Abstract:
A system and method for wrapping sheet material to produce finished mailpieces includes an upstream content module, a downstream mailpiece assembly module including a wrapper module adapted to encapsulate content material, and a buffer module interposing the upstream content and downstream assembly modules. The buffer module includes a plurality of buffer gates adapted to convey the content material from an upstream gate to a downstream gate to maintain a threshold pitch distance between successive pieces of content material. A controller is operatively coupled to the modules and controls the conveyance of content material through the buffer gates. More specifically, the controller coordinates the delivery and insertion of content material into the wrapper module to minimize dry-holes, maintain stresses below a threshold level to ensure continued operation, and optimize system throughput.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority under 35 U.S.C. section 119(e) from Provisional Patent Application Ser. No. 61/492,987, filed Jun. 3, 2011, entitled Mailpiece Buffer for Mailpiece Wrapping System (Attorney Docket G-587), and PCT International Application No. PCT/US2012/040422, entitled Inter-Machine Buffer for Mailpiece Fabrication System, by Carl R. Chapman, et al., which are both incorporated herein by reference in their entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to mailpiece creation systems, and, more particularly, to a new and useful inter-machine buffer interposing a chassis and wrapper module of a mailpiece fabrication system to ensure matched-mailing of the content with the external wrap of a pre-printed web of sheet material. 
       BACKGROUND OF THE INVENTION 
       [0003]    Mailpiece creation systems such as mailpiece inserters and mailpiece wrappers 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. 
         [0004]    Mailpiece inserters include a variety of apparatus/modules for conveying and processing a substrate/sheet material along the feed path. Commonly mailpiece inserters include apparatus/modules for (i) feeding and singulating printed content in a “feeder module”, (ii) accumulating the content to form a multi-sheet collation in an “accumulator”, (iii) folding the content 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, in a “chassis module” (v) inserting the folded/unfolded and/or nested content into an envelope in an “envelope inserter”, (vi) sealing the filled envelope in “sealing module” and (vii) printing recipient/return addresses and/or postage indicia on the face of the mailpiece envelope at a “print station”. 
         [0005]    In lieu of a module for inserting the content material into an “envelope”, some mailpiece creation systems employ a wrapping system operative to encapsulate the mailpiece content in an outer wrapping material. While such wrapping systems offer a low-cost alternative to those which employ conventional pre-fabricated mailpiece envelopes, wrapping systems of the prior art have generally been limited to those using plastic materials, rather than paper-based materials, to wrap the content. Wrapping systems of the type described herein are produced by Sitma Machinery S.p.A. located in Spilamberto, Italy, a world class leader in mailpiece finishing systems. 
         [0006]    Attempts to employ paper-based wrapping materials have been limited by an inability to produce “matched mailpieces”. That is, wrapping systems of the prior art, have been unable to “match” content intended for a specific recipient with an envelope having the recipient&#39;s destination address pre-printed on the exterior of the envelope. Such difficulties have arisen, at least in part, due to the inability to start/stop the web of wrapping material, i.e., a system with a large inertial mass, with the agility necessary to coordinate with a relatively nimble content creation system at the upstream end of the wrapping system. As a consequence, such wrapping systems have typically used “windowed” wrap material to allow a destination address of the content to be viewable through the wrapping material. 
         [0007]    It is, therefore, the object of the present invention to provide a mailpiece fabrication system which successfully integrates a downstream mailpiece wrapping system with high-throughput content fabrication equipment. 
       SUMMARY OF THE INVENTION 
       [0008]    A system and method for wrapping sheet material to produce finished mailpieces includes an upstream content module, a downstream mailpiece assembly module including a wrapper module adapted to encapsulate content material, and a buffer module interposing the upstream content and downstream assembly modules. The buffer module includes a plurality of buffer gates adapted to convey the content material from an upstream gate to a downstream gate to maintain a threshold pitch distance between successive pieces of content material. A controller is operatively coupled to the modules and controls the conveyance of content material through the buffer gates. More specifically, the controller coordinates the delivery and insertion of content material into the wrapper module to minimize dry-holes, maintain stresses below a threshold level to ensure continued operation, and optimize system throughput. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    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. 
           [0010]      FIG. 1  is a schematic block diagram of the mailpiece creation system according to the present invention. 
           [0011]      FIG. 2  is a broken-away schematic top view of the mailpiece creation system including a buffer module interposing an upstream content fabrication module and a downstream mailpiece assembly module. 
           [0012]      FIG. 2   a  is a cross-sectional view taken substantially along line  2   a - 2   a  of  FIG. 2  depicting the relevant details of two buffer gates of the buffer module. 
           [0013]      FIG. 3  is a broken away perspective view of the buffer module including six (6) buffer gates for dispensing content material to an upstream conveyor of the mailpiece assembly system. 
           [0014]      FIG. 4  is a schematic view of a controller operatively coupled to a plurality of photocell and rotary encoder sensors for driving a plurality of buffer module motors. 
           [0015]      FIG. 5  is a schematic top view of the mailpiece fabrication module including an upstream conveyor, a mailpiece wrapper, a plurality of mailpiece finishing modules. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    The present invention is directed to a system and method for integrating an upstream mailpiece content mailpiece wrapping system with content creation systems modules typically employed in mailpiece inserters wherein content is inserted into a dedicated mailpiece envelope. While the invention is described in the context of a paper-based wrapping system, i.e., a system which is fed by a paper web, for creating finished mailpieces, the invention is equally applicable to wrapping systems which employ plastic wrapping materials to encapsulate mailpiece content. Consequently, the detailed description and illustrations are merely indicative of an embodiment of the invention, and, accordingly, the invention should be broadly interpreted in accordance with the appended claims. 
         [0017]    The following detailed description will be facilitated by the definition of several terms of art used to describe mailpiece fabrication systems. For example, the “pitch” of a mailpiece creation system is the distance between the leading/trailing edge of one piece of content material and the leading/trailing edge of an adjacent piece of content material along the conveyance feed path. A “cycle” relates to the time required to process one mailpiece, but is measured in distance. In the described embodiment, the distance that a piece of content material  12  travels in one cycle is about 250 millimeters, or 0.250 meters. The “throughput” of a mailpiece creation system is defined as the number of mailpieces produced/unit of time. A high-output mailpiece creation system will produce between 10,000 to 26,000 mailpieces per hour. A “dry-hole” is an empty space in the feed path of a mailpiece fabrication system. A dry-hole can be produced as a result of an operation requiring additional processing time, e.g., multi-sheet collation having a gate-fold configuration, or as a result of a processing error requiring that a piece of content material be out-sorted. 
         [0018]    Before discussing some of the more relevant components of the system and method of the present invention, a brief overview of the overall system will be provided.  FIGS. 1 and 2  depict schematic block diagrams of a mailpiece creation system  10  according to the present invention wherein content material  12  is produced by a variety of upstream content fabrication modules  100  and finished by a variety of downstream mailpiece assembly modules  200 . A buffer module  300  interposes the upstream and downstream modules  100 ,  200  while a system controller  50  is responsive to various system sensors/encoders B1-B9, E1-E7 to control the operation of all of the modules  100 ,  200 ,  300 . While a single system processor  50  is depicted to control the various system modules  100 ,  200 ,  300 , it should be appreciated that the mailpiece creation system  10  may be controlled by multiple processors which may integrated to perform the various system operations. Furthermore, it should be appreciated that only a small fraction of the total number of sensors/encoders are shown in the drawings and that many more system sensors are employed to monitor and control the system modules  100 ,  200 ,  300 . 
       Upstream Content Fabrication Modules 
       [0019]    In the described embodiment, the upstream content fabrication modules  100  include a first preprinted web  116  which contains the sheet material used to produce the mailpiece content material  12 . The preprinted web  116  is supported by a rotating spool and paid-out to a content cutter  118 . A conventional web-loop device, e.g., a vacuum-plenum box (not shown) may be disposed between the web  116  and the cutter  118  to prevent the web from tearing under high accelerations induced by conveyance rollers (not shown) of the content cutter  118 . 
         [0020]    Once cut, each sheet of content material  12  may be scanned to read information relating to the processing of a particular mailpiece. For example, a Beginning Of Collation (BOC) mark may be read by a scanner  120  to indicate that the current sheet is the first in a series of sheets which comprise a collation, i.e., the sheets which are part of the same mailpiece. These marks, also known as scan codes, are typically used to provide a plethora of processing information, e.g., whether the collation will be folded, stitched, or stapled. 
         [0021]    Once scanned, the sheets of content material  12  may then be grouped in an accumulator module  122  to produce a stacked collation of content material  12 . The stacked collation may then be conveyed to a folding module  124  to produce a folded collation. The folding module  124  manipulates the stacked collation around several press rollers to produce a bi-fold, C-fold, Z-fold or gate-fold configuration into the content material  12 . As will be discussed in greater detail hereinafter, these operations may consume more than one cycle, hence, the distance between pieces of content material may vary from one cycle to several cycles depending upon the operations performed on the content during fabrication/assembly. As a result, a dry-hole may be created along the feed path of the mail run. 
         [0022]    The content material  12  may then pass through a chassis module  126  where additional mailpiece content may be added by a series of overhead feeders (not shown). Inasmuch as the system controller  50  knows the specific processing requirements of each mailpiece and the location of each piece of content material  12  at any station along the feed path, the overhead feeders may selectively add inserts to build the content material  12 . For example, a specific advertisement, targeted to one mailpiece recipient, may be added by one of the feeders, while a coupon offering may be added to the content material  12  of another mailpiece recipient. 
         [0023]    Upstream content fabrication systems such as the type described above are produced by Pitney Bowes Inc., located in Stamford, Conn., a world-class leader in the manufacture of mailpiece inserters, sorters and mailpiece finishing equipment. 
       Downstream Mailpiece Fabrication Modules 
       [0024]    As content material  12  is completed by one or more of the upstream content fabrication modules  100 , mailpieces are finished by one or more of the downstream mailpiece assembly modules  200 .  FIGS. 2 and 5  depict schematic top views of the downstream mailpiece assembly modules  200  including a web feed module  210 , a wrapping module  230 , and a plurality of mailpiece finishing modules  250 . The web feed module  210  includes a second preprinted web  216  which comprises the sheet material used to wrap the content material  12 , i.e., the wrapping material  212 . More specifically, the wrapping material  212  of the preprinted web  216  may include a continuous two-dimensional flat pattern of material which, when cut and folded, forms a container for wrapping the content material  12 . The wrapping material  212  may include the destination address of each mailpiece recipient printed on one panel while other another portion may include a pressure sensitive adhesive for encapsulating the content material  12 . Alternatively, a glue application module  218  may apply adhesive to a face surface of the two-dimensional flat pattern in accordance with a predefined folding/cutting scheme of the wrapping material  212 . 
         [0025]    In the described embodiment, the web feed module  210  may include one or more Right Angle Turn (RAT) modules  220  to direct the wrapping material  212  to the wrapping module  230 . Additionally, a tensioning module  222  interposes the web  216  and the wrapping module  230  to apply a predetermined tensile load on the wrapping material  212 . Such tensile loads are conventionally imposed by one or more spring-biased rollers (not show) which support the wrapping material  212  in a serpentine arrangement. While the tensioning module  222  applies a predetermined load on the wrapping material  212 , the principle method for controlling the loads on the wrapping material  212 , is the buffer module  300  discussed in greater detail hereinafter. 
         [0026]    The wrapping module  230  is adapted to convey the wrapping material  212  along a conveyance deck  232  while guiding the wrapping material  212  to form a flattened, tube-shaped, wrap  212 S. More specifically, the wrapping material  212  is drawn upwardly (i.e., normal to the plane of the conveyance deck  232  shown in  FIG. 5 ) and horizontally over a guide roller, or smooth guide surface  234 , in the direction FP of the conveyance deck  232 . As the wrapping material  212  is drawn over the guide roller  234 , the edges  212 E thereof are pulled across a pair of primary guide rods  236  to converge at a point P downstream of the guide roller  234 . Secondary guide rods  238  may also be employed to augment the formation of the tube-shape wrap  212 S as the wrapping material  212  is conveyed downstream of the guide roller  234 . 
         [0027]    As the wrapping material  212  is drawn together along the conveyance deck  232 , the tube-shaped wrap  212 S produces an open end  212 O for accepting content material  12 . That is, as the tube-shaped wrap  212 S is formed, an internal surface  212 S is exposed/available to accept the leading edge of each piece of content material  12 . 
         [0028]    In the described embodiment, the mailpiece finishing assembly modules  200  may include an upstream conveyor  240  to accept the content material  12  from the buffer modules  300  (described in greater detail below). The upstream conveyor  240  may include several modules including a content feed module  242 , a feed path Right Angle Turn (RAT) module  244  and an input conveyor deck  246 . While each module has a unique function, suffice it to say that these modules function to accept and deliver the content material  12  from the buffer module  300  to the open end of the wrapping module  230 . 
         [0029]    In the described embodiment, several pieces of content material  12  have been inserted into the tube-shaped wrap  212 S and have been separated by a predefined pitch distance PI. Once wrapped, the tube-shaped wrap  212 S and content material  12  are compressed by a triage of press rollers  246  and cut into individual mailpieces  14  by a rotary cutter  248 . Thereafter, the individual mailpieces  14  are completed by a series of mailpiece finishing modules  250  which may include a scanner  252  to determine the size/volume of the mailpiece  14 , a scale  254  to weigh the mailpiece  14 , a meter  256  to apply a postage indicia based upon the size/weight of the mailpiece  14 , and a stacker/bin  258  to sort the mailpieces  14  into one or more trays/containers (not shown). 
         [0030]    Downstream mailpiece assembly systems such as the type described above are produced by Sitma Machinery S.p.A. located in Spilamberto, Italy, a world-class leader in the manufacture of mailpiece wrapping and finishing equipment. 
       Buffer Module 
       [0031]    During the course of examining various ways to integrate paper-based wrapping systems with conventional mailpiece fabrication equipment, the inventors discovered that paper-based wrapping systems have certain inherent limitations which make the integration thereof with content fabrication systems of the prior art incompatible and/or highly problematic. These limitations where principally due to the inability to accelerate the large inertial mass of the wrapping material web  210 , at or near, the accelerations achievable by conventional content fabrication modules  100 . As such, throughput of a paper-based wrapping system can be less than one-half (½) of the throughput of conventional mailpiece inserters. Consequently, a solution was necessary for paper-based wrapping systems to compete in the marketplace with conventional mailpiece inserters. 
         [0032]    The inventors discovered that a wrapping solution was achievable by an inter-machine buffer  300  disposed between the downstream mailpiece assembly module  200  and the upstream content fabrication modules  100 . In  FIGS. 2 ,  2   a  and  3 , the buffer module  300  of the present invention includes a plurality of buffer gates G0-G5 disposed in serial arrangement between the upstream content fabrication modules  100  and the downstream mailpiece assembly modules  200 . In the described embodiment, the buffer module  300  includes six (6) buffer stations comprising one (1) in-feed buffer gate G0 and five (5) buffer gates G1-G5. While six buffer gates G0-G5 are disclosed, as few as four (4) buffer gates may be employed as will be discussed in greater detail hereinbelow. 
         [0033]      FIG. 2   a  depicts a cross-sectional view taken along line  2   a - 2   a  of  FIG. 2  depicting adjacent buffer gates G1, G2 of the buffer module  300 . Each of the buffer gates G1, G2 includes upper and lower transport elements having opposing belts  310 ,  312  (see  FIG. 2   a ) for conveying content material  12  along a conveyance deck  314 . The belts  310 ,  312  wrap around a plurality of rolling elements  316  and are commonly driven by a single drive motor. 
         [0034]    Each of the gates G0-G5 is driven by motors M1-M6 which are individually controlled by the controller  50 . Information regarding the motion of the transport elements  310 ,  312  of each of the gates G0-G5 is provided by a plurality of encoders E1-E6 which provide rotary position signals to the controller  50 . Information regarding the position of the leading and/or trailing edge of each piece of content material  12 , is provided by a plurality of photocells B1-B6 which provide position signals to the controller  50 . Accordingly, position signals, both rotary and linear, are provided to the controller  50  to track the motion of content material  12  as each piece travels along the feed path of the buffer module  300 . It should also be appreciated that similar encoders and photocells are provided throughout the mailpiece fabrication system  10  to monitor and track the location of each piece of content material and each mailpiece fabricated. 
         [0035]    The length PI of each buffer gate G1, G2 is equal to the distance that a mailpiece will travel in one cycle or 250 millimeters. The length of the entire buffer module  300 , i.e., from the in-feed buffer gate G0 to the final buffer gate G5, is between about 1.250 meters to 1.750 meters, and is preferably about 1.50 meters in length. 
         [0036]    To define the length of a single buffer gate PI, the length from the second roller  316  of the first gate G1 to the second roller of the second gate G2 may be taken as the period length of the buffer gates G1-G5. Within this period length PI is a first region R1 of a buffer gate G1 wherein a piece of content material  12  is under the control of the upstream gate and a second region R2 wherein a piece of content material  12  is under the control of both the upstream and downstream gates G1 and G2. The import of the first and second regions will become apparent when discussing the operation of the mailpiece fabrication system  10  and the buffer module  300 . 
         [0037]    In the broadest sense of the invention, the buffer module  300  is governed by a control algorithm which ensures that the wrapping module  230  is not exposed to accelerations which may rupture, tear or fail the wrapping material  212 . While the control algorithm is most accurately related to the maximum allowable tensile stress of the wrapping material  212 , the method of control and control algorithms will be described in terms of threshold velocities/acceleration to eliminate the requirement to address the inertia functions/cross-sectional area of a material. 
         [0038]    To meet the foregoing criteria, the system and method of the present invention determines a threshold level of acceleration which is acceptable for handling the wrapping material  212 S of the wrapping module  230 . That is, to the extent that the wrapping material  212 S follows a convoluted/tortuous path from the pre-printed web  216  to the conveyance deck  232 , it is necessary to determine the changes in velocity, i.e., acceleration, which may be handled without tearing, wrinkling or otherwise distorting the material during use. In the described embodiment, it was determined that a threshold level of acceleration of below about 0.5 g&#39;s of acceleration, and preferably below about 0.4 g&#39;s of acceleration, be maintained in the wrapping module  230  to mitigate failure of, or other difficulties associated with, handling the wrapping material  212 . Furthermore, it was determined that, to coordinate the acceleration/deceleration of the wrapping module  230  with the upstream mailpiece fabrication modules  100 , it would be necessary to accelerate/decelerate the wrapping module  230  over the course of about 500 millimeters, or 0.500 meters, in about 0.28 seconds or, over a length of about two buffer gates (recalling that a buffer gate is about 250 millimeters in length). 
         [0039]    Accordingly, for the wrapping module to (i) decelerate from a maximum velocity to zero, and to once again, (ii) accelerate from a stop to the maximum velocity, the buffer module  300  must include at least four (4) buffer gates, i.e., (2) two buffer gates to decelerate the wrapping module, and (2) two buffer gates to accelerate the wrapping module, meet the criteria associated with the threshold acceleration. While it was determined that a minimum of four (4) buffer gates was necessary to properly coordinate the acceleration of the wrapping module  230  with the upstream content fabrication modules  100 , e.g., the chassis module  126 , it was also determined that a greater number of buffer gates provides additional length to smooth the delivery of content material  12  to the downstream mailpiece assembly modules  200 . Consequently, it was determined that a total of six (6) buffer gates G0-G5 spanning a distance of 1.500 meters be employed to optimize the throughput of the mailpiece fabrication system  10 . 
         [0040]    In operation, each of the buffer gates G0-G5 is autonomously controlled and certain conditions must be met before the conveyance velocity of any individual buffer gate is changed. Firstly, it should be appreciated that the velocity of one buffer gate is dependent upon the velocity of a buffer gate immediately downstream of the buffer gate. Secondly, each buffer gate is driven such that the error in pitch distance, i.e., the error between a desired pitch distance and the actual measured pitch distance (measured using the photocell sensors B1-B6) is driven to a zero value. For example, if the pitch distance from the leading edge of the last piece of content material to the leading edge of the current piece of content material is 270 millimeters i.e., the actual measured pitch distance, and the desired pitch distance is 250 mm, then the pitch error is 20 millimeters, i.e., the difference between or 270 mm-250 mm. This type of control algorithm is known as a “pitch control” algorithm inasmuch as the error in pitch distance is driven to zero as the content material  12  moves from an upstream buffer gate, e.g.,  01 , to a downstream buffer gate e.g., G2. Thirdly, it should be appreciated that in order to accelerate/decelerate a piece of content material  12  within a gate, the content material  12  must be within the predefined first region R1 of the buffer gate (see  FIG. 2   a ). This first region R1 is centrally disposed relative to each end of the respective buffer gate. If, on the other hand, a piece of content material  12  is located within the second region R2 which spans adjacent buffer gates G1 and G2 (i.e., the leading edge of the content material  12  is under a downstream belt G2 while the trailing edge is under an adjacent upstream belt G1), then the content material  12  may not be accelerated/decelerated by either of the buffer gates G1, G2. This logic is invoked to prevent the piece of content material  12  from being pulled-apart, or pushed-together/crushed, when the content material  12  is under the control of two adjacent buffer gates G1, G2. 
         [0041]    While the buffer gates G0-G4 are principally governed by a pitch control algorithm such as that described above, the last, or downstream buffer gate G5 (i.e., the gate which delivers content material  12  to the wrapping module  230 ), is controlled by an intercept profile/algorithm. Like the pitch control algorithm described above, an intercept algorithm is a term of art and does not require a lengthy description. However, suffice to say that intercept profile/algorithm effects a zero pitch error signal when the content material reaches its final destination on the upstream conveyor  240  of the wrapping module  230 . It should also be appreciate that the intercept algorithm is only invoked under conditions wherein the difference between the velocity of the feed module  242  of the upstream conveyor  240  is greater than a threshold speed, e.g., greater than zero, and the difference in velocity between the content feed module  242  and the downstream buffer gate G5 is within a threshold range, e.g., 1 mm/s. If these conditions are not met, i.e., the content material will not be precisely located within a pocket of the upstream conveyor  240 , the controller  50  cues the mailpiece fabrication system  10  to abort or shut down to prevent downstream errors and/or jams. 
         [0042]    In summary, the present invention integrates a mailpiece fabrication assembly system, i.e., one which employs a mailpiece wrapping module with a content material fabrication system, e.g., a chassis module with overhead feeders to build the content material. The system and method of the present invention employs a buffer module to accommodate the significant differences in acceleration between the upstream and downstream modules. Furthermore, the buffer module employs a plurality of serially arranged buffer gates to fill “dry-holes” which are routinely created by the upstream content fabrication modules. Finally, the system and method optimizes throughput will maintaining the reliability and integrity of the mailpiece fabrication system. 
         [0043]    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.