Methods, apparatus and devices relating to magnetic markers for elongated hidden objects
First Claim
1. A method of making a magnetic marker, comprising applying magnetic material to a substrate that is elongated, and forming at least a portion of said material into a helical permanent magnet pattern having a helix axis extending along the length, of said substrate, and wherein said forming of said helical magnetic pattern includes permanently magnetizing at least said portion of said material.
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0 Petitions
Accused Products
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.
116 Citations
24 Claims
- 1. A method of making a magnetic marker, comprising applying magnetic material to a substrate that is elongated, and forming at least a portion of said material into a helical permanent magnet pattern having a helix axis extending along the length, of said substrate, and wherein said forming of said helical magnetic pattern includes permanently magnetizing at least said portion of said material.
- 13. Apparatus for making a magnetic marker, comprising means for providing a substrate that is elongated, means for applying magnetic material to said substrate, and means for forming at least a portion of said material into a helical permanent magnet pattern having a helix axis extending along the length of said substrate, and wherein said forming means permanently magnetizes at least said portion of magnetic material.
- 17. Apparatus for making a magnetic marker, comprising means for providing a substrate that is elongated, means for applying magnetic material to said substrate, and means for forming from said material a helical permanent magnet pattern having a helix axis extending along the length of said substrate, wherein said providing means provides said substrate in the form of an extruded tube.
- 20. Apparatus for making a magnetic marker, comprising means for providing a substrate that is elongated, means for applying magnetic material to said substrate, and means for forming said material a helical permanent magnet pattern having a helix axis extending along the length of said substrate, wherein said providing means comprises means for forming said substrate as a cylinder that is advanced along its length, and wherein said applying means comprises an extruder die having an outlet that rotates about the axis of said cylinder as the cylinder is advanced along its length, said magnetic material being applied to said cylinder from said outlet.
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22. Apparatus for making a magnetic marker, comprising means for providing a substrate that is elongated, means for applying magnetic material to said substrate, and means for forming from said material a helical permanent magnet pattern having a helix axis extending along the length of said substrate, wherein said providing means comprises means for extruding said substrate as a cylinder that advances along its length and a take-up spool that rotates about a winding axis for winding the cylinder thereon, wherein said applying means applies said magnetic material to said cylinder as a strip extending substantially parallel to the axis of the cylinder as the cylinder is extruded, and wherein said forming means comprises means for rotating said take-up spool about an axis substantially perpendicular to said winding axis and substantially parallel to the length of said cylinder.
Specification