摘要 |
A wrench has a pair of jaws which oppose each other to define the wrench opening. One of these jaws is pivotally mounted on the wrench body while the other may be fixed and integral with the wrench body. The pivotal jaw pivots in opposite directions so as to close the wrench opening and engage and drive a nut or bolt head when turned one way and to open the wrench opening and turn freely about the nut or bolt when turned the opposite way. The pivot about which the pivotal jaw rotates is on the same side of the wrench opening as the pivotal jaw itself such that the sum of the moments of the forces on the pivotal jaw close the jaw and align it with the nut or bolt head automatically at the start of the forward or driving stroke without any lost rotational motion or the need for springs or special cam surfaces.
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