WO2000004519A1 - Antivol - Google Patents

Antivol Download PDF

Info

Publication number
WO2000004519A1
WO2000004519A1 PCT/GB1999/002196 GB9902196W WO0004519A1 WO 2000004519 A1 WO2000004519 A1 WO 2000004519A1 GB 9902196 W GB9902196 W GB 9902196W WO 0004519 A1 WO0004519 A1 WO 0004519A1
Authority
WO
WIPO (PCT)
Prior art keywords
tag
inductance
tags
inductance coils
resonant circuits
Prior art date
Application number
PCT/GB1999/002196
Other languages
English (en)
Inventor
Anthony Parfitt
Original Assignee
Clan Holdings Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Clan Holdings Ltd filed Critical Clan Holdings Ltd
Priority to AU46383/99A priority Critical patent/AU4638399A/en
Priority to EP99929602A priority patent/EP1099201A1/fr
Publication of WO2000004519A1 publication Critical patent/WO2000004519A1/fr

Links

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
    • 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
    • G08B13/2434—Tag housing and attachment details

Definitions

  • the invention relates to a security tag for the protection of articles, and more particularly to a security tag for use in an Electronic Article Surveillance (EAS) system.
  • EAS Electronic Article Surveillance
  • Such systems are usually installed in clothing, book, pharmacy, hi-fi, white good, and some music retail outlets to prevent unauthorised removal of articles therefrom.
  • the systems typically comprise one or more transmitters and detectors in the form of pedestals located at the customer entry/exit points of a retail outlet. These pedestals transmit a signal to a tag attached to the article which responds by re-radiating a second signal which is detected by the said pedestals thus triggering an alarm to indicate an attempt at unauthorised removal of articles.
  • the tags may be permanently or releasably attached to the article. At the point of sale of the article, the tag is either removed from the article, or is deactivated if permanently attached thereto.
  • EAS tags and systems are designed around different operating parameters, and the primary systems currently in use are Split Frequency (SF) , Radio Frequency (RF) , Acousto-magnetic (AM) , Microwave Frequency (MF) , Electromagnetic (EM) .
  • SF Split Frequency
  • RF Radio Frequency
  • AM Acousto-magnetic
  • MF Microwave Frequency
  • EM Electromagnetic
  • an alternating magnetic field is transmitted between the pedestals and the tag is typically provided with a pair of LC resonant circuits which are electrically and/or magnetically coupled such that the second resonant circuit re- radiates a signal at a different frequency to that transmitted by the pedestals .
  • This allows the pedestals to detect an active tag on an article as it passes therebetween.
  • tags may be attached to a large number of articles within the retail premises where the EAS system is installed, there is a requirement that the tags are inexpensive, and therefore the inclusion of complex circuitry in the tag or the provision of a battery powered circuit are precluded.
  • a further disadvantage of the magnetically coupled resonant circuits incorporated within certain tags is that there is a often a mathematical restriction on the mutual coupling between the first and second circuits. Circuits which are too effectively mutually coupled fail to re-radiate a signal at a second and different frequency from that transmitted by the pedestals. Furthermore, it has be shown that certain resonant circuits become more sensitive and as a result more difficult to "tune" as the mutual coupling therebetween is increased. More specifically, the mutual coupling between the inductance coils of a resonant circuit affects the resonant frequency of each of said resonant circuits because the mutual inductance between the coils is reflected as an additional impedance in each of the resonant circuits .
  • the extent to which the inductance coils are disposed on a ferromagnetic core linking the two coils can affect both the mutual inductance between the coils and the self-inductance value within a resonant circuit. It will thus be appreciated by persons skilled in the art that by adjusting the position of the resonant circuits on the ferromagnetic core, the circuits can be tuned to provide a maximum response characteristic to magnetic radiation transmitted by the pedestal and received by the tag at a first frequency.
  • a yet further disadvantage of current tags which incorporate magnetically coupled resonant circuits is their generally linear configuration which results from the linear nature of the ferromagnetic core which often couples the two circuits within the tag.
  • the pedestals transmit a substantially uniaxial magnetic field, and that it is essential that this field induces a current in a inductance coil provided in at least one of the resonant circuits within the tag, the particular orientation of the tag as it passes through the field becomes important. More particularly, if a linear core and henceforth the longitudinal axis of the inductive coil thereon is perpendicularly orientated to said transmitted uniaxial field, then no current will be induced in the coil, and the tag will fail to re-radiate a second signal for detection.
  • a tag for use in an EAS system said tag being provided with first and second resonant circuits between which there is at least some mutual magnetic coupling and/or electrical coupling, said first resonant circuit comprising a first inductance coil and said second resonant circuit comprising a second inductance coil, characterised in that the longitudinal axes of said first and second inductance coils subtend an angle of ⁇ °, where 0° ⁇ ⁇ ° ⁇ 180°, ⁇ ° ⁇ >90°.
  • a ferromagnetic core enhances the coupling between the first and second inductance coils .
  • the longitudinal axes of the first and second inductance coils subtend an angle of ⁇ °, where 90° ⁇ ⁇ ° ⁇ 180°.
  • first and second inductance coils are at least partially disposed around either end of a single ferromagnetic core which couples first and second inductance coils, the ends of said ferromagnetic core being inclined towards one another by an amount ⁇ °, where 90° ⁇ ⁇ ° ⁇ 180°.
  • the "cranked" configuration of the tag according to the invention mitigates the problems associated with inducing a current in at least one of the resonant circuits because regardless of the orientation of the tag, at least one of the ends of the ferromagnetic core will always receive at least some magnetic flux from the transmitted uniaxial magnetic field. Furthermore, the mutual coupling between the respective first and second inductance coils is retained with this configuration.
  • tags according to the invention are only marginally increased on account of the reshaping of the moulds from which the tag bodies are produced. Furthermore, it is a simple matter to produce a "cranked" ferromagentic material core for use in the tags as opposed to a linear core, and thus it can be seen that the cost of tags according to the invention, and currently available tags will be only fractionally different.
  • a further advantage of the invention arises from the facility for providing a simple transmitting system within the pedestals at the entry/exit points of the retail outlet in which the system is installed, as there is no need for sophisticated systems which transmit magnetic signals in a variety of differently orientated planes.
  • Figure 1 shows a pair of resonant circuits disposed around a ferromagnetic core shaped according to the invention and for incorporation in an EAS tag;
  • Figure 2 shows a perspective view of a tag according to the invention provided internally with the core arrangement of Figure 1 , and
  • Figure 3 demonstrates the efficacy of the tag which positioned in a uniaxially applied magnetic field.
  • a "cranked" ferromagnetic core 2 is provided at its ends 4, 6 with inductance coils LI , L2 (the numerals representing first and second resonant circuits which are formed with the said inductance coils by capacitors Cl , C2 respectively) which are wound on hollow bobbins 8, 10, the hollow of which is shaped according to the cross-sectional shape of the ferromagnetic core 2.
  • the longitudinal axes of the inductance coils are denoted by LI * , L2 * , and it can be seen from the Figure that these axes subtend an angle of ⁇ °. It is the intention of the invention that this angle is not 90°, for if this were the case, the inductance coils LI and L2 would not be mutually coupled.
  • the core and circuits disposed thereon may be inserted into a tag of the type shown in Figure 2.
  • a tag 12 is of essentially two-piece construction having an upper half 14 and a lower half 16, each of said halves being provided with cavities (not shown) capable of receiving the upper and lower half of the core shown in Figure 1 and the inductance coil bobbins 8, 10 shown in Figure 1.
  • the core 2 can thus be sandwiched between the said upper and lower halves l 4, 16 and encased thereby.
  • the said upper and lower halves are ideally formed of a rigid plastics material.
  • the tag 12 is provided with a protrusion 18 which houses a clutch arrangement (not shown) for receiving a pin shank 20 and securing same therein.
  • a clutch arrangement is disclosed in United States Patent No. 4523356 to Lincoln Chariot, and comprises a spring loaded anvil which forces a set of ball bearings into a cup. The anvil may be displaced against the action of the spring under magnetic means thus releasing the pin shank 20.
  • the pin shank 20 has reduced diameter portions 22 on which the ball bearings within the clutch mechanism engage and prevent release of said pin shank.
  • a pair of pedestals are diagrammatically indicated at 32, 34 at comprise in their simplest form loops of wire 36, 38 through which is passed an alternating current via electrical connections 40, 42.
  • the loops of wire 36, 38 shown are transmission loops.
  • the loops of wire 36, 38 effectively form inductive coils through which is generated a magnetic flux B, of alternating frequency identical to that of the current passed through the loops.
  • the tags detect this magnetic signal and re-radiate a second magnetic signal of different frequency, and it is this signal which is detected by detection loops which are provided adjacent with or internally of the transmission loops . In the interests of clarity the detection loops are not shown.
  • Figure 3 is a schematic representation provided only to aid understanding of the invention. It will be appreciated that the particular orientation and powering of the transmission and detection loops provided within the pedestals may be complex, and as it is not the subject of the invention, specific disclosure is not provided herein.
  • the directional component of magnetic flux is concentrated by the core, and the magnitude of the current induced in a particular resonant circuit is increased. This increases the efficacy of the tag in re-radiating the second signal at the second frequency which is detected by the pedestals.

Landscapes

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

Abstract

L'invention concerne un antivol pour un système électronique de surveillance d'article. De tels antivols comprennent normalement un circuit répondeur interne constitué d'un premier et d'un second circuit résonant dont chacun comprend des composants inductifs entre lesquels se produit au moins un faible couplage magnétique et/ou électrique. Cet antivol est caractérisé par l'angle d'opposition des axes des composants inductifs du premier et du second circuit résonant. Les déposants ont en effet découvert que cet angle influence sensiblement le 'taux de captage' de l'antivol, c.-à-d. le rapport entre le nombre de fois qu'un antivol particulier est détecté par un système, et le nombre de fois que l'antivol passe à travers le système. Les axes longitudinaux de la première et de la seconde bobine à inductance sont séparés dans l'idéal par un angle de υ°, respectant la formule 90°∫ υ° ∫180°, υ°∫⊃ 90°, 180°.
PCT/GB1999/002196 1998-07-14 1999-07-08 Antivol WO2000004519A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
AU46383/99A AU4638399A (en) 1998-07-14 1999-07-08 Security tag
EP99929602A EP1099201A1 (fr) 1998-07-14 1999-07-08 Antivol

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GBGB9815118.6A GB9815118D0 (en) 1998-07-14 1998-07-14 Security tag
GB9815118.6 1998-07-14

Publications (1)

Publication Number Publication Date
WO2000004519A1 true WO2000004519A1 (fr) 2000-01-27

Family

ID=10835388

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1999/002196 WO2000004519A1 (fr) 1998-07-14 1999-07-08 Antivol

Country Status (5)

Country Link
EP (1) EP1099201A1 (fr)
AU (1) AU4638399A (fr)
GB (1) GB9815118D0 (fr)
TW (1) TW392136B (fr)
WO (1) WO2000004519A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001086967A2 (fr) 2000-05-08 2001-11-15 Checkpoint Systems, Inc. Systeme de detection et d'identification par frequence radioelectrique

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0338660A1 (fr) * 1988-04-15 1989-10-25 Esselte Meto International GmbH Système anti-vol
EP0469769A2 (fr) * 1990-08-03 1992-02-05 Security Tag Systems, Inc. Etiquette à division de fréquence ayant un circuit birésonnant accouplé magnétiquement
DE4415801A1 (de) * 1994-05-05 1994-09-22 Siegfried Mehl Diebstahlsicherungselement

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0338660A1 (fr) * 1988-04-15 1989-10-25 Esselte Meto International GmbH Système anti-vol
EP0469769A2 (fr) * 1990-08-03 1992-02-05 Security Tag Systems, Inc. Etiquette à division de fréquence ayant un circuit birésonnant accouplé magnétiquement
DE4415801A1 (de) * 1994-05-05 1994-09-22 Siegfried Mehl Diebstahlsicherungselement

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2001086967A2 (fr) 2000-05-08 2001-11-15 Checkpoint Systems, Inc. Systeme de detection et d'identification par frequence radioelectrique
EP1285417A2 (fr) * 2000-05-08 2003-02-26 Checkpoint Systems, Inc. Systeme de detection et d'identification par frequence radioelectrique
JP2003533143A (ja) * 2000-05-08 2003-11-05 チエツクポイント システムズ， インコーポレーテツド 無線周波数検出識別システム
EP1285417A4 (fr) * 2000-05-08 2005-03-23 Checkpoint Systems Inc Systeme de detection et d'identification par frequence radioelectrique
US7187289B2 (en) 2000-05-08 2007-03-06 Checkpoint Systems, Inc. Radio frequency detection and identification system
JP4663200B2 (ja) * 2000-05-08 2011-03-30 チエツクポイント システムズ， インコーポレーテツド 無線周波数検出識別システム

Also Published As

Publication number Publication date
AU4638399A (en) 2000-02-07
GB9815118D0 (en) 1998-09-09
TW392136B (en) 2000-06-01
EP1099201A1 (fr) 2001-05-16

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