| 摘要 |
<p>A drilling apparatus boring a hole in soil or rock, the working drill bit assembly of which comprises a ring bit unit (5), boring the outer portion of hole and a pilot bit unit (2), boring the center of hole, which units are detachable from each other and, upon, drilling locked to rotate together at least in one direction and able to move axially in regard to one another in guides (19) or grooves (8). The hammering gear is direct behind the drill bit assembly while bit (2) drilling the bore center is fixed to rod (1) of the hammering gear and the glide guides/grooves (8), are arranged between pilot bit (2) and ring bit (5).</p> |
