System utilizing galvanic potentials for detecting buried conductive structures

• US 3,916,298 A
• Filed: 07/11/1973
• Issued: 10/28/1975
• Est. Priority Date: 07/11/1973
• Status: Expired due to Term

• Current Assignee: Donald E. Ulrich
• Original Assignee: Donald E. Ulrich
• Inventors: Ulrich, Donald E.
• Primary Examiner(s): Strecker, Gerard R.
• Application Number:
  US05/378,148
• Time in Patent Office: 839 Days
• Field of Search: 324/1,3,9,29.5,65,67,72.5,29,72 37/DIG.19,86 340/421 317/18
• US Class Current: 324/326
• CPC Class Codes: E02F 9/245 for preventing damage to underground objects during excavation, e.g. indicating buried pipes or the like detection of pipes in the ground F16L1/11
• CPC Class Codes: G01V 3/082 operating with fields produced by spontaneous potentials, e.g. electrochemical or produced by telluric currents G01V3/26 takes precedence
• CPC Class Codes: Y10S 37/904 Vibration means for excavating tool

Abstract

A system is described for detecting underground electrically conductive structures such as pipelines which are likely to be contacted during excavation, but without the need for any external electrical connections with the buried structure. A reference electrode and the excavating machine establish a galvanic circuit which uses the earth as the electrolyte and in which current is monitored. The current in this circuit changes abruptly when contact is made with the buried structure. An electronic switch is operated in response to this abrupt current change and operates a warning device or otherwise controls the actuating machine such that damage to the buried structure may be prevented.

Claims

1. A system for detecting electrically conductive structures which are buried in the earth, said system comprising;

a. a reference electrode disposed in contact with the earth, b. a base electrode also disposed in contact with the earth, said base electrode being in proximity to said reference electrode and spaced therefrom so as to be out of contact therewith, c. current monitoring means connected between said base electrode and said reference electrode, said base electrode, reference electrode and current monitoring means establishing a base galvanic circuit which extends through the earth between said base electrode and said reference electrode, d. movable probe means connected to said base electrode and adapted to contact said buried conductive structures to establish another galvanic circuit when contact is made between said probe means and said buried conductive structures, said other circuit extending between said probe means in contact with said conductive structures and said reference electrode through the earth therebetween and then from said reference electrode through said current monitoring means back to said probe means, whereby the detection of said buried conductive structures is indicated by said current monitoring means when galvanic current therethrough changes abruptly upon contact of said probe means with said buried conductive structures.

2. The invention as set forth in claim 1 wherein said probe means is provided by the earth removing element of an excavating machine, said base electrode is provided by a conductive member on said machine disposed on the surface of the earth, and said reference electrode is provided by a second conductive member which is disposed in contact with the earth.

3. The invention as set forth in claim 2 wherein said second conductive member is disposed adjacent to said first conductive member.

4. The invention as set forth in claim 1 wherein said current monitoring means includes circuit element means providing a path for direct current therethrough, said circuit element means being connected between said reference electrode and said base electrode.

5. The invention as set forth in claim 4 wherein said circuit element means includes a transformer having an input winding connected between said reference electrode and said base electrode.

6. The invention as set forth in claim 5 wherein said circuit element means further comprises the output winding of said transformer and means responsive to the voltage across said output winding for providing an output signal.

7. The invention as set forth in claim 6 wherein said means responsive to the voltage across said output winding includes switch means operated by said output signal.

8. The invention as set forth in claim 7 wherein said circuit element means further comprises alarm means operated by said switch means.

9. The invention as set forth in claim 6 wherein said means responsive to the voltage across said transformer output winding includes an amplifier for providing said output signal and also threshold control means which are included in said amplifier for inhibiting said output signal unless that voltage is above a certain level.

10. The invention as set forth in claim 1 wherein said current monitoring means includes means responsive to abrupt changes in current therethrough for indicating the detection of said buried conductive structures.

11. The invention as set forth in claim 1 wherein said current monitoring means comprises an electronic switch having an input circuit connected between said reference electrode and said base electrode, said input circuit including means for operating said switch in response to a transient in the current through said input circuit.

12. The invention as set forth in claim 1 wherein said reference electrode is provided by a plate, said plate being disposed in the earth below a stabilizing shoe of an excavating machine, and an insulating member disposed between said plate and said shoe.

13. The invention as set forth in claim 12 wherein said shoe insulating member and plate are integral with each other.