| 摘要 |
PROBLEM TO BE SOLVED: To provide a piston which reliably prevents a ring from being loosened and coming off, and is manufactured at low cost. SOLUTION: In the piston P comprising a piston body 1 and a ring 2 fitted to the outer circumference of the piston body in which the piston body has a plurality of annular grooves 1a, 1b, 1c, 1d, 1e and 1f on the outer circumference along the axial direction, and comprises a ring body 2a along the outer circumference of the piston body formed by heating and softening a ring-disk shaped synthetic resin material A and pressing the material against the outer circumference of the piston body, and an inner circumferential side annular projection 2c formed of the synthetic resin material flowing in each annular groove, the bottom side of each annular groove is formed in a ridge-shaped section. COPYRIGHT: (C)2004,JPO&NCIPI
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