Patent Publication Number: US-9421796-B2

Title: Sheet processing apparatus and image forming system

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     The present invention claims priority under 35 U.S.C. §119 to Japanese Application No. 2014-240923 filed Nov. 28, 2014, the entire content of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet processing apparatus and an image forming system. 
     2. Description of Related Art 
     Sheet processing apparatuses that perform trimming to cut off a part of a sheet, such as fore edge trimming to trim the fore edge of a saddle-stitched booklet, have been known in the art. 
     Typically, an apparatus for trimming includes a container to collect chips produced in the trimming process and is configured such that a detector detects whether the top of chips piled up in a mountain shape in the container has reached a predetermined height. For example, when the detector detects that the top of the piled chips has reached the full level of the container, it is notified to a user so that he/she can take out the container from the apparatus to dispose the chips. 
     In such apparatuses, it is desirable that chips are collected in a container with leaving as little space as possible in order to reduce a burden on the user of disposing the chips. For this reason, a proposal has been made in which a container moves back and forth so as to flatten the piled chips in the container (e.g. see JP 2014-043328A). 
     However, a problem with the technique of JP 2014-043328A is that when a chip sticks to a detecting area of the detector, for example, due to reasons that the chip is electrostatically charged or a part of the chip gets stuck inside the apparatus, the detector erroneously detects it even though the top of the piled chips has not reached the predetermined height yet. 
     SUMMARY OF THE INVENTION 
     The present invention was made in view of the above-described problem with the prior art, and an object thereof is to provide a sheet processing apparatus and an image forming system that can correctly detect that the top of piled chips has reached a predetermined height while they perform processing that produces a chip. 
     In order to realize the above object, according to a first aspect of the present invention, there is provided a sheet processing apparatus, including: 
     a trimming section which performs trimming to trim a sheet or sheet set; 
     a container which collects a chip produced by the trimming in the trimming section; 
     a detector which detects a presence of the chip at a predetermined height; and 
     a control section which controls the trimming section, 
     wherein the control section makes the trimming section perform the trimming of a next sheet or sheet set when the detector detects the chip and then determines that a top of piled chips in the container has reached the predetermined height when the detector still detects the presence of the chip after the trimming of the next sheet or sheet set. 
     Preferably, the sheet processing apparatus further includes a movable part which is disposed above the detector and which comes in contact with the chip produced by the trimming in the trimming section to apply a force in at least one of horizontal and downward directions. 
     Preferably, in the sheet processing apparatus, the movable part comprises a movable member that extends in a width direction of the sheet. 
     Preferably, in the sheet processing apparatus, the movable member comprises a rotating shaft which extends in the width direction of the sheet and fins which are disposed on the rotating shaft. 
     Preferably, in the sheet processing apparatus, the control section makes the trimming section perform the trimming of a next plurality of sheets or sheet sets when the detector detects the chip and which then determines that the top of the piled chips in the container has reached the predetermined height when the detector still detects the presence of the chip after the trimming of the next plurality of sheets or sheet sets. 
     Preferably, the sheet processing apparatus further includes an estimating section which estimates the amount of free space of the container, wherein the control section selects the number of times of the trimming that the trimming section performs to the next plurality of sheets or sheet sets according to the amount of free space of the container estimated by the estimating section. 
     Preferably, in the sheet processing apparatus, the control section makes the trimming section perform the trimming of the next sheet or sheet set when the detector detects the chip and which then determines that the top of the piled chips in the container has reached the predetermined height when the detector still detects the presence of the chip after a predetermined time has elapsed since the trimming of the next sheet or sheet set. 
     According to a second aspect of the present invention, there is provided an image forming system, including: 
     an image forming apparatus which forms an image on a sheet or sheet set; and 
     the sheet processing apparatus which is connected with the image forming apparatus and which performs trimming of the sheet or sheet set on which the image is formed by the image forming apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other objects, advantages and features of the present invention will become more fully understood from the detailed description given herein below and the appended drawings which are given by way of illustration only, and thus are not intended as a definition of the limits of the present invention, and wherein: 
         FIG. 1  is a schematic view illustrating the entire configuration of an image forming system; 
         FIG. 2  illustrates an example of a configuration including a clamping section and a trimming section; 
         FIG. 3  illustrates an example of the configuration of a trimming section; 
         FIG. 4  is a schematic view illustrating an example of the configuration of a movable part; 
         FIG. 5  is a block diagram illustrating the main configuration of the operation control in the image forming system; 
         FIG. 6  is a flowchart of height determination performed in a trimming process according to a first embodiment; 
         FIG. 7  illustrates a detecting state of a detector in the height determination according to the first embodiment; 
         FIG. 8  is a flowchart of height determination performed in a trimming process according to a second embodiment; 
         FIG. 9A  illustrates a detecting state of a detector in the height determination according to the second embodiment; 
         FIG. 9B  illustrates a detecting state of a detector in the height determination according to the second embodiment; 
         FIG. 10  is a flowchart of height determination performed in a trimming process according to a third embodiment; and 
         FIG. 11  illustrates a detecting state of a detector in the height determination according to the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENT 
     First Embodiment 
     Hereinafter, an image forming system  1  according to a first embodiment of the present invention will be described referring to the drawings. 
       FIG. 1  is a schematic view illustrating the entire configuration of the image forming system  1 . 
     The image forming system  1  includes an image forming apparatus  100 , an intermediate conveyance apparatus  200 , a sheet processing apparatus  300  and a side stitching apparatus  400 . 
     In the following description, the vertical direction is referred to as Z direction. The direction in which the image forming apparatus  100 , the intermediate conveyance apparatus  200 , the sheet processing apparatus  300  and the side stitching apparatus  400  in  FIG. 1  are connected with each other is referred to as X direction. The direction orthogonal to both the X and Z directions is referred to as Y direction. 
     The X direction has front and rear sides, the Y direction has right and left sides, and the Z direction has up and down sides. The front side is upstream and the rear side is downstream when a sheet is conveyed in the image forming system  1 . The right side is upstream and the left side is downstream when a sheet is conveyed in half folding and saddle stitching processing by the saddle stitching apparatus  300 . 
     The image forming apparatus  100  forms an image on a sheet of paper. 
     In specific, the image forming apparatus  100  for forming an image on a sheet includes, for example, a conveyance section to extract and convey a sheet from the sheets stored as recording media from a sheet tray, a developing section to develop a toner image based on bitmap data onto a first transfer member such as transfer roller, a first transfer section to transfer the toner image developed on the first transfer member onto a second transfer member such as a transfer drum  150 , a second transfer section to transfer the toner image on the second transfer member onto the sheet conveyed by the conveyance section, a fixing section to fix the transferred toner image onto the sheet, and an ejecting section to eject the sheet after the fixation by the fixing section. 
     The image forming apparatus  100  passes the ejected sheet which has the image formed thereon to the intermediate conveyance apparatus  200 . That is, the connection in the image forming system  1  allows the sheet ejected from the image forming apparatus  100  to be passed to the intermediate conveyance apparatus  200 . 
     The intermediate conveyance apparatus  200  can temporarily stack a sheet and score and trim the sheet. 
     Specifically, the intermediate conveyance apparatus  200  includes, for example, a standby section (stacker) which conveys downward a sheet conveyed from the image forming apparatus  100  and makes the sheet stop once to standby with the sheet surface along the Z direction; an alignment section which aligns the position of the sheet during standby; a scoring section (creaser) which scores the aligned sheet; and a margin trimming section (slitter) which trims off margins in the sheet while the conveyance of the scored sheet. 
     That is, the intermediate conveyance apparatus  200  once stops the sheet passed from the image forming apparatus  100  at the standby section, aligns the sheet with the alignment section, scores the sheet with the scoring section, and thereafter trims the margins in the sheet with the margin trimming section while conveying the scored sheet. Then, the intermediate conveyance apparatus  200  passes the sheet with the margins trimmed off by the margin trimming section to the sheet processing apparatus  300 . 
     The intermediate conveyance apparatus  200  can also pass the sheet received from the image forming apparatus  100  to the sheet processing apparatus  300  without performing a part or all of the various processes by the intermediate conveyance apparatus  200 . 
     The sheet processing apparatus  300  performs half folding that is folding the sheet in half (in two), saddle stitching that is stapling a predetermined number of stacked half-folded sheets to create a saddle-stitched booklet, trimming that is trimming a fore edge of the booklet, square back forming that is forming a square back, and such like. 
     In specific, the sheet processing apparatus  300  includes, for example: 
     a half folding section  310  which folds the sheet received from the intermediate conveyance apparatus  200  in half along the Y direction; 
     a saddle stitching section  320  which overlays the folded sheets and which inserts staples into the sheet bundle to form a saddle-stitched booklet; 
     a sheet conveying section  330  which receives the saddle-stitched booklet and which conveys the booklet in the direction perpendicular to the crease (X direction) along a horizontal plane; 
     a clamping section  340  which clamps a part around the crease of the saddle-stitched booklet conveyed by the sheet conveying section  330 ; 
     an edge trimming section  350  which trims a fore edge of the saddle-stitched booklet held by the clamping section  340 ; and 
     an ejecting section  360  which ejects the saddle-stitched booklet outward. 
     This sheet processing apparatus  300  can also pass the sheet received from the intermediate conveyance apparatus  200  to the side stitching apparatus  400  without performing a part or all of the various processes by the sheet processing apparatus  300 . In addition to the above-described components, for example, the sheet processing apparatus  300  may further include a square back forming section that forms the spine of a saddle-stitched booklet into a square shape, and the like. 
     The half folding section  310  includes, for example, a pair of half folding rollers  311 ,  311  and a plate-like folding knife  312  which is located along the Y-Z plane below the pair of half folding rollers  311 ,  311  and which is movable so as to come between the half folding rollers  311 ,  311 . 
     A sheet received from the image forming apparatus is conveyed until the center of the sheet in the X direction faces the folding knife  312 . Then the folding knife  312  comes between the half folding rollers  311 ,  311 , and thereby pushes the sheet into the nip unit. Thus, the sheet is folded in two so as to have a crease along the Y direction at the position contacting the folding knife  312 . That is, the sheet is in what is called a mountain fold shape with the crease up and the both edges down (mountain-shaped sheet). 
     The half-folded sheet is conveyed in the direction (Y direction) along the crease to the saddle stitching section  320  by a conveyance section, which is not shown in drawings. 
     The saddle stitching section  330  includes a saddle unit  321  to overlay and accumulate sheets conveyed from the half folding section  310 , a staple inserting section  322  provided above the saddle unit  321 , a staple receiving section  323  provided inside the saddle unit  321 , etc. 
     After a predetermined number of sheets are stacked on the saddle unit  321 , the staple inserting section  322  and the staple receiving section  323  cooperate to insert a staple into the crease of the sheets so that a saddle-stitched booklet is formed. The formed saddle-stitched booklet is pushed out to the sheet conveying section  330  downstream by an alignment section (not shown in drawings) provided at the right end (the upstream end in the conveyance direction) of the saddle unit  321 . 
     The sheet conveying section  330  includes a plate-like buffer saddle  331  placed along the Y-Z plane and a movable unit  332  which is movable both ways in the X direction. 
     After the saddle-stitched booklet is pushed out of the saddle stitching section  320 , the buffer saddle  331  supports the crease (stitch portion) of the booklet from below. After the buffer saddle  331  supports the saddle-stitched booklet, the movable unit  332  moves to the front side from the rear side in the X direction to pass the booklet to the clamping section  340 . 
       FIG. 2  illustrates an example of the configuration of a clamping section  340  and a fore edge trimming section  350  of the sheet processing apparatus  300 .  FIG. 3  illustrates an example of the configuration of the fore edge trimming section  350 . 
     As shown in  FIG. 2 , the clamping section  340  is Placed above the edge trimming section  350  and can move up and down along a guide rail L placed along the Z direction. 
     The clamping section  340  includes a pair of clamp members  341 ,  342 . The clamping section  340  clamps the saddle-stitched booklet near the crease with the clamp members  341 ,  342  after the sheet conveyance mechanism  330  conveys the booklet from the rear to the front, so as to hold the booklet. 
     As the clamping section  340  goes down clamping the saddle-stitched booklet, the fore edge side of the saddle-stitched booklet enters the edge trimming section  350 . 
     The fore edge trimming section  350 , which is Located below the clamping section  340 , performs trimming to cut off the fore edge of the saddle-stitched booklet that comes down while the clamping section  340  holds it. 
     As illustrated in  FIG. 3 , the fore edge trimming section  350  includes, for example, an approach guiding section  351 , a trim and clamp members  352 ,  353 , a trimming knife  354 , an electrically conductive sheet  355 , an antistatic brush  356 , a container  357 , a detector  358 , a movable part  359  and the like. 
     The trim and clamp members  352 ,  353  and the trimming knife  354  constitute a trimming section. 
     The approach guiding section  351  is to guide the fore edge of the saddle-stitched booklet approaching from above. The approach guiding section  351  has, for example, an inclined face that extends upward from the location of the trim and clamp member  352 , which is located to the rear side among the trim and clamp members  352 ,  353 , and that spreads in a fan shape toward the rear side in the X direction. The inclined face continues to the gap between the trim and clamp members  352 ,  353  so as to guide the approaching saddle-stitched booklet. 
     After the saddle-stitched booklet enters the gap between the trim and clamp members  352 ,  353 , the approach guiding section  351  may be retracted, for example, by swinging backward as illustrated in  FIG. 2  or the like. 
     The trimming clamping sections  352 ,  353  are disposed separately from each other with a gap having a predetermined width in the X direction so that the saddle-stitched booklet can enter therebetween. 
     Among the trim and clamp members  352 ,  353 , the rear trim and clamp member  352  is disposed movably in the X direction. After the fore edge of the saddle-stitched booklet enters the gap between the trim and clamp members  352 ,  353  to reach a predetermined position, the rear trim and clamp member  352  moves in the direction toward the front trim and clamp member  353  so as to clamp the saddle-stitched booklet near the fore edge in cooperation with the rear trim and clamp member  353 . 
     The trimming knife  354 , which is long in the Y direction and has a blade at the rear side, is disposed movably in the X direction. While the trim and clamp members  352 ,  353  are clamping the saddle-stitched booklet near the fore edge, the trimming knife  354  moves to trim the fore edge of the saddle-stitched booklet. As a result, the uneven fore edge of the saddle-stitched booklet is cut horizontally into a flat shape. Further, produced chips D fall in the downward direction. 
     The electrically conductive sheet  355  is a plate member that is disposed parallel to the Y-Z plane. The electrically conductive sheet  355  is disposed such that it extends downward from the location of the trim and clamp member  352 , which is located to the rear side among the trim and clamp members  352 ,  353 , so as to form a falling pathway of the chips D. 
     The electrically conducive sheet  355  is made of a material that can prevent the chips D from sticking. By forming the falling pathway of the chips D with the electrically conductive sheet  355 , the chips D are less likely to electrostatically stick to the falling pathway. 
     The antistatic brush  356  is disposed at the lower end of the electrically conductive sheet  355 . 
     The chips D falling down from above come in contact with the antistatic brush  356 , and the electrostatic charge is thereby eliminated. 
     The container  357  is a box that is open upwardly for collecting the chips D falling down from above. 
     The container  357  is drawable to the fore side, and the user draws it to the fore side to dispose the chips D. 
     The detector  358 , which is disposed below the trim and clamp members  352 ,  353  and the trimming knife  354  and above the container  357 , detects a chip D that is present in the detecting area of the detector  358  (at a predetermined height). 
     The detector  358  may be constituted by, for example, a reflective optical sensor having a light emitting unit and a light receiving unit. That is, when a chip D is present at a height approximately opposed to the detector  358 , light emitted from the light emitting unit is reflected on the chip D. The light receiving unit receives the reflected light, and a detection signal is output to the sheet processing control section  505  (described below). 
     This optical sensor is merely an example, and the configuration of the detector  358  is not limited thereto. For example, a detector described in JP 2011-136375A, which detects the loading state of chips by means of electromagnetic wave, may also be used. 
     The predetermined height to be detected by the detector  358  depends on the location of the detector  358 . Accordingly, the amount of chips D in the container  357  when the detector  358  becomes “ON” can be suitably adjusted by changing the location of the detector  358 . For example, when the detector  358  is disposed near the opening of the container  357  with which the chips D falling down from the fore edge trimming section  350  are collected, the detector  358  can detect that the chips D are collected approximately to the full level of the container  357 . When the detector  358  is disposed near the center in the vertical direction of the container  357 , the detector  358  can detect that the chips D are collected approximately to a half level of the container  357 . 
     The movable part  359  starts to move when the fore edge trimming of a saddle-stitched booklet starts and then comes in contact with the produced chips D to help the chips D fall in the downward direction. 
       FIG. 4  is a schematic view illustrating an example of the movable part  359 .  FIG. 4  is a view of the movable part  359  from the rear side. 
     As illustrated in  FIG. 4 , the movable part  359  includes a rotating member (movable member)  359 A that is rotated in the direction of the arrow A to come in contact with the chips D at a predetermined timing, and a drive unit  359 B that rotates the rotating member  359 A. 
     The rotating member  359 A extends in the width direction of the saddle-stitched booklet (Y direction). Specifically, for example, the rotating member  359 A includes a rotating shaft  3591  that extends in the Y direction (width direction of the saddle-stitched booklet) and fins  3592  disposed on the rotating shaft  3591 . 
     The fins  3592  are made of a pilable material such as a plastic material. The fins  3592  are rotated around the rotating shaft  3591  to come in contact with the produced chip D, so as to apply a force to the chip D in the diagonal direction toward the rear down side (horizontal and downward directions) to help the chip D fall down in the downward direction. 
     It is preferred that the fins  3592  are disposed at the same phase with respect to the rotating shaft  3591 . That is, it is preferred that the fins  3592  are aligned in the Y direction. When the rotating member  359 A is rotated, this allows the fins  3592  to come in contact with the overall part of the chip D which is long in the Y direction. As a result, the chip D can fall down in a more horizontal state. 
     In this way, the movable part  359  applies a force to the chip D in the direction toward the rear down side to let the chip D fall down. Therefore, when a chip D sticks to the vicinity of the detector  358 , a newly produced chip D is more likely to fall down on the stuck chip D, which helps the stuck chip D fall down. 
     The drive unit  359 B is constituted by, for example, a motor or the like driven by a control of the sheet processing control section  505 . When the trimming process starts, the driving unit  395 B is driven to rotate the rotating shaft  3591  and thus the rotating member  359 A. 
     Returning to  FIG. 1 , the ejecting section  360  is above the clamping section  340 . The ejecting section  360  includes a loading unit on the upper surface of the sheet processing apparatus  300  and a turnabout unit which receives the saddle-stitched booklet from the clamping section  340  and which ejects the booklet to the loading unit. 
     After the fore edge trimming section  350  performs The fore edge trimming and the clamping section  340  conveys the saddle-stitched booklet in a vertical state upward, the turnabout unit turns the booklet into an approximately horizontal state. The booklet is then ejected such that booklets are piled up on the loading unit one after another. 
     The side stitching apparatus  400  performs side stitching, etc. for a plurality of sheets. 
     Specifically, the side stitching apparatus  400  includes, for example, a stapling section which staples sheets received from the sheet processing apparatus  300 , a page end trimming section which trims a part of an end portion of the stapled sheets that are parallel to the spine so as to align the end portion, and an ejecting section which ejects the sheets that have been processed by the connected apparatuses. 
     The side stitching apparatus  400  can eject the sheets received from the sheet processing apparatus  300  without performing a part or all of the various processes by the side stitching apparatus  400 . 
     Next, the operation control of the image forming system  1  will be described. 
       FIG. 5  is a block diagram showing the main configuration according to the operation control in the image forming system  1 . 
     The image forming system  1  includes an operation display section  501  which receives input operation from a user in relation to the operation of the image forming system  1  and which displays in accordance with the operation of the image forming system  1 , a central control section  502  which controls operations of the entire image forming system  1 , an image formation control section  503  which controls operations of the image forming apparatus  100 , an intermediate conveyance control section  504  which controls operations of the intermediate conveyance apparatus  200 , a sheet processing control section (control section)  505  which controls operations of the sheet processing apparatus  300  and a side stitching control section  506  which controls operations of the side stitching apparatus  400 . 
     The operation display section  501  includes, for example, a touch panel type operation display unit or switches and keys for various types of input to send a signal according to the input from the user to the central control section  502 . 
     Each of the central control section  502 , the image formation control section  503 , the intermediate conveyance control section  504 , the sheet processing control section  505 , and the side stitching control section  506  includes a CPU (Central Processing Unit), a RAM (Random Access Memory), a ROM (Read Only Memory) and such like to read out a software program and various types of data according to processing and execute the processing. 
     In response to the input from the user via the operation display section  501 , the central control section  502  sets various types of conditions concerning the image forming system  1 . 
     These conditions include a sheet size, the number of colors to form images (for example, full-color, gray scale, monochrome, etc.), the number of sheets to be half-folded, nip pressure in the half folding processing, the number of sheets in a single booklet to be saddle-stitched, the type, size and weight of sheets to be saddle-stitched, the number of staples to be inserted into the crease of the sheets in saddle stitching, a position where staples are inserted in saddle stitching, whether to trim the fore edge of the saddle-stitched booklet, etc. 
     Then, the central control section  502  outputs instructions to perform the processing according to the setting to the image formation control section  503 , the intermediate conveyance control section  504 , the sheet processing control section  505  and the side stitching control section  506 . The control sections control operations of the respective apparatuses to be controlled according to the instructions. 
     For example, the central control section  502  outputs an instruction for performing half folding, saddle stitching, trimming, etc. to the saddle stitching control section  505 . 
     In response to this, the sheet processing control section  505  controls the sections to perform processing. 
     For example, the sheet processing control section  505  controls the fore edge trimming section  350  to perform the trimming. 
     Further, the sheet processing control section  505  performs height determination which is to make a determination as to whether the top of the piled chips D that are produced by the trimming and collected in the container  357  has reached the predetermined height. 
     Specifically, when the detector  358  detects a chip D (i.e. the detector  358  becomes “ON”), the sheet processing control section  505  performs the trimming of the next saddle-stitched booklet. Then, when the detector  358  is still “ON” after the trimming of the next booklet, the sheet processing control section  505  determines that the top of the piled chips D in the container  357  has reached the predetermined height. 
     Hereinafter, the above-described height determination performed during the trimming process will be described with the flowchart of  FIG. 6 . Before the process, the clamping members  341 ,  342  of the clamping section  340  hold the saddle-stitched booklet and take it down toward the gap between the trim and clamp members  352 ,  353 . 
     First, in Step S 1 , the sheet processing control section  505  drives the drive unit  359 B to start rotation of the rotating shaft  3591  and the rotating member  359 A. 
     Next, in Step S 2 , after the saddle-stitched booklet is taken down to a predetermined position, the sheet processing control section  505  clamps the saddle-stitched booklet by the trim and clamp members  352 ,  353  and moves the trimming knife  354  to trim the fore edge of the saddle-stitched booklet. 
     As a result, chips D are produced, and the produced chips D fall in the downward direction. 
     Next, in Step S 3 , the sheet processing control section  505  makes a determination as to whether the detector  358  is “ON”. 
     In view of the fall time of the chips D, the determination in Step S 3  is made after a predetermined time has elapsed since the fore edge of the saddle-stitched booklet is trimmed in Step S 2 . 
     If the detector  358  is not “ON” (Step S 3 : NO), in the following Step S 4 , the sheet processing control section  505  makes a determination as to whether there is another booklet to be processed. If there is another booklet to be processed (Step S 4 : YES), the process continues to Step S 2 . If there is no booklet to be processed (Step S 4 : NO), the process ends. 
     If the detector  358  is “ON” (Step S 3 : YES), in the following Step S 5 , the sheet processing control section  505  makes a determination as to whether there is another booklet to be processed. If there is no booklet to be processed (Step S 5 : NO), the process ends. 
     If there is another booklet to be processed (Step S 5 : YES), in the following Step S 6 , the sheet processing control section  505  clamps the saddle-stitched booklet by the trim and clamp members  352 ,  353  and moves the trimming knife  354  to trim the fore edge of the saddle-stitched booklet. 
     Next, in Step S 7 , the sheet processing control section  505  makes a determination as to whether the detector  358  is “ON”. 
     As with the determination in the above-described Step S 3 , the determination in Step S 7  is made after a predetermined time in view of the fall time of the chips D has elapsed since the fore edge of the saddle-stitched booklet is trimmed in Step S 6 . 
     If the detector  358  is not “ON” (Step S 7 : NO), the Sheet processing control section  505  continues the process to the above-described Step S 4 . 
     If the detector  358  is “ON” (Step S 7 : YES), in the following Step S 8 , the sheet processing control section  505  determines that the top of the piled chips D has reached the predetermined height. 
     Next, in Step S 9 , the sheet processing control section  505  displays a message on the operation display section  501  so as to notify the user that the top of the piled chips D has reached the predetermined height, i.e. a predetermined amount of chips D has been collected. 
     Alternatively, the notification may be made by, for example, making a predetermined sound, turning on a lamp or the like. 
     Next, in Step S 10 , the sheet processing control section  505  stops the operation of the fore edge trimming section  350 , and the process ends. 
     In Step S 10 , the operation of the fore edge trimming section  350  may be stopped either immediately or a predetermined time after it is determined in Step S 8  that the top of the piled chips D has reached the predetermined height. 
       FIG. 7  illustrates a detecting state of the detector  358  in the height determination according to this embodiment. 
     As illustrated in  FIG. 7 , in the height determination according to this embodiment, when the detector  358  becomes “ON” (t 1 , Step S 3  in  FIG. 6 : YES), the sheet processing control section  505  trims the next booklet (t 2 , Step S 6  in  FIG. 6 ). Then, when the detector  358  is still “ON” after the trimming (Step S 7  in  FIG. 6 : YES), the sheet processing control section  505  determines that the top of the piled chips D has reached the predetermined height (t 3 , Step S 8  in  FIG. 6 ). 
     In this process, even when the detector  358  becomes “ON” due to a chip D that wrongly sticks to the vicinity of the detector  358  in the middle of the falling pathway, chips D produced by trimming the next booklet can collide with the stuck chip D to let it fall down. Then, the state of the detector  358  changes to an undetected state. 
     Since the movable part  359  applies a force to produced chips D, the newly produced chips D are more likely to fall down on the stuck chip D. 
     In this embodiment, the trimming section trims a sheet set (saddle-stitched booklet), but it can also trim a single sheet. 
     As described above, this embodiment includes: the trimming section (the trim and clamp members  352 ,  353  and the trimming knife  354 ) that performs the trimming to trim the fore edge (a part) of a sheet or sheet set (saddle-stitched booklet); the container  357  that is disposed below the trimming section to collect the chip D produced by the trimming in the trimming section; the detector  358  that detects the presence of the chip D at the predetermined height; and the sheet processing control section  505  that makes the trimming section perform the trimming of the next saddle-stitched booklet when the detector  358  detects the chip D and then determines that the top of the piled chips D in the collector  357  has reached the predetermined height when the detector  358  still detects the presence of the chip D after the trimming of the next saddle-stitched booklet. 
     Accordingly, even when a chip D wrongly sticks to the vicinity of the detector  358  during the trimming, a determination as to whether the top of the piled chips D has reached the predetermined height is made after a chip D produced by the next trimming collides with the stuck chip D to let it fall down. This can prevent false detection by the detector  358 , and it can be therefore correctly detected that the top of the piled chips D has reached the predetermined height. 
     This embodiment includes the movable part  359  that is disposed above the detector  358  and that comes in contact with the chips D produced by the trimming in the trimming section to apply a force in the horizontal and downward directions. 
     Therefore, the chips D produced by the trimming fall down from the trimming section such that they are more likely to collide with the chip D stuck in the vicinity of the detector  358 , which helps the stuck chip D fall down. 
     In this embodiment, the movable part  359  includes a movable member that extends in the width direction of the saddle-stitched booklet (Y direction). Specifically, the movable member includes the rotating shaft  3591  that extends in the width direction of the saddle-stitched booklet (Y direction) and the fins  3592  that are disposed on the rotating shaft at the same phase. 
     When the movable member is driven, it comes in contact with the overall part of a chip D that is long in the Y direction so that the chip D can fall down in a more horizontal state. Therefore, the chip D is more likely to collide with the chip D stuck in the vicinity of the detector  358 , which helps the stuck chip D fall down. 
     Second Embodiment 
     Next, a second embodiment of the present invention will be described mainly in the features that are different from the first embodiment. 
     In the second embodiment, when a detector  358  detects the presence of a chip D, a sheet processing control section  505  makes a trimming section perform trimming of the next plurality of sheets or sheet sets (saddle-stitched booklets). Then, when the detector  358  still detects the presence of a chip D after the trimming of the next plurality of sheets or sheet sets, the sheet processing control section  505  determines that the top of the piled chips D in a container  357  has reached a predetermined height. 
     The second embodiment may further include an estimating section that estimates the amount of free space of the container  357 . The estimating section is constituted by, for example, a counter that counts the number of times of successively performed trimming or a scale that measures the weight of the container  357 , and the amount of free space of the container  357  may be estimated from the value counted or measured by the estimating section  357 . However, the method of estimating the amount of free space of the container  357  is not limited to these examples. 
     In this case, the sheet processing control section  505  may be configured such that the number of times of trimming that the fore edge trimming section  350  performs to the next sheets or sheet sets is selected according to the amount of free space of the container  357 . 
     For example, when the amount of free space of the container  357  is 50%, the sheet processing control section  505  performs the trimming for five times. When the amount of free space of the container  357  is 10%, it performs the trimming for two times. 
     Alternatively, the sheet processing control section  505  may be configured to perform a predetermined calculation or the like in order to estimate the amount of free space of the container  357 . In this case, the sheet processing control section  505  serves as the estimating section. 
     Hereinafter, height determination performed during the trimming process according to the second embodiment will be described with the flowchart of  FIG. 8 . The same reference signs are denoted to the same steps as those in  FIG. 6 , and the description thereof is omitted. 
     When the detector  358  is “ON” in Step S 7  (Step S 7 : YES), in the following Step S 11 , the sheet processing control section  505  makes a determination as to whether the trimming has been performed to a predetermined plural number of saddle-stitched booklets. If the number of trimmed saddle-stitched booklets is less than the predetermined number (Step S 11 : NO), the process returns to Step S 5  to repeat the following steps. If the number of trimmed saddle-stitched booklets has reached the predetermined number (Step S 11 : YES), the process continues to Step S 8 . 
       FIG. 9A  and  FIG. 9B  illustrate a detecting state of the detector  358  in the height determination according to this embodiment, where  FIG. 9A  illustrates a case in which the estimating section estimates the amount of free space of the container  357  as 50%, and  FIG. 9B  illustrates a case in which the estimating section estimates the amount of free space of the container  357  as 10%. 
     As illustrated in  FIG. 9A , when the amount of free space of the container  357  is 50%, the next four booklets are trimmed (t 12  to t 15 , Step S 6  in  FIG. 8 ) after the detector  358  becomes “ON” (t 11 , Step S 3  in  FIG. 8 : YES). Then, when the detector  358  is still “ON” after the four booklets are trimmed (Step S 11  in  FIG. 8 : YES), it is determined that the top of the piled chips D has reached a predetermined height (t 16 , Step S 8  in  FIG. 8 ). 
     As illustrated in  FIG. 9B , when the amount of free space of the container  357  is 10%, the next two booklets are trimmed (t 12  and t 13 , Step S 6  in  FIG. 8 ) after the detector  358  becomes “ON” (t 11 , Step S 3  in  FIG. 8 : YES). When the detector  358  is still “ON” after the two booklets are trimmed (Step S 11  in  FIG. 8 : YES), it is determined that the top of the piled chips D has reached the predetermined height (t 16 , Step S 8  in  FIG. 8 ). 
     In this way, in this embodiment, when the detector  358  detects the presence of a chip D, the sheet processing control section  505  makes the trimming section perform the trimming of the next plurality of sheets or sheet sets (saddle-stitched booklets). Then, when the detector  358  still detects the presence of the chip D after the trimming of the next plurality of sheets or sheet sets, the sheet processing control section  505  determines that the top of the piled chips D in the container  357  has reached the predetermined height. 
     Accordingly, even when a chip D sticks to the vicinity of the detector  358  during the trimming, a determination as to whether the top of the piled chips D has reached the predetermined height is made after the chips D produced by the next plural times of trimming collide with the stuck chip D to let it fall down. Therefore, false detection by the detector  358  can be prevented more certainly. 
     This embodiment includes the estimating section that estimates the amount of free space of the container  357 , and the sheet processing control section  505  selects the number of times of trimming that the trimming section performs to the next saddle-stitched booklet according to the amount of free space of the container  357 . 
     Accordingly, the number of times of trimming can be suitably selected according to the amount of free space of the container  357 . Therefore, false detection by the detector  358  can be prevented more certainly, and it can also be prevented that the top of the piled chips D goes beyond the predetermined height. 
     Third Embodiment 
     Next, a third embodiment of the present invention will be described mainly in the features that are different from the first embodiment. 
     In the third embodiment, when a detector  358  detects a chip D, the sheet processing control section  505  makes a trimming section perform trimming of the next sheet or sheet set (saddle-stitched booklet). Then, when the detector  358  still detects the presence of the chip D after a predetermined time has elapsed since the trimming of the next saddle-stitched booklet, the sheet processing control section  505  determines that the top of the piled chips D in the container  357  has reached the predetermined height. 
     Hereinafter, height determination performed during the trimming process according to the third embodiment will be described with the flowchart of  FIG. 10 . The same reference signs are denoted to the same steps as those in  FIG. 6 , and the description thereof is omitted. 
     After the fore edge of a saddle-stitched booklet is trimmed in Step S 6 , in the following step S 21 , the sheet processing control section  505  makes a determination as to whether the predetermined time has elapsed. If the predetermined time has not elapsed yet (Step S 21 : NO), Step S 21  is repeated. If the predetermined time has elapsed (Step S 21 : YES), the sheet processing control section  505  continue the process to Step S 7 . 
       FIG. 11  illustrates a detecting state of the detector  358  in the height determination according to this embodiment. 
     As illustrated in  FIG. 11 , when the detector  358  becomes “ON” (t 21 , Step S 3  in  FIG. 10 ), the next booklet is trimmed (t 22 , Step S 6  in  FIG. 10 ). Then, when the detector  358  is still “ON” (Step S 7  in  FIG. 10 : YES) after the predetermined time has elapsed (Step S 21  in  FIG. 10 : YES), it is determined that the top of the piled chips D has reached a predetermined height (t 23 , Step S 8  in  FIG. 10 ). 
     In this way, in this embodiment, when the detector  358  detects a chip D, the sheet processing control section  505  makes the trimming section perform the trimming of the next sheet or sheet set (saddle-stitched booklet). Then, when the detector  358  still detects the chip D after the predetermined time has elapsed since the trimming of the next sheet or sheet set, the sheet processing control section  505  determines that the top of the piled chips D in the container  357  has reached the predetermined height. 
     Accordingly, even when a chip D sticks to the vicinity of the detector  358  during the trimming, a determination as to whether the top of the piled chips D has reached the predetermined height is made after the chip D produced by the next trimming collides with the stuck chip D to let it fall down and a certain time has further elapsed while the stuck chip D falls down due to release of the static electricity, vibration of the apparatus or the like. Therefore, false detection by the detector  358  can be prevented more certainly. 
     The above-described embodiments are examples in Which the rotating member  359 A with the fins  3592  is provided as the movable part  359 . However, the movable part  359  may be constituted by any member that is long in the width direction of the sheet. For example, a single plate that is long in the width direction of the sheet may be provided instead of the fins  3592 . 
     The above-described embodiments are examples in which the movable part  359  is configured such that the rotating member  359 A rotates. Instead of rotation, for example, a knife may move linearly in the horizontal or downward direction so as to come in contact with a chip D. 
     The above-described embodiments are examples in which the fore edge of a saddle-stitched booklet is trimmed. However, the determination process of the collected amount in these embodiments is also applicable to other trimming that produces chips (e.g. punching). 
     The entire disclosure of Japanese Patent Application No. 2014-240923 filed on Nov. 28, 2014 including description, claims, drawings, and abstract are incorporated herein by reference in its entirety.