| 摘要 |
PROBLEM TO BE SOLVED: To maintain a ride-up amount of a brush to an approximately constant value while avoiding complexity of a structure of a brush holder to the utmost. SOLUTION: A collet 50 is forwarded in resistant to urging force of a spring 66 by application of a liquid pressure of a liquid pressure cylinder 52. A brush retaining unit 20 is forwarded by a constant distanceαwith the collet 50 in the former stage of positive direction operation of the liquid pressure cylinder 52. The forwarding of a tapered member 90 is inhibited in the latter stage of the positive direction operation and the collet 50 is forwarded to the brush retaining unit 20. When the liquid pressure of the liquid pressure cylinder 52 is canceled, the collet 50 is retreated by the urging force of the spring 66. When tapered surfaces 88, 98 are engaged with each other, the tapered member is together retreated. Thereafter, when the collet 50 is further retreated in the state that the retreating of the tapered member 90 is inhibited, the tapered surfaces 88, 98 are pressed each other and an inner peripheral surface 86 and a shaft part 38 are again friction-engaged. The brush 32 is axially pushed out by a set amountαin every number of set working. COPYRIGHT: (C)2004,JPO
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