EP0509289A2 - Method for deactivating a resonant tag - Google Patents

Abstract

The essence of the method of producing a deactivable resonant circuit is essentially that, to treat the resonant circuit with a view to subsequent deactivation, the two capacitor surfaces are moved towards one another by means of a heated plunger. The heated plunger melts the dielectric underneath the plunger and the two capacitor surfaces are short-circuited. By applying a certain current/voltage source, this short-circuit is removed again by burning off, producing a crater-like hole in the thinner capacitor surface. This achieves the condition which makes short-circuiting possible in a subsequent deactivation. After the treatment, the electrical connection between the two capacitor surfaces should be disconnected and should only be permanently formed when the tag is in a deactivation station.

Description

The present invention relates to a method for deactivating a resonance label, as e.g. is used in anti-theft systems, in which labels on a carrier layer designed as a dielectric are arranged on the front or rear side of the preferably aluminum surfaces of a capacitor of the resonant circuit arranged on one side, with a state in view of the deactivation between the two capacitor surfaces is created, which upon induction of a deactivation current between the two surfaces, the formation of an electrical connection, ie a short circuit is guaranteed.

One of the major problems with the resonance labels that are common in anti-theft systems today is the reliable and contactless deactivation of the labels at the payment points (checkouts) of the secured retail stores. It is important that the deactivation can be carried out in a relatively simple manner and on the other hand that the deactivation carried out is reliable and final, i.e. the label can no longer trigger an alarm.

The deactivation is usually carried out by creating a short circuit between the two capacitor surfaces of the resonant circuit, so that the label can no longer trigger an alarm when it passes the curfew. Unfortunately, it has been shown in today's systems that deactivation is not guaranteed with full reliability and false alarms are triggered by clients who have properly paid for the goods. It is obvious that this harms the reputation of a sales business.

The object of the present invention is to provide a novel deactivation method for resonance labels of the type mentioned at the outset, in which the deactivation can be carried out with significantly increased security compared to the prior art and, above all, no reactivation can occur.

This object is achieved in the method according to the invention of the type mentioned at the outset in that in a first phase for preparing the label, i.e. To create the state mentioned, the two capacitor surfaces are guided or pressed locally in the direction of one another by means of a heated plunger, the plunger resting on the one capacitor surface being connected to one pole of a current / voltage source and the other capacitor surface being connected to the other pole of the current source, so that when a current flows, ie in the case of touching and / or crimped capacitor surfaces, the desired state can be regarded as having been reached and the mutual movement of the capacitor surfaces is thus interrupted.

The two capacitor areas are now short-circuited and the dielectric layer is completely displaced in a certain area.

In a further step (phase 2), a current-voltage source is again applied to the short-circuited capacitor and this crimping is burned off by electrical overload. Appropriate regulation of the ampere / volt ratio ensures that one capacitor surface, namely the thinner one, burns off in such a way that the distance between the edge of the burnt-out hole and the second capacitor surface corresponds precisely to the distance that can be deactivated.

A label prepared in this way can be deactivated at the desired point in time by induction of an electric current in an existing conventional deactivation station with the formation of a permanent conductive connection between the capacitor surfaces.

The flow of a current achieved during the preparation of the label can simultaneously be used to control the device which drives the plunger.

The plunger for preparing the label is usually heated to a temperature of 300 ° C to 500 ° C. The current source, which is used to determine the contact of the two capacitor surfaces, preferably outputs a current or a voltage of 50-100 mA or 1 to 2 V.

A resonant circuit is preferably used, the dielectric of which is a plastic film with good electrical properties, for example: polyethylene of 20 μm thickness.

The two capacitor areas e.g. made of aluminum, must have a certain thickness ratio, e.g. 10 j1. and 50 u preferably 1: 5. When preparing, the polyethylene is heated locally under the heated plunger (diameter approx. 3-7 mm) and displaced under the pressure of the plunger. The plunger can be attached to both the thicker and the thinner capacitor surface, but preferably from the thinner one. As soon as the approach of the two capacitor surfaces ends in a flat contact, the process, i.e. phase 1, can be ended. Once this approximation or crimping has been made, current can flow. It can therefore be measured that a complete approximation of the two metal surfaces has taken place. This current flow is then also used to control the plunger.

If, when preparing a label, the electrical connection is not interrupted after the plunger is withdrawn, this automatically ensures that the label is removed will be divorced. In this way, labels that are initially defective are eliminated in production.

In a preferred embodiment of the method according to the invention, the two capacitor areas are locally approximated to 1.5 to 3.0 u when preparing the label, so that commercially available deactivation stations can be used for the actual deactivation.

In the next step, phase 2, this crimping is used for the final preparation for deactivation. This crimp connection is burnt down due to electrical overload. The resulting heat not only burns one or more holes in the thinner capacitor surface, but also burns the plastic film of the dielectric in this area. This burning process depends on the current / voltage source applied and controls the desired distance between the lower edge of the hole and the second capacitor surface.

This burn-off process creates at least one hole in the thinner capacitor surface. These holes have an irregular crater-like rim. The current / voltage source mentioned should be able to deliver 10 to 20 volts and 2 to 3 amps. The resulting crater-like holes have a diameter of e.g. 70 u, whereby an air gap of 1.5 to 3 u was created in the area of the crater rim between the two capacitor surfaces. This completes the preparation of the resonant circuit for later deactivation.

The actual deactivation only takes place in the sales business, namely through the usual deactivation station. In this station, a current is induced between the prepared capacitor surfaces, which in the present case certainly creates an electrical connection in the form of an aluminum thread between the two capacitor surfaces by melting the aluminum. This short circuit can no longer be destroyed under normal conditions, and the label is therefore deactivated with the greatest possible certainty.

It was also found that the holes (craters) are always formed in the thinner capacitor layer during the preparation of the labels. This is due to the fact that a complete fusion of the material takes place first in the thinner layer.

The invention is explained in more detail below on the basis of an exemplary embodiment, the drawing showing what happens during the preparation of the label.

• Fig. 1 einen Ausschnitt (im Vertikalschnitt) einer Resonanz-Etikette für Sicherheitssysteme, mit den beiden Kondensatorflächen, vor einer Präparierung zur Deaktivierung;
• Fig. 2 zeigt ebenfalls schematisch, entsprechend Fig. 1, den angestrebten Idealzustand einer präparierten Etikette mit stark angenäherten, aber nicht kurzgeschlossenen Kondensatorflächen, welche sich zur Deaktivierung eignen (entspricht US-A-4 498 076);
• Fig. 3 eine ähnliche Darstellung, aus welcher hervorgeht, wie mit einem beheizten und unter Strom stehenden Stössel die erfindungsgemässe Präparierung einer Etikette in Phase 1 erfolgt;
• Fig. 4 einen Schnitt durch eine Resonanz-Etikette, welche nach Phase 2 gemäss dem erfindungsgemässen Verfahren präpariert wurde und für eine Deaktivierung bereit ist, und
• Fig. 5 illustriert die eigentliche Deaktivierung einer Resonanz-Etikette, wobei eine dauernde metallische Verbindung zwischen den beiden Kondensatorflächen geschaffen wird.

Show it:

• 1 shows a detail (in vertical section) of a resonance label for security systems, with the two capacitor surfaces, before preparation for deactivation;
• Fig. 2 also shows schematically, corresponding to Fig. 1, the desired ideal condition of a prepared label with closely approximated but not short-circuited capacitor areas which are suitable for deactivation (corresponds to US-A-4,498,076);
• 3 shows a similar representation, from which it can be seen how the preparation of a label according to the invention takes place in phase 1 with a heated and energized plunger;
• 4 shows a section through a resonance label which was prepared after phase 2 in accordance with the method according to the invention and is ready for deactivation, and
• 5 illustrates the actual deactivation of a resonance label, a permanent metallic connection being created between the two capacitor surfaces.

A resonance label is shown in Fig. 1 in section at the point where on both sides of a dielectric 1, usually made of polyethylene, are covered by capacitor surfaces 2, 3 made of aluminum foil. In view of the purposes of the present invention, it is advantageous to design the one capacitor area 2 to be substantially thinner than the opposite capacitor area 3. In practice, a thickness ratio of 1: 5 is selected.

According to US Pat. No. 4,498,076, FIG. 2 shows how a minimum distance d should be present at least at one point by bringing the capacitor areas closer together in order to obtain a short circuit in a conventional deactivation station by applying a voltage or a current. The distance between the two capacitor surfaces should be about 1 to 2.0 u. Specifically, it should be noted that in this patent a thin layer of the dielectric remains between the capacitor surfaces. When deactivating, it can now happen that carbonized dielectric creates the short circuit.

3 of the drawing illustrates how, according to the method according to the invention, the two capacitor surfaces 2, 3 are brought closer to one another by means of a plunger 4 which can be moved forwards and backwards and which is preferably heated to approximately 300 ° C. to 500 ° C. Thanks to the heated plunger 4, the dielectric (polyethylene) below the plunger is melted and completely displaced. If on the one hand the plunger 4, which bears directly against the one capacitor surface 2, and the other Since the second capacitor surface 3 is applied to a current / voltage source, specifically to different poles, a current will flow between the capacitor surfaces 2 and 3 at a certain time in the procedure according to the invention. The current flow thus serves to check that the dielectric has been completely displaced between capacitor surfaces 2 and 3.

4 shows the capacitor section after phase 2. The crimping has been removed due to electrical overload. It is a combustion-like process in which a crater-like irregular hole or several holes are created in the thinner condenser surface. At the same time, the dielectric burns in the area of the hole edge between the two capacitor surfaces. This creates the air gap S of about 1.5 to 3 u width.

This hole 6 has a diameter of e.g. about 70u. Part of the molten aluminum is piled up at the edge of the hole and forms the so-called crater.

It can also be seen from FIG. 4 that the air gap continues beyond the edge of the crater, specifically beyond the area where the lower crater rim is 3 u from the second condenser surface. This ensures that the deactivation always takes place using a metal thread.

This process can also be used as a quality control. After phase 2, no more current may flow from one capacitor surface to the other, since the crimping has been removed. If current still flows, the resonant circuit was faulty from the start or the crimping could not be released. The fact that electricity is still flowing can be converted into a control signal and the faulty label can thus be eliminated.

5 of the drawing illustrates a prepared label as it is in a deactivation station. Thanks to the type of preparation, during this deactivation there is certainly a fusion of the edge of the opening 6 of the capacitor surface 2 with the freely opposite capacitor surface 3. This creates a solid aluminum thread 7 which ensures the short circuit of the two capacitor surfaces and thereby ensures that that the label is deactivated and remains so.

Claims (12)

1. Method for deactivating a resonance label, such as this e.g. is used in shoplifting security systems, in which labels, preferably made of aluminum, of a capacitor of the capacitor of the resonant circuit arranged on one side are arranged on a carrier layer designed as a dielectric on the front or rear, with regard to the deactivation between the two capacitor surfaces a condition is created which, when a deactivation current is induced between the two surfaces, forms an electrical connection, ie ensures a short circuit, characterized in that in a first phase for preparing the label, i.e. To create the state mentioned, the two capacitor surfaces are pressed locally in the direction of one another by means of a heated plunger, the plunger resting on the one capacitor surface being connected to one pole of a current / voltage source and the other capacitor surface being connected to the other pole of the current source, so that when a current flows, ie In the case of touching and / or crimped surfaces, the desired state can be regarded as having been reached and the movement of the capacitor surfaces against one another is interrupted, so that in a second phase the electrical connection generated in this way is interrupted again by electrical overload, and finally such a label prepared in this way Desired time is deactivated by induction of an electric current in a deactivation station to form a permanent electrically conductive connection between the capacitor surfaces. 2. The method according to claim 1, characterized in that the plunger for preparing the label is heated to a temperature of 300 ° C to 500 ° C. 3. The method according to at least one of claims 1 or 2, characterized in that after the first phase in a certain area between the capacitor surfaces, there is no longer a dielectric layer and the resonant circuit is short-circuited. 4. The method according to at least one of claims 1 or 2, characterized in that a current or a voltage of 2 to 3 A or 10 to 20 V is applied to prepare the label between the two capacitor surfaces. 5. The method according to at least one of claims 1 to 4, characterized in that after the second phase the resonant circuit is no longer short-circuited and therefore again in essentially has its original resonance frequency. 6. The method according to at least one of claims 1 to 5, characterized in that the deactivatable label in the thinner of the two capacitor surfaces has at least one hole (Druchbrennpunkt). 7. The method according to at least one of claims 1 to 6, characterized in that each hole has an irregular crater-like edge. 8. The method according to at least one of claims 1 to 7, characterized in that there is no longer a dielectric layer in the region of the crater rim between the two opposite capacitor surfaces. 9. The method according to claim 4, characterized in that in the second phase by applying the current, the crimping, which was produced in the first phase, is burned off by overloading, a hole being created in one of the two capacitor surfaces by this process, the higher the power supply, the bigger the hole. 10. The method according to claims 4 and 9, characterized in that, depending on the power supply, the distance of the lower crater rim in one capacitor surface to the other capacitor surface can be regulated, a distance of 1.5 to 3 u being preferred. 11. The method according to at least one of claims 1 to 9, characterized in that the label to be prepared for deactivation is a dielectric made of a plastic film of 15 to 25 u, preferably a thickness of 20 u. (± 10%), the thickness of the two capacitor areas having a certain thickness ratio, e.g. between 1: 3 to 1: 7, preferably 1: 5. 12. The method according to at least one of claims 1 to 11, characterized in that the short circuit in the deactivated oscillating circuit is always a metal thread, since there is no plastic (dielectric) in the area around the crater rim where the deactivation takes place.

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