Abstract:
This invention provides a slitter assembly with automated adjustment of slitter elements that allows for driven rotation of elements on the associated drive shaft during operation while enabling the elements to be moved freely along the drive shaft during setup and subsequently secured to the shaft free of lateral movement. This ensures that adjustment of the slitter elements is accurate, repeatable and reliable. In an illustrative embodiment, the slitter elements each comprise a pair of coaxial members including a blade member and a locking member. The blade member contains a slitter blade and overlies the locking member which is nested therewith. The locking member directly engages the drive shaft surface with a wedge assembly structure. The members are spring-loaded with respect to each other so that the two surfaces are normally biased to cam together and exert a hoop stress on the drive shaft.

Description:
FIELD OF THE INVENTION 
     This invention relates to web and sheet cutting and slitting mechanisms, and more particularly to slitters with slitting elements that are adjustable in relative spacing to provide slit sheets of a desired width. 
     BACKGROUND OF THE INVENTION 
     The creation of finished, bound books using “print on-demand” processes and electronic print engines is becoming ever more popular for publishers of all sizes. Unlike traditional printing processes, which employ fixed plate presses to transfer images to the web or sheet, electronic printing allows for the creation of smaller print runs that can be customized, on a book by book basis. To maximize efficiency, pages for finished books are often printed on a larger overall web or sheet, which is subsequently cut and slit into the desired page dimensions. These cut pages are thereafter fed to a collection point and stacked into finished “book blocks.” The book blocks are trimmed into squared-off stacks using a three-knife trimmer, and directed to a binding process, wherein an outer cover is bound to the book page stack. 
     The creation of book blocks often involves a number of manual steps. For example, printers often generate a plurality of page images on a larger sheet (sized 11×17 inch, for example). These images must be separated into separate pages of appropriate size. The manipulating of sheets from the printer can entail forming secondary stacks and thereafter physically moving and directing the stacks through cutters and slitters to generate the final set of pages in the appropriate page order. This book block stack is then directed to the trimming and binding process by another set of manual tasks. Any defective pages or stacks are removed and dealt with by hand, typically requiring the reassembly of the defective stack with new replacement pages as appropriate. 
     Currently available electronic printers, such as the Indigo™ 5500 Digital Press, available from the Hewlett-Packard Company of Palo Alto, Calif., offer a wide range of print versatility at high levels of print quality. Such printers allow for the duplex (two-sided) printing of full color photo-quality images on a variety of paper types (matte, glossy, etc.), fed from sheets. These printers, and other of similar type, offer a high throughput speed (for example, currently up to approximately 70 pages per minute (ppm) for color print and up to approximately 270 ppm for monochrome print). Completed sheets, typically containing multiple, two-sided page images in appropriate sizes are stacked on an output stack that is subsequently divided into appropriate pages for binding in a finished book. A printing computer and associated software application(s), which interconnected with the print engine controller, organizes the order and location of images on each side of each sheet. 
     To fully take advantage of the speed and versatility of such electronic printers, the automation of the handling of output sheets is highly desirable. In general, it is desirable that the output sheets be automatically cut and slit to appropriate sizes and that this sizing process allow for the creation of accurate, full-bleed (e.g. marginless) pages that are ready to stack into completed books. The slitter arrangement is a significant element in the sizing of sheets. A common form of slitter provides a pair of rotating wheels that overlap in an impinging manner to form a scissor or shear surface. At the sheet is directed between these slitter wheels, it is cut along the upstream-to-downstream feed direction, thereby removing edge gutters and establishing a width dimension for the sheet. Slitters can be placed to provide inboard slits to the sheet that create a plurality of side-by-side sheets, each of a predetermined with. The widthwise dimension of the sheet is directly related to the lateral (widthwise) spacing between each pair of impinging slitter elements (wheels) and an adjacent pair of impinging slitter elements. 
     During setup, before a print job begins, slitter elements are typically moved along their associated drive shaft by hand to an appropriate location and then fixed in a position on the shaft using a set screw, clamp or other fastening mechanism that is manually secured. The placement of the slitter elements along the shaft (and resulting page width) is largely dependent on the operator&#39;s accuracy in setting up the slitter assembly. This requires time and may entail a plurality of test runs before the slitter is ready for runtime use. Automation of the positioning of slitter elements is somewhat challenging. The elements should be positively secured once they are in a desired position on the shaft, but should be free to move along the shaft during the adjustment process. Likewise, not all the slitter elements may be desired for a particular job, and the unused elements should be movable to a position where they do not interfere with the paper/sheet path. Moreover, the elements must be free to rotate during operation. These challenges can render ineffective certain types of adjustment mechanisms, such as a lead-screw that continually engages the slitter elements. 
     It is therefore desirable to provide a slitter adjustment mechanism that allows for free rotation of the slitter elements on their shaft, allows unused elements to be moved out of the paper/sheet path and that accurately adjusts the slitter elements to a desired position within the overall slitter assembly substantially free of manual contact by the operator. 
     SUMMARY OF THE INVENTION 
     This invention overcomes disadvantages of the prior art by providing a slitter assembly with automated adjustment of slitter elements that allows for driven rotation of elements on the associated drive shaft during operation while enabling the elements to be moved freely (axially) along the drive shaft during setup and subsequently secured to the shaft in a manner that is free of lateral movement. This ensures that adjustment of the slitter elements is accurate, repeatable and reliable. In an illustrative embodiment, the slitter elements each comprise a pair of coaxial members including a blade member and a locking member. The blade member contains a slitter blade and overlies the locking member which is nested therewith. The locking member directly engages the drive shaft surface with a wedge assembly structure defining a relatively thin wall separated by a plurality of splits or slots. The splits or slots allow for flexure. The outer surface of the wedge assembly structure is frustoconical and mates with a frustoconical inner surface on the locking member. The members are spring-loaded with respect to each other so that the two surfaces are normally biased to cam together and exert a hoop stress on the drive shaft surface. This maintains a secure engagement between the slitter element and the drive shaft. The hoop stress is relieved, and the slitter element can be relocated along the shaft when a key on a moving carriage (a key assembly) is temporarily inserted between the blade member and the locking member, thereby overcoming the spring force and un-camming the wedge assembly. The carriage then moves the engaged slitter element to a new location according to a programmed position. In general, two impinging slitter elements are provided in a stacked arrangement, with the key releasably engaging and moving both simultaneously so that the pair of impinging slitter elements is moved along the shaft to a new location as a unit. 
     In an illustrative embodiment, each key carriage is provided on a track that allows the carriage to move laterally along the slitter assembly. The carriage is moved by a belt or lead screw drive under control of a servo, stepper or other appropriate drive motor. The slitter assembly can comprise a removable cartridge that includes detachable electrical connections between the carriage and the underlying feed unit. The carriage can be removed from and replaced within the paper/sheet feed path as appropriate. The slitter assembly/cartridge also includes a plurality of lateral guide rails on the upstream side of the assembly that slidably support movable blocks. The blocks contain downstream-directed feed guides that funnel sheets into the adjacent slitter elements. The blocks include grooves that are selectively engaged by the key when it is directed into the slitter elements to release them. Thus, when the key and carriage move the slitter elements laterally along the shaft it simultaneously moves the feed guides to maintain the guides in lateral alignment with the slitter elements. This ensures that the slit portion of each sheet is properly presented to the impingement point of the slitter blades. 
     In another illustrative embodiment, a method for adjustably slitting sheets includes the steps of initially locating a plurality of slitter element pairs on drive shafts in a first adjustment position. At least one of the slitter element pairs is engaged with a key assembly. While engaged and unlocked, at least one of the slitter element pairs is moved to a location on the drive shafts defining a second adjustment position. The key assembly is then disengaged from at least one of the slitter element pairs to lock the at least one of the slitter element pairs in the second adjustment position. A sheet guide assembly located adjacent to the at least one of the slitter element pairs is also engaged with the key assembly and, while engaged, the sheet guide assembly is moved in conjunction with at least one of the slitter element pairs 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention description below refers to the accompanying drawings, of which: 
         FIG. 1  is a perspective view of a plurality of illustrative slitter assemblies in the form of replaceable slitter cartridges that are arranged by way of example at right angles to provide cross-slit sheets; 
         FIG. 2  is a top view of the exemplary arrangement of slitter assemblies of  FIG. 1 ; 
         FIG. 3  is a fragmentary perspective view of the illustrative moving key assemblies and associated carriages with respect to each of the slitter assemblies of  FIG. 1 ; 
         FIG. 4  is a side cross section of an illustrative slitter element for use with the illustrative slitter assemblies of  FIG. 1 ; 
         FIG. 5  is a fragmentary rear view of a pair of illustrative slitter elements in an impinging relationship and associated sheet guides for use with the illustrative slitter assemblies of  FIG. 1 ; 
         FIG. 6  is a perspective view of an illustrative moving key assembly and associated drive motor on a carriage for use with the illustrative slitter assemblies of  FIG. 1 ; 
         FIG. 7  is a fragmentary, bottom-oriented perspective view of the moving key assembly with associated drive motor and carriage shown in engagement with the pair of illustrative slitter elements of  FIG. 4 ; 
         FIG. 8  is a fragmentary, top-oriented perspective view of the pair of illustrative slitter elements and the engaged key assembly of  FIG. 7 ; 
         FIG. 9  is a top view of the pair of illustrative slitter elements and the engaged key assembly of  FIG. 7 ; 
         FIG. 10  is a fragmentary front-oriented perspective view of a pair of illustrative slitter elements for using the slitter assemblies of  FIG. 1  showing the sheet guides, blocks and associated guide rails therefor, in addition to a gutter strip diverting guide; 
         FIG. 11  a fragmentary front view of a pair of illustrative slitter elements, sheet guides, blocks and associated guide rails of  FIG. 11 ; and 
         FIG. 12  is a fragmentary rear view of two sets of slitter elements of the upstream slitter assembly of  FIG. 1  located in an adjacent orientation to provide a gutter strip between slit sheets and showing one of the slitter elements sets engaged by the moving key. 
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1-3  show an arrangement  100  of slitter assemblies  110  and  120  for use in a sheet feeding device, the details of which have been omitted for clarity. In general, either, or both of, the slitter assemblies  110  and  120  can be provided in an appropriate sheet-feeding device or arrangement according to illustrative embodiments herein. The depicted, exemplary right-angle arrangement is employed in conjunction with a right-angle turn (bump turn) module in which sheets (not shown) enter (arrow  130 ) the upstream slitter assembly  110 , and are separated into a pair (or more) of side-by side sheets. These sheets are then directed (by appropriate drive elements) at a substantially 90-degree angle (right-angled arrow  132 ) into the downstream slitter assembly  120 . Each side-by-side sheet is, in turn slit into a plurality of smaller side-by-side sheets that are driven (arrow  134 ) downstream for merging, stacking and further processing (e.g. binding). The exemplary, downstream slitter assembly  120  is arranged to produce four side-by-side sheets from each of the upstream slit sheets. Thus a total of eight sheets (pages) are generated from an original input sheet. This can be termed an eight-up configuration. Of course this arrangement is only by way of example of a variety of configurations. By way of further useful background information, a right-angle slitter arrangement as described herein, for use in a book-stack production system, is shown and described in commonly-assigned US Published Patent Application No. US 2011/0049781 A1, entitled SYSTEM AND METHOD FOR INLINE CUTTING AND STACKING OF SHEETS FOR FORMATION OF BOOKS, by Steven P. Lewalski and Hans Eliasson, the teachings of which are expressly incorporated herein by reference. This exemplary system is only one of a variety of arrangements that can benefit by the illustrative embodiments described herein. 
     Each slitter assembly  110 ,  120  is in the form of a removable cartridge in an illustrative embodiment, constructed with a self-contained framework having a pair of opposing side plates  140  and  142  (for upstream assembly  110 ), and  144  and  146  (for downstream assembly  120 ). The side plates rotatably support a pair of parallel drive shafts  150  and  152  (for upstream assembly  110 ), and  154  and  156  (for downstream assembly  120 ). The drive shafts each rotatably support a plurality of lower and upper slitter elements  160  and  162 , respectively. In this embodiment, the lower slitter elements  160  define a blade geometry that forms a shear surface with respect to the blade geometry of the upper slitter elements when the blade portions overlap as shown. The blade portions of the slitter elements  160 ,  162  can define a conventional shape or a modified shape as appropriate. 
     The side plates ( 140 ,  142 ) and ( 144 ,  146 ) are held in place by a plurality of horizontal rails ( 170 ,  172 ) and ( 174 ,  176 ), respectively. These rails are illustrative of a variety of supporting arrangements. They allow each slitter assembly  110  and  120  to be a self-contained unit that can act as a removable cartridge in an overall sheet transport device, such as that shown and described in the above-incorporated US Published Patent Application No. US 2011/0049781 A1. In this manner, a cartridge can be removed for service, or to be substituted with another cartridge having a different arrangement of slitters and associated components (or a cartridge with no slitters where sheets are to be directed through the unit free of slitting). Note various supporting members have been omitted from  FIGS. 1-3  for clarity of the operating components. Each slitter assembly/cartridge  110 ,  120  includes, among other components a top plate  180  and  182 , respectively that supports components of the slitter assembly. The drive shafts ( 150 ,  152 ) and ( 154 ,  156 ) in each assembly  110 ,  120  rotated together by a pair of gears  184  and  186 , respectively, positioned adjacent an end plate  142  and  146 , respectively. The gears cause the shafts to rotate together and removably mesh with a drive gear of a drive motor assembly within the transport unit (not shown). The drive motor assembly can be any acceptable drive arrangement, such as a stepper or servo motor and an associated power transmission assembly. 
     Each slitter assembly/cartridge  110 ,  120  is served by an integral key assembly  190  and  192 , respectively. The key assembly defines a moving carriage structure that is constructed and arranged to selectively and vertically drive a fork-shaped key  194  and  196 , respectively, into and out of engagement with the slitter elements  160  and  162  when they are stacked together as shown to form a shearing (impingement) surface. As shown, the key  194  is extended into an engaged with the slitter elements and the key  196  is retracted/withdrawn into a disengaged position. The keys  194 ,  196  selectively lock and unlock the slitter elements with respect to the drive shaft. When locked, by removal of the key, the slitter elements ( 160 ,  162 ) are essentially fixed to the shaft, both laterally (axially) and rotatably. When unlocked, by engaging the key with the slitter elements, the slitter elements can be moved laterally (axially) along the shaft (double arrows  193  and  195 ) to a desired location along its elongated length between the end plates. This allows the key assembly  190 ,  192  to shuttle along the shaft, selectively engaging and disengaging various pairs of slitter elements (that together form a shear surface), and place each pair of slitter elements at a desired location. This location can be a slitting position with respect to a sheet of a predetermined size, or the location can be outside the width of the feed path so that a particular pair of slitter elements is rendered inactive for that job. The internal mechanism that enables locking and unlocking of slitter elements is described further below. 
     In order to ensure that sheets are positively guided into the shear surface formed between each pair of active slitter elements ( 160 ,  162 ), a funnel-shaped sheet guide assembly  230  is provided with respect to at least some of the slitter element pairs. The guide assembly  230  consists of an upper guide element  320  (See  FIG. 3 ) and a lower guide element  322 . The two guide elements  320 ,  322  include elongated upper and lower guide plates  330 ,  332  that form an open funnel mouth at their upstream end as shown, and taper to an extended, narrow guide surface that provides sufficient clearance for sheets within a desired range of thicknesses. The guide surface formed between the pair of upper and lower guide plates  330  and  332  has a length that is sufficient to ensure that the sheet remains positively engaged with the shear surface of an adjacent slitter element pair  160 ,  162 . The guide plates  330  and  332  are mounted on a pair of respective upper and lower base blocks  340  and  342  that reside above and below the sheet path (the sheet path being defined by the guide surface between confronting guide plates  320 ,  322 ). The base blocks, in turn, ride laterally on an upper pair of rails  350 ,  360  (on each of assemblies  110 ,  120 , respectively) and lower pair of rails  352 ,  362  (on each of assemblies  110 ,  120 , respectively). These rails are mounted between respective assembly side plates  140 ,  142  and  144 ,  146  in this embodiment. The guide blocks  304 ,  342  move along these rails (which include a smooth and/or polished metal surface) with a snug engagement so that they experience predetermined friction with minimal play. In particular, a spring-loaded, adjustable brake assembly (not shown) can be employed to increase friction. The brake can be any conventional friction-causing mechanism (e.g. a metal ball and spring), and is contained in a well within the block  340 ,  342 . The well defines an opening against one of the rails that allows the brake element to pressurably engage the rail. A movable screw cap  250  (See  FIG. 2 ) at the top of upper block  340  and bottom of lower block  342  allows access to the brake mechanism and allows adjustment of the spring or other brake component. The brake component is optional in alternate embodiments. 
     In an embodiment, each block  340  includes at least one keyway (and illustratively a pair of side-by-side keyways) that are constructed and arranged to engage an upstream end of the respective key  194 ,  196  in each assembly  110 ,  120 . Thus, when the forked portion of the key engages the slitter pair, the upstream edge of the key engages the  380  slot in an adjacent pair of confronting, upper and lower base blocks  340  and  342 . In this manner, when the key assembly ( 190 ,  192 ) shuttles laterally to move the slitter element pair, it concurrently moves the base blocks  340 ,  342  and thus, it moves the overall associated guide assembly  230 . Once the fork disengages and locks the slitter pair in place at the new location along the drive shaft, the guide assembly  230  remains at the new location along its rail pairs  350 ,  352  and  360 ,  362  based upon friction and the fact that there is little or no lateral force applied by the sheets or other system components during runtime operation. That is, the lateral force on the guide assembly through sheet movement, vibration, etc., is less than the frictional holding force of the guide assembly with respect to its rails. 
     In this embodiment, the rails are round min cross section, but in alternate embodiments they can have a regular or irregular polygonal cross section and/or a non-circular, curvilinear cross section. Likewise, while two rails are used in this embodiment to support each base block, in alternate embodiments, a single rail having, for example a non-circular or keyed cross section can be employed. 
     With reference to  FIG. 4 , the locking structure of a slitter element is described in further detail. The depicted slitter element is an upper blade element  162  as shown in  FIGS. 1-3 . The internal construction of the locking mechanism from lower slitter elements  160  is essentially the same, and thus this description applies to both the upper and lower elements. Thus, where the components in each type of slitter element are similar, such components are provided with like reference numerals. As shown, the element  162  consists of two main concentric components, a base member  410  that seats on the drive shaft (not shown in this figure for clarity) and a coaxial blade-carrying member  420 . The blade-carrying member  420  includes a hardened circular blade, which can be conventional in design at a front end opposite the base  410 . As shown in the stacked slitter arrangement of  FIG. 5 , the blade  422  includes a forward cutting surface  424  that overlaps a raised surface  520  shear-carrying member  530  of the lower slitter element  160  to define the overall, impinging shear. The blade  422  is biased against an annular shoulder  426  by a flat spring  428  that resides between the blade&#39;s inner surface  430  and an opposing wall  432  on the member  420 . This allows the blade to maintain a floating, pressurable contact against the lower slitter element&#39;s ( 160 ) shear surface and also to absorb (and counteract) axial displacement of the blade-carrying member  420  (described below). Note that the blade and member can be slidably (in an axial direction) keyed to each other in various embodiments so the blade does not freewheel when the member  420  rotates. Because the lower slitter element  160  includes a fixed rim, the key restrains this element before it engages the upper slitter element  162 . Upon engaging the upper slitter element, the axial displacement of the wedge assembly requires that the blade move axially against the now-fixed rim or the upper wedge assembly would seize. 
     The blade-carrying member  420  also includes a barrel  440  that seats within an annular cup  442  in a manner that allows axial movement (double arrow  444 , aligned with rotational axis RA). The rear (inner) wall  445  of the cup  442  includes two or more holes  446 ,  466  through which threaded fasteners  450  pass. The fasteners  450  are threadingly engaged with the blade-carrying member  420 , and include opposing heads  452  that bear upon a coaxial spring assembly  454 . The spring assembly  454  also bears upon the opposite (outer) wall  460  of the cup  442 . The spring assembly  454  can be any acceptable biasing mechanism, For example, a plurality of stacked Bellville (cupped) spring washers can be employed as shown, or a conventional coil spring can be used. The overall biasing force should be sufficient to provide the required locking pressure to secure the slitter element to the drive shaft free of any rotational or axial movement when locked. 
     The locking force is provided by the selective interaction wedge arrangement between the base member  410  and the blade-carrying member  420 . As shown, the base member  410  includes an inner surface  470  having an inner diameter IDB of approximately 0.75 inch, which conforms closely to the outer diameter of the drive shaft. The drive shaft and base  410  can be keyed, splined, polygonal or keyless (as shown), so long as the base is free to slide axially along the shaft when unlocked. If the shaft is keyed, splined or otherwise non-circular in cross section, the base includes a similar geometry along its inner surface. The shaft-engaging inner surface  470  is continuously cylindrical in the section  474  extending rearwardly approximately from the cup wall  445  to the rear end  476  of the base  410 . The forward portion  478  of the base&#39;s inner surface  470  includes a wedge-shaped outer side  480  defining a wedge angle WA of between approximately 1 and 3 degrees in an embodiment. This surface is overridden by a corresponding wedge surface  482  on the inside of the blade-carrying member  420 . Illustratively, the members  410  and  420  are constructed from steel alloy, and the thickness of the wedge-shape forward portion ranges from 0.010 to 0.002 inch. The wedge-shaped forward portion  478  of the base  410  is split at four (or more) diametrically evenly positioned splits  486  (e.g. at 90-degree separations around the circumference of the portion  478 ). These allow the divided segments of the wedge-shaped forward portion  478  to flex radially inwardly when the wedge is forced together under the action of the spring assemblies  454 . This flexure is sufficient to provide a desired hoop stress to the drive shaft to effect positive locking of the base member  410  with respect to the drive shaft. 
     Note, as used herein, orientational terms such as “front”, “rear”, “top”, “bottom”, “inner”, “outer”, “vertical”, “horizontal”, and the like are meant only as relative conventions and (unless otherwise indicated) not as absolute indicators of direction with respect to the operation of gravity. 
     In a resting state, the slitter element is locked to the drive shaft by the action of the spring assemblies in conjunction with the wedge arrangement. The locking force is overcome by relieving the axial biasing force that drives the wedge faces  480 ,  482  together. This is accomplished, by directing the key between a pair of external, annular walls  490  and  492  that confront each other to from a slot  494 . One wall  490  is formed on the base member  410  and the other, confronting wall  492  is formed of the blade-carrying member  420 . The slot  494  defined between them has a radial depth DS of approximately 0.120 inch, and a resting axial width SW of approximately 0.250. These measurements, and others described above are highly variable in alternate embodiments, dependent in part upon the overall size of the slitter element and associated drive shaft. With reference to the illustrative key assembly  190  in  FIG. 6 , the key  194  has a span SK between tines  610  and  612  that is sized to allow it to slide into the slot  494 . Thus SK is slightly greater than or approximately equal to the diameter of the inner surface  497  of the slot  494 . Notably, the thickness TK of the main portion (remote from tips  620  of the key tines  610 ,  612 ) of each key tine  610 ,  612  is greater that the resting width SW of the slot  494 . In an embodiment, the key tine thickness TK is approximately 0.280 inch. The tips  620  of the tines  610 ,  612  are tapered inwardly toward their respective ends to a minimum thickness TT of approximately 0.125 inch, which is sufficiently less than the slot width SW to ensure insertion of the keys without binding. In this manner, the key can move upwardly into engagement with the slot, and when the main (non-tapered) portion of the tine passes into the slot, it can cause the slitter element members  410  and  420  to move axially away from each other. The axial movement caused by entry of the key is sufficient to un-wedge the members  410 ,  420  and relieve the locking hoop stress on the drive shaft. This allows for unlocking and axial movement of the stacked pair of slitter elements as they are engaged by the key. In particular the slot, in this captures the key in this orientation, and any axial/lateral movement (double arrows  193 ,  195 ) along by the key assembly results in simultaneous movement of the engaged slitter elements along the drive shaft. 
     It should be clear that the use of a key with one or more times that are offset from the axis of the drive shaft and engage the periphery of the slitter elements allows the assembly to move freely along the vertically stacked drive shafts, while capturing the slitter element pair. 
     With further reference to  FIGS. 6 and 7 , the key assembly  190  is shown and described in further detail. The structure and function of the key assembly  192  should be considered similar or identical and like reference numerals refer to like components in both assemblies  190 ,  192 . As shown, the key  194  is mounted on a base block  630 . The base block  630  includes a threaded member  631  that rides on a screw shaft  632 . The key assembly  190  includes a vertical support plate  633  having a vertical track  634 . The track  634  guides a slider  636  that is mounted to the base block  630 . This arrangement ensures that the base block  630  moves linearly (free of rotation relative to the vertical support plate  633 ) as it is selectively driven upwardly and downwardly (double arrow  635  by the screw  632 . The vertical support plate  633  carries, at a bottom end, a motor mount  640 , which includes a drive motor  642  and a timing belt assembly  644 . The belt assembly  644  operatively interconnects the motor  642  with the base of the screw  632 . The motor  642  can be any controllable drive, and the belt assembly  644  can be substituted for gears or another appropriate transmission mechanism in alternate embodiments. The motor is controlled by a controller or control processor  370  ( FIG. 3 ) that selectively raises and lowers the key by rotating the motor through a predetermined range of rotational motion. The motor can be a stepper motor, servo or other appropriate type. It can include an encoder to track relative motion. The motor can optionally be interconnected with limit switches (not shown) that stop movement of the mechanism at the top and/or bottom ranges of vertical key motion. 
     The vertical support plate  633  also includes a block  650  having a threaded member  710  ( FIG. 7 ) that rides upon a horizontal lead screw  720 . The lead screw  720  is rotated in each of opposing directions by a separate drive motor (not shown) and drive belt assembly  722 , which receives signals from the controller. The motor, which can be a stepper, servo, or other type having an optional encoder to track movement, operates to move the key assembly  190  in a widthwise (lateral) direction to various points along the slitter assembly ( 110 ). A track  750  is mounted laterally on the slitter assembly frame, and guides a slider  752 . The slider  752  is fixed to the vertical support plate  633  beneath the thread block  650 . This track and slider arrangement  750 ,  752  maintains a lateral movement and prevents rotation of the key assembly when the lead screw  720  rotates. The motor is controlled by the controller to move a predetermined distance based upon a number of steps or encoder pulses relative to the previous position. The controller tracks the location of each slitter element pair along the shaft (i.e. the location of the slots  494  for the pair), with respect to the assembly&#39;s key. This tracking can use conventional techniques, such as those used form moving and tracking the motion of robotic components along an axis. The controller initially establishes a base position for each slitter element. This can be accomplished using an optical sensor or by a manual mechanism. For example, as shown in  FIG. 7 , an optical sensor  770  can be attached by a bracket  772  in the vertical support plate  633  of the key assembly  190  so that it faces each lower slitter hub  160 . An optical reflection from the hub&#39;s  160  blade edge instructs the controller (which is operatively connected to the sensor  770 ) that the key assembly carriage (and associated key) is aligned with a given hub. By initially passing laterally over all hubs, the controller can determine a relative position for each one. That is, the detection of each hub is correlated with a discrete encoder signal (e.g. pulse count) associated with the key assembly horizontal screw drive  720 . The controller stores these positions, and when a hub is to be moved to a new location, the controller directs the carriage to align with that hub based upon the stored controller position signals. 
     Once the locations of the slitter elements is established and stored, the assembly can shuttle between them under the drive of the horizontal screw  720 , and engage and disengage each one using the vertical drive screw  632 . The controller tracks and stores any new locations (e.g. pulse counts from a stored encoder reference point/baseline) for each hub. The controller logic is constructed and arranged so that the slitter elements are engaged and moved along the drive shafts by the key assembly in an order that avoids collisions with other slitter elements. Conventional decision algorithms can be used to control this motion sequence based upon the stored knowledge of the current positions of each of the slitter elements. Some slitter elements are potentially unused in certain jobs. These are moved sufficiently to the sides of the assembly to be free of interference with the paper/sheet path. 
     With further reference to  FIGS. 8 and 9 , the key  194  engages a pair of slitter elements  160  and  162  that are adjacent to the side plate  142 . The tines  610  and  612  of the key  194  engage the slot  494  and cause the members  410  and  420  to spread apart against the biasing force of the spring assemblies  454 . Concurrently, the upstream edge of the tine  612  engages one of the grooves  380  in the guide-carrying block  340 . When the engaged key assembly  190  moves laterally along the drive shafts  150  and  152 , it carries the respective slitter elements  160  and  162 , and the block  340 . 
     With further reference to  FIGS. 10 and 11 , the upstream side of the assembly  110  is depicted with reference to the side plate  140 . A slitter element pair  160 ,  162  is depicted adjacent to the side plate  140 , thereby defining a widthwise edge of the cut sheet. Where the input sheet is wider than the slitter element placement, the slitter elements will trim a gutter strip from the edge. To avoid clogging of the device, the upper block  340  includes an extension base  1020  that can be attached using clips, fasteners, or the like. This base  1020  carries a downwardly directed deflector  1030 , which diverts the trimmed gutter strip beneath the adjacent feed surface  850  (see  FIG. 8 ). Illustratively, the deflector is constructed and arranged to overlie the trimmed strip and engage the strip&#39;s top surface. The downwardly directed angle of the deflector plate (along the downstream direction) ensures that the strip follows a downward path, out of the plane of the feed path (i.e. below the feed plane defined between the guide plates. A waste bin (not shown), or other removal arrangement (e.g. a vacuum collection system), receives and stores the trimmed sheet material. The base  1020  and deflector  1030  are provided to blocks  340  that are adjacent to the opposing ends of the slitter assembly. These blocks are positioned according to the desired overall width of the slit sheet(s) passing through the assembly, and thus the deflectors are permanently attached to the opposing outboard edges of each block. The deflectors are adapted to move with the block as it (and the slitter element pair) is repositioned laterally along the assembly. In alternate embodiments, the deflector assemblies can remain free-floating with respect to the rails  350 , moved by a separate mechanism, or be omitted. Likewise, when not in use, the deflector assembly(ies) can be removed from their underlying blocks  340 . 
     With reference particularly to  FIG. 10 , the funnel-shaped opening  1040  between guide plates is more-clearly depicted. The angle AF of each of the guide plates  330 ,  332  with respect to line  1060  (which resides generally in the feed path&#39;s plane) is highly variable. In an embodiment, the angle AF is between approximately 3 and 10 degrees. Likewise the funnel angle AF of each confronting guide plate  330 ,  332  can differ with respect to the other. The overall height HF ( FIG. 11 ) at the opening is also highly variable. In an embodiment, the funnel height HF is sufficient to endure sheets of varying thicknesses are guided into the feed plane in the region of the slitter elements. In an embodiment, the height HF can be between approximately ⅜ and ¾ inch. 
     With reference now to  FIG. 12 , showing two slitter pairs  160 ,  162  in a relatively close, confronting arrangement along the mid region of the respective drive shafts  150 ,  152 . This arrangement represents a slitter configuration located along the interior of a fed sheet, adapted to divide the single fed sheet into a plurality of side-by side exiting sheets. In this embodiment, the slit edge of each side-by-side sheet is cleanly defined by generating a central gutter strip between them. The gutter strip is directed downwardly to a waste location (described above) using a narrow deflector plate  1210  attached to a removable base  1220 . The base  1220  is likewise attached to a block  1240  having an extended height to accommodate the base  1220 . The base is attached by one or more fasteners  1250 , or by another attachment mechanism that allows for removability. As shown the key  194  engages the right (taken in a downstream direction, opposite the viewing direction) slitter element pair  160 ,  162  and block  1240 . The use of ambidextrous slots  380 ,  1280  allows the key to engage each block  340 ,  1240  along a side of the block opposite to the side that carries the guide plate ( 330 ,  332 ). This allows for manufacture of a single block for both right and left guide plate placement. In the depicted example, the key  194  engages the leftmost slot ( 1280 ) of the right block  1240  and the rightmost slot ( 380 ) of the left block  340 . In alternate embodiments, a single groove can be provided to some or all blocks. 
     It should be clear that the above-described slitter assembly provides a versatile an effective mechanism for automatically and rapidly adjusting the slitter elements to accommodate a given sheet size. The mechanism allows for size adjustments during normal runtime and rapid change-out of slitter configurations based upon the novel cartridge configuration of the slitter assembly. This assembly can be adapted to a wide range of sheet feeding and handling devices. 
     The foregoing has been a detailed description of illustrative embodiments of the invention. Various modifications and additions can be made without departing from the spirit and scope of this invention. Each of the various embodiments described above may be combined with other described embodiments in order to provide multiple features. Furthermore, while the foregoing describes a number of separate embodiments of the apparatus and method of the present invention, what has been described herein is merely illustrative of the application of the principles of the present invention. For example, in an alternate embodiment, a key having a single tine can be employed. This tine can be located between the guide-carrying block and slitter element slot in an embodiment. Likewise, while the impinging slitter elements and respective drive shafts are stacked in a vertical orientation, it is expressly contemplated that the axes of the respective slitter elements/drive shafts can be aligned non-vertically, and the key assembly can be oriented to insert and remove the key in a direction generally parallel to the orientation of the axes. Assemblies that travel non-linear paths to direct a key into engagement with slitter elements and/or the guides can also be provided. Likewise, separate assemblies can be used to lock/unlock and move the slitter elements and/or the guides. In another alternate embodiment, one of the stacked slitter elements is lockable and captures the other slitter element using, for example using a pair of axially spaced rims that laterally capture the opposing blade or raised annular surface. In such an embodiment, the captured element is generally freely slidable when the lockable slitter element slides laterally along the drive shaft. The freely sliding, captured element can be rotationally fixed using a spline arrangement, keyway or the like. Also, in another alternate embodiment, the sheet guide assembly can be mounted with respect to the drive shaft(s) and slitter elements so that movement of the slitter elements causes the guide assembly to move laterally based directly upon lateral implement of the slitter elements. Accordingly, this description is meant to be taken only by way of example, and not to otherwise limit the scope of this invention.