RU2332713C1 - Electromagnetic label deactivator - Google Patents

Abstract

FIELD: physics.

SUBSTANCE: electromagnetic label deactivator containing casing, metal plate with fixed permanent magnets forming magnetic field for label deactivation (labels, tabs, markers, etc) comprises as constant magnets the ferrite ring magnets with opposite magnetising polarity placed on the plate and mutually shifted, enabling magnetic field of longitudinal and transverse asymmetric distribution. This field structure of deactivator provides label deactivation within initial or final stage of single moving along deactivator surface.

EFFECT: provided reliable label deactivation without design complication and device dimensional increase.

3 cl, 6 dwg

Description

The invention relates to electronic theft protection systems, in particular to tag deactivators applied to various products in order to prevent theft of goods and to ensure that a good buyer passes through an anti-theft device.

Theft today is one of the most difficult problems that owners of shops and supermarkets face. The fact is that it is impossible for the human eye to keep track of each specific unit of goods, and video systems do not always give a one hundred percent result. A universal solution was found thanks to which thieves have no chance of success. This solution is to install an anti-theft system. The most common means of protecting goods from unauthorized removal today are anti-theft systems that help to find unpaid goods at the exit from the store (trading floor). They are, as a rule, a construction of two transceiver antennas-racks (they are installed in the form of a "gate" in the protected passage), equipped with signaling equipment.

The system of protection against unauthorized removal of goods consists of special pedestals equipped with sound and light alarms installed in the control place, special tags attached to the product, and devices for removing or deactivating protective tags. One of the pedestals is a receiver, the other is a transmitter. The transmitter emits a signal at a certain frequency, in a strictly defined period of time. If a mark appears in the field of action of the system, resonant oscillations occur. The receiver picks up the resonant vibrations of the mark and an alarm is triggered. When selling a product, the tag is deactivated and when the tag hits the field of the system, no resonant resonance vibrations occur. Such is the general principle of the operation of anti-theft systems. These or those differences are inherent in various technologies on the basis of which systems are constructed.

Theft protection systems have three varieties. The first of them are used to transmit the signal from the label to the antenna in the frequency range of the radio waves, the second - the frequency of the electromagnetic spectrum, and the principle of operation of the third is based on the use of waves close in range to acoustic. All of them have a very wide range of applications, however, in each case, it is necessary to analyze a number of parameters in order to determine which type of equipment is optimal for the store, because each type of system has strengths and weaknesses (T. Bogatova “To protect is to prevent” Computer Week, No. 42 (312), M., 2001).

When choosing a system, they increasingly prefer electromagnetic technology, believing that a small inconspicuous “sticker” is able to effectively protect the product, despite the fact that it only works in 70 percent of cases.

The principle of operation of electromagnetic systems is as follows: a low-frequency electromagnetic field (frequency from 70 to 1000 Hz) is induced between two antennas.

The most famous electromagnetic systems on the market are Certus, Checkpoint Meto, Gateway, Sensormatic. Many regional stores prefer to install equipment based on electromagnetic technology.

One of the reasons for this decision may be the simplicity of tuning systems offered by a number of manufacturers. For example, antennas manufactured by Certus do not require complicated configuration - connecting a laptop, special devices. The system is configured manually. The rather large distance between the antennas, which on some models reaches 1.6 m, and the small size of the labels, which allows them to be less noticeable on the product, also speak in favor of choosing electromagnetic equipment.

The main advantage of electromagnetic systems is protective self-adhesive labels. Thanks to the features of electromagnetic technology, they are made in the form of small price tags of typical or invisible glued thin strips. As a result, the protective label is almost impossible to find on the product. This label, unlike radio frequency technology, is capable of working on metal objects, on a product in the packaging of which a foil is applied, thin non-ferromagnetic metal.

In addition, radio frequency technology has an additional drawback, because it destroys tags, i.e. they are disposable, and when using electromagnetic technology, the label can be restored. This is very important for libraries, rental offices of audio and video discs, etc.

Electromagnetic technology is best suited to food (supermarkets), bookstores, libraries, pharmacies, as well as when trading a number of other goods. Despite all the efforts of the library staff to preserve library collections, books and other materials still disappear. Moreover, unique instances that cannot be repaired are lost.

Each anti-theft system includes special sets of markers with an adhesive layer that are attached to a book, video, audio cassette or CD-ROM.

The marker is difficult to detect and impossible to remove throughout the life of a book or other storage medium. The adhesive layer of the marker does not harm the paper, so you can mark even rare and old books. All markers are delivered to the library in an activated state, therefore, after sticking a marker on a book, it immediately receives protection against unauthorized removal from the library. Any attempt to take away a book or other material without the permission of the librarian on duty will be detected and suppressed by an electronic pass-through anti-theft system installed at the exit from the library. At the moment of carrying a book with an activated marker, a light and sound alarm will turn on (www.armosystems.ru).

Current trends in shoplifting prevention are expressed in the use of small, thin and flexible markers with the maximum achievable passage width, which requires the highest sensitivity in severe conditions at a given outlet in the harsh conditions. In addition, the rapid development of security labeling technologies in production makes it desirable for the anti-theft system to work with different types of markers, be it markers of the "harmonic" type, as in Meto, or the Barkhausen type, as in Sensomatatic, or others used markers (tags, tags, labels, etc.).

A known marker, comprising a base with an adhesive layer and a sensing element of soft magnetic material, which further comprises a layer of hard magnetic powder with a coercive force Hc = 960-1200 kA / m, located on top and / or bottom of the sensitive element, while the layer of hard magnetic powder consists of an alloy neodymium-iron-boron in the following percentage ratio: Nd - from 10.5 to 36.5 wt.%; B - from 1.0 to 4.5 wt.%; Fe - the rest, and the particle size of the hard magnetic powder is 5-30 microns. The amount of hard magnetic powder by mass is equal to or greater than the mass of the sensing element.

In the initial state, when the hard magnetic powder is not magnetized, the marker is in the activated state. In this case, when an attempt is made to unauthorized removal of goods, a security alarm is triggered. To deactivate the marker, devices (deactivators) located at the cash desks to pay for goods are used. Such devices should generate pulses of a magnetic field with a strength of 800-1100 kA / m with a duration of 0.05-5 ms. In this case, the hard magnetic powder is magnetized and magnetizes a soft magnetic amorphous tape. In this state, the amorphous tape in the marker does not generate magnetic fields at frequencies that are picked up by the burglar alarm, because markers are deactivated (RF Patent No. 2172024).

The disadvantage of this marker is the need to use a strong magnetic field to magnetize hard magnetic material. In addition, the cost of such a label is quite high.

A label is known which contains a first magnetic material with high magnetic permeability and with a small coercive force in combination with a ferromagnet element with an average coercive force capable of being in a state of constant magnetization, and a second magnetic material that acts as a magnetic magnetizing material, preferably has an average coercive force, and its appearance is less critical; it may be, for example, steel, nickel, ferrite, etc. (RF patent No. 2183033).

The described label is in many respects similar in structure and materials to most types of labels used to ensure safety in trade and supplied by companies such as Sensematic (USA), Knogo (USA), ZM (USA) and Esselt Meto (Germany).

The marker (label, label) is a sensitive element of soft magnetic material with an adhesive base that responds to the signal of the exciting antenna. In addition, short strips of magnetically rigid material with an average coercive force, in the form of strokes, are superimposed or placed next to a wire of soft magnetic material. Elements of magnetically rigid material after magnetization by the constant magnetic field of the deactivator, retain the residual magnetization. The magnetic field of the “strokes” creates a constant bias field acting on the soft magnetic element, as a result of which it does not respond to the field of the exciting antenna, i.e. marker is deactivated.

Deactivators for electromagnetic systems are available in two versions: contact and non-contact. Contact is more economical, but takes more time to neutralize tags, because Be sure to touch the deactivator with a protective mark. Sellers are unhappy with these deactivators - a low degree of deactivation, because tags may not be visible and the seller does not know where it is located exactly. There is a danger of a conflict with a respectable buyer when he passes the anti-theft system.

Contactless deactivating is more expensive, but they are more convenient, especially with a large flow of goods passing through the cash register. Meto’s standard deactivators (EM series) are the most popular, which allow you to deactivate the mark at a distance of about 7 cm. In some models, the power can be increased, and they will work at a greater distance. These standard deactivators are taken as a prototype of the claimed invention.

The design of the deactivator is shown in figure 1. It consists of a housing 1 made of non-magnetic material (aluminum), inside of which is placed a metal substrate 2 with three rectangular permanent magnets 3 located on it along a horizontal axis at a certain distance from each other and having the same direction of magnetization. The deactivator is fixed at the installation site by means of screws.

Permanent magnets create a symmetric magnetic field of magnetization of the magnetically rigid label element (tags, price tags, etc.), which is shown in FIG. 2 and FIG. 3, and in FIG. 2, the structure of the magnetic field when the electromagnetic tag is moved along the X axis, and figure 3 - relative to the axis Y.

The letter designations shown in these figures mean: M is the electromagnetic label, Bx and By are the magnitude of the magnetic induction along the X and Y axes, respectively.

Analysis of the structure of the magnetic fields of the prototype shows that:

- the magnetic field (in FIGS. 2 and 3) has a symmetrical distribution with respect to the longitudinal and transverse axes (X and Y);

- the longitudinal component of the magnetic field (figure 2) has six extrema and five transverse regions with a minimum value of the magnetic field induction. Similar areas cross the entire working surface of the deactivator in the longitudinal direction (Fig. 3), forming the so-called “dead” zones of the deactivator. When moving a label with a longitudinal orientation in the direction of the X axis in the region of these “dead” zones, deactivation does not occur;

- the transverse component of the magnetic field (figure 3) has six extrema and three areas representing the "dead" zone. When moving a label with a transverse orientation in the direction of the Y axis in the region of these "dead" zones, deactivation is also not observed.

In addition, magnetic fields have a pronounced symmetric structure, therefore, the deactivation distance of 7 cm corresponds only to the zones of maximum magnetic field, therefore, it is practically possible to speak of reliable deactivation of marks at a distance of 3-4 cm, and even less in “dead” zones.

Thus, the known deactivators of electromagnetic labels of anti-theft systems have a common drawback - unreliable deactivation of labels, which is determined by the regular configuration of the magnetic field and the presence of a large number of "dead" zones.

The technical task of the invention is the creation of a deactivator of electromagnetic tags that provides reliable deactivation of labels (tags, markers, etc.) regardless of the direction of their movement above the surface of the deactivator (along or across), without complicating the design of the device and increasing its size.

The technical result is achieved due to the fact that changes are made to the well-known deactivator of electromagnetic tags containing a housing, a metal substrate with permanent magnets placed on it, forming a magnetic field for deactivating tags (labels, tags, etc.), namely:

- as permanent magnets used ferrite ring magnets with the opposite polarity of magnetization;

- ring magnets are placed on the substrate with a shift relative to each other, providing the formation of a magnetic field having an asymmetric arrangement in the longitudinal and transverse directions;

- the geometric dimensions of the metal substrate are determined depending on the outer diameter of the annular magnet, the length (L) being (3.3-3.6) D and the width (B) being (0.43-0.50) L;

- geometric aspect ratios, which are selected in the range: d / D = 0.36-0.40 and h / D = 0.16-0.25, where D and d are the outer and inner diameters of the ring magnet, in mm; h is the height (thickness) of it, in mm;

- ring magnets are placed on a metal substrate so that the distance between their geometric axes in the longitudinal (a) and the shift in the transverse (b) directions relative to the substrate is (0.60-0.65) L and (0.19- 0.23) B, respectively.

In addition, some design changes were made that do not significantly affect the technical result, but reduce the weight of the deactivator and improve its design, namely:

The case of the deactivator is made of two parts - the upper and lower - of plastic, with a decorative layer being applied to the upper part and an adhesive-based tape for attaching the deactivator to the installation site.

The use of permanent ring magnets allows you to create a structure of magnetic fields without "gaps" - "dead" zones - in the main working area of the deactivator, as well as shift the "dead" zones to the edges of the working area of the deactivator, thereby increasing the reliability of the deactivation of labels.

The different polarity of magnetization of ferrite ring magnets increases the magnetic induction of the field and allows the use of ferrite magnets instead of rare earths.

The geometric ratios of ferrite ring magnets are selected in such a way that without increasing the dimensions of the device to increase the working zone of deactivation. So, with a d / D ratio of less than 0.56, the “dead” zones shift to the main working area of the deactivator, and greater than 0.40 decreases the induction of the magnetic field, and hence the height of deactivation.

When the h / D ratio is less than 0.16, the magnitude of the magnetic field induction decreases, and with a larger - 0.25, it practically does not affect the increase in the magnetic field strength, After a certain height of the ring magnet, an increase in height almost does not affect the magnitude of the magnetic induction of the field, but increases its value.

The distance between the geometric axes of the ring magnets (a) relative to the substrate allows you to overlap the magnetic fields formed by each of the permanent magnets and provide an optimal length of deactivation, and the shift (b) between the geometric axes creates an asymmetric structure of the magnetic field, in which the difference in its strength in maximum and other areas much less pronounced.

When the ratio of the length of the metal substrate - L / D is less than 3.3, the working area of the deactivator is reduced, and with a larger 3.6 - the working area of the deactivator is increased, but the strength of the magnetic field, and therefore the height of deactivation, is reduced.

When the ratio of the width (B) of the metal substrate to its length is less than 0.43, the working area of the deactivator decreases, and with a larger 0.5, the dimensions of the deactivator increase without a noticeable increase in deactivation efficiency.

When the ratio of the distance between the geometric axes (a) of the ring magnets to the length of the metal substrate (L) is less than 0.6, the working area of the deactivator is reduced, and with a larger 0.65, the working area of the deactivator increases and the magnetic induction of the field decreases.

When the ratio of the shift (b) between the geometric axes of the ring magnets and the width of the metal substrate (B) is less than 0.19, an additional “dead” zone appears along the longitudinal axis of the deactivator, and when the ratio is greater than 0.23, the magnetic induction of the field decreases and label deactivation height decreases.

The indicated relationships between the geometric dimensions of the permanent ring magnets and the metal substrate and the optimal placement of the magnets on the metal substrate were established as a result of numerous experiments and analysis of the experimental results.

As our studies have shown, the adopted arrangement of permanent ring magnets with a different polarization direction of magnetization made it possible to create a complex (asymmetric) structure of magnetic fields, and the indicated relations allowed us to obtain the optimal dimensions of the main working area of the deactivator and the height of deactivation of electromagnetic marks, which ensures reliable deactivation of labels when carrying a protected object above the surface of the deactivator at a distance of at least 6 cm.

The essence of the invention is illustrated in figures 4-6.

Figure 4 shows the design of the deactivator of electromagnetic tags. It contains a housing made of plastic and consisting of two parts: upper 1 and lower 3. In the lower part of the housing there is a metal substrate 2 on which ferrite permanent magnets 4 of ring type are placed. Bottom on the lower part of the body applied adhesive film 5 on an adhesive basis for mounting the deactivator at the installation site. The upper part of the deactivator body is covered with a decorative film 6.

Figure 4 also shows the geometric dimensions of the ring magnets and the metal substrate, which are important for determining the efficiency of the deactivator, namely: D, d, h, a, L, b, B.

Figure 5 shows the structure of the magnetic field along the longitudinal axis X, figure 6 shows the transverse magnetic field along the Y axis. The designations Bx and By correspond to magnetic induction along the X and Y axis, and M is the electromagnetic label. The arrows indicate the direction of movement of the marks along the surface of the deactivator.

Analysis of the structure of the magnetic fields of the claimed technical solution shows that:

- the magnetic field (in FIGS. 5 and 6) has an asymmetric distribution with respect to the longitudinal and transverse axes (X and Y);

- the longitudinal component of the magnetic field (Fig. 5) has four extrema and two transversely spaced regions with a minimum value of magnetic field induction. These two regions intersect the entire working surface of the deactivator in the longitudinal direction (Fig. 5), forming the so-called “dead” zones of the deactivator, but the axes of these regions do not coincide with the longitudinal axes of the deactivator and have different orientations at each end of the deactivator. Along the transverse axis of the deactivator, “dead” zones are not observed;

- the transverse component of the magnetic field (Fig.6) has four extrema and two zones of minimum magnetic fields, which are not "dead" zones, because the combinations of the maxima and minima of the magnetic field turn out to be asymmetric, therefore, when the mark is carried over the surface of the deactivator, the latter will necessarily fall into the region of the deactivation field in some part of the deactivator.

As a result of the fact that magnetic fields have a pronounced asymmetric structure, a deactivation distance of 6-7 cm is observed over almost the entire surface of the deactivator.

Below is the data for a specific deactivator using ferrite ring permanent magnets with the following geometric dimensions:

D = 86 mm, d = 32 mm and h = 20 mm, which corresponds to the ratios - d / D = 0.372 and h / D = 0.23.

The length of the metal substrate is L = 290 mm, and the width B = 140 mm, i.e. L = 3.37 D, and the ratio B / L = 0.482.

The distance (a) between the geometric axes of the ring magnets in the longitudinal direction relative to the substrate was 180 mm, and the shift (b) between the geometric axes of the ring magnets in the transverse direction was 28 mm. This corresponds to the relations - a / L = 0.62, and b / B = 0.20.

Thus, all parameter values are within the claimed limits.

The working area of the deactivator was 275 × 120 mm, and the height of the deactivation mark 6 cm, and reliably deactivates the electromagnetic mark at any orientation of the mark.

A standard deactivator with such dimensions has a smaller deactivation working area, and its reliability is 70%.

The proposed deactivator, unlike the prototype, has only one significant “dead” zone for the label with the Y orientation when moving along the Y axis at an angle to the axis.

In the proposed deactivator, it is sufficient to carry the electromagnetic mark over the deactivator once, regardless of the direction of orientation of the mark, because the structure of the fields of the deactivator is such that deactivation occurs either at the initial stage of movement above the surface of the deactivator, or at the final stage.

The deactivation reliability is at least 95%.

In addition, the use of ferrite permanent magnets and a plastic case greatly facilitates and reduces the cost of the device.

Currently, deactivator prototypes are being tested in several supermarkets in St. Petersburg.

Claims (3)

1. The deactivator of electromagnetic tags, comprising a body of non-magnetic material, a metal substrate with permanent magnets placed on it, forming a magnetic field for deactivating electromagnetic tags, characterized in that as the permanent magnets are used multipolarly magnetized ferrite ring magnets placed on a metal substrate with a shift relative to each other, providing the formation of a magnetic field having an asymmetric distribution in the longitudinal and transverse directions, moreover, the length of the metal substrate is determined depending on the outer diameter of the annular magnet. 2. The deactivator of electromagnetic labels according to claim 1, characterized in that the ratio of the geometric dimensions of the ferrite permanent ring magnets are in the following limits: d / D = 0.36-0.40; h / D = 0.16-0.25, where d is the inner diameter of the annular magnet, mm; D is the outer diameter of the annular magnet, mm; h is the height (thickness) of the annular magnet, mm 3. The deactivator of electromagnetic labels according to claim 1, characterized in that the length of the metal substrate L is determined from the equation: L = (3.3-3.6) D, and the width of the metal substrate B is from the ratio: B / L = 0, 43-0.50.

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