Sealing device and damper for hydraulic equipment

A damper comprising:

• a cylinder;
• a piston including an outer member having an annular shape and an inner member inserted into the outer member, inserted into the cylinder while being axially movable, being configured to partition an interior of the cylinder into an extension side chamber and a compression side chamber, and including a passage communicating the extension side chamber and the compression side chamber;
• a rod inserted into the cylinder while being axially movable;
• a seal ring housed in an annular groove disposed in one of the outer member and the inner member and abutting on another of the outer member and the inner member to prevent a liquid from passing through a gap between the outer member and the inner member;
• and
• a valve configured to open and close the passage,
• the annular groove is formed by a bottom portion and a pair of side walls extending in parallel from both ends of the bottom portion in an axial direction and opposing each other,
• the bottom portion of the annular groove includes a recess or a recess and protrusion for restraining axial displacement of the seal ring relative to the annular groove,
• the valve comprises a primary valve body and a secondary valve body disposed in the passage in series,
• the primary valve body being configured to create a damping force when piston speed is in a medium- or high-speed range,
• the secondary valve body being configured to create a damping force when piston speed is in an extremely low-speed range, and
• the seal ring placed in the annular groove being fitted into the recess or the recess and protrusion to be restrained from moving axially and to be in contact with the pair of side walls.