| 摘要 |
<p>A reverse circulation, pneumatic drilling assembly (10) wherein the bit assembly is operatively connected to a dual wall pipe assembly (12). A supply of compressed air is conducted through the annulus (20) of the dual wall pipe assembly (12) to a down hole pneumatic hammer (13). Exhaust air from the down hole hammer (13) is directed to the bit assembly for continuous removal of drilling debris through a central evacuation tube (43) of the dual wall pipe assembly (12). Sections of the dual wall pipe are joined by hex head couplings (180, 182) which are quickly and easily engaged and disengaged.</p> |
