Patent Publication Number: US-8123222-B2

Title: Compliant conveyance system for mailpiece transport along an arcuate feed path

Description:
TECHNICAL FIELD 
     This invention relates to an apparatus for handling sheet material and more particularly to a pneumatic conveyance system which facilitates the handling of stiff planar sheets along an arcuate, e.g., circular feed path. 
     BACKGROUND ART 
     Automated equipment is typically employed in industry to process, print and sort sheet material for use in manufacture, fabrication and mailstream operations. One such device to which the present invention is directed is a mailpiece sorter which sorts mail into various bins or trays for delivery. 
     Mailpiece sorters are often employed by service providers, including delivery agents, e.g., the United States Postal Service USPS, entities which specialize in mailpiece fabrication, and/or companies providing sortation services in accordance with the Mailpiece Manifest System (MMS). Regarding the latter, most postal authorities offer large discounts to mailers willing to organize/group mail into batches or trays having a common destination. Typically, discounts are available for batches/trays containing a minimum of two hundred (200) or so mailpieces. 
     The sorting equipment organizes large quantities of mail destined for delivery to a multiplicity of destinations, e.g., countries, regions, states, towns and/or postal codes, into smaller, more manageable, trays or bins of mail for delivery to a common destination. For example, one sorting process may organize mail into bins corresponding to various regions of the U.S., e.g., northeast, southeast, mid-west, southwest and northwest regions, i.e., outbound mail. Subsequently, mail destined for each region may be sorted into bins corresponding to the various states of a particular region e.g., bins corresponding to New York, New Jersey, Pennsylvania, Connecticut, Massachusetts, Rhode Island, Vermont, New Hampshire and Maine, sometimes referred to as inbound mail. Yet another sort may organize the mail destined for a particular state into the various postal codes within the respective state, i.e., a sort to route or delivery sequence. 
     The efficacy and speed of a mailpiece sorter is generally a function of the number of sortation sequences or passes required to be performed. Further, the number of passes will generally depend upon the diversity/quantity of mail to be sorted and the number of sortation bins available. At one end of the spectrum, a mailpiece sorter having four thousand (4,000) sorting bins or trays can sort a batch of mail having four thousand possible destinations, e.g., postal codes, in a single pass. Of course, a mailpiece sorter of this size is purely theoretical, inasmuch as such a large number of sortation bins is not practical in view of the total space required to house such a sorter. At the other end of the spectrum, a mailpiece sorter having as few as eight (8) sortation bins (i.e., using a RADIX sorting algorithm), may require as many as five (5) passes though the sortation equipment to sort the same batch of mail i.e., mail to be delivered to four thousand (4,000) potential postal codes. The number of required passes through the sorter may be evaluated by solving for P in equation (1.0) below:
 
P (# of Bins) =# of Destinations  (1.0)
 
     In view of the foregoing, a service provider typically weighs the technical and business options in connection with the purchase and/or operation of the mailpiece sortation equipment. On one hand, a service provider may opt to employ a large mailpiece sorter, e.g., a sorter having one hundred (100) or more bins, to minimize the number of passes required by the sortation equipment. On the other hand, a service provider may opt to employ a substantially smaller mailpiece sorter e.g., a sorter having sixteen (16) or fewer bins, knowing that multiple passes and, consequently, additional time/labor will be required to sort the mail. 
     The principal technical/business issues include, inter alia: (i) the number/type of mailpieces to be sorted, (ii) the value of discounts potentially available through sortation, (iii) the return on investment associated with the various mailpiece sortation equipment available and (iv) the cost and availability of labor.  FIG. 1  depicts a conventional linear mailpiece sorter  100  having a plurality of sortation bins or collection trays  110  disposed on each side of a linear sorting path SP. In operation, the mailpieces  114  are first stacked on-edge in a feeder module  116  and fed toward a singulation belt  120  by vertical separator plates  122 . The plates  122  are driven along, and by means of, a feed belt  124  which urges the mailpieces  114  against the singulation belt  120 . As a mailpiece  114  engages the singulation belt  120 , the mailpiece  114  is separated from the stack and conveyed along the sorting path SP. Inasmuch as the singulation belt  120  and sorting path SP are disposed orthogonally of the feed path FP, each mailpiece  114  may be conveyed directly along the sorting path SP without any further requirements to manipulate the direction and/or orientation of the mailpiece  114 , e.g., a right-angle turn. 
     As each mailpiece  114  is conveyed along the sorting path SP, a mailpiece scanner  126  typically reads certain information i.e., identification, destination, postal code information, etc., contained on the face of the mailpiece  114  for input to a processor  130 . Inasmuch as each of the sortation bins or trays  110  correspond to a pre-assigned location in the RADIX sortation algorithm, the processor  130  controls a plurality of diverter mechanisms  134  (i.e., one per bin/tray  110 ) to move into the sorting path SP at the appropriate moment time to collect mailpieces  114  into the trays  110 . That is, since the mailpiece sorter  110  knows the identity and location of each mailpiece  114  along the sorting path SP, the processor  130  issues signals to rapidly activate the diverter mechanisms  134  so as to re-direct a particular mailpiece  114  into its pre-assigned collection tray  110 . A linear mailpiece sorter of the type described above is manufactured and distributed by Pitney Bowes Inc. located in Stamford, State of Connecticut, USA, under the tradename “Olympus II”. 
     As mentioned in a preceding paragraph, the total space available to a service provider/operator may prohibit/preclude the use of a large linear mailpiece sorter such as the type described above. That is, since each collection tray  110  must accommodate a conventional type-ten (No. 10) mailpiece envelope, each tray  110  spans a distance slightly larger than one foot (1′) or about fourteen inches (14″), corresponding to the long edge of the rectangular mailpiece  114 . As a result, a linear mailpiece sorter can occupy a large area or “footprint”, i.e., requiring hundreds of lineal feet and/or a facility competing with the size of a conventional aircraft hanger. 
     In an effort to accommodate service providers with less available space/real estate, other mailpiece sortation devices are available which employ a multi-tiered bank of collection trays (i.e., arranged vertically). These sortation devices (not shown) include an intermediate elevation module disposed between the feeder and bank of collection trays. More specifically, the elevation module includes a highly inclined table or deck for supporting a labyrinth of twisted conveyor belt pairs. The belt pairs capture mailpieces therebetween and convey mailpieces along various feed paths which are formed by a series of “Y”-shaped branches. Each Y-shaped branch/intersection bifurcates or diverts mailpieces to one of two downstream paths, and additional branches downstream of each new path increase the number of paths by a factor of two. Further, each branch functions to change the elevation of a mailpiece to feed the multi-tiered arrangement of collection trays. A multi-tiered mailpiece sorter of the type described above is manufactured and distributed by Pitney Bowes Inc. located in Stamford, State of Connecticut, USA, under the tradename “Olympus II”. 
     Multi-tiered mailpiece sorters can significantly reduce the space/footprint required by linear mailpiece sorters, though such multi-tiered sorters are costly to fabricate, operate and maintain. Typically, these multi-tiered mailpiece sorters are nearly twice as costly to fabricate and maintain as compared to linear mailpiece sorters having the same or greater sorting capacity. 
     In addition to the difficulties associated with space and expense, the mailpiece sorters described above are highly complex, require highly-skilled technicians to perform maintenance and, if not maintained properly, can result in damage to sorted mailpieces. For example, if particulate matter (e.g., paper dust) from envelopes is allowed to accumulate along the sorting path and/or in the actuation mechanisms of a diverter, the mailpiece sorter can become prone to paper jams. Further, inasmuch as the mailpieces travel at a high rate of speed along the sorting path SP, the mailpieces can be damaged or jammed when re-directed by the by the diverter mechanism. Moreover, in addition to damage caused by jamming, the sortation order of the mailpieces, which is critical to perform a RADIX sort, can inadvertently be altered. 
     Yet other difficulties relate to the handling of relatively stiff, planar, material/packages such as a plastic container for holding/housing computer discs, e.g., CDs and DVDs. Due to the rigidity of these packages difficulties arise when transporting such material around a bend or arcuate feed path. That is, when transporting such packages between opposing belts, damage to the plastic container can occur when negotiating a bend, especially when the bend radius thereof is small. 
     A need, therefore, exists for a sheet material handling apparatus of minimal size for space efficiency, provides a smooth conveyance/diversion path for preventing paper jams along the feed path, and facilitates the handling of relatively stiff, planar material packages to prevent damage as the package travels along an arcuate feed path. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate presently preferred embodiments of the invention and, together with the detailed description given below, serve to explain the principles of the invention. As shown throughout the drawings, like reference numerals designate like or corresponding parts. 
         FIG. 1  is a top view of a prior art mailpiece sorter including a plurality of sorting bins disposed on each side of a mailpiece sorting path. 
         FIG. 2  is a partially broken away and sectioned top view of a mailpiece sorter including: a feeder, a displacement module/system operative to transpose the orientation of each mailpiece, and a sortation bin module operative to convey and divert mailpieces. 
         FIG. 3  depicts a side schematic view of the displacement module/system including a plurality of cooperating rollers, i.e., pairs of rollers, which are differentially controlled to displace and rotate the mailpiece from an on-edge lengthwise orientation to an on-edge widthwise orientation. 
         FIG. 4  depicts an enlarged top view of the displacement module including a processor for controlling a plurality of rotary actuators or motors to drive the cooperating rollers. 
         FIG. 5  depicts the speed profile of the rollers wherein the motors are controlled to alternately linearly displace and rotationally position each mailpiece along the feed path. 
         FIG. 6  depicts an alternate embodiment of the invention wherein sensors provide mailpiece position feedback to the processor such that corrective action can be taken, i.e., a modification to the speed profile, when the actual mailpiece position deviates from a scheduled mailpiece position. 
         FIG. 7  is a sectional view taken substantially along line  7 - 7  of  FIG. 2  depicting a view through sortation bins/trays of a sortation bin module. 
         FIG. 8  is a sectioned and partially broken-away top view of pneumatic conveyor and diverter modules for transporting and sorting mailpieces from a central envelope feed path to a sortation bin. 
         FIG. 9  is a sectional view taken substantially along line  9 - 9  of  FIG. 8  depicting a lengthwise side view through the pneumatic diverter of the sortation bin module. 
         FIG. 10  is a sectioned and partially broken-away top view of a compliant conveyance system, e.g., a compliant diverter, for transporting and sorting relatively stiff/rigid, planar mailpieces from a central envelope feed path to a sortation bin along an arcuate feed path. 
         FIG. 11  is a sectional view taken substantially along line  11 - 11  of  FIG. 10  depicting a lengthwise side view through the compliant diverter. 
         FIG. 12  is an enlarged broken away view through a section of the complaint diverter having an exterior layer of resilient foam which is perforated and compliant to allow a pressure differential to develop while conforming to the external shape of the rigid mailpiece. 
         FIG. 13  is an enlarged broken away view through a section of the complaint diverter, similar to the view shown in  FIG. 12 , including an exterior layer of poly-tetra-flora-ethylene (PTFE) disposed over a resilient elastomer. 
         FIG. 14  is an enlarged broken away view through a section of the complaint diverter, similar to the view shown in  FIG. 12 , including an array of radially oriented compliant tubes forming a bed of vacuum feet which conform to the external surface of the mailpiece. 
     
    
    
     SUMMARY OF THE INVENTION 
     A compliant conveyance system is provided for conveying and diverting sheet material along a feed path. The system includes a diverter having at least one sidewall structure defining an internal chamber in fluid communication with a pressure source. The sidewall structure includes a compliant interface surface for conveying sheet material along the feed path and a plurality of orifices facilitating fluid communication between the compliant interface surface and the internal chamber. The system further includes a means for developing a pressure differential across the sheet material through the orifices to urge an interface surface of the sheet material against the compliant interface surface of the diverter such that the compliant interface surface conforms to at least a portion of the sheet material interface surface. The system employs a means for driving the diverter about a rotational axis from a first to a second rotational position and a controller operative to control the pressure differential such that, in the first rotation position, the sheet material is secured against the compliant interface surface and, in the second rotational position, the sheet material is released from the compliant interface surface. 
     DETAILED DESCRIPTION 
     A sortation system is described for handling sheet material in a mailpiece sorter. While the invention is described in the context of a mailpiece sorter, it will be appreciated that the various inventive features are equally applicable to any sheet material handling apparatus. Hence the sorting system is merely illustrative of an embodiment of the invention and other embodiments are contemplated. 
     The sortation apparatus includes a displacement module which transposes sheet material from a first on-edge orientation/position to a second on-edge orientation/position, substantially ninety-degrees (90° from the angular position of the first position. The angular displacement or transposition allows sheet material to be stacked within trays of a sheet material sorter which, in combination, reduce the overall length requirements of the sorter and, consequently, the space requirements thereof. 
     In the context used herein, “sheet material” means any sheet, page, document, or media wherein the dimensions in a third dimension are but a small fraction, e.g., 1/100th of the dimensions and stiffness characteristics in the other two dimensions. As such, the sheet material is substantially “flat” or planar. In addition to individual sheets of paper, plastic or fabric, objects such as envelopes and folders may also be considered “sheet material” within the meaning herein. Furthermore, mailpieces having relatively slender/thin/stiff objects contained within an envelope also are embraced within the definition of sheet material. 
     The invention described and illustrated herein discloses various features of a sheet material handling apparatus including: (i) a displacement system/module for transposing sheet material from a first to a second on-edge orientation (ii) a pneumatic conveyance/diverting system for delivering sheet material conveyed along a central feed path and diverting the sheet material to sortation bins on either side of the feed path, and (iii) a compliant conveyance system for transporting relatively stiff, planar mailpieces along an arcuate or “curved” feed path. 
       FIGS. 2 ,  3 , and  4  illustrate a displacement module  10  that includes a series of cooperating elements  12  which act on a mailpiece  14  to transpose its orientation from a first on-edge orientation to a second on-edge orientation. In the context used herein, the mailpiece  14  is generally rectangular in shape such that one side is necessarily longer or shorter than an adjacent side. For example, a typical type-ten (No. 10) mailpiece envelope has a length dimension of about eleven and one-half inches (11.5″) and a width dimension of about four and one-half inches (4.5″). 
     Displacement Module for Transposing Sheet Material 
     The mailpiece  14  is fed and singulated in a conventional manner by a sheet feeding apparatus  16 . The sheet feeding apparatus  16  feeds each mailpiece  14  in an on-edge lengthwise orientation towards the displacement module  10  which accepts the mailpiece  14  between or within coupled pairs of cooperating elements such as rollers  20   a ,  20   b . Prior to being accepted within the displacement module  10 , a scanner SC typically reads the mailpiece  14  and communicates the information to a processor  30  ( FIGS. 2 and 4 ) for the purposes of performing a sortation algorithm. This sortation algorithm is subsequently used to control the various diverter mechanisms  26  ( FIG. 2 ) within the sortation bin module  50 . 
     Furthermore, the scanner SC may process the data obtained to “verify” the mailing address prior to sortation. More specifically, it is often desirable to check the veracity of a mailing address prior to sorting to ensure that the mailing address is correct and current. This is accomplished by producing an Optical Character Recognition (OCR) image of the address and communicating with a central database to compare the OCR data with “validated address” data the determine whether the address is accurate and up-to-date, e.g., to check whether the recipient has moved to a new address. Once scanned and validated, it is also common to print a barcode representation of the mailing address, at a print station (not shown) downstream of the scanner SC and upstream of the displacement module  10 , to facilitate subsequent delivery of each mailpiece  14 . Valid mailpieces may then be sorted while invalid mailpieces may be outsorted for further processing, e.g., returned to sender. 
     Each coupled pair comprises a first pair of rollers  20   a  defining an upper nip  22   a  (see  FIGS. 3 and 4 ) which accepts an upper portion  14 U of the mailpiece  14  and a second pair of rollers  20   b  defining a lower nip  22   b  which accepts a lower portion  14 L of the mailpiece  14 . In the context used herein, a “nip” means any pair of opposing surfaces, or cooperating elements, which secure and hold an article, or portion of an article, therebetween. Consequently, a nip can be defined as being between rolling elements, spherical surfaces, flat bands or compliant belts. 
     As the mailpiece  14  traverses the displacement module  10 , the coupled pairs  20   a ,  20   b  cooperate to linearly displace and rotate the mailpiece  14  along the envelope feed path EFP. As best seen in  FIG. 3 , five (5) pairs of upper rollers  20   a  and five (5) pairs of lower rollers  20   b  move the mailpiece  14  linearly along the sheet path SP. Simultaneously, or as the mailpiece moves from left to right in  FIG. 3 , several of the coupled pairs  20   a ,  20   b  rotate the mailpiece  14  about virtual axes VA to transpose its orientation from an on-edge lengthwise orientation to an on-edge widthwise orientation. To effect rotation, the displacement module  10  includes a means to differentially drive the coupled pairs  20   a ,  20   b  such that the lower portion  14 L of the mailpiece  14  incrementally travels at a different, e.g., a higher, speed or velocity. In the described embodiment, as each mailpiece  14  fed through the displacement module  10  reaches various threshold positions between the coupled pairs  20   a ,  20   b , each of the lower pairs  20   b  may be driven at a higher rotational speed relative to the respective upper pair  20   a.    
     More specifically, the processor  30  (see  FIG. 4 ) is operative to control a plurality of rotary actuators or motors  32  which drive the upper and lower pairs  20   a ,  20   b  of rollers. The motors  32  may drive only one of the rollers in each of the pairs  20   a ,  20   b , while the other roller serves as an idler to define the upper and lower nips  22   a ,  22   b . As a mailpiece  14  moves along the feed path EFP and between the coupled pairs  20   a ,  20   b , the motors  32  may be driven at the same or differential speeds to effect linear or rotational motion. For example, the motors  32  may be driven in unison such that both upper and lower portions  14 U,  14 L of the mailpiece  14  are displaced at the same speed. Under such control, the mailpiece  14  moves linearly from one coupled pair  20   a ,  20   b  to another pair  20   a , and  20   b . When the mailpiece  14  reaches a threshold position between a coupled pair  20   a ,  20   b , the motors  32  may be differentially driven such that the upper and lower portions  14 U,  14 L of the mailpiece  14  are differentially displaced, e.g., the lower portion  14 L moves at a higher speed than the respective upper portion  14 U. Under this control, the mailpiece  14  rotates about the virtual axis VA such that the mailpiece  14  changes orientation, e.g., is rotationally displaced. 
     In  FIG. 5 , a dimensionless speed profile of the coupled pairs  20   a ,  20   b  is depicted to demonstrate the method of motor control. Therein, the rotational velocity of the driven rollers  20   a ,  20   b  are plotted relative to the mean position of the mailpiece  14  along the envelope feed path EFP. Upon reaching the nips  22   a ,  22   b  of the upper and lower pairs  20   a ,  20   b , the speed V 1  of both pairs  20   a ,  20   b  is equal or matched such that the mailpiece  14  translates linearly without rotation. That is, each of the upper and lower portions  14 U,  14 L of the mailpiece is displaced at the same rate of speed. Upon reaching a threshold position between the upper and lower nips  22   a ,  22   b  of a subsequent or downstream pair of rollers  20   a ,  20   b , the processor  30  drives the motors  32  to increase the rotational speed of the lower pair  20   b  to a second speed V 2  while decreasing the rotational speed of the upper pair  20   a  to a third speed V 3 . The solid line SPL denotes the speed profile of the upper rollers  20   a , while the dashed line SPU represents the speed profile of the lower pair of rollers  20   b . This speed differential effects rotation of the mailpiece  14  as the mailpiece  14  continues to move downstream along the feed path EVP. 
     In the described embodiment, the second, third and forth pair of rollers  20   a ,  20   b  rotate the mailpiece, while the first and fifth pairs  20   a ,  20   b  effect pure linear translation of the mailpiece  14 . While the amount of rotation effected by each of the cooperating pairs  20   a ,  20   b  may differ from an upstream to a downstream pair, in the described embodiment, each of the intermediate pairs  20   a ,  20   b  rotates the mailpiece  14  about thirty degrees (30° about the respective virtual axis VA. Further, by examination of the speed profiles SPL, SPU, it will be noted that the profiles diverge or differ when the processor  30  effects controlled rotation of the mailpiece  14  and may converge to the same speed to effect pure linear motion of the mailpiece  14 . Moreover, it should also be noted that the speed of both pairs  20   a ,  20   b  remains positive (i.e., does not reverse directions) to continue linear movement of the mailpiece  14  along the feed path EFP while, at the same time, rotating the mailpiece  14 . 
     Finally, it may be desirable to vary the separation distance between the upper and lower rollers  20   a ,  20   b  of each coupled pair. For example, to achieve a controlled rotation of the mailpiece  14 , the separation distance SD 2 , SD 3  of the second and third pairs  20   a ,  20   b  of rollers, i.e., from an upstream to a downstream pair, may increase to optimally control the displacement and rotation of the mailpiece  14 . 
     In  FIG. 6 , an alternate embodiment of the invention is shown which includes a plurality of sensors disposed along the feed path EFP and between the coupled pairs  20   a ,  20   b  of rollers. Therein, rows of light-detecting photocells OS 1 , OS 2  sense the position of the mailpiece as it transitions from an on-edge lengthwise orientation to an on-edge widthwise orientation. The array of photocells OS 1 , OS 2  is directed across the plane of the mailpiece  14  to detect the linear and angular position of the mailpiece leading edge  14 L. Orientation signals are fed to the processor (not shown in  FIG. 6 ) to determine whether the mailpiece is accurately or appropriately positioned relative to prescribed position data, i.e., a position schedule recorded and stored in processor memory. 
     If an error exists between the actual position and the scheduled position of the mailpiece  14 , the processor may increase or decrease the differential speeds of one or more coupled pairs  20   a ,  20   b  to implement a corrective displacement/rotation. For example, the actual leading edge position of the mailpiece  14 , shown in solid lines, may correspond to a first line AP intersecting photocells  26   a ,  26   b . If, however, the scheduled position corresponds to a second line DP intersecting photocells  26   a ′  26   b ′, the processor may change the speed profile SPU′ of a downstream pair of rollers  20   a ,  20   b  to increase the speed of the lower rollers  20   b  to a velocity V 4 . As such, the processor may implement a corrective action to change the mailpiece position or rotation i.e., as the mailpiece traverses from an intermediate upstream position to a subsequent downstream position. 
     In  FIGS. 2 and 7 , the displacement system  10 , therefore, changes the orientation of the mailpiece  14  from an on-edge lengthwise orientation in the feeder  16  to an on-edge widthwise orientation for use in a bin/tray module  50 . Additionally, the mailpiece sorter  40  ( FIG. 2 ) can be adapted to include sortation bins/trays  44  which accept and stack the on-edge widthwise dimension of the mailpieces  14 . Specifically, the sortation bins/trays  44  are adapted to support the short edge or width dimension W of the mailpiece  14  while guiding the long edge or length dimension L on each side thereof. That is, the base  44 B of the bins/trays  44  support the on-edge width dimension W, while sidewall guides  44 S, disposed at substantially right angles to the base  44 B, support the length dimension L of each mailpiece  14 . 
     Inasmuch as the widthwise dimension W ( FIG. 7 ) of many mailpiece types can be significantly less than the lengthwise dimension L, the sortation bin module  50  can occupy less space or accommodate more sortation bins/tray  44 . By examination and comparison of  FIGS. 1 and 2 , it will be appreciated that the mailpiece sorter  40  ( FIG. 2 ), which incorporates the displacement system  10  of the present invention, can be combined with a bin module  50  having eight (8) additional sortation bins/trays  44 . In  FIG. 2 , the additional bins/trays  44  are shown in dashed lines and in series with an upstream set of sixteen (16) bins/trays  44 . Accordingly, twenty-four (24) sortation bins/trays  44  occupy the same space as the sixteen (16) bins  110  used in the prior art mailpiece sorter  100  ( FIG. 1 ). Alternatively, the sortation bin  50  may occupy fifty percent (50%) less floor space than an equivalent sortation module of a prior art sorter  100 . 
     Although the invention has been described with respect to a preferred embodiment 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 scope of this invention. 
     Sortation Bin Module for Sorting Mailpieces 
     In  FIGS. 2 and 8 , a sortation bin module  50  includes first and second back-to-back conveyor modules  60   a ,  60   b  operative to feed mailpieces  14  to one (1) of two (2) banks  70   a ,  70   b  of sortation bins  44 . The first and second banks  70   a ,  70   b  of sortation bins  44  are each disposed along each side and opposing one of the conveyor modules  60   a ,  60   b . To send a mailpiece  14  to the correct bank  70   a ,  70   b  of sortation bins  44 , the sortation bin module  50  includes a diverter flap  54  for bi-directionally sending mailpieces  14  to either of the conveyor modules  60   a ,  60   b . The processor  30  controls the diverter flap  54  based upon information obtained from the mailpiece  14  and processed by the sortation algorithm. In addition to the diverter flap  54 , each bank of sortation bins  70   a ,  70   b  includes a plurality of diverter modules  80  disposed at the input ends  74  of the individual sortation bins  72 . The diverter modules  80  are operative to divert mailpieces  14  from the feed path EFP, i.e., from of either of the back-to-back conveyor modules  60   a ,  60   b , to the proper sortation bin  44 . 
     For ease of discussion and illustration, the structure and function of the conveyor and diverter modules  60   a ,  60   b ,  80  will be discussed in the order that a mailpiece may travel along a module and within the sortation bin module  50 . Furthermore, only one of the back-to-back conveyors  60   a  and a single diverter module  80  (see  FIG. 8 ) will be discussed inasmuch as the conveyor modules  60   a ,  60   b  are essentially mirror images of the other and the diverter module  80  is identical from one sortation bin  44  to another. 
     A mailpiece  14  is accepted by the sortation bin module  50  from the displacement module  10  discussed above. As such, the mailpiece  14  is in an on-edge widthwise orientation as the diverter flap  54  directs the mailpiece  14  to one of the conveyor modules  60   a ,  60   b . Each conveyor module  60   a ,  60   b  includes a flexible conveyor belt  62  which defines a conveyor surface  62 S, and a pneumatic system or means  64  for developing a pressure differential across the conveyor surface  62 S. Each diverter module  80  similarly includes a cylindrical diverter sleeve  82  which defines an arcuate diverter surface  82 S and, similar to each of the conveyor modules  60   a ,  60   b , a pneumatic system or means for developing a pressure differential across the diverter surface  84 . In the described embodiment, a common pneumatic system  64  is employed to develop a pressure differential across the diverter surface  82 S, i.e., the same pneumatic system  64  is used for both the conveyor and diverter modules  60   a ,  60   b ,  80 . 
     The flexible conveyor belt  62  of each module  60   a  is driven about end rollers  66  similar to any conventional conveyor belt system, however, the conveyor surface  62 S thereof is porous and includes a plurality of orifices  62 O for allowing the flow of air therethrough. More specifically, at least one pneumatic chamber  68 - 1  is disposed between the strands of the conveyor belt  62  (only one strand is depicted in  FIG. 8 ) and includes a plurality of apertures  68 A which are aligned/in fluid communication with the orifices  62 O of the conveyor surface  62 S. That is, the apertures  68 A of a pneumatic chamber  68 - 1  are disposed in a sidewall structure  68 S thereof which lie adjacent to interior face  62 SI of the flexible conveyor belt  62 . 
     As mentioned earlier, the pneumatic chamber  68 - 1  is in fluid communication with a pneumatic source  64  capable of generating a positive or negative pressure (i.e., a vacuum) in the chamber  68 - 1  which, in turn, develops a pressure differential across the conveyor surface  62 S. While any processor may be used to control the pneumatic source  64 , it is preferable that the main system processor  30  be employed to orchestrate the flow of air. Specifically, the processor  30  controls the pneumatic source  64  such that a negative pressure differential is developed to accept and hold mailpieces  14  to the conveyor surface  62 S and/or a positive pressure differential is developed to release mailpieces  14  from the conveyor surface  62 S. 
     To improve the fidelity and/or flexibility of the conveyor module, the internal plenum may be segmented into a plurality of chambers  68 - 1 ,  68 - 2  to develop a plurality of linear control regions, i.e., along the length of the conveyor surface  62 S. That is, as a mailpiece  14  passes a particular linear control region, the pneumatic source  64  may be controlled to develop a negative pressure to hold the mailpiece  14 , or a positive pressure to release the mailpiece  14 . Alternatively, the pressure differential may be neutralized to allow another pneumatic conveyor or diverter to remove the mailpiece from the conveyor surface  62 S. 
     The diverter module  80  is generally cylindrical in shape and opposes the conveyor module  60   a  such that the conveyor and diverter surfaces  62 S,  82 S define a transfer interface TI therebetween. The diverter module  80  is driven about an axis  80 A and disposed over an internal system of plenum chambers  86   a ,  86   b ,  86   c  having a substantially complementary shape, i.e., cylindrical. In the described embodiment, the diverter sleeve  82  is driven by a motor  90  which drives a pair of friction rollers  94  via an internal drive shaft  92 . More specifically, the rollers  94  frictionally engage an internal wall  82 SW of the diverter sleeve  82  to drive the external diverter surface  82 S thereof about the internal plenums  86   a ,  86   b ,  86   c.    
     The diverter surface  82 S includes a plurality of orifices  82 O which are in fluid communication with each of the plenum chambers  86   a ,  86   b ,  86   c . More specifically, the plenum chambers include arcuate sidewalls  86 S which define a plurality of apertures  88 A which are in fluid communication with the orifices  82 O of the diverter surface  82 S. Each of the plenum chambers  86   a ,  86   b ,  86   c  are in fluid communication with the pneumatic source  64  such that a positive, negative or neutral pressure differential may be developed across the diverter surface  82 S. Similar to the conveyor module  60   a , the pneumatic source  64  may be controlled such that a variable pressure differential, i.e., positive, negative or neutral, may be developed across various arcuate control regions which correspond to the radial position of each of the plenum chambers  86   a ,  86   b ,  86   c.    
     In  FIGS. 8 and 9 , a mailpiece  14  is held by a vacuum V developed in chamber  68 - 1  and conveyed along the feed path EVP by the linear motion of the conveyor surface  62 S. As the leading edge of the mailpiece  14  reaches the transfer interface TI, the conveyor surface  62 S is exposed to a second chamber  68 - 2  wherein the vacuum or negative pressure V is either neutralized or pressurized to develop a positive pressure differential. In the illustrated embodiment, a positive pressure P forcibly removes the mailpiece  14  from the conveyor surface  62 S. 
     At the same time, a first plenum chamber  86   a , or quadrant of the diverter module  80 , develops a negative pressure differential to remove and hold the mailpiece to the diverter surface  82 S. As the diverter sleeve  82  rotates, the diverter surface  82 S and mailpiece  14  traverses a second plenum chamber  86   b  or second quadrant of the diverter module  80 . A negative pressure differential is developed in the respective control region such that the mailpiece  14  is held against the diverter surface  82 S and is moved away, or transversely, from the conveyor surface  62 S. Continued rotation of the diverter sleeve  82  causes the diverter surface  82 S and mailpiece  14  to traverse a third plenum chamber  86   c  or third quadrant of the diverter module  80 . 
     When the mailpiece  14  is aligned with the entrance of the sortation bin  44 , a neutral or positive pressure differential may be developed in the final control region such that the mailpiece  14  is released from the diverter surface  82 . In  FIG. 8 , the mailpiece  14  is shown in dashed lines to illustrate an intermediate position immediately prior to being stacked in the sortation bin  44 . To augment the removal of the mailpiece  14  from the diverter surface  82 S, other active pneumatic devices may be employed. For example, an air knife ARN may be employed to supply a sheet of pressurized air tangentially of, and interposing, the diverter surface  82 S and the mailpiece  14 . The sheet of air assists in the removal of the mailpiece  14  by peeling away an edge of the mailpiece  14  from the diverter surface  82 S. 
     In summary, the conveyor and diverter modules  60   a ,  60   b ,  80  pneumatically transport and sort mailpieces  14  in a sortation bin module  50 . Pneumatic control of the conveyor and diverter modules  60   a ,  60   b ,  80 , along with the use of independently controlled pneumatic plenums/chambers, improves the reliability of the sortation apparatus  40  while decreasing the opportunity for mailpiece damage/jamming. Further, the conveyor and diverter modules  60   a ,  60   b ,  80  are ideally suited to transport mailpieces  14  in an on-edge widthwise orientation, i.e., along the width dimension thereof. Since the width dimension W (see  FIG. 7 ) of many mailpieces can be significantly less than the length dimension L, the sortation bin module  50  may be adapted to occupy less space and/or accommodate the introduction of additional sortation bins  44 . 
     Compliant Diverter for Mailpiece Transport 
     In view of today&#39;s ever widening variety of packages delivered through the mail (e.g., products associated with on-line sales and internet auctions), it will be appreciated that the conveyor and diverter modules  60   a ,  60   b ,  80 , must handle/process a variety of mailpiece sizes, shapes, and other physical properties. Whereas some mailpieces, having conventional printed content material, are flexible along axes which lie in the plane of the mailpiece  14 , others containing commercial products such as media or video discs, i.e., CDs and DVDs, are substantially rigid in the plane of the envelope. That is, the plastic containers used to package such products produce a substantially stiff, planar mailpiece. 
     As such, greater difficulties are experienced to produce the requisite pressure differential to secure the mailpiece  14  against the diverter surface  82 S, especially when centrifugal forces developed as the diverter sleeve  82  rotates oppose the forces induced by vacuum. That is, the rigidity of the mailpiece  14  causes the mailpiece  14  to contact the diverter sleeve  82  at a point of tangency rather than along an arcuate surface, e.g., as a flexible mailpiece wraps around an arcuate portion of the sleeve  82 . As a result, only a small number of orifices  82 O, i.e., along a vertical line, may be available to produce the requisite pressure differential. If the pressure differential produced is less than the weight induced moment loads, i.e., the loads tending to pull the mailpiece  14  away from the diverter surface  82 S, the mailpiece  14  will not be retained or secured by the pneumatic diverter module  80 . 
     The present invention addresses these concerns by adapting the diverter sleeve  82  to conform to the shape of the mailpiece  14 . More specifically, in  FIGS. 10 ,  11  and  12 , the diverter sleeve  82  comprises a rigid inner portion  82 SI and a resilient outer portion  82 SO. Similar to the embodiment discussed supra, the rigid inner portion  82 SI rotates about, and is in fluid communication with, the various stationary pneumatic plenum chambers  86   a ,  86   b ,  86   c . Consequently, the inner portion  82 SI is essentially the same as previously described, but for a small change in radial thickness. That is, to accommodate the dimensional changes which may result from the outer portion  82 SO. 
     In  FIGS. 12 ,  13  and  14 , the outer portion  82 SO is disposed over the inner portion  82 SI and forms a compliant interface surface  82 C for conveying mailpieces  14 . In one embodiment shown in  FIG. 12 , the outer portion  82 SO comprises an exterior layer of resilient foam  100  having a plurality of perforations or apertures  100 A which are in fluid communication with the orifices  82 O of the rigid inner sleeve portion  82 SI. The resilient foam  100  is sufficiently soft to compress a full forty (40) to eighty (80) percent of the original thickness i.e., T L=FULL /T L=0\ , under the vacuum load produced by the vacuum source  64 . As a result, the resilient foam  100  is sufficiently compliant to conform to the external shape of the rigid mailpiece, i.e., the surface  104  of the outer portion  82 SO in contact with the rigid mailpiece  14  conforms to the planar external surface of the mailpiece  14 . 
     In another embodiment of the invention shown in  FIG. 13 , the resilient outer portion  82 SO includes a flexible outer layer  110  of poly-tetra-flora-ethylene (PTFE) disposed over a resilient support layer  112 . The PTFE outer layer is sufficiently thin to deform under load and, in the described embodiment, has a thickness dimension T within a range of between 0.020 inches to about 0.050 inches. The resilient support layer  112  may be comprised of an elastomer material to bias the PTFE layer outwardly, thereby producing a soft, compliant spring. Preferably the elastomer material is a polychloroprene rubber made from a family of synthetic rubbers that are produced by polymerization of chloroprene and is characterized by a low durometer of between about 30 to 40. Similar to the previous embodiment, apertures  110 A are formed in, and extend through, the outer layer  110 A of poly-tetra-flora-ethylene (PTFE) and underlying resilient support layer  112 . 
     In another embodiment of the invention shown in  FIG. 14 , the resilient outer portion  82 SO of the diverter sleeve  82  includes an array of closely-spaced, highly flexible, rubber tubes  120  which project radially from the orifices  82 O of the rigid inner portion  82 SI. In the described embodiment the rubber tubes  120  are fabricated from short lengths of surgical rubber tubing defining a flexible conduit  120 A for pneumatic fluid flow. Preferably, the rubber tubes  120  are fabricated from a Latex or a “gum” rubber material. In the described embodiment, the rubber tubes  120  are between about one-quarter (¼) to three-quarter (¾) inches in length and may vary in diameter from one-eighth (⅛th) to one-half (½) inches in diameter. The array of tubes  120 , therefore, define a plurality of short, densely-packed suction cups which are sufficiently flexible to conform to the surface of the mailpiece  14 . 
     Operationally, and referring once again to  FIGS. 10 and 11 , the diverter  80  of the compliant conveyance system may be used/controlled in the same manner as was previously described when discussing the conveyor and diverter modules  60   a ,  60   b ,  80  of the sortation bin module  50 . That is, mailpieces  14  may be transferred from one of the conveyor modules  60   a ,  60   b  to a diverter  80  by alternately producing a positive pressure differential to release a mailpiece  14  (e.g., from a conveyor module  60   a  or  60   b ) and a negative pressure differential to receive and secure a mailpiece  14  (e.g., to the diverter module  80 ). Similarly, the release a mailpiece  14  from the diverter  80  may be achieved by producing a neutral or positive pressure differential within one of the plenum chambers  86   a ,  86   b ,  86   b.    
     Inasmuch as the diverter  80  of the compliant conveyance system may handle substantially rigid, planar mailpieces, the compliant interface surface  82 C conforms to at least a portion of the interface surface of the mailpiece  14 . As such, the compliant interface surface  82 C augments the pressure differential developed across each respective mailpiece  14  (i.e., by increasing the number of vacuum orifices acting on the surface of the mailpiece. 
     To ensure that a mailpiece  14  remains in contact with the compliant interface surface  82 C, the conveyance system includes a guide rail  98  disposed about, and spaced apart from, at least a portion of the compliant interface surface  82 C. More specifically, the guide rail  98  is operative to retain a portion of the mailpiece  14  as the mailpiece is diverted along the feed path, i.e., from the conveyor belt  62  to the sortation bin  44 . 
     Although the invention has been described with respect to a preferred embodiment 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 scope of this invention.