Magneto-elastically excitable tag having a reliably deactivatable amorphous alloy for use in a mechanical resonance monitoring system

US5728237A · kind A · utility

Assignee

• Vacuumschmelze GmbH & Co. KG · DE

Inventor

• Giselher Herzer · Bruchköbel, DE

Key dates

• Filing date: Dec 9, 1996
• Grant date: Mar 17, 1998
• Expiry date: Dec 9, 2016

Classification

• Technology area (CPC H): Electricity
• CPC primary: H10N35/85
• WIPO field: Control
• WIPO sector: Instruments

Abstract

Amorphous alloys having the formula EQU Fe.sub.a Co.sub.b Ni.sub.c Si.sub.x B.sub.y M.sub.z are employed as monitoring strips for mechanically oscillating tags, for example for anti-theft protection, together with a source of a pre-magnetization field in which the strip is disposed so as to place the strip in an activated state. In the formula, M denotes one or more elements of groups IV through VII of the periodic table, including C, Ge and P, and the constituents in at % meet the following conditions: a lies between 20 and 74, b lies between 4 and 23, c lies between 5 and 50, with the criterion that b+c>14, x lies between 0 and 10, y lies between 10 and 20, and z lies between 0 and 5 with the sum x+y+z being between 12 and 21. These alloys have a resonant frequency associated therewith and when passed through an alternating field whose alternation frequency coincides with the resonant frequency, a pulse having a signal amplitude is produced. These alloys can be deactivated by removing the pre-magnetization field, which causes a change in the resonant frequency and the resulting signal amplitude. These alloys exhibit a change in resonant frequency and signal amplitude due to chang…