US Patent 7231937 Automatic shutoff valve

An automatic shutoff valve is provided. The valve is preferably constructed of a check valve (which is normally shut) and a shutoff valve which is open during static, no-flow, operation. Upon initiation of flow, even a drip flow, the check valve opens, and the pressure differential from the inlet to the outlet causes a piston in the shutoff valve to move toward a shut position. As long as the pressure differential stops before the piston closes, the shutoff valve resets to the fully open position. However, if the shutoff valve shuts, it preferably must be manually reset.