Abstract:
A remaining-stack carrying device ( 3 ) in a sheet feeder ( 2 ) is used in non-stop stack changing. The remaining-stack carrying device ( 3 ) is integrated into the stack feeder ( 2 ) to simplify retrofitting. A remaining-stack lifting gear ( 5 ) uses the lifting elements present in each sheet feeder ( 2 ) for lifting and lowering during stack exchange.

Description:
FIELD OF THE INVENTION 
     The present invention relates to sheet-fed printing machines and, more particularly to an improved stack changing device for sheet feeders of sheet-fed printing machines. 
     BACKGROUND OF THE INVENTION 
     It is a known practice, in sheet feeders of sheet printing machines or other sheet-processing machines to provide arrangements for automated stack changing. These can consist of rack-type structures, so-called remaining-stack carrying devices, which are provided with thrusting and lifting drives for horizontal and vertical movement. Such so-called nonstop stack changers are suited for example during the printing of paper sheets, i.e. in machine running, to remove remainders of worked-out sheet stacks from a pallet provided, for example, with grooves and to deposit them again on a new sheet stack subsequently installed into the sheet feeder. Known devices are marked by high construction and assembly expenditures, and require special constructions of the sheet feeders. Further, devices are used in which the remaining-stack carrying device(s) have a rack engaging into the grooves of the pallet. This rack has to be removed when the remaining-stack is joined with the newly installed sheet stack to form a whole stack comprising the two stack parts. This involves high driving forces, and very severely strains the sheets of the stack lying next to the section point. Furthermore, restraining means have to be provided that prevent a shifting of the stack parts, and in so doing severely strain the stack edges. Furthermore, the operation of the sheet feeder itself is severely hampered or even rendered impossible. The sheetflow is difficult to control during the changing process, so that again and again waste sheets result. 
     Devices have already been developed that partly avoid some of the disadvantages described. Thus, from DE 3931710 C2 there is known a nonstop sheet feeder for rotary sheet-fed printing machines. It has a remaining-stack carrying device which is arranged underneath a conveyor table. The remaining-stack carrying device has a closed frame on which nonstop rods are arranged, which can be driven as piston rods of individual cylinders by means of a pressure medium, and which are drivable into grooves of a pallet carrying a sheet stack. The nonstop rods lie in the driven-in state on both sides of the frame and are to be removed successively from the area of the sheet feeder. Nothing is said about the sequence of operation. The bridging of the gap conditioned by the nonstop rods between main stack and remaining-stack constitutes, in the stack unification, an obstacle to a faultless continuous process. The device is not usable, since the sheet stack must be tilted. 
     From DE 4203500 A1 a sheet feeder is known. It has parallel to the sheet feeder and allocated to the sheet feeder on the face side, an auxiliary stack carrying device as an independent component. With this device, over a common drive, there are provided individually drivable pointed bars which are drivable into grooves of a pallet carrying a sheet stack. The drive has individual chain drives which are coupleable onto the respective pointed bars. For guiding and accessing the chain drives, special constructive measures are required. The chain drives completely block the space in front of the sheet feeder, so that the latter is not accessible. In the stack changing, the pointed bars are removed from the stack zone, in the joining of main stack and remaining-stack, first on the outside, then in the middle, and last in the zone between the already pulled pointed bars, so that there is supposed to result a gentle depositing of the remaining-stack on the sheet stack. This, however, is possible with the requisite precision only in the case of heavy materials, such as sheets of metal, since the sheets arch in different directions and must descend over a large gap that is formed by the pointed bars. 
     Further, from DAS 1095297 a sheet carrier with several stack-lifting mechanisms is known. It has a fork-shaped remaining-stack carrying device, which is provided with remaining-stack bars slidable into grooves of a pallet. The device makes possible the taking over of a remainder of a sheet stack from the pallet for the continuous in-feed of the sheets while a new sheet stack is installed into the sheet feeder. The remaining-stack is connected with a separate lifting mechanism parallel to the main stack lifting mechanism inside the sheet feeder, so that the remaining-stack is continuously liftable. The operating range of the remaining-stack carrying device is restricted. The remaining-stack carrying device hampers access of the sheet feeder. 
     OBJECTS AND SUMMARY OF THE INVENTION 
     In view of the foregoing, an object of the present invention is to provide an improved stack changing device which overcomes the problems associated with prior art designs. 
     A more specific object of the present invention is to provide a stack changing device which can be easily integrated into a sheet feeder. 
     The present invention provides these and other advantages and overcomes the drawbacks of the prior art by providing a stack changing device which utilizes an improved apparatus for receiving a remaining-stack and transferring the remaining stack to a newly fed-in sheet stack. 
     It is advantageous that carrying bars movable independently from one another are provided in the device, which for the unburdening of the sheet material are pulled out of the stacking zone not simultaneously, but offset from one another. The drive forces are thereby kept low and the cost of the drives of the remaining-stack bars is reduced. The device can be used, therefore, instead of a manual nonstop arrangement on a sheet feeder, and also be reequipped without the need for expensive constructive measures and large space requirements. 
     These and other features and advantages of the invention will be more readily apparent upon reading the following description of preferred exemplary embodiments of the invention and upon reference to the drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side elevation view of an illustrative embodiment of a sheet feeder constructed in accordance with the present invention. 
     FIG. 2 is a plan view of a sheet feeder; and 
     FIGS. 3-5 are schematic side views of the sheet feeder of FIG. 1 showing the operation of the stack changing device. 
    
    
     While the invention will be described and disclosed in connection with certain preferred embodiments and procedures, it is not intended to limit the invention to those embodiments. Rather it is intended to cover all such alternative embodiments and modifications as fall within the spirit and scope of the invention. 
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In FIG. 1 a sheet feeder  2  is represented joined with a sheet processing machine, for example with a sheet printing machine  1 . In the sheet feeder  2  there is installed a sheet stack S for processing. The sheet stack S can be lifted by means of a main stack lifting mechanism, which is not shown in detail here, in the rhythm of the sheet processing. The sheets of the sheet stack S are singled on its upper side and fed to the sheet printing machine  1  in a sheet stream. In the sheet feeder  2  there is provided, for this purpose, a sheet singling arrangement  4 . In the sheet feeder  2  there is arranged, further, a remaining-stack carrying device  3  which is assigned to the face side of the sheet feeder  2  turned away from the sheet printing machine  1 . 
     The remaining-stack carrying device  3  is provided with a frame, in which there are borne, longitudinally shiftably, remaining-stack bars  7 . By means of the frame  6  the remaining-stack carrying device  3  is suspended on a remaining-stack lifting mechanism  5 . The remaining-stack lifting mechanism  5 , here, is shown only in its position, but not in details. The remaining-stack lifting mechanism  5  serves to hold a remaining-stack in the sheet feeder  2 , and to lift it in the rhythm of the sheet processing. For this reason the remaining-stack lifting mechanism  5  is also controllable synchronously with the main-stack lifting mechanism. The remaining-stack lifting mechanism consists of vertical guide rails  8  connected with the sheet feeder  2 , on which (rails) the frame  6  is guided, and it has, for example, lifting chains by means of which the remaining-stack carrying device  3  is raisable or lowerable. 
     In FIG. 2 the sheet feeder  2  is shown in a top view. Upon the sheet feeder  2  there follows in the sheet running direction, indicated by an arrow, a so-called conveyor table  20 , over which the sheet stream generated by the singling is transported to the sheet-processing machine, for example to the printing machine  1 . The orientation of the remaining-stack bars  7  is represented in their arrangement with respect to the sheet feeder  2 , only the two outer remaining-stack bars  7  being shown, while others are indicated with action lines. The position shown is, for example, the readiness position before the onset of a changing process, or the waiting position outside of the servicing zone of the sheet feeder  2 . The remaining-stack bars  7  are guided there inside the remaining-stack carrying device  3 , so that in the position shown they occupy a horizontal placement outside the range of the sheet feeder  2 . The remaining-stack bars  7  are subdivided into thicker carrying bars and thinner spacing bars and are arranged in an alternating arrangement. 
     The remaining-stack carrying device  3  with its frame  6  is guided by means of the guide rails  8  on the sheet feeder  2 , and it is vertically movable. The remaining-stack lifting mechanism  5  is indicated in its position and is located as is generally the case on the upper side of the guide rails  8 , for example on the frame of the sheet feeder  2 , it engages from there onto the rack  6  of the remaining-stack carrying device  3  and moves the latter up and down on the guide rails  8 . 
     FIG. 1 shows that the remaining-stack carrying device  3  is installed directly into the sheet feeder  2 , by means of the guide rails  8 . The remaining-stack lifting mechanism  5 , on the one hand, is movable up and down during the supplying of the printing machine  1  with sheets, and the remaining-stack carrying device  3 , on the other hand, is movable outside of the processing zone for the stack changing proper. 
     The stack changing proceeds, therefore, as follows: 
     I. Start on reaching a limit height of the sheet stack S. 
     II. Remaining-stack bars  7  are thrust in common from the rack  6  into the grooves of the pallet underneath the sheet stack S. 
     III. Carrying bars are undercut by a remaining-stack lifting rail and raised until the remaining-stack H is carried by the carrying bars  7 . 
     IV. The pallet is lowered and removed from the sheet feeder  2 . 
     V. Lifting of the remaining-stack with the remaining-stack lifting mechanism  5  to the sheet singling element. 
     VI. Install the new sheet stack S into the sheet feeder  2 . 
     VII. On contact of the upper side of the sheet stack S with the carrying bars the pulling process is initiated: the carrying bars  7  are pulled in pairs from inside outward between the remaining-stack H and the sheet stack S. 
     VIII. The remaining-stack places itself from inside and outward upon the spacing bars. 
     IX. The remaining-stack lifting rail becomes free, the remaining-stack carrying device  3  no longer takes on any load, the spacing bars control the stack unification. 
     X. Spacing bars are continuously drawn out from inside outward between the remaining-stack and the sheet stack S. 
     XI. Remaining-stack deposits itself continuously on the sheet stack S. 
     In a modified version of the run-off, the following procedure is followed: 
     I. Remaining-stack carrying device  3 , after pulling of the carrying/spacing bars is immediately lowered to the stack underedge of the new sheet stack S. 
     II. The carrying/spacing bars are introduced into the grooves of the pallet, in which operation the thrusting-in path is shorter than the total thrusting-in path. 
     III. Remaining-stack carrying device  3  is raised load free, synchronously with the sheet stack S. 
     IV. On reaching the limit height of the sheet stack S the carrying/spacing bars are thrust-in entirely. 
     V. The remaining-stack lifting rail takes over the carrying bars. 
     The run-off is continued as described above. 
     For implementing this run-off, in FIGS. 3 to  5  how the remaining-stack lifting mechanism  5  functions is schematically shown. The remaining-stack lifting mechanism  5  has three pairs of lifting chains  60 ,  61  and  62 . The lifting chains  60  (dashed) are arranged on the front side of the remaining-stack lifting mechanism  5  corresponding to the sheet-processing machine. On this side the remaining-stack lifting rail is also coupled with the lifting chains  60 . It lies, for example, in a vertical guide on supporting stops (not shown here) and can be lifted from there by means of the remaining-stack lifting mechanism  5 . The lifting chains  61  (line double-pointed) are assigned to the oppositely lying rear side of the remaining-stack lifting mechanism  5 . The lifting chains  62  (dotted-dashed) are assigned to the rack  6  of the remaining-stack carrying device  3 . The lifting chains  60  and  61  (dashed-double-dotted) are led over chain-deflecting wheels in the frame of the sheet feeder  1  to a remaining-stack lifting drive  63 . The lifting chains  60  to  62  are led on both sides of the sheet feeder  2  over deflecting wheels (here only indicated) in traverses  64 . The traverses  64  are joined in the frame of the sheet feeder  2  with the remaining-stack carrying device  3  and are guided vertically slidably on the guide rails  8  in common with the remaining-stack carrying device  3  by means of the remaining-stack lifting mechanism  5 . The traverses  64  have supports on their front ends on which the remaining-stack lifting rail can be led along. For this, the remaining-stack lifting rail, in the lifting movement of the remaining-stack lifting mechanism  5  and therewith of the traverses  64 , is lifted off from its lower end position or waiting position, and raised with the remaining-stack carrying device  3 . The remaining-stack lifting rail can obviously also be firmly joined with the traverses  64 . 
     The ends of the lifting chains  60  and  61  are firmly joined on the traverses  64  with a slidable bearing block  65 . On the slidable bearing block  65  there is borne a deflecting chain wheel  66 . Around the deflecting chain wheel  66  the lifting chain  62  is led in a loop. The lifting chain  62  is further led over a deflecting chain wheel  67  from the traverse  64  upward to a deflecting chain wheel  68  on a support  69  carried along with the remaining-stack carrying device  3 , or on the upper end of the guide rail  8  and it extends from there downward again. The ends of the lifting chain  62  are firmly attached, on the one hand, to the traverse  64  and, on the other hand, to the frame  6  of the remaining-stack carrying device  3 . As a consequence of the weight of the remaining-stack carrying device  3  together with the traverses  64 , the lifting chain  62  is tensioned over the loop about the deflecting chain wheel  66  against the lifting chains  60  and  61  and therewith also against the remaining-stack lifting drive  63 . 
     In the bottom position shown in FIG. 3, the lifting chains  60  and  61  are largely driven out. The slidable bearing block  65 , with the deflecting chain wheel  66 , is fixed in this operating position by means of the chain loop, to the right against a stop. The frame  6  of the remaining-stack carrying device  3  is suspended by the lifting chains  62 . The frame can also become seated, with respect to the traverses downward on a stop. The lifting chain  62  is then tensioned over the chain loop on the bearing block  65 . 
     In the raising of the remaining-stack carrying device  3 , as shown in FIG. 4, the lifting chains  60  and  61  are drawn in by the remaining-stack lifting drive  63 . The bearing block  65  is further held over the chain loop in its right hand end position bounded by the length of the lifting chain  62 . In the highest possible operating position of the remaining-stack carrying device  3  in the stack zone the traverses  64  run against stops, which are not shown in this case. Now a further lifting movement of the traverses  64  together with the rack  6  is not possible. 
     In FIG. 5 finally there is shown the out-of-operation position of the remaining-stack carrying device  3 . By further actuating of the remaining-stack lifting drive  63 , over the lifting movement of the lifting chains  60  and  61 , the bearing block  65  is shifted to the left on the traverses  64 . Here the lifting chain  62  runs off over the deflecting chain rolls  66 ,  67  and  68 . The loop in the lifting chain  62  is lengthened there, while the end of that lifting chain  62  that is fastened to the rack  6  is drawn in. Thereby, the frame  6  is lifted by the traverses  64  and raised beyond the upper-end position of the traverses  64 . The frame  6  carrying the remaining-stack bars  7  of the remaining-stack carrying device  3  is thus brought into a parked position. In this position it is taken out of operation. 
     In the lowering of the rack  6  and extension of the traverses  64  the two parts of the remaining-stack carrying device  3  join again and descend in common under the weight load with tensioned lifting chain  62 . 
     The remaining-stack lifting mechanism  5  also is otherwise constructed with further details. Thus, the lifting action of the lifting chain  62  can be increased or decreased by altered deflections in the area of the loop. In this case, for example, there comes in question the action of a pulley block. Further, the connection both of the bearing block  65  and also the connection of the frame  6  with the traverses  64  can be made lockable. This, however, according to experiences of hitherto, is not required. 
     The remaining-stack carrying device  3 , integrated into the sheet feeder with automatic hoisting of the rack  6  carrying the remaining-stack bars  7 , permits the re-equipping of existing sheet feeders  2  with the equipment mentioned for the automatic stack changing. In this instance, despite extended functional possibilities, no additional construction space is required as is the case with other known devices.