Drilling tool

Patent metadata

Field	Value
Publication number	US-10107045-B2
Application number	US-201515126055-A
Country	US
Kind code	B2
Filing date	Mar 10, 2015
Priority date	Mar 31, 2014
Publication date	Oct 23, 2018
Grant date	Oct 23, 2018

Abstract

The drilling tool includes a circular-cylindrical casing pipe; an annular ring bit disposed at a leading end of the casing pipe so as to be coaxial with the casing pipe and rotatable around a central axis of the casing pipe; and a pilot bit inserted into the casing pipe and has a leading end disposed at an inner peripheral part of the ring bit. The ring bit is engaged with the pilot bit in a rotational direction, and thereby is rotatable integrally with the pilot bit and is locked to the leading end of the pilot bit. Drilling tips are mounted on the leading ends of the pilot bit and the ring bit, and first drilling tips at an outermost periphery of the pilot bit and second drilling tips at an innermost periphery of the ring bit overlap each other in a rotational trajectory around the central axis.

First claim

The invention claimed is:

1. A drilling tool comprising:
a circular-cylindrical casing pipe;
an annular ring bit that is disposed at a leading end of the casing pipe so as to be coaxial with the casing pipe and rotatable around a central axis of the casing pipe; and
a pilot bit that is inserted into the casing pipe from a rear end side of the casing pipe and has a leading end disposed at an inner peripheral part of the ring bit, wherein
the ring bit is engaged with the pilot bit in a rotational direction during drilling, and thereby is rotatable integrally with the pilot bit around the central axis and is locked to the leading end of the pilot bit in a direction of the central axis,
a plurality of drilling tips are mounted on the leading ends of the pilot bit and the ring bit so as to protrude therefrom, and
a first drilling tip positioned at an outermost periphery of the pilot bit and a second drilling tip positioned at an innermost periphery of the ring bit overlap each other in a rotational trajectory around the central axis during drilling.

2. The drilling tool according to claim 1 , wherein
a protruding strip extending in the direction of the central axis is formed at an outer periphery of the leading end of the pilot bit,
a recessed groove capable of accommodating the protruding strip is formed at an inner peripheral part of the ring bit, and
the pilot bit and the ring bit are engaged with each other in the rotational direction during drilling by accommodating the protruding strip in the recessed groove.

3. The drilling tool according to claim 2 , wherein
a leading end of the protruding strip is continuous with a leading end surface of the pilot bit,
the recessed groove is open to a leading end surface of the ring bit,
the first drilling tip positioned at the outermost periphery of the pilot bit is mounted on a leading end of the protruding strip so as to be protruded therefrom, and
the second drilling tip positioned at the innermost periphery of the ring bit is mounted between openings of the recessed grooves adjacent to each other in a circumferential direction of the ring bit, and is protruded from the leading end of the ring bit.

4. The drilling tool according to claim 2 , wherein
n recessed grooves are formed at the inner peripheral part of the ring bit,
each recessed groove is formed such that a central angle at which both ends of the recessed groove in the circumferential direction are formed with respect to the central axis falls within a range of 180/n±10(°), wherein “n” is an integer equal to or greater than 1.

5. The drilling tool according to claim 1 , wherein the ring bit is removable with respect to the pilot bit so as to be separated from the casing pipe to the leading end side in the direction of the central axis.

6. The drilling tool according to claim 1 , wherein the ring bit is locked to the casing pipe to the leading end side in the direction of the central axis.

Assignees

• Mitsubishi Materials Corp

Inventors

• Nakamura Kazuyoshi
• Ota Hiroshi

Classifications

• E21B10/26

  Drill bits with leading portion, i.e. drill bits with a pilot cutter; Drill bits for enlarging the borehole, e.g. reamers (percussion drill bits with leading portion E21B10/40) · CPC title

• E21B10/64 Primary

  characterised by the whole or part thereof being insertable into or removable from the borehole without withdrawing the drilling pipe · CPC title

• E21B10/60

  characterised by conduits or nozzles for drilling fluids (for roller bits E21B10/18; for percussion drill bits E21B10/38) · CPC title

• E21B10/46

  characterised by wear resisting parts, e.g. diamond inserts · CPC title

• E21B7/208

  using down-hole drives (E21B7/203 and E21B7/206 take precedence) · CPC title