Patent ID: 7181998
Filing Date: 2007-02-27
Classification: B25B

Abstract:
1. A wrench for tightening or loosening a fastening member with respect to another member, comprising: a wrench body having a ring portion which has an inner diameter suitable for disengageable engagement with an outer circumference of a fastening member, and a handle portion projecting from an outer circumference of the ring portion; a plurality of wedge members each assuming a roller shape; a retainer disposed inside the ring portion in such a manner that the retainer rotates along an inner circumferential surface of the ring portion, the retainer rotatably holding the wedge members at predetermined intervals in a circumferential direction of the ring portion, the retainer being provided with elongated holes for allowing the wedge members to contact the outer circumferential surface of the fastening member when said fastening member is engaged in the ring portion; wedge guide grooves formed on the inner circumferential surface of the ring portion arranged along the circumferential direction of the ring portion at intervals corresponding to those of the wedge members, each of the wedge guide grooves having a free region which extends in the circumferential direction of the ring portion and maintains the corresponding wedge member in a free state in which the wedge member moves freely between a bottom surface of the corresponding wedge guide groove and the outer circumferential surface of the fastening member, and a wedge region which extends in the circumferential direction of the ring portion and maintains the corresponding wedge member in a caught state in which the wedge member is caught between the bottom surface of the corresponding wedge guide groove and the outer circumferential surface of the fastening member; and a changeover mechanism for operating the retainer in order to move each wedge member to a position at which the wedge member faces the free region of the corresponding wedge guide groove or a position at which the wedge member faces the wedge region of the corresponding wedge guide groove; wherein the changeover mechanism includes a changeover lever mounted on the handle portion at a position near the ring portion in such a manner that the lever can pivot horizontally; a first end portion of the changeover lever passes through the ring portion and is coupled to the retainer; a positioning mechanism is provided at a second end portion of the changeover lever in order to hold the changeover lever at a position at which the retainer is moved to a circumferential position at which each wedge member faces the corresponding free region, or a position at which the retainer is moved to a circumferential position at which each wedge member faces the corresponding wedge region; and wherein the positioning mechanism is composed of a click stop mechanism which includes a steel ball accommodated in the second end portion of the changeover lever; a spring member for urging the steel ball toward the handle portion; and first and second engagement holes which are formed on the surface of the handle portion and with which the steel ball selectively engages, wherein when the steel ball engages the first engagement hole, the retainer is positioned at the circumferential position at which each wedge member faces the corresponding free region, and when the steel ball engages the second engagement hole, the retainer is positioned at the circumferential position at which each wedge member faces the corresponding wedge region.