Patent Publication Number: US-9409740-B2

Title: Sheet bundle binding processing apparatus and image forming system having the same

Description:
RELATED APPLICATIONS 
     The present application is based on, and claims priority from, Japanese Application No. JP2013-149859 filed Jul. 18, 2013, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sheet bundle binding processing apparatus which performs a binding process on sheets fed from an image forming apparatus or the like after stacking the sheets into a bundle shape, and relates to improvement of a sheet bundle discharging mechanism with a non-staple binding unit which bonds mutually overlapped sheets with pressure deformation. 
     2. Description of Related Arts 
     In general, as a post-processing apparatus, there has been widely known an apparatus which performs a binding process with a binding processing unit after stacking, on a processing tray, sheets fed from an image forming apparatus and stores the sheets on a stack tray at the downstream side. In a structure thereof, a sheet introducing path is connected to a sheet discharging port of an image forming apparatus, image-formed sheets are collated and stacked on the processing tray arranged at the sheet discharging port, a binding process is performed on the sheets with the binding processing unit arranged at the processing tray, and then, the sheets are stored in a stack tray at the downstream side. 
     A binding processing unit which performs a binding process using a staple has been widely used for such a post-processing apparatus. Here, to solve problems in difficulty of sheet separation, disposal of bound sheets (shredding and the like), and the like, binding processing units without using a staple have been variously evaluated. 
     For example, Japanese Patent Application Laid-open No. 2011-190021 discloses a structure for an operator to select a staple binding process or a non-staple binding process to be performed on a sheet bundle stacked on a processing tray from a sheet discharging port of an image forming apparatus. For performing the non-staple binding process, there are disclosed a unit to mutually bond sheets as pressure-contacting a pair of corrugation-shaped pressurizing faces and a post-processing mechanism using the same. 
     Here, it is disclosed, as in  FIG. 11  of the above application, a bonding method to bond a sheet bundle as pressure-nipping the sheet bundle with a convex pressurizing face and a concave pressurizing face which are to be mutually engaged. According to such a bonding method, there are features that a bonding mechanism is relatively simple, a sheet bundle is easily separated, and disposal of bound sheets (shredding and the like) are easy. On the contrary, it is difficult to obtain reliable bonding and the number of sheets to be bound is limited. 
     SUMMARY OF THE INVENTION 
     As described above, there has already been known a post-processing apparatus in which sheets discharged from an image forming apparatus are collated and stacked on a processing tray and a binding process is performed on the sheets with a non-staple binding device (press binding unit). Japanese Patent Application Laid-open No. 2011-190021 proposes an apparatus in which sheets are stacked on a processing tray into a bundle shape, the sheet bundle is moved in a direction (sheet width direction) perpendicular to the sheet discharging direction, a binding process is performed on the sheet bundle, and the sheet bundle is discharged in the same direction as the sheet discharging direction. 
     According to such a binding processing unit, overlapped sheets are bonded with pressing deformation by vertically pressure-nipping the sheet bundle with pressurizing faces having corrugation-shaped faces. With such a structure, a conventional non-staple binding unit causes following problems. 
     There is a fear that an end face of sheets is stuck to a corrugation part of the pressurizing face and the sheets are folded or skewed when the sheets are conveyed to a binding position. In addition, since the sheet bundle is discharged as being slid on the corrugation part of the binding device, there arises a problem of image blurring. 
     Further, in a case that sheets are made of material, for example, having soft fibers, the sheets are apt to remain pressure-contacted to the corrugation-shaped pressurizing face. In this case, there may be a case that bonding is weakened or released when the sheet bundle is forcedly discharged. 
     In particular, when the pressurizing faces are corrugated for deep drawing to bond a thick sheet bundle more strongly, there arises a problem for discharging the sheet bundle from the binding unit. When the corrugation shape is formed in a direction perpendicular to the sheet discharging direction, the bonding is more likely to be released and the sheet bundle is more likely to be separated when being discharged. The corrugation shape is formed in a direction perpendicular to or intersecting (for example, at 45 degrees) with the sheet discharging direction to prevent the bound sheet bundle (document) from being separated during flipping through pages. Therefore, the above-mentioned problem becomes serious in binding processes. 
     An object of the present invention is to provide a sheet bundle binding processing apparatus capable of providing relatively strong bonding when a plurality of sheets are bound with nip-pressure deformation and causing less frictional damage on a sheet face when a sheet bundle is introduced to and discharged from the binding unit. 
     In this specification, “offset conveyance of a sheet bundle” denotes to move (bias) a sheet bundle (sheets introduced from a sheet discharging port) in a direction perpendicular to (or intersecting with) a sheet conveyance direction. “Offset amount” denotes a movement amount thereof. “Alignment of a sheet bundle” denotes to align sheets having different sizes introduced from a sheet discharging port in accordance with reference (center reference or side reference). Accordingly, “offset after sheet alignment” denotes to move the whole sheets in a direction perpendicular to the sheet conveyance direction after the sheets having different sizes are aligned in reference. 
     In view of the above, a sheet bundle binding processing apparatus of the present invention includes a processing tray which includes a sheet placement face on which sheets are stacked, a press binding device which bonds mutually overlapped sheets stacked on the processing tray with pressure-bonding deformation, a taking-off device which applies a taking-off force to sheets bound by the press binding device along the sheet placement face for taking off the sheets from the press binding device, and a sheet bundle discharging device by which the sheets taken off from the press binding device by the taking-off device is discharged from the processing tray. 
     In the present invention, a binding process is performed on a plurality of sheets by pressure-nipping the sheets with the corrugation-shaped pressurizing faces and forming linear scars thereon, and then, the bound sheet bundle is offset by a predetermined amount in a direction intersecting with the bundle discharging direction and discharged in the bundle discharging direction. According to the above, following effects are obtained. 
     The taking-off device applies a force (feeding force), in a direction of taking-off from the corrugation-shaped pressurizing faces, to an end face of a sheet bundle which is mutually intimately-contacted with pressure-nipping by the pressurizing faces. Accordingly, the bound sheet bundle is prevented from being separated or getting incomplete even with discharging action of the bound sheet bundle from the binding position. 
     Along with the above, since the bound sheet bundle is discharged in the bundle discharging direction after being offset from the binding position by a predetermined amount in the direction intersecting with the bundle discharging direction, a face of the sheet bundle to be discharged is prevented from rubbing against the pressurizing faces at the binding position during being discharged. Accordingly, the sheet face is prevented from getting dirty and damaged. 
     Further, in the present invention, the taking-off device is structured with the side regulating plate which biases and regulates sheets on the processing tray. Accordingly, a sheet bundle can be taken off from the binding position in a state of maintaining the bonded state and jumping of the sheet bundle due to the taking-off can be prevented with a simple structure without requiring a special mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an explanatory view of a whole configuration of an image forming system according to the present invention; 
         FIG. 2  is an explanatory perspective view illustrating a whole configuration of a post-processing apparatus in the image forming system of  FIG. 1 ; 
         FIG. 3  is a side sectional view (at an apparatus front side) of the apparatus of  FIG. 2 ; 
         FIGS. 4A and 4B  are explanatory views of a sheet introducing mechanism of the apparatus of  FIG. 2 , while  FIG. 4A  illustrates a state that a paddle rotor is at a waiting position and  FIG. 4B  illustrates a state that the paddle rotor is at an engaging position; 
         FIG. 5  is an explanatory view illustrating an arrangement relation among respective areas and alignment positions in the apparatus of  FIG. 2 ; 
         FIG. 6  is a structural explanatory view of the side aligning device in the apparatus of  FIG. 2 ; 
         FIG. 7  is an explanatory view of a moving mechanism of a stapling unit; 
         FIG. 8  is an explanatory view illustrating binding positions of the stapling unit; 
         FIG. 9  is an explanatory view of multi-binding and left corner binding of the stapling unit; 
         FIGS. 10A to 10C  illustrate states of the stapling unit at binding positions, while  FIG. 10A  illustrates a state at a right corner binding position,  FIG. 10B  illustrates a state at a staple loading position, and  FIG. 100  illustrates a state at a manual binding position; 
         FIGS. 11A to 11D  are explanatory views of a sheet bundle discharging mechanism in the apparatus of  FIG. 2 , while  FIG. 11A  illustrates a waiting state,  FIG. 11B  illustrates a transitional conveying state,  FIG. 11C  illustrates a structure of a second conveying member, and  FIG. 11D  illustrates a state of discharging to a stack tray; 
         FIGS. 12A to 12G  illustrate a binding processing method of a sheet bundle; 
         FIG. 13A  is a structural explanatory view of the stapling unit and  FIG. 13B  is a structural explanatory view of a press binding unit; 
         FIG. 14  is a structural explanatory view of the stack tray in the apparatus of  FIG. 2 ; 
         FIGS. 15A to 15F  are explanatory views of the taking-off device in the apparatus of  FIG. 2 , while  FIG. 15A  illustrates an aligned state of a sheet bundle,  FIG. 15B  illustrates a state of performing an eco-binding process,  FIG. 15C  illustrates a state that the taking-off device overruns,  FIG. 15D  illustrates a state that the sheet bundle is to be taken off,  FIG. 15E  illustrates a state that the sheet bundle is discharged, and  FIG. 15F  illustrates a relation between the taking-off device and a direction in which a conveyance force is applied. 
         FIG. 16  is an explanatory view of a control configuration of the apparatus of  FIG. 1 ; 
         FIG. 17  illustrates operational flows of a staple-binding processing mode; 
         FIG. 18  illustrates operational flows of an eco-binding mode; 
         FIG. 19  illustrates operational flows of a printout mode; 
         FIG. 20  illustrates operational flows of a sorting mode; 
         FIG. 21  illustrates common operational flows of introducing sheets onto a processing tray; and 
         FIG. 22  illustrates operational flows of a manual staple-binding process. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     In the following, the present invention will be described in detail based on preferred embodiments illustrated in the drawings. The present invention relates to a sheet bundle binding processing mechanism which performs a binding process on a collated and stacked sheet bundle with images formed thereon in a later-mentioned image forming system. The image forming system illustrated in  FIG. 1  includes an image forming unit A, an image reading unit C, and a post-processing unit B. A document image is read by the image reading unit C. Based on the image data, the image forming unit A forms an image on a sheet. Then, the post-processing unit B (i.e., sheet bundle binding processing apparatus, as the case may be) performs a binding process with the image-formed sheets collated and stacked and stores the sheets on a stack tray  25  at the downstream side. 
     The post-processing unit B which will be described later is built in as a unit at a sheet discharge space (stack tray space)  15  which is formed in a housing of the image forming unit A. The post-processing unit B has an inner finisher structure having a post-processing mechanism which performs a binding process after the image-formed sheets conveyed to a sheet discharging port  16  are collated and stacked on a processing tray and subsequently stores the sheets on the stack tray  25 . Not limited to the above, the present invention may have a stand-alone structure that the image forming unit A, the image reading unit C, and the post-processing unit B are independently arranged and the respective units are connected by network cables to be systematized. 
     [Sheet-Bundle Binding Processing Apparatus (Post-Processing Unit)] 
     As illustrated in  FIGS. 2 and 3  being a perspective view and a sectional view of the post-processing unit B, the post-processing unit B includes an apparatus housing  20 , a sheet introducing path  22  which is arranged in the apparatus housing  20 , a processing tray  24  which is arranged at the downstream side of a path sheet discharging port  23 , and a stack tray  25  which is arranged at the downstream side further therefrom. 
     [Apparatus Housing] 
     The apparatus housing  20  includes an apparatus frame  20   a  and an external casing  20   b . The apparatus frame  20   a  has a frame structure to support later-mentioned mechanisms (a path mechanism, a tray mechanism, a conveying mechanism, and the like). In the drawings, a binding mechanism, the conveying mechanism, a tray mechanism, and a driving mechanism are arranged at a right-left pair of side frames (not illustrated) which are mutually opposed to form a monocoque structure as being integrated with the external casing  20   b.    
     The external casing  20   b  has the monocoque structure obtained by integrating, with mold processing using resin or the like, right-left side frames  20   c ,  20   d  and a stay frame (later-mentioned bottom frame  20   e ) which connects the side frames  20   c ,  20   d . Here, a part (at the apparatus front side) thereof is exposed to be operable from the outside. 
     That is, the frames are stored in the sheet discharge space  15  of the later-mentioned image forming unit A with an outer circumference thereof covered by the external casing  20   b . In the above state, a front side of the external casing  20   b  is exposed to be operable from the outside. A later-mentioned cartridge mount opening  28  for staples, a manual setting portion  29 , and a manual operation button  30  (in the drawing, a switch having a built-in lamp) are arranged at the front side of the external casing  20   b.    
     The external casing  20   b  has a length Lx in a sheet discharging direction and a length Ly in a direction perpendicular to the sheet discharging direction which are set based on the maximum sheet size as being smaller than the sheet discharge space  15  of the later-mentioned image forming unit A. 
     [Sheet Introducing Path (Sheet Discharging Path)] 
     As illustrated in  FIG. 3 , the sheet introducing path  22  (hereinafter, called a sheet discharging path) having an introducing port  21  and a discharging port  23  is arranged at the above-mentioned apparatus housing  20 . In  FIG. 3 , the sheet discharging path  22  is structured as receiving a sheet in the horizontal direction and discharging the sheet from the discharging port  23  after conveying approximately in the horizontal direction. The sheet discharging path  22  includes an appropriate paper guide (plate)  22   a  and incorporates a feeder mechanism which conveys a sheet. 
     The feeder mechanism is structured with pairs of conveying rollers arranged at predetermined intervals in accordance with a path length. In  FIG. 3 , a pair of introducing rollers  31  is arranged in the vicinity of the introducing port  21  and a pair of discharging rollers  32  is arranged in the vicinity of the discharging port  23 . A sheet sensor Set to detect a sheet leading end and/or a sheet tailing end is arranged at the sheet discharging path  22 . 
     The sheet discharging path  22  includes a linear path arranged approximately in the horizontal direction as traversing the apparatus housing  20 . Here, a sheet is prevented from receiving stress which is caused by a curved path. Accordingly, the sheet discharging path  22  is formed as having linearity which is allowed by apparatus layout. The pair of introducing rollers  31  and the pair of discharging rollers  32  are connected to the same driving motor M 1  (hereinafter, called a conveying motor) and convey a sheet at the same circumferential speed. 
     [Processing Tray] 
     As illustrated in  FIG. 3 , the processing tray  24  is arranged at the downstream side of the sheet discharging port  23  of the sheet discharging path  22  as forming a step d therefrom. For upward stacking of sheets fed from the sheet discharging port  23  into a bundle shape, the processing tray  24  includes a sheet placement face  24   a  which supports at least a part of the sheets.  FIG. 3  illustrates a structure (bridge-support structure) in which a sheet leading end side is supported by the later-mentioned stack tray  25  and a sheet tailing end side is supported by the processing tray  24 . Thus, the processing tray  24  is downsized. 
     At the processing tray  24 , there are arranged a stapling unit  26  to staple-bind a sheet bundle, a press binding unit  27  to perform a binding process by pressing a sheet bundle whose section becomes into a concave-convex state without using a staple, a sheet introducing device  35  to introduce sheets, a sheet end regulating device  40  to stack introduced sheets into a bundle shape, an aligning device  45 , and a sheet bundle discharging mechanism  60 . According to the above, on the processing tray  24 , sheets fed from the discharging port  23  are stacked into a bundle shape, and a binding process is performed by a binding device being either the stapling unit  26  or the press binding unit  27  after the sheets are aligned into a predetermined posture. Subsequently, the processed sheet bundle is discharged to the stack tray  25  at the downstream side. Since the press binding unit  27  operates without using a staple as being advantageous in resource saving, the binding process with the press binding unit  27  is hereinafter called eco-binding. 
     [Sheet Introducing Mechanism (Sheet Introducing Device)] 
     Since the processing tray  24  is arranged as forming the step d from the sheet discharging port  23 , it is required to arrange the sheet introducing device  35  which smoothly conveys a sheet onto the processing tray  24  with a correct posture. In the drawings, the sheet introducing device  35  (friction rotor) is structured with a lifting-lowering paddle rotor  36 . When a sheet tailing end is discharged from the sheet discharging port  23  onto the processing tray  24 , the paddle rotor  36  conveys the sheet in a direction (rightward in  FIG. 3 ) opposite to the sheet discharging direction, so that the sheet is abutted to a later-mentioned sheet end regulating device  40  to be aligned (positioned). 
     A lifting-lowering arm  37  which is axially-supported swingably by a support shaft  37   x  at the apparatus frame  20   a  is arranged at the discharging port  23 . The paddle rotor  36  is axially-supported rotatably at a top end part of the lifting-lowering arm  37 . A pulley (not illustrated) is arranged at the support shaft  37   x  and the abovementioned conveying motor M 1  is connected to the pulley. 
     In addition, a lifting-lowering motor (hereinafter, called a paddle lifting-lowering motor) M 3  is connected to the lifting-lowering arm  37  via a spring clutch (torque limiter) and is structured so that the lifting-lowering arm  37  is lifted and lowered with rotation of the lifting-lowering motor M 3  between a waiting position Wp at the upper side and an operating position (sheet engaging position) Ap at the lower side. 
     That is, the spring clutch lifts the lifting-lowering arm  37  from the operation position Ap to the waiting position Wp with rotation of the paddle lifting-lowering motor M 3  in one direction and keeps the lifting-lowering arm  37  waiting at the waiting position Wp after abutting to a stopper (not illustrated). On the contrary, the spring clutch is released with rotating of the paddle lifting-lowering motor M 3  in the opposite direction, so that the lifting-lowering arm  37  is lowered under own weight thereof from the waiting position Wp to the operating position Ap at the lower side to be engaged with the upmost sheet. 
     In the illustrated apparatus, a pair of the paddle rotors  36  are arranged in a bilaterally symmetric manner with respect to a sheet center Sx (center reference) as being apart by a predetermined distance, as illustrated in  FIG. 5 . Alternatively, three paddle rotors in total may be arranged at the sheet center and both sides thereof, or one paddle rotor may be arranged at the sheet center. 
     The paddle rotor  36  is structured with a flexible rotor formed of a rubber-made plate-shaped member, plastic-made blade member, or the like. Instead of the paddle rotor  36 , it is possible that the sheet introducing device  35  is structured with a friction rotating member such as a roller body and a belt body. In the above description, the illustrated apparatus includes the mechanism with which the paddle rotor  36  is lowered from the waiting position Wp at the upper side to the operating position Ap at the lower side after a sheet tailing end is discharged from the discharging port  23 . However, instead of the above, it is possible to adopt a lifting-lowering mechanism described below. 
     With a lifting-lowering mechanism being different from the illustrated mechanism, for example, when a sheet leading end is discharged from the discharging port  23 , a friction rotor is lowered from a waiting position to an operating position and rotated concurrently in the shoot discharging direction. Then, at the timing when a sheet tailing end is discharged from the discharging port  23 , the friction rotor is reversely rotated in a direction opposite to the sheet discharging direction. According to the above, it is possible that the sheet discharging from the discharging port  23  is conveyed to a predetermined position of the processing tray  24  at high speed without being skewed. 
     [Raking Rotor] 
     A raking rotor  33  is arranged so that a sheet tailing end (a leading end in the sheet discharging direction) of a curled sheet or a skewed sheet is reliably guided to a regulating device at the downstream side when a sheet is conveyed to a predetermined position of the processing tray  24  by the puddle rotor  36 . The raking rotor  33  is arranged below the pair of sheet discharging rollers  32  and guides a sheet fed by the paddle rotor  36  to the regulating device  40 . The raking rotor  33  is structured with a ring-shaped belt member  34  ( FIG. 4 ) and conveys the upmost sheet on the processing tray  24  to the regulating device  40  as being abutted thereto. 
     The illustrated apparatus includes a raking rotor (raking-conveying device)  33  which applies a conveying force, to a regulating member side, on the upmost sheet of the sheets stacked at the upstream side of the later-mentioned sheet end regulating stopper  40  below the pair of sheet discharging rollers  32 . In the drawings, a ring-shaped belt member (hereinafter, called a raking belt)  34  is arranged above the top end part of the processing tray  24 . The raking belt  34  is engaged with the upmost sheet on the sheet placement face  24   a  and rotated in a direction to convey the sheet toward the regulating member side. 
     The raking belt  34  is structured with a belt member (roulette belt, or the like) having a high frictional force made of soft material such as rubber material. The raking belt  34  is nipped and supported between an idle shaft  34   y  and a rotating shaft  34   x  which is connected to a drive motor (in the drawing, the conveying motor M 1  is commonly used). A rotational force in the counterclockwise direction in  FIG. 3  is applied to the raking belt  34  from the rotating shaft  34   x . Along with the above, the raking belt  34  presses a sheet introduced along the upmost sheet stacked on the processing tray  24  and causes a leading end of the sheet to be abutted to the regulating stopper  40  at the downstream side. 
     The raking belt  34  is configured to be moved upward and downward above the upmost sheet on the processing tray  24  by a belt shifting motor (hereinafter, called a roulette lifting-lowering motor) M 5 . Here, a lifting-lowering mechanism therefor is skipped. At the timing when a sheet leading end enters between a belt face and the upmost sheet, the raking belt  34  is lowered and engaged with the introduced sheet. When a sheet bundle is conveyed from the processing tray  24  to the stack tray  25  at the downstream side by a sheet bundle conveying device  60  as described later, the roulette motor M 5  is controlled so that the raking belt  34  is separated from the upmost sheet and kept waiting at the upper side. 
     [Sheet Aligning Mechanism] 
     A sheet aligning mechanism  45  which performs positioning of an introduced sheet at a predetermined position (processing position) is arranged at the processing tray  24 . The sheet aligning mechanism  45  in the drawings includes the sheet end regulating device  40  which positionally regulates an end face (a leading end face or a tailing end face) in the sheet discharging direction of the sheet fed from the discharging port  23  and a side aligning device  45  which performs biasing and aligning in a direction (sheet side direction) perpendicular to the sheet discharging direction. In the following, description will be performed in the order thereof. 
     [Sheet End Regulating Device] 
     The illustrated sheet end regulating device  40  includes a tailing end regulating member  41  which performs regulation with abutting against a sheet tailing end in the sheet discharging direction. The tailing end regulating member  41  includes a regulating face  41   a  which performs regulation with abutting the tailing end in the sheet discharging direction of the sheet introduced along the sheet placement face  24   a  of the processing tray  24 . The tailing end regulating member  41  causes the tailing end of the sheet fed by the abovementioned raking rotor  33  to be abutted and stopped. 
     When multi-binding is performed with the later-mentioned stapling unit  26 , the stapling unit  26  is moved along a sheet tailing end (in a direction perpendicular to the sheet discharging direction). To prevent obstruction against movement of the stapling unit  26 , the tailing end regulating member  41  is configured to adopt any one of the structures of: 
     (1) adopting a mechanism with which the tailing end regulating member proceeds to and retracts from a movement path (motion trajectory) of the binding unit, 
     (2) adopting a mechanism with which the tailing end regulating member is moved integrally with the binding unit, and 
     (3) forming the tailing end regulating member, for example, as a channel-shaped folded piece arranged at the inside of a binding space which is formed by a head and an anvil of the binding unit. 
     The illustrated tailing end regulating member  41  includes a plate-shaped folded member whose section has a U-shape (channel shape) arranged in the binding space of the stapling unit  26 . Here, a first member  41 A is arranged at the sheet center based on the minimum sheet size, and second and third members  41 B,  41 C are arranged bilaterally as being mutually distanced (see  FIG. 5 ). According to the above, the stapling unit  26  is allowed to be moved in a sheet width direction. 
     As illustrated in  FIGS. 5 and 7 , a plurality of the tailing end regulating members  41  formed of channel-shaped folded pieces is fixed to the processing tray  24  as top end parts thereof being fixed to a back face wall of the processing tray  24  with screws. The regulating face  41   a  is formed at each of the tailing end regulating member  41  and an inclined face  41   b  which guides a sheet end to the regulating face  41   a  is continuously formed at a top end part of the folding thereof. 
     [Side Aligning Device] 
     The processing tray  24  is provided with an aligning device which performs positioning of a sheet abutted to the abovementioned tailing end regulating member  41  in a direction perpendicular to the sheet discharging direction (sheet width direction). 
     The aligning device  45  is structured differently based on whether sheets having different sizes are aligned on the processing tray  24  in center reference or side reference. In the apparatus illustrated in  FIG. 5 , sheets of different sizes are discharged from the discharging port  23  in the center reference and the sheets are aligned on the processing tray  24  in the center reference. A binding process is performed by the stapling unit  26  on a sheet bundle which is aligned into a bundle shape in center reference, in accordance with the binding process, at binding positions Ma1, Ma2 in an aligned posture for multi-binding and at binding positions Cp1, Cp2 with the sheet bundle offset by a predetermined amount in the width direction for a lateral corner binding. 
     As illustrated in  FIG. 6 , the aligning device  45  includes a right side aligning member  46 E′ (at the apparatus front side) and a left side aligning member  46 R (at the apparatus rear side). Slit grooves  24   x  penetrating the sheet placement face  24   a  are formed at the processing tray  24 . The right side aligning member  46 F and the left side aligning member  46 R are fitted to the slit grooves  24   x  and attached to the processing tray  24  as protruding thereabove. Each of the side aligning plates  46 F,  46 R is integrally formed with a rack  47  and is slidably supported by a plurality of guide rollers  49  (or rail members) at the back face side of the processing tray  24 . Aligning motors M 6 , M 7  are connected to the right-left racks  47  respectively via a pinion  48 . The right-left aligning motors M 6 , M 7  are structured with stepping motors. Positions of the right-left aligning plates  46 F,  46 R are detected by position sensors (not illustrated). Based on the detected values, the side aligning plates  46 F,  46 R can be moved respectively in either right or left direction by specified movement amounts. 
     The side aligning plates  46 F,  46 R slidable on the sheet placement face  24   a  have regulating faces  46   x  which abut to side edges of a sheet. Here, the regulating faces  46   x  can reciprocate by a predetermined stroke mutually in a closing direction or a separating direction. The stroke is determined from difference between the maximum sheet size and the minimum sheet size and the offset amount of positional movement (offset conveyance) of an aligned sheet bundle rightward or leftward. That is, the movement stroke of the right-left side aligning plates  46 F,  46 R is determined from a movement amount for aligning sheets having different sizes and the offset amount of the aligned sheet bundle. Here, not limited to the illustrated rack-pinion mechanism, it is also possible to adopt a structure that the side aligning plates  46 F,  46 R are fixed to a timing belt and the timing belt is connected to a motor via a pulley to reciprocate laterally. 
     According to the above structure, binding process controller  75  causes the right-left side aligning members  46 F,  46 R at predetermined waiting positions (distanced by a sheet width+α therebetween) based on sheet size information which is provided from the image forming unit A or the like. In the above state, a sheet is introduced onto the processing tray  24 . At the timing when a sheet end is abutted to the sheet end regulating member  41 , aligning operation is started. In the aligning operation, the right-left aligning motors M 6 , M 7  are rotated in opposite directions (closing directions) by the same amount. Accordingly, sheets introduced onto the processing tray  24  are stacked in a bundle shape as being positioned in reference to the sheet center. According to repetition of the introducing operation and the aligning operation, sheets are collated and stacked on the processing tray  24  in a bundle shape. Here, sheets of different sizes are positioned in center reference. 
     It is possible to perform a binding process at a plurality of positions at a predetermined interval (i.e., multi-binding process) on the sheets stacked on the processing tray  24  in center reference as described above in the above posture at a tailing end (or a leading end) of the sheets. In a case of performing a binding process on a sheet corner, one of the right-left side aligning members  46 F,  46 R is moved to and stopped at a position where a sheet side end is matched with a specified binding position. Then, the side aligning member at the opposite side is moved in the closing direction. A movement amount in the closing direction is calculated in accordance with a sheet size. Accordingly, a sheet introduced onto the processing tray  24  is aligned so that a right side end is matched with a binding position in a case of right corner binding and a left side end is matched with a binding position in a-case of left corner binding. 
     When a sheet bundle aligned at a predetermined position on the processing tray  24  as described above is offset-moved for a later-mentioned eco-binding process, (1) drive control that the aligning member at the rear side in the movement direction is moved in a direction perpendicular to the sheet conveying direction by a previously set amount in a state that the aligning member at the front side in the movement direction is retracted to a position being apart from an offset assumed position, or (2) drive control that the right-left aligning members are moved in a direction perpendicular to the sheet conveying direction by the same amount. 
     Here, position sensors (not illustrated) such as a position sensor and an encode sensor are arranged at the right-left side aligning members  46 F,  46 R and the aligning motors M 6 , M 7  therefor to detect positions of the side aligning members  46 F,  46 R. Owing to that the aligning motors M 6 , M 7  are structured with stepping motors, home positions of the side aligning members  46 F,  46 R are detected by position sensors (not illustrated), and the motors are PWM-controlled, the right-left side aligning members  46 F,  46 R can be controlled with a relatively simple control configuration. 
     [Sheet Bundle Discharging Mechanism] 
     Next, the sheet bundle discharging mechanism (sheet bundle discharging device  60 ) illustrated in  FIG. 11  will be described. The sheet bundle discharging mechanism which discharges a sheet bundle bound by the stapling unit  26  or the press binding unit  27  to the stack tray  25  at the downstream side is arranged at the abovementioned processing tray  24 . At the processing tray  24  described based on  FIG. 5 , the first sheet tailing end regulating member  41 A is arranged at the sheet center Sx and the second and third sheet tailing end regulating members  41 B,  41 C are arranged bilaterally as being mutually distanced. A sheet bundle stopped by the regulating members  41  is to be discharged to the stack tray  25  at the downstream side after a binding process is performed thereon by the stapling unit  26  or the press binding unit  27 . 
     The sheet bundle discharging device  60  is arranged along the sheet placement face  24   a  of the processing tray  24 . The illustrated sheet bundle discharging device  60  includes a first conveying member  60 A and a second conveying member  60 B. Here, conveyance in a first zone L1 on the processing tray  24  is performed by the first conveying member  60 A and conveyance in a second zone L2 is performed by the second conveying member  60 B, so that relay conveyance is performed. Since a sheet bundle is conveyed serially by the first and second conveying members  60 A,  60 B, mechanisms of the first and second conveying members  60 A,  60 B can be differently arranged. Here, it is required that the member which conveys a sheet bundle from a starting point being approximately the same as the sheet tailing end regulating device  40  is formed of a less swaying member (elongated supporting member) and a member which causes the sheet bundle to drop at an end point of conveyance is downsized (for travelling on a loop trajectory). 
     The first conveying member  60 A is structured with a first discharging member  61  formed of a folded piece whose section has a channel shape. The first discharging member  61  includes a stopper face  61   a  which stops a tailing end face of a sheet bundle, and a sheet face pressing member  62  (an elastic film member; Mylar piece) which presses an upper face of the sheet bundle stopped by the stopper face  61   a . As illustrated in the drawing, the first conveying member  60 A is formed of a folded piece whose section has a channel shape. Accordingly, fixed to a later-mentioned carrier member  65   a  (belt), the first conveying member  60 A moves (feeds) the tailing end of the sheet bundle in the conveying direction as travelling integrally with the belt with less swaying. The first conveying member  60 A reciprocates with a stroke Str1 on an approximately linear trajectory without travelling on a loop trajectory curved as described later. 
     The second conveying member  60 B is structured with a second discharging member  63  which has a pawl shape. The second discharging member  63  includes a stopper face  63   a  which stops a tailing end face of a sheet bundle, and a sheet face pressing member  64  which presses an upper face of the sheet bundle. The sheet face pressing member  64  having a sheet face pressing face  64   a  is swingably axis-supported by the second discharging member  63 . An urging spring  64   b  is arranged to cause the sheet face pressing face to press the upper face of the sheet bundle. 
     The sheet face pressing face  64   a  is formed as an oblique face oblique to a travelling direction as illustrated and is engaged with the tailing end of the sheet with a setting angle of γ when moved in the arrow direction in  FIG. 11B . At that time, the sheet face pressing face  64   a  is deformed upward (counterclockwise in  FIG. 11C ) in the arrow direction against the urging spring  64   b . Then, the sheet face pressing face  64   a  presses the upper face of the sheet bundle toward the sheet placement face  24   a  side by the action of the urging spring  64   b.    
     According to the above structure, the first discharging member  61  reciprocate with the first carrier member  65   a  and the second discharging member  63  reciprocate with a second carrier member  65   b  between a base end part and an exit end part of the sheet placement face  24   a . Driving pulleys  66   a ,  66   b  and a driven pulley  66   c  are arranged at the sheet placement face  24   a  as being mutually distanced by the conveyance stroke. Idling pulleys  66   d ,  66   e  are arranged as illustrated in  FIG. 10A . 
     The first carrier member  65   a  (toothed belt in the drawings) is routed between the driving pulley  66   a  and the driven pulley  66   c . The second carrier member  65   b  (toothed belt) is routed between the driving pulley  66   b  and the driven pulley  66   c  via the idling pulleys  66   d ,  66   e . A drive motor M 4  is connected to the driving pulleys  66   a ,  66   b . Here, the first driving pulley  65   a  is formed to have a small diameter and the second driving pulley  65   b  is formed to have a large diameter so that rotating of the drive motor M 4  is transmitted to the first carrier member  65   a  at a low speed and to the second carrier member  65   b  at a high speed. 
     That is, the first conveying member  60 A and the second conveying member  60 B are connected, to travel respectively at a low speed and a high speed, commonly to the drive motor M 4  via a decelerating mechanism (belt pulleys, gear coupling, or the like). In addition, a cam mechanism is incorporated in the second driving pulley  66   b  to delay the drive transmission. This is, as described later, because of difference between the movement stroke Str1 of the first conveying member  60 A and the movement stroke Str2 of the second conveying member  60 B and positional adjustment of waiting positions of the respective members. 
     According to the above structure, the first conveying member  60 A reciprocates on a linear trajectory with the first stroke Str1 from the tailing end regulation position of the processing tray  24 . Here, the first zone Tr1 is set within the first stroke Str1. The second conveying member  60 B reciprocates on a semi-loop trajectory with the second stroke Str2 from the first zone Tr1 to the exit end of the processing tray  24 . Here, the second zone Tr2 is set within the second stroke Str2. 
     The first conveying member  60 A is moved from the sheet tailing end regulation position to the downstream side (from  FIG. 11A  to  FIG. 11B ) at a speed V1 with rotation in one direction of the drive motor M 4  to convey the sheet bundle as pushing the tailing end thereof with the stopper face  61   a . Being delayed by a predetermined time from the first conveying member  60 A, the second conveying member  60 B projects above the sheet placement face  24   a  from the waiting position ( FIG. 11A ) at the back face side of the processing tray  24  and is moved at a speed V2 as following the first conveying member  60 A in the same direction. Here, since the speed V2 is set to be higher than the speed V1, the sheet bundle on the processing tray  24  is relayed from the first conveying member  60 A to the second conveying member  60 B. 
       FIG. 11B  illustrates a state of the relay conveyance. The second conveying member  60 B travelling at the speed V2 catches up with the sheet bundle travelling at the speed V1. That is, after passing through the first zone Tr1, the second conveying member  60 B catches up with the first conveying member  60 A and performs conveyance to the downstream side in the second zone Tr2 as being engaged with the tailing end face of the sheet bundle. 
     When the second conveying member  60 B is abutted, at the relay point at a high speed, to the sheet bundle travelling at the speed V1, the sheet bundle is discharged toward the stack tray  25  while the tailing end of the sheet bundle is held as being nipped between the sheet face pressing member  64  and the carrier member (belt)  65   a  ( 65   b ) with the upper face of the sheet bundle pressed by sheet face pressing face  64   a.    
     [Method of Binding Process (Binding Position)] 
     As described above, sheets conveyed to the introducing port  21  of the sheet discharging path  22  are collated and stacked on the processing tray  24  and positioned (aligned) by the sheet end regulating member  40  and the side aligning members  46 F,  46 R at the previously-set location and in the previously-set posture. Thereafter, a binding process is performed on the sheet bundle and the sheet bundle is discharged to the stack tray  25  at the downstream side. In the following, a method of the binding process is described. 
     Multi-binding positions Ma1, Ma2 where sheets are staple-bound at a plurality of positions, corner binding positions Cp1, Cp2 where sheets are bound at a corner, a manual binding position Mp where a binding process is performed on manually-set sheets, and an eco-binding position Ep where sheets are bound at a corner by the press binding unit  27  without using a staple are defined for performing a binding process with the stapling unit  26  or the press binding unit  27  on a sheet bundle aligned into a bundle shape in center reference by the side aligning members  46 F,  46 R. In the following, positional relation among the respective binding positions will be described. 
     [Multi-Binding] 
     As illustrated in  FIG. 5 , in the multi-binding process, a sheet bundle positioned on the processing tray  24  by the sheet end regulating member  41  and the side aligning members  46 F,  46 R (hereinafter, called an aligned sheet bundle) is bound at an end edge (a tailing end edge in the drawings). The multi-binding positions Ma1, Ma2 where a binding process is performed on two distanced positions is defined in  FIG. 9 . The later-mentioned stapling unit  26  is moved from a home position to the binding position Ma1 and the binding position Ma2 in the order thereof and performs a binding process respectively at the binding positions Ma1, Ma2. Here, not limited to two positions, the binding process may be performed at three or more positions as the multi-binding positions Ma.  FIG. 12A  illustrates a multi-bound state. 
     [Corner Binding] 
     The corner binding process defines binding positions as two bilateral positions being a right corner binding position Cp1 where a binding process is performed on a right corner on an aligned sheet bundle stacked on the processing tray  24  and a left corner binding position Cp2 where a binding process is performed on a left corner of an aligned sheet bundle. Here, the binding process is performed with a staple being oblique by a predetermined angle (approximately between 30 to 60 degrees). The later-mentioned stapling unit  26  is mounted on the apparatus frame with the entire unit being oblique by the predetermined angle thereat.  FIGS. 12B and 12C  illustrate corner-bound states. 
       FIGS. 12B and 12C  illustrate cases that the binding process is performed on either the right or left of a sheet bundle by selection while a staple is set oblique by the predetermined angle. Not limited to the above, even in a case that binding is performed on only one of the right and left corners, it is also possible to adopt a structure that the binding is performed with a staple being parallel to a sheet end edge without being oblique. 
     [Manual Binding] 
     In the illustrated apparatus, it is possible to perform a manual stapling process to bind sheets prepared outside the apparatus with the stapling unit  26 . Here, the manual setting portion  29  is arranged for setting a sheet bundle to the external casing  20   b  from the outside. A manual setting face  29   a  on which a sheet bundle is set is formed at the casing. The stapling unit  26  is configured to be moved from a sheet introducing area Ar to a manual-feeding area Fr of the processing tray  24 . The manual setting face  29   a  is arranged in parallel at a position being adjacent to the sheet placement face  24   a  via the side frame  20   c  at a height to form approximately the same plane with the sheet placement face  24   a  of the processing tray  24 . Here, both the sheet placement face  24   a  of the processing tray  24  and the manual setting face  29   a  are arranged approximately at the same height position as supporting sheets approximately at horizontal posture.  FIG. 12D  illustrates a manual-bound state. 
     As illustrated in  FIG. 5 , the manual binding position Mp for the manual stapling process with the stapling unit  26  is arranged on the same straight line as the abovementioned multi-binding positions Ma1, Ma2. Here, there are arranged, on the processing tray  24 , the sheet introducing area Ar, the manual-feeding area Fr at the apparatus front side, and a later-mentioned eco-binding area Rr at the apparatus rear side. 
     [Eco-Binding Position] 
     The eco-binding position Ep is defined so that a binding process is performed on aside edge part (corner part) of sheets as illustrated in  FIG. 5 . The illustrated eco-binding position Ep is defined at a position where the binding process is performed on one position at the side edge part in the sheet discharging direction of a sheet bundle. Then, the binding process is performed as being oblique to sheets by a predetermined angle. The eco-binding position Ep is defined in the eco-binding area Rr which is distanced to the apparatus rear side from the sheet introducing area Ar of the processing tray  24 . 
     [Mutual Relation Among Respective Binding Positions] 
     The multi-binding positions Ma1, Ma2 are defined in the sheet introducing area Ar (at the inside thereof) where sheets are introduced to the processing tray  24  from the sheet discharging port  23 . Each of the corner binding positions Cp1, CP2 is defined outside the sheet introducing area Ar at a reference position which is apart rightward or leftward (side alignment reference) by a predetermined distance from the sheet discharging reference Sx (center reference). As illustrated in  FIG. 6 , at the outer side from a side edge of a maximum size of sheets to be bound, the right corner binding position Cp1 is defined at a position deviated rightward from a sheet side edge by a predetermined amount (δ1) and the left corner binding position Cp2 is defined at a position deviated leftward from a sheet side edge by a predetermined amount (δ2). The deviation amounts are set to be the same (δ1=δ2). 
     The manual binding position Mp is defined approximately on the same straight line as the multi-binding positions Ma1, Ma2. Further, the corner binding positions Cp1, Cp2 are defined at positions each having an oblique angle (e.g., 45 degrees) to be bilaterally symmetric about the sheet discharging reference Sx. 
     The manual binding position Mp is defined in the manual-feeding area Fr in the apparatus front side and outside the sheet introducing area Ar. The eco-binding position Ep is defined in the eco-binding area Rr at the apparatus rear side Re and outside the sheet introducing area Ar. 
     Further, the manual binding position Mp is defined at a position which is offset by a predetermined amount (Of1) from the right corner binding position Cp1 of the processing tray  24 . The eco-binding position Ep is defined at a position which is offset by a predetermined amount (Of2) from the left corner binding position Cp2 of the processing tray  24 . Thus, the multi-binding positions Ma1, Ma2 are defined based on the sheet discharging reference (center reference) of the processing tray  24  to which sheets are introduced, and the corner binding positions Cp1, Cp2 are defined based on the maximum sheet size. Further, the manual binding position Np is defined at the position which is offset by the predetermined amount (Of1) from the right corner binding position Cp1 to the apparatus front side. Similarly, the eco-binding position Ep is defined at the position which is offset by the predetermined amount (Of2) from the left corner binding position Cp2 to the apparatus rear side. According to the above, arrangement can be performed in an orderly manner without causing interference of sheet movement. 
     Next, the sheet movement for the respective binding processes is described. In the multi-binding process, sheets are introduced to the processing tray  24  in center reference (or side reference) and aligned in the above state, and then, the binding process is performed thereon. After the binding process is performed, the sheets are discharged to the downstream side in the above posture. In the corner binding process, sheets are aligned at the alignment position at a specified side and the binding process is performed thereon. After the binding process is performed, the sheets are discharged to the downstream side in the above posture. In the eco-binding process, sheets introduced onto the processing tray  24  are offset by the predetermined amount Of2 to the apparatus rear side after being stacked into a bundle shape. The binding process is performed thereon after the offset movement. After the binding process, the sheets are offset by a predetermined amount (for example, being the same as or smaller than the offset Of2) to the sheet center side and discharged to the downstream side thereafter. 
     Further, in the manual binding, an operator sets sheets on the manual setting face  29   a  as being offset by the predetermined amount Of1 from the alignment reference which is positioned at the front side from the processing tray  24 . According to the above, a plurality of the binding processes are performed while sheet setting positions therefor are defined in the direction perpendicular to the sheet conveying direction. Therefore, sheet jamming can be suppressed while keeping high processing speed. 
     In the eco-binding process, the later-mentioned binding process controller  75  defines the eco-binding position Ep with sheets offset by a predetermined amount Of3 in the sheet discharging direction from the tailing end reference position. This is to avoid interference between the stapling unit  26  for the left corner binding and an eco-binding unit (press binding unit  27  described later). Here, if the press binding unit  27  is mounted on the apparatus frame  20   a  movably between the binding position and a retracting position retracting therefrom similarly to the stapling unit  26 , sheets are not required to be offset by the amount Of3 in the sheet discharging direction. 
     Here, the apparatus front side Fr denotes a front side of the external casing  20   b  set by apparatus designing where various kinds of operation are performed by an operator. Normally, a control panel, a mount cover (door) for a sheet cassette, and an open-close cover through which staples are replenished for a stapling unit are arranged at the apparatus front side. Further, the apparatus rear side Re denotes a side of the apparatus facing to a wall face of a building, for example, when the apparatus is installed (installation conditions; the back face is designed to face a wall). 
     Thus, in the illustrated apparatus, the manual binding position Mp is defined at the apparatus front side Fr and the eco-binding position Ep is defined at the apparatus rear side Re outside the sheet introducing area Ar with reference thereto. A distance Ofx between the manual binding position Mp and the reference of the sheet introducing area Ar (sheet introducing reference Sx) is set larger than a distance Ofy between the eco-binding position Ep and the sheet introducing reference Sx (i.e., Ofx&gt;Ofy). 
     Thus, the manual binding position Mp is defined to be apart from the sheet introducing reference Sx of the processing tray  24  and the eco-binding position Ep is defined to be close to the sheet introducing reference Sx. This is because operation of setting a sheet bundle to the manual binding position Mp from the outside is facilitated to be convenient owing to that the manual binding position Mp is apart from the processing tray  24 . Further, the eco-binding position Ep is defined to be close to the sheet introducing reference Sx. This is because the movement amount when sheets (aligned sheet bundle) introduced onto the processing tray  24  are offset-moved to the eco-binding position Ep can be small for speedy performance of the binding process (i.e., improvement of productivity). 
     [Moving Mechanism for Stapling Unit] 
     The stapling unit  26  includes a unit frame  26   a  (first unit frame), a staple cartridge  39 , a stapling head  26   b , and an anvil member  26   c . Structures thereof will be described later. The stapling unit  26  is supported by the apparatus frame  20   a  to reciprocate by a predetermined stroke along a sheet end face of the processing tray  24 . The supporting structure will be described in the following. 
       FIG. 7  illustrates a front structure that the stapling unit  26  is attached to the apparatus frame  20   a  and  FIG. 8  illustrates a plane structure thereof.  FIGS. 9 and 10  illustrate partial explanatory views of a guide rail mechanism which guides the stapling unit  26 . 
     As illustrated in  FIG. 7 , a chasses frame (hereinafter, called a bottom frame)  20   e  is attached to the right-left side frames  20   c ,  20   d  structuring the apparatus frame  20   a . The stapling unit  26  is mounted on the bottom frame  20   e  to be movable by the predetermined stroke. A travel guide rail (hereinafter, simply called a guide rail)  42  and a slide cam  43  are arranged at the bottom frame  20   e . A travel rail face  42   x  is formed at the guide rail  42  and a travel cam face  43   x  is formed at the slide cam  43 . The travel rail face  42   x  and the travel cam face  43   x  in mutual cooperation support the stapling unit  26  to be capable of reciprocating by the predetermined stroke and control the angular posture thereof. 
     The travel rail face  42   x  and the travel cam face  43   x  are formed so that the travel guide rail  42  and the slide cam  43  allows the stapling unit  26  to reciprocate within a movement range SL (the sheet introducing area Ar, the manual-feeding area Fr, and the eco-binding area Rr) (see  FIG. 8 ). The travel guide rail  42  is structured with a rail member having the stroke SL along the tailing end regulating member  41  of the processing tray  24 . In the drawing, the travel guide rail  42  is structured as an opening groove formed at the bottom frame  20   e . The travel rail face  42   x  is formed at the edge of the opening and is arranged on the same straight line as the tailing end regulating member  41  of the processing tray  24  as being in parallel thereto. The slide cam  43  is arranged as being distanced from the travel rail face  42   x . In the drawing, the slide cam  43  is structured with a groove cam which is formed at the bottom frame  20   e . The travel cam face  43   x  is formed at the groove cam. 
     A drive belt  44  connected to a drive motor M 11  is fixed to the stapling unit  26 . The drive belt  44  is wound around a pair of pulleys axially supported by the apparatus frame  20   a . The drive motor M 11  is connected to one of the pulleys. Thus, the stapling unit  26  reciprocates by the stroke SL with forward and reverse rotation of the drive motor M 11 . 
     The travel rail face  42   x  and the travel cam face  43   x  are arranged to include a parallel distance sections  43   a ,  43   b  (having a span G1) where the faces are in parallel, a narrow slant distance sections  43   c ,  43   d  (having a span G2), and a narrower slant distance section  43   e  (having a span G3). Here, the spans satisfies the relation of “G1&gt;G2&gt;G3”. The span G1 causes the stapling unit  26  to be in a posture as being in parallel to a sheet tailing end edge. The span G2 causes the stapling unit  26  to be in a slant posture rightward or leftward. The span G3 causes the stapling unit  26  to be in a posture slant at a larger angle. Thus, the angle of the stapling unit  26  is varied. 
     Not limited to the opening groove structure, the travel guide rail  42  may adopt a variety of structures such as a guide rod, a projection rib, and others. Further, not limited to the groove cam, the slide cam  43  may adopt a variety of shapes as long as having a cam face to guide the stapling unit  26  in a predetermined stroke direction, such as a projection stripe rib member. 
     The stapling unit  26  is engaged with the travel guide rail  42  and the slide cam  43  as follows. As illustrated in  FIG. 7 , the stapling unit  26  is provided with a first rolling roller (rail fitting member)  50  that is engaged with the travel rail face  42   x  and a second rolling roller (cam follower member)  51  that is engaged with the travel cam face  43   x . Further, the stapling unit  26  is provided with a sliding roller  52  that is engaged with a support face of the bottom frame  20   e . The illustrated stapling unit  26  includes two ball-shaped sliding rollers  52   a ,  52   b  at two positions thereof. Further, a guide roller  53  that is engaged with a bottom face of the bottom frame  20   e  is formed at the stapling unit  26  to prevent the stapling unit  26  floating from the bottom frame  20   e.    
     According to the above structure, the stapling unit  26  is supported by the bottom frame  20   e  movably via the sliding rollers  52   a ,  52   b  and the guide roller  53 . Further, the first rolling roller  50  and the second rolling roller  51  are rotated and moved along the travel rail face  42   x  and the travel cam face  43   x  respectively as following the travel rail face  42   x  and the travel cam face  43   x  respectively. 
     The travel rail face  42   x  and the travel cam face  43   x  are arranged so that the parallel distance sections (having the span G1) are arranged at the position  43   a  corresponding to the abovementioned multi-binding positions Ma1, Ma2 and the position  43   b  corresponding to the manual binding position Mp. With the span G1, the stapling unit  26  is maintained in a posture as being perpendicular to a sheet end edge without being slant, as illustrated in  FIGS. 9 and 10C . Accordingly, at the multi-binding positions Ma1, Ma2 and the manual binding position Mp, a sheet bundle is bound with a staple being in parallel to a sheet end edge. 
     Further, the travel rail face  42   x  and the travel cam face  43   x  are arranged so that the slant distance sections (having the span G2) are arranged at the position  43   c  corresponding to the right corner binding position Cp1 and the position  43   d  corresponding to the left corner binding position Cp2. The stapling unit  26  is maintained in a rightward-angled posture (for example, rightward-angled by 45 degrees) or in a leftward-angled posture (for example, leftward-angled by 45 degrees), as illustrated in  FIGS. 9 and 10A . 
     Further, the travel rail face  42   x  and the travel cam face  43   x  are arranged so that the slant distance section (having the span G3) is arranged at the position  43   e  corresponding to a position for staple loading. The span G3 is formed to be shorter than the span G2. In this state, the stapling unit  26  is maintained in a rightward-angled posture (for example, rightward-angled by 60 degrees) as illustrated in  FIG. 10B . The reason why the angular posture of the stapling unit  26  is varied at the staple loading position is that the posture is matched with an angular direction in which the staple cartridge  39  is mounted thereon. Here, the angle is set in relation with the open-close cover arranged at the external casing  20   b.    
     For varying the angular posture of the stapling unit  26  using the travel rail face  42   x  and the travel cam face  43   x , it is preferable from a viewpoint of layout compactification to arrange a second travel cam face or a stopper cam face for angle varying in cooperation with the travel cam face  43   x.    
     Next, the stopper cam face will be described with reference to  FIG. 8 . As illustrated in  FIG. 8 , stopper faces  43   y ,  43   z  to be engaged with apart of the stapling unit  26  (in the drawing, the sliding roller  52   a ) are arranged at the side frame  20   e  to vary a posture of the stapling unit between the right corner binding position Cp1 and the manual binding position Mp at the apparatus front side. The stapling unit  26  inclined at the staple loading position is required to be corrected in inclination at the manual binding position Mp. When the angle is varied only by the travel rail face  42   x  and the travel cam face  43   x , the movement distance becomes long. 
     When the stapling unit  26  is moved toward the manual binding position Mp in a state of being locked by the stopper face  43   y , the inclination of the stapling unit  26  is corrected. Further, when the stapling unit  26  is returned to the opposite direction from the manual binding position Mp, the stapling unit  26  is (forcedly) inclined to face toward the corner binding position Cp1 by the stopper face  43   z.    
     [Stapling Unit] 
     The stapling unit  26  has been widely known as means to perform a binding process using a staple. An example thereof will be described with reference to  FIG. 13A . The stapling unit  26  is structured as a unit separated from the sheet bundle binding processing apparatus (post-processing apparatus B). The stapling unit  26  includes a box-shaped unit frame  26   a , a drive cam  26   d  swingably axis-supported by the unit frame  26   a , and a drive motor M 8  mounted on the unit frame  26   a  to rotate the drive cam  26   d.    
     The stapling head  26   b  and the anvil member  26   c  are arranged at a binding position as being mutually opposed. The stapling head  26   b  is vertically moved between a waiting position at the upper side and a stapling position at the lower side (the anvil member  26   c ) with the drive cam  26   d  and an urging spring (not illustrated). Further, the staple cartridge  39  is mounted on the unit frame  26   a  in a detachably attachable manner. 
     Linear blank staples are stored in the staple cartridge  39  and fed to the head portion  26   b  by a staple feeding mechanism. A former member to fold a linear staple into a U-shape and a driver to cause the folded staple to bite into a sheet bundle are built in the head portion  26   b . With such a structure, the drive cam  26   d  is rotated by the drive motor M 8  and energy is stored in the urging spring. When the rotational angle reaches a predetermined angle, the head portion  26   b  is vigorously lowered toward the anvil member  26   c . Owing to this action, a staple is caused to bite into a sheet bundle with the driver after being folded into a U-shape. Then, leading ends of the staple are folded by the anvil member  26   c , so that staple-binding is completed. 
     The staple feeding mechanism is built in between the staple cartridge  39  and the stapling head  26   b . A sensor (empty sensor) to detect staple absence is arranged at the staple feeding mechanism. Further, a cartridge sensor (not illustrated) to detect whether or not the staple cartridge  39  is inserted is arranged at the unit frame  26   a.    
     The staple cartridge  39  adopts a structure that belt-shaped connected staples are stacked as being layered or are stored in a roll-shape in a box-shaped cartridge. 
     Further, a circuit to control the abovementioned sensors and a circuit board to control the drive motor M 8  are arranged at the unit frame  26   a  and transmit an alarm signal when the staple cartridge  39  is not mounted or the staple cartridge  39  is empty. Further, the stapling control circuit controls the drive motor M 8  to perform the stapling operation with a staple signal and transmits an operation completion signal when the stapling head  26   b  is moved to an anvil position from the waiting position and returned to the waiting position. 
     [Press Binding Unit] 
     A structure of the press binding unit  27  will be described based on  FIG. 13B . As a press binding mechanism, there have been known a fold-binding mechanism (see Japanese Patent Laid-open Application No. 2011-256008) to perform binding by forming cutout openings at a binding portion of a plurality of sheets and mating as folding a side of each sheet and a press binding mechanism to perform binding by pressure-bonding a sheet bundle with corrugated faces formed on pressurizing faces  27   b ,  27   c  which are capable of being mutually pressure-contacted and separated. 
       FIG. 13B  illustrates the press binding unit  27 . A movable frame member  27   d  is axis-supported by a base frame member  27   a  and both the frames are swung about a support shaft  27   x  as being capable of being mutually pressure-contacted and separated. A follower roller  27   f  is arranged at the movable frame member  27   b  and is engaged with a drive cam  27   e  arranged at the base frame  27   a.    
     A drive motor M 9  arranged at the base frame member  27   a  is connected to the drive cam  27   e  via a deceleration mechanism. Rotation of the drive motor M 9  causes the drive cam  27   e  to be rotated and the movable frame member  27   d  is swung by a cam face (eccentric cam in  FIG. 13B ) thereof. 
     The lower pressurizing face  27   c  and the upper pressurizing face  27   b  are arranged respectively at the based frame member  27   a  and the movable frame member  27   d  as being mutually opposed. An urging spring (not illustrated) is arranged between the base frame member  27   a  and the movable frame member  27   d  to urge both the pressurizing faces  27   a ,  27   d  in a direction to be separated. 
     As illustrated in an enlarged view of  FIG. 13B , convex stripes are formed on one of the upper pressurizing face  27   b  and the lower pressurizing face  27   c  and concave grooves to be matched therewith are formed on the other thereof. The convex stripes and the concave grooves are formed respectively into rib-shapes as having predetermined length. A sheet bundle nipped between the upper pressuring face  27   b  and the lower pressurizing face  27   c  is intimately contacted as being deformed into a corrugation shape. A position sensor (not illustrated) is arranged at the base frame member (unit frame)  27   a  and detects whether or not the upper and lower pressurizing faces  27   b ,  27   c  are at the pressurization positions or separated positions. 
     [Stack Tray] 
     A structure of the stack tray  25  will be described based on  FIG. 14 . The stack tray  25  is arranged at the downstream side of the processing tray  24 . A sheet bundle stacked on the processing tray  24  is stacked and stored onto the stack tray  25 . A tray lifting-lowering mechanism is arranged so that the stack tray  25  is sequentially lowered in accordance with a stacked amount thereon. Height of a stack face  25   a  of the stack tray  25  is controlled so that the upmost sheet thereon is to be approximately flush with the sheet placement face  24   a  of the processing tray  24 . Further, stacked sheets are inclined by an angle with a tailing end edge in the sheet discharging direction abutted to a tray aligning face  20   f  by gravity. 
     Specifically, a lifting-lowering rail  54  is vertically anchored in the stacking direction to the apparatus frame  20   a . A tray base body  25   x  is fitted to the lifting-lowering rail  54  as being capable of being lifted and lowered using a slide roller  55  or the like in a slidable manner. A rack  25   r  is formed in the lifting-lowering direction integrally with the tray base body  25   x . A drive pinion  56  axis-supported by the apparatus frame  20   a  is engaged with the rack  25   r . Then, a lifting-lowering motor M 10  is connected to the drive pinion  56  via a worm gear  56  and a worm wheel  58 . 
     Accordingly, when the lifting-lowering motor M 10  is rotated forwardly and reversely, the rack  25   r  connected to the drive pinion  56  is moved to the upper side and lower side of the apparatus frame  20   a . With the above structure, the tray base body  25   x  is lifted and lowered in a cantilevered state. Besides such a rack-pinion mechanism, the tray lifting-lowering mechanism may adopt a pulley-mounted belt mechanism or the like. 
     The stack tray  25  is integrally attached to the tray base body  25   x . Sheets are stacked and stored on the stack face  25   a  thereof. The tray alignment face  20   f  to support sheet tailing end edges is vertically formed in the sheet stacking direction. In  FIG. 14 , the tray alignment face  20   f  is formed with the apparatus casing. 
     Further, the stack tray  25  integrally attached to the tray base body  25   x  is arranged as being inclined in an angled direction as illustrated in  FIG. 14 . The angle (for example, 20 to 60 degrees) is set so that sheet tailing ends are abutted to the tray alignment face  20   f  by gravity. 
     [Sheet Holding Mechanism] 
     A sheet holding mechanism  53  to press the upmost stacked sheet is arranged at the stack tray  25 . The illustrated sheet holding mechanism includes an elastic pressing member  53   a  to press the upmost sheet, an axis-supporting member  53   b  to cause the elastic pressing member  53   a  to be rotatably axis-supported by the apparatus frame  20   a , a drive motor M 2  to rotate the axis-supporting member  53   b  by a predetermined angle, and a transmitting mechanism thereof. The drive motor M 2  is drive-connected to the drive motor of the sheet bundle discharging mechanism  60  as a drive source. When a sheet bundle is introduced (discharged) to the stack tray  25 , the elastic pressing member  53   a  is retracted to the outside of the stack tray  25 . After a tailing end of the sheet bundle is stored on the upmost sheet on the stack tray  25 , the elastic pressing member  53   a  is rotated counterclockwise from the waiting position and presses the upmost sheet as being engaged therewith. 
     Then, owing to an initial rotational operation of the drive motor M 2  to discharge a sheet bundle on the processing tray  24  toward the stack tray  25 , the elastic pressing member  53   a  is retracted from a sheet face of the upmost sheet on the stack tray  25  to the retracting position. 
     [Level Sensor] 
     A level sensor to detect a sheet height of the upmost sheet is arranged at the stack tray  25 . The lifting motor is rotated based on a detection signal of the level sensor, so that the tray sheet placement face  25   a  is lifted. A variety of mechanisms are known as the level sensor mechanism. In the drawing, the level sensor mechanism adopts a detection method to detect whether or not a sheet exists at the height position by emitting detection light from the tray alignment face  20   f  of the apparatus frame  20   a  to the tray upper side and detecting reflection light thereof. 
     [Stack Sheet Amount Sensor] 
     Similarly to the level sensor, a sensor to detect detaching of sheets from the stack tray  25  is arranged at the stack tray  25 . It is possible to detect whether or not sheets exists on the stack face, for example, by arranging a sensor lever which is rotated integrally with the elastic pressing member  53   a  of the sheet holding mechanism  53  and detecting the sensor lever with a sensor element. Here, detailed description on the structure thereof is skipped. When the height position of the sensor lever becomes different (varied) between before and after discharging of a sheet bundle, the later-mentioned binding process controller  75  stops the sheet discharging operation or lifts the stack tray  25  to a predetermined position, for example. Such an operation is performed in an abnormal case, for example, in a case that a user carelessly removes sheets from the stack tray  25  during apparatus operation. Further, a lower limit position is defined for the stack tray  25  not to be lowered abnormally. A limit sensor Se 3  to detect the stack tray  25  is arranged at the lower limit position. 
     [Image Forming System] 
     As illustrated in  FIG. 1 , the image forming unit A includes a sheet feeding portion  1 , an image forming portion  2 , a sheet discharging portion  3 , and a signal processing portion (not illustrated) as being built in an apparatus housing  4 . The sheet feeding portion  1  includes a cassette  5  in which sheets are stored. In  FIG. 1 , the sheet feeding portion  1  includes a plurality of the cassettes  5   a ,  5   b ,  5   c  to be capable of storing sheets having different sizes. Each of the cassettes  5   a ,  5   b ,  5   c  incorporates a sheet feeding roller  6  to feed a sheet and a separating device (a separating pawl, a separating roller, or the like) to separates sheets one by one. 
     Further, a sheet feeding path  7  is arranged at the sheet feeding portion  1  for feeding a sheet from each cassette  5  to the image forming portion  2 . A pair of resist rollers  8  are arranged at an end of the sheet feeding path  7 , so that a sheet fed from each cassette  5  is aligned at a leading end thereof and caused to wait to be fed in accordance with image forming timing of the image forming portion  2 . 
     Thus, the sheet feeding portion  1  includes a plurality of cassettes in accordance with apparatus specifications and feeds a sheet of a size selected by a controller to the image forming portion  2  at the downstream side. Each cassette  5  is mounted on the apparatus housing  4  in a detachably attachable manner to be capable of replenishing sheets. 
     The image forming portion  2  may adopt one of various image forming mechanisms to form an image on a sheet.  FIG. 1  illustrates an electrostatic image forming mechanism. As illustrated in  FIG. 1 , a plurality of drums  9   a  to  9   d  each including a photo conductor in accordance with color elements are arranged at the apparatus housing  4 . A light emitter (laser head or the like)  10  and a developer  11  are arranged at each of the drums  9   a  to  9   d . A latent image (electrostatic image) is formed by the light emitter  10  at each of the drums  9   a  to  9   d  and toner ink is caused to adhere thereto by the developer  11 . The ink images adhering on the respective drums  9   a  to  9   d  are superimposed to be an image as being transferred on a transfer belt  12  with respect to the respective color elements. 
     The transferred image formed on the transfer belt  12  is transferred by a charger  13  onto a sheet fed from the sheet feeding portion  1  and fixed by a fixing device (heating roller)  14 , and then, is fed to the sheet discharging portion  3 . 
     The sheet discharging portion  3  includes the sheet discharging port  16  to discharge a sheet to the sheet discharging space  15  formed in the apparatus housing  4  and a sheet discharging path  17  to guide the sheet from the image forming portion  2  to the sheet discharging port  16 . A later-mentioned duplex path  18  is continuously arranged at the sheet discharging portion  3 , so that a sheet having an image formed on the front face thereof is re-fed to the image forming portion  2  after being face-reversed. 
     The sheet having an image formed on the front face thereof by the image forming portion  2  is face-reversed and re-fed to the image forming portion  2  through the duplex path  18 . The sheet is discharged from the sheet discharging port  16  after an image is formed on the back face by the image forming portion  2 . The duplex path  18  includes a switchback path to re-feed a sheet fed from the image forming portion  2  in the apparatus as inverting the conveying direction thereof and a U-turn path  18   a  to face-reverse the sheet re-fed into the apparatus. In the illustrated apparatus, the switchback path is formed on the sheet discharging path of the later-mentioned post-processing unit B. 
     [Image Reading Unit] 
     The image reading unit C includes a platen  19   a  and a reading carriage  19   b  which reciprocates along the platen  19   a . The platen  19   a  is formed of transparent glass and includes a still image reading face to scan a still image with movement of the reading carriage  19   b  and a travel image reading face to read a document image travelling at a predetermined speed. 
     The reading carriage  19   b  includes a light source lamp, a reflection mirror to polarize reflection light from a document, and a photoelectric conversion element (not illustrated). The photoelectric conversion element includes line sensors arranged in the document width direction (main scanning direction) on the platen  19   a . The reading carriage  19   b  reciprocates in a sub scanning direction being perpendicular thereto, so that a document image is to be read in line order. Further, an automatic document feeding unit D to cause a document to travel at a predetermined speed is arranged above the travel image reading face of the platen  19   a . The automatic document feeding unit D includes a feeding mechanism to feed document sheets set on a sheet feeding tray to the platen  19   a  one by one and to store each document sheet in a sheet discharging tray after each image is read. 
     [Description of Control Configuration] 
     A control configuration of the abovementioned image forming system will be described with reference to a block diagram in  FIG. 16 . The image forming system illustrated in  FIG. 16  includes a controller (hereinafter, called a main body controller)  70  for the image forming unit A and a binding process controller  75  being a controller for the post-processing unit B (sheet bundle binding processing apparatus, as the case may be). The main body controller  70  includes a print controller  71 , sheet feeding controller  72 , and an input portion (control panel)  73 . 
     Setting of an image forming mode and a post-processing mode is performed with the input portion (control panel)  73 . The image forming mode requires setting of mode setting such as color/monochrome printing and double-face/single face printing, and image forming conditions such as a sheet size, sheet quality, the number of copies, and enlarged/reduced printing. The post-processing mode is required to be set, for example, into a printout mode, a staple-binding processing mode, an eco-binding processing mode, or a jog sorting mode. Further, the illustrated apparatus includes a manual binding mode. In this mode, operation of a sheet bundle binding process is performed offline as being separate from the main body controller  70  for the image forming unit A. 
     The main body controller  70  transfers, to the binding process controller  75 , selection of the post-processing mode and data such as the number of sheets, the number of copies, and thickness of sheets on which images are formed. Further, the main body controller  70  transfers a job completion signal to the binding process controller  75  each time when image forming is completed. 
     The post-processing mode will be described in the following. In the printout mode, a sheet from the sheet discharging port  23  is stored at the stack tray  25  via the processing tray  24  without a binding process performed. In this case, sheets are overlapped and stacked on the processing tray  24  and a stacked sheet bundle is discharged to the stack tray  25  with a jog completion signal from the main body controller  70 . 
     In the staple-binding processing mode (second sheet discharging mode), sheets from the sheet discharging port  23  are stacked and collated on the processing tray  24  and the sheet bundle is stored on the stack tray  25  after the binding process is performed thereon. In this case, sheets on which images are to be formed are specified by an operator basically to have the same thickness and size. In the staple-binding processing mode, any of the multi-binding, right corner binding, and left corner binding is selected and specified. The binding positions thereof are as described above. 
     In the jog sorting mode, sheets are divided into a group whose sheets having images formed at the image forming unit A are offset and stacked on the processing tray  24  and a group whose sheets are stacked thereon without being offset. An offset sheet bundle and a non-offset sheet bundle are alternately stacked on the stack tray  25 . In the illustrated apparatus, an offset area (see  FIG. 5 ) is arranged. Then, sheets discharged from the sheet discharging port  23  onto the processing tray  24  in center reference Sx are divided into a group whose sheets are stacked as maintaining the above posture and a group whose sheets are stacked as being offset to the apparatus front side Fr by a predetermined amount. 
     The reason why the offset area is arranged at the apparatus front side Fr is to maintain an operational area at the apparatus front side Fr for the manual binding process, a replacing process of a staple cartridge, and the like. The offset area is set to have dimensions (in the order of several centimeters) to divide sheet bundles. 
     [Manual Binding Mode] 
     The manual setting portion  29  where an operator sets a sheet bundle on which the binding process is to be performed is arranged at the apparatus front side Fr of the external casing  20   b . A sensor to detect a set sheet bundle is arranged at the manual setting face  29   a  of the manual setting portion  29 . With a signal from the sensor, the later-mentioned binding process controller  75  moves the stapling unit  26  to the manual binding position. Subsequently, when an operation switch  30  is depressed by an operator, the binding process is performed. 
     Thus, in the manual binding mode, the binding process controller  75  and the main body controller  70  perform controlling offline. Here, in a case that the manual binding mode and the staple-binding mode are to be performed concurrently, either mode is set to have priority. 
     [Binding Process Controller] 
     The binding process controller  75  causes the post-processing unit B to operate in accordance with the post-processing mode set by the image forming controller  70 . The illustrated binding process controller  75  is structured with a control CPU as including a ROM  76  and a RAM  77 . The later-mentioned post-processing operation is performed with control programs stored in the ROM  76  and control data stored in the RAM  77 . Here, drive circuits for all the abovementioned drive motors are connected to the control CPU  75 , so that start, stop, and forward-reverse rotation of the motors are controlled thereby. 
     [Description of Post-Processing Operation] 
     In the following, operational states of the respective binding processes will be described with reference to  FIGS. 17 to 20 . For convenience of description, “a paddle” denotes sheet introducing device (paddle rotor  36  or the like), “a roulette” denotes a raking rotor  33 , “an aligning plate” denotes a side aligning member  45 , “assists” denote the first and second conveying members  60 A,  60 B, “a button” denotes an operation switch of a stapling device, and “an LED” denotes an indication lamp indicating that a stapling operation is running. 
     [Stapling Mode] 
     In  FIG. 17 , an image is formed on a final sheet for image forming and the final sheet is discharged from an image forming unit main body at the upper side (St 01 ). At that time, a job end signal is transmitted from the image forming unit and the binding process controller  75  causes the paddle  36  to position and wait at a predetermined position (waiting of paddle vanes) (St 02 ). At the same time, the right-left aligning plates  46 R,  46 F are moved to waiting positions (St 03 ). A sheet fed from the sheet discharging port  16  of the image forming unit A is introduced from the introducing port  21  of the sheet introducing path (sheet discharging path)  22 . Then, discharging of the sheet tailing end by the sheet discharging roller  32  is detected by the sheet sensor Set (St 04 ). 
     The binding process controller  75  lowers the paddle  36  waiting on the processing tray  24  at the time when the sheet tailing end is separated from the sheet discharging roller  32  (St 05 ). This operation is performed by activating the lifting-lowering motor M 5 . Concurrently with the paddle lowering operation, the binding process controller  75  lifts the roulette  33  to be retracted above the upmost sheet on the processing tray  24  (St 08 ). 
     With the above operation, the sheet fed from the image forming unit A is fed to the sheet introducing path  22 , and after the sheet tailing end passes through the sheet discharging roller  32 , the sheet is reversely conveyed by rotating the paddle  36  in the direction opposite to the sheet discharging direction in a state that the roulette  33  is retracted above the processing tray  24 . Thus, the sheet fed to the sheet introducing path  22  is stored on the processing tray  24  below the sheet discharging port  23  with the conveying direction thereof reversed at the sheet discharging port  23 . 
     Next, the binding process controller  75  lifts the paddle  36  to be retracted from the sheet when a predetermined time passes after the sheet is reversely conveyed from the sheet discharging port  23  in the direction opposite to the sheet discharging direction (St 06 ). Concurrently with the above, the roulette  33  rotating in the direction opposite to the sheet discharging direction is lowered from the waiting position and engaged with the sheet introduced onto the processing tray  24  (St 09 ). 
     According to the above operation, the sheet is fed from the sheet discharging port  23  by the sheet discharging roller  32  and introduced onto the processing tray  24  as being reversely conveyed from the sheet discharging port  23  by the paddle  36  in the direction opposite to the sheet discharging direction. Then, the sheet is fed toward a predetermined position (toward the tailing end regulating member  41 ) of the processing tray  24  by the roulette  33 . In the above sheet discharging operation, sheets having different sizes are discharged from the sheet discharging port  23  in center reference Sx. It is also possible to perform discharging from the sheet discharging port  23  in side reference. Here, for convenience, description is performed on a case of discharging in center reference Sx. 
     Next, the binding process controller  75  moves the paddle  36  to a home position (HP) at the time when the railing end of the sheet introduced onto the processing tray  24  is assumed to be abutted to the tailing end regulating stopper (tailing end regulating member)  41  with reference to a detection signal of the sheet discharging sensor Se 2  (St 07 ). Similarly, the roulette  33  is moved to a home position HP (St 10 ). 
     Next, the binding process controller  75  causes the aligning device  45  to bias and align the sheet in a state that the tailing end thereof is abutted to the tailing end regulating member  41 . The aligning operation differentiates sheet alignment positions between a case that the multi-binding mode is specified and a case that the corner binding mode is specified. When the multi-binding mode is specified, the binding process controller  75  causes the right-left side aligning members  46 F,  46 R to reciprocate (center alignment) between alignment positions where the sheet introduced onto the processing tray  24  is matched with a size width in discharging sheet reference (center reference Sx in the drawing) and waiting positions separated outward therefrom. That is, the binding process controller  75  biases and aligns the sheet by causing the side aligning members  46 F,  46 R to move from the waiting positions being wider than the size width to the alignment positions being matched with the size width based on size information sent from the image forming unit A (St 11  to St 13 ). 
     When the corner binding mode is specified, the binding process controller  75  causes one of the right-left aligning members  46 F,  46 R at a binding position side to move to and stop at the binding position based on size information and to move the other thereof to move to an alignment position from a waiting position retracting therefrom based on the size width of the sheet introduced to the processing tray  24 . The alignment position (of the aligning member at the movable side) is set to have a distance against the alignment position (of the aligning member at the binding position side) to be matched with the size width (corner binding position alignment). That is, in the corner binding process, one of the side aligning members  46 F,  46 R is moved and kept stopped at the specified binding position being right or left, and then, the other thereof is moved by an amount being matched to the size width after the sheet is introduced to the processing tray  24  to perform aligning (in side reference) (St 14  to St 16 ). 
     Next, the binding process controller  75  performs the binding operation (St 17 ). In the multi-binding, the stapling unit  26  previously staying at the binding position is activated to perform the binding process thereat, and then, the binding process is performed at the second binding position after the stapling unit  26  is moved by a predetermined distance along the sheet tailing end edge (St 18  to St 20 ). In the corner binding, the stapling unit  26  previously staying at the binding position is activated and the binding process is performed thereat. 
     Next, when an operation completion signal is received from the stapling unit  26 , the binding process controller  75  causes the sheet bundle discharging device  60  to operate to discharge the sheet bundle from the processing tray  24  toward the stack tray  25  at the downstream side (St 21 ). When the sheet bundle discharging operation is completed, the binding process controller  75  moves the sheet bundle discharging device  60  to return to the initial position (St 22 ). Concurrently with the above, the aligning device  46  is moved to return to the initial position (the waiting position to introduce a sheet to the processing tray  24 ) (St 23 ). 
     Further, the binding process controller  75  causes the drive motor (in the drawing, the drive motor M 2  commonly used for the paddle rotor  36 ) to rotate the bundle holding device (elastic holding member)  53  arranged on the stack tray  25  (St 24 ), so that the upmost sheet of the sheet bundle introduced to the stack tray  25  is pressed and held (St 25 ). 
     [Eco-Binding Mode] 
     In the eco-binding operation, the binding process controller  75  performs the operation from step St 1  to step St 10  in which the sheet introduced onto the processing tray  24  is positioned as being abutted to the tailing end regulating member  41  as being similar to the abovementioned operation. Here, description of the above is skipped with the same reference provided. 
     When the eco-binding process is specified, the binding process controller  75  causes the left side aligning member  46 R located at the binding unit side to move to an alignment position (eco-alignment position Ap2) being close to the eco-binding position Ep and to wait in a state of staying thereat (St 26 ). Concurrently with this operation, the binding process controller  75  causes a sheet bundle guide to move from a retracting position above the processing tray  24  to an operating position on the processing tray  24  (St 27 ). In the drawing, the shifting of the sheet bundle guide is performed so that the height position of a guide face is moved from the retracting position being a high position to the operating position being a low position as being synchronized with movement of the stapling unit  26 . That is, the binding process controller  75  causes the stapling unit  26  to move from a predetermined position (home position) to a position to be engaged with the sheet bundle guide. In this application, the stapling unit  26  is arranged to be engaged with the sheet bundle guide when located at a position Gp in  FIG. 5  between Ma2 (the left multi-binding position) and Cp2 (the left corner binding position). 
     Subsequently, the binding process controller  75  causes the right side aligning member  46 F at the opposite side to move to a waiting position distanced from a side edge of the sheet introduced onto the processing tray  24  (St 28 ). Then, the right side aligning member  46 F is moved to an alignment position as driving the aligning motor (St 29 ). The alignment position is set to a position so that a distance against the left side aligning member  46 R staying at the eco-alignment position is matched with the sheet width size. 
     Thus, the present invention has a feature that a sheet introduced onto the processing tray  24  is aligned for eco-binding to the eco-alignment position Ap2 being apart from the binding position without being aligned at the binding position. When the sheet from the sheet discharging port  23  is set in sheet discharging reference (for example, center reference), the eco-alignment position Ap2 becomes the same as the alignment position in the multi-binding process. When the eco-alignment position Ap2 is set at a position being close to the eco-binding position Ep, the sheet is prevented from being interfered with the press binding unit  27  as preventing sheet jamming when being aligned. Further, after the alignment, it is possible to shorten a distance of moving the sheet bundle to the eco-binding position Ep. Accordingly, it is preferable that the eco-alignment position Ap2 is set to a close position to the extent possible within a range in which the sheet is not interfered with the press binding unit  27 . 
     Next, the binding process controller  75  causes the side aligning member  46  to offset-move the sheet bundle aligned at the eco-alignment position Ap2 to the eco-binding position Ep (St 30 ). Then, the side aligning member  46 F at the apparatus front side is retracted to be apart from the sheet by a predetermined amount (St 31 ). Then, the aligning device  45  drives the sheet bundle conveying device  60  so that the sheet bundle is moved downward in the sheet discharging direction by a predetermined amount (St 32 ). Concurrently with the above, the stapling unit  26  is moved to the initial position and the sheet bundle guide (not illustrated) is kept waiting at the retracting position above the processing tray  24  (St 33 ). Next, the binding process controller  75  causes the right side aligning member  46 F to move to the home position (St 34 ). 
     The controller  75  transmits a command signal to the non-staple binding device (press binding unit)  27  to cause the binding process operation to be performed (St 35 ). Then, the controller  75  operates a taking-off device structured with the side aligning member  46 R (at the apparatus rear side) at the eco-binding position side. As the operation of the taking-off device, first, the side aligning member  46 R is moved to a back-swing position by an overrun amount (see  FIGS. 15C and 15D ) being separated from a position for engaging with the sheet side edge. The back-swing amount is determined in consideration of a rising time (self-exciting time) of the aligning motor M 6 . That is, the overrun amount is determined in consideration of a rising time in which the aligning motor M 6  provides a predetermined output torque as providing running time to the aligning member  46 R (taking-off device). Here, the back-swing motion can be performed during an operation to separate the upper pressurizing face  27   b  and the lower pressurizing face  27   c  after the binding process is performed. 
     When a process end signal is received from the press binding unit  27 , the binding process controller  75  causes the left side aligning member  46 R to move toward the sheet center by a predetermined amount by driving the aligning motor for the left side alignment member. According to this operation, the sheet bundle pressure-nipped by the press binding unit  27  is taken off and offset to the sheet center side by being kicked to the sheet center side from a state of being intimately contacted to the corrugation-shaped pressurizing faces  27   b ,  27   c  (St 37 ). 
     The kicker mechanism (taking-off device) will be described in the following. 
     (1) The kick direction (the direction in which a conveyance force is applied to sheets, hereinafter being the same) of the left side aligning member  46 R (taking-off device) is preferably the same as the strip direction (rib direction) of the pressurizing faces or a direction being slightly inclined (for example, approximately by 0 to 30 degrees) to either side with reference thereto. When a conveyance force is applied in a direction of arrow z in  FIG. 15F  (a direction perpendicular to the rib), the sheet bundle is likely to be unbound with the binding released. When a conveyance force is applied in a direction of arrow w in  FIG. 15F , the sheet bundle is likely to be taken off from the pressurizing faces  27   b ,  27   c  while the sheet bundle is kept bound. The angular direction is determined by experiment. In experiments of the inventors, it is preferable that the direction is set in a range between −30 degrees to 30 degrees with the reference of the rib direction. 
     (2) The taking-off device  46 R adopts a mechanism to push (feed) an end edge of a binding-processed sheet bundle toward the sheet center side. For example, as illustrated, the taking-off device is structured with the left side aligning member  46 R (the right side aligning member  46 F in a case of right corner binding) to bias and align sheets on the processing tray (in a direction perpendicular to the sheet discharging direction). Thus, it is preferable to adopt a conveying mechanism to apply a force to the entire sheet bundle in a direction for taking-off when the bound sheet bundle is to be taken off from the pressurizing faces  27   b ,  27   c . Here, if the aligning member  46 F at the opposite side is moved to the sheet center side at the same time when the aligning member  46 R is engaged with a sheet side edge after back-swinging, bound sheets are to be taken off from the binding device  27  in a state of being nipped. Accordingly, it is possible to suppress variation of sheets when being taken off. The bound sheets are guided by the sheet bundle discharging device  60  (more specifically, the first conveying member  61  in  FIG. 11 ) during the taking-off operation of the aligning member  46 R, so that shaking of the sheets can be prevented. Further, when the bound sheets are moved to the apparatus front side (in the vicinity of the alignment position Ap1 in  FIG. 5 ) or the eco-alignment position Ap2 after the taking-off operation, the bound sheets can be easily taken out. 
     On the other hand, when a sheet bundle is discharged by a nipping roller in the kick direction from the upper face of the sheet bundle, there occurs a problem that only a sheet contacting the nipping roller is taken off and the binding is released. 
     (3) It is possible for the taking-off device to adopt a floating mechanism to float a bottom face of a sheet bundle from the pressurizing faces of the binder mechanism concurrently with applying a kick force in a direction to separate the bound sheet bundle (in a direction intersecting with the sheet discharging direction). For example, there are arranged a curved bottom piece  40  ( FIG. 13B ) to be engaged with the sheet bundle bottom face and an inclined cam face to protrude the curved bottom piece above the sheet placement face at the binding position (arranged at a back face of the processing tray or the like). In addition, a regulating face to be engaged with an end face of the sheet bundle on the sheet placement face is arranged at the side aligning member. 
     When the side aligning member  46 R (taking-off device) is located outside the sheet placement face (back-swing area), the curved bottom piece supports sheets at the same plane with the sheet placement face without receiving action of the inclined cam face. Subsequently, when the side aligning member is kick-moved toward the binding position, the curved bottom piece pushes up the sheet bundle. At the same time, the regulating face provides action to push out an end face of the sheet bundle toward the sheet leading end. That is, an operational member (bottom face supporting member) to push up the bound sheet bundle from the pressurizing face and an operational member (side face regulating member) to push out the sheet bundle end edge toward the sheet center are arranged as operating when the side aligning member  46 R is caused to perform kick operation toward the binding position. As a result, the sheet bundle can be taken off from the pressurizing faces more reliably. 
     That is, an operational member (bottom face supporting member) to push up the bound sheet bundle from the pressurizing faces  27   b ,  27   c  and an operational member (side face regulating member) to push out the sheet bundle end edge toward the sheet center are arranged as operating when the side aligning member  46 R is caused to perform kick operation toward the binding position. As a result, the sheet bundle can be taken off from the pressurizing faces more reliably. Further, owing to that the side aligning member  46 R is moved to the home position after the kicking operation, positional deviation and the like due to the pushing operation is prevented. Furthermore, owing to a spring member or the like which urges the side aligning member  46 F in the sheet width direction, the sheet bundle moved with the kicking operation is received. Accordingly, jumping of the sheet bundle and impact to the sheet bundle can be reduced. 
     [Printout Sheet Discharging] 
     Description will be performed based on  FIG. 19 . When a sheet is discharged from the image forming unit A (St 40 ), the sheet sensor detects a leading end thereof and the paddle rotor  36  is moved to the waiting position (St 41 ). Concurrently with the above, the side aligning members  46 F,  46 R are moved to the waiting positions (St 42 ). Next, when the sheet tailing end passes through the sheet discharging roller  32  (St 43 ), the binding process controller  75  lowers the paddle rotor  36  to the operating position (St 44 ). Along with the above, the roulette rotor  33  is lifted to be retracted (St 45 ). 
     When a predetermined time passes after the sheet tailing end passes through the sheet discharging roller  32 , the binding process controller  75  lifts and moves the paddle rotor  36  to the retracting position (St 46 ). Along with the above, the roulette rotor  33  is lowered to the operating position and feeds the sheet toward the tailing end regulating member  41  (St 47 ). The binding process controller  75  moves the paddle rotor  36  to the home position at the time when the sheet tailing end is assumed to reach the tailing end regulating member  41  (St 48 ). Further, the roulette rotor  33  is lifted to the home position (St 49 ). 
     Then, the binding process controller  75  causes the side aligning member  45  to move to the alignment position and perform the aligning operation. In the aligning operation, sheets having different sizes are stacked in center reference and fed to the stack tray  25  with the subsequent sheet discharging operation. In the printout sheet discharging operation, a later-mentioned non-standard size sheet discharging operation is performed when a large size sheet is introduced onto the tray. 
     According to the binding process controller  75 , sheets are aligned and stacked on the processing tray  24  and the sheet bundle is discharged to the stack tray  25  at the downstream side. In the operation, the first conveying member  60 A of the sheet bundle discharging mechanism  60  is moved in the sheet discharging direction (St 50 ). Next, the tray sheet holding member  53  is moved to the waiting position (St 51 ). Then, the upmost sheet is pressed by rotating the tray sheet holding member  53  by a predetermined angle at the timing when the sheet bundle is introduced onto the stack tray  25  (St 52 ). Subsequently, the binding process controller  75  causes the side aligning member  45  to return to the sheet introducing position (St 53 ). 
     [Sort (Jog) Mode] 
     In a jog mode, approximately the same steps are performed as in the printout mode. Here, description thereof is skipped with the same reference provided to the same step. In the following, different steps will be described. Sheets introduced onto the processing tray  24  are stacked at different positions as being divided into a group whose sheets are aligned in center reference Sx and a group whose sheets are aligned in right side reference (St 54 ). Then, the sheets are conveyed to the stack tray  25  at the downstream side as maintaining posture thereof. Here, the processing tray  24  is arranged at a position deviated to the apparatus front side and some sheets are aligned in right side reference. Then, sheets in center reference and sheets in right side reference biased toward an operator are stacked on the sheet placement face  24   a . Accordingly, sheet bundles are easy to be removed from the stack tray  25 . 
     [Common Operation in Respective Modes] 
     In the following, operation for introducing a sheet onto the processing tray  24  commonly performed in the abovementioned respective post-processing modes will be described with reference to  FIG. 21 . When a sheet is discharged from the image forming unit A (St 60 ), the binding process controller  75  causes, with a leading end detection signal from the sheet sensor Set, the paddle rotor  36  to be positioned at the waiting position (St 61 ) and the predetermined aligning member  45  to be moved to the waiting position (St 62 ). In this operation, the aligning member  45  is positioned at the waiting position to have a width size being slightly larger than the sheet size based on the sheet size signal sent from the image forming unit A. 
     Next, at the timing when the sheet tailing end passes through the sheet discharging roller  32  (St 63 ), the binding process controller  75  causes the paddle rotor  36  to be lowered from the waiting position at the upper side to the operating position at the lower side (St 64 ). Along with the above, the roulette rotor  34  is lowered from the waiting position above the sheet placement face  24   a  to the operating position on the sheet placement face  24   a  (St 68 ). At that time, both of the paddle rotor  36  and the roulette rotor  34  are rotated in the direction opposite to the sheet discharging direction. 
     When a predetermined time (assumed time for the sheet tailing end to reach the position of the roulette rotor  34 ) passes, the binding process controller  75  causes the paddle rotor  36  to be lifted from the operating position to the waiting position (St 65 ). When a predetermined time (assumed time for the sheet leading end to reach the tailing end regulating member), the binding process controller  75  causes the roulette rotor  36  to be lifted by a small amount (St 69 ). The lifting amount of the paddle rotor is previously set by experiment to reduce a pressing force against a sheet. 
     Next, the binding process controller  75  causes the side aligning member  45  to move to the alignment position (St 70 ). The alignment position is set to a different position in each binding processing mode, so that sheets are stacked at the abovementioned reference position in each mode, as described above. 
     (1) For multi-binding in the staple-binding processing mode, sheets introduced onto the processing tray  24  are aligned in center reference. For right corner binding, sheets introduced onto the processing tray  24  are aligned in right side reference Ap1. For left corner binding, sheets introduced onto the processing tray  24  are aligned in left side reference Ap2. In any case of the above, the stapling unit  26  is prepared for the subsequent binding process operation as waiting at the binding position. 
     (2) In the eco-binding processing mode, the binding process controller  75  causes sheets to be aligned at the eco-binding alignment position Ap3 defined at a position biased toward the sheet center from the eco-binding position or to be aligned in center reference. 
     (3) In the printout mode, the binding process controller  75  causes sheets to be aligned in center reference. 
     (4) In the jog processing mode, the binding process controller  75  causes the group being aligned in center reference and the group being aligned in right side reference to be alternately aligned in a repeated manner and to be discharged to the stack tray  25  as maintaining posture thereof. 
     Next, after the abovementioned aligning operation is completed, the binding process controller  75  causes the side aligning member  45  to move to the initial position (St 71 ), and then, the roulette rotor  34  to be lowered in a direction to press sheets (St 72 ). Along with the above, the binding process controller  75  causes the paddle rotor  36  to be lifted to the waiting position as the home position and to stay thereat (St 73 ). 
     [Manual Binding Operation] 
     The manual binding operation will be described with reference to a flowchart in  FIG. 22 . A sheet presence-absence sensor Sm is arranged at the manual feeding portion. When the sheet presence-absence sensor Sm detects sheets, the binding process controller  75  causes the staple binding operation to be performed. 
     The binding process controller  75  determines whether or not the stapling unit  26  is performing the binding process operation while the sensor Sm indicates an ON signal (St 80 ). In a case of determining that the binding process operation can be interrupted, the stapling unit  26  is moved to the manual binding position Mp (is kept staying when the staling unit  26  is at the binding position) (St 81 ). Then, an LED lamp is turned on to indicate that manual operation is running (St 82 ). 
     Next, after confirming that the sensor Sm is ON (St 83 ), the binding process controller  75  determines whether or not the operation button  30  is operated (St 84 ). When the sensor Sm is ON or when a predetermined time passes (St 85 ) after the LED lamp is turn on (in the drawing, the time is set to two seconds) even if the sensor Sm is OFF, the LED lamp is turned on again (St 86 ). Then, after confirming that the sensor Sm is ON (St 87 ), the binding process controller  75  further determines whether or not a predetermined time passes after the LED lamp is turned on. Then, the stapling operation is performed (St 88 ). 
     Subsequently, when the sensor Sm is in an ON state after the stapling operation is performed, the binding process controller  75  performs the stapling operation again as returning to a predetermined step. According to the above, the binding process can be performed on a plurality of positions of a sheet bundle. When the sensor Sm detects a sheet-absence state and the sheet absence state continues even after a predetermined time, the stapling unit  26  is returned to the home position as assuming that the sheets are removed for the setting face. Here, if the home position of the stapling unit  26  is set at the manual binding position, the stapling unit  26  stays thereat (St 93 ). 
     In the present invention, during preparation or operation of the printout process, the jog sorting process, or the non-staple binding process on the processing tray, the manual stapling operation is performed based on ON/OFF signals of the abovementioned sensor Sm. Further, during operation of the multi-binding operation or the corner binding operation on the processing tray, the manual operation can be performed when sheet stacking is in operation and a jog completion signal is not transmitted from the image forming unit A. Even if a jog completion signal is transmitted, the manual stapling operation is performed when an interruption process is instructed. 
     Thus, it is preferable for apparatus designing to adopt means that determines which has a priority between the manual stapling operation and stapling operation on the processing tray or that has an operator perform selection with a priority selection key. 
     As described above, in the present invention, the press binding unit  27  is arranged at the apparatus rear side Re of the processing tray  24 , and then, a sheet bundle is guided to the binding position (eco-binding position) Ep as follows. Sheets having different sizes are discharged from the sheet discharging path  22  to the processing tray  24  in center reference. Then, the sheets are aligned by the aligning device (side aligning member  46 ) with reference to a sheet side edge (side reference) adjacent to the eco-binding position Ep. Subsequently, the sheet bundle stacked at the aligning position Ap2 is moved to be set at the eco-binding position Ep. After the binding process is performed, the sheet bundle is conveyed toward the sheet center (backward conveying) and discharged. 
     In such a structure, the sheet alignment position on the processing tray  24  is set at the corner binding position Cp2 of the stapling unit  26  (so that the sheet side edge is matched therewith). According to the above, it is possible to select to perform staple binding on a sheet bundle aligned on the processing tray  24  or to perform eco-binding with a sheet bundle offset by a predetermined amount. Here, the sheet bundle aligned at the alignment position Ap2 is moved in the sheet discharging direction by a predetermined amount while being moved (offset) concurrently by a predetermined amount in the direction perpendicular to the sheet discharging direction, so that the sheet bundle is set to the eco-binding position Ep. 
     Further, the sheet bundle on which the binding process is performed on the eco-binding position Ep is discharged in the sheet discharging direction after being moved (offset back) toward the sheet center by a predetermined amount. Accordingly, the sheet bundle to be discharged is prevented from rubbing against the pressurizing faces  27   b ,  27   c  of the press binding unit  27 .