Claims
- 1. A drag-type drill bit comprising:
- a bit body having an operating end face;
- and a multiplicity of superhard cutting elements interlocked to said bit body, said cutting elements defining a multiplicity of cutting areas dispersed over said operating end face of said bit body in a pattern adapted to cause said cutting areas to cut an earth formation to a desired three-dimensional profile as said bit body is rotated, said cutting areas having back rake angles which become more negative with distance from said profile.
- 2. The apparatus of claim 1 wherein each of said cutting areas has, respectively, a plurality of back rake angles which become more negative with distance from said profile.
- 3. The apparatus of claim 2 wherein each of said cutting elements defines a respective one of said cutting areas.
- 4. The apparatus of claim 3 wherein each of said cutting areas defines a concave curve in the plane of measurement of said back rake angles.
- 5. The apparatus of claim 2 wherein each of said cutting elements has a rear face opposite said cutting area, and wherein said bit body is configured to underlie and support a substantial portion of each such rear face.
- 6. The apparatus of claim 5 wherein there is a respective self-sharpening edge at the interface between each such cutting element and said bit body.
- 7. The apparatus of claim 6 wherein each of said cutting areas defines a concave curve in the plane of measurement of said back rake angle.
- 8. The apparatus of claim 7 wherein each of said cutting elements is a wafer comprising polycrystalline diamond.
- 9. The apparatus of claim 8 wherein said bit body comprises a tungsten carbide matrix material.
- 10. The apparatus of claim 7 wherein each of said cutting areas defines a portion of a cylinder.
- 11. The apparatus of claim 3 wherein each of said cutting elements is a wafer comprising polycrystalline diamond, and wherein said bit body comprises a tungsten carbide matrix material.
- 12. The apparatus of claim 2 wherein said cutting elements are arranged in a multiplicity of groups, each of said cutting areas being defined jointly by the cutting elements in a respective one of said groups.
- 13. The apparatus of claim 12 wherein each of said cutting elements has a cutting face, and wherein the cutting faces of each such group are arranged in a mosaic-like pattern to define the respective cutting area.
- 14. The apparatus of claim 13 wherein the cutting faces of each such group are arranged in generally parallel rows, the cutting faces in adjacent rows of such group being staggered.
- 15. The apparatus of claim 14 wherein each of said groups generally defines a cutting edge for engaging such earth formation, and said rows of each such group extend transverse to said cutting edge.
- 16. The apparatus of claim 13 wherein each of said cutting elements has a rear face opposite said cutting face, and wherein said bit body is configured to underlie and support a substantial portion of each such rear face.
- 17. The apparatus of claim 12 wherein each of said cutting faces is generally planar.
- 18. The apparatus of claim 12 wherein the cutting elements of each of said groups define a self-sharpening edge at the interface with said bit body.
- 19. The apparatus of claim 12 wherein each of said cutting elements is a thin block comprising polycrystalline diamond.
- 20. The apparatus of claim 19 wherein said bit body comprises a tungsten carbide matrix material.
- 21. The apparatus of claim 20 wherein said bit body comprises a multiplicity of blades radiating across said operating end face and having respective leading surfaces with respect to an intended direction of rotation of such bit, said cutting elements being mounted on said blades with said cutting faces facing outwardly along said leading surfaces.
- 22. The apparatus of claim 21 wherein at least some of said blades have a plurality of distinct groups of said cutting elements thereon, and the groups of cutting elements on adjacent blades are staggered.
- 23. The apparatus of claim 22 wherein each of said blades has such a group of cutting elements thereon, extending along a major portion of the length of said blade.
CROSS REFERENCE
This is a continuation-in-part application of U.S. patent application Ser. No. 468,668 filed Feb. 22, 1983 now U.S. Pat. No. 4,538,690.
US Referenced Citations (9)
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
468668 |
Feb 1983 |
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