Seal ring extrusion preventing device

Claim 1

IN A FLUID PRESSURE SEALING STRUCTURE: A FIRST MEMBER HAVING A SEALING SURFACE EXTENDING LONGITUDINALLY OF ITS AXIS: A SECOND MEMBER HAVING A RING GROOVE EXTENDING FRONTING SAID SURFACE, THE SIDES OF SAID GROOVE EXTENDING TRANSAVERSELY OF THE AXIS OF SAID SECOND MEMBER; ONE OF SAID MEMBERS SURROUNDING SAID OTHER MEMBER; A PLIANT SEAL RING IN SAID GROOVE ENGAGING SAID SURFACE TO PREVENT FLUID LEAKAGE BETWEEN SAID MEMBERS; SAID SECOND MEMBER HAVING A BACKING FLANGE EXTENDING TRANVERSELY OF THE AXIS OF SAID SECOND MEMBER AND FIXED THERETO AT THE DOWNSTREAM SIDE OF SAID SEAL RING, THE NORMAL PERIPHERY OF SAID BACKING FLANGE HAVING A CLOSE NORMAL WORKING CLEARANCE WITH THE PERIPHERY OF SAID SEALING SURFACE; SAID FLANGE HAVING A FACE INCLINED AT AN OBTUSE ANGLE TO SAID SEALING SURFACE AND PROVIDING THE DOWNSTREAM SIDE OF SAID GROOVE, THE SLIDE OF SAID FLANGE OPPOSITE SAID INCLINED FACE BEING FREE FROM SUPPORT; SAID FLANGE FEEDING MADE OF SUCH MATERIAL AND HAVING A LONGITUDINALLY EXTENDING ROOT PORTION OF SUCH DIMENSIONS AS TO ENABLE SUCH FLANGE TO PIVOT ABOUT ITS ROOT PORTION INTO CONTACT WITH SAID SEALING SURFACE UNDER THE ACTION OF FLUID PRESSURE FORCING SAID SEAL RING AXIALLY AGAINST SAID INCLINED FACE BEFORE SAID FLUID PRESSURE CAN FORCE SAID SEAL RING INTO THE WORKING CLEARANCE SPACE BETWEEN SAID FLANGE PERIPHERY AND SEALING SURFACE.