Technical Field

This invention relates to extendable blade knives, and particularly to folding knives having multiple blades.

If different blades are employed at various times, with existing models it is necessary to use both hands to select the blade of interest, open the blade, later unlock and close the blade, and then find the next blade and repeat the process. Each time a new blade is selected, the user of the knife must divert attention from the ultimate use of the knife, and must use both hands, to find and operate the blade to be deployed. For some knife applications, this sequence of events in the use of the knife poses serious problems. To cite an example, an emergency rescue worker may require both a conventional blade and a seat-belt cutting tool to rescue a trapped person from a damaged vehicle. The rescue may be accomplished in a confined space under highly adverse conditions such as near-total darkness, where the need to use two hands to operate the knife is a serious disadvantage and can lead to confusion and the loss of time in the rescue. This example highlights the problem, but the same difficulties can arise in many other uses of folding knives in emergency, sporting, home, or industrial situations.

Thus, there is a need for an improved multiple-blade knife that offers greater selectivity and control in managing the use of the knife.

Disclosure of Invention

The present invention provides a knife with at least two extendable blades. The blade to be opened is selected by the user and opened from its closed position. After opening, the selected blade is positively locked in the open position. To return the blade to the closed position, the user disengages the lock and rotates the blade to the closed position. The knife is oriented for using the next blade. The knife user can accomplish all blade selection, opening, closing, and use functions with one hand, leaving the other hand free. Selection, functional, and convenience features are provided. In accordance with the invention, a folding knife comprises an elongated knife body having a first end, a first blade pivotably mounted to the first end of the knife body to move between open and closed positions, and a second blade pivotably mounted to the first end of the knife body to move between open and closed positions. The blades open by rotation in opposite directions, one from the knife top and the other from the knife bottom. The blades are locked in their open positions by a side lock plate positioned between the first blade and the second blade. The side lock plate includes a first finger biased toward the first blade so that the first finger engages the first blade in its open position, and a second finger biased toward the second blade so that the second finger engages the second blade in its open position.

Blade selection is accomplished by rotation of the knife about its elongation axis, to bring the selected blade into position to rotate open. The user firmly grasps the knife during this rotational

selection, rather than risking loss of grip by turning the knife end-for-end. The knife handle may be provided with features such as different textures or symbols on the two sides of the knife body to indicate the orientation of the knife, and thence the blade in position to be opened, by touch.

The blades are held in place when closed by a smoothly functioning, readily produced detent mechanism. A thumb pin on the side of each blade aids in its opening against the retention force. The blade is locked into the open position by the engagement with the finger, and can be selectively unlocked by the user pressing against the finger. After the blade is rotated to the closed position, the other blade is selected by rotating the knife 180 degrees about its axis of elongation.

The knife is made to be quite strong yet relatively narrow in width for a knife with two blades. The side lock plate engages the knife side pieces to form a strong single unit, and a belt clip, where present, is firmly seated to the knife body.

Brief Description of the Drawings

Figure 1 is a perspective exploded view of one embodiment of the knife of the invention;

Figure 2 is a side view of the knife of Figure 1 showing the first blade in the closed position and with portions of the structure in phantom view; Figure 3 is a side view of the knife of

Figures 1 and 2 with the first blade in the open position and with portions of the structure in phantom view;

Figure 4 is a top view of the knife of Figure 3, with the first blade in the open and locked position and with portions of the structure in phantom view; Figure 5 is a top view of the side lock plate of Figure 1, as it is manufactured and without any external constraints;

Figure 6 is a perspective view of an integral sidepiece structure; Figure 7 is a perspective view of the knife of the invention held in a hand during opening of one of the blades;

Figure 8 is a perspective view of the knife of the invention held in a hand during unlocking and closing of one of the blades;

Figure 9 is a side elevational view of tactile coding on a first side of the knife of Figure 1;

Figure 10 is a side elevational view of the tactile coding on a second side of the knife of Figure 1 ;

Figure 11 is a perspective exploded view of a further embodiment of the knife of the invention.

Figure 12 is an exploded perspective view of a knife according to the invention;

Figure 13 is a sectional view through the region of the blade axle of the knife of Figure 1, along line 13-13 of Figure 12, but after assembly of the knife components; Figure 14a is an elevational view of the interior side of the first side piece;

Figure 14b is an elevational view of the locking plate as it is oriented with respect to the first side piece as shown in Figure 14a; Figure 15a is an elevational view of the interior side of the second side piece;

Figure 15b is an elevational view of the locking place as it is oriented with respect to the first side piece as shown in Figure 15a;

Figure 16 is a sectional view of a conventional detent mechanism;

Figure 17 is a sectional view of a detent mechanism according to the invention;

Figure 18 is an elevational view of the thumb pin; and Figure 19 is a sectional view through one of the side pieces of the knife of Figure 1, taken along line 19-19 of Figure 12.

Best flfcde for Carrying Out the Invention

A folding knife 20 according to a preferred embodiment of the invention is shown in Figures 1-5. (The term "folding knife" is commonly used to describe knives wherein the blades are contained within the body of the knife when closed, and are pivoted about a pivot pin to an opened position. ) The knife 20 utilizes a side lock plate 22 operable to lock two blades, a first blade 24 and a second blade 26. The side lock plate and the blades are preferably made of steel , and most preferably a stainless steel of any type known in the art. In the figures, the first blade 24 is depicted as a conventional single-sided cutting blade, and the second blade 26 is depicted as a hooked blade that may be used by law enforcement and emergency personnel to cut fabric webs such as a seat belt to free a trapped person. As used herein, the term "blade" includes conventional single-edged cutting blades and other types of implements known for use in a folding knife format. Such implements can

include, for example, screwdrivers, scissors, pliers, saws, can openers, gut hooks, awls, and the like, in addition to conventional single-edged cutting blades. The present invention is not restricted as to the types of blades used, and is operable with all types of blades known to the inventors .

The side lock plate 22 is positioned between and parallel to the pivoting planes of the two blades 24 and 26. A first sidepiece 28 overlies and is positioned outside of the first blade 24, so that the first blade 24 is disposed between the first sidepiece 28 and the side lock plate 22. A second sidepiece 30 overlies and is positioned outside of the second blade 26, so that the second blade 26 is disposed between the second sidepiece 30 and the side lock plate 22.

A common pivot pin 32 extends through aligned bores 34 and 36 in the blades 24 and 26, respectively, so that the blades pivot about that pivot pin 32. As a convenience in construction and assembly, the pivot pin 32 typically extends through commonly aligned bores 38 40, and 42 in the side lock plate 22, the first sidepiece 28, and the second sidepiece 30, respectively. The use of a single pivot pin for both blades 24 and 26 permits the blades to be pivoted and deployed to their open positions at different times, without turning the knife 20 end-for-end, as is required in some other types of folding knives.

The knife 20 of the invention is formed as the separate elements 22, 24, 26, 38, 30, and 32. The side lock plate 22 and the sidepieces 28 and 30 are provided with commonly aligned rivet holes 44. To assemble the knife 20, the elements 22, 24, 26, 28, and 30 are stacked in the proper order into an

assembly jig. The pivot pin 32 is placed through the commonly aligned bores 34, 36, 38, 40, and 42. Rivets 44 (or screws) are fastened through the rivet holes 46 (only one of the rivets 44 is shown to avoid clutter in the drawings). The pivot pin 32 also acts as a rivet, as its ends are upset during assembly.

Alternatively, the sidepieces 28 and 30 can be formed as a single molded sidepiece unit 47, shown in Figure 6. Such a sidepiece unit 47 can be conveniently fabricated by plastic injection molding, for example. In this case, a bridge is formed between side piece segments 28' and 30' to hold the side piece segments in their proper positions. The other elements 22, 24, 26, 32, and 44 are assembled to this single sidepiece unit 47 in the manner described.

Returning to the embodiment of Figures 1-5, when assembled the integral unit formed of the sidelock plate 22 and the sidepieces 28 and 30 is termed a body 48 of the knife. The blades 24 and 26 fold into the body 48 in their respective closed positions (shown in Figure 2 for the first blade) and fold out of the body 48 to their respective open positions (shown in Figure 3 for the first blade). The first blade 24 and the second blade 26 pivot in respective planes that are parallel to each other and to the plane of the side lock plate 22 as the blades are moved between their respective open and closed positions.

A desirable feature of the present knife 20 is that the blades 24 and 26 are contained entirely within the body 48 when they are in the closed position. The locking structure is also contained entirely within the profile or outline of the body 48. Only the small flick projections, to be

discussed subsequently, may optionally extend slightly above the smooth sides, top, and bottom of the knife. Consequently, there are no (or very minor) projections on the knife 20 that can snag on clothing or injure the user of the knife (as by gouging into the user's hand) during service.

A further aspect of the preferred knife 20 is that the blades 24 and 26 move between their respective open and closed positions by rotation in opposite directions about the pivot pin 32. That is, as shown by the arrow 50 in the view of Figure 1, the first blade 24 moves from its open to its closed position by a counterclockwise movement. The second blade 24 moves from its open to its closed position by a clockwise movement, arrow 52. Stated alternatively, defining a top 54 and a bottom 56 of the knife, the first blade opens through the top 54 and the second blade opens through the bottom 56.

In describing the details of the construction and operation of the knife 20, it is useful to define two directions perpendicular to the side lock plate 22. A first perpendicular direction 58 extends perpendicularly out of the side lock plate 22 toward the first blade 24 and the first sidepiece 28. A second perpendicular direction 60 extends perpendicularly out of the side lock plate 22 toward the second blade 26 and the second sidepiece 30. A longitudinal axis 62 of the knife extends along its long direction. Turning to the details of the elements of the knife, the side lock plate 22 is formed with four regions. In the preferred construction, these four regions are integrally connected in a slotted plate structure, but in an alternative approach separate pieces could be fabricated and joined. The side lock plate 22 includes a plate base 64 at the end of

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the side lock plate 22 remote from the blades 24 and 26 and from the pivot pin 32. A T-shaped plate central region 66 extends from the plate base 64 parallel to the longitudinal axis 62, with the bore 38 through the "T" shaped region 66.

On either side of the central region 66 are fingers 68 and 70. The first finger 68 is bent or sprung in the first perpendicular direction 58, and therefore biased in this direction 58. The second finger 70 is bent or sprung in the second perpendicular direction 60, and therefore biased in this direction 60. The bending of the fingers 68 and 70 is not seen in the exploded view of Figure 1, as when the knife is assembled the fingers are pressed flat by their contact with the respective adjacent blades 24 and 26. Figure 5 shows the side lock plate 22 as it is manufactured, with the fingers 68 and 70 in their bent and biassed positions. The extended, bent positions of the two fingers 68 and 70, as shown in Figure 5, are termed their respective finger locking positions.

The first finger 68 has a first finger locking shoulder 72 thereon at the end of the first finger 68 adjacent to the T cross bar of the central region 66. Similarly, the second finger 70 has a second finger locking shoulder 74 at the end of the second finger 70 adjacent to the T cross bar of the central region 66. The cooperation of these finger locking shoulders 72 and 74 with their respective blades 24 and 26 will be described subsequently.

The first blade 24 has a first blade locking shoulder 76 at the end of the blade remaining within the body 48 of the knife 20, when the first blade 24 is opened. The second blade 26 has a second blade locking shoulder 78 at the end of the blade remaining within the body 48 of the knife 20, when

the second blade 26 is opened. The respective blade locking shoulders 76 and 78 are positioned on the blades so as to engage the respective finger locking shoulders 72 and 74 , when the respective blades 24 and 26 are opened to their open position, thereby providing the respective blades 24 and 26 with positive open-position locks that prevent the blades 24 and 26 from closing until the locks are released. The operation of the locks can be seen by referring to Figures 2-4 and 7-8, which show the operation of the open-position lock for the case of the first blade 24. The operation of the open-position lock for the second blade 26 is similar. In Figure 2, the blade 24 is in the closed position within the body 48. The side of the blade 24 compresses the first finger 48 from the extended, finger locking position shown in Figure 5 to the flat position shown in Figure 1, so that the first finger 48 is coplanar with the central region 66. As the blade 24 is opened (by a clockwise rotation progressing as shown in Figure 6 from the view of Figure 2 to that of Figure 3), the inward compressive force on the first finger 48 is released and the first finger 68 springs outwardly in the first perpendicular position 58. When the first blade 24 is in its fully open position shown in Figure 3, the first finger locking shoulder 72 engages the first blade locking shoulder 76, as may be seen in Figure 4. The first blade 24 is thereby locked into the fully open position by this positive lock. The first blade cannot be rotated back (counterclockwise) to the closed position until the lock is released. The lock is released when the user manually presses against the side of the -first finger 68, as indicated by the arrow 80 in Figure 4 and as depicted in Figure 8. The structures which

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aid in opening and permit easy manual access to the side of the first finger 68 to achieve unlocking of the blade will be described subsequently.

The open position lock just described prevents the blade from closing unless the lock is released. The blade must also be prevented from rotating too far, past the blade open position shown in Figures 1 and 3. To provide this blade stop function, the first sidepiece 28 has an inward (toward the side lock plate 22) first sidepiece projection 82 with a first sidepiece stop shoulder 84 thereon. Similarly, the second sidepiece 30 has an inward (toward the side lock plate 22) second sidepiece projection 86 with a second sidepiece stop shoulder 88 thereon. The first and second sidepiece stop shoulders 84 and 86 face toward the end of the knife 20 where the blades 24 and 26 are attached with the pivot pin 32. The cooperation of these stop shoulders 84 and 86 with their respective blades 24 and 26 will be described subsequently.

The first blade 24 has a first blade stop shoulder 90 at the end of the blade remaining within the body 48 of the knife 20, when the first blade 24 is opened. The second blade 26 has a second blade stop shoulder 92 at the end of the blade remaining within the body 48 of the knife 20, when the first second 26 is opened. The respective blade stop shoulders 90 and 92 are positioned on the blades so as to butt against the respective sidepiece stop shoulders 84 and 88, when the respective blades 24 and 26 are opened to their open positions, thereby providing the respective blades 24 and 26 with positive stops that prevent the blades 24 and 26 from rotating past their desired fully ^' open positions when the blades lie parallel to the longitudinal axis 62.

The operation of the stops can be seen by referring to Figures 2-3, which show the operation of the stops for the case of the first blade 24. The operation of the stop for the second blade 26 is similar. In Figure 2, the blade 24 is in the closed position within the body 48. The stops do not come into play.

As the blade 24 is opened (by a clockwise rotation progressing from the view of Figure 2 to that of Figure 3) to the point that it is in its fully open position shown in Figure 3, the first sidepiece stop shoulder 84 butts against the first blade stop shoulder 90. The clockwise rotation of the first blade 24 is thereby stopped so that it cannot be rotated further. In combination with the open position lock described previously, the stop structure rigidly locks the blade 24 so that it cannot rotate in either direction from its fully open position, unless the open position lock is released.

The opening and closing of the knife blades are facilitated by providing a cutout in each of the sidepieces and a cooperating element on the respective blades. Thus, a first sidepiece cutout 94 is formed in the first sidepiece 28 along the edge of the first sidepiece adjacent the knife top 54. Similarly, a second sidepiece cutout 96 is formed in the second sidepiece 30 along the edge of the first sidepiece adjacent the knife bottom 56. As an aid in opening the knife blades 24 and 26, flick projections are formed on the sides of the knife blades. As seen in Figures 1 and 4, a first blade flick projection 98 is formed in the first perpendicular direction 58 on the side of the ^' first blade 24 facing the first sidepiece 28. As seen in Figure 1 in a phantom view, a second blade flick

projection 100 is formed in the second perpendicular direction 60 on the side of the second blade 26 facing the second sidepiece 28.

The use of the flick projections in opening of the blades can be seen by referring to Figures 2 and 7, which show the opening operation for the case of the first blade 24. The operation of the stop for the second blade 26 is similar. When the first blade 24 is in the closed position, Figure 2, the first blade flick projection 98 is received within the first sidepiece cutout 94. The first blade flick projection 98 is preferably made no longer than the thickness of the first sidepiece 28 in the region of the first sidepiece cutout 94, so that it does not project out of the body 48 and provide a possible source of snags when the knife 20 is removed from the pocket of the user. However, because its rounded shape has little likelihood of causing a snag, the first blade flick projection 98 may be made about the same length or even slightly greater in length than the thickness of the first sidepiece 28 without having a significant adverse effect on the smooth-surface, antisnag characteristics of the knife. Making the first blade flick projection 98 slightly longer than the thickness of the first sidepiece 28 may improve the ease of opening the first blade 24 using the flick projection 98.

To open the first blade 24 from the closed position of Figure 2, the user holds the knife in one hand and applies pressure with the thumb (or one of the fingers, but preferably the thumb) against the first blade flick projection 98 as shown in Figure 7, and continues that pressure until the first blade rotates to the open position of Figure 3 and locks at that position in the manner described

previously.

The unlocking of the blade open lock is also facilitated by the sidepiece cutout for that blade, as can be seen by referring to Figures 3 and 8, which show the manner of releasing the lock for the case of the first blade 24. The releasing of the lock for the second blade 26 is similar. When the first blade 24 is in the open position, a portion of the first finger 68 is accessible to the thumb (preferably) or the finger of the user of the knife through the first sidepiece cutout 84. The user applies pressure to the first finger 68 in the region exposed through the first sidepiece cutout 94, in the direction 80 against the bias force of the first finger 68. Simultaneously, the user rotates the first blade 24 in the counterclockwise direction 50 (of Figures 3 and 8), past the point where the first finger locking shoulder 72 engages the first blade locking shoulder 76. From this point onward in the closing of the first blade 24, there is no need to continue to apply pressure to the first finger 68, as the side of the first finger 68 rides over the adjacent side of the first blade 24. When the blades 24 and 26 are closed, they can be retained in the closed position by frictional force, a spring, or any other operable mechanism. A preferred approach is a ball-detent mechanism. With the ball detent mechanism, a small recess is made in the side of the fingers 68 and 70 that face outwardly toward the respective sides 28 and 30. A steel ball 102, preferably about 0.020 inches in diameter, is placed into each of the recesses during assembly of the knife. Each of the steel balls 102 is captured between its respective finger 68 or 70 and the facing side of the respective blade 24 or

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26. As the blades 24 or 26 are opened or closed, the balls 102 act as ball bearing to ensure a smooth pivoting motion. A closed-position retention recess 104 is formed in each of the sides of the respective blades 24 and 26 that face the respective steel balls 102, at a location such that the respective balls 102 roll into the respective recesses 104 when the respective blades reach their desired closed positions. As the ball 102 falls into the recess 104, the finger upon which the ball is supported relaxes outwardly by a small amount. To open the blade from this closed position, a small force must be exerted to force the finger inwardly. The blade is thereby retained in the closed position by this detent mechanism until a small force is exerted to open the blade.

A prototype knife has been constructed according to the preferred embodiment discussed above and depicted in Figures 1-5. Experience with the knife validated the various mechanisms and structures discussed herein. When the knife was held in one hand, pressure by the thumb of the user against the blade flick projection moved the blade from the closed position toward the open position as shown in Figure 7. The pressure applied with a extending and circling motion of the thumb brought the blade to the fully open position where it was stopped and then locked into position. When the blade was to be closed, the thumb was pressed against the side of the first finger 68 through the sidepiece cutout to unlock the blade lock mechanism as shown in Figure 8, and at the same time the index finger rotated the blade to the closed position where it achieved a weak retention with the detent. During all of these operations, the knife was readily grasped firmly within the palm and remaining

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fingers of the user. One handed operation, a desirable feature many knife users, is readily obtained .

When the knife was held and opened in the manner just described, the blade rotated away from the hand of the user. To use the other blade, the user closed the first-used blade. The user rotated the entire knife 180 degrees about the longitudinal axis 62 using only the hand holding the knife, so that the other blade opened away from the hand of the user. Then the one-handed opening, locking, unlocking, and closing motions previously described were used, for the other blade.

By this approach, the user of the knife could select the blade to be used and fully operate the knife, entirely with one hand. With a minimal amount of practice to develop coordinated movements, the user could operate the knife with little thought to the mechanics of the operation. The user was free to devote the use of the other hand and most of his or her attention to the use of the knife rather than the operation of the knife.

It is recognized that the use of a knife having at least two blades involves two distinct steps: first, selecting the blade to be used and positioning the knife in the hand so that the blade is ready for use (even though in a closed position, and, second, operating the blade in opening, locking, unlocking, and closing functions. To aid in the selecting function, the knife

20 may be provided with coding that allows the user to tactilely distinguish between the two sides of the knife, and thence which of the two blades is in a position to be opened away from the hand of the user. Figures 9 and 10 illustrate some tactile coding approaches that can be used. The knife 20 is

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desirably provided with a grip surface 300 made of a natural or synthetic material such as rubber, plastic, or other material that provides a firm, nonslipping grip for the user. One tactile coding approach is to provide different textures to the grip surface 300 on the different sides of the knife. For example, on a first side as shown in Figure 9, a rougher texture 302 is provided on the grip surface 300, and on a second side as shown in Figure 10, a smoother texture 304 is provided. Such texture differences do not interfere with the gripping of the knife, but do provide a tactile code for distinguishing between the sides of the knife and thence the blade that is positioned for opening. A second tactile coding approach utilizes symbols. For example, in Figure 9 a raised pictorial symbol 306, here a symbolic representation of the blade 24 that will be selected when the symbol 306 is felt against the thumb of the user of the knife, is placed ^* on the first side of the grip surface 300. In Figure 10 a raised internationally recognized triangular symbol 308 is placed on the second side of the grip surface 300. Other types of tactile coding could also be used, such as a coding on one side but not the other, letters, Braille symbols, etc. The several different types of coding in Figures 9 and 10 are shown for illustration. In most cases, only one of the types of tactile coding (e.g. , symbols or texture) would be needed and used. When the user of the knife grasps the knife in one hand in the conventional fashion, the coding on the gripping surface of the knife handle permits the user to recognize the orientation of the knife without visually inspecting the knife. If the desired blade is oriented for opening away from the single hand of the user, the knife is ready for

use. If the desired blade is oriented for opening into the single hand of the user, the user need only rotate the knife by 180 degrees about its longitudinal axis, sense the coding on the side of the knife brought into position by this rotation, and use the knife.

The tactile coding enables the user to accomplish blade selection without visual inspection of the knife. If the previously described structure for one-handed operation of the blades as described previously are also provided, the selecting, positioning, opening, locking, unlocking, and closing of a desired blade can be accomplished with a single hand and without visual inspection of the knife. This capability is highly desirably for many knife users, so that the second hand and the primary attention of the user can be directed elsewhere, and in particular toward the primary application for which the knife is being used. In a further variation of the knife of the invention, single side lock pieces can be used in a manner so as to permit the rollover feature to be used with additional blades as well. Figure 11 depicts this embodiment. Inasmuch as many of the features and functions of individual elements are the same as described for the knife 20, the prior description is incorporated to that extent.

A knife 400 has a first blade 402 and a second blade 404. The first blade 402 has an associated first single side lock plate 406, and the second blade 404 has an associated second single side lock plate 408. The first side lock plate 406 has a single first finger 410 disposed to engage the first blade 402 and lock it closed in the manner discussed previously. The second side lock plate 408 has a single first finger 412 disposed to engage

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the second blade 404 and lock it closed in the manner discussed previously. A first side piece 414 overlies the first side lock plate 406, and a second side piece 416 overlies the second side lock plate 408. The side lock plates 414 and 416 have the same stopping structure as described previously, and also may be made as a single injection molded unit. A common pivot pin 418 extends through bores in the blades 402 and 404, the side lock plates 406 and 408, and the side pieces 414 and 416.

Additional blades can also be provided in the knife 400. A single additional blade, here depicted as a pliers blade 420, is shown in Figure 11, but the same principles of construction can be used to add more blades to the knife 400. The pliers blade 420 is pivoted about the same pivot pin 418 as the other blades 402 and 404. The blade 420 is retained in the closed position and locked into the extended position by any suitable retention and locking mechanism. Here, a conventional spring arm 422 presses against the back of the blade 420 to provide both retention and open-lock (but not positive open lock) functions. A positive open lock could be provided, for example, by a conventional lock-back mechanism.

The knife 400 permits the addition of more blades, but at the cost of increased weight and complexity of the knife. In some cases the increased weight and complexity may be warranted, however. The rollover feature for the outermost blades (here blades 402 and 404) is retained, while providing the other blades (here blade 420) as well.

The knife of the invention can be provided with various structural improvements that can be used with a single-blade or a multiple-blade knife. In the following discussion, these features are

discussed in relation to a single-blade knife, with the understanding that they may be used with a multiple-blade knife as well.

Figure 12 depicts a knife 520 including a knife body 522, which serves as a handle when the blade is opened. The knife body 522 includes a first side piece 524 and a second side piece 526. The side pieces 524 and 526 are elongated along a knife axis 527 to fit comfortably in the hand of a user. A root portion 528 of a blade 530 and a locking plate 532 are disposed between the two side pieces 524 and 526, with the locking plate 532 positioned between the blade 530 and the first side piece 524 in the illustrated embodiment. The knife 520, its component side pieces 524 and 526, the blade 530, and the locking plate 532 may be described as having a top side 534 and a bottom side 536. The top and bottom sides of the movable blade 530 are defined in reference to its orientation in the illustrated open blade position. The knife 520, its component side pieces 524 and 526 and, the locking plate 532 may be further described as having a front end 537 from which the the blade 530 projects when open, and a back end 538 at the opposite end of the knife. The top side, bottom side, front end, and back end of the knife are defined for reference in describing the interrelation of the components and features of the knife. The knife 520 is of the preferred side lock type, in which the blade 530 is locked in its open position by the locking plate 532 in a manner to be described. However, the features of the present knife not related directly to the locking plate may be used in conjunction with other types of extendable blade knives such as, for example, lock

back folding knives.

A first plurality of grooves 540 are present on the top side 534 of the blade root portion 528. A second plurality of grooves 542 are present on the bottom side 536 of the blade root portion 528. The grooves 540 and 542 extend perpendicular to the long axis of the knife, the knife axis 527. These grooves 540 and 542 are used in grasping the knife 520 to retrieve it from a stored location. The knife 520 may be provided with a clip 544 for attachment to a belt, or it may have no clip and be used in conjunction with a storage pouch or stored in a pocket of the user. In any of these storage approaches, when the knife is to be used the user reaches to grasp the knife to retrieve it. Particularly when the knife is wet or tightly retained in the storage position, it may be difficult to grasp the knife to accomplish retrieval. The two sets of grooves 540 and 542 can be felt by the fingers of the user and firmly grasped. (During retrieval, the blade 530 is normally closed, but the presence of two sets of grooves 540 and 542 ensure that grooves will be accessible to the fingers on both the top side and the bottom side of the knife when the blade is closed. )

It has been known to provide a single set of grooves along the top side (also sometimes called the back) of the blade 530, but these grooves serve primarily to give leverage for the thumb of the user in cutting operations when the blade is open. The top side grooves 540 of the present knife 520 can be used in this manner. However, they also cooperate with the second set of grooves 542 for the retrieval function described above. This cooperation is absent when only a single set of grooves is used.

The blade 530 is pivotable between an open position, illustrated in Figure 12 , and a closed position in which the blade is folded into the knife body 522. To accomplish the pivoting action, the root portion 528 of the blade pivots about a pivot axle 550 positioned near the front end 537 of the knife body 522. The pivot axle 550 is generally cylindrical but with a key structure to be described. The generally cylindrical form allows the blade to rotate on the majority of the cylindrical surface of the pivot axle 550, but also provides a keying structure that aids in holding the knife components in a defined position.

The pivot axle 550 is oriented transverse to the knife axis 527. Referring to Figures 12 and 13, the pivot axle 550 extends through a pivoting bore 552 that is formed by aligning during assembly a pivoting bore opening 552a in the clip 544, a pivoting bore opening 552b in the first side piece 524, a pivoting bore opening 552c in the locking plate 532, a pivoting bore opening 552d in a first washer 554, a pivoting bore opening 552e in the root portion 528 of the blade 530, a pivoting bore opening 552f in a second washer 556, and a pivoting bore opening 552g in the second side piece 526. The pivoting bore opening 552e in the blade 530 is circular, so that the blade 530 can pivot on the cylindrical portion of the pivot axle 550. The pivoting bore openings 552d and 552f are also preferably circular, because there is no reason to prevent the turning of the washers 554' and 556 and because conventional washers are available with circular central openings.

The pivot axle 550 has a key 558 thereon. At least two of the pivoting bore openings 552a, 552b, 552c, and 552g have a keyway 560 in the opening

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which matches to the key 558. The terms "matches to", "matching to", or the like, as used here, mean that two components have surfaces that conform to each other when the components are placed into a facing relationship. For example, in the preferred approach ^' , the key 558 is a flat surface on one side of the pivot axle, produced by machining a flat onto the cylinder. The keyway 560 is a matching flat surface on the interior of the opening. The pivot axle 550 can be inserted through the opening only by aligning the flat surface of the key with the flat surface of the keyway. Once the pivot axle 550 has been inserted into the opening, the pivot axle cannot be rotated with respect to the opening due to the engagement of the key with the keyway.

The engagement of the key on the pivot axle 550 with the keyways on the pivoting bore openings 552a, 552b, 552c, and/or 552g prevents the keyed elements from rotating with respect to each other, thereby serving to hold them in place in the assembled knife. In the preferred embodiment, all of the openings 552a, 552b, 552c, and 552g have keyways, so that the clip 544, the first side piece 524, the locking plate 532, and the second side piece 526 are locked together by the key 558 against rotational movement and also act together when cutting forces are applied to the knife body 522 by the user's hand during use of the knife 520. This engagement thus strengthens the knife body 522 so that its acts as a single unit, without the need for multiple additional fasteners at the front end 537 of the knife body 522.

By this approach, the clip 544 is engaged to the knife body 522 to resist rotational movement when the clip is placed over a belt or the like. Rotation of the clip 544 is also prevented by

providing a noncircular, shaped engagement region 562 at the end of the clip nearest the front end 537 of the knife body 522, as shown in Figure 13. A recess 564 in the exterior side of the first side piece 524 has a shape matched to that of the engagement region 562, so that the engagement region 562 is received into the recess 564.

The pivot axle 550 is preferably provided with a head 566 at one end. The opposite end is internally threaded. A pivot axle retainer screw 568 has a head 570 at one end and is externally threaded at the other end to threadably engage the internal threads in the pivot axle 550. As shown in Figure 12, during assembly the pivot axle 550 is placed through the pivoting bore openings 552, and the pivot axle retainer screw 568 is engaged and tightened to hold the front end 537 of the knife together.

The locking plate 532 is engaged to the side pieces 524 and 526 by a geometric fit rather than a separate fastener, thereby minimizing the use of fasteners in the knife 520. Figures 14a and 14b show the relation of the inside-facing surface of the first side piece 524 and the locking plate 532, and Figures 15a and 15b show the relation of the inside-facing surface of the second side piece 526 and the locking plate 532. The view of Figures 15a and 15b is rotated about the knife axis 527 of Figure 12, as compared with the view of Figures 14a and 14b, for clarity.

Referring to Figure 14a, the first side piece 524 is generally flat on its inside surface 578 but has a first rim 580 that is raised about 0.040 inch above an inside surface 578 of the first side-piece 524. (All dimensions set forth herein are presented by way of example for a preferred version of the

knife 520. ) The first rim 580 extends from a point about midway down the bottom side 536 to the back end 538 of the first side piece 524, at the periphery of the first side piece 524. Referring to Figure 14b, the locking plate 532 has a matching first cutout region 582. When the locking plate 532 is assembled with the first side piece 524, the locking plate rests against the inside surface 578 with the cutout 582 matched to and engaged to the first rim 580.

Referring to Figure 15a, the second side piece 526 has a generally flat inside surface 584 with two distinct raised regions. A shelf 586 that is raised with respect to the flat surface 584 by about 0.040 inches extends over a portion of the interior of the second side piece 526 from just behind the root portion 528 of the blade to the back end 538 of the knife body 522. A second rim 588 is raised with respect to the shelf 586 by about 0.040 inches. The second rim 588 extends from a point about midway down the top side 534 to the back end 538 of the second side piece 526 (a distance of about 1.155 inches in a preferred version of the knife), at the periphery of the second side piece 526. The shelf 586 is adjacent to, but located more centrally than, the second rim 588. Referring to Figure 15b, the locking plate 532 has a matching second cutout region 590 that is matched to the second rim 588. In the assembly, as shown in Figure 12, the second washer 556 (not shown in Figure 15a or 15b) is placed adjacent to the inside surface 584, and the root portion 528 of the blade 530 is placed over the second washer 556. The locking plate 532 is positioned over the root portion 528 of the blade 530, with the back and top regions of the locking

plate resting against the shelf 586. The inside surface 584 and adjacent periphery of the shelf 586 thereby form a pocket into which the blade 530 is folded when the blade is closed. The second cutout region 590 matches to and engages to the second rim 588. A fastener 592 is placed through a fastener bore 594 formed by aligned bores in the first side piece 524, the locking plate 532, and the second side piece 526 as shown in Figure 12. The cooperation of the keyed structure of the pivot axle 550, the fastener 592, and the matching engagement of the cutouts 582 and 590 of the locking plate 532 to the respective rims 580 and 588 imparts to the knife 520 high structural rigidity while using only the two fastening components 550 and 592 that extend through the thickness of the knife. In a preferred version of the knife 520, the side pieces 524 and 526 are formed of a relatively thin plastic. The side pieces 524 and 526 by themselves are not of sufficient structural rigidity for normal knife uses. The cooperative engagement of the locking plate 532 to the side pieces 524 and 526 increases the overall rigidity of the knife body 522 so that it is suitable for moderately heavy duty cutting.

When the blade 530 is rotated about the pivot axle 550 to the closed position within the knife body 522, it is desirable that there be a detent structure to hold the blade 530 in place. The detent structure draws the blade into its proper closed position over the last portion of the closing pivoting movement. The detent structure should be easily overcome by the user to rotate the blade 530 to the open position. Ball-and-recess detent mechanisms are well known in the art, and Figure 16 illustrates such a

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detent mechanism. One of the facing elements 600 has a semicircular protruding ball 602. The ball 602 is normally installed into the element 600 by drilling a bore 603 through the element 600. The bore 603 has a diameter slightly smaller than that of the ball 602, so that the ball 602 is force fit into the bore 603 during installation. The other of the facing elements 604 has a recess 606 into which the ball 602 is received. In Figure 16, the elements 600 and 604 are separated slightly for illustrative purposes. In practice, the elements 600 and 604 are pressed tightly together. The ball 602 extends about 0.020 inches above the surface of the element 600, and the recess 606 is slightly more than 0.020 inches deep so that the ball 602 does not bottom out in the recess 606. As the elements are moved from the open position in which the ball 602 and recess 606 are not in facing relation to the closed position in which the ball 602 and the recess 606 are placed into facing relation as shown in Figure 16, the ball 602 slides down the side of the recess 606, drawing the elements 600 and 604 into the final closed position. When the elements are to be moved back to the open position, the slightly resilient elements 600 and 604 are separated by manual force. The required separating force is the force that holds the elements in the closed position until opening is desired. While operable, such a conventional detent mechanism is relatively expensive to produce. The bore 603 and ball 602 must be precisely sized. The ball 602 must be precisely force fit into the bore 603, and this installation is often accomplished only with some difficulty. It is difficult to achieve ^'• good repeatability of the installation and of the detent mechanism.

An improved detent mechanism according to the present approach is illustrated in Figure 17. A first element 608, which in the present case is the locking plate 532, has a detent protrusion 610 thereon. The detent protrusion 610 has a detent protrusion surface profile 612. The detent protrusion 610 is preferably machined onto the first element 608 during manufacture. It is not typically prepared as a separate element that is thereafter attached to the first element 608, as in the case of the conventional ball-detent mechanism.

A second element 614, which in the present case is the root portion 528 of the blade 530, has a recess 616 therein. The recess 616 has a recess protrusion surface profile 618. In the preferred case, the recess surface profile 618 includes a flat bottom 620 parallel to a top surface 624 of the second element 614 and an inclined side surface 622, which is most preferably inclined at an angle of about 45 degrees to the flat bottom 620.

The detent protrusion surface profile 612 has a shape that is matched to the surface profile 618 of the recess 616, over at least a portion of their areas. In this case, the detent protrusion 610 has a flat elevated surface 626 parallel to a top surface 628 of the first element 608. The elevated surface 626 is raised above the top surface 628 by a height H of about 0.020 inches in the preferred embodiment. The recess 606 is slightly more than 0.020 inches deep, so that the elevated surface 626 of the detent protrusion 610 does not bottom out on the bottom of the recess 606 when the detent elements are engaged together. The detent protrusion 610 has an inclined side surface 630, which is most preferably inclined at an angle of about 45 degrees to the elevated surface 626.

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The profiles 612 and 618 are illustrated in Figure 17 as being matched over their entire areas, but this is not necessarily the case and is done in this manner for ease in machining the parts. The profiles need only be matched for the portions that are moved past each other during the closing and opening operations. For example, if the element 608 is held stationary and the element 614 is moved to the closed position by motion in the direction of the arrow 632, only the inclined sides 622a and 630a that first encounter each other during the closing movement .

To aid in moving the blade 530 from the closed to the open position, a thumb pin 640 protrudes from a side 642 of the blade 530. When the blade is closed, the thumb pin 640 is received into a cutout 644 on the second side piece 526. The use of thumb pins for this purpose is known in the art. Such prior art thumb pins are engaged to the blade by a further component, a threaded fastener. The fastener protrudes on the opposite side of the blade from the thumb pin, requiring for the provision of space within the knife body for the protruding fastener when the blade is in the closed position and also adversely affecting the appearance of the knife. Additionally, the thumb pin can loosen with time and use in service.

Figure 18 illustrates the thumb pin 640 of the present invention in greater detail. The thumb pin 640 is generally cylindrical with two parts. A first portion 646 has a first size and cross sectional shape, and has a length equal to the thickness of the portion of the blade 530 to which it is assembled. The first portion includes -a key 648. The key 648 has a shape that is matched to, but before assembly slightly oversize with respect

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to, the shape of a thumb pin receiver opening 650 in the blade 530. That is, the thumb pin receiver opening 650 acts as a keyway for the receipt of the key 648. In the present case, the key 648 is of a "D" shape, matched to a "D" shape of the thumb pin receiver opening 650. The first portion 646 is roughened, preferably by knurling. To assemble the thumb pin 640 to the blade 530, the key 648 of the first portion 646 is aligned to the thumb pin receiver opening 650. The first portion 646 is force fit into the thumb pin receiver opening 650, slightly compressing the roughened structure of the first portion 646 to fit within the receiver opening. This compressive fit holds the thumb pin 640 tightly in the thumb pin receiver opening 650, and the keying action prevents the thumb pin from rotating during service. No separate fastener is required.

The thumb pin 640 includes a second portion 652 that is radially enlarged over at least a part of its length, to provide a thumb contact surface for the user of the knife. The radially enlarged part of the second portion 652 may be smooth, as shown, or slightly roughened to provide a frictional surface for the user. The thumb pin structure and the detent mechanism previously described cooperate to aid in the reliable retention of the blade at the closed position within the knife and its smooth opening. The side pieces 524 and 526 are preferably made of a durable plastic such as Zytel^ plastic made by Dupont. Such a material, however, is smooth and can become slippery when wet. To aid in the grasping of the knife 520 by the user, the side pieces 524 and 526 are preferably provided with flexible elastomeric inserts 660 facing outwardly.

The inserts 660 are preferably made of Alcryn^ elastomer made by Dupont. The use of such inserts 660 requires great care in their design and assembly to ensure that they do not loosen and separate from the knife body 522 during service. The inserts are designed to be held in place by a combination of structural constraint and bonding.

Figure 12 shows an inside surface 662 of the insert 660a in the first side piece 524, and an outside surface 664 of the insert 660b in the second side piece 526. The inserts 660a and 660b are identical in structure and mode of attachment to their respective side pieces. In the illustrated embodiment, the inserts 660 are oval, extending most of the length of the central portion of their respective side pieces.

Figure 19 is a sectional view through one of the side pieces, generically indicated at numeral 166. The side piece 666 has an opening 668 therethrough. The opening 668 includes a stepped inwardly facing shoulder 670 by which the size of the opening is changed through the thickness of the side piece 666. The shoulder 670 is such that the larger part 672 of the opening 668 faces inwardly toward the interior of the knife and the smaller part 674 of the opening faces outwardly toward the exterior of the knife. The elastomeric insert 660 is matched in size to the opening 668 and has a matching stepped outwardly facing shoulder 676. The insert 660 is assembled to the side piece 666 so that the shoulders 670 and 676 are in facing contact. The insert 660 is thereby constrained in place against outwardly movement to the exterior of the knife by the contact of the shoulders 670 and 676. The insert 660 is fixed in place against inward movement by bonding it to the side piece

along the shoulders and any other contacting points. The bonding can be accomplished by any operable technique, most preferably sonic welding. An adhesive can also be used, but is less preferred. The inserts 660 are thus held firmly in place in the sides of the knife, and aid the user in grasping the knife during service.

Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims.