trepan a reverse flow under depression, under pressure - depression, or under pressure using a suction assisted by a jet

摘要

Drill cuttings are effectively removed from the bottom of a bore before they can adversely affect the operation of the bit. The bit includes a body member rotatably supporting individual cutter members. A shield means projects from the body member proximate the cutter members. A first portion of the shield means has an outside diameter substantially equal to the outside diameter of the cutter means and substantially equal to the diameter of the bore and a second portion having an outside diameter substantially less than the outside diameter of the cutter members and substantially less than the diameter of the bore. A first passage extending through the bit is adapted to provide communication with a vacuum source to assist in removing the drill cuttings. A second passage extending along the length of the bit is adapted to provide communication with a gas pressure source to assist in removing the drill cuttings. The second passage has a portion in communication with the first passage to provide a pressurized jet-assist to the vacuum removal of the drill cuttings.