Abstract:
A device and a method for turning stacks of sheet-shaped material include a device for transporting the stacks into a pivot fork. The pivot fork is part of a turning unit and includes upper grippers, lower grippers and a stack stop. The pivot fork is open on one side to receive the stacks. The pivot fork is supported at its other end to pivot on a horizontal pivot shaft that extends in a direction transverse to a direction of introduction of the stacks and is disposed off-center relative to the pivot fork.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2010 049 376.7, filed Oct. 26, 2010; the prior application is herewith incorporated by reference in its entirety. 
       BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The present invention relates to a device and a method for turning stacks of sheet-shaped material, including a device for transporting the stacks into a pivot fork of a turning unit, the pivot fork including at least one upper gripper, at least one lower gripper and at least one stack stop and the pivot fork having an opening on one side for introducing stacks and being pivotable on its other end about a horizontal pivot shaft extending transverse to the direction of introduction of the stacks. 
         [0003]    In the production of printed products, for instance folding boxes, for the packaging industry, sheets are printed across their width in a printing press. Each sheet includes a number of blanks of the folding box to be produced. After the printing process, the individual blanks are cut out in a flat-bed die cutting machine in which they are positioned with their printed side facing upward and are deposited in stacks. The cut and stacked folding box blanks are then fed to a folder-gluer with their printed sides facing downward. The blanks are then processed into folding boxes in the folder-gluer. 
         [0004]    The stacked folding box blanks thus need to be turned over before being processed in the folder-gluer. That is a very troublesome process which sometimes requires a machine operator to turn over several tons of cardboard every day. 
         [0005]    German Published, Prosecuted Patent Application DE-AS 1 065 075 discloses a turning table for a stacking device. The turning table includes a clamping plate and a clamping and conveying unit. An actuating drive is provided to drive a closing movement between the clamping plate and the conveying unit to clamp an object. A further actuating drive is used to turn the device in the direction of transport of the object through 180° about pivots disposed at the center of the turning table in order for the clamped stacked cardboard blanks to be turned. Having been turned, the blanks rest on the conveying unit which will then transport them out of the turning device. 
         [0006]    A further turning device is known from European Published Patent Application EP 1 350 748 A2, corresponding to U.S. Pat. No. 6,793,454. The disclosed turning device includes a turning clamp that pivots about a horizontal axis disposed at the center. The turning clamp includes two transport elements. One of the transport elements is a series of rollers and is used to receive the stacks that enter the device. The other transport element is a conveying belt that is used to move the stacks out of the device with the aid of a pusher carriage after they have been turned over. 
         [0007]    Another device for turning stacks is known from U.S. Pat. No. 5,743,374. The disclosed device includes a clamp for receiving the stacks and is moved laterally by a motor to receive and transport the stack. Another motor moves the clamp of the device along a U-shaped path in the device through rollers provided on an outer side of the clamp, thus turning the stack and depositing it on a hopper. 
       SUMMARY OF THE INVENTION 
       [0008]    It is accordingly an object of the invention to provide an alternative device and method for turning stacks of sheet-shaped material, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices and methods of this general type and which operate in a simple, safe and reliable way. 
         [0009]    With the foregoing and other objects in view there is provided, in accordance with the invention, a device for turning stacks of sheet-shaped material, comprising a device for transporting the stacks into a pivot fork of a turning unit. The pivot fork of the turning unit includes upper grippers, lower grippers, and a stack stop. At one end, the pivot fork has an opening for introducing stacks. At the other end, the pivot fork is supported to pivot about a horizontal pivot shaft that extends in a direction transverse to the direction of introduction of the stack. The pivot shaft is disposed off-center relative to the pivot fork. Adaptability to different formats is advantageously achieved by arranging the stack stop to be adjustable relative to the lower grippers. In accordance with a further advantageous embodiment, the stack stop is subdivided into two or more parts. Due to this feature, the device can be easily adapted to guiding asymmetrical blanks. 
         [0010]    In accordance with another, particularly preferred, feature of the invention, the pivot shaft which is disposed off-center relative to the pivot fork, is in the upper region of the pivot fork. Due to this feature, pivot angles of the pivot fork of more than 180° can easily be achieved. Thus, it is possible to deposit the stack on an inclined plane. A horizontal change of path as well as a height change of the stack is attained by the pivoting movement, due to the placement of the pivot shaft off-center in the upper region. 
         [0011]    In accordance with a further advantageous feature of the invention, the lower grippers are disposed in lateral parts of the device and are adjustable in terms of their height relative to the upper grippers. Height adjustment is advantageously achieved by servomotors or pneumatic or hydraulic cylinders. Thus, the stack can be clamped in a simple manner between the upper grippers and the lower grippers to ensure that the stack is securely held during the pivoting movement. Since the clamping may occur at any time during the pivoting movement, it is advantageously possible to pivot the stack without its being clamped at first up to a pivot angle of 70°. Consequently, the stack will automatically align against the stack stop and the lower grippers. If desired, the alignment of the stack may additionally be assisted by vibrating the pivot fork. After the alignment process, i.e. after the stack has been pivoted through an angle of approximately 70°, the stack may be clamped to ensure that it is safely held during the remaining pivoting process. 
         [0012]    In accordance with an added particularly preferred, feature of the invention, the upper grippers are embodied as rolling tracks. This embodiment has a number of advantages: the rolling tracks can be moved out from below the stack after the turning process without causing the blanks to be marked as the belts roll off directly underneath the stack. At the same time, it is possible to provide maximum support even to stacks of asymmetrical blanks when a number of rolling tracks are used, since the rolling tracks may be inserted to different extents and may be moved individually when they are to be retracted. 
         [0013]    In accordance with an additional feature of the invention, the lower grippers and/or upper grippers are disposed to be freely positionable in a direction transverse to the direction of introduction of the stacks. Thus, easy adaptability to different blank formats is achieved. In addition, when more than two lower grippers and/or upper grippers are being used, further adaptation to asymmetrical blanks is easily possible. 
         [0014]    In accordance with yet another preferred feature of the invention, the pivot fork is adjustable through the use of a height adjustment device. The height adjustment device is disposed on the lateral parts of the device and the pivot shaft is supported in guides in the lateral parts of the device. Thus, the height of the turned stack relative to the residual stack in the feeder is easily adjustable. Likewise, while the rolling tracks are being pulled out, the pivot fork may be further adapted to the decreasing residual stack in the feeder. Thus, the spacing between the upper edge of the residual stack and the lower edge of the turned stack remains approximately constant. This fact has a positive effect on the falling behavior of the turned stack. Advantageously, the height adjustment device is disposed obliquely in the lateral parts of the device and the pivot shaft is supported in oblique guides in the lateral parts of the device. In accordance with a preferred embodiment, the height adjustment device may be formed of a rack and a driven pinion. However, any other height adjustment by motor, pneumatic cylinder, or hydraulic cylinder is likewise possible. 
         [0015]    In accordance with yet a further, particularly preferred, feature of the invention, the transport device for transporting the stacks into the pivot fork has a bipartite construction. The first part of the transport device is located in the stack feeding device and extends almost as far as the start of the pivot fork. The second part of the transport device extends across the depth of the pivot fork. The two transport devices advantageously have independent individual drives. Thus, they can be separately operated using sensors and controls. Even different speeds are possible. Thus, gaps of varying sizes between the individual stacks can be compensated for and a new stack will always be available in a stand-by position while a stack is being turned in the pivot fork. 
         [0016]    With the objects of the invention in view, there is concomitantly provided a method of turning stacks, which comprises the following steps:
       a) feeding a stack into the pivot fork against a stack stop;   b) lifting the stack through the use of height-adjustable lower grippers or by rotating the pivot fork;   c) pivoting the pivot fork through an angle of approximately 70°;   d) aligning the stack against the stack stop and the lower grippers;   e) clamping the stack between lower grippers and upper grippers by further height-adjustment of the lower grippers;   f) continuing the pivoting operation until a final position is reached;   g) retracting the upper grippers;   h) depositing the turned stack;   i) rotating the pivot fork back and extending the upper grippers into the starting position; and   j) repeating steps a) to i) until all stacks are turned.       
 
         [0027]    Advantageously, the stacks are aligned up to a pivoting angle of approximately 70°. Since the pivoting angle may be more than 180°, it is possible to deposit the stacks on an inclined plane. 
         [0028]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0029]    Although the invention is illustrated and described herein as embodied in a device and a method for turning stacks of sheet-shaped material, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
         [0030]    The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0031]      FIG. 1  is a diagrammatic, perspective view of a device according to the invention including a stack feeding device, a turning unit, and a feeder; 
           [0032]      FIG. 2  is a perspective view of the device shown in  FIG. 1  after completion of a turning process; 
           [0033]      FIG. 3  is a side-perspective view of important parts of the turning unit of the invention; 
           [0034]      FIG. 4  is a further side-perspective view of the important parts of the turning device of the invention; 
           [0035]      FIG. 5  is an enlarged, fragmentary, sectional view of an upper gripper; 
           [0036]      FIGS. 6A-6H  are side-elevational views representing movement of a pivoting process; and 
           [0037]      FIGS. 7A-7D  are side-elevational views representing partial movements of the pivoting movement. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0038]    Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a device  1  according to the invention for turning stacks  5 . The stacks  5  are fed to a pivot fork  12  of a turning unit  3  through the use of a stack feeding device  2 . Roller cheeks  6  are provided to feed the stacks  5 , which are aligned in the lateral direction, against a stack alignment plate  7 . The stack alignment plate  7  may advantageously include height marks  37  to aid the operator in providing stacks of acceptable weight with respect to given tolerances. The roller cheeks  6  transport the stacks  5  as far as a stack stop  11  formed on the pivot fork  12 . Alternatively, this transport can be carried out by a subdivided roller cheek system  6 ,  6 ′, which will be explained in more detail with reference to  FIG. 7A . Lower grippers  10  of the pivot fork  12  are provided underneath and between the roller cheeks  6 . The lower grippers  10  are adjustable in terms of their height and lift the stack  5  that has been introduced into the pivot fork  12 . Alternatively, the stack may be lifted by pivoting the pivot fork. The pivot fork  12  additionally includes upper grippers  9 , which are disposed on a pivot shaft  8  through drive heads  24  so as to pivot about the pivot shaft  8 . The lower grippers  10  are disposed on the pivot shaft  8  through a crossbar  26  and lateral parts  25  and likewise pivot about the pivot shaft  8 . During a pivoting process, the stack  5  will align against the lower grippers  10  and the stack stop  11  and will then be clamped between the upper and lower grippers  9 ,  10  by a further height adjustment of the lower grippers  10  relative to the upper grippers  9 . During a further pivoting movement, the stack  5  rests on the upper grippers  9 . When the pivoting movement is completed, the upper grippers  9  will be retracted and the stack  5  will fall down a chute closed on four sides and formed by adjustment tongues  14 , lateral stack guides  13  and the stack stop  11 , to be deposited in a feeder  4 . The device  1  has lateral parts  32  with guides  33  extending obliquely therein. A height adjustment device  31  is disposed on the lateral parts  32  for adjusting a height of the pivot fork  12 . The pivot shaft  8  is supported in the guides  33 . 
         [0039]      FIG. 2  illustrates a condition at an end of the pivoting movement. The stack  5  has been turned and is clamped between the upper and lower grippers  9 ,  10 . 
         [0040]      FIGS. 3 and 4  illustrate important parts of the turning unit  3  of the invention within the device  1 . The turning device  3  includes the pivot fork  12  including the upper grippers  9  and lower grippers  10  as well as the stack stop  11 . The stack stop  11  is adjustably disposed on the lower grippers  10 . Thus, the pivot fork  12  is easy to adjust to accommodate stacks of different, even asymmetrical formats. The stack may be turned using only one lower gripper  10  for blanks of small width. In order to prevent the stack from tilting, a clip-on element  35  may advantageously be mounted to the lower gripper  10  to increase the support surface for the stack, thus contributing to an easier alignment of the lower gripper relative to the center of gravity of the stack. The clip-on element is advantageously of smaller width than two lower grippers next to each other. The upper grippers  9  are embodied as rolling tracks  22  that are driven by belts  21  which are in turn driven by a motor  17 , a sprocket  20 , a timing or sprocket belt  23 , and a square shaft  16  (as will be explained in more detail below with reference to  FIG. 5 ). When the stack is turned or an emergency stop occurs, the rolling tracks  22  may slowly slide downward, depending on the position of the pivot fork  22  (for instance in the vertical position). This is advantageously prevented by the torque of the short-circuited motor  17  as well as by a spring force brake  36 . 
         [0041]    The upper grippers  9  are mounted in the so-called drive heads  24 . The drive heads  24  are supported on the pivot shaft  8  about which the entire pivot fork  12  may be pivoted. The lower grippers  10  are mounted to the crossbar  26 , which is supported in guides  18  in the lateral parts  25  of the pivot fork  12  and can be adjusted in terms of their height relative to the upper grippers  9  by a linear drive  15 . The linear drive may be a servomotor, a pneumatic cylinder, or a hydraulic cylinder. 
         [0042]    The functioning of the upper grippers  9  becomes apparent from  FIG. 5 . A belt  21 , guided by various rollers  34  and a drive shaft  16 , extends within the rolling track  22 . A tensioning element  27  is provided for adjusting the tension of the belt. When the belt  21  is driven by the drive shaft  16 , the rolling track is displaced relative to the drive head  24  in the direction of the arrow. 
         [0043]      FIGS. 6A-6H  are diagrammatic representations of the sequence of movements of the turning device of the invention. 
         [0044]    In  FIG. 6A , the stack feeding device  2  introduces the stack  5  into the pivot fork  12  as far as the stack stop  11 . Subsequently, ( FIG. 6B ) the pivot fork  12  starts its pivoting movement about the pivot shaft  8  and lifts the stack  5 . During this movement, the stack  5  aligns against the lower grippers  10  and the stack stop  11 . This alignment process is completed after a pivoting movement through approximately 70°. Then the lower grippers  10  move in the direction of the upper grippers  9  ( FIG. 6C ) to clamp the stack  5  between the upper grippers  9  and the lower grippers  10 . The stack  5  is pivoted further until it reaches its final position which is at a pivot angle of approximately 195° in the illustrated example ( FIG. 6D ). 
         [0045]      FIG. 6D  further illustrates two sensors  29 ,  30 . The height of the sensor  29  is manually adjustable by an operator. The sensor  29  provides signals to the pivot fork  12  when the stack provided in the feeder  4  has been processed down to a target height to indicate that a new stack  5  to be turned needs to be provided. The height of the lower sensor  30  is likewise adjustable. The sensor  30  provides a signal when the stack provided in the feeder  4  has reached a critical minimum height without a new turned stack having been introduced. The result of this signal may be that a downstream machine may be switched off. Once the turning process has been completed, the pivot fork  12 , as shown in  FIG. 6E , will be lowered almost down to the upper edge of the residual stack through the use of the height adjustment device  31  (seen in  FIG. 1 ). Then the upper grippers  9 , which are embodied as rolling tracks  22  as described above, are pulled out. While the movable rolling tracks  22  are being pulled out, the stack  5  continues to be clamped between the upper gripper  9  and the lower gripper  10  to prevent the stack  5  from prematurely sliding out of the pivot fork  12 . As soon as the rolling tracks  22  have been completely pulled out from under the stack  5 , the turned stack ( FIG. 6F ) as a whole will fall down the chute which is closed on four sides and formed by the adjustment tongues  14 , the lateral stack guides  13  and the stack stop  11  into the feeder. In order to provide further assistance, the pivot fork  12  may additionally be lowered in the direction of the arrow by the height adjustment device  31 . The height adjustment device  31  is controlled by the sensors  29  and a non-illustrated control unit. Subsequently, the pivot fork  12  rotates back into a position approximately 15° before the vertical position. At the same time, the pivot fork  12  is moved back into its uppermost position in the direction of the arrow through the use of the height adjustment device  31 . Then the extendable rolling tracks  22  move into their initial position and the pivot fork finishes its rotation back into the initial position ( FIG. 6H ). 
         [0046]      FIG. 7A  illustrates an alternative sequence of movements during the feeding of the stack  5  into the pivot fork  12 . In contrast to the stack feeding process illustrated in  FIG. 6A , the roller cheeks  6  and  6 ′ in  FIG. 7A  have a bipartite construction. The roller cheeks  6  have their own drive M. They transport the stack into the stack feeding device  2 . The roller cheeks  6 ′, which are likewise driven by their own drive M, transport the stack  5  into the pivot fork  12 . The roller cheeks  6 ,  6 ′ are controlled by non-illustrated sensors and a control unit. In the stack feeding device, the stacks  5  are transported to a park position at the end of the roller cheeks  6 . When the pivot fork  12  is in a receiving position, the roller cheeks  6 ,  6 ′ receive a signal causing them to transport the next stack  5  into the pivot fork  12 . Different gaps in the stack feeding device  2  are compensated for due to the independent drives. 
         [0047]      FIGS. 7B-7D  illustrate an alternative further sequence of movements when the turned stack  5  is deposited in the feeder  4 . The feeder may optionally include a front edge support  28  for supporting a front edge of the stack. The front edge support  28  may be adjustable in terms of its height and may be extended and retracted. It is extended to receive the front edge of the pivoted stack  5 . The pivoted stack rests on the upper grippers  9  and on the front edge support  28 . As shown in  FIGS. 7C and 7D , the upper grippers  9 , which are embodied as rolling tracks as described above, are pulled out. At the same time, the front edge support  28  is pulled out. Thus, the turned stack ( FIG. 7D ) will fall down the chute which is closed on four sides and formed by the adjustment tongues  14 , the lateral stack guides  13  and the stack stop  11 , to be deposited in the feeder  4  as described above.