Ball valve having heat destructible seal

Claim 1

A FIREPROOF BALL VALVE COMPRISING, IN COMBINATION, A VALVE BODY DEFINING A VALVE CHAMBER AND DEFINING TWO PASSAGES OPENING INTO SAID CHAMBER, SAID BODY DEFINING TWO FLAT SEAT SUPPORT SURFACES ENCIRCLING THE INNER ENDS OF SAID RESPECTIVE PASSAGES AND CONVERGING IN ONE DIRECTION, A ROTARY VALVE BALL DISPOSED WITHIN SAID CHAMBER, TWO ANNULAR VALVE SEATS SLIDABLY POSITIONED ON SAID RESPECTIVE SUPPORT SURFACES AND ENGAGING OPPOSITE SIDES OF SAID BALL, AN OPERATOR ELEMENT CONNECTED TO ROTATE SAID BALL BETWEEN OPEN AND CLOSED POSITIONS, SAID BALL BEING MOVABLE WITH RESPECT TO BOTH SAID OPERATOR ELEMENT AND SAID BODY TO MOVE UNDER THE FORCE OF FLUID PRESSURE ON THE BALL TOWARD THE INNER END OF EITHER OF SAID PASSAGES, EACH VALVE SEAT COMPRISING AN ANNULAR SEAL FORMED OF A YIELDABLE MATERIAL DEFINING A BASE SURFACE SLIDABLY ENGAGING THE ADJACENT SUPPORT SURFACE AND DEFINING AN ANNULAR FACE SURFACE SLIDABLY ENGAGING THE BALL, EACH SEAT INCLUDING AN ANNULAR SEAT RING OF METAL CONCENTRIC WITH THE SEAT SEAL AND BOUNDING ONE PERIPHERAL EDGE OF THE SEAL, EACH SEAL BEING DIMENSIONED TO SUPPORT THE BALL OUT OF CONTACT WITH THE ADJACENT SEAT RING, EACH SEAT RING