Patent Publication Number: US-2007095183-A1

Title: Sheet cutting apparatus, and sheet processing apparatus and image forming apparatus having the sheet cutting apparatus

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      This invention relates to a sheet cutting apparatus for cutting a side surface of a sheet bundle upon forming the sheet bundle with a postprocessing apparatus from sheets such as photocopying sheets conveyed out of an image forming apparatus such as a photocopier, a printer, and a facsimile machine and to a sheet processing apparatus and an image forming apparatus, which are having the sheet cutting apparatus.  
      2. Description of Related Art  
      Conventionally known methods for cutting sheet bundles are mainly a pushingly cutting method for performing cutting in hitting a cutting blade as shown in  FIG. 19 ( a ) to a reception mat, see, e.g., Japanese Unexamined Patent Publication No. Heisei 10-225,893, and a shearing method for cutting sheet bundles by pressingly contacting two blades as shown in  FIG. 19 ( b ), see, e.g., Japanese Unexamined Patent Publication No. 2000-198,613. The reception mat in the cutting machine using the pushing cutting method is in a rectangular prism shape made of a material such as generally rubber urethane molded or the like, and has a duration of times of about 300 cuts per one surface. The reception conventionally increases the cut number four times, or namely 1200 cuts at four surfaces, by using the mat as rotating the surface at a position at which the cutting is received. The replacement of the mat exceeding the duration of times is done upon confirmation of the reception mat&#39;s state by the user.  
      There are various methods for processing sheet dusts when cut, and conventionally some processings are used, for example, in which a dust box absorbs the dusts by absorbing air, and in which a rectangular prism shaped reception mat supported rotatably to an arm is moved and further rotated to remove the dusts (see, e.g., Japanese Patent Unexamined Publication No. Heisei 06-170,788).  
     SUMMARY OF THE INVENTION  
      A representative structure of the invention to accomplish the above objects is characterized in having: cutting means for cutting a sheet bundle; receiving means for receiving the cutting means; receiving position moving means for moving a receiving position on the receiving means for receiving the cutting means; and counting means for counting a number of cutting times of the sheet bundles, wherein the receiving position moving means moves the receiving position on the receiving means according to information out of the counting means. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a structural diagram showing an image forming apparatus and a sheet processing apparatus according to the first embodiment;  
       FIG. 2  is a cross section showing the sheet processing apparatus;  
       FIG. 3  is a structural diagram showing an alignment vertical path;  
       FIG. 4  is an illustration for removal of obliquely feeding in a front page path and registration alignment;  
       FIG. 5  is a diagram showing a pasting unit;  
       FIG. 6  is a diagram showing a mechanism for adhering a front page to a pasted sheet bundle;  
       FIG. 7  is a diagram showing a buffer mechanism with the alignment vertical path;  
       FIG. 8 ( a ) is a diagram showing a conveyance state of the sheet bundle from a pasting process to a rotation stage;  FIG. 8 ( b ) is a diagram showing a conveyance state of the sheet bundle from the rotation stage to a trimmer portion;  FIG. 8 ( c ) is a diagram showing a conveyance state of the sheet bundle from the rotation stage to a sheet bundle tray;  
       FIG. 9  is an illustration showing the rotation stage;  
       FIG. 10  is an illustration showing the trimmer unit;  
       FIG. 11  is an illustration showing a cutting means and a receiving means;  
       FIG. 12  is an illustration showing the cutting means and the receiving means;  
       FIG. 13  is an illustration showing a sheet bundle holding means;  
       FIG. 14  is an illustration showing a mechanism dropping dusts into a pusher by means of a mat rotation;  
       FIG. 15  is an illustration showing a controller for mat drive of the sheet processing apparatus;  
       FIG. 16  is a flowchart showing trimmer operation;  
       FIG. 17  is a flowchart showing mat rotation operation;  
       FIG. 18 ( a ) and  FIG. 18 ( b ) are illustrations for receiving means in respective belt shapes according to other embodiments; and  
       FIG. 19 ( a ) and  FIG. 19 ( b ) are illustrations for pushingly cutting method and shearing method as conventional sheet bundle cutting methods. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     First Embodiment  
      Referring to the drawings, a first embodiment of the sheet bundle apparatus according to the invention is described. A photocopier is structured in coupling an image forming apparatus body A and a sheet processing apparatus B. The sheet processing apparatus B has a function cutting after aligning, pasting, and binding sheets to which images are recorded at the image forming apparatus body A.  
      [The Whole Structure of the Image Forming Apparatus] 
      The image forming apparatus body A optically reads with a scanner section  2  original documents automatically fed from an original document feeding apparatus  1  attached to a top of the apparatus, transmits the information as a digital signal to an image forming section  3  as an example of an image forming means, and records the information on recording sheets such as plain paper and OHP sheets.  
      Plural sheet cassettes  4  containing sheets in various sizes are attached below the image forming apparatus body A, and images are recorded in an electrophotographic method at the image forming section  3  with respect to sheets conveyed from the sheet cassettes  4  with a conveyance roller  5 . That is, latent images are formed by radiation of laser beam to a photosensitive drum  3 b out of a light emitter  3 a based on the information read at the scanner section  2 , are transferred to a sheet upon being developed with toner, and are permanently fixed upon conveyance to a fixing section  6  and application of heat and pressure.  
      In a case of the one side recording mode, the sheet is fed to the sheet processing apparatus B. In a case of the double side recording mode, the sheet is conveyed to a re-feeding path  7  via a switchback and is fed into the sheet processing apparatus B after formed with images on an one side upon conveying, again to the image forming section  3 , the sheet on the other side of which images are recorded. A signal about paper size and the like is transmitted from the image forming apparatus body A to the sheet processing apparatus B before feeding the sheets, thereby performing switching of the paths in the sheet processing apparatus B in advance.  
      It is to be noted that sheet feeding can be done not only from the sheet cassettes  4  but also from a multi-tray  8 .  
      As shown in  FIG. 2 , the sheet processing apparatus B is structured of a conveyance alignment unit C and a trimmer unit D, and can selectively do bookbinding with pasting and cutting in addition to the normal delivery mode. Cutting, in the sheet processing apparatus B, can be made in three directions other than the pasting edge.  
      The sheets P delivered from the image forming apparatus body A to the sheet processing apparatus B according to the embodiment are conveyed with conveyance roller pairs  10   a,    10   b,    10   c,    10   d  serving as examples of sheet conveying means during the normal mode, and is then delivered on a stacking tray  11 . During the bookbinding with pasting mode, the sheets are delivered to a stacking tray E after processed with a prescribed treatment described below.  
      [Stacking on the Alignment Vertical Path] 
      During the bookbinding mode, the sheet P delivered from the image forming apparatus body A is fed to a bookbinding intermediate paper path  14  by operation of a first flapper  12  and a second flapper  13 . The first flapper  12  switches the path between a non-sorting path  15  and a top page path  16 , and the second flapper  13  switches the path between the bookbinding intermediate paper path  14  and the top page  16 .  
      As shown in  FIG. 3 , the sheets P conveyed by the conveyance roller pairs  10   a,    17   a,    17   b  are aligned in a sheet conveyance direction by returning a rear end of the sheet P to a position contacting to a rear end stopper  20  in aid of a half moon roller  19  and a delivery roller pair  18  after delivered to the alignment vertical path  35  by the delivery roller pair  18 . The sheet P is pushed in a direction of the sheet center by an alignment plate  21 , so that the sheets P are aligned in a direction perpendicular to the sheet conveyance direction.  
      The rotation speed of the delivery roller pair  18  is controlled to be a low speed when the rear end of the sheet P passes through the delivery roller pair  18 . This renders the sheet P delivered in the alignment vertical path  35  surely pulled into the roller by rotation of the half moon roller  19 , thereby making the rear end alignment.  
      It is to be noted that whether the rear end of the sheet passes by the delivery roller pair  18  is judged in passing a prescribed period of time after the sheet P passes by the delivery sensor  22  or in detecting the rotation number of the motor.  
      [Half Moon Roller] 
      Next, the half moon roller  19  for pulling back, in a direction reverse to the delivery direction, the sheet P delivered on the alignment vertical path  35 , is described.  
      As shown in  FIG. 3 , the half moon roller  19  is in a shape of a half moon cut out, and the cutout portion of the half roller  19  is normally positioned on a side of the alignment vertical path  35 , thereby not disturbing the delivery of the sheet P which is delivered by the delivery roller pair  18 . The half moon roller  19  rotates in the reverse direction to the sheet delivery direction at each sheet delivery of the sheets P on the alignment vertical path  35 , and pulls back the sheet P by frictional force produced between the sheet P and the roller  19  upon contacting to the rear end of the sheet P on the alignment vertical path  35 .  
      [Alignment Vertical Path Plate] 
      The alignment vertical path plate  36  is movable in a direction of arrow a set forth in  FIG. 3  by an alignment vertical path motor, not shown, thereby adjusting a distance between the paths of the alignment vertical path  35 . According to the sheet number of the sheet delivered on the alignment vertical path  35  to maintain contact pressure to the topmost sheet delivered onto the alignment vertical path  35  at approximately a constant amount with respect to the half moon roller  19 , the alignment vertical path plate  36  is moved in a direction widening the path.  
      [Operation Timing of the Half Moon Roller] 
      With respect to operation timing of the half moon roller  19 , the roller  19  operates after the delivery roller pair  18  releases the rear end of the sheet P. More specifically, the half moon roller  19  rotates in a direction reverse to the sheet delivery direction after passing a predetermined period of time after the rear end of the sheet P passes by a delivery sensor  22  formed on an upstream side of the delivery roller pair  18 .  
      [Top Page Path] 
      The sheet P delivered from the image forming apparatus body A is fed to the top page path  16  in association with the first flapper  12  and the second flapper  13 .  
      As shown in  FIG. 2  and  FIG. 4 , a registration roller pair  23  is disposed at a midway of the top page path  16 , and a registration front end sensor  23   a  is disposed on an upstream side of the registration roller pair  23 . The registration roller pair  23  stops at a time when the top page sheet P 2  is guided to the top page path  16 , and begins rotating after a prescribed time passes after the front end of the top page sheet P 2  comes in contact with the registration roller pair  23 . Whether the front end of the top page sheet P 2  contacts to the registration roller pair  23  can be judged by passing the prescribed period of time after the top page sheet P 2  passes the registration front end sensor  23   a  or by detecting the motor rotation number.  
      With this control, a loop can be made at a front end of the top page sheet P 2  guided to the top page path  16 , and obliquely feeding of the top page sheet P 2  can be corrected.  
      The registration roller pair  23  is movable in a direction perpendicular to the sheet conveyance direction with a rack  38  via a top page motor  37 . The registration roller pair  23  moves in a direction of b in  FIG. 4  as contacting with pressure to and conveying the top page sheet P 2  after the rear end of the top page sheet P 2  passes by the conveyance roller pair  17   a,  moves in a direction of c after the registration sensor  24  is shielded, and stops upon movement of a prescribed amount after the registration sensor  24  is released. Because the registration sensor  24  is disposed at a paper end position of the sheet bundle P 1  in the alignment vertical path  35 , the top page sheet P 2  in the top page path  16  and the sheet bundle P 1  in the alignment vertical path  35  are moved to a position shifted by a prescribed amount in a direction perpendicular to the sheet conveyance direction.  
      The registration roller pair  23  receives a paper size signal from the image forming apparatus body A and stops upon conveying the top page sheet P 2  within the top page path  16  in a prescribed amount according to the paper size.  
      [Gripper] 
      A gripper  41  is located below the alignment vertical path  35 , grips the sheet bundle P 1  stacked on the alignment vertical path  35 , and has a function for guiding the bundle to the top page sheet P 2 .  
      [Pasting Unit] 
       FIG. 5  shows a diagram of a pasting unit  25 . As shown in  FIG. 5 , the pasting unit  25  is structured of a paste pot  25   a,  a pasting roller  25   b,  a paste  25   c,  a paste pot heater  25   d,  a shaft  25   e,  and a pot driver  25   f.    
      The paste pot  25   a  is movable more than the sheet width in a sheet width direction perpendicular to the sheet conveyance direction along the shaft  25   e,  has escaping positions at two locations outside the sheet width, and moves in association with the pot driver  25   f.  According to movement from the first escaping position to the second escaping position, a portion of the paste pot  25   a  pushes a part of a link  26  coupled to a rear end stopper  20 , thereby moving the rear end stopper  20  in a direction escaping from a lower portion of the sheet bundle P 1  in  FIG. 3 . The paste roller  25   b  is arranged at the paste pot  25   a  and rotates in synchrony with the movement of the paste pot  25   a.    
      The pot heater  25   d  is attached to the exterior of the paste pot  25   a,  and the pot heater  25   d  heats the paste pot  25   a  at the beginning of the bookbinding mode, thereby melting the paste  25   c  in the paste pot  25   a.  The melted paste  25   c  reaches out the entire outer peripheral surface of the paste roller  25   b  because the paste roller  25   b  rotates in association with movement of the paste pot  25   a  driven by the pot driver  25   f.    
      The sheet bundle P 1  stacked in the alignment vertical path  35  is held with the gripper  41 , and the paste  25   c  is coated on a lower end surface at the pasting unit  25  upon escaping the rear end stopper  20  from the lower portion of the sheet bundle P 1  where the paste pot  25   a  moves from the first escaping position to the second escaping position.  
      [Bookbinding Process] 
      As shown in  FIG. 6 ( a ), a shutter path  27  is positioned on a downstream side of the top page path  16 , and the shutter path is closed while the top page sheet P 2  is conveyed.  
      During the bookbinding process the shutter motor  28  drives the shutter rack  29  as shown in  FIG. 6 ( b ), and a spring  30  engaging the shutter path  27  with the shutter rack  29  moves the shutter path  27  up to the opening position. After the shutter path  27  is opened, the shutter path  27  comes in contact with a stopper, not shown, so that the shutter path  27  stops.  
      After the paste  25   c  is coated on the sheet bundle P 1  held at the gripper  41 , the gripper  41  is moved as to render the sheet bundle P 1  with paste come in contact with the top page sheet P 2  on a folding line application table  34 , thereby contacting the sheet bundle P 1  with the top page sheet P 2 .  
      Subsequently, as shown in  FIG. 6 ( c ), when the shutter motor  28  is driven, a cam  32  driven with a belt  31  from the shutter motor  28  further rotates to make the folding line application table  34  slide in association with a guide shaft  33 . Folding lines are given for a prescribed period of time with the folding line application table  34 , thereby completing a bookbinding sheet P 3 .  
      It is to be noted that an escaping mechanism is formed at the folding line application table  34  as to correspond to changes of the paper thickness. Furthermore, as shown in  FIG. 6 ( d ), rotation of the cam  32  escapes the folding line application table  34 , and the bookbinding sheet bundle P 3  is pushed toward a downstream side with a pushing roller  39  and conveyed to a bundle curvature path  40 .  
      [Buffer Mechanism] 
      A buffer mechanism  50  temporarily escaping the sheets P conveyed from the image forming apparatus body A during the sheet postprocessing period such as bookbinding with pasting or the like, is described.  
      The buffer mechanism  50  has a structure movable in the same direction to as well as in a direction perpendicular to the sheet conveyance direction as shown in  FIG. 3  and  FIG. 7 . Where the buffer mechanism  50  moves in the same direction to the conveyance direction, an electromagnetic clutch gear  50   c  only is operated to transmit the motor&#39;s drive, and the buffer mechanism  50  is moved upon transmitting the drive to a rack  50   e  via a gear  50   d.    
      At that time, utilizing a photo sensor  50   f  and a protrusion formed at one end of the buffer mechanism  50  for shielding the photo sensor, a position and an amount of movement in the same direction to the conveyance direction of the buffer mechanism  50  are controlled.  
      When movement is made in a direction perpendicular to the conveyance direction, a current is sent to only the electromagnetic clutch gear  50   g  thereby rendering the drive of motor transmit. The drive is transmitted to the rack  50   b  via the gear  50   h,  thereby moving a reception table  50   a.    
      At that time, utilizing a photo sensor  50   i  and a protrusion formed at one end of the rack  50   b  for shielding the photo sensor, a position and an amount of movement in a direction perpendicular to the conveyance direction of the reception table  50   a  of the buffer mechanism  50  are controlled.  
      The reception table  50   a  of the buffer mechanism  50  escapes outside of the width of the sheet P in  FIG. 7  except a situation that the sheet P has to be buffered, so that the table  50   a  will not disturb the sheet conveyance.  
      The basic operation of the buffer mechanism  50  is described. First, as shown in  FIG. 3 , a sheet bundle P 1  stacked and aligned at the alignment vertical path  35 , and it is assumed that the sheet bundle is not yet delivered from the alignment vertical path  35 . At that time, the reception table  50   a  is moved in a sliding manner to a position receiving the sheet P shown in  FIG. 7  from the escaping position so as not to disturb the conveyance of the sheet P to buffer the sheet P successively conveyed from the image forming apparatus body A.  
      Where the sheet bundle P 1  is delivered from the alignment vertical path  35 , the buffer mechanism  50  is moved in the same direction to the conveyance direction, or namely in a direction toward the rear end stopper  20  shown in  FIG. 7 . When the rear end of the buffered sheet P is supported to the rear end stopper  20 , the movement is stopped, and the reception table  50   a  is moved to an escaping position. Finally, the buffer mechanism  50  is returned in a direction reverse to the rear end stopper  20  and moves to the initial escaping position (home position) to end the operation. The above operation is repeated until completion of the targeted number of the booking binding process.  
      [Rotary Stage] 
      Referring to  FIG. 8 ,  FIG. 9 , a rotary stage  301  for rotating the bookbinding sheet bundle P 3  that has been subject to bookbinding and for conveying the bundle in the trimmer unit D.  
      As shown in  FIG. 8 ( a ), a bundle conveyance unit  302  rotates around a rotary shaft  315  as a center upon winding a wire  305 . The wire  305  is secured to an up down gear driven with an up down motor  303 . When a sensor  306  detects a protrusion  302   a  on the bundle conveyance unit  302 , the up down motor  303  is stopped to render the bundle conveyance unit  302  wait at a position in  FIG. 8 ( a ).  
      The bookbinding sheet bundle P 3  bookbinded at the bookbinding step is conveyed with a bundle conveyance roller pair  307 . A first conveyance belt  309 , a second conveyance belt  310 , a third conveyance belt  320 , and a fourth conveyance belt  321  are driven with a conveyance belt motor F 322  and a conveyance belt motor R 323  at a timing that the front end of the bookbinding sheet bundle P 3  is detected with a sensor  308  and rotate in the arrow direction.  
      The bookbinding sheet bundle P 3  is conveyed in a conveyance path  311  of the bundle conveyance unit  302  with the bundle conveyance roller pair  307 . The up down motor  303  rotates reverse at a time that the rear end of the bookbinding sheet bundle P 3  passes by the sensor  308  to render the bundle conveyance unit  302  move to the position in  FIG. 8 ( b ). When a sensor  312  detects the protrusion  302   a  on the bundle conveyance unit  302 , the drive of the up down motor  303 , the conveyance belt motor F 322 , and the conveyance belt motor R 323  is stopped, thereby rendering the bookbinding sheet bundle P 3  wait in a state as nipped between the conveyance belts  310 ,  321  and a weight roller  314  located at a weight  313 .  
      The bookbinding sheet bundle P 3  is aligned with alignment plates F 315 , R 316  driven with a motor, not shown, at this timing and is positioned on the side of the alignment plate R 316 . Because the bookbinding sheet bundle P 3  at that time is bookbinded as the top page is shifted when this bookbinding is made with the alignment vertical path  35  and the top page path  16 , the edge of the bookbinding sheet bundle P 3  can be positioned with a high accuracy on the side of the alignment plate R 316  when aligned with the alignment plates. Where the motor, not shown, drives the timing belt  317  at the same time, a hitting plate  318  moves up to a designated position from the position of the sensor  319 , thereby conveying the bookbinding sheet bundle P 3  in the trimmer unit D. At that time, the bookbinding sheet bundle P 3  is conveyed as three edges are restricted by the alignment plates F 315 , R 316  and the hitting plate, thereby improving the conveyance accuracy up to the trimmer portion.  
      When cutting starts at the trimmer unit D, the alignment plates F 315 , R 316  and the hitting plate  318  move to the home position and wait. When cutting completes, the conveyance belts  309 , 310 ,  320 ,  321  rotate in the counterclockwise direction to convey the bookbinding sheet bundle P 3  nipped with the weight roller  314  to a place at which the weight roller  314  is located near the center of the bookbinding sheet bundle P 3 , and the conveyance belts  309 , 310 ,  320 ,  321  stop at that position.  
      Thereafter, the conveyance belts  309 ,  310  and the conveyance belts  320 ,  321  rotate the in a direction opposite to each other as shown in  FIG. 9 , thereby rotating  90  degrees the bookbinding sheet bundle P 3  around the weight roller  314  as a center. After rotation of 90 degrees, the conveyance belts  309 ,  310 ,  320 ,  321  are stopped, and the bookbinding sheet bundle P 3  is aligned again by the alignment plates F 315 , R 316  and the hitting plate, is conveyed to the prescribed position in the trimmer unit D, and is subject to cutting.  
      After the bookbinding sheet bundle P 3  is then conveyed to the weight roller  314  in the same operation, the bundle is rotated by 180 degrees to be loaded again in the trimmer unit D and to be cut. The bookbinding sheet bundle P 3  after completion of cutting is conveyed to the weight roller  314 , and after rotated by 90 degrees, the bookbinding sheet bundle P 3  is conveyed to the stacking tray E upon rotating the conveyance belts  309 ,  310 ,  320 ,  321  in an arrow direction in  FIG. 8 ( c ). At the same time, the rear end of the bookbinding sheet bundle P 3  being conveyed is operated as to be pushed out by rotating a hitting plate  318  in one turn in the arrow direction, thereby delivering the bookbinding sheet bundle P 3  surely on the stacking tray E.  
      [Trimmer Structure] 
      Referring to  FIG. 2  and FIGS.  10  to  13 , a structure of the trimmer unit D is described. The trimmer unit D is aiming to finish the sheet bundles with high quality and makes cutting at three edges of the sheet bundles bookbinded with pasting except the edge with pasting in use of the pasting unit  25 .  
       FIG. 10  is a diagram showing the trimmer unit D. A cutting blade  81  is formed as an example of a cutting means for cutting the bookbinding sheet bundle P 3 . As shown in  FIG. 11 ( a ),  FIG. 11 ( b ), the shape of the cutting blade  81  is in a plate shape or a disc shape, and the blade has an inclined face on one side only.  
      Where the cutting blade  81  is in a plate shape, the cutting blade  81  performs cutting as moving reciprocally parallel with respect to the cutting surface. It is like as a similar motion a motion of cutting wood with a saw. Because the cutting blade  81  necessarily rides always on the bookbinding sheet bundle P 3  even while moving thus, the longitudinal direction is required to be longer than the maximum sheet size. For example, if the maximum sheet size is in the longitudinal direction of A4 size, the length is needed more than 297 mm plus the moving distance of the cutting blade  81 .  
      The cutting blade  81  is secured to a longitudinal direction moving member  82  capable of sliding only parallel to the cutting face of the bookbinding sheet bundle P 3 . The longitudinal direction moving member  82  is supported to rollers  83   a,    83   b,  and the rollers  83   a,    83   b  move only parallel with respect to the cutting face in the longitudinal direction along hitting portions  84   a,    84   b  of the longitudinal direction moving member  82 . The parallel movement in the longitudinal direction is done by a horizontal motor  85 , and drive is transmitted to a rotation receiver  87  via a rotary cam  86  to render the longitudinal direction moving member  82  move reciprocally. The speed of the reciprocal movement can be changed freely by equipping an encoder at the horizontal motor  85 . The encoder counts up the number of the reciprocal movement in the longitudinal direction, and the information is submitted to a CPU  200  in  FIG. 15 , thereby informing the user of the replacement period of the cutting blade  81  upon comparative execution of the information and the prescribed number stored in the CPU  200  in advance.  
      The movement of the cutting blade  81 in the thickness direction of the bookbinding sheet bundle P 3  is done by a vertical movement member  88 , and where posts  89   a,    89   b  coupling to a housing are provided at each end of the bookbinding sheet bundle P 3 , the cutting blade  81  moves in a vertical direction along grooves of the posts  89   a,    89   b.  Because the vertical movement member  88  has the rollers  83   a,    83   b  supporting the longitudinal direction moving member  82 , the cutting blade  81  moves in the vertical direction according to the vertical movement of the longitudinal direction moving member  82 . Pulling spring  90   a,    90   b  are formed at the vertical movement member  88  to apply a load to the cutting blade  81 . The cutting blade  81  is structured as to always receive the load in the thickness direction of the bookbinding sheet bundle P 3  by the pulling springs  90   a,    90   b  through the vertical movement member  88  and to move downward.  
      Furthermore, as shown in  FIG. 13 , a sheet pusher  103  pushes the bookbinding sheet bundle P 3  as contracting a paper pushing spring  101  upon movement of a linkage  100  to a lower pivotal center position according to rotation of a cam  99  by the drive of a vertical motor  104  (see,  FIG. 15 ). An attachment member of the linkage  100  is separated from a contacting member  88   a  of the vertical movement member  88 , and the cutting blade  81  pushes and cuts the bookbinding sheet bundle P 3  by the pulling springs  90   a,    90   b  via the vertical movement member  88 . This mechanism also serves as a mechanism lifting up the cutting blade  81 . The attachment member of the linkage  100  hits the contacting portion  88   a  of the vertical movement member  88  when the cam  99  rotates to move the linkage  100  up to the upper pivotal center position and to disengage the sheet pusher  103 , thereby rendering the cutting blade  81  move upward in the thickness direction of the bookbinding sheet bundle P 3  via the vertical movement member  88 . Those mechanisms allow the cutting blade  81  up and down reciprocally movable in the thickness direction.  
      As shown in  FIG. 10 , a blade position sensor flag  105  is provided at the vertical movement member  88 , and a blade position sensor  102  is arranged at a post  89   a  to detect the flag. Cutting of the bookbinding sheet bundle P 3  done by the cutting blade  81  is performed until that the blade position sensor flag  105  detects the blade position sensor  102 . Counting of the cutting times is done by counting up the detection signal from the blade position sensor  102 .  
      A mat  91  as an example of a receiving means for the cutting blade  81  is arranged at a lower portion of the bookbinding sheet bundle P 3  to prevent the cutting blade  81  from receiving damages. The material of the mat  91  is preferably of a soft material, such as rubber, molded materials, or urethane. The shape of the mat  91  in this embodiment is in a roller shape having a cross section in a circular shape, and the mat  91  is rotatable in an arrow direction shown in  FIG. 14  in association with rotation of a mat rotation motor  92  described below.  
      With such a structure of the mat  91 , a gap to the roller surface can be maintained at a fixed amount with a scraping member or the like, so that cutting dusts attached to the surface can be scraped off easily. That is, if the roller is in a rectangular shape as in the conventional example, the gap between the scraping member and the rectangular roller may be deviated larger or smaller when the roller is rotated at the position as in this embodiment, so that there raises a problem that dusts attached to the surface may not be scraped off effectively. Where the mat  91  is rotated, the cutting dusts P 4  after cutting can be dropped upon moved to a dust box  98  as an example of a storing means.  
      The mat  91  in a roller shape is structured so that a rubber layer is formed with pressure or with a thermal treatment on a surface of a metal shaft or a metal pipe shaft. This structure brings a rigidity to some extent to the roller-shaped mat  91  itself, so that the cut position is not bent even where receiving the pushing force from the cutting blade  81  during cutting of the bookbinding sheet bundle P 3 .  
      As shown in  FIG. 12 , before any groove is formed on the mat  91  by the cutting operation, the bookbinding sheet bundle P 3  is cut upon moving a blade receiving position to a new region at which no groove is formed by rotatively moving the receiving position of the cutting blade  81  at each cutting operation. This makes the durability of the mat  91  extended, thereby avoiding troubles from occurring such that some groove is formed on the mat  91  due to contacts between the mat  91  and the cutting blade  81  at many times to render the cutting face of the lowermost sheet of the sheet bundle (or namely a sheet directly contacting to the mat  91 ) rough or to render the sheet bundle cut completely.  
      The mat  91  experimentally has durability against cutting of 200 to 300 times at a position. Therefore, with the mat  91 , cutting of 300 times can be done at a position. The mat  91  slightly moves rotatively by a prescribed amount (e.g., 5 degrees in this embodiment) to shift the blade reception position during the cutting operation after the dust treatment operation. Accordingly, the mat  91  can be used for cutting at 72 portions as 360 degrees divided by 5 degrees, where durable against 300-time cutting per one position, so that the mat  91  can have durability against 21600 time cutting as cutting of 72 positions for one turn of the mat multiplied by 300 times at one position.  
      Although in this embodiment the blade reception position is controlled to rotatively move at each cutting, control is possible such that the blade reception position may be the same until reaching 300 times of cutting and that the mat  91  rotatively moves by five degrees upon 300 time cutting. Although in this embodiment the rotational moving amount of the mat  91  is set as 5 degrees, the amount is not limited to five degrees according to the shape or the like of the mat  91  and can be set freely as to move a slight amount.  
      As an example of a cutting blade receiving position moving means, drive force is transmitted from a mat rotary motor  92  via a gear  93  and a drive belt  94 , thereby rotatively moving the mat  91 . The rotary moving amount of the mat  91  is controlled by controlling the mat rotation motor  92  where the CPU as described below receives information from a mat sensor flag  95  and a mat sensor  96  serving as a moving amount detecting means. The information about the cutting times and the cutting position is memorized in the CPU  200 . Even where the power supply of the image forming apparatus is cut off, the cutting operation begins at the next cutting at a position proceeded by a prescribed amount (or 5 degrees in this embodiment) from the receiving position at the time of power-off. The cutting time is counted up, and the information thereof is sent to the CPU  200 , so that the replacement period can be informed to the user at a time reaching the duration times of the mat  91  upon comparative execution of the information above and the prescribed times memorized in the CPU  200  in advance. Otherwise, the CPU can detect the cutting position on the mat  91 (the moving amount detecting means) according to information from the mat sensor  96 , and the replacement period can be informed to the user, for example, when the cutting position carries out on the mat  91  for one round.  
      The mat  91  after completion of the cutting operation is rotated to remove the cutting sheet dusts P 4  on the mat  91 , thereby dropping the cutting sheet dusts P 4  in the dust box  98 . For example, the mat  91  is rotated twice with the mat rotation motor  92  to drop the cutting sheet dusts P 4 . After twice rotated, the mat  91  waits at a reception position proceeding from the previous cutting position by the prescribed amount (or  5  degrees in this embodiment) for preparing the subsequent cutting operation. The cutting dusts P 4  dropped from the mat  91  are dropped in front of the pusher  97  according to the rotation of the mat  91  as shown in  FIG. 14  and are conveyed to the dust box  98  with the pusher  97  movable by a motor not shown.  
      [Structure of the Controller Regarding Mat Rotation Drive in the Sheet Processing Apparatus] 
      Now, referring to  FIG. 15 , the structure of the controller regarding the drive of the mat  91  according to this embodiment is described briefly.  
      In  FIG. 15 , as a controlling means, numeral  200  is a central processing unit (CPU) performing controlling in executing programs memorized in ROM. Numeral  201  is a read only memory (ROM) storing a control program for controlling the sheet processing apparatus B, which serves for control programs corresponding to control steps shown in  FIG. 16  and  FIG. 17  and control steps for other portions. Numeral  202  is a random access memory (RAM) for storing operation data used for execution of the above control programs in the CPU  200 , control data sent from the image forming apparatus body A, count data about cutting times as described below, various work data, and input data. The CPU  200  executes the control programs based on the control data sent from the image forming apparatus body A and the control programs stored in the ROM  201  in association with various data or the like in the RAM  202 , as well as based on the information from the various sensors electrically coupled thereto, thereby controlling drives of the various motors and the entire sheet processing apparatus B, and performing telecommunications with the sheet processing apparatus B and the image forming apparatus body A.  
      The CPU  200  inputs signals from the blade position sensor  102  used for count signals of cutting completion detection and cutting times, the mat sensor  96  used for the rotation amount of the mat  91  and controlling of the blade receiving position movement, and the like.  
      The movement amount and the speed of the horizontal motor  85 , the mat rotation motor  92 , the vertical motor  104 , and the like are controlled by control input pulses and encoder inputs detecting the rotation amount via the respective drivers D 1 , D 2 , D 3  based on the signals.  
      [Operation of the Trimmer] 
      With the trimmer and the controller thus constituted, in reference to a flowchart shown in  FIG. 16  from the conveyance of the bookbinding sheet bundle P 3  to the dust processing and a flowchart shown in  FIG. 17  relating to the rotation of the mat  91 , the operation of the trimmer unit D and the operation of this embodiment are described.  
      As shown in  FIG. 16A , the CPU  200  controls to drive the conveyance belt motor F 322  and the conveyance belt motor R 322  based on such as paper size and set trimming width information from the image forming apparatus body A, thereby conveying the bookbinding sheet bundle P 3  located on the rotary state  301  and conveying the sheet bundle up to the prescribe cutting position (S 1 ). The trimming width of the bookbinding sheet bundle P 3  at that time is about, e.g., 2 to 20 mm.  
      After the bookbinding sheet bundle P 3  is conveyed, the CPU  200  drives the vertical motor  104  and controls rotatively the cam  99  until that the linkage  100  reaches the lower pivotal center position. The linkage  100  contracts the paper pushing spring  101  and concurrently pushes the bookbinding sheet bundle P 3  with the sheet pusher  103  (S 2 ). The cutting blade  81  via the vertical movement member  88  also moves according to the movement of the linkage  100  together with the sheet pusher  103  at that time, so that the cutting blade  81  contacts to a surface of the bookbinding sheet bundle P 3  (S 3 ).  
      After completion of pushing the bookbinding sheet bundle P 3 , the CPU  200  drives the horizontal motor  85  to move reciprocally the cutting blade  81  in the vertical direction with respect to the sheet bundle thickness direction via the rotary cam  86  and the longitudinal direction movement member  82 . In association with the reciprocal movement, cutting the bookbinding sheet bundle P 3  starts (S 4 ), and the cutting blade  81  is pulled by the pulling springs  90   a,    90   b  and moves in the thickness direction of the bookbinding sheet bundle P 3  while cutting the bookbinding sheet bundle P 3 . Cutting operation done by reciprocal movement of the cutting blade  81  continues until the detection of the blade position sensor  102  by the blade position sensor flag  105  (S 5 ).  
      The signal of cutting completion of the blade position sensor  102  by the blade position sensor flag  105  is sent to the CPU  200 , and is memorized in the RAM  202  as the sheet cutting times as described below (S 6 )  
      As shown in  FIG. 17 , after completion of cutting the bookbinding sheet bundle P 3 , the CPU  200  drives the vertical motor  104  again, controls to rotate the cam  99  until that the linkage  100  reaches the upper pivotal center position, disengages the sheet pusher  103  (S 7 ), and renders the cutting blade  81  escape from the mat  91  at the same time (S 8 ). Cutting sheet dusts P 4  may be dropped in the dust box  98  and may be remaining on the mat  91 . As a processing operation for the cutting sheet dusts P 4 , as shown in  FIG. 14 , the CPU  200  drives the mat  92  to rotate the mat  91  twice (S 9 ), thereby compulsively dropping the cutting dusts P 4  in front of the pusher  97  without remaining the cutting sheet dusts P 4  on the mat  91  (S 10 ). Although in this embodiment the rotary amount to drop off the cutting sheet dusts P 4  is twice, the rotation amount can be set arbitrarily because the CPU  200  can control upon detecting the rotation amount with the mat sensor  96  described below.  
      The rotation amount information of the mat  91  thus rotated by the mat rotation motor  92 , the gear  93 , and the drive belt  94  is sent to the CPU  200  upon detection by the mat sensor flag  95  and the mat sensor  96  (S 11 ). The CPU  200  controls to drive the mat rotation motor  92  based on the information, controls to return the mat  91  to the original receiving position after rotating, e.g., twice the mat  91  as describe above to drop off cutting sheet dusts P 4 , and then controls the mat  91  to wait at the position slightly moved rotatively by the prescribed amount (five degrees in this embodiment) to move the receiving position of the cutting blade  81  as a preparation for the subsequent cutting (S 12 ). Accumulation of the movement mount of the mat  91  slightly rotatively moved in the prescribed amount (five degrees in this embodiment) from the receiving position of the cutting blade  81  is memorized in the RAM  202  in the CPU  200  (S 13 ). It is to be noted that because the information regarding the receiving position of the cutting blade  81  is memorized in the RAM  202  even where the power supply for the image forming apparatus is cut off, the mat  91  can wait so as to receive the cutting blade  81  at the subsequent cutting position based on the information when the image forming apparatus is turned on again.  
      As shown in  FIG. 16B , the CPU  200  comparatively executes the cutting time memorized in a manner of a counter value in the RAM  202  inside the CPU  200  with the prescribed times memorized in the ROM  201  inside the CPU according to the detection signal of the blade position sensor  102  as described above, and sends a replacement sign of the mat  91  to the CPU of the image forming apparatus if the counted cutting number reaches the durable time of the mat  91  (S 14 ). The CPU  200  can inform the user of the replacement period of the mat  91  by displaying at a display of the sheet processing apparatus or the image forming apparatus or by informing with voice or the like (S 15 ).  
      Although in this embodiment the replacement sign of the mat  91  is generated upon comparison with the cutting number, the apparatus can be so controlled that the replacement sign of the mat  91  is provided based on comparative execution of the mat movement amount from the receiving position of the cutting blade  81  of the mat  91  with the prescribed value memorized in the ROM  201  in advance. For example, with a control that the receiving position is moved slightly rotatively to repeat the cutting operation at the subsequent position where a prescribed number of cutting is made at a cutting receiving position and where the cutting number reaches the cutting number permissive at the same cutting receiving position, it is enough and effective to comparatively execute the accumulation of the movement amount.  
      In this embodiment, the CPU  200  controls as described above where disposed in the sheet processing apparatus, but can be disposed in the sheet cutting apparatus or the image forming apparatus and can make control directly as described above.  
      As shown in  FIG. 16C , the cutting dusts P 4  dropped off from the surface of the mat  91  by the rotation of the mat  91  (S 16 ) are conveyed by the pusher  97  (S 17 ), and then dropped off in the dust box  98  (S 18 ). After the rotary operation for the dust processing of the mat  91 , the CPU  200  judges the cutting direction of the bookbinding sheet bundle P 3  based on the sheet bundle cutting times memorized in the RAM  202 , and if three directions of the bookbinding sheet bundle P 3  are not cut (No at S 19 ), the CPU sends the sheet bundle to the rotary stage  301  as described above to rotate the bookbinding sheet bundle P 3  by  90  degrees (S 20 ) and to return the operation to S 1 . If the CPU  200  judges that three directions of the bookbinding sheet bundle P 3  are cut (Yes at S 19 ) as described above, the bookbinding sheet bundle P 3  is delivered to the stacking tray E by the rotary stage  301  (S 21 ).  
     Other Embodiments] 
      With reference to FIGS.  18 ( a ), ( b ), other embodiments of the sheet processing apparatus according to the invention are described. Portions overlapping as descriptions in the first embodiment are omitted upon assigning the same reference numbers.  
      In this embodiment, as a receiving means as shown in FIGS.  18 ( a ),  18 ( b ), in lieu of the mat  91  exemplified in the first embodiment, a rotary belt  401  in a belt shape made of an elastic body is provided. With this belt, the area of the receiving portion of the cutting blade  81  is widened, and the receiving position can be used widely by a length portion of the rotary belt  401  by driving the rotary belt  401 , so that the durability of the rotary belt  401  can be improved.