Abstract: A seal assembly adapted for use in sealing two mating surfaces spaced apart by a gap is provided. The seal assembly includes a sealing element adapted to be located in a groove in one of the mating surfaces. A back-up ring assembly is provided which includes a first back-up ring made from a relatively soft material and a second back-up ring made from a relatively hard material. The first back-up ring includes a body with first and second sides, with one of a groove and an interlocking projection being located on the body along the second side. The second back-up ring includes a body with first and second sides, with the other of the groove and the interlocking projection being located along the first side.

Abstract: A ring shaped seal (10) for preventing fluid flow through a gap (32) between a rotating shaft (30) and a cylindrical wall (34) is positioned in a groove (28) in the shaft. The seal has, in cross section, a generally rectangular body (11) that has a slightly lesser width than the width of the groove. The body has a first end wall (12) that includes first pockets (18) and a second end wall (14) that includes second pockets (20). The seal has an outer wall (22) with a contact portion (26) that is in abutting contact with the cylindrical wall. When a higher pressure is applied on one side of the seal, the end wall of the seal on the side away from the higher fluid pressure is pushed against a side wall of the groove. The pockets in the end wall of the seal that is pushed against the groove, are open to the higher pressure and exert a force which counteracts the forces pushing the end wall of the seal against the side of wall of the groove.