Abstract:
A method and apparatus of buffering sheets of cut stock in block-shaped stacks ranged in rows between stock-cutting machinery and further processing machinery, whereby each row is also block-shaped. Each row produced by the cutting process is forwarded to a buffer&#39;s intake and thence to a marshaling area where it is combined with previously forwarded rows into a group. Each group is forwarded to the buffer&#39;s outtake and combined with any other rows already there. The most downstream row of the group is forwarded to the further-processing machinery.

Description:
BACKGROUND OF THE INVENTION 
     The present invention concerns a method of and a device for buffering sheets of cut stock in block-shaped stacks ranged in rows between stock-cutting machinery and further-processing machinery. 
     A method of and a device for cutting stacked sheets of paper, cardboard, plastic, etc., especially sheet assemblages, is known from German A 3 101 911. The device is a guillotine. To ensure that the blade always cuts the stack along the intended line, the stack must be advanced below the blade very precisely. Even slight displacements, dimensional deviations due to curling paper for instance, can force the blade to cut the paper away from the intended line. Assemblages especially, with a number of labels printed on them, can accordingly be cut inside the print. To prevent this malfunction the sheets are printed with the separate printed matter not immediately mutually adjacent but with empty passages left between them. It is accordingly admittedly necessary to make additional cuts between the main cuts, although the procedure does prevent cutting into the printed matter. The stacks can also be trimmed at their margins before they are cut. The advantage of this approach is that, once the margins have been trimmed, the stack will be in a prescribed shape or format, a decisive feature for ensuring the accuracy of the following major cut. When labels are cut, the margin-trimmed block-shaped stack is initially cut parallel to the main cut and then parallel to any intermediate cuts and rotated 90° to allow main cuts and intermediate cuts if any to be made perpendicular to the original cuts. Subsequent to every 90° rotation, accordingly, every main cut will leave a row of smaller block-shaped stacks adjacent parallelling the blade, every row itself being block-shaped. The smaller stacks are forwarded to further-processing machinery, where they are punched or bundled for example. 
     From the processing steps hereintofore described it will be evident that the stock will necessarily leave the stock-cutting machinery discontinuously. It will accordingly take several minutes, two or three for instance, to make the marginal cuts and to cut the main stack into strips. During this time, no cut stock can be forwarded to the further-processing machinery. The further processing machinery, however, could easily handle the smaller stacks, bundling them or punching out irregularly shaped labels and then bundling them. 
     Every row of smaller stacks produced by the guillotine described in German A 3 101 911 must be removed from the vicinity of the blade manually and transferred to an adjacent counter, whence they can be forwarded manually to the further-processing machinery. 
     Stock-cutting machinery with two guillotines is known from European A 0 242 763. The downstream guillotine generates the rows of stacks, and a pusher removes them longitudinally. In practice, the pusher transfers each row generated in this system onto an adjacent counter and hence directly to further-processing machinery, where each stack is banded. 
     A multiple bundler with a feed is known from German U 29 804 929. This device is employed to bundle discontinuously supplied rows of finished stacks, large-format stock in other words, and not to handle rows of smaller stacks. 
     SUMMARY OF THE INVENTION 
     The object of the present invention is accordingly a method of and a device for buffering rows of stacked sheets of stock for cutting that will allow downstream continuous processing in further processing machinery of material discontinuously cut in stock cutting machinery. 
     This object is attained in accordance with the present invention by providing a special approach to buffering the rows of stacks resulting from each cut. Each row is forwarded to the buffer&#39;s intake and thence to a marshaling area. Depending on the cutting process and accordingly on the further supply of rows to the buffer&#39;s intake, several rows are assembled in the buffer&#39;s marshaling area and forwarded to its outtake. If there are any rows already there, the new rows are combined along with them into a group. Otherwise, they are forwarded directly to where the most downstream row will be the next supplied to the further-processing machinery. Whereas the rows in the outtake can be continuously supplied for further processing, the rows at the marshaling area will continue to be assembled and supplied to the outtake before the rows in the outtake can be processed. Thus, stacks or rows of stacks will always be available for further processing. 
     The stacks are composed of separate layers and not easy to handle. There is in particular a risk of the individual layers sliding over each other. The stacks and rows must accordingly be rotated as little as possible in the buffer. The rows must accordingly be forwarded from the buffer&#39;s intake to its marshaling area and from its marshaling area to its outtake in one direction. To ensure optimal spacing of the mechanical components that carry out the method, the rows should be forwarded from the stock-cutting machinery to the buffer&#39;s intake at a right angle to the direction they are forwarded from its intake to its marshaling area in. The rows should similarly be forwarded from the buffer&#39;s marshaling area to its outtake at a right angle to the direction they are forwarded from its outtake to the further-processing machinery in. The rows can in particular be forwarded from the stock-cutting machinery to the buffer&#39;s intake in a direction opposite the direction they are forwarded from its outtake to the further processing machinery in. 
     The rows or groups can in particular be forwarded in accordance with the present invention by pushing. This is an especially simply way to ensure that the evident stacks will be forwarded precisely into their intended positions. To ensure particularly simple forwarding of the individual rows, the row produced by a specific cutting process in one particular embodiment of the present invention can be electrostatically block-formed, especially before it is forwarded to the buffer&#39;s intake. Electrostatically block-forming a row allows it to be forwarded in various ways, especially by belts that can be positioned to convey the individual stacks in a row. 
     It should be impossible to initiate forwarding of the group from the marshaling area to the outtake while a row is being forwarded from the intake to the marshaling area. This feature will prevent forwarding from the intake to the marshaling area and forwarding from the marshaling area to the outtake from interfering with each other at the marshaling area. 
     It will be preferable for a row being forwarded to the further processing machinery to be separated from its adjacent row before being forwarded. This feature will prevent relative motion between the individual sheets while adjacent rows are being forwarded. 
     Another object of the present invention is a device for carrying out the method hereintofore described. 
     It is practical for some or all of the row-forwarding mechanisms to be pushers and especially pneumatically or electromechanically actuated pushers. The second row-forwarding mechanism is intended to forward a row released from the stock-cutting machinery far enough to allow the next row to be released. The third row forwarding mechanism forwards several rows released from the second row-forwarding mechanism to the fourth row-forwarding mechanism. The fourth row-forwarding mechanism forwards each row to the further-processing machinery individually. All row forwarding mechanisms, or pushers, are accordingly intelligently networked. The device can accordingly be provided with detectors that detect at least the ends of the strokes traveled by the row forwarding mechanism. These detectors can for example be light barriers, limit switches, etc. The row-forwarding mechanisms, the pushers, are regulated to prevent actuation of the second mechanism while the first is forwarding a row into the vicinity of the second and to prevent the third row-forwarding mechanism from initiating any forwarding motions toward the rows in the vicinity of the marshaling area on the counter while the second mechanism is about to forward a row. Furthermore, the third row-forwarding mechanism must not forward a group into the vicinity of the fourth row-forwarding mechanism while the latter is forwarding the row in question to the further-processing machinery. 
     Forwarding can be optimized, especially with respect to time, if the first and/or the third row-forwarding mechanism and/or the fourth row-forwarding mechanism can be raised and lowered. The third row-forwarding mechanism can in this event forward a group while the fourth row-forwarding mechanism is raised in order to forward the next row to the further-processing machinery, in particular when the latter is to punch or bundle the material. 
     One practical means of electrostatically block-forming the rows as hereintofore described is a component in the vicinity of the first row-forwarding mechanism. 
     Further characteristics of the method and device in accordance with the present invention will be evident from the subsidiary claims, the specification, and the figures. All characteristics and combinations thereof are essential to the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the method and device in accordance with the present invention will now be specified but without limiting its scope in any way with reference to the accompanying drawing, wherein 
     FIG. 1 is a top view of the buffer, 
     FIG. 2 is a section through the buffer along the line II—II in FIG. 1, 
     FIG. 3 is a section through the buffer along the line III—III in FIG. 1 but showing only the essential components, 
     FIG. 4 is a section through the buffer along the line IV—IV in FIG. 1 but showing only the essential components, and 
     FIG. 5 is an illustration similar to FIG. 4 but showing one row separated from a group of rows. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The buffer includes a counter  1  comprising an intake area  2 , a marshaling area  3  and a layoff area  4 . Areas  2 ,  3 , and  4  are rectangular, appropriate for accommodating stacks of stock for cutting. Intake area  2  adjoins the longer side  6  of marshaling area  3  adjacent one shorter side  7 . The longer side  8  of layoff area  4  adjoins the other shorter side  9  of marshaling area  3 . The intake area  2  has a longer side  10  that essentially aligns with the shorter side  7  of marshaling area  3 . In this vicinity is a straightedge  11  that extends along intake area  2  and is elevated above the surface  5  of marshaling area  3  slightly higher than the tallest stack of material being cut. Sliding back and forth in marshaling area  3  in a plane paralleling that of lateral straightedge  11  is a pusher  12 , also in the form of a straightedge and similar in structure to straightedge  11 . When pusher  12  is in the advanced position represented by the continuous lines in FIG. 1, the contact surfaces of straightedge  11  and pusher  12  are aligned. The opposite position of pusher  12  is represented in FIG. 1 by broken lines. Pusher  12  extends essentially over the total width of marshaling area  3 . In the vicinity of the second longer side  13  of marshaling area  3  is a lateral straightedge  14  that extends over the total length of marshaling area  3  and considerably over the width of layoff area  4 . Lateral straightedge  14  is similar in shape to lateral straightedge  11 . In the vicinity of the second longer side  13  of marshaling area  3  is a pusher  15  in the form of a moving straightedge. Pusher  15  is similar in shape to pusher  12  and travels over a plane paralleling the plane traveled by pusher  12 , although pusher  15  can travel essentially over the total length of marshaling area  3  and can be raised and lowered. Layoff area  4  has in the vicinity of its second longer side  16  a lateral straightedge  17  that parallels pushers  12  and  15  and extends over the total length of layoff area  4 . Paralleling lateral straightedge  17  is a narrow pusher  18  that can be raised and lowered perpendicular to the surface  5  of marshaling area  3  and travels essentially over the total length of layoff area  4 . Pusher  18  is located on the side of lateral straightedge  17  facing pusher  15  and is narrower and accordingly able to forward a row  19  of stacks longitudinally. Corresponding to pusher  18  is a pusher  20  in the vicinity of intake area  2 . Pusher  20  travels parallel to and near the longer side  10  of intake area  2  and can forward a row  19  of stacks longitudinally. Pusher  20  can also be raised and lowered. 
     Pusher  12  can accordingly travel only horizontally, paralleling the surface  5  of marshaling area  3 . Only that portion of pusher  20  in contact with row  19  of stacks is depicted. It is powered by a mechanism similar to the mechanism that drives pusher  18  and that will be specified hereinafter. These mechanisms are actuated in accordance with the actions carried out in buffering the stock, and it will also be possible to detect the ends of their strokes. Pusher  12  is connected to two connecting rods  21  and  22  that extend through stationary bearings  23  and  24 . Pusher  12  is engaged by a piston rod  25  that operates in conjunction with a stationary pneumatic cylinder  26 . Pushers  20  and pusher  12  are synchronized such that pusher  12  cannot move while pusher  20  is traveling toward marshaling area  3  and pusher  20  cannot move while pusher  12  is traveling toward pusher  12 . 
     A flat pusher accommodation  27  paralleling the surface  5  of marshaling area  3  accommodates the upper edge of pusher  15 . Two connecting rods  27  and  28  are accommodated in counter  1  in the vicinity of the second longer side  13  of marshaling area  3  and extending along it. Connecting rods  27  and  28  accommodate a carriage  30 . Carriage  30  accommodates vertical bearings  31  and  32 . Connecting rods  33  and  34  extend through bearings  31  and  32  and are connected to pusher accommodation  27 . Carriage  30  accommodates a pneumatic cylinder  35 , its piston rod  36  engaging a component  37  mounted on pusher accommodation  27 . Carriage  30  is provided with a threaded accommodation bore  38  that a spindle  39  fits into. The mechanisms that drive the spindle  39 , a motor for example, are not illustrated. As the spindle rotates, carriage  30  will travel toward connecting rods  28  and  29 , moving pusher  15  horizontally or, when pneumatic cylinder  35  is engaged, vertically. What is essential here is that spindle  39  and pneumatic cylinder  35  conform to the particular stage of events involved in the buffering process and in particular that the vertical and horizontal motions of pneumatic cylinder  35  will be intelligently controlled. Means must accordingly be provided of detecting the horizontal position of pusher  15  at any time, whether for instance, it happens to be above spindle  39 . This capability depends on the overlap between the operating ranges involved, more precisely between the ranges of pusher  12  and pusher  15  on the one hand and between those of pusher  15  and pusher  18  on the other, as will be specified hereinafter. 
     Pushers  18  and  20  are mounted similar to pusher  15 , allowing them to move both vertically and horizontally. The accommodation for pusher  18  is similar to the accommodation  27  for pusher  15  and the same reference number is employed for simplicity&#39;s sake. Pusher  18  is accommodated in a bearing  40  similar to the accommodation  27  illustrated in FIG.  2 . Like pusher  15 , pusher  18  is controlled intelligently to confirm with the particular operations involved. 
     A row  19  of already cut stacks is forwarded by pusher  20  from an unillustrated guillotine to intake area  2  and hence to marshaling area  3 . FIG. 1 illustrates an intermediate position of pusher  20 , in which it remains until downstream pusher  12  has forwarded farther the row  19  previously forwarded to it by pusher  20 . As pneumatic cylinder  26  engages, each row  19 , comprising ten stacks  42 , is forwarded to a prescribed extent along marshaling area  3  by pusher  12 , now represented by the broken lines. Once row  19  has been forwarded this distance, pusher  12  rises and retreats and descends again behind and ready to forward a new row produced by the continuous action of the guillotine. Pusher  20  now forwards the next row  19  into the vicinity of pusher  12 . Pusher  12  engages again and forwards the row. This row in turn forwards farther the latest row forwarded by pusher  12 . The rows combine into a group. In contrast to the repeatedly operating pusher  12 , the intelligently controlled pusher  15  forwards a group  43  of rows  19  farther, constantly supplying pusher  18  with rows to be forwarded out. Once enough rows  19  have been forwarded by pusher  12  and a large enough group  43  has accumulated, pusher  15  is lifted and, as pusher  12  returns, retracted into the limiting position  44  illustrated in FIG. 3, which, however, is to be considered only an indicator, where it descends behind group  43 . Now, the finished group  43  if forwarded by pusher  15  and combined with the rows  19  still in the vicinity of layoff area  4  and in the adjacent vicinities of marshaling area  3 . This situation is illustrated in FIG.  1 . Four rows  19  can for example have been forwarded by pusher  15  and combined with four other rows  19  still remaining in marshaling area  3  and layoff area  4 . The intelligently controlled pusher  15  will accordingly move only when and only to the extent required by the buffering process. When the guillotine does not release any rows  19  for some time, while for example it is cutting margins and intermediates, pusher  18  might expel only the last row in the vicinity of layoff area  4 , in which event intelligently controlled pusher  15  would forward the group  43  obtained from the vicinity of pusher  12  into the vicinity adjacent to pusher  18 . The intermediate position  45  of pusher  15 , also to be considered only an indicator, is illustrated in FIG.  1 . Also illustrated is the position  46  of pusher  18 . 
     FIGS. 4 and 5 show that a front row  19  of stacks associated with pusher  18  is never immediately expelled by pusher  18  once it has been forwarded by pusher  18 , but is separated from its neighboring row by an in-itself known cylinder  47  with spines that extend through slots in layoff area  4  and revolve down into contact with the individual stacks  42  as the cylinder turns, forcing them against the lateral straightedge  17  in layoff area  4 . FIG. 1 shows pusher  18  in two positions, specifically in a position, before its adjacent row  19  has been separated out by spined cylinder  47 , and in an intermediate position as the row is being forwarded to further-processing machinery  49 , some of the stacks  42  already being further processed. 
     FIG. 1 shows a component  50  in the vicinity of intake area  2  that electrostatically block-forms a row  19  of stacks produced by the cutting process. A component of this type (the VBS 951, manufactured by Segbert GmbH &amp; Co., 48619 Heek) is state of the art. Each row  19  is forwarded through the buffer block-formed and is unformed just before being released to the further-processing machinery, accordingly advancing through the buffer in the form of a more or less stable group.