Folding Knife With Moveable Pivot Axis

The present invention relates generally to knives having blades pivotally foldable with respect to a casing. More specifically, the present invention relates to knives having a manually actuated button slidably mounted to the casing which, upon a user exerted force, transmits pivotal motion to the blade, as well as translatory movement of the pivot axis relative to the casing.

Folding knives having user actuated, mechanical drives for opening a knife blade pivotally mounted to a casing are well known in the art. Most common among these folding, or pocket type knives are those having a spring loaded, user-actuated, blade release mechanism. Examples of such knives can be readily seen in U.S. Pat. Nos. 4,893,409 to Poehlmann; 4,897,922 to Brooker; and 4,918,820 to Korb, et al. The springs in these knives tend to lose their resiliency over time, therefore making them less economically attractive and less useful. Furthermore, these knives do not include any means for locking the blade in any one position, thereby permitting the risk of accidental opening or closing of the blade.

Another type of prior art folding knife is having a user-actuated button slidably mounted to the exterior surface of the casing. When the user exerts a force to slide the actuator, the force is transmitted to pivot the blade from its closed to its open position.

This type of knife is exemplified in applicant's issued U.S. Pat. No. 4,719,700. The knife disclosed in this patent uses a non-extensible linkage having one end connected to the actuator and its second end wrapped around a wheel connected to the blade. The user exerted force, in this case, is transmitted by the non-extensible linkage to rotate the wheel, thereby pivoting the blade from its closed to its open position.

An alternate embodiment of the above described patent reveals a similar operation using a plurality of intermeshing gears instead of a non-extensible linkage and wheel. Both embodiments utilize a blade locking mechanism typically found in what is known in the art to be "lock back" knives.

A common feature of all conventional folding knives, regardless of the manner of effecting blade movement, is a blade pivot axis which is stationary relative to the casing.

It is a principal object of the present invention to provide a folding knife having an improved, user-actuated blade opening mechanism.

It is a further object of the present invention to provide a folding knife which is easily manipulated by a user thereof.

It is an additional object of the present invention to provide a folding knife having an improved locking mechanism to prevent the accidental opening or closing of the blade.

It is another object of the present invention to provide a folding knife of minimal dimensions so as to be easily stored and held.

It is yet a further object of the present invention to provide a folding knife which is readily attachable to a variety of knife handles.

Another object is to provide a folding knife having a blade pivotally moveable between closed and open positions with respect to a casing wherein the blade pivot axis moves as the blade rotates.

Other objects and advantages of the present invention will in part be obvious and in part appear hereinafter.

In accordance with the foregoing objects and advantages, the present invention provides several embodiments of a folding knife having a user-actuated blade opening mechanism. The knife itself is generally comprised of a casing having first and second opposed walls; a blade pivotally mounted for movement between closed and open positions with respect to the casing; and a user-actuated button slidably mounted to the casing for producing simultaneous pivotal movement of the blade and translatory movement of the pivot axis. The knife further includes a blade locking feature which prevents accidental displacement of the blade from the closed or open positions.

In two of the disclosed embodiments, first and second axially aligned slots are respectively, longitudinally formed through the casing's two walls. A line of equally spaced apart bosses protrude from the outwardly facing surface of the first casing wall in parallel, laterally offset relation to the slot formed therethrough with the peripheries of the bosses in one of the embodiments being round and the bosses of the other embodiment being semi-circular.

The user-actuated button is connected to one end of an elongated shaft which extends through a coiled spring, a pawl, both slots formed through the casing walls, and an aperture formed through the tang portion of the blade, thus defining the blade pivot axis. The pawl is positioned adjacent the outwardly facing surface of the first casing wall, and the spring is disposed between the pawl and the button. The pawl further includes a legged portion which extends downwardly into the casing where it is fixedly attached to the blade.

Upon initiation of a user exerted force applied to the button, the shaft freely, longitudinally slides within the confines of the slots. As the shaft slides along, the longitudinal, sliding motion thereof is transferred to the pawl. The pawl has peripheral, spaced teeth which engage the spaces defined between the bosses. Indented portions between successive teeth are semicircular or otherwise cooperatively shaped to conform to the peripheries of the bosses. This engagement causes the pawl to rotate about the shaft while simultaneously sliding longitudinally across the casing wall. Due to the pawl's attachment to the blade, the sliding-rotary motion of the pawl is directly transferred to the blade, thereby causing it to pivot into and out of the casing as the pivot axis, defined by the shaft extending through the blade tang, moves along the casing.

The shaft further includes a flanged end positioned opposite the button. This flanged end lockingly engages in either of two detent openings formed in intersecting relation with the slots of the second casing wall. When the button is released by a user's thumb, the spring causes the entire shaft to move axially in the direction of the end carrying the button. This causes the flanged end to become engaged in one of the detents, which securely locks the blade in either its fully open or fully closed positions.

The most significant difference between the two embodiments discussed above, is that one of the embodiments minimizes the size of the blade casing, and further includes means positioned on the casing for attachment of any of a plurality of differently styled knife handles, while the other includes a more conventional casing. The details of this will be discussed in greater detail hereinafter.

In a third, alternate embodiment, the shaft defining the blade pivot axis which fully extends through elongated slots in the casing walls, a circular gear or pinion fixedly attached to the tang end of the blade. An elongated, toothed gear rack is integrally formed along one side of one of the casing slots in operable position with respect to the pinion. Movement of the blade is effected by the user sliding the button along the slot, thereby causing the stationary rack to rotate the pinion. This rotary motion effects pivotal movement of the blade between its open and closed terminal positions. This blade, like the ones of the other embodiments may be releasably locked in either of the two previously mentioned positions.

A fourth, alternate embodiment differs from the other three in that it includes an cam shaped gear fixedly attached to or formed integrally with the tang end of the blade and positioned between the two casing walls. This embodiment further includes a curved gear bed positioned between the two casing walls for meshing engagement with the cam shaped gear. As the button is slid along the casing wall, in the same manner as all the other embodiments, the cam shaped gear engages corresponding teeth of the curved gear bed. Therefore, as the gear moves along the gear bed, the blade pivotally moves between its open and closed positions as the pivot axes moves with respect to the casing.

FIG. 1 is a perspective view of a first embodiment of a folding knife, embodying the present invention, shown in its open position;

FIG. 2 is a bottom plan view of the knife of FIG. 1, with portions broken away;

FIG. 3 is a side elevational view of the knife of FIG. 1;

FIG. 4 is a top plan view of the knife of FIG. 1 showing, in phantom, alternate positions of the blade;

FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 4;

FIG. 6 is an exploded perspective view of a second embodiment of a folding knife;

FIG. 7 is a bottom plan view of the knife of FIG. 6 with portions broken away and a removable handle attached thereto;

FIG. 8 is a side elevational view of the knife of FIG. 7;

FIG. 9 is a cross-sectional view taken along line 9--9 of FIG. 8;

FIG. 10 is a top plan view of FIG. 7;

FIG. 11 is a cross-sectional view taken along line 11--11 of FIG. 10;

FIG. 12 is an exploded, perspective view of a third embodiment of a folding knife, shown in its open position;

FIG. 13 is a top plan view of the knife of FIG. 12 showing portions cut away;

FIG. 14 is a cross-sectional view taken along line 14--14 of FIG. 13;

FIG. 15 is a bottom plan view of the knife of FIG. 12;

FIG. 16 is side elevational view of the knife of FIG. 12;

FIG. 17 is an exploded, perspective view of a fourth embodiment of a folding knife, shown in its open position;

FIG. 18 is a side elevational view of the knife of FIG. 17;

FIG. 19 is a bottom plan view of the knife of FIG. 17;

FIG. 20 is a top plan view of the knife of FIG. 17; and

FIG. 21 is a cross-sectional view taken along line 21--21 of FIG. 20; and

FIG. 22a-c are enlarged, fragmentary, cross-sectional views showing, in sequence, the blade movement operating principles used by the instant invention.

Referring now to the drawing figures wherein like reference numerals denote like parts throughout all views, there is seen in FIG. 1 a folding knife generally denoted by reference numeral 10. Knife 10 is seen to be generally comprised of a casing 12, a blade 14 pivotally mounted for movement between closed and open positions with respect to casing 12, and a user actuated button 16 slidably mounted with respect to casing 12 for producing pivotal movement of blade 14 and translatory movement of the axis about which blade 14 pivots.

Casing 12 is seen to include first and second opposed walls 18 and 20, respectively, having corresponding, axially aligned, longitudinally elongated, first and second slots 22 and 24 formed therethrough. Casing 12 further includes a blade receiving edge 25 and a closed edge 27, as well as a plurality of equally spaced apart, circular bosses 26 (the end bosses are denoted as 26' and 26") protruding from the outwardly facing surface of first wall 18 in a line extending in parallel, laterally offset relation between slot 22 and blade receiving edge 25. A plurality of open spaces 28 are defined between adjacent bosses 26. As clearly seen in FIGS. 2 and 5, casing 12 further includes two laterally spaced circular detent openings 30 and 32 cut out from wall 20 in intersecting relation to slot 24. Detent openings 30 and 32 are used to securely lock blade 14 in either its fully open or fully closed positions, respectively, the details of which will be more fully explained hereinafter. In addition, the circular shape and predetermined number of detents are disclosed as a preferred embodiment, but the spirit and scope of the invention should extend as defined by the appended claims.

User actuated button 16 is fixedly attached to one end of an elongated shaft 36 which fully extends through a coiled spring 38, a pawl 40, first slot 22, an aperture 42 formed through the tang portion 43 of blade 14 which is located opposite pointed tip 44, and second slot 24, thus defining the blade pivot axis X--X which, as mentioned earlier, moves with respect to casing 12 in response to the sliding of button 16. (Axis X--X will be used in all disclosed embodiments.) Pawl 40 is positioned adjacent the outwardly facing surface of first casing wall 18, and spring 38 is disposed between pawl 40 and button 16. When button 16 is securely attached to shaft 36, spring 38 becomes slightly compressed, thereby producing equal and opposite biasing forces to button 16 and pawl 40. Pawl 40 includes a legged portion 46 which extends downwardly into casing 12 where it is fixedly attached to blade 14 about the periphery of aperture 42, and a plurality of teeth 47 which are alternately positioned between arcuate cutouts, or indentations, 49 formed in pawl 40. Teeth 47 are appropriately spaced to correspondingly engage with respective spaces 28, with arcuate cutouts 49 wrappingly engaging respective bosses 26.

Shaft 36 further includes a circularly flanged end 48 positioned opposite button 16. Flanged end 48 is configured to correspond in shape to detent openings 30 and 32. When no downward force is applied to button 16, flanged end 48 will become lockingly engaged within an aligned one of detent openings 30 and 32 due to the biasing force supplied to button 16 by spring 38. When flanged end 48 engages detent opening 32, blade 14 will be locked in its operable, fully open position. Likewise, when it engages detent opening 30, blade 14 is locked in its fully closed position.

Upon application of an inward, user exerted force to button 16, flanged end 48 will become disengaged from detent opening 30 or 32. Application of force to button 16 longitudinally of the handle will then cause shaft 36, along with its connected parts, to slide within the confines of slots 22 and 24 in the direction of applied longitudinal force. Due to shaft 36 extension through pawl 40, the sliding motion of shaft 36 is transferred directly thereto. As pawl 40 moves longitudinally of slot 22, teeth 47 successively engage respective spaces 28 and arcuate cutouts 49 wrappingly engage respective bosses 26, thereby imparting rotational motion to pawl 40. This longitudinal-rotational motion of pawl 40 is, in turn, directly transferred to blade 14 due to its fixed connection to the pawl, thus affecting translatory movement of pivot axis X--X with respect to casing 12. The translational motion supplied to blade 14 causes it to pivotally move between its open and closed positions. Once pawl 40 engages either of the end bosses 26', 26" blade 14 is nearly positioned in it corresponding terminal position. To fully position blade 14 in its terminal positions it is necessary for the user to continue to longitudinally slide button 16 a slight distance in the appropriate direction (approximately 1/16 inch) after engaging end boss 26' or 26". In doing this, pawl 40 becomes disengaged from end bosses 26', 26" and does not rotate, causing pin 50 on tang 43 to engage an appropriately positioned notch 52 or L-shaped notch 54 in wall 18. Pin 50 and notches 52 and 54 will be described in further detail hereinafter. By pulling button 16 towards the rear of casing 12, blade 14 will pivotally move towards it open position. It is therefore obvious that pushing of button 16 towards the front of casing 12 will cause blade 14 to pivotally move towards its closed position. It should further be noted that while button 16 and shaft 36 slide with pawl 40, they do not rotate along with pawl 40 thereby decreasing internal friction and permitting easy opening and closing of blade 14.

Blade 14 includes pin 50 which projects outwardly in a direction perpendicular to the plane in which wall 18 lies. When blade 14 is in either its fully open or fully closed positions, pin 50 engages notch 52 or L-shaped notch 54, respectively, which secures its position and prevents any inadvertent movement from those positions. Notches 52 and 54 are formed at appropriate positions in blade receiving edge 25 of wall 18 as is clearly seen in FIG. 1 to permit flange 48 to securely engage detent openings 30 or 32 when pin 50 is engaged in the corresponding notch.

Knife 10 further includes a blade lock cover 56. Cover 56 is fixedly attached to the outwardly facing surface of wall 20 in covering relation to slot 24 and detents 30 and 32. Cover 56 prevents any dust or other foreign particles which could accumulate and cause the locking mechanism to become jammed and unfunctionable. Cover 56 does not hinder the performance of knife 10 whatsoever as it includes a wall contacting portion 58 which surrounds, but does not contact, any portion of slot 24 and detents 30 and 32, and a bubble portion 60 which projects in spaced, covering relation to slot 24 and detents 30 and 32. Bubble 60 is spacious enough to permit flanged end 48 to slide between detents 30 and 32, but is not overly large so as to become burdensome to a user holding knife 10.

Referring now to FIG. 6, there is seen a second embodiment of a folding knife, denoted generally by reference numeral 100. As with knife 10, knife 100 is generally comprised of a casing 102, a blade 104 pivotally mounted for movement between closed and open positions with respect to casing 102, and a user actuated button 106 slidably mounted to casing 102 for producing pivotal movement of blade 104 and translatory movement of blade pivot axis X--X.

Casing 102 is seen to include first and second opposed walls 108 and 110 having corresponding, axially aligned, longitudinally elongated, first and second slots 112 and 114 formed therethrough, respectively. Casing 102 further includes a blade receiving edge 115 and a closed edge 117, as well as a plurality of equally spaced apart, semi-circular bosses 116 (the end bosses are denoted by 116' and 116") protruding from the outwardly facing surface of wall 108 in a line extending in parallel, laterally offset relation to slot 112. The circular portion of bosses 116 are positioned in closest proximity to slot 112 with their flattened portions being positioned farthest therefrom. A plurality of spaces 118 are clearly defined between adjacent bosses 116. As seen most clearly in FIG. 7, casing 102 further includes two laterally spaced circular detent openings 120 and 122 cut out from wall 110 in intersecting relation with slot 114. As with detent openings 30 and 32, detent openings 120 and 122 are used to securely retain blade 104 locked in one of the two positions.

The main difference between casing 12 and 102 is that casing 102 is of the minimum size necessary to contain all the operable blade opening elements. Therefore, to permit knife 100 to be safely held by a user thereof, a knife handle 126 must be attached to casing 102. Casing 102 includes handle detents 128 and 130 protruding in aligned relation respectively from the outwardly facing surfaces of walls 108 and 110. Detents 128 and 130 permit handle 126 to be releasably attached to casing 102.

Handle 126 includes opposing walls 131 and 133 which straddle casing 102, and further include respective, laterally aligned, detent receiving apertures 132 and 134 formed through walls 131 and 133, a cut out portion 135 for permitting access to user actuated button 106, and a hollowed out clearance area 137 positioned around detents 120 and 122. As is clearly seen in FIG. 7, handle 126 may be slid onto casing 102 in the direction indicated by the arrows, until detents 128 and 130 securely engage apertures 132 and 134. Although handle 126 is shown as being an elongated, curvilinear shape, it may include any ornamentalities and desirous shapes, as long as it includes a means for attaching itself to casing 102.

As in the previously described embodiment, user actuated button 106 is fixedly attached to one end of an elongated shaft 136 which fully extends through a coiled spring 138, a circular pawl 140, first slot 112, an aperture 142 formed through the tang portion 144 of blade 104 positioned opposite pointed tip 146, and second slot 114, again defining pivot axis X--X. Pawl 140 is positioned adjacent the outwardly facing surface of wall 108, and spring 138 is disposed between pawl 140 and button 106. Spring 138 is slightly compressed between button 106 and pawl 140, thus producing equal and opposite biasing forces respectively to button 106 and pawl 140. Pawl 140 includes a legged portion 148 which extends downwardly into casing 102 where it is fixedly attached to blade 104 about the periphery of aperture 142, and a plurality of teeth 150 alternately positioned between arcuate cutouts, or indentations, 152 formed in pawl 140. Teeth 150 are appropriately spaced to correspondingly engage with respective spaces 118, with arcuate cutouts 152 wrappingly engaging respective bosses 116.

Shaft 136, as before, includes a substantially circularly flanged end 153 positioned opposite button 106. Flanged end 153 is shaped to lockingly engage either of detents 120 and 122 as described in the previous embodiment.

Once pawl 140 engages either of the end bosses 116', 116", blade 104 is nearly positioned in either of its terminal positions. As with the first embodiment, to fully position blade 104 in one of its terminal positions it is necessary for the user to continue to longitudinally slide button 106 a slight distance in the appropriate direction (approximately 1/16 inch). In doing this, pawl 140 becomes disengaged from end bosses 116', 116" and a pin 154 engages an appropriately positioned notch 156 or L-shaped notch 158. Pin 154 projects outwardly from blade 104 in a direction perpendicular to plane in which wall 108 lies. When blade 104 is in either its fully open or fully closed positions, pin 154 engages notch 156 or L-shaped notch 158, respectively, which secures its position and prevents any inadvertent movement from that position. Notches 156 and 158 are formed at appropriate positions in the blade receiving edge 115 of wall 108 as is clearly seen in FIG. 6 to permit flange 153 to securely engage detent openings 120 and 122 when pin 154 is engaged in the corresponding notch. Furthermore, a notch 160 is formed in handle 126 to accommodate pin 154 when blade 104 is in its open position.

It should again be noted that while button 106 and shaft 136 slide along with pawl 140, they do not rotate along with pawl 140, thereby decreasing internal friction and permitting easy opening and closing of blade 104.

The functional operation of knife 100 is substantially identical to that of knife 10 and will therefore not be explained in any further detail.

Referring now to FIGS. 12-16, there is seen a third alternate embodiment of a folding knife, designated generally by reference numeral 200. Knife 200 is generally comprised of a casing 202, a blade 204 pivotally mounted for movement between closed and open positions with respect to casing 202, and a user actuated button 206 slidably mounted to casing 202 for producing pivotal movement of blade 204 and translatory movement of pivot axis X--X.

Casing 202 is seen to include first and second opposed walls 208 and 210, respectively, first wall 208 having a rectangular opening 212 longitudinally formed therethrough, and second wall 210 having a longitudinally elongated slot 214, as in the first two embodiments, formed therethrough. Casing 202 further includes a blade receiving edge 215 and a closed edge 217. The elongated edge of opening 212 adjacent the blade receiving 215 of casing 202 includes a longitudinally elongated gear rack 218 (the end teeth of the gear rack are denoted 218' and 218") integrally attached thereto. Wall 210 includes two, longitudinally spaced apart, circular detent openings 220 and 222 cut out therefrom in intersecting relation to slot 214. Detent openings 220 and 222 are used to securely lock blade 204 in either of the two detent positions in the same manner as with the first two embodiments.

User actuated button 206 is fixedly attached to one end of an elongated shaft 226 which fully extends through a coiled spring 228, flanged bushing 230, a segmented gear, or pinion, 232, opening 212, an aperture 234 formed through the tang portion 236 of blade 204, and slot 214, again defining pivot axis X--X. Segmented gear 232 is fixedly connected to the tang portion 236 of blade 204 adjacent wall 208, and positioned in meshing engagement with gear rack 218, while bushing 230 extends through and is fixedly attached to gear 232 and aperture 234 with its flanged portion abutting gear 232 opposite blade 204.

Shaft 226 further includes a flanged end 240 positioned opposite button 206. Flanged end 240 provides the blade locking mechanism for knife 200, just as flanged ends 48 and 153 do for their respective knives.

Upon initiation of a downward and longitudinally applied user exerted force to button 206, flanged end 240 becomes disengaged from detent 220 or 222. Therefore, shaft 226, along with its connected parts, slides within the confines of slot 212 in the direction of the applied force. Due to shaft's 226 extension through gear 232, the sliding motion of shaft 226 is transferred directly to gear 232. As gear 232 slides longitudinally along, its teeth cooperatively engage respective spaces formed between the teeth of gear rack 218, thereby imparting rotational motion thereto as well as translatory motion to axis X--X. Due to gear's 232 permanent attachment to blade 204, the simultaneous linear-rotational motion of the gear is translated directly to the blade, thus pivoting the blade between its open and closed positions. Therefore, as button 206 is slid either towards the rear or the front of casing 202, blade 204 will pivot either into or out of casing 202, respectively.

It should once again be noted that while button 206 and shaft 226 slide along with gear 232, they do not rotate along with gear 232, thereby decreasing internal friction and permitting easy opening and closing of blade 206.

Once gear 232 engages either of the end teeth 218' and 218" on rack 218, blade 204 is nearly positioned in either of its terminal positions. To fully position blade 204 to its terminal positions it is necessary for the user to continue to longitudinally slide button 206 a slight distance in the appropriate direction (approximately 1/16 inch). In doing this, gear 232 becomes disengaged from end teeth 218', 218" and a pin 242 engages an appropriately positioned notch 244 or L-shaped notch 246. Pin 242 is attached to blade 204, and notches 244 and 246 are formed in casing 202 for receiving pin 242, and a detent cover 248 positioned in covering relation over detents 220 and 222. These are all completely analogous to the corresponding parts discussed in knives 10 and 100.

Referring now to FIGS. 17-21 there is seen a fourth alternate embodiment of a folding knife, denoted generally by reference numeral 300. As with the knives of the previously described embodiments, knife 300 is generally comprised of a casing 302, a blade 304 pivotally mounted for movement between closed and open positions with respect to casing 302, and a user activated button 306 slidably mounted to casing 302 for producing pivotal movement of blade 304 and translatory movement of pivot axis X--X.

Casing 302 is seen to include first and second opposed walls 308 and 310 having corresponding, axially aligned, longitudinally elongated, first and second slots 312 and 314 formed therethrough, respectively. Casing 302 further includes an open, blade receiving edge 315 a closed edge 317, and a curvilinear gear rack 319 (the end tooth nearest the butt of knife 300 are denoted 319') integrally formed between casing walls 308 and 310 adjacent closed edge 317. As seen most clearly in FIGS. 19 and 21, wall 310 includes two, laterally spaced apart, circular detent openings 320 and 322 cut out therefrom. Detent openings 320 and 322 are formed in intersecting relation with slot 314. As with the corresponding detent openings of the previously described embodiments, detent openings 320 and 322 are used to securely retain blade 304 in either of two positions.

Again in reference to the previously described embodiments, user actuated button 306 is fixedly attached to one end of an elongated shaft 324 which fully extends through a coiled spring 326, a flanged bushing 327, first slot 312, a cam-shaped gear 328 which is integrally formed into the tang portion 330 of blade 304, and second slot 314, again defining pivot axis X--X. Obviously, gear 328 and tang portion 330 have a common aperture 332 formed therethrough which permits for the passage of shaft 324. Bushing 327 includes a flanged portion which is positioned exteriorly adjacent to wall 308 and further includes a legged portion which extends downwardly through aperture 332 where it is attached to blade 304. Spring 326 is disposed, in a slightly compressed position, adjacently between button 306 and flanged bushing 327, thus creating an upward biasing force to button 306.

Shaft 324 further includes a flanged end 334 fixedly attached thereto and opposite button 306. Flanged end 334, as with all the previously described embodiments, provides the blade locking mechanism for knife 300.

Upon initiation of a downward and longitudinally applied user exerted force to button 306, flanged end 334 becomes disengaged from detent opening 320 or 322. Therefore, shaft 324, along with all parts connected thereto, slide within the confines of slot 312 in the direction of applied force. Due to shaft's 324 extension through gear 328, the sliding motion of shaft 324 is transferred directly to gear 328. As gear 328 slides in a longitudinal direction, its teeth cooperatively engage respective spaces formed between the teeth of gear rack 319, thereby imparting rotational motion thereto. Due to gear's 328 permanent attachment to blade 304, the simultaneous linear-rotational motion of the gear is translated directly to the blade and translated to axis X--X, thus pivotally moving the blade between its open and closed position. Therefore, as button 306 is slid either towards the front or the rear of casing 302, blade 304 will pivot either out of or into casing 302, respectively.

It should again be noted that while button 306 and shaft 324 slide along with gear 328, they do not rotate along with the gear, thereby decreasing internal friction of the moving parts and permitting easy opening and closing of blade 306.

Once gear 328 engages end tooth 319' on rack 319, blade 304 is nearly positioned in its terminally closed positions. To fully position blade 304 in its terminal, closed position, it is necessary for the user to continue to slide button 306 a slight distance in the appropriate direction (approximately 1/16 inch). In doing this, gear 328 becomes disengaged from end tooth 319' and a pin 336 engages an appropriately positioned J-shaped notch 340, respectively. Pin 336 and notch 340 are substantially identical to each of the pins and notches described in the previous embodiments.

Knife 300 also includes a blade lock cover 342. Cover 342 is fixedly attached to the outwardly facing surface of wall 310 in covering relation to slot 314 and detents 320 and 322. As in all previously described embodiments, cover 342 prevents foreign particles from accumulating within casing 302, thereby insuring the blade locking mechanism does not become jammed and unfunctionable.

Referring now to FIGS. 22a-c, there is seen a sequence of events which effect pivotal movement of blade 304 (using the fourth embodiment of the present invention for illustrative purposes) between its closed and open positions.

In FIG. 22a, blade 304 is seen to be in its open positions. Flanged end 334 is securely positioned within detent opening 320 and spring 326 is a slightly compressed state.

FIG. 22b includes an arrow 350 representative of a user exerted force applied to button 306. Upon initiation of such a force, spring 326 is seen to become fully compressed and flanged end 334 disengages detent opening 320. Button 306, along with all its connected parts, is then slid in the direction represented by arrows 352.

Once blade 304 becomes fully closed, the user applied force to button 306 may be removed. Flanged end 334 engages detent opening 322 and pin 336 engages notch 340, thereby securely locking blade 304 in its closed position.

To move blade 304 back to its open position, it is necessary for a user to reverse the steps recited above.

FIGS. 22a-c were intended to represent the blade movement operating principles of each of the four disclosed embodiments. The reference numerals used were strictly for illustrative purposes only, and it should not be thought that only the knife disclosed in the fourth embodiment operates by the recited principles.