Abstract:
A folding tool includes a handle and an implement pivotally coupled to the handle according to one embodiment. The implement is adapted to travel between a closed position and an open position and has a tang with a contoured surface. A spring arm has a first end coupled to the handle and a second end adapted to interact with the implement. The spring arm exerts an opening force on the implement during at least a portion of the travel of the implement between the closed position and the open position and also locks the implement into the open position.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/416,830, filed Oct. 8, 2002, which is incorporated herein by reference in its entirety. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The present invention relates to a folding knife. In particular, the present invention relates to a folding knife having a mechanism used to assist the user in opening the knife.  
       BACKGROUND OF THE INVENTION  
       [0003]     Folding knives typically include a handle and one or more blades pivotally attached to the handle, the blades having a compact closed position and an extended open position. A user opens the blade by grasping the blade or pushing a knob protruding from the blade in order to rotate the blade into the open position.  
         [0004]     Additional features are added to folding knives in order to make such knives more useful and easier to operate. Such features may include a mechanism used to assist the user in opening the knife, a mechanism used to lock the blade into an open position, and a mechanism to bias the blade into the closed position. Adding additional features increases the cost and complexity of the folding knife. Cost considerations may outweigh the desire for additional features for folding knives that are intended for sale at moderate prices. Accordingly, there is a need for a mechanism that provides additional features that does not unacceptably raise manufacturing costs. Further, there is a need for such a mechanism that performs multiple desired functions using the same parts.  
         [0005]     The components required to effectuate features such as an assisted opening function or a blade lock function utilize space in a folding knife that may otherwise be used for other purposes. Accordingly, there is need for a simplified mechanism that provides desirable features but does not utilize a great deal of space within a knife handle.  
         [0006]     It would be desirable to provide a folding knife that includes a mechanism that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention relates to a folding tool having a handle and an implement pivotally coupled to the handle. The implement is adapted to travel between a closed position and an open position and includes a tang with a contoured surface. A spring arm has a first end coupled to the handle and a second end adapted to interact with the implement. The spring arm both exerts an opening force on the implement during at least a portion of the implement&#39;s travel between the closed position and the open position and locks the implement into the open position.  
         [0008]     The invention further relates to a folding knife having a handle and a blade pivotally coupled to the handle. The blade has a closed position and an open position and includes a tang with a contoured surface. The folding knife further includes a spring located in a plane defined by the blade, the spring having a proximal end coupled to the handle and a distal end adapted to exert a force on the blade via contact with the contoured surface.  
         [0009]     The invention is capable of other embodiments and of being practiced or carried out in various ways. Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, in which:  
         [0011]      FIG. 1  is a front elevation view of folding knife with the blade in the open position;  
         [0012]      FIG. 2  is an exploded view of a folding knife according to an exemplary embodiment;  
         [0013]      FIG. 3  is a cut-away front elevation view of a folding knife with the blade in the closed position;  
         [0014]      FIG. 4  is a cut-away front elevation view of a folding knife with the blade in a partially opened position;  
         [0015]      FIG. 5  is a cut-away front elevation view of a folding knife with the blade in a partially opened position;  
         [0016]      FIG. 6  is a cut-away front elevation view of a folding knife with the blade in a fully opened and locked position;  
         [0017]      FIG. 7  is a cut-away front elevation view of a folding knife with the blade in a partially closed position and a disengaged blade lock mechanism;  
         [0018]      FIG. 8  is a cut-away front elevation view of a folding knife with the blade in a partially closed position; and  
         [0019]      FIG. 9  is a cut-away front elevation view of a folding knife with the blade in the fully closed position and showing an unlocking mechanism according to an exemplary embodiment. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0020]     Referring to  FIG. 1 , a knife, shown as folding knife  10 , includes a handle  12  pivotally coupled to an implement, shown as, but not limited to blade  14 . The blade  14  is coupled to the handle by a blade axle  16  that extends through a tang  18  of the blade. A thumb stud  20  may extend outwardly from a portion of the blade for gripping by the user.  
         [0021]     Referring to  FIG. 2 , in an exemplary embodiment, folding knife  10  is enclosed by a pair of handle sides  22 ,  24 . Liners  26 ,  28  fit within handle sides  22 ,  24 . A leaf spring  30  is coupled to liners  26 ,  28  by engaging with slots  32 ,  34  and liners  26 ,  28 . A spring arm  36 , which may comprise one or more pieces, is coupled to liners  26 ,  28  via pivot axle  38 . An unlocking mechanism, shown as unlocking latch  40 , may be disposed between handle side  24  and liner  28  and include a knob  42  that extends through an aperture  43  in handle side  24 . A rod  39  may extend through spring arm  36  and through a slot  45  in liner  28  such that it may engage unlocking latch  40  during a portion of its travel.  
         [0022]     Referring to  FIGS. 2 and 3 , spring arm  36  is curved in its relaxed position (see  FIG. 2 ) such that it exerts a force against blade  14  when blade  14  is in the closed position shown in  FIG. 3 . In a preferred embodiment, spring arm  36  is the same width as blade  14  and is installed directly in the plane of blade  14 . Blade tang  18  includes a contoured surface  44  that serves as the contact point between tang  18  and a distal end  48  of spring arm  36  when the blade  14  is in the closed position.  
         [0023]     Further referring to  FIG. 3 , due to the angle of contoured surface  44 , when blade  14  is fully closed, spring arm  36  exerts a counterclockwise (closing) force on blade  14  as seen by force vector  46 , which results from the contact between distal end  48  and contoured surface  44 . Accordingly, although a user forces the blade  14  into the closed position against the bias of spring arm  36 , once the blade  14  is near the closed position, the interaction between spring arm  36  and contoured surface  44  maintains the blade in the closed position to prevent accidental opening of the blade  14 .  
         [0024]     Referring to  FIG. 4 , as a user manually opens blade  14 , distal end  48  rides along contoured surface  44 , thus changing the point of tangency and the direction of force vector  46 . When force vector  46  crosses to the right-hand side (in the view of  FIG. 4 ) of the centerpoint of blade axle  16 , spring arm  36  exerts a clockwise force on blade  14 , thus biasing the blade  14  into the open position. In an exemplary embodiment, spring arm  36  exerts an opening force on blade  14  once the blade  14  has been manually opened to a position approximately ten degrees from the fully closed position. The number of degrees the blade  14  must be manually opened prior to receiving assistance from spring arm  36  may be changed by altering contoured surface  44  of tang  18  to achieve the desired effect. Note that in an exemplary embodiment, leaf spring  30  has an insignificant effect on the mechanics detailed in  FIGS. 3 and 4 .  
         [0025]     Referring to  FIG. 5 , spring arm  36  pivots the blade  14  into the fully opened position as it rides along contoured surface  44  of blade tang  18 . Ideally, spring arm  36  is configured to drive blade  14  from the position shown in  FIG. 4  into the fully opened position of  FIG. 6  without further manual intervention by the user.  
         [0026]     Referring to  FIG. 6 , once blade  14  is in the fully opened position, distal end  48  of spring arm  36  locks the blade  14  into the fully open position by wedging behind catch face  50 . In this configuration, the blade  14  is prevented from rotating out of the open position. In the embodiment depicted in  FIG. 6 , leaf spring  30  provides an upward bias on spring arm  36  to ensure distal end  48  maintains its position behind catch face  50 , thus maintaining blade  14  in the locked open position. In alternative embodiments, the spring arm  36  may be configured to maintain position behind catch face  50  in other ways.  
         [0027]     Referring to  FIG. 7 , a user must disengage spring arm  36  from the locked position in order to close blade  14 . One way of doing so is through the use of unlocking latch  40 , which is coupled to spring arm  36  via rod  39  such that when a user slides latch  40  away from blade  14 , rod  39  slides down ramp  41 , forcing distal end  48  out of engagement with catch face  50 , permitting the user to close blade  14 . Once the blade  14  is partially moved from the fully opened position, the user may release unlocking latch  40 , as distal end  48  will then ride along contoured surface  44  as the blade  14  is closed.  
         [0028]     Referring to  FIG. 8 , as a user closes blade  14 , blade tang  18  forces distal end  48  upward (in the reference frame of  FIG. 8 ) against the bias of spring arm  36  until the blade  14  nears the fully closed position and the spring arm  36  begins exerting a counterclockwise force on blade  14 , thus moving the blade  14  into the fully closed position (see  FIG. 3 ).  
         [0029]     Referring to  FIG. 9 , in an exemplary embodiment, unlocking latch  40  may be biased toward the blade axle  16  by a spring mechanism  52  such that it automatically slides into its normal use position (not disengaging spring arm  36 ) when the user is not grasping knob  42 . In another embodiment, unlocking latch  40  may be braced into its normal use position by a coil spring (not shown).  
         [0030]     The utilization of spring arm  36  directly in the plane of blade  14  and having a width approximately equal to blade  14  rather than disposed out of the plane of the blade permits the folding knife  10  to be less bulky than other designs, which require additional space inside the handle to accommodate the mechanism. Further, because in a preferred embodiment, spring arm  36  also functions as a blade lock, space within handle sides  22 ,  24  is further efficiently utilized due to the lack of an additional blade lock mechanism.  
         [0031]     Many folding knife designs utilize a liner lock that includes a leaf spring disposed parallel to the plane of the blade that springs behind the blade tang when the blade has moved to the fully open position in order to lock the blade in the open position. A liner lock may require additional manufacturing costs because the blade tang may require a secondary grinding process in order to mate properly with the liner lock. Such an additional manufacturing step adds to the cost of a folding knife. The blade lock of the present invention may reduce manufacturing costs due to greater dimensional tolerances for the blade and spring arm locking mechanism.  
         [0032]     The unlocking mechanism depicted in  FIG. 9  is only one exemplary embodiment. Other unlocking mechanisms may include a swiveling cam or any number of mechanical devices having a pin and guide intended to disengage the spring arm from the blade tang.  
         [0033]     The spring arm  36  may be coupled to liners  32 ,  34  via pivot axle  38 . This configuration may be altered depending on the configuration of the folding knife, such as by the use of other attachment mechanisms known in the art to attach the spring arm and handle components.  
         [0034]     In an exemplary embodiment, the blade  14  stops rotating in the opening direction when thumb stud  20  engages one or both liners  32 ,  34 . Other ways of preventing over-rotation of the blade are well known in the folding knife art.  
         [0035]     The components depicted in  FIG. 2  are constructed of materials known in the folding knife art. Typically, the liners  32 ,  34  are metallic. The spring arm  36  requires a spring temper to maintain the proper bias against the blade to ensure assisted opening functionality and is of the same degree of hardness as the blade in an exemplary embodiment. Leaf spring  30  is of a configuration and material chosen to properly ensure that the spring arm  36  maintains its position against the catch face  50  when locking the blade in the open position.  
         [0036]     In an alternative embodiment, the folding knife may be configured to have the assisted opening feature described herein, but not the blade lock mechanism. Instead, the contoured surface of the blade tang may be configured such that the spring arm  36  provides a bias in the opening direction to aid in maintaining the blade in the open position while not requiring the user to manually unlock the spring arm  36 .  
         [0037]     While the detailed drawings and specific examples given describe various exemplary embodiments of the folding knife, they serve the purpose of illustration only. It is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the preceding description or illustrated in the drawings. For example, the folding knife may have multiple blades and may include multiple spring arms configured to assist the opening of those blades and lock the blades into the open position. The space-saving mechanism of the present invention may permit the use of such multiple blades where other folding knives having similar functionality would be too bulky to do so. Rather than a blade, another implement such as a saw may be substituted and have the same functionality. Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangements of the exemplary embodiments without departing from the scope of the invention as expressed in the appended claims.