Boring or penetrating the earth – Cutter element laterally shiftable below ground – Cutter element shifted by cam or gear axially rotatable...
Reexamination Certificate
1998-07-24
2001-04-03
Neuder, William (Department: 3672)
Boring or penetrating the earth
Cutter element laterally shiftable below ground
Cutter element shifted by cam or gear axially rotatable...
C175S286000, C175S389000
Reexamination Certificate
active
06209665
ABSTRACT:
BACKGROUND OF THE INVENTION
Eccentrically mounted underreamers are known which include an arm which travels in an orbit for underreaming operation, and which are retractable toward the hole axis for tool removal purposes. However, eccentrically mounted underreamers can be diverted off-axis if the underreamer encounters rock fragments, buried metal objects, etc. Any diversion of a large drill bit is unacceptable in most drilling operations, and particularly where a series of closely spaced holes are being formed. The installation of casing in a drilled ground hole is also greatly hindered by any such diversion.
Other known underreaming equipment utilizes three bit mounted plates which are outwardly displaceable, but which incorporate a total working surface which is substantially less than the perimeter of the bore. Such undersized plates are subject to excessive wear and result in slow drilling operation.
Underreaming can also be achieved by use of a crown or ring bit, but components of those bits must be left in the underreamed area when drilling is complete, which is costly and otherwise unacceptable in some drilling operations.
Each of these problems is addressed by my co-pending U.S. application Ser. No. 08/674,123, and by the additional related underreamer embodiments disclosed and claimed below.
In addition to the foregoing problems associated with known underreamers, quick and efficient removal of drilling debris from the hole and drilling bits remains a problem. In my U.S. Pat. No. 5,511,628, which is hereby expressly incorporated by reference into this application, I disclosed a pneumatic down-hole drill with a central evacuation outlet. The apparatus of U.S. '628 permits continuous evacuation of large debris fragments through a central axial bore formed in the bit and through a central evacuation tube attached thereto. Compressed air is directed downwardly through peripheral channels, under the drill bit, and into a central evacuation tube. The flow of compressed air through the central evacuation tube provides continuous and efficient removal of earthen fragments from the bore, including rapid removal of fragments that would be too large for removal through peripheral pathways along the casing.
However, a need remains for a reverse circulation pneumatic drill which provides for underreaming of the bore, continuous evacuation of drilling debris fragments from the drilling face in the bore, and for ready removal of the drill bit through the casing during or after completion of the drilling operation.
SUMMARY OF THE INVENTION
The present invention is embodied in a reverse circulation system that addresses the shortcomings of the prior art.
It is therefore an object of the invention to provide an underreamer that includes a pilot bit on which are mounted underreamer arms which can be extended and retracted by relative rotation between the pilot bit and the underreamer arms. Each underreamer arm includes a strengthening boss. The strengthening boss includes axial bearing surfaces that engage corresponding axial surfaces of the pilot bit. The bearing surfaces of the arm bosses and the bits include surfaces shaped to extend the arms as the pilot bit is rotated relative to the pilot bit. Surfaces are also provided for locking the arm in its extended underreaming position. As the bit is rotated in the opposite direction, the locking surfaces disengage and the arm can be retracted without vertical movement of the driver.
In another aspect of the invention, provision is made to continually flush the bit with compressed air which is exhausted from the down hole hammer. The flow of exhaust air is routed through porting in the bit assembly into the central evacuation tube. A second flow of compressed air may also be provided to continually flush the perimeter region of the bit. In one embodiment, the perimeter flushing air is received from compressed air introduced at the well-head to pressurize the casing.
These and other aspects of the invention will be described in further detail with reference to the drawings.
REFERENCES:
patent: 5052503 (1991-10-01), Lof
patent: 5186265 (1993-02-01), Henson et al.
patent: 5511628 (1996-04-01), Holte
patent: 5978222 (1999-11-01), Holte
Marger & Johnson & McCollom, P.C.
Neuder William
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