Marker for use in an electronic article surveillance system
US6137412A · kind A · utility
Assignee
Inventor
Key dates
| Filing date | Jun 21, 1999 |
| Grant date | Oct 24, 2000 |
| Priority date | — |
| Expiry date | Jun 21, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG08B13/2442
- WIPO fieldControl
- WIPO sectorInstruments
Abstract
A marker for employment in a magnetic merchandise monitoring system is composed of one or more oblong, ductile, magnetostrictive strips composed of amorphous ferromagnetic material. These strips experience a change in resonant frequency due to a change of a pre-magnetization field and are excited to longitudinal, mechanical resonant oscillation at the resonant frequency f.sub.r due to an alternating magnetic field, whereby the mechanical stresses resulting from the resonant oscillations cause a change in magnetization of the strips and, thus, a detectable change of the alternating magnetic field. The material of which the strips are composed exhibits a flat B-H loop that proceeds optimally linearly into the range of saturation; further, the strips exhibit a magnetic anisotropy transverse to the longitudinal strip direction, whereby the anisotropy field strength is greater than the pre-magnetization field strength. The strips experience a change of the resonant frequency compared to the change of the pre-magnetization field strength of df.sub.r /dH.sub.Bias .gtoreq.1500 Hz/Oe and thereby exhibit the resonator quality Q.gtoreq.100 in a field range dH.sub.Bias .gtoreq.1 Oe.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.