JPH08235460A - Identification mark and burglar prevention system - Google Patents

Abstract

PURPOSE: To provide an identification mark and a burglar prevention system which are capable of exactly performing detections without generating the increases of scale and manufacturing cost. CONSTITUTION: An identification mark 10 is provided with a metal wire which is formed by Fe-Si-Mo alloy and generates steep reversal of magnetization when alternating field exceeding the coercive force is imparted, and the Si density is set to 2.5 to 3.5wt.% and the Mo density is set to 3.5 to 14.5wt.% The wire diameter of the metal wire is formed to 30 to 125μm and the length is formed to 300 to 500 times as many as the wire diameter. The detector 20 detecting the identification mark 10 is provided with a transmitter 24 impressing the alternating field of the amplitude which is larger than the coercive force of the metal wire on an inspection area 22, a receiver 26 detecting the magnetic field of the inspection area and an alarm device 44 giving an alarm when the pulselike output generated by the reversal of magnetization of the metal wire is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an identification mark used for identifying articles and the like, and an antitheft system using the identification mark.

[0002]

2. Description of the Related Art Conventionally, as identification marks used for theft prevention, such as Fe and Co as disclosed in JP-A-55-143695 and JP-A-58-39396 are used. An identification mark composed of a ferromagnetic amorphous metal piece is known.

Such an amorphous metal piece sharply reverses the magnetization direction when receiving an alternating magnetic field. Therefore, when this magnetization reversal is detected by a detection coil or the like, the detection output is an output containing many high frequency components. The signal is obtained. Therefore, by detecting the presence or absence of the high frequency component in the output signal, the presence or absence of the amorphous metal piece in the alternating magnetic field can be detected.

Then, the above-mentioned amorphous metal piece is attached as an identification mark to an article such as a book or a wrapping of clothes, and an area where an alternating magnetic field is generated is provided at a predetermined place such as an exit of a building to provide an identification mark. By issuing an alarm when the attached article passes through the generation area, it becomes possible to prevent the article from being stolen.

Further, by using the above-mentioned amorphous metal piece as an identification mark showing the characteristic of the article, the characteristic of the article can be detected in a non-contact state, and the identification mark can be used for physical distribution management of the article. Can be used.

[0006]

However, the above-mentioned amorphous metal piece has a low saturation magnetic flux density, and the output voltage induced in the detection coil due to the magnetization reversal is also small. Therefore, to accurately detect the presence or absence of magnetization reversal,
It is necessary to take measures to increase the output voltage, such as increasing the number of turns of the detecting coil, increasing the cross-sectional area and length of the amorphous metal piece, or reducing noise.

For example, in order to obtain a required output level, it is necessary to form the amorphous metal wire to have a wire diameter of about 100 μm or more. Further, the amorphous metal wire will inevitably have a length of 100 mm or more because a sharp magnetization reversal does not occur unless the length thereof is formed to be 800 times or more the wire diameter. In this case, there is a problem that the amorphous metal wire is too large to be used as an identification mark of an article.

Further, if the number of turns of the detection coil is increased or noise is reduced in order to obtain the required output level, the detection device becomes large and the manufacturing cost increases. .

The present invention has been made in view of the above points, and an object thereof is to provide an identification mark and an antitheft system which can be accurately detected without causing an increase in size and an increase in manufacturing cost.

[0010]

In order to achieve the above object, the identification mark according to the present invention has a Si concentration of 2.5 to
Fe-S with 3.5 wt% and Mo concentration of 3.5-4.5 wt%
It is composed of a metal piece made of an i-Mo alloy that causes a sharp magnetization reversal when an alternating magnetic field exceeding its coercive force is applied.

The metal piece is formed in a linear shape and has a wire diameter of 30.
To 125 μm, and the length is 300 to 500 times the wire diameter. The antitheft system according to the present invention has a Si concentration of 2.5 to 3.5 wt% and a Mo concentration of 3.5.
An anti-theft sign attached to an article, which has a metal piece formed of an Fe-Si-Mo alloy of 4.5 wt% to cause a sharp magnetization reversal when an alternating magnetic field exceeding its coercive force is applied. A detection device that determines the presence or absence of the anti-theft sign with respect to an article passing through a predetermined inspection area and issues an alarm when the presence of the anti-theft sign is detected.

The above-mentioned detection device includes magnetic field applying means for applying an alternating magnetic field having a strength exceeding the coercive force of the metal piece to the inspection area, and receiving means for outputting a change in the magnetic field in the inspection area as an output signal. Detecting means for detecting a pulsed output caused by magnetization reversal of the metal piece from the output signal, comparing means for comparing the detected pulsed output with reference data prepared in advance, and the pulsed output And an alarm means for issuing an alarm when the above-mentioned reference data matches.

[0013]

The metal piece of the identification mark constructed as described above is
When an alternating magnetic field having an amplitude larger than the coercive force is received, steep magnetization reversal occurs due to the large Barkhausen effect. A pulsed output is detected by capturing the change in the magnetic field associated with this magnetization reversal with a receiving means such as an electromagnetic induction coil. The magnetization reversal hardly depends on the frequency of the applied alternating magnetic field, and even when the frequency of the alternating magnetic field is low, the same pulsed output can be obtained. By comparing this pulsed output with predetermined reference data, etc.,
The type etc. can be discriminated.

When the identification mark is attached to an article and used as an anti-theft sign, the presence or absence of the anti-theft sign is detected by detecting the presence or absence of the anti-theft sign by a detection device when the article passes through a predetermined inspection area. If given, an alarm will be issued.

In the detection of the anti-theft sign, the detecting device applies an alternating magnetic field having a strength exceeding the coercive force of the metal piece to the inspection area by the magnetic field applying means, and the magnetic field in the inspection area is detected by the receiving means such as the detection coil. Convert the change into an output signal. Since this output signal contains a low-frequency output signal corresponding to the alternating magnetic field applied by the magnetic field applying means, by removing this low-frequency output signal by a low-pass filter or the like, a high frequency due to magnetization reversal is obtained. The pulsed output of is detected. Then, the detected pulsed output is compared with predetermined reference data by the comparison means, and if they match, the presence of the anti-theft sign is discriminated and an alarm is issued by the alarm means.

The administrator of the detection device can detect that the article with the anti-theft sign passes through the inspection area by the alarm, and can prevent the article from being stolen.

[0017]

Embodiments of the present invention will now be described in detail with reference to the drawings. 1 and 2 show an embodiment of an anti-theft system using an identification mark according to the present invention. In FIG. 1, an identification mark 10 as an anti-theft mark attached to a box-shaped article, In addition, in FIG.
Each detection device 20 for detecting an identification mark is shown.

As shown in FIG. 1, the identification mark 10 is provided with an elongated metal wire 12 as a metal piece. The metal wire 12 has a Si concentration of 2.5 to 3.5 wt%, a Mo concentration of 3.5 to 4.5 wt%, a wire diameter of 30 to 125 μm, and a length of about 200 to 600 times the wire diameter, preferably 300-500
It is composed of a Fe-Si-Mo single crystal alloy wire that is doubled in thickness. The cross-sectional shape of the metal wire 12 is preferably a circle, but it may have an irregular cross section such as an ellipse or a polygon. The metal wire 12 has a saturation magnetic flux density which is about 1.2 to 2.0 times that of the amorphous metal wire.

The metal wire 12 has a strong magnetic anisotropy in the axial direction due to the magnetic effect of its shape and crystal structure. Therefore, when the metal wire 12 is subjected to an alternating magnetic field having an amplitude larger than its coercive force (for example, 0.1 to 1.0 Oersted), the metal Bark 12 causes an extremely sharp magnetization reversal due to the large Barkhausen effect.

When this magnetization reversal is detected by, for example, a solenoid coil, a pulsed output as shown in FIG. 3 is obtained. That is, in FIG. 3, when the positive coercive force of the metal wire 12 is Hp and the negative coercive force thereof is −Hp, the metal wire 1 is at a time point when the alternating magnetic field exceeds these coercive force Hp, −Hp.
A magnetization reversal of 2 occurs, and a pulse-shaped output voltage corresponding to this magnetic reversal is detected. The width of this pulse is 10 to 10
Since it is as small as 0 μsec, the output voltage contains many high frequency components of several KHz or more. Also, the magnetization reversal is
Almost independent of the frequency of the applied alternating magnetic field, it is possible to obtain an equivalent pulsed output even when the frequency is low.

The above-mentioned pulsed output voltage obtained when an alternating magnetic field is applied to the metal wire 12 changes depending on the length of the metal wire with respect to the wire diameter, Si concentration (wt%), and Mo concentration (wt%). To do. FIG. 4 shows the measurement results obtained by measuring the relationship between the length / wire diameter ratio and the output voltage for the metal wire 12 of the present example made of the Fe—Si—Mo alloy and the metal wire made of the amorphous alloy. There is. The measurement was performed in a state in which an alternating magnetic field having an exciting magnetic field of ± 1.5 Oersted and an exciting frequency of 50 Hz was applied to a metal wire having a wire diameter of 90 μm arranged in a detection coil of 200 turns / 5 mm.

As can be seen from FIG. 4, Fe-Si-Mo
The metal wire 12 of this embodiment made of an alloy has a length of 3 mm
If it is 00 times or more, it is possible to obtain a larger output voltage and a sufficient output voltage as compared with a metal wire of an amorphous alloy. Note that, for example, in the case of a metal wire having a wire diameter of 30 to 125 μm, if the length exceeds 500 times the wire diameter, it becomes large and unpractical, so the length of the metal wire is 300 to 50 μm with respect to the wire diameter.
It is desirable that the range is set to 0 times.

FIG. 5 shows Fe under the same measurement conditions as above.
The measurement result which measured the relationship between Mo density | concentration and the output voltage regarding the metal wire 12 which consists of -Si-Mo alloy is shown. The Si concentration was fixed at 3 wt% for the measurement. As can be seen from this figure, the Mo concentration is about 3.5.
A sufficient output voltage can be obtained by setting it within the range of 4.5 wt%.

Further, FIG. 6 shows the metal wire 1 of the present embodiment made of a Fe--Si--Mo alloy under the same measurement conditions as above.
The measurement result which measured the relationship between Si concentration and output voltage about 2 is shown. The Mo concentration was fixed at 4 wt% for the measurement. As can be seen from this figure, by setting the Si concentration within the range of about 2.5 to 3.5 wt%,
Sufficient output voltage can be obtained.

As shown in FIG. 1, such a metal wire 12 is fixed to a label 14 whose back surface is coated with an adhesive,
The label is attached to an article by attaching the label to an arbitrary part of the article 16. Further, as shown in FIG. 7, the metal wire 12 is attached to the label 14 on which the barcode is printed.
May be fixed in advance, and in this case, the label dedicated to the metal wire can be omitted. Here, since the metal wire 12 is very thin and flexible, it can be easily attached not only to an article having a flat surface but also to an article having a curved surface such as a bottle or a can.

Further, not limited to the label, the metal wire 12 may be fixed to a tag such as a luggage tag or a price tag, and the tag may be detachably attached to the article. On the other hand, as shown in FIG. 2, the detection device 20 for detecting the identification mark 10 provided with the metal wire 12 includes a transmitter 24 that functions as a magnetic field application unit that generates an alternating magnetic field in the inspection region 22 through which the article 16 passes. And a receiver 26 that detects a change in the magnetic field in the inspection region 11.

The transmitter 24 has a transmission coil 27 and an AC generator 30 which supplies an AC current to the transmission coil via an amplifier 28. And the transmission coil 27
Generates an alternating magnetic field according to the alternating current supplied from the alternating current generator 30 via the amplifier 28, and applies the alternating magnetic field to the inspection region 22.

The receiver 26 includes a detection coil 32 that functions as an electromagnetic induction coil and a detection circuit 34 connected to the detection coil. The detection coil 32 is arranged at an interval such that a person can pass through it, for example, at an interval of 1 m, and the transmission coil 2
7 and the inspection area 22 between the transmission coil 27 and the transmission coil 27.
Is formed. Then, a current corresponding to the magnetic field in the inspection region 22 is induced in the detection coil 32 forming the receiving means, and this current is output to the detection circuit 34 as an output signal.

The detection circuit 34 includes a low pass filter 36, an amplifier 38, and a comparator 40 which are sequentially connected to the transmission coil 32. The low-pass filter 36 constitutes a detecting means, and cuts the low-frequency output signal corresponding to the alternating magnetic field generated by the transmitter 24 among the output signals from the detection coil 32, and reverses the magnetization of the identification mark 10. Only the output signal of the high frequency component with the resulting pulsed output is taken out. Since the pulsed output contains a high frequency component, it is taken out without being attenuated by the low pass filter 32. Further, since the pulsed output is periodically output every time the positive and negative of the alternating magnetic field changes, it is detected almost in an instant without moving the article 16 with the identification mark 10 relative to the alternating magnetic field. It

The comparator 33, which functions as a comparison means, collates the identification mark 10 by comparing the detected pulsed output with reference data prepared in advance. An alarm device 44 is connected to the comparator 40 via a drive unit 42. The drive unit 42 activates the alarm device 44 in accordance with the comparison result of the comparator 40, and the alarm device informs a third party of the comparison result by means of display means such as an indicator lamp and a notification sound.

The detection device 20 having such a configuration is installed at, for example, an exit of a building, and monitors articles passing through the inspection area 22 to prevent theft. That is,
Usually, the transmitter 24 generates an alternating magnetic field larger than the coercive force of the metal wire 12 of the identification mark 10 in the inspection area 22, and the receiver 26 constantly monitors the magnetic field change in the inspection area 22.

As shown in FIG. 2, when the person carrying the article 16 with the identification mark 10 passes through the inspection area 22,
A pulsed output is detected by the receiver 26, and the comparator 4
0 is compared with the reference data corresponding to the identification mark 10. As a result of the collation, when the detected pulsed output and the reference data match, the detection circuit 34 determines that the identification mark 10 attached to the article 16 is an anti-theft sign, and via the drive unit 42. The alarm device 44 is activated. Therefore,
The administrator of the inspection area 22 can recognize that the article 16 is a stolen article by the alarm from the alarm device 44, and can prevent the theft.

According to the identification mark 10 constructed as described above, since the metal wire 12 is made of the Fe--Si--Mo alloy, its saturation magnetic flux density is the same as that of the metal wire made of the amorphous alloy. 1.2 to 2.0 times as large as the comparison,
If the cross-sectional area is the same as that of the amorphous alloy wire, the level of the pulsed output detected due to the magnetization reversal also becomes large. Therefore, by setting the length of the metal wire 12 to about 300 to 500 times the wire diameter, a sufficient detection output can be obtained, and as a result, an identification mark that can be accurately recognized without increasing the size can be obtained. Obtainable. Further, since the detection output is large, the S / N ratio is also improved, and more accurate recognition is possible.

When the detection output of the metal wire 12 is set to be equal to that of the amorphous alloy wire, the wire diameter can be made thinner and the length can be made shorter than that of the amorphous alloy wire. Therefore, the identification mark can be downsized.

Further, since the detection output is increased, accurate detection is possible even when the number of turns of the detection coil 32 of the detection device 20 for detecting the presence or absence of the identification mark is reduced, and as a result, the detection device and the antitheft system. Overall size reduction and cost reduction can be achieved.

The present invention is not limited to the above-mentioned embodiments, but can be variously modified within the scope of the present invention. For example, since the identification mark according to the present invention can detect passage of an article in a non-contact state,
Not only the prevention of theft of important documents and articles such as books but also the physical distribution management of cargo.

When the identification mark is used for such physical distribution management of the cargo, as shown in FIG. 8, the identification mark 10 having the same structure as that of the above embodiment is provided on the surface or inside of the cargo 50, and The transmission coil 27 and the detection coil 32 of the detection device 20 are installed on both sides of the transport path 52. Then, the pulse-shaped output based on the identification mark 10 attached to the cargo 50 passing between the transmitting coil 27 and the detection coil 32 is detected, and the cargo 50 is identified. As a result of the identification, for example, when the predetermined identification mark 10 is detected, the drive unit 42
By operating the sorting mechanism 54 via the, the transport path 52 can be switched to automatically sort the cargo 50.

[0038]

As described in detail above, according to the present invention,
A large pulsed output with a high S / N ratio can be obtained,
It is possible to provide a small identification mark that enables accurate identification. Along with this, it is possible to reduce the size and cost of the detection device that detects the identification mark, and to reduce the size and cost of the entire antitheft system.

[Brief description of drawings]

FIG. 1 is a perspective view showing an article with an identification mark according to an embodiment of the present invention.

FIG. 2 is a perspective view showing the entire anti-theft system that uses the identification sign as an anti-theft sign.

FIG. 3 is a diagram showing a relationship between an excitation magnetic field of a metal wire of the identification mark and an output.

FIG. 4 is a diagram showing a relationship between a length / diameter ratio of the metal wire and an output voltage in comparison with an amorphous metal wire.

FIG. 5 is a diagram showing the relationship between the Mo concentration of the metal wire and the output voltage.

FIG. 6 is a diagram showing the relationship between the Si concentration of the metal wire and the output voltage.

FIG. 7 is a plan view showing an embodiment in which an identification mark according to the present invention is combined with a barcode label.

FIG. 8 is a perspective view schematically showing an embodiment in which the identification mark according to the present invention is applied to physical distribution management of cargo.

[Explanation of symbols]

10 ... Identification mark, 12 ... Metal wire, 20 ... Detection device,
22 ... Inspection area 24 ... Transmitter, 26 ... Receiver, 34 ... Detection circuit

Claims (5)

[Claims] 1. An Fe-Si-Mo alloy having a Si concentration of 2.5 to 3.5 wt% and a Mo concentration of 3.5 to 4.5 wt%, and an alternating magnetic field exceeding its coercive force was applied. An identification mark with a piece of metal that causes a sharp reversal of magnetization. 2. An Fe-Si-Mo alloy having a Si concentration of 2.5 to 3.5 wt% and a Mo concentration of 3.5 to 4.5 wt%, and an alternating magnetic field exceeding its coercive force was applied. In this case, a metal wire that causes a sharp magnetization reversal is provided, and the wire diameter of the metal wire is 30 to 125 μm, and the length thereof is 300 to the wire diameter.
Identification mark formed 500 times. 3. An Fe-Si-Mo alloy having a Si concentration of 2.5 to 3.5 wt% and a Mo concentration of 3.5 to 4.5 wt%, and an alternating magnetic field exceeding its coercive force was applied. The presence of the anti-theft sign is determined by determining the presence or absence of the anti-theft sign attached to the article equipped with a metal piece that causes a sharp magnetization reversal and the presence of the above-mentioned anti-theft sign on the article that passes a predetermined inspection area. An anti-theft system that includes a detection device that issues an alarm when detected. 4. The metal piece has a wire diameter of 30 to 125 μm.
The antitheft system according to claim 3, wherein the antitheft system is formed in an elongated linear shape having m and a length of 300 to 500 times the wire diameter. 5. The detection device comprises a magnetic field applying means for applying an alternating magnetic field having a strength exceeding the coercive force of the metal piece to the inspection area, and a reception for outputting a change in the magnetic field in the inspection area as an output signal. Means, detecting means for detecting a pulsed output caused by magnetization reversal of the metal piece from the output signal, comparison means for comparing the detected pulsed output with reference data prepared in advance, and The antitheft system according to claim 3, further comprising: an alarm unit that issues an alarm when the pulsed output matches the reference data.