US Patent 7117772 Wrench having a safety device

A wrench includes a shank having a drive head, a handle slidably mounted on the shank, and a resistance member mounted between the shank and the handle to provide a resistance to damp movement of the handle. Thus, when a force is applied on the handle to rotate the shank about the drive head, the force produces an axial component force which drives the handle to move relative to the shank, so that the resistance member is compressed, and the handle is moved on the shank to a determined position. In addition, the shank is provided with an indication portion to indicate a safety parameter of motion of the handle during movement of the handle.