| 摘要 |
PURPOSE:To improve durability and operability, by a method wherein a piston is designed to have an outer size decreased over the inner size of a cylinder, and O-rings are secured to the outer peripheral surface of the piston. CONSTITUTION:A piston 4 is designed to have an outer size decreased over the inner size of a chamber 2 of a cylinder 3, O-rings 15 and 16 are secured to the outer peripheral surface of the piston. A hollow part 10, having its front end surface being closed and its rear end surface being open, is formed in the inner surface of the piston 4, and the front end side of the hollow part 10 is communicated with the outside of the piston 4 through a pass 11. This constitution prevents the piston 4 from direct contact with the inner wall of the chamber 2 but causes the piston to make contact with the inner wall through the O-rings 15 and 16, resulting in improvement of durability and operability.
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