Abstract:
A print media stack clamp and method for processing print media in an output receptacle. In one embodiment, a print media output device includes an output receptacle and a surface extending over and facing the receptacle. One or both of the receptacle and the surface are movable relative to one another such that print media output to the receptacle can be alternately clamped between the surface and the receptacle and released. In another embodiment, a method for processing print media in an output receptacle includes outputting a first document to the receptacle, moving the first document toward one side of the receptacle, clamping the first document in the receptacle, outputting a second document to the receptacle on top of the first document while the first document is clamped, releasing the first document, and moving the second document toward the one side of the receptacle.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention is directed to a print media stack clamp and method for processing print media in an output receptacle.  
         BACKGROUND  
         [0002]    Printed documents output by printers and post print finishing devices on to a stack of documents can dislodge the top documents in the stack as they “bulldoze” into the stack. Where the documents in the stack are aligned with one another, it is often important to maintain that alignment as new documents are added to the stack. The present invention was developed in an effort to help minimize “bulldozing” as new documents are output to the stack. 
       
    
    
     DESCRIPTION OF THE DRAWINGS  
       [0003]    [0003]FIG. 1 is a perspective side view illustrating a printer with an attached post print finishing device.  
         [0004]    [0004]FIG. 2 is an elevation side view illustrating the major components and media path through a post print finishing device such as the one shown in FIG. 1.  
         [0005]    [0005]FIG. 3 is a perspective rear side view of an output device that incorporates a stack clamp according to one embodiment of the invention.  
         [0006]    [0006]FIG. 4 is a perspective front side view of the output device of FIG. 3.  
         [0007]    [0007]FIGS. 5-11 are perspective views showing the structure and sequence of operation of a stack clamp according to one embodiment of the invention.  
         [0008]    [0008]FIG. 12 is a detail perspective view of the stack position sensor of the stack clamp of FIGS. 5-10 in the position shown in FIG. 8.  
         [0009]    [0009]FIG. 13 is a detail elevation section view of the stack position sensor shown in FIG. 12.  
         [0010]    [0010]FIGS. 14 and 15 are detail views of the side plate position sensor of the stack clamp of FIGS. 5-11 in the positions shown in FIGS. 8 and 9, respectively. 
     
    
     DETAILED DESCRIPTION  
       [0011]    [0011]FIG. 1 illustrates a printer  10  with an attached post print finishing device  12 .  
         [0012]    [0012]FIG. 2 illustrates the major components and media path through a post print finishing device such as the one shown in FIG. 1. FIGS. 1-2 illustrate one exemplary environment in which embodiments of the invention may be implemented. The finishing device of FIG. 2 includes sheet coating, trimming and stapling, and booklet making capabilities. While it is believed that embodiments of the clamp of the present invention will be particularly useful for booklets and other multi-page documents, such as might be output by finishing device  12 , embodiments of the invention may be used with any printer or print media output device in which it may be desirable to clamp documents in the output tray or bin.  
         [0013]    Printer is used broadly in this document to mean any printing device including, for example, laser printers, inkjet printers, copiers and multi-function devices.  
         [0014]    Referring to FIG. 2, printed media sheets are output to finishing device  12  as noted by arrow  14 , and discharged from finishing device  12  to output tray  16  as noted by arrow  18 .x The media path through finishing device  12  is indicated by broken line  20  in FIG. 2. Media sheets output to finishing device  12  are transported through or around coating unit  22  to a pre-trim registration unit  24 , trimming unit  26 , folding unit  28  and stapling unit  30  before they are discharged to output tray  16 .  
         [0015]    Coating unit  22  coats printed media with a film of clear flexible material. Such coatings can be formulated and applied to help protect the printed image, enhance the printed image or provide a more uniform gloss level across the entire media (including both printed and unprinted areas). If a coating is not desired, then media sheets are moved along a bypass path around coating unit  22 . Pre-trim registration unit  24  registers each sheet to trimming unit  26  before it enters trimmer  26 . That is to say, registration unit  24  straightens or “deskews” each sheet as necessary to ensure the sheet is properly aligned in the media path as it enters trimmer  26 . Trimming unit  26  trims the leading edge of each sheet or the trailing edge of each sheet, or both, as necessary to make the sheet the desired size for the finished booklet or other document. Folding unit  28  folds each sheet by creasing the sheet along the desired fold line. Stapling unit  30  staples each booklet after the sheets are trimmed, folded and assembled.  
         [0016]    [0016]FIGS. 3 and 4 are perspective rear and front views, respectively, of an output device  32  that incorporates a clamp  34  constructed according to one embodiment of the invention. Referring to FIGS. 3 and 4, output device  32  includes output tray  16 , clamp  34 , frame  36 , and a tray drive system  38 . Clamp  34  includes an upper sensing module  40 , a lower sensing module  42 , a side plate  44  that extends between the sensing modules  40 ,  42  and pressure fingers  46  that extend out from the top of side plate  44 .  
         [0017]    Frame top member  48  and frame bottom member  50  extend between frame side members  52 . Side plate  44  is mounted along one side member  52  on shoulder bolts  54  or other suitable fasteners that project out from frame side member  52 . Shoulder bolts  54  ride in slots  56  in side plates  44  so that side plates  44  can slide up and down relative to frame  36  and tray  16 .  
         [0018]    Tray drive system  38  includes a reversing motor  58 , drive shafts  60  and endless loop belts  62 . Tray  16  is mounted between and moves along a pair of rails  63  attached to or integral with frame side members  52  at the urging of motor  58 . Belts  62  are operatively connected to reversing motor  58  through shafts  60  and gears  64 . Motor  58  is mounted to frame bottom member  50 . Each side of tray  16  is connected to one run of each belt  62  so that belts  62  carry tray  16  along rails  63 ,as motor  58  drives belts  62  up and down together. The outboard ends of drive shafts  60  are supported on bearings or bushings (not shown) in frame bottom member  50 . One side of output tray  16  is formed with a slot  66  or otherwise configured to fit around side plate  44  so that side plate  44  and tray  16  can move up and down relative to one another. Preferably, side plate  44  is enlarged through an area  68  covering the full range of motion of tray  16 . Frame  36  and tray drive system  38  are described in more detail in commonly assigned U.S. patent application Ser. No.______ (Attorney Docket No.100203756)______ filed and entitled “Print Media Output Receptacle Rail Support And Drive System”, incorporated herein by reference in its entirety.  
         [0019]    A programmable controller  70  electrically coupled to motor  58  controls the position of tray  16 . Although it is expected that controller  70  will be implemented as part of the controller for finishing device  12  shown in FIGS. 1 and 2, controller  70  could also be implemented as a discrete output device controller or as part of the printer controller for systems in which the printer controller controls print and post print operations or in systems in which the printer outputs directly to tray  16 . As with conventional printer and finishing device controllers, controller  70  will typically include a processor and associated memory. Random access memory (RAM) or other suitable operational memory contains job data from the attached printer or host computer along with programming and other data currently being executed or used by the processor. Read only memory (ROM) or other suitable operational/storage memory contains the device firmware that provides programming instructions to control the operation of finishing device  12  and output device  32 . Controller  70  executes firmware programming instructions according to command inputs from the attached printer or host computer and in response to input from sensors and other components of finishing device  12  and output device  32 . Some embodiments of the invention, therefore, may be implemented through a computer readable medium with instructions that, when executed by controller  70  and/or another computer, control the operation of printer  10 , finishing device  12  and/or output device  32 . As used in this document, computer readable medium means any medium that can contain, store or propagate computer readable instructions.  
         [0020]    [0020]FIGS. 5-11 illustrate the structure and sequence of operation of clamp  34 .  
         [0021]    [0021]FIG. 12 is a detail view of stack position sensor  40  with document stack  41  in the position shown in FIG. 8. FIGS. 13 and 14 are detail views of side plate position sensor  42  with the side plate in the positions shown in FIGS. 8 and 9, respectively. Referring to FIGS. 5-13, pressure fingers  46  are positioned at the upper reach of side plate enlarged area  68  and extend out over tray  16 . Side plate  44  and a back stop  72  intersect to form a corner  74 . Back stop  72  may be constructed as an integral part of tray  16  or as a discrete structural component positioned at the rear of tray  16 . Each sheet, booklet or other document  71  is output to tray  16  through printer or finishing device output port  76  generally towards the center of tray  16  and, when necessary or desirable, moved against side plate  44  to align one edge of the documents, or into corner  74  to align two edges of the documents. Aligning the edges of the document is commonly referred to as registration, or registering the document. The technique for two edge alignment is commonly referred to as corner registration because each document is moved toward the corner of the tray. Registration devices are well known in the printing and paper handling arts. Any suitable registration device may be used to move the documents toward side plate  44  or into corner  74 . For example, the registration device shown and described in commonly assigned U.S. patent application Ser. No.______ (Attorney Docket No.100203756)______ filed and entitled “Print Media Output Receptacle Rail Support And Drive System” may be adapted for use with stack clamp  34 .  
         [0022]    Pressure fingers  46  are positioned to reach out over the back corner of documents stacked into corner  74 . As described in more detail below, pressure fingers  46  are used to hold or “clamp” documents in place while the next document is output to the stack. While two fingers  46  are shown, any number of fingers may be used. What is important is that fingers  46  create enough friction with the top document in the stack to hold that document in place while the next document is output to the stack.  
         [0023]    As best seen in FIGS. 12 and 13, stack position sensor  40  is mounted to side plate  44  near pressure fingers  46 . In the embodiment shown, stack position sensor  40  is mounted immediately behind fingers  46  at corner  74 . Stack position sensor  40  may be mounted at any location where it will accurately detect the top of stack  41  under pressure fingers  46 . In the embodiment shown, sensor  40  includes a pair of fixed optical sensors  78 ,  80  and a rotating gate  82  mounted to a U-shaped housing  84 . Gate  82  is a pie-shaped plate that rotates on a pin  86  extending out from housing  84 . Gate  82  passes through a detection zone  88  between an optical transmitter  90  and an optical receiver  92  mounted opposite one another across detection zone  88  for each sensor  78 ,  80 . Each receiver  92  is electronically connected to controller  70  (controller  70  is shown in FIGS. 3 and 4). Although two optical sensors and a gate are shown, any magnetic, electronic or electro-mechanical device or combination of devices suitable for detecting the position of the top of stack  41  relative to pressure fingers  46  may be used.  
         [0024]    Optical transmitters  90  may use a light emitting diode (LED), tungsten lamp, neon lamp or any other suitable source of light, preferably infrared light. Optical receivers  92  may use a phototransistor, photodiode, photoresistor or any other suitable light sensor. An opening  94  is formed through a portion of gate  82  . Opening  94  is positioned in gate  82  such that light emitted by transmitters  90  will pass through gate  82  when gate  82  is toward the lower reach of its rotation through detection zone  88 , as described in more detail below. The output signal from each receiver  92 , which is transmitted to controller  70 , indicates the presence or absence of gate  82  in detection zone  88 . Gravity, a torsional spring (not shown) operatively coupled between pin  86  and gate  82  or another suitable biasing mechanism biases gate  82  to the fully clockwise and lowered position shown in FIG. 5. A stop bar  96  prevents gate  82  from rotating beyond the desired lowered position.  
         [0025]    As shown in FIGS. 14 and 15, side plate position sensor  42  is mounted to frame bottom  50  at the bottom end  98  of slide plate  44 . In the embodiment shown, sensor  42  includes a fixed optical sensor  100 . The bottom end of side plate  44  acts as a gate that moves into and out of a detection zone  102  between an optical transmitter  104  and an optical receiver  106  mounted opposite one another across detection zone  102  for sensor  42 . Although an optical sensor is shown, any magnetic, electronic or electromechanical device or combination of devices suitable for detecting the position of side plate  44  may be used. Side plate position sensor  42  may be mounted at any location where it will accurately signal when side plate  42  has reached the desired raised position, as discussed in more detail below. For example, a magnetic sensor that reads a strip encoded with position information affixed to side plate  44  could be located anywhere along side plate  44 .  
         [0026]    Optical transmitter  104  may use a light emitting diode (LED), tungsten lamp, neon lamp or any other suitable source of light, preferably infrared light. Optical receiver  106  may use a phototransistor, photodiode, photoresistor or any other suitable light sensor. Sensor  42  is positioned relative to side plate bottom end  98  such that light emitted by transmitter  104  is blocked when side plate  44  is at the lower reach of its travel that, preferably, is defined by the bottom of slots  56 . The output signal from receiver  106 , transmitted to controller  70 , indicates the presence or absence of side plate bottom end  98  in detection zone  102 .  
         [0027]    A spring  108  operatively coupled between side plate  44  and frame  36  or another suitable biasing mechanism pulls down on side plate  44 .  
         [0028]    Referring now in sequence to FIGS. 5-11, clamp  34  rests with side plate  44  fully lowered and output tray  16  positioned below pressure fingers  46  a distance sufficient to allow the first document  71  to slide easily into corner  74 , as shown in FIG. 5. In this position, stack position sensor gate  82  is rotated down, opening  94  is positioned in sensor detection zone  88  for both sensors  78  and  80  (FIGS. 12 and 13) and, therefore neither sensor  78 ,  80  is blocked.  
         [0029]    In operation, document  71  is output through port  76  on to tray  16  as shown in FIGS. 5 and 6. In FIG. 7, document  71  is registered to corner  74 , and re-designated as stack  41  now that it is in the stack position. Controller  70  then energizes reversing motor  58  (FIGS. 3 and 4) to move tray  16  up to press the top of stack  41  against pressure fingers  46  and raise side plate  44  until the bottom end  98  of side plate  44  clears detection zone  102 , as best seen by comparing FIGS. 8-9 and  14 - 15 . When side plate bottom end  98  clears detection zone  102 , side plate position sensor  42  signals controller  70  that side plate  44  and pressure fingers  46  have reached the raised/clamping position shown in FIG. 9. Controller  70  then shuts down motor  58 . In this position, spring  108  is extended to pull down on side plate  44  and exert a clamping force on stack  41  through pressure fingers  46 . In this position, and referring also to the components shown in FIGS. 12 and 13, stack position sensor gate  82  is pushed up into detection zone  88  for both sensors  78  and  80  and, therefore both sensors  78 ,  80  are blocked.  
         [0030]    In FIG. 10, a second document  71  is output to stack  41  while stack  41  is clamped. Then, as shown in FIG. 11, controller  70  energizes reversing motor  58  to lower tray  16  until stack  41  drops below pressure fingers  46 , gate  82  clears detection zone  88  and stack position sensor  40  signals controller  70  that neither sensor  78 ,  80  is blocked. Controller  70  then reverses motor  58  to raise output tray  16  until gate  82  (FIG. 12) enters detection zone  88  again and stack position sensor  40  signals controller  70  that lower sensor  80  is blocked. Controller  70  then shuts down motor  58 . In this way, tray  16  is accurately positioned at the desired distance below pressure fingers  46  so that second document  71  can be registered into corner  74  and the clamping sequence is repeated until all documents have been output to the stack. When upper sensor  78  is open and lower sensor  80  is blocked, then tray  16  is in the correct position to allow registration of the next document. If both sensors  78  and  80  are open, then tray  16  is too low for next document registration. If both sensors  78  and  80  are blocked, then tray  16  is too high for next document registration.  
         [0031]    The exemplary embodiments shown in the figures and described above illustrate but do not limit the invention. Other forms, details, and embodiments may be made and implemented. Hence, the foregoing description should not be construed to limit the spirit and scope of the invention, which is defined in the following claims.