Abstract: A dynamic seal for effecting the sealing of a piston which is axially movable in a cylinder bore comprising a primary sealing element formed of a non-elastomeric sealing material having a hub portion secured to the piston element and an outwardly flaring skirt portion sealingly engagable with the cylinder bore. A secondary sealing element formed of a resilient metal has its central body portions secured to the piston element and defines a frustro-conical lip portion snugly engaging the exterior of the skirt portion of the primary seal element. Fluid pressure applied to the primary seal element causes it to expand the secondary seal element into a metal-to-metal sealing engagement with the bore of the cylinder.

Abstract: A sealing system for a valve disposed downhole in a subterranean well and subject to a high-temperature and high-pressure environment, comprises an annular valve seat defining a primary annular metallic seating surface surrounded by a groove within which is mounted a nonresilient, nonmetallic sealing element which is spring urged to project axially beyond the end of the primary sealing surface. The valve head is provided by a primary metallic sealing surface which, as the valve head moves toward engagement with the valve seat first engages the nonresilient, nonmetallic sealing element and deflects same axially and concurrently expands it radially outwardly so that the nonmetallic, nonresilient sealing element ends up engaging a cylindrical surface surrounding the primary sealing surface formed on the valve head.