Control for guiding a boring tool

Claim 1

A system for boring a bore hole comprising: a boring tool having a longitudinal tool axis and including a motive means for advancing the tool through the earth and steering means for directing the motion of the tool relative to said tool axis in response to control signals; axial electromagnetic source means for generating an axial alternating magnetic field directed along an axial source axis; a sensing assembly remote from said source means and including first and second pickup coils for sensing said alternating magnetic field, each coil of said first and second pickup coils: being responsive to the change of magnetic flux linked thereby by generating respective electrical signals systematically related thereto, having a respective coil axis, being rigidly mounted in respect to the other coil with the coil axis of said first coil at a substantial angle with respect to the coil axis of said second coil, said coil axes defining a sensing assembly axis substantially normal to both said coil axes, and being balanced in respect to said sensing assembly axis to generate a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis at said sensing assembly axis; one and only one of said source means and said sensing assembly being rigidly mounted on said tool; indicating means responsive to electrical signals generated by respective said first and second pickup coils for indicating the direction of lines of magnetic flux at said sensing assembly relative to said sensing assembly axis, thereby indicating the attitude of said source means relative to said first and second pickup coils; and control means for providing control signals for controlling said steering means.

Claim 2

A system for boring a bore hole comprising: a boring tool having a longitudinal tool axis and including a motive means for advancing the tool through the earth and steering means for directing the motion of the tool relative to said tool axis in response to control signals; axial electromagnetic source means for generating an axial alternating magnetic field directed along an axial source axis; a sensing assembly remote from said source means and including first and second pickup coils for sensing said alternating magnetic field, each coil of said first and second pickup coils: being responsive to the change of magnetic flux linked thereby by generating respective electrical signals systematically related thereto, having a respective coil axis, being rigidly mounted in respect to the other coil with the coil axis of said first coil at a substantial angle with respect to the coil axis of said second coil, said coil axes defining a sensing assembly axis substantially normal to both said coil axes, and being balanced in respect to said sensing assembly axis to generate a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis at said sensing assembly axis; one and only one of said source means and said sensing assembly being rigidly mounted on said tool; indicating means responsive to electrical signals generated by respective said first and second pickup coils for indicating the direction of lines of magnetic flux at said sensing assembly relative to said sensing assembly axis, thereby indicating the attitude of said source means relative to said first and second pickup coils; and control means for providing control signals for controlling said steering means.

Claim 8

A system for boring a bore hole comprising: a boring tool having a longitudinal tool axis and including motive means for advancing the tool through the earth; axial electromagnetic source means for generating an axial alternating magnetic field directed along an axial source axis; a sensing assembly remote from said source means and including first and second pickup coils for sensing said alternating magnetic field, each coil of said first and second pickup coils: being responsive to the change of magnetic flux linked thereby be generating respective electrical signals systematically related thereto, having a respective coil axis, being rigidly mounted in respect to the other coil with the coil axis of said first coil at a substantial angle with respect to the coil axis of said second coil, said coil axes defining a sensing assembly axis substantially normal to both said coil axes, and being balanced in respect to said sensing assembly axis to generate a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis at said sensing assembly axis; one and only one of said source means and said sensing assembly being rigidly mounted on said tool; indicating means responsive to electrical signals generated by respective said first and second pickup coils for indicating the direction of lines of magnetic flux at said sensing assembly relative to said sensing assembly axis, thereby indicating the attitude of said source means relative to said first and second pickup coils; means for determining the advance of the tool in said bore hole by producing displacement signals systematically related thereto; incremental displacement means, responsive to incremental changes in said displacement signals and to said attitude as indicated by said indicating means, for producing incremental movement signals indicating incremental movement of said tool; and integrating means responsive to said incremental movement signals for locating said tool in said bore hole.

Claim 9

A system for boring a bore hole comprising: a boring tool having a longitudinal tool axis and including motive means for advancing the tool through the earth; axial electromagnetic source means for generating an axial alternating magnetic field directed along an axial source axis; a sensing assembly remote from said source means and including first and second pickup coils for sensing said alternating magnetic field, each coil of said first and second pickup coils: being responsive to the change of magnetic flux linked thereby be generating respective electrical signals systematically related thereto, having a respective coil axis, being rigidly mounted in respect to the other coil with the coil axis of said first coil at a substantial angle with respect to the coil axis of said second coil, said coil axes defining a sensing assembly axis substantially normal to both said coil axes, and being balanced in respect to said sensing assembly axis to generate a respective null electrical signal when the lines of magnetic flux at the respective coil are normal to the respective coil axis at said sensing assembly axis; one and only one of said source means and said sensing assembly being rigidly mounted on said tool; indicating means responsive to electrical signals generated by respective said first and second pickup coils for indicating the direction of lines of magnetic flux at said sensing assembly relative to said sensing assembly axis, thereby indicating the attitude of said source means relative to said first and second pickup coils; means for determining the advance of the tool in said bore hole by producing displacement signals systematically related thereto; incremental displacement means, responsive to incremental changes in said displacement signals and to said attitude as indicated by said indicating means, for producing incremental movement signals indicating incremental movement of said tool; and integrating means responsive to said incremental movement signals for locating said tool in said bore hole.

Claim 13

A system according to anyone of claims 1 to 10 including transverse electromagnetic source means for generating a transverse alternating magnetic field substantially at said axial source means having a transverse source axis transverse of said axial source axis, and means for energizing said axial electromagnetic source means and said transverse electromagnetic source means alternatively, whereby said means for indicating indicates the rotational position of said tool about said tool axis.