| 摘要 |
PURPOSE:To raise the verticality accuracy of kelly bar by a method in which a driver to hold, turn, and drive the kelly bar is provided in a vertically movable manner along a leader vertically erected on the ground's surface, ad a motor is used for a rotary drive source. CONSTITUTION:A leader 2 is moved to a construction site by a traveling vehicle 1 and vertically supported by an arm 5. A drive 11 holding a kelly bar 8 by a holder 12 is lowered along the leader 2 and a drilling bucket 10 is landed. The motor of the driver 11 is operated to turn the bar 8, and when wires 27 and 40 are loosened, the bucket 10 penetrates into the ground under the weight of the driver 11 to excavate a hole.
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