Method for providing magnetic markers on elongated hidden objects

• US 5,173,139 A
• Filed: 02/12/1992
• Issued: 12/22/1992
• Est. Priority Date: 03/15/1989
• Status: Expired due to Term

• Current Assignee: Schonstedt Instrument Co. LLC (SPX Corporation)
• Original Assignee: Schonstedt Instrument Company
• Inventors: Rippingale, John B., Schonstedt, Erick O.
• Primary Examiner(s): Weston, Caleb
• Application Number:
  US07/834,388
• Time in Patent Office: 314 Days
• Field of Search: 156/53, 156/185, 156/186, 156/187, 156/195, 29/605, 29/607, 29/609, 428/100, 428/103, 428/108, 242/7.11, 242/7.3
• US Class Current: 156/185
• CPC Class Codes: B29C 48/0016 using a plurality of extrusion dies
• CPC Class Codes: B29C 48/09 Articles with cross-sections having partially or fully enclosed cavities, e.g. pipes or channels
• CPC Class Codes: B29C 48/21 the layers being joined at their surfaces
• CPC Class Codes: B29K 2995/0003 having particular electrical or magnetic properties, e.g. piezoelectric
• CPC Class Codes: B29L 2011/0075 Light guides, optical cables
• CPC Class Codes: F16L 1/11 for the detection or protection of pipes in the ground
• CPC Class Codes: G01V 15/00 Tags attached to, or associated with, an object, in order to enable detection of the object record carriers for use with machines having a detectable tag or marker G06K19/00
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: G02B 6/562 locatable, e.g. using magnetic means
• CPC Class Codes: Y10T 29/49071 by winding or coiling
• CPC Class Codes: Y10T 29/49075 including permanent magnet or core
• CPC Class Codes: Y10T 29/49078 Laminated

Abstract

A magnetic marker serving to locate, trace, and identify an elongated hidden object, such as a buried utility pipe, duct, conduit, or fiber optic cable, is manufactured by applying magnetic material to a substrate that is elongated and by forming from the material a helical or twisted permanent magnet pattern extending along the length of the substrate. The magnetic material, which may be coextensive with the substrate or applied to a portion only of the substrate, may be formed as a strip coextruded with the substrate and magnetized in the direction of the width of the strip. Alternatively, magnetic material may be mixed with the material from which the substrate is extruded or may be coated on the substrate. A strip may also be preformed and applied to an elongated object as the object is buried, or the strip may form a separate warning tape that is buried with the object and that is provided with a desired magnetic signature by twisting the strip lengthwise as it is advanced for burial.

Claims

1. A method of providing a magnetic marker on an elongated object so that the object can be located and identified magnetically while hidden from view, comprising advancing said object lengthwise, providing an elongated tape of magnetic material permanently magnetized in a direction transverse to the length of the tape, and helically winding said tape about said object as said object is advanced so as to provide a magnetic field having a series of peaks and valleys along the length of said object, whereby the object may be located and identified by detecting variations of the magnetic field with a magnetic field detector moved along the length of the object.

2. A method in accordance with claim 1, wherein said tape is wound on a tape supply reel through which said object is advanced and is unwound from said tape supply reel as it is wound helically about said object.

3. A method in accordance with claim 2, wherein said tape supply reel is maintained stationary during the unwinding of said tape therefrom and wherein the tape is pulled off of an end of said tape supply reel as it is wound about said object.

4. A method in accordance with claim 2, wherein said tape supply reel rotates about said elongated object as said tape is pulled off of said tape supply reel, and wherein, as said tape is pulled off of said tape supply reel, it passes over a tape guide that rotates about said elongated object as the object is advanced.

5. A method in accordance with claim 1, wherein the method is performed as the elongated object is buried in the ground substantially horizontally.

6. A method of providing an elongated magnetic marker capable of being located and identified magnetically while hidden from view, comprising providing an elongated tape of magnetic material permanently magnetized in a direction transverse to its length, and twisting the tape lengthwise so as to provide a magnetic field having a series of peaks and valleys along the length of the tape, whereby the magnetic marker may be located and identified by detecting variations of the magnetic field with a magnetic field detector moved along the length of the magnetic marker.

7. A method in accordance with claim 6, wherein the tape is twisted by pulling it off of one end of a stationary reel on which the tape is wound.

8. A method in accordance with claim 6, wherein the method is performed as the magnetic marker is buried in the ground substantially horizontally and substantially parallel to an object that is buried in the ground concurrently and that is to be located and identified by virtue of the magnetic marker.