| 摘要 |
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 (26) 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 (26) or applied to a portion only of the substrate, may be formed as a strip (46) coextruded with the substrate (26) and magnetized in the direction of the width of the strip (46). Alternatively, magnetic material may be mixed with the material from which the substrate (26) is extruded or may be coated on the substrate (26). A strip (104) may also be preformed and applied to an elongated object (100) as the object (100) is buried, or the strip (130) 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 (130) lengthwise as it is advanced for burial. |
