Abstract:
A sheet binding device includes a binding operation unit including a first tooth-shaped member that has plural arrayed teeth, a second tooth-shaped member that has plural arrayed teeth and binds sheets by biting the first tooth-shaped member to clamp the sheets in cooperation with the first tooth-shaped member, and a link structure that opens and closes the first tooth-shaped member and the second tooth-shaped member to perform a binding operation, and two side frames that are arranged to hold the binding operation unit therebetween and to support the binding operation unit on both sides of the binding operation unit.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2016-139807 filed Jul. 14, 2016, No. 2016-139808 filed Jul. 14, 2016, No. 2016-139809 filed Jul. 14, 2016, No. 2016-139810 filed Jul. 14, 2016, and No. 2016-221572 filed Nov. 14, 2016. 
       BACKGROUND 
     (i) Technical Field 
       [0002]    The present invention relates to a sheet binding device. 
       (ii) Related Art 
       [0003]    There is known a recording-material binding device in which plural stacked recording materials are joined together by being clamped, pressurized, and deformed in a wavy form by a pair of tooth-shaped members each having a tooth row. 
         [0004]    In the recording-material binding device, a binding operation unit is needed to cause two tooth-shaped members to bite each other for a binding operation. When recording materials are clamped and deformed by the tooth-shaped members, a reaction force of this operation acts on the binding operation unit. If the binding operation unit is supported only at one side surface, a structure for receiving the reaction force becomes large, and this increases the size of the recording-material binding device. 
       SUMMARY 
       [0005]    According to an aspect of the invention, there is provided a sheet binding device including a binding operation unit including a first tooth-shaped member that has plural arrayed teeth, a second tooth-shaped member that has plural arrayed teeth and binds sheets by biting the first tooth-shaped member to clamp the sheets in cooperation with the first tooth-shaped member, and a link structure that opens and closes the first tooth-shaped member and the second tooth-shaped member to perform a binding operation, and two side frames that are arranged to hold the binding operation unit therebetween and to support the binding operation unit on both sides of the binding operation unit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    An exemplary embodiment of the present invention will be described in detail based on the following figures, wherein: 
           [0007]      FIG. 1  is a schematic view illustrating a general configuration of an image forming system; 
           [0008]      FIG. 2  is a perspective view illustrating an outward appearance of a recording-material binding device; 
           [0009]      FIG. 3  is a perspective view illustrating an internal structure of the recording-material binding device; 
           [0010]      FIG. 4  is a perspective view illustrating the internal structure of the recording-material binding device; 
           [0011]      FIG. 5  is an exploded perspective view of the recording-material binding device; 
           [0012]      FIG. 6  is a perspective view illustrating a state in which a binding operation unit is separated from right and left side frames in the recording-material binding device; 
           [0013]      FIG. 7  is a perspective view of the binding operation unit in the recording-material binding device, when viewed from a different direction; 
           [0014]      FIG. 8  is a perspective view of a push-out spring; 
           [0015]      FIG. 9  is a perspective view of a support spring; 
           [0016]      FIG. 10  is an explanatory view of a binding operation, and illustrates a home position of the binding operation unit; 
           [0017]      FIG. 11  is an explanatory view of the binding operation, and illustrates a state in which upper and lower tooth-shaped members are slightly closed; 
           [0018]      FIG. 12  is an explanatory view of the binding operation, and illustrates a state immediately before the upper and lower tooth-shaped members bite each other; 
           [0019]      FIG. 13  is an explanatory view of the binding operation, and illustrates a state in which the upper and lower tooth-shaped members have bitten each other; 
           [0020]      FIG. 14  illustrates the positional relationship between an accumulation tray and the recording-material binding device; 
           [0021]      FIG. 15  illustrates a cross-sectional shape of a distal end wall of the accumulation tray; and 
           [0022]      FIG. 16  illustrates a comparative example of the positional relationship between the accumulation tray and the recording-material binding device. 
       
    
    
     DETAILED DESCRIPTION 
       [0023]    An exemplary embodiment of the present invention will be described below with reference to the drawings.  FIG. 1  is a schematic view illustrating a general configuration of an image forming system  11  including a recording-material binding device  10  according to the exemplary embodiment. The image forming system  11  includes an image forming apparatus  12  having a printing function and a copying function using, for example, electrophotography, and a recording-material post-processing apparatus  13  that conducts post processing, for example, punching and binding, on recording materials after images are formed thereon in the image forming apparatus  12 . The recording-material binding device  10  of the exemplary embodiment may be installed in the recording-material post-processing apparatus  13 . 
         [0024]    The image forming apparatus  12  includes an image forming section  14  that forms a toner image on the basis of acquired document information. The document information may be acquired by reading a document with a document reading unit  15  provided in the image forming apparatus  12 , or may be acquired from an external apparatus. The image forming apparatus  12  further includes a recording-material feeding mechanism  16 . Recording materials to be fed are recording materials having a predetermined shape, for example, sheet-like recording materials cut in a rectangular shape. The recording materials are made of, for example, paper. The recording-material feeding mechanism  16  includes supply trays  17  that hold stacked recording materials, and a transport path  19  through which the recording materials are transported from the supply trays  17  to an output port  18 . In a process of being transported through the transport path  19 , a recording material receives a toner image formed in the image forming section  14 , and the toner image is fixed thereon. The recording material sent out from the output port  18  is received by the recording-material post-processing apparatus  13 . 
         [0025]    In the recording-material post-processing apparatus  13 , received recording materials are stacked on an accumulation tray  20 , as required. When accumulation is unnecessary, the recording materials are output into an output tray  21 . When a predetermined number of recording materials are accumulated on the accumulation tray  20 , the recording materials are subjected to post processing such as punching and binding. The recording-material binding device  10  performs post processing for binding the recording materials. The recording-material binding device  10  includes a pair of two tooth-shaped members  22  and  24  in each of which plural teeth are arrayed. To distinguish the two tooth-shaped members, for convenience, the tooth-shaped member located on an upper side of  FIG. 1  is referred to as an upper tooth-shaped member  22 , and the tooth-shaped member located on a lower side of  FIG. 1  is referred to as a lower tooth-shaped member  24 . It is only required that the two tooth-shaped members  22  and  24  should be opposed to each other with recording materials to be bound being interposed therebetween, and, for example, the tooth-shaped members may be arranged in the right-left direction. 
         [0026]    Both or one of the upper tooth-shaped member  22  and the lower tooth-shaped member  24  is advanced or retreated relative to the other tooth-shaped member by a driving mechanism. When both or one of the upper tooth-shaped member  22  and the lower tooth-shaped member  24  advances, the upper tooth-shaped member  22  and the lower tooth-shaped member  24  bite each other. When the upper tooth-shaped member  22  and the lower tooth-shaped member  24  bite each other, recording materials clamped therebetween are deformed in a wavy form, joined, and bound. After bound, a bundle of the recording materials is output to the output tray  21 . 
         [0027]    The image forming system  11  further includes a controller  25  that controls operations of parts and mechanisms in the image forming apparatus  12  and the recording-material post-processing apparatus  13 . The controller  25  acquires a request from the user, and controls the operations of the parts of the image forming system  11  according to the request. 
         [0028]      FIG. 2  is a perspective view illustrating an outward appearance of the recording-material binding device  10 . The recording-material binding device  10  has an outer shape like a substantially rectangular parallelepiped. For plain explanation, front-rear, up-down, and right-left directions orthogonal to one another are determined in accordance with extending directions of sides of the rectangular parallelepiped. The up-down direction nearly coincides with a direction in which the upper tooth-shaped member  22  and the lower tooth-shaped member  24  are opposed to each other, and the front-rear direction nearly coincides with an extending direction of an upper arm  26  and a lower arm  28  (see  FIG. 3 ) to which the upper tooth-shaped member  22  and the lower tooth-shaped member  24  are respectively attached. The upper tooth-shaped member  22  and the lower tooth-shaped member  24  are disposed in an upper front corner region  38  near a corner of the rectangular parallelepiped that defines the outer shape of the recording-material binding device  10  where a device upper surface  32  and a device front surface  36  intersect. The device upper surface  32  is defined by an upper surface plate  30   a  of an upper frame  30  of the rectangular parallelepiped, and the device front surface  36  is defined by a front surface plate  34   a  of a front frame  34  of the rectangular parallelepiped. In this upper front corner region  38 , recording materials are clamped and bound by the upper and lower tooth-shaped members  22  and  24 . Left and right sides of the recording-material binding device  10  are mostly covered with two side frames, namely, a left side frame  40 L and a right side frame  40 R. 
         [0029]      FIG. 3  is a perspective view of the recording-material binding device  10  from which the right side frame  40 R is removed so that the inside is seen. The upper frame  30  includes a rear surface plate  30   c  having an opening  30   b  and a support plate  30   d  extending frontward from a lower edge of the rear surface plate  30   c.  The rear surface plate  30   c  is curved at a portion where the opening  30   b  is provided. Thus, the outer shape of the recording-material binding device  10  is round-chamfered in an upper rear corner region. A home position sensor  42  is provided on the support plate  30   d . The home position sensor  42  detects the home position of a binding operation unit  100  to be described later (see  FIG. 6 ). Detection of the home position will be described in conjunction with the operation of the binding operation unit  100 . 
         [0030]    A motor  46  is disposed at a position diagonal to the upper front corner region  38 , that is, in a lower rear corner region  44 . The motor  46  has a motor pinion  46   a  (see  FIG. 5 ) on an output shaft, and the motor pinion  46   a  is meshed with one gear  48   a  in a gear train  48  disposed on an outer side of the left side frame  40 L (see  FIG. 5 ). The gear train  48  constitutes a reduction gear train, and the motor  46  rotates a cam shaft  50  through the gear train  48 . 
         [0031]      FIG. 4  is a perspective view of the recording-material binding device  10  from which the motor  46  is also removed from the state of  FIG. 3 . An encoder bracket  52  is fixed to the left side frame  40 L, and an encoder  54  for detecting the rotation angle of the motor  46  is disposed on the encoder bracket  52 . The encoder  54  includes a rotor  54   a  rotatably supported by the encoder bracket  52 , and a photosensor  54   b  fixed to the encoder bracket  52 . The rotor  54   a  is shaped like an impeller having a rotation shaft, and an encoder pinion  54   c  is provided at an end of the rotation shaft. The encoder pinion  54   c  is meshed with one gear  48   a  in the gear train  48  (see  FIG. 5 ). When the motor  46  rotates, the rotor  54   a  also rotates. The gear  48   a  with which the encoder pinion  54   c  is meshed may be a first stage gear of the gear train  48 . The photosensor  54   b  has two opposed portions, and detects passage of blades of the rotor  54   a  between the opposed portions. By counting the number of passages of the blades, the rotation angle of the output shaft of the motor  46  is detected. The photosensor  54   b  may be replaced with a sensor of another type that detects the passage of the blades of the rotor  54   a.    
         [0032]      FIG. 5  is an exploded view of the recording-material binding device  10 , and  FIGS. 6 and 7  illustrate the principal part of the binding operation unit  100 . The binding operation unit  100  is constituted of the above-described upper and lower arms  26  and  28 , a lever link  56  and a support lever  72  to be described later, and a connecting pin  58 , an arm pin  64 , and a guide pin  70  for coupling these elements. 
         [0033]    The upper arm  26  includes an arm portion  26   a  extending in a substantially frontward direction and having a distal end portion to which the upper tooth-shaped member  22  is attached, and a connecting portion  26   b  branching from the arm portion  26   a  and extending downward to be coupled to a lever link  56 . The connecting portion  26   a  has a portion that is curved beyond the cam shaft  50 . The connecting portion  26   b  and the lever link  56  are connected by a connecting pin  58  to be turnable on the connecting pin  58 . To a distal end portion of the upper arm  26 , an upper guide plate  60  is attached to be located near the upper tooth-shaped member  22 . Portions of the upper guide plate  60  located on the right and left of the upper tooth-shaped member  22  have V-shaped portions  60   a  formed by bending a steel plate, such as a spring steel plate, and opening frontward. The V-shaped portions  60   a  are closed when recording materials are bound, and the bound recording materials are separated from the upper tooth-shaped member  22  by an elastic opening force of the V-shaped portions  60   a . The connecting pin  58  has a columnar shaft portion  58   a  and guide projections  58   b  projecting from both ends of the shaft portion  58   a.    
         [0034]    The lower arm  28  includes two arm plates  28   a  and  28   b  arranged on the right and left sides with a space therebetween and extending frontward, and a distal end base  28   c  disposed at distal ends of the arm plates  28   a  and  28   b  to connect the arm plates  28   a  and  28   b.  The lower arm  28  may be integrally formed, or may be formed by assembling the two arm plates  28   a  and  28   b  and the distal end base  28   c  provided separately. The lower tooth-shaped member  24  is mounted on the distal end base  28   c.  A lower guide plate  62  is disposed to surround the lower tooth-shaped member  24 . The lower guide plate  62  is V-shaped to open frontward by bending a steel plate such as a spring steel plate. When recording materials are bound, the V-shaped lower guide plate  62  is closed, and the bound recording materials are separated from the lower tooth-shaped member  24  by an elastic opening force of the V-shaped lower guide plate  62 . 
         [0035]    The upper arm  26  and the lower arm  28  are connected at rear ends thereof by an arm pin  64  to be independently turnable. When connected, the upper arm  26  is located between the two arm plates  28   a  and  28   b  of the lower arm  28 . The connecting portion  26   b  of the upper arm  26  passes between the arm plates  28   a  and  28   b  of the lower arm  28 , and extends to a side opposite from the connecting portion  26   a  of the upper arm  26 . When the upper arm  26  and the lower arm  28  turn on the arm pin  64 , the upper tooth-shaped member  22  and the lower tooth-shaped member  24  move close to each other, and move away from each other. The arm pin  64  has a columnar shaft portion  64   a  and guide projections  64   b  projecting from both ends of the shaft portion  64   a.    
         [0036]    The two arm plates  28   a  and  28   b  of the lower arm  28  have their respective openings  28   d  through which the cam shaft  50  extends. To the cam shaft  50 , two driving cams, that is, a left driving cam  66 L and a right driving cam  66 R are fixed to be located on the left and right of the upper arm  26  and the lower arm  28  when assembled. At two positions on the cam shaft  50 , modified-section shaft portions  50   a  having a cross section other than a circular cross section, for example, a fan-shaped cross section from which a center portion is removed are provided. The left and right driving cams  66 L and  66 R have modified-section holes  66   a  that conform to this cross sectional shape. Fixing pins  68  stand on the modified-section shaft portions  50   a  of the cam shaft  50  in a direction intersecting the axis, or penetrate the modified-section shaft portions  50   a.  The left and right driving cams  66 L and  66 R have pin receiving grooves  66   b  for receiving the fixing pins  68  (see  FIG. 7 ). The left and right driving cams  66 L and  66 R are fixed to the cam shaft  50  in the rotating direction by engaging with the modified-section shaft portions  50   a  and the fixing pins  68  of the cam shaft  50 . The left and right driving cams  66 L and  66 R are more firmly fixed in the rotating direction by engaging not only with the modified-section shaft portions  50   a  but also with the fixing pins  68 . 
         [0037]    A fitting portion  50   b  having two parallel flat faces is provided at a left end of the cam shaft  50 . The fitting portion  50   b  is fitted in one gear of the gear train  48 , for example, a fitting hole  48   c  provided in the last stage gear  48   b  in the gear train  48 . This fitting allows the cam shaft  50  to be rotated by the motor  46  through the gear train  48 . 
         [0038]    The lever link  56  is further coupled to a support lever  72  by a guide pin  70 . The guide pin  70  has a shaft portion  70   a  and guide projections  70   b  extending from both ends of the shaft portion  70   a.  The shaft portion  70   a  has a noncircular cross-sectional shape, for example, a noncircular cross-sectional shape defined by one chord of a circle and a larger one of arcs divided by this chord, as illustrated in  FIG. 7 . Holes of the lever link  56  for receiving the guide pin  70  have such a shape as to fit the shaft portion  70   a  of the guide pin  70 . Thus, the guide pin  70  is fixed to the lever link  56  in the rotating direction. 
         [0039]    When recording materials are bound, the support lever  72  supports the distal end base  28   c  of the lower arm  28  from below, and receives a reaction force of the binding operation. The support lever  72  includes a support  72   a  located below the distal end base  28   c  of the lower arm  28  when the recording materials are bound, and two lever portions  72   b  extending rearward from the support  72   a  outside the lower arm  28 . The support lever  72  may be integrally formed, or may be formed by connecting the support  72   a  and the two lever portions  72   b  separately formed. A support bar  74  is fixed on the support  72   a.  The support bar  74  has a columnar shaft portion  74   a  and guide projections  74   b  projecting from both ends of the shaft portion  74   a.  At rear ends of the two lever portions  72   b,  cam followers  72   c  are provided to be in contact with the left and right driving cams  66 L and  66 R. 
         [0040]    The left side frame  40 L has a left side panel  76 L and a left guide plate  78 L. When assembled, the left side panel  76 L and the left guide plate  78 L are superposed into one. The right side frame  40 R has a right side panel  76 R and a right guide plate  78 R. When assembled, the right side panel  76 R and the right guide plate  78 R are superposed into one. 
         [0041]    The cam shaft  50  is rotatably supported by the left and right side frames  40 L and  40 R by being passed through a bearing bush  80  attached to the left side frame  40 L and a bearing hole  78 Ra provided in the right guide plate  78 R. 
         [0042]    The left and right guide plates  78 L and  78 R respectively have guide grooves  82 ,  84 , and  88  and guide holes  86  for guiding movements of the connecting pin  58 , the arm pin  64 , the guide pin  70 , and the support bar  74 . 
         [0043]    The guide projections  58   b  provided at both ends of the connecting pin  58  are fitted in left and right connecting-pin guide grooves  82 . The guide projections  58   b  have a stepped columnar shape. Correspondingly thereto, the connecting-pin guide grooves  82  have such a stepped groove shape as to be deep in a center portion thereof and to be shallow near an edge thereof. The connecting-pin guide grooves  82  have their respective bottoms, and are not open to outer surfaces of the left and right guide plates  78 L and  78 R. The connecting-pin guide grooves  82  are bent, but extend in a substantially up-down direction. 
         [0044]    The guide projections  64   b  provided at both ends of the arm pin  64  are fitted in arm-pin guide grooves  84 . The arm-pin guide grooves  84  extend in a substantially front-rear direction, and guide frontward and rearward movements of the upper arm  26  and the lower arm  28 . The arm-pin guide grooves  84  extend through the entire thickness of the left and right guide plates  78 L and  78 R. 
         [0045]    The guide projections  70   b  provided at both ends of the guide pin  70  are put in guide holes  86 . The guide projections  70   b  have a modified cross-sectional shape nearly like an oval. The cross-sectional shape of the guide holes  86  is substantially trapezoidal, and the guide holes  86  are larger than the guide projections  70   b  as a whole. For this reason, upward, downward, frontward, and rearward movements of the guide projections  70   b  are permitted within the guide holes  86 . The dimension of the guide holes  86  in the right-left direction is extended by extension walls  86   a  standing on the outer side surfaces of the left and right guide plates  78 L and  78 R. 
         [0046]    At both ends of the support bar  74  provided integrally with the support lever  72 , the columnar guide projections  74   b  are provided, and are fitted in support-lever guide grooves  88 . The support-lever guide grooves  88  extend in a substantially up-down direction, and guide the movement of the support lever  72 , particularly, the support  72   a  in the up-down direction. The support-lever guide grooves  88  extend through the entire thickness of the left and right guide plates  78 L and  78 R. 
         [0047]    The left and right driving cams  66 L and  66 R respectively have first cam faces  66   c  in contact with the arm pin  64  and second cam faces  66   d  in contact with the cam followers  72   c  provided in the support lever  72  (see  FIGS. 6 and 7 ). The first cam faces  66   c  and the second cam faces  66   d  project from cam base bottom faces  66   e  constituted by parts of cylindrical surfaces having an axis common to the cam shaft  50 . The first cam faces  66   c  project more than the second cam faces  66   d.    
         [0048]    As illustrated in  FIG. 7 , a home-position detector  90  is attached to a left end portion of the arm pin  64  to be turnable on the arm pin  64 . The home-position detector  90  has a detection piece  90   a  serving as a detection object for the home position sensor  42  and a cam follower  90   b  in contact with the second cam face  66   d  of the left driving cam  66 L. As the left driving cam  66 L turns, the home-position detector  90  pivots, and the detection piece  90   a  advances or retreats relative to the home position sensor  42 . A photosensor may be used as the home position sensor  42 . When the detection piece  90   a  is put between two portions of the home position sensor  42 , the home position of the binding operation unit  100  is detected. 
         [0049]      FIG. 8  illustrates a push-out spring  92 . The push-out spring  92  abuts on the upper arm  26 , and biases the entire binding operation unit  100  to the lower front side. The push-out spring  92  has an operating portion  92   a  to abut on a spring receiving face  26   c  (see  FIG. 5 ) provided on a slightly rear portion of an upper part of the upper arm  26 . The operating portion  92   a  has a substantially angular U-shape, and fixed portions  92   c  are connected to the operating portion  92   a  with coil portions  92   b  at both ends being interposed therebetween. The fixed portions  92   c  are fixed to an inner surface of the upper surface plate  30   a  of the upper frame  30 , and the operating portion  92   a  is turnable on the coil portions  92   b.  The push-out spring  92  biases the entire binding operation unit  100  to push out the binding operation unit  100  to the lower front side. 
         [0050]      FIG. 9  illustrates a support spring  94 . The support spring  94  supports the support lever  72  so that the positions of the cam followers  72   c  of the support lever  72  are not excessively lowered when the support lever  72  is separate from the driving cams  66 L and  66 R. Since the support spring  94  supports the support lever  72 , when the driving cams  66 L and  66 R turn, the second cam faces  66   d  come into contact with the cam followers  72   c.  A cylindrical coil portion  94   a  of the support spring  94  is attached to a boss  78 Rb of the right guide plate  78 R (see  FIG. 6 ). Bent distal ends of fixed arms  94   b  extending from the coil portion  94   a  are engaged with engaging holes  78 Rc provided in an outer side surface of the right guide plate  78 R, and the support spring  94  is thereby fixed in the rotating direction. A support arm  94   c  of the support spring  94  extends from the coil portion  94   a  along an inner surface of the right guide plate  78 R. A distal end of the support arm  94   c  supports a lower surface of one of the lever portions  72   b  in the support lever  72 . The support arm  94   c  may be separate from the support lever  72  when the driving cams  66 L and  66 R are in contact with the support lever  72 . 
         [0051]      FIGS. 10 to 13  are operation explanatory views of the binding operation unit  100  in the recording-material binding device  10 . The binding operation unit  100  operates to bind recording materials by using the driving cams  66 . In the description of the operation, when the left and right driving cams  66 L and  66 R do not need to be distinguished, they are simply referred to as driving cams  66  for simplicity. For the connecting-pin guide grooves  82 , only the deep portions in the stepped grooves are illustrated for simplicity. 
         [0052]      FIG. 10  illustrates a state in which the binding operation unit  100  is at a home position. At the home position, the first cam faces  66   c  of the driving cams  66  are in contact with the shaft portion  64   a  of the arm pin  64 . Thus, the first cam faces  66   c  maximally retreat the arm pin  64 , and the entire binding operation unit  100  is retreated. The upper tooth-shaped member  22  and the lower tooth-shaped member  24  are also retreated, and are most separate from each other. The connecting portion  26   b  of the upper arm  26  is pulled up until the guide projections  58   b  of the connecting pin  58  are located near upper ends of the connecting-pin guide grooves  82 . Correspondingly to this position of the connecting pin  58 , the guide projections  70   b  of the guide pin  70  are located at the centers of upper sides of the guide holes  86 , and the guide projections  74   b  of the support bar  74  are located near upper ends of the support-lever guide groove  88 . At this time, as illustrated in  FIG. 7 , in the home-position detector  90 , the cam follower  90   b  abuts on the second cam face  66   d,  and the detection piece  90   a  is located at a detection object position of the home position sensor  42 . On the basis of detection of the home position sensor  42  for the detection piece  90   a,  the controller  25  recognizes that the binding operation unit  100  is at the home position. 
         [0053]    When the driving cams  66  turn from the home position in a counterclockwise direction F in  FIG. 10 , the shaft portion  64   a  of the arm pin  64  separates from the first cam faces  66   c  at a certain position, and is brought into contact with the cam base bottom faces  66   e.    
         [0054]      FIG. 11  illustrates a state immediately after the shaft portion  64   a  of the arm pin  64  separates from the first cam faces  66   c.  Since the shaft portion  64   a  and the first cam faces  66   c  are disengaged from each other, the binding operation unit  100  is entirely pushed out to the lower front side (lower right side in  FIG. 11 ) by a biasing force U of the push-out spring  92 . The arm pin  64  moves frontward along the arm-pin guide grooves  84 , and the upper arm  26  moves frontward along therewith. At the same time, the upper arm  26  also moves downward as the guide projections  58   b  of the connecting pin  58  at the lower end of the connecting portion  26   b  are guided downward along the connecting-pin guide grooves  82 . For this reason, the upper tooth-shaped member  22  advances frontward, and also moves downward. The lower arm  28  moves frontward along the frontward movement of the arm pin  64 . Also, the lower arm  28  is guided by the cam shaft  50  penetrating the openings  28   d,  and moves almost frontward without turning. For this reason, the lower tooth-shaped member  24  also advances frontward. Since the upper tooth-shaped member  22  advances to the lower front side and the lower tooth-shaped member  24  advances frontward, the upper and lower tooth-shaped members  22  and  24  approach each other while advancing frontward. 
         [0055]    Since upper parts of the connecting-pin guide grooves  82  obliquely extend to the lower front side, the lever link  56  moves to the lower front side along with the movement of the connecting pin  58  along the connecting-pin guide grooves  82 . However, when the guide projections  70   b  of the guide pin  70  come into contact with front edges of the guide holes  86 , the lever link  56  does not further move frontward, but subsequently turns on the guide pin  70  in the counterclockwise direction. As the guide pin  70  moves to the lower front side, the support lever  72  also moves. Since the support bar  74  provided integrally with the support lever  72  moves along the support-lever guide grooves  88  that extend in a substantially up-down direction, the support bar  74  does not move frontward even when the guide pin  70  moves frontward. As illustrated in  FIG. 11 , the support-lever guide grooves  88  extend rearward as they extend downward. For this reason, the support lever  72  is turned in the counterclockwise direction. Thus, the cam followers  72   c  at the rear end of the support lever  72  move downward. At this time, the support spring  94  supports a rear portion of the support lever  72  from below so that the cam followers  72   c  do not excessively move. 
         [0056]    The home-position detector  90  moves frontward together with the arm pin  64 , and the detection piece  90   a  comes out of the detection object position of the home position sensor  42 . 
         [0057]      FIG. 12  illustrates a state in which the driving cams  66  are further turned in the counterclockwise direction F and the second cam faces  66   d  are in contact with the cam followers  72   c  of the support lever  72 . The arm pin  64  is in contact with the cam base bottom faces  66   e  of the driving cams  66 , and is located at a position further shifted frontward from the position of  FIG. 11 . Thus, the upper arm  26  also further moves to the lower front side from the state of  FIG. 11 , and the lower arm  28  further moves frontward. Along with the downward movement of the connecting portion  26   b  of the upper arm  26 , the guide projections  58   b  of the connecting pin  58  are guided along the connecting-pin guide grooves  82 . The connecting-pin guide grooves  82  are bent, and portions on a lower side of bent points extend rearward as they extend downward. Since the lower portions of the connecting-pin guide grooves  82  extend rearward, the upper arm  26  turns clockwise. The lever link  56  is pulled downward by the connecting pin  58 , and turns counterclockwise because the downward movement of the guide projections  70   b  of the guide pin  70  is restricted by the guide holes  86 . By the movement of the connecting pin  58  to the rear lower side and the counterclockwise turn of the lever link  56 , the guide projections  70   b  of the guide pin  70  are moved to the center portions of the guide holes  86 . At the same time, the guide projections  74   b  of the support bar  74  move upward along the support-lever guide grooves  88 , and the support lever  72  moves upward. Since the rearward movement of the guide projections  74   b  of the support bar  74  is restricted by the support-lever guide grooves  88 , when the guide pin  70  moves rearward, the support lever  72  turns on the support bar  74  in the clockwise direction. Along with the clockwise turn of the support lever  72 , the cam followers  72   c  move up to a position where the second cam faces  66   d  of the driving cams  66  abut on the cam followers  72   c.  This upward movement of the cam followers  72   c  is assisted by the support spring  94 . When the second cam faces  66   d  of the driving cams  66  come into contact with the cam followers  72   c  of the support lever  72 , the support lever  72  is turned clockwise by further turn of the driving cams  66 . Also, the support bar  74  comes into contact with the lower surface of the lower arm  28 . 
         [0058]      FIG. 13  illustrates a state in which the driving cams  66  are further turned counterclockwise and recording materials are clamped by the upper tooth-shaped member  22  and the lower tooth-shaped member  24 . The cam followers  72   c  of the support lever  72  are further pushed upward from the state of  FIG. 12  by the second cam faces  66   d.  On the other hand, the guide projections  74   b  of the support bar  74  reach the upper ends of the support-lever guide grooves  88 , and the support lever  72  turns on the support bar  74  in the clockwise direction. Along with the turn of the support lever  72 , the guide projections  70   b  of the guide pin  70  move to the rear ends of the guide holes  86 , and the lever link  56  further turns counterclockwise. Through these operations, the connecting pin  58 , the guide pin  70 , and the support bar  74  are aligned nearly on a straight line. Also, the support bar  74  pushes up the lower arm  28  so that the upper tooth-shaped member  22  and the lower tooth-shaped member  24  bite each other. 
         [0059]    When the upper tooth-shaped member  22  and the lower tooth-shaped member  24  bite, recording materials clamped by the upper tooth-shaped member  22  and the lower tooth-shaped member  24  are deformed in a wavy form, and the recording materials are joined and bound. The second cam faces  66   d  of the driving cams  66  are shaped to gradually push up the cam followers  72   c  as they turn. When the recording materials are thin, it is required that the upper and lower tooth-shaped members  22  and  24  should bite deeper than when the recording materials are thick. Hence, the driving cams  66  are turned more. Information about the thickness of the recording materials is input to the controller  25 , for example, by the user of the image forming system  11 . On the basis of this information, the turn angle of the driving cams  66 , that is, the rotation angle of the motor  46  is determined by the controller  25 . The rotation angle of the motor  46  from the home position is detected by the encoder  54 . When the rotation angle reaches a rotation angle corresponding to the thickness of the recording materials at this time, the rotation of the motor  46  is stopped. 
         [0060]    After that, the motor  46  reverses, and the driving cams  66  turn in reverse in the clockwise direction R. When the driving cams  66  turn in reverse and reach, for example, the position of  FIG. 12 , the upper tooth-shaped member  22  and the lower tooth-shaped member  24  separate from each other. By the action of the upper guide plate  60  and the lower guide plate  62  disposed around the upper and lower tooth-shaped members  22  and  24 , the bundle of recording materials is pulled away from the upper tooth-shaped member  22  or the lower tooth-shaped member  24 . When the driving cams  66  further turn in reverse and the first cam faces  66   c  come into contact with the shaft portion  64   a  of the arm pin  64 , the arm pin  64  is moved rearward along the arm-pin guide grooves  84 . With this, the binding operation unit  100  is entirely moved to the upper rear side. When the binding operation unit  100  returns to the position of  FIG. 10  and the home position is detected by the home position sensor  42 , the rotation of the motor  46  is stopped. 
         [0061]      FIG. 14  illustrates the positional relationship between the accumulation tray  20  and the recording-material binding device  10 .  FIG. 15  is an end face view taken along line XV-XV in  FIG. 14 . The accumulation tray  20  includes a bottom plate  20   a  on which recording materials P are placed, and side walls  20   b  standing on the bottom plate  20   a  to regulate the positions of both side edges of the recording materials P. Further, distal end walls  20   c  stand on the bottom plate  20   a  so that distal ends of transported recording materials P abut on the distal end walls  20   c.  As illustrated in  FIG. 15 , the distal end walls  20   c  have bent upper ends, and are shaped like an inverse L. The distal ends of the recording materials P are placed inside the L-shaped portions to be positioned. 
         [0062]    A side of the bottom plate  20   a  where the distal end walls  20   c  are provided (hereinafter referred to as a distal end side) has cutouts  20   d  at two positions. The cutouts  20   d  extend from the distal end side in a direction orthogonal to the distal end side. A cutout  20   e  is provided at one corner portion of the distal end side of the bottom plate  20   a.  The cutout  20   e  extends in a direction at an angle to the distal end side. This direction is at an angle of, for example, 45° to the distal end side. The distal end walls  20   c  are provided at such positions as not to interfere with the cutouts  20   d  and  20   e.    
         [0063]    The recording-material binding device  10  is moved along a rail  96  by an unillustrated driving mechanism. The rail  96  includes a side portion  96   a  along the distal end side of the bottom plate  20   a  and a corner portion  96   b  bent from one end of the side portion  96   a  and corresponding to the corner portion of the bottom plate  20   a.  When recording materials P are bound at the corner portion, the recording-material binding device  10  is moved to a position  10 - 1  in  FIG. 14 , that is, a position corresponding to the cutout  20   e.  When the recording materials P are bound at the position of the cutout  20   e,  the bottom plate  20   a  does not hinder the binding operation of the recording-material binding device  10 . When recording materials P are bound at two positions along the side of the recording materials P, the recording-material binding device  10  is moved to a position  10 - 2  in  FIG. 14  corresponding to one of the cutouts  20   d,  where the recording materials P are bound. Next, the recording-material binding device  10  is moved to a position  10 - 3  corresponding to the other cutout  20   d,  and the recording materials P are bound at this position. 
         [0064]    A cutout may be provided at a corner opposite from the corner where the cutout  20   e  is provided, and the rail  96  may be extended so that the recording materials P are also bound at this corner. Alternatively, cutouts may be provided at three or more positions along the side so that the recording materials are bound at the three or more positions. 
         [0065]    The above-described binding operation unit  100  has a link structure. The binding operation unit  100  includes the upper arm  26 , the lower arm  28 , the lever link  56 , and the support lever  72  as link elements of the link structure, and includes the arm pin  64 , the connecting pin  58 , and the guide pin  70  as connecting elements for connecting the link elements. The arm pin  64 , the connecting pin  58 , and the guide pin  70  also function as support elements for supporting the binding operation unit  100  relative to the left and right side frames  40 L and  40 R. The cam shaft  50  and the support bar  74  also function as support elements for supporting the binding operation unit  100  relative to the left and right side frames  40 L and  40 R. The arm pin  64 , the connecting pin  58 , the guide pin  70 , and the support bar  74  are guided by guide elements provided in the left and right side frames  40 L and  40 R, and this guides movements of the link elements. Specifically, the guide elements are the connecting-pin guide grooves  82 , the arm-pin guide grooves  84 , the guide holes  86 , and the support-lever guide grooves  88 . The lower arm  28  is guided not only by the arm-pin guide grooves  84 , but also by the openings  28   d  which are provided in the lower arm  28  so that the cam shaft  50  extends therethrough. 
         [0066]    In the state of  FIG. 13  in which the recording materials are clamped by the binding operation unit  100 , the reaction force of the force for clamping the recording materials is principally received by the guide holes  86  for supporting the guide pin  70 , the arm-pin guide grooves  84  for supporting the arm pin  64 , the bearing hole  78 Ra of the right guide plate  78 R and the bearing bush  80  for supporting the cam shaft  50 . The force received by the lower arm  28  is transmitted to the driving cams  66  and the lever link  56  through the support lever  72 . A part of the force received by the lower arm  28  is transmitted to the left and right guide plates  78 L and  78 R having the support-lever guide grooves  88  through the support bar  74 . The force transmitted to the driving cams  66  is transmitted to the cam shaft  50 . On the other hand, the force transmitted to the lever link  56  is transmitted through the connecting pin  58  and the guide pin  70  to the left and right guide plates  78 L and  78 R having the connecting-pin guide grooves  82  and the guide holes  86 . Further, the force transmitted to the lever link  56  is transmitted to the connecting portion  26   b  of the upper arm  26  through the connecting pin  58 . This force counters the reaction force received by the connecting portion  26   a  of the upper arm  26  when the recording materials are clamped, and a resultant force of these forces is transmitted to the arm-pin guide grooves  84  and the cam shaft  50  through the arm pin  64 . Most of the reaction force of the force for clamping the recording materials acts on the cam shaft  50 . The force acting on the cam shaft  50  is transmitted to the right guide plate  78 R having the bearing hole  78 Ra and the left guide plate  78 L having the bearing bush  80 . 
         [0067]    In this way, the binding operation unit  100  is supported by the left and right guide plates  78 L and  78 R, that is, the left and right side frames  40 L and  40 R through the cam shaft  50 , the connecting pin  58 , the arm pin  64 , the guide pin  70 , and the support bar  74 . Each of the cam shaft  50 , the connecting pin  58 , the arm pin  64 , the guide pin  70 , and the support bar  74  is supported at both ends. 
         [0068]    The connecting pin  58 , the arm pin  64 , the guide pin  70 , and the support bar  74  are supported on both sides by the corresponding guide grooves or guide holes. 
         [0069]    Each of the upper tooth-shaped member  22  and the lower tooth-shaped member  24  has a tooth row in which plural teeth are arrayed. The direction in which the teeth are arrayed is the right-left direction, and is parallel to the extending direction of the connecting elements, such as the arm pin  64 , in the binding operation unit  100 , or is orthogonal to the extending direction of the upper arm  26  and the lower arm  28  to which the upper tooth-shaped member  22  and the lower tooth-shaped member  24  are attached.  FIG. 16  illustrates a recording-material binding device  110  as a comparative example, in which an upper tooth-shaped member  122  and a lower tooth-shaped member  124  are disposed obliquely to the right-left direction of the recording-material binding device  110 . Even when the recording-material binding device  110  is disposed at such a position  110 - 1  that the front-rear direction of the recording-material binding device  110  is orthogonal to a side of a recording material P, a joining region with the tooth-shaped members is obliquely formed in a corner area of the recording material P. On the other hand, since the upper and lower tooth-shaped members  122  and  124  are obliquely disposed, the dimension of the recording-material binding device  110  in the front-rear direction is increased. Further, when recording materials P are bound at two positions along the side, the recording-material binding device  110  is disposed obliquely to the side of the recording materials P so that joining regions of the tooth-shaped members are provided along the side. For this reason, when the recording-material binding device  110  is moved along a rail  196  from the position  110 - 1  corresponding to the corner of the recording materials P to positions  110 - 2  and  110 - 3  corresponding to a center portion of the side, it is necessary to turn the recording-material binding device  110  itself, as shown by an arrow Q. That is, a mechanism for turning the recording-material binding device  110  is needed. In contrast, according to the structure illustrated in  FIG. 14 , the orientation of the recording-material binding device  10  is changed by bending the rail  96  at the position corresponding to the corner of the recording materials P. Thus, there is no need to provide a new turning mechanism. 
         [0070]    The recording-material post-processing apparatus  13  may include an accumulation tray  20  on which plural rectangular recording materials P are accumulated, a rail  96  extending along one side of the recording materials P, bent, and further extending to a position corresponding to a corner of the recording materials P, and a recording-material binding device  10  in which the arrangement direction of teeth in an upper tooth-shaped member  22  and a lower tooth-shaped member  24  is parallel to the axial direction of pins for connecting link elements in a binding operation unit  100 . 
         [0071]    The foregoing description of the exemplary embodiment of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiment was chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the following claims and their equivalents.