Fluid pressure tight joint

Claim 1

IN A PLUG VALVE ASSEMBLY CHARACTERIZED BY A BODY HAVING A THROUGH PASSAGE FOR LINE FLUID AND A PLUG SEATING BORE INTERSECTING SAID PASSAGE, A PORTED PLUG ROTATABLY MOUNTED IN SAID BORE AND ADAPTED TO TURN TO OPEN OR CLOSE SAID PASSAGE, AN OPERATING STEM FOR SAID PLUG EXTENDING THROUGH SAID BODY AT ONE END OF THE BORE, A COVER REMOVABLY SECURED OVER THE OTHER END OF SAID BORE, AND A FLEXIBLE METAL DIAPHRAGM EXTENDING OVER SAID COVER WITHIN THE BORE, THE IMPROVEMENT WHICH COMPRISES MEANS PROVIDING A PRESSURE TIGHT JOINT BETWEEN THE COVER AND BODY COMPRISING A BODY SHOULDER IN SAID BORE FACING THE COVER, SAID SHOULDER AND COVER HAVING AXIALLY SPACED SURFACES IN THE ASSEMBLY, OPPOSED ANNULAR RECESSES IN THE SHOULDER AND COVER SURFACES AND DISPOSED RADIALLY OUTWARDLY OF THE OPENING OF SAID BORE AT SAID SHOULDER, SAID FLEXIBLE METAL DIAPHRAGM EXTENDING OVER SAID COVER RECESS, A SOLID HARD METAL RING OF UNIFORM CROSS SECTION HAVING ITS OPPOSITE SIDES DISPOSED WITH RADIALLY CONFINED INTERFIT IN SAID SHOULDER RECESS AND UPON SAID DIAPHRAGM IN SAID COVER RECESS AND AXIALLY DISPOSED BERWEEN SAID COVER AND SHOULDER WHEREBY SAID DIAPHRAGM IS DEFLECTED INTO SAID COVER RECESS AND IS THERE CLAMPED BETWEEN SAID RING AND THE COVER, MEANS FOR DRAWING SAID COVER TIGHT UPON SAID BODY TO AXIALLY COMPRESS SAID RING WITH THE LONGITUDINALLY OPPOSITE SIDES OF SAID RING TIGHT AGAINST THE BOTTOM OF THE SHOULDER RECESS AND AGAINST THE DEFLECTED DIAPHRAGM IN THE COVER RECESS, AND COACTING ANNULAR FACES ON THE BODY AND COVER DISTINCT FROM SAID COVER AND BODY SHOULDER SURFACES ABUTTING TO STOP MOVEMENT OF THE COVER TOWARD THE BODY AND PREVENT APPLICATION OF EXCESSIVE AXIAL PRESSURE ON SAID RING, SAID RING BEING AXIALLY CONFINED BETWEEN SAID COVER AND BODY SHOULDER WITH SUFFICIENT PRESSURE TO PROVIDE AN OPERATIVE FLUID TIGHT METAL TO METAL SEAL WHEN SAID FACES ABUT.