×

Magnetic asymmetric antipilferage marker

  • US 4,075,618 A
  • Filed: 07/15/1976
  • Issued: 02/21/1978
  • Est. Priority Date: 07/15/1976
  • Status: Expired due to Term
First Claim
Patent Images

1. An antipilferage marker adapted for use in a system for sensing the presence of an object to which is affixed a said marker in an interrogation zone having therein a magnetic field periodically varying at a predetermined fundamental frequency, said marker comprising asymmetric sections of ferromagnetic material including a center section having end portions and having a permeability of not less than 104 and a coercive force of not more than 0.5 oersted, and two substantially planar flux concentrator sections having a permeability of not less than 10% of the permeability of the center section and a coercive force of not more than one oersted, one of which concentrator sections is secured to each end portion of the center section such that a low reluctance path exists therebetween, said concentrator sections having a predetermined area, the maximum dimension of which parallel to the width of the end portion of the center section to which it is secured is at least three times the width of said end portion such that magnetic lines of flux are collected and concentrated in the center section when a magnetic field periodically alternating at a predetermined frequency is impressed on the marker so as to provide an effective field impressed upon the center section of sufficient intensity to cyclically reverse the magnetization of the center section to result in the production of a detectable characteristic signal containing harmonics of the predetermined frequency in excess of the twentieth order.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×