Automatic shut-off valve for power tools

摘要

A fluid-actuated shut-off valve for a fluid-powered tool such as a wrench including a spool valve urged to open position by a spring and having respective valve-operating surfaces subject to both regulated inlet and exhaust pressures in the tool. The valve operating surfaces and spring are arranged so the valve is thrown to its closed position by a combination of a constant regulated control pressure and the drop in exhaust pressure as the tool motor slows down and stalls under load. The valve operating mechanism also includes an element for preventing high pressure fluid from venting to the workplace during motor stall.