Classifications

• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2405—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used
  • G08B13/2414—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting characterised by the tag technology used using inductive tags
  • G08B13/242—Tag deactivation
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2428—Tag details
  • G08B13/2437—Tag layered structure, processes for making layered tags
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2428—Tag details
  • G08B13/2437—Tag layered structure, processes for making layered tags
  • G08B13/244—Tag manufacturing, e.g. continuous manufacturing processes
• • G—PHYSICS
  • G08—SIGNALLING
  • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
  • G08B13/00—Burglar, theft or intruder alarms
  • G08B13/22—Electrical actuation
  • G08B13/24—Electrical actuation by interference with electromagnetic field distribution
  • G08B13/2402—Electronic Article Surveillance [EAS], i.e. systems using tags for detecting removal of a tagged item from a secure area, e.g. tags for detecting shoplifting
  • G08B13/2428—Tag details
  • G08B13/2437—Tag layered structure, processes for making layered tags
  • G08B13/2442—Tag materials and material properties thereof, e.g. magnetic material details

Definitions

• the invention relates to a method of producing tag which can be activated and deactivated according to th preamble of claim 1.
• a known and very spread method of securing article against theft - especially in self-service stores - is t employ electronic security systems elaborated, for example with a transmitter for emitting electromagnetic waves and corresponding receiver.
• the articles are marked with specia tags on which are placed one or more resonant circuit/ built up of a connection between a coil and a capacitor however, several coils and capacitors may be used in th single circuits.
• these elements are made of alumi nium on a bearing layer consisting of plastic or simila material having insulating properties, and the conductiv layer may be placed whether on the one side only or on bot sides of the bearing layer, as the bearing layer is actin as a dielectric medium within the used capacitor/ ⁇ .
• Th circuit is supposed to have a high quality factor (Q-value)
• the transmitter is emitting signals having frequencie which systematically are varied within a specified * rang where the resonant frequency of the resonant circuit i lying, and due to the high Q-value of the circuit, the re DCver will be able to detect the resonant circuit when th natural frequency of said resonant circuit is emitted.
• said tag By applying a tag, said tag is exposed to an electro ⁇ magnetic field in order to detect whether the resonant cir ⁇ cuit of the tag has a specified natural frequency and ob ⁇ viously, said field may not cause modifications of the reso- nant .circuit.
• a field which is applied in order to modify the circuit be able to accomplish that task perfectly at a determined field strength, thus it has to be required that the disctance between the capacitor plates in the area to be destroyed is well defined by a uniform size. It has appeared to be appropriate to apply a thickness upon the dielectric medium located between the capacitor plates in the area to be destroyed of about 3 ⁇ m. Minor thicknesses may reduce the Q-value of the circuit.
• US Patent Specification No. 4.498.076 discloses method of producing a* resonant circuit suitable for modifi cation, in as much as a small distance between two capacito plates within the resonant circuit is created by pressin the conductive layer - normally aluminium but other conduc tive materials may be used as capacitor plates as well into the intermediate dielectric medium by means of a pisto so that in a small region, the thickness of the dielectri medium becomes smaller than outside this region and thu ⁇ i is possible to generate a breakdown in the capacitor at lower voltage than it is the case outside such a region.
• the conductive layer is pressed down in such a manner that the thickness of the conductive layer is reduced, which may - as will be explained later on - result in the fact that the capacitor, in spite of sparking breakdown may continue to act as a capacitor (self-healing capacitor) , and the des ⁇ truction is uncertain,
• the present invention provides a method where by means of heat impact on the insulated materials placed on the tags, regions are established where the thickness of the insulants by a slight pressure is reduced to a predetermined thickness with high precision so that a breakdown can be produced by applying electromagnetic or electric fields with low field strength.
• the method comprises the heating of one or more smal- ler regions on a capacitor forming part of the resonant cir ⁇ cuit.
• the dielectric medium is softened or possibly melted, and by applying a slight pressure on the heated region, there is with high precision brought ' about a region having the predetermined thickness of the dielectric medium layer.
• the invention provides a method which is cheap, tech ⁇ nically simple and easy to control, as the method comprises several parameters, such as temperature, size of the impact region,, time of the impact, ' size of the pressure applied, shape of the impact region, which can be combined in accor ⁇ dance with the conditions of production.
• the invention offers a complete liberty of choosi the way of heating as a heating element, laser, ultrasoun microwave or another appropriate process may be used, a finally, it has to be emphasized that the necessary pressu on the dielectric material is substantially lower than t pressures used in known prior art.
• the production result obtained is well defined wi a minor failure rate, and the thickness of the dielectr layer in the treated regions is procured with a bigger a curacy and uniformity than in the known prior art.
• An alternative method of providing a region in t dielectric medium where the dielectric medium has the desir thickness provides a dielectric medium with a hole throug out it. In this hole, a dielectric medium having the desir thickness is placed in such a way that in this area, on one thickness of the dielectric medium is pre ⁇ ent whi corresponds to the size of the desired fields applied, that a breakdown occurs for sure.
• the dielectric medium there can be plac a piece of a conductive material having a suitable thickne and being in conductive electrical connection with the o capacitor plate.
• the capacitor is finished by co pres ⁇ ive stress.
• t hollowing of the dielectric medium could be avoided by pla cing on the one capacitor plate as above a piece of conduc tive material of suitable dimensions in electrical connecti with this capacitor plate, whereupon the dielectric laye under pressure is applied to the capacitor plate and th other capacitor plate whether is applied at the same tim with it or during another operational step.
• Fig. 1 is a plane representation of a resonant circui forming part of a tag
• Figs. 2 and 2A show a section across a part of capacitor in the circuit of Fig. 1,
• Fig. 3 shows a section across a number of conductor being part of the winding of the coil in the circuit o Fig. 1,
• Fig. 4 is a section across the capacitor where th dielectric layer between the capacitor plates has a thickness of 'a proportional size compared with the thickness of the capacitor plates,
• Fig. 5 is a section across a capacitor where the dielectric layer between the capacitor plates has a rela ⁇ tively small thickness compared with the thickness of the capacitor plates
• Fig. 6 shows a section across a capacitor with a hole in the dielectric medium in which is placed a precisely dimensioned piece of dielectric medium
• Fig. 7 shows a section across a capacitor with a hole in the dielectric medium in which is placed a precisely dimensioned piece of conductive material
• Fig. 8 shows a section across a capacitor being as ⁇ VISd and where a piece of conductive material is pressed into the dielectric medium.
• the conductive material in the resonant circuit 1 shown in Fig. 1 will preferably be aluminium but other con ⁇ ductive materials may be used as well.
• the conductive layer may be produced by acid etching and placed whether on t one side only of a bearing plastic material 2, or on .bo sides of said plastic material. In the latter, the beari material can immediately act as a dielectric medium in t capacitor 3.
• a dielectric medium has to placed on the capacitor plate located on the bearing laye whereupon a conductive layer is applied to the dielectr medium.
• the one end 5 of the coil 4 is directly connect with the one plate in the capacitor 3, while the other e 6 for example is closed by a plate which is connected wi the other plate in the capacitor, for instance as sho with the two dotted lines 4a, by means of leading a condu tive path across the turns of the coil with an insulatin layer between the turns of the coil and the conductive pat or also - in connection with a bearing layer having a con ductive layer on both sides - by means of leading a connec tion through the plastic layer.
• the conductive layer may also be produced by mean of blank cutting.
• Fig. 2 shows a cross-section across a part of a capa citor where the capacitor plates 7 formed in a conducti material are separated by a dielectric medium 8.
• this dielectric mediu is subjected to, for instance, a heating element 9, by mean of which a suitable insulating material is inflicted a con sistency which makes it possible to reduce the thickness o the dielectric medium to the intended size by a slight pres sure.
• the heating may be performed by a heating element bu also other means for energy transfer may be used, such a for instance ultrasound, laser or microwaves.
• the pressur on the dielectric medium may be performed by the heatin element or by creating vacuum or excess pressure on th surfaces of the capacitor.
• Fig. 3 shows a part of a section across a coil in a resonant circuit on a tag where ' the single turns in the coil 10 are placed on a dielectric layer 11, and where above a number of turns 10 is located another dielectric layer 12 with the intended small thickness provided by the method explained herein / and on which is placed a conductive layer 13.
• a suitable field impact a breakdown will occur and after that, a subsequent short-circuiting of the coil.
• the plate 13 with the dielectric layer 12 may be placed in any area on the coil, it shall only cover two or more turns 10, or be located above the inlets of the coil.
• Figs. 4 and 5 show a section through a capacitor for illustrating how such a capacitor can be "self-healing" after a breakdown.
• Fig. 4 shows a capacitor where the dielectric material 15 is substantially thicker than the plates 16.
• the holes resulting from sparking breakdown are bigger in the capacitor plates 16 than in the dielectric material 15.
• the two capacitor plates 16 continue to be insulated from each other, and therefore, the capacitor continues to act like this and thus, an in ⁇ table short-circuiting is provided.
• Fig. 5 shows an embodiment of a capacitor which in a stable manner is destroyed by a deactivation signal.
• the dielectric layer is much thinner than the capacitor plates 16, and the hole in the metal plates 16 after the breakdown is smaller than the hole in the dielectric layer 15, and therefore, a stable short-circuiting is provided.
• Figs. 6, 7 and 8 show alternative methods of producing an element in the re ⁇ onant circuit for activa ⁇ tion and deactivation on tags, in as much as uniform parts have the same numeral reference.
• the dielectric medium 18 in Fig. 6 having a thickness of e.g. 10 ⁇ m is provided with a hole 19 wherei is placed a small piece of a dielectr medium 20 with the intended thickness, e.g. 3 ⁇ m.
• a strip of condu tive material 21 in electric connection with the capacit plate 17 could be inserted, as ⁇ hown in Fig. 7, in order obtain the intended precise distance between the capacit plates 17.
• Fig. 8 hows a method where a strip of co ductive material 21 being in conductive connection with t plate 17 by pressure is pressed into the dielectric materi 18 in such a manner that again, the intended preci ⁇ e distan between the capacitor plates 17 is obtained.
• the resonant circuit may again be cut o with a stronger field, as explained before.
• a modification of the natural frequen of the circuit occurs.
• the deactivation of the tag may be perform with two frequencies in order to detect the state of th tag.

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• Physics & Mathematics (AREA)
• Engineering & Computer Science (AREA)
• Automation & Control Theory (AREA)
• Computer Security & Cryptography (AREA)
• Electromagnetism (AREA)
• General Physics & Mathematics (AREA)
• Manufacturing & Machinery (AREA)
• Burglar Alarm Systems (AREA)

Applications Claiming Priority (2)

Publications (1)

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ID=8115872

Family Applications (1)

Country Status (4)

Families Citing this family (8)

Family Cites Families (8)

• 1990
  • 1990-11-23 DK DK279690A patent/DK166176C/da not_active IP Right Cessation
• 1991
  • 1991-11-20 JP JP3518658A patent/JPH06502733A/ja active Pending
  • 1991-11-20 EP EP19910920554 patent/EP0558579A1/de not_active Withdrawn
  • 1991-11-20 WO PCT/DK1991/000346 patent/WO1992009978A1/en not_active Application Discontinuation

Non-Patent Citations (1)

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