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AssigneeInnovatum, Inc.
InventorsPaul A. Cloutier, Timothy I. Marzolf, Delbert R. Oehme, Ronald F. Stebbings
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Ferromagnetic material of an elongated object, such as a fiber optic cable, is permanently magnetized in a manner that results in a substantially cylindrically symmetric radial external magnetic field around the object. The produced magnetization is substantially greater than natural magnetization of the ferromagnetic material by the earth's magnetic field. The radial external magnetic field varies periodically along the length of the object. If the wavelength of the periodic variations is long compared to the width (diameter) of the object, the strength of the radial external magnetic field decreases approximately inversely with distance from the object for distances that are small compared to the wavelength. The periodic magnetic field variations may have a square wave or a sine wave pattern, for example. Magnetization of the ferromagnetic material is achieved by a magnetizer having pairs of counter-rotating mirror-image magnets adjacent to an object that is moved longitudinally relative to the magnets. By virtue of the magnetization, buried objects, such as pipes and cables can be detected magnetically at substantial distances from the objects.
An elongated object comprising ferromagnetic material magnetized to provide multiple cycles of longitudinal magnetization that extends along the length of the object and that varies continually throughout each cycle, and that results in multiple cycles of a radial external magnetic field around the object that extends along the length of the object over a plurality of meters, and wherein each cycle of the radial external magnetic field includes a half-cycle in which radial flux lines of one polarity emanate from the object through 360° and another half-cycle in which radial flux lines of opposite polarity emanate from the object through 360 °.
An elongated object comprising ferromagnetic material magnetized so as to produce multiple cycles of a radial external magnetic field around the object that extends along the length of the object over a plurality of meters and so that the fall-off of the magnitude of the radial eternal field with distance R from the center line of the object is in accordance with 1/Rn, where R is in a range of several meters and where n is less than 2, irrespective of the radial direction from the object.
Dependencies are inferred from the claim text.