Abstract:
An image forming apparatus including a sheet loader, the sheet loader including: a discharger configured to discharge a first sheet and a second sheet after the first sheet; a tray configured to support the second sheet on the first sheet; a support configured to support the first sheet on the tray; a controller configured to control the support to lower a first angle than a second angle, the first angle being an angle of the first sheet against a direction to which the discharger discharges the second sheet at a position where the second sheet hits on the first sheet, the second angle being an angle of the tray against the direction at a position where the first sheet hits on the tray.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from: U.S. provisional application 61/036,449, filed on Mar. 13, 2008; U.S. provisional application 61/036,454, filed on Mar. 13, 2008; U.S. provisional application 61/061,998, filed on Jun. 16, 2008; and U.S. provisional application 61/081,693, filed on Jul. 17, 2008, the entire contents of each of which are incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     Described herein relates to a sheet loader and an image forming apparatus, and, more particularly to a sheet loader and an image forming apparatus capable of preventing occurrence of a paper jam between sheets put on standby on standby trays. 
     BACKGROUND 
     Recently, an image forming apparatus of an electrophotographic system such as a laser printer, a digital copying machine, or a laser facsimile includes a post-process apparatus (a finisher) that staples a sheet bundle. The finisher includes a stapler for stapling the sheet bundle. The finisher in the past includes, on an upstream side in a sheet conveying direction of a process tray, standby trays for temporarily storing sheets. The standby trays temporarily store (buffer) one to several sheets while the finisher staples sheets on the process tray. The standby trays temporarily store (buffer) one to several sheets while the finisher sorts sheets on the process tray. 
     However, when the finisher puts sheets on standby on the standby trays, it is also likely that the finisher further puts another sheet on standby on top of a sheet already put on standby on the standby trays. When friction between the sheet already put on standby on the standby trays and the sheet put on standby on top of the sheet is large or when a contact angle between the sheets is large, a paper jam occurs. 
     SUMMARY 
     Described herein relates to a sheet loader including: a discharger configured to discharge a first sheet and a second sheet after the first sheet; a tray configured to support the second sheet on the first sheet; a support configured to support the first sheet on the tray; a controller configured to control the support to lower a first angle than a second angle, the first angle being an angle of the first sheet against a direction to which the discharger discharges the second sheet at a position where the second sheet hits on the first sheet, the second angle being an angle of the tray against the direction at a position where the first sheet hits on the tray. 
     Described herein relates to an image forming apparatus including a sheet loader, the sheet loader including: a discharger configured to discharge a first sheet and a second sheet after the first sheet; a tray configured to support the second sheet on the first sheet; a support configured to support the first sheet on the tray; a controller configured to control the support to lower a first angle than a second angle, the first angle being an angle of the first sheet against a direction to which the discharger discharges the second sheet at a position where the second sheet hits on the first sheet, the second angle being an angle of the tray against the direction at a position where the first sheet hits on the tray. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       In the accompanying drawings: 
         FIG. 1  is a diagram illustrating an entire image forming apparatus according to an embodiment. 
         FIG. 2  is a diagram of a configuration of a finisher according to an embodiment; 
         FIG. 3  is a diagram of a state in which the finisher guides a sheet bundle to a stapler after the finisher sequentially guides the sheet bundle to a process tray through standby trays; 
         FIG. 4  is a perspective view of the finisher shown in  FIG. 2 ; 
         FIG. 5  is another perspective view of the finisher shown in  FIG. 2 ; 
         FIG. 6  is still another perspective view of the finisher shown in  FIG. 2 ; 
         FIG. 7  is a sectional view of the finisher shown in  FIG. 2 ; 
         FIG. 8  is still another perspective view of the finisher shown in  FIG. 2 ; 
         FIG. 9  is a diagram for explaining a discharge operation for a sheet bundle in the finisher; 
         FIGS. 10A and 10B  are diagrams for explaining the discharge operation for a sheet bundle in the finisher; 
         FIG. 11  is a block diagram of a schematic configuration of the inside of a control system of the finisher according to the embodiment; 
         FIG. 12  is a diagram for explaining a paper jam that could occur if a sheet put on standby on the standby trays is a second or subsequent sheet; 
         FIG. 13  is a diagram for explaining a method of moving a pedestal position if a sheet put on standby on the standby trays is a second or subsequent sheet in the embodiment; 
         FIG. 14  is a diagram of movable guides provided in the standby trays; 
         FIGS. 15A and 15B  are diagrams of a state in which the finisher stacks a sheet in a V shape and conveyed in a V shape on the standby trays; 
         FIGS. 16A and 16B  are diagrams of a method of smoothly conveying a sheet in the embodiment; 
         FIG. 17  is a diagram of a state in which the finisher smoothly conveys a sheet on the standby trays; 
         FIG. 18  is a diagram of a state of a paper jam that occurs if the leading end of a sheet enters a space between a slide rail unit and pivoting rollers; 
         FIG. 19  is a diagram of a state in which, by extending a form of a tapping arm, the finisher prevents the leading end of a second sheet from entering the space between the slide rail unit and the pivoting rollers; 
         FIG. 20  is a perspective view of the tapping arm; 
         FIG. 21  is another perspective view of the tapping arm; 
         FIGS. 22A to 22C  are diagrams of operations of standby trays in the past in the case of active drop; and 
         FIGS. 23A to 23F  are diagrams of operations of the standby trays in the embodiment in the case of active drop. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are explained below with reference to the accompanying drawings. 
     The entire disclosures of U.S. Pat. No. 7,043,192 filed on Dec. 10, 2004, U.S. Pat. No. 7,206,542 filed on Dec. 10, 2004, U.S. Pat. No. 7,406,293 filed on Dec. 10, 2004, U.S. Pat. No. 7,159,860 filed on Dec. 10, 2004, and U.S. Pat. No. 7,215,922 filed on Dec. 10, 2004 including specifications, claims and summaries are incorporated herein by reference in their entireties. 
     First Embodiment 
       FIG. 1  is a diagram illustrating an entire image forming apparatus  201  according to the embodiment. As  FIG. 1  shows, the image forming apparatus has an image forming unit  202  and a finisher  1 . 
       FIG. 2  is a diagram of a configuration of a finisher (a post-process apparatus)  1  according to an embodiment. Entry rollers  11   a  and  11   b  are a pair of rollers and receive a sheet P supplied from an image forming unit  202  provided on the outside of the finisher  1 . The entry rollers  11   a  and  11   b  convey the received sheet P to exit rollers  12   a  and  12   b . Standby trays  13  temporarily store the sheet P conveyed from the exit rollers  12   a  and  12   b . The finisher  1  opens the standby trays  13  and drops and supplies the temporarily stored sheet P to a process tray  14 . A sheet guide  18  guides the trailing end of the sheet P on the process tray  14 , to a stapler  19 . Lateral alignment plates  16  laterally align the sheet P on the process tray  14 . A paddle  15  and longitudinal alignment rollers  17  strike the trailing end of the sheet P on the process tray  14  against a rear stopper  26  and longitudinally align the sheet P. The paddle  15  includes a long paddle  15   a  and a short paddle  15   b . The standby trays  13  have movable guides  51  including a movable fulcrum. The finisher  1  has pivoting rollers  52 . 
     As  FIG. 3  shows, the finisher  1  sequentially guides sheets P to the process tray  14  through the standby trays  13  and, thereafter, guides sheets P to the stapler  19  by the process explained above. The sheet guide  18  moves to increase a space between the sheet guide  18  and the process tray  14 . If the finisher  1  guides the sheet P of the last page to the stapler  19 , the stapler  19  staples a sheet bundle of the sheets P. Ejectors  20  have eject arms. The ejectors  20  push out the sheet bundle stapled by the stapler  19  in the direction of a stacking tray  23  and pass the sheet bundle to a bundle pawl belt  21 . The bundle pawl belt  21  has a bundle pawl  21   a . The bundle pawl belt  21  catches the sheet bundle with a bundle pawl  21   a  and discharges the sheet bundle to the stacking tray  23  in association with a discharge operation by discharge rollers  22 . A bundle pawl motor that drives the bundle pawl belt  21  drives the ejectors  20  via an electromagnetic spring clutch. If the electromagnetic spring clutch is turned on, the electromagnetic spring clutch transmits driving force of the bundle pawl motor to the ejectors  20 . 
       FIGS. 4 to 6  are perspective views of the finisher  1 . Push rods  25  integrally form with the ejectors  20 . Resin bonds to the distal ends of the push rods  25 .  FIG. 7  is a sectional view of the finisher  1 . The finisher  1  shown in  FIGS. 3 to 6  has two push rods  25 . On the other hand, the finisher  1  shown in  FIG. 8  has four push rods  25 . 
     A discharge operation for the sheet bundle in the finisher  1  is explained with reference to  FIG. 9  and  FIGS. 10A and 10B . When stapling of the sheet bundle is completed, the electromagnetic spring clutch is turned on and driving force is transmitted to the ejectors  20 , whereby the ejectors  20  are driven. The bundle pawl belt  21  and the discharge rollers  22  are simultaneously driven. As  FIGS. 9A and 9B  show, the bundle pawl  21   a  of the bundle pawl belt  21  overtakes the ejectors  20  and receives the sheet bundle from the ejectors  20 . The bundle pawl  21   a  catches the sheet bundle and discharges the sheet bundle to the stacking tray  23  in association with the discharge operation of the discharge rollers  22 . The bundle pawl  21   a  moves along a curve track, which is away from a center of rotation N by a distance r, in order to return to a home position after the discharge of the sheet bundle. A part in which the pawl bundle  21   a  rotates is defined as “rotation part M”. 
       FIG. 11  is a diagram of a schematic configuration of the inside of a control system of the finisher  1  according to this embodiment. As  FIG. 11  shows, the control system of the finisher  1  includes a CPU (Central Processing Unit)  101 , a ROM (Read Only Memory)  102 , a sensor input circuit  103 , a driving circuit  104 , and a driver  105 . The CPU  101  executes various kinds of processing according to various application programs stored in the ROM  102 , generates various control signals, and supplies the control signals to the respective units of the finisher  1  to thereby collectively control the finisher  1 . The ROM  102  stores necessary data if the CPU  101  executes the various kinds of processing. The sensor input circuit  103  supplies inputs from a group of various sensors to the CPU  101 . The driving circuit  104  switches ON and OFF of various electromagnetic spring clutches according to the control by the CPU  101 . The driving circuit  104  drives respective solenoids according to the control by the CPU  101 . The driver  105  drives respective motors according to the control by the CPU  101 . 
     The finisher  1  includes the standby trays  13  on an upstream side in a sheet conveying direction of the process tray  14 . The standby trays  13  temporarily store one to several sheets discharged from the exit rollers  12   a  and  12   b  while the finisher  1  staples the sheets on the process tray  14 . The standby trays  13  temporarily store one to several sheets discharged from the exit rollers  12   a  and  12   b  while the finisher  1  sorts the sheets on the process tray  14 . The standby trays  13  include lower standby trays  13 - 1  and upper standby trays  13 - 2 . When a sheet put on standby on the standby trays  13  is a first sheet, no sheet is put on standby on the lower standby trays  13 - 1 . Therefore, a sheet discharged from the exit rollers  12   a  and  12   b  to the standby trays  13  rubs against the lower standby trays  13 - 1  made of which has a resin member. However, a coefficient of friction of the lower standby trays  13 - 1  that rub against the sheet which the exit rollers  12   a  and  12   b  discharge to the standby trays  13  is small. Since the coefficient of friction of the lower standby trays  13  is small, a paper jam less easily occurs. 
     As  FIG. 12  shows, the finisher  1  has a pedestal  42  that supports the trailing end of a sheet put on standby on the lower standby trays  13 - 1 , in a rotation center shaft  41  as the center in rotating the long paddle  15   a  and the short paddle  15   b . A stepping motor as a driving unit that rotates the long paddle  15   a , the short paddle  15   b , and the pedestal  42  around the axis of the rotation center shaft  41  connects to the rotation center shaft  41 . 
     However, as  FIG. 12  shows, if a sheet put on standby on the standby trays  13  is a second or subsequent sheet, a sheet is already put on standby on the lower standby trays  13 - 1 . Therefore, a sheet discharged from the exit rollers  12   a  and  12   b  to the standby trays  13  rubs against the sheet already put on standby on the lower standby trays  13 - 1 . A coefficient of friction of the sheet already put on standby on the lower standby trays  13 - 1  is larger than the coefficient of friction of the lower standby trays  13 - 1 . If the coefficient of friction of the sheet is large, it is anticipated that a paper jam occurs. Specifically, as  FIG. 12  shows, the sheet which the exit rollers  12   a  and  12   b  discharge to the standby trays  13  has a contact angle θ between the sheet and the sheet already put on standby on the lower standby trays  13 - 1 . If the contact angle θ is large, the leading end of the next sheet discharged to the standby trays  13  bends. By bend of the leading end of the sheet, a paper jam may occur. In particular, if a sheet is long in the sheet conveying direction, it is more likely that the sheet bends in the lower standby trays  13 - 1 . If the sheet bends in the lower the standby tray  13 - 1 , the contact angle θ increases and a paper jam tends to occur. 
     In this embodiment, as shown in  FIG. 13 , if a sheet put on standby on the standby trays  13  is a second or subsequent sheet, the control unit  101  rotates the pedestal  42  around the axis of the rotation center shaft  41  using the stepping motor to move the pedestal  42  to a position T 2  higher than an initial position Ti of the pedestal  42  used if the first sheet is started to be put on standby on the standby trays  13 . This makes it possible to move, according to the movement of the pedestal  42 , the trailing end of the sheet put on standby on the lower standby trays  13 - 1  to nearly the position T 2 . By moving the trailing end of the sheet, it is possible to reduce the contact angle θ by an angle θ′ shown in  FIG. 13 . The angle θ′ increases according to an increase amount of the movement of the position of the pedestal  42 . The control unit  101  can control a movement amount of the position of the pedestal  42  by managing a pulse applied to the stepping motor that rotates the paddle  15  and the pedestal  42 . 
     After a last sheet that should be put on standby on the standby trays  13  is put on standby on the lower standby trays  13 , the control unit  101  rotates the pedestal  42  around the axis of the rotation center shaft  41  using the stepping motor to move the pedestal  42  from the position T 2  to the initial position T 1 . Thereafter, in order to drop the sheets put on standby on the standby tray  13  onto the process tray  14 , the control unit  101  rotates the pedestal  42  and the paddle  15  around the axis of the rotation center shaft  41  using the stepping motor. The finisher  1  performs an aligning operation on the process tray  14 . This makes it possible to suitably prevent occurrence of paper jam between the sheets put on standby on the standby trays  13  without occurrence of paper jam, put the sheets on standby and stack the sheets on the standby trays  13 , and suitably perform the aligning operation. 
     The contact angle θ may be changed according to a size of a sheet that enters the standby trays  13 . In other words, the contact angle θ may be reduced stepwise according to an increase in a sheet conveyance distance based on a size of a sheet put on standby on the standby trays  13 . 
     Second Embodiment 
     The finisher  1  in the past bends a sheet between the exit rollers  12  (the exit rollers  12   a  and  12   b ) and the pivoting rollers  52  using the movable guides  51  and stacks the sheet and puts the sheet on standby on the standby trays  13 . The finisher  1  bends the sheet in order to limit an area above the sheet conveying path because the distance in the height direction of the sheet conveying path is larger than the thickness of the sheet on the standby trays  13 . By bend of the sheet, it is possible to fix a conveyance amount of a sheet conveyed to the standby trays  13  and fix a sheet conveyance amount between the exit rollers  12  and the pivoting rollers  52  regardless of whether the sheet conveyed to the standby trays  13  is curled up or down. As  FIG. 14  shows, the movable guides  51  can move in an arc shape with a movable guide rotation fulcrum C as a fulcrum. 
     As  FIG. 15A  shows, two standby tray  13  respectively supports both the ends of the sheet that enters the standby trays  13 . However, if the movable guides  51  that limit the area above the sheet conveying path is used, an entrance angle of a sheet entering the standby trays  13  is large compared with an entrance angle at the time when the movable guides  51  are not used. The sheet entering the standby trays  13  may bend in the sheet conveyance height direction because of the gravity. As a result, as  FIGS. 15A and 15B  shows, the finisher  1  may stack the sheet in a V shape and convey the sheet in a V shape on the standby trays  13 . 
     When the next sheet is buffered in the standby trays  13 , if the preceding sheet already put on standby on the standby tray  13  is stacked in a V shape, the next sheet collides with the trailing end of the preceding sheet lifted in a V shape and pushes out the preceding sheet from the standby tray  13 . If the preceding sheet already put on standby on the standby tray  13  is stacked in a V shape, a paper jam occurs. When the sheet stacked in a V shape on the standby tray  13  falls onto the process tray  14  keeping a V shape, the paddle  15  collides with the trailing end of the preceding sheet lifted in a V shape. A deficiency occurs in a longitudinal aligning operation by the paddle  15  on the process tray  14 . 
     In this embodiment, as  FIG. 16A  shows, when a sheet enters the standby trays  13 , in order to limit the area above the sheet conveying path, the finisher  1  sets the movable guides  51  in a position where a rotation angle is an angle δ. The finisher  1  bends the sheet between the exit rollers  12  and the pivoting rollers  52  and conveys by the movable guides  51 . The exit rollers  12   a  and  12   b  are driven by an exit roller motor which drives the exit roller. Subsequently, as  FIG. 16B  shows, when the sheet reaches the pivoting rollers  52  in the standby trays  13 , the finisher  1  separately controls a pivoting roller motor for driving the pivoting rollers  52  on a downstream side in the sheet conveying direction and an exit roller motor for driving the exit rollers  12   a  and  12   b  on the upstream side in the sheet conveying direction. The finisher  1  sets the number of revolutions of the pivoting rollers  52  is set higher than the number of revolutions of the exit rollers  12   a  and  12   b . The finisher  1  sets rotating speed of the pivoting rollers  52  higher than rotating speed of the exit rollers  12 . The finisher  1  slightly stretches the sheet between the exit rollers  12  and the pivoting rollers  52 . The sheet pushes up the movable guides  51  in the sheet conveyance height direction and moves the movable guides  51  in a position where the rotation angle of the movable guides  51  is nearly 0. After the finisher  1  bends and conveys the sheet by the movable guides  51 , it is possible to convey the sheet while moving the movable guides  51  in the sheet conveyance height direction. It is possible to prevent the sheet from being stacked in a V shape and conveyed in a V shape on the standby trays  13 . As  FIG. 17  shows, it is possible to smoothly convey the sheet. It is also possible to smoothly convey the sheet. Therefore, it is possible to prevent the next sheet from colliding with the trailing end of the preceding sheet lifted in a V shape to cause a paper jam. It is possible to prevent the paddle  15  from colliding with the trailing end of the preceding sheet lifted in a V shape and perform the longitudinal aligning operation by the paddle  15  on the process tray  14 . 
     A sheet feeding amount of the pivoting rollers  52  may be set larger than a sheet feeding amount of the exit rollers  12  by setting a roller diameter of the pivoting rollers  52  larger than a roller diameter of the exit rollers  12 . This makes it possible to stretch the sheet between the exit rollers  12  and the pivoting rollers  52 . 
     Third Embodiment 
     As  FIG. 18  shows, the finisher  1  has a slide rail unit  53  that slides the standby trays  13  in order to drop a sheet onto the process tray  14  after putting the sheet on standby on the standby tray  13 , in an upper surface section behind the pivoting rollers  52 . If the sheet is buffered in the standby trays  13 , the pivoting rollers  52  are lifted by a magnet. Therefore, if the sheet is excessively curled up, the leading end of the sheet enters a space between the slide rail unit  53  and the pivoting rollers  52  and a paper jam occurs.  FIG. 18  indicates a first sheet buffered in the standby trays  13  by a broken line and a second sheet buffered in the standby trays  13  by a solid line. As  FIG. 18  shows, if the second sheet buffered in the standby trays  13  is excessively curled up, the leading end of the second sheet enters the space between the slide rail unit  53  and the pivoting rollers  52 . In  FIG. 18 , the finisher  1  has a tapping arm  54  that taps the sheet downward in order to drop the sheet onto the process tray  14  after putting the sheet on standby on the standby tray  13 . 
     In this embodiment, as  FIG. 19  shows, the leading end of the second sheet is prevented from entering the space between the slide rail unit  53  and the pivoting rollers  52  by extending a form of the tapping arm  54 .  FIG. 20  is a perspective view of the tapping arm  54 . As  FIG. 20  shows, the finisher  1  has a tapping arm extending section  55  at the distal end of the tapping arm  54 . By the tapping arm extending section  55 , it is possible to prevent the leading end of the second sheet from entering the space between the slide rail unit  53  and the pivoting rollers  52 .  FIG. 20  is another diagram of the tapping arm  54 . Rather than providing the tapping arm extending section  55  at the distal end of the tapping arm  54 , a guide plate may be provided in the tapping arm  54 . 
     Fourth Embodiment 
     As  FIG. 22A  shows, the two standby trays  13  put a sheet on standby. When the sheet put on standby on the standby trays  13  is dropped onto the process tray  14 , as  FIG. 22B  shows, the two standby trays  13  are opened and closed in a direction orthogonal to the sheet conveying direction to increase the distance between the two standby trays  13 . As  FIG. 22C  shows, the sheet put on standby on the waiting on the standby trays  13  is active-dropped onto the process tray  14 . Thereafter, the distance between the two standby trays  13  increased in the direction orthogonal to the sheet conveying direction is reduced and the two standby trays  13  are reset to initial positions, respectively. 
     However, if the sheet is active-dropped as  FIG. 22C  shows, it is necessary to increase the distance between the two standby trays  13  to be equal to or larger than the width of the sheet. The width of a housing of the finisher  1  needs to be at least equal to or larger than width obtained by adding the width of the two standby trays  13  to the increased distance between the two standby trays  13 . Lateral alignment plates that align sheets on the process tray  14  in the width direction also operate in the same manner as the operation of the standby trays  13  in the active drop. Therefore, the width of the housing of the finisher cannot be reduced. 
     In this embodiment, the sheet put on standby on the standby trays  13  is dropped onto the process tray  14  by rotating the two standby trays  13  in the respective initial positions without opening and closing the two standby trays  13  in the active drop.  FIGS. 23A to 23F  show specific operations of the standby trays  13 . 
     As  FIG. 23A  shows, two standby trays  13   a  and  13   b  put the sheet on standby. The finisher  1  has a driving unit for rotating the standby tray  13   a , in the standby tray  13   a . The finisher  1  has a driving unit for rotating the standby tray  13   b , in the standby tray  13   b . The finisher  1  has an elastic paddle  56   a  made of an elastic body, in the standby tray  13   a . The finisher  1  has an elastic paddle  56   b  made of an elastic body, in the standby tray  13   b . If the sheet put on standby on the standby tray  13  is dropped onto the process tray  14 , as  FIG. 23B  shows, the standby tray  13   a  rotates 90 degrees to the left and stops. When the standby tray  13  stops, the standby tray  13   b  rotates to the right at a rotation angle larger than 90 degrees. According to the rotation of the standby tray  13   b , the elastic paddle  56   b  provided in the standby tray  13   b  taps down the sheet onto the process tray  14 . As  FIG. 23C  shows, according to the rotation of the standby tray  13   b , the elastic paddle  56   b  comes into contact with the sheet dropped onto the process tray  14 . Thereafter, according to the rotation of the standby tray  13   b , the elastic paddle  56   b  pulls the sheet dropped onto process tray  14  to a lateral alignment plate  57   b  side. This makes it easy to laterally align the sheet dropped onto the process tray  14 . The standby tray  13   b  rotates nearly 180 degrees. Thereafter, the standby tray  13   b  temporarily stops. 
     As  FIG. 23D  shows, the standby tray  13   a  starts to rotate to the right. When the standby tray  13   a  rotates to the right by an angle the same as a rotation angle of the standby tray  13   b  that rotates to the right, the standby tray  13   b  also starts to rotate to the right. As  FIG. 23E  shows, the elastic paddle  56   a  and the elastic paddle  56   b  move the sheet on the process tray  14  to the lateral alignment plate  57   b  side and strike the sheet against the lateral alignment plate  57   b . This makes it possible to sort the sheet dropped onto the process tray  14 . Thereafter, as  FIG. 23F  shows, the standby trays  13   a  and  13   b  further rotate to the right and return to the respective initial positions shown in  FIG. 23A . The standby trays  13   a  and  13   b  temporarily stop to be synchronized when necessary. However, the standby trays  13   a  and  13   b  may be asynchronously rotated without being stopped. In  FIGS. 23A to 23F , the standby tray  13   a  and  13   b  sort the sheet to the lateral alignment plate  57   b  side. However, the standby trays  13   a  and  13   b  may operate oppositely to the operations shown in  FIGS. 23A to 23F  such that the standby tray  13   a  and  13   b  sort the sheet to the lateral alignment plate  57   a  side. 
     As explained above, it is possible to drop the sheet onto the process tray  14  and laterally align the sheet without opening and closing the standby trays  13  and the lateral alignment plates  57  in the direction orthogonal to the sheet conveying direction as in the past. Therefore, it is possible to keep the width of the housing of the finisher  1  small.