| 摘要 |
PROBLEM TO BE SOLVED: To provide double-pipe type excavating equipment which prevents a ring bit from being accidentally disconnected from an inner bit, even if an excavating force does not act, and which enables the inner bit to be surely disconnected from the ring bit, when the inner bit is recovered. SOLUTION: In this double-pipe type excavating equipment, an almost annular percussion imparting part 12 and a rotation imparting part 15 protruding to an outer peripheral side are provided on the outer peripheral surface of the inner bit 10; an almost annular percussion receiving part 22 and a rotation receiving part 25 protruding to an inner peripheral side are provided on the inner peripheral surface of the ring bit 20; and a rotation restraining part 13, which allows the free intrusion or abutment of a part of the receiving part 25 of the ring bit 20, is installed between the imparting parts 12 and 15 of the inner bit 10. The restraining part 13, which is recessed in an approximate U-shape, is integrally formed on the rear surface of the imparting part 12 of the inner bit 10. COPYRIGHT: (C)2005,JPO&NCIPI
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