| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an excavation tool capable of surely expanding and contracting a diameter of a bit head. <P>SOLUTION: A disk-shaped plate 4 centered about an axis O is attached to a tip of a tool body 1, which is rotated around an axis O, so that the plate 4 is rotatable about the axis, and a bit head 7 retractable in a radial direction to the axis O is interposed between the plate 4 and the tool body 1. When the plate 4 is rotated, with respect to the tool body 1, in an opposite direction of a rotating direction T of the tool body 1 during excavating operation, the bit head 7 projects on a periphery side with respect to the radial direction, and when the plate 4 is rotated, with respect to the tool body 1, in the rotating direction T of the tool body 1 during excavation operation, the bit head 7 retracts on a radial inner periphery side with respect to the radial direction. <P>COPYRIGHT: (C)2012,JPO&INPIT |
