Patent Publication Number: US-7900899-B2

Title: Creasing device in accordance with sheet kind

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is based upon and claims the benefit of priority from the prior U.S. Patent Application No. 60/952,844, filed on Jul. 30, 2007; the entire contents of all of which are incorporated herein by reference. 
     This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2008-65672, filed on Mar. 14, 2008, the entire contents of all of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to a sheet post-processing apparatus to perform a post process for sheets. 
     DESCRIPTION OF THE BACKGROUND 
     Japanese Patent Application Publication No. 2000-153958 discloses a sheet post-processing apparatus for performing stitching and folding processes. 
     In the sheet post-processing apparatus, a sheet positioning member movable up and down for receiving the leading edge of each sheet in the conveying direction, a stapler unit for stitching a sheet bundle stored in the sheet positioning member, a folding roller pair for folding the stitched sheet bundle, and a folding drive mechanism having a projection unit are arranged sequentially downward from above. When sheet bundles for each document are all loaded by the sheet positioning member, they are stitched by the stapler unit. Thereafter, the sheet positioning member is moved, thus the sheet bundles are moved to the position of the folding drive mechanism, and the folding roller pair and projection unit perform the folding process. The folding drive mechanism pushes the sheet bundle pushed by the projection unit into the nip portion of the folding roller pair from one side, holds under pressure and discharges it from the opposite side, and then book-binds and loads it on the receiving tray. 
     However, the apparatus aforementioned performs the stitching process for the sheet bundle and then performs the folding process, so that the sheet positioning member must move from the position where the sheet bundle is subjected to the stitching process to the position where the folding process is performed. Further, when processing a plurality of sheet bundles, the sheet positioning member must return from the position where the folding process for the sheet bundle performs to the position where the stitching process performs again. Therefore, the processing of the sheet bundles takes a lot of time. 
     Further, in the apparatus aforementioned, the sheet positioning member supports the sheet bundle while processing one sheet bundle. Therefore, until the bookbinding process of the sheet bundle is completed, the succeeding sheets cannot be conveyed, thus when processing a plurality of sheet bundles, a problem arises that the throughput until completion of all the jobs is not good. 
     Further, in the apparatus aforementioned, the stitching process is performed for sheets in correspondence to the number of job copies and then the folding-in-two process is performed, so that when heavy paper is used, the number of sheets cannot be increased. Further, if glossy paper is used, when holding under pressure and conveying them by the folding roller pair, between the overlaid sheets, slipping occurs and a problem arises that the outside sheet in contact with the rollers slips and is conveyed prior. 
     Further, in the apparatus aforementioned, the sheet conveying path during loading, stitching, and folding the sheets is arranged almost perpendicularly, so that a problem arises that the apparatus is enlarged in the longitudinal direction. Furthermore, to perform the folding process for a heavy paper bundle, a strong structure is necessary and a problem arises that the apparatus is enlarged. 
     SUMMARY OF THE INVENTION 
     In an embodiment of the present invention, there is provided a sheet post-processing apparatus comprising a taking-in portion configured to support sheets conveyed with their leading edges in a conveying direction directed downward in a standing position and release the support of the sheets; a folding portion configured to crease the sheets, which are supported by the taking-in portion, by pressing and release the creased sheets into the taking-in portion; a loading portion arranged under the taking-in portion to load the creased sheets conveyed from the taking-in portion; a stitching portion configured to stitch a sheet bundle loaded on the loading portion; and a controller configured to execute conveying of the sheets to the taking-in portion and creasing of the sheets supported on the taking-in portion by the folding portion during stitching the creased sheet bundle loaded on the loading portion by the stitching portion. 
     Furthermore, in an embodiment of the present invention, there is provided a sheet post-processing method comprising supporting sheets conveyed with their leading edges in a conveying direction directed downward in a standing position by a taking-in portion; creasing the sheets supported in the standing position by the taking-in portion by a folding portion and then releasing again the sheets into the taking-in portion; conveying the creased sheets in the taking-in portion to a loading portion arranged under the taking-in portion; loading the creased sheets conveyed on the loading portion; stitching a creased sheet bundle loaded on the loading portion by a stitching portion; and executing conveyance of the sheets to the taking-in portion and creasing of the sheets supported by the taking-in portion by the folding portion during stitching the sheet bundle by the stitching portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic block diagram of the image forming apparatus of the first embodiment; 
         FIG. 2  is a schematic block diagram of the image post-processing apparatus of the first embodiment; 
         FIG. 3  is a schematic block diagram of the control system of the image forming apparatus and sheet post-processing apparatus; 
         FIG. 4A  is a schematic side view for explaining the taking-in portion of the first embodiment; 
         FIG. 4B  is a schematic view for explaining the mechanism around the taking-in portion viewed in the direction of the arrow A shown in  FIG. 4A ; 
         FIG. 5  is a schematic view for explaining the alignment portion of the first embodiment; 
         FIGS. 6A to 6D  are schematic views for explaining the folding operation; 
         FIGS. 7A to 7D  are schematic views for explaining the operation of the taking-in portion when processing sheets one by one; 
         FIGS. 8A to 8D  are schematic views for explaining the operation of the taking-in portion when processing a plurality of sheets at one time; 
         FIG. 9  is a flow chart for explaining the flow of the post processing operation for sheets; 
         FIG. 10  is a flow chart for explaining the flow of the post processing operation for sheets relating to a modification of the first embodiment; and 
         FIG. 11  is a schematic view for explaining the taking-in portion of a modification of the first embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, the embodiments will be explained with reference to the accompanying drawings. 
     (First embodiment)  FIG. 1  is a schematic block diagram of the image forming apparatus. 
     An image forming apparatus  1  includes an image reading portion  2  for reading an image to be read and an image forming portion  3  for forming an image. There is an operation panel  5  including a display  6  of a touch panel type and various kinds of operation keys  7  in the upper part of the image forming apparatus  1 . 
     The operation keys  7  of the operation panel  5 , for example, include ten keys, a reset key, a stop key, and a start key. The display  6  is used to set the sheet size, number of sheets, and print concentration and input various processes such as the stitching process. 
     The image reading portion  2  includes a light-transmissible original table  8 , a carriage  9 , an exposure lamp  10 , a reflection mirror  11 , an imaging lens  12  for converging reflected light, and a CCD (charge coupled device)  13  for fetching the reflected light and converting image information by light to an analog signal. 
     The image forming portion  3  includes an intermediate transferring belt  14  as a transfer medium and four processing units  16 Y,  16 M,  16 C, and  16 K corresponding to toner of the respective colors of yellow (Y), magenta (M), cyan (C), and black (K) which are arranged side by side along the intermediate transferring belt  14 . 
     The processing unit  16 K includes a photoconductor  18 K as an image carrier, a laser unit  20 K for forming an electrostatic latent image on the photoconductor  18 K, a charger  22 K and a developing device  24 K which are arranged sequentially around the photoconductor  18 K, and a primary transferring device  26 K, a cleaner  27 K, and a charge elimination lamp  28 K which are opposite to a photosensitive drum  8 K across the intermediate transferring belt  14 . The processing units  16 Y,  16 M, and  16 C have the same constitution as that of the processing unit  16 K. Hereinafter, the constitution will be explained by referring to the processing unit  16 K of black (K). 
     To a document put on the original table  8  or a document sent by an automatic document feeder  30 , by an exposure means including the carriage  9  and the exposure lamp  10  supported on the carriage  9 , light is irradiated from the underneath of the original table  8 . Then, the reflected light from the document is induced by the reflection mirror  11  and is focused by the imaging lens  12 , thus the reflected light is projected to the CCD  13 . The image information fetched by the CD  13  is output as an analog signal, then is converted to a digital signal, is subject to the image process, and then is transmitted to the laser unit  20 K. 
     When the image formation is started in the image forming portion  3 , the charger  22 K gives a charge to the outer peripheral surface of the photoconductor  18 K rotating. To the outer peripheral surface of the photoconductor  18 K which is charged at a uniform potential in the axial direction by the charger  22 K, according to the image information transmitted from the CCD  13 , a laser beam is irradiated from the laser unit  20 K. When an electrostatic latent image corresponding to the image information of the document is formed on the outer peripheral surface of the photoconductor  18 K by the irradiation of the laser beam, a developer of black (for example, toner) is fed to the outer peripheral surface of the photoconductor  18 K by the developing device  24 K and the electrostatic latent image is converted to a black toner image. 
     The developing device  24 K has a developing roller which rotates and the developing roller is arranged and rotated opposite to the photoconductor  18 K, thus toner is fed to the photoconductor  18 K. When a toner image is formed on the outer peripheral surface of the photoconductor  18 K, the black toner image is transferred electrostatically to the intermediate transferring belt  14  by the primary transferring device  26 K. Further, the toner remaining on the photoconductor  18 K without transferred is removed by the cleaner  27 K positioned on the downstream side of the photoconductor  18 K in the rotational direction rather than the primary transferring device  26 K. Furthermore, the residual electric charge on the outer peripheral surface of the photoconductor  18 K is removed by the charge elimination lamp  28 K. When forming a color image, the aforementioned operation is performed similarly for the processing units  16 Y,  16 M, and  16 C. 
     The toner image transferred to the intermediate transferring belt  14  is transferred electrostatically onto a sheet conveyed by a sheet feeder  32  via a conveying path  34  by a secondary transferring device  36 . The sheet onto which the toner image is transferred is conveyed to a fixing device  38  and the toner image transferred onto the sheet is fixed onto the sheet by the fixing device  38 . The toner image is fixed, thus the sheet on which the image formation is completed is conveyed toward a conveying roller  40 . 
     When performing double side print, the conveying roller  40  is rotated reversely and conveys the sheet to a conveying path  42 . The sheet sent to the conveying path  42  is conveyed again to the secondary transferring device  36  and fixing device  38  and an image is formed on the opposite-side surface of the sheet. 
     The sheet that the toner image is fixed, thus the image formation is completed is discharged from the image forming apparatus  1  by the conveying roller  40  and is sent to the sheet post-processing apparatus  4 . The sheet is referred to as, for example, plain paper, a paper board, thin paper, glossy paper, or an OHP sheet. 
     Next, the sheet post-processing apparatus  4  will be explained.  FIG. 2  is a schematic view of the sheet post-processing apparatus. 
     The sheet post-processing apparatus  4  post-processes sheets discharged from the image forming apparatus  1  according to an input instruction from the operation panel  5  or a processing instruction from a personal computer. The sheet post-processing apparatus  4  includes an end stitch portion  44  for performing the post process other than the folding process and saddle stitching process, for example, the ordinary sorting process or sheet bundle end stitching process and a folding portion (a sheet folding apparatus)  46  for performing the folding process and saddle stitching process. Further, for the end stitch portion  44 , the post-processing apparatus described in Japanese Patent Application Publication No. 2007-86862 and well-known arts can be used. 
     The folding portion  46  includes a taking-in portion  50  for receiving the leading edges of sheets conveyed downward from above in the conveying direction and temporarily loading the sheets until the folding process is performed, a folding portion  80  for performing the folding process for the sheets loaded on the taking-in portion  50 , an alignment portion  88  for storing and aligning the sheets folded and conveyed, a saddle stitch member  104  for performing the saddle stitching process for the aligned sheet bundle, and a sheet bundle receiving tray  122  for receiving the sheet bundle stitched. 
     When performing the folding process and saddle stitching process, entrance rollers  47  carry the sheets discharged from the image forming apparatus  1  into the sheet post-processing apparatus  4 . When the sheets are carried into the sheet post-processing apparatus  4 , a branching member  48  deflects the conveying direction of the sheets and first conveying rollers  49  convey the sheets to the taking-in portion  50 . In the taking-in portion  50 , a stack portion  62  receives the leading edges of the sheets in the conveying direction. The stack portion  62  can move vertically so that the portion of each sheet to be folded comes to the folding position by the folding portion  80 . In this embodiment, the portion of each sheet to be folded will be explained as the central part of each sheet. 
     When the stack portion  62  receives the leading edges of the sheets in the conveying direction, the folding portion  80  starts the folding process. Hereinafter, in the taking-in portion  50 , the leading edge of each sheet in the conveying direction is defined as a lower end of the sheet and inversely, the rear end of each sheet in the conveying direction is defined as an upper end. 
     The folding portion  80  includes a metallic thin folding plate  82  and a folding roller pair  83 . The folding plate  82  is generally shifted in order to avoid obstruction of conveyance of sheets and when folding the sheets, moves and pushes the sheets and presses out them toward the nip portion of the folding roller pair  83 . When the folding plate  82  of the folding portion  80  pushes the sheets into the nip portion of the folding roller pair  83 , the folding roller pair  83  holds the sheets under pressure in the nip portion and creases the sheets. Here, the sheets are in the state that they are not folded in two. 
     Then, second conveying rollers  84  convey creased sheets toward a third conveying roller  86  and the third conveying roller  86  carries out the sheets to the alignment portion  88 . 
     The alignment portion  88  includes a loading member  90  arranged on the bottom of the sheet post-processing apparatus  4  for loading carried-out sheets on each side and a positioning member  92  for moving by a conveying device  94 . 
     When sheets in correspondence to the number of job copies are stored in the loading member  90  of the alignment portion  88 , the positioning member  92  moves so that the fold position comes to the stitching position by the saddle stitch member  104  and a saddle stitching stapler  106  of the saddle stitch member  104  and an anvil  108  perform the stitching process for the sheet bundle. The sheet carried out to the alignment portion  88  is given a fold, so that the alignment of the sheet crossing the fold of the succeeding sheet in the length direction, that is, the alignment of the sheets in the conveying direction can be executed easily. 
     When the stitching process is performed for the sheet bundle, the conveying device  94  furthermore drives the positioning member  92  and conveys the sheet bundle toward exit rollers  120 , thus the exit rollers  120  discharge the sheet bundle to the sheet bundle receiving tray  122 . 
       FIG. 3  is a schematic block diagram of the control system of the image forming apparatus and sheet post-processing apparatus. 
     The image forming apparatus  1  has a main controller  130  for controlling the whole image forming apparatus  1 . The main controller  130  controls synthetically the image reading portion  2 , image forming portion  3 , operation panel  5 , and controller  140  of the sheet post-processing apparatus  4 . The main controller  130  furthermore performs the image process such as correction, compression, or expansion of image data, stores the compressed image data or print data, and executes data communication with a PC (personal computer)  150  installed outside the image forming apparatus  1 . 
     The controller  140  of the sheet post-processing apparatus  4 , on the basis of an instruction from the main controller  130 , controls various operations of the folding portion  46 , that is, the operation of each unit of the entrance rollers  47 , branching member  48 , a conveying/sheet discharge driver  142  of the first conveying rollers  49 , taking-in portion  50 , folding portion  80 , alignment portion  88 , and saddle stitch member  104 . 
       FIGS. 4A and 4B  are schematic diagrams for explaining the taking-in portion  50 , and  FIG. 4A  is a schematic side view of the taking-in portion  50 , and  FIG. 4B  is a schematic diagram for explaining the mechanism around the taking-in portion  50  viewed in the direction of the arrow A shown in  FIG. 4A . 
     The taking-in portion  50  includes a stack unit  52  and a driving portion  54  for driving up and down the stack unit  52 . The driving portion  54  includes a support bar  56  for supporting the stack unit  52  in the movement direction, a belt  60  wound and suspended by a pulley  58 , and a motor M 1 . Power is transmitted from the motor M 1 , thus the belt  60  is moved, and the stack unit  52  attached to the belt  60  moves up and down in the conveying direction of sheets. 
     To the stack unit  52 , the stack portion  62  for receiving the leading edge of each sheet in the conveying direction, that is, the lower end is attached. The stack portion  62  has a sheet leading edge sensor  64  for detecting arrival of the lower end of each sheet, for example, a micro-sensor or a micro-actuator. A taking-in aid member  65  is used when loading a plurality of sheets on the stack portion  62  and will be described later in detail. 
     As shown in  FIG. 4B , the stack unit  52  includes bridging members  66   a  and  66   b  which are parallel with each other, are partially opposite to each other, and slide the stack portion  62  in the width direction (hereinafter, referred to as the sheet width direction) crossing the sheet conveying direction, a pinion gear  68 , and a motor M 2 . 
     The bridging members  66   a  and  66   b  have a rack respectively on the opposite surfaces and between the bridging members  66   a  and  66   b , the pinion gear  68  simultaneously fitted into the respective racks is arranged. The power of the motor M 2  is transmitted to the pinion gear  68  via a gear  69 . When the pinion gear  68  is rotated, the bridging members  66   a  and  66   b  slide in the width direction of the sheet in the opposite directions. Further, the arrow B shown in the drawing indicates the position where the stack portion  62  receives the lower end of the sheet. 
     The taking-in portion  50  has a lateral alignment unit  70 . The lateral alignment unit  70  has lateral alignment members  72   a  and  72   b  for aligning sheets loaded on the stack portion  62  in the width direction. The lateral alignment members  72   a  and  72   b  are in the position which counters mutually. Bridging members  74   a  and  74   b  are parallel respectively toward the lateral alignment members  72   a  and  72   b , and a part counters. The lateral alignment unit  70  has a pinion gear  76  and a motor  3 . 
     The bridging members  74   a  and  74   b  have a rack respectively on the opposite surfaces and between the bridging members  74   a  and  74   b , the pinion gear  76  simultaneously fitted into the respective racks is arranged. The power of the motor M 3  is transmitted to the pinion gear  76  via a gear  77  and when the pinion gear  76  is rotated, the bridging members  74   a  and  74   b  slide in the width direction of the sheet in the opposite directions. Further, the positions of the lateral alignment members  72   a  and  72   b  in the direction of the sheet width, for example, are detected by a position sensor  78  having a micro-sensor or a micro-actuator. In the taking-in portion  50 , when the folding process is instructed from the operation panel  5  or the PC  150 , if the stack portion  62  receives the lower ends of sheets and the lateral alignment unit  70  aligns the sheets in the width direction, the folding plate  82  and folding roller pair  83  of the folding portion  80  perform the folding process for the sheets. The loading operation of the taking-in portion  50  and the folding operation of the folding portion  80  will be described later. 
       FIG. 5  is a schematic view for explaining the alignment portion. 
     The loading member  90  of the alignment portion  88  is arranged on the bottom of the sheet post-processing apparatus  4  with a slight slope to the horizontal direction and loads carried-out sheets on each side. The alignment portion  88  can rotate and has a loading aid member  96  arranged away from the surface of the loading member  90 . 
     The loading aid member  96 , when sheets are conveyed to the loading member  90 , stands by at a position free of disturbance of conveyance. If the sheets are loaded on the loading member  90 , the loading aid member  96 , as shown by a dotted line in  FIG. 5 , rotates at a fulcrum of one end thereof and makes contact with the loaded sheets at the other end. The loading aid member  96  has, for example, a rotary roller  97  at the other end making contact with sheets and the roller  97  rotates, thereby presses one end of each loaded sheet against the positioning member  92 . This operation is repeated for each conveyance of sheets and a sheet bundle is loaded on the loading member  90 . Particularly, the alignment portion  88  turns sheets sideways and loads them on the loading member  90  on each side and moreover, since the sheets carried out to the alignment portion  88  are given a fold, the loading aid member  96  performs the aforementioned operation, thus the succeeding sheets, when carried out onto the loaded sheets, are overlapped easily on the basis of the fold. Due to this overlap, the alignment of sheets crossing the fold in the length direction, that is, the alignment of sheets in the conveying direction can be executed easily. The loading aid member  96  may move up and down to separate from and make contact with sheets. The loading aid member  96  may be a belt which runs to align the sheets. 
     Further, the alignment portion  88  has lateral alignment members  98   a  and  98   b  for aligning sheets in the width direction. For the lateral alignment members  98   a  and  98   b , for example, ones similar to the lateral alignment members  72   a  and  72   b  may be used. Further, as lateral alignment timing, it is possible to execute the alignment for each conveyance of sheets or to execute the alignment at the stage that sheets in correspondence to the number of job copies are loaded. 
     The conveying device  94  includes a belt  102  wound and suspended by a pulley  100  and a motor M 4 . The power is transmitted from the motor M 4 , thus the belt  102  moves and the positioning member  92  attached to the belt  102  moves long the loading member  90 . 
     When sheets in correspondence to the number of job copies are stored on the loading member  90  and are aligned laterally, the positioning member  92  moves the folding position of each sheet to the stitching position of the saddle stitch member  104  and stops. 
     Then, the saddle stitching stapler  106  of the saddle stitch member  104  and the anvil  108  perform the stitching process for the sheet bundle. When the stitching process is performed for the sheet bundle, the positioning member  92  moves furthermore toward the exit rollers  120  and conveys the sheet bundle and the sheet bundle is discharged onto the sheet bundle receiving tray  122  by the exit rollers  120 . 
     Next, by referring to  FIGS. 6A to 6D , the folding operation of the folding portion  60  will be explained briefly. As shown in  FIG. 6A , the folding plate  82 , when the sheet P is conveyed, stands by at the position free of disturbance of conveyance of the sheet P ( FIG. 6A ). If the folding process is started, the folding plate  82  moves toward the folding roller pair  83  and the leading edge of the folding plate  82  pushes the sheet P ( FIG. 6B ). The folding plate  82  pushing the sheet P moves furthermore toward the folding roller pair  83  and leads the sheet P to the nip portion of the folding roller pair  83 . The first roller  83   a  and second roller  83   b  of the folding roller pair  83  rotate respectively along the arrows b and c and hold the sheet P under pressure to give a fold (FIG. c). Then, the first roller  83   a  and second roller  83   b  of the folding roller pair  83 , unless they fold straight the sheet in two, rotate respectively in the directions of the arrows b′ and c′ which are the opposite directions of the arrows b and c and release the sheet P from the nip portion. The sheet P creased by the aforementioned operation, if the holding of the lower end by the bridging members  66   a  and  66   b  is released, falls by its own weight or moves more downward by the second conveying rollers  84 , and thereafter is conveyed to the alignment portion  88 . 
     In an apparatus for folding sheets in two as conventional, for sheets in correspondence to the number of job copies, the stitching process is performed and then the folding process for folding sheets in two is performed. Therefore, when heavy paper is used, the number of sheets of a sheet bundle cannot be increased. Further, when sheets having a small friction coefficient of the surface thereof such as glossy paper are used, if they are conveyed by being held under pressure by the folding roller pair, a slip occurs between the outside sheet in contact with the rollers and the inside sheet thereof and a problem arises that the outside sheet is conveyed prior. In this embodiment, when heavy paper, glossy paper, or OHP sheets are selected as a sheet, the folding process of one sheet is performed. When plain paper or thin paper is selected as a sheet, a plurality of sheets are buffered and folded. 
     The operation of the taking-in portion  50  when processing sheets one by one will be explained by referring to  FIGS. 7A to 7D . As shown in  FIG. 7A , when the sheet P is conveyed, the stack portion  62  stands by in the state that it is closed in the sheet width direction. If the sheet leading edge sensor  64  detects that the lower end of the sheet P is received by the stack portion  62 , the lateral alignment members  72   a  and  72   b  move in the directions of the arrows B and B′ shown in  FIG. 7B  and strike both edges of the sheet to align the sheet in the width direction. In this state, the folding plate  82  and folding roller pair  83  perform the folding process for the sheet P and form a fold on the sheet P. 
     When the lateral alignment is performed for the sheet, in the directions of the arrows C and C′ shown in  FIG. 7C , the bridging members  66   a  and  66   b  move and open mutually in the opposite directions in the width direction of the sheet and the holding of the lower end of the sheet P by the stack portion  62  is released. The lateral alignment members  72   a  and  72   b  may open in the sheet width direction and stand by before the succeeding sheet is conveyed. At this stage, the lateral alignment members  72   a  and  72   b  may open in the sheet width direction. When the holding of the lower end of the sheet P is released, the sheet P falls by its own weight or moves in the direction of the arrow D by the second conveying rollers  84  and then is carried out to the alignment portion  88  via the third conveying roller  86  ( FIG. 7D ). The aforementioned operation is repeated for each sheet and the creased sheet is conveyed to the alignment portion. In the case of processing sheets one by one, the lateral alignment does not always need to be performed. By performing such a one-sheet process, the load on the folding portion  80  during the folding operation can be reduced and no slip occurs naturally between the sheets, so that even if heavy paper or glossy paper is used, the post process can be performed without trouble. 
     Next, the operation of the taking-in portion  50  when processing a plurality of sheets at one time will be explained by referring to  FIGS. 8A to 8D .  FIGS. 8A to 8D  are all schematic views of the taking-in portion  50  viewed from the side of the taking-in portion  50 . A first conveying guide  110  and a second conveying guide  111  guide sheets to the stack portion  62 . A taking-in guide  112  supports sheets loaded on the stack portion  62  in a standing position. The taking-in guide  112  is opposite to the first conveying guide  110  installed on the side of the taking-in aid member  65  at a more interval than the second conveying guide  111  and is arranged partially opposite to the second conveying guide  111  at an interval. Even when processing a plurality of sheets at one time, the operations of the stack portion  62  and lateral alignment members  72   a  and  72   b  are basically similar to those explained in  FIGS. 7A to 7D . 
     Firstly, if the sheet P is conveyed between the first and second conveying guides  110  and  111 , the stack portion  62  stands by at the standby position (hereinafter, referred to as the home position or HP) in the state that it is closed in the sheet width direction and receives the lower end of the sheet P ( FIG. 8A ). If the sheet leading edge sensor  64  detects that the stack portion  62  receives the sheet P, the taking-in aid member  65  operating by a solenoid rotates and strikes the surface of the sheet P, thus the upper end of the sheet P moves toward the taking-in guide  112 . If the sheet P moves toward the taking-in guide  112 , the stack position  62  moves up until the upper end of the sheet P comes between the second conveying guide  111  and the taking-in guide  112  ( FIG. 8B ). In this state, the stack portion  62  receives a succeeding sheet P′. If the sheet leading edge sensor  64  detects that the stack portion  62  receives the sheet P′, the stack portion  62  moves down to the position where the upper end of the sheet P′ comes lower than the lower end of the second conveying guide  111 , for example, the HP ( FIG. 8C ). If the stack portion  62  moves up to the HP, the taking-in aid member  65  rotates and strikes the surface of the sheet P′ and moves the upper end of the sheet P′ toward the taking-in guide  112 , and the stack portion  62  moves up until the upper end of the sheet P′ comes between the second conveying guide  111  and the taking-in guide  112  ( FIG. 8D ). Here, the HP of the stack portion  72 , for example, may be detected by a position sensor  114  having a micro-sensor or a micro-actuator or may be subject to the pulse control using a stepping motor for the motor M 1 . 
     The aforementioned operation is repeated until a predetermined number of sheets, for example, two or three sheets are loaded on the stack portion  62  and at the stage that the predetermined number of sheets are loaded, the lateral alignment members  72   a  and  72   b  perform the lateral alignment. Then, the folding plate  82  and folding roller pair  83  perform the folding process for the sheet bundle and crease the sheet bundle. If the folding process is performed for the sheet bundle, the bridging members  66   a  and  66   b  open mutually in the opposite directions in the sheet width direction and the sheet bundle falls because the holding of the lower end is released or is conveyed by the second conveying rollers  84 . Furthermore, the sheet bundle is carried out to the alignment portion  88  via the third conveying roller  86 . As mentioned above, the taking-in portion  50  has a buffering mechanism and before the stitching process, can load, fold, and convey for each plurality of sheets. 
     In  FIG. 8A , the HP where the stack portion  62  stands by may be a position where the position of the upper end of the sheet P conveyed comes below the lower end of the second conveying guide  111 . The stack portion  62  located upper part from the HP receives the sheet P, the taking-in aid member  65  moves the sheet P toward the taking-in guide  112  after the stack portion  62  moved to the HP, then the sheet P may be moved upwards by the stack portion  62 . The position where, as for the HP in which the stack portion  62  stands by, the stack portion  62  caught the sheet P may be the upper part from the HP. The HP in which the stack portion  62  stands by should be just low to sufficient grad for the upper edge of the sheet P making it move to between the second conveying guide  112  and the taking-in guide  112  by the taking-in aid member  65 . 
     Next, the flow of the sheet post-processing operation will be explained briefly by referring to  FIG. 9 . 
     At  901 , the controller  140  of the sheet post-processing apparatus  4  obtains information such as an operation instruction and sheet kind and thickness from the operation panel  5  or PC  150  and starts the post process such as the folding process or saddle stitching process. The controller  140 , at  902 , judges the sheet kind carried in the sheet post-processing apparatus  4  form the image forming apparatus  1 . When sheets are plain paper or thin paper (hereinafter, all referred to as first sheets, in the flow chart, referred to as plain paper), the taking-in portion  50 , at  903 , loads temporarily a predetermined number of sheets, for example, three sheets in a standing position. If the predetermined number of sheets are loaded on the taking-in portion  50 , at  904 , the folding portion  80  performs the folding process for the first sheets loaded on the taking-in portion  50 . If the folding process is performed for the first sheets, at Step  905 , the taking-in portion  50  releases the holding of the first sheets and the conveying member such as the second conveying rollers  84  or the third conveying roller  86  conveys the first sheets to the alignment portion  88 . The controller  140 , at  906 , until the first sheets (in correspondence to the sheet bundle) of the number of job copies are conveyed to the alignment portion  88 , repeats the aforementioned process. 
     At  906 , if the first sheets in correspondence to the sheet bundle are loaded on the loading member  90  of the alignment portion  88 , at  907 , they are aligned laterally and the saddle stitch member  104  stitches the sheet bundle at the folding position. If the stitching process is performed, at  908 , the exit rollers  120  discharge the sheet bundle to the sheet bundle receiving tray  122 . The controller  140 , at  909 , until the post process is performed for the sheet bundle in correspondence to the number of job copies, repeats the aforementioned process. Further, when performing repeatedly the process at  909 , at  902 , the controller  104  does not always need to judge again the sheet kind. 
     On the other hand, at  902 , when sheets are thicker than the first sheets such as heavy paper or glossy paper or sheets are ones having a smaller friction coefficient of the surface than the friction coefficient of the surface of the first sheets (hereinafter, all referred to as second sheets), at  910 , the taking-in portion  50  loads temporarily one second sheet in a standing position. Whenever one of the second sheets is loaded on the taking-in portion  50 , the folding portion  80 , at  911 , performs the folding process for the second sheets. Whenever the folding process is performed for the second sheets, at  912 , the taking-in portion  50  releases the holding of the second sheets and the conveying member such as the second conveying rollers  84  or the third conveying roller  86  conveys the second sheets to the alignment portion  88 . The controller  140 , at  913 , until the second sheets (in correspondence to the sheet bundle) of the number of job copies are conveyed to the alignment portion  88 , repeats the aforementioned process and executes  907  to  909 . 
     Further, at  907 , while the alignment portion  88  performs the lateral aligning process and the saddle stitch member  104  performs the stitching process, the taking-in portion  50  performs the folding process. 
     The sheet post-processing apparatus  4  of the first embodiment aforementioned includes the taking-in portion  50  for supporting sheets in a standing position and the alignment portion  88  for loading sheets carried out at a slight slope to the horizontal direction on the downstream side in the conveying direction on each side. Before performing the stitching process by the alignment portion  88 , in addition to execution of the folding process, the one-sheet folding process and plural-sheets folding process are performed selectively depending on the sheet kind, thus a sheet bundle composed of more sheets than the conventional apparatus for folding sheets in two can be post-processed. Further, even if heavy paper or glossy paper is used, the post process can be performed without trouble. 
     Further, the folding process and the succeeding stitching process are performed at different positions in the conveying direction. Therefore, at the same time that the alignment portion  88  and saddle stitch member  104  perform the lateral alignment process and stitching process, the taking-in portion  50  can perform the folding process and the throughput of processing sheets is good. Further, when plain paper is used, the taking-in portion  50  performs buffering, thus in the sheet post-processing apparatus  4 , the sheet conveying speed can be increased and the throughput becomes better. 
     Further, in the aforementioned apparatus, the alignment portion  88  loads sheets, and in the folding portion  80 , the load at time of execution of the folding process is small, and a strong structure is not necessary, so that the apparatus can be miniaturized. 
     (Modification of the first embodiment) In this embodiment, the processing operation when a sheet bundle to be post-processed is composed of a mixture of plain paper and another paper such as heavy paper or glossy paper will be explained. Further, in the respective units of this embodiment, to the same parts as those of the sheet folding apparatus of the aforementioned embodiment, the same numerals are assigned and the characteristic parts of this embodiment will be explained by referring to  FIG. 10 . 
     The controller  140  of the sheet post-processing apparatus  4 , at  1014 , obtains information such as an operation instruction and sheet kind and thickness from the operation panel  5  or PC  150  and obtains information for each page. The controller  140 , upon receipt of the information, at  1015 , starts the post process such as the folding process or saddle stitching process. 
     The controller  140 , from the page information obtained, at Step  1016 , judges the thickness and kind of sheets to be conveyed to the taking-in portion  50  for each page. When the sheets are the first sheets, at  1017 , the taking-in portion  50  loads one sheet in a standing position. At  1018 , when a predetermined number of sheets, for example, three first sheets are loaded on the taking-in portion  50 , at  1019 , the folding portion  80  performs the folding process for the first sheets loaded on the taking-in portion  50 . After the folding process, at  1020 , the taking-in portion  50  releases the holding of the first sheets and the conveying member such as the second conveying rollers  84  or the third conveying roller  86  conveys the first sheets to the alignment portion  88 . 
     On the other hand, at  1018 , when the predetermined number of first sheets are not loaded, the controller  140  returns to  1016  and judges whether the sheets to be loaded next on the taking-in portion  50  are the first sheets or the second sheets. Here, when the sheets are the second sheets, at  1021 , the controller  140  judges existence of the first sheets loaded already on the taking-in portion  50 . When there are no first sheets loaded, at  1023 , the controller  140  conveys the second sheets to the taking-in portion  50 . On the other hand, when there are the first sheets loaded, before conveying the second sheets to the taking-in portion  50 , at  1022 , the folding portion  80  performs the folding process. After the creased first sheets are conveyed from the taking-in portion  50 , at  1023 , the controller  140  conveys the succeeding second sheets to the taking-in portion  50 . 
     Then, whenever one of the second sheets is loaded on the taking-in portion  50 , at  1024 , the folding portion  80  performs the folding process for the second sheets. After the folding process, at  1025 , the taking-in portion  50  releases the holding of the second sheets and the conveying member such as the second conveying rollers  84  or the third conveying roller  86  conveys the second sheets to the alignment portion  88 . 
     Until sheets in correspondence to a sheet bundle are loaded on the loading member  90  of the alignment portion  88 , at  1026 , the controller  140  repeats the aforementioned operation. When the sheets in correspondence to a sheet bundle are loaded, at  1027 , the lateral alignment is performed and the saddle stitch member  104  stitches the sheet bundle at the folding position. If the stitching process is performed, at  1028 , the exit rollers  120  discharge the sheet bundle to the sheet bundle receiving tray  122 . Further, the controller  140 , at  1029  repeats the aforementioned process until the post process is performed for the sheets of the number of job copies. 
     According to the sheet post-processing apparatus  4  of a modification of the first embodiment, even if a sheet bundle to be post-processed is a mixture with plain paper and the paper of other kinds containing heavy paper or glossy paper, the similar effects to those of the first embodiment can be obtained. 
     Further, the judgment of the page information executed by the controller  140  is not limited to the execution at  1016  and it is possible to at the point of time when it is received at  1015 , store beforehand judgment results corresponding to each page in the memory and at  1016 , read the judgment results from the memory. 
     Further, in the aforementioned embodiment, the stack portion  62  opening and closing in the sheet width direction is described, though the present invention is not limited to it. Namely, the stack portion  62  may support temporarily sheets and then release the support and for example, as shown in  FIG. 11 , the stack portion  62  may be rotate at a fulcrum of the rotary shaft  144 . Further, in this case, the stack portion  62  may make it rotate by solenoid, a stepping motor, etc. 
     Although the invention is shown and described with respect to certain illustrated aspects, it will be appreciated that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components, the terms used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (e.g., that is functionally equivalent), even though not structurally equivalent to the disclosed structure, which performs the function in the herein illustrated exemplary aspects of the invention.