Anti-Tracking Feature for Rock Bits
The harmful effects of tracking are reduced for a drill bit having roller cones with at least one of the outermost rows of active teeth containing one or more teeth having a height that does not extend to the height of at least one of the outermost rows on another roller cone on the bit. The crest on this tooth may have a length in a circumferential direction that is wider than an overall width of the tooth in the outer to inner direction. The invention may be used on any cutter row, not just the outermost row. The design may be used on a different roller cone or row, or more than one cutter row. The anti-tracking feature may be located between the leading and trailing edges of the tooth on one or more roller cones.
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This application claims priority to U.S. Provisional Pat. App. No. 61/046,508, filed on Apr. 21, 2008, and is incorporated herein by reference in its entirety.
BACKGROUND OF THE INVENTION1. Technical Field
The present invention relates in general to drill bits and, in particular, to an improved system, method, and apparatus for reducing the harmful effects of tracking with drill bits.
2. Description of the Related Art
A roller cone earth-boring drill bit has a number of cones, typically three, each of which is rotatably mounted to a bearing pin. Each cone rotates about its axis when the bit body rotates around the bit axis. The cones have cutting elements, often in rows, which may be teeth integrally formed in the cone metal, or tungsten carbide inserts pressed into mating holes in the cone metal.
Each cone has an outermost or heel row near a gage surface of the cone and one or more inner rows. One or more of the cones have cutting elements located near or on the nose of the cone. In some cases the cutting elements in the adjacent row closest to the heel row will be staggered or alternate with the cutting elements in the heel row.
The inner rows of each cone are arranged at different distances from the bit axis for cutting different portions of the borehole bottom. Normally at least two of the cones have heel rows that are located at substantially the same distance from the bit axis. When all three cones are rotated into a single section plane, the heel row cutting elements superimpose or overlap (at least partially) on one another. The inner rows are normally spaced at different distances from the bit axis and thus provide single row coverage on the remaining portions of the borehole bottom. When the cones are rotated about their axes, the rows of teeth make indentations on the borehole bottom. When the teeth fall into the same indentations on consecutive rotations, a detrimental process commonly referred to as “tracking” results.
With tracking, one or more rows of the cutting elements on one or more cones tend to fall into the same holes in the borehole bottom, thereby building up ridges on the bottom. These ridges are detrimental because they grow in height until they contact the supporting metal of the cone. This lowers the unit load on the cutting elements and causes undesirable erosion and wear.
In the prior art, attempts to reduce tracking typically consist of methods to vary pitch (i.e., the distance between center lines of the cutting elements) on overlapping heel rows on different cones, and/or within a single row on one cone. For example, a common approach uses a combination of a closely-spaced heel row on one cone and a wider pitch (e.g., 1.5 times the close pitch) on an overlapping heel row on another cone. A wider pitch tends to break up the ridges that form between the impressions made by the more closely-spaced heel row cutting elements. While workable, a wider pitch means fewer cutting elements and less durability. On the other hand, the more closely-spaced row is more likely to ball in softer, sticky formation. Thus, an improved solution for overcoming tracking without sacrificing bit life or penetration rate would be desirable.
SUMMARY OF THE INVENTIONEmbodiments of a system, method, and apparatus for reducing the harmful effects of tracking with drill bits are disclosed. A roller cone has a plurality of active teeth arranged generally in circumferential rows. At least one of the outermost rows contains one or more teeth having a projection that does not extend to the height of at least one of the outermost rows on another roller cone on the bit. This row is designed to engage and remove the formation that remains as a result of the uncut formation from the space between adjacent active teeth of the other roller cone. The crest on this tooth may have a length in a circumferential direction that is wider than an overall length of the tooth in the outer to inner direction.
The cutter design removes the peak of the uncut bottom left by the other roller cones, significantly removing the depth of the pocket and allowing the other roller cones to continue to cut with their crests rather than with the sides of their active teeth or with their cones. Tracking is reduced regardless of the tooth count in the other rows or weight on bit. The invention may be used on any cutter row that shares a common bit diameter and not just the outermost row. Moreover, the invention may be used on a different roller cone or row, or more than one cutter row that shares a common bit diameter.
The teeth on each cutter may be a combination of full projection cutting elements dispersed with any of the anti-tracking or tracking limiter elements described herein. The anti-tracking feature may be located between the leading and trailing edges of the tooth on one or more roller cones. The anti-tracking feature may also be formed more than once and in different locations on any tooth or combination of teeth. Furthermore, the invention may be used with gage cutting features, such as a “bar trimmer” aligned with the cone centerline and also at an angular position.
Alternatively, a heel row may have a high count of teeth on a roller cone with teeth configured at a depth that is shorter than a formation contact depth for active teeth on the other roller cones. The heel row also may be milled with narrow slots to define teeth having properties and features as described herein.
The foregoing and other objects and advantages of the present invention will be apparent to those skilled in the art, in view of the following detailed description of the present invention, taken in conjunction with the appended claims and the accompanying drawings.
So that the manner in which the features and advantages of the present invention, which will become apparent, are attained and can be understood in more detail, more particular description of the invention briefly summarized above may be had by reference to the embodiments thereof that are illustrated in the appended drawings which form a part of this specification. It is to be noted, however, that the drawings illustrate only some embodiments of the invention and therefore are not to be considered limiting of its scope as the invention may admit to other equally effective embodiments.
Referring to
Each roller cone 29 has a plurality of cutting elements 36 (
Referring now to
The embodiments of
Although heel tracking can be reduced by increasing the tooth count, such a configuration results in an increased tendency to ball, with less effective projection and lower rate of penetration. Furthermore, it is still subject to tracking although at a smaller distance between impressions. With the present invention, the detrimental effect of tracking is reduced even with low tooth counts in the other rows. The invention may be used on any cutter row that shares a common distance from the center of the bit and not just the outermost row as shown. Moreover, the invention may be used on multiple cutter rows, or within a single cutter row that has the same distance from the center of the bit.
In addition, the teeth on each cutter may be a combination of full-length cutting elements dispersed with any of the anti-tracking (or, tracking limiter) elements described herein. For example, as shown in
As shown in
Referring now to
The proper difference in projection of teeth 303 from the active teeth may be varied according to the application. In addition, teeth 303 may be in any combination of 100% hardfacing material, hardfaced milled teeth, tungsten carbide inserts, etc.
Another embodiment of the invention for a drill bit 401 is depicted in
One embodiment of an overall cutting profile for a bit constructed in accordance with the invention is shown in the superimposed view of
As described above,
If any cones share a common row position where the formation is generally removed by two cones, at least one cone could be populated with only the tracking limiter features. The shape of the active and/or tracking limiter features are not limited to traditional hardfaced radial teeth. The shapes of other either type could be any combination of pyramid, disk, non-hardened, hybrid, tungsten carbide inserts, etc.
This written description uses examples to disclose the invention, including the best mode, and also to enable those of ordinary skill in the art to make and use the invention. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal languages of the claims. While the invention has been shown or described in only some of its forms, it should be apparent to those skilled in the art that it is not so limited, but is susceptible to various changes without departing from the scope of the invention.
Claims
1.-25. (canceled)
26. An earth boring bit, comprising:
- a body having at least one bearing pin with an axis;
- a cone rotatably mounted to the bearing pin, the cone having a cutting surface;
- a disk fanned on an outward portion of the cutting surface of the cone, the disk having a circular edge extending circumferentially around the cutting surface of the cone concentric with the axis, the disk having slots formed therein spaced around a circumference of disk and extending generally radially relative to the axis, defining individual heel row teeth; and
- an adjacent row of teeth machined on the cutting surface of the cone adjacent and inward from the heel row teeth, each of the teeth in the adjacent row being generally pyramidal in configuration.
27. The bit according to claim 26, wherein each of the teeth of the adjacent row has a leading flank and a trailing flank sloping toward each other to define a crest.
28. The bit according to claim 26, wherein each of the slots has opposed side walls that are substantially parallel with each other.
29. The bit according to claim 26, wherein a circumferential width of each of the heel row teeth measured at the edge of the disk is greater than a circumferential width of each of the heel row teeth measured at a base of the slots.
30. The bit according to claim 26, wherein the edge of the disk defines a circumferentially extending crest of each of the heel row teeth.
31. The bit according to claim 26, wherein the disk has a conical outer surface, and the slots extend into the outer surface to define outer flanks for each of the heel row teeth.
32. The bit according to claim 26, wherein the disk has a conical inner surface, and the slots extend into the inner surface to define inner flanks for each of the heel row teeth.
33. An earth boring bit, comprising:
- a body having at east a plurality of bearing pins, each having a bearing pin axis;
- first, second and third cones, each rotatably mounted on one of the bearing pins, each of the cones having a cutting surface;
- a disk formed on an outward portion of the cutting surface of the first cone, the disk having a circular edge extending circumferentially around the cutting surface of the cone concentric with the axis, the disk having slots formed therein spaced around a circumference of the disk and extending generally radially relative to the axis, defining individual first cone heel row teeth;
- the edge of the disk defining a circumferentially extending crest for each of the first cone heel row teeth, each of the first cone heel row teeth having a greater circumferential width measured at the crest than at bases of the slots;
- the slots in the disk defining leading and trailing flanks for each of the first cone heel row teeth;
- an adjacent row of teeth machined on the cutting surface of the first cone adjacent and inward from the first cone heel row teeth, each of the teeth in the adjacent row being generally pyramidal in configuration; and
- the second and the third cone having heel row teeth with a circumferential width measured at a crest that is less that a circumferential width measured at a base of each of the heel row teeth of the second and third cones.
34. The bit according to claim 33, wherein a height of each of the heel row teeth of the second and third cones, measured from the bases to the crests, is greater than a height of the first cone heel row teeth, measured from the bases to the crests of the heel row teeth.
35. The bit according to claim 33, wherein the crests of the heel row teeth of the second cone have a length extending from an inward to outward direction that is greater than a circumferentially extending width.
36. The bit according to claim 33, wherein each of the slots has opposed side walls that are substantially parallel with each other.
37. The bit according to claim 33, wherein the disk has a conical outer surface, and the slots extend into the outer surface to define outer flanks for each of the first cone heel row teeth.
38. The bit according to claim 33, wherein the disk has a conical inner surface, and the slots extend into the inner surface to define inner flanks for each of the first cone heel row teeth.
39. An earth boring bit, comprising:
- a body having at least a plurality of bearing pins, each having a bearing pin axis;
- first, second and third cones, each rotatably mounted on one of the bearing pins, each of the cones having a cutting surface;
- a disk formed on an outward portion of the cutting surface of the first cone, the disk having a circular edge extending circumferentially around the cutting surface of the cone concentric with the axis, the disk having slots formed therein spaced around a circumference of the disk and extending generally radially relative to the axis;
- an adjacent row of teeth machined on the cutting surface of the first cone adjacent and inward from the disk, each of the teeth in the adjacent row being generally pyramidal in configuration;
- the second and the third cone having first and second cone heel row teeth, respectively;
- the second and third cone heel row teeth having crests that are a distance from the bearing pin axis greater than an outer diameter of the disk.
40. The bit according to claim 39, wherein a circumferential distance between adjacent ones of the slots is greater at an edge of the disk than at a base of the slots.
41. The bit according to claim 39, wherein each of the slots has opposed sides that are generally parallel with each other.
42. The bit according to claim 39, wherein the heel row teeth of the second cone are pyramidal in shape.
43. The bit according to claim 39, wherein the heel row teeth of the third cone have crests that are elongated and have lengths perpendicular to a direction of rotation of the cone.
Type: Application
Filed: Sep 7, 2011
Publication Date: Dec 29, 2011
Applicant: Baker Hughes Incorporated (Houston, TX)
Inventors: Robert J. Buske (The Woodlands, TX), James L. Overstreet (Tomball, TX), Rudolf Carl Pessier (Galveston, TX)
Application Number: 13/227,186
International Classification: E21B 10/16 (20060101);