Abstract:
A stapler apparatus includes a fixed frame, a movable frame pivotably mounted to the fixed frame, a staple driving device, and a staple bending device to bend the staples. A drive mechanism reciprocally moves the movable frame with respect to the fixed frame to clamp a stack of sheets between the fixed frame and the movable frame. A transmission member is movably supported on the movable frame without any connection utilizing an elongated slot. An urging member is disposed to bias the transmission member with respect to the movable frame, the transmission member being coupled to the drive mechanism such that the drive mechanism engages and moves the transmission member with respect to the movable frame, thereby overcoming the bias of the urging member, to compensate for a stack height of the stack of sheets clamped between the fixed frame and the movable frame.

Description:
DETAILED DESCRIPTION OF THE INVENTION 
     1. Field of Application 
     The present invention relates to a stapler apparatus for stapling a bundle of predetermined sheets put thereon with motor-driven staple driving means. 
     2. Prior Art 
     Previous stapler apparatuses for automatically stapling a sheet bundle with staples have a fixed frame and a movable frame attached swingably thereto. Either one of the frames has staple driving means, and the other has staple bending means for bending ends of the staple. In the course that the fixed frame and the movable frame clamp the sheet bundle, the staple driving means forms the linear staples to a U-shape. After that, the staple bending means bends the ends of the staple passed through the sheet bundle. Cam members are provided and interlocked with a drive motor for the operations of the movable frame to clamp the sheet bundle and of the staple driving means to drive the staple into the sheet bundle. That is, the movable frame separated with a predetermined distance is moved close to the fixed frame until it contacts a surface of the sheet bundle before driving the staple in. It is known that the movable frame may have the staple driving means or the staple bending means mounted thereon. 
     In either type, it is needed that the movable frame is positioned with the predetermined distance from the fixed frame, places the sheet bundle onto the fixed frame, then comes close to the fixed frame, and drives the staple into the sheet bundle with it abutted to the surface of the sheet bundle. The cam members perform the clamping operation of clinching the sheet bundle. Therefore, the cam members and the movable frame must be interlocked together with levers or similar transmission members. The movable frame is different depending on thickness of the sheet bundle in movement distance from a home position (initial position) to the contact position at the surface of the sheet bundle. The moving distance is short for thick sheet bundle and long for thin one. The previous way of interlocking the cam members with the movable frame, as disclosed in, for example, Japanese Laid Open Patent Tokkai Hei 9-169006, is that a transmission member is disposed with one end thereof fitted to the cam member and the other fitted to the movable frame to transmit movement of the cam to the movable frame. In mounting the transmission member (usually lever member) on the fixed frame rotatably by a shaft, the shaft of the transmission member is put in a long hole formed on the fixed frame and is urged to the cam face by a spring as in the long hole. Therefore, the movable frame is swung by the cam with a center of an axis of the fixed frame when it is not resisted by anything. The movement of the cam is transmitted to the movable frame with the transmission member rotating with the center, prompting the movable frame to do the clamping movement. When the movable frame abuts against the surface of the sheet bundle and cannot move any more, excess movement of the cam face serves for the shaft of the transmission member to resist against the spring force to move in the long hole, and the movable frame fits to the cam face with the center of the end abutting on the sheet bundle, allowing only the end to move. 
     Problems to be Solved by the Invention 
     As described above, such a previous method is disadvantageous in that in transmitting the movement of the driving cam to the movable frame by swinging of the transmission member, the shaft as the center for swinging is thrust-moved in the long hole to adjust the movement distance with the thickness of the sheet bundle. This may not allow the shaft to move smoothly in the long hole, but locks the drive system. The failure is due to looseness of the members until abutting from the driving cam to abutting of the movable frame on the sheet bundle and due to frequent non-smooth movement of the transmission member for rotation and thrusting depending on abutting condition of the movable frame on the sheet bundle. In particular, such an arrangement as the driving cam and the long hole for supporting the transmission member and the driving cam are paired right and left, is devised so that the shafts of the transmission members are passed through the right and left long holes to serve for centers of rotation and thrusting movement. Dispersion of parts of the paired members will cause the failure increase. 
     In view of solving the foregoing problems of the prior arts, it is an object of the present invention to provide a stapler apparatus that clamping of the sheet bundle is smoothly shifted to staple driving operation at little failure occurrence irrespective of thickness of the sheet bundle. 
     Means to Solve the Problems 
     The stapler apparatus according to claim  1  of the present invention is for clamping sheet bundles between a fixed frame and a movable frame for binding, equipped with a fixed frame, a movable frame pivotably mounted to the fixed frame, a staple driving means disposed on one of the fixed frame and the movable frame, a staple bending means for bending the leading ends of staples disposed on the other and a drive cam means for reciprocally moving the movable frame, wherein a transmission member comprising an abutting portion to abut one end of the movable frame, mounted rotatably pivoted to the movable frame, an activating member reciprocated by the drive cam means, interlocked to the drive cam means, and an urging means to urge the transmission member so that the abutting portion abuts the movable frame, and wherein the activating member abutting the transmission member so that the activating means separates the abutting portion from the movable frame resisting the urging means. 
     The invention according to claim  2  is equipped with a fixed frame, a movable frame pivotably swinging on the fixed frame, a staple driving means disposed on one of the fixed frame and the movable frame, a staple bending means to bend the leading ends of staples disposed on the other, and a drive cam means to reciprocally move the movable frame, to clamp sheet bundles between the fixed frame and the movable frame and to bind sheet bundles, wherein the movable frame is rotatably supported by a shaft on one point to the fixed frame, a transmission member comprising an abutting portion to abut the movable frame, rotatably supported on a shaft on one point on the movable frame, an urging means is disposed to urge the transmission member so that the abutting portion abuts the movable frame, the transmission member interlocked to the drive cam to separate the abutting portion from the movable frame in resistance to the urging means. 
     With the invention of claims  1  and  2 , adjustment of the movement distance depending on thickness of the sheet bundle is not made by moving the swinging shaft of the movable frame, but by use of turning of the transmission member supported swingably by shaft on the movable frame. This feature does not need the thrusting movement of the swinging fulcrum shaft of the movable frame in the long hole as in the previous apparatus. For the reason, the shaft will not be caused in the failure that it does not move smoothly in the long hole, not resulting in locking of the drive system. Also, it is advantageous that smooth operations are assured as not affected by dispersion of parts of the members because of just swinging. 
     The stapler apparatus according to claim  3  of the present invention is characterized in that in the stapler apparatus in claim  1 , the urging means is made up of a spring member disposed between the movable frame and the transmission member. 
     According to the invention, the spring member disposed between the movable frame and the transmission member is stretched by adjustment of the movement distance depending on thickness of the sheet bundle. The reaction serves for clamping the sheet bundle. This means that even for clamping only one sheet, minimum necessary clamping force can be obtained not to escape the sheet when driving the staple into the sheet. 
     The stapler apparatus according to claim  4  of the present invention is characterized in that in the stapler apparatus in claim  1 , the urging means is made up of a spring member disposed between the transmission member and the fixed frame. 
     According to the invention, as the spring member does not swing together with the movable member, they can be easily arranged even in limited space. 
     The invention according to claim  5  is characterized in that in the stapler apparatus in claim  1  or  2 , each of said movable frame and the transmission member is paired with distance from the fixed frame respectively. 
     According to the invention, as the paired movable frame and the paired transmission members are disposed to have the fixed frame therebetween and are urged by the respective spring members, smooth swinging operation can be made without deviation. 
     Embodiments 
     The following describes an embodiment of the stapler apparatus of the present invention by reference to the accompanying drawings.  FIG. 1  is a perspective view of an overall structure of a stapler apparatus of the present invention.  FIG. 2  is a side view of the stapler apparatus shown in  FIG. 1 .  FIG. 3  is a perspective view of main units of the stapler apparatus, including a driver unit and an anvil unit.  FIG. 4  is an exploded perspective view of main parts of the driver unit.  FIG. 5  is a perspective view of main units of the stapler apparatus, including a driver unit and an anvil unit.  FIGS. 6 through 8  are views of main parts of drive structure of the anvil unit. 
     The stapler apparatus  10  in the embodiment, as shown in  FIGS. 1 and 2 , has a U-shaped fixed frame  11  forming the stapler apparatus  10 , a driver unit  20  having drive cam means for driving a staple driving member and a staple bending member as built in the fixed frame  11 , an anvil unit  30  having a movable frame as supported rotatably with respect to the fixed frame  11 , and a staple supply unit  40  arranged detachably at a rear of the fixed frame  11 . The driver unit  20  is structured so as to separate staples one by one from the sheet-like staple band having many staples interlocked together like a band, to form the separated staples to a U-shape, and to drive in thickness direction the staples into the sheet bundle fed in the anvil unit  30  positioned above. The anvil unit  30  arranged against the driver unit  20 , on the other hand, is structured so as to receive both ends of the staple driven in the sheet bundle before to bend the both ends inward, thereby finally stapling the sheet bundle. 
     The fixed frame  11  has a mount  12  disposed for mounting a staple supply unit  40  at a rear thereof and has a sheet table  13  for bundling sheets at a front thereof. The fixed frame  11  also has a driver unit  20  for driving sheet-like staples fed from the staple supply unit  40  therein and has a drive motor for driving the driver unit  20  therein. The staple supply unit  40  has a cassette  41  containing the staples interlocked together like a sheet and has a holder  42  for containing the cassette  41 , being detachably mounted on a mount  12  of the fixed frame  11 . The driver unit  20  is described below in detail by reference to  FIGS. 3 through 5 . The driver unit  20  comprises a drive motor  21 , deceleration gears  22 , a first cam member  23 , a second cam member  24 , and a driver  60 . The deceleration gears  22 , the first cam member  23  and the second cam member  24  are assembled in a housing  25  having a partition wall therein and are swingably supported by an outside wall and the partition wall. The drive motor  21  is made up of a single dc motor an output gear  21   a  of which has the deceleration gears  22  interlocked thereto. The deceleration gears  22  comprise a first deceleration gear  22   a , a second deceleration gear  22   b , a third deceleration gear  22   c , a fourth deceleration gear  22   d , a fifth deceleration gear  22   e , a sixth deceleration gear  22   f , and a seventh deceleration gear  22   g  as looked outward from the output gear  21   a . The sixth deceleration gear  22   f  is a final gear stage to swing the first cam member  23 . The seventh deceleration gear  22   g  is a final gear stage to swing the second cam member  24 . 
     Both the first cam member  23  and the second cam member  24  are formed of the same member and arranged in parallel with the drive motor  21 . The first cam member  23  and the second cam member  24  are made up of drive gears  23   a  and  24   a  that have the torque to rotate in different directions by the sixth deceleration gear  22   f  and the seventh deceleration gear  22   g , eccentric cams  23   c  and  24   c  that are fitted via shafts  23   b  and  24   b , and rotating cams  23   e  and  24   e  for reciprocally moving the driver  60 , respectively. The eccentric cams  23   c  and  24   c  are shaped virtually semicircle, peripheries of which drives the anvil unit  30  to swing. The eccentric cams  23   c  and  24   c  also have clincher swinging shafts  23   d  and  24   d  projected thereout for swinging a clincher unit disposed inside the anvil unit  30 , respectively. The rotating cams  23   e  and  24   e , on the other hand, are rotatably supported by the eccentric cams  23   c  and  24   c  and engaging pins  23   f  and  24   f  and are rotated in synchronization with the drive gears  23   a  and  24   a . The rotating cams  23   e  and  24   e  have driver swinging pins  23   g  and  24   g  arranged symmetrically in a standing condition at positions separated from centers thereof on front surfaces thereof, respectively. The driver swinging pins  23   g  and  24   g  are engaged with slits  62   a  and  62   b  opened on a driver body  61 , respectively. As described above, the first cam member  23  and the second cam member  24  operate the anvil unit  30 , the clincher unit  50 , and the driver  60  at the same time. 
     The driver  60 , as shown in  FIGS. 3 through 5 , is made up of the driver body  61  having a paired horizontally long right and left slits  62   a  and  62   b  of identical shape formed thereon and of a vertically long driver head  63  disposed orthogonally with the driver body  61 . The driver head  63  is formed of a plate material thickness which is virtually same as the staple at a leading edge  64  thereof. The driver head  63  has a long hole  65  for engaging a staple forming member  77  (which will be described later) in a longitudinal direction at a central portion thereof and has guide plate springs  66   a  and  66   b  disposed for engaging with the staple forming member  77  to press in while driving the staple. 
     The driver  60  formed as described above moves the driver head  63  one reciprocal stroke while the driver swinging pins  23   g  and  24   g  fitted with the respective slits  62   a  and  62   b  of the driver body  61  rotate one turn. This completes stapling operation. The driver swinging pints  23   g  and  24   g  are symmetrically put not to deviate an acting point for the driver  60 . As described above, the driver  60  features that the rotations of the rotating cams  23   e  and  24   e  arranged symmetrically make upward or downward pushing while moving the acting points in sequence, not causing the driver head  63  to shake right or left. This allows the staples to pass securely through even a large amount of sheet bundle. 
     The anvil unit  30 , as shown in  FIG. 5 , is made up of an anvil  31  for pressing the sheet bundle and paired movable frame (hereinafter referred to as anvil arms  32   a  and  32   b ) extended from respective ends of the anvil  31  for pinching both sides of the fixed frame  11 . The anvil  31  has a flat sheet pressing surface  33  and a clincher covered with a cover  34  on the sheet pressing surface  33 . The anvil arms  32   a  and  32   b  are made swingable with centers of first swing pivots  35   a  and  35   b  supported axially at the fixed frame  11 . It should be noted that the anvil arms  32   a  and  32   b  and the fixed frame  11  are urged at their respective lower ends by the first spring  36   a  and  36   b  as shown in  FIGS. 1 and 2  so that the anvil  31  can be placed at a position opened for the sheet table  13  to put the sheet bundle therein in normal state. 
     The anvil unit  30 , as shown in  FIGS. 3 and 5 , has an activating member (hereinafter referred to as anvil swinging shaft  37 ) swung as being made to abut on peripheries of the eccentric cams  23   c  and  24   c  in the driver  20  and by virtually elbowed transmission members (hereinafter referred to as activating levers  27   a  and  27   b ) made to abut on the anvil swinging shaft  37 . The activating levers  27   a  and  27   b , as shown in  FIGS. 5 and 6 , have respective ends of the anvil arms  32   a  and  32   b  supported by shaft at second swing pivots  38   a  and  38   b . The activating levers  27   a  and  27   b  are fitted at ends thereof with respective abutting protrusions  28   a  and  28   b  disposed to project on respective ends of the anvil arms  32   a  and  32   b  as urged by second springs  39   a  and  39   b . Swinging of the activating levers  27   a  and  27   b , as shown in  FIG. 7 , is made by the anvil swinging shaft  37  abutted on the peripheries of the eccentric cams  23   c  and  24   c . The anvil swinging shaft  37  is reciprocally moved up and down once while contacting the peripheries of the eccentric cams  23   c  and  24   c  as the eccentric cams  23   c  and  24   c  rotate one turn. Such a vertical reciprocal movement resists against the first spring  36   a  and  36   b  urged to the fixed frame  11  to press down the activating levers  27   a  and  27   b . The anvil arms  32   a  and  32   b  are moved down with centers of the first swing pivots  35   a  and  35   b  to clamp the sheet bundle put on the sheet table  13 . 
       FIG. 8  is views of another embodiment of the anvil swinging shaft. The anvil swinging shaft  37   a  in the embodiment has small rollers  23   k  and  24   k  built thereon in parallel with the paired shafts  23   b  and  24   b . The rollers  23   k  and  24   k  are supported to contact peripheries of the eccentric cams  23   c  and  24   c . Such an anvil swinging shaft  37   a  allows for further smooth rotations of the eccentric cams  23   c  and  24   c  and less noise during driving as having the rollers  23   k  and  24   k  arranged. 
     The following describes operation of the anvil unit  30  by reference to  FIG. 9 . The figures for steps a through e are views showing a clamping operation of the sheet bundle, particularly in movements of the paired anvil arm  32   a  and the activating lever  27   a . The following description is for the component members and symbols on one side, but same as on the other sides. Steps a through c described below are of operations of clamping the sheet bundle. 
     Step a. The figure shows a state before clamping the sheet bundle. The anvil  31  is stopped at a position farthest from the sheet table  13 . The anvil arm  32  in the state is urged to swing clockwise with a center of the first swing pivot  35   a  by the first spring  36   a  as the anvil swinging shaft  37  is at a position escaped from the cam face of the above-mentioned eccentric cam  23   c . The anvil swinging shaft  37  is brought up to a highest position by the activating lever  27   a  abutting on the abutting protrusion  28   a  on the anvil arm  32   a  by the second spring  39   a , the activating lever  72   a  being supported by shaft with a center of the second swing pivot  38   a  together with the anvil arm  32   a . In such a state, the anvil arm  32   a  abuts on a stop of an apparatus frame (not shown) by the first spring  36   a  to keep in the initial state that opens a space available for loading the bundle of maximum allowable sheets to staple. 
     Step b. When a staple start signal is received from an external apparatus with the sheet bundle placed in position on the sheet table  13  in step a before, the eccentric cam  23   c  starts rotation. At the same time, the anvil swinging shaft  37  presses down the activating lever  27   a  to resist against the first spring  36   a . Then the anvil arm  32   a  starts turning toward the sheet table  13  with the center of the first swing pivot  35   a . In the event, the second spring  39   a  turns the activating lever  27   a  and the anvil arm  32   a  together. The state becomes one that the maximum allowable bundle sheets can be stapled. 
     Step c. The anvil arm  32   a  turns further. The figure shows the state that zero to several sheets are clamped. 
     The following steps d and e are for a bundle thickness absorption operation to adjust the moving distance for thickness of the sheet bundle with turning of the eccentric cam  23   c  after clamping the sheet bundle at steps b and c above. 
     Step d. First, when the anvil  31  clamps the sheet bundle of a desired thickness in the state of step b, the anvil arm  32   a  stops swinging once. Even in the state, the eccentric cam  23   c  continues rotation further to press the anvil swinging shaft  37  downward. This resists against urging of the second spring  39   a  to rotate the activating lever  27   a  counterclockwise until the eccentric cam  23   c  rotates one turn. Also the reaction given by the rotation of the activating lever  27   a  resisting against the urging force of the second spring  39   a  allows the anvil  31  to clamp the sheet bundle. This completes the clamping operation the force of which is enough not to escape the sheet bundle when the staple is driven in upward. The clamping operation also prevents the activating lever  27   a  and the eccentric cam  23   c  from being damaged. 
     Step  3 . The figure shows the state that the sheet bundle is thinner than at step d. The operation is similar to step d above. Description is omitted. 
     As explained above, the anvil unit  30  having the arrangement mentioned above can perform secure clamping operation irrespective of the thickness of sheet bundle. 
     The cover  34  of the anvil  31  has the clincher unit  50  disposed therein. The clincher unit  50  is an arrangement for bending edges of the staples passed through the sheet bundle by the driver head  63  inside the driver  60 . The clincher unit  50 , as shown in  FIG. 10 , is made up of paired clinchers  51   a  and  51   b  for guiding to open and close the both edges of the staples, a clinch plate  52  for pressing at centers of clinchers  51   a  and  51   b  to bend the both edges of the staples, and a U-shaped clinch arm  53  supported swingably at the first swing pivots  35   a  and  35   b  of the anvil arms  32   a  and  32   b . The clinch arm  53  is rotatably supported at the first swing pivots  35   a  and  35   b  on the fixed frame  11  together with the anvil arms  32   a  and  32   b . After the anvil arms  32   a  and  32   b  support the sheet bundle by clamping it, the clinch arm  53  is independently swung with centers of the first swing pivots  35   a  and  35   b  by joint levers  26   a  and  26   b  interlocked with the clinch swinging pins  23   d  and  24   d . The clinch arm  53  then moves the clinch plate  52  interlocked with the clinch arm  53 . The joint levers  26   a  and  26   b , as shown in  FIG. 2 , are rotatably supported at the respective swing pivots of the anvil arms  32   a  and  32   b  and the clinch arm  53 . The joint levers serve to transmit swinging of the first cam member  23  and the second cam member  24  in the driver unit  20  to the anvil unit  30  and the clinch unit  50 . 
       FIG. 11  shows a staple feeding arrangement  70  for sequentially feeding the band-shaped staples  43  held in the staple supply unit  40  toward the driver  60  and the clincher unit  50 . The staple feeding arrangement  70  has a staple feeding lever  71  supported swingably on the fixed frame  11  via the staple swinging shaft  73 , a staple feeding pawl  72  disposed at an end of the staple feeding lever  71 , and a plate spring  74  for urging the staple feeding lever  71  to a predetermined position. Feeding the band-shaped staple  43  is made by rotating the drive gears  23   a  and  24   a  with the drive motor  21 . The rotation allows staple feeding pings  23   h  and  24   h  mounted to stand at the drive gears  23   a  and  24   a  pushes rightward the staple feeding lever  71  supported to resist against the plate spring  74 . This hooks the staple feeding pawl  72  on the staples  43 . When the drive gears  23   a  and  24   a  are rotated, further, the staple feeding pins  23   h  and  24   h  are taken out of the staple feeding lever  71 , which is then pushed back leftward by force of the plate spring  74 . In such an operation, the staples  43  are fed out toward a bending block  75  (which will be later) by the staple feeding pawl  72 . 
     The staples  43  moved forward sequentially by the staple feeding arrangement  70 , as shown in  FIG. 12 , are abutted against a staple catching groove of the square bending block  75  disposed at a front of the fixed frame  11 . A staple forming member  77  placed through a homer pin  76  at a long hole  65  of the driver head  63 , then can form the staple  43  to U-shape as the driver head  63  moves up. After that, the both side plate springs  66   a  and  66   b  on the driver head  63  are moved on guide blocks  78   a  and  78   b . This disengages the plate springs  66   a  and  66   b  from the staple forming member  77 . Only the driver head  63  pushes up the U-shaped staple  43  onto the anvil  31  positioned further upward to pass it through the sheet bundle. The clincher unit  50  bends the both legs of the staple  43 , completing the stapling operation. 
       FIG. 13  shows the sequential stapling operation of the stapler apparatus  10  as looked to the front thereof. The following describes operation steps in the order shown in the figure. 
     a. Initial State 
     This shows a state right before start of the stapling operation. The staple  43  is fed under the bending block  75  by the means described by reference to  FIGS. 11 and 12 . The sheet bundle  79  is aligned on the sheet table  13 . The driver  60  is put at a home position at the bottom, while the anvil  31  is open as separated away from the sheet bundle  79 . 
     b. Sheet Bundle Clamping State 
     When a stapling start signal is received in the state a above, the paired rotating cams  23   e  and  24   e  start rotation in arrow directions. The rotations of the rotating cams  23   e  and  24   e  make the driver swinging pins  23   g  and  24   g  press the driver  60  up. At the same time, through the serial operations shown in  FIG. 9 , the anvil  31  moves down to clamp the sheet bundle  79  in the sheet table  13 . 
     c. Staple Forming State 
     The staple forming member  77  bends upward the both ends of the staple  43  put on the bending block  75  as interlocked with upward movement of the driver  60  in step b above. 
     d. Stapling Start State 
     The driver  60  and the staple forming member  77  are disengaged from the state at step c above. Only the driver  60  moves up. The end  64  on the driver head  63  then is butted against the U-shaped staple  43 . The staple  43  is at the state right before being driven into the sheet bundle  79 . 
     e. Stapling Setup State 
     When the driver  60  moves up further from the state at step d above, the both ends on the U-shaped staple  43  are passed through the sheet bundle  79  and run into the clinchers  51   a  and  51   b , allowing clinching to start. 
     f. Clinching State 
     Finally, the clinching plate  52  is pushed down to bend the both ends of the staple inward. This ends the sequence of stapling operations. 
     The operations at steps a to f can be completed in a single turn of the driver swinging pins  23   g  and  24   g  made to stand on the rotating cams  23   e  and  24   e . As described so far, the stapler apparatus  10  according to the present invention is excellently stable as the drive parts are driven by the two systems of cam members  23  and  24  of identical members. In particular, the rotating cams  23   e  and  24   e  and the driver swinging pins  23   g  and  24   g  for driving the driver  60  can perform smooth driving as they are symmetrical in shape and position. 
       FIG. 14  is a timing chart illustrating the sequential operations of the stapler apparatus. The sequential operations are described below by reference to  FIGS. 14 ,  2 , and  3  through  5 . The drive motor  21  starts rotation as receiving the stapling start signal from an apparatus body (not shown). The drive motor  21 , as shown in  FIG. 3 , transmits rotational torque through the deceleration gears  22  to the first cam member  23  and the second cam member  24 . The first cam member  23  and the second cam member  24  start swinging of the anvil unit  30  first, which is large in amount of swinging. The sheets are clamped in a range of an amount of swing for two sheets (85 degrees of the sixth deceleration gear  22   f ) to an amount of swing for 50 sheets shown by dotted line in the figure. In the start, swinging of the anvil swinging shaft  37  butted against the eccentric cams  23   c  and  24   c  is absorbed by the second springs  39   a  and  39   b  as the anvil unit  30  clamps the sheet bundle not to swing further. The driver  60  driven by the rotating cams  23   e  and  24   e  is moved a little later after swinging of the anvil unit  30 . The staple forming member  77  interlocked with the driver  60  forms the staples  43  to U-shape before the driver head  63  drives the U-shaped staple  43  in position on the sheet bundle. After driving, the clincher unit  50  is returned up first by spring force together with release of the cam members. Then the anvil unit  30  also is returned up by spring force together with release of the cam members. At the same time, also, the driver unit  20  is returned down with release of the cam members, being reset to the home position. 
     The embodiments described so far have the anvil unit  30  swung to clamp the sheet bundle between it and the driver unit  20  placed in position. Alternatively, of course, the driver unit  20  can be swung, and both the driver unit  20  and the anvil unit  30  can be swung one another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an overall structure of a stapler apparatus of the present invention. 
         FIG. 2  is a side view of the stapler apparatus shown in  FIG. 1 . 
         FIG. 3  is a perspective view of main parts of the driver unit. 
         FIG. 4  is a perspective exploded view of the driver unit. 
         FIG. 5  is a perspective view of main units of the stapler apparatus, including a driver unit and an anvil unit. 
         FIG. 6  is a cross-sectional view of main parts of cam members and operating levers. 
         FIG. 7  is a view of main parts of an eccentric cam and an anvil swinging shaft. 
         FIG. 8  is a view of main parts of another embodiment of the eccentric cams and the anvil swinging shaft. 
         FIG. 9  is an illustration showing a clamping operation of a sheet bundle. 
         FIG. 10  is a perspective view of main parts of a clincher unit. 
         FIG. 11  is a perspective view of main parts of a staple feeding arrangement. 
         FIG. 12  is an illustration showing a forming structure of staples. 
         FIG. 13  is an illustration showing a sequential operation of the staples. 
         FIG. 14  is a timing chart showing the sequential operation of the staples in  FIG. 11  above. 
     
    
    
     SYMBOLS 
       10 =Stapler apparatus 
       20 =Driver unit 
       21 =Drive motor 
       23 =First cam member 
       24 =Second cam member 
       27   a  and  27   b =Activating levers 
       28   a  and  28   b =Abutting protrusions 
       30 =Anvil unit 
       32   a  and  32   b =Anvil arms 
       38   a  and  38   b =Second swing pivots 
       39   a  and  39   b =Second springs 
       40 =Staple supply unit 
       50 =Clincher unit 
       60 =Driver 
       70 =Staple feeding arrangement