System for in situ replacement of cutting means for a ground drill

Abstract

A retractable drill bit system (10) comprises a drive sub (18) which is adapted for connection to a lower end of a drill (12), a tool (20) for installing and retractable drill bit segments (22) from the drive sub (18); and an insert (24) for selectively locking the bit segments (22) to an end of the drive sub (18) and releasing the bit segments (22). A plurality of recesses (5B) are formed about an inner circumferential wall at one end of the drive sub (18) and a landing seat (32) formed about the inner wall upstream of the recesses (58). The area of the interior wall between the landing seat (32) and recesses (58) is profiled with a series of tapered and level surfaces. The tool (20) includes a slidable cradle (176) extending from one end about which the bit segments (22) are held during installation and retrieval. The bit segments (22) being held in place about the cradle by an elastic band (198). The insert (24) is provided at one end with a series of keyways (218) which locate over the bit segments (22) when the bit segments are locked to the drive sub (18). The insert (24) is always retained within the drive sub (18). Bit segments (22) are carried by the tool (20) to the drive sub (18) and locked in place by the insert (24). The tool (20) can then be withdrawn and the drill (12) operated in the normal manner. To receive the bit segments (22), the tool (20) is relowered into the drill and then withdrawn a short distance to retract the insert (24) so that the bit segments (22) collapse back onto the cradle (176) and can then be withdrawn from the drill (12).

Dependencies are inferred from the claim text.