JP2000266860A - Magnetic tape-detecting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a magnetic tape-detecting device that can detect not only the presence or absence of a magnetic tape being used for preventing a book and merchandise from being illegally taken out, but also the number of the magnetic tapes. SOLUTION: A detection coil 4 is provided at the rear side of first and second plates 1a and 1b being provided while being inclined for composing a reference plate 1, and a bias coil 5 is further provided at the rear side of the detection coil 4. A bias circuit 8 supplies an AC current with a frequency of 300 Hz to the bias coil 5. By the AC current, the bias coil 5 generates an AC magnetic field of 5-6 gausses. When a magnetic tape 2 is subjected to the AC magnetic field, the magnetic tape 2 generates a pulse magnetic field of 600 Hz that is the half cycle of the AC magnetic field being energized by magnetic characteristics of the magnetic tape 2. The pulse magnetic field of 600 Hz is detected by the detection coil 4 with an energized AC magnetic field of 300 Hz, and a pulse magnetic field signal is selectively detected by a detection circuit 7 for outputting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic tape detecting device for detecting a magnetic tape used in a library, a supermarket, various rental stores, or the like to prevent unauthorized removal of books and products.

[0002]

2. Description of the Related Art For example, in a library, a supermarket, various rental stores, etc., magnetic tapes are used to prevent theft, such as monitoring for unauthorized removal of books and products. This magnetic tape generates a pulse magnetic field having a period half that of the alternating magnetic field under an alternating magnetic field of several Gauss. A pulse having a half cycle is detected as an induced voltage of the coil, and the presence or absence of a fraud is determined based on the presence or absence of the pulse voltage.

[0003] Such a magnetic tape is composed of an elongated tape-shaped soft magnetic material, and a rectangular ferromagnetic material provided at regular intervals on the soft magnetic material. The soft magnetic material has a rectangular magnetic hysteresis characteristic, and the ferromagnetic material can easily change the direction of magnetization by an external magnetic field.

In a rental or checkout counter of a library or a supermarket, etc., a predetermined processing device applies a DC magnetic field in the longitudinal direction of a magnetic tape,
The ferromagnetic material on the magnetic tape is magnetized in the longitudinal direction of the magnetic tape to make the soft magnetic material magnetically saturated. A magnetic tape in a magnetically saturated state does not generate a pulsed magnetic field under an alternating magnetic field of several Gauss, and is not detected by a magnetic tape detecting device provided near an exit of a library or a supermarket.

On the other hand, when the ferromagnetic material on the magnetic tape is magnetized in a direction perpendicular to the magnetic tape, the soft magnetic material is magnetically unsaturated and generates a pulse magnetic field due to an external alternating magnetic field. Is detected by a magnetic tape detecting device.

[0006]

The magnetic tape detecting device provided near the exit of a library, a supermarket, etc.
It only detects the presence or absence of a pulse magnetic field having a constant period, but does not detect the number (number) of magnetic tapes. In addition, the processing device of the lending or checkout counter in libraries and supermarkets also detects magnetic pulses with a constant period,
Although the magnetization state of the magnetic tape is detected, the number is not detected.

As described above, since the conventional magnetic tape detecting device does not have a function of detecting the number of magnetic tapes, for example, the self-service of library lending work and the improper payment and settlement of procedures for unmanned shops. It could not be applied for prevention.

Accordingly, an object of the present invention is to provide a magnetic tape detecting device capable of detecting not only the presence / absence of a magnetic tape used to prevent unauthorized removal of books or commodities, but also the number of magnetic tapes.

[0009]

A magnetic tape detecting device according to the present invention comprises a magnetic tape comprising a long and thin tape-shaped soft magnetic material and a rectangular ferromagnetic material disposed on the soft magnetic material at regular intervals. A reference plate on which a tape is disposed, an annular detection coil disposed near the reference plate and detecting a magnetic change generated from the magnetic tape, and disposed substantially concentrically close to the detection coil; An annular bias coil for applying a bias magnetic field to the magnetic tape, and a detection circuit for detecting the presence or absence of the magnetic tape and the number of the magnetic tapes based on the output of the detection coil.

In the magnetic tape detecting device according to the present invention, the reference plate abuts the first plate and the second plate at a substantially right angle, and abuts the abutting portion of the first and second plates. A detection coil and a bias coil are provided along the gap.

Further, in the magnetic tape detecting device according to the present invention, the detecting coil and the bias coil may include a first detecting coil and a first bias coil disposed along a butted portion of the first and second plates. , A second detection coil and a second bias coil movably provided at a position facing one of the first and second plates.

In the magnetic tape detecting device of the present invention, a magnetic tape comprising an elongated tape-shaped soft magnetic material and a rectangular ferromagnetic material arranged at regular intervals on the soft magnetic material is arranged. A reference plate, an odd number of a plurality of K annular detection coils disposed at regular intervals in the longitudinal direction of the magnetic tape along the vicinity of the reference plate and detecting a magnetic change generated from the magnetic tape; Each of the plurality of detection coils is disposed substantially concentrically in proximity to both ends or each of the detection coils located inside one of the detection coils, and each of the inside of each of the detection coils inside the both ends or one of the detection coils is located inside. A plurality of K-2 annular bias coils which are disposed substantially concentrically in proximity to every other detection coil and apply a bias magnetic field to the magnetic tape; It is provided with a detection circuit for detecting the number of presence and the magnetic tape of the magnetic tape based on the output of yl.

[0013] The magnetic tape detecting device of the present invention is arranged such that a plurality of detecting coils are connected in series in the same winding direction, and a plurality of bias coils are connected in series in an opposite winding direction to adjacent bias coils. Features.

Further, in the magnetic tape detecting device according to the present invention, the reference plate abuts the first plate and the second plate at a substantially right angle, and abuts the abutting portion of the first and second plates. A plurality of detection coils and a plurality of bias coils are respectively provided along the plurality of detection coils.

Furthermore, the magnetic tape detecting device of the present invention
A plurality of detection coils and a plurality of bias coils, a first detection coil group and a first bias coil group disposed along the butting portion of the first and second plates;
A second detection coil group movably provided at a position facing either the first or second plate;
And a bias coil group.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows the present embodiment, for example,
In a library, the structure of a magnetic tape detecting device for detecting the presence and the number of magnetic tapes for preventing unauthorized removal of books is schematically shown. In FIG. 1, a reference plate 1 is such that a book 3 having a magnetic tape 2 stuck on a back cover (or a front cover) is placed with the sticking surface of the magnetic tape 2 down. The plate 1a and the second plate 1b are configured to abut each other at a substantially right angle. In addition,
In the case of the book 3 in which the magnetic tape 2 is affixed to the spine, either cover may be on the lower side.

First plate 1a and second plate 1b
An annular detection coil 4 having a substantially L-shaped cross section for detecting a magnetic change generated from the magnetic tape 2 is disposed along the abutting portion with the magnetic tape 2. An annular bias coil 5 having a substantially L-shaped cross section for applying a bias magnetic field to 2 and being arranged substantially concentrically is provided.

On the back side of the second plate 1b, a dummy coil 6 used for temperature compensation of the detection coil 4 is provided. The detection coil 4 and the dummy coil 6
Are connected to a detection circuit 7 for detecting the presence or absence of the magnetic tape 2 and the number of the magnetic tapes 2. The bias coil 5 is connected to a bias circuit 8 that supplies an alternating current for generating a bias magnetic field.

More specifically, the detection coil 4 is provided on the back side of the first plate 1a and the second plate 1b which are provided with an inclination, and the bias is further provided on the back side of the detection coil 4. A coil 5 is provided.
In addition, a dummy coil 6 is provided at a distance from the first plate 1a and the second plate 1b. here,
The magnetic tape 2 is located within the range of the detection coil 4 on the reference plate 1.

The bias circuit 8 has, for example, a frequency of 3
An oscillation circuit that generates a 00 Hz signal and a power amplifier that amplifies the output of the signal supply a 300 Hz AC current to the bias coil 5. By this AC current, the bias coil 5 generates an AC magnetic field of 5 to 6 Gauss. When the magnetic tape 2 receives this AC magnetic field, it generates a pulse magnetic field of 600 Hz which is half the cycle of the AC magnetic field energized by the magnetic characteristics of the magnetic tape 2.

The 600 Hz pulse magnetic field is detected by the detection coil 4 together with the energized 300 Hz AC magnetic field, and the detection circuit 7 selectively detects and outputs a pulse magnetic field signal.

Hereinafter, the operation of detecting the magnetic tape 2 will be described in detail.

FIG. 2 shows the arrangement of the detection coil 4 and the bias coil 5. The detection coil 4 is composed of an odd number of K detection coils, for example, five detection coils 4a, 4b, 4c, 4d, and 4e, and these detection coils 4a, 4b, 4c, 4d, and 4e are connected to the reference plate 1.
The magnetic tapes 2 placed thereon are arranged at regular intervals in the longitudinal direction.

The bias coil 5 includes a plurality of K-2 bias coils, for example, three bias coils 5a and 5a.
b, 5c, and the detection coils 4a, 4b, 4c, 4
The detection coils 4a and 4e located at both ends of d and 4e and the detection coil 4c located at the center are arranged approximately concentrically and close to each other.

Here, the detection coils 4a, 4b, 4c, 4
d and 4e are connected in series with the same winding direction of the coils, and the bias coils 5a, 5b and 5c are generated from the bias coil 5b in the same direction as the lines of magnetic force 9a and 9c generated from the bias coils 5a and 5c. The magnetic field lines 9b are connected in the opposite directions. With this connection, the lines of magnetic force of the bias magnetic field that intersect the detection coils 4a, 4b, 4c, 4d, and 4e have substantially the same amount but different directions. When the magnetic tape 2 is placed on the reference plate 1, the intensity of the bias magnetic field becomes substantially the same in each of the detection coils 4a, 4b, 4c, 4d, and 4e, and the detection coils 4a, 4b, 4c, 4d, A bias magnetic field can be applied between the coils 4e in the longitudinal direction of the magnetic tape 2.

Next, the configuration and function of the magnetic tape 2 will be described. The magnetic tape 2 is, for example, as shown in FIG.
As shown in (b), a plurality of rectangular ferromagnetic materials 2b are adhered at regular intervals on an elongated tape-shaped soft magnetic material 2a. As shown in FIG. 4, the soft magnetic material 2a has a small coercive force, and has a magnetic characteristic in which the magnetic flux density changes rapidly due to a small external magnetic field near zero magnetic field.

When the ferromagnetic material 2b on the soft magnetic material 2a having such characteristics is magnetized in the direction perpendicular to the longitudinal direction of the soft magnetic material 2a as shown in FIG. When the magnetic material 2a is applied in the longitudinal direction, the magnetization of the magnetic tape 2 changes rapidly when the bias magnetic field (see 5 (b)) is near zero as shown in FIG. 5 (c). When this change in magnetization is detected by the detection coil 4, FIG.
As shown in (d), a sudden magnetization change together with the AC bias magnetic field can be captured as a pulse signal.

On the other hand, as shown in FIG. 3B, when the ferromagnetic material 2b is magnetized in the longitudinal direction of the soft magnetic material 2a, the soft magnetic material 2a is magnetized in the longitudinal direction. For example, the magnetic field changes around the point a in FIG. 4 and no AC magnetic field is applied near the zero point, so that the magnetization change of the magnetic tape 2 does not change abruptly. Therefore, no pulse signal appears in the output signal of the magnetic tape 2.

As described above, the ferromagnetic material 2b of the magnetic tape 2
The detection signal can be changed by changing the direction of the magnetization of, and it can be used for theft prevention of books and the like. For example, if you have already booked at the book lending counter,
The magnetic tape 2 is brought into the state shown in FIG. 3B so as not to generate a pulse-like signal. In the case of a non-procedure (storage state), the state shown in FIG.

FIG. 6 shows the relationship between the magnetic tape 2 shown in FIG. 2, the detection coil 4 and the bias coil 5 in a three-dimensional manner, and shows a bias magnetic field 9 generated from the bias coil 5.
Is also generated in the longitudinal direction (the direction of the arrow) of the magnetic tape 2, so that a magnetic field can be applied to the magnetic tape 2 in the longitudinal direction. The detection coil 4 captures a change in the bias magnetic field 9 and a pulsed magnetic field generated from the magnetic tape 2. The change in the pulsed magnetic field generated from the magnetic tape 2 is proportional to the number of the magnetic tapes 2. Therefore, by detecting the magnitude of the pulse magnetic field, the number of magnetic tapes 2 can be known.

FIG. 7 specifically shows a configuration of the detection circuit 7 for detecting a change in magnetism with high sensitivity by the detection coil 4. In FIG. 7, the bridge circuit 11
Resistors R1, R2, detection coil 4, and dummy coil 6
It is composed of The AC oscillation circuit 12 includes the bridge circuit 1
1 supplies an alternating current and a phase setting circuit 1
3 is supplied with a reference signal. Here, the AC oscillation circuit 12
Is desirably 10 times or more the frequency of the bias magnetic field 9.

The differential amplifier 14 extracts the difference signal of the bridge circuit 11. The phase detection circuit 15 is for extracting the change of the pulse magnetic field of the magnetic tape 2 with the highest sensitivity. The output of the differential amplifier 14 is supplied, and the phase setting circuit 13 sets the phase so that the pulse magnetic field has the maximum sensitivity. Is set. The band-pass filter (BPF) 16 is supplied with the output of the phase detection circuit 15, has a frequency twice the frequency of the bias magnetic field 9 at the center frequency, and outputs an AC voltage near the center frequency when a pulse magnetic field is present.

The rectifier circuit 17 includes a band-pass filter 16
Rectifies the output of Low-pass filter (LPF) 18
Converts the output (pulse magnetic field signal) of the rectifier circuit 17 into a DC signal. Since the pulse magnetic field signal increases in proportion to the number of magnetic tapes 2, the output signal of the low-pass filter 18 is a detection signal proportional to the number of magnetic tapes 2. The signal discriminating circuit 19 is supplied with the output of the low-pass filter 18 and outputs a signal to a terminal corresponding to the number of the plurality of terminals according to the number of the magnetic tapes 2.

As described above, the plurality of detection coils 4a, 4
b, 4c, 4d, 4e and a plurality of bias coils 5a, 5
b, 5c, and at least one of the AC bias magnetic fields.
The detection coil 4a, 4b, 4c,
By detecting the magnetic change generated by the magnetic tape 2 in addition to 4d and 4e, not only the presence or absence of the unerased magnetic tape 2 but also the number of magnetic tapes 2 can be detected at the same time.

In the description of the above embodiment, the magnetic tape 2 is attached to the back cover (or the front cover) of the book 3 and the book 3 is set with the attaching surface of the magnetic tape 2 down. Is the case. On the other hand, when the book 3 is set with the sticking surface of the magnetic tape 2 on the upper side, for example, as shown in FIG. 8, a movement that reciprocates in a direction perpendicular to the first plate 1a of the reference plate 1 A coil unit 20 is provided,
The book 3 is sandwiched between the moving coil unit 20 and the first plate 1a with the sticking surface of the magnetic tape 2 facing upward. In this way, even if the book 3 is set with the sticking surface of the magnetic tape 2 facing upward, the magnetic tape 2 can be detected.

The moving coil section 20 includes a detection coil 24 and a bias coil 25 similar to the detection coil 4 and the bias coil 5 in the above embodiment. That is, for example, as shown in FIG.
, Four detection coils 24a, 24b, 24c, 24d, 24e similar to the detection coils 4a, 4b, 4c, 4d, 4e and the bias coils 5a, 5b, 5c, and three bias coils 25a, 25b, 25c. Have been.

In this case, the detection coils 4a, 4b, 4c,
4d, 4e and bias coils 5a, 5b, 5c and detection coils 24a, 24b, 24c, 24d, 24e and bias coils 25a, 25b, 25c are opposed to each other, and the detection coils 24a, 24b, 2
4c, 24d, 24e are detection coils 4a, 4b, 4c,
4d, 4e and a bias coil 2
5a, 25b, 25c are bias coils 5a, 5b, 5
c and connected in series. However, the bias coil 25
lines of magnetic force 29a, 29b, 29 from a, 25b, 25c
The direction of c is opposite to the direction of the magnetic lines of force 9a, 9b, 9c from the bias coils 5a, 5b, 5c, and repels each other, so that it becomes zero at the center of the book 3 sandwiched therebetween. I have.

The moving coil section 20 is reciprocated at right angles to the first plate 1a by a coil section moving mechanism (not shown).

The bias coil is a detection coil 4d,
Even if it is provided corresponding to 4e, the effect does not change.

[0041]

As described above in detail, according to the present invention, there is provided a magnetic tape detecting device capable of detecting not only the presence or absence of a magnetic tape used for preventing unauthorized removal of books and products, but also the number of magnetic tapes. it can.

[Brief description of the drawings]

FIG. 1 is a side view schematically showing a configuration of a magnetic tape detection device according to an embodiment of the present invention.

FIGS. 2A and 2B schematically show the arrangement of a detection coil and a bias coil. FIG. 2A is a plan view, and FIG.

FIG. 3 is a plan view and a side view showing a configuration example of a magnetic tape.

FIG. 4 is a diagram showing magnetic properties of a magnetic tape.

FIG. 5 is a diagram illustrating functions of a magnetic tape.

FIG. 6 is a diagram for explaining a magnetic tape detecting operation.

FIG. 7 is a block diagram illustrating a configuration example of a detection circuit.

FIG. 8 is a side view schematically showing a configuration of a magnetic tape detection device according to a modification of the present invention.

FIG. 9 is a vertical sectional side view schematically showing an arrangement state of a detection coil and a bias coil in a modification of FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Reference plate 1a ... First plate 1b ... Second plate 2 ... Magnetic tape 3 ... Book 4 ... Detection coil 5 ... Bias coil 6 ... Dummy coil 7 ... Detection circuit 8 ... ... bias circuit 2a ... soft magnetic material 2b ... ferromagnetic material 4a, 4b, 4c, 4d, 4e ... detection coil 5a, 5b, 5c ... bias coil 9a, 9b, 9c ... bias magnetic field (lines of magnetic force) 11 ... Bridge circuit 12 AC oscillator circuit 13 Phase setting circuit 14 Differential amplifier 15 Phase detection circuit 16 Bandpass filter 17 Rectifier circuit 18 Low-pass filter 19 Signal discrimination circuit 20 moving coil unit 24 detecting coil 25 bias coil 24a, 24b, 24c, 24d, 24e detecting coil 25a, 25b, 25c Ascoils 29a, 29b, 29c ... bias magnetic field (lines of magnetic force)

Claims (7)

[Claims] 1. A reference plate on which a magnetic tape composed of an elongated tape-shaped soft magnetic material and a rectangular ferromagnetic material disposed at regular intervals on the soft magnetic material is arranged; An annular detection coil disposed near and detecting a magnetic change generated from the magnetic tape; and an annular detection coil disposed substantially concentrically close to the detection coil and applying a bias magnetic field to the magnetic tape. A magnetic tape detection device, comprising: a bias coil; and a detection circuit that detects the presence or absence of the magnetic tape and the number of the magnetic tapes based on an output of the detection coil. 2. The reference plate abuts a first plate and a second plate at a substantially right angle, and the detection coil and the bias coil along an abutting portion of the first and second plates. 2. The magnetic tape detecting device according to claim 1, further comprising: 3. The first detection coil and the first bias coil, wherein the first detection coil and the first bias coil are disposed along a butting portion of the first and second plates; The magnetic tape detection device according to claim 2, further comprising: a second detection coil and a second bias coil movably provided at a position facing one of the plates. 4. A reference plate on which a magnetic tape composed of an elongated tape-shaped soft magnetic material and a rectangular ferromagnetic material disposed at regular intervals on the soft magnetic material is arranged; An odd number of a plurality of K annular detection coils for detecting magnetic changes generated from the magnetic tape, disposed at regular intervals in the longitudinal direction of the magnetic tape along the vicinity, and both ends of the plurality of detection coils or Each of the detection coils located on the inner side thereof is disposed substantially concentrically in proximity to each other, and every other end of each of the detection coils located on the inner side of each of the detection coils located on the inner side thereof. A plurality of K-2 annular bias coils which are respectively arranged substantially concentrically and apply a bias magnetic field to the magnetic tape, and the magnetic tape based on outputs of the plurality of detection coils And a detection circuit for detecting the presence or absence of the magnetic tape and the number of the magnetic tapes. 5. The plurality of detection coils are connected in series in the same winding direction, and the plurality of bias coils connect adjacent bias coils in series in a reverse winding direction. Magnetic tape detection device. 6. The reference plate abuts a first plate and a second plate at a substantially right angle, and the plurality of detection coils and the plurality of detection coils extend along an abutting portion of the first and second plates. 5. The magnetic tape detecting device according to claim 4, wherein each of the plurality of bias coils is provided. 7. A plurality of detection coils and a plurality of bias coils, a first detection coil group and a first bias coil group disposed along a butted portion of the first and second plates; 7. A second detection coil group and a second bias coil group movably provided at a position facing one of the first and second plates. Magnetic tape detector.