| 摘要 |
PROBLEM TO BE SOLVED: To eliminate return failure of a piston while compressed air is surely stored in a return air chamber, and to prevent reduction of thrust force of the piston caused by inflow of the compressed air in the return air chamber into the front of the piston at the time of fastening a screw. SOLUTION: The piston comprises a main piston 21 and an auxiliary piston.The compressed air is supplied to the return air chamber 20 from the time when a seal part 45 of the main piston 21 passes through a compressed air outflow hole 23. After the main piston 21 abuts on a piston bumper 31, the compressed air in a return air chamber 20 is prevented from being applied to the auxiliary piston by such abutting, and the thrust force of the piston is prevented from being reduced. COPYRIGHT: (C)2005,JPO&NCIPI
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