Abstract:
A sheet stacking apparatus having: a sheet discharge tray to move upward and downward; an alignment section including first and second regulating members to align a side edge of a sheet on the tray; a first drive section for moving the tray upward or downward; a second drive section for moving the regulating members in a conveyance width direction; and a control section for controlling the first and the second drive sections so as to: align the side edge of the sheet discharged on the tray on the basis of the position of the first regulating member; when a predetermined amount of the sheets are discharged on the tray, separate the sheets from the first regulating member and the second regulating member by moving the tray or the alignment section and, after that, move the regulating members in the conveyance width direction; and align the side edge of the sheets.

Description:
RELATED APPLICATION 
     This application is based on Japanese Patent Application No. 2007-185433 filed on Jul. 17, 2007, in Japanese Patent Office, the entire content of which is hereby incorporated by reference. 
     BACKGROUND 
     1. Field of the Invention 
     The present invention relates to an improvement of a sheet discharge part in a sheet processing apparatus used in combination with an image forming apparatus. 
     2. Description of the Related Art 
     When delivering sheets on which images are formed or sheets on which images are formed and post processing such as punch processing, binding processing, and punching processing is conducted, to a sheet discharge tray, sorting processing is conducted and delivered. 
     In the sorting processing, there is a shift processing which is simple and most widely conducted, and this shift processing is a processing in which, for each number of setting sheets, the sheets are displaced in a conveyance width direction, that is, a direction perpendicular to the conveyance direction and parallel to the sheet surface of the conveyed sheet, and discharged. 
     As the shift processing, a method in which, in the sheet discharge port, the sheet is freely dropped from sheet discharge port and stacked on the sheet discharge tray, is common. 
     In such a shift sheet discharge, because the sheet is separated from sheet discharge port and freely dropped, the deviation is generated in the movement of the sheet in the process of the drop, and the grounding position on the sheet discharge tray of the sheet, is deviated, and there is a problem that the alignment condition of the sheet on the sheet discharge tray is not so good. 
     In Japanese Unexamined Patent Application Publication No. 2001-187665 (hereinafter referred to as JPA 2001-187655), in order to solve this problem, it is proposed that an aligning means for guiding the sheet on the stage that the sheet is not separated from the sheet discharge port is used, and the sheet is aligned. 
     In JPA 2001-187655, in order to shift the sheet, the discharge tray is displaced in the conveyance width direction. 
     Although the shift processing is not conducted, in Japanese Unexamined Patent Application Publication No. 2003-2524 (hereinafter referred to as JPA 2003-2524), a regulating member which guides the side edge of the sheet on the sheet discharge tray is used. 
     In JPA 2001-187655 and JPA 2003-2524, when the sheet is placed on the sheet discharge tray, the sheet is guided not by free-dropping, but by regulating member, and stacked. 
     Then, for the shift processing which changes the sheet position to the conveyance width direction, in JPA 2001-187655, the sheet discharge tray is displaced, and in JPA 2003-2524, it does not have the shift function. 
     In the shift processing of the JPA 2001-187655, the sheet discharge tray displaces in the conveyance width direction. Therefore, when a lot of sheets are stacked on the sheet discharge tray, because the sheet discharge tray having a large mass reciprocates and the inertia functions, the drive mechanism corresponding to this, is necessary, and a large drive mechanism becomes necessary. 
     Further, because the stacked sheets repeat the movement in the conveyance width direction, there is a case where the alignment condition is broken. 
     Further, because the sheet discharge tray moves in the conveyance width direction, when the sheet discharge tray is elevated and lowered, there is a problem that the drive mechanism of the sheet discharge tray becomes complicated. 
     SUMMARY 
     One aspect of the present invention is to provide a sheet stacking apparatus comprising: a sheet discharge tray adapted to support on which discharged sheets, and to move upward and downward; an alignment section including a first regulating member and a second regulating member with which the alignment section aligns a side edge of a sheet discharged on the sheet discharge tray; a first drive section for moving the sheet discharge tray or the alignment section upward or downward; a second drive section for moving the first regulating member and the second regulating member in a conveyance width direction; and a control section for controlling the first drive section and the second drive section, wherein the control section controls the first drive section and the second drive section so as to: align the side edge of the sheet discharged on the sheet discharge tray on the basis of the position of the first regulating member, by fixing the position of the first regulating member and moving the second regulating member in the conveyance width direction; when a predetermined amount of the sheets are discharged on the sheet discharge tray, separate the sheets discharged on the discharge tray from the first regulating member and the second regulating member by moving the sheet discharge tray or the alignment section and, after that, move the first regulating member and the second regulating member in the conveyance width direction; and align the side edge of the sheets discharged on the sheet discharge tray by fixing the position of the second regulating member and moving the first regulating member in the conveyance width. Further aspect of the present invention is to provide a sheet processing apparatus comprising: a shift member adapted to discharge a sheet by displacing the sheet in a conveyance width direction; and the above-sheet stacking apparatus. Further aspect of the present invention is to provide an image forming system comprising: an image forming apparatus for forming an image on a sheet; and the above-sheet processing apparatus which carries out a processing to a sheet carrying an image formed by the image forming apparatus. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an overall drawing of the image forming system having a sheet stacking apparatus and a sheet processing apparatus. 
         FIG. 2  is a view showing a sheet bundle which is shift processed. 
         FIGS. 3  ( a ) and  3  ( b ) are front sectional views of the sheet stacking apparatus. 
         FIG. 4  is a front sectional view of the sheet stacking apparatus. 
         FIG. 5  is a plan view of the sheet stacking apparatus. 
         FIG. 6  is a block diagram of the control system for conducting the shift control. 
         FIG. 7  is a view showing the operation sequence of the sheet stacking apparatus. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Next, although by using the shown embodiments of the present invention, the description is made, however, the present invention is not limited to the embodiments. 
       FIG. 1  is an overall view of the image forming system having the sheet stacking apparatus and the sheet processing apparatus. 
     The image forming system  100  is provided with the image forming apparatus A and the post-processing apparatus FS. 
     The image forming apparatus A is provided with the image reading part  1 , image processing part  2 , image writing part  3 , image forming part  4 , cassette sheet feed part  5 , sheet feed roller part  6 , fixing apparatus  7 , sheet discharge part  8 , automatic double sides copy sheet feeding part (ADU)  9  and system control part SC. 
     On the upper part of this image forming apparatus A, the automatic document feeding apparatus DF is mounted. The document placed on the document table of the automatic document feeding apparatus DF is conveyed in the arrow mark direction, the image of the single surface or images of double surfaces are read by the optical system of the image reading part  1 , and read into the CCD image sensor  1 A. 
     The analog signal photoelectrically converted by the CCD image sensor  1 A, is subjected to analog processing, A/D conversion, shading correction, and image compression processing in the image processing part  2 , and then the signal is sent to the image writing part  3 . 
     In the image writing part  3 , the output light from the semiconductor laser is irradiated on the photoreceptor drum  4 A of the image forming part  4 , and a latent image is formed. In the image forming part  4 , processing such as charging, exposing, developing, transferring, separating, cleaning, are conducted, and the image is transferred onto the sheet S conveyed from the cassette sheet feed part  5  through the sheet feed roller part  6 . 
     The sheet S on which the image is carried, is subjected to fixing process by the fixing apparatus  7  and discharged from the sheet discharge part  8 . 
     The system control part SC controls the overall operation of the image forming system  100 . 
     That is, the system control part SC simultaneously control other than the image forming apparatus A, also the operation of post-processing apparatus FS. 
     The sheet S discharged from the sheet discharge part  8  of the image forming apparatus A is delivered through the conveyance path P 1  or the conveyance path P 2  to the sheet discharge tray  20  or sheet discharge tray  60 . 
     The sheet discharge tray  20  is a fixed sheet discharge tray, and does not conduct post-processing, and when small-number of job, the sheet S is discharged to the sheet discharge tray  20 . 
     The sheet discharge tray  60  is a tray which elevates and lowers as shown by arrow-mark W 1 , by the drive of the motor M 1  as the first drive section and when a lot of image formation, and when staple processing is conducted, the sheet S is discharged on the sheet discharge tray  60 . 
     In the staple processing, the sheet S elevates on the intermediate tray  30  from the sheet introduction part  10  through the conveyance path P 2 . The intermediate tray  30  is inclined as shown in the drawing, and after the sheet S sent from the conveyance path P 2  is elevated in the left slanting direction on the intermediate tray  30 , after separating from the sheet discharge roller P 2 R of the conveyance path P 2 , slides and drops on the intermediate tray  30 , and stacks on the staple position. 
     On the stage on which a predetermined number of sheets S are stacked, the stapler  40  is operated and staple-processes the sheet bundle. 
     The sheet bundle after staple processing elevates on the intermediate tray  30  and discharged to the sheet discharge tray  60  by the sheet discharge roller  50 . 
     In the shift processing, the sheet S discharged from the sheet discharge roller P 2 R of the conveyance path P 2  slides and drops on the intermediate tray  30 , and stops at the predetermined position. 
     After the stop of the sheet S, the aligning plate  31  as the shift member, reciprocally moved in the conveyance width direction parallel to the surface of the sheet and perpendicular to the conveying direction, and aligns the sheet S. 
     Although not shown, the alignment of the sheet S by the aligning plate  31  is conducted by the well-known mechanism. 
     That is, a pair of aligning plates  31  arranged on the both sides of the intermediate tray  30  reciprocally moves 1 to several times, in the conveyance width direction and the sheet S is aligned. 
     In the shift processing, the aligning position of the sheet is set by the aligning plate  31 , and changed to the conveyance width direction for each shift unit of a predetermined amount. 
     As the result, as shown in  FIG. 2 , the sheet bundle SA which is shift processed, is stacked on the discharge tray  60 . 
     In the field of POD (Print On Demand), as shown in  FIG. 2 , to the sheet bundle SA, there is many cases that the processing is conducted further by the off-line book-binder for each shift unit. 
     For this purpose, for example, in the book-binding processing, it is required that there is no concave and convex on the side edge SB of the sheet bundle for each shift unit, and side edge is flat surface like. 
     The sheet stacking apparatus described below, satisfies such needs. 
       FIGS. 3(   a ),  3 ( b ), and  4  are front sectional views of the sheet stacking apparatus according to the embodiment of the present invention,  FIG. 5  is a plan view of the sheet stacking apparatus,  FIG. 6  is a block diagram of the control system for conducting the shift control,  FIG. 7  is a view showing an operation sequence of the sheet stacking apparatus. 
     The sheet stacking apparatus which discharges the sheet S to the sheet discharge tray  60  has the sheet discharge tray  60 , the regulating member  61 A as the first regulating member, the regulating member  61 B as the second regulating member, the pressing member  62 A,  62 B, and the sensor  63 . 
     As shown in  FIG. 5 , a pair of regulating members  61 A,  61 B and a pair of pressure members  62 A,  62 B are arranged parallel in the conveyance width direction. 
     Hereupon, the sheet discharge roller  50 , as shown in  FIG. 3 ,  5 , the upper roller which is the drive roller, and the lower roller which is a following roller, and arranged three in parallel in conveyance width direction. 
     The regulating members  61 A,  61 B are to align the sheet S discharged by the sheet discharge roller  50 , and separates from the sheet discharge roller  50 , in the conveyance width direction, and the sheet S discharged from the sheet discharge roller  50  is guided to a predetermined position in the conveyance width direction, and is grounded on the sheet discharge tray  60 . By the regulating members  61 A,  61 B, the side edge in the conveyance width direction of the sheet S is aligned very accurately. 
     At the sheet discharge time, as described next, one direction alignment in which the regulating member  61 A is fixed, the regulating member  61 B is moved in the conveyance width direction, and the sheet S is brought into contact with the regulating member  61 A, or another direction alignment in which the regulating member  61 B is fixed, the regulating member  61 A is moved in the conveyance width direction, and the sheet S is brought into contact with the regulating member  61 B, is conducted. 
     The movement of the conveyance width direction of the regulating member  61 A is conducted by the motor M 2  which functions as the second drive section, and the movement of the conveyance width direction of the regulating member  61 B is conducted by the motor M 3  which functions as the second drive section. 
     The regulating member  61 A and  61 B, further, by the manual operation of the operator, can rotate to the retreat position shown by dotted line of  FIG. 4 . 
     Pressing members  62 A,  62 B are driven by the solenoid SL, as shown by  FIGS. 4 and 5 , press the sheet S on the discharge sheet tray  60 , and hold so as not to collapse the alignment condition. 
     By using  FIG. 7 , the alignment of the sheet S in the sheet discharge at the time of shift processing will be described. 
     In STEP  1 -STEP  4  . . . , the alignment in the shift processing of 1 unit is conducted. 
     The operation of motor M 1  for driving the sheet discharge tray  60 , the operation of motors M 2 , M 3  for driving the regulating members  61 A,  61 B, and the operation of solenoid SL for driving the pressing members  62 A,  62 B is conducted under the control of the control part CR of  FIG. 6 . 
     In STEP  1 , the sheet stacking apparatus is in the condition shown in  FIGS. 3(   a ) and  3 ( b ) and shown by the solid line of  FIG. 5 . 
     That is, the regulating members  61 A,  61 B are rotatably supported on the axis, and its front edge is held at a predetermined lower limit position by a not shown stopper. 
     Then, the regulating member  61 A is placed on the sheet S on the sheet discharge tray  60  as shown in  FIG. 3(   a ), and the regulating member  61 B is at the position which presses the side edge of the conveyance width direction of the sheet S. 
     In STEP  1 , the first sheet S 1  in the shift unit  1  is discharged on the sheet discharge tray  60 . When the sheet S exists on the sheet discharge tray  60 , the sheet S 1  is placed on the sheet of the sheet discharge tray. 
     Hereupon, in the condition of STEP  1 , the upper most surface of the sheet S is set at a predetermined position by the sensor  63 . That is, the control section CR controls the motor M 1  by the sheet surface detecting signal produced by the sensor  63 , and makes the sheet discharge tray  60  up and down, and the upper most surface of the sheet S is maintained at a predetermined position. 
     In the condition shown in  FIGS. 3(   a ) and  3 ( b ), the regulating member  61 B conducts one reciprocal movement of arrow mark W 2  in  FIG. 5 , by the drive of motor M 3 , and the sheet S 1  is brought into contact with the regulating member  61 A (STEP  2 ). 
     In STEP  2 , the regulating member  61 A, which is the first regulating member, is fixed at the first reference position, and one direction alignment which the sheet S is aligned at the first reference position, is conducted by the regulating member  61 B which is the second regulating member. 
     By this alignment movement of the regulating member  61 B, the sheet S 1  is aligned in the conveyance width direction. 
     In STEP  3 , the second sheet S 2  is discharged, in STEP  4 , to the second sheet S 2 , the one direction alignment in the same manner as STEP  2 , is conducted, and the sheet S 2  is aligned. 
     Until the sheet S of numbers constituting the shift unit is discharged, the one direction alignment is conducted below. 
     On the stage in which one unit shift sheet discharge is completed, in STEP  5 , the solenoid SL is operated and the pressing members  62 A,  62 B are rotatably driven counterclockwise, the pressing members  62 A,  62 B press the sheet S on the sheet discharge tray, and hold the sheet S not so as the alignment condition collapse. 
     In STEP  6 , the sheet discharge tray  60  is lowered by a predetermined amount, by the drive of the motor M 1 , and is in the condition shown in  FIG. 4 . 
     In the condition of STEP  6 , the lower ends of the regulating members  61 A,  61 B, and the uppermost surface of the sheet S are separated from each other. 
     By this separation, the regulating members  61 A,  61 B can move in the conveyance width direction, and the regulating members  61 A,  61 B respectively moves to the position of  61 A 1 ,  61 B 1  shown by the dotted line of  FIG. 5  (STEP  7 ). 
     The movements in STEP  7  are conducted by the drive of motors M 2 , M 3 , and these movements are movements to a position that corresponds to a position where the sheet discharge position shifts in the conveyance width direction, for example, a position shifted by 30 mm from the solid line position of  FIG. 5 . 
     In the dotted line positions  61 A 1 ,  61 B 1 , the regulating member  61 B is positioned in the area of the sheet S, and the regulating member  61 A is positioned out of area of the sheet S. 
     Next, in STEP  8 , the motor M 1  operates, and stops by the sheet detecting signal of the sensor  63 , the sheet discharge tray  60  elevates again to the position of  FIGS. 3(   a ) and  3 ( b ). 
     In STEP  8 , although the regulating member  61 A is in out of area of the sheet S, because the regulating member  61 B is in the area of the sheet S, the regulating member  61 A is in the position which brought into contact with the side edge of the sheet S in the same manner as the regulating member  61 B of  FIG. 3(   b ), the regulating member  61 B is on the sheet S in the same manner as the regulating member  61 A of  FIG. 3(   a ). 
     In STEP  9 , the solenoid SL is turned off, the sheet pressure by the pressing members  62 A,  62 B is released. 
     In STEP  10 , the first sheet S 1  in the shift unit  2 , is shifted in the opposite direction to the case of STEP  1 , and discharged. 
     In STEP  11 , the regulating member  61 A reciprocates once in the conveyance width direction by the drive of the motor M 1 , the sheet S is brought into contact with the regulating member  61 B, and aligned in another direction. 
     In STEP  11 , the regulating member  61 B which is the second regulating member is fixed at the second reference position, another direction alignment in which the sheet S is aligned at the second reference position is conducted by the regulating member  61 A which is the first regulating member. 
     In STEP  12 , the second sheet S 2  is discharged, in STEP  13 , another direction alignment in the same manner as STEP  11  is conducted. 
     The sheets S of the number of sheets constituting the shift unit  2  are delivered and thereafter, the alignment of another direction is conducted. 
     The shift unit  2  is formed by this sheet discharge and another direction alignment. 
     In case of multiple sheets discharge which form many shift units, the processing of  FIG. 7  to the shift units  1 ,  2  is repeatedly conducted. 
     As described above, the present invention is described based on embodiments, however, the present invention includes various modification examples other than the embodiments. 
     For example, as the shift member, instead of the alignment plate, a device in which the conveying roller is moved in the rotation axis direction which is conveyance width direction and shifting is conducted, can be used. 
     Further, as the mechanism by which the sheet on the sheet discharge tray and the regulating member are separated, the mechanism by which the sheet discharge tray is not lowered, but the pressing member is elevated, can also be used. 
     In the present invention, under the condition that the regulating member which aligns the sheet on the sheet discharge tray, and the discharged sheet are separated on the sheet discharge tray, when the position relationship between the regulating member and the sheet discharge tray is changed, the alignment of the sheet corresponding to the shift sheet discharge is conducted on the sheet discharge tray. 
     Accordingly, the position at which the sheet grounds on the sheet discharge tray can be regulated high accurately. 
     However, the moving mechanism of the sheet discharge tray and regulating member are simple, and the sheet stacking apparatus and the sheet processing apparatus having low cost and high accurate sheet position aligning function are realized.