Snap-closing gas lift valve

Claim 1

A GAS LIFT VALVE, COMPRISING, A GENERALLY TUBULAR HOUSING, A VALVE SEAT PORT IN THE HOUSING, A VALVE MEMBER RECIPROCABLE RELATIVE TO THE PORT FOR CONTROLLING THE SAME, AN ELONGATE STEM SECURED TO THE VALVE MEMBER, ANNULAR ABUTMENT MEANS IN THE HOUSING HAVING AN AXIAL OPENING THROUGH WHICH THE STEM IS RECIPROCABLE, ANNULAR SHOULDER MEANS CARRIED ON SAID STEM FOR LONGITUDINAL MOVEMENT THEREWITH RELATIVE TO SAID ABUTMENT MEANS, RESILIENT MEANS BIASING THE VALVE MEMBER TOWARD THE PORT-CLOSING POSITION, AND A SNAP-ACTING MECHANISM FOR CONTROLLING THE CLOSING MOVEMENT OF THE VALVE MEMBER COMPRISING,A BELLEVILLE SPRING WASHER SEATED ON SAID ABUTMENT MEANS SURROUNDING SAID STEM IN LONGITUDINALLY SPACED RELATION TO SAID SHOULDER MEANS, THE SPACING BEING SUCH AS TO PERMIT INITIAL LIMITED FREE LONGITUDINAL MOVEMENT OF THE STEM IN THE PORT-CLOSING DIRECTION FOLLOWED BY ENGAGEMENT OF THE WASHER BY SAID SHOULDER MEANS WHEREBY TO RESIST FURTHER MOVEMENT OF SAID STEM THROUGHOUT AT LEAST A PORTION PRECEDING THE TERMINAL PORTION OF SAID MOVEMENT, SAID WASHER HAVING A PRE-SELECTED H/T RATIO, AS HEREINABOVE DEFINED, SUCH THAT WHEN THE DEFLECTION OF SAID WASHER UNDER THE CLOSING PRESSURE OF SAID BIASING MEANS EXCEEDS A PRE-DETERMINED FRACTION OF H, THE WASHER WILL COLLAPSE ALLOWING THE VALVE MEMBER TO SNAP THROUGH SAID TERMINAL PORTION TO THE PORT-CLOSING POSITION.