Tools – Tool jaw – Adjustable relationship between jaw
Reexamination Certificate
1999-03-01
2001-12-11
Meislin, D. S. (Department: 3723)
Tools
Tool jaw
Adjustable relationship between jaw
C081S421000, C081S405000, C081S409000, C081S900000
Reexamination Certificate
active
06327943
ABSTRACT:
BACKGROUND OF THE INVENTION
Self-adjusting pliers are described, for example, in U.S. Pat. No. 4,651,598, which is incorporated by reference herein in its entirety. Self-adjusting, or “auto-grip,” pliers such as disclosed in this patent provides the capability of one-handed adjustment, wherein the pliers jaws automatically adjust to the size of a work piece in response to a user's manual closing action on the pliers' handles.
Many prior art hand tools, such as the pair of pliers disclosed in the 4,651,598 patent, are produced via forging operations, wherein the pliers' main body members are of essentially one-piece, forged steel construction. Usually, the tool begins as pieces of bar stock that are forged to obtain the basic shape of the pliers' body members. The roughly shaped pliers body members are then machined to get the final, desired tool shape. These multiple operations are inefficient, resulting in waste and added labor costs which, in turn, increase the cost of the finished tool. To partially compensate for the costs of the waste produced with forged construction, inexpensive materials, such as high-carbon steel, are typically used for fabricating tools such as pliers. This, however, may result in pliers, especially pliers jaws, that do not have the proper hardness characteristics required for many applications.
U.S. Pat. Nos. 4,662,252 and 5,351,584, incorporated herein by reference in their entirety, disclose self-adjusting pliers that operate in a similar manner. However, the main body members, including the pliers jaws, are constructed out of laminated sheet metal stampings, rather than one-piece, forged steel. While this may result in a cost and efficiency improvement over tools constructed via forging processes, the laminated construction does not provide pliers jaws having the hardness characteristics desired for many applications.
A pliers jaw assembled entirely of laminated sheet metal stampings rather than a single forged piece must be held together by fasteners such as rivets. Shear stresses placed on the jaw during use of the pliers tend to concentrate in the fasteners, sometimes causing them to fail. This difficulty would be somewhat intensified if the jaws of the pliers were made of stronger material, as suggested above, because the fasteners holding the jaw to the handle would become the weak point in the tool. Thus a complete solution requires that the handle carry the shear stresses from the jaw directly rather than through intervening fasteners or other small cross-section components.
A further difficulty sometimes encountered with some self-adjusting pliers of the type described above is that the locking mechanism of the jaw can sometimes engage when the tool is in its full open position, allowing the tool to stick or jam in that position.
Thus, a need exists for a pair of self-adjusting pliers that addresses the shortcomings of the prior art.
SUMMARY OF THE INVENTION
In one aspect of the present invention, an improved pliers tool is disclosed. The tool comprises upper and lower handle assemblies, each of laminated construction and having a first end comprising at least two layers. A jaw fabricated by a casting process is disposed between the layers of each handle assembly at its first end. Further aspects of the invention include preferred details of the fabrication technique and a replacement jaw for self-adjusting pliers tools produced by the technique.
In another aspect of the invention, the cast jaw comprises an extension portion of the jaw, by which the jaw is held between the handle end layers; a toothed gripping portion wider than the extension portion; and handle contact surfaces disposed opposite the gripping surface on either side of the extension portion. The handle contact surfaces allow the handle ends to support a somewhat wider jaw and to bear some of the load transmitted by the jaw so that the entire load is not concentrated at the fastener holding the jaw to the handle end.
In still another aspect of the invention, the jaw end of the laminated handle assembly is shaped with a notch adapted to receive a projecting edge of the cast jaw. This additional contact surface helps prevent the jaw from sliding and distributes shear stresses to the handle assembly that would otherwise be borne predominantly by the fastener holding the jaw to the handle end.
In still another aspect, the pliers tool is equipped with a nonengaging feature that prevents the pliers' locking mechanism from engaging when the pliers jaws grasp a large object. The feature comprises an offset segment of the elongated handle slot in which the locking pawl travels. The biasing features of the tool that drive the pliers to the full open position also move the locking pawl into the offset segment, causing it to move out of contact with the locking track on the far side of the slot. Because the pawl does not lock the handles in position, the user can continue to squeeze the handles together until they reach a predetermined separation that is comfortable for the user to grip and substantially independent of the size of the object.
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Hile Jeffrey B.
Li Frank
Wrigley Harold K.
Emerson Electric Co.
Howrey Simon Arnold & White , LLP
Meislin D. S.
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