Abstract:
Providing a sheet collecting device capable of being downsized and of operating stably wherein a sheet ejecting device that conveys and ejects a sheet in the direction for making the sheet fall along a slanted sheet collecting board is provided, and a leading edge stopper that holds sheets on the sheet collecting board is set so that a trailing edge of the sheet may be at a constant height independently of a sheet size.

Description:
[0001]    This application is based on Japanese Patent Application No. 2008-041346 filed on Feb. 22, 2008 in Japanese Patent Office, the entire content of which is hereby incorporated by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates to improvement of a sheet collecting device which is provided on an image forming apparatus or on a post-processing apparatus. 
         [0003]    A stapler that binds a plurality of sheets generally has a sheet collecting board on which plural sheets are stacked, and it conducts stitching process for sheets stacked on the sheet collecting board. 
         [0004]    A folding device that folds therein a center portion of a sheet also has a sheet collecting board, and it conducts folding process for sheets stacked on the sheet collecting board. 
         [0005]    In a technology disclosed in Unexamined Japanese Patent Application Publication No. 2000-63031, a sheet collecting board (compile tray) is provided, and a sheet is caused to go up above the sheet collecting board by conveyance by a sheet ejection device, and the sheet released from the sheet ejection device falls on the sheet collecting board to be stopped at a prescribed position on the sheet collecting board. 
         [0006]    Then, by repeating these operations, a plurality of sheets are stacked on the sheet collecting board. 
         [0007]    In a technology disclosed in Unexamined Japanese Patent Application Publication No. 2000-63031, a leading edge (trailing edge in the case of carrying-in) of a sheet is stopped at a fixed position or at a position for saddle stitching or center folding. 
         [0008]    In Unexamined Japanese Patent Application Publication No. 11-322163, there is disclosed a sheet processing device wherein plural sheets are stacked on a slanted sheet collecting board (vertical path) by repeating sheet conveyance in which a sheet is supplied to the vertical path and the sheet is dropped along the vertical path to be stopped by a stopper, and thereby, the stacked sheets are stitched. 
         [0009]    In Unexamined Japanese Patent Application Publication No. 11-322163, when stacking sheets which are ejected continuously, a trailing edge (upper end) of the precedent sheet hits a leading edge (lower end). Therefore, to avoid this problem, a position of a sheet ejection exit of a sheet ejection device is switched by use of a flapper. 
         [0010]    In the case of sheet ejection by a sheet ejection device in Unexamined Japanese Patent Application Publication No. 2000-63031 wherein a sheet is caused to rise above a collecting board, and a sheet released from a sheet ejection device is allowed to fall on the sheet collecting board to be stacked on a prescribed position, a space for securing a conveyance path for switchback of a sheet is required, resulting in a problem that a size of the apparatus is increased. 
         [0011]    There is also a problem that high-speed conveyance becomes difficult, because switchback of a sheet makes a conveyance time per one sheet longer. 
         [0012]    In a sheet processing device wherein sheets in various sizes are stacked on the sheet collecting board through switching of sheet ejection exits by using a flapper, like the device disclosed in Unexamined Japanese Patent Application Publication No. 11-322163, a mechanism is complicated and operations are not stabilized to cause conveyance troubles easily, because a conveyance path switching mechanism is needed. 
         [0013]    Further, in the case of sheet sizes wherein a difference of the length is small, there is a problem that coping with various sizes is difficult, because switching conveyance paths is difficult. 
       SUMMARY 
       [0014]    The aforesaid problems are solved by the following embodiments of the invention.
   1. A sheet collecting device having therein a sheet collecting board that has a sheet supporting surface which is slanted so that the upstream side thereof in the sheet conveyance direction in the case of sheet carrying-in is higher than the downstream side, an ejecting device that is arranged upstream of the sheet collecting board, and that conveys a sheet in a direction so that the sheet falls along the sheet collecting board to be ejected onto the sheet collecting board, a leading edge stopper that stops the sheet on the sheet collecting board, a stopper moving device that changes the position of the aforesaid leading edge stopper and a control device that controls the stopper moving device, wherein the control device controls the stopper moving device so that the trailing edge of the sheet in the case of sheet carrying-in on the sheet collecting board is at a fixed position regardless of a sheet size difference.   2. A post-processing apparatus having therein the sheet collecting device described in the aforesaid Item  1  and a stapler that conducts a stitching process on the sheet collecting board for sheets stacked on the aforesaid sheet collecting board, wherein the aforesaid control device controls the stopper moving device to set the leading edge stopper at the first stop position for sheet collecting, and then, to move the leading edge stopper to be set at the second stop position, and the aforesaid stapler conducts the stitching process for the sheets supported by the leading edge topper that is set at the second stop position.   3. A post-processing apparatus having therein the sheet collecting device described in the aforesaid Item 1 and a folding device that conducts a folding process for sheets collected on the sheet collecting board, wherein the aforesaid control device controls the stopper moving device to set the leading edge stopper at the first stop position for sheet collecting, and then, to move the leading edge stopper to be set at the third stop position, and the aforesaid folding device conducts the folding process for the sheets supported by the leading edge stopper that is set at the third stop position.   4. An image forming apparatus that has the sheet collecting device described in the aforesaid Item 1.   
 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  shows an overall view of an image forming apparatus relating to an embodiment of the invention. 
           [0020]      FIG. 2  is a diagram showing a sheet collecting device relating to an embodiment of the invention. 
           [0021]      FIG. 3  is a diagram showing a sheet carry-in section of a sheet collecting device. 
           [0022]      FIG. 4  is a block diagram of a control system of a post-processing apparatus relating to Embodiment 1 of the invention. 
           [0023]      FIG. 5  is a flow chart of operations of a post-processing apparatus in saddle stitching/center folding. 
           [0024]      FIG. 6  is a block diagram of a control system of a post-processing apparatus relating to Embodiment 1 of the invention. 
           [0025]      FIG. 7  is a flow chart of operations of a post-processing apparatus in side stitching. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0026]    The invention will be described as follows, referring to the illustrated embodiments to which, however, the invention is not limited. 
       &lt;Image Forming Apparatus&gt; 
       [0027]      FIG. 1  is an overall view of an image forming apparatus relating to an embodiment of the invention equipped with image forming apparatus main body A and post-processing apparatus FS. 
         [0028]    Illustrated image forming apparatus main body A is equipped with image reading section  1 , image processing section  2 , image writing section  3 , image forming section  4 , sheet-feeding cassette  5 , sheet-feeding device  6 , fixing unit  7 , sheet discharge section  8  and automatic two-sided copying sheet-feeding section (ADU)  9 . 
         [0029]    On the upper part of the image forming apparatus main body A, there is mounted automatic document feeding device DF. The post-processing apparatus FS is connected on the illustrated left side of the image forming apparatus main body A, that is, the sheet discharge section  8  side. 
         [0030]    A document placed on a document stand of automatic document feeding device DF is conveyed in the direction of an arrow, and images on one side or on two sides of the document are read by an optical system of image reading section  1  and further read into CCD image sensor  1 A. 
         [0031]    Analog signals which have been converted photoelectically by CCD image sensor  1 A are subjected to analog processing, A/D conversion, shading correction and image compression in image processing section  2 , and then, are sent to image writing section  3 . 
         [0032]    When forming images, output light is emitted from a semiconductor laser of image writing section  3 , to irradiate photoconductor drum  4 A of image forming section  4 , so that a latent image is formed on the photoconductor drum  4 A. In the image forming section  4 , processes such as charging, exposure, developing, transfer, separation and cleaning are conducted. Recording sheet S 1  fed by sheet-feeding device  6  from sheet-feeding cassette  5  comes in contact with the photoconductor drum  4 A on which the latent image is made to be a toner image through developing process, and the toner image is transferred by transfer device  4 B onto the recording sheet S 1 . The recording sheet S 1  carrying the toner image is subjected to fixing by fixing unit  7 , and is fed into post-processing apparatus FS from sheet discharge section  8 . In the case of two-side copying, the recording sheet S 1  whose one side has been finished in terms of image processing is fed into automatic two-side copying sheet feeding section  9  through conveyance path switching plate  8 A, and is subjected to image processing on its reverse side in image forming section  4  to be discharged from sheet discharge section  8  after being fixed. 
         [0033]    Next, a post-processing apparatus relating to an embodiment of the invention will be described, referring to  FIG. 1 . 
         [0034]    Post-processing apparatus FS has therein sheet carry-in section  20 , insertion sheet feeding sections  30   a  and  30   b  and a plurality of post-processing sections. The post-processing section has therein punching process section  40 , folding process section  50 , superposing process section  60 , staplers  71  and  103  and sheet discharge section  80 . 
         [0035]    Insertion sheet S 2  is loaded in insertion sheet feeding section  30   a , and another insertion sheet S 3  is loaded in insertion sheet feeding section  30   b.    
         [0036]    Insertion sheets S 2  and S 3  are sheets to be inserted in recording sheet S 1  discharged from image forming apparatus main body A, such as a cover sheet and an inserted sheet, and they can be subjected to punching process and folding process in the same way as recording sheet S 1 . 
         [0037]    Inserted sheets S 2  and S 3  fed out of insertion sheet feeding sections  30   a  and  30   b  are conveyed to sheet carry-in section  20  through a conveyance path running downward (having no reference symbol). 
         [0038]    Punching process section  40  is arranged on sheet carry-in section  20 . 
         [0039]    Meanwhile, in the description hereafter, recording sheet S 1 , insertion sheets S 2  and S 3  are given a generic name of sheet S. 
         [0040]    Folding process section  50  is arranged on conveyance path H 1  that is branched downward from sheet carry-in section  20 . 
         [0041]    Superposing process section  60  is arranged at downstream side of conveyance path H 2  that is branched upward from sheet carry-in section  20 , and is equipped with conveyance paths H 3 , H 4  and H 5 . 
         [0042]    The superposing process section  60  causes succeeding sheet S to stand by at conveyance path H 4  and conveyance paths H 3  and H 5  to secure a period of time for preceding sheet S to conduct stitching process in stapler  71  located on the downstream side. 
         [0043]    The conveyance path positioned at the downstream side of conveyance path H 2  is branched into conveyance paths which are curved doubly as inside conveyance path H 4  and outside conveyance paths H 3  and H 5 . 
         [0044]    On an exit of conveyance path H 4  that is branched from conveyance path H 2  to form a curved inside conveyance path, there is provided conveyance roller  21 . When the first sheet of sheets S to be stitched is conveyed there, the conveyance roller  21  is at standstill and stops a leading edge of the first sheet. It causes the first sheet to stand by under the condition that the first sheet is in contact with conveyance roller  21 . 
         [0045]    Sheet S conveyed through conveyance path H 4  stands by under the state where its leading edge is stopped by conveyance roller  21  as stated above, while, a succeeding sheet S enters conveyance path H 3  from conveyance path H 2  and arrives at the conveyance roller  21 . 
         [0046]    From the conveyance roller  21 , preceding sheet S and succeeding sheet S are conveyed together under the state where both sheets S are superposed, and are conveyed to collecting section  70 . 
         [0047]    Conveyance path H 3  is connected with conveyance path H 2  at the downstream side of the conveyance path H 2 , and conveyance path H 5  is connected with conveyance path H 3 . 
         [0048]    The conveyance path H 3  is branched into conveyance path H 5  and conveyance path H 6 . 
         [0049]    Conveyance path H 6  forms a sheet discharge path through which sheet S is discharged to fixed sheet discharge tray  81 . 
         [0050]    Fixed sheet discharge tray  81  is arranged at a position so as to be protruded from post-processing apparatus FS that is at the downstream side of conveyance path H 6  branched from superposing process section  60  at conveyance rollers  24  on conveyance path H 3 . 
         [0051]    As stated above, sheet S conveyed through conveyance paths H 2 , H 3  and H 6  and discharged is stacked on the fixed sheet discharge tray  81 . 
         [0052]    Sheet discharge section  80  has sheet discharge roller  22 , and discharges sheet S on elevating sheet discharge tray  82 . 
         [0053]    The sheet discharge rollers  22  are composed of a pair of rollers, and in the case of non-sheet-discharge, the paired rollers stay apart from each other, while, in the case of sheet discharge, the paired rollers come in contact with each other to nip and convey sheet S to discharge it on the elevating sheet discharge tray  82 . 
         [0054]    Sheet S conveyed by conveyance roller  21  travels in the direction toward a left side between a pair of rollers  22  which stay away from each other, and when a trailing edge of the sheet S leaves the conveyance roller  21 , the sheet S falls on collecting section  70  to slide down its slope, and it is caught by a stopper (not shown) to stop on the collecting section  70 . 
         [0055]    After the set number of sheets S have been stacked on the collecting section  70 , stapler  71  operates to stitch the sheets S. 
         [0056]    The sheets S thus stitched are lifted up by the aforesaid stopper, and move on the collecting section  70  toward a left side. 
         [0057]    In this case, a pair of rollers constituting the sheet discharge rollers  22  come in contact with each other to nip and convey sheet S to discharge it on the elevating sheet discharge tray  82 . 
         [0058]    In the folding mode, sheet S is conveyed downward through conveyance path H 1  from sheet carry-in section  20 , and then, is subjected to center folding or folding into three in folding process section  50 , and is discharged to lower sheet discharge tray  83 . 
         [0059]    In the saddle stitching mode, sheet S is conveyed downward through conveyance path H 1  from sheet carry-in section  20 . The sheet S is subjected to saddle-stitching process in stapler  103  and is discharged to lower sheet discharge tray  83  after being subjected to center folding process in folding process section  50 . 
         [0060]    Sheet discharge paths for sheet S include the following four paths;
   1) sheet carry-in section  20 →conveyance path H 2 →conveyance path H 3 →conveyance path H 6 →fixed sheet discharge tray  81     2) sheet carry-in section  20 →conveyance path H 2 →conveyance paths H 3 , H 4  and H 5 →collecting section  70 →sheet discharge section  80 →elevating sheet discharge tray  82     3) sheet carry-in section  20 →conveyance path H 2 →H 4 →sheet discharge section  80 →elevating sheet discharge tray  82     4) sheet carry-in section  20 →conveyance path H 1 →folding process section  50 →lower sheet discharge tray  83     
 
         [0065]    Paths 1), 2) and 4) are those described above. 
         [0066]    Path 3) is selected when forming a large amount of images without conducting stitching process and folding process. 
         [0067]    Sheet S is discharged on elevating sheet discharge tray  82  without any post processing, and the elevating sheet discharge tray  82  moves downward as shown by chain lines in  FIG. 1  so that the uppermost surface of discharged sheets S may be always at the constant height. 
         [0068]    Therefore, several thousand sheets may be stacked on the elevating sheet discharge tray  82 . 
       &lt;Sheet Collecting Device&gt; 
       [0069]    A sheet collecting device relating to Embodiment 1 of the invention will be described as follows, referring to  FIGS. 2 and 3 . 
         [0070]      FIG. 2  is a diagram showing a sheet collecting device relating to an embodiment of the invention, and  FIG. 3  is a diagram showing a sheet carry-in section of a sheet collecting device. 
         [0071]    The numeral  100  represents an intermediate stack tray that is a sheet collecting board supporting sheets S to be stitched or folded,  101  represents a guide that constitutes conveyance path H 1  in  FIG. 1 ,  102  represents a conveyance roller that forms a lower end of a sheet ejection section which ejects a sheet to intermediate stack tray  100 ,  103  represents a stapler that conducts stitching process for sheets S,  104  represents an aligning member that aligns sheets S in their width direction (direction perpendicular to the conveyance direction),  105  represents a leading edge stopper that stops sheet S having been conveyed and that supports sheet S on intermediate stack tray  100 ,  106  represents an gripping member that grips sheet S,  52  represents a folding plate, and  53 - 55  represent folding rollers. The folding rollers  53 - 55  constitute a folding process section  50 . 
         [0072]    The intermediate stack tray  100  is provided below conveyance path H 1  as is illustrated. 
         [0073]    Further, the intermediate stack tray  100  is provided to be inclined so that a downstream side in the conveyance direction may be positioned to be lower and an upstream side may be positioned to be upper, thus, sheet S ejected on the intermediate stack tray  100  slides down along the intermediate stack tray  100  and is caught by the leading edge stopper  105  to be stopped. 
         [0074]    The stapler  103  conducts stitching operations to staple sheets on the intermediate stack tray  100 . 
         [0075]    The aligning member  104  is driven by motor M 2  to be reciprocated in the width direction that is perpendicular to the conveyance direction of sheet S, to align edges of sheets S in the width direction. 
         [0076]    The leading edge stopper  105  is driven by motor M 1  representing a stopper moving device to move in the sheet conveyance direction, and is set at the position corresponding to a sheet size. 
         [0077]    A position for the leading edge stopper  105  to be set at will be described as follows, referring to  FIG. 3 . 
         [0078]    Sheet S conveyed by conveyance roller  102  that serves as an ejecting device that ejects sheet S to the intermediate stack tray  100  falls at the moment when it leaves conveyance rollers  102  that forms an ejection exit through which the sheet is ejected, and it is caught by the leading edge stopper  105  to be placed on the intermediate stack tray  100 . 
         [0079]    The leading edge stopper  105  is set so that the sheet S may stop after the trailing edge leaves conveyance roller  102  surely. 
         [0080]    The leading edge stopper  105  is driven by motor M 1  to move to be set so that trailing edge position H 2  of sheet S that is placed on the intermediate stack tray  100  may be always at a constant height, even in the case where sheets S each having a different size are conveyed. 
         [0081]    A plurality of sheets S are placed on the intermediate stack tray  100  and when plural sheets are placed, succeeding sheet S is supplied to the intermediate stack tray  100  under the state where preceding sheet S exists on the intermediate stack tray  100 . 
         [0082]    In this case, it is necessary to set the position of the leading edge stopper  105  so that a trailing edge of carry-in (upper end) of the preceding sheet may not hit a leading edge of carry-in (lower end) of the succeeding sheet. 
         [0083]    The leading edge of the succeeding sheet is ejected along a path shown with chain line L 1  from conveyance roller  102 . 
         [0084]    Path L 1  is determined by a shape of a conveyance path although it may be slightly changed depending on properties of sheet S, and it does not take a position that is higher than the upper limit leading edge landing point shown by landing position height H 3  where the Leading edge of sheet S lands on the intermediate stack tray  100 . 
         [0085]    The upper limit of height H 3  of the landing position is determined, in a design stage of the device, by a sheet-feeding test wherein the maximum thickness of sheets S stacked on the intermediate stack tray  100  is estimated. 
         [0086]    By setting the leading edge stopper  105  so that height H 2  of a position of a trailing edge of sheet S on the intermediate stack tray  100  may be higher than height H 3  of a landing position, sheets S supplied continuously on the intermediate stack tray  100  are stacked on the intermediate stack tray  100  smoothly, without any collision between respective sheets. 
         [0087]    As described above, when the position of the leading edge stopper  105  is set so that height H 2  of a trailing edge of sheet S stacked on the intermediate stack tray  100  may be lower than the lower bottom (ejection exit) of conveyance roller  102  that forms a lower end of a sheet ejection section of conveyance path Hi, and height H 2  of a trailing edge of sheet S may be higher than height H 3  of a landing position of sheet S, sheets S supplied continuously on the intermediate stack tray  100  are stacked smoothly. 
         [0088]    When sheets S of the set quantity are stacked on the intermediate stack tray  100 , gripping member  106  rotates in the direction of arrow W 1  to grip sheet S. In this case, the gripping member  106  moves together with leading edge stopper  105 . 
         [0089]    The gripping member  106  is driven by solenoid SL to rotate in the direction of arrow W 1 , and grips sheet S between the intermediate stack tray  100  and the gripping member  106 . 
         [0090]    In the processing of saddle stitching for a plurality of sheets S, leading edge stopper  105  is set to the position where a center line of sheet S in its conveyance direction agrees with a stapling position of stapler  103 , under the state where sheet S is gripped by gripping member  106 . 
         [0091]    Under this state, a stitching process is conducted by stapler  103 . 
         [0092]    Folding process section  50  has folding plate  52  and folding rollers  53 ,  54  and  55 . 
         [0093]    In center folding process, leading edge stopper  105  is set to the position where a center line of sheet S agrees with a middle position between folding roller  53  and folding roller  54 . Under this condition, when folding plate  52  enters a space between folding roller  53  and folding roller  54 , then, sheet S is inserted in a space between both rollers  53  and  54 , and when folding rollers  53  and  54  are rotated under the condition that sheet S is inserted, the sheet S is conveyed while it is subjected to the folding process. 
         [0094]    A processing apparatus that conducts folding process by using folding plate and three folding rollers  53 - 55  is widely known, and for example, those disclosed in Unexamined Japanese Patent Application Publication No. 2006-56669 can be used. 
         [0095]    As stated above, leading edge stopper  105  moves to the first stop position that is a position for stacking sheets S, the second stop position for a stitching process and to the third stop position for a folding process, and as is shown with dotted lines in  FIG. 2 , the leading edge stopper  105  and the gripping member  106  move unitedly when they move between the aforesaid plural stop positions. 
         [0096]    Operations of the post-processing apparatus with the aforesaid structure will be described as follows, referring to  FIGS. 4-6 . 
         [0097]      FIG. 4  is a block diagram of a control system of a post-processing apparatus relating to Embodiment 1 of the invention,  FIG. 5  is a flow chart of operations of a post-processing apparatus in saddle stitching-center folding and  FIG. 7  is a flow chart of operations of a post-processing apparatus in side stitching. 
         [0098]    In  FIG. 4 , the numeral  200  represents a control device provided on post-processing apparatus FS, and  201  represents a main control device that is provided on an image forming apparatus main body and controls an overall image forming apparatus. 
         [0099]    The control device  200  controls post-processing apparatus FS shown in  FIG. 1 . 
         [0100]    In step ST 1  sheet size information, namely, size information such as A4 size and B4 size are acquired from the main control device  201 . Meanwhile, this size information includes information of longitudinal feeding (conveyance wherein a length in a width direction is of the long side) and information of lateral feeding (conveyance wherein a length in a conveyance direction is of the long side). 
         [0101]    In step ST 2 , motor M 1  operates, and leading edge stopper  105  moves to the first stop position. 
         [0102]    The first stop position is a position where sheet S is supported so that the trailing edge of sheet S on intermediate stack tray  100  in the case of carry-in in all sheet sizes may be at the height shown by H 2  in  FIG. 3 . 
         [0103]    Sheets S of the set quantity are supplied to intermediate stack tray  100  while leading edge stopper  105  is set to the first stop position. 
         [0104]    Sheet alignment in step ST 3  means operations wherein the aligning member  104  is driven by motor M 2  to be reciprocated in the width direction, and this sheet alignment is carried out every time each sheet S is supplied. 
         [0105]    When sheets S of the set quantity have been stacked, solenoid SL operates in step ST 4  to rotate gripping member  106 , whereby, edges of sheets S are gripped. 
         [0106]    Next, in step ST 5 , a judgment is made whether the mode is for saddle stitching-center folding or for center folding in which no saddle stitching is carried out. The judgment in step ST 5  is made based on information coming from main control device  201 . 
         [0107]    In the case of the saddle stitching-center folding (Y of step ST 5 ), motor M 1  operates to move leading edge stopper  105  in step ST 6 . A movement of the leading edge stopper  105  is a movement to the second stop position where a center line of sheet S in its conveyance direction agrees with a stapling position of stapler  103 . 
         [0108]    In step ST 7 , stitching process for stapling on sheets S is carried out, and in step ST 8 , edges of sheets S are gripped again by gripping member  106 . 
         [0109]    Gripping of sheet S is continued while leading edge stopper  105  is moving, and the gripping is released when the movement of the leading edge stopper  105  is completed and when the sheet S is set to the set height. 
         [0110]    In step ST 9  following the step ST 8 , leading edge stopper  105  moves and stops. This movement in ST 9  is to move leading edge stopper  105  to the third stop position where the center line of sheet S agrees with a middle position between folding roller  53  and folding roller  54 . 
         [0111]    In step ST 10 , the sheets are folded. The folded sheets S are discharged to lower sheet discharge tray  83 . 
         [0112]    In a folding process without stitching, namely, in a center folding process, the procedure proceeds from step ST 5  to step ST 11 , then, leading edge stopper  105  is moved to the third stop position, and a center line of sheet S in the conveyance direction is caused to agree with a middle position between folding roller  54  and folding roller  55 . 
         [0113]    In step ST 12  that follows step ST 11 , a folding process is carried out, and the sheet S folded in step ST 12  is discharged to end the processes. 
         [0114]      FIG. 6  is a diagram showing a sheet collecting device relating to Embodiment 2 of the invention, and  FIG. 7  is a flow chart of operations of Embodiment 2. 
         [0115]    Embodiment 2 is an example wherein side stitching is carried out for sheets S stacked on an intermediate stack tray. 
         [0116]    Side stitching is a processing to stitch edges of sheets S. In the side stitching, stitched sheets S are discharged without being folded. 
         [0117]    Leading edge stopper  105  supports sheet S under the illustrated state, in collecting and in stitching process of sheet S. 
         [0118]    When the stitching process has been completed, leading edge stopper  105  is driven by solenoid SLa to rotate in the direction of arrow W 2 , and releases sheet holding. 
         [0119]    Sheet S released in terms of holding falls along intermediate stack tray  100  to be discharged. 
         [0120]    In  FIG. 7 , steps from step ST 1  to step ST 4  are the same as those in  FIG. 5 , and sheet S is gripped by gripping member  106  at the first stop position. 
         [0121]    In step ST 20  following ST 4 , leading edge stopper  105  moves so that a stitching position of sheet S may agree with stitching position of stapler  103 . 
         [0122]    In step ST  21 , stapler  103  conducts a stitching process, and in step ST 22 , gripping member  106  releases gripping and leading edge stopper  105  rotates in the direction of arrow W 2  to cause sheet S to fall, thus, sheet S is discharged. 
         [0123]    In the present embodiment, a sheet is caused to fall in the direction of ejecting from a sheet ejecting device on a sheet collecting board, and a position of a leading edge stopper is set so that a trailing edge of the sheet (upper end) may be at a constant position, whereby, downsizing is possible and a sheet collecting device that operates stably can be realized.