GB2388472A

GB2388472A - System for the bulk magnetisation or demagnetisation of security tags

Info

Publication number: GB2388472A
Application number: GB0210729A
Authority: GB
Inventors: Mervyn Frederick Lear
Original assignee: Redcliffe Magtronics Ltd; Redcliffe Ltd
Current assignee: Redcliffe Magtronics Ltd; Redcliffe Ltd
Priority date: 2002-05-07
Filing date: 2002-05-09
Publication date: 2003-11-12
Anticipated expiration: 2022-05-09
Also published as: GB0210373D0; GB0210729D0; GB2388472B

Abstract

Apparatus, suitable for bulk magnetisation or demagnetisation of electronic security tags randomly oriented in a container, comprises an open ended elongate housing 6 which can bridge over a conveyor 3 on which a container may travel. The opposed sides of the said housing 8, 9 are on either side of the conveyor 3. A coil 11, 12 is associated with each of the said housing sides. The coils 11, 12 are connected in series. A further coil 13 is associated with the top side 10 to the housing and is arranged to pass above the container. Container position detectors 15, 16 are arranged to control capacitor discharge signals applied to the coils 11, 12, 13 such that there is substantially no interaction between the magnetic fields produced across the conveyor to that perpendicular to the conveyor. The system may possibly process hundreds of randomly oriented tagged articles within a non-magnetic tote box. Magnetic shielding may be formed around the coils to protect an operator form the large magnetic fields produced. The system may be used to prepare goods for retail outlets and/or mail order customers.

Description

( BULK ACTIVATION/DEACTIVATION OF ELECTRONIC

ARTICLE SURVEILLANCE TAGS

Field of the Invention:

5 This invention is concerned with electronic article surveillance (EAS) devices. Background of the Invention:

It is well known to provide electronic article surveillance systems to prevent or deter unauthorized removal of articles from a controlled area such 10 as a shop or department store. In a typical system, tags designed to interact with an electromagnetic field generated by detectors at the exits from the

controlled area are attached to articles to be protected. If an active tag is brought into the detector field, the presence of the tag is detected and

appropriate action results, such as the sounding of an alarm.

15 While the invention will be described in the following by reference to the deactivation of EAS tags by subjecting them to a demagnetizing magnetic field, the magnetised state thus being the "active" state of the tags and the

demagnetized state being their "deactivated" state, it is to be appreciated that the "active" state of such a tag could be designated as its demagnetized state 20 and its "deactivated" state could be its magnetised state. The state of a tag is detected as a function of its interaction with the fields produced by detectors

provided at the perimeter of the controlled area and it is the arrangement and operation of the detectors that determines which of the magnetised and

l demagnetized states of a tag is to be regarded as its "active" state and which its "inactive" state. The present invention extends to both of these possibilities. Sensormatic Electronics Corporation (now a division of ADT, Inc) of 5 Rosa Raton, Florida, USA are manufacturers of EAS tags which are used worldwide. There are various kinds of EAS tags and the most commonly utilized Sensormatic EAS tag is constructed to provide an LC resonant circuit that includes a magnetic material that exhibits a so- called giant magneto-impedance (GMI) effect when exposed to a magnetic field. As

10 described for example in Sensorrnatic US Patent No. 6 356 197, a GMI effect is a substantial change in impedance of the magnetic material when it is exposed to a magnetic field. A detector at an exit of a controlled area

transmits a magnetic field which interacts with the magnetic material in the

tag to produce the GMI effect and this causes the impedance of the magnetic 15 material to change. The change in impedance of the material changes the resistance of the material, thus causing the quality factor, Q. of the LC circuit to change. The change in Q results in a change in the output of the LC circuit at resonance and these changes can be detected by suitable equipment in the detector so as to cause the sounding of an alarm, for example.

20 Market preference is for disposable EAS tags which are attached to the articles to be protected by means of adhesive or are inside the article packaging or even inside the article itself. Such tags must be deactivated before they are removed from a store, for example, by a customer who has

properly paid for the article. Deactivation devices use coils which are energized to generate a magnetic field such as to render the EAS tag inactive

insofar as its effect on the store exit detectors is concerned. As described in Sensormatic US Patent No. 5 859 587, in one type of deactivation system the 5 checkout sales assistant deactivates the article tags one at a time by passing them in a particular orientation through a magnetic field generated by an

appropriately oriented coil, and in another type of system the sales assistant can deactivate several tags all at one time and irrespective of their orientations by placing the tagged articles into a bag which is then passed through the 10 magnetic fields generated by three orthogonally-arranged sets of coils

Current market preference is also for the attachment of such disposable tags to articles at source, namely by the manufacturer of the articles. This has given rise to problems for large retailers who not only have many retail outlets, but also operate thriving mail-order businesses. Such 15 retailers may have one or more distribution centres which receive incoming goods from manufacturers and output such goods selectively to the mail order customers and also to the retail outlets, namely the high street stores. The tagged articles are received at the distribution centres with the tags in activated condition, which is the condition in which they are manufactured.

20 Alternatively the tags can be affixed at the distribution centre. Within the distribution centre, the articles are selectively divided into mail order and retail outlet quantities to be dispatched appropriately. In some such distribution centres, the various articles are placed into tote boxes which arc

bar coded as regards their intended mail order or retail outlet destinations and the tote boxes move through an intelligently controlled conveyor system which delivers them selectively to different loading stations where they are loaded onto lorries for onward transhipment to their final destinations.

5 The provision of bulk quantities of articles with active tags to a retail outlet is not a problem. The tote boxes, which typically have an internal volume of the order of 100 litres, may contain hundreds of articles each tagged with an active tag. The articles are simply unloaded into the retail outlet and put on sale display or into store. When an article is sold, its tag is 10 deactivated as described above before the customer takes the article out of the store. If a tag is not properly deactivated by the sales assistant, which might happen occasionally, the detector at the store exit sounds an alann and the customer returns to the sales assistant where the tag is properly deactivated and apologies made to the customer.

15 For mail order, the situation is, however, rather different. The tagged articles leave the distribution centre and arrive with the customer with the tags in active condition. If the active tag is removed and discarded with packaging, then no problems arise. If' however, the tag is on or in the article and is not removed, then detection systems in various retail outlets might be 20 activated as a mail order customer shops around, leading not only to a high degree of embarrassment for the customer, but also to inconvenience and irritation to security staff in the respective stores. This is a well known

problem, referred to in the art as "tag pollution" which has to date not found a solution. Objects and Summary of the Invention:

It is the object of the present invention to overcome or at least 5 substantially reduce the abovementioned problem.

According to the present invention, a system is proposed to be provided which, when installed with the conveyor system of a typical tagged product distribution centre as aforementioned, will enable all of the tags on articles in a tote box to be demagnetized as the tote box passes on a conveyor, 10 from the location(s) whereat it was loaded to the location wherefrom it will be despatched. The system in question comprises an add-on unit for convenient assembly with a conveyor, such unit comprising spaced-apart walls designed to locate on opposite sides of the conveyor and a top wall bridging the spaced 15 apart walls, the spaced-apart walls incorporating series connected coils for generating a magnetic field predominantly traversing the conveyor (horizontal

field) and the top wall incorporating a separate coil for generating a magnetic

field predominantly perpendicular to the conveyor (vertical field), a first

sensor upstream of said unit for detecting the approach of a tote box or the 20 like to the unit and a second sensor at a predetermined position within said unit for detecting arrival of a tote box within said unit, first and second oscillatory capacitor discharge systems for driving respective ones of said horizontal and vertical coils with a decaying oscillatory current for causing

( the coils to generate corresponding oscillatory decaying magnetic fields for

demagnetising EAS tags on articles in said tote box, and a control system responsive to the output of said first sensor for initiating the charging of the capacitors in said first and second oscillatory capacitor discharge systems and 5 responsive to the output of said second sensor for initiating separate oscillatory discharges spaced apart from one another such that the discharge current in one of said horizontal and vertical coils has substantially terminated before the discharge current in the other is initiated.

As compared to the three orthogonal coils tag deactivation system 10 available to sales assistants as mentioned hereinbefore, such systems being capable of simultaneously deactivating just a few tags in a shopping bag and being only a very low power system, the system of the present invention will be a very high power system with the horizontal coils producing around 300 gauss (0.03 Tesla) at peak and the vertical coil producing around 500 gauss 15 (0.05 Tesla) at peak and the side and top walls incorporating shielding for the protection of operating personnel from the intense magnetic fields which, at

their maximum, are an order of magnitude greater than the field required to

demagnetise and deactivate the security tag.

The relative timings of the oscillatory capacitor discharges through the 20 horizontal and vertical coils is a function, inter alia, of the speed of movement of the conveyor system, the intention being that the tote boxes move continuously through the demagnetizing unit and the article tags are deactivated on the fly. In an exemplary embodiment of the invention, which

will be described in detail hereinafter, the first capacitor discharge is initiated with the respective tote box slightly upstream from the centre of the demagnetising unit and the second capacitor discharge through the other coil(s) is initiated with the tote box located centrally of the respective coil(s).

5 The time between the two capacitor discharges is typically of the order of 100 m/sees, being determined also by the decay times of the capacitor discharge currents so that the second firing is not initiated until the first is complete and so that no' or substantially no, electromagnetic interaction exits between the horizontal and vertical coils.

10 In order to increase throughput, two such demagnetising units could be provided in tandem, with one arranged to deactivate tags in a first tote box travelling on the conveyor and the other arranged to deactivate tags in an immediately following tote box. By virtue of such an arrangement, the relationship between conveyor speed and the timings of the charging and 15 discharging phases of the two sets of capacitors becomes less critical and increased conveyor speeds can be accommodated.

It has conventionally been the thought, even by Sensorrnatic, that bulk deactivation of EAS tags on the scale proposed by the present invention, namely with possibly hundreds of randomly oriented tagged articles in a 100 20 litre tote box, was not possible. Historically, bulk deactivation has referred to the system mentioned hereinbefore where two or three tagged articles in a shopping bag could have their tags deactivated. The present invention thus

constitutes a surprising and remarkable development of great potential utility in the art.

It is possible that a requirement could arise for magnetization of EAS tags in bulk and the present invention also embraces this possibility. As 5 described hereinafter, a facility is provided whereby an apparatus according to the present invention has selectable magnetising and demagnetizing modes.

The above and other features of the present invention are set forth in the appended claims and will best be understood from consideration of the following detailed description given with reference to the accompanying

10 drawings which show an exemplary embodiment ofthe invention.

Description of the Drawings:

Figure I shows a schematic view of a conveyor system at a distribution centre, the conveyor system being provided with a facility in accordance with the present invention for bulk deactivation by 15 demagnetization of EAS tags affixed to articles destined for mail order distribution; Figure 2 is an electrical block diagram of the tag deactivation facility of Figure 1; Figure 3 shows the oscillatory decaying waveform produced by 20 capacitive discharge through the deactivation coils of the tag deactivation facility of Figure 1; and

Figure 4 is a timing diagram illustrating the response of the tag deactivation facility of Figure I to two tote boxes of tagged articles closely following each other.

Detailed Description of the Embodiment:

5 The tag deactivation facility to be described in the following is intended for the bulk deactivation by demagnetization of Sensorrnatic Ultra*Max low energy electronic article surveillance security labels/tags types MUS 11 and MUS 111 at a distribution centre where articles destined for selected retail outlets and for mail order customers are separate loaded into 10 plastics material tote boxes which travel along an automatic intelligent conveyor system and are segregated from each other in dependence upon their retail outlet or mail order destinations.

Referring to Figure 1, a schematically represented conveyor system I has retail outlet and mail order branches 2 and 3 respectively with a switch 15 point 4 controlled, for example, by a barcode reader 5 or other control device arranged so that tote boxes filled with tagged articles are automatically directed to one of conveyor branches 2 and 3.

Mail order conveyor branch 3 leads to a tag deactivation station 6 whereat tags affixed to articles in tote boxes travelling on the conveyor 20 system can be deactivated in bulk as the tote boxes pass through. The deactivation station 6 comprises an inverted U-shaped structure 7 having opposed plane vertical side walls 8 and 9 spaced apart from each other, one on either side of the conveyor 3, and a horizontal plane top wall 10 bridging the

t upper edges of the two side walls. The U-shaped structure 7 facilitates retrofitting of the subject tag deactivation system to an existing conveyor system. Within side walls 8 and 9, which are sheathed in aluminium on their 5 external surfaces to reduce electromagnetic flux leakage, there are provided respective ones of a pair of series-connected coils 11 and 12. The coils 11 and 12 are shown schematically in broken lines in the drawing. A third coil 13 is provided in the top wall 10 which also carries aluminium shielding The coils 11, 12 and 13 are connected to electronics unit 14 which, as will be 10 described in the following, is adapted to drive the coils with oscillatory capacitor discharge currents timed in accordance with inputs derived from optoelectronic box detector sensors 15 and 16.

Electronics unit 14 is shown in more detail in Figure 2. A single phase mains supply is inputted to the unit at 20 and is filtered at filter 21 to provide IS a clean sinusoidal waveform. The filtered mains supply is supplied through safety system circuit breaker 22 to a solid state relay switch 23 which is controlled by an input from a control logic unit 24 which, in turn, receives control inputs from the optoelectronic box detector sensors I S and 16. When the solid state relay switch 23 is switched on, it passes the mains voltage to 20 transformer 25 which is designed to output a voltage of the order of 3.0 kV to rectifier 26. The output of rectifier 26 is applied to capacitors 27 and 28 through respective thyristors 29 and 30 the operation of which is controlled by a phase and voltage control circuit 31 which, for example, may be as

described in WO-A-/29883 the disclosure whereof is incorporated herein

by reference. The capacitors 27 and 28 are connected, respectively, to series connected coils 11, 12 and to coil 13, these coils being formed of a relatively small number (ea. 30) of turns of heavy strip wire having, very little resistance 5 to provide a high Q. The coils 11, 12 and 13 are in turn connected to earth via respective ante-parallel diode and thyristor circuits 32 and 33, and the thyristors of these circuits are controlled by the control logic unit 24. A further transformer 34 provides a low voltage to the phase and voltage control unit 31 inter alla to provide zero-crossing synchronization.

10 In operation of the electronics unit 14 of Figure 2, when a tote box on the conveyor is detected by box sensor 15, this causes solid state relay 23 to be switched on which energises transformer 25 and causes capacitors 27 and 28 to charge, under control of the phase and voltage control circuit 31, to about 3000V (DC). When the tote box advances to the point where box 15 sensor 16 is activated, the solid state relay 23 and the thyristors 29 and 30 are first switched off and then, after a slight delay of 10 to 20 m/sees, the thyristors in the output circuits 32, 33 are fumed on at respective times by the control logic 24. When the output circuit thyristors are turned on and held on for a set time period, the respective LC circuit constituted by the capacitor 27 20 and coils 11, 12 or by the capacitor 28 and coil 13 goes into an oscillatory ringing discharge (see Figure 3) which drives the respective coil(s) to produce an oscillatory decaying magnetic field within the enclosure defined by the

side walls 8, 9 and top wall 10 of the tag deactivation station.

In an exemplary embodiment of the abovementioned system which we have built and tested, the conveyor speed was about l m/see, the thyristors in the output circuits 32, 33 were switched on for periods of about 50 m/sees with a time period of about 75 m/sees between the switching on of one 5 thyristor and the subsequent switching on of the other thyristor, the two spaced-apart series-connected coils I 1, 12 developed a peak magnetic field of

the order of 300 gauss and the coil 13 developed a peak magnetic field of the

order of 500 gauss. There was a steel plate underlying the conveyor and this had an effect upon the directions of the magnetic fields developed by the

10 coils, but this effect is not considered to be crucial to operation of the system which would operate just as effectively without the plate. In the tests that we have conducted, 100% of EAS tags were successfully deactivated in bulk and irrespective of the orientations of the tags in the tote boxes. The tested embodiment thus very effectively and convincingly achieved the staged 15 objectives of the present invention.

Figure 4 is a timing diagram illustrating the response of the abovedescribed system to the approach to the deactivation station of two closely-spaced tote boxes. As shown, at time zero box detector 15 (box sensor I of Figure 4) senses the presence of the first box and the 20 abovedescribed process is initiated with the capacitors 27 and 28 being charged 0.6 seconds later. When detector 16 (box sensor 2 of Figure 4) senses the first box, the thyristor in output circuit 32 is switched on which causes series-connected coils 11 and 12 to be fired so as to develop the

previously described oscillatory decaying magnetic field generally

horizontally across the conveyor. The discharge of capacitor 27 takes about 50 m/sees and shortly after the end of that discharge sequence, the thyristor of output circuit 32 is switched off and the thyristor of output circuit 33 is 5 switched on so as to cause coil 13 to be fired so as to develop the previously described oscillatory magnetic field generally vertically with respect to the

conveyor. Figure 4 shows detector 16 responding to the presence of the first box and causing the firing of coils 11 and 12 at 1.0 seconds after time zero, and shows the firing of coil 13 0.075 seconds later. The process then repeats 10 itself if detector 15 senses the presence of a closely-following second box at a time 1.15 seconds after time zero, the capacitors 27 and 28 being recharged by time 1.75 seconds and coils 11, 12 and coil 13 being fired at time 2.0 seconds and time 2.075 seconds respectively.

It will be seen from Figure 4 that the described system is capable of 15 achieving a substantial throughput, with tagged articles in tote boxes being deactivated with 100% certainty on a continuous flow basis in not much more than a second per box. As previously mentioned herein, even higher throughput could if desired be achieved by use of a tandem system having two deactivation stations which deactivated alternate tote boxes arriving on the 20 conveyor. The invention having been described in the foregoing by reference to a specific embodiment, it is to be appreciated that the embodiment is in all respects exemplary and that modifications and variations thereto could be

( made without departure from the spirit and scope of the invention as set forth in the appended claims. For example, the function of box detector 15 could be carried out by the barcode reader 5 with appropriate adjustment made for the transit time of tote boxes from the conveyor switch 4 to the deactivation 5 station 6. Furthermore, the electrical block diagram of Fig 2 could, if desired, be modified to provide selectivity between a demagnetizing output from the coils, as described in the foregoing, and a magnetising output, it being appreciated that a requirement could arise for bulk magnetization of EAS tags. Such a modification could for example be implemented by 10 provision of an additional thyristor across series-connected coils I 1, 12 and an additional thyristor across coil 13, the additional thyristors being connected oppositely to the thyristors in the output circuits 32 and 33 and being arranged to be fired at the same times as the thyristors in the output circuits if a magnetising output from the respective coils 11, 12 and 13 is required, and to 15 be kept switched off if a demagnetizing output is required.

Claims

CLAIMS:

An apparatus for the bulk demagnetization of electronic article surveillance tags attached to pluralities of articles in containers wherein the tags have random orientations, the apparatus comprising 5 an open ended, elongate housing to be placed over a conveyor along which said containers are travelling with opposed sides of the housing disposed on opposite sides of the conveyor and a top of the housing bridging said opposed sides and spaced above the container, the containers passing on the conveyor through the open ends of said 10 housing, first and second series-connected coils provided in the opposed sides of the housing for generating a magnetic field

predominantly directed across the conveyor and a third coil provided in the top of the housing for generating a magnetic field predominantly

directed perpendicularly to said conveyor, first means for detecting the 15 approach of a container travelling on the conveyor to the input end of the housing and second means for detecting the presence of a container at a predetermined location within the housing, first and second capacitors associated respectively with said first and second series-connected coils and with said third coil, means for charging said 20 capacitors, first and second capacitor discharge circuits associated respectively with said first and second series-connected coils and their associated capacitor and with said third coil and its associated capacitor, said capacitor discharge circuits being selectively operable

( to cause discharge of the respective capacitor through the respective coil(s) so as to generate respective magnetic fields within said

housing, and control means responsive to inputs from said detectors for determining the charging of said capacitors and the time spaced 5 operation of said capacitor discharge circuits such that said magnetic fields do not substantially interact.

2. An apparatus as claimed in claim I wherein the capacitor discharge through said coils is arranged to develop peak magnetic field strengths

10 of the order of hundreds of gauss, the field developed by the third coil

being substantially greater, at peak, than that developed by the first and second coils.

3. An apparatus as claimed in claim I or 2 wherein the capacitors are 15 arranged to be charged from the mains supply via a step-up transformer and a rectifier and a series-connected switching circuit controlled by said control means, a controllable switch being provided in the input to said step-up transformer and being under control of said control means, the arrangement being such that the series-connected 20 switching circuit and the controllable switch are both switched off by the control means before discharge of said capacitors is initiated.

4. An apparatus as claimed in claim 3 wherein said switching circuit comprises first and second thyristors coupling the output of said rectifier to respective ones of said capacitors.

5 5. An apparatus as claimed in claim 3 or 4 wherein said controllable switch comprises a solid-state relay.

6. An apparatus as claimed in any of the preceding claims wherein said capacitor discharge circuits each comprise a thyristor connected in 10 anti-parallel with a diode, the arrangement being such that when the thyristor is switched on the LC circuit constituted by the respective capacitor and its associated coil(s) adopts a ringing oscillatory discharge mode.

15 7. An apparatus as claimed in any of the preceding claims wherein selectively operable means are provided to enable said capacitors to discharge unidirectionally through said coils for generating magnetising magnetic fields rather than demagnetizing fields.

20 8. An apparatus as claimed in claim 7 as dependent upon claim 6 and wherein a respective additional thyristor is connected across said first and second series-connected coils and across said third coil, said

( additional thyristors being arranged to be rendered conductive at the same time as the thyristors in the respective output circuits.

9. An apparatus for the bulk demagnetization of electronic article 5 security tags, said apparatus being substantially as herein described with reference to the accompanying drawings.

10. An apparatus for the bulk magnetization of electronic article surveillance tags attached to pluralities of articles in containers 10 wherein the tags have random orientations, the apparatus comprising an open ended, elongate housing to be placed over a conveyor along which said containers are travelling with opposed sides of the housing disposed on opposite sides of the conveyor and a top of the housing bridging said opposed sides and spaced above the container, the 15 containers passing on the conveyor through the open ends of said housing, first and second series-connected coils provided in the opposed sides of the housing for generating a magnetic field

predominantly directed across the conveyor and a third coil provided in the top of the housing for generating a magnetic field predominantly

20 directed perpendicularly to said conveyor, first means for detecting the approach of a container travelling on the conveyor to the input end of the housing and second means for detecting the presence of a container at a predetermined location within the housing, first and

( second capacitors associated respectively with said first and second series-connected coils and with said third coil, means for charging said capacitors, first and second capacitor discharge circuits associated respectively with said first and second series-connected coils and their S associated capacitor and with said third coil and its associated capacitor, said capacitor discharge circuits being selectively operable to cause discharge of the respective capacitor through the respective coil(s) so as to generate respective magnetic fields within said

housing, and control means responsive to inputs from said detectors 10 for determining the charging of said capacitors and the time spaced operation of said capacitor discharge circuits such that said magnetic fields do not substantially interact.

An apparatus as claimed in any of the preceding claims in combination 15 with a conveyor system along which tagged articles travel in non magnetic containers.

12. A combination as claimed in claim 11 wherein said conveyor system includes a track switch which is selectively operable to divert 20 containers out of a section of conveyor along which they are travelling and onto a separate section of conveyor with which a tag demagnetization apparatus is associated.

13. A combination as claimed in claim 12 wherein an output from said track switch to said control means performs the function of said first detecting means.