Butterfly valve having radially shiftable and fluid pressure responsive seat

Claim 1

A SEAT ASSEMBLY FOR A BUTTERFLY VALVE INCLUDING A PASSAGE AND AN ANNULAR BODY RECESS ABOUT THE PASSAGE WHICH COMPRISES, A SUBSTANTIALLY U-SHAPED RESILIENT BACKING RING, AND A RESILIENT METALLIC VALVE SEAT, SAID VALVE SEAT INCLUDING A BOTTOM WALL TERMINATING AT EITHER END IN AN ARCUATE SECTION WITH ONE SAID SECTION ENGAGING IN TANGENTIAL POINT CONTACT RELATIONSHIP WITH THE BACKING RING AND THE OTHER SAID ARCUATE SECTION ENGAGING A WALL OF THE RECESS IN POINT CONTACT RELATIONSHIP, AND SAID SEAT INCLUDING A RADIALLY INWARDLY DIRECTED PORTION EXTENDING SUFFICIENTLY INWARDLY OF THE VALVE PASSAGE AND THENCE DOWNSTREAM OF THE PASSAGE TO FORM A LOOPED PORTION WHEREBY THE LOOPED PORTION HAS AN EXTENSION DIRECTED AXIALLY OF THE PASSAGE IN AN UPSTREAM DIRECTION SO THAT PRESSURE FLUID ENGAGING AGAINST THE UPSTREAM SIDE OF THE SEAT MEMBER WILL ACT UPON THE SEAT TO PIVOT THE SEAT ABOUT ITS ARCUATE POINT CONTACT WITH THE RECESS WALL WHEREBY TO EFFECTIVELY SEAL THE VALVE AGAINST LEAKAGE ABOUT THE SEAT IN THE AREA OF THE BODY RECESS.