Patent Publication Number: US-7900904-B2

Title: Modular finishing assembly with function separation

Description:
BACKGROUND 
     The exemplary embodiment relates generally to the sheet processing arts. It finds particular application in connection with a modular finishing assembly in which various finishing functions are separated among the modules. 
     High speed reprographic devices, such as printers, copiers, and multifunction (print/copy/fax) machines are being formed with increasingly higher output speeds to meet customer demands. In the image rendering process, pages of a multi-page document are formed by printing images on sheets of paper, or other print media substrate, using colorants, such as inks or toners. The printed pages are conveyed singly to a finisher, which outputs the finished document. The finisher may incorporate several different functions, such as folding, stapling, collating, binding, and the like. Typically, the finisher must compile, register, staple and drop a set of pages prior to the next set being loaded. Each of these steps takes a certain amount of time and thus the throughput of the printing system may be limited by the capabilities of the finisher. Any increase in throughput generally requires a direct decrease in function timing and a corresponding increase in velocity. This requires each function to operate at high speed, which may put a strain on the paper handling, the mechanics and overall reliability and function of the finisher. While increases in speed may be achieved by distributing print jobs among plural finishers, this adds to the cost of the printing system. 
     INCORPORATION BY REFERENCE 
     The following references, the disclosures of which are incorporated herein in their entireties by reference, are mentioned: 
     The following references relate generally to systems and methods for compiling and transferring substrates, such as sheets of paper: U.S. Pat. Nos. 4,017,066; 4,589,645; 4,637,598; 4,934,683; 5,026,034; 5,088,714; U.S. Pat. No. 5,915,688; and U.S. Pat. No. 5,649,695. 
     U.S. Pub. No. 20060244202, published Nov. 2, 2006, entitled PRINTED SHEETS STACKING TRAY WITH AUTOMATIC ALTERNATE STACKING SUPPORT AND MANUAL STACK LIFTING ASSISTANCE, by Douglas K. Herrmann, et al. discloses a sheet stacking and unloading system in which sheets are stacked on a stacking tray which is then moved from its sheet stacking position to an unloading position for removing the sheet stack from the stacking tray, and the stacking tray has a sheet stacking surface partially interrupted by at least one handhold area for allowing manual lifting access underneath a portion of a stack, there is automatically inserted into the handhold area at least one supplemental sheet stack supporting member to provide supplemental sheet stacking support, preventing the sheets from sagging in those areas, which supplemental sheet stack supporting member is automatically removed from the handhold area when the stacking tray is moved to its unloading position. 
     U.S. Pat. No. 7,021,617, issued Apr. 4, 2006, entitled CLAMP ACTUATOR SYSTEM AND METHOD OF USE, by Douglas K. Herrmann, et al. discloses a substrate compiling system which includes an actuator, cable and tamper device. The tamper device includes a clamp assembly. The clamp assembly is retracted and extended. The clamp assembly can be used to clamp an edge of each compiled set of substrates and transfer the compiled set to a stacking tray, platform or the like. The clamp assembly may remain in an extended position until all other substrate supporting structures no longer support the substrates and an opposing unclamped edge of the compiled set engages the stacking tray below. 
     U.S. Pub. No. 20040253033, published Dec. 16, 2004, entitled UNIVERSAL FLEXIBLE PLURAL PRINTER TO PLURAL FINISHER SHEET INTEGRATION SYSTEM, by Lofthus, et al., discloses a multifunction printed sheets interface system with sheet input areas for receiving printed sheets and output areas for outputs to different sheet processing systems. A sheet transporting system provides selectable sheet translation from selected plural sheet input areas to selected plural sheet output areas so as to provide selectable sheet feeding from selected printers to selected sheet processing systems, and selectable sheet rotation of selected sheets and selectable sheet merging in a selected sheet sequence of sheets from plural printers. 
     U.S. Pat. No. 6,973,286, issued Dec. 6, 2005, entitled, HIGH PRINT RATE MERGING AND FINISHING ASSEMBLY FOR PARALLEL PRINTING by Barry P. Mandel, et al. discloses a system for printing media which includes a plurality of marking engines for outputting printed media in a stream, a media path system operable to transport the printed media from the marking engines to one or more finishing stations such that the streams are merged and transported one on top of the other and one or more finishing stations capable of compiling media in groups of 2 or more sheets for post processing the printed media into one or more completed jobs. 
     U.S. Pub. No. 20060176336, published Aug. 10, 2006, entitled Printing systems, by Steven R. Moore, et al. discloses a printing system which includes first and second output modules which receive print media from first and second marking modules. The first and second output modules each include a finisher. The first and second output modules each include a portion of a print media network. 
     BRIEF DESCRIPTION 
     In accordance with one aspect of the exemplary embodiment, a finishing assembly includes a plurality of finishing modules, each of which performs a finishing function. The plurality of finishing modules includes a compiler module which compiles sheets into a set of sheets and at least one stacker module, downstream of the compiler module, which is configured for receiving compiled sets of sheets compiled by the compiler module and stacking a plurality of the sets of sheets into a stack. Optionally, at least one sheet processing module is intermediate the compiler module and the stacker module and receives a compiled set of sheets compiled by the compiler module and processes the compiled set of sheets. 
     In accordance with another aspect of the exemplary embodiment, a method of finishing previously marked sheets includes performing a first finishing operation on a first set of sheets in a first finishing module and performing a second finishing operation on a second set of sheets in a second finishing module contemporaneously with the first finishing operation. Thereafter, the first set of sheets is advanced from the first finishing module to a first downstream finishing module. Contemporaneously with advancing the first set of sheets, the second set of sheets is advanced from the second finishing module to a second downstream finishing module. 
     In accordance with another aspect, a printer includes a marking engine which marks sheets of print media. A finishing assembly receives marked print media from the marking engine and sequentially applies at least first and second post-marking finishing operations thereto. The first and second finishing operations are performed contemporaneously on respective sets of the marked sheets whereby a first of the sheet sets is undergoing a first finishing operation while a second set of the marked sheets is undergoing a second finishing operation and in which the first set of marked sheets which has undergone the first finishing operation is advanced in a horizontal direction contemporaneously with the advancement of a second set of marked sheets which has undergone the second finishing operation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic side sectional view of a xerographic printer incorporating a finishing assembly in accordance with one aspect of the exemplary embodiment; 
         FIG. 2  is a schematic side sectional view of a finishing assembly in accordance with another aspect of the exemplary embodiment; 
         FIG. 3  is a perspective view of part of a finishing assembly in accordance with another aspect of the exemplary embodiment with a stack of sheets in a first position; and 
         FIG. 4  is a perspective view of the finishing assembly of  FIG. 3  after the stack has moved to a second position. 
     
    
    
     DETAILED DESCRIPTION 
     In various aspects of the exemplary embodiment disclosed herein, a finishing assembly includes a plurality of finishing modules, each of the modules assuming a different function of a finishing operation. By separating the functions, the finishing assembly can act as a production line. Through breaking down the entire process into parts, each piece can be performed at a set rate. A product is then produced at what is referred to in manufacturing as a takt time. Once the queue is filled, the finishing assembly can produce a set in a short period of time, which is substantially a function of the longest step in the process. Since each job, such as compiling, registration, stapling, stacking, may be performed separately, the timing can be significantly reduced without necessarily having to speed up any of the individual processes. Moreover, with the processes separated, the finisher can now be separated into specialized units that can be mixed and matched to meet customer requirements. Each function can be assigned to a separate module. 
     The term “reproduction apparatus” or “printer” as used herein broadly encompasses various printers, copiers or multifunction machines or systems, xerographic or otherwise. The term “sheet” herein refers to a usually flimsy physical sheet of paper, plastic, or other suitable physical print media substrate for images. The term “sheet stacking tray” broadly encompasses various sheet stacking bins or drawers unless indicated otherwise. A “print job” or “document” is normally a set of related such sheets, usually one or more collated or other sets copied from a set of original document sheets or electronic document page images from a particular user, or for a particular customer, or otherwise related. The operation of applying images to print media, for example, graphics, text, photographs, etc., is generally referred to herein as printing or marking. 
     With reference to  FIG. 1 , an exemplary printer  10  includes at least one feeder module  12 , at least one marking engine module  14 , and a finishing assembly  16 , which includes a plurality of finishing modules, herein illustrated as a compiling module  18 , a sheet set processing module, such as a stapling module  20 , and a stacker module  22 . A conveyor system  24 , which provides a network of print media pathways, conveys sheets of print media from the feeder module  12  to the marking engine module  14  for printing and thereafter coveys the printed media to the finishing assembly  16  for performing various finishing operations. 
     The printing system  10  executes print jobs. Print job execution involves printing images, such as selected text, line graphics, photographs, magnetic ink character recognition (MICR) notation, and the like on front, back, or front and back sides or pages of one or more sheets of paper or other print media. Some sheets may be left completely blank. Some sheets may have both color and monochrome images. Execution of the print job may also involve compiling a set of the sheets in a certain order. Still further, the print job may include one or more sheet set processing operations performed on a compiled set of sheets, such as stapling, punching holes into, binding or otherwise physically manipulating a compiled set. Finally, the print job may include stacking a plurality of the compiled and processed sets to form a stack of the sets. The printing, finishing, paper handing, and other processing operations that can be executed by the printing system  10  are determined by the capabilities of the paper feeder module  12 , marking engine module  14 , and finisher modules  18 ,  20 ,  22  of the printing system  10 . These capabilities may increase or decrease over time due to addition of new components, upgrading of existing components or removal of components. The components  12 ,  14 ,  18 ,  20 ,  22  of the printing system  10  may all be under the control of a common control system  26 , resident in the printer&#39;s computer commonly referred to as the digital front end (DFE). A human operator may interact with the control system  26  through a user interface  28 , here illustrated as a graphical user interface (GUI). 
     With reference to  FIG. 2 , another embodiment of a finishing assembly  30  is shown which may be employed in the printing system  10  of  FIG. 1 . In the embodiments of  FIGS. 1 and 2 , the finishing assembly  16 ,  30  generally operates to compile and finish printed media. The modular finishing assembly  30  is similarly configured to system  16  of  FIG. 1 , where similar elements are accorded the same numerals. Assembly  30  includes a compiling module  18 , a stapling module  20 , and three stacker modules  22 ,  32 ,  34 , in place of the single stacker module  22  shown in  FIG. 1 . As will be appreciated, the finishing assembly  16 ,  30  may include any number of stacker modules, such as one, two, three, or more. 
     The printing system  10  shown in  FIGS. 1 and 2  is illustrative. In general, any number of print media feeders, media handlers, marking engines, finisher modules or other processing units can be connected together by a suitable print media conveyor configuration. As will be appreciated, there may be additional modules interposed between the marking engine module  14  and the finishing assembly  16 ,  30  such as a buffer module, a merge module (for merging sheets from a second marking module), or the like. 
     The conveyor system  24  includes a plurality of drive members, here illustrated as rollers  40 , which convey the printed sheets generally horizontally in a downstream direction, between the various components of the printer. Other drive members, such as airjet transport modules, spherical nips (“SNIPS”) spin-roller drives, omni-directional drive systems, and the like may also be used. 
     The marking engine  14  can be any suitable device for applying images to the print media sheets. In the illustrated embodiment, the marking engine is a xerographic marking engine comprising a charge retentive surface, such as a rotating photoreceptor  42  in the form of a belt or drum. The images are created on a surface of the photoreceptor. Disposed at various points around the circumference of the photoreceptor are the xerographic subsystems, which include a cleaning device, a charging station for each of the colors to be applied (one in the case of a monochrome marking engine, four in the case of a CMYK printer), such as a charging corotron, an exposure station, which forms a latent image on the photoreceptor, such as a Raster Output Scanner (ROS) or LED bar, a developer unit, associated with each charging station for developing the latent image formed on the surface of the photoreceptor by applying a toner to obtain a toner image, a transfer unit, such as a transfer corotron, transfers the toner image thus formed to the surface of a print media substrate, such as a sheet of paper. A fuser  44  fuses the image to the sheet by applying at least one of heat and pressure to the sheet. While a xerographic marking engine is illustrated, other marking engines, such as ink-jet or solid ink marking engines are also contemplated. The finishing assembly  16 ,  30  thus receives marked and optionally fused sheets from the marking engine  14 . 
     With continued reference to  FIGS. 1 and 2 , the modules  18 ,  20 ,  22 ,  32 ,  34 , are arranged sequentially. Sheets processed by an upstream module are transferred to the next downstream module, and so forth. A sheet set advancement assembly  50  is configured for pushing sets  52  of sheets between finishing modules. The illustrated sheet set advancement assembly  50  is configured for moving sets of printed sheets between finishing modules, such as a set  52  of ten or more sheets, laid on top of each other. As will be appreciated, the number of sheets in a set will depend on the particular print job, and in some instances, a set may comprise as few as a single sheet. In general, however, sets typically comprise a plurality of sheets. The set  52  of sheets being moved may be bound or unbound. 
     The illustrated advancement assembly  50  is positioned above the sheet sets and includes at least one and generally a plurality of pusher members  54  which are driven by a drive system, here illustrated as comprising a horizontally extending continuous timing belt  56 , which travels in a loop in the direction illustrated by arrow A. The timing belt is vertically spaced from a finishing assembly paper path  58 . As discussed below, the paper path  58  is defined by baffles, which support the sheets from below as the sheet sets are moved by the advancement assembly along the paper path. The sets of sheets generally slide across the baffles, while the baffles remain stationary. The sheet advancement assembly  50  may include two (or more) conveyor belts  56 A and  56 B, spaced apart and running in parallel, as illustrated in  FIG. 3 , such that pairs of pusher members  54 A,  54 B are arranged in tandem to push the sheet sets  52  from two spaced locations in the cross-process direction. In one embodiment, the pusher members are integrally formed with or welded on to the belt  56 , and may be formed, for example, from plastic, such as a polyurethane. In other embodiments, the pusher members may be removable from the conveyor belt and may be re-positionable in different suitable positions along the belt. Suitable belts and pusher members are available from Brecoflex Co., LLC, and include ATN polyurethane timing belts with repositionable or weld-on profiles which serve as the exemplary pusher members. 
     As illustrated in  FIG. 1 , the two conveyor belts  56  are mounted on horizontally spaced rollers  60 , at least one of the rollers being a driven roller. The pusher members  54  are spaced around the conveyor belt at intervals of about one module  18 ,  20 ,  22  apart. In this way, a first set of pusher members pushes a sheet set between modules  18  and  20  while, at the same time, a second set of pusher members pushes a sheet set between modules  20  and  22 . The illustrated pusher members  54  are each in the form of a rigid planar member which extends vertically away from the conveyor belt  56  to engage the trailing (upstream) edges an entire set  52  of sheets and move the set as a unit. Optionally, the pusher member  54  may be L-shaped and have a small hook  62  at its distal end which slides under the trailing edge of the bottom sheet in the set to aid in guiding an unbound set of sheets ( FIG. 3 ). The illustrated conveyor belts  56  extend from the first module  18  to the last module (module  34  in  FIG. 2 ). However, in other embodiments, two or more conveyor belts may be arranged in sequence. For example, each module  18 ,  20 ,  22 ,  32 ,  34  may have its own conveyor belt or parallel pair of conveyor belts. 
     With reference to  FIG. 1 , the illustrated finisher modules  18 ,  20 ,  22  may be separable and interchangeable modules. In the illustrated embodiment, each module includes a housing or frame  70 ,  72 ,  74 , etc which may be carried on wheels  76 . The functional components of each finishing module are supported by the respective housing  70 ,  72 ,  74 . 
     In the illustrated embodiment, module  18  is a compiling module. The compiling module includes a compilation platform  80 . Platform  80  is in the form of a horizontally extending plate which defines part of the paper path  58  and serves as a stationary baffle for the module  18 . The platform  80  receives sheets, generally singly, which are stacked one on top of each other as they arrive to form a set. The sheets may be released in turn from nip rollers  82  of the conveyor system  40 , which are positioned slightly above the compilation platform. Once a set of the desired number of sheets has formed on the compiling platform, a tamper device  84 , which may normally be a retracted position, can be raised from its retracted position to an extended position, slightly above the compilation platform  80 . The tamper device compiles a set of sheets, generally by tamping them from process and cross process directions with pairs of opposed tamping members  86 ,  88  ( FIG. 3 ). Once the sheets have been compiled into a set, the conveyor system advances the next pair of pusher members  54  to push the set  52  along the print media pathway to the next finishing module  20 . The compiling module  18  then works on compiling the next set of sheets while the module  20  performs further finishing steps on the first set. The compiling module thus only performs a compiling function and does not perform punching, stapling, or other sheet processing functions. 
     Module  18  has an inlet  90  at a first, upstream end of the housing and an outlet  92  at a second, downstream end and defines a first portion of the print media path  58  therebetween. 
     The illustrated set processing module  20  is a stapling module, which receives a set  52  of compiled sheets from the compiling module  18 . The sheets are pushed by the pushers  54  across a pair of horizontally spaced stationary baffles  93  in the form of horizontal plates. The stapling module staples the set of sheets in the set to form a stapled set of sheets. In the illustrated embodiment, the stapling module includes a stapler  94  which, when open, allows the stapled set of sheets to pass therethrough. As illustrated in  FIG. 3 , an upper portion  96  of the stapler may be located between the two conveyor belts  56 A,  56 B, so that it does not interfere with the pusher members  54 A,  54 B. While travelling through the stapler module, the set  52  may be supported on the pair of horizontally spaced baffle plates  93 , which provide access therethrough to a lower portion  98  of the stapler. In particular, the pusher members  54  push the set  52  to a position in which the leading edge of the set can be clamped by the stapler  94  and a staple or staples applied to the set. In other embodiments, the stapler may be retracted to one side of the paper path, allowing the stapled sheet set to pass by. As will be appreciated, the stapling module  20  may include a stapler for stapling an upper edge of the sheet in addition to or as an alternative to the side edge stapler  94  illustrated. 
     Once the sheets have been stapled together, the advancement of the advancement system  50  advances the pusher members  54  which push the set  52  along the print media pathway  58  to the next finishing module  22 . The stapling module  20  then works on stapling the next set of sheets while the module  22  performs further finishing steps on the first set. As will be appreciated, the module  20  may additionally or alternatively perform other sheet processing operations, such as binding, stitching, hole punching, or the like. The stapling module thus performs only sheet set processing functions, and does not perform a compiling or stacking function. In the event that the document is to be unbound, the set  52  of sheets proceeds through the module  20  and no stapling or other binding is performed. Alternatively, the compiled set to be left unbound may be routed around the stapling module on a bypass path (not shown). 
     Module  20  has an inlet  100  at a first, upstream end of the housing and an outlet  102  at a second, downstream end and defines a portion of the print media path  58  therebetween. 
     Module  22  is a stacking module which receives sets of compiled and optionally bound sheets from the stapling module  20 . The stacking module  22  stacks multiple sets of bound or unbound sheets. The stacker module includes a stacker tray  104  which is moved vertically by an elevator mechanism (illustrated in  FIG. 2  by a two-direction arrow  106 ) to accommodate the increasing height of a stack of sets  52  of sheets. The stacker tray can be any platform, surface, or the like capable of holding a stack of sets of compiled and optionally stapled sheets or sets of sheets. The elevator mechanism  106  may include a sensor (not shown) which, when it senses sheets or a clamp for the sheets in the path of its beam, causes the elevator mechanism to move the tray  104  progressively downward so that the stacker tray may accommodate additional sets of sheets. 
     Various release mechanisms for releasing the set of sheets from the paper path onto the stacker tray  104  are contemplated. In the embodiment illustrated in  FIG. 2 , the release mechanism includes a moveable baffle or gate  108 , which is moveable between first and second positions. In the first position, shown on module  32 , the baffle allows a set of sheets to drop onto the elevator. In the second position, shown on modules  22  and  34 , by way of example, the baffle  108  closes off access to the stacker tray and allows sets of sheets pass through the module without stacking. The illustrated baffle  108  is a pivotable baffle which is pivoted, about a downstream end thereof, between the first and second positions. 
     Different stacking modules  22 ,  32 ,  34  may have their baffles  108  in different positions, depending on whether they are currently in use. Thus, in  FIG. 2 , the first stacking module  22  has a full stack of sheet sets and so the baffle  108  is closed until that stack has been removed from the module. Sheet sets are pushed by the pushers  54  so that they travel across the stationary, closed baffle to the next available stacker module, in this case, module  32 . This stacker module receives sets of sheets until its stack is full, and so forth. The trays of other stacker modules, such as module  34 , can remain empty and their baffles closed until the upstream stacker modules are full. 
     In the embodiment shown in  FIGS. 3 and 4 , an alternative release mechanism for the stacker modules comprises a pair of sliding baffles  110 ,  112  and a clamping mechanism  114 . The sliding baffles may be in the form of plates which move horizontally apart to allow the sheet set  52  to drop between them. The plates  110 ,  112  may be driven by suitable drive mechanisms (not shown) in the directions illustrated by arrows B. In one embodiment, the sheet set is pushed across the baffles  110 ,  112  by the pushers  54  from the position shown in  FIG. 3  until its trailing edge  116  is over the stacker tray, as shown in  FIG. 4 . At this point, the sheet set may be clamped by a trailing edge clamp  120  of clamping mechanism  114 . The trailing edge clamp  120  may be positioned above the paper path  58  and lowered onto the trailing edge sheet set after the set is in position. In another embodiment, it may be raised from below, after the set has passed over it, or pivoted into a clamping position. The trailing edge clamp  120  clamps the set  52  of sheets and holds it while the baffles  110 ,  112  are moved to their open, second position. Shortly thereafter, as the leading edge  122  of the sheet set begins to tip downward, under its own weight, one or more sheet set separators  124  are raised to a position in which they overlie the leading edge  122  of the sheet set ( FIG. 4 ). The trailing edge clamp  120  thereafter releases the trailing edge of the sheet set. The sets of sheets form a stack on the stacker tray  104  of the stacker module. The sheet set separators  124  clamp the top set  52  onto the stack. At this point, the elevator mechanism sensor may detect the position of leading edge clamp  124  and adjust the height of the stacker tray accordingly. The stacker tray can be any platform, surface, or the like capable of holding a set of compiled and optionally processed sheets after the compiled set is clamped and transferred. In one embodiment, the arrangement of trailing edge clamps  120  may operate analogously to the clamping mechanism described in U.S. Pat. No. 7,021,617, incorporated herein by reference. The sheet separators  124  may operate analogously to the sheet separators disclosed in U.S. Pat. No. 6,702,278, the disclosure of which is incorporated herein by reference in its entirety. 
     As will be appreciated, in another embodiment, the positions of the forward edge clamps and sheet set separators  120 ,  124  may be reversed such that the leading edge of the set is clamped while the trailing edge of the set is allowed to drop toward the stacker tray. In yet another embodiment, the baffle plates  110 ,  112  may be arranged in locations which are rotated 90 degrees to the positions shown and thus may open in a direction parallel to the process direction. In this embodiment, the clamps  120 ,  124  may be arranged to clamp the sides of the sheet set, rather than its trailing and leading edges. 
     As will be appreciated, each of the stacker modules in the finishing assembly may be similarly configured to stacker module  22 . The stacker modules  22 ,  32 ,  34  are not limited to the designs illustrated and described herein, but may be of any suitable configuration which allows sets of sheets to be stacked or, where multiple stacker modules are provided, to pass through to a downstream stacker module. 
     Where multiple stacker modules are present, as shown in  FIG. 2 , module  22  has an inlet  130  at a first, upstream end of the housing and an outlet  132  at a second, downstream end and defines a portion of the print media path therebetween. Additional stacker modules  32 ,  34  may be similarly configured and thus interchangeable. Optionally, one of the stacker modules (module  22  in  FIG. 1 , module  34  in  FIG. 2 ) is configured as a terminal stacker module which lacks an outlet  132  to the horizontal paper path  58  and defines a downstream end of the conveyor belt  56 . 
     By separating finishing operations in the manner thus described, one set of sheets can be in the process of being compiled while the previous (downstream) set is being stapled and the previous set to that is being stacked. The process can be performed at a much slower and controlled velocity while the overall output of the finishing assembly  16 ,  30  is increased. In particular, once the print job is underway, sets move through the finishing assembly  16 ,  30 , in a step-wise advancement at a predetermined speed, which may be determined by the time taken by the module which takes the longest time to complete is operating function(s). Each finishing module may thus be performing its operations contemporaneously on a respective set of sheets. By contemporaneously it means that the times at which these operations take place overlap, at least in part. Once the respective finishing operations are complete, the conveyor system  50  is actuated to move each upstream set contemporaneously from the module in which it is located to the next respective downstream module. Thus, at any one time, a sheet set is being advanced from the compiler module  18  to the sheet set processing module  20  (or to a first of the sheet set processing modules, if there are more than one) at the same time as another sheet set is being advanced from the sheet set processing module  20  (or from a last of the sheet set processing modules, if there are more than one) to the stacker module  22 . Contemporaneously with this, if more than one stacker module is present and the upstream one is full, a sheet set may be being advanced from a first of the stacker modules to a second of the stacker modules, and so forth. As will be appreciated, there may be additional modules, such as buffer modules, in between pairs of modules  18 ,  20 ,  22 ,  32 ,  34 . The inlets and outlets  92 ,  100 ,  102 ,  130 ,  132  of all the modules may be arranged at the same height above a support surface  140 , such as the floor, whereby the paper path  58  is substantially horizontal. 
     In general, the compiler module  18  is typically the module which takes the longest to perform its function, since sheets typically arrive singly and sequentially at the compiler module. In one embodiment, the control system  26  determines the time taken for the compiler module  18  to complete the compiling step, e.g., based on the number of sheets to be compiled in the set, and adjusts the time between actuations of the pusher members  54  in accordance therewith, i.e., allows a longer time between actuations for a larger set of sheets. 
     While the exemplary finisher modules are illustrated in terms of a compiler module, a stapler module, and one or more stacker modules, one or more of the finisher modules can be any post-printing accessory device, such as a sorter, mailbox, folder, hole puncher, collater, stitcher, binder, envelope stuffer, postage machine, or the like. Exemplary envelope stuffers, also known as envelope inserters or fillers, are described in U.S. Pat. Nos. 4,462,199, 6,755,411, and 7,188,459, the disclosures of which are incorporated herein by reference). Each unit may have a bypass to further speed the system and improve modularity. Additional functions can then be added as new products are created. 
     While the illustrated finishing assembly  16 ,  30  is shown as a linear system, in other embodiments, modules may be stacked vertically, and or in parallel. In one embodiment, one or more of the modules has a outlet which is arranged generally at right angles to its inlet or an additional module may be added in between two of the illustrated modules which provides for redirection and optionally rotation of the print media sets. In this way, a right angle transfer may be provided in line to change from short edge feed to long edge feed which would shorten the pitch and allow for differing configurations. 
     The finishing assembly  16 ,  30  and other components of the printer  10 , operate under the control of control system  26  in accordance with a program stored in a memory (not shown) and/or in response to feedback from any desired or necessary sensors (not shown), as will be appreciated by those skilled in the art. The memory can be implemented using any appropriate combination of alterable, volatile or non-volatile memory or non-alterable, or fixed, memory. The alterable memory, whether volatile or non-volatile, can be implemented by using any one or more of static or dynamic RAM, a floppy disk and disk drive, a writeable or rewriteable optical disk and disk drive, a hard drive, flash memory or the like. Similarly, the non-alterable or fixed memory can be implemented using any one or more of ROM, PROM, EPROM, EEPROM, and gaps in optical ROM disk, such as a CD ROM or DVD ROM disk and disk drive, or the like. 
     The modular finishing assembly  16 ,  30  has many advantages. One is that modules can be mixed and matched to provide customized finishing functions for a particular customer. Another advantage is that as an additional finishing function is created, a new interchangeable module can be readily designed and added to the assembly. Some or all of the preexisting modules can remain unchanged. Another advantage is that multiple stackers can be added without the added cost incurred to provide the other functions such as compiling. Because the modules can now have a smaller number of functions, new modules for providing new finishing operations are easier to design. Field repairs are simplified by allowing the modules to be removable and easily replaced as a unit. 
     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.