| 摘要 |
PROBLEM TO BE SOLVED: To provide a boring device capable of preventing the intake of excessive slime into a casing when boring under pressurized water. SOLUTION: This boring device is provided with a double pipe formed of the casing 3 having a ring bit 2 at the tip thereof and an inner rod 4 for supplying boring water. A movable bit 6 formed of a slime flow passage 8 in the periphery thereof and hit by the inner rod 4 is movably fitted in the inner periphery of the tip of the casing 3. A stopper 7 for opening/closing the slime flow passage 8 is provided in the rear of the movable bit 6. COPYRIGHT: (C)2004,JPO
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