| 摘要 |
PCT No. PCT/GB92/00644 Sec. 371 Date Dec. 9, 1993 Sec. 102(e) Date Dec. 9, 1993 PCT Filed Apr. 10, 1992 PCT Pub. No. WO92/18703 PCT Pub. Date Oct. 29, 1992.A hydraulic ram assembly is provided to be used, singly or in multiples, in raising a weighted member, such as a hammer (30) for pile driving, each having means whereby fluid used to extend a respective piston (26) can readily escape to give a sudden release, gravity induced return movement.
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