Random-filament, multi-directionally responsive marker for use in electronic article surveillance systems

• US 4,857,891 A
• Filed: 04/29/1988
• Issued: 08/15/1989
• Est. Priority Date: 04/29/1988
• Status: Expired due to Term

• Current Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Original Assignee: Minnesota Mining and Manufacturing Co (3M Company)
• Inventors: Heltemes, Eugene C.
• Primary Examiner(s): Swann, III, Glen R.
• Assistant Examiner(s): Mullen, Jr., Thomas J.
• Application Number:
  US07/188,456
• Time in Patent Office: 473 Days
• Field of Search: 340/551, 340/572
• US Class Current: 340/551
• CPC Class Codes: G08B 13/2411 Tag deactivation
• CPC Class Codes: G08B 13/2437 Tag layered structure, processes for making layered tags
• CPC Class Codes: G08B 13/2442 Tag materials and material properties thereof, e.g. magnetic material details

Abstract

A magnetic marker for use with electronic article surveillance (EAS) systems in which a two-directional response is obtained. The marker comprises a substantially two-dimensional, sheet-like substrate having multiple metallic filaments randomly dispersed in or adhered thereto, so as to be substantially parallel to the plane thereof. The filaments are selected of low coercive force, high permeability material, and the random orientation results in certain filaments intersecting with the being magnetically coupled to other filaments to thereby collect and concentrate lines of flux associated with an applied field of an EAS system into filaments parallel to the field.

Claims

1. A marker for use in an electronic article surveillance system of the type in which an alternating magnetic field in an interrogation zone produces remotely detectable magnetization changes in the marker, wherein the marker comprises a substantially two-dimensional, sheet-like substrate and multiple metallic filaments randomly dispersed in or adhered thereto so as to be substantially parallel to the plane thereof, said filaments being selected of a high permeability, low coercive force, magnetic material, with said filaments thereby randomly intersecting each other to magnetically couple therewith.

2. A marker according to claim 1, wherein all of said filaments are substantially the same dimension.

3. A marker according to claim 1, wherein all of said filaments are substantially the same composition.

4. A marker according to claim 1, further comprising at least one section of permanently magnetizable material positioned adjacent to a portion of said multiple filaments, and magnetically coupled thereto such that when so magnetized the detectable response resulting from the marker is altered.