Patent ID: 7686351

Claim:
A gasket comprising an inner ring having an outer surface, an outer ring having an inner surface, and an intermediate ring disposed between the inner ring and the outer ring, wherein the inner ring, the outer ring and the intermediate ring are coaxial rings (having a same axis); the intermediate ring has an inner surface in contact with the outer surface of the inner ring along the axial direction and an outer surface in contact with the inner surface of the outer ring along the axial direction; the intermediate ring has a first surface orthogonal to the inner surface and the outer surface and has a second surface generally parallel to the first surface, wherein at least one of the first surface and the second surface of the intermediate ring has a circular groove therein that is coaxial with the intermediate ring; and the intermediate ring is made of a material that has a hardness less than the hardness of the material of each of the inner ring and the outer ring.