Patent Publication Number: US-2012031945-A1

Title: Stapler With Leaf Spring Actuation Mechanism

Description:
FIELD OF THE INVENTION 
     The present invention relates to a stapling apparatus, and more particularly, to a spring actuated stapler with a simple leaf spring actuation mechanism. 
     BACKGROUND OF THE INVENTION 
     In a spring-actuated stapler, when an external force is applied to the stapler (usually by pressing a cover of the stapler), a spring element is loaded, and at the same time a striking plate is moved from an initial position to a release position. When the striking plate arrives at the release position, the spring element is unloaded to powerfully drive the striking plate from the release position back to the initial position to individually dispense a staple from a staple magazine. 
     There are numerous spring actuation mechanisms to carry out the above operations, however, efforts have never stopped in designing better ones with improvement in simplicity, preciseness and reliability. 
     SUMMARY OF THE INVENTION 
     The present invention provides a stapler with a novel leaf spring actuation mechanism. According to the teaching of the present invention, the stapler comprises a striking plate for dispensing a staple from a staple magazine, a leaf spring engaged with the striking plate for driving said striking plate, and an actuation bar for lifting the leaf spring from a first position to a second position whereby lifting the striking plate from an initial position to a release position in which the leaf spring is released from the actuation bar to powerfully drive the striking plate towards the initial position. 
     In a preferred embodiment, the actuation bar comprises a laterally protruding lug which is adapted to push upward a tab provided on the leaf spring so as to lift the leaf spring when an external force is applied to the actuation bar. 
     Preferably, the tab disengages itself from the lug when the leaf spring reaches the second position where the striking plate is lifted to the release position. 
     Preferably, the actuation bar has a front end movable along a guiding ramp when the external force is applied to the actuation bar, thus improving reliability and accuracy of the engagement between the lug of the actuation bar and the tab of the leaf spring. 
     Preferably, the engagement between the tab and the lug is such that the tab slides on an upper surface of the lug towards an edge of the lug when the front end of the actuation bar moves along the guiding ramp, and drops from the edge of the lug when the leaf spring reaches the second position, whereby releasing the leaf spring from the actuation bar. 
    
    
     
       BRIEF EXPLANATION OF THE DRAWINGS 
       The above and other features and advantages of the present invention can be understood better after reading the following detailed description of the preferred embodiment of the present invention with reference to the accompanying drawings, in which: 
         FIG. 1   a  schematically and partially illustrates a preferred embodiment of the stapler according to the present invention; 
         FIG. 1   b  schematically illustrates the paths of the returning movement of the lugs and tabs in  FIG. 1   a ; and 
         FIG. 2   a - 2   d  are partial perspective views showing the actuation mechanism of the stapler of  FIG. 1  at various operational stages. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Similar to a conventional stapler, the stapler according to the present invention mainly comprises a magazine  40  for accommodating a staple stick  41 , a base  50  for placing a work piece  70  (such as a stack of paper) thereon, and a cover  60  for accepting a pressing force from a user for a stapling operation, as illustrated in  FIG. 1 . During a stapling operation, the striking plate  10  is first lifted from an initial position to a release position (as shown in dashed line), leaving a slot space below into which a single staple is pushed from the staple stick  41  under a biasing force from the compressed spring  42 . When the striking plate  10  is driven from the release position back to its initial position, the single staple is driven into the work piece  70  on the base  50  to staple the work piece  70 . 
     The improvement of the present invention is generally in the mechanism for actuating the striking plate  10  during the stapling operation, as will be described in detail below. 
     As schematically illustrated in  FIG. 1   a , the actuation mechanism of the preferred embodiment of the present invention mainly comprises a leaf spring  20  for driving the striking plate  10  between the initial position and the release position, and an actuation bar  30  for lifting the leaf spring  20  from a lower position to an upper position (as shown in dashed lines) so as to lift the striking plate  10  from the initial position to the release position. As will explained in more detail below, when the leaf spring  20  reaches the upper position and therefore the striking plate  10  is brought to the release position, the leaf spring  20  is released from the actuation bar  30 , and powerfully drives the striking plate  10  from the release position back to the initial position when the leaf spring returns from the upper position back to the lower position. 
     A front end  22  of the leaf spring  20  engages with the striking plate  10  (e.g., by a hole in the striking plate  10 ) so that the front end  22  of the leaf spring  20  moves together with the striking plate  10 , whereby driving the striking plate  10  to move vertically between the initial position and the release position. A back end  23  of the leaf spring  20  is fixed to the magazine  40 , for example, on an upper surface  43  of the housing body of the magazine  40 . 
     When there is no external force applied to actuation bar  30 , the actuation bar  30  is in an idle position, the leaf spring  20  remains in the lower position and the striking plate  10  rests in the initial position, as shown by the solid lines. During the stapling operation, the leaf spring  20  is lifted from the lower position to the upper position and brings the striking plate  10  from the initial position to the release position. At the same time, the leaf spring  20  is loaded when it is lifted upwards. 
     In the stapling operation, an external force (“F” in  FIG. 1   a ) is applied to the actuation bar  30 , e.g., by pressing on the cover  60 . Under the external force, the actuation bar  30  comes into engagement with the leaf spring  20  and lifts the leaf spring  20  from the lower position to the upper position, whereby bringing the striking plate  10  from the initial position to the release position, as described above. 
     In the preferred embodiment illustrated in  FIG. 1   a , the actuation bar  30  has a rounded L-shaped front end  32 . In the idle position, the L-shaped front end  32  is slightly apart from a ramp  33  formed on the upper surface  43  of the magazine  40 . When the external force is applied to the actuation bar  30 , the front end  32  is pushed forward to abut against the ramp  33  and moves upward along the ramp  33 . 
     A pair of lugs  31  are provided on the actuation bar  30  (as best shown in  FIGS. 2   a - 2   d ), which protrude laterally from the length of the actuation bar  30 . When the L-shaped front end  32  is pushed forward by the external force applied to the actuation bar  30 , the lugs  31  come into contact with a pair of tabs  21  (best shown in  FIGS. 2   a - 2   d ). When the L-shaped front end  32  is pushed, under the external force applied to the actuation bar  30 , to moves upward along the ramp  33 , the lugs  31  push the tabs  21  upward, whereby lifting the leaf spring  20  toward its upper position as shown in dashed lines, and at the same time loading the leaf spring  20 . Consequently, the striking plate  10  is lifted by the front end  22  of the leaf spring  20  to the release position against a biasing force from the leaf spring  20 , as shown in dashed lines. 
     Preferably, when the front end  32  moves upward along the ramp  33 , the tabs  21  are able to slide backward along an upper surface of the lugs  31 . Thus, the upper surface of the lugs  31  function as a ramp for the tabs  21 . In a preferred design, the lugs  31  may assume an angle (e.g., 30 degree) from a main flat body of the actuation bar  30 . 
     When the leaf spring  20  reaches the upper position and therefore the striking plate  10  reaches the release position, the tabs  21  reach back edges  31   a  of lugs  31  and drop from the lugs  31  to disengage themselves from the lugs  31 . Under the biasing force loaded in the leaf spring  20 , the tabs  21  return to their initial positions (i.e., the lower position shown in solid lines), and the load in the leaf spring  20  is released, which powerfully drives the striking plate  10  from the release position to the initial position where the striking plate  10  strikes a stapler into the work piece  70 . 
     Preferably, a biasing mechanism is provided to the actuation bar  30  so that after the external force applied to the actuation bar  30  is released, the actuation bar  30  can automatically return to its initial position (as shown in solid lines) under a biasing force. In the embodiment shown in  FIG. 1   a , the biasing force is provided by a resilient lever  34  which connects the actuation bar  30  at a back end  35  to the upper surface  43  of the magazine  40 . When the actuation bar  30  moves forward under the external force applied to it through the cover  60 , the resilient lever  34  is brought to bend forward and the biasing force is loaded in the resilient lever  34 . When the external force is removed, the load built in the resilient lever  34  is released, and the resilient lever  34  returns to its initial position and pulls the actuation bar  30  back to its initial position as well. 
     It is important that the lugs  31  of the actuation bar  30  are not obstructed by the tabs  21  (which have returned to their initial positions) on their way of returning to their initial positions after the external force is removed. As illustrated in  FIG. 1   b , after the external force is removed, the lugs  31  are pulled backward by the biasing force from the resilient lever  34  and move along path “B” which is not obstructed by the tabs  21  which have dropped to their initial positions from the lugs  31  along the path “A”. 
     The engagement between the lugs  31  and the tabs  21  are illustrated more clearly in perspective views  2   a - 2   d , which show the actuation mechanism according to the present invention in various operational stages. 
       FIG. 2   a  shows the actuation mechanism in a position before or after a stapling operation, in which the actuation bar  30  rests in its initial idle position because there is no external force applied on it. The lugs  31  on the actuation bar  30  are not engaged with the tabs  21  of the leaf spring  20 . The striking plate  10  rests in the initial position, and the leaf spring  20  is in the lower position. 
     During the loading stage of the stapling operation, when the front end  32  of the actuation bar  30  is pushed forward by an external force, the lugs  31  come into engagement with the tabs  31  and push the tabs  21  upward when the front end  32  moves upward along the ramp  33 , until the leaf spring  20  reaches the upper position where the striking plate  10  is lifted to the release position, as shown in  FIGS. 2   b  and  2   c  in different angels of view. In this stage, the tabs  21  slide backward along the upper surface of the lugs  31  toward the back edges  31   a  of the lugs  31 . 
     After the leaf spring  20  reaches the upper position and the striking plate  10  reaches the release position as shown in  FIGS. 2   b  and  2   c , when the L-shaped front end  32  further moves upwards along the ramp  33 , the tabs  21  of the leaf spring  10  drops from the back edges  31   a  of the lugs  31  to disengage the leaf spring  10  from the actuation bar  30 . Under the biasing force built in the leaf spring  20  during the loading stage, the leaf spring  20  snaps back to the lower position, and at the same time powerfully drives the striking plate  10  back to the initial position for stapling the work piece  70 , as shown in  FIG. 3   d.    
     After the stapling operation is finished, the external force is removed from the actuation bar  30 . Under the biasing force from the resilient lever  34  (see  FIG. 1   a ), the actuation bar  30  returns to its initial position, as shown in  FIG. 2   a , and ready for a next stapling operation. 
     Although the above has described several preferred embodiments, it is appreciated that numerous adaptations, changes, variations and modifications are possible to a person skilled in the art without departing the spirit of the present invention. For example, the flat shaped tabs  21  may be implemented as a pair of laterally protruding rods mounted on the leaf spring  20 . The resilient lever  34  can be replaced by any proper biasing mechanism for returning the actuation bar  30  toward its initial position. For example, the actuation bar  30  can also be a leaf spring with the back end  35  connected to the cover  60 . Therefore, the scope of the present invention is solely intended to be defined by the accompanying claims.