Safety valve

Claim 1

IN A SAFETY VALVE CONSTRUCTION, A HOUSING HAVING A VALVE PASSAGE THEREIN AND OPPOSED VALVE SEATS ALONG SAID PASSAGE, A VALVE IN SAID VALVE PASSAGE AND ADAPTED TO MOVE IN OPPOSITE DIRECTIONS AND CLOSE AGAINST EITHER ONE OF SAID OPPOSED VALVE SEATS, SPRING MEANS BIASING THE VALVE TOWARD AN INTERMEDIATE POSITION BETWEEN SAID SEATS, A CENTRAL IMPELLER DISC RADIALLY POSITIONED ON SAID VALVE AND SPACED FROM THE SURFACE OF SAID PASSAGE, STEMS EXTENDING IN OPPOSITE DIRECTIONS FROM THE VALVE, GUIDE MEANS FOR SAID STEMS TO BE GUIDED IN MOVEMENT OF SAID VALVE FROM SAID INTERMEDIATE POSITION TO EITHER OF SAID OPPOSED SEATS, SAID GUIDE MEANS INCLUDING A CYLINDER COOPERATING WITH EACH OF SAID STEMS TO RETARD MOTION OF SAID VALVE FROM SAID INTERMEDIATE POSITION OF THE VALVE TO ONE OF SAID SEATING POSITIONS AND HAVING AN ANNULAR WALL WHICH CONSTITUTES ONE OF SAID MEANS FOR GUIDING THE STEMS, AND ORIFICE MEANS FOR RESTRICTING FLOW OF FLUID FROM SAID CYLINDER TO SAID VALVE PASSAGE WHEN SAID VALVE, UNDER DIFFERENTIAL OF FLUID PRESSURE APPLIED TO SAID IMPELLER IN SAID PASSAGE, MOVES AGAINST BIAS OF SAID SPRING MEANS FROM SAID INTERMEDIATE POSITION TOWARD SAID ONE OF SAID SEATING POSITIONS, AND FOR FLUID TO RESTORE IN SAID CYLINDER WHEN SAID VALVE MOVES FROM SAID ONE OF SAID SEATING POSITIONS BACK TOWARD SAID INTERMEDIATE POSITION UNDER BIAS OF SAID SPRING MEANS.