Claims
- 1. A method for boring a hole through rock using a horizontal drilling apparatus and steering a drill head of the drilling apparatus, comprising:pushing the drill head, the drill head located at a front end of a drill string, through a medium; delivering impacts to a drill bit located at a distal end of the drill head with a hammer driven by a liquid, wherein the drill bit includes an effective steering geometry suitable for steering the drill head; periodically determining the angular orientation of the drill bit using a device for detecting angular orientation disposed on the drill head; and steering the drill head by pushing and rotating the drill bit repeatedly over an angle defined by less than a full rotation of the drill bit while delivering impacts to the drill bit with the hammer, so that the drill head deviates in the direction of the cutting action of the effective steering geometry.
- 2. The method according to claim 1, wherein the effective steering geometry is a gage tower radially outwardly offset from an outermost point away from a longitudinal axis of the drill string and having one or more frontwardly facing gage cutting teeth disposed thereon, the one or more gage cutting teeth being suitable for cutting over an angle defined by less than one full rotation of the drill bit.
- 3. A method according to claim 2, wherein the drill bit further comprises a frontwardly facing main cutting surface having one or more cutting teeth disposed thereon.
- 4. A method according to claim 1, wherein the medium being bored comprises both soil and rock during the same boring run using the same drill bit.
- 5. A method for boring a hole through a medium using a horizontal drilling apparatus and steering a drill head of the drilling apparatus, comprising:pushing the drill head located at a front end of a drill string through a medium while delivering impacts to a drill bit located at a distal end of the drill head with a hammer driven by a liquid, wherein the drill bit includes an effective steering geometry suitable for steering the drill head and the drill head; periodically determining the angular orientation of the drill bit using a device for detecting angular orientation disposed on the drill head; and steering the drill head by: (a) if boring through a compressible soil, changing direction during boring by pushing the drill string, so that the drill head deviates in the direction of an offset coupling member, which is offset from a center line of a longitudinal axis of the drill string without delivering impacts to the drill bit with the hammer and without rotating the drill string; or (b) if boring through rock, delivering impacts to the drill bit with the hammer, so that the drill head deviates in the direction of the effective steering geometry.
- 6. A method according to claim 5, further comprising:if boring in a predetermined medium, changing direction during boring by pushing the drill string, so that the drill head deviates in the direction of the offset coupling member and delivering impacts to the drill bit with the hammer and without rotating drill string.
- 7. A method according to claim 5, further comprising determining whether the drill head is boring through compressible soil or rock.
- 8. A method according to claim 5, further comprising determining whether to activate the hammer.
- 9. In a horizontal directional drilling apparatus having a drill string adapted to bore through rock and compressible soil, the drilling apparatus having an aggressive flushing type hammer driven by a liquid, a method of operating an aggressive flushing type hammer, comprising:determining whether to activate the aggressive flushing type hammer; (a) if drilling in rock and the hammer is to be activated: reducing the liquid flow for driving the hammer to a first value substantially close to zero; applying a thrust force exceeding a predetermined threshold by a drive member of the drilling apparatus to the drill string and causing the hammer to shift out of a flushing position; and increasing the liquid flow to a predetermined threshold and continuing drilling in rock with the hammer activated; (b) if drilling in compressible soil and the hammer is not to be activated: reducing the thrust force below a predetermined threshold while maintaining liquid pressure above a predetermined threshold on the hammer, thereby shifting the hammer into the flushing position; and continuing drilling in compressible soil without the hammer activated.
- 10. A method according to claim 9, wherein if the hammer is activated:controlling the liquid flow as a function of the thrust force, wherein if the thrust force is below a predetermined threshold, the liquid flow is reduced to a level below a predetermined threshold to prevent the hammer from shifting into the flushing position.
- 11. A method according to claim 9, wherein if the hammer is not activated:controlling the drive member of the drilling apparatus so that a thrust force is not applied in the absence of liquid flow.
- 12. In a horizontal directional drilling apparatus having a drill string adapted to bore through rock and compressible soil, the drilling apparatus having a standard type hammer driven by a liquid, a method of operating a standard type hammer, comprising:determining whether to activate the standard type hammer; (a) if drilling in rock and the hammer is to be activated: increasing the liquid flow to a value above a predetermined threshold; increasing a thrust force generated by a drive member of the horizontal drilling apparatus to a value above a predetermined threshold; and continuing drilling in rock with the hammer activated; (b) if drilling in compressible soil and the hammer is not to be activated: limiting the liquid flow to a value below a predetermined threshold required to activate the hammer; limiting the thrust force to a value below a predetermined threshold required to activate the hammer; and continuing drilling in compressible soil without the hammer activated.
- 13. In a horizontal directional drilling apparatus having a drill string adapted to bore through rock and compressible soil, the drilling apparatus having a hammer driven by a liquid, a method of operating the hammer, comprising:(a) controlling the thrust force of a drive member of the drilling apparatus to the drill string, the thrust force being controlled to a predetermined thrust level; and (b) controlling the liquid flow for driving the hammer, the liquid flow being controlled to a predetermined flow level corresponding to the predetermined thrust level such that the predetermined flow level and the predetermined thrust level cooperate to activate and de-activate the hammer.
- 14. The method of claim 13, wherein the hammer is an aggressive flushing type hammer, and drilling is being performed in rock, the method of operating the aggressive flushing type hammer further comprising:(a) determining to activate the aggressive flushing type hammer; (b) reducing the liquid flow for driving the hammer to the predetermined flow level, the predetermined flow level being substantially close to zero; and (c) applying the predetermined thrust level of thrust force, the predetermined thrust level exceeding a predetermined thrust threshold of the drive member of the drilling apparatus to the drill string, and causing the aggressive flushing type hammer to shift out of a flushing position; and (d) increasing the liquid flow from the predetermined flow level and continuing drilling in rock with the aggressive flushing type hammer activated.
- 15. The method of claim 13, wherein the hammer is a standard type hammer, and drilling is being performed in rock, the method of operating the standard type hammer further comprising:(a) determining to activate the standard type hammer; (b) increasing the liquid flow for driving the hammer to the predetermined flow level, the predetermined flow level being a value above a predetermined flow threshold; (c) applying the predetermined thrust level of thrust force, the predetermined thrust level exceeding a predetermined thrust threshold of the drive member of the drilling apparatus to the drill string; and (d) continuing drilling in rock with the standard type hammer activated.
- 16. The method of claim 13, wherein the hammer is an aggressive flushing type hammer, and drilling is being performed in compressible soil, the method of operating the aggressive flushing type hammer further comprising:(a) determining to de-activate the aggressive flushing type hammer; (b) reducing the thrust force to the predetermined thrust level, the predetermined thrust level being lower than a predetermined thrust threshold of the drive member of the drilling apparatus to the drill string; (c) maintaining the liquid flow for driving the hammer at the predetermined flow level, and causing the aggressive flushing type hammer to shift into a flushing position; and (d) continuing drilling in compressible soil without the aggressive flushing type hammer activated.
- 17. The method of claim 13, wherein the hammer is a standard type hammer, and drilling is being performed in compressible soil, the method of operating the standard type hammer further comprising:(a) determining to de-activate the standard type hammer; (b) reducing the liquid flow for driving the hammer to the predetermined flow level, the predetermined flow level being a value below a predetermined flow threshold required to activate the hammer; (c) reducing the thrust force to the predetermined thrust level, the predetermined thrust level being a value below a predetermined thrust threshold required to activate the hammer; and (d) continuing drilling in compressible soil without the standard type hammer activated.
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a continuation of application Ser. No. 09/518,419, filed Mar. 3, 2000, issued Sep. 24, 2002, as U.S. Pat. No. 6,454,025, which claims the benefit of U.S. Provisional Application Ser. No. 60/122,593, filed Mar. 3, 1999, both applications of which are incorporated herein by reference.
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