Check valve for use in a tubular flow conductor

Claim 1

A VALVE INCLUDING: A TUBULAR HOUSING ADAPTED TO BE SECURED IN A TUBULAR FLOW CONDUCTOR TO FORM A SECTION THEREOF, SAID HOUSING HAVING A LONGITUDINAL FLOW PASSAGE; VALVE MEANS MOUNTED IN SAID FLOW PASSAGE FOR PERMITTING FLOW IN ONE DIRECTION THROUGH SAID PASSAGE WHEN IN OPEN POSITION AND PREVENTING FLOW IN A DIRECTION OPPOSITE TO SAID ONE DIRECTION WHEN INCLOSED POSITION; AND OPERATING MEANS IN SAID FLOW PASSAGE FOR MOVING SAID VALVE MEANS BETWEEN OPEN AND CLOSED POSITIONS, SAID OPERATING MEANS INCLUDING A PAIR OF LONGITUDINALLY SPACED MEMBERS AND MEANS CONNECTING SAID MEMBERS FOR CAUSING SAID MEMBERS TO MOVE SIMULTANEOUSLY IN SAID FLOW PASSAGE, SAID VALVE MEANS BEING DISPOSED BETWEEN AND BEING ENGAGED BY SAID VALVE MEMBERS WHEREBY SAID VALVE MENS IS MOVED BY AND WITH SAID OPERATING MEANS, SAID OPERATING MEANS BEING EXPOSED AND RESPONSIVE TO PRESSURE WITHIN SAID FLOW PASSAGE AND ALSO TO PRESSURE EXTERIORLY OF SAID HOUSING, SAID OPERATING MEANS MOVING SAID VALVE MEANS TO CLOSED POSITION WHEN THE PRESSUR EXTERIORLY OF SAID HOUSING EXCEEDS THE PRESSURE WITHIN SAID PASSAGE AND MOVING SAID VALVE MEANS TO OPEN POSITION WHEN THE PRESSURE WITHIN SAID LONGITUDINAL FLOW PASSAGE EXCEEDS THE PRESSURE EXTERIORLY OF SAID HOUSING, SAID VALVE MEANS BEING MOVABLE BETWEEN SAID CLOSED AND OPEN POSITIONS ONLY BY THE FORCE EXERTED ON SAID OPERATING MEANS BY THE PRESSURE WITHIN SAID FLOW PASSAGE AND THE FORCE EXERTED THEREON BY THE PRESSURE EXTERIORLY OF SAID HOUSING.