Subsurface well tubing safety valve

Claim 1

A SAFETY SHUTOFF FOR FLUID CONDUCTING TUBING WHICH COMPRISES: A CONTROL TUBING POSITIONED WITHIN THE FLUID CONDUCTING TUBING AND HAVING A FIRST END THEREOF TERMINATING WITHIN THE FLUID CONDUCTING TUBING, SAID CONTROL TUBING HAVING AN OUTER DIAMETER LESS THAN THE INNER DIAMETER OF THE FLUID CONDUCTING TUBING TO FORM AN ANNULAR PASSAGE BETWEEN THE CONTROL AND FLUID CONDUCTING TUBINGS; A SOURCE OF CONTROL FLUID CONNECTED TO A FIRST END OF THE FLUID CONDUCTING TUBING FOR DIRECTING CONTROL FLUID THROUGH SAID ANNULAR PASSAGE TOWARD SAID FIRST END OF THE CONTROL TUBING; A FLUID-RESPONSIVE VALVE ASSEMBLY SECURED TO SAID FIRST END OF THE CONTROL TUBING, SAID VALVE ASSEMBLY INCLUDING: A HOUSING HAVING AN OPENING THEREIN, SAID HOUSING BEING SECURED TO THE CONTROL TUBING ADJACENT THE SECOND END OF SAID FLUID CONDUCTING TUBING, PACKING BETWEEN THE HOUSING AND THE ADJACENT FLUID CONDUCTING TUBING FOR DIRECTING FLUIDS INTO AND THROUGH THE HOUSING AND CONTROL TUBING TOWARD THE SECOND END OF THE CONTROL TUBING, A CLOSURE PIVOTALLY MOUNTED ON THE HOUSING AND MOVABLE IN A GIVEN PATH THROUGH SAID OPENING IN THE HOUSING INTO AND OUT OF THE CENTRAL PORTION OF THE VALVE ASSEMBLY, MEANS IN OPERATIVELY ENGAGEMENT WITH A PORTION OF THE CLOSURE FOR BIASING THE CLOSURE TOWARD THE CENTRAL PORTION OF THE VALVE ASSEMBLY TO PREVENT THE FLOW OF FLUID THERETHROUGH, RECIPROCAL MEANS MOVABLE WITHIN A PORTION OF THE HOUSING TOWARD AND AWAY FROM THE PATH OF SAID CLOSURE, SAID RECIPROCAL MEANS BEING IN OPERATIVE ENGAGEMENT WITH THE CLOSURE AND HAVING A PRESSURE RECEIVING SURFACE THEREON IN COMMUNICATION WITH THE ANNULAR PASSAGE, MEANS FOR DIRECTING SAID CONTROL FLUID FROM THE ANNULAR PASSAGE AGAINST THE PRESSURE RECEIVING SURFACE FOR MOVING THE RECIPROCAL MEANS TOWARD THE PATH OF THE CLOSURE TO MOVE SAID CLOSURE AWAY FROM THE INTERIOR OF SAID VALVE ASSEMBLY TO PERMIT PASSAGE OF FLUID THERETHROUGH, AND MEANS CARRIED BY THE HOUSING FOR BIASING THE RECIPROCAL MEANS AWAY FROM THE PATH OF THE CLOSURE TO PERMIT MOVEMENT OF THE CLOSURE INTO THE INTERIOR OF THE VALVE ASSEMBLY, SAID BIASING MEANS EXERTING A FORCE INSUFFICIENT TO OVERCOME THE FORCE EXERTED BY THE CONTROL FLUID ON THE PRESSURE RECEIVEING SURFACE DURING NORMAL OPERATION OF THE VALVE.