Claims
- 1. A boring head for use in mounting to a drill pie of a rotary drilling rig for enlarging a pilot bore in horizontal boring, the boring head comprising;
- (a) an axial member positioned along a central axis of the boring head for connecting the boring head to the drill pipe of the drilling rig;
- (b) a plurality of pockets mounted about the periphery of said axial member, each said pocket being externally configured for fixed attachment to said boring head and having an internal cavity with a longitudinal axis generally parallel to said central axis, said cavities being tapered along said longitudinal axis;
- (c) a plurality of bit bodies fitting tightly within said tapered cavities; and
- (d) an independently rotatable cutter bit mounted on each said bit body and rotating about a rolling axis, fixed with respect to its said bit body and extending at an acute angle between ten degrees and eighty degrees relative to said central axis.
- 2. The boring head according to claim 1, wherein said axial member further comprises a concentrically attached cylindrical guide of a diameter chosen to engage said pilot bore.
- 3. The boring head according to claim 1, wherein said axial member comprises:
- a cylindrical tubing having a connector adapted for securing said cylindrical tubing to the drill pipe for retaining the boring head on the drill pipe.
- 4. The boring head according to claim 1, wherein at least one of said plurality of pockets is mounted at a first radial distance from said central axis, said first radial distance being less than a second radial distance at which at least one other said pocket is mounted, so that a first said rotatable cutting bit, fitted into said at least one pocket, and a second said rotatable cutting bit, fitting into said at least one other pocket, follow offset arcuate paths when said axial member is rotated.
- 5. The boring head according to claim 4, wherein the first radial distance from the central axis is substantially equal to the radius of the pilot bore, and the second radial distance is greater than the radius of the pilot bore.
- 6. The boring head according to claim 4, wherein the difference between the first radial distance and the second radial distance is such that said first and second cutter bits cut across different but overlapping widths of arcuate cutting paths relative to the central axis.
- 7. The boring head according to claim 4, wherein said axial member comprises: a cylindrical tubing having a connector adapted for securing said cylindrical tubing to the drill pipe for retaining the boring head on the drill pipe.
- 8. A replaceable cutter bit assembly for mounting on a boring head to be driven by a rotary drilling rig drill pipe, comprising:
- (a) a pocket having a longitudinal axis, the pocket being internally tapered along said longitudinal axis and externally configured for fixed attachment to said boring head;
- (b) a bit body, said bit body being externally tapered and fitting tightly within said pocket;
- (c) an independently rotatable cutter bit mounted on said bit body so as to rotate about a rolling axis, fixed with respect to said bit body and extending at an acute angle ranging between ten degrees and eighty degrees relative to said longitudinal axis; and
- (d) retaining means acting alone said longitudinal axis for holding said bit body in said pocket.
- 9. The replaceable cutter bit assembly according to claim 8 and further comprising:
- an axial member for connection with said drill pipe, with said pocket being fixedly attached to said axial member.
- 10. The replaceable cutter bit assembly according to claim 8, wherein said retaining means comprises a threaded bolt acting along said longitudinal axis for holding said bit body in said pocket.
- 11. A method for replaceable mounting of independently rotatable cutter bit assemblies on a boring head, the boring head having a longitudinal axis, the method comprising the steps of:
- attaching to the boring head a pocket that is externally configured for fixed attachment to the boring head and having an internally tapered cavity matching a tapered body and oriented to receive the tapered body of an independently rotatable cutter bit, the tapered cavity having a longitudinal axis parallel to the longitudinal axis of the boring head;
- drawing the tapered body into the tapered cavity with a threaded retainer acting along the longitudinal axis of the tapered cavity;
- forcing the tapered body into the tapered cavity with working loads against the independently rotatable cutter bit.
- 12. A boring head for use in mounting to a drill pipe of a rotary drilling rig for enlarging a pilot bore in horizontal boring, the boring head comprising;
- (a) an axial member positioned along a central axis of the boring head for connecting the boring head to the drill pipe of the drilling rig;
- (b) a cylindrical guide of a diameter chosen to engage said pilot bore, concentrically attached to said axial member so as to be positioned to extend into said pilot bore and guide said boring head along the path thereof;
- (c) a plurality of pockets mounted on said axial member, each said pocket having an internal cavity with a longitudinal axis generally parallel to said central axis, said cavities being tapered along said longitudinal axis of said pocket;
- (d) a plurality of bit bodies fitting tightly within the respective internal cavities of said plurality of pockets; and
- (e) an independently rotatable cutter bit mounted on each said bit body and rotating about a rolling axis, fixed with respect to its respective said bit body and extending at an acute angle ranging between approximately ten and eighty degrees relative to said central axis;
- (f) at least one of said plurality of pockets is mounted at a first radial distance from said central axis, said first radial distance being less than a second radial distance at which at least one other said pocket is mounted, so that a first said rotatable cutting bit, fitted into said at least one pocket, and a second said rotatable cutting bit, fitted into said at least one other pocket, follow offset arcuate paths when said axial member is rotated and so that at least said second rotatable cutting bit is positioned to enlarge said pilot bore to a second bore diameter; and
- (g) a second cylindrical guide of a diameter chosen to engage said second bore diameter, concentrically attached to said axial member so as to be positioned to extend into said second bore and stabilize said boring head for boring along the path of said pilot bore.
- 13. The boring head according to claim 12, wherein said axial member comprises: a cylindrical tubing having a connector adapted for securing said cylindrical tubing to the drill pipe for retaining the boring head on the drill pipe.
- 14. The boring head according to claim 12, wherein the first radial distance from the central axis is substantially equal to the radius of the pilot bore, and the second radial distance is greater than the radius of the pilot bore.
- 15. The boring head according to claim 12, wherein the difference between the first radial distance and the second radial distance is such that said first and second cutter bits cut across different but overlapping widths of arcuate cutting paths relative to the central axis.
Parent Case Info
This application is a continuation-in-part of U.S. application Ser. No. 08/855,328, filed May 13, 1997 entitled "Horizontal Boring Apparatus and Method".
US Referenced Citations (10)
Foreign Referenced Citations (4)
Number |
Date |
Country |
832325 |
Jan 1970 |
CAX |
962996 |
Feb 1975 |
CAX |
1067-190 |
Jan 1984 |
SUX |
8808480 |
Nov 1988 |
WOX |
Non-Patent Literature Citations (1)
Entry |
"Trenchless Technology Special Product Focus", Utility Construction & Maintenance, Jun./Jul., 1992. p. 29. |
Continuation in Parts (1)
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Number |
Date |
Country |
Parent |
855328 |
May 1997 |
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