Boring or penetrating the earth – Bit or bit element – Rolling cutter bit or rolling cutter bit element
Reexamination Certificate
1999-04-29
2001-05-08
Neuder, William (Department: 3673)
Boring or penetrating the earth
Bit or bit element
Rolling cutter bit or rolling cutter bit element
C175S339000, C175S353000
Reexamination Certificate
active
06227314
ABSTRACT:
TECHNICAL FIELD
This invention relates in general to earth-boring bits and in particular to earth-boring bits with six-point stabilization to resist lateral vibration.
BACKGROUND ART
One type of earth-boring bit has a body with three legs formed on it. A cutter is rotatably mounted to each of the legs, the cutter having teeth or hard-metal inserts. Drilling fluid is pumped down the drill string and discharged out three nozzles. Each nozzle is located between two of the bit legs. The nozzles are housed in a nozzle boss which is a cylindrical protruding portion on a curvilinear exterior surface of the bit body. The drilling fluid strikes the bottom and returns back up channels adjacent each side of each of the nozzle bosses. The bit will contact the borehole wall at three points, each of the points being on the heel row of each of the cutters. The point of contact is on a leading portion of each cutter. Under certain circumstances, a bit may experience rapid lateral displacements, such as when drilling in an oversized hole, during horizontal drilling, within dog legs, or within key seats. These lateral displacements cause disruptions from desired rotation about the geometric centerline of the bit, which is the intended rotational axis. Lateral displacements can cause accelerated wear and catastrophic failure of the cutting elements. Wear resistant inserts have been employed on the upper portions of the bit legs to resist lateral vibration. In this prior art type, the centerline of the wear resistant insert pattern is generally directly above the rotational axis of each cutter. While such wear resistant inserts are beneficial, they do not adequately arrest severe lateral vibration.
Another prior art bit has a stabilizing area containing wear resistant inserts between each of the bit legs. Each stabilizing portion or pad encloses one of the nozzles, replacing the protruding nozzle boss used in other types of bits. The centerline of each stabilizing pad is diametrically opposed to the borehole wall contact point of one of the cutters. The stabilizing pads add three more stabilizing points offset circumferentially or rotationally from the stabilizing points on the cutters. This six-point contact adds more lateral stability to the bit than the prior three-point contact bits. However, the relatively large stabilizing pad on each bit leg tends to reduce the return flow area for drilling fluid and cuttings on smaller diameter bits more than it does on larger diameter bits, where this type of stabilizing pad is successfully used in many commercial applications.
SUMMARY OF INVENTION
In the bit of this invention, each of the bit legs has an upper portion protruding radially from the bit body and a lower portion extending below the bit body. The lower portion of each bit leg is offset circumferentially from the upper portion. The lower portion is inclined so as to position the cutter borehole contact point in a leading direction relative to the upper portion of the bit leg. The upper portion of the bit leg has low friction wear-resistant elements which are preferably slightly under the gage diameter, providing stabilizing areas. The centerline of each stabilizing area is approximately diametrically opposed to the borehole contact point of one of the cutters. The additional stabilizing areas result in six-point borehole contact to resist lateral vibration during drilling.
A nozzle boss is located between each of the bit legs. Each nozzle boss protrudes radially outward from the curvilinear exterior surface of the bit body. Each nozzle boss is generally cylindrical and spaced between two of the bit legs. Furthermore, each nozzle boss may be inclined generally at the same angle of inclination as the lower portion of the bit leg. This inclination results in an inclined flow channel between the nozzle boss and the leading edge of the inclined lower portion of the bit leg. There is also an inclined flow channel between the nozzle boss and the trailing edge of the adjacent bit leg.
REFERENCES:
patent: Re. 32495 (1987-09-01), Coates
patent: 2885186 (1959-05-01), Hammer
patent: 4558754 (1985-12-01), Childers et al.
patent: 5289889 (1994-03-01), Gearhart et al.
patent: 5415243 (1995-05-01), Lyon et al.
patent: 5586612 (1996-12-01), Isbell et al.
patent: 5755297 (1998-05-01), Young et al.
patent: 5791423 (1998-08-01), Overstreet et al.
Hughes Christensen HydraBoss; Hydraulically Enhanced Drill Bits; 1997.
U.S. application No. 08/690,887 filed Sep. 20, 1997, Pessier et al.
Brannon Kenneth C.
Grimes Robert E.
Ricks Gregory L.
Schader Kevin W.
Zadrapa Glenn R.
Baker Hughes Inc.
Bracewell & Patterson L.L.P.
Bradley James E.
Neuder William
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