopes serve as the objects to be palletized for the purposes of the present invention. They are each deposited on a conveyor belt  19 , which transports them to the respective automatic palletizer  17 . 
   Besides a palletizing robot, which picks up the packaging boxes from conveyor belt  19  and stacks them on a pallet, each automatic palletizer  17  includes the device according to the invention for changing pallets as shown in  FIGS. 2 to 4 .  FIG. 2  shows a side view of the device according to the invention, as it appears essentially when the lower automatic palletizer in  FIG. 1  is viewed from the left. Automatic palletizer  17  includes a racking system  15 , within which transfer vehicle  2  as shown in  FIG. 2  is located. As is most clearly seen in  FIGS. 3 and 4 , transfer vehicle  2  is supported so as to be movable linearly in two guide rails  11  of a rack frame  12 , which is essentially U-shaped when viewed from above, wherein rotatably affixed guide rollers  13  that are attached to the sides of transfer vehicle  2  engage with guide rails  11  that have an essentially U-shaped cross-section. 
   An electric motor  5  mounted on the underside of transfer vehicle  2  serves as the drive unit for driving two wheels  9  of transfer vehicle  2 , which are guided in rails  10  and may be seen most clearly in  FIGS. 2 and 4 . With electric motor  5 , transfer vehicle  2  may be moved from a first position, as shown in  FIGS. 1 ,  2  and  3 , and into a second position, which is shown as it refers to the upper automatic palletizer  17  in  FIG. 1 . As transfer vehicle  2  is moved into the second position it travels to the right as in  FIG. 2  and/or downwards as in  FIG. 3 . As is shown in  FIG. 3 , about half of the length of transfer vehicle  2  is extended onto guide rails  11  in the first position. In the second position, transfer vehicle  2  is extended almost entirely off guide rails  11 , in which position however it is still supported by the right ends of guide rails  11  as in  FIG. 2  or the lower end of the guide rails as in  FIG. 3 , to prevent tilting about the axis of wheels  9 , which as shown in  FIGS. 2 and 3  are arranged essentially in the middle of transfer vehicle  2 . 
   In the embodiment shown, a total of three multiple strand roller chains  6  are fitted on transfer vehicle  2 , each of which circulates endlessly about two deflection pulleys  7  and  8  as is shown in  FIGS. 2 and 3 . Multiple strand roller chains  6  are not driven actively, but simply roll over deflection pulleys  7  and  8  when a pallet  1  is retained relative to racking system  15  or rack frame  12 . A first pallet area  3  and a second pallet area  4  of transfer vehicle  2  are visible in  FIG. 3 . In the example illustrated, these are essentially rectangular areas on the upper surface of transfer vehicle  2 , in which pallets  1  may be arranged on transfer vehicle  2 . 
     FIG. 2  shows a supply station A, a loading station B and a collection station C that is located away from racking system  15 . An empty pallet  1  may be moved to supply station A in the direction of arrows PA in  FIG. 1 , for example with a forklift or manual pallet truck  20 . At loading station B, a pallet located there may be loaded with the packaging boxes using the palletizing robot. A fully loaded pallet may be removed for subsequent shipping from collection station C in the direction of arrows PC when transfer vehicle  2  is in its second position, as shown at the top of  FIG. 1 . At the bottom of  FIG. 1 , transfer vehicle  2  is in its first position, in which it is located entirely inside the framework of racking system  15  of automatic palletizer  17 . Collection station C, to which second area  4  of transfer vehicle  2  is moved only temporarily in the direction of double arrow PT is indicated by dashed lines in  FIG. 1 . Collection station C is thus permanently located outside of the racking system  15  of automatic palletizer  17 , and thus does not represent a spatial component of the device according to the invention. It must only be available as a free area at the site where the device is installed, so that it may be used temporarily in the course of the proper operation of the device according to the invention. 
   The particularly advantageous space-saving effect of the present invention is shown clearly in  FIG. 1 . The two adjacent envelope manufacturing machines and their associated automatic packaging devices  16  as well as the automatic palletizers  17  may be moved closer together than in the prior art, since the space provided for collection station C space is no longer occupied permanently by roller and/or chain conveyors. A free passage between the envelope manufacturing machines that is essential for proper operation thereof is assured without further arrangement when transfer vehicle  2  is returned from its second position, shown at the top of  FIG. 1 , to its first position, shown at the bottom of  FIG. 1 . 
   For positioning transfer vehicle  2  at and moving the pallets between supply station A, loading station B and collection station C, the invention provides for various limit stops and attachments to be mounted on transfer vehicle  2  or on stationary rack frame 
     12  with the U-shaped cross-section when viewed from above. Two preferably angled limit stops  21  are secured to rack frame  12  as positioning aids for an empty pallet at supply station A. In addition, two attachments  22  are also fixed to rack frame  12  as positioning aids for an empty pallet at supply station A. Two limit stops  23  that are traversable in one direction from left to right in  FIG. 2  and from top to bottom in  FIG. 3  are attached to rack frame  12  for positioning a pallet on loading station B, and are preferably spring-biased when a pallet magazine is not used and preferably actuated externally when a pallet magazine is used. Two limit stops  24  that are traversable in one direction are attached to transfer vehicle  2  for taking an empty pallet from supply station A to loading station B when transfer vehicle  2  is moved from its second position to its first position. In addition, two limit stops  25  that are traversable in one direction from left to right in  FIG. 2  and from top to bottom in  FIG. 3  are attached to transfer vehicle  2  for securing a pallet at loading station B and at collection station C. Finally, 2 immovable, rigid limit stops  26  are attached to transfer vehicle  2  for securing a pallet at loading station B and collection station C. The number of limit stops and attachments in each set may also be reduced to one if required. 
   The process sequence for changing a pallet with the device according to the invention will be described in the following, with reference to one exemplary embodiment without and one with a pallet magazine. 
     FIGS. 5 to 13  show the chronological sequence of states during the pallet changing process according to the present invention, no pallet magazine being used in this sequence. 
   Initially, transfer vehicle  2  is in its first position as shown in  FIG. 5 , in which it is entirely surrounded by racking system  15  of automatic palletizer  17 . An empty pallet  1  is deposited on the first pallet area  3  of transfer vehicle  2 , which is at supply station A. The pallet is positioned using limit stop  21  and attachment  22 . Transfer vehicle  2  then 
   moves to its second position, as shown in  FIG. 6 , in which step empty pallet  1  is moved to loading station B at the same time by limit stop  24 , and limit stop  23  on rack frame  12  is passed over. It would be possible for the palletizing operation to begin even at this point while transfer vehicle  2  is in its second position. 
   As shown in  FIG. 7 , transfer vehicle  2  then moves back to its first position, during which step limit stop  23  secures empty pallet  1  in position at loading station B and limit stop  25  is passed over. As a result, pallet  1 , which is either empty or has already passed through the palletizing process, moves from first pallet area  3  to second pallet area  4  and the three multiple strand roller chains  6  circulate round their respective deflection pulleys  7  and  8 . If the palletizing process has not yet started, as shown in  FIG. 8  the pallet robot may then begin loading pallet  1 , which is at loading station B. Packaging boxes  27  containing the envelopes are arranged on pallet  1  according to a preprogrammed stacking scheme. Either before the start of pallet  1  being loaded or after a brief interruption in the palletizing process, an empty pallet  1 ′ may be placed on first pallet area  3  of transfer vehicle  2 , which is at supply station A. 
   When pallet  1  has been fully loaded or palletized, transfer vehicle  2  moves to its second position, as shown in  FIG. 9 , at which time limit stop  23  is passed over by empty pallet  1 ′ and full pallet  1  is transported to collection position C. In an advantageous manner according to the invention, full pallet  1  is removed from loading station B and empty pallet  1 ′ is positioned at loading station B at the same time.  FIG. 9  clearly shows that the right half of transfer vehicle  2  extends out of racking system  15  in the manner of a self-supporting cantilever arm. This is particularly advantageous from the point of view of workplace safety, since an operator in the direct vicinity of collection station C does not run the risk of having his foot run over. A further advantage consists in that an ideally unoccupied space for a movement of a floor transport vehicle is provided underneath transfer vehicle  2 . However, it is also conceivable to support the protruding half of transport vehicle  2 , as shown in  FIG. 9 , with one or more carrying wheels. As soon as 
   empty pallet  1 ′ arrives at loading station B, the palletizing process may begin again, i.e. pallet  1 ′ may be loaded with packaging boxes  27  by the pallet robot, as shown in  FIG. 10 . 
   As shown in  FIG. 11 , the full pallet  1  may now be collected from collection station C and an empty pallet  1 ″ may be positioned at supply position A with the aid of limit stop  21  and attachment  22 . At this point, it is of no importance whether pallet  1  is collected before or after the empty pallet  1 ″ is supplied. Since supplying the empty pallet  1 ″ requires entry into the space defined by racking system  15  in which the palletizing robot is moving, a short interruption is necessary in the palletizing process. After full pallet  1  has been removed from second pallet area  4 , which is at collection station C, and if necessary before empty pallet  1 ″ is supplied, transfer vehicle  2  is moved back to its first position, as shown in  FIG. 12 , at which time limit stop  23  retains pallet  1 ′ securely at loading station B and limit stop  24  is passed over by empty pallet  1 ″. The transfer vehicle  2  may thus be moved back to its first position, as shown in  FIG. 12  without interrupting the palletizing process for pallet  1 ′. 
   When pallet  1 ′ has been palletized, transfer vehicle  2  is returned to is second position, as shown in  FIG. 13 , limit stop  23  being passed over by pallet  1 ″. Pallet  1 ′, which is now full, is transported from loading station B to collection station C, while at the same time empty pallet  1 ″ is positioned at loading station B. The full pallet  1 ′ may be collected from collection station C, which was occupied temporarily by the second pallet area  4  of transfer vehicle  2 . Then, the pallet changing process is begun again and repeated as often as necessary starting from the position shown in  FIG. 10 . 
     FIGS. 14 to 23  illustrate the process sequence for changing pallets with a device according to the invention that includes a pallet magazine for storing empty pallets. 
   As shown in  FIG. 14 , a stack of empty pallets is first deposited at supply station A and lifted up using pallet magazine  14 . In the embodiment shown, seven empty pallets are stored in pallet magazine  14 . Transfer vehicle  2  is then moved to its first position, as 
   shown in  FIG. 15 , in which the first pallet area  3  thereof may be loaded with an empty pallet  1 , which has been separated in pallet magazine  14  beforehand. 
   Then, transfer vehicle  2  is moved to its second position, as shown in  FIG. 16 , pallet  1  being moved at the same time to loading station B due to limit stop  24 , and traversing limit stop  23 . Thereafter, transfer vehicle  2  is moved to its third position as shown in  FIG. 17 , pallet  1  being retained in place at loading station B by limit stop  23  and limit stop  25  being passed over. In this third position, first pallet area  3 , which as shown in  FIG. 17  is located in the left half of transfer vehicle  2 , cannot be loaded with an empty pallet from pallet magazine  14 . This is because pallet magazine  14  must be sufficiently distant from loading station B to allow the palletizing robot to approach pallet  1  from the left side of loading station B also, as shown in  FIG. 17 . 
   As is shown in  FIG. 18 , loading of pallet  1  with packaging boxes  27  begins, and at the same time another empty pallet  1 ′ may be separated in pallet magazine  14 . Transfer vehicle  2  does not move. When palletizing of pallet  1  has been completed, as shown in  FIG. 19  it is returned to its first position, for which purpose limit stop  23  may be reversed by external means and limit stop  24  is passed over by pallet  1 ′. As soon as transfer vehicle  2  has reached its first position, pallet  1 ′, which was separated previously in pallet magazine  14 , may be deposited on first pallet area  3 . Full pallet  1  lies directly beside pallet magazine  14 . 
   Then, as shown in  FIG. 20 , transfer vehicle  2  is moved to its second position from its first position as shown in  FIG. 19 , limit stop  23  being passed over both by pallet  1  and by pallet  1 ′. In this step, full pallet  1  is transported to collection station C and empty pallet  1 ′ is placed at loading station B. Now, as shown in  FIG. 21 , the loading of pallet  1 ′ with packaging boxes  27  begins, and at the same time another empty pallet may be separated in pallet magazine  14 . 
   As is shown in  FIG. 22 , full pallet  1  is then collected from collection station C, while the palletizing process of pallet  1 ′ at loading station B continues without interruption. Finally, also while pallet  1 ′ is still being palletized, transfer vehicle  2  is returned from its second position as shown in  FIG. 22  to its third position as shown in  FIG. 23 , limit stop  23  retaining pallet  1 ′ securely in place at loading station B and limit stop  24  being passed over. Then, the pallet changing process is begun again and repeated as often as necessary starting from the position shown in  FIG. 19 . 
   As is evident from the preceding description, the method according to the invention may be performed in conjunction with the device according to the invention without a pallet magazine in such manner that the empty pallet is disposed in the first pallet area of the transfer vehicle while the pallet in the second pallet area is being palletized, the only effect being that the palletizing process must be interrupted briefly. On the other hand, when the device according to the invention is used with a pallet magazine, the empty pallet may not be disposed in the first pallet area until after the pallet in the second pallet area has been fully palletized, since the empty pallet must not be fetched from the pallet magazine until palletizing is completed, as shown in  FIG. 19 . 
   If it is essential to be able to deposit the empty pallet in first pallet area  3  of transfer vehicle  2  while the pallet in second pallet area  4  is being palletized in the embodiment with the pallet magazine  14  also, it is further conceivable to construct transfer vehicle  2  correspondingly longer, so that it extends under pallet magazine  14  fully even in the position shown in  FIG. 18 . Then, an empty pallet  1 ′ may be positioned in the first pallet area  3  while pallet  1  in second pallet area  4  is palletized at loading station B. In this case, the third position provided in the embodiment with the pallet magazine  14  may be dispensed with, and in its second, extended position transfer vehicle  2  protrudes farther out of racking system  15  than is the case in which a shorter transfer vehicle  2  may be moved to a third position. 
     FIG. 24  shows a plan view of two further embodiments of the device according to the invention, similar to the plan view in  FIG. 3 . Unlike the embodiment shown in  FIG. 3 , the limit stop  24  in these embodiments is not able to be passed over but is fixedly attached to transfer vehicle  2 . When transfer vehicle  2  returns from the second position as shown in  FIG. 11  to the first position as shown in  FIG. 12 , this fixed limit stop  24  raises empty pallet  1 ″ slightly. Instead of limit stop  21  and attachment  22 , at least two elongated supports, particularly tubes  28 , as are shown in  FIG. 24 , may be provided and attached to rack frame  12  and of which at least the upper surfaces project above the plane spanned by multiple strand roller chains  6 . As a result, an empty pallet may be deposited on tubes  28  in first pallet area  3  of transfer vehicle  2  at supply station A. Moreover, limit stop  23  may be omitted, since as shown in  FIG. 24  frontal surfaces  29  at the lower ends of the support, particularly tubes  28 , may function as fixed limit stops for positioning a pallet at loading station B. 
   For this purpose, the lower ends of tubes  28  may be lengthened or shortened as shown in  FIG. 24  by inserting or screwing relatively short tubular elements in the ends or removing them therefrom. 
   In the embodiment in  FIG. 24 , limit stops  25  provided on transfer vehicle  2  have been removed without replacement. If necessary, however, the limit stops  25  may be replaced by means for limiting the movement of relative pallet movement means  6 . In such case, relative pallet movement means  6 , which have unrestricted movement per se, are limited or blocked in such a way that a pallet in second pallet area  4  on transfer vehicle  2  is not able to leave the transfer vehicle  2  downwards, as shown in  FIG. 24 . A corresponding restriction of the movement of relative pallet movement means  6  may be realized for example via overrunning pulleys cooperating with deflection pulleys  7  and  8 . 
     FIG. 25  shows a plan view of a further embodiment of the device according to the invention, similar to the plan views shown in  FIGS. 3 and 24 . The same key is used to designate parts in  FIG. 25  that are the same as those of the embodiments in  FIGS. 3 and 24 . 
   The transfer vehicle  2  shown in  FIG. 25  is designed for operation with a pallet magazine, as described with reference to  FIGS. 14 to 23 . Unlike the previous descriptions, rack frame  12  extends essentially over the entire length of transfer vehicle  2 . Rack frame  12  is secured and supported on the floor of the installation site by a total of six feet  30 . The entire rack frame  12  is accommodated inside racking system  15 , which is not shown in  FIG. 25  (cf.  FIGS. 2 and 14  to  23 ). Supply station A and loading station B are indicated at the left edge of  FIG. 25 . 
   Unlike the embodiments previously described, the electric motor  5  provided for driving transfer vehicle  2  is not mounted on the transfer vehicle  2  itself, but is arranged in fixed manner below the plane in which the pallets are deposited at loading location B. The drive impulse is transmitted from electric motor  5  to transfer vehicle  2  via a drive belt, no shown in  FIG. 25 , which is clamped to transfer vehicle  2 . This advantageously reduces the mass of transfer vehicle  2  that needs to be displaced. In a further difference from the previously described embodiments, in the embodiment shown in  FIG. 25 , rotating guide rollers  13  are attached to stationary rack frame  12 , and not to transfer vehicle  2 . Accordingly, the preferably U-shaped guide rails  11  are not arranged on rack frame  12 , but on transfer vehicle  2 , and are moved together with the vehicle. 
   A total of six sliding strips  31  is provided, attached to transfer vehicle  2 , and thus also moving therewith, as non-driven means for relative pallet movement for the purposes of the present invention in the embodiment as shown in  FIG. 25 . Multiple strand roller chains are thus not present, in a difference from the previous embodiments. In addition, a total of three end limit sliding strips  32  may be seen in  FIG. 25 , each of which is secured to rack frame  12  and between two sliding strips  31 , so that they do not move in concert with transfer vehicle  2 . The stationary end limit sliding strips  32  do not extend for the entire length of rack frame  12  or transfer vehicle  2 , but their frontal surfaces  33  terminate where loading station B begins, as is shown in  FIG. 25 . Seen from the opposite perspective to that shown in  FIG. 25 , end limit sliding strips  32  project slightly above the plane formed by the surfaces of sliding strips  31 . As a result, frontal surfaces  33  of end limit sliding strips  32  serve as end stops when transfer vehicle  2  is returned from its second position to its first or third position, and they retain the pallet located at loading station B securely in place. Sliding strips  31 , which move together with transfer vehicle  2  are then in contact with the underside of the pallet and slide along the bottom thereof. In this situation, end limit sliding strips  32  have the same function as tubes  28  in the embodiment shown in  FIG. 24 . 
   Unlike the previous embodiments, the embodiment as shown in  FIG. 25  has no fixed limit stops for taking an empty pallet from supply station A to loading station B, but swiveling limit stops  24  instead. These limit stops  24  are raised by mechanical force when supply station A is occupied and retract downwards out of the way und the effect of gravity when the vehicle returns from loading station B to supply station A. This enables an empty pallet at supply station A to be lowered without difficulty. A pallet to be loaded at loading station B is centering or positioned by the return of transfer vehicle  2  towards supply station A, which causes the pallet to be loaded to strike against frontal surfaces  33  of end limit sliding strips  32 . 
   If supply station A is not supplied from a pallet magazine, the pallet supplied may be centered or positioned at supply station A in the direction perpendicular to the longitudinal direction of transfer vehicle  2  using a suitable limit stop at supply station A. If supply station A is supplied with pallets from a pallet magazine, end limit sliding strips  32  may be replaced by rails having rollers arranged at an angle to the longitudinal direction of transfer vehicle  2 , at least in the area of supply station A, which have the effect of centering or positioning the pallet perpendicularly to the longitudinal direction of transfer vehicle  2  as it moves toward loading station B.