1. Field of the Invention
My invention relates generally to an adjustable box wrench and particularly to a box wrench that positively grips the workpiece in response to torque applied to a cam lever separately articulated from the wrench body.
2. Discussion of the Related Art
The box-end or box wrench is known in the art for turning polygonal nuts and bolts located in tight and inaccessible locations. The box wrench usually includes a thin-walled polygonally-fluted box structure on one or both ends. Because this thin-walled box structure is sized to fit snugly over the generally polygonal nut or bolt workpiece, the workpiece can be engaged for torquing even where there is only a few millimeters of clearance.
Adjustable wrenches, including adjustable box-end wrenches, are also known in the art. For instance, in U.S. Pat. No. 4,325,275, David S. Colvin discloses an adjustable open-end and box-end wrench that uses a pair of spaced pins and skewed slots to allow adjustment of a member that cooperates with a box-end to re-size the box structure for a range of workpiece dimensions. Although Colvin's box-end wrench can be used to engage a workpiece in tight spaces, he neither considers nor suggests "gripping" means for positively engaging a deformed workpiece and instead relies on the matching polygonal geometry of box structure and workpiece to transfer torque therebetween. Similarly, in U.S. Pat. No. 3,858,465, Erik Lind discloses an adjustable wrench employing an axially displaceable and lockable external sleeve to adjust the geometry of the box structure but neither considers nor suggests means for positively gripping a deformed workpiece. In U.S. Pat. No. 3,363,490, K. Maichen discloses a double-ended simultaneously-adjustable wrench that operates by manually turning an eccentric pin to move two members cooperating to form surfaces for receiving and torquing polygonal workpieces. Maichen also neither considers nor suggests means for positively gripping a deformed workpiece. Swiss Patent No. 386 948 issued to August Samuel Aegerter and U. K. Patent 251,544 issued to Andrew Arbuckle both disclose adjustable box-end wrenches that rely on the manual rotation of a cam to urge a sliding adjusting rod into a position that fixes the effective engagement dimensions of a box structure. Neither Aegerter nor Arbuckle consider or suggest means for positively gripping a deformed workpiece.
The common problem of transferring effective torque to deformed nuts and bolts is well-known in the art. When a nut is "frozen" onto a threaded bolt, the torque applied in attempting to remove it may deform the polygonal geometry of the outer nut surface to such an extent that a common box-end wrench (even an adjustable one) no longer properly engages the deformed surface to transfer torque. Rounded comers merely slip within the engaging box structure when torque is applied, accomplishing nothing.
Gripping pliers and wrenches are known in the art for torquing deformed workpieces. For instance, in U.S. Pat. No. 3,611,843, Joachim E. Engel discloses an adjustable socket wrench that has a gripping handle and a pair of relatively movable jaws, one of which is secured to the gripping handle and the other of which is cammed into engagement with its neighbor. Engel's handle includes a coarse adjusting member coupled to an axially movable jaw to permit adjustment of the socket dimensions by turning a threaded member. Engel's wrench increases the gripping force in the jaws responsive to an increase in the pivotal rotation of the jaws relative to the gripping handle arising from torque applied to the handle but cannot grip deformed workpieces in tight spaces. Similarly, in U.S. Pat. No. 4,174,646, Simon Cotler discloses a universal tool with gripping action and replaceable jaws that has a body with an opening adapted to interchangeably receive cassette-type work elements such as a box-end wrench element or the like. Cotler uses a cam-locking lever integrated into the universal tool to apply a predetermined gripping force on the workpiece. Disadvantageously, his universal tool employs a bulky structure to receive the cassette-type working element and is not suited for gripping polygonal workpieces in tight spaces. Moreover, contrary to Engel's advantageous feature of increasing gripping force proportionately with applied torque, Cotler's cam-locking scheme provides an unvarying gripping force that may be insufficient to retain the workpiece at high torque levels. Finally, in U.S. Pat. No. 2,486,523, P. E. Deschenes discloses a similar cam-locking adjustable gripping wrench for use with bottle caps.
Thus, although gripping wrenches are known in the art, including cam-operated and cam-locking gripping pliers and wrenches, no gripping wrench suitable for use in the tight spaces serviced by box-end wrenches has been known in the art until now. A wrench adapted to gripping and torquing polygonal workpieces in tight spaces could satisfy a clearly-felt need in the art. The related unresolved problems and deficiencies are clearly felt in the art and are solved by my invention in the manner described below.