Abstract:
An improved sheet accumulator for stacking serially fed sheets transported on a paper path. The accumulator includes a guide deck. Above the guide deck, a plurality of parallel belts are positioned to provide a driving force for sheets on the deck. Within the accumulator, a ramp apparatus is positioned across the paper path whereby sheets driven by the belts on an upstream portion of the accumulator deck are driven over the ramp apparatus and deposited in an accumulating region of the accumulator deck on a downstream side of the ramp apparatus. Preferably, snap-down belts are provided between ramp structures snap transported sheets quickly into place on the stack and to hold them there. Sheets are stopped by an accumulator stop mechanism located at a downstream end of the accumulating region that prevents movement of sheets by the belts while sheets for an accumulation are being collected. When an accumulation is completed, the accumulator stop mechanism allows sheets to be transported from the accumulating region. Preferably the guide deck and ramp are adjustable for different sized sheets.

Description:
TECHNICAL FIELD 
   The present invention relates to an accumulator for collating serially fed sheets into stacks. 
   BACKGROUND OF THE INVENTION 
   Inserter systems, such as those applicable for use with the present invention, are typically used by organizations such as banks, insurance companies and utility companies for producing a large volume of specific mailings where the contents of each mail item are directed to a particular addressee. Also, other organizations, such as direct mailers, use inserts for producing a large volume of generic mailings where the contents of each mail item are substantially identical for each addressee. Examples of such inserter systems are the 8 series, 9 series, and APS™ inserter systems available from Pitney Bowes Inc. of Stamford Conn. 
   In many respects, the typical inserter system resembles a manufacturing assembly line. Sheets and other raw materials (other sheets, enclosures, and envelopes) enter the inserter system as inputs. Then, a variety of modules or workstations in the inserter system work cooperatively to process the sheets until a finished mail piece is produced. The exact configuration of each inserter system depends upon the needs of each particular customer or installation. 
   Typically, inserter systems prepare mail pieces by gathering collations of documents on a conveyor. The collations are then transported on the conveyor to an insertion station where they are automatically stuffed into envelopes. After being stuffed with the collations, the envelopes are removed from the insertion station for further processing. Such further processing may include automated closing and sealing the envelope flap, weighing the envelope, applying postage to the envelope, and finally sorting and stacking the envelopes. 
   The input stages of a typical inserter system are depicted in  FIG. 1 . At the input end of the inserter system, rolls or stacks of continuous printed documents, called a “web,” are fed into the inserter system by a web feeder  10 . The continuous web must be separated into individual document pages. This separation is typically carried out by a web cutter  20  that cuts the continuous web into individual document pages. Depending on the mail run specifications, the cutter  20  can be set to cut sheets of different sizes. For example, some mailings may require letter size sheets, while others might include legal sized pages, or smaller than letter sized pages. Downstream of the web cutter  200 , a right angle turn  300  may be used to reorient the documents, and/or to meet the inserter user&#39;s floor space requirements. 
   The cut pages must subsequently be accumulated into collations corresponding to the multi-page documents to be included in individual mail pieces. This gathering of related document pages occurs in the accumulator module  400  where individual pages are stacked on top of one another. 
   The control system for the inserter senses markings on the individual pages to determine what pages are to be collated together in the accumulator module  400 . In a typical inserter application, mail pieces may include varying number of pages to be accumulated. When a document accumulation is complete, then the accumulation is discharged as a unit from the accumulator  400 . An accumulator module  400  should also be adjustable so that it is capable of handling sheet accumulations of different sizes. 
   A conventional accumulator module  400  is described in U.S. Pat. No. 5,083,769 to Young, which is hereby incorporated by reference in its entirety. While this conventional accumulator has been found to operate successfully in transporting paper sheets at up to 150 inches per second (ips), it has been found to become unstable at higher speeds, such as 300 ips. Also, the conventional accumulator has been successful at accumulating sets of documents having on the order of eight sheets. However for improved processing capabilities it has become desirable to collate as many as twenty sheets. 
   Downstream of the accumulator  400 , a folder  500  typically folds the accumulation of documents to fit in the desired envelopes. To allow the same inserter system to be used with different sized mailings, the folder  500  can typically be adjusted to make different sized folds on different sized paper. As a result, an inserter system must be capable of handling different lengths of accumulated and folded documents. 
   Downstream of the folder  500 , a buffer transport  600  transports and stores accumulated and folded documents in series in preparation for transferring the documents to the synchronous inserter chassis  700 . By lining up a backlog of documents in the buffer  600 , the asynchronous nature of the upstream accumulator  400  will have less impact on the synchronous inserter chassis  700 . On the inserter chassis  700  inserts are added to the folded accumulation prior to insertion into an envelope at a later module. 
   SUMMARY OF THE INVENTION 
   While the prior art accumulator described above often performs satisfactorily at speeds in the range of 150 ips, it has been found that at higher speeds, such as 300 ips, paper sheets will flutter and be damaged. The improved accumulator also allows high speed stacking of a greater number of sheets. Using a prior art accumulator, stacks of up to eight sheets could be created, where the preferred embodiment of the present invention can reliably handle stacks of up to twenty sheets. 
   The improved sheet accumulator, typically for use in an inserter system, includes, stacks serially fed sheets transported on a paper path. The accumulator includes a stationary accumulator guide deck having a smooth upper surface and forming a lower portion of the paper path. Above the guide deck, a plurality of parallel belts are positioned to provide a driving force for sheets on the deck. To assist in transporting the sheets, the lower runs of the plurality of belts may be downwardly biased against the stationary deck. 
   Within the accumulator, a ramp apparatus is positioned across the paper path whereby sheets driven by the belts on an upstream portion of the accumulator deck are driven over the ramp apparatus and deposited in an accumulating region of the accumulator deck on a downstream side of the ramp apparatus. Sheets are stopped and stacked by an accumulator stop mechanism located at a downstream end of the accumulating region that prevents movement of sheets by the belts while sheets for an accumulation are being collected. When an accumulation is completed, the accumulator stop mechanism allows sheets to be transported from the accumulating region. 
   To adjust for different sized sheets, in a preferred embodiment, the guide deck and ramp are adjustable to accommodate different sized sheet stacks. The adjustable paper path guide deck apparatus includes a first roller proximal the input end and a second roller proximal to the output end. These rollers support a flexible sheet of non-permanently deforming material wrapped around them. The surface of the sheet forms a guide deck for the paper path. 
   The adjustable guide deck is movable back and forth along a paper path direction while moving around the first and second rollers. A locking mechanism is coupled to the adjustable paper path guide deck apparatus for preventing the flexible sheet from moving around the first and second rollers when in a locked position, and allowing movement around the first and second rollers when in an unlocked position. 
   In the preferred embodiment, the accumulator ramp is coupled to the flexible sheet and operates on sheets transported in the paper path. A position of the ramp between the input end and the output end of the paper path is adjustable by moving the flexible sheet around the first and second rollers. 
   In a further preferred embodiment, the accumulator may be comprised of dual paper paths. In the dual arrangement, an input transport for receives serially fed sheets from an upstream module. Sheets are diverted to either a top accumulator or a bottom accumulator, each accumulator operating substantially as described above. The dual accumulator arrangement allows for stacking to continue in a second accumulator, while a completed collation is being removed from a first accumulator. Thus the dual accumulators typically alternate in handling accumulations, and allow for uninterrupted processing. 
   Downstream of the dual accumulators, a merging transport receives completed accumulations from both accumulators and merges them back into a single output transport path. 
   Further details of the present invention are provided in the accompanying drawings, detailed description and claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram of the input stages of an inserter system for use with the present invention. 
       FIG. 2  depicts an isometric view of an improved dual accumulator. 
       FIG. 3  depicts a cut-away side view of the improved dual accumulator. 
       FIG. 4  depicts an isometric view of a lower assembly of an accumulator utilizing the present invention. 
       FIG. 5  depicts a side view of an adjustable paper path deck. 
       FIG. 6  depicts an isometric view of an accumulator with its upper assembly in place. 
       FIG. 7  depicts a side view of an accumulator using the adjustable paper path deck. 
       FIG. 8  depicts a tensioning mechanism for the adjustable paper path deck. 
       FIG. 9  is a close-up view of a ramp assembly for the accumulator. 
       FIGS. 10   a  and  10   b  depict a side view of the ramp assembly with no sheets being transported over the ramp. 
       FIGS. 11   a  and  11   b  depict a side view of the ramp assembly while a sheet is being transported over the ramp. 
   

   DETAILED DESCRIPTION 
     FIG. 2  provides an overview of the major components included in a preferred embodiment of a dual accumulator  400  in accordance with the present invention. The dual accumulator  400  includes an upper accumulator  1  and a lower accumulator  2 . Each of the upper and lower accumulators  1 ,  2  include a lower assembly  3  and an upper assembly  4 . Preferably the upper assembly  4 , including the array of belts  30  ( FIG. 6 ), can be lifted from the lower assembly  3  ( FIG. 4 ), by manual lifting of handle  7 . A divert mechanism  8  is located at the downstream-most end of the dual accumulator  400  to remove any misprocessed collations before transporting them to the next downstream module (typically a folder  500 ). 
   Sheets are provided to an upstream end of the accumulator  400  by input module  5 . As seen in the cut away side view of  FIG. 3 , input module  5  begins with a high-speed nip section  41 , which can either match velocity with an upstream module, or accelerate sheets to a higher velocity. The need to accelerate sheets would be to increase the gaps between them or physically create a gap from an overlap or underlap. 
   Following the high-speed nip  41  is a standard flipper gate  42 , which is used to select between the upper accumulator  1  and lower accumulator  2 . Guide brackets  43  guide sheets between the flipper  43  and the individual accumulators  1  or  2 . 
   The entrance to each accumulator  1  or  2  consists of a belted nip between rollers  32  and  40 , with evenly spaced flat belts  30  overhead, driving idler roller  40  underneath. The belt  30  speed is matched to the high speed nip  41  (or slightly faster to create a “tug”) to ensure good registration of the sheets. The overhead belts  30  are driven from a common motor (not shown) and drive roller  33 , to ensure that each belt  30  maintains the same speed throughout the transport. The relatively wide belts  30  (as compared to prior art o-ring arrangement described in U.S. Pat. No. 5,083,769) combined with the high number of them help maintain the sheets orientation throughout the transport. As a result, sideguides are not needed to correct for skew errors. 
   Following the entrance nip between rollers  32  and  40  is a flat transport section. Here, all the belts  30  participate in driving the paper while at the same time holding it flat against the flexible deck  10 . 
   Following the upstream transport section of deck  10  is the ramp section  20 , as seen in  FIG. 4 , and a closer view in  FIG. 9 . The ramp structures  23  are angled to lift each sheet approximately 10 mm above the sheets already residing in the collation area on deck  10  downstream of ramp assembly  20 . Just before the ramps  23 , the overhead belts  30  are constrained from above by an idler roller  34 , as seen in  FIGS. 3 ,  7 ,  9 ,  10 , and  11 . This roller  34  ensures that the belt portions above the upstream transport section are not affected by paper in the ramp section  20 . It also creates a pivot point close enough to the ramps  23  for the belts  30  to provide a very quick “snap” of the trail edge. This arrangement of the deck  10 , ramp  20 , and belts  30  allow the accumulator to run very small gaps between sheets. 
   To assist in describing the interaction of the ramp apparatus  20  and the belts  30 , close-up side view  FIGS. 10   a ,  10   b ,  11   a , and  11   b  are provided. In  FIGS. 10   a  and  10   b , operation is depicted while no sheet is being transported over the ramp apparatus  20  comprised of ramp structures  23  and rollers  22 . Idler rollers  22  are preferably supported on a common shaft  27 . In  FIGS. 11   a  and  11   b , a sheet P′ is being transported over the ramp apparatus  20 . 
   As seen in these figures, downstream of idler roller  34 , the belts  30  interact with the ramp apparatus  20  split in two distinct ways. In the preferred embodiment, every other belt  30  remains a drive means, which passes up each ramp structure  23  to another idler roller  22  at the apex of each ramp. For this description, the drive means belts are referred to as  30 ′, as seen in  FIGS. 10   a  and  11   a . This first group of belts  30 ′ and idler rollers  22  ensure positive drive on each sheet until it reaches the dump roller  6  at the far downstream end of the accumulator  1  or  2 . 
   The other half of the belts  30 , between the drive belts  30 ′, becomes a “snap” belt  30 ″. For this description the snap belts will be referred to by the number  30 ″, as seen in  FIGS. 10   b  and  11   b . These snap belts  30 ″ fit in between the ramps  23  and idler rollers  22  and are nominally flat to the flexible deck  10  when no paper is present at the ramp  23 , or flat against previously stacked sheets P in the accumulation area (see  FIG. 10   b ). When a sheet enters the ramp section  20 , the sheet P′ physically lifts the snap belts  30 ″ up over the ramps  23  with it. This action creates deformation of the snap belts  30 ″ and additional tension along their length. When the trail edge of the sheet P′ clears the ramps  23 , this tension is released and the belt  30 ″ quickly snaps the trail edge of the sheet against the deck (or previous sheet P) and holds it there. 
   As a sheet P′ progresses over the ramps  23 , it is driven by the drive belt  30 ′ running over the idler roller  22  built into the ramps  23 . These drive belts  30 ′ then proceed to the main drive roller  33 , which returns them to the entrance roller  32 . In the preferred embodiment, the drive belts  30 ′ act as paper guides once in the post-ramp accumulation area of deck  10  (they are nominally above the collation at all times). The snap belts  30 ″ maintain intimate contact with the top sheet at all times and are responsible for damping any paper flutter and impact waves from contact with the dump roller  6 . Snap belts  30 ″ also provide any additional drive necessary to ensure the sheet reaches the dump roller  6  ( FIGS. 2 ,  3 ). 
   The post-ramp accumulation area is a continuation of the flexible deck  10 , with the flat belts  30  running overhead. At the flat belt drive roller  33 , a transition is made between the drive roller  33  and flexible deck  10  to a pair of short, solid decks  42 ,  43  which are permanently spaced apart to accommodate the largest collation (preferably 20 sheets). These decks  42 ,  43  lead the sheets into the full-width dump rollers  6 . The dump rollers  6  are preferably about two inches in diameter and are comprised of a relatively soft material that allows them to absorb the impact energy of each successive sheet. 
   The bottom of the dump rollers  6  is preferably harder than the top, which create a solid floor on which to build the collation. The two rollers  6  are geared together to provide positive drive to the entire collation during the high acceleration portion of the dump motion profile, to prevent shingling of the collation. The snap belts  30 ″ overhead provide an additional urge to ensure the collation exits as a coherent pack. 
   Following the dump section, the upper and lower paper paths  44  are once again merged into a single path. A divert mechanism  8  ( FIG. 2 ) then allows collations to be selectively outsorted before the module  400  transports the paper to downstream modules (folder, inserter, etc.) 
   In the preferred embodiment, the transport deck  10  is adjustable to accommodate different sized sheets. The adjustable paper path guide deck is depicted in  FIGS. 4–7 .  FIG. 4  depicts the paper path guide deck  10  used in a lower assembly  3  of an accumulator apparatus  1  or  2 . Reference is made to co-pending application Ser. No.:10/938,814, titled Continuously Adjustable Paper Path Guide Deck, filed concurrently herewith, and incorporated by reference in its entirety. 
   As discussed above, and as depicted in  FIG. 6 , transported sheets are driven from above by belts  30 , while on the flexible sheet  10 . Deck sheet  10  has a low coefficient of friction to allow paper to slide over it while being driven by belts  30  from above. 
   Preferably, as seen in  FIG. 4  and the side view in  FIG. 5 , the flexible sheet  10  is a thin sheet non-permanently deforming material. The sheet  10  is wrapped around an upstream support roller  12  and a downstream support roller  15 . In the preferred embodiment, the sheet  10  does not form a continuous loop and the ends of the sheet  10  are fixed around clamping bars  17  on an upper reach of the sheet wrapped around the rollers. The clamping bars  17  are coupled to a sheet-manipulating device, the position of which can be adjusted in an upstream or downstream direction by moving the sheet  10  around the rollers. 
   In an alternate embodiment, deck sheet  10  is comprised of a continuous belt loop wrapped around the rollers  12  and  15 . In that embodiment, no clamping bars  17  are needed, and the ramp section  20  is coupled to the continuous sheet loop  10 . 
   In the preferred embodiment the ramp apparatus  20  and the clamping bars  17  are mutually supported on moving side frames  21  on both lateral sides of the ramp  20 . The moving side frames  21  are supported in slots  14  in lower side support members  11 . 
   During normal operation sheet  10  remains stationary and does not move around the rollers  12  and  15 . Likewise the ramp apparatus  20  and moving side frame  21  coupled between the ends of the sheet  10  remain stationary. However, for an accumulator to operate on different sized sheets, it may become necessary to adjust the positions of those components. In the preferred embodiment, the ramp apparatus  20  must be moved in an upstream direction in order to make more room for storing longer sheets in the accumulation region of sheet  10  downstream of the ramp apparatus  20  ( FIG. 7 ). Conversely, for smaller sheets the ramp apparatus  20  would be moved in the downstream direction, while simultaneously shortening the region of sheet  10  that is downstream of the ramp apparatus  20 . For the preferred application, the adjustable deck is adjustable to accommodate sheets from seven inches to fourteen inches long, resulting in at least a seven inch range of adjustability. 
   In the preferred embodiment a threaded locking knob  24  is tightened via a threaded rod member potion of side frame  21  to hold the side frame  21  in place during normal operation. The threaded rod member portion of side frame  21  is slidably supported in slots  14 . To make an adjustment for different sized sheets, the locking knob  24  would be loosened, allowing the side frames  21  to move in the upstream and downstream directions along the slots  14 . As the side frames  21  and ramp apparatus  20  were moved in the upstream and downstream directions, the deck sheet  10  moves around rollers  12  and  15 , allowing more or less deck to be provided for supporting the sheets, as needed. 
   In the preferred embodiment, the adjustment of the flexible sheet  10  is achieved by rotating the roller  15  using adjustment knob  16  coupled thereto. Once adjustment knob  16  has been turned to adjust the accumulator ramp  20  and deck sheet  10  to their proper positions, locking knob  24  is tightened to hold the adjustable components in place. Preferably, rollers  12  and  15  incorporate ball-bearings, or other means to maintain smooth rolling action under load, to make adjustments easy. 
   In an alternative embodiment, rollers  12  and  15  may be turn-bars that do not rotate themselves, but that have sufficiently low friction that the sheet  10  can be bent and rotated around their surfaces when adjustments are being made. In any embodiment, a minimum radius of the rollers is determined by the choice of material for deck sheet  10 , so that the deck sheet will not deform permanently. 
   The belt rollers  32  and  33  are preferably supported on upper side support members  31  positioned above lower side support members  11 . At a downstream end of the accumulator apparatus, output guides  42  and  43  guide accumulations downstream of the adjustable portion of the accumulator. 
   As seen in  FIGS. 4–7 , a third deck roller  13  may be positioned between the primary deck rollers  12  and  15 . The top of this third roller  13  is positioned to intersect and lift the top plane of the sheet  10  between the roller  12  and  15 . This lifting provides a slope to the deck at a downstream end of the accumulator. This slope can serve to keep the belts  30 ″ firmly pressed against the sheets on the upstream part of the slope, while opening some space for sheets, and reducing friction on sheets on the downstream portion of the slope proximal to dump rollers  6 . 
     FIG. 8  depicts the preferred embodiment for tensioning the sheet  10  around the rollers  12  and  15 . In this preferred embodiment, the sheet  10  is secured to the movable side frame  21  by clamping bars  17 . Sheet  10  is wrapped around the clamping bar  17  and is tightened to provide the desired tension on the deck sheet  10 . As the clamping bar  17  is rotated, tension is developed in the deck, making it flat and rigid. As discussed previously, two clamping bars  17  are used and locked in place (after tensioning) to movable side frames  21 , which move as the deck is adjusted. 
   In the preferred embodiment, the material for sheet  10  is a thin sheet of stainless steel shim stock of 0.005 inches thick. Alternatively, the sheet  10  may be comprised of any metal or synthetic material that provides sufficient stiffness to serve as a guide deck, while having the flexibility to be wrapped around the rollers  12  and  15  without being permanently deformed. This preferred material is also corrosion resistant, wear resistant, and has the ability to be tensioned and wrapped around small pulleys without permanent deforming. 
   Although the invention has been described with respect to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and various other changes, omissions and deviations in the form and detail thereof may be made without departing from the spirit and scope of this invention.