Gas lift valve mechanism

Claim 1

GAS LIFT VALVE MECHANISM COMPRISING A TUBULAR BODY ADAPTED FOR COAXIAL CONNECTION INTO A TUBING STRING FOR INSERTION WITH THE STRING INTO A WELL CASING, AN ANNULAR VALVE CHAMBER CONCENTRICALLY SURROUNDING SAID BODY AND HAVING LONGITUDINALLY SPACED INLET AND OUTLET PORTS COMMUNICATING RESPECTIVELY WITH THE INTERIOR OF SAID CASING AND THE INTERIOR OF SAID BODY, A TUBULAR VALVE MEMBER CONSTRUCTED OF FLEXIBLE MATERIAL SURROUNDING THE BODY, SAID VALVE MEMBER BEING ANNULARLY EXPANSIBLE AND CONTRACTIBLE TO CONTROL THE PASSAGE OF FLUID THROUGH THE VALVE CHAMBER, A PRESSURE CHAMBER SURROUNDING THE BODY ADJACENT SAID VALVE CHAMBER SAID VALVE MEMBER FORMING A COMMON WALL BETWEEN SAID CHAMBERS, AN ANNULAR DIAPHRAGM FORMED OF FLEXIBLE MATERIAL IN AND DIVIDING SAID PRESSURE CHAMBER TO FORM AN UPPER CHAMBER SECTION BETWEEN SAID DIAPHRAGM AND SAID VALVE MEMBER AND A LOWER CHAMBER SECTION BENEATH THE DIAPHRAGM, A LIQUID COMPLETELY FILLING SAID UPPER CHAMBER SECTION, AND PILOT VALVE MEANS ACTUATED BY THE PRESSURE OF THE FLUID IN THE CASING AND PRESSURE OF THE FLUID IN THE BODY FOR CONTROLLING THE PRESSURE OF FLUID IN SAID LOWER CHAMBER SECTION TO CAUSE FLEXING OF SAID DIAPHRAGM TO INCREASE AND DECREASE THE PRESSURE IN SAID UPPER CHAMBER SECTION TO CAUSE OPENING AND CLOSING MOVEMENT OF SAID VALVE MEMBER, SAID VALVE MEMBER PREVENTING PASSAGE OF FLUID THROUGH SAID VALVE CHAMBER WHEN THE PRESSURE WITHIN THE LOWER CHAMBER SECTION AND THE PRESSURE WITHIN THE INTERIOR OF SAID CASING ARE EQUAL.