Patent Publication Number: US-10331071-B2

Title: Sheet processing device and image forming device provided with the same

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This is a divisional application of Ser. No. 15/078,465 filed on Mar. 23, 2016 claiming priorities of Japanese Patent Applications No. 2015-088021 filed on Apr. 23, 2015, No. 2015-107405 filed on May 27, 2015, and No. 2015-107406 filed on May 27, 2015. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a processing device that bonds sheets carried out from an image forming device such as a copier or a printer to form a sheet bundle and folds the sheet bundle at a predetermined folding position as needed and, more particularly, to a processing device capable of creating a booklet by means of an adhesive or a booklet by means of staplers according to a user&#39;s request. 
     Description of the Related Art 
     A sheet processing device that aligns sheets carried out from an image forming device and staples the sheets or folds the sheets in a booklet form is widely known. Such a sheet processing device is provided with a plurality of sheet storage means for sheet post-processing. Further, there is disclosed a device capable of performing stapling or bonding for binding sheets according to a user&#39;s request, followed by folding of the resultant bound sheet bundle in two. 
     For example, Japanese Patent No. 5,168,474 discloses a bookbinding device provided with a unit housing section that can alternatively houses one of a staple-binding unit that staples a sheet bundle and a paste binding unit that applies pasting onto sheets and pressure-bonds them to form a sheet bundle. To this end, one of the staple-binding unit and the paste binding unit is set so as to be detachably attached to the unit housing section. Further, this device includes a folding section that folds the sheet bundle bound by one of the above units in two. 
     Further, Japanese Patent No. 5,382,597 discloses a device provided with both a paste binding unit that applies pasting onto sheets and pressure-bonds them to form a sheet bundle and a staple-binding unit that performs staple-binding processing. The device alternatively executes the paste binding and the staple-binding followed by folding processing. With this configuration, a booklet can be created by paste binding or staple-binding. 
     SUMMARY OF THE INVENTION 
     However, in both the devices disclosed in Japanese Patent No. 5,168,474 and Japanese Patent No. 5,382,597, when the sheet bundle bound by the staple-binding unit or paste binding unit is folded by a folding mechanism section, more specifically, a folding roller and a folding knife (folding blade) that pushes the sheet bundle into the folding roller, whether the sheet bundle has been bound by the staple-binding unit or paste binding unit is not taken into account. 
     The sheet bundle bound by the staple-binding unit has high strength since metal staples are used to bind the sheet bundle at its folding position. That is, in this case, a rotation speed of the folding roller or a moving speed of the folding blade can be made high. On the other hand, for the sheet bundle bound by the paste binding unit, when the sheet bundle is folded, the paste serving as an adhesive between the sheets is also subjected to the folding, and the paste on the folding roller side is largely deformed and moved. Therefore, when a folding speed for the sheet bundle bound by the staple-binding unit, i.e., a comparatively high speed is applied as it is to the folding of the sheet bundle bound by the paste binding unit, the adhesive applied to the outermost side cannot withstand the folding speed, which may result in peeling-off of the adhesive or break of the sheet. On the other hand, when a folding speed for the sheet bundle bound by the paste binding unit, i.e., a comparatively low speed is applied as it is to the folding of the sheet bundle bound by the staple-binding unit, staple-binding processing speed is also lowered, resulting in deterioration of the entire processing speed. The above tendencies become more conspicuous as the number of sheets to be bound is increased. On the other hand, in case the number of sheets to be bound is large in the paste binding procedure, it is necessary to apply a relatively large amount of the paste in order to keep the bonding strength. 
     The present invention has been made based on an idea that object of the present invention is to reduce an amount of the adhesive to be used in the adhesive-binding processing even when the number of sheets to be bound is large while maintaining adhesive strength. 
     To achieve the above object, the present invention adopts the following configuration. 
     There is provided a sheet processing device that binds sheets and then folds a resultant sheet bundle, the device including: a stacker section that stores sheets conveyed along a conveying path; an adhesive-binding unit that applies an adhesive onto the sheets stored in the stacker section to adhesive-bind the sheets; a folding roller that folds a sheet bundle in two at a predetermined folding position; and a folding blade that pushes the sheet bundle into the folding roller, wherein when the number of sheets to be bonded by the adhesive-binding unit applying the adhesive onto the sheets exceeds a predetermined number, the adhesive is applied at a two position separated from each other across the folding position. 
     According to the present invention, it is possible to reduce an amount of the adhesive to be used while maintaining a sufficient bonding strength of the adhesive-bound sheet bundle. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory view illustrating an entire configuration that combines an image forming device and a sheet processing device according to the present invention; 
         FIG. 2  is an explanatory view illustrating an entire configuration of the sheet processing device provided with an adhesive-binding unit and a staple-binding unit according to the present invention; 
         FIG. 3  is an explanatory view illustrating mechanisms around the adhesive-binding unit and the staple-binding unit of  FIG. 2 ; 
         FIG. 4  is a perspective view of the adhesive-binding unit of  FIG. 2 ; 
         FIGS. 5A to 5C  are views explaining the adhesive-binding unit of  FIG. 3 , in which  FIG. 5A  is a plan view of adhesive tape stampers,  FIG. 5B  illustrates an engagement state between a stamper holder and a cam member that moves the stamper holder, and  FIG. 5C  is an explanatory view of the cam member; 
         FIGS. 6A to 6D  are explanatory views of an adhesive tape stamper for applying an adhesive, in which  FIG. 6A  is an outer appearance view,  FIG. 6B  is a view illustrating a state where an adhesive tape is wound around a reel,  FIG. 6C  is a view illustrating a gear state before pressing of the adhesive tape stamper, and  FIG. 6D  is a view illustrating a gear state upon pressing of the adhesive tape stamper; 
         FIGS. 7A to 7C  are explanatory views illustrating an operation state of a stamper holder supporting the adhesive tape stamper, in which  FIG. 7A  illustrates a state where two stamper holders are situated at a raised position,  FIG. 7B  illustrates a state where one stamper holder starts to descending, and  FIG. 7C  illustrates a state where a sheet presser presses a sheet; 
         FIGS. 8A to 8C  are explanatory views, continued from  FIG. 7C , illustrating the operation state of the stamper holder supporting the adhesive tape stamper, in which  FIG. 8A  illustrates a state where another stamp holder starts to descend,  FIG. 8B  illustrates a state where the adhesive tape stampers of the one stamper holder press and apply an adhesive onto the sheet, and  FIG. 8C  illustrates a state where the adhesive tape stampers of both stamper holders press and apply an adhesive onto the sheet; 
         FIGS. 9A and 9B  are views each illustrating a configuration of the staple-binding unit positioned downstream of the adhesive-binding unit, in which  FIG. 9A  is a side view of the staple-binding unit, and  FIG. 9B  is a configuration view of a driver unit of the staple-binding unit; 
         FIG. 10A  is an explanatory view of a stopper section moved vertically in a stacker section and a gripper, and  FIG. 10B  is a plan view of the stopper section and the gripper; 
         FIG. 11  is a perspective view of a drive mechanism in the folding mechanism section illustrated in  FIGS. 2 and 3 , which illustrates a state where a folding blade is situated at a home position; 
         FIG. 12  is a perspective view of the drive mechanism illustrated in  FIG. 11 , which illustrates a state where the folding blade is situated at a sheet folding position; 
         FIGS. 13A to 13D  are explanatory views of folding processing for a staple-bound sheet bundle performed in the folding mechanism section illustrated in  FIGS. 11 and 12 , in which  FIG. 13A  illustrates a state where the sheet bundle is stored,  FIG. 13B  illustrates a state where the sheet bundle is inserted into a folding roller by the folding blade,  FIG. 13C  illustrates an initial state of the folding processing by the folding roller, and  FIG. 13D  illustrates a state where the sheet bundle is being folded by the folding roller; 
         FIGS. 14A to 14D  are explanatory views of folding processing for an adhesive-bound sheet bundle, in which  FIG. 14A  illustrates a state where the sheet bundle is stored,  FIG. 14B  illustrates a state where the sheet bundle is inserted into a folding roller by the folding blade,  FIG. 14C  illustrates a state where an initial state of the folding processing by the folding roller, and  FIG. 14D  illustrates a state where the sheet bundle is being folded by the folding roller; 
         FIGS. 15A to 15D  are views illustrating the staple-bound sheet bundle and adhesive-bound sheet bundles which are in a folded state, in which  FIGS. 15A and 15B  illustrate a folded state of the staple-bound sheet bundle and  FIGS. 15C and 15D  illustrate a folded state of the adhesive-bound sheet bundle; 
         FIGS. 16A to 16C  are sheet flow diagrams for explaining a process in which the adhesive-binding unit is used to bond the sheets to form a sheet bundle, in which  FIG. 16A  illustrates a state where a first sheet is carried in a carry-in path,  FIG. 16B  illustrates a state where a rear end of the first sheet passes through a branching point between the carry-in path and a retreat path, and  FIG. 16C  illustrates a state where an adhesive is applied to a surface of the first sheet which has been retreated to the retreat path; 
         FIGS. 17A to 17C  are sheet flow diagrams continued from  FIG. 16C , in which  FIG. 17A  illustrates a state where an adhesive applied position of the first sheet is moved to the retreat path for carry-in of a second sheet,  FIG. 17B  illustrates a state where a center of the second sheet is bonded to the adhesive applied position of the first sheet and then the bonded sheets are moved to a stacker downstream side, and  FIG. 17C  illustrates a state where rear ends of the bonded sheets that have passed through the carry-in path and the retreat path are biased toward the retreat path side by a deflection guide; 
         FIGS. 18A to 18C  are sheet flow diagrams continued from  FIG. 17C , in which  FIG. 18A  illustrates a state where an adhesive is applied to the second sheet, and the application position thereof is retreated to the retreat path for carry-in of a third sheet,  FIG. 18B  illustrates a state where the bonded sheets in the retreat path and the third sheet are aligned and carried in the stacker section, and  FIG. 18C  illustrates a state where the adhesive applied position of the bonded three sheets is conveyed to a folding processing position for folding processing; 
         FIGS. 19A to 19C  are sheet flow diagrams for explaining a process in which the staple-binding unit as a saddle-stitching stapler is used to bind the sheets, in which FIG.  19 A illustrates a state where a first sheet is carried in a carry-in path,  FIG. 19B  illustrates a state where a rear end of the first sheet that has passed through the branching point between the carry-in path and the retreat path is biased to the retreat path side by the deflection guide, and  FIG. 19C  illustrates a state where a second sheet is carried in the stacker section; 
         FIGS. 20A to 20C  are sheet flow diagrams continued from  FIG. 19C , in which  FIG. 20A  illustrates a state where a third sheet is carried in the stacker section,  FIG. 20B  illustrates a state where a center of the third sheet is situated at a position corresponding to the staple-binding unit, and  FIG. 20C  illustrates a state where a saddle-stitched position of the sheet bundle saddle-stitched by means of metal staples is conveyed to the folding mechanism section for folding processing; 
         FIG. 21  is a flowchart of sheet bundle folding processing for a staple-bound sheet bundle and an adhesive-bound sheet bundle; 
         FIG. 22  is an explanatory view of a control configuration of the entire configuration illustrated in  FIG. 1 ; 
         FIG. 23  is an explanatory view of a modification of a drive path in the folding mechanism section illustrated in  FIG. 11 ; 
         FIG. 24  is an explanatory view of a modification in which the staple-binding unit and the adhesive-binding unit are not juxtaposed but can be selectively attached; 
         FIGS. 25A to 25D  are views for explaining transfer of the adhesive onto the sheet by the adhesive tape stamper, in which  FIG. 25A  is a bottom view of the adhesive tape stamper,  FIG. 25B  is a view for explaining that the adhesives are transferred with the same length,  FIG. 25C  is a view explaining a state where the adhesive is applied at two positions on a cover sheet across the folding position (Y), and  FIG. 25D  is a view explaining a state where a pressing portion of the stamper holder is pressed against the sheets including the cover sheet for bonding; 
         FIGS. 26A to 26C  are views illustrating a state where the adhesive tape (adhesive) is transferred onto the folding position (Y), in which  FIG. 26A  illustrates adhesive transfer processing for a small number of sheets, where the adhesive tape is transferred across the folding position;  FIG. 26B  illustrates the adhesive transfer processing for a large number of sheets, where the adhesive tape is transferred at two positions slightly separated from each other (very close to each other) in the sheet conveying direction across the folding position; and  FIG. 26C  illustrates the adhesive transfer processing for a further large number (exceeding a predetermined number) of sheets, where the adhesive tape is transferred at two positions separated from each other by a predetermined interval (S) across the folding position Y; 
         FIGS. 27A to 27D  are views for explaining a state where the sheet bundle formed by a number of sheets exceeding a predetermined number bonded in  FIG. 26C  is folded by the folding mechanism section illustrated in  FIGS. 11 and 12 , in which  FIG. 27A  illustrates a state where the sheet bundle is stored,  FIG. 27B  illustrates a state where the sheet bundle is inserted into the folding roller by the folding blade,  FIG. 27C  illustrates a state where an initial state of the folding processing by the folding roller, and  FIG. 27D  illustrates a state where the sheet bundle is being folded by the folding roller; 
         FIGS. 28A to 28D  are views illustrating an adhesive-bound sheet bundle and a folded state thereof, in which  FIG. 28A  is a view for explaining a state where the adhesives are applied with the same length irrespective of whether the number of sheets is small or large,  FIG. 28B  illustrates a booklet obtained by folding the adhesive-bound sheet bundle of  FIG. 28A  at the folding position (Y),  FIG. 28C  is a view explaining the adhesive application for sheets whose number exceeds a predetermined number, where the adhesive is applied at two positions separated from each other by an interval (S) across the folding position (Y), and  FIG. 28D  illustrates a booklet obtained by folding the adhesive-bound sheet bundle of  FIG. 28C  at the folding position (Y); 
         FIG. 29  is a flowchart illustrating adhesive tape (adhesive) application processing; 
         FIG. 30  is a flowchart illustrating a processing flow of “tight bonding mode” continued from that of  FIG. 29 ; and 
         FIG. 31  is a flowchart illustrating a modification of the adhesive tape (adhesive) application processing. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Hereinafter, the present invention will be described in detail based on illustrated preferred embodiments.  FIG. 1  illustrates an entire system that combines an image forming device and a sheet processing device according to the present invention.  FIG. 2  is an explanatory view illustrating an entire configuration of the sheet processing device.  FIG. 3  and subsequent drawings are explanatory views illustrating configurations of mechanisms provided in the sheet processing device. A system illustrated in  FIG. 1  is constituted by an image forming device A and a sheet processing device B. The sheet processing device B incorporates therein, as a unit, an adhesive-binding unit  50  that applies an adhesive to a center of sheets in a sheet conveying direction and a staple-binding unit  240  that saddle-stitches, with staple needles, a sheet bundle at a center in the sheet conveying direction. 
     [Configuration of Image Forming Device] 
     The image forming device A illustrated in  FIG. 1  feeds a sheet from a sheet supply section  1  to an image forming section  2 , performs printing on the sheet in the image forming section  2 , and carries out the sheet after printing from a main body discharge port  3 . Sheets of a plurality of sizes are accommodated in sheet cassettes  1   a ,  1   b , and  1   c  of the sheet supply section  1 , and the sheet supply section  1  separates, one from another, sheets of a specified size and feeds them one by one to the image forming section  2 . The image forming section  2  includes, e.g., an electrostatic drum  4 , a print head (laser emitter)  5 , a developing unit  6 , a transfer charger  7 , and a fixing unit  8 . The print head  5 , the developing unit  6 , the transfer charger  7 , and the fixing unit  8  are disposed around the electrostatic drum  4 . An electrostatic latent image is formed on the electrostatic drum  4  using the laser emitter  5 , the developing unit  6  adds toner to the image, the transfer charger  7  transfers the image onto the sheet, and the fixing unit  8  thermally-fixes the image onto the sheet. The sheet with thus formed image is sequentially carried out from the main body discharge port  3 . A reference numeral  9  in  FIG. 1  denotes a circulation path, which is a path for two-side printing in which the sheet printed on the front side from the fixing unit  8  is reversed via a main body switchback path  10  and is conveyed to the image forming section  2  again for printing on the back side thereof. The sheet thus printed on both sides is reversed in the main body switchback path  10  and is carried out from the main body discharge port  3 . 
     A reference numeral  11  in  FIG. 1  denotes an image reader, where a document sheet set on a platen  12  is scanned by a scan unit  13  and is electrically read by a photoelectric conversion element  14  through a reflective mirror and a condensing lens. This image data is subjected to, e.g., digital processing by an image processing section and is subsequently transferred to a data storage section  17 , and an image signal is sent to the laser emitter  5 . A reference numeral  15  denotes a document feeder that feeds document sheets stored on a stacker  16  to the platen  12 . 
     The image forming device A having the above-described configuration is provided with a control section (controller). Image forming conditions such as, printout conditions such as a sheet size specification, a color or black-and-white printing specification, a print copy count specification, single- or double-side printing specification, and enlarged or reduced printing specification are set via a control panel  18 . On the other hand, in the image forming device A, image data read by the scan unit  13  or transferred through an external network is stored in the data storage section  17 . The image data stored in the data storage section  17  is transferred to a buffer memory  19 , which sequentially transfers data signals to the laser emitter  5 . 
     Simultaneously with the image forming conditions, sheet processing conditions are input and specified via the control panel  18 . The sheet processing conditions will be described later. The image forming device A forms an image on the sheet in accordance with the image forming conditions and the sheet processing conditions. 
     [Configuration of Sheet Processing Device] 
     The sheet processing device B connected to the above-described image forming device A receives a sheet with the image formed thereon from the main body discharge port  3  of the image forming device A and is configured to (1) store the sheet in a first sheet discharge tray  21  (printout mode), (2) align the sheets from the main body discharge port  3  in a bundle to staple them and then store the aligned sheet bundle in the first sheet discharge tray  21  (staple-binding mode), (3) bond the sheets from the main body discharge port  3  one by one to form a sheet bundle, fold the resultant sheet bundle into a booklet form, and store the resultant booklet in a second sheet discharge tray  22  (adhesive-bound sheet bundle folding mode), or (4) accumulate and align the sheets from the main body discharge port  3 , then staple them, fold them into a booklet form, and then store the resultant booklet in the second sheet discharge tray (staple-bound sheet bundle folding mode). 
     Thus, as illustrated in  FIG. 2 , the sheet processing device B is provided with the first sheet discharge tray  21  and the second sheet discharge tray  22  in a casing  20 . Further, the sheet processing device B is provided with a sheet carry-in path P 1  having a carry-in port  23  continued to the main body discharge port  3 . The sheet carry-in path P 1  is formed of a straight-line path extending in a substantially horizontal direction in the casing  20 . Further, there are provided a first switchback conveying path SP 1  and a second switchback conveying path SP 2  that branch off from the sheet carry-in path P 1  to convey a sheet in a reverse direction. The first switchback conveying path SP 1  branches off from the sheet carry-in path P 1  at the downstream side of the sheet carry-in path P 1 , the second switchback conveying path SP 2  branches off from the sheet carry-in path P 1  at the upstream side of the sheet carry-in path P 1 , and the paths SP 1  and SP 2  are disposed spaced apart from each other. 
     In such a path configuration, in the sheet carry-in path P 1 , there are disposed a carry-in roller  24  and a sheet discharge roller  25 , and the rollers  24  and  25  are coupled to a drive motor (M 1 ) capable of rotating forward and backward. Further, in the sheet carry-in path P 1 , there is disposed a path switching piece  27  for guiding a sheet to the second switchback conveying path SP 2 , and the piece  27  is coupled to an operation means such as a solenoid. Further, the sheet carry-in path P 1  has, on the downstream side of the carry-in roller  24 , a punch unit  28  for punching the sheet from the carry-in port  23 . The illustrated punch unit  28  is disposed, on the upstream side of the carry-in roller  24 , at the carry-in port  23  so as to be detachably mounted to the casing  20  depending on a device specification. Further, below the punch unit  28 , a punch chip box  26  for housing punch chips generated upon the punch processing is detachably attached to the casing  20 . 
     [Configuration of First Switchback Conveying Path SP 1 ] 
     The first switchback conveying path SP 1  disposed, as illustrated in  FIG. 2 , on the downstream side (rear end portion of the device) of the sheet carry-in path P 1  is configured as described below. The sheet carry-in path P 1  is provided, at its exit end, with a sheet discharge roller  25  and a sheet discharge port  25   a . A first processing tray (hereinafter, referred to as “processing tray  29 ”) is provided downward of the sheet discharge port  25   a  across a level difference formed therebetween. The processing tray  29  includes a tray for loading and supporting the sheet discharged from the sheet discharge port  25   a . There is disposed, above the processing tray  29 , a forward/backward rotation roller  30 . The forward/backward rotation roller  30  is coupled with the forward/backward rotation motor M 1  and is controlled to be rotated in a clockwise direction in  FIG. 2  when a sheet approaches the processing tray  29 , while rotating in a counterclockwise direction after a sheet rear end enters the tray. The forward/backward rotation roller  30  has a lifting roller  31  coupled to a caterpillar belt so as to be movable between positions contacting the tray and separated therefrom. Therefore, the first switchback conveying path SP 1  is configured above the processing tray  29 . 
     Further, the first sheet discharge tray  21  is located downstream of the first switchback conveying path SP 1  and is configured to support a leading end of a sheet guided to the first switchback conveying path SP 1  and the second switchback conveying path SP 2 . 
     With the above-described configuration, the sheet from the sheet discharge port  25   a  reaches the processing tray  29  and is conveyed toward the first sheet discharge tray  21  by the forward/backward rotation roller  30 . Once the rear end of the sheet reaches the processing tray  29  from the sheet discharge port  25   a , the forward/backward rotation roller  30  is reversely rotated (counterclockwise in the figure) to convey the sheet on the processing tray  29  in a direction opposite to a sheet discharge direction. At this time, the lifting roller  31  coupled to the caterpillar belt cooperates with the forward/backward rotation roller  30  to switchback-convey the rear end of the sheet along the processing tray  29 . 
     A rear end regulating member  33  and an end surface stapler  35  are disposed at a rear end portion of the processing tray  29  in the sheet discharge direction. The rear end regulating member  32  regulates a position of the rear end of the sheet. The illustrated end surface stapler  35  staples rear end edge of a sheet bundle stored on the tray at one or more portions. The rear end regulating member  33  is also used to provide a function of carrying out the staple-bound sheet bundle to the first sheet discharge tray  21  located downstream of the processing tray  29 . To this end, the rear end regulating member  33  is configured to be able to reciprocate in the sheet discharge direction along the processing tray  29 . The illustrated rear end regulating member  33  is coupled to a not illustrated bundle discharge motor (M 7 ) so as to be reciprocated. 
     The processing tray  29  has a side aligning plate  36  with which the sheets stored on the tray are aligned in a width direction thereof. The side aligning plate  36  includes a pair of left and right (front and rear in  FIG. 2 ) aligning plates so as to align the sheets with reference to a sheet center and is configured to approach and leave the sheet center. The side aligning plate  36  is coupled to a not illustrated side aligning plate motor (M 6 ). 
     The first switchback conveying path SP 1  configured as described above aligns the sheets from the sheet discharge port  25   a  on the processing tray  29  in the “staple-binding mode” described above, and the end surface stapler  35  staples the sheet bundle at one or more portions of the rear end edge of this sheet bundle. In the “printout mode”, a sheet from the sheet discharge port  25   a  is not subjected to the switchback, but the sheet conveyed along the processing tray  29  is carried out to the first sheet discharge tray  21  by the forward/backward rotation roller  30 . Thus, the illustrated device is characterized in that the sheet to be staple-bound is bridged between the processing tray  29  and the first sheet discharge tray  21  to allow the device to be compactly configured. 
     [Configuration of Second Switchback Conveying Path SP 2 ] 
     The following describes a configuration of the second switchback conveying path SP 2  branching off from the sheet carry-in path P 1 . As illustrated in  FIG. 2 , the second switchback conveying path SP 2  is located in a substantially vertical direction inside the casing  20 . A path carry-in roller  45  is located at an entrance of the second switchback conveying path SP 2 , and a conveying roller  46  is located at an exit of the second switchback conveying path SP 2 . The conveying roller  46  is configured to be movable between a position nipping the sheet and a position separated from the sheet. Although this configuration is not illustrated, a pinch roller or the like pressure contact to the conveying roller  46  is separated therefrom by an arm mechanism. 
     The path carry-in roller  45 , located at the entrance of the second switchback conveying path SP 2 , is configured to be rotatable forward and backward. A sheet carried in the first switchback conveying path SP 1  located downstream is temporarily held (temporarily reside) on the second switchback conveying path SP 2 . The reason for the temporary holding is as follows. That is, the preceding sheets are stored on the processing tray  29 , staple-bound in response to a job completion signal, and the resultant sheet bundle is carried out to the first sheet discharge tray  21 . During this carry-out, a sheet conveyed from the image forming device A to the sheet carry-in path P 1  is temporarily held on the second switchback conveying path SP 2 . Then, after the processing of the preceding sheet bundle is finished, the standing-by sheet is conveyed from the first switchback conveying path SP 1  onto the processing tray  29 . 
     A stacker section  40  constituting the second processing tray that aligns and temporarily stores the sheets conveyed along the second switchback conveying path SP 2  is provided downstream of a carry-in path  41  constituting the second switchback conveying path SP 2  and serving also as a sheet carry-in path. The illustrated stacker section  40  includes a conveying guide that conveying the sheets. The conveying guide is constituted by a stacker upper guide  40   a  and a stacker lower guide  40   b  and configured so that the sheets are loaded and housed therein. The illustrated stacker section  40  is connected to the carry-in path  41  and located in a center portion of the casing  20  in the left-right direction so as to extend in the substantially vertical direction. This allows the device to be compactly configured. The stacker section  40  is shaped to have an appropriate length to house maximum sized sheets therein. There are provided, inside the stacker section  40 , an adhesive-binding unit  50  as an adhesive applying section for applying an adhesive to the sheet, a staple-binding unit  240  that saddle stitches the sheet bundle with staples, and a folding mechanism section  80  including a folding blade  86  and a folding roller  81  for folding the sheet bundle. These components will be described later in detail. 
     [Configuration of Retreat Path (Third Switchback Path SP 3 )] 
     A retreat path  47  constituting a third switchback path SP 3  is continuously provided from a rear end side of the stacker section  40  in a sheet conveying direction. The retreat path  47  branches off from the carry-in path  41  constituting the above-described second switchback conveying path SP 2  and serving also as a path for carrying the sheet in the stacker section  40  and configured to overlap an exit end of the carry-in path and make the sheet advance thereinto in a switchback manner. As illustrated in  FIGS. 2 and 3 , the retreat path  47  is constituted by a switchback guide  42  formed of a plate material. Ribs are formed on a surface of the switchback guide  42  along the sheet conveying direction to smooth sheet conveying operation. Further, to cope with a case where a jam of the sheet bundle occurs in the retreat path, the switchback guide  42  is configured to turn about a guide releasing shaft  43  to be released. 
     When the rear end of the sheet carried in from the carry-in path  41  to the stacker section  40  passes through a position at which the retreat path  47  branches off from the carry-in path  41 , the sheet is moved (lifted up) by a stopper section  90  as a regulating member for regulating the leading end of the sheet, and the rear end side of the sheet is switchback-conveyed to the retreat path  47  together with the sheet bundle in the stacker section  40 . 
     At a merging point between the carry-in path  41  and the retreat path  47 , a deflection guide  44  biased by a guide tension spring  44   a  toward the switchback guide  42  side of the retreat path  47  is provided. Further, at the merging point, the adhesive-binding unit  50  for applying an adhesive onto the sheet is located so as to immediately follow the deflection guide  44 . The adhesive-binding unit  50  has adhesive tape stampers  51  each serving as an adhesive means. Although details will be described later, when a sheet (second sheet) is carried in from the carry-in path  41  after an adhesive tape is applied (transferred) onto a preceding sheet (first sheet) by the adhesive tape stampers  51  of the adhesive-binding unit  50 , the leading end of the second sheet is adhered to the adhesive-applied portion of the first sheet, making it impossible to apply the adhesive onto a center portion of the second sheet in the sheet conveying direction, thus failing to form a sheet bundle. For this reason, it is necessary to convey the sheet to the adhesive tape stampers  51  after the preceding sheet is switchback-conveyed to the retreat path  47 . Thus, the retreat path  47  functions as a retreat path for the adhesive-applied sheet. 
     [Outline of Configurations of Components Provided along Path between Retreat Path and Stopper Section] 
     Based on  FIGS. 2 and 3 , an outline of configurations of components provided along a path between the retreat path  47  branching off from the carry-in path  41  and the stopper section  90  will be described. 
     At the merging point between the carry-in path  41  and the retreat path  47 , the deflection guide  44  is provided, in which a spring is stretched so as to slightly press the sheet toward the switchback guide  42  of the retreat path  47 . The deflection guide  44  has such a comb shape as to avoid the adhesive-applied position of the sheet. Thus, even when the adhesive-applied sheet passes under the deflection guide  44 , the adhesive is not adhered to the conveying path. A flow of the sheet in this section will be described separately later. 
     As illustrated in detail in  FIG. 3 , at the merging point between the carry-in path  41  on the downstream side of the deflection guide  44  and the retreat path  47 , the adhesive-binding unit  50  for applying an adhesive onto the sheet is provided in the stacker section  40 . A sheet presser  65  for pressing a sheet stopped at an adhesive position for regulation is mounted to the adhesive-binding unit  50  so as to be vertically movable. Further, a sheet pressing slider  71  configured to be moved vertically to press the sheet and feed an adhesive tape AT as an adhesive is provided on a leading end side of the sheet presser  65 . A transfer head  72  for backing up the adhesive tape AT fed from a reel is provided above the sheet pressing slider  71 . The transfer head  72  is also moved between the adhesive position at which it presses the sheet to apply the adhesive tape AT onto the sheet and a separated position at which it is separated from the sheet to allow the sheet to be conveyed/moved therethrough. 
     The “application” in the present invention includes so-called “transfer” that transfers the adhesive from a tape to the sheet by pressing the sheet. Further, the “application” includes spraying of the adhesive to the sheet while pressing the sheet. Further, a member to be applied may be a pasting member. 
     The staple-binding unit  240  is disposed downstream of the adhesive-binding unit  50 . The staple-binding unit  240  is a saddle-stitching stapler that performs saddle-stitching for a sheet bundle using a metal staple  239 . The staple-binding unit  240  uses a driver unit  241  to drive the metal staple  239  into a conveying direction center portion (staple-binding position SP) of a sheet bundle aligned/stored on the stacker section  40  and then uses a clincher unit  250  to bend leg portions of the driven staple in a direction facing each other, whereby the sheet bundle is bound. The details will be described later in  FIGS. 9A and 9B . 
     When the sheet bundle is bound by the staple-binding unit  240 , the sheet bundle to be bound is once housed in the stacker section  40 . In this case, when a rear end of a previously housed sheet is jumped up, a leading end of the next sheet collides with the jumped up rear end of the previously housed sheet. This may prevent the next sheet from being inserted into the stacker section  40  properly or make the next sheet enter between the previously housed sheets to disturb the order of pages. Thus, in the device of the present embodiment, the above-mentioned deflection guide  44  is used to bias the sheet toward the retreat path  47  to allow the next sheet to be stacked onto the preceding sheet properly. Further, by switching back the preceding sheet bundle to the retreat path upon insertion of the next sheet, a surface of the preceding sheet guides the next sheet to more smoothly carry the next sheet in the stacker section. 
     An aligning member  48  configured to be moved in the sheet width direction to press a side edge of the sheet housed in the stacker section  40  is disposed downstream of the staple-binding unit. The aligning member  48  has a substantially U-shape, at a center portion of which folding rollers  81   a  and  81   b  serving as the folding mechanism section and the folding blade  86  for pressing the sheet against the folding rollers  81   a  and  81   b  are movably provided so as to press and separate from the sheet. Further, a pressure roller  49  is provided so as to immediately follow the aligning member  48  and to contact and separate from the stacker lower guide  40   b  which is one of the guide members constituting the stacker section  40 . The pressure roller  49  is separated from the sheet until the leading end of the sheet passes therethrough and, after the sheet leading end passes through the pressure roller  49 , the pressure roller  49  is rotated while pressing the sheet against the stacker lower guide  40   b.    
     A sheet regulating member (hereinafter, referred to as “stopper section  90 ”) for regulating a leading end of the sheet in the sheet conveying direction is provided on a lower end side of the stacker section  40 . The stopper section  90  is supported by a guide rail of a device frame and is configured to be movable vertically by an elevating belt  93  stretched between vertically arranged upper and lower pulleys  94   a  and  94   b . These pulleys  94  are moved by a motor (M 10 ) to move the elevating belt  93 . As described below, the elevating belt  93  is configured to move the stopper section  90  to and stop the same at positions of Sh 0 , Sh 1 , Sh 2 , Sh 31 , Sh 32 , and Sh 4 . 
     The Sh 0 , which is the lowermost position, is a home position of the stopper section  90 . A sensor (not illustrated) is used to detect this position for initial position setting. The Sh 1  is a receiving position of a first sheet and a position at which the rear ends of the sequentially stacked sheets that have passed through the carry-in path  41  are pressed by the deflection guide  44  toward the switchback guide  42  of the retreat path  47 . The Sh 2  is a position at which the sheet bundle is subjected to the folding at a substantially half position of the sheet in the sheet conveying direction. The Sh 31  is a position at which the staple-binding unit  240  is used to drive, in the sheet width direction, the metal staple  239  into a substantially half position of the sheet bundle in the sheet conveying direction for binding. The Sh 32  is a position at which the adhesive-binding unit  50  is used to apply (transfer), in the sheet width direction, the adhesive tape AT onto the sheet at a substantially half position of the sheet in the sheet conveying direction. The Sh 4  is a position at which the adhesive-applied position at which the adhesive tape AT is applied onto the sheet is moved to the retreat path  47 . More specifically, when a sheet (second sheet) is carried in from the carry-in path  41  into the stacker section  40 , the adhesive-applied position of the preceding sheet (first sheet) can be retracted to a position (application retreat position  100 ) separated away from the carry-in path of the second sheet so as to prevent a sheet jam or adherence of the adhesive to an unintended position due to contact of the second sheet with the adhesive-applied position of the first sheet. 
     As described above, in this device, carry-in of the sheet, application of the adhesive onto the sheet or staple-binding of the sheet bundle, movement of the adhesive-applied position to the retract path, carry-in of the subsequent sheet, and application of the adhesive onto the subsequent sheet are performed to bond the sheets by the adhesive, and the above operations are repeatedly performed to form the sheet bundle. 
     The resultant sheet bundle is then folded in two by the folding mechanism section  80  and discharged to the second sheet discharge tray by a bundle discharge roller  95  provided with a bundle kick-out piece  95   a . The discharged sheet bundle is stored on the second sheet discharge tray by a bundle press guide  96  and a bundle presser  97  positioned downward of the bundle press guide  96 . The bundle press guide  96  and the bundle presser  97  are used for preventing a sheet loading range from being narrowed due to opening of the bundle. The above sheet bundle formation and operation of the folding mechanism section will be described more in detail later. 
     [Configuration of Adhesive Application Device] 
     The following describes the adhesive-binding unit  50  with reference to  FIGS. 3  to  FIGS. 8A to 8C . A range surrounded by a dashed line of a cross-sectional view of  FIG. 3  corresponds to the adhesive-binding unit  50  in the present embodiment.  FIG. 4  is a perspective view of the adhesive-binding unit  50 , and the adhesive-binding unit  50  is attached to the sheet processing device B with an illustrated range as a unit.  FIGS. 5A to 5C  are explanatory views of a main part of adhesive tape units  50   a  and  50   b  constituting an adhesive section.  FIG. 5A  is a plan view of a cam member  57  and the like.  FIG. 5B  is a front view illustrating an engagement state between the cam member  57  and a stamper holder  52 . An upper part of  FIG. 5C  illustrates a state where the cam member  57  is moved to a position causing the adhesive tape stampers  51  to be separated from the sheet, and a lower part of  FIG. 5C  illustrates a state where the cam member  57  is moved to a position causing the stamper holders  52  to be pressed against the platen  79 , at which the adhesive tape stampers contact the sheet.  FIGS. 6A to 6D  are explanatory views of the adhesive tape stampers  51 .  FIG. 6A  is a perspective view,  FIG. 6B  is an internal mechanism view, and  FIGS. 6C and 6D  are views for explaining a drive mechanism for winding the adhesive tape AT in a stamping operation.  FIGS. 7A to 7C  and  FIGS. 8A to 8C  are explanatory views illustrating an operation of applying/transferring the adhesive tape AT onto the sheet performed by the adhesive tape units  50   a  and  50   b  each supporting a plurality of adhesive tape stampers  51 . 
     There are disposed, within the dashed-line range of  FIG. 3 , members constituting the adhesive-binding unit  50 . The members are: an adhesive tape stamper  51 , a stamper holder  52  for grouping the adhesive tape stampers  51  and supporting them in parallel, a cam member  57  that moves vertically the stamper holder  52  between a position at which the stamper holder  52  is brought close to a platen  79  to press the adhesive tape stampers  51  against the sheet for application of the adhesive thereonto and a position at which the stamper holder  52  is separated from the platen  79 , and a cam moving motor  60  (M 13 ) that moves the cam member  57  in a direction crossing the sheet conveying direction. Further, a plurality of adhesive tape units  50   a  and  50   b  are configured to be attachable, as units, respectively, to the sheet processing device B, more specifically, to an upstream position of the stacker section  40 . Further, in order to prevent the sheet from being shifted upon carry-in of the sheet into the stacker section  40  or switchback thereof to the retreat path  47 , a part of the carry-in path  41  (more specifically, a portion from a unit path entrance  143  to a carry-in path exit  144  of  FIG. 3 ), deflection guide  44 , a part of the branching retreat path  47  (more specifically, a retreat path exit  145 ), and the platen  79  are incorporated in the adhesive-binding unit  50  as units, respectively. The adhesive-binding unit  50  corresponding to the range surrounded by the dashed line of  FIG. 3  is thus configured and is illustrated in a perspective view of  FIG. 4 . 
     Attachment of the adhesive-binding unit  50  to the sheet processing device B is made by fixing a not illustrated fixing portion of the sheet processing device B and a stop screw hole  50   cb  formed in a frame of the adhesive-binding unit  50  by an illustrated screw, as illustrated in  FIG. 4 . In place of the fixing structure using the screw, rails may be provided in the sheet processing device B and the adhesive-binding unit  50 , respectively, so as to allow the adhesive-binding unit  50  to be pulled out. 
     The above unitized configuration allows an increase in accuracy of a positional relationship among the components as compared to a case where the components are individually attached to the sheet processing device B, thereby, in particular, suppressing adherence of the adhesive to an unintended position due to displacement upon movement of the sheet after application of the adhesive. 
     In the adhesive-binding unit  50 , left and right application device frames  50   c , a center support frame  63 , a rear support frame  64   a , and a lower support frame  64   b  constitute one casing. The center support frame  63  connects the left and right application device frames  50   c  at center portions thereof. The rear support frame  64   a  connects the left and right application device frames  50   c  at rear portions thereof. The lower support frame  64   b  connects the left and right application device frames  50   c  at portions thereof below the platen  79 . The cam moving motor  60  (M 13 ) is mounted to one of the left and right application device frames  50   c . Drive of the cam moving motor  60  (M 13 ) is transmitted to a moving belt  58  through a gear train  59 . The moving belt  58  is connected to the cam member  57  which is configured to be slidable along two cam guide rods  57   a  extending between the left and right application device frames  50   c  in the sheet width direction. Thus, when the cam moving motor  60  (M 13 ) is driven, the cam member  57  is moved to the left or right according to a rotating direction of the cam moving motor  60 . 
     Cam grooves  61  as illustrated in  FIGS. 5B and 5C  are formed in the cam member  57 . As illustrated, the cam member  57  includes an upper horizontal cam groove  61   a , a lower horizontal cam groove  61   c , and an inclined cam groove  61   b . The upper horizontal cam groove  61   a  is positioned at an upper portion of the cam member  57 . The lower horizontal cam groove  61   c  is positioned at a lower portion of the cam member  57 . The inclined cam groove  61   b  connects the upper horizontal cam groove  61   a  and the lower horizontal cam groove  61   c . As illustrated, two left and right cam grooves  61  are formed in the cam member  57  and are slightly different in phase. A roller  56  serving as a cam follower and fixed to a moving block  54  for moving vertically the stamper holder  52  is fitted into each of the cam grooves  61 . 
     The roller engaged with (fitted into) each cam member  61  is fixed to the moving block  54  through a shaft. Referring to  FIG. 7A  (which is an explanatory view as viewed from the back of the cam member  57  of  FIG. 4 ), the moving block  54  is slidably supported by inner two guide rods  53  of four guide rods  53  provided in the stamper holder  52  that supports the adhesive tape stamper  51  so as to vertically extend. On the other hand, each of the remaining (outer) two guide rods  53  is slidably supported by a support block  55  fixed to the center support frame  63  connecting the left and right application device frames  50   c . Accordingly, the stamper holder  52  supporting the adhesive tape stampers  51  is supported by the support block  55  in which the outer guide rods  53  slide. 
     On the other hand, the moving block  54  is mounted to the two guide rods  53  at a center of the stamper holder  52  so as to be freely slidable. The moving block  54  is fixed to the roller  56  engaged, as a cam follower, with the above cam groove  61 . Further, a pressure spring  62  is wound around the center two guide rods  53  between a bottom surface of the moving block  54  and a rear surface  52   c  of a bottom surface of the stamper holder  52 . The pressure spring  62  constantly biases the moving block  54  in a direction pressing the same against an upper portion of the stamper holder  52 . Accordingly, when the cam member  57  is moved to cause the roller  56  engaged with the cam groove  61  to descend, a transfer head  72  to be described later of the adhesive tape stamper  51  abuts against the sheet to stop the descent of the stamper holder  52 . Then, the pressure spring  62  is compressed between the bottom surface of the moving block  54  and the rear surface  52   c  of the bottom surface  52   b  of the stamper holder  52 . As a result, the transfer head  72  is pressed more strongly against the sheet by an elastic force of the pressure spring  62  compressed by the moving block  54 , allowing the adhesive on the transfer tape AT to be reliably applied (transferred) onto the sheet. 
     Further, as illustrated in  FIG. 5C , the left and right cam grooves  61  with which the rollers  56  are engaged respectively are different in phase and the initial position of the roller  56 . Thus, the left side roller  56  starts to descend earlier, and the right side roller  56  reaches the lower horizontal cam groove  61   c  later. Therefore, the left side lower horizontal cam groove  61   c  is formed longer than the right side lower horizontal cam groove  61   c . As a result, the left side adhesive tape unit  50   a  having the adhesive tape stampers  51  presses the sheet earlier than the right side adhesive tape unit  50   b , and the right side adhesive tape unit  50   b  presses the sheet later. A considerable pressing force is required in order for the adhesive tape units  50   a  and  50   b  press the sheet at a time, so that a more powerful drive motor needs to be used to move the cam member  57 ; however, by deviating the timing of pressing the sheet as described above, it is possible to reduce a size of the motor or weight of the frame. 
     [Adhesive Means (Adhesive Tape Stamper)] 
     The adhesive tape stamper  51  configured to be detachably mounted to the stamper holder  52  constituting each of the adhesive tape units  50   a  and  50   b  will be described using  FIGS. 6A to 6D .  FIG. 6A  illustrates an outer appearance of the adhesive tape stamper  51 . There are shown, in  FIG. 6A , a stamper cover  70 , a transfer tape AT having an adhesive on a tape base material and configured to be sequentially delivered, a transfer head  72  around which the transfer tape AT is wound and configured to back up the transfer tape AT so as to press the same against the sheet, and a sheet pressing slider  71  positioned beside the transfer head  72  and configured to be moved vertically between a position protruding from the transfer head  72  and a retreat position corresponding to the transfer head  72 . When the transfer head  72  is moved down and applies/transfers the transfer tape AT onto the sheet, the sheet pressing slider  71  presses the sheet positioned thereunder. With this pressing operation, the transfer tape AT is delivered, and a new adhesive surface appears. The transfer head  72  then backs up and presses the adhesive surface to thereby apply/transfer the adhesive onto the sheet. 
     The following describes a configuration in which the transfer tape AT is delivered by extension/contraction of the sheet pressing slider  71 . As illustrated in  FIG. 6B , there are disposed, inside the stamper cover  70 , a supply reel  74  freely rotatable about a supply reel shaft  74   a , around which an unused transfer tape AT is wound and a winding reel  75  free rotatable about a winding reel shaft  75   a  and configured to wind the transfer tape AT that is delivered from the supply reel  74  and stretched over the transfer head  72 .  FIG. 6C  illustrates a state before the transfer tape AT is delivered from the supply reel  74 . Above the sheet pressing slider  71  provided inside the stamper cover  70  so as to be extendable/contractible, a resin slider rack  77  is provided. The slider rack  77  is engaged with a gear rotating together with the winding reel  75 . Further, the gear of the winding reel  75  is engaged with a gear rotating together with the supply reel  74  through inter-reel gears  76 . 
     Further, a slider spring  73  is provided in the sheet pressing slider  71  and constantly biases outward (downward in  FIGS. 6A to 6D ) the sheet pressing slider  71 . Thus, when the adhesive tape stamper  51  in a state of  FIG. 6C  where the slider spring  73  is extended is pressed down, the slider spring  73  is compressed as illustrated in  FIG. 6D . At the same time, the slider rack  77  is engaged with a winding reel gear  75   b  of the winding reel  75  to rotate the winding reel  75  in a clockwise direction in the drawing. The winding reel gear  75   b  is engaged with one of the inter-reel gears  76 , and the other one of the inter-reel gears  76  is engaged with a supply reel gear  74   b . Thus, when the winding reel  75  is rotated in the clockwise direction in the drawing, the supply reel  74  is also rotated to cause the adhesive tape AT to be wound around the winding reel. At the same time, the transfer tape AT is delivered from the supply reel, and a new adhesive surface is positioned at the transfer head  72 . 
     Then, when the adhesive tape stamper  51  is moved up in the state of  FIG. 6D , the slider spring  73  is elastically restored to press down the sheet pressing slider  71 . At this time, the winding reel gear  75   b  is engaged with the slider rack  77  and is thus rotated in a counterclockwise direction; however, a ratchet mechanism that transmits rotation only in one direction is interposed between the winding reel gear  75   b  and the winding reel  75 , so that the winding reel  75  is not rotated. Further, the inter-reel gear  76  engaged with the winding reel gear  75   b  and the supply reel gear  74   b  are also rotated in the counterclockwise direction; however, a ratchet mechanism that transmits rotation only in one direction is interposed between the supply reel gear  74   b  and the supply reel  74 , so that the supply reel  74  is not rotated. With this mechanism, only when the sheet pressing slider  71  is pressed down, the supply reel  74  and the winding reel  75  are rotated, and a new adhesive surface of the adhesive tape AT is delivered to the transfer head  72  and positioned thereat. In the present embodiment, as the ratchet mechanisms which are not illustrated, a one-way clutch that transmits rotation only in one direction between the reel gear and the reel may be adopted. 
     The movement from the state of  FIG. 6C  to state of  FIG. 6D  is made by the cam member  57  vertically moving the stamper holder  52  that supports a plurality of adhesive tape stampers  51  in the sheet width direction. This mechanism is as described above. Note that, as illustrated in  FIG. 3 , a foamed resin cushion material  52   a  for buffering an impact upon the vertical movement is interposed between the stamper holder  52  and the adhesive tape stamper  51 . This improves application (transfer) performance of the adhesive from the adhesive tape AT onto the sheet. 
     The adhesive tape AT in the present embodiment has the adhesive on the tape base material and is configured to press the tape base material against the sheet to thereby transfer the adhesive onto the sheet. 
     [Sheet Bundle Presser adjacent to Stamper Holder] 
     The following describes, using  FIGS. 3 and 4 , and particularly  FIG. 7A , a sheet presser  65  that regulates movement or flapping of the sheet before the sheet pressing slider  71  of the adhesive tape stamper  51  described using  FIGS. 6A to 6D  presses the sheet against the platen  79  as the adhesive position. 
     As described above, the sheet presser  65  for regulating the sheet stopped at the adhesive position for bonding is mounted to the adhesive-binding unit  50  so as to be vertically movable with respect to the platen  79 . As illustrated in  FIG. 7A , there is provided, on both side of the two stamper holders  52  each supporting the adhesive tape stampers  51 , a sheet presser support block  67  that slidably supports a sheet presser guide rod  68  having the sheet presser  65 . The sheet presser support block  67  is fixed to the center support frame  63  by screws or the like inserted into illustrated round holes formed therein. Further, a pressing pressure spring  65   c  wound around the sheet presser guide rod  68  is provided at both side ends of the sheet presser support block  67  and a side edge presser  65   a  of the sheet presser  65 . 
     The sheet presser  65  is constantly biased in a direction pressing the sheet, and one (left side of  FIGS. 7A to 7C ) stamper holder  52  and the sheet presser  65  are engaged with each other through an engagement portion  69  to stop the sheet presser  65  at a position separated from the sheet on the platen  79 . Thus, when the stamper holder  52  is not moved down, the sheet presser  65  stays at the position separating from the sheet, allowing passage of the sheet. When the stamper holder  52  starts being moved down toward the sheet with the movement of the cam member  57 , the engagement portion  69  between the stamper holder  52  and the sheet presser  65  is moved down as illustrated in  FIG. 7C , and the sheet presser  65  is moved down to regulate displacement or flapping of the sheet on the platen  79 . This can prevent the displacement or flapping of the sheet when the stamper holder  52  is moved down to cause the sheet pressing slider  71  to press the sheet, or when the stamper holder  52  is further moved down to cause the transfer head  72  supporting the adhesive tape AT and pressing the same against the sheet to press the sheet. 
     After each adhesive tape stamper  51  applies (transfers) the adhesive of the adhesive tape AT onto the sheet in the width direction thereof with the moving down of the two stamper holders  52 , the cam member is returned to a state of  FIG. 7B , and the engagement portion of the sheet presser  65  is engaged with the stamper holder  52  and moved up to a position retreated from the sheet by moving up of the stamper holder  52 . As described above, the sheet presser  65  in the present embodiment presses the sheet, interlocking with the vertical movement of the stamper holder  52 , before other members do. This sheet presser may be moved down before the moving down of the stamper holder  52  by means of a solenoid or the like. Further, although the side edge presser  65   a  and a center presser  65   b  are provided so as to press the sheet over the entire width thereof, only one of them suffices. That is, it is only necessary to prevent the sheet from being moved before application of the adhesive. 
     [Operation of Adhesive-binding Unit] 
     The following describes an operation of applying (transferring) the adhesive onto the sheet by the adhesive-binding unit  50  using  FIGS. 7A to 7C  and  FIGS. 8A to 8C .  FIGS. 7A to 7C  and  FIGS. 8A to 8C  are each an explanatory view as viewed from the back of the cam member  57 , that is, from an opposite side to the tape stamper  51 . 
     In a state of  FIG. 7A , the cam member  57  is situated at an initial position, and the moving block  54  that makes the stamper holder  52  mounted with the adhesive tape stampers  51  slide along the inner guide rods  53  and roller  56  are engaged with the cam groove  61  of the cam member  57 . As described above, the moving block  54  has the pressure spring  62  which is interposed between itself and the moving block  54  and brings the pressure spring  62  into contact with and presses the rear surface  52   c  of the stamper holder  52 , as illustrated in  FIG. 7A . Further, the stamper holder  52  is configured to slide along the outside guide rods  53  slidably supported by the support block  55 , which is fixed to the center support frame  63  connecting the left and right application device frames  50   c , so as to be moved vertically. 
     In  FIG. 7A , the stamper holder  52  and the sheet presser  65  locked to the stamper holder  52  are separated from the platen  79 , thereby maintaining a space for allowing passage of the sheet. In this state, the sheet pressing slider  71  and the transfer head  72  of each adhesive tape stamper  51  are situated at a position farthest from the sheet. The other stamper holder  52  is situated at the same position. 
     In  FIG. 7B , the sheet is situated at the adhesive position, and the cam moving motor  60  (M 13 ) is driven by a signal for commanding application of the adhesive tape AT to move the cam member  57  to the right in the drawing. Then, the roller  56  on the left side in the drawing starts being moved down along the inclined cam groove  61   b . This movement causes the left side stamper holder  52  to be moved down with the support block  55  sliding along the guide rods  53 . The moving down of the stamper holder  52  causes the engagement portion  69  engaged with the stamper holder  52  to be moved down, thereby starting pressing the sheet on the platen  79 . On the other hand, the sheet pressing slider  71  and the transfer head  72  of each adhesive tape stamper  51  are also moved down, but do not contact the sheet. The stamper holder  52  on the right side in the drawing is not moved down since the roller  56  is only slid in the upper horizontal cam groove  61   a  of the cam groove  61 . 
     When the cam member  57  is further moved, the roller  56  on the left side in the drawing is further slid down along the inclined cam groove as illustrated in  FIG. 7C . This sliding down releases the engagement between the sheet presser  65  and the right side stamper holder  52  which are engaged with each other at the engagement portion  69 . When the engagement is released, the sheet presser  65  presses the sheet more reliably for position regulation by means of the pressing pressure spring  65   c  interposed between itself and the sheet presser support block  67 . On the other hand, the sheet pressing slider  71  of the adhesive tape stamper  51  starts to contact the sheet. With this contact, the adhesive tape AT is moved from the state of  FIG. 6C  to state of  FIG. 6D  to expose a new adhesive surface. In this state, the transfer head  72  has not yet contact the sheet. The stamper holder  52  on the right side in the drawing is not moved down since the roller  56  is only slid in the upper horizontal cam groove  61   a  of the cam groove  61 . 
     Subsequently, when the cam member  57  is moved to the right as illustrated in  FIG. 8A , the stamper holder  52  on the left side in the drawing is moved down to cause the sheet pressing slider  71  and the transfer head  72  to abut against the sheet. When the transfer head  72  abuts against the sheet, the moving down of the stamper holder  52  is stopped, while the moving block  54  is slid along the inclined cam groove  61   b  and moved down. With this movement, the pressure spring  62  starts being compressed, and the elastic force of the pressure spring  62  acts on the transfer head  72  through the stamper holder  52  as a pressurizing force, with the result that the adhesive tape AT is pressed against the sheet more strongly. Thus, the adhesive can be reliably applied/transferred onto the sheet. 
     On the other hand, the roller  56  of the right side stamper holder  52  starts being slid down along the inclined cam groove  61   b , and the sheet pressing slider  71  of the adhesive tape stamper  51  of the right side stamper holder  52  starts pressing the sheet. 
     When the cam member  57  is further moved, a state of  FIG. 8B  is reached. In this state, the stamper holder  52  on the left side in the drawing is maintained in a pressurized state by the elastic force of the pressure spring  62 . On the other hand, the roller  56  of the stamper holder  52  on the right side in the drawing reaches an end point of the inclined cam groove  61   b , with the result that the sheet pressing slider  71  and the transfer head  72  of the adhesive tape stamper  51  of the right side stamper holder  52  press the sheet. 
     When the cam member  57  is situated at the rightmost position as illustrated in  FIG. 8C , the left side stamper holder  52  is maintained in a more pressurized state by the elastic force of the pressure spring  62 . On the other hand, the roller  56  of the stamper holder  52  on the right side in the drawing reaches the lower horizontal cam groove  61   c , with the result that the sheet pressing slider  71  and the transfer head  72  of the adhesive tape stamper  51  of the stamper holder  52  on the left side press the sheet and that the pressure spring  62  is compressed. This elastic force acts on the transfer head  72  through the stamper holder  52  as a pressurizing force, with the result that the adhesive tape AT is pressed against the sheet more strongly. Thus, the adhesive can be reliably applied (transferred) onto the sheet. When there exists a preceding sheet applied with the adhesive, bonding between the sheets is strengthen. 
     After the transfer heads  72  have applied the adhesive onto the sheet by the moving down of the left- and right-side stamper holders  52 , the cam member  57  is moved to the left in the drawing to move up the stamper holder  52  in a reverse order of the moving-down procedure. When the state of  FIG. 7B  is reached, the stamper holder  52  on the left side is engaged with the engagement portion  69  of the sheet presser  65  to move the sheet presser  65  to a position separated from the sheet. Subsequently, the state of  FIG. 7A  is restored, and the application of the adhesive onto a next sheet is prepared for. 
     As described above, in the present embodiment, the sheet is previously pressed by the sheet presser  65  to regulate movement of the sheet before the transfer head  72  of the adhesive tape stamper  51  applies the adhesive onto the sheet. This prevents displacement or flapping of the sheet, thus making it possible to apply the adhesive onto a predetermined position on the sheet. Further, even after the transfer head  72  abuts against the sheet, the stamper holder  52  that supports the transfer head  72  is pressed by the pressure spring  62 . This makes it possible to press the transfer head  72  against the sheet more strongly, allowing the adhesive on the adhesive tape AT to be reliably transferred onto the sheet. 
     Further, as described in the explanation of the operation of the adhesive-binding unit, the left and right stamper holders  52  illustrated in  FIGS. 7A to 7C  and  FIGS. 8A to 8C  do not press the transfer heads  72  simultaneously, but the timing of pressing the sheet is deviated such that first the left side transfer head  72  group is pressed against the sheet, and then the right side transfer head  72  group is pressed against the sheet while the pressuring state of the left side transfer head  72  group is maintained. Thus, it is possible to reduce a drive force as compared to a case where the both the left- and right-side transfer head  72  groups are pressed against the sheet at a time, which in turn can reduce a size of the cam moving motor  60  (M 13 ). Further, the device can be formed even with a slightly brittle frame structure, allowing a reduction in weight of the device. 
     The following sequentially describes the staple-binding unit  240  positioned downstream of the adhesive-binding unit  50 , aligning member  48 , conveying roller  46  and the pressure roller  49  which are configured to be separated from the sheet during the alignment operation, stopper section  90  as a leading end regulating member that regulates a leading end of the sheet carried in into the stacker section  40 , and the gripper  91  provided in the stopper section  90  and configured to grip the sheet. 
     [Staple-Binding Unit] 
     The following describes the staple-binding unit  240  disposed, in the stacker section  40 , downstream of the adhesive-binding unit  50 . The staple-binding unit  240  is a saddle stitching stapler that saddle stitches, in the stacker section  40 , a sheet bundle with a metal staple  239  at a center of the sheet bundle in the sheet conveying direction. A configuration of the staple-binding unit  240  will be described based on  FIGS. 9A and 9B . The staple-binding unit  240  includes a driver unit  241  and a clincher unit  250 . The driver unit  241  includes a head member  242  that inserts the metal staple  239  through the sheet bundle set at the binding position, a cartridge  243  housing the metal staples  239 , a drive cam  244 , and a staple motor (M 16 ) that drives the drive cam  244 . The head member  242  as a frame body incorporates, as illustrated in  FIG. 3B , a driver member  246 , a former  247 , and a bending block  248  which are vertically arranged in this order from above. The driver member  246  and the former  247  are vertically slidably supported by the head member  242  so as to be reciprocatable between a top dead center and a bottom dead center. The bending block  248  is fixed to the head member  242  as a molding die that bends the metal staple  239  having a linear shape into a U-shape. 
     The clincher unit  250  is disposed at a position facing the above-described driver unit  241  across the sheet bundle. The illustrated clincher unit  250  is constituted by a structure separated from the driver unit  241  and bends a needle point (leading end) of the metal staple  239  inserted through the sheet bundle by the driver unit  241 . To this end, the clincher unit  250  has a bending groove  250   a  for bending the leading end of the metal staple  239 . Particularly, the illustrated clincher unit  250  has two bending grooves  250   a  which are arranged in the width direction of the sheet bundle stacked in the stacker section  40 , and the driver units  241  corresponding to the bending grooves  250   a  staple-bind the sheet bundle at the plurality of positions in the sheet width direction. 
     That is, as illustrated in  FIG. 3A , the driver unit  241  is fixed and supported on the sheet bundle by stapler support rods  251 . With this configuration, it is possible to staple-bind the sheet bundle supported by the stacker section  40  at the left and right positions without moving the clincher unit  250  but with the same in a fixed state. 
     The clincher unit  250  may be configured to have a wing member (not illustrated) for bending the leading end of the staple and to swing/rotate the wing member in conjunction with (in synchronization with) the needle point to be inserted through the sheet bundle by the driver unit  241 . In this case, a pair of bending wings is axially swingably supported on a frame of the clincher unit  250  at a position facing both ends of the U-shaped needle. Then, the pair of bending wings are swung in conjunction with the insertion operation of the metal staple  239  through the sheet bundle by the driver unit  241 . The swinging of the pair of wings causes the leading ends of the staple to be bent along a back surface of the sheet bundle in a flat state. That is, when the metal staple  239  is bent by means of the bending groove, the needle leading end is bent in a U-shape (eyeglass clinch); while when the metal staple  239  is bent by means of the wing member, the needle leading end is bent linearly (flat clinch). In the present embodiment, the clincher unit  250  may adopt either the eyeglass clinch type or a flat clinch type. 
     In the configuration described above, a rotation of the staple motor MD causes the drive cam  244  to press down the drive lever  245  through the energy accumulating spring from the top dead center to bottom dead center, with the result that the driver member  246  and the former  247  incorporated in the head member  242  and connected to the drive lever  245  move down from the top dead center to bottom dead center. The driver member  246  is formed of a plate-like member so as to press down a back part of the staple bent in a U-shape, and the former  247  is formed of a U-shaped member as illustrated in  FIG. 9B  so as to bend the staple into a U-shape with the bending block  248 . That is, the metal staple  239  is supplied from the above-described cartridge  243  to bending block  248 . The linear metal staple  239  is press-molded into the U-shape between the former  247  and the bending block  248 . Then, the driver member  41   e  forcefully presses down the U-shaped metal staple  239  toward the sheet bundle to thereby insert the metal staple  239  through the sheet bundle, whereby the sheet bundle is saddle-stitched. 
     [Sheet Alignment Mechanism] 
     As described in  FIG. 3 , the aligning member  48  configured to be moved in the sheet width direction to press a side edge of the sheet in the stacker section  40  is disposed on both sides of the downstream side of the adhesive-binding unit  50 . 
     Although not illustrated particularly, an aligning motor M 12  (not illustrated) that drives the aligning member  48  is drive/rotation controlled by a sheet binding/bonding operation controller  201  to be described later. In the present embodiment, an application position at which the adhesive is applied onto the sheet is retreated to the retreat path  47 . This allows a new sheet to be bonded to be positioned in the carry-in path  41 . That is, it is possible to align the new and preceding sheets in a state where the leading ends thereof whose rear ends are positioned in the different paths (the carry-in path  41  and the retreat path  47 ) abut against the stopper section  90 . Further, the aligning member  48  is positioned at this position, allowing the alignment processing to be performed immediately before the bonding between the sheet on a surface of which the adhesive has been applied and a next sheet, which improves alignment accuracy of the sheet to be bonded. 
     [Separating Mechanism (Conveying Roller, etc.)] 
     It is necessary to release nipping and pressure contact with the sheet upon the alignment operation using the aligning member  48 . Although this mechanism is not illustrated particularly, in a case of the conveying roller  46  illustrated in  FIG. 3 , for example, a pinch roller configured to be brought into pressure contact with the conveying roller  46  is supported by an arm, and this arm is moved to thereby allow the pinch roller to contact and separate from the conveying roller  46 . Similarly, the pressure roller positioned downstream of the aligning member  48  is supported by an illustrated arm so as to be moved between a position denoted by a continuous line and a position denoted by a dashed line. As a result, at the continuous line position, the pressure roller conveys the sheet downstream while pressuring the sheet; while at the dashed line position, the pressure roller is separated from the sheet to allow the sheet to be moved upstream by the stopper section  90 . The pressure roller  49  may be lifted and lowered by a solenoid or the like directly connected thereto. 
     [Stopper Section Gripper Opening/Closing Mechanism] 
     With reference to  FIGS. 10A and 10B , a closing state where the gripper  91  positioned at a leading end of the stopper section  90  grips the sheet and an opening state where the gripping of the sheet by the gripper  91  is released will be described. The vertical movement of the stopper section  90  has already been described, so description thereof will be omitted here. 
       FIG. 10A  illustrates the entire moving range of the gripper  91 , in which the gripper  91  at the uppermost and lowermost positions is denoted by a virtual line.  FIG. 10B  is a plan view illustrating the gripper  91  and the stopper section  90  as viewed from above. The gripper  91  is disposed at the leading end of the stopper section  90 , and a moving piece  91   b  of the gripper  91  is separated from a fixed piece  91   a  of the stopper section  90 . A gripper connecting portion  152  connecting the moving pieces  91   b  is disposed below the stopper section  90  and a stopper section connecting portion  151  so as to be overlapped therewith and to freely advance and retreat with respect thereto. Further, a closing spring  91   c  constantly biasing the moving piece  91   b  in a closing direction is provided below the moving piece  91   b.    
     The gripper connecting portion  152  has a connecting arm  153  protruding rearward from the stopper section  90 . The connecting arm  153  has an opening hole. A turning bracket  154  supports upper and lower portions of a turning bar  156  penetrating the opening hole of the connecting arm  153 . The turning bracket  154  is turned in a direction denoted by an arrow of  FIG. 10B  about a turning support point  155 . The turning bracket  154  has a turning cam  157  having a bracket pressing surface  158 . The turning cam  157  is rotated by a gripper opening/closing motor  160  (M 11 ). When the bracket pressing surface  158  presses the turning bracket  154  with the rotation of the turning cam  157 , the turning bracket  154  swings about the turning support point  155 . With this swing, the turning bar  156  whose upper and lower portions are supported by the turning bracket  154  advances/retreats. Since the turning bar  156  penetrates the opening hole of the connecting arm  153 , the moving piece  91   b  at the leading end of the connecting arm  153  contacts and separates from the fixed piece  91   a  of the stopper section  90 . 
     Further, as illustrated in  FIG. 10A , the turning bar  156  is positioned in the vertical movement range of the stopper section  90 , so that even when the stopper section  90  is moved vertically, the above connecting arm  153  can make the moving piece  91   b  constituting the gripper  91  advance/retreat at any vertical position. Thus, the closing state where the gripper  91  grips the sheet by the turning of the gripper opening/closing motor  160  and opening state where the gripping of the sheet is released are realized by the stacker section storage operation controller  200 . As illustrated in  FIG. 10A , the stacker section  40  is disposed in an inclined manner, so that the turning bracket  154  is constantly brought into abutment against the turning cam  157 . The turning bracket  154  may be brought into abutment against the turning cam  157  by a spring or the like. 
     [Drive Mechanism of Folding Mechanism Section] 
     The following describes, using  FIGS. 11 and 12 , a drive mechanism of the folding mechanism section  80  that folds in two a sheet bundle bound by the adhesive-binding unit  50  or staple-binding unit  240 .  FIG. 11  is a perspective view of the drive mechanism, illustrating a state where the folding blade  86  waits at a home position, and  FIG. 12  is a perspective view of the drive mechanism, illustrating a state where the folding blade  86  enter between the folding rollers  81   a  and  81   b  and reaches a sheet folding position. 
     [Drive Path for Folding Blade] 
     A drive path for reciprocating the folding blade  86  illustrated in  FIGS. 11 and 12  is denoted by a long dashed double-short dashed line in the drawing. Drive of the folding blade  86  is made by a folding drive motor  300  (M 16 ) disposed at a lowermost part in the drawing. The drive is transmitted from a pulley  302  mounted to a drive shaft of the folding drive motor  300  to a drive pulley  306  through a drive belt  304 . Then, the drive is further transmitted from a transmission gear  308  mounted to a shaft of the drive pulley  306  to a one-way clutch gear  310 . When the one-way clutch gear  310  is rotated in one direction, it is engaged with the shaft to rotate a transmission gear  312 ; on the other hand, when the one-way clutch gear  310  is rotated in the other direction, the engagement with the shaft is released, and only the one-way clutch gear  310  is rotated in the other direction. 
     The drive is transmitted to a shaft gear  324  through illustrated transmission gears  314 ,  316 ,  318 ,  320 , and  322 . A moving cam  328  is turnably mounted to both sides of a rotary shaft  326  mounted with the shaft gear  324 . A rotation of the drive motor  300  in one direction rotates the moving cam  328 ; however, the rotary shaft  326  of the moving cam  328  is provided at a decentered position. Therefore, a cam engagement member  334  engaged with a groove formed in the moving cam  328 , a blade support plate  336  mounted with the cam engagement member  334 , and the folding blade  86  mounted to the blade support plate  336  are moved in a front-rear direction in the drawing. That is, the folding blade  86  is moved to a home position ( 330 ) of  FIG. 11  separated from the folding roller  81  and a moved position ( 328 ) of  FIG. 12  where the folding blade  86  is inserted between the folding rollers  81   a  and  81   b . A sheet biasing plate that presses the sheet bundle against the folding roller before sheet pushing operation of the folding blade  86  to the folding roller is movably mounted to the blade support plate  336  so as to be biased by a not illustrated spring. 
     [Drive Path for Folding Roller] 
     A rotational drive path of the folding roller  81  that folds the sheet bundle in two is denoted by a long dashed short dashed line in  FIGS. 11 and 12 . That is, the drive is transmitted from the same drive motor as that used as a drive source for moving the folding blade, i.e., the drive motor  300  to a transmission gear  350  through the transmission gear  308  and the one-way clutch gear  310 . That is, the drive of the drive motor  300  branches off at the transmission gear  350  to a drive system of the folding roller  81 . Therefore, the transmission gear  350  is rotated normally or reversely according to the rotation direction of the drive motor. The drive of the transmission gear  350  is transmitted to a transmission gear  354  through a transmission gear  352 . 
     As illustrated in a circle outlined by a long dashed double-short dashed line of  FIG. 11  (lower-left part), there are arranged downstream of the transmission gear  354 , a normal/reverse transmission gear  356  that transmits the drive to a shaft thereof according to the rotation direction of the folding drive motor  300 , a normal rotation one-way clutch gear  358  that is coaxially mounted to the normal/reverse transmission gear  356  and receives transmission of the drive only when the folding drive motor  300  is rotated normally, and a reverse rotation one-way clutch gear  357  that is coaxially mounted to the normal/reverse transmission gear  356  and receives transmission of the drive only when the folding drive motor  300  is rotated reversely. The normal rotation one-way clutch gear  358  is engaged with a large diameter part of a two-stage transmission gear  360 . The reverse rotation one-way clutch gear  357  is engaged with an intermediate gear  359 , and the intermediate gear  359  is engaged with a small diameter part of the two-stage transmission gear  360 . 
     Thus, when the folding drive motor  300  is normally rotated, the drive of the folding drive motor  300  is transmitted sequentially to the transmission gear  354 , normal/reverse transmission gear  356 , normal rotation one-way clutch gear  358 , and the two-stage transmission gear  360  in this order. On the other hand, when the folding drive motor  300  is reversely rotated, the drive of the folding drive motor  300  is transmitted sequentially to the transmission gear  354 , the normal/reverse transmission gear  356 , reverse rotation the one-way clutch gear  357 , the intermediate gear  359 , and the two-stage transmission gear  360  in this order. That is, irrespective of whether the folding drive motor  300  is rotated normally or reversely, a shaft  361  of the two-stage transmission gear  360  is rotated in one same direction (sheet folding direction of the folding roller  81 ). 
     The shaft  361  configured to be rotated only in one direction is provided with, at its outside, a transmission gear  362 . The drive of the transmission gear  362  is transmitted sequentially to transmission gears  364  and  366 , a transmission belt a 368 , a belt pulley  370 , a transmission gear  372 , and a bundle discharge roller gear  374  in this order. The drive of the bundle discharge roller gear  374  is transmitted, through a shaft thereof, to a bundle discharge roller  95 . The drive of the bundle discharge roller  95  is transmitted to folding rollers  81   a  and  81   b  through a transmission gear  378  and a transmission belt b 377 , respectively. 
     In the thus configured drive transmission configuration of the folding mechanism section  80 , the normal rotation of the folding drive motor  300  causes the folding blade  86  to be reciprocated between the home position and moved position where the folding blade  86  pushes the sheet bundle into the folding roller  81  and causes the folding roller  81  to be rotated in the folding direction. On the other hand, with the reverse rotation of the folding drive motor  300 , the folding blade  86  is stopped by action of the one-way clutch gear  310 ; however, the folding roller  81  is not stopped, but rotated in the folding direction by action of the normal rotation one-way clutch gear  358  and reverse rotation one-way clutch gear  357 . Thus, even when the folding drive motor  300  is rotated reversely after completion of the reciprocation of the folding blade  86 , the folding roller  81  continues being rotated in the folding direction. That is, even a sheet bundle formed by long sized sheets can be folded with a single drive motor. 
     [Speed Control for Folding Blade and Folding Roller] 
     An encoder  305  is mounted to the shaft of the drive pulley  306  that drives the transmission gear  308 , and a detection sensor  307  that detects a rotation amount of the encoder  305  is provided. A rotation speed of the folding drive motor  300  is detected by a signal from the detection sensor, and the detection sensor is input to a sheet bundle folding processing controller  202  to be described later. The sheet bundle folding processing controller  202  controls a supply current such that the folding roller  81  and the folding blade  86  operate at high speed (in the present embodiment, a rotation speed of the folding roller is 200 mm/sec, and a moving speed of the folding blade is 260 mm/sec) when the sheet bundle to be folded has been staple-bound by the staple-binding unit  240  to maintain a drive speed of the folding drive motor  300  at high speed. On the other hand, when the sheet bundle to be folded has been bonded by the adhesive-binding unit  50 , the sheet bundle folding processing controller  202  controls the supply current such that the folding roller  81  and the folding blade  86  operate at low speed (in the present embodiment, the rotation speed of the folding roller is 100 mm/sec, and the moving speed of the folding blade is 130 mm/sec). As described above, in the present embodiment, the rotation amount of the folding drive motor  300  is controlled to thereby realize high and low speed operation. 
     The moving speed of the folding blade  86  is set to about 1.3 times the rotation speed of the folding roller  81  irrespective of whether the operation speed is high or low. That is, if the rotation speed of the folding roller  81  is increased due to speed fluctuation upon pushing of the sheet bundle into the folding roller  81  by the folding blade  86 , outside sheets of the folded sheet bundle advance faster to leave inside sheets behind. The above speed setting is to prevent this phenomenon. 
     Further, in the embodiment illustrated in  FIGS. 11 and 12 , the folding roller  81  and the bundle discharge roller  95  are operated by the same drive system. That is, the folding roller  81  and the bundle discharge roller  95  change their rotation speeds depending on the binding type of the sheet bundle, thereby suppressing peeling-off of the bonded sheets from one another or generation of wrinkles. 
     The above-described folding drive motor  300  according to the present embodiment is a DC motor. Thus, when resistance is high, that is, when the number of sheets that form the sheet bundle is large, a torque of the folding drive motor  300  is increased to cope with the high resistance. Further, by controlling the speed, folding processing according to the binding type can be performed in a certain range. When a stepping motor is used as the folding drive motor  300 , operation control can be made finer by controlling both the rotation speed and torque. 
     [Operation of Folding Mechanism Section] 
     The following describes an operation of the folding mechanism section  80  that applies folding processing to the staple-bound or adhesive-bound sheet bundle at the adhesive-bound sheet bundle folding position Sh 2 . First, in  FIGS. 13A to 13D , an operation of folding the sheet bundle that has been staple-bound by the staple-binding unit  240  using the metal staples will be described. Then, in  FIGS. 14A to 14D , an operation of folding the sheet bundle that has been adhesive-bound by the adhesive-binding unit will be described. 
     [Folding Processing for Staple-Bound Sheet Bundle] 
     As illustrated in  FIG. 13A , there are provided, at a folding position Y disposed downstream of the staple-binding unit  240 , the folding roller  81  for folding the staple-bound sheet bundle and the folding blade  86  for inserting the sheet bundle into a nip position of the folding roller  81 . The folding roller  81  is constituted by the rollers  81   a  and  81   b  brought into pressure contact with each other. The rollers  81   a  and  81   b  are each formed to have a length substantially corresponding to the maximum width of the sheet. Rotary shafts  81   ax  and  81   bx  of the respective rollers  81   a  and  81   b  constituting the folding roller  81  are fitted respectively into long grooves of a not illustrated device frame and are biased in a pressure-contact direction by respective compression springs  81   a S and  81   b S so as to allow the rollers  81   a  and  81   b  to be brought into pressure contact and coupled with each other. The folding roller may have a structure in which at least one of the rollers  81   a  and  81   b  is axially supported so as to be movable to the pressure-contact direction and is provided with the compression spring. 
     The pair of rollers  81   a  and  81   b  is each formed of a material, such as a rubber, having a large friction coefficient. This is for conveying the sheet bundle in a roller rotation direction while folding the same by a soft material such as a rubber, and the rollers  81   a  and  81   b  may be formed by applying lining to a rubber material. 
     The following describes an operation of folding the sheet bundle by means of the above folding roller  81  with reference to  FIGS. 13A and 13D . The pair of rollers  81   a  and  81   b  are positioned above the stacker section  40  and below the adhesive-binding unit  50 , and the folding blade  86  having a knife edge is provided at a position facing the roller pair  81   a  and  81   b  with the adhesive-bound sheet bundle supported by the stacker section  40  interposed therebetween. The folding blade  86  is supported by a device frame so as to be reciprocatable between a home position illustrated in  FIG. 13A  and an operation position illustrated in  FIG. 13C . 
     The sheet bundle supported in a bundle in the stacker section  40  is stopped by the stopper section  90  at a leading end of the stacker section  40  in a state illustrated in  FIG. 13A , and a fold position of the sheet bundle is set to a staple-bound position of the sheet bundle. 
     The sheet bundle folding processing controller  202  moves the folding blade  86  from the standby position to nip position at a comparatively high speed VH (in the present embodiment, the moving speed of the folding blade is 260 mm/sec). Then, as illustrated in  FIG. 13B , the sheet bundle is bent by the folding blade  86  at the fold position and is inserted between the rollers  81   a  and  81   b . At this time, the pair of rollers  81   a  and  81   b  is driven into rotation along with the movement of the sheet bundle by the folding blade  86 . Then, the sheet bundle folding processing controller  202  reversely rotates the folding drive motor  300  after elapse of an estimated time period during which the sheet bundle reaches a predetermined nip position to stop the folding blade  86  at a position illustrated in  FIG. 13C . On the other hand, the folding roller  81  continues to be rotated in the folding direction. As a result, the sheet bundle is fed in a delivery direction (leftward in  FIG. 13C ). Thereafter, the sheet bundle folding processing controller  202  normally rotates the folding drive motor  300  once again. Then, as illustrated in  FIG. 13D , the folding blade  86  positioned at the nip position is moved toward the standby position concurrently with the delivery of the sheet bundle by the folding roller  81 . 
     As described above, when the sheet bundle to be folded is the staple-bound sheet bundle bound by the metal staples, it is possible to operate the folding blade  86  and the folding roller  81  at the comparatively high speed VH (in the present embodiment, the rotation speed of the folding roller is 200 mm/sec, and the moving speed of the folding blade is 260 mm/sec), whereby the folding processing can be performed efficiently. 
     The folding speed is changed while constantly transmitting the drive system to both the folding roller  81  and the folding blade  86  illustrated in  FIGS. 13A to 13D  and  FIGS. 14A to 14D , the operation speed control can be made reliably. Alternatively, however, a configuration may be adopted, in which a one-way clutch is coupled to the shafts  81   ax  and  81   bx  of the folding roller  81  to make the shafts  81   ax  and  81   bx  follow the pushing operation of the folding blade  86 . That is, the shafts  81   ax  and  81   bx  are driven into rotation when the folding blade  86  reaches a predetermined pushing position. In this case, change of the folding speed is made by the folding blade. 
     [Folding Processing for Adhesive-Bound Sheet Bundle] 
     The folding of the sheet bundle bound by the adhesive-binding unit  50  is also performed by using the folding roller  81  and the folding blade  86 , so description with respect to the same member or the same operation will be omitted. The sheet bundle to be folded bound by the adhesive-binding unit  50  is folded with the folding position Y disposed downstream of the above-described staple-binding unit  240  coinciding with a center of the bonding range of the sheet bundle. 
     As illustrated in  FIG. 14A , there are provided the folding roller  81  for folding the adhesive-bound sheet bundle bound by means of the adhesive AT and the folding blade  86  for inserting the sheet bundle into the nip position of the folding roller  81 . 
     The sheet bundle supported in a bundle in the stacker section  40  is stopped by the stopper section  90  at the leading end of the stacker section  40  in a state illustrated in  FIG. 14A , and a fold position of the sheet bundle is set to an adhesive-bound position of the sheet bundle. The sheet bundle folding processing controller  202  moves the folding blade  86  from the standby position to nip position at a comparatively low speed VL (in the present embodiment, the moving speed of the folding blade is 130 mm/sec). Then, as illustrated in  FIG. 14B , the sheet bundle is bent by the folding blade  86  at the fold position and is inserted between the rollers  81   a  and  81   b . At this time, the pair of rollers  81   a  and  81   b  are driven into rotation at the same speed as that of the sheet bundle moved by the folding blade  86 . 
     Then, the sheet bundle folding processing controller  202  reversely rotates the folding drive motor  300  after elapse of an estimated time period during which the sheet bundle reaches a predetermined nip position to stop the folding blade  86  at a position illustrated in  FIG. 14C . On the other hand, the folding roller  81  continues to be rotated in the folding direction. As a result, the sheet bundle is fed in the delivery direction (leftward in  FIG. 14C ). Thereafter, the sheet bundle folding processing controller  202  normally rotates the folding drive motor  300  once again. Then, as illustrated in  FIG. 14D , the folding blade  86  positioned at the nip position is moved toward the standby position concurrently with the delivery of the sheet bundle by the folding roller  81 . 
     As described above, when the sheet bundle to be folded is the adhesive-bound sheet bundle bound by the adhesive, it is possible to operate the folding blade  86  and the folding roller  81  at the comparatively low speed VL (in the present embodiment, the rotation speed of the folding roller is 100 mm/sec, and the moving speed of the folding blade is 130 mm/sec). This suppresses peeling-off of the sheets from one another or break of the sheets at the bonded portion. 
     With reference to  FIGS. 15A to 15D , the above point will be described more in detail using the bound sheet bundle. The staple-bound sheet bundle illustrated in  FIGS. 15A and 15B  is subjected to the folding processing at the high speed (VH); on the other hand, the adhesive-bound sheet bundle illustrated in  FIGS. 16A and 16B  is subjected to the folding processing at the low speed (VL). That is, in a case of the staple-binding, the staples are driven into the sheet bundle to fix the sheets to one another, so that the sheet bundles are bound comparatively strongly and can thereby be folded without displacement. On the other hand, in a case of the sheet bundle bound by means of the adhesive or a tape paste, as illustrated in  FIGS. 15C and 15D , a folding area of the sheets on the folding roller side (front cover side) becomes longer upon folding, so that the adhesive on the front cover side is extended. Thus, when the folding operation is performed at high speed like the folding operation for the staple-bound sheet bundle, the adhesive may be peeled off or break or wrinkles of the sheet may be generated. To prevent this, the folding processing for the adhesive-bound sheet bundle is performed at low speed in the present invention. 
     Referring back to  FIG. 2 , a sheet transfer path (hereinafter, referred to merely as “transfer path”) for guiding the sheet bundle folded in a booklet form to the second sheet discharge tray  22  for storage is provided downstream of the folding roller  81 , and the sheet bundle folded in two into a booklet by the folding roller  81  is carried out to the second sheet discharge tray  22  by the bundle discharge roller  95  provided at an exit of the transfer path and having the bundle kick-out piece. The carried-out sheet bundle is stored orderly on the second sheet discharge tray  22  by the bundle press guide  96  and the bundle presser  97  for preventing opening of the folded sheet bundle. 
     Next, with reference to  FIGS. 16A to 16C  to  FIGS. 18A to 18C , an adhesive-bound sheet bundle generation operation will be described, taking an example in which the adhesive-binding unit  50  in the stacker section  40  is used to apply the adhesive onto three sheets conveyed from the image forming device A. Further, with reference to  FIGS. 19A to 19C  to  FIGS. 21A to 21C , a staple-binding operation will be described, taking an example in which the staple-binding unit  240  that performs saddle stitching is used to staple three sheets. 
     [Adhesive-Bound Sheet Bundle Generation Operation] 
     First, a state where the sheets are bonded to one another by an adhesive to generate a sheet bundle will be described. In the image forming device, the “adhesive-bound sheet bundle folding mode” is specified. In the “adhesive-bound sheet bundle folding mode”, the sheets discharged from the main body discharge port  3  are bonded to one another to form a sheet bundle, and the sheet bundle is folded in a booklet form and stored on the second sheet discharge tray  22 . 
       FIG. 16A  is a view illustrating a state where a first sheet fed from the image forming device A along the sheet carry-in path P 1  is passed through the second switchback path SP 2  and carried in the stacker section  40  along the carry-in path  41 . The stopper section  90  may be in a stand-by state at the Sh 1  in  FIG. 2  or may descend toward the Sh 1  while pulling the sheet as illustrated. 
     As illustrated in  FIG. 16B , when a rear end of the sheet reaches the branching position between the carry-in path  41  and the retreat path  47  constituting the third switchback path SP 3 , the sheet is once stopped. The sheet rear end is biased to the retreat path  47  side by the deflection guide  44  provided at the branching position. 
     Then, as illustrated in  FIG. 16C , when the stopper section  90  is moved up, the sheet rear end side is moved along the retreat path  47 . When a half position of the sheet in the sheet conveying direction is situated below the adhesive-binding unit  50 , the sheet is once stopped, and the adhesive tape stampers  51  are pushed against the sheet to apply the adhesive. The reason for applying the adhesive during move-up of the sheet is that when the adhesive is applied on ahead during move-down of the sheet, the sheet is conveyed with the adhesive applied thereon. When the adhesive is applied during move-up of the sheet, the sheet is immediately moved to the application retreat position, thereby preventing the adhesive from being adhered to an unnecessary portion. 
     In  FIG. 17A , in order for a second sheet to be carried in the carry-in path  41 , the application position of the first sheet is retreated to the retreat path  47 . As a result, it is possible to carry the second sheet into the stacker section  40  while preventing a leading end of the second sheet from contacting the adhesive-applied position of the first sheet. In a state where the first and second sheets are overlapped with each other, they are aligned by means of the aligning member  48  for arrangement before bonding. 
     In  FIG. 17B , in a state where the stopper section  90  and the pressure roller  49  are pressed against the first and second sheets at a position where the application position of the first sheet is overlapped with a half position of the second sheet, the stopper section  90  is moved downstream to carry the first and second sheets in the stacker section  40 . 
     In  FIG. 17C , the stopper section  90  is temporarily stopped at a position where rear ends of the two overlapped sheets pass through the branching position. When the stopper section  90  is moved up in this state, the two overlapped is switchback-conveyed (retreated) in the retreat path  47  of the third switchback path SP 3  since the rear ends thereof are biased by the deflection guide  44 . This operation is the same as that illustrated in  FIG. 16B . Thereafter, the tape stampers  51  are pressed against the half position of the sheet to apply the adhesive. 
     When the sheet is switchback-conveyed, the pressure roller  49  is separated from the sheet. 
     In  FIG. 18A , in order for a third sheet to be carried in the carry-in path, the adhesive-applied position of the second sheet is retreated to the retreat path  47 . This state is the same as that illustrated in  FIG. 17A . Thus, when the third sheet is carried in the stacker section  40 , the leading end of the third sheet has no possibility of being caught by the adhesive portion of the second sheet. In  FIG. 18B , the three sheets are aligned in a state where a half position of the third sheet is overlapped with the adhesive position of the first and second sheets and moved downstream by the stopper section  90 . In  FIG. 18C , since the third sheet is the last sheet, it is not subjected to adhesive application by the adhesive-binding unit  50  but pressed by the sheet presser  65  and the pressure roller  49  after being lowered. Then, the third sheet is bonded to the second sheet by the pressing to form the sheet bundle of the first to third sheets, and the half position of the sheet bundle is moved to a position corresponding to the folding roller  81  and the folding blade  86  (folding mechanism section  80 ). The folding speed (folding speed VL) for this adhesive-bound sheet bundle is lower than the folding speed for a staple-bound sheet bundle. Then, the sheet bundle is pushed into the folding roller  81  by the folding blade  86  for folding, and a booklet obtained through bonding and folding is stored on the second sheet discharge tray. 
     As described above, when the sheets are bonded by the adhesive-binding unit, the preceding sheet that has been applied with the adhesive is temporarily retreated to the retreat path  47  for each bonding operation to isolate the application position from the leading end of the next sheet. This prevents the adhesive on the preceding sheet from being adhered to an unintended position such as the leading end of the next sheet, whereby a bonded booklet with an excellent finished state can be generated. Further, the adhesive-bound sheet bundle is folded at a comparatively low speed VL (in the present embodiment, the rotation speed of the folding roller is 100 mm/sec, and the moving speed of the folding blade is 130 mm/sec) so that the adhesive on the sheets follows a shape of the folded part well. As a result, peeling-off of the adhesive or break of the sheet upon folding processing can be suppressed. 
     [Staple-binding Operation] 
     The following describes, with reference to  FIGS. 19A  to C to  FIGS. 20A to 20C , a state where the staple-binding unit is used to bind three sheets at a center thereof in the sheet conveying direction by means of binding needles such as metal staples to generate a sheet bundle. In this case, in the image forming device, “staple-bound sheet bundle folding mode” in which the sheets from the main body discharge port  3  is aligned in a bundle, saddle-stitched by means of staples, folded into a booklet form, and stored on the second sheet discharge tray  22  is specified. 
       FIG. 19A  is a view illustrating a state where a first sheet fed from the image forming device A along the sheet carry-in path P 1  is passed through the second switchback path SP 2  and carried in the stacker section  40  along the carry-in path  41 . The stopper section  90  may be in a stand-by state at the Sh 1  in  FIG. 2  or may descend toward the Sh 1  while pulling the sheet as illustrated. 
     As illustrated in  FIG. 19B , when a rear end of the sheet reaches the branching position between the carry-in path  41  and the retreat path  47  constituting the third switchback path SP 3 , the sheet is once stopped. The sheet rear end is biased to the retreat path  47  side by the deflection guide  44  provided at the branching position. After completion of the carry-in operation, sheet alignment is performed by the aligning member  48 . 
       FIG. 19C  illustrates a state where a second sheet is carried in with the first sheet biased toward the retreat path  47  side. In this state, a rear end of the second sheet is also biased toward the retreat path  47  side by the deflection guide  44 . In this case, after completion of the carry-in operation, sheet alignment is performed by the aligning member  48 . 
     In  FIG. 20A , a third sheet has been carried in the stacker section  40 , and a rear end thereof is biased toward the retreat path  47  constituting the third switchback path SP 3  by the deflection guide  44 . As illustrated in an enlarged view, the sheet rear end is biased toward the retreat path by a bending portion of the deflection guide  44 . The biasing can prevent the sheet rear end from closing an exit of the carry-in path  41 . This allows the next sheet to be carried in the stacker section  40  without being caught by the rear end of the preceding sheet. 
     In the present embodiment, the deflection guide  44  is biased toward the retreat path  47  side by the guide tension spring  44   a ; alternatively however, the deflection guide may bias the sheet not by means of the spring but by its own weight. Alternatively, the deflection guide  44  may be connected to a solenoid such that it is moved up/down every time the new sheet is carried in the stacker section  40 . Further, in order for the new sheet to be carried in the stacker section  40  more smoothly, the rear end of the preceding sheet situated at the retreat path  47  side may be moved to a deep side of the retreat path  47  such that the surface of the preceding sheet guides the next sheet. 
     In  FIG. 20B , the three sheets have been carried in the stacker section  40 , and the sheet alignment is performed by the aligning member  48 . Thereafter, the stopper section  90  having the gripper  91  is moved up and stopped at a position where a half position of the sheet in the sheet length direction coincides with the binding position of the staple-binding unit  240 . In this case, when the sheet to be carried in is a long sheet, a rear end thereof is moved along the retreat path  47 . A moving amount of the sheet to the retreat path  47  when the sheet is bound by the adhesive-binding unit  50  is larger than a moving amount of the sheet to the retreat path  47  when the sheet is bound by the staple-binding unit  240 . In other words, since the adhesive-binding unit  50  is disposed closer to the retreat path  47  than the staple-binding unit  240  is to, a length of the retreat path  47  is sufficient for staple-binding operation of the staple-binding unit  240 . Thereafter, the staple-binding unit  240  is used to perform the sheet binding by means of the metal staples  239 . 
     In  FIG. 20C , the binding position of the staple-bound sheet bundle is moved to the folding mechanism section  80  (the folding roller  81  and the folding blade  86 ) disposed downstream of the staple-binding unit  240  for folding processing. The folding roller rotation speed and the folding blade moving speed (in the present embodiment, a rotation speed of the folding roller is 200 mm/sec, and a moving speed of the folding blade is 260 mm/sec) are higher than those in the folding operation for the adhesive-bound sheet bundle. Thereafter, the staple-bound booklet is stored on the second sheet discharge tray. 
     As described above, in the present embodiment, also when the sheet bundle is staple-bound by the staple-binding unit  240 , the sheet rear end is biased toward the retreat path  47  which is used in the adhesive-binding operation of the adhesive-binding unit  50  using the deflection guide  44 . Further, for the staple-binding operation, the retreat path  47  which is used for switchback of the sheet in the adhesive-binding operation of the adhesive-binding unit  50  is used as needed. 
     Thus, the stacker section  40 , stopper section, deflection guide  44 , and the retreat path  47  are commonly used for staple-binding and adhesive-binding of the sheet bundle by the staple-binding unit  240  and the adhesive-binding unit  50  to simplify the structure of the device and reduce cost. 
     Further, making the folding speed for the adhesive-bound sheet bundle lower than the folding speed for the staple-bound sheet bundle can suppress peeling-off or deviation of the adhesive or break of the sheet. On the other hand, the folding processing for the staple-bound sheet bundle is performed at high speed, thus preventing productivity of the staple-bound sheet bundle from being degraded. 
     Hereinafter, folding processing speed setting control will be described using a flowchart of  FIG. 21 . First, when the “adhesive-bound sheet bundle folding mode” wherein the adhesive is used is set in a “sheet processing mode”, the sheet bundle to be folded is determined to be “adhesive-bound sheet bundle” (S 01 ). Here, “adhesive-bound sheet” is set (S 02 ), and the folding speed of the folding roller  81  and the folding blade  86  is set to the low speed VL (in the present embodiment, the rotation speed of the folding roller is 100 mm/sec, and the moving speed of the folding blade is 130 mm/sec) (S 03 ). At a timing when the adhesive-bound sheet bundle reaches the folding position (Y), the folding processing is executed at the low speed VL (S 04 ). When there is a subsequent sheet bundle, the low speed folding processing is repeated (S 05 ). When there is no subsequent sheet bundle, this routine is ended. 
     When the “staple-bound sheet bundle folding mode” wherein the staples are used to bind the sheet bundle is set in the “sheet processing mode”, the sheet bundle to be folded is determined not to be “adhesive-bound sheet bundle” (S 01 ), and the “staple-bound sheet” is set (S 10 ). Accordingly, the folding speed of the folding roller  81  and the folding blade  86  is set to the high speed VH (in the present embodiment, the rotation speed of the folding roller is 200 mm/sec, and the moving speed of the folding blade is 260 mm/sec) (S 11 ). At a timing when the staple-bound sheet bundle reaches the folding position (Y), the folding processing is executed at the high speed VH (S 12 ). When there is a subsequent sheet bundle, the high speed folding processing is repeated (S 13 ). When there is no subsequent sheet bundle, this routine is ended. 
     As another embodiment, a flow surrounded by a dashed line of  FIG. 21  can be added. After determination of whether or not the sheet processing mode is the “adhesive-bound sheet bundle folding mode” (S 01 ), “whether or not the number of sheets forming the sheet bundle is larger than a predetermined number” is further determined. For example, when the number of sheets forming the sheet bundle is 1 to 10, the flow proceeds to “set folding speed to low speed VL” ( 03 ), and the low speed (in the present embodiment, the rotation speed of the folding roller is 100 mm/sec, and the moving speed of the folding blade is 130 mm/sec) is set for folding processing. 
     When the number of sheets forming the sheet bundle exceeds  10 , the folding speed is set to a very low speed VLL (S 21 ). In this case, the folding processing is executed at the very low speed VLL (in the present embodiment, the rotation speed of the folding roller is 70 mm/sec, and the moving speed of the folding blade is 90 mm/sec) (S 23 ). When there is a subsequent sheet bundle, the number of sheets forming the sheet bundle is checked again and, when the number of sheets forming the sheet bundle is 1 to 10, the folding processing is executed at the low speed VL; when the number of sheets forming the sheet bundle exceeds 10, the folding processing is executed at the very low speed VLL. 
     The number of sheets forming the sheet bundle may be counted as follows. The number of sheets set in the image forming device A may be transmitted from an image forming device controller  180  (to be described later) of the image forming device A to the sheet processing device B. Alternatively, a not illustrated detection sensor provided at the carry-in port of the sheet processing device B may be used to count the number of sheets. Further alternatively, a position of the sheet presser  65  for pressing the adhesive-bound sheet bundle in the adhesive-binding unit  50 , that is, a thickness of the adhesive-bound sheet bundle may be detected, followed by conversion of the detected thickness into the number of sheets. 
     As described above, when the number of sheets to be bound taken into consideration, the sheet bundle formed by a large number of sheets is folded by low speed, so that the folding processing can be performed without loss of the adhesion of the adhesive, especially the adhesive positioned on the folding roller side which may be extended upon the folding operation. 
     [Control Configuration] 
     The following describes a system control configuration of the above-described image forming device with reference to a block diagram of  FIG. 22 . The system for the image forming device illustrated in  FIG. 1  includes an image forming device controller  180  for the image forming device A and a sheet processing controller  191  for the sheet processing device B. The image forming device controller  180  includes an image forming controller  181 , a sheet supply controller  186 , and an input section  183 . A user sets “image forming mode” or “sheet processing mode” through a control panel  18  provided in the input section  183 . As described above, in the image forming mode, the image forming conditions such as a print copy count specification, a sheet size specification, a color or black-and-white printing specification, enlarged or reduced printing specification, a single- or double-side printing specification are set. Then, the image forming device controller  180  controls the image forming controller and the sheet supply controller according to the set image forming conditions to form an image onto a predetermined sheet and sequentially carries out the resultant sheet through the main body discharge port  3 . 
     At the same time, the user sets the sheet processing mode through the control panel  18 . The sheet processing mode includes, as described above, the “printout mode”, the “staple-binding mode”, the “adhesive-bound sheet bundle folding mode”, and the “staple-bound sheet bundle folding mode”. The image forming device controller  180  transfers the set sheet processing mode, the number of sheets, copy number information, and the adhesive-binding mode or the staple-binding mode (binding at one or a plurality of positions, or saddle-stitching) information to the sheet processing controller  191 . 
     The sheet processing controller  191  includes a control CPU  191  that operates the sheet processing device B in accordance with the specified finishing mode, a ROM  193  that stores an operation program, and a RAM  194  that stores control data. The control CPU  192  includes a sheet conveying controller  195  that executes conveyance of the sheet fed to the carry-in port  23 , a sheet punch controller  196  that uses a punch unit  28  to perform punch operation for the sheet, a processing tray storage operation controller  197  that uses the processing tray  29  to perform sheet storage operation, a processing tray discharge operation controller  198  that discharges the sheet bundle from the processing tray  29 , and a first sheet discharge tray sheet loading operation controller  199  that moves vertically the first sheet discharge tray in accordance with a storage amount of the sheets or sheet bundle discharged from the processing tray  29 . 
     The sheet processing controller  191  further includes a stacker section storage operation controller  200  for controlling bonding and folding operations while storing the sheets in the stacker section  40 , a sheet binding/bonding operation controller  201  for instructing a sheet bonding operation, and a sheet bundle folding processing controller  202  for folding the adhesive-bound sheet bundle or staple-bound sheet bundle in two. The sheet binding/bonding operation controller  201  also controls the end surface stapler  35  that binds the sheets stored on the processing tray  29  using a staple, the adhesive-binding unit  50  that bonds the sheets carried in the stacker section  40  to one another, and the staple-binding unit  240  that saddle-stitches the sheets stored in the stacker section  40 . Although not illustrated, the above controllers each receive a position signal from a sensor that detects a position of the sheet conveying path or each member. 
     A connection between the controllers and the motors will be described using  FIG. 22 . The sheet conveying controller  195  is connected to a control circuit of a drive motor M 1  so as to control drive of the carry-in roller  24  and the like that receive the sheet from the image forming device A and conveys it. The sheet conveying controller  195  once switchback-conveys the sheet to the second switchback path SP 2  to put the sheet on standby therein when carrying the sheet in the processing tray  29  and then discharges the sheet together with a next sheet. This is done so as to continue a series of processing without stopping the operation on the image forming device A side. The sheet conveying controller  195  controls the drive motor M 2  that can forward/backward rotate the path carry-in roller  45  in the carry-in path  41  so as to enable the switchback conveyance. The sheet conveying controller  195  also controls a separating motor  131  (M 3 ) that separates the pinch roller  125  from the drive roller  120  when sheet alignment is performed with the leading end of the sheet positioned in the stacker section  40  and the rear end thereof positioned in the carry-in path  41 . 
     The sheet punch controller  196  is connected to a control circuit of a punch motor M 4  so as to punch a punch hole in the sheet. 
     The processing tray storage operation controller  197  is connected to a control circuit of a nip/separation motor M 5  that nips and separates the sheet discharge roller  25  so as to carry the sheet in the processing tray  29  or first sheet discharge tray  21  or carry out the sheet from the processing tray  29 . The processing tray storage operation controller  197  is also connected to a control circuit of a side aligning plate motor M 6  that reciprocates the side aligning plate  36  in the sheet width direction so as to align the sheets on the processing tray  29 . 
     The processing tray discharge operation controller  198  is connected to a control circuit of a bundle discharge motor M 7  that moves the rear end regulating member  33  toward the sheet discharge port  25   a  so as to discharge, to the first sheet discharge tray, the sheet bundle whose end portion is bound by means of the end surface stapler  35  in the processing tray  29 . A control circuit of a first tray elevating motor M 8  that elevates the first sheet discharge tray  21  in accordance with an amount of sheets stored therein is connected to the first sheet discharge tray sheet loading operation controller  199  and controlled thereby. 
     The following describes controllers for applying the adhesive onto the half position of the sheet in the sheet conveying direction to bond the sheets to one another to form the sheet bundle or staple-binding the accumulated sheets to form the sheet bundle and then folding the sheet bundle at the adhesive-applied position or staple-bound position will be described using the drawing. 
     The stacker section storage operation controller  200  is connected to a control circuit of a pressure roller nip/separation motor  141  (M 9 ) and control the same. The pressure roller nip/separation motor  141  (M 9 ) moves and normally and reversely rotates the pressure roller  49 . The pressure roller  49  is positioned around the middle of the stacker section  40  and configured to convey downstream the sheet carried in the stacker section  40  while pressing the sheet. With the drive from the pressure roller nip/separation motor  141  (M 9 ), the pressure roller  49  is moved to a sheet pressing position to convey the sheet or to a separating position separated from the sheet. 
     The stacker section storage operation controller  200  is further connected to a control circuit of a stopper section  90  moving motor M 10  so as to move the stopper section  90  to move the sheet entering the stacker section  40  to the initial home position Sh 0 , sheet (bundle) rear end branching point passing position Sh 1  at which the rear end of the sheet is situated at the branching position between the carry-in path  41  and the retreat path  47 , adhesive-bound sheet bundle folding position Sh 2  at which the adhesive-bound sheet bundle is folded in two, staple-binding position Sh 31  at which the metal staples are driven into a substantially half position of the sheet bundle for binding, adhesive tape transfer position Sh 32  at which the adhesive tape AT as an adhesive is applied onto the sheet at a substantially half position, and an adhesive tape concealing position Sh 4  to which the preceding sheet is switchback-conveyed so as to prevent the adhesive-applied onto the preceding sheet from being adhered to the next sheet to be carried in the stacker section  40  from the carry-in path  41 . The movement of the sheet between the above positions is as described above in detail using  FIGS. 16A to 16C to 20A to 20C . 
     The stacker section storage operation controller  200  is further connected to a control circuit of a gripper opening/closing motor  160  (M 11 ) so as to grip the leading end of the sheet at the leading end of the stopper section  90  and release its gripping. The timing of the gripping operation of the gripper has already been described, so description thereof is omitted. The stacker section storage operation controller  200  is further connected to a control circuit of an aligning motor  117  (M 12 ) that reciprocates, in the sheet width direction, the aligning member  48  that can align even the sheets whose leading ends are positioned at the stacker section  40 , while whose rear ends are positioned over the carry-in path  41  and the retreat path  47 . 
     The sheet binding/bonding operation controller  201  is connected to a control circuit of a cam moving motor  60  (M 13 ) that reciprocates the cam member  57  between a position that presses the adhesive tape stampers  51  of the adhesive-binding unit  50  against the sheet to apply the adhesive and a position separated from the sheet. The sheet binding/bonding operation controller  201  is also connected to a control circuit of a saddle-stitching staple motor M 15  that saddle-stitches the sheet bundles stored in the stacker section  40  at a center portion thereof by means the metal staples. The sheet binding/bonding operation controller  201  is also connected to an end surface binding staple motor M 14  of the processing tray  29 . 
     As already described, the sheet bundle folding processing controller  202  is configured to rotate or reciprocate the folding blade  86 , folding rollers  81   a ,  81   b , and the bundle discharge roller  95  by means of a common motor  300  and is connected to a drive circuit so as to control the drive motor  300  (M 16 ). Further, as already described, the drive motor  300  (M 16 ) is controlled so as to be driven at the low speed VL in the “adhesive-bound sheet bundle folding mode” and at the high speed VH in the “staple-bound sheet bundle folding mode”. 
     The controllers configured as described above control the sheet processing device to execute the following operation modes: the printout mode; the staple-binding mode; the adhesive-bound sheet bundle folding mode; and the staple-bound sheet bundle folding mode. The operations in the respective modes have already been described, so description thereof will be omitted here. In particular, the adhesive-bound sheet bundle folding mode has been described in detail based on  FIGS. 16A to 16C  to  FIGS. 18A to 18C , and the staple-bound sheet bundle folding mode has been described in detail based on  FIGS. 19A to 19C  and  FIGS. 20A to 20C . 
     Further, the control to drive the drive motor  300  (M 16 ) at a low speed in the “adhesive-bound sheet bundle folding mode” and to drive the drive motor  300  (M 16 ) at a high speed in the “staple-bound sheet bundle folding mode” has been described in detail based on the flowchart of  FIG. 21 . 
     [Modification of Folding Drive Path] 
     In the embodiment described above, as illustrated in detail in  FIGS. 11 and 12 , a single folding drive motor  300  (M 16 ) is used to drive rotation of the folding roller  81  and reciprocation of the folding blade, and a supply current to the folding drive motor  300  is controlled to change the rotation speed of the folding roller  81  and the moving speed of the folding blade  86 . Alternatively, as illustrated in  FIG. 23 , the rotation drive of the folding roller  81  and the moving drive of the folding blade  86  may be separated. In this configuration, the rotation directions of the respective drive motors are switched between the normal/reverse directions to switch a drive transmission path for speed change or torque change. 
     That is, in  FIG. 23 , a folding blade drive motor  400  for reciprocating the folding blade  86  and a folding roller drive motor  450  for driving the folding roller  81  are disposed at the front and rear of the stacker section  40 . 
     Drive of the folding blade drive motor  400  is transmitted to a blade selection gear  406  by a transmission belt  404  wound around an output pulley  402 . A drive transmission path is switched (between a long dashed short dashed arrow route and a long dashed double-short dashed arrow route) depending on a rotation direction of the blade selection gear  406 . Then, a blade moving gear  414  receives the drive from one of the two paths to be rotated about a moving gear rotary shaft  416 . 
     The blade moving gear  414  is connected to a moving lever  418  whose one end is fixed to the blade moving gear  414  and other end is connected to a blade unit  424  supporting the folding blade  86 . In the blade unit  424 , a connection pin  420  and a guide pin  422  can be slid along a frame guide groove  426  formed in a not illustrated frame. Thus, when the blade moving gear is rotated in illustrated arrow directions (continuous arrow direction/dashed arrow direction), the folding blade  86  is reciprocated between an insertion position into the folding roller  81  and a stand-by (home) position separated from the folding roller  81 . 
     The moving speed of the folding blade  86  changes depending on the rotation direction of the blade drive motor  400 . When the folding blade drive motor  400  is rotated in the continuous arrow direction, the blade moving gear  414  receives the drive directly from the blade selection gear  406  to be moved at a high speed. On the other hand, when the folding blade drive motor  400  is rotated in the illustrated dashed arrow direction, the drive is transmitted from the blade selection gear  406  to the blade moving gear  414  not directly but through a deceleration gear  410 . That is, the drive is transmitted with deceleration, with the result that the folding blade is reciprocated at a low speed. 
     Similarly, the folding roller drive motor  450  illustrated in  FIG. 23  has substantially the same two (continuous line/dashed line) drive systems. That is, drive from an output pulley  452  is transmitted to a folding roller selection gear  456  through a transmission belt  454  so as to allow the folding roller selection gear  456  to be rotated normally or reversely. When the folding roller drive motor  450  is rotated in the illustrated continuous arrow direction, the folding roller  81   b  drive gear receives the drive directly from the folding roller selection gear  456  to be rotated at the high speed VH. On the other hand, when the folding roller drive motor  450  is rotated in the illustrated dashed arrow direction, the drive is transmitted from the folding roller selection gear  456  to the folding roller  81   b  drive gear not directly but through a deceleration gear one-way clutch, with the result that the folding roller  81   b  drive gear is rotated at the low speed VL. The above switching of the drive direction is made by the folding roller selection gear  456  and the one-direction drive transmission mechanism of the deceleration gear one-way clutch  462  which is driven by rotation of the folding roller selection gear  456  in one direction. 
     With the above configuration, in the modification illustrated in  FIG. 23 , by selecting the rotation directions of the respective folding blade drive motor  400  and the folding roller drive motor  450 , the folding roller  81  and the folding blade  86  can be driven at a low speed (in the present embodiment, the rotation speed of the folding roller is 100 mm/sec, and the moving speed of the folding blade is 130 mm/sec) in the folding processing for the adhesive-bound sheet bundle, and the folding roller  81  and the folding blade  86  can be driven at a high speed (in the present embodiment, the rotation speed of the folding roller is 200 mm/sec, and the moving speed of the folding blade is 260 mm/sec) in the folding processing for the staple-bound sheet bundle. Further, in this case, a torque is not reduced in the low-speed folding operation, whereby the sheet bundle can be folded reliably. 
     [Modification of Binding Unit Arrangement] 
     In the embodiment described above, particularly as illustrated in  FIGS. 2 and 3 , the adhesive-binding unit  50  that binds the sheets by means of an adhesive and the staple-binding unit  240  that binds the sheets by means of staples are arranged in this order from the upstream side of the stacker section  40  as the second processing tray. With this arrangement, the adhesive-binding can be done with a comparatively short movement of the adhesive-applied position. However, the adhesive-binding unit  50  may be disposed downstream of the staple-binding unit  240 . 
     Further, a configuration may be possible, in which the adhesive-binding unit  50  and the staple-binding unit  240  are not juxtaposed. That is, a unit housing  261  replaceably housing the adhesive-binding unit  50  and the staple-binding unit  240  is provided in the casing  20  of the sheet processing device B, as illustrated. In this case, a not illustrated attachment detection sensor is used to detect which one of the binding units  50  and  240  is currently attached. When the adhesive-binding unit  50  is attached, the folding processing is performed at a comparatively low speed, and when the staple-binding unit  240  is attached, the folding processing is performed at a comparatively high speed. 
     [Transfer of Adhesive by Adhesive Tape Stamper] 
     The following describes, with reference to  FIGS. 25A to 25D  and  FIGS. 26A to 26C , the adhesive application (transfer) position by the adhesive tape stamper  51  described in  FIGS. 5A to 5C  to  FIGS. 7A to 7C .  FIG. 25A  is a bottom view of the adhesive tape stamper  51 . As illustrated in  FIG. 25A , the adhesive tape stamper  51  includes a pressing portion  170  having a substantially quadrangular shape and configured to press a comparatively wide area of the sheet, a side pressing portion  171  extending from both sides of the pressing portion  170 , and a leading end pressing portion  172  connecting leading sides of the side pressing portions  171 . Inside the above pressing portions, the transfer head  72  supporting the adhesive tape AT is positioned. A symbol X in the drawing denotes a center position of the adhesive tape AT, and the adhesive of the adhesive tape is applied onto the sheet with the position X as a center. A symbol Z denotes a sheet pressing position at which the adhesive-applied positions of the sheets preceding a last sheet to be described later are subjected to pressing. 
       FIG. 25B  is a cross-sectional side view of the adhesive tape stamper  51 , explaining that the adhesives are transferred with the same length.  FIG. 25B  illustrates a state where the adhesive tape AT is applied onto a newly conveyed and positioned sheet. For descriptive convenience, the sheets are illustrated every five sheets. Further, in  FIG. 25B , for all 11 sheets, the adhesive is applied across the folding position Y. As already described, first the paper sheets are pressed against the platen by the sheet pressing slider  71 . Then, with the movement of the sheet pressing slider  71 , a new adhesive surface of the adhesive tape AT is exposed, and the transfer head  72  is pressed against the sheet on the platen  79 . As a result, the adhesive of the adhesive tape AT is applied onto a new sheet, and preceding first to 10th sheets and the new 11th sheet are bonded to one another at the adhesive-applied position. After completion of the adhesive application and the sheet bonding, the transfer head  72  and the sheet pressing slider  71  are separated from the sheet as illustrated. 
     The above adhesive application and sheet bonding are repeated up to carry-in of the next-to-last sheet. The adhesive application and sheet bonding are performed for each carry-in of the paper sheet, and the carried-in paper sheets are bound together. 
     In  FIG. 25C , the adhesive of the adhesive tape AT is applied onto the first to fifth sheets at the folding position Y, and the adhesive application different from that for the first to fifth sheets is performed for the sixth and subsequent sheets. That is, for sixth to 10th sheets, the adhesive is applied at two positions slightly separated from each other (very close to each other) in the sheet conveying direction across the folding position. As a result, the adhesive-applied position becomes wider in the sixth to 11th sheets which are the outside sheets in the sheet folded state, so that even when the resultant sheet bundle is folded at the folding position Y, peeling-off the adhesive is prevented. Further, for the 11th sheet, the adhesive is applied at two positions further separated from each other across the folding position Y. When the adhesive tape AT is applied at two positions as described above, the adhesive is not applied in a solid manner between the 11th and 12th sheets, so that the sheets are easily folded, and the adhesive is comparatively unlikely to be peeled-off. Further, an amount of the adhesive to be used can be reduced. 
     An application method of the adhesive of the adhesive tape AT performed in  FIG. 25C  will be described using  FIGS. 26A to 26C .  FIGS. 26A to 26C  illustrate the gripper  91  and the stopper section  90  of the stacker section  40  illustrated in  FIG. 2 , in which the adhesive portion of the adhesive tape AT is represented in a sheet-like shape (AT) for descriptive convenience. As described above, in order for the adhesive of the adhesive tape AT to be applied onto the sheet, the transfer head  72  of the adhesive tape stamper  51  is pressed against the sheet. Thus, it is possible to adjust the application position of the adhesive by moving the sheet by means of the stopper section  90 . 
     In  FIG. 26A , for first to fifth sheets, the adhesive is applied across the folding position of the sheet. In this case, the sheet is moved to the right in the drawing (upward in the stacker section). Then, movement of the stopper section  90  is temporarily stopped when the folding position reaches just below the transfer head  72 , and the transfer head  72  is pressed against the sheet. More specifically, as to the movement of the sheet, at a timing when the rear end of the sheet carried in the stopper section  90  passes through a merging position between the carry-in path  41  and the retreat path  47 , the sheet is switchback-conveyed toward the retreat path  47  side. This movement is denoted by a right arrow in the drawing. Thereafter, when the folding position Y of the sheet coincides with the bonding position X, the movement of the sheet is stopped, and the transfer head  72  of the adhesive tape stamper  51  is pressed against the sheet to transfer the adhesive tape AT onto the sheet. The transferred six adhesive tapes are each represented as “AT” in  FIG. 26A . Then, in order for the transferred adhesive tape AT position to be moved to the retreat path  47 , the sheet is moved to the right by the stopper section  90 . In the present embodiment, the above operation is performed for the first to fifth sheets. The resultant state is denoted by “1 to 5” in  FIG. 25C . 
       FIG. 26B  illustrates the transfer position of the adhesive tape AT for sixth to 10th sheets. In this case, in the process of movement of the rear end side of the sheet toward the retreat path  47  side, the movement of the sheet is stopped slightly before the folding position Y, and the adhesive tape AT is transferred. Thereafter, the sheet is slightly moved and then stopped for transfer of the adhesive tape AT. The transferred two adhesive tapes AT are very close to each other ( 2 AT) across the folding position Y. The resultant state is denoted by “6 to 10” in  FIG. 25C . When the sheet bundle is folded in this state, the sheets forming the sheet bundle are bonded to one another in a wider area by the adhesive tape AT serving as an adhesive between the sheets. 
       FIG. 26C  illustrates the transfer position of the adhesive tape AT for an 11th sheet. The adhesive tape AT is applied at two positions spaced apart from each other across the folding position in the sheet conveying direction. In this case, in the process of movement of the rear end side of the sheet toward the retreat path  47  side, the movement of the sheet is stopped before the folding position Y (at a position more distant from the folding position Y than in  FIG. 26B ), and the adhesive tape AT is transferred. Thereafter, the sheet is moved to be spaced apart from the previously transferred first adhesive tape AT by a predetermined interval (S) and then stopped for transfer of the second adhesive tape AT. The transferred two adhesive tapes AT are spaced apart from each other ( 2 AT) by the interval (S) across the folding position Y (a state of “ 2 AT+S”). The state of “ 2 AT+S” is denoted by “11” in  FIG. 25C . To fold the sheet bundle at the folding position Y in this state is to fold the interval position between the two adhesive tapes AT, so that the sheet bundle is more easily folded and an amount of the adhesive to be used is more reduced than in the case where the adhesive is applied in a solid manner. In addition, since the sheets are bonded to one another at two positions in the sheet conveying direction, suppressing peeling-off of the bonded sheets forming a booklet from one another. 
     Here, a state where a 12th sheet is bonded to the 11th sheet will be described using  FIG. 25D . The adhesive is not applied onto the 12th sheet, so that, as illustrated, the pressing portion  170  of the sheet pressing slider  71  is pressed against a last sheet pressing portion of the platen  79 . In  FIG. 25D , a sheet pressing position (Z) is set as a position to be pressed without adhesive by the pressing portion  170 . With this pressing, the 12th sheet is reliably bonded to the 11th sheet. Further, by moving the pressing portion in a pressing state, adhesion between the 12 sheets is further strengthened. 
     The platen  79  includes a platen guide portion  176  for guiding conveyance of the sheet from the upstream side, a last sheet pressing portion  175 , and a platen cushioning portion  174  positioned facing the transfer head  72  and applied with a slightly elastic sheet for backup of the adhesive application and sheet bonding. With this configuration, the sheets are reliably bonded to one another. 
     [Folding Operation] 
     The following describes an operation of folding, by the folding mechanism section illustrated in  FIGS. 11 and 12 , the sheet bundle obtained by bonding the sheets by means of the adhesive of the adhesive tape AT. The folding operation for a sheet bundle formed by a small number of sheets has been described in  FIGS. 14A to 14D  and is thus omitted here. Here, the folding operation for a sheet bundle formed by a large number of sheets (that is, for a sheet bundle that has been subjected to the processing as illustrated in  FIG. 26C  will be described using  FIGS. 27A to 27D . 
     [Folding Processing for Bonded Sheet Bundle Formed by Large Number of Sheets] 
       FIGS. 27A to 27D  are views for explaining folding processing for a sheet bundle formed by a large number of sheets (in the present embodiment, 12 sheets) exceeding a predetermined number. The folding processing for a sheet bundle formed by a large number of sheets bonded by the adhesive-binding unit  50  is also performed by the folding roller  81  ( 81   a  and  81   b ) and the folding blade  86  illustrated in  FIGS. 14A to 14D . That is, as illustrated in  FIG. 27A , the folding roller  81  for folding the sheet bundle bonded by means of the applied adhesive tape AT and the folding blade  81  for inserting the sheet bundle into the nip position of the folding roller  81  are provided. 
     The sheet bundle supported in a bundle by the stacker section  40  is stopped by the stopper section  90  at the leading end of the stacker section  40  in a state illustrated in  FIG. 27A , and the folding position of the sheet bundle is positioned as a center position of the bonding by the adhesive-binding unit  50 . The sheet bundle folding processing controller  202  performs control such that the folding position of the sheet bundle is bent by the folding blade  86  as illustrated in  FIG. 27B  to be inserted between the rollers. At this time, the pair of folding rollers are driven into rotation at the same speed as that of the sheet bundle moved by the folding blade  86 . 
     Then, the sheet bundle folding processing controller  202  reversely rotates the folding drive motor  300  illustrated in  FIGS. 11 and 12  after elapse of an estimated time period during which the sheet bundle reaches a predetermined nip position to stop the folding blade  86  at a position illustrated in  FIG. 27C . On the other hand, the folding roller  81  continues to be rotated in the folding direction. As a result, the sheet bundle is fed in a delivery direction (leftward in  FIG. 27C ). Thereafter, the sheet bundle folding processing controller  202  normally rotates the folding drive motor  300  once again. Then, as illustrated in  FIG. 27D , the folding blade  86  positioned at the nip position is moved toward the standby position concurrently with the delivery of the sheet bundle by the folding roller  81 . 
     As illustrated in  FIG. 26C , in the sheet bundle to be folded illustrated in  FIGS. 27A to 27D , the adhesive is applied at one position on the folding position for the bonded first to fifth sheets, and the adhesive of the adhesive tape AT is applied at two positions very close to each other in the sheet conveying direction across the folding position for the sixth to 10th sheets. Further, for the 11th sheet (between the 11th and 12th sheets), the adhesive is applied at two positions separated from each other across the folding position Y by the interval (S). This allows the sheet bundle to be easily nipped between the folding rollers  81  ( 81   a  and  81   b ) as illustrated in  FIG. 27B . 
       FIGS. 28A to 28D  are views illustrating an adhesive-bound sheet bundle and a folded state thereof.  FIG. 28A  is a view for explaining a state where the adhesives are applied with the same length irrespective of whether the number of sheets is small or large. In the above description, the adhesive tape AT is applied at one position across the folding position when the number of sheets to be bonded is small; however, whether or not the adhesive tape AT is applied in such a manner may be determined by an operator on a case-by-case basis. That is, when a high adhesion is not required, the adhesive tape AT may be applied at one position across the folding position even when the number of sheets to be bonded is large.  FIG. 28A  illustrates a state where the adhesive of the adhesive tape AT is applied onto the 11 sheets at the folding positions thereof. In this case, when the sheets are folded, the adhesive is slightly extended at the bent portion of the folded sheet bundle at the outside thereof as illustrated in  FIG. 28B , but the adhesive is likely to be peeled-off. 
     As described above, the adhesive is applied such that the bonding area is increased as the number of sheets is increased, and when the number of sheets exceeds a predetermined number, the adhesive is applied at two positions separated from each other by a predetermined interval. This state is illustrated in  FIG. 28C . That is, the sheets are bonded as illustrated in  FIG. 25C ,  FIG. 26C , and  FIGS. 27A to 27D . When this adhesive-bound sheet bundle is folded, the adhesive is not applied onto a portion to be nipped first by the folding roller  81 , as can be seen in  FIG. 28D , thus making it easy for the sheet bundle to be nipped. The resultant booklet illustrated in  FIG. 28D  has advantages of reducing an amount of the adhesive to be used and allowing the pages comparatively to be easily opened. 
     [Procedure of Sheet Bonding Depending on Number of Sheets] 
     The following describes, with reference to flowcharts of  FIGS. 29 to 31 , a procedure of switching the application position of the adhesive tape (adhesive) AT depending on the number of sheets to be bonded. First, with reference to  FIGS. 29 and 30 , a procedure of increasing an application range of the adhesive tape AT depending on the number of sheets will be described. 
     An operator specifies the above-described “adhesive-bound sheet bundle folding mode”, and the adhesive tape application processing is executed. Here, it is checked whether or not a “tight bonding mode” in which the application range of the adhesive tape AT is increased depending on the number of sheets is performed (S 1 ). When “NO” (not execute) is selected, the bonding mode is shifted to a “normal bonding mode” (S 2 ). In the normal bonding mode, the transfer head  72  of the adhesive tape stamper  51  is pressed, once for each sheet, against a position corresponding to the folding position Y which is a substantially center position in the conveying direction of the sheets to be bonded (S 3 ). As a result, the adhesive tape AT is applied onto the sheet. This operation is repeated up to the next-to-last sheet (S 4 ). For the last sheet, the sheet pressing is performed using the pressing portion  170  illustrated in  FIG. 25D  (S 5 ). As a result, the adhesive tape AT is applied as illustrated in  FIG. 28A . Then, when the folding processing as illustrated in  FIGS. 14A to 14D  is executed, the folded sheet bundle with adhesive tapes AT having substantially the same size is created as illustrated in  FIG. 28B . Although the obtained booklet is not so strong in terms of adhesion between sheets, it can be created comparatively fast. 
     On the other hand, when the operator selects “YES” (execute) for the “tight bonding mode” (S 1 ) in the flowchart of  FIG. 29 , the bonding mode is shifted to the “tight bonding mode” (S 10 ). Assuming that 15 sheets are to be bonded, for every five sheets, the application range of the adhesive tape AT is increased, and the application position of the adhesive tape AT is adjusted. First, for the first to fifth sheets, the same procedure as that in the normal bonding mode is taken. That is, as illustrated in  FIG. 26A , the transfer head  72  of the adhesive tape stamper  51  is pressed, once for each sheet, against a position corresponding to the folding position Y which is a substantially center position in the conveying direction of the sheets to be bonded (S 11 ). 
     If the number of sheets to be bonded is equal to or less than five, the pressing portion  170  is pressed against the last sheet without application of the adhesive tape AT thereto as illustrated in  FIG. 25D , and the adhesive tape application processing is ended (S 21 , S 22 ). 
     Then, as illustrated in the flowchart of  FIG. 30 , for the sixth and subsequent sheets, the adhesive tape AT is applied at two positions very close to each other in the sheet conveying direction across a position corresponding to the folding position Y which is the substantially center position in the conveying direction of the sheets to be bonded, as illustrated in  FIG. 26B  (S 16 ). Also in this case, if the number of sheets to be bonded is equal to or less than ten, the pressing portion  170  is pressed against the last sheet without application of the adhesive tape AT thereto, and the adhesive tape application processing is ended (S 21 , S 22 ). 
     For the 11th and subsequent sheets, the adhesive tape AT is applied at two positions separated from each other by a predetermined interval (S) across a position corresponding to the folding position Y which is the substantially center position in the conveying direction of the sheets to be bonded, as illustrated in  FIG. 26C  (S 19 ). As a result, two adhesive tapes AT are applied with an interval interposed therebetween. When the next sheet is the last 15th sheet, the pressing portion  170  is pressed against the last sheet without application of the adhesive tape AT thereto, and the adhesive tape application processing is ended (S 21 , S 22 ). 
     When, for example, a sheet bundle formed by 12 sheets is subjected to the folding processing according to the above procedure, a sheet bundle bonded and folded in a state as illustrated in  FIGS. 28C and 28D  is obtained. Thus, it is possible to reduce an amount of the adhesive tape AT while maintaining a binding strength of the booklet and to allow the booklet to be easily opened at time of use. 
     [Another Procedure of Sheet Bonding Depending on Number of Sheets] 
     The following describes, with reference to  FIG. 31 , a modification of the procedure illustrated in  FIGS. 29 and 30 . The procedure of  FIG. 31  differs from that of  FIGS. 29 and 30  in that the sheet processing device B acquires sheet thickness information (S 01 ) and that when it is determined, based on the acquired sheet thickness information, that a sheet thickness is smaller than a prescribed sheet thickness, the “normal bonding mode” is set (S 2 ). On the other hand, when it is determined that the sheet thickness is larger than a prescribed sheet thickness, the “tight bonding mode” is set (S 10 ). In S 1 , an operator is made to confirm the setting of the “tight bonding mode”. An amount of the adhesive tape AT to be used is increased in the “tight bonding mode” and, thus, whether or not the “tight bonding mode” is appropriate for a usage of the booklet is confirmed here. The procedure after the confirmation is the same as that described in  FIGS. 29 and 30 , so description thereof will be omitted. Further, in this modification, when the sheet thickness is small, the sheets are unlikely to be peeled-off from one another even with the bonding range therebetween is small, so that the “normal bonding mode” is automatically set. 
     It should be appreciated that the present invention is not limited to the present embodiment, and various modifications may be made thereto. Further, all technical matters included in the technical ideas set forth in the claims should be covered by the present invention. While the invention has been described based on a preferred embodiment, various substitutions, corrections, modifications, or improvements may be made from the content disclosed in the specification by a person skilled in the art, which are included in the scope defined by the appended claims.