Deactivatable electronic article surveillance markers using short semi-hard magnetic wires

A deactivatable electronic article surveillance marker is produced by placing elongated magnetically soft elements on a support and aligning short sections of magnetically semi-hard wires parallel to one another in bands with the bands being perpendicular to the elongated ferromagnetic materials. In another embodiment a criss-cross configuration of magnetically soft elements are provided and the bands of magnetically semi-hard wires are placed diagonally relative to the criss-cross elongated soft magnetic elements.

BACKGROUND OF THE INVENTION 
A high degree of interest has been shown over the past years in the field 
of theft detection using electronic article surveillance systems wherein 
electronically sensitive devices, know as markers, are introduced into a 
electromagnetic field known as an interrogation zone, to emit a signal in 
response to such magnetic field. Electronic article surveillance (EAS) 
systems and markers for use therein were disclosed by P.A. Picard in 
French Patent Number 763,681 (1934). Generally, certain ferromagnetic 
alloys exhibit high magnetic permeability and low coercivety thereby 
making their use as EAS marker attractive. Materials for such markers have 
been made as disclosed in U.S. Pat. Nos. 4,581,524 and 4,568,921 and U.S. 
patent application Ser. No. 290,547. Although these markers generally work 
well, without the ability to deactivate such markers, i.e. rendering them 
unresponsive in an interrogation zone, the use of EAS systems becomes 
limited. For example, when an article with a marker attached thereto is 
purchased in a first store and the purchaser subsequently enters a second 
store with the article bearing the marker, the marker could generate an 
alarm in the EAS system of the second store unless measures are taken to 
avert the same. As is generally known, there are walk around systems as 
used in institutions such as libraries where the books are checked out. 
Thereafter, the individual walks through the gates of the EAS system 
without the book and is then given the book as it is it is passed around 
the gates. Although this system works well in controlled areas, such as 
libraries, it is not adequate in the commercial use of EAS systems. 
In U.S. Pat. No. 3,747,086, a deactivatable marker is described that has a 
soft magnetic strip which is detectable in an interrogation zone of an EAS 
system. In addition to such soft magnetic strip, two hard magnetic strips 
elements are placed adjacent to the soft magnetic strip and these have 
distinctive magnetic properties which are not the same as the detectable 
soft magnetic strip. After a marker has been used for the purposes of 
theft detection, it is then deactivated by placing the marker in a 
magnetic field of high strength to magnetize the two hard magnet strips 
thereby rendering the marker undetectable. Although this marker functions 
adequately, it requires a relatively high magnetic field in order to 
deactivate the marker. Such high magnetic field is not only energy 
inefficient, and expensive, but also could present health hazards to those 
about the high magnetic field for extended periods. Furthermore, a 
relatively high amount of magnetic material is used in such prior art 
deactivatable markers. 
It clearly would be advantageous to provide an EAS marker that can be 
readily deactivated in a relatively low magnetic field and uses a low 
quantity of magnetic material. 
BRIEF SUMMARY OF THE INVENTION 
This invention is concerned with the field of theft detection using an 
electronic article surveillance (EAS) system. More particularly, it is 
directed to deactivatable EAS markers and method of making the same. 
Elongated soft magnetic materials responsive to a interrogation zone are 
aligned on a surface label so as to provide a signal when introduced into 
an interrogation zone of an EAS system. Shorter length wire of 
magnetically hard materials are aligned with the magnetically soft 
materials and secured with the latter to a support member. When the marker 
is to be deactivated, it is introduced into a relatively high magnetic 
field to magnetize the wires. With such magnetization of the wires, when a 
marker is reintroduced into an interrogation zone, a detectable signal 
will not be generated by the marker.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
With initial reference to FIG. 1, an EAS marker is shown generally at 10 
and includes a support 12, such as paper or plastic tape, to which a 
plurality elongated magnetically soft elements 14 are attached. As shown, 
the soft magnetic elements 14 are in the form of fibers as described in 
U.S. patent application No. 290,547, which will have a coercivity of less 
then one. Although the invention is described in connection with the use 
of fibers, it will be appreciated that other forms of elongated soft 
magnetic materials can be used such as in strip form as described in U.S. 
Pat. No. Re 32,427 or wires as described in U.S. Pat. No. 4,568,921. 
The magnetically soft elements 14 are attached to the support 12 as by an 
adhesive. Normally, the marker 10 will have the soft magnetic fibers 14 
secured by a second support member that overlies and is attached to the 
first support member 12, as by adhesives, but for purposes of clarity and 
convenience, the invention will be described in conjunction with the use 
of only one support member 12. In any case, the soft magnetic fibers 14 
are generally 1 to 2 mils in diameter and parallel to one another. 
Adjacent to and intermediate the soft magnetic fibers 14 are a plurality 
of semi-hard magnetic wires 16 made of a material such vicalloy (38% Fe, 
50% Co and 12% V). Generally, the semi-hard magnetic material will have a 
coercivety of 50 to 300 O.sub.e and a reminence of 8,000 to 12,000 Gauss. 
The lengths of the semi-hard magnetic wires 16 should be approximately 
0.067 inches when used with the soft magnetic fibers 14, but the length of 
such wires may be between 0.032 and 0.10 inches depending upon the type of 
soft magnetic element with which it is used. The diameter of the wires 
should be 0.5 mils to 2.0 mils depending upon the diameter or quantity of 
the soft magnetic fibers 14. As can be seen, the semi-hard magnetic wires 
16 are aligned in a plurality of laterally extending rows, six such rows 
being seen in FIG. 1 and the wires within each row are generally parallel 
to one another and located adjacent to the outside fibers 14 and 
intermediate all of the fibers. 
One mil vicalloy wire was sectioned into lengths of approximately 0.067 
inches. An amount of wire was weighed equal to 1.5 to 4 times the amount 
of fiber 14 present on the support 12. The wires were layered randomly 
over of the parallel fibers on the support 12. The support 12 was then 
placed upon a multipole pair strip magnet having 10 or more poles per inch 
(ppi) and a strength of 600 Gauss so that the magnetic wires 16 were 
shorter than the pole spacing of the strip magnet. 
The strip magnet was vibrated and the short wires 16 settled in an 
orientation similar to the pole configuration of the strip magnet. After 
settling, adhesive was applied to the support 12 to hold the fibers 14 and 
wires 16. Alternatively the wires 16 can also be aligned by applying an AC 
electromagnetic field in short bursts instead of vibrating over a magnetic 
strip. 
The final configuration of the wires 16 consists of bands 18 of short 
wires, which bands are disposed perpendicular to the fibers 14 as seen in 
FIG. 1. The short wires 16 that make up each band 18 are aligned generally 
parallel to the fibers 14. Such a marker 10 is readily detectable in a 
magnetic field of 2 O.sub.e. 
The configuration described results in the short wires 16 magnetically 
biasing the longer fibers 14 in specific areas along the lengths of the 
fibers 14 after the wires 16 have been magnetized. This biasing of 
sections makes the fibers 14 appear as if they were actually multiple 
short magnetic elements thereby effectively reducing the magnetic aspect 
ratio of the fibers. As the aspect ratio of the fibers 14, length to 
diameter ratio, decreases below 400, the signal of the fibers degrades. As 
a consequence, the greater the magnetic sectioning of the fibers 14 by the 
shorter wires 16, the greater the switching signal will be altered after 
the short wires are magnetized. Alteration of the fiber 14 signals will 
result in the EAS detection gates discriminating against the original 
signal after the marker 10 has been deactivated. Such magnetization of the 
semi-hard magnetic short wires 16 is accomplished by placing the marker 10 
in a magnetic field of 200 to 600 O.sub.e with the wires being parallel to 
the flux of the magnetic field. After such magnetizing of the wires 16, 
the markers will not be detected in an interrogation zone, particularly 
they will not be detected in a interrogation zone of greater than 25 
O.sub.e. 
It is possible to fabricate the wire deactivation process within a marker 
10 with as low as a 1.5:1 ratio of deactivation material 16 to soft 
magnetic material 14 with a ratio range of 2:1 to 4:1 being acceptable. 
This low amount of semi-hard magnetic material is only possible because 
the wires 16 are all aligned parallel to each other. When an external 
field of 200 to 600 O.sub.e is applied and is parallel to the wires, all 
the wires 16 are fully magnetized. In this case, the deactivation material 
is used in its most efficient magnetic state. If the wires were randomly 
placed, the applied field would only fully saturate the wires that were 
parallel to the field. The magnetization of the non-parallel wires would 
be proportional to the angle between the magnetizing field and the wire. 
This is a poor and inefficient use of the material's magnetic properties 
and would force a higher amount of semi-hard to deactivate the marker 12. 
If the wires 16 are too randomly oriented, deactivation may not be 
possible at all. 
It was been found that markers of this type are particularly advantageous 
because the magnetic aspect ratio of the fibers 14 are affected rather 
than a masking of the soft magnetic materials as is taught in the prior 
art. 
With reference now to FIG. 2, another embodiment of the instant invention 
is shown in connection with a label 10A, having a support 12 and fibers 14 
aligned on a criss-cross pattern, i.e, two sets of a plurality of fibers 
each set aligned perpendicular to the other. Semi-hard magnet wires 16 are 
aligned in bands 18 with the bands being oriented diagonally relative to 
the fiber 14. Using this configuration, it has also been found that such 
markers 10A have a greater pick rate. The short wires 16 are placed in 
diagonal rows 18 as seen in FIG. 2 to assure deactivation of the marker 
10A after magnetization of the short wires.