SEALING DEVICE

PROBLEM TO BE SOLVED: To prevent the generation of damage in a back-up ring 4 installed in a sealing device in advance, due to floating thereof from an installation groove 21 when inserting a piston 2 into a housing 1. SOLUTION: The sealing device has an O-ring 3 made of a rubbe-like elastic material and the back-up ring 4 made of a material harder than that of the O-ring 3 and cut at one position in the circumferential direction in the installation groove 21 formed in any one of the inner peripheral surface 1a of the housing 1 and the outer peripheral surface 2a of the piston 2 arranged in the inner periphery of the housing freely to move in the axial direction and continued in the circumferential direction. A groove inside surface 21a, to which the O-ring 3 is pushed when inserting the piston 2 into the housing 1, is formed into a tapered surface by narrowing groove width on a groove shoulder 21c side, and a back surface 4c on the opposite side in relation to the O-ring 3 in the back-up ring 4 as a side, to which the O-ring 3 is pushed when inserting the piston 2 into the housing 1, is formed into a shape corresponding to the groove inside surface 21a. COPYRIGHT: (C)2005,JPO&NCIPI