Lubricated ball valve having seating rings with preformed matching seating surfaces

Claim 1

IN A PLUG VALVE ASSEMBLY, A BODY HAVING UPSTREAM AND DOWNSTREAM FLUID PASSAGE SECTIONS, A PORTED PLUG ROTATABLE WITHIN SAID BODY BETWEEN POSITIONS WHERE IT BLOCKS AND PROVIDES FLUID COMMUNICATION BETWEEN SAID PASSAGE SECTIONS, AN UPSTREAM SEAT RING WITHIN THE BODY, SAID PLUG HAVING A NORMALLY SPHERICAL SURFACE FOR ENGAGING A SEATING SURFACE ON SAID RING, MEANS MOUNTING SAID SEAT RING FOR SUBSTANTIALLY AXIAL DISPLACEMENT WITH RESPECT TO THE UPSTREAM PASSAGE SECTION, SAID SEATING SURFACE OF THE SEAT RING BEING PREFORMED TO A CONTROLLER THAT SUBSTANTIALLY CONFORMS TO THE CONTOUR ASSUMED BY THE SPHERICAL SURFACE OF SAID PLUG IS IN CLOSED VALVE POSITION AND SUBJECTED TO PREDETERMINED HIGH LINE FLUID PRESSURES ENCOUNTERED DURING NORMAL OPERATION, AND MEANS FOR RESILIENTLY BIASING SAID SEAT RING TOWARD ENGAGEMENT WITH THE PLUG SURFACE FOR DISTORTING SAID SEAT RING TOWARD SUBSTANTIALLY SPHERICAL SURFACE CONTACT WITH SAID PLUG WHEN THERE IS LITTLE OR NO SUBSTANTIAL LINE PRESSURE DIFFERENTIAL ACROSS SAID VALVE ASSEMBLY AND ENABLING SAID SEAT RING TO RELAX SAID DEFORMATION TO ENABLE ITS SEATING SURFACE TO CHANGE TOWARD SAID PERFORMED CONTOUR TO MATCH DEFORMATION OF SAID SPHERICAL PLUG SURFACE UNDER PREDETERMINED LINE PRESSURES.