| 摘要 |
PROBLEM TO BE SOLVED: To provide an excavator which stably maintains bit devices such that ends of the respective bit devices protrude out of a pipe of the excavator, to thereby excavate accurate hole. SOLUTION: A bottom surface of a device 36 has recesses 52 formed therein, for housing the respective bit devices 58, and the recesses 52 also open in an external wall surface of the device 36. Each bit device 58 includes an eccentric shaft 60 erected on an upper surface thereof, and the eccentric shaft 60 is inserted into a shaft hole formed in the recess 52 of the device 36 in a slipout- preventive manner. When the device 36 is rotated in an excavating direction, the bit device is rotated in a relatively reverse direction about the eccentric shaft 60, and the bit device 58 collides on one of internal wall faces 53 of the recess 52 while having a front end thereof outward protrude from the recess 52 by a predetermined excavation amount out of the peripheral surface of the device 36. Thereafter, the bit device is rotated in the excavating direction while being stopped by the one internal wall face 53 as a stopper surface. When the device 36 is backward rotated, the bit device is housed in the recess 52.
|
