Multi-directionally responsive, dual-status, magnetic article surveillance marker having continuous keeper
First Claim
1. A marker for use in an electronic article surveillance system having in an interrogation zone an alternating magnetic field, comprising a substantially planar sheet of high permeability, low coercive force responder material having a width not less than one half the length, having at least two elongated areas proximate to the periphery of the sheet, the length of at least one elongated area being substantially perpendicular to the length of another elongated area, each said area having a narrow width forming a switching section and extending on each end along the length into extensive regions thereby forming flux collector sections for the adjacent switching section, anda continuous uninterrupted sheet of remanently magnetizable material having substantially the same overall dimensions as said sheet of responder material, overlying and magnetically coupled to said sheet of responder material, which sheet, when substantially uniformly magnetized in the plane of the sheet causes alternate switching pulses resulting from a reversal of magnetization of said switching sections to be shifted in time and/or altered in amplitude, thereby enabling markers having said magnetizable sheet magnetized or demagnetized to be distinguished from each other.
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Accused Products
Abstract
A multi-directionally responsive, dual-status marker for use in electronic article surveillance systems having an alternating magnetic field within an interrogation zone. The marker comprises a piece of a high permeability, low coercive force magnetic material substantially coextensive with a piece of remanently magnetizable material, in which the first piece is configured to exhibit at least two elongated responsive areas adjacent to edges of the piece perpendicular to each other, each area having a narrow width region forming a switching section and adjacent extensive regions forming flux collectors. In a preferred embodiment, the inner edges of all of the regions are defined by a narrow band of removed material, the remaining material in the center thereby being magnetically isolated from the responsive areas. The marker is desensitized by uniformly magnetizing the pace of unmagnetizable material.
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Citations
13 Claims
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1. A marker for use in an electronic article surveillance system having in an interrogation zone an alternating magnetic field, comprising a substantially planar sheet of high permeability, low coercive force responder material having a width not less than one half the length, having at least two elongated areas proximate to the periphery of the sheet, the length of at least one elongated area being substantially perpendicular to the length of another elongated area, each said area having a narrow width forming a switching section and extending on each end along the length into extensive regions thereby forming flux collector sections for the adjacent switching section, and
a continuous uninterrupted sheet of remanently magnetizable material having substantially the same overall dimensions as said sheet of responder material, overlying and magnetically coupled to said sheet of responder material, which sheet, when substantially uniformly magnetized in the plane of the sheet causes alternate switching pulses resulting from a reversal of magnetization of said switching sections to be shifted in time and/or altered in amplitude, thereby enabling markers having said magnetizable sheet magnetized or demagnetized to be distinguished from each other.
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10. An electromagnetic article surveillance system comprising
(a) means for generating within an interrogation zone an alternating magnetic field, (b) a plurality of markers, each comprising a substantially planar sheet of high permeability, low coercive force responder material having a width not less than one half the length, having at least two elongated areas proximate to the periphery of the sheet the length of at least one elongated area being substantially perpendicular to the length of another elongated area, each said area having a narrow width forming a switching section and extending on each end along the length into extensive regions thereby forming a flux collector sections for the adjacent switching section and a continuous uninterrupted sheet piece of remanently magnetizable material substantially the same overall size as the sheet of low coercive force, high permeability material, and extending coextensive therewith, (c) means for magnetizing said remanently magnetizable material to provide therein a single, substantially uniform magnetic dipole, one edge of the sheet of magnetizable material thereby having a one magnetic polarity and an opposite edge having the opposite polarity, (d) means for receiving signals resulting from flux changes in a said marker produced when the marker is exposed to said alternating fields in said zone, and for distinguishing between signals from said markers when said sheet of magnetizable material is either magnetized to have a said single magnetic dipole or is demagnetized, and from other signals as may be caused by ambient effects, random ferromagnetic objects and the like, said distinguishing means further comprising means responsive to differences in amplitude of marker produced signals and relative displacements of alternate signal components as typically occur when said magnetizable sheets are alternatively unmagnetized or magnetized for producing an alarm signal when appropriate.
Specification