| 摘要 |
PROBLEM TO BE SOLVED: To provide an earth drill which is equipped with a means for detecting the degree of opening of an enlarged base blade, enabling the degree of the opening of the enlarged base blade during the excavation of an enlarged base hole to be surely grasped by a simple structure. SOLUTION: A cable reel 37 for being driven by a hydraulic motor is provided on a rotary table 20 which is provided in the lower portion of a Kelly-bar driving unit 19 and rotated integrally with a Kelly-bar in the state of undergoing the ascendable/descendable insertion of the Kelly-bar 17. A leading end of a cable 34 wound around the cable reel 37 is connected to a slider 28 for bringing about the expansion/contraction operation of the enlarged bottom blade 25 of an enlarged bottom bucket 21. The degree of the opening of the enlarged bottom blade is computed by detecting the rotation of the cable reel 37 by a rotary encoder and detecting the amount of the movement of the cable. COPYRIGHT: (C)2009,JPO&INPIT
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