Compound pliers tool with linked handles

Abstract

Cooperating jaws are pivoted together such that working end portions of the jaw members are movable toward and away from each other. The jaws have butt portions extending opposite the jaw pivot from the working end portions. Such butt portions are, in turn, pivoted to elongated handles for swinging about axes parallel to the axis of the jaw pivot. The handles are channel shaped and define recesses into which the interconnected jaw members can be swung so as to be nested in the handles or, alternatively, into which the interconnected jaw members can be retracted so as to be partially contained within the handles. The handles have forward portions interconnected by a tension spring, and cooperating cam surfaces to bias the handles to predetermined angular positions.

Description

BACKGROUND OF THE INVENTION

Leatherman U.S. Pat. No. 4,744,272, issued May 17, 1988, discloses a "Foldable Tool" including pliers jaws having respective tangs or butt portions remote from the cooperating work or grasping end portions of the jaws. The butt portions are pivoted to channel-shaped handles. The pivots for the jaws and handles are parallel. The handles are swingable relative to the jaws for compact nesting of the jaws within the handles. Pocket knife implements can be separately pivoted to the channel-shaped handles.

Other types of compound tools having cooperating jaws swingable relative to handles are disclosed in German Patentschrift 30788, published Aug. 14, 1984, and in the following U.S. patents: Meloos, U.S. Pat. No. 649,344, issued May 8, 1900; Di Maio, U.S. Pat. No. 1,524,694, issued Feb. 3, 1925; Leatherman U.S. Pat. No. 4,238,862, issued Dec. 16, 1980; Leatherman U.S. Pat. No. 4,888,869, issued Dec. 26, 1989; and Collins et al., U.S. Pat. No. 5,062,173, issued Nov. 5, 1991.

Yet another compound tool having cooperating pliers jaws swingable relative to handles is disclosed in my U.S. patent application Ser. No. 07/891,990, filed May 27, 1992, and issued on Dec. 7, 1993 as U.S. Pat. No. 5,267,366.

In the tools of the patents and application referred to above, the handles of the tools normally form extensions of the butt portions of the jaws, and the handles usually are longer than the grasping or working end portions of the jaws. In order to achieve a mechanical advantage, the handles must be grasped at their end portions remote from the jaws. Nevertheless, such tools often are formed with handles shorter than the handles of standard tools, for compactness when the jaws are swung or otherwise retracted into the handles. Therefore, the mechanical advantage that can be achieved is limited.

SUMMARY OF THE INVENTION

The present invention provides a multipurpose tool having cooperating jaw members pivoted together such that working end portions of the jaw members are movable toward and away from each other. The jaw members have tang or butt portions extending opposite the jaw pivot from the working end portions. Such butt portions are, in turn, pivoted to elongated handles for swinging about axes parallel to the axis of the jaw pivot. The handles are channel-shaped and define recesses into which the interconnected jaw members can be swung or retracted so as to be nested in the handles.

More specifically, in the "open" position of the tool, the handles form extensions of the jaw members and have forward ends adjacent thereto and rear ends remote therefrom. The tool can be "closed" by swinging the handles away from each other. The handles are moved relative to the jaws through angles approaching 180.degree. in order to receive the jaw members within the handles.

In accordance with the present invention, a resilient biasing member interconnects the forward end portions of the handles. Such member is positioned between the jaw pivot and the handle pivots when the tool is open and urges the forward end portions of the handles together. The member also acts as a link such that the jaws are swung through a relatively small angle when the handles are swung through a larger angle, thereby increasing the mechanical advantage obtained when using the tool. The forward ends of the handles can have cooperating cam surfaces to bias the handles to selected positions. In the preferred embodiment, the handles are biased to a closed position, but after opening a predetermined amount are biased to a position just short of a fully opened position.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same becomes better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a top perspective of a compound pliers tool with linked handles in accordance with the present invention, including cooperating jaw members pivotally connected to a pair of handles;

FIG. 2 is a top plan of the tool of FIG. 1 with parts broken away, illustrating the closed condition of the tool with the jaw members nested in the handles;

FIG. 3 is a top plan corresponding to FIG. 2, but with parts in different positions, illustrating an intermediate condition of the tool with the jaw members and the handles spread apart;

FIG. 4 is a top plan corresponding to FIGS. 2 and 3, with parts in different positions, illustrating the open condition of the tool with the handles forming extensions of the jaw members;

FIG. 5 is an enlarged fragmentary top plan of a modified compound pliers tools with linked handles in accordance with the present invention;

FIG. 6 is an enlarged fragmentary top plan of the modified tool of FIG. 5 with parts in different positions;

FIG. 7 is a top plan of another modified compound pliers tool with linked handles in accordance with the present invention, illustrating the closed condition of the tool with the jaw members slidably retracted into the handles;

FIG. 8 is a top plan corresponding to FIG. 7, but with parts broken away;

FIG. 9 is a top plan corresponding to FIG. 7, but with parts in different positions, illustrating the open condition of the tool with the handles forming extensions of the jaw members;

FIG. 10 is a top plan corresponding to FIG. 9, but with parts broken away;

FIG. 11 is an enlarged fragmentary section taken along line 11--11 of FIG. 9;

FIG. 12 is a side elevation of the modified tool of FIG. 7;

FIG. 13 is an enlarged fragmentary side elevation of the modified tool of FIG. 7, with parts broken away;

FIG. 14 is an enlarged fragmentary side elevation of the modified tool of FIG. 7, corresponding to FIG. 12, but with parts in different positions;

FIG. 15 is a top plan of another modified compound pliers tool with slidably retractable jaws, illustrating an alternative means for linking the handles;

FIG. 16 is an enlarged fragmentary section taken along line 16--16 of FIG. 15;

FIG. 17 is a top perspective of another modified compound pliers tool with linked handles in accordance with the present invention;

FIG. 18 is an enlarged fragmentary top perspective of the tool of FIG. 17, with parts in different positions;

FIG. 19 is a side elevation of the tool of FIG. 17, with parts in different positions and parts broken away;

FIG. 20 is a top perspective of still another modified compound pliers tool with linked handles in accordance with the present invention;

FIG. 21 is a top plan of the tool of FIG. 20;

FIG. 22 is a front elevation of the tool of FIGS. 20 and 21, with parts in different positions, namely, with the pocket knife implements opened or partially opened;

FIGS. 23-27 are front elevations of the tool of FIGS. 20-22, illustrating progressive positions when opening the tool from a closed position to a fully opened position;

FIGS. 23A-27A are corresponding diagrammatic views illustrating the relative positions of components of the tool of FIGS. 21-22 when in the positions illustrated in FIGS. 23-27, respectively;

FIG. 28 is a graph illustrating forces applied to components of the tool of FIGS. 20-22 as a function of the angles through which handles of the tool have moved from the closed position toward the fully opened position; and

FIG. 29 is a diagrammatic side elevation of a modified form of the tool of FIGS. 20-22 having a particular type of modified implement, namely, tweezers.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a tool of the type having cooperating jaw members pivoted to opposing handles. The handles are swingable relative to each other and are movable relative to the jaw members for compact nesting of the jaw members in the handles. In addition, the handles can carry a variety of pocketknife implements each of which can be swung relative to its handle between a projected working position and a closed position retracted into the handle.

FIG. 1 illustrates a compound pliers tool 1 in accordance with the present invention with each of the pocketknife implements 2 projected or partially projected. Such tool 1 includes opposing jaw members 3 connected by a pivot 4. The working end portions 5 of the jaw members are swingable toward and away from each other about the axis of the pivot. In this embodiment, the jaw members are pliers jaws.

The butt portions 6 of the jaws extend from the pivot 4 in a direction opposite the direction that the working end portions 5 project from the pivot. The butt portions are connected to handles 7 by pivots 8 that extend parallel to the jaw pivot 4. Each handle defines a channel 9 which opens outward, away from the channel of the other handle when the tool is in the open condition illustrated in FIG. 1. In such open condition of the tool, the handles 7 appear to form extensions of the jaw members 3.

Each handle 7 has a leading or forward end portion 10 projecting from its pivot 8 generally toward the opposing jaw members 3 and a trailing or rear end portion 11 projecting from its pivot generally away from the jaw members. In addition, each handle includes a top plate 12, a bottom plate 13, and an inner upright web 14 extending between such plates. The pocketknife implements 2 are swingable between retracted positions fitted between the handle top and bottom plates 12 and 13 and working positions projected from the handles. More specifically, the pocketknife implements have root portions 16 swingably connected to the rear end portions 11 of the handles by upright pivots 15. Pivots 15 are parallel to the jaw pivot 4 and the handle pivots 8. The root portion 16 of each implement 2 is engaged by a leaf spring 17 formed as an extension of the vertical web 14 connecting the corresponding top and bottom plates 12 and 13. The leaf spring also can limit the degree to which an implement can be swung to its open position. One or more of the top and bottom plates 12 and 13 can have a finger notch 18 for access to edge portions of the implements when they are retracted.

Handles 7 are swingable relative to the jaw members 3 about the axes of the pivots 8. In accordance with the present invention, the leading end portions 10 of the handles are interconnected by a short link 20 extending over the top plates 12 of the handles. Link 20 has its opposite ends connected to the front end portions 10 of the handles by short pivot pins 21. In the open condition of the tool 1 illustrated in FIG. 1, link 20 is positioned between the jaw pivot 4 and the handle pivots 8.

Each handle 7 is freely swingable through an angle approaching 180.degree. about the axis of its pivot 8 from the open condition of the tool illustrated in FIG. 1 to the closed condition shown in FIG. 2. As seen in FIG. 2, in such closed condition the jaw members 3 are received in the channels 9 of the handles between the handle top and bottom plates. The pocketknife implements 2 are arranged in the channels so that they do not interfere with nesting of the jaw members. Preferably, in the closed condition of the tool illustrated in FIG. 2, the inner edges of the handles are closely adjacent, as are the facing surfaces of the working end portions 5 of the jaw members.

FIG. 3 and 4 illustrate the relative positions of the jaws 3, link 20 and handles 7 as the tool is opened. With reference to FIG. 3, as the handles 7 are swung away from each other from the closed position illustrated in broken lines, the handle pivots 8 travel in circular arcs centered about the associated link pivots 21. When each handle has been swung through an angle of 90.degree. to the solid line position illustrated in FIG. 3, pivots 8, which control the positions of the jaw butt portions 6, are at their maximum distance from each other so that the working end portions 5 of the jaws 3 are at their most spread apart positions. With reference to FIG. 4, as the handles 7 continue to be swung away from the jaws 3, the handle pivots 8 and, consequently, jaw portions 5 are moved toward each other. The result is that the working end portions 5 of the jaws 3 are closed. Preferably, in the fully "open" condition of the tool illustrated in solid lines in FIG. 4, the handles still diverge from each other at a small acute angle even though the working end portions 5 of the jaws are in engagement, so that the strong grasping force can be continued to be supplied to the jaws.

In a tool in accordance with the present invention, i.e., having handles linked as described above, the mechanical advantage achieved by swinging the handles no longer is a function of only the relative length of the handles as compared to the length of the working end portions of the jaws. Rather, the handles are swung through relatively large angles while the jaws are swung through a smaller angle. For example, with reference to FIG. 3, in the illustrated embodiment when each handle is swung through an angle of 90.degree. from the broken line position of FIG. 3 to the solid line portion, the jaws are swung through an angle of less than 45.degree.. The actual mechanical advantage achieved is a function of the location of the handle pivots 8 along the circular arc centered about the corresponding link pivot 21. In the solid line position shown in FIG. 3, the handle pivots would move toward other only slightly for a given angle of swing of the handles, and a large mechanical advantage is achieved. As the handles approach the solid line position shown in FIG. 4, the handle pivots 8 move toward or away from each other to a greater degree for the same swing angle, although still much less than the angle through which the jaws are swung. The length of the handles, the relative positions of the jaw pivots and the link pivots, the length of the jaw butt portions, and the length of the jaw working end portions all can be selected to achieve a desired mechanical advantage depending on the particular application.

FIGS. 5 and 6 illustrate a modification for the tool with linked handles in accordance with the present invention. In the modified form, the leading end portions 10' of the handle top and/or bottom plates have rounded gear teeth or fingers 23 designed to interdigitate as the handles 7' are swung relative to each other. In that case, the handles always will swing together through the same angle. FIG. 5 illustrates the closed position of the modified tool whereas FIG. 6 illustrates the partially open position. In all other respects, the modified form of the invention shown in FIGS. 5 and 6 is identical to the form shown in FIGS. 1-4.

In the modified tool 31 illustrated in FIGS. 7-14, the jaw members 33 are slidably retractable for partial containment of the jaw members in the handles 37 in the closed condition shown in FIGS. 7 and 8. In such closed condition the jaw members 33 are received in the channels 39 of the handles 37 between the top and bottom plates 42 and 43. The pocketknife implements 32 are arranged in the channels 39 so that they do not interfere with retracting of the jaw members 33.

The butt portions 36 of the jaw members are connected to the handles 37 by fasteners 53 that extend parallel to the jaw pivot 34. The top plate 42 of each handle has a linear slot 54 which extends along the axis of the handle. The forward end portion 55 of the slot includes an aperture 56 for receiving the fastener 53 in the open position. Similarly, the rear end portion 57 of the slot 54 can include a second aperture 58 for receiving the fastener 53 in the closed position. In addition, each channel 39 opens inward, toward the channel of the other handle and away from the outer upright web 44 extending between the top and bottom plates of the handle.

The fasteners 53, and hence jaw members 33, are slidable relative to the handles along the slot 54. In accordance with the present invention, a short link 50 extends over the top plates 42 of the handles and connects the leading end portions 40 of the handles. In the closed position shown in FIG. 7, the working end portions 35 of the jaw members protrude partially from the channels of the handles.

FIGS. 9 and 10 illustrate the relative positions of the jaw members 33, link 30 and handles 37 when the tool is in the open position. Preferably, the handles 37 still diverge from each other at a small acute angle even though the working end portions 35 of the jaw members are in engagement, so that a strong grasping force can be continued to be supplied. With reference to FIG. 9, as the fasteners 53 are slidably moved along the slot 54 from the open position to the closed position, the rear end portions 41 of the handles converge because the longitudinal slots 54 extend at small angles relative to the longitudinal centerlines of the handles. In the preferred embodiment, the angle of each slot is 15.degree. from the longitudinal centerline of the corresponding handle.

FIG. 11 illustrates the fastener 53 for slidably coupling the butt portions 36 of the jaw members to the handles 37. The fastener includes a top head 60, a narrower stepped shank 61, 62, and a broader foot 63. The foot 63, which also can be stepped, fits in a blind bore 64 that opens through the top of the jaw member butt portion 36. The head 60 of the fastener lies outside the handle channel and is substantially circular in shape with a diameter at least slightly larger than the diameter of apertures 56 and 58. The top portion 61 of the stepped shank is substantially cylindrical with a diameter slightly less than the width of the central portion of the slot 54. The lower portion 62 of the shank is substantially cylindrical with a diameter slightly less than the diameters of the apertures 56 and 58.

A compression spring 65 is fitted between the base of bore 64 and the underside of the fastener foot 63 to bias the fastener upward. When registered with an aperture 56 or 58, the larger portion 62 of the fastener shank fits in the aperture. This position of the fastener prevents the jaw members from sliding with respect to the handles when the jaws are in the fully extended position shown in FIGS. 12 and 13. Nevertheless, the interconnection does not inhibit swinging of the handles relative to the jaw members about the upright axis of the fastener.

With reference to FIGS. 13 and 14, the jaw members can be moved from the filly extended position to the retracted position by applying a slight downward force to the head 60 of the fastener to overcome the spring bias, and then slidably moving the fastener toward the rear end of the handle along the longitudinal slot 54. When the jaws are not in the fully extended or fully retracted position, the fastener shank portion 61 rides in the longitudinal slot 54 as seen in FIG. 14. When the jaw members are fully retracted, the fastener pops up to the position shown in FIG. 11 so that the jaw members are held retracted until the fastener head is pushed down to allow the sliding movement of the jaw members in the handles.

With reference to FIG. 12, the leading portions 66 of the handle top and bottom plates 42 and 43 converge to receive the jaw members 33 between them when the tool is "open." This provides a sturdier, more secure interconnection of the handles with the jaw members when the tool is used.

With reference to FIGS. 9 and 10, the geometry of the tool 31 when in the open condition is identical to the geometry of the first described embodiment, that is, the relative positions of the jaw pivot 34, link pivots 51, and handle pivots (fasteners 53) are the same. Consequently, the same mechanical advantage is achieved. The jaw members move through a smaller angle than the handles. In all other respects, the modified form of the invention shown in FIGS. 7-14 is identical to the form shown in FIGS. 1-4.

FIGS. 15 and 16 illustrate a modification for the tool illustrated in FIGS. 7-14. In the modified form, the leading end portions of the handles 37' are curved inward and are interconnected by a pivot 67 that extends parallel to the jaw pivot 34. In the open condition of the tool illustrated in FIG. 15, pivot 67 is positioned between the jaw pivot 34 and the handle fasteners 53. In all other respects, the modified form of the invention shown in FIGS. 15 and 16 is identical to the form shown in FIGS. 7-14.

With reference to FIGS. 17, 18 and 19, one preferred embodiment of the tool 71 in accordance with the present invention has many of the features of the embodiments previously described. FIG. 17 illustrates the preferred embodiment with each of the pocket knife implements 72 projected or partially projected. Tool 71 includes opposing jaw members 73 connected by a pivot 74. The working end portions 75 of the jaw members are swingable toward and away from each other about the axis of the pivot. The butt portions 76 of the jaw members extend from the pivot 74 in a direction opposite the direction that the working end portions 75 project from the pivot. The butt portions are connected to handles 77 by pivots 78 that extend parallel to the jaw pivot 74. Each handle defines a channel 79 which opens outward, away from the channel of the other handle, when the tool is in the open condition illustrated in FIG. 17. In such open condition of the tool, the handles 77 appear to form extensions of the jaw members 73.

Each handle 77 has a leading or forward end portion 80 projecting from its pivot 78 generally toward the opposing jaw members 73, and a trailing or rear end portion projecting from its pivot generally away from the jaw members. In addition, each handle includes a top plate 82, a bottom plate 83, and an inner upright web 84 extending between such plates. The pocket knife implements 72 are swingable between retracted positions fitted between the handle top and bottom plates 82 and 83 and working positions projected from the handles. The connection of the pocket knife implements 72 to the rear end portions of the handles is the same as for the embodiment of the present invention shown in FIG. 1.

Handles 77 are swingable relative to the jaw members 73 about the axes of the pivots 78. In accordance with the present invention, the leading end portions 80 of the handles are interconnected by a short link 90 extending over the top plates 82 of the handles. The opposite end portions of the top link are connected to the top plates by short pivots 91. As seen in FIGS. 18 and 19, an identical link 90 extends below the handle bottom plates 83 between short bottom pivots 91. Preferably, the leading end portions 80 of both the top and bottom plates 82 and 83 are formed with rounded gear teeth 93 designed to interdigitate as the handles 77 are swung relative to each other. Thus, the handles always will swing together through the same angle. The jaw member butt portions 76 fit between the top and bottom plates 82 and 83, i.e., within the channels of the handles, as compared to the links 90 which are positioned outside the channels at the top and bottom.

As best seen in FIGS. 18 and 19, the leading end portions of the handle top and bottom plates 82 and 83 converge in the areas of the pivots 78 and 91. The jaw member butt portions 76 are closely embraced at such leading end portions. The rear portions of the channels defined between the top and bottom plates 82 and 83 are substantially wider, both at the top and bottom of the tool. This provides room adjacent to each top plate and each bottom plate for a longer, wider pocket knife implement to fit above or below the jaw members when the tool is closed. Shorter and/or narrow implements can be mounted between the longer implements, i.e., in registration with the jaw members, for fitting alongside the jaw members when the tool is closed.

Preferably, the upright webs 84 of the handles have scattered holes 94 to allow water that otherwise would collect in the channels to pass out, and to permit ventilation and evaporation.

The geometry of the preferred tool 71 is identical to the geometry of the firstdescribed embodiment, that is, the relative positions of the center jaw pivot, link pivots, and handle pivots are the same. Consequently, the same mechanical advantage is achieved. The jaw members move through a smaller angle than the handles; and, in the closed position, the working end portions 75 of the jaw members abut, with the jaw members fully nested within the handles, and with the inner edges of the handles in engagement, as illustrated for the first-described embodiment of the invention in FIG. 2.

With the handles 77 swung to their open positions, the working end portions of the jaw members engage when the handles still are at a small angle relative to each other, so that a strong grasping force can continue to be applied. Alternatively, the grasping action of the jaw members can be obtained when the handles are swung past their open-most positions toward their closed positions, i.e., the approximate positions shown in FIG. 18. In that case, one handle can rest on a supporting surface while the other handle is forced toward the supporting surface to achieve a strong grasp. The long, straight, flat webs of the handles help to steady the tool in this position for convenience and safety.

With reference to FIGS. 20-27, another preferred embodiment of a tool 100 in accordance with the present invention has many of the features of the embodiments previously described, but uses crossing scissors jaws 101 connected by a pivot which is approximately aligned with a link 103 between the leading end portions of handles 104 and therefore is not visible in FIG. 20. The scissors jaws 101 have working end portions 105 extending in one direction from the pivot and butt portions 106 extending in the opposite direction from the pivot. The butt portions are connected to handles 104 by separate pivot pins 107 that extend parallel to the jaw pivot. Each handle has a channel 108 which, when the tool is in the open position illustrated in FIG. 20, opens outward, away from the channel of the other handle. Each channel is formed between a top plate 109, bottom plate 110 and inner upright web 111.

Each handle 104 has a leading or forward end portion 112 that can include rounded gear teeth 113 formed on the top and bottom plates 109, 110. The gear teeth interdigitate throughout most of the travel of the handles relative to each other, as described in detail below. The handles 104 also include rear end portions 114 projecting oppositely from the pivots 107 with reference to the leading or forward end portions 112. Pocket knife implements 115 can be pivoted close to the rear ends of portions 114 by pivot pins 116, including root portions that cooperate with leaf springs 117 formed as extensions of the webs 111.

Link 103 is connected to the leading end portions 112 of the handles 104 by short pins 118, but does not constitute the main connection between such handle end portions. Rather, a strong tension spring 119 extends between the pins at the inside surfaces of the forward handle end portions 112, at opposite sides of the jaw members 101. Such springs 119 are visible in the plan view of FIG. 21 and can have the shape shown in FIG. 23A, for example. In that case, each spring includes hooked ends 120 wrapped around the pins 118, and a central loop or loops 121, preferably a single loop. The spring 119 is formed of a strong resilient metal, such as stainless steel, and applies a biasing force tending to move pins 118 together, and resisting spreading of the pins apart. With reference to FIG. 22, link 103 has elongated slots 122 which permit some relative movement of the pins 118, but which prevent overstretching of the spring by limiting the extent to which the pins can be moved away from each other (links 103 are not shown in FIGS. 23-27 for ease of description of operation of this embodiment).

The forward ends 112 of the handles 104, in this case the forward ends of the top and bottom plates 109, 110, are configured as cam surfaces to bias the handles to selected rotated positions relative to each other. More specifically, starting from the closed position of FIG. 23 where the handles 104 abut along their inner edges, the leading end portions 112 are configured such that relative opening movement of the handles 104 necessarily requires that the pivots 118 be moved away from each other and, consequently, that the tension springs extending between the pivots be stretched. In the illustrated embodiment, this can be accomplished simply by making the inward projecting gear tooth 125 longer than the others so that as it moves toward a line connecting the centers of pins 118, the pins must be forced apart. FIGS. 24-27 show increasingly open positions of the handles 104, and the corresponding FIGS. 24A-27A are enlarged diagrammatic views showing the relative positions of the pivot 102 connecting the jaws, pivots 107 by which the jaws are connected to the handles, and pins 118, which connect the forward end portions of the handles. In FIG. 24, the longer tooth 125 is in line with a line connecting the centers of pins 118, and therefore the pins are at their widest spread apart condition. This is a first overcenter equilibrium position. From this position, if the handles are moved slightly toward each other, the biasing force of the tension spring 119 will tend to move the handles together, whereas if the handles are spread apart slightly from the position of FIG. 24, the biasing force of the spring will tend to swing the handles apart.

When the handles reach the position of FIG. 25, tension continues to be applied by the spring 119 to urge the leading end portions 112 of the handles together, but the cammed ends of the handles are approximately concentric about the pivots 118. Thus, from the position of FIG. 25 to a position close to that illustrated in FIG. 26, essentially only frictional forces prevent opening rotation of the handles 104. Stated in another way, the middle teeth of the leading end portions 112 of the handles 104 are not configured to require substantial stretching or permit substantial contraction of the spring 119 during this center part of the opening rotation of the handles. A final slightly longer tooth 126, however, does require some spreading of the pivots 118 which creates a second overcenter equilibrium position just before the position of FIG. 26 is reached. FIG. 26 illustrates the position after such overcenter position has been reached, such that the handles have been biased in the opening direction, with the scissors jaws 101 angled apart at a convenient open cutting position. In this position, the inside surfaces 127 of the leading end portions of the handles form much more pronounced cams which force the leading end portions of the handles apart, i.e., the pivots 118, in order to continue rotation of the handles from the position of FIG. 26 to the position of FIG. 27 where the scissors jaws have crossed in a cutting action. From the position of FIG. 27, the tension spring 119 tends to return the handles to approximately the position of 26, and must be overcome in order to have the snipping action of the scissors jaws which results from moving the handles from the position of FIG. 26 to the position of FIG. 27. Contouring of the leading end portions of the handles, in this case tooth 126, prevents unintentional overswinging of the handles toward the closed position.

The force applied by the spring also can be described with reference to the graph of FIG. 28. Point 130 on the graph represents the closed position of FIG. 23, and point 131 represents the first overcenter equilibrium position of FIG. 24. In the illustrated embodiment, the first overcenter equilibrium position is reached at a relative angle of the handles of less than 90.degree., preferably approximately 41.degree.. Thus, at angles less than 41.degree., the handles are biased back to the closed position of FIG. 23, whereas at angles greater than 41.degree., the handles are biased toward a more open position.

The second overcenter equilibrium position, approximately the position of FIG. 26, is represented at point 132 on the graph of FIG. 28. This occurs at an angle in excess of 270.degree., preferably approximately 296.degree.. For most of the travel from point 131 to point 132 (41.degree. to 296.degree.) the cammed forward ends of the handles are approximately neutral and the handles can be swung smoothly with no substantial biasing toward one angular position or another. Shortly before reaching point 132 (296.degree.), the cam surfaces are contoured to require that the pivots 118 be spread apart, against the biasing force of the tension spring, and thereafter the surfaces are indented toward their respective pivot pins such that there is a strong tendency for the tension spring to move the handles to the position of FIG. 26. This is represented as point 133 on the graph of FIG. 28. From that position, the pivot pins must be spread apart against the biasing force of the tension spring in order to continue rotation of the handles, which would be along the section 134 of the graph to the right of point 133, and if the handles are released, the spring tends to return them to point 133 again, i.e., the position of FIG. 26.

When it is desired to close the tool, movement from the position of FIG. 26 (point 133 of graph 28) toward a closed position requires some stretching of the spring until point 132 is passed, then essentially no stretching of the spring until the first overcenter equilibrium position at point 131 (FIG. 24) is reached. From that point toward the left of the graph of FIG. 28, the spring will tend to snap the handles closed and retain them in a closed position. In a preferred embodiment, the overall length of the tool when closed is approximately 2 1/2", and the length when opened (FIG. 26) is about 3 3/4". A convenient snipping action can be achieved by simply pressing the handles together from the position of FIG. 26 to the position of FIG. 27, and when the handles are released the force of the spring is sufficient to return the handles to the position of FIG. 26.

FIG. 29 illustrates one preferred implement for inclusion in a tool of the type shown in FIGS. 20-27, namely, tweezers 140. In this embodiment, the tweezers are formed in one piece with long, substantially parallel jaws 141 that can be pressed together against their natural tendency to return to the spread apart position. The jaws are joined by a looped end 142 configured to closely receive the central portion of one of the pins 116. The looped end 142 includes one side 143 extending generally tangentially to the periphery of pin 116. From such portion 143, the looped end curves around the pin through an angle greater than 180.degree., preferably about 270.degree., such that the other side 144 of the looped end is convex. The tweezers are situated on the pin 116 such that the tangential or flat side of the looped end 142 is positioned toward the interior or "bottom" of the channel 108 of the handle 104 in which the tweezers are mounted. Preferably, the tweezers are located approximately centrally of the pin 116, which puts them in line with the jaw 101 of the tool which nests in the channel when the handles 104 are closed. The jaws 101 are tapered from approximately their point of pivotal connection to their tips, such that the jaws will nest fully within their channels, over the tweezers 140 when the handles are closed, i.e., in the condition illustrated in FIG. 23. Other than the design of the tweezers 140, the embodiment of FIG. 29 is identical to the embodiment of FIGS. 20-27. In the earlier embodiment of FIGS. 20-27, tweezers 140', best seen in FIG. 22, have jaws which are spaced apart transversely of the handles and with root portions pivoted on the appropriate pin 116, rather than jaws that are spaced apart in the direction in which the tweezers swing relative to the handles.

While the preferred embodiments of the invention has been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

Claims

1. A tool comprising a pair of opposed jaw members, a first pivot swingably connecting said jaw members for movement relative to each other, each of said jaw members having a working end portion extending from said pivot in a first direction and a butt portion extending from said pivot in a second, generally opposite direction, two elongated handles each having a channel therein, said jaw members being movable relative to said handles between an open position in which said jaw member working end portions are exposed and a closed position in which said jaw members are substantially nested in said channels of said handles, two second pivots swingably connecting said two handles, respectively, to said jaw butt portions, each of said handles having a forward end portion extending from the second pivot of such handle generally toward the jaw to which such handle is connected when said jaw members are in the open position and a rear portion extending from such second pivot in a direction generally opposite the direction of extension of the corresponding forward portion, said forward end portions of said handles having cooperating cam surfaces engaged against each other as said jaw members are moved between the open and closed positions, and a resilient biasing member interconnecting said forward end portions of said handles and biasing said cooperating cam surfaces toward each other.

2. The tool defined in claim 1, in which the forward end portions of the handles, the cooperating cam surfaces and the resilient biasing member are constructed and arranged relatively to bias the handles to predetermined angular positions relative to each other.

3. The tool defined in claim 2, in which the resilient biasing member is a tension spring biasing the cam surfaces against each other, the amount of stretching of the spring and the force applied by the spring being different for different relative angular positions of the handles and the cam surfaces.

4. The tool defined in claim 3, in which the cam surfaces include interdigitating projections.

5. The tool defined in claim 4, in which at least some of the interdigitating projections are of unequal length.

6. The tool defined in claim 3, in which one of the predetermined angular positions to which the handles are biased is the closed position of the handles.

7. The tool defined in claim 6, in which one of the predetermined angular positions to which the handles are biased is a stable equilibrium position from which the handles may be moved relatively apart and toward each other against the biasing force of the tension spring.

8. The tool defined in claim 3, in which one of the predetermined angular positions to which the handles are biased is a stable equilibrium position from which the handles may be moved relatively apart and toward each other against the biasing force of the tension spring.

9. The tool defined in claim 3, including a link having opposite ends pivoted to the forward end portions of the handles and permitting limited movement of such forward end portions of the handles away from each other to prevent overstretching the tension spring.

10. The tool defined in claim 3, in which the tension spring is mounted inside the channels of the handles.

11. The tool defined in claim 3, in which the tension spring and cam surfaces are constructed and arranged relatively to bias the handles toward the closed position when the angle between the handles is less than a first predetermined angle, and to apply a force within a predetermined range of forces when the angle between the handles is between the first predetermined angle and a second predetermined angle, and to bias the handles to a predetermined relative angular position close to the open position when the angle between the handles is a third predetermined angle greater than the second predetermined angle.

12. The tool defined in claim 11, in which the first predetermined angle is less than 90.degree. and the second predetermined angle is greater than 270.degree..

13. The tool defined in claim 1, in which the handles include rear end portions opposite the forward end portions, a third pivot extending transversely of one of the handles in the rear end portion thereof, and a tweezers implement mounted on the third pivot for swinging into and out of the channel of the handle having the third pivot, the tweezers implement including a pair of spaced apart, generally parallel jaws and a looped end connecting said jaws, the looped end extending around the third pivot and having one side extending generally tangentially of the periphery of the third pivot and a convex side generally opposite the first side, the loop defining an arc of an angle greater than 180 degrees.

14. A tool comprising a pair of opposed jaw members, a first pivot swingably connecting said jaw members for movement relative to each other, each of said jaw members having a working end portion extending from said pivot in a first direction and a butt portion extending from said pivot in a second, generally opposite direction, two elongated handles, two second pivots swingably connecting said two handles, respectively, to said jaw butt portions, each of said handles having a forward end portion adjacent to the second pivot of such handle and a rear end portion opposite the forward end portion, the handles having channels therein, the jaw members being movable relative to said handles between an open position in which the working end portions are exposed and a closed position in which the working end portions are substantially nested in the channels of the handles, a third pivot extending transversely of one of the handles in the rear end portion thereof, and a tweezers implement mounted on the third pivot for swinging into and out of the channel of the handle having the third pivot, the tweezers implement including a pair of spaced apart, generally parallel jaws and a looped end connecting said jaws, the looped end extending around the third pivot and having one side extending generally tangentially of the periphery of the third pivot and a convex side generally opposite the first side, the loop defining an arc of an angle greater than 180 degrees.