Low pressure shutoff valve for fluid operated tool

Abstract From the Canadian patent

A low pressure shutoff valve adapted to be interposed in the fluid supply conduit of a fluid operated torque tool comprises a piston closure member having opposed differential pressure faces exposed to fluid supply pressure and a coil spring for biasing the piston toward a fluid shutoff position. The piston is disposed in a chamber which may be vented by actuating an axially slidable sleeve on the exterior of the valve body whereby the valve is opened to supply pressure fluid to the tool as long as the fluid pressure is greater than a predetermined minimum value.