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Shutoff valve apparatus includes a spring-loaded piston with two guide portions disposed in bores and the piston includes a fluid passage extending through the piston and communicating with one of the bores in which a guide element is disposed. Any back pressure works with the bias of the spring to

Shutoff valve apparatus includes a spring-loaded piston with two guide portions disposed in bores and the piston includes a fluid passage extending through the piston and communicating with one of the bores in which a guide element is disposed. Any back pressure works with the bias of the spring to help seat the valve piston to prevent fluid from leaking past the valve. Positive pressure from the working fluid opens the valve.

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Valve apparatus for a fluid, comprising, in combination: first housing means; first bore means in the first housing means, including a first valve bore having a first diameter, a first guide bore communicating with the first valve bore through which fluid flows to the first valve, and a first should

Valve apparatus for a fluid, comprising, in combination: first housing means; first bore means in the first housing means, including a first valve bore having a first diameter, a first guide bore communicating with the first valve bore through which fluid flows to the first valve, and a first shoulder between the first valve bore and the first guide bore; second housing means secured to the first housing means; second bore means in the second housing means, including a second valve bore communicating with the first valve bore and having a second diameter which is greater than the first diameter of the first valve bore, a spring bore communicating with the second valve bore, and a second guide bore communicating with the spring bore; and valve means movable in the first and second housing means, including a valve element movable in the first and second valve bores between a closed position in the first valve bore and an open position in the second valve bore, a first face on the valve element against which fluid pressure may bear to urge the valve element to the open position and which, when disposed on the first shoulder, defines a fully closed position, a guide rod secured to the first face and extending into the first guide bore for guiding the valve element as the valve element moves in the first and second valve bores, a second face on the valve element against which fluid back pressure may bear to urge the valve element to its closed position in the first valve bore, a guide tube secured to the second face and extending into the second guide bore for guiding the valve element as it moves in the first and second valve bores, a fluid bore in the guide tube through which fluid flows, spring means disposed about the guide tube and extending into the spring bore and between the second face and the spring bore for urging the valve element to its off position in the first valve bore, passage means extending through the valve element and communicating with the fluid bore through which fluid flows to the fluid bore when the valve element is at least partially out of the first valve bore and into the second valve bore, and sealing means extending circumferentially about the valve element between the first face and the passage means for sealing the valve element when the sealing means and the adjacent portion of the valve element is disposed in the first valve bore to prevent the flow of fluid from the first and second valve bores into the passage means and the fluid bore.