| 摘要 |
PURPOSE: To move a movable body substantially in parallel by connecting the movable body, a ram, and a drill rod in a non-friction manner mutually. CONSTITUTION: Since the elongation on a thin wall part 64 side of a drill rod 12 and the compression on a thin wall part 65 side of a ram 26 are larger than those on thick wall part sides of each when pressure medium acts in a rotating drill head 10, the ram 26 is curved to the thin wall part 65 side, and the drill rod 12 is curved to the thick wall part side. Here, since the curve line of the ram 26 coincides with the curve line of the drill rod 12 completely or substantially completely, a force vertical to an axis does not occur at all or slight force only occurs between the ram 26 and the drill rod 12. As a result, a position of a cutting bit 18 is displaced in a scope ofμm on a trajectory which is curved and extended in arrow 63 direction vertical relative to a rotary shaft 70 from a stationary position due to the action of pressure medium. The displacement of the cutting bit 18 is larger than a distance at which the center of the movable body 28 moves due to pressure change for a fixed member 11 as a base. |
