Boring or penetrating the earth – Bit or bit element – Rolling cutter bit or rolling cutter bit element
Reexamination Certificate
1999-01-25
2001-07-17
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Rolling cutter bit or rolling cutter bit element
C384S095000
Reexamination Certificate
active
06260635
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to rotary cone drill bits and more specifically to a rotary cone drill bit with an enhanced journal bushing.
BACKGROUND OF THE INVENTION
Various types of rotary drill bits or rock bits may be used to form a borehole in the earth. Examples of such rock bits include roller cone bits or rotary cone bits used in drilling oil and gas wells. A typical roller cone bit comprises a bit body with an upper portion adapted for connection to a drill string. A plurality of support arms, typically three, depend from the lower portion of the bit body with each support arm having a spindle or journal protruding radially inward and downward with respect to a projected rotational axis of the bit body.
A cutter cone assembly is generally mounted on each spindle or journal. Each cutter cone typically has a opening at its base, and a cavity extending from the base almost to the tip of the cutter cone. The cavity is formed such that it conforms with the associated journal. The cutter cone is supported rotatably on bearings acting between the exterior of the journal and the interior of the cutter cone assembly. The bearings in a typical rotary cone drill bit are heavily loaded during downhole drilling operations. In such drilling operations, the drill bit is rotated in a borehole, which causes the associate cutter cone assemblies to rotate on their respective journals. The drill bit typically operates at a low speed with heavy weight applied to the bit. This produces a high load on the associated bearings.
The journal typically includes a thrust flange. The top of the thrust flange typically bears the load applied to the journal that is generally parallel to the axis of the journal about which the cutter cone rotates. Such forces are applied to the journal by the cutter cone assembly, and to the cutter cone assembly by the borehole wall. A thrust washer or bushing may be placed between the thrust flange and the cutter cone assembly to help bear this load. In addition, the thrust flange may also be used to contain the ball bearings. In such a situation, the thrust flange also must bear the load applied by the ball bearings when forces are acting to pull the cutter cone assembly off of its respective journal.
Drill bits also typically include a journal bushing. The journal bushing is positioned around the journal, and between the journal and the cutter cone assembly. The journal bushing is used to bear some of the forces transmitted between the journal and the cutter cone assembly, and to facilitate the rotation of the cutter cone assembly about the journal.
SUMMARY OF THE INVENTION
In accordance with teachings of the present invention, a roller cone drill bit having support arms with a spindle or journal extending from each support arm, and a respective cutter cone assembly rotatably mounted thereon is provided with an improved journal bearing.
The present invention allows the load carrying capability of a drill bit journal bearing or bushing to be increased. The present invention teaches increasing the length of the journal bushing by using the ball bearings to retain the journal bushing at a desired location between the journal and the cutter cone assembly. Normally, the journal bushing is retained by a flange formed on the interior surface of the cutter cone assembly. In the present invention, this flange is removed, and the ball bearings are used as a retention device for the journal bushing. With the flange removed, the length of the journal bushing may be increased.
Technical advantages of the present invention include an increase in the load carrying capabilities of the journal bushing and the drill bit bearing system due to the increase in the length of the journal bushing. In addition, the use of a lengthened journal bushing increases the stability of the cutter cone assembly on the journal. This increased stability results in an increased useful life of the drill bit.
Other technical advantages will be readily apparent to one skilled in the art from the following figures, descriptions, and claims.
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Bagnell David
Dresser Industries Inc.
Formby Betty
Groover Robert
Groover & Associates
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