Multi-purpose plug valve

Claim 1

A PLUG VALVE TO BE INSERTED IN THE PORT OF A WELL HEAD ASSEMBLY WHICH CONNECTS TO THE CASING ANNULUS, COMPRISING A TUBULAR BODY HAVING AN EXTERNALLY THREADED SPIGOT ON ITS INNER END, AN INWARDLY TAPERED FIRST VALVE SEAT ON THE INNER END OF THE SPIGOT, A TUBULAR VALVE STEM FIXED TO AND CLOSING THE OUTER END OF THE VALVE BODY AND PROJECTING INWARDLY BEYOND THE INNER END THEREOF, SAID VALVE BODY HAVING PORTS THEREIN SURROUNDING SAID VALVE STEM, A FIRST VALVE SLIDABLY MOUNTED ON THE STEM AND ENGAGING SAID FIRST SEAT, MEANS NORMALLY BIASING SAID FIRST VALVE AGAINST SAID FIRST SEAT, SAID VALVE BEING UNSEATABLE BY PRESSURE OF FLUID ENTERING SAID PORTS IN SAID VALVE BODY, A SECOND VALVE SEAT FORMED WITHIN SAID TUBULAR VALVE STEM, A SECOND VALVE SEATED AGAINST SAID SECOND VALVE SEAT TO PREVENT FLUID FLOW THROUGH SAID TUBULAR VALVE STEM, MEANS BIASING SAID SECOND VALVE AGAINST SAID SECOND SEAT, AND ROD MEANS FOR UNSEATING SAID SECOND VALVE, SAID ROD MEANS BEING SLIDABLY MOUNTED IN SAID TUBULAR VALVE STEM IN CONTACT WITH SAID SECOND VALVE AND PROJECTING OUT OF THE OUTER END OF SAID VALVE STEM.