| 摘要 |
PROBLEM TO BE SOLVED: To provide a drive for a rotary press-in pile capable of driving the pile at high torque and, if necessary, setting torque low. SOLUTION: The rotary press-in pile is rotated and driven into the ground by a vertically movable pile drive having a hydraulic motor, At least two hydraulic motors whose displacements are variable depending on control pressure are provided in parallel with each other via a selector valve 11 from a hydraulic pump 10. In a flow passage where a supply passage 25 and a discharge passage 26 for pressure oil to and from the hydraulic motors 21 and 22 are in communication with each other, a circulating valve 23 is provided for shutting off a supply passage 27 and a discharge passage 28 to and from the hydraulic motor 22 and for selecting either the supply passage 27 or the discharge passage 28 for the hydraulic motor 22 in such a manner that the supply path and the discharge passage are in communication with each other. When low torque is required, the circulating valve 23 is shifted to drive the pile using only the hydraulic motor 21.
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