Pressure-responsive safety valve

Claim 1

A PRESSURE CHARGE OPERATED SAFETY VALVE INCLUDING: A HOUSING HAVING A LONGITUDINAL BORE THEREIN WITH AN ANNULAR SEAT SURROUNDING SAID BORE INTERMEDIATE THE ENDS THEREOF; SAID HOUSING HAVING LATERAL FLUID FLOW INLET MEANS ADJACENT SAID SEAT COMMUNICATING THE EXTERIOR OF SAID HOUSING WITH SAID BORE BELOW AND ADJACENT SAID SEAT; VALVE MEANS MOVABLE LONGITUDINALLY IN SAID HOUSING BORE BELOW SAID SEAT AND HAVING AN ANNULAR SEAT SURFACE THEREON ENGAGEABLE WITH SAID ANNULAR SEAT OF SAID HOUSING TO CLOSE OFF FLOW THROUGH SAID BORE OF SAID HOUSING FROM SAID FLUID FLOW INLET MEANS TO SAID PASSAGE BEYOND SAID SEAT; MEANS IN SAID HOUSING BORE OPERATIVELY CONNECTED WITH SAID VALVE MEANS PROVIDING AN EXPANSIBLE AND CONTRACTABLE PRESSURE CHARGE CHAMBER FOR A CHARGE OF EXPANSIBLE FLUID UNDER PRESSURE FOR BIASING SAID VALVE MEANS TOWARD CLOSED POSITION IN WHICH THE SEAT OF SURFACE OF SAID VALVES MEANS ENGAGES SAID SEAT OF SAID HOUSING TO CLOSE OFF FLOW THERETHROUGH; SAID EXPANSIBLE CHAMBER BEING DISPOSED IN SAID HOUSING BORE BELOW SAID FLOW INLET MEANS, SAID PRESSURE CHAMBER HAVING A CROSS-SECTIONAL AREA EXPOSED TO FLUID PRESSURE FROM EXTERIORLY OF SAID HOUSING OF LESSER AREA THAN THE AREA OF THE SEAT SURFACE OF THE VALVE MEANS AND VALVE SEAT, WHEREBY FLUID PRESSURE ACTING ON SAID VALVE MEANS FROM EXTERIORLY OF SAID HOUSING THROUGH SAID FLOW INLET MEANS POSITIVELY RETAINS SAID VALVE MEANS IN SEATED