Patent Publication Number: US-8123023-B2

Title: Mailpiece conveyance system

Description:
TECHNICAL FIELD 
     The present invention relates to a system and method for processing mailpieces and more particularly, to a new and useful compliant conveyance system operative to process mailpieces (e.g., print on a face surface thereof) which vary in thickness. 
     BACKGROUND OF THE INVENTION 
     Mailpiece creation systems such as mailpiece inserters are typically used by organizations such as banks, insurance companies, and utility companies to periodically produce a large volume of mailpieces, e.g., monthly billing or shareholders income/dividend statements. In many respects, mailpiece inserters are analogous to automated assembly equipment inasmuch as sheets, inserts and envelopes are conveyed along a feed path and assembled in or at various modules of the mailpiece inserter. That is, the various modules work cooperatively to process the sheets until a finished mailpiece is produced. 
     A mailpiece inserter includes a variety of apparatus/modules for conveying and processing sheet material along the feed path. Commonly mailpiece inserters include apparatus/modules for (i) feeding and singulating printed content material in a “feeder module”, (ii) accumulating the content material to form a multi-sheet collation in an “accumulator”, (iii) folding the content material to produce a variety of fold configurations such as a C-fold, Z-fold, bi-fold and gate fold, in a “folder”, (iv) feeding mailpiece inserts such as coupons, brochures, and pamphlets, in combination with the content material, in a “chassis module” (v) inserting the folded/unfolded and/or nested content material into an envelope in an “envelope inserter”, (vi) sealing the filled envelope in “sealing module” (vii) printing recipient/return addresses and/or postage indicia on the face of the mailpiece envelope at a “print station” and (viii) controlling the flow and speed of the content material at various locations along the feed path of the mailpiece inserter by a series of “buffer stations”. In addition to these commonly employed apparatus/modules, mailpiece inserter may also include other modules for (i) binding/to close the module to close and seal filled mailpiece envelopes and a (vi) a printing module for addressing and/or printing postage indicia. 
     With respect to the printing module, it is common to register a face surface of each mailpiece with a registration plate such that an array of print heads may print information such as destination and return addresses on the face of each mailpiece. More specifically, the registration plate includes an aperture for accepting a stepped array of print head nozzles. The thickness of the registration plate provides a threshold “stand-off” dimension from the face surface of each mailpiece to each of the print head nozzles such that ink droplets may be precisely deposited. 
     Furthermore, the array of print heads and registration plate are typically disposed over, and in opposed relation to, and underlying conveyance system such as one or more conveyor belts. Mailpieces are conveyed along the belt(s), move under the registration plate and passed by the print head nozzles as ink is deposited. To ensure that mailpieces slide smoothly beneath the registration plate, i.e., without jamming, the spacing between the underlying conveyance system, e.g., the conveyance belt (s), and the registration plate must be closely controlled. That is, with each mail run/print job performed by the print module, the necessary clearance gap must be established based upon the anticipated thickness of mailpieces being processed. As such, print head modules and underlying conveyance systems are typically limited to processing mailpieces having a constant, i.e., non-variable, thickness dimension. While such print head modules are capable of printing on thin and thick mailpieces, they are unable to print consecutive thin and thick mailpieces inasmuch as the clearance gap differs for each of the mailpieces. 
     Commonly, the mailpieces are conveyed along a feed path to the print heads by a vacuum manifold system. The vacuum manifold system develops a pressure differential across each of the mailpieces to urge each mailpiece into frictional engagement with one or more conveyor belts. A fluid communication path is created from the drive surface of the conveyor belts to a vacuum source by a combination of apertures, conduits and plenums. More specifically, rows of apertures are typically formed in the belts which communicate with a combination of elongate slots and circular apertures formed in the underlying support deck. Conventionally, a system of plenums are disposed beneath, and attached to an underside surface of, the support deck to draw air through the apertures of the belt and elongate slots/circular apertures of the support deck. The elongate slots are aligned with the apertures formed in the belts to ensure a flow of air to each of the apertures as the belts are driven along the feed path. To ensure that airflow is not restricted along the length of the elongate slots, i.e., due to deformation of the belt into an elongate slot, elongate slots are fabricated to maintain a a threshold thickness dimension. That is, by maintaining a threshold minimum thickness, deformation of the belt may be obviated to prevent the belt from restricting or closing the flow through the slots and circular apertures of the support deck. 
     A need, therefore, exists for a print module and conveyance system which is capable of processing consecutive mailpieces which vary in thickness dimension. 
     SUMMARY OF THE INVENTION 
     A compliant conveyance system is provided for processing mailpieces along a feed path, e.g., printing on a first surface of a mailpiece, while being registered against a contact surface of a registration plate. The conveyance system comprises at least one conveyor belt opposing the contact surface of the registration plate, a continuous, uninterrupted, compliant deck disposed beneath and supporting an underside surface of the conveyor belt, and a spring biasing device operative to bias the compliant deck and the conveyor belt toward the contact surface of the registration plate. The conveyor belt includes a drive surface for engaging a second surface of each of the mailpieces for conveyance along the feed path. As each of the mailpieces pass the registration plate, the compliant deck and spring biasing device urge the second surface of each mailpiece into engagement with the contact surface during processing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings illustrate presently preferred embodiments of the invention and, together with the general description given above and 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 perspective view of a compliant conveyance system according to the present invention wherein consecutive thin and thick mailpieces are fed along a mailpiece feed path and between a print head assembly and a compliant deck of the conveyance system. 
         FIG. 2  is a top view of the compliant conveyance system shown in  FIG. 1  wherein a central vacuum belt frictionally engages a face surface of each mailpiece to transport the mailpieces along the feed path. 
         FIG. 3  is a bottom perspective view of the compliant conveyance system including a spring biasing device operative to bias the compliant deck upwardly toward a registration plate of the print head assembly. 
         FIG. 4  is an broken-away partially exploded top view of the compliant deck including a high elongation surface layer and a high yield strength support layer which cooperate to provide a continuous flexible deck. 
         FIG. 5  is a partially broken away sectional view of the compliant conveyance system taken substantially along line  5 - 5  of  FIG. 3  depicting the relevant details of the spring biasing device. 
         FIG. 6  is an enlarged, partially broken away sectional view taken substantially along line  6 - 6  of  FIG. 2  depicting the compliant conveyance system as consecutive thin and thick mailpieces are fed along the feed path and processed by the print head assembly. 
         FIG. 7  is an broken-away partially exploded bottom view of the compliant deck including the relevant details of a flexible vacuum conveyance/manifold system adapted to maintain high flexibility and reliability. 
         FIG. 8  is a partially broken away sectional view taken substantially along line  8 - 8  of  FIG. 2  depicting the fluid communication path from the central vacuum belt to a vacuum source through corrugated flexible tubing. 
         FIG. 9  is a partially exploded rear perspective view of the print head assembly including a staggered array of print heads, a registration plate, a spacer plate, a mounting plate, and a plurality of runners affixed to the mounting plate. 
         FIG. 10  is an isolated rear perspective view of the print head assembly depicting the print heads, plates and runners when arranged and assembled. 
         FIG. 11  is an enlarged sectional view taken substantially along line  11 - 11  of  FIG. 10  depicting a mailpiece being processed beneath/by the print head assembly and the runners engaging the mailpiece to maintain a desired stand-off dimension between the print head assembly nozzles and the face surface of each mailpiece. 
         FIG. 12  depicts a perspective view of a pivotable support/instrumentation rack operative to support the print head assembly with respect to the underlying compliant conveyance system and mount a variety of instrumentation, e.g., photocells/position sensors, for monitoring the progress and condition of mailpieces being processed. 
         FIG. 13  depicts the support/instrumentation rack pivoted to a closed position and secured by a pair of locking mechanisms to the top deck of a housing structure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention is described in the context of a printing module and underlying conveyance system for a mailpiece inserter, though it will be appreciated that the system and method described herein is applicable to processing variable thickness mailpieces which are fed consecutively. Furthermore, the system and method of the present invention is applicable to mailpieces wherein a face surface thereof is disposed in register and guided along a registration plate during processing. For example, such registration may be required when inspecting a mailpiece, reading postage indicia or interpreting scan codes on the face of a mailpiece. Consequently, the detailed description and illustrations are merely indicative of an embodiment of the invention and the invention should be broadly interpreted in accordance with the appended claims. 
     Compliant Conveyance System 
       FIGS. 1 and 2  depict perspective and top views of a print head assembly  8  disposed over a compliant conveyance system  10 . The compliant conveyance system  10  is operative to process mailpieces  14  which vary in thickness from about 0.10 inches to about 0.5 inches. In one embodiment of the compliant conveyance system  10 , a compliant deck  12  is provided having a low characteristic stiffness in a direction parallel to the feed path FP of mailpieces being processed and a high characteristic stiffness in a direction orthogonal to the feed path. That is, the characteristic stiffness parallel to the feed path is lower (i.e., 50% or more) than the characteristic stiffness in the orthogonal direction. 
     The compliant conveyance system  10  is adapted for operation with a bank of print heads  16  arranged in a staggered or stepped array. Furthermore, the bank of print heads  16  includes a registration/skid plate  18  having a contact surface  18 S for registering a first surface  14 FS of each mailpiece  14 . A pivotable support/instrumentation rack (not shown in the subject illustrations) supports the print head module  8 , to maintain the position of the print heads  16  relative to the underlying compliant conveyance system, i.e., a clearance gap therebetween. The support/instrumentation rack will be discussed in greater detail hereinafter. 
     The compliant conveyance system  10  includes at least one conveyor belt  20  having a drive surface  20 S which is adapted to oppose the contact surface  18 S of the registration plate  18 . In the illustrated embodiment, the compliant conveyance system  10  employs three (3) belts  20   a ,  20   b ,  20   c  which are spaced apart, though it should be appreciated that a fewer or greater number of belts  20  may be employed. In  FIGS. 1 ,  2  and  3 , the conveyor belts  20  rotate around a plurality of rollers, e.g., end turn-around rollers  22 ,  24 , tensioning rollers  26 ,  28  (see  FIG. 3 ) and drive rollers (not shown) which are driven by a drive motor (also not shown). The end rollers  22 ,  24  are each mounted for rotation to side beam members  30 ,  32  to produce a rigid box structure having a generally rectangular shape. Each of the side beam members  30 ,  32  have a generally S-shaped or Z-shaped cross-section wherein an upper flange  30 T,  32 T (see  FIGS. 1 and 3 ) projects outwardly away from the conveyor belts  20  and a lower flange  30 L,  32 L (see  FIG. 3 ) projects inwardly toward the conveyor belts  20 . Furthermore, the web  30 W,  32 W of at least one of the beam members  30 ,  32  includes a plurality of apertures  30 A,  32 A which are used to receive a plurality of flexible tubes  34  employed in a Flexible Manifold Vacuum System  50  (described in greater detail hereinbelow). 
     The compliant deck  12  is disposed beneath and supports the conveyor belts  20 . In  FIGS. 3 ,  4  and  5 , the compliant deck  12  comprises at least one continuous, i.e., uninterrupted, layer of a high-modulus, low-friction, high yield strength material such as a polished spring steel. In the described embodiment, the compliant deck  12  includes a support layer  40 S (see  FIGS. 4 ,  5  and  6 ) of spring steel and a surface layer  40 T of Teflon® (“Teflon” is a registered trademark of the Dupont Nemours Corporation located in Wilmington, state of Del.) or Poly-Tetra-Flora-Ethylene (PFTE). The support layer  40 S spring steel has a thickness dimension T 1  (see  FIG. 6 ) of between about 0.010 inches to 0.015 inches, a Young&#39;s Modulus (e) of between about 2×10 5  MPa to about 2.2×10 5  MPa, an elongation (s) of between about 6% to about 8%, and a Yield strength (σ) of between about 1100 MPa to about 1300 MPa. The surface layer  40 T of PFTE has a thickness dimension T 2  (see  FIG. 6 ) of between about 0.058 inches to 0.072 inches, a Young&#39;s Modulus (e) of between about 400 MPa to about 800 MPa, an elongation of between about 300% to 600% and a friction coefficient (K) of less then about 0.15. The characteristic stiffness of the compliant deck  12 , i.e., the combined layers  40 S,  40 T, parallel to the feed path is about two-hundred percent (200%) to about four hundred percent (400%) of the characteristic stiffness of the compliant deck  12  in a direction orthogonal to the feed path. 
     The support layer  40 S dominates the flexure and stiffness of the compliant deck  12  due to the high modulus, high yield strength of spring steel. As a result, the bending neutral axis of the compliant deck  12 , i.e., the combined layers  40 S,  40 T, lies within the thickness dimension of the support layer  40 S. Despite the much larger thickness dimension of the PFTE layer  40 T and its distance from the bending neutral axis, its contribution to the overall stiffness of the compliant deck  12  is negligible due to the high elongation, low modulus of the PFTE layer  40 T. Consequently, the compliant deck  12  may also be characterized as a combination of layers  40 S,  40 T having a high modulus, high yield strength material at the core of the deck  12 , i.e., proximal to the bending neutral axis, and a high elongation, low friction material at a free edge of the deck  12 , i.e., an edge which is distal from the core and parallel thereto. This characterization of the compliant deck  12  will be more clearly understood when discussing the thickness requirements of the Flexible Vacuum Manifold system hereinafter. 
     Both the support and surface layers  40 S,  40 T are disposed between the side beam members  30 ,  32  and retained by forward flanges  40 F which mount to a cross beam member  36  (see  FIG. 3 ) disposed immediately downstream of the forward turn-around roller  22 . Additionally, edge retention strips  38   a ,  38   b  (see  FIG. 5 ) are affixed to the upper flanges  30 T,  32 T of the respective side beam members  30 ,  32  and project inwardly over the upper peripheral edge  12 E (see  FIG. 5 ) of the compliant deck  12  i.e., over the surface layer  40 T thereof. 
     In  FIGS. 3 ,  4  and  5 , the compliant deck  12  is supported by a spring biasing device  42  comprising a plurality of transverse stiffening members  44  and spring biasing members  46 . More specifically, each transverse stiffening member  44  has a generally L-shape and is disposed beneath and across the support layer  40 S of the compliant deck  12 , i.e., orthogonal to the compliant belts  20 . Furthermore, the stiffening members  44  are disposed at regular intervals, i.e., are evenly spaced across the underside of the support layer  40 S of the compliant deck  12 . In the described embodiment, the stiffening members  44  are disposed at intervals of between one (1) to two (2) inches. A flange portion  44 F of each stiffening member  44  abuts the underside of the support layer  40 S while a stiffening portion  44 S projects downwardly to increase the stiffness of the support layer  40 S in a direction orthogonal to the feed path FP (shown as a point going into the plane of the drawing sheet in  FIG. 5 ) of the conveyance system  20 . Each end  44 E of a stiffening member  44 , i.e., along the upper surface of the flange portion  44 F, is affixed to the underside peripheral edge  40 SE of the support layer  40 S. 
     Pairs of spring biasing members  46  support each end  44 E of a respective stiffening member  44  and, due to the structural integration of the stiffening portion  44 S, function to provide a vertical spring biasing force across the width, i.e., orthogonal to the feed path, of the compliant deck  12 . Each spring biasing member  46  is disposed between the underside of the flange portion  44 F of a respective stiffening member  44  and the inwardly projecting flanges  30 L,  32 L of the side beam members  30 ,  32 . 
       FIG. 6  depicts an enlarged view of the compliant deck  12  when conveying consecutive thin and thick mailpieces  14 TN,  14 TK. The mailpieces  14 TN,  14 TK are aligned along an upper face or first surface  14 FS against the registration surface  18 S of the registration plate  18 . Furthermore, friction forces, (forces developed along and between the lower face or second surface  14 SS of the mailpiece  14  and the conveyor belts  20 ), convey the mailpieces  14 TN,  14 TK beneath and passed the nozzles of the print heads  16 . As mailpieces  14  move beneath the print module  8 , the underlying compliant deck  12  undulates in a wave-like manner. The highly resilient support layer  40 S of spring steel flexes vertically downward to accommodate the thickness dimension of, and thickness variations between, each of the thin and thick mailpieces  14 TN,  14 TK. 
     Registration against the plate  18  is maintained by vertical forces imposed by the spring biasing device  42 . The vertical forces originate with each pair of spring members  46  at the proximal ends  44 E of each stiffening member  44  and are conveyed in a substantially uniform manner across the complaint deck  12 . That is, the each stiffening member  44  transfers the downward motion of each mailpiece, i.e., at the center of the compliant deck  12 , to the peripheral edges  44 E, where the spring biasing members  46  impose a vertical force in a direction opposing the downward displacement. Furthermore, the spring biasing device  42  may be viewed as a collection of independently operating springs which define a plurality of discrete rows. That is, the stiffening member  44  may be viewed as a substitute for additional spring members disposed across the width of the compliant deck  12 . As such, the regions between the stiffening members  44  are soft and compliant to facilitate vertical displacement of each mailpiece. In the described embodiment, the compliant deck  12  and spring biasing device  42  accommodates up to about one-half (½) inches of displacement. While the support layer  40 S is highly compliant, the use of a high yield strength spring steel prevents plastic deformation of the compliant deck  12 , and can perform millions of cycles without failure. 
     The spring rate constant of each spring member  46  is principally a function of the desired vertical deflection of the compliant deck  12 , the number of transverse stiffening members  44 , and the stiffness of the support layer  40 S of spring steel. Secondary considerations relate to the tension loads applied to the compliant belts  20  and the mass of the flexible vacuum conveyance/manifold system  50  which is structurally integrated with the spring biasing device  42 . As a general rule, the vertical forces imposed by the spring members  46  are sufficiently high to maintain the mailpieces  14 TN,  14 TK against the registration plate  18 , yet sufficiently low to prevent damage to the upper face surface  14 FS of each mailpiece  14 . 
     While the compliant conveyance system  10  of the present invention includes a spring biasing device  42  including a plurality of coil springs  46 , it will be appreciated that other devices or materials may be employed to provide the requisite spring rate. For example, a high elongation elastomer rubber (not shown) may be disposed between the transverse stiffening members  44  and the support platform, i.e., the flange portion of the side beam members  30 ,  32 , to provide the necessary spring biasing forces. Alternatively, a high elongation foam/foam rubber (also not shown) may be molded between the underside of the support layer  40 S and an underlying support. 
     In summary, the combination of continuous support and surface layers  40 S,  40 T, i.e., without breaks or segments, along with a spring biasing device which imparts anisotropic stiffness properties to the compliant deck  12  (low stiffness properties parallel to the feed path and high stiffness properties orthogonal thereto), significantly enhances the fatigue life of the conveyance system  10 . Furthermore, the high degree of compliance enables processing of consecutive thin and thick mailpieces. That is, the compliant deck  12  is capable of processing mailpieces  14 TN,  14 TK up to one-half inches (½″) in thickness. Moreover, throughput, i.e., the number of mailpieces processed per unit of time, increases inasmuch as mailpieces  14 TN,  14 TK, whether or not disparate in thickness, may be closely spaced, i.e., between four (4) to six (6) inches apart. 
     The following discusses the functional and structural interaction of the compliant deck  12  and the flexible vacuum conveyance/manifold system  50 . It will be appreciated that, while the teachings associated with each are separate and distinct, the systems are structurally integrated and interdependent. 
     Flexible Vacuum Manifold System 
     In  FIGS. 4 ,  7  and  8 , the flexible vacuum conveyance/manifold system  50  is operative to produce a pressure differential across each mailpiece  14  to urge the lower face or second surface  14 SS of each mailpiece  14  into frictional engagement with the upper drive surfaces  20 D (see  FIG. 8 ) of the compliant belts  20 . More specifically, the flexible vacuum conveyance/manifold system  50  is adapted to accommodate the motion of the compliant deck  12  without increasing or affecting the stiffness and/or mass properties thereof. With respect to the latter, the fatigue life of the compliant deck  12  (i.e., particular the spring biasing device  42 ) is a function its mass. Accordingly, an objective of the vacuum conveyance/manifold system  50  is to minimize the weight added to the compliant conveyance system  10 . 
     The flexible vacuum conveyance/manifold system  50  comprises: a plurality of apertures  52  disposed in at least one of the conveyor belts  20 , a plurality of apertures  54 ,  56  (see  FIGS. 4 and 8 ) disposed in the compliant deck  12  and in fluid communication with the apertures  52  of the at least one conveyor belt  20 , a plurality of apertures  44 A (see  FIG. 8 ) disposed in the flange portion  44 F of the stiffening member  44  and in fluid communication with the apertures  54 ,  56  disposed in the compliant deck  12 , a linear plenum  58  (see  FIGS. 7 and 8 ) disposed in combination with each of the stiffening members  44  and in fluid communication with the apertures  44 A of the respective stiffening member  44 , ( FIG. 8 ), a plurality flexible vacuum tubes  34  (see  FIGS. 7 and 8 ) disposed in fluid communication with each linear plenum  58 , a vacuum manifold  60  disposed in fluid communication with the plurality of flexible vacuum tubes  34 , and a vacuum source  62  disposed in fluid communication with the vacuum manifold  60 . 
     In the described embodiment, the central conveyor belt  20   b  includes rows of apertures  52  which are aligned with elongate slots  54  formed in the surface layer  40 T of the compliant deck  12 . The elongate slots  54  are disposed over, and are aligned with, rows of apertures  56  disposed through the support layer  40 S, i.e., the sheet of spring steel, of the compliant deck  12 . Furthermore, rows of apertures  44 A are aligned with the apertures  56  of the support layer  40 S to permit airflow through the flange portion  44 F of the stiffening member  44 . Each linear plenum  58  defines a plenum chamber  66  which is disposed over, and in fluid communication with, both apertures  44  formed in the stiffening member  44 . The flexible tubing  34  provides a flexible path from each plenum chamber  66  to the vacuum manifold  60 . While  FIGS. 4 and 7  do not show the flow through the vacuum manifold  60 , it will be appreciated that the vacuum manifold  60  may vary in diameter or provide multiple flow paths to ensure relatively constant flow/pressure to each of the plenum chambers  66 . 
     In operation, the vacuum source  62  draws a vacuum which initiates fluid flow through the vacuum manifold  60 , through the system of flexible tubing  34  and into the plenum chambers  66  of each linear plenum  58 . The pressure differential established by the vacuum source  62  in each of the linear plenums  58  effects fluid flow through the apertures  52  of the central conveyor belt  20   b , through the elongate slots  54  of the upper surface layer  40 T and the aligned apertures  56 ,  44 A of the support layer  40 S and the stiffening member  44 . As the conveyor belt  20   b  slides over the surface layer  40 T, the each aperture  52  of the conveyor belt  20   b  remains in fluid communication with at least one of the elongate slots  54  inasmuch the slots  54  span several conveyor belt apertures  52 . Consequently, all of the apertures  52  are operative to produce a pressure differential along the drive surface  20 D of the belt  20   b  and across each mailpiece  14 , wherever the mailpiece  14  may be located. 
     To accommodate the motion of the compliant deck  12  and ensure adequate flexibility of the compliant conveyance system  10 , the flexible vacuum conveyance/manifold system  50  employs flexible corrugated tubing  34  between each linear plenum  58  and the vacuum manifold  60 . Furthermore, the flexible corrugated tubing  34  extends through oversized apertures  30 A in the side beam member  30  to eliminate points of restraint with may stiffen or reduce the flexibility of the vacuum conveyance/manifold system  50 . 
     Yet another feature of the flexible vacuum conveyance/manifold system  50  relates to producing a robust reliable vacuum without increasing the stiffness of the compliant deck  12 . More specifically, to produce an adequate vacuum, the depth or thickness of the elongate slots  54  must remain large, e.g., greater than about 0.050 inches in thickness, to prevent the conveyor belt  20   b  from flexing/deforming into the aperture channel and retarding airflow in a longitudinal direction along the elongate slots  54 . 
     To address this concern, the flexible vacuum conveyance/manifold system  50  varies the stiffness and elongation properties of the deck  12  to obtain the requisite thickness, i.e., thickness/height of the elongate slots  54  without adversely impacting the stiffness or flexibility of the compliant conveyance system  10 . More specifically, the compliant deck  12  incorporates a high elongation, low modulus material in the portion of the deck  12  which is exposed to the maximum bending strains (i.e., elements farthest from the bending neutral axis). Another property of this portion relating to the power requirements to drive the conveyor belts  20 , is that the material have a characteristic low friction coefficient to facilitate sliding between the belts  20  and the deck  12 . Additionally, the compliant deck  12  incorporates a high yield strength, high modulus material in the portion of the deck  12  which lies coincident with the bending neutral axis, i.e., at the core of the deck  12 . As such, in portions of the deck  12  where a threshold thickness is required to form deep slots  54 , the deck  12  is composed of high elongation, low modulus material, and in portions of the deck  12  which require high strength, the deck  12  is composed of high yield strength, high modulus material. 
     In the described embodiment, the deck  12  employs multiple layers to establish the stiffness and elongation properties for the flexible vacuum conveyance/manifold system  50 . Specifically, the elongate slots  54  are formed in a surface layer  40 T of high elongation material such as PTFE. Accordingly, the depth/thickness of the vacuum slot is maintained without adversely impacting the overall stiffness of the compliant deck  12 . Furthermore, the surface layer  40 T of high elongation material is not affixed to the underlying support layer  40 S, i.e., not affixed along the mating interface, but relies on the vacuum pressure to maintain contact between the layers  40 T,  40 S and effect fluid flow through the elongate slots  54  and circular apertures  56  of the compliant deck  12 . The layers  40 T,  40 S, therefore, provide a-slip plane therebetween to minimize the contribution of the area moment of inertia I (a function of the thickness cubed) to the stiffness of the compliant deck  12 . While the present invention depicts a compliant deck having support and surface layers  40 S,  40 T, it will be appreciated that three or more layers may be employed to build the necessary thickness and depth of the elongate slots  54 . 
     The flexible vacuum conveyance/manifold system  50  employs lightweight polymers/plastic materials to minimize the weight/mass of the compliant conveyance system  10 . The flexible tubing  34  is fabricated from corrugated molded plastic while the linear plenum is manufactured from a lightweight machinable phenolic block. Similarly, the PTFE is a lightweight polymer which minimizes the weight of the compliant conveyance system  10 . 
     In summary, the flexible vacuum conveyance/manifold system  50  integrates with the compliant conveyance system  10  in a manner which compliments the desired stiffness properties. Flexible polymer tubing is employed facilitate motion of the compliant deck  12 . Moreover, the thickness of the surface layer  40 T is maintained to ensure that the elongate slots  54  are sufficiently deep to prevent the disruption of airflow and ability to draw a vacuum. Furthermore, the flexible vacuum conveyance/manifold system is fabricated from lightweight polymer/plastic material to reduce the mass and improve the fatigue life of the compliant conveyance system  10 . 
     Registration/Skid Plate 
     Referring again to  FIG. 1 , the compliant conveyance system  10 , and its ability to process consecutive thin and thick mailpieces  14 , presents several unique challenges with respect to the design/construction of the registration plate  18 . While prior art skid plates merely prevent a face surface of a mailpiece from contact with the print head nozzles, the registration plate  18  according to the present invention, not only maintains a “stand-off” distance between the mailpiece  14  and the print heads  16 , but also provides a contact surface which presses against each mailpiece  14 , (particularly thick mailpieces  14 TK). That is, as mailpieces  14  move along the deck  12  and pass under the registration plate  18 , the spatial position of the registration plate  18  remains fixed while the compliant deck  12  deforms/deflects in response to the pressure applied by each passing mailpiece  14 . 
     The vertical loads imposed on each mailpiece  14  can present difficulties when printing, particularly when printing on a mailpiece surface which deforms under load. An example of such a mailpiece includes one which may contain material to protect the internal contents of the mailpiece (e.g., padding or bubble-wrap). It will be appreciated that when such a mailpiece passes under a registration/skid plate having a large opening, the soft compliant face surface of the mailpiece can bow inwardly, toward the print head nozzles. As a result the requisite stand-off distance is not maintained and print quality can be compromised. 
     In  FIGS. 1 ,  9  and  10 , a registration plate assembly  70  (best seen in  FIG. 9 ) is provided for the compliant conveyance system  10 . The registration plate assembly  70  is adapted for use in combination with the array of print heads  16  and is operative to react vertical loads applied by the mailpiece  14  during processing. The registration plate assembly  70  comprises: (i) a mounting plate  72  having at least one aperture  72 A therein for accepting a print head nozzle  16 N associated with each of the print heads  16 , (ii) the registration plate  18  affixed to the mounting plate  72  and having at least one opening  18 A formed therein for permitting the deposition of ink from each of the print head nozzles  16 N, the opening  18 A having a width dimension W T  orthogonal to the feed path of the conveyance system which is at least equal to the sum of the individual width dimensions W I  associated with each of the print head nozzles  16 N, and (iii) a plurality of runners  76  affixed to the mounting plate  72  and aligned with the feed path FP of the conveyance system, each runner  76  having a blade portion disposed at a location between adjacent print head nozzles  16 N and operative to maintain a stand-off distance from a face surface of the mailpiece to one of the print head nozzles  16 N. 
     More specifically, in  FIGS. 9 and 10 , the mounting plate  72  is affixed to a housing  78  which envelopes and supports the array of print heads  16 . While the mounting plate  72  is depicted as a separate element mounted to and between side wall structures  78 W of the housing  78 , it will be appreciated that the mounting plate  72  may be integrated with the housing  78 , i.e., function as a bottom wall or plate of the housing  78 . Accordingly, in the context used herein, the mounting plate  72  is any structure which interposes the print heads  16  and the registration plate  18 , and functions to mount other structure beneath the print heads  16  such as the registration plate  18 . 
     The aperture  72 A of the mounting plate  72  generally compliments the shape and position of the print head nozzles  16 N, i.e., in the plane of the nozzles  16 N. While individual apertures  72 A may be formed or machined for each of the nozzles  16 N, the mounting plate employs a single aperture  72 A which accepts all of the nozzles  16 N. Furthermore, the aperture  72 A is stepped to accommodate the array of print head nozzles  16 N which are staggered to provide print coverage over a large print zone. That is, as the mailpiece  14  moves under the array of print heads  16 , each nozzle  16 N thereof is available to print within a linear print zone, i.e., a zone equal to the width of a single print head nozzle  16 N. Moreover, while the single aperture  72 A essentially spans the entire length of the housing, i.e., in the direction of the mailpiece feed path FP, the width of the aperture  72 A at any point along the length is only slightly larger than the width dimension W I  of a single print head nozzle  16 N. As a result, a region  80  of the mounting plate  72  is maintained for affixing other structure to the mounting plate  72 . 
     While the registration plate  18  may be affixed directly to an underside surface  72 U of the mounting plate  72 , the registration plate  18  mounts to an spacer plate  82  which interposes an upper surface  18 U of the registration plate  18  and the underside surface  72 U of the mounting plate  72 . Functionally, the spacer plate  82  is one of the elements employed to establish the stand-off distance between the print head nozzles  16 N and the face surface  14 S of the mailpiece  14 . Furthermore, one or more additional spacer plates (not shown) may be substituted for, or disposed in combination with the spacer plate  82 , to vary the stand-off distance between the print head nozzles  16 N and the face surface  14 S of each mailpiece  14 . Occasionally, it may be necessary to vary the stand-off distance to process mailpieces having different physical properties or to accommodate the implementation of different print heads  16 . Finally, the spacer plate  82  includes an opening  82 A which corresponds in shape to the opening  18 A of the underlying registration plate  18 . The characteristics of the registration plate opening  18 A will be discussed in greater detail in the subsequent paragraph which characteristics are also applicable to the spacer plate opening  82 . 
     Similar to the aperture  72 A of the mounting plate, the opening  18 A of the registration plate  18  is stepped to accommodate the staggered arrangement of the print head nozzles  16 N. However, to prevent deposited ink from smearing or smudging, the opening  18 A is open-ended. That is, the opening  18 A is configured such that portions of the registration plate  18  downstream of each print head nozzle  16 N are removed. As a consequence, the width dimension of the opening  72 A increases incrementally downstream of the first print head nozzle  16 NF, i.e., the initial print head nozzle available to deposit ink on a mailpiece  14 . That is, the width dimension of the opening  72 A increases by an amount equal to about the width of an individual print head nozzle  16 N. Finally, the maximum width dimension W T  of the opening  18 A corresponds to the downstream end portion  18 DE of the registration plate  18  and is generally equal to the sum of the width dimensions W 1  associated with each of the print head nozzles  16 N. 
     While the opening  18 A of the registration plate  18  has a stepped edge  18 SE, it will be appreciated that other shapes may be employed. For example, to approximate the shape of the staggered print head array, the opening  18 A may resemble a right triangle having a hypotenuse  84  which substitutes for the stepped edges  18 SE of the opening  18 A. Alternatively, the opening  18 A may define a rectangle  86 , though, it is generally believed that an opening which corresponds to the size and shape of the array of print nozzles  16  provides optimum characteristics, e.g., prevents the mailpiece  14  from catching on edges of the registration plate assembly  70  and provides optimum print quality. 
     In  FIGS. 9 and 11 , the described embodiment of the registration plate assembly  70  includes three (3) runners  76  which define channels within the registration and spacer plate openings  18 A,  82 A. The runners  76  are aligned with, e.g., parallel to, the feed path FP of the conveyance system  10  and are spaced-apart evenly in a lateral direction, e.g., orthogonal to the feed path FP. Inasmuch as the length dimension L of the registration and spacer plate openings  18 A,  82 A vary due to the stepped edges  18 SE,  82 SE thereof, the length LR of each of the runners  76  may vary by a commensurate amount. 
     In  FIGS. 10 and 11 , each runner  76  has a generally L-shaped cross section and includes: (i) a blade portion  76 B which projects downwardly from the mounting plate  72  and (ii) a flange portion  76 F which lies in a plane parallel to the underside surface  72 U of the mounting plate  72  The blade portion  76 B has a leading edge which is curved and defines a blade edge  76 E which slideably engages the face surface  14 S of each mailpiece  14 . The flange portion  76 F includes a plurality of slotted apertures  76 A (see  FIG. 10 ) which accept a fastener  88  (see  FIG. 11 ) for affixing the runner  76  to the mounting plate  72 . The apertures  76 A permit a small degree of lateral adjustment such that the blade portion  76 B of each runner  76  may be accurately positioned within the registration and spacer plate openings  18 A,  82 A. Generally, the blade portion  76 B of each runner  76  is aligned with one of the steps  18 SE,  82 SE of the registration and spacer plate openings  18 A,  82 A. Furthermore, the forward end  76 FE (see  FIG. 10 ) of each runner  76  is disposed aft, or downstream, of one of the steps  18 SE,  82 SE and/or is longitudinally aligned with a riser edge  18 RE,  82 RE disposed downstream of the respective step  18 SE,  82 SE. As such, each runner  76  does not interfere with ink deposited from the print head nozzle  16 N disposed upstream of the respective runner  76 , i.e., the nozzle corresponding to the respective step  18 SE,  82 SE. 
     In operation, the registration plate assembly  70  provides the necessary stand-off distance from the print head nozzles  16 N to the face surface  14 FS of the underlying mailpiece  14 . The compliant conveyance system  10  transports the mailpieces  14  to the print head assembly  8  and, as the mailpieces  14  approach the array of print heads  16 , an inclined leading edge  181 E of the registration plate  18  guides each mailpiece  14  beneath the registration plate  18 . The inclined edge  181 E defines an angle θ of between about ten (10) degrees to about forty (40) degrees relative to the plane of the compliant deck  12  to ensure that both thin and thick mailpieces  14 TN,  14 TK are accepted/ingested smoothly beneath the plate  79  and in register with the contact surface  18 S. As the mailpieces  14  engage the registration plate assembly  70 , the print head assembly  8  presses downwardly on the face surface  14 FS of the mailpiece  14  during processing/printing. Any tendency for the mailpiece  14 , i.e., the face surface  14 FS, to bow upwardly toward the print head nozzles is mitigated by the runners  76 . More specifically, the face surface  14 FS is vertically supported by the runners  76  at locations between the stepped and opposing lateral edges  18 SE,  82 SE,  18 LE,  82 LE of the registration and spacer plate openings  18 A,  82 A. Inasmuch as the blade portion  76 B of each runner  76  is aligned with, and parallel to, one of the stepped edges  18 SE,  82 SE, the blade edge  76 E does not smear or smudge ink deposited by an upstream nozzle  16 N. The blade edge  76 E contacts the face surface  14 FS at a position between nozzles  16 N and does not interfere with the deposited ink, i.e., ink deposited in linear zones to each side of a runner  76 . Such zones may correspond to the white space between printed lines of a destination or return address. 
     Pivotable Support/Instrumentation Rack for Print Head Assembly 
     In  FIGS. 12 and 13 , the print head assembly  8  is affixed to a pivotable support/instrumentation rack  90  to perform routine maintenance on the print head assembly  8  and underlying compliant conveyance system  10 . More specifically, the compliant conveyance system  10  is disposed in combination with a housing  92  which mounts the pivotable support/instrumentation rack  90 . The housing  92  accepts the conveyance system  10  such that the compliant deck  12  is essentially co-planar with a top deck  92 D of the housing  92 . The top deck  92 D includes first and second portions  92 D- 1 ,  92 D- 2  which extend outwardly from the side beam members  30 ,  32  of the conveyance system  10 . The first portion  92 D- 1  of the deck  92 D pivotally mounts the support/instrumentation rack  90  about an axis  90 A while the second portion  92 D- 2  of the top deck  92 D mounts a pair of locking mechanisms  94   a ,  94   b.    
     The support/instrumentation rack  90 , furthermore, includes a pair of structural longerons  96   a ,  96   b  disposed parallel to the feed path of the conveyance system  10  and a plurality of stiffening ribs  98   a ,  98   b ,  98   c ,  98   d ,  98   e  which structurally interconnect the longerons  96   a ,  96   b  in a lateral direction. A pair of gas springs  100   a ,  100   b  is interposed between the housing  92  and a pair of the stiffening ribs  98   a ,  98   b , to rotate the support instrumentation rack  90  about the pivot axis  90 A. More specifically, the gas springs  100   a ,  100   b  impose a counterclockwise moment M 1  about the axis  90 A to bias the support/instrumentation rack  90  upwardly, i.e., to an open position. Furthermore, the support/instrumentation rack  90  may be moved to a closed position by imposing a clockwise moment M 2  about the axis  90 A (i.e., a vertically downward force F applied by an operator). The closed position is achieved when a pair of high tolerance feet  102   a ,  102   b , mounted to the outboard longeron  100   b , abut each of the locking mechanisms  94   a ,  94   b . An anvil portion  104  of each of the locking mechanisms  94   a ,  94   b  rotates to engage an upper surface of the feet  102   a ,  102   b , thereby locking the position of the support/instrumentation rack  90  against the upward biasing force of the gas springs  100   a ,  100   b.    
     The print head assembly  8  is mounted to one of the stiffening ribs  98   a ,  98   b ,  98   c ,  98   d ,  98   e  and positioned therealong such that, when the support/instrumentation rack  90  is closed, the print head and registration plate assemblies  8 ,  70  are precisely located, i.e., in a vertical direction, with respect to the underlying conveyance system  10 . In addition to mounting the print head assembly  8 , the stiffening ribs  98   a ,  98   b ,  98   c ,  98   d ,  98   e  may also locate and support a variety of instrumentation such as a plurality of photocells  110   a ,  110   b ,  110   c ,  110   d ,  110   e . These photocells  110   a ,  110   b ,  110   c ,  110   d ,  110   e  may be used to locate the position of each mailpiece  14  as mailpieces  14  are conveyed along the compliant deck  12 . Sensors (not shown) disposed beneath the deck  12  receive a beam of light through apertures  112  (see  FIG. 2 ) in the compliant deck. 
     The pivotable support/instrumentation deck  90  facilitates access to the print head assembly  8  and underlying compliant conveyance system  10 . When the locking assemblies  102   a ,  102   b  are released, the support/instrumentation deck  90  immediately rotates to the open position under the force of the gas springs  100   a ,  100   b . The print heads  16  may be repaired and replaced as required while the photocells  110   a ,  110   b ,  110   c ,  110   d ,  110   e  may be inspected and cleaned, i.e., of paper dust debris. 
     It is to be understood that all of the present figures, and the accompanying narrative discussions of preferred embodiments, do not purport to be completely rigorous treatments of the methods and systems under consideration. For example, while the invention describes an interval of time for completing a phase of sorting operations, it should be appreciated that the processing time may differ. A person skilled in the art will understand that the steps of the present application represent general cause-and-effect relationships that do not exclude intermediate interactions of various types, and will further understand that the various structures and mechanisms described in this application can be implemented by a variety of different combinations of hardware and software, methods of escorting and storing individual mailpieces and in various configurations which need not be further elaborated herein.