| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a leading body for drilling ground, and a ground drilling machine, which can enhance the removability of excavated soil and can properly maintain excavating performance. <P>SOLUTION: In a pilot head 20 for use in the ground drilling machine, a jet orifice 22A for emitting a jet of an excavating liquid is opened in the state of being directed to a rear side at an angleθ1 (168°) within the range of an obtuse angle with respect to a rotational central axis N. Thus, when a leading hole D is excavated from a starting shaft, the flow velocity of the excavating liquid, which flows to the side of the starting shaft from the tip side of the leading hole D, can be increased, and the excavated soil, which is produced by the excavation, can be efficiently removed for the great improvement of earth-removability. <P>COPYRIGHT: (C)2004,JPO</p> |
