| 摘要 |
PROBLEM TO BE SOLVED: To facilitate the cleaning of a ring groove formed in the inside of a piston ring. SOLUTION: An O-ring 30 around a piston 12 maintains air tightness in contact with a cylinder 13. However, when the piston 12 is pulled from the cylinder 13 in order to wash, the obstacle around a cylindrical plastic wear ring 28 is removed. Therefore, the diameter of the wear ring 28 increases from an axial slit 29 and the wear ring 28 is moved along the outside of a flange 27, so that the O-ring 30 is freely moved. Accordingly, by moving the O-ring 30 along the axis of the piston 12, cleaning becomes possible.
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