Abstract:
An electric stapler capable of handling multiple sheets of paper. A motor-driven pair of wheel gears turn a swing arm having a symmetrical structure for driving a staple firing assembly and a clinch mechanism, thereby applying large pressure uniformly on staples. The clinch mechanism bends staple legs in different directions so that they do not overlap each other, preventing the clinched part of paper from increasing in the thickness of the stacked paper.

Description:
The present disclosure relates to subject matter contained in priority Japanese Patent Application No. 2002-286170, filed on Sep. 30, 2002, the contents of which is herein expressly incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a clinch mechanism for a stapler that drives a staple through stacked sheets of paper with a hammer and clinches the piercing legs of the staple to hold the paper together, and an electric stapler using this clinch mechanism. 
     2. Description of Related Art 
     An electric stapler, which automatically drives a staple into an inserted stack of paper, is suitably used for handling a large number of paper or when paper handling is frequently necessary. Commercially available electric staplers include both battery-powered type and AC-powered type. While the former has the advantage of being cordless, the latter is more preferable in that it is free of battery exhaustion; also, the latter can be constructed smaller and more lightweight because it need not accommodate many batteries for supplying power necessary to staple multiple paper sheets. 
     FIG. 12 illustrates an AC-powered electric stapler shown in Japanese Patent Laid-Open Publication No. 2000-153470 (reference A). A motor  8  rotates a crank gear  25  and turns a crank rod  26 , thereby moving a hammer  3  at the distal end of the rod  26  downward to drive a staple accommodated in a staple holder  30  into a stack of paper placed on a clinch plate  32 . The legs of the staple penetrated through the stack are bent by the clinch plate  32 , thus holding the paper together. 
     The clinch plate  32  has a guide groove so as to bend legs of driven staples inwards to face each other. This bending of staples by the clinch plate  32  deforms the legs of staples in an arc, so the problem is that the thickness of the stack of paper in the stapled portion is larger than the other portions. Also, this structure with the clinch plate  32  has a drawback that the bending is achieved with less certainty particularly when the stack is thick. In order to staple multiple paper sheets, staples with longer legs are necessary; one requirement here is to clinch the driven staples in a non-overlapping manner so that the clinched part will not cause an increase in the thickness of the stacked paper. 
     FIG.  13 A and FIG. 13B illustrate the construction of a stapler clinch mechanism shown in Japanese Patent Laid-Open Publication No. Hei 10-118956 (reference B), which bends long-legged staples in a non-overlapping manner. Two movable clinchers  53   a,    53   b  are arranged in grooves  45   a,    45   b  that are respectively formed between stationary walls  44   a,    44   b  and receiving plates  43   a,    43   b  having different thicknesses. The receiving plates  43   a,    43   b  are formed with guide slopes  48  at locations in point symmetry around the center O therebetween for receiving legs  52   a  of a staple  52 . The staple legs  52   a  are guided in opposite directions by the guide slopes  48  into the grooves  45   a,    45   b  and clinched by the clinchers  53   a,    53   b.    
     Driving staples with long and wide apart legs into multiple sheets requires a large power supply with uniform pressure application. 
     The conventional electric stapler of the above reference A is structurally incapable of applying large and uniform pressure with the hammer on the staple legs. The clinch plate cannot bend large-sized staple legs; a clinch mechanism is necessitated for heavy duty stapling tasks. 
     The conventional clinch mechanism of the above reference B, however, has a drawback that staple legs can easily be deformed in a central part because of the symmetric design in which the movable clinchers are accommodated in the grooves formed by oppositely arranged plates with different thicknesses. Thus stable clinching may not be achieved in repeated use applications. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an improved clinch mechanism for a stapler that bends staple legs in a non-overlapping manner, and an electric stapler using this clinch mechanism. 
     To achieve the above object, the present invention provides a clinch mechanism for a stapler that pushes and drives a staple out of a staple magazine into a stack of paper by a lowering motion of a hammer, and clinches legs of the staple that has penetrated the paper inward to hold the paper together, including: a pair of base plates arranged parallel with a spacing therebetween that conforms to a direction in which the legs of the staple that has penetrated the paper are oriented; a thin-plate partition forming equally spaced gaps on both sides thereof by halving the spacing between the pair of base plates, the partition including a pair of protruding pieces on an top side thereof respectively corresponding to each of staple legs, which protruding pieces are bent in opposite directions at a preset angle to form slanted faces that partly close the equally spaced gaps, respectively; a pair of clinch plates rotatably arranged inside the equally spaced gaps; and a clinch arm for rotating the pair of clinch plates simultaneously with the lowering motion of the hammer. 
     With this clinch mechanism, the legs of the staple that has penetrated the paper are driven onto the top side of the partition and guided into the equally spaced gaps by the slanted faces of the pair of protruding pieces. The pair of clinch plates disposed in these gaps are then turned by the clinch arm so as to clinch the staple legs to hold the paper together. The staple legs are first bent in opposite directions by the pair of protruding pieces before being clinched by the clinch plates, so that they do not overlap each other and the clinched part of paper is prevented from causing an increase in the thickness of the stacked paper. 
     The present invention also provides an electric stapler that pushes and drives a staple out of a staple magazine into a stack of paper by a lowering motion of a motor-driven hammer, and clinches legs of the staple that has penetrated the paper inward to hold the paper together, including: a support stand having a pair of upright walls facing each other; a magazine holder holding the staple magazine, arranged between the upright walls, pivotable around an axis at a rear end, and biased upwards; a staple firing assembly including a structure for moving up and down the hammer along a vertical staple firing line at a front end of the support stand and a structure for lowering the staple magazine; a clinch mechanism having a clinch plate disposed below the staple firing line for bending staple legs; a pair of wheel gears attached to the upright walls of the support stand, respectively, and driven by the motor synchronously; a swing arm bridging across the upright walls, turned by the pair of wheel gears to drive the staple firing assembly around a shaft that is biased downwards by a pair of springs; and a clinch arm turned by the pair of wheel gears to drive the clinch mechanism. 
     With this electric stapler, a large pressure is applied equally on both legs of staples because of the configuration in which the staple firing assembly is driven by the swing arm that is turned by the pair of wheel gears driven by the motor. Staples with long and wide apart legs are thus driven successfully into a thick stack of paper. The pair of wheel gears also rotate the pair of clinch plates of the clinch mechanism through the clinch arm simultaneously with the operation of the staple firing assembly, ensuring clinching of long staple legs. 
     In this electric stapler constructed as above, the clinch mechanism includes a pair of base plates arranged parallel with a spacing therebetween that conforms to a direction in which the legs of the staple that has penetrated the paper are oriented; a thin-plate partition forming equally spaced gaps on both sides thereof by halving the spacing between the pair of base plates, the partition including a pair of protruding pieces on an top side thereof respectively corresponding to each of staple legs, which protruding pieces are bent in opposite directions at a preset angle to form slanted faces that partly close the equally spaced gaps, respectively; and a pair of clinch plates rotatably arranged inside the equally spaced gaps. This makes it possible to bend the staple legs so that they do not overlap each other. 
     While novel features of the invention are set forth in the preceding, the invention, both as to organization and content, can be further understood and appreciated, along with other objects and features thereof, from the following detailed description and examples when taken in conjunction with the attached drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1A is a bottom plan view and FIG. 1B is a side view illustrating the internal structure of an electric stapler according to one embodiment of the present invention; 
     FIG. 2A is a top plan view, FIG. 2B is a side view, and FIG. 2C is a front view, illustrating the structure of a power transmission mechanism in an initial state; 
     FIG. 3A is a top plan view, FIG. 3B is a side view, and FIG. 3C is a front view, illustrating the structure of the power transmission mechanism when driven; 
     FIG. 4A is a top plan view, FIG. 4B is a side view, and FIG. 4C is a front view, illustrating the structure of the power transmission mechanism when firing a staple; 
     FIG. 5 shows a magazine holder in plan and side views; 
     FIG. 6A is a top plan view, FIG. 6B is a side view, and FIG. 6C is a bottom plan view, illustrating a driven gear; 
     FIG. 7 is a perspective view of a clinch arm; 
     FIG. 8A is a top plan view, FIG. 8B is a front view, and FIG. 8C is a side view, illustrating the structure of a clincher; 
     FIG. 9 is an exploded plan view of the clincher; 
     FIG. 10A is a top plan view and FIG. 10B is a side view of a partition; 
     FIG. 11 is a top plan view of a clinched staple; 
     FIG. 12 is a cross-sectional view illustrating the structure of a conventional electric stapler; and 
     FIG. 13A is a perspective view and FIG. 13B is a top plan view illustrating the structure of a conventional clinch mechanism. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be hereinafter described with reference to the accompanying drawings. 
     FIG.  1 A and FIG. 1B illustrate the overall structure of an electric stapler according to one embodiment of the invention. Upon a bottom case  70  are arranged a power transmission mechanism  101  and a transducer  122  constituting a power supply device for a staple firing assembly. An upper case  74  is closed on the bottom case  70  to cover these elements. On the front side of the bottom case  70  is a clinch table  99 , above which is arranged the upper case  74  such as to form a space for allowing insertion of a stack of paper. A start switch lever  124  stands upright on the clinch table  99 . When this lever  124  is pushed by a stack of paper inserted onto the clinch table  99 , it turns on a start switch  126  to activate the power transmission mechanism  101 , which supplies power to the staple firing assembly  72  for driving staples into stacked sheets and to a clinch mechanism  73  for bending legs of the staple that has penetrated the sheets to hold them together. The stapler automatically shuts off afterwards. Stapling is thus achieved simply by inserting a stack of paper onto the clinch table  99 . The stapling position is adjustable in forward or backward direction by changing the position of the lever  124  with a setting knob  125 . 
     The power transmission mechanism  101  is configured upon a support stand  71  fixed on the bottom case  70 , as shown in FIG. 2A to FIG.  4 C. As is seen from FIG. 2A, the support stand  71  includes a first stand  71 a and a second stand  71 b that form upright walls standing on the bottom case  70 . Between these two stands  71   a  and  71   b  is arranged a magazine holder  115  shown in FIG. 5 that detachably holds a staple magazine  114  accommodating multiple staples. The magazine holder  115  is pivotable around an axis  77  defined at the back end and biased upwards by a spring which is not shown in the drawing. The staple firing assembly  72  for driving staples into stacked paper is configured at the front end of the support stand  71 , and the clinch mechanism  73  for bending the legs of staples that have penetrated the stacked paper is configured therebelow. The staple firing assembly  72  and clinch mechanism  73  are both driven by a motor  75  and a gear train. 
     The motor  75  is mounted to the first stand  71   a.  A motor gear  81  fixed to the shaft of the motor  75  interlocks with a drive gear  82 , which rotates a first idler gear  83   a.  The first idler gear  83   a  is fixed on the side of the first stand  71   a  of a shaft  84  that is rotatably supported on the first and second stands  71   a,    71   b.  A second idler gear  83   b  is fixed to the shaft  84  on the side of the second stand  71   b,  and is rotated together with the first idler gear  83   a  by the drive gear  82 . The first idler gear  83   a  and second idler gear  83   b  engage with a first driven gear  85   a  and a second driven gear  85   b,  respectively, thereby rotating them. The drive gear  82 , and first and second idler gears  83   a,    83   b  include pinions integrally formed therewith to achieve preset reduction ratios. 
     To the first and second driven gears  85   a,    85   b  are attached drive pins  80  on the outer face thereof as shown in FIG.  6 A. On the inner face are formed cam grooves  86  and switch driving bosses  98  as shown in FIG.  6 C. These driven gears  85   a,    85   b  drive the staple firing assembly  72  and clinch mechanism  73  as they are rotated. The drive pins  80  fit into curved slots  87  formed in a swing arm  78  for driving the staple firing assembly  72 . The swing arm  78  and clinch arm  79  have a symmetrical configuration so that their left and right parts are driven synchronously by the first and second driven gears  85   a,    85   b  on both sides. The clinch arm  79  is formed with rollers  96  at the distal end as shown in FIG. 7, which fit in the cam grooves  86  for the purpose of driving the clinch mechanism  73 . The cam grooves  86  are continuous circumferential grooves with differing radii, so that rotation of the first and second driven gears  85   a,    85   b  turns the clinch arm  79  through engagement between the rollers  96  and cam grooves  86 . 
     The swing arm  78  rests in notches at the top of the first and second stands  71   a,    71   b  and turns around a support shaft  88  that is biased downward by a pair of springs  91 , by the drive pins  80  fitted in the curved slots  87  on both left and right sides. FIGS. 2A-2C through FIGS. 4A-4C illustrate each step that the swing arm  78  goes through as the first and second driven gears  85   a,    85   b  rotate one turn. With a further rotation of the driven gears  85   a,    85   b,  the swing arm  78  eventually returns to the position shown in FIGS. 2A-2C. At one end of the swing arm  78  are formed elliptic holes  89  for supporting either end of a drive shaft  90 . As the swing arm  78  turns, the drive shaft  90  moves up and down, causing a hammer  76  for driving staples into stacked paper to move up and down, and also pulling the upwardly biased magazine holder downwards. 
     The clinch arm  79  is configured as shown in FIG.  7 . It turns around a shaft  92  passed through holes  93  and supported on the first and second stands  71   a,    71   b,  causing a pressing piece  94  at one end to move up and down so as to activate a clincher  100  to be described later. The rollers  96 , attached at the distal ends of a pair of plates  97   a,    97   b,  fit in the cam grooves  86  respectively of the first and second driven gears  85   a,    85   b,  so that the clinch arm  79  turns as the driven gears rotate. 
     The clincher  100  has a pair of movable clinch plates  103   a,    103   b  arranged in a gap between base plates  105 ,  106  in a rotatable manner as shown in FIG. 8A to FIG.  8 C. These clinch plates  103   a,    103   b  are driven by the pressing piece  94  of the clinch arm  79  to bend the legs of staples that have penetrated stacked paper. The base plates  105 ,  106  are respectively attached to support arms  102   a,    102   b  extending from the first and second stands  71   a,    71   b,  whereby the clincher  100  is located below the staple firing assembly  72 . 
     Between the parallel clinch plates  103   a,    103   b  is interposed a partition  107  shown in FIG. 10A made of a thin metal sheet. FIG. 9 shows the constituent elements of the clincher  100  in an exploded view. The partition  107  is formed with a pair of slanted lugs (protruding pieces)  104   a,    104   b.  As is seen from FIG. 10B, the slanted lug  104   a  is bent at about 45° toward the side of the base plate  106 , while the other lug  104   b  is bent at about 45° toward the opposite side. The distance between the centers of the lugs  104   a,    104   b  corresponds to the distance between staple legs. 
     Referring to FIG. 9, the base plate  105  has holes for receiving one end of shafts  108   a,    108   b,  and the movable clinch plate  103   a,  partition  107 , and the other clinch plate  103   b  are superposed thereon in this order, the shafts  108   a,    108   b  passing through holes respectively formed in these parts. Lastly, the other end of the shafts  108   a,    108   b  is fitted into holes in the base plate  106 , and screws  109   a,    109   b  are tightened from both sides into the holes in the opposite base plates  105 ,  106 , whereby the clincher  100  shown in FIG. 8A to FIG. 8C is formed. The tips of the lugs  104   a,    104   b  respectively rest on notches  110   a,    110   b  formed on the base plates  106 ,  105 , as shown in FIG.  8 A. 
     The clincher  100  is disposed such that the partition  107  is located directly below the plate-like hammer in the staple firing assembly  72 . When the assembly  72  is driven to fire a staple by the hammer, its legs penetrate through stacked paper and are driven onto the lugs  104   a,    104   b  of the partition  107 . The slanted faces of the lugs  104   a,    104   b  direct the staple legs in opposite directions and bent them onto the clinch plates  103   a,    103   b,  respectively. Turning the clinch plates  103   a,    103   b  in this state by the clinch arm  79  bends the legs  113   a,    113   b  of the staple  113  so as to be offset relative to the partition  107 , thus forming a non-overlapping clinch. 
     AC power is used both for powering the motor  75  of the power transmission mechanism  101  and for the overall control. The electric circuit is constructed roughly as follows: AC power supplied through a cord  121  is decreased in voltage to a preset level by a transducer  122  and converted into DC power by a rectifying circuit configured on a control circuit substrate  123  so as to constitute a DC power source for the motor  75  and control circuit. The control circuit controls the motor  75  based on an ON/OFF input from a switch suitably provided to a movable component, and detects abnormality such as crunching of a staple. 
     Referring to FIG.  1 A and FIG. 1B, to start the stapler, a stack of paper is inserted onto the clinch table  99  formed with an opening above the clincher  100  to push in the start switch lever  124 , turning on the start switch  126 . This information is input to the control circuit  123 , which in turn activates the motor  75  to rotate the first and second driven gears  85   a,    85   b  from the angle position shown in FIG. 2B, to turn the swing arm  78  by the drive pins  80 . When the swing arm  78  reaches the angle position shown in FIG. 3B, the drive shaft  90  engaging with the elliptic holes  89  are moved downward by the swing arm  78  to lower the hammer  76 . At the same time, the magazine holder is lowered so that its bottom end makes pressure contact with the stack of paper on the clinch table  99 . 
     A further rotation of the first and second driven gears  85   a,    85   b  turns the swing arm  78  to the angle position shown in FIG. 4B, where a large drive force is applied to the hammer  76  by the downward bias of the springs  91  on both sides, the hammer  76  thereby pushing a staple out of the staple magazine and driving it into the stack of paper. The position in up and down direction of the support shaft  88  is adjustable by the pair of springs  91  that are biasing the shaft  88  downward in accordance with the thickness of the stack so that the hammer  76  exerts constant drive force irrespective of the thickness of the stack. 
     Instantly after this staple firing into the stack of paper, the rollers  96  of the clinch arm  79  engaging with the cam grooves  86  of the driven gears  85   a,    85   b  enter the large radius zone of the cam grooves  86 , turning the clinch arm  79 , which then turns the pair of clinch plates  103   a,    103   b  by the pressing piece  94  at the distal end. The legs of the staple that has penetrated the stacked paper and inserted into the clincher  100  are thereby clinched, holding the stack of paper together. The staple legs are bent in different directions, not overlapping each other. 
     The driven gears  85   a,    85   b  further rotate after this clinching operation, thereby turning the distal end of the swing arm  78  upward by the drive pins  80  to lift up the hammer  76 . The rollers  96  enter the small radius zone of the cam grooves  86 , thereby turning the clinch arm  79  to move its pressing piece  94  downward. In returning of the driven gears  85   a,    85   b  to the angle position shown in FIG. 2B after rotating one turn, the switch driving boss  98  on the first driven gear  85   a  turns on a stop switch  120 . When this information is input to the control circuit, the motor  75  is stopped, and the stapling operation is completed. 
     The electric stapler starts up automatically when a stack of paper is inserted onto the clinch table  99 . Should an abnormality arise such as crunching of a staple, the control circuit lights up an indication lamp  117 . The lamp  117  is lit all through while the power transmission mechanism  101  is operating, with the start switch lever  124  being pushed by a stack of paper, to indicate that the stapler is in operation. The indication lamp  117  is also illuminated in a suitable manner when the staples  113  in the staple magazine  114  have run out, so as to notify the user of the need to reload staples  113 . Pushing an eject button  118  downward releases the hold of the staple magazine  114  by the magazine holder  115 , allowing the staple magazine  114  to eject out to the front by the biasing force of a spring. Staples  113  can then be reloaded into a mouth of the staple magazine. The staple magazine  114  is reset into the magazine holder  115  by pressing a knob  116  at the front end thereof. 
     The clincher  100  of the invention can also be applied to a manually operated stapler for achieving flat clinch stapling. 
     According to the invention, the electric stapler successfully handles multiple sheets of paper because it applies a large, uniform pressure on large and long-legged staples. The clinch mechanism has such a structure that the clinching effect does not deteriorate over time and is applicable to a powerful staple firing assembly. Moreover, the clinch mechanism bends the staple legs in different directions so as not to overlap each other, allowing the paper sheets to stack more neatly. 
     Although the present invention has been fully described in connection with the preferred embodiment thereof, it is to be noted that various changes and modifications apparent to those skilled in the art are to be understood as included within the scope of the present invention as defined by the appended claims unless they depart therefrom.