Abstract:
A transporting system and method for use in a high velocity document processing system using lower velocity print technology. The invention including an upstream transport conveying spaced apart documents at a first transport velocity. A deceleration transport decelerates documents from the high speed to a lower print velocity before passing the documents a print transport. A sensor located at the deceleration transport, detects the presence of documents at the deceleration transport, and triggers the deceleration profile to be performed on the document. The deceleration transport is controlled such that a leading portion of a document that is being decelerated overtakes a trailing portion of a downstream document that already traveling at the lower print velocity in the control of the print transport. An overlapping arrangement urges the lead portion of the upstream document to overlap on top of the trailing portion of the downstream document when the upstream document overtakes the downstream document. A print head prints on the transported documents at the print transport velocity.

Description:
TECHNICAL FIELD 
     The present invention relates to a module for printing postage value, or other information, on an envelope in a high speed mass mail processing and inserting system. Within the printing module, the printing device may operate at a lower velocity than other parts of the system. To allow the documents to be slowed for printing without causing jams, the present invention overlaps documents as they are transported and printed at the reduced speed. 
     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 Advanced Productivity System (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 plurality of different 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. 
     Current mail processing machines are often required to process up to 18,000 pieces of mail an hour. Such a high processing speed may require envelopes in an output subsystem to have a velocity in a range of 80-85 inches per second (ips) for processing. Leading edges of consecutive envelopes will nominally be separated by a 200 ms time interval for proper processing while traveling through the inserter output subsystem. At such a high rate of speed, system modules, such as those for sealing envelopes and putting postage on envelopes, have very little time in which to perform their functions. If adequate control of spacing between envelopes is not maintained, the modules may not have time to perform their functions, and jams and other errors may occur. In particular, postage meters are time sensitive components of a mail processing system. Meters must print a clear postal indicia on the appropriate part of the envelope to meet postal regulations. The meter must also have the time necessary to perform bookkeeping and calculations to ensure the appropriate funds are being stored and printed. 
     A typical postage meter currently used with high speed mail processing systems has a mechanical print head that imprints postage indicia on envelopes being processed. Such conventional postage metering technology is available on Pitney Bowes R150 and R156 mailing machines using model 6500 meters. The mechanical print head is typically comprised of a rotary drum that impresses an ink image on envelopes traveling underneath. Using mechanical print head technology, throughput speed for meters is limited by considerations such as the meter&#39;s ability to calculate postage and update postage meter registers, and the speed at which ink can be applied to the envelopes. In most cases, solutions using mechanical print head technology have been found adequate for providing the desired throughput of approximately five envelopes per second to achieve 18,000 mail pieces per hour. 
     However, use of existing mechanical print technology with high speed mail processing machines presents some challenges. First, some older mailing machines were not designed to operate at such high speeds for prolonged periods of time. Accordingly, solutions that allow printing to occur at lower speeds may be desirable in terms of enhancing long term mailing machine reliability. 
     Another problem is that many existing mechanical print head machines are configured such that once an envelope is in the mailing machine, it is committed to be printed and translated to a downstream module, regardless of downstream conditions. As a result, if there is a paper jam downstream, the existing mailing machine component could cause even more collateral damage to envelopes within the mailing machine. At such high rates, jams and resultant damage may be more severe than at lower speeds. Such damage often includes the result of moving envelopes crashing into the edges of stationary downstream envelopes. Accordingly, improved control and lowered printing speed, while maintaining high throughput rate in a mechanical print head mailing machine could provide additional advantages. 
     Controlling throughput through the metering portion of a mail producing system is also a significant concern when using non-mechanical print heads. Many current mailing machines use digital printing technology to print postal indicia on envelopes. One form of digital printing that is commonly used for postage metering is thermal inkjet technology. Thermal inkjet technology has been found to be a cost effective method for generating images at 300 dpi on material translating up to 50 inches per second. Thus, while thermal inkjet technology is recognized as inexpensive, it is difficult to apply to high speed mail production systems that operate on mail pieces that are typically traveling in the range of up to 80 to 85 ips in such systems. 
     As postage meters using digital print technology become more prevalent in the marketplace, it is important to find suitable substitutes for the mechanical print technology meters that have traditionally been used in high speed mail production systems. This need for substitution is particularly important as it is expected that postal regulations will require phasing out of older mechanical print technology meters, and replacement with more sophisticated digital based meters. Although digital print technology exists that is capable of printing the requisite 300 dpi resolution on paper traveling at 80 to 85 ips, such devices are so expensive as to be considered cost prohibitive. Accordingly, it would be beneficial to have a solution that would allow lower velocity digital print technology, like thermal inkjet technology, to be utilized with the high speed mail production systems. 
     Some systems that have been available from Pitney Bowes for a number of years address some related issues. These systems utilize R150 and R156 mailing machines using 6500 model postage meters installed on an inserter system. The postage meters operate at a slower velocity than that of upstream and downstream modules in the system. When an envelope reaches the postage meter module, a routine is initiated within the postage meter. Once the envelope is committed within the postage meter unit, this routine is carried out without regard to conditions outside the postage meter. The routine decelerates the envelope to a printing velocity. Then, the mechanical print head of the postage meters imprints an indicia on the envelope. After the indicia is printed, the envelope is accelerated back to close to the system velocity, and the envelope is transported out of the meter. 
     One problem with this current solution is that the conventional postage meters are inflexible in adjusting to conditions present in upstream or downstream meters. For example, if the downstream module is halted as a result of a jam, the postage meter will continue to operate on whatever envelope is within its control. This often results in an additional jam, and collateral damage, as the postage meter attempts to output the envelope to a stopped downstream module. 
     Another problem with the current solution is that it is very sensitive to gaps between consecutive envelopes. In the process of slowing down the documents, the gap between documents is reduced, and an error in the spacing between documents becomes more significant. The inserter may not be able to maintain controlled spacing between documents accurately enough to prevent collisions between consecutive envelopes during the slow down process. This problem is further exacerbated because the R150 and R156 mailing machines are a bit too long to have time to carry out the routine on the envelopes, and to still have some margin for error in the arrival of a subsequent envelope. As such, a module with better space utilization and less sensitivity to gap variations is desirable. 
     SUMMARY OF THE INVENTION 
     The present invention provides a transporting system and method for use in a high velocity document processing system using lower velocity print technology. A transport path through the system is made up of an upstream transport conveying spaced apart documents at a first transport velocity. This first transport velocity represents the high processing speeds available in current high speed inserter machines. Downstream of the upstream transport, a deceleration transport decelerates documents from the high speed to a lower print velocity before passing the documents to a print transport. Both the upstream transport and the lower speed print transport normally operate at their respective constant velocities. The deceleration transport adjusts to match the speeds of the respective upstream or downstream modules when receiving and passing documents from them. 
     Preferably, a sensor located at the deceleration transport, detects the presence of documents at the deceleration transport, and triggers the deceleration profile to be performed on the document. After it is sensed that a document has passed out from the deceleration transport, the deceleration transport must accelerate back to the higher transport velocity in order to receive the next document. 
     The deceleration transport is further controlled such that a leading portion of a document being decelerated overtakes a trailing portion of a downstream document that is already traveling at the lower print velocity in the control of the print transport. Unlike conventional systems, there is no need or attempt to rigorously maintain and control a gap between subsequent documents. 
     The invention further includes an overlapping arrangement whereby the lead portion of the upstream document is urged to overlap on top of the trailing portion of the downstream document when the upstream document overtakes the downstream document. Such overlapping arrangement may cause a rear portion of the lead document to be positioned downward relative to the overtaking upstream document. Alternatively, the upstream document may be upwardly biased, or some combination of upward and downward biasing may be used. In any case, the lead portion of the trailing document should be positioned overlapping on a trailing portion of a leading document. 
     The overlapped documents are transported to a print head contiguous with the print transport. The print head prints the desired marks on the overlapped documents as they pass beneath at the print transport velocity. 
     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 a postage printing module utilizing the present invention. 
         FIGS. 2A-2D  depict a first exemplary embodiment for overlapping envelopes. 
         FIGS. 3A-3C  depict further exemplary embodiments for overlapping envelopes 
         FIG. 4  depicts an exemplary sensor for detecting leading edges of overlapped documents. 
         FIG. 5  depicts an exemplary transport system for maintaining the top surfaces of overlapped documents at a relatively constant distance from an overhead print head. 
         FIG. 6  depicts an exemplary timing diagram for displacement of documents within a system utilizing the present invention. 
         FIGS. 7A and 7B  depict scenarios in which conveyed documents are damaged as a result of jams. 
     
    
    
     DETAILED DESCRIPTION 
     As seen in  FIG. 1 , the present invention includes a postage printing module  10  positioned between an upstream module  20  and a downstream module  30 . Upstream and downstream modules  20  and  30  can be any kinds of modules in an inserter output subsystem. Typically the upstream module  20  could include a device for wetting and sealing an envelope flap. Downstream module  30  could be a module for sorting envelopes into appropriate output bins or a stacker module. 
     Postage printing module  10 , upstream module  20 , and downstream module  30 , all include transport mechanisms for moving an envelope  1  along the processing flow path. In the depicted embodiment, the upstream module  20  includes nip rollers  21  driven by motor  22 . Similarly, the downstream module  30  includes a transport comprised of nip rollers  31  driven by motor  32 . In the preferred embodiment, rollers  21  and  31  are hard-nip rollers to minimize variation. As an alternative to nip rollers, the transport mechanism and transport path may comprise sets of conveyor belts (like belts  14 ) between which envelopes are transported. 
     Print head  15  is preferably located near the output end of the print transport portion of the postage printing module  10 . To comply with postal regulations the print head  15  should be capable of printing an indicia at a resolution of 300 dots per inch (dpi). In the preferred embodiment, the print head  15  is an ink jet print head capable of printing 300 dpi on media traveling at 50 ips. Alternatively, the print head  15  can be any type of print head, including those using other digital or mechanical technology, which may benefit from printing at a rate less than the system velocity. 
     In the preferred embodiment, the transport within print module  10  may be identified in several segments. At the upstream end of the postage printing module  10 , a first segment is comprised of a set of deceleration roller nips  41  that are driven at a variable speed by servo motor  43 . Downstream of the deceleration roller nips  41 , the transport mechanism is a dual belt transport arrangement comprised of inlet rollers  11  and further downstream rollers  12  around all of which belts  14  are driven. In the preferred embodiment depicted in  FIG. 1 , the downstream rollers  12  are positioned at a higher elevation in the transport path than the inlet rollers  11 . As a result, envelopes are transported in a sloped upward path between belts  14 . Downstream of the belts  14 , nip rollers  13  further transport envelopes as the print head  15  performs printing operations upon them. In the preferred embodiment, roller sets  11 ,  12  and  13  are driven at a uniform print velocity by one or more motors  18  during operation. 
     In  FIG. 1 , deceleration nips  41  are depicted as being part of the print module  10 , however, it will be understood by one skilled in the art that such rollers may also be part of a downstream portion of upstream module  20 , or even in their own intermediate module between upstream module  20  and print module  10 . 
     As an envelope  1  travels through the system depicted in a preferred embodiment shown in  FIG. 1 , it is initially transported at a constant velocity of approximately 85 inches per second (ips) in upstream module  20 . From the upstream module  20 , the envelope  1  is passed to deceleration rollers  41  in the print module  10 . As the lead edge envelope  1  arrives at deceleration rollers  41 , deceleration rollers  41  are rotating at a speed equivalent to the module  20  speed of 85 ips. As long as any portions of envelope  1  are engaged by both rollers  21  and  41 , rollers  41  continue to operate at the same speed as rollers  21 . When envelope  1  comes under the sole control of deceleration rollers  41 , it is decelerated to a preferred print velocity of approximately 42.5 ips. Preferably, this deceleration is Initiated based on sensing the presence of the envelope  1  at the deceleration roller  41  with optical sensors  42 . Based on a signal from sensors  42  a controller  17  controls the motion of deceleration rollers  41  via servo motor  43 . The deceleration rollers  41  pass the envelope  1  to the inlet rollers  11 . So long as envelope  1  is in the control of both nip rollers  41  and  11 , rollers  41  continue to operate at 42.5 ips. When the trail edge of envelope  1  passes by nip rolls  41 , controller  17  signals motor  43  to accelerate nip rollers  41  back up to the initial 85 ips speed prior to the arrival of the lead edge of the next envelope. Rollers  11 ,  12 ,  13  and associated belts  14  provide transport at the constant print velocity of 42.5 ips. A lead edge sensor  16  detects the presence of envelopes approaching the print head  15 , and the controller  17  activates the print head  15  to print upon envelope  1  as appropriate. 
     As an alternative to relying solely on sensors for sensing positions of documents, the controller  17  may receive encoder pulses from motors  22 ,  43 , or  18 . These pulses can be interpreted by controller  17  as displacements, and such displacement information may supplement the sensor information for greater accuracy. Known techniques for predicting positions of documents based on known past locations and subsequent velocities may also be used to determine when events should be triggered, as opposed to relying on sensors for immediate tripping of a routine. 
     A process for creating an overlap of consecutive envelopes using the embodiment of  FIG. 1  is depicted in  FIGS. 2A-2D . In  FIG. 2A , envelope  1  is still within the control of the upstream module  20  and is passing between the upstream roller nips  21  at location A at a high upstream velocity of 85 ips. The arrival of the envelope  1  at the deceleration roller nips  41  is sensed by optical sensor  42 . Preferably optical sensor  42  is located at location B, which is at, or immediately upstream, from location C, the position of the deceleration rollers  41 . After the arrival of the envelope  1  has been sensed by sensor  42 , controller  17  calculates an appropriate time delay until the trail edge of envelope  1  passes nip rollers  21 . At that time, envelope  1  is within the sole control of the deceleration rollers  41 , the envelope  1  is decelerated from 85 ips to 42.5 ips. 
     The relative positions of lead and tail edges of documents during the overlapping process are further depicted over time in the graph in FIG.  6 . On the vertical axis, positions within the system, including locations A, B, C, D, and E, are represented. The locations of documents within the system are therefore represented with respect to time by the lines on the graph. The locations on the vertical axis correspond to the locations shown in  FIGS. 1 and 2 . A first pair of lines starting from the left side of the graph depict the LEAD EDGE  1  and TRAIL EDGE  1  of envelope  1 . Similarly, the subsequent positions of lead and trail edges of envelopes  2  and  3  are shown over time. Thus, for example, a situation similar to that depicted in  FIG. 2A  is shown on the left side of the graph of  FIG. 6  at a point in time  101  when the LEAD EDGE  1  is almost to location B as shown at  102 , and the TRAIL EDGE  1  is still approaching location A, as shown at  103 . 
     As seen in  FIG. 2B , after envelope  1  has been decelerated to the lower print velocity of 42.5 ips, it is passed from rollers  41  to the inlet rollers  11  at position D for the lower speed portion of the print transport. Rollers  41  continue to operate at the lower velocity of 42.5 ips until envelope  1  has passed completely out of the deceleration rollers  41 . At that time rollers  41  are immediately accelerated back to the upstream transport velocity of 85 ips, so that a subsequent envelope  2  may be accepted. Meanwhile, the upstream envelope  2  is starting to arrive from the upstream module  20  as shown at  105  in  FIG. 6  at time  104 . 
     Shortly afterwards, as seen in  FIG. 2C , envelope  1  has started to travel up a sloped path formed by rollers  11  and  12  and belts  14 . In doing so, a rear portion of envelope  1  that has not passed inlet rollers  11  is lowered below the horizontal plane in which it was previously traveling. At the same time, the sensor  42  has indicated that envelope  2  is within the deceleration roller  41  and controller  17  causes the deceleration rollers to decelerate envelope  2  after its trail edge passes rollers  21  from its initial velocity of 85 ips. The deceleration of envelope  2  is controlled so that a leading portion of envelope  2  overtakes a trailing portion of envelope  1 , before envelope  2  is completely reduced to the print velocity of 42.5 ips. This event is depicted at  107  in  FIG. 6  at time  106 . 
     In  FIG. 2D , as a result of the controlled deceleration of envelope  2 , an overlap of the lead portion of envelope  2  over a trailing portion of envelope  1  is created. The overlapped envelopes are driven together between the inlet roller  11  and are further driven downstream for processing. This event is depicted at time  108  in FIG.  6 . Lead edge  2  at  109  overlaps TRAIL EDGE  1  at  110 . 
     Once again referring to  FIG. 6 , a graphical depiction of the overlapping action can be seen. It is seen that the dashed line for the LEAD EDGE  2  overtakes the solid line for the TRAIL EDGE  1  at point  107 , at a time when envelope  2  is within the control of the deceleration rollers  41  at location C. Further, it is seen that at time  106 , the lead edge of envelope  2  overtakes the trail edge of envelope  1  during the deceleration process of envelope  2 , and before the trail edge of envelope  1  has passed though the inlet nips at location D. While  FIG. 6  is not to scale, it does depict the cyclical overlapping that occurs as a procession of envelopes is handled by the print module  10 . 
       FIG. 3A  depicts an alternative to the overlapping arrangement depicted in FIGS.  1  and  FIGS. 2A-2D . Instead of the upward sloped transport path, the alternative embodiment includes rollers  35  and  36  which form a horizontal transport path that is below the upstream horizontal transport path between the deceleration rollers  41 . Accordingly, a rear portion of the lead envelope  1 , within the control of rollers  35  and  36 , will be below a leading portion of the overtaking trailing envelope  2 . 
     As depicted in  FIG. 3A , a lead edge of the envelope  2  is guided downward on top of the rear portion of envelope one by the rotation of roller  35 . In a preferred embodiment, roller  35  may have a larger radius to provide a more gradual redirection of envelopes coming into contact with it. 
     Yet another alternative overlapping arrangement is depicted in  FIG. 3B. A  roller arrangement  37  is pivotably interposed in the document flow path so that a trailing edge of the lead envelope  1  is biased downwards as the leading edge of the trailing envelope  2  overtakes envelope  1 . In this arrangement, the roller arrangement  37  is positioned above the document flow path, and is positioned proximal to the inlet rollers  11 . 
     In a further alternative overlapping arrangement shown in  FIG. 3C , a leading portion of the trailing envelope  2  is biased upward by a ramp structure  38 , so that once again, the overlap of the lead edge of the trailing envelope  2  is assured to be positioned on top of the trail edge of the leading envelope  1 , as envelope  2  undergoes its deceleration to the print velocity. It will further be understood that the ramp structure  38  can be used to provide a downward bias in place of the roller arrangement  37  in FIG.  3 B. Similarly, the roller arrangement  37  can be swapped for the ramp structure  37  in FIG.  3 C. 
     In  FIG. 4 , a more detailed embodiment of lead edge sensor  16  is depicted. In this preferred embodiment, lead edges of overlapped envelopes  1 ,  2 , and  3  are detected as a consequence of the movement of a member  51  that drags along the surface of the envelopes moving beneath. The member  51  is mounted on a rotating disc  52 . As envelopes move beneath the member  51  variations in the surface will cause the attached rotating disc  52  to move about its axis. The most radical movement will occur when a sudden obstruction, such as an edge, forces the member  51  to rotate sharply to the right and slightly upward. The greater angular displacement of the disc  52  can be interpreted to indicate that a lead edge of a document is present. 
     Preferably, displacements of the member  51  are measured by an encoder-like arrangement in which movement of holes  53  on the outer perimeter of the disc  52  are sensed by an optical sensor  54 . The sensor  54  generates pulses corresponding to the movement of the holes  53  by the sensor  54 . The pulses are communicated to controller  17  that interprets the pulses to identify lead edges of envelopes when a sufficient displacement has occurred over short enough of a time. Based on the detection of the lead edge, the print head  15  may print on a leading portion of the surface of an overlapped envelope. 
     A further feature to assist in proper printing on overlapped envelopes is depicted in FIG.  5 . In preferred embodiments, print head  15  uses ink jet technology. Ink jet technology preferably prints onto surfaces of documents within a uniform range of distances below the print head  15 . Accordingly, varying thicknesses resulting from overlapping, or from different thicknesses of mail pieces can result in potential difficulties. To address the problem of presenting surfaces a uniform distance below the print head  15 , the embodiment in  FIG. 5  provides a transport arrangement that allows variations in thickness if the documents being transported to be absorbed by movable rollers below the transport plane, while keeping the print surfaces a common distance below the print head  15 . 
     Accordingly, rollers  13  with a belt  14  are fixedly positioned above the transport path. The top surfaces of the overlapped documents will consistently be controlled by the position of the rollers  13  and plane formed by belt  14 . Meanwhile, below the transport path, rollers  61  are individually mounted and are vertically movable. Preferably, the rollers  61  are mounted on moving mounting arms  62 , which are rotatably mounted at the end distal to the rollers  61 . The moving mounting arms  62  are upwardly biased by springs  63 . Thus, the position of the rollers  61  may vary relative to the upper plane formed by rollers  13  and belt  14  above, depending on the varying thickness of the overlaps, and of the mail pieces. 
     A further benefit of overlapping mail pieces is that upon the occurrence of a downstream jam, fewer mail pieces may be damaged. In  FIG. 7A , the conventional linear and spaced arrangement of envelopes traveling on an inserter transport is depicted. Nominally, the conventional envelope transport  70  moves documents at speeds up to 85 ips, with a 17 inch distance between lead edge of one document to lead edge of the next document and a 7.5 inch gap between subsequent documents. When a downstream jam  75  occurs, and is detected the system is stopped. While stopping, the transport  70  typically requires about 37.5 inches of displacement during deceleration. As a result of this displacement, damage is caused to six envelopes  71  from end-to-end collisions and crumpling of envelopes upstream of the jam  75 . 
     In contrast, in  FIG. 7B , the envelope transport  72  is depicted during normal operation with overlapped envelopes in accordance with the present invention. Upon occurrence of a jam  75  among the overlapped documents, as few as one mail piece is damaged as upstream documents slide over the tops of downstream documents during deceleration. 
     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.