| 摘要 |
PROBLEM TO BE SOLVED: To overcome a difficulty of returning of an excavating bit extended from side to side to its compacted position in an extensively excavated portion, the difficulty being caused by resistance of earth and gravel, in order to contract an excavating rod for pulling up the same and in order to insert a tendon into the extensively drilled hole after the pulling-up. SOLUTION: There is provided an extending excavator which is constructed in the following manner. When an external pipe 1 is rotated in a direction (rotating direction at the time of drilling) reverse to a bent direction of an upper end hook portion of a slit 7 together with a bit joint 2, a pin 8 is engaged with a bent end to rotate a bit main body 3 in the same direction, whereby drilling is achieved by an excavating bit 6. On the other hand, when the external pipe 1 is rotated in the bent direction (direction reverse to the rotating direction at the time of the drilling) of the upper end hook portion of the slit together with the bit joint, the pin moves from the bent end to a linear portion. Then, by raising the external pipe with the pin remaining at the linear portion, the pin slips out of a lower opening of the slit, and at the same time the bit main body disengages from the bit joint, whereby the former is separated from the latter.
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