| 摘要 |
PROBLEM TO BE SOLVED: To increase sealing function between an inner surface of a cylinder and an outer surface of a piston with a simple structure for providing high degree of vacuum in an evacuation chamber and avoid increase of slide resistance of the piston due to thermal expansion of a piston ring or the like in an oil-free type vacuum pump. SOLUTION: The oil-free type vacuum pump has an annular groove 6 engraved on the outer circumference surface of the piston 4 facing the inner surface of the cylinder 3, and has the piston ring installed in the annular groove 6. The piston ring is composed of a string shape body 7, The annular groove 6 having a width "h" wider than double of width of the string shape body is engraved on the piston outer circumference surface 21 in a piston slide direction. The string shape body 7 is wound and fixed in the annular groove 6 by a plurality of windings under a condition where adjacent string shape bodies are adhered. COPYRIGHT: (C)2009,JPO&INPIT
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