Portable transmitter apparatus for inducing alternating current in a buried metallic line

• US 5,055,793 A
• Filed: 05/08/1990
• Issued: 10/08/1991
• Est. Priority Date: 05/08/1990
• Status: Expired due to Term

• Current Assignee: Thomas W., D/B/A/ Goldak/Udsec Mulcahey
• Original Assignee: Thomas W. Mulcahey
• Inventors: Mulcahey, Donald M.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US07/520,528
• Time in Patent Office: 518 Days
• Field of Search: 324/67, 324/326-329, 324/334, 340/551
• US Class Current: 324/326
• CPC Class Codes: G01V 3/06 using ac

Abstract

A system of apparatus for locating underground metallic lines includes a transmitter apparatus at a first work station above ground for inducing a current in the line and a receiver at a second work station for making field measurements. The transmitter apparatus includes a battery-powered transmitter circuit supported from a portable housing, a ferrite core antenna incorporated within the transmitter circuit, and a separate tank circuit which includes a loop antenna and a capacitor and is tuned to a predetermined operating frequency and is electrically isolated from the ferrite core antenna. The ferrite core antenna transfers energy through a magnetic flux field to the loop antenna, and a magnetic field generated from the loop antenna inductively creates an alternating current in the line which then generates an alternating electromagnetic field about the line at the second work station.

Claims

1. In a system of apparatus for locating an underground metallic line, an improved transmitter apparatus for use at a first station above ground to inductively create an alternating current in the line and to thereby generate an alternating electromagnetic field about an extended length of the line, while a retriever at a second station above ground makes measurements within that alternating electromagnetic field which are determinative of both the horizontal location and the depth of the line at that station, said transmitter apparatus comprising:

a portable transmitter circuit for providing an alternating current at a predetermined operating frequency;

a tank circuit including a loop antenna and a capacitor tuned to substantially the same operating frequency as said transmitter circuit;

a ferrite core antenna incorporated into said transmitter circuit and driven by said alternating current and electrically isolated from said tank circuit for producing magnetic flux coupled to said tank circuit; and

means for supporting said loop antenna and said ferrite core antenna in such positions relative to each other and to the ground that the axis of the loop is substantially horizontal and also perpendicular to the direction of the underground metallic line, the longitudinal axis of said core extends within and through the loop of said loop antenna, and a magnetic field generated from said loop antenna by current induced therein by the magnetic flux produced by said ferrite core drives lines of flux substantially perpendicular to and underneath the underground line.

2. A transmitter apparatus as in claim 1 wherein said ferrite core is a rod the longitudinal axis of which passes through a central plane occupied by said loop antenna.

3. A transmitter apparatus as in claim 1 wherein said means for supporting said loop antenna and said ferrite core is a portable housing.

4. A transmitter apparatus as in claim 1 wherein said ferrite core is a toroid which encircles and encloses the winding of said loop antenna.

5. A transmitter apparatus as in claim 1 wherein said ferrite core is a partial toroid which partially encircles and encloses the winding of said loop antenna.

6. A transmitter apparatus as in claim 1 wherein said supporting means includes a housing made of non-conductive material, said transmitter circuit is fixedly mounted within said housing, said loop antenna is permanently secured within the periphery of said housing, and said ferrite core is fixedly supported from said housing in its desired positional relation to said loop antenna.

7. In a system of apparatus for locating an underground metallic line, an improved transmitter apparatus for use at a first station above ground to inductively create an alternating current in the line to thereby generate an alternating electromagnetic field about an extended length of the line, while a receiver at a second station above ground makes measurements within that alternating electromagnetic field that are determinative of both the horizontal location and the depth of the line at that station, said transmitter apparatus comprising:

a portable housing adapted to be placed in a normal resting position on the ground at the first station;

a battery-powered transmitter circuit fixedly supported from said housing, for providing an alternating current at a predetermined operating frequency;

a loop antenna having an associated capacitor, thus providing a tank circuit tuned to substantially the same frequency, said loop antenna being fixedly supported from said housing such that in the normal resting position of said housing the axis of the loop is substantially horizontal;

a ferrite core antenna incorporated into said transmitter circuit and driven by said alternating current, electrically isolated from said loop antenna for producing magnetic flux coupled to said loop antenna, and fixedly supported from said housing in such position that the axis of the core passes within and through the loop of said loop antenna; and

said housing supporting said loop antenna and said ferrite core antenna in such positions relative to the ground that the axis of the loop is substantially horizontal and may also be perpendicular to the direction of the underground metallic line, and a magnetic field generated from said loop antenna by current induced therein by the magnetic flux produced by said ferrite core then alternates in planes substantially perpendicular to the longitudinal axis of the underground line.

8. A transmitter apparatus as in claim 7 wherein said ferrite core is a rod which passes through a plane occupied by said loop antenna.

9. A transmitter apparatus as in claim 7 wherein said ferrite core is a toroid which encircles and encloses the winding path of said loop antenna.

10. A transmitter apparatus as in claim 7 wherein said ferrite core is a partial toroid which partially encircles and encloses the winding path of said loop antenna.

11. A transmitter apparatus as in claim 7 wherein said housing is made of non-conductive material, said loop antenna is permanently secured within the periphery of said housing, and said ferrite core is fixedly supported from said housing in its desired positional relation to said loop antenna.

12. A system of apparatus for locating an underground metallic line, comprising:

a carrying case made of a non-conductive material;

a battery-powered transmitter circuit supported within said case, for providing an alternating current at a predetermined operating frequency;

a loop antenna permanently secured within the periphery of said case;

a capacitor connected to said loop antenna to provide a tank circuit tuned to said predetermined operating frequency;

a ferrite core antenna incorporated into said transmitter circuit and driven by said alternating current, electrically isolated from said loop antenna and supported from said case in such position that the longitudinal axis of the core passes within the loop of said loop antenna for producing magnetic flux coupled to said tank circuit;

said carrying case being adapted to removably receive a portable receiver; and

said carrying case having a normal resting position on the ground above the underground line such that the axis of said loop antenna is substantially horizontal, whereby the axis of the loop may be aligned perpendicular to the direction of the underground metallic line so that a magnetic field may then be generated from said loop antenna by current induced therein by the magnetic flux produced by said ferrite core which alternates in planes substantially perpendicular to the longitudinal axis of the underground line.

13. A system of apparatus as in claim 12 wherein said ferrite core is a rod which passes through a plane occupied by said loop antenna.

14. A system of apparatus as in claim 12 wherein said ferrite core is a toroid which encircles and encloses one side of said loop antenna.

15. A system of apparatus as in claim 12 wherein said ferrite core is a partial toroid which partially encircles and encloses one side of said loop antenna.

16. A system of apparatus as in claim 12 which further includes a portable receiver removably carried within said case, whereby said case may be positioned at a first station above ground for inductively creating an alternating current in the line and hence an alternating electromagnetic field about an extended length of the line, and said receiver may be positioned at a second station above ground to make measurements determinative of both the horizontal location and the depth of the line at the station.