Methods, apparatus and devices relating to magnetic markers for elongated hidden objects

• US 5,206,065 A
• Filed: 02/12/1992
• Issued: 04/27/1993
• 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): Thomas, Alexander S.
• Application Number:
  US07/834,155
• Time in Patent Office: 440 Days
• Field of Search: 428/900, 428/371, 428/592, 428/98, 156/196
• US Class Current: 428/98
• 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: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10S 428/906 Roll or coil
• CPC Class Codes: Y10T 428/12333 Helical or with helical component
• CPC Class Codes: Y10T 428/24 Structurally defined web or sheet [e.g., overall dimension, etc.]
• CPC Class Codes: Y10T 428/2925 Helical or coiled

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 magnetic marker capable of being located and identified when hidden from view, comprising an elongated flexible strip of magnetic material magnetized transverse to its length and twisted lengthwise so as to provide a magnetic field that varies repetitively along the length of the strip in a pre-determined manner, whereby the strip can be located and identified by detecting variations of the magnetic field with a magnetic field detector moved along the length of the strip.