Torque Wrenches

Abstract

The piston 32 and cylinder 30 of a torque wrench 18 are provided with pressurised fluid from a source 12 through an advance port 16, or from a pump 42 through a return port 38. The source 12 includes a large piston 26 driven from the pump 42 during the advance stroke, and a small piston 22 driving fluid to the advance port 46, or receiving fluid returned from the port 16, during the return stroke. Accordingly, the pistons 22 and 32 form a closed system for fluid moving between the cylinder 24 and the cylinder 30. The pistons 22, 26 are connected by a shaft 68 so that relatively low pressure applied to the piston 26 results in high pressure fluid delivered to the advance port 16. Consequently, a low pressure pump 42 can be used to provide high pressure drive via the source 12, or a low pressure return stroke via the return port 38.

Dependencies are inferred from the claim text.