Abstract:
A forward acting stapler includes a unique linkage for driving a firing lever. The linkage includes two links that are each connected to the trigger lever by a roller. The roller is movable within a spot in the trigger lever. As the handle is driven, the two links cause the triggering level to pivot. As the trigger lever pivots it lifts a plunger against a spring force. At some point, the trigger portion releases the plunger allowing the plunger to be returned by the spring force by a staple.

Description:
This application is a continuation of Ser. No. 10/285,719 filed on Nov. 1, 2002 now U.S. Pat. No. 6,789,719. 

   BACKGROUND OF THE INVENTION 
   This invention relates to a forward acting stapler. 
   Forward acting staplers are known in the art, and have a handle which is pivoted at one end of a stapler body. The handle is pivoted downwardly with the hand of the user received on an end of the handle remote from the pivot point. This end is generally vertically spaced above the location where a plunger and knife combination will drive a staple or nail into a workpiece. For purposes of this application, the term “plunger” should be understood to also include the knife which moves with the plunger. The forward acting stapler is an improvement over staplers which have the pivot point of the handle on the end of a stapler body which receives the plunger in that the force of the hand can be applied more directly to the plunger. 
   In the prior art, such forward acting staplers have been known for decades. However, the forward acting staplers known to date have had complex linkages which have made them difficult to use and sometimes unreliable. 
   SUMMARY OF THE INVENTION 
   The present invention provides a linkage including a handle lever which is connected by a pair of links to a trigger lever. In fact, each of the links have two sides which are positioned on each side of the handle lever in a preferred embodiment. The trigger lever is controlled to pivot as the firing handle is pivoted downwardly. The trigger lever has a trigger portion adjacent the end of the housing which receives the firing plunger. The two-part linkage between the handle lever and the trigger lever includes a first link pinned to the handle lever and which moves a roller. The roller is also fixed to a holding link which is pivotally attached to the housing. The roller is received in a slot in the trigger lever. The arrangement of the two links, the handle lever, and the trigger lever slot is such that as the handle lever is moved downwardly, the first link forces the roller to move in a direction to pivot the trigger lever in such a way that the trigger portion at the end of the trigger lever moves in a direction upwardly. When this movement occurs, the holding link causes the roller to move within the slot in a direction away from a pivot point of the trigger lever. The trigger portion of the trigger lever includes a member which is spring biased to a holding position at which it is received under a ledge on an actuating plunger. A flat power spring extends through the body of the stapler and biases the plunger to drive a staple or nail into a work surface once the plunger is released by the trigger lever. 
   As the handle is moved downwardly, the movement between the two links and the two levers continues with the trigger portion of the trigger lever continuing to pull the plunger upwardly against the force of the spring. During this movement, the geometry of the trigger portion tends to move the trigger away from the plunger. At some point, the power spring drives the plunger to drive a staple into the workpiece. 
   In a preferred embodiment, the trigger portion is mounted near the end of the trigger lever on a pair of pins and a bias spring combination. One pin is fixed to the trigger lever and is received within a slot in the trigger portion. The trigger portion has its own pin received in a slot on the trigger lever. A spring biases the trigger portion pin toward the trigger lever pin, and thus biases the trigger portion outwardly toward the plunger. This spring force holds the trigger portion under the plunger as the plunger is raised, and up until the firing point. When the trigger lever is returned after firing, this spring allows the trigger portion to cam along a ramp surface on the plunger and be returned beneath the plunger ledge. 
   The present invention provides a reliable and simplified linkage. Further, the trigger portion is also simple and yet quite reliable. 
   The present invention can be best understood from the following specification and drawings, the following of which is a brief description. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  shows a stapler in a relaxed position. 
       FIG. 2  shows a point during the initial movement of the stapler towards a firing position. 
       FIG. 3  shows a point subsequent to the  FIG. 2  point. 
       FIG. 4  shows yet another subsequent point. 
       FIG. 5A  shows yet another subsequent point. 
       FIG. 5B  shows the position of the linkages and roller at the beginning of movement. 
       FIG. 5C  shows a point subsequent to the  FIG. 5A  point, and in particular the firing point. 
       FIG. 5D  shows the structure and movement of the trigger portion as it moves toward the firing point. 
       FIG. 5E  shows the structure and movement of the trigger portion as it is returned to its original rest position. 
       FIG. 6A  shows a first view of a return spring. 
       FIG. 6B  shows a second view of the return spring. 
       FIG. 7  shows an alternate embodiment. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  shows a forward acting stapler  20 . As shown, handle lever  22  is pivotally attached at pivot point  24  within a stapler housing  25 . A pin creates a pivot point  26  pivotally connects a first link  28  to the handle lever  22 . A roller  30  moves with the link  28 , and is received in a slot  32  in a trigger lever  31 . A holding link  34  also moves with the roller  30  and is pivotally attached at pivot point  36  to the stapler housing  25 . Notably, the pivot point  36  and the pivot point  26  are on opposed sides of the handle lever  22 , and on opposed sides of the pivot point  24 . Also, notably, in this figure, the roller  30  is spaced toward the left hand side of the forward acting stapler  20  from pivot points  26 ,  24  or  36 . The trigger lever  31  is pivotally connected at  40  to the housing by a structure having a surface  41  in contact with an upper surface of an elongate power spring  17 . A trigger portion  46  of the trigger lever  31  extends forwardly of the nominal end  44  of the trigger lever  31 . The trigger portion is mounted on the trigger lever with a pin/spring arrangement that will be described below. 
   A plunger  54  includes a plunger ledge  56  that is generally aligned with a forward portion  57  of the trigger portion  46 . A magazine  58  indexes staples or nails to a position under the plunger, such that the plunger can drive the staple or nail into a work surface. A forward end  59  of the elongate power spring  17  is also received in the plunger. 
   The return spring  90  holds the handle lever  22  against a handle stop  18  in this position. 
   Generally, as the handle lever  22  is pivoted downwardly it causes the trigger lever  31  to pivot clockwise as shown in this figure. As this occurs, the forward portion  57  lifts the plunger  54  through the plunger ledge  56  and against the force of the elongate power spring  17 . The forward portion  57  continues to lift the plunger  54  to a point at which the plunger  54  becomes disengaged from the trigger portion. 
   As shown in  FIG. 2 , as the handle lever  22  begins to be pivoted about pivot point  24  and counterclockwise as shown in this figure, the connection of the handle lever  22  to pivot point  26  also drives the links  28  and  34  in a similar direction. As this movement occurs, the roller  30  moves within the slot  32 . However, with such movement the link  34  begins to constrain the roller  30  to move downwardly and to the right as shown in this figure that increases the distance between pivot point  40  and roller  30  (see  FIGS. 5B and 5C ). When this occurs, the trigger lever  31  also begins to pivot about its pivot point  40 , downwardly with the roller  30 . As this occurs, and as can be seen in the left side of  FIG. 2 , the forward portion  57  begins to lift the plunger ledge  56 , lifting the plunger  54 . As is clear from this figure, the elongate power spring  57  begins to flex, and urge the plunger in an opposed direction. 
   As the handle lever  22  continues to pivot as shown in  FIG. 3 , the trigger portion  46  eventually begins to move away from the plunger ledge  56 . At the point shown in  FIG. 3 , the linkage is about to fire the plunger. 
   As shown in  FIG. 4 , the trigger portion  46  of the trigger has now allowed the plunger ledge  56  to move past. The elongate power spring  57  then fires the plunger  54  back downwardly. With this movement a staple or nail is driven into a workpiece, as known. 
   As shown in  FIG. 5A , the staple has now been fired. A return spring  90  now provides a return force driving the linkages back to the  FIG. 1  position. As shown in  FIG. 5 , the trigger portion  46  of the trigger lever  31  has moved past the top of the plunger ledge  56 . During this movement, a ramped surface  91  underneath the forward portion  57  and a ramped surface  93  above the plunger ledge will allow the forward portion to move further to the right until eventually it can move beyond the plunger ledge  56 . At this point, the system will return to the position as shown in  FIG. 1 . 
   As shown in  FIGS. 5B and 5C , the distance between pivot point  40  and the roller  30  will change between the rest position and the firing point. As shown, if the distance between the two at rest ( FIG. 5B ) is X, then at the firing point ( FIG. 5C ) the distance is X+d. This change in distance controls movement as set forth above. 
   Further details of the trigger portion and trigger lever are shown in  FIGS. 5D and 5E .  FIG. 5D  shows the movement as the trigger lever  31  is being driven to lift the plunger. As shown, the forward portion  57  of the trigger lever  31  is retained beneath the plunger ledge  56 . A pin  204  attached to the trigger lever  31  is movable within a slot  202  in the trigger portion  46 . A pin  206  is fixed to the trigger portion  46  and is movable within a slot  200  in the trigger lever. A spring  208  biases the pin  206  toward to the pin  204 , thus drawing the trigger portion  46  to the left as shown in this figure and beneath the plunger ledge  56 . As can be seen, the trigger portion  46  spans both sides of the trigger lever  31 . Thus, both pins  204  and  206  preferably extend through the trigger lever  31  and are received in both sides of the trigger portion  46 . 
   The two pin and spring combination serves to allow the trigger portion to return to the rest position once the staple or nail has been fired.  FIG. 5E  shows the movement back to the  FIG. 5A  position. As shown in  FIG. 5E , the ramped surface  91  cams along the ramped surface  93  of the plunger ledge  56 . During this movement, the trigger portion  46  is forced to the right. Pin  206  can move within the slot  200 , while the pin  204  moves within the slot  202 . As shown in the intermediate position in  FIG. 5E , this movement guides the trigger portion as it moves along the ramp surface  93 . Once the forwardmost portion  57  of the trigger portion  46  is moved beyond the plunger ledge  56 , the spring  208  returns the trigger portion  46  back to the left, such that it can again reach its rest position. 
   As shown in  FIG. 6A , the return spring  191  includes a first leg  192  and a second leg  193 . In all positions shown within  FIGS. 1–5 , the return spring is biased away from this relaxed position. 
     FIG. 6B  shows a top view of the return spring  91 . 
     FIG. 7  shows an alternative embodiment in which the return spring  100  is pivotally attached to both the housing  104  and to the trigger lever  106 . 
   Preferred embodiments of this invention have been disclosed, however, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.