Method of finding an above-ground point in relation to an in-ground boring tool

• US 5,926,025 A
• Filed: 04/13/1998
• Issued: 07/20/1999
• Est. Priority Date: 03/01/1991
• Status: Expired due to Term

• Current Assignee: Merlin Technologies Incorporated
• Original Assignee: Digital Control Incorporated
• Inventors: Mercer, John E.
• Primary Examiner(s): Snow, Walter E.
• Application Number:
  US09/059,240
• Time in Patent Office: 463 Days
• Field of Search: 324/326, 324/327, 324/328, 324/329, 324/225, 324/226, 324/207.26, 324/207.13, 324/207.16, 324/207.17, 324/207.24, 324/338, 324/339, 324/332, 324/333, 175/40, 175/45
• US Class Current: 324/326
• CPC Class Codes: E21B 47/0228 using electromagnetic energy or detectors therefor
• CPC Class Codes: E21B 47/0232 at least one of the energy sources or one of the detectors being located on or above the ground surface
• CPC Class Codes: E21B 47/024 of devices in the borehole determining slope or direction of the borehole E21B47/022
• CPC Class Codes: G01C 9/06 Electric or photoelectric indication or reading means
• CPC Class Codes: G01C 9/20 the indication being based on the inclination of the surface of a liquid relative to its container
• CPC Class Codes: G01V 3/165 operating with magnetic or electric fields produced or modified by the object or by the detecting device with electromagnetic waves G01V3/17

Abstract

The present invention provides a locator/monitor capable of locating a boring tool and monitoring the progress of the tool for control purposes. The locator/monitor may be used in expedited locating methodology and straightforward calibration techniques of the present invention. A durable and cost effective pitch sensor is also provided by the present invention. In addition, the present invention provides a slotted transmitter housing formed of an electrically conductive material, where the magnetic field generated by the transmitter is capable of penetrating to the surface.

Claims

1. A method of finding a point on the ground related to the position of a generally horizontally extending dipole magnetic field transmitter which is disposed underground within a particular vertical transmitter plane defined by its dipole axis and which generates a magnetic dipole field containing magnetic flux lines, each one of which extends from one end of the transmitter around to its opposite end and all of which are spaced from one another about the dipole axis of said transmitter, said method comprising the steps of:

(a) providing a locating receiver including an antenna arrangement and means for producing

(i) a first signal if any given one of said flux lines impinges said antenna configuration in a first way,

(ii) a second signal if any given one of said flux lines impinges said antenna arrangement in a second way, and

(iii) a third signal if any given one of said flux lines impinges said antenna arrangement in a third way; and

(b) moving said locating receiver above the ground at a predetermined orientation and within a first vertical receiver plane transverse to the vertical transmitter plane containing the axis of said transmitter either ahead of or behind the transmitter with respect to its general direction of movement so as to cause said receiver to produce successively first, second and third signals at certain respective first, second and third locations within said first receiver plane.

2. A method according to claim 1 wherein said antenna arrangement includes first and second antennae, each of which independently senses the magnetic field generated by said transmitter, and wherein

(a) each of said first signals indicates when the field strength sensed by said first antenna is stronger than the field strength sensed by said second antenna,

(b) each of said third signals indicates when the field strength sensed by said second antenna is stronger than the field strength sensed by said first antenna, and

(c) each of said second signals indicates the transition point between said first and third signals when the field strengths sensed by both antennae are equal.

3. A method according to claim 1 wherein said flux lines include horizontal and vertical components, wherein said antenna arrangement consists of a single antenna and wherein

the second signal produced while moving in said first receiver plane is a signal resulting from said receiver sensing a substantially vertical component of said flux lines.

4. A method according to claim 1 wherein said antenna arrangement consists of a single antenna and wherein the second signal produced while moving in said first receiver plane is a null signal.

5. A method according to claim 1 wherein said antenna configuration includes first and second antennae disposed within a common plane and having straight axes fixedly positioned with respect to one another so as to define a fixed angle between one another within the common plane.

6. A method according to claim 5 wherein said fixed angle is approximately 90 degrees.

7. A method according to claim 6 wherein when said locating receiver is moved in said first receiver plane, the common plane containing said antennae is maintained in the receiving plane with the first antenna oriented at an angle of 45 degrees above the horizontal in the forward direction and the second antenna oriented at an angle of 45 degrees above the horizontal in the rearward direction.