Communications: electrical – Condition responsive indicating system – Specific condition
Patent
1999-06-11
2000-12-05
Hofsass, Jeffery A.
Communications: electrical
Condition responsive indicating system
Specific condition
3405681, 148310, G08B 1314
Patent
active
061573019
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a marker (also called a tag or a label) for use in a magnetic electronic article surveillance system (EAS), the marker being of the type having an elongated alarm strip composed of an amorphous ferromagnetic alloy and at least one activation strip composed of a semi-hard magnetic alloy.
2. Description of the Prior Art
Magnetic antitheft systems and markers are well known and have been described in detail, for example, in European Application-0 121 649 and in PCT Application WO 90/03652. On the one hand, there are magnetoelastic systems in which the activation strip serves to activate the alarm strip by magnetization and, on the other hand, there are harmonic systems in which the activation strip serves, after its magnetization, to deactivate the alarm strip.
The alloys with semihard magnetic properties which are used for premagnetization strips include Co--Fe--V alloys, which are known as Vicalloy, Co--Fe--Ni alloys, which are known as Vacozet, and Fe--Co--Cr alloys. These known semihard magnetic alloys contain high proportions of cobalt, in some cases of at least 45% by weight, and are correspondingly expensive. In addition, these alloys are brittle in the magnetically final-annealed state, so that they do not have sufficient ductility to meet sufficiently the requirements for the display elements for antitheft systems. It is in fact a requirement for the display elements in magnetic antitheft systems that they have to be insensitive to bending and deformation.
In addition, the approach now being adopted is to introduce the display elements of antitheft systems directly into the product to be protected (source tagging). As a result, there is additionally the need to be able to magnetize the semihard magnetic alloys even from a relatively large distance or with relatively small fields. It has become apparent that the coercive force has to be restricted to values of 60 A/cm at maximum.
On the other hand, however, sufficient opposing field stability, as a result of which the lower limit of the coercive force is defined, is also required. Only coercive forces of at least 30 A/cm are suitable for this.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a marker for an electronic article surveillance system which has a pre-magnetization strip which satisfies the aforementioned requirements of having properties which are relatively insensitive to bending and deformation of the marker, and a coercive force between 30 and 60 A/cm.
This object is achieved according to the invention in a marker having a premagnetization strip comprising a semihard magnetic alloy which is composed of 0.1 to 10% by weight nickel, 0.1 to 15% by weight chrome, 0.1 to 15% by weight molybdenum and iron making up the rest with an overall proportion of iron, nickel and molybdenum of less than 95% by weight of the alloy.
The alloy may also contain 0 to 5% by weight cobalt and/or at least one of the elements Mn, Ti, Zr, Hf, V, Nb, Ta, W, Cu, Al, Si in individual proportions of less than 0.5% by weight of the alloy and with an overall proportion of less than 1% by weight of the alloy and/or at least one of the elements C, N, S, P, B, H, O in individual proportions of less than 0.2% by weight of the alloy and with an overall proportion of less than 1% by weight of the alloy. The alloy is distinguished by a coercive force H.sub.c of 30 to 60 A/cm and a remanence B.sub.r of at least 1.0 T (10,000 gauss).
The alloys according to the invention are ductile and can be excellently cold shaped before tempering, with the result that even reductions in cross section of more than 90% are possible. Premagnetization strips can be manufactured from such alloys, in particular by cold rolling, with thicknesses of 0.04 to 0.07 mm. In addition, the alloys according to the invention are distinguished by excellent magnetic properties and by high resistance to corrosion.
In a further embodiment of the invention has a pre-magnetization strip comprised
REFERENCES:
patent: 3971676 (1976-07-01), Detert et al.
patent: 4298862 (1981-11-01), Gregor et al.
patent: 4391656 (1983-07-01), Jin et al.
patent: 4415380 (1983-11-01), Jin et al.
patent: 4510489 (1985-04-01), Anderson, III et al.
patent: 4536229 (1985-08-01), Jin et al.
patent: 4960651 (1990-10-01), Pettigrew et al.
patent: 5313192 (1994-05-01), Ho et al.
patent: 5539380 (1996-07-01), Hasegawa et al.
patent: 5653824 (1997-08-01), Manning et al.
Ferromagnetic Materials Structure and Properties, McCurrie (1994), pp. 211-266.
"Ferromagnetism," Bozorth (1951), pp. 134-152.
Hausch Gernot
Radeloff Christian
Roth Ottmar
Hofsass Jeffery A.
Previl Daniel
Vacuumschmelze GmbH
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