Folding knife with open position lock

[0002] The present invention relates to knives having one or more blades pivotally movable between open and closed positions, and more particularly to novel structure for retaining a folding knife blade in the open position until manually released.

[0003] In one form of so-called pocket knives, the blade or blades are movable about a pivot pin between open and closed positions with respect to a handle piece. In the fully open position the blade(s) extend substantially linearly from the handle, and in the closed position at least a portion including a sharpened edge is positioned in a space provided for such purpose between two portions of the handle. The open position of the blade(s) is usually defined by engagement of a locking surface (e.g., a shoulder or notch) formed in the blade with stationary structure on or connected to the handle. In order to ensure that the blade does not move from the fully open toward the closed position inadvertently, as when pressure is applied to the back of the blade while in use, it has been a common practice to provide folding knives with a so-called “lock-back” feature. The prior art includes lock-back structures which require manipulation by the user both for activating and deactivating the locking feature, as well as those which operate automatically, as by spring bias, upon movement of the blade to the open position. It is with the latter type of lock-back mechanism with which the present invention is concerned.

[0004] The object of the invention is to provide a folding blade knife having novel and improved structure which is automatically operable upon movement of the blade(s) to the fully open position to prevent movement away from such position, and which is quickly and easily manually manipulated to permit movement from open to closed position when desired.

[0005] Other objects will in part be obvious and will in part appear hereinafter.

[0006] In the disclosed embodiment, the knife of the invention has but a single blade although it will be immediately recognized and understood that a plurality of blades, tools, or the like, each movable between fully open and closed positions with respect to a handle piece, may be provided within the scope of the invention. The disclosed blade has a sharpened edge and a back, blunt edge. The blade has the usual tang portion at its proximal end, and is supported by a pivot pin passing through the tang and anchored in spaced portions of the handle piece. Each of the two handle portions includes a liner and a cover piece. A locking arm is pivotally mounted by a pin in one of the cover pieces and extends through a slot in the adjacent liner, across the space between the two liners, through a slot in the other liner and terminates at a manually engageable head in a slot in the other cover piece.

[0007] A plunger and spring are positioned in a recess in the other cover piece facing the adjacent liner. The plunger urges the locking arm toward rotation to a position wherein the portion of the arm spanning the space between the two cover portions blocks movement of the blade tang in the direction in which it must move to close the blade. That is, when the blade is in its fully open position the locking arm is moved, by the spring biased force of the plunger, to a position directly in the path in which the tang must be moved in order to move the blade away from the open position, thus preventing inadvertent, closing movement of the blade with possible injury to the user. When it is desired to close the blade, the head on the locking arm is moved within its slot to pivot the arm away from its blocking position against the spring bias.

[0008] The foregoing and other features of construction and operation of the lock-back structure of the invention will be more readily understood and fully appreciated from the following detailed disclosure, taken in conjunction with the accompanying drawing.

[0009] FIG. 1 is an elevational view of a folding knife embodying the invention;

[0010] FIG. 2 is an enlarged, fragmentary, elevational view of a portion of the knife of FIG. 1 with portions broken away;

[0011] FIGS. 3 and 4 are enlarged, fragmentary, plan views of substantially the same portions of the knife as those shown in FIG. 2 with certain movable elements in two, terminal positions of movement; and

[0012] FIG. 5 is an enlarged, fragmentary plan view of an alternate embodiment of the movable elements illustrated in FIGS. 3 and 4.

[0013] Knife 10 includes blade 12, having sharpened and blunt edges 14 and 16, respectively, and handle 18. Blade 12 has pointed, distal end 20 and conventional tang portion 22 at its proximal end. Pivot pin 24 passes through tang 22 and is anchored in spaced portions of handle 18 in conventional fashion for pivotal movement of blade 12 between a closed position, wherein portions of the blade including edge 14 are positioned between the two handle portions, and an open position illustrated in FIG. 1. As seen in FIGS. 3 and 4, each handle portions includes a liner and a cover piece, normally of metal and plastic, respectively, the liner and cover piece of one portion being denoted by reference numerals 26 and 28, respectively, and those of the other portion by numerals 30 and 32. Opposing surfaces of liners 26 and 30 are maintained in spaced, parallel relation by spacer member 34, extending along back 36 of knife 10, defining cavity 38 wherein tang 22 is mounted and wherein a portion of blade 12 is positioned when in the closed position.

[0014] As best seen in FIG. 2, tang 22 includes a 90 degree notch, forming shoulders 40 and 42. Stop pin 44 extends across cavity 38 and is anchored in the two handle portions. The fully open position of blade 12 is defined by contact of shoulder 40 with stop pin 44, as seen in FIG. 2. Lock arm 46 is pivotally mounted by pin 48, extending through one end of aim 46 within recess 50 in cover piece 28, as seen in FIGS. 3 and 4. From its pivotally mounted end, lock arm 46 extends through open slot 52 in liner 26, across cavity 38, through open slot 54 in liner 30, through recess 56 in cover piece 32 and into open slot 58 where it terminates in head portion 60. Recess 56 communicates with slot 58, providing a through opening in cover piece 32 over a portion of recess 56, and the remainder of the recess is bounded on one side by liner 30, providing an enclosed chamber wherein a spring 62 and plunger 64 are mounted.

[0015] One end of spring 62 bears against one end of plunger 64, the other end of which bears against lock arm 46, biasing the latter toward rotation about pin 48 in a clockwise direction, in the orientation shown in FIGS. 3 and 4. Lock arm 46 contacts rounded portion 66 of tang 22 in all positions of blade 12 except the fully open position. When the blade reaches the fully open position, arm 46 is moved to the left, as seen in FIG. 2, by spring 62 and plunger 64. In this position, the portion of arm 46 spanning cavity 38 engages over shoulder 42, thereby locking blade 12 in the open position, defined by contact of shoulder 40 with pin 44 and shoulder 42 with arm 46. In order to moe blade 12 to the folded or closed position, the user must engage head 60 with a thumb or finger and move it from the position of FIG. 3 to that of FIG. 4. Locking arm 46 is thereby moved away from engagement with shoulder 42, permitting rotation of the blade away from the fully open, to the closed position.

[0016] Referring to FIG. 5, an alternate embodiment having the spring/plunger arrangement and pivot pin reversed from the principal embodiment is illustrated. Specifically, pivot pin 48′ extends through lock arm 46′, adjacent head portion 60′, and spring 62′ and plunger 64′ are mounted within a chamber formed within cover piece 28′ and bear against the end of lock arm 48′ opposite head portion 60′. The result of this alternate embodiment is the same as with the principal embodiment with the exception being that slightly more user force is required to disengage lock arm 48′ from blade 12′.