Shut-off valve and method for using same

Claim 1

Automatic shut-off valve for controlling the pulsating flow of fluid in a line, comprising: (a) a body having a formed therein: a valve cavity having a first end, a second end, and central region; a fluid input port having a fluid inlet coupled to a source of intermittingly pulsating fluid and a fluid output port having a fluid outlet coupled to the line, both fluid input and fluid output ports communicating with the valve cavity central region; an outlet pressure port connecting the valve cavity first end to the fluid outlet; and an inlet pressure port connecting the valve cavity second end to the fluid inlet; (b) valve means for controlling flow between the fluid input and output ports, said valve means sealingly cooperating with the valve cavity and shiftable relative thereto from an open position in which the input and output ports are coupled to a closed position where said flow is shut-off; and (c) a normally closed check valve placed between the fluid inlet and the fluid outlet, downstream of the inlet pressure port and upstream of the outlet pressure port, said check valve opening in response to the incoming pulsating fluid flow, and closing thereafter to prevent backflow through said valve; whereby the shut-off valve will normally transmit liquid from the fluid inlet to the fluid outlet passing through the check valve, input port, valve cavity central region and output port, resulting in a pulsating pressure in both the first and second ends of the valve cavity such that the valve means is maintained in the open position, said valve means shifting to the closed position in the event of a broken link resulting in a reduction in the fluid pressure causing the valve means to shift to the closed position due to the increase pressure in the valve cavity second end from the check valve restriction.