Abstract:
A sheet accumulator has a circular paper path and a compact design. Individual sheets of paper moving along a main linear path are diverted into the accumulator one by one, and each sheet enters a gripper having jaws that grip the sheets of paper. The gripper jaws pull the sheets along the circular paper path until the gripper returns to a home location, at which point the gripper stops, opens, accepts another sheet, closes, and makes another rotation. When the accumulation is complete, the gripper jaws open to release an accumulated stack of sheets, and a roller is then engaged to exit the sheets out of the accumulator and into the main linear paper path.

Description:
CROSSFERENCE TO RELATED APPLICATION  
       [0001]    Reference is made to Application Ser. No.______ (Attorney Docket No. F-140), entitled SHEET ACCUMULATOR HAVING A CIRCULAR FEED PATH, assigned to the assignee of this application and filed on even date herewith. 
     
    
     
       TECHNICAL FIELD  
         [0002]    This invention relates to paper sheet accumulators, and more specifically to a paper sheet accumulator wherein paper sheets are accumulated individually and then dispensed collectively as a stack.  
         BACKGROUND OF THE INVENTION  
         [0003]    Numerous accumulators have been used for accumulating paper sheets and documents into stacks and then transporting the accumulated stacks. For instance, Driscoll et al. (U.S. Pat. No. 5,147,092) discloses a flat accumulator comprised of upper and lower sets of driven elastic belts.  
           [0004]    Although a flat type of accumulator is appropriate for some applications, its dimensions are too large or bulky for other applications. This related art cannot conform to the space limitations and layout of certain machines in which a sheet accumulator must form a component part. In addition to problems of size and shape, the related art also has problems when accumulating paper that does not have normal buckling properties, such as perforated paper. For example, Miller, (U.S. Pat. No. 5,356,263) discloses a sheet accumulator in which it is necessary for sheets of paper to buckle very substantially, which becomes problematic when the sheet of paper has characteristics inconsistent with normal buckling (e.g. perforated paper). Another problem encountered with some of the related art is that the accumulation process may yield sheets that are out of order or inverted; in other words, the stack of paper produced may be either face down or lead-edge trailing relative to the input sheets of paper.  
         SUMMARY OF THE INVENTION  
         [0005]    The main objective of this invention is to provide a sheet accumulator for accumulating sheets of paper one by one which arrive at the sheet accumulator along a main linear paper path, and for then allowing the stack of accumulated sheets to exit the accumulator. Another objective of the present invention is to minimize the amount of space required by the sheet accumulator. Accordingly, the present invention is a compactly designed sheet accumulator in which the paper path is circular. This design conforms to space limitations which other sheet accumulators, such as flat accumulators, are unable to achieve.  
           [0006]    According to the present invention, individual sheets of paper moving along a main path enter into the accumulator one at a time, whereupon each sheet registers its lead edge against a backstop. Then a set of gripper jaws seizes the lead edge of that sheet of paper, while also seizing the lead edges of any other sheets of paper that are already registered against the backstop, whereupon the jaws pull all of the gripped sheets of paper along a circular path until the gripper jaws return to a home location. At the home location, the jaws open so as to accept an additional sheet of paper. The process repeats itself until a predetermined number of sheets are accumulated into a complete stack. Once this complete stack of sheets is registered against the backstop, the stack is exited out of the sheet accumulator into the main linear paper path.  
           [0007]    The present invention is designed to offer an economical sheet accumulator with a compact configuration that allows the accumulator to fit into spaces where many other sheet accumulators cannot fit. The present invention is also designed in such a way as to easily handle paper prone to buckling, such as perforated paper. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    [0008]FIG. 1 is a side view of the sheet accumulator showing the paper guide, with the gripper jaws at the home location, ready to accept a sheet of paper.  
         [0009]    [0009]FIG. 2 is a side view of the sheet accumulator which has accepted an initial sheet of paper, with the gripper jaws again at the home location (the paper guide is again shown).  
         [0010]    [0010]FIG. 3 is a side view of the sheet accumulator with the gripper jaws closed and the sheet of paper being pulled along a circular path (the paper guide is not shown).  
         [0011]    [0011]FIG. 4 is a side view of the sheet accumulator with the gripper jaws open, at the home location, and accepting an additional sheet of paper (the paper guide is not shown).  
         [0012]    [0012]FIG. 5 is a side view of the sheet accumulator with the jaws ungripped at the home location (the paper guide is not shown).  
         [0013]    [0013]FIG. 6 is a side view of the sheet accumulator with the ungripped jaws revolved out of the way, enabling the stack of sheets to be exited out of the apparatus (the paper guide is not shown).  
         [0014]    [0014]FIG. 7 is a front view of the sheet accumulator, with the jaws ungripped at the home location (the paper guide is not shown). 
     
    
     DETAILED DESCRIPTION  
       [0015]    As best seen in FIGS. 1 and 2, the sheet accumulator  10  has gripper jaws  12  which define a mouth  14  for accepting the lead edge  16  of a sheet of paper  18 . Each sheet of paper  18  that arrives at the entry point  19  of the sheet accumulator  10  enters the mouth  14 , and registers against a backstop  20 . The gripper jaws  12  are revolvable, and pull each sheet of paper  18  along a circular paper path defined by the outer perimeter  22  of a circular device  24 , and the inner perimeter  27  of a circular paper guide  29 .  
         [0016]    As best seen in FIGS. 3 and 4, the gripper jaws  12  pull each sheet of paper  18  as the gripper jaws revolve. When the gripper jaws  12  are open, they define a mouth  14  which is adjacent to the outer perimeter  22 . While pulling each sheet of paper  18 , the gripper jaws  12  are in a closed position so as to tightly grip the lead edge  16 , as seen in FIG. 3. The mouth  14  opens after it revolves to a home location  21  where the jaws release the lead edge  16 , as seen in FIG. 4.  
         [0017]    The backstop  20 , against which each sheet of paper registers, is perpendicular to the outer perimeter  22  and extends outward from the outer perimeter  22 . As best seen in FIGS. 4 and 5, sheets  18  enter the sheet accumulator  10  one by one, register against the backstop  20 , and then all the sheets are pulled around the outer perimeter  22 . As seen in FIG. 6, a complete stack of sheets  25  will exit the sheet accumulator  10  after a predetermined number of sheets have been ungripped by the gripper jaws  12 .  
         [0018]    Further description of the best mode for operating the present invention can be seen in FIG. 7, which is a view from the front of the sheet accumulator  10 , instead of a side view as in FIGS.  1 - 6 . In FIG. 7, the mouth  14  is at the home location  21  and is open, as in FIGS. 1, 2,  4 , and  5 . FIG. 7 shows that the circular device  24  comprises a rotatable drum  26  and two rotatable disks  28 , the mouth  14  being adjacent to the rotatable drum  26  and not adjacent to the two rotatable disks  28 . The rotatable drum  26  and the two rotatable disks  28  all have substantially the same circumference as each other.  
         [0019]    The mouth  14  of the gripper jaws  12  is opened and closed by movement of the inner jaw  30  only, while the outer jaw  34  remains stationary relative to the outer perimeter  22 . The inner jaw  30  is attached to a pivot member  32 , and the inner jaw  30  moves toward the outer jaw  34  by pivoting around the pivot member  32 . This is best seen in FIGS. 3 and 4 where the mouth  14  is closed and open, respectively. The fact that the outer jaw  34  of FIG. 4 is pivoted with respect to the outer jaw  34  of FIG. 3 is easily seen with the help of the reference box  35 . The inner jaw  30  is also attached to a spring  36  which urges the inner jaw  30  to pivot toward the outer jaw  34  and thus to close the mouth  14 . The inner jaw  32  pivots away from the outer jaw  34 , against the force of the spring  36 , when a cam  38  forces the inner jaw  32  away from the rotation axis of the cam  38 . The cam is attached to a cam shaft  40 , as shown in FIG. 7, which rotates the cam  38  so as to open and close the mouth  14 .  
         [0020]    The sheet accumulator  10  operates in a repetitive manner, accumulating a stack of sheets  25  by accepting sheets one by one into the mouth  14  defined by the gripper jaws  12 . Each sheet  18  stops when it hits the back throat  42 , the back throat being the only surface of the backstop  20  that comes into contact with each sheet of paper  18 . The back throat  42 , the gripper jaws  12 , the cam  38 , the spring  36 , the cam shaft  40 , and the rotatable drum  26  are all coupled together and move in unison around the central drum shaft  44 . The gripper jaws  12  grip a successively greater number of sheets until a predetermined number of sheets has revolved around the circular device  24  in the rotation direction  46 . The gripper jaws  12  will always open and then close at the home location, except after a complete stack of sheets  25  is released, in which case the gripper jaws  12  will revolve away from the home position while remaining open, as best seen in FIG. 6.  
         [0021]    In the embodiment of this sheet accumulator  10  shown in FIGS.  1 - 6 , a sensor  48  detects when a sheet has registered against the backstop  20 , so that the cam will then close the mouth  14 . This sensor  48  can be situated at various places, such as near the trail edge  50  of the registered sheet of paper  18 .  
         [0022]    The rotatable disks  28  are free to rotate independently of the rotatable drum  26 , the latter rotation being powered by a drum motor  51 . The driven rollers  52  shown in FIGS.  1 - 6  form disk nips  54  with the rotatable disks  28 , but do not form any nip with the rotatable drum  26  which rotates at angular velocities that differ from the angular velocities of the rotatable disks  28 . The driven rollers  52  cause the rotatable disks  28  to rotate, the rotatable disks  28  otherwise rotating freely. The driven rollers  52  hold each sheet  18  securely in place whenever the mouth  14  is opened, by being actuated against the rotatable disks  28 . The driven rollers  52  will be rotated and activated by a roller motor/actuator  56  when a complete stack of sheets  25  has been accumulated, so as to rotate the complete stack  25  away from the circular device  24  and into a set of takeaway rollers  58 .  
         [0023]    Because the cam shaft  40  is coupled to the rotatable drum  26 , the cam shaft  40  will revolve whenever the drum motor  51  causes it to revolve via drum gears  53 . However, the cam shaft  40  also requires an additional motor  60 . The cam shaft  40 , in addition to revolving around the central drum shaft  44 , will also rotate so as to open and close the gripper jaws  12 , and that rotation is powered by a separate cam rotation motor  60 . Thus, this sheet accumulator requires at least three motors: the drum motor  51 , the roller motor/actuator  56 , and the cam rotation motor  60 . Of course, any other driven rollers, for example the takeaway rollers  58 , may be powered by supplementary motors.  
         [0024]    As described thus far, the process by which collations are built can be thought of in two phases: a build phase and an exit phase. The build phase is a repetitive process involving a predetermined number of revolutions of the gripper jaws  12 . The exit phase involves the gripper jaws  12  moving out of the way just once, so that the complete stack of sheets  25  can exit the apparatus via the takeaway rollers  58 .  
         [0025]    During the build phase, the cam rotation motor  60  enables the cam  38  to be rotated whenever the gripper jaws  12  are at the home location, utilizing concentric shafting, cam motor gears  62  coupled to an electromagnetic clutch  64 , central cam shaft gears  66 , and peripheral cam shaft gears  67 . When the gripper jaws  12  are at the home location, the rotatable drum  26  is stationary, the electromagnetic clutch  64  is deenergized, and the cam shaft  40  is driven independently of the central drum shaft  44 . Then, when the cam  38  rotates so as to close the gripper jaws  12 , the electromagnetic clutch  64  is energized causing the cam shaft  40  and the central drum shaft  44  to rotate as one. This in essence preserves the relative configuration of the cam and the main drum.  
         [0026]    It is noteworthy that the order in which each stack of sheets  25  is built preserves the order in which each sheet of paper  18  is generated and presented to the accumulator  10 . For instance, if a collation of four sheets is generated and presented face up, the accumulator  10  will ensure that the stack of sheets  25  upon completion will have the sheets in the identical order and face up.  
         [0027]    Certain changes may be made in the above construction without departing from the scope of the invention, as will be understood by those skilled in the art, and it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.