Resilient Lock for a Hand Tool

This invention relates, generally, to tools such as scissors, shears, pruners, and the like, which are resiliently biased to an open position, and which have a locking mechanism to keep these tools in a closed configuration. In particular, this invention relates to tools having an improved and simplified locking mechanism. Although it will become apparent from the following description that certain features of the present invention may be utilized in tools of various construction for application to specific uses, for ease of understanding and convenience, the following description will from time to time specifically refer to a pruning shears as the most preferred implementation of the present invention.

It is generally known to provide hand-held garden tools such as pruning shears of the pass-by or anvil-type, wire snips, pliers, and various other cutting implements such as scissors, with a spring mechanism for urging the handles in the "open" position, thereby exposing the jaws or cutters to facilitate operation of the implement by the user. These implements typically include a lock mechanism, functioning against the action of the spring, to maintain the blades in closed position where they are least susceptible to damage and least likely to cause injury to the user when not in use.

Presently, hand-held cutters are locked in the closed position by, for example, a pivoting member secured to one of the cutting jaws, which may be pivoted into abutting relationship with the opposing jaw. Other devices employ a pivoting ratchet mechanism which can be moved from a locked to an unlocked position by the user's thumb. Examples of such pruning implements are described in U.S. Pat. No. 4,156,311, issued on May 29, 1979 to Wallace, et al.; U.S. Pat. No. 4,268,963, issued on May 26, 1981 to Harrison; and U.S. Pat. No. 4,341,016, issued Jul. 27, 1982 to Harrison, et al. As more particularly disclosed in these patents, the locking mechanism comprises a pin slidably positioned in a slot formed in one of the pivoted members to engage a recess or protrusion formed in the other member.

Other locking mechanisms comprise a spring biased stationary pin extending into a mating cavity when the tool is in closed configuration. Examples of such locking means are disclosed in U.S. Pat. No. 3,357,287 issued on Dec. 12, 1967 to Wertepny, and U.S. Pat. No. 4,947,553 issued on Aug. 14, 1990 to Bendickson et al.

It has been found, however, that latching mechanisms of the kind described in these prior art patents have various limitations. For example, certain locking mechanisms of the slidable type do not readily retain their positional adjustment, because the slidable pin tends to slide away from its selected position during normal operation of the implement and may impair normal operation of the tool. On the other hand, other mechanisms which are more reliable are of rather complex construction necessitating several parts, thereby increasing the cost of the tool, and possibly rendering these tools less durable.

Thus, it is desirable to provide an inexpensive lock mechanism for items such as pruning shears or the like which can alleviate the problems associated with conventional latch mechanisms, i.e., which provides a lock having improved positional retention properties, and which requires only a limited number of components of simple configuration to facilitate manufacturing and assembly.

The present invention provides an inexpensive lock mechanism for tools having a pair of jaws or other working pieces cooperatively connected to each other for effecting scissor movement, and a pair of handles for actuating the jaws, the implement being biased in the open position. The implement has a resilient lock comprising a button compressively joined to a cap, both button and cap being made of yieldable material thereby permitting certain flexing of the button and cap to prevent undesirable sliding of the lock out of its selected position during normal operation of the implement. This novel approach simplifies manufacturing and assembly of the tool and reduces cost without sacrificing quality.

According to another embodiment of the present invention, in a pivoted tool having a pair of elongated members, the pivot member incorporates a self-compensating resilient assembly comprising a resilient button compressively joined to a resilient cap.

According to a preferred embodiment of the present invention, in a pruning shear having two cooperating elongated members, means interconnecting the members in mutually overlapping relationship to permit movement of the members relative to one another by operating the force applying ends of these members, a resilient lock mechanism comprises a resilient cap releasably secured to a resilient button by a fastener.

Other advantages of the present invention will become apparent from the detailed description given hereinafter. It should be understood, however, that the detailed description and specific embodiments are given by way of illustration only since, from this detailed description, various changes and modifications within the spirit and scope of the invention will also become apparent to those skilled in the art.

The preferred exemplary embodiment of the present invention will hereinafter be described in conjunction with the appended drawings, wherein like numerals denote like elements, and:

FIG. 1 is a side elevation view of a pruning shear according to the present invention in the closed position;

FIG. 2 is a side elevation view of the pruning shear of FIG. 1, shown in the open position;

FIG. 3 is a cross-sectional view taken along line 3--3 shown in FIG. 1; and

FIG. 4 is an exploded view of the components of the pruning shear shown in FIG. 1.

Referring to the Figures, a pruning shear in accordance with the present invention, designated generally as 10, having a force applying end 10A and an opposed working end 10B, is shown to include an upper elongated member 12 and a lower elongated member 14, pivotally joined by a pivot bolt 16. Members 12 and 14 are being covered by the usual rubber or plastic covering members 18 and 20, respectively.

Referring more particularly to FIG. 4, upper elongated member 12 is channel-shaped, and a web 22 connects respective side panels 24 and 26. Web 22 is generally flat, and includes a substantially straightforward edge 23 disposed proximate pivot bolt 16. Side panels 24 and 26 terminate proximate pivot bolt 16 by cheeks 28 and 30, respectively. Lower elongated member 14 is extendable between opposite cheeks 28 and 30. Cheeks 28 and 30 are also disposed on opposite sides of a lower hook or anvil blade 32 and an adjacent confronting upper cutting blade 34 of lower member 14. As shown in FIG. 4, upper cutting blade 34 and lower elongated member 14 are preferably unitary.

Lower hook or anvil blade 32 is in pivotal relationship with upper cutting blade 34 by pivot bolt 16, which is extendable transversely through opposite cheeks 28 and 30 and through aperture 36 of lower hook or anvil blade 32. Pivot bolt 16 also extends through aperture 38 of upper cutting blade 34. Pivot bolt 16 is secured by pivot nut 40, threaded thereon in known manner. Pivot bolt 16, extended through suitably aligned apertures 42 of cheeks 28 and 30, and apertures 36 and 38 defines a fulcrum on which elongated members 12 and 14 are pivoted.

A lower blade bushing 44 is extendable through suitably aligned aperture 46 of cheek 30 (not shown), spacing collar 50, aperture 48 of lower blade 32, aligned aperture 46 in cheek 28, and lower blade screw 52. Collar 50 is sleeved on bushing 44 between lower blade 32 and cheek 30, distantly thereof to allow a space for the vertical movement of upper blade 34 relative to lower blade 32. Collar 50 also serves as a stop for the open position of the tool, the curvilinear lower face 54 of upper elongated member 14 coming to bear on spacing collar 50.

Relative pivotal movement between, on the one hand, upper blade 34 and unitary lower elongated member 14, and on the other hand, lower blade 32 and upper elongated member 12 fixedly secured thereto, is allowed by pivot bolt 16, so that the blades are actuated by convergence or divergence of members 12 and 14.

A spring actuated biasing means, preset so as to bias blades 32, 34 to open position, is in the form of a leaf spring 56 concealed within upper elongated member 12 and secured at its outer extremity to the inwardly facing surface of web 22 by a leaf spring rivet 58. Leaf spring 56 is ribbed intermediate its extremities at rib 60 to increase the biasing force applied to the cutting blades. Leaf spring 56 rides along a flat 62 on the upper spine of lower member 14. As lower member 14 is brought upwardly relative to upper member 12 by the pressure of the operator's hand, terminal portion 64 of leaf spring 56 is caused to ride along flat 62.

In accordance with the present invention and as best illustrated in FIGS. 3 and 4, a resilient lock generally designated as 68 comprises a button 70 having a resilient cap, which for ease of reference will hereinafter be referred to as head 72, and a shank 74 projecting from head 72. Head 72, which is advantageously circular, has a concavely-shaped (i.e., dish-shaped) face 76. Thus, face 76 is effectively in contact with cheek 28, preferably at the periphery of head 72, along an annular region 79 of face 76, as can readily be seen in FIG. 3. This construction permits a certain degree of flexing of head 72 when suitable compressive force is applied to button 70 along its longitudinal axis (i.e., along an axis drawn horizontally in FIG. 3). As a result, the area of annular region 79, which increases or decreases with such compressive force determines the degree of frictional engagement of face 76 with cheek 28.

Head 72 is also provided with a central driver-engageable recess 77 extending inwardly from the outer surface of head 72. Recess 77 is suitably formed for engagement by a driver tool designed for installation of the lock such as an "Allen" driver. This releasable engagement capability greatly facilitates and renders safer the assembling of lock 68 in tool 10 as production personnel is no longer required to hold button 70 in place while driving it.

Resilient lock 68 also comprises a resilient cap 78, preferably configured like head 72, i.e., dish-shaped, having a generally concavely shaped face 80 adjacent cheek 30. Cap 78 is releasably connected to button 70 by fastener 82 engaging a bore 83 of button 70. A centering recess 84 is advantageously formed in face 80 to matingly receive the free end of shank 74, thereby facilitating assembling and operation of lock 68 as cap 78 remains centered with button 70.

As in the case of button 70, face 80 is effectively in contact with cheek 30, preferably at the periphery of cap 78 along an annular region 85 of face 80, as can also readily be seen in FIG. 3. This construction permits a certain degree of flexing of cap 78 when suitable compressive force is applied to cap 78 along its axis of symmetry (i.e., along an axis drawn horizontally in FIG. 3). As a result, the area of annular region 85, which increases or decreases with such compressive force (adjustable in a simple and inexpensive manner by fastener 82), determines the degree of frictional engagement of face 80 with cheek 30. Thus, the areas of annular regions 79 and 85 cooperate to provide controlled positional retention of lock 68.

The novel configuration of resilient lock 68, as particularly described in the foregoing, permits limited flexing of head 72 and cap 78 in response to rotational adjustment of fastener 82. Such continuous adjustment of frictional engagement of concavely shaped faces 76 and 80 with cheeks 28 and 30, i.e., of the areas of annular regions 79 and 85, respectively, improves, in a relatively inexpensive manner, positional retention of lock 68 during normal operation of tool 10.

As more readily apparent in FIG. 4, to permit locking or unlocking of tool 10, upper member 12 is provided with an elongated slot 86, formed in spaced relationship to aperture 42 through member 12, and extending in a direction generally parallel web 22 (i.e., in a direction parallel the longitudinal axis of tool 10). In addition, lower member 14 has a generally L-shaped slot 88 formed, in spaced relationship to aperture 38, through member 14. As shown in FIG. 3, when tool 10 is in the closed position, elongated slot 86 and the lower portion of L-shaped slot 88 are substantially in registration. Thus, in closed configuration, lock 68 can be slid toward rear terminus 90 of slot 86 and rear terminus 92 of slot 88 to maintain tool 10 closed against the biasing force of spring 56. Conversely, to unlock tool 10, lock 68 is moved toward front terminus (not identified) of slots 86, 88, thereby allowing lower member 14 to pivot around pivot 16 into the open position. In both instances, due to the resilient construction of lock 68, desired positional location of lock 68 is effectively maintained.

In addition to improving positional retention without requiring numerous parts, lock 68 also presents other advantages. In particular and significantly, the substantially identical configuration of head 72 and cap 78 permits ambidextrous operation of tool 10. In addition, head 72 and cap 78 being advantageously circular, the assembly of lock 68 in tool 10 does not necessitate rotational orientation of button 72 or cap 78 with respect to cheeks 28 and 30. Moreover, lock 68 which is preferably made of a self-lubricating resilient material such as nylon 66, is relatively inexpensive to manufacture.

In accordance with a second exemplary embodiment of the present invention, and as readily apparent to those skilled in the art, lock 68 could also be used as the pivot of a pair of scissors comprising a pair of elongated members disposed for cooperative engagement about a pivotable joint. In that second embodiment, the joint consists of a resilient button 70 and a cap 78 releasably connected thereto by a fastener 82. In particular, pivot bolt 16 can be constructed using resilient lock 68 of suitable size, thereby permitting self-compensation of wear in the pivot developed by repeated operation of tool 10.

It is understood that the above description is of preferred exemplary embodiments of the present invention and that the invention is not limited to the specific forms described herein. For example, tools having this novel resilient lock mechanism may not have a pair of elongated members as described herein. Each of such elongated members may be formed in one piece having spaced apart inner and outer surfaces, or having working surfaces other than cutting blades. These members may also be hingedly connected as opposed to forming a pivot as described in the preferred embodiments. Moreover, even though the embodiments shown in the Figures are the preferred embodiments, it is to be noted that this invention, which is based on tools having a resilient lock mechanism or a resilient pivot wherein the lock or pivot is comprised of a resilient button compressively joined to a resilient cap, can be carried out in other manners. For example, head 72 and cap 78 need not be of identical configuration or need not have recesses or apertures as disclosed herein. Conversely, button 70 could include only head 72, compressively joined to cap 78 by means other than those described in the preferred embodiments. However, such other constructions and features are considered to be within the scope of this invention. Accordingly, these and other substitutions, modifications, changes and omissions may be made in the design and arrangement of the elements disclosed herein without departing from the scope of the appended claims.