| 摘要 |
PROBLEM TO BE SOLVED: To generate an oil shock efficiently, and to utilize the generated oil shock effectively. SOLUTION: A hydraulic cylinder 1 is expanded and contracted by discharged oil from a hydraulic pump 5, a pile 3 is pressed in and pulled out to and from a ground 4 by the expansion-contraction force of the hydraulic cylinder 1 while a hydraulic-fluid flow being discharged from the hydraulic pump 5 and flowing in an electromagnetic on-off valve 11 is closed suddenly by the electromagnetic on-off valve 11, and a generated oil shock is introduced to the hydraulic cylinder 1 and the expansion-contraction force of the hydraulic cylinder 1 is assisted. The length of a pipeline reaching the discharge opening (a point (f)) through a point (b) from a place (a point (a)), where oil shock waves are generated, is taken sufficiently, and the time required for the propagation of oil shock waves is lengthened at that time. The oil shock waves are propagated at acoustic velocity, and reciprocate as shown in a-b-f-b-a at a time and disappear, but the propagation time is made longer than the response time of a check valve 10 and the time required for operating the closing of the electromagnetic on-off valve 11.
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