Abstract:
An assisted opening folding knife having a blade with an engagement surface extending generally radially outwardly with respect to the pivot axis of the blade. A cantilevered leaf spring contacts the engagement surface and immediately urges the blade to the extended position upon the blade pivoting through a predetermined angle from the retracted position. An elongated engagement member is pivotally connected to the handle and configured for pivoting between a blade locking position and an unlocking position. In one embodiment, the cantilevered leaf spring also urges the engagement member towards the blade locking position. The engagement member automatically locks the blade in the extended position, and the cantilevered leaf spring, the blade, and the engagement member all substantially extend in the pivot plane.

Description:
BACKGROUND OF THE INVENTION 
   This invention relates generally to an assisted folding knife. 
   Various versions of folding knives are known, one such version being assisted-opening knives. Assisted opening knives generally require the user to initiate movement of the blade from the folded, or, retracted, position towards the extended position, and at a certain point, the blade automatically continues from that point towards the extended position. In the extended position, the blade may either be locked manually, automatically, or remain unlocked. 
   Numerous folding knife designs have been patented. For example, U.S. Pat. No. 273,858, issued to Korn, discloses a folding knife having a leaf-type spring for moving a blade to an extended position. U.S. Pat. No. 1,603,914, issued to Hermann, discloses a folding knife having a coil spring connected to a metal tape, which pulls the blade to a retracted position. U.S. Pat. No. 2,601,999, issued to Sly, discloses a foldable gaff hook having a similar opening mechanism. U.S. Pat. No. 2,407,897, issued to Newman also discloses a spring for pivoting blade open upon actuation of a locking lever. U.S. Pat. No. 698,080, issued to Treas, also discloses use of an actuating spring for pivoting a blade to an open position. 
   SUMMARY OF THE INVENTION 
   Generally, one aspect of the present invention includes an assisted opening knife, and includes providing a handle having a blade pivotally connected to the handle for pivoting between an extended position and a retracted position with respect to the handle. In one preferred embodiment, the knife includes biasing member, such as an elongated cantilevered leaf spring, having one end fixed to the handle and the free end configured for contacting the blade. 
   The blade includes a tang having an engagement portion against which the free end of the spring bears upon the blade being moved to a predetermined position from the retracted, or, closed, position towards the extended, or, open, position. The spring and engagement portion are configured such that upon the spring contacting the engagement portion, the spring immediately biases the engagement portion away from the retracted position, and, in turn, the blade towards the extended position. 
   The knife also includes, in one preferred embodiment, a lock member pivotally connected to the handle and pivotable between a blade locking position and an unlocked position. The lock member is biased towards the blade locking position with a biasing member, means, or spring. The lock member is configured such that it automatically pivots to the blade locking position to lock the blade upon the blade being in the extended position. In one preferred embodiment, the blade, leaf spring, lock member, and lock member biasing means all extend generally in and parallel to the same plane. 
   In other embodiments of the present invention, the biasing member, such as the cantilevered leaf spring used to bias the blade towards the engagement position, also biases the lock member towards the blade locking position. In one such embodiment, the cantilevered spring includes an apex portion which bears against the lock member to bias the lock member towards the blade locking position. In another such embodiment, the lock member includes a projection which is engaged by the cantilevered leaf spring, and such leaf spring biases the locking member towards the blade locking position. 
   The present invention also includes a method of opening a knife with a cantilevered spring and for biasing a locking member towards a blade locking position using the same cantilevered spring, or an additional biasing member. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing, as well as other objects of the present invention, will be further apparent from the following detailed description of the preferred embodiment of the invention, when taken together with the accompanying specification and the drawings, in which: 
       FIG. 1  is a perspective view of a knife constructed in accordance with the present invention, having a blade in a retracted position; 
       FIG. 2  is an exploded view of the knife shown in  FIG. 1 ; 
       FIG. 3A  is a sectional view of the knife shown in  FIG. 1 , with the blade being in the closed position; 
       FIG. 3B  is a sectional view of the knife shown in  FIG. 1 , with the blade being in a first intermediate position between the retracted position and the extended position; 
       FIG. 3C  is a sectional view of the knife shown in  FIG. 1 , with the blade being in a second intermediate position between the first intermediate position and the extended operable position; 
       FIG. 3D  is a sectional view of the knife shown in  FIG. 1 , with the blade being in the extended position; 
       FIG. 4A  is a sectional view of a first alternate embodiment of a knife constructed in accordance with the present invention, with the blade being in an intermediate position between the retracted position and the extended position; 
       FIG. 4B  is a sectional view of the knife shown in  FIG. 4A , with the blade in the extended position; 
       FIG. 5A  is a sectional view of a second alternate embodiment of a knife constructed in accordance with the present invention, with the blade being in an intermediate position between the retracted position and the extended position; and 
       FIG. 5B  is a sectional view of the knife shown in  FIG. 5A , with the blade in the extended position. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The accompanying drawings and the description which follows set forth this invention in its preferred embodiment. However, it is contemplated that persons generally familiar with assisted-opening folding knives will be able to apply the novel characteristics of the structures illustrated and described herein in other contexts by modification of certain details. Accordingly, the drawings and description are not to be taken as restrictive on the scope of this invention, but are to be understood as broad and general teachings. 
   Referring now to the drawings in detail, wherein like reference characters represent like elements or features throughout the various views, the assisted-opening folding knife of the present invention is indicated generally in the figures by referencing character  10 . 
   A folding knife constructed in accordance with the present invention  10  is shown in  FIG. 1 , having a blade, generally B, in a retracted, or closed, position within a blade compartment  12  ( FIG. 2 ) defined by handle members  14 ,  16 , of a handle, generally H. It is to be understood that as used herein, “blade,” can refer to a number of items, including a tool, implement, cutting blade, or a holder for such tool, implement, or cutting blade, and is not to be limited to the blade depicted in the Figures. 
   As shown in  FIG. 2 , handle members  14 ,  16  are provided with bores  18  and  20  which receive male and female threaded connectors  22 ,  24 . Blade B includes a hole  26  for receipt of a bushing  28  carried by connectors  22 ,  24 , which permits blade B to pivot between the retracted and extended positions in a pivot plane about a pivot axis A, the pivot plane being generally perpendicular to pivot axis A. Bushing  28  provides a pivotal connection blade B with respect to handle H between a retracted position, as shown in  FIGS. 1 ,  2 , and  3 A, and an extended position, as shown in  FIG. 3D . 
   In addition to connectors  22 ,  24 , pin  30  is provided, which passes through holes  32 ,  34  of handle members  14 ,  16 , respectively, and also through a hole  36  within a lock member, generally L, which is carried by pin  30  for pivoting movement within a channel  38  ( FIG. 1 ) defined between handle members  14 ,  16 . Lock member L includes a forward portion, having a downwardly extending finger  40  which engages with an locking surface  42  defined in on the tang  44  of blade B, when blade B is in the retracted position. The engagement of finger  40  with locking surface  42  serves to retain blade B within compartment  12 , so that blade B does not inadvertently leave compartment  12 . 
   Lock member L includes at its other end a recess  46 , on the underside thereof for receipt of a biasing member, which in one preferred embodiment is a wire-type spring  48  having a free end  50  for receipt in recess  46 , and an end which is fixed within a channel  52  defined in handle member  16 . Spring  48  forces recess  46  of locking member L upwardly, which, in turn, forces finger  40  downwardly into engagement with locking surface  42 , when blade B is in a retracted position, as mentioned above, and also, for causing finger  40  to bear against curved profile  54  of tang  44 , which spans between locking surface  42  and a lock notch  56  defined in tang  44  generally diametrically opposite from locking surface  42 . 
   When blade B is in the extended position, as shown in  FIG. 3D , finger  40  of lock member L automatically seats within lock notch  56 , due to the upward biasing of spring  48  against the underside of lock member L at recess  46 , such that blade B is automatically locked in the extended position. 
   As shown in  FIG. 3A , when blade B is in a retracted position, finger  40  of lock member L engages with locking surface  42 , and the free-end  58  of a cantilever leaf spring  60  bears against a curved profile  59  of tang  40  which spans between an impelling surface  62  and choil  64  of blade B. The other end  66  of spring  60  is received within a channel  68  of handle member  16  in a generally fixed fashion. It is to be understood that spring  60  is not limited to a leaf spring, but could be a wire, a plastic finger molded or integral with a handle member (not shown), or some other elongated biasing or spring force member. 
   Spring  60  is biased such that free-end  58  exerts a generally downward force, i.e., towards blade B, as shown in  FIG. 3A . This downward biasing of the free-end  58  of spring  60  assists movement of blade B towards the extended position, as discussed in more detail below. 
     FIG. 3B  illustrates blade B being moved from the retracted position towards the extended position, and such movement may be initiated by the user pulling on an upper portion of blade B, or by engaging the thumb/finger stud or post, generally  70 , provided on blade B. As shown in  FIG. 3B , blade B has been moved such that the free-end  58  of spring  60  is at the intersection I of impelling surface  62  and curved surface  59 . Impelling surface  62  extends generally radially with respect to the pivot axis A ( FIG. 2 ) of blade B. As blade B is pivoted slightly further towards the retracted position, the free-end  58  of spring  60  clears such intersection and bears directly against impelling surface  62 , and due to the downward force exerted by free-end  58 , propels impelling surface  62  with a generally tangential force, which causes blade B to be propelled to the engagement position, under the force of spring  60 . 
   As shown in  FIG. 3D , blade B is now in the extended position, having been automatically locked in that position due to the engagement of finger  40  with lock notch  56 . Note that free-end  58  of spring  60  is in a generally relaxed position below the pivot axis A of blade B. 
   A first alternate embodiment knife  100  of the present invention is illustrated in  FIG. 4A . In this embodiment, spring  48  has been eliminated altogether, and cantilever spring  60   a  performs both the function of spring  48 , discussed above, in biasing upwardly the rearward portion of lock member L, and in also biasing blade B towards the extended position.  FIG. 4A  illustrates blade B in a position similarly as shown in  FIG. 3B , wherein the free-end  58   a  of spring  60   a , is at the intersection of impelling surface  62  and curved profile  59 . At or near this point, the free-end  58   a  of spring  60   a  engages impelling surface  62  to kick, or impel, blade B to the extended position, shown in  FIG. 4B . 
   Cantilever leaf spring  60   a  includes an apex, or knee,  74  defined at an intermediate portion thereof. This knee  74  bears upwardly on underside U of lock member L to provide finger  40  of lock member L with a downward force such that finger  40  automatically engages with lock notch  56  of blade B upon blade B reaching the extended position. 
     FIGS. 5A and 5B  illustrates a second alternate embodiment knife  200  of the present invention. In this embodiment, spring  48  discussed above in regards to knife  10  is also eliminated, as is the case too, with knife  100 . Knife  200  includes a lock member L′ having a projection  78  on the underside thereof. Projection  78  is positioned rearward of pin  30  and is engaged by cantilever leaf spring  60 . Leaf spring  60  may also include an apex, such as discussed above with regard to spring  60   a , if desired. Leaf spring  60  by virtue of its curvature, exerts an upward force on projection  78 , which in turns causes a downward force to be exerted by finger  40  of lock member L′. Thus, when blade B moves to the extended position, finger  40 , as discussed above, automatically engages with notch  56  to lock blade B in the extended position. 
     FIG. 5A  illustrates blade B in an intermediate position, with the free-end  58  of leaf spring  60  at or near the point where it exerts tangential force against the end of impelling surface  62  in order to propel blade B to the extended position. Impelling surface  62  is preferably generally radially disposed with respect to pivot axis A, such that the downward force of the free end of a leaf spring provides a maximum moment arm affect delivered torque to impelling surface  62  sufficient for causes blade B to move to the extended position. 
   It is to be noted that in each of the embodiments of the present invention, i.e., knifes  10 ,  100 , and  200 , in order to move blade B from the extended position towards the retracted position, lock member L is depressed downwardly at its rearward end, preferably at or near surface S of lock member L, such that finger  40  is raised out of engagement with lock notch  56  of blade B. This allows the user to then, simultaneously, pivot blade B back to the retracted position. 
   Components which are common to knives  10 ,  100 ,  200 , bear the same reference number and perform the same, or generally the same, function as compared to one another. 
   The free-ends  58 ,  58   a  of cantilever leaf spring  60 ,  60   a , respectively, are preferably rounded and polished to facilitate smooth operation during the transition from contact from intersection I to impelling surface  62 , and to the subsequent disengagement with surface  62 . 
   Upon the blade moving approximately twenty degrees from the retracted position, the leaf spring “kicks,” or impels, the impelling surface  62  to move the knife to the extended position. 
   Because of the arrangement of the leaf spring  60 ,  60   a  are generally in the same plane as blade B, and also in substantially the same plane through which the blade moves between the retracted and extended positions, knifes  10 ,  100  and  200  can be of a relatively thin profile, since no spring, biasing device, spring and plunger arrangement, etc. is required to be offset to either side of blade B. The resulting thin profile of knives  10 ,  100 , and  200  may provide for less bulk, which may be particularly desirable when such knives are to be carried in a user&#39;s pocket, purse, garment, backpack, etc. 
   While preferred embodiments of the invention have been described using specific terms, such description is for present illustrative purposes only, and it is to be understood that changes and variations to such embodiments, including but not limited to the substitution of equivalent features or parts, and the reversal of various features thereof, may be practiced by those of ordinary skill in the art without departing from the spirit or scope of the following claims.