| 摘要 |
<p>A flushing means for drilling tools comprises a guide member (10) carrying a drill bit (20) and being rotatably centered by the mouth of a casing tube (11) which is adapted to follow the drilling tool downhole during drilling. The drill bit (20) has a bit portion (22) that projects laterally beyond and is spaced axially in front of the casing tube (11) so as to drill a hole larger than the casing tube (11). There are external flushing grooves (70,71) on the guide member (10) adapted to lead the outflow of flushing medium and debris from the hole during drilling into the casing tube (11). At least one of these grooves (70) extends from front to rear of the guide member (10). One or more further grooves (71) are open towards said rear while ending blindly into the periphery of the guide member (10) spaced from its front. By retraction of the guide member (10) its front enters the casing tube (11). That closes the blind grooves (71) and an intensified flushing is thus possible via the remaining open grooves (70) that extends from front to rear of the guide member (10). The cutting front (40) of the bit portion (22) is flushed rotatively in counter flow to the rotational drilling direction (8) towards the full length groove (70).</p> |
