A DEVICE AND A METHOD FOR SAFEGUARDING AN ARTICLE AGAINST THEFT

DISPOSITIF ET METHODE DE PROTECTION D'ARTICLES CONTRE LE VOL

English Abstract

The invention relates to a device and a method for electronic
supervision of articles, consisting of a security element which
is connected to an article to be safeguarded and which is
excited by a magnetic alternating field generated within an
inquiry zone to send a characteristic signal by which an alarm
is triggered. The objective of the invention is to propose a
device and a method which respectively render removal of a
security element from an article to be safeguarded considerably
difficult. The task is solved by the device in that a
protective film is provided which completely covers the
security element and the article at least in the area of the
security element.

Claims

1. A device for electronic supervision of an article,
comprising at least one security element which is connected to
an article to be safeguarded and which is excited by a magnetic
alternating field generated within an inquiry zone to send a
characteristic signal by which an alarm is triggered, and
a protective film which completely covers the article, at
least in the area of the security element,
the security element being in the form of a strip made
from a soft magnetic material,
the security element being an integral part of the
protective film,
the protective film being a laminate comprising a
plurality of layers with the security element sandwiched
between two adjacent layers of the laminate, and
the protective film being a tube which is either drawn
over the article or made from a sheet of protective film
wrapped and fixed around the article.
2. A device in accordance with claim 1, wherein the security
element is a thin film made from a soft magnetic material.
3. A device in accordance with claim 1 or 2, wherein the
protective film is a heat-shrink film which contracts with
application of heat.
4. A device in accordance with claim 3, wherein said at least
one security element comprises a plurality of security elements
each sandwiched between two adjacent layers of the laminate and
arranged in areas lying parallel to each other.
5. A method of electronic supervision of an article, in which
at least one security element is used which is connected to an
article to be safeguarded and in which the security element is
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excited by a magnetic alternating field generated inside an
inquiry zone to send a characteristic signal which triggers an
alarm, wherein
a protective film is connected, at least in the area of
said at least one security element, to the article to be
safeguarded in such a way that the said protective film can be
detached by destruction of said article,
the security element is formed as an integral part of the
protective film which is a laminate comprising a plurality of
layers with the security element sandwiched between two
adjacent layers of the laminate, and the protective film is
then wrapped and fixed around or drawn over the article to form
a tube around the article.
6. A method in accordance with claim 5, wherein said at least
one security element comprises a plurality of security elements
arranged parallel to each other and in which the laminate is
cut to the necessary size according to the article to be
safeguarded.
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Description

CA 02205213 1997-OS-12
device and a me hod for safeguardin~w an article
against theft
The invention relates to a device and a method for
electronic safeguarding of an article against theft.
Various security elements have already been published
for electronic safeguarding of articles against theft.
One particularly advantageous design of a security
element in the form of a thin film label is described in
EP 0 295 028 B1. Thin film labels consist of a thin
layer of soft magnetic material, preferably within the
~m range. The soft magnetic layer is preferably placed
on a carrier substrate by a physical process of
depositing under vacuum conditions.
Besides thin film labels, so-called "strip" security
elements are used especially for safeguarding articles
in the foodstuffs sector. Such elements consist of a
strip of soft magnetic material or a soft magnetic wire.
Oscillating resonance circuits are also used as security
elements for safeguarding articles. Such security
elements are, for example, described in detail in EP 285
559 Bl. EP 0 093 281 B1 describes security elements
which are excited by mechanical oscillations when an
alternating magnetic field is applied and which generate
a detectable signal.
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CA 02205213 1997-OS-12
Furthermore, so-called 'intelligent' transponders are
described in EP 0 494 114 A2, which in addition to
safeguarding articles of merchandise to which they are
fixed, also enable unequivocal identification of the
articles concerned. The same patent specification also
describes the design of a suitable detection system.
A large number of different methods have already been
published for detection of security elements in an
inquiry zone. For instance, EP 123 586 B proposes, in
addition to two inquiry fields with frequencies fl and
f2 in the kHz range, the sending of one field with a
frequency within the Hz range into the inquiry zone.
The two inquiry fields having fl and f2 frequencies
excite a security element situated in the inquiry zone
to send a characteristic signal having intermodulation
frequencies n.f1 ~ m.f2 (n, m = 0, 1, 2, ...). The low-
band inquiry field causes the security element in this
field frequency to be driven from saturation in one
direction to saturation in the other direction. The
characteristic signal therefore takes place periodically
at the frequency of the low-band field.
As an alternative solution, use of only one inquiry
field within the kHz range for excitation of the
security element has also been published, in which the
characteristic signal of the security element again
takes place at the frequency a low-band field which
drives the soft magnetic material backwards and forwards
between the two saturations.
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CA 02205213 1997-OS-12
For detection by security elements with oscillating
resonance circuits, a narrow band alternating field
which excites the security element to send a
characteristic signal in its resonance frequency range
is radiated into the inquiry zone.
The object of the present invention is to propose a
device and a method which respectively render removal of
a security element from the article to be safeguarded
considerably difficult.
With regard to the device, this task is solved in that, a
protective film is provided which completely covers the
security element and the article, at least in the area
of the security element.
In accordance with beneficial further developments of
the device according to the present invention, the
security element consists either of a strip or a thin
film made from soft magnetic material or of an
oscillating resonance circuit having capacitance C,
resistance R and inductivity L, or of a
magnetomechanical security element which is excited into
mechanical oscillations by a magnetic alternating field.
By way of protective film, it has proved to be extremely
advantageous to use a film which contracts with changes
of temperature (shrink film). Such films are well known
and serve i.a. to protect an article from damage. They
are also widely used , in cases where it is necessary to
protect products against unauthorized opening, thus
ensuring, especially for packages containing valuable
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CA 02205213 1997-OS-12
products, that no exchange or mixing of the .original
product can take place.
In accordance with the present invention, the protective
films also fulfil the additional function of connecting
the article to be safeguarded to the security element
and preventing any manipulation of the security element
in a simple but nevertheless extremely effective way.
The version in which the film takes the form of a tube
which is drawn over the article and the security element
can be regarded as particularly advantageous. An
alternative to the tubular-shaped protective film is a
sheet formation which is wrapped round the article and
the security element. The film is either heated after
wrapping round the article or it is wrapped around the
article in an already heated state. When the film cools
it shrinks and adjusts optimally to the shape of the
article to be safeguarded.
It can be regarded as especially advantageous if the
protective film is a laminate, in which the security
elements are embedded and preferably arranged in zones
lying parallel to each other. The size of the
protective film can easily be adjusted to the article to
be safeguarded by subdividing it in appropriate laminate
segments.
With regard to the method, the task is solved in that a
protective film is connected to the article to be
safeguarded at least in the area of one security element
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CA 02205213 1997-OS-12
in such a way that the said protective film can only be
removed from the article by destruction.
According to a first possibility, the security element
is connected to the article, e.g. laid or glued onto the
article; the protective film is then wrapped round the
article at least in the area of the security element or
drawn over the article.
As an alternative version of the method according to the
present invention, it is proposed that the security
element is connected to the protective film; the
protective film is then wrapped round the article or
drawn over the article so that in this case also the
security element is situated between the article and the
protective film. In this example it is particularly
beneficial if the protective film together with the
integrated security elements is manufactured as a
laminate with the security elements arranged parallel to
each other; the laminate is then cut to the necessary
size according to the article to be safeguarded.
A third advantageous further development of the method
according to the present invention proposes the security
element as an integral component of the protective film.
In this way, placing the security element and the
protective film on the article is rendered considerably
easier, since handling of separate parts is no longer
necessary.
The invention is explained more closely on the basis of
the following figures, which show:

CA 02205213 2001-05-08
Figure 1: a diagram of a version of the device
according to the invention.
Figure 2a: a top view of a strip security element.
Figure 2b: a top view of a thin film security element.
Figure 2c: an exploded view of a security element with
an oscillating resonance circuit.
Figure 3a: a top view of a protective film.
Figure 3b: a perspective view of a tubular protective
film, and
Figure 4: a perspective view of an advantageous further
development of the device according to the invention.
Figure 1 gives a diagram of a version of the device
according to the invention. The security element 3 - in
the version represented the security element is a strip
3.1 made from soft magnetic material - is rigidly fixed
between the article 1 and the protective film 2.
In Figure 2a the strip security element 3.1 is shown
separately. Figures 2b and 2c show a thin film label
3.2 and a label 3.3 with an oscillating resonance
circuit. As shown in the exploded view in Figure 2c,
the security element 3.3 with oscillating resonance
circuit consists of a spiral conductor element 4 (-->
inductivity L and resistance R and a capacitor 5 (-->
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CA 02205213 2001-05-08
capacitance C), in which the two capacitor boards 5 are
distanced from each other by a dielectric layer 6.
Figure 3a shows a top view of a sheet formation of
protective film 2 which is wrapped round an article 1,
such that the security element 3 is fixed between the
article 1 and the protective film 2. An especially
beneficial design of the protective film 2 in tubular
form is illustrated in Figure 3b.
Figure 4 shows a perspective view of an advantageous
further development of the device according to the
invention. In this version, the protective film 2
inclusive of the security elements 3.1 takes the form of
a laminate 7. The security elements 3.1 are arranged in
areas lying parallel to each other. According to the
size of the article to be safeguarded, the laminate 7 is
divided into areas B of differing size.

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List of Reference Numbers
Article
2 Protective Film
3.1 Strip Security Element
3.2 Thin Film Security Element
3.3 Security Element with Oscillating Resonance Circuit
Spiral Conductor Element
Capacitor Board
6 Dielectric Layer
Laminate
Area
C Capacitance
L Inductivity
R Resistance
_ g _

Representative Drawing