US Patent 7954823 Sealing ring for reciprocating motion

A sealing ring used for reciprocating motion and having low friction characteristics. The sealing ring is held at one of two members that move relative to each other and slidably in intimate contact with the other. The sealing ring has an end sliding part having an arcuate cross section and slidably in intimate contact with the other and also has a recessed surface formed in at least either a rear face or both side faces in an axial direction. The sealing ring satisfies the relationships of A/2<R<13A2 and 0.5A<C<A, where R is the radius of curvature of the end sliding part, A is the axial width of the sealing ring, and C is the thickness of the sealing ring between the deepest parts of the recessed surfaces.