Auxiliary, external, pressure seal for shank of plug valve

Claim 1

IN A ROTARY PLUG VALVE ASSEMBLY, A BODY HAVING A ROTARY PLUG THEREIN AND A COVER PLATE SECURED THEREON OVER AND IN SPACED RELATION WITH THE TOP OF THE PLUG, THE PLUG HAVING A SHANK EXTENDING FROM THE TOP THEREOF THROUGH AN OPENING IN THE COVER PLATE, THE PLUG FURTHER HAVING A RELATIVELY WIDE UPWARDLY FACING SHOULDER EXTENDING WIDTHWISE FROM THE SHANK A DISTANCE SHORT OF THE OUTSIDE EDGE OF THE PLUG, A DIAPHRAGM SEAL OVERLYING THE TOP OF THE PLUG AND PERIPHERALLY SECURED BETWEEN SAID COVER AND SAID BODY AND HAVING A CENTRAL OPENING THROUGH WHICH THE PLUG SHANK EXTENDS, THE DIAPHRAGM RESTING ON SAID SHOULDER, AN EXTERNAL PRESSURE SEAL COMPRISING AN ANNULAR THRUST COLLAR ENCIRCLING THE PLUG AND AXIALLY AND RADIALLY SPACED FROM SAID COVER, THE THRUST COLLAR HAVING AN INNER CORNER BEVEL PROVIDING AN INCLINED SURFACE DIRECTED TOWARD THE SHANK AND INTERSECTING A FLAT RADIAL LOWER SURFACE PORTION OF THE COLLAR, SAID INCLINED SURFACE OVERLYING SAID SHOULDER AND SAID LOWER SURFACE PORTION OF THE COLLAR RESTING UPON THE DIAPHRAGM SEAL RADIALLY OUTWARDLY BEYOND THE OUTER EDGE OF THE SHOULDER, THE SAID BEVEL SURFACE FORMING AN ANNULAR RECESS WITH THE SHANK AND DIAPHRAGM SEAL SURFACE, AN ANNULAR SEAL IN SAID RECESS AND COMPRISING FIRST AND SECOND SEALING RINGS, THE FIRST SEALING RING BEING SUBSTANTIALLY L-SHAPED IN VERTICAL CROSS SECTION AND INCLUDING AN UPSTANDING LEG AND A SECOND LEG NORMAL TO AND EXTENDING OUTWARDLY FROM THE LOWER END OF THE FIRST LEG, EACH OF SAID LEGS HAVING INNER AND OUTER SURFACES, THE OUTER SURFACE OF THE UPSTANDING LEG BEARING AGAINST THE SHANK OF THE PLUG, THE OUTER SURFACE OF THE SECOND LEG RESTING UPON THE UPPER SURFACE OF THE DIAPHRAGM SEAL, THE SECOND SEALING RING BEING POSITIONED IN THE ANGLE BETWEEN THE INNER SURFACES OF THE LEGS OF THE FIRST SEALING RING AND BEING POSITIONED AGAINST THE SAID INCLINED SURFACE PROVIDED BY SAID CORNER BEVEL, AND MEANS CARRIED BY SAID COVER AND BRIDGING THE SPACE BETWEEN THE COVER AND SAID THRUST COLLAR AND ENGAGING THE TOP OF THE COLLAR FOR IMPOSING THRUST UPON THE COLLAR TOWARD THE SAID TOP OF THE PLUG FOR MAINTAINING SAID ANNULAR SEAL IN SEALING ENGAGEMENT WITH THE SHANK AND WITH THE DIAPHRAGM SEAL.