JP2000194963A - Anti-theft device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an anti-theft device small in size, low in cost and capable of generating an alarm at the time of being applied with a strong impact, in the anti-theft device to be used for an anti-theft support system for preventing shoplifting of commodities, etc. SOLUTION: In this anti-theft device 11, a piezoelectric buzzer 37 is used as an alarming means 15 and a receiving coil 31 is connected in series to the piezoelectric buzzer 37. Thus, an electric signal induced by an impact to the piezoelectric buzzer 37 is inputted to a detecting means 13 via a receiving means 12, the impact from the outside is detected and the alarm is generated from the piezoelectric buzzer 37 via an alarm driving means 14.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an antitheft device used for preventing shoplifting of goods.

[0002]

2. Description of the Related Art As shown in FIG. 2, an anti-theft support system including an anti-theft device currently in practical use transmits an electromagnetic wave from a monitoring antenna 100 to a predetermined area and is monitored by the monitoring antenna 100. When the anti-theft device 101 attached to the article 1 detects that it has entered a predetermined area, the anti-theft device 101 issues an alarm by a buzzer sound or the like.

The anti-theft device 101 includes a receiving means 102 for receiving an electromagnetic wave transmitted from the monitoring antenna 100, and an input signal connected to the receiving means 102 and which receives an input signal by the electromagnetic wave transmitted from the monitoring antenna 100. It is constituted by a detecting means 103 for determining whether or not there is, an alarm driving means 104 connected to the detecting means 103, and an alarm means 105 connected to an output of the alarm driving means 104.

The operation of the anti-theft device configured as described above will be described below. First, as shown in FIG. 2, the anti-theft device 101 is attached to the article 1. Examples of the attachment method include a method of winding the anti-theft device 101 around the article 1 with a tape, a method of attaching a double-sided adhesive tape to the attachment surface of the anti-theft device 101, and attaching the article to the article 1.

On the other hand, a monitoring antenna 100 installed at an outlet of a store, for example, an outlet of a retail store, transmits an electromagnetic wave of a specific frequency to a predetermined area.

If the user attempts to take out the article 1 from the exit with the anti-theft device 101 attached, the electromagnetic wave of a specific frequency transmitted from the monitoring antenna 100 is received by the receiving means 102 built in the anti-theft device 101. The signal is received by an LC parallel resonance circuit formed by the coil 111 and the resonance capacitor 112, and the received signal is supplied to the detection circuit unit 114 via the filter capacitor 113 of the detection unit 103. The detection circuit unit 114 determines whether the received signal is an electromagnetic wave of a specific frequency transmitted from the monitoring antenna 100. In the case of a transmission signal from the monitoring antenna 100, power is supplied to the alarm driving unit 104,
A buzzer drive signal is generated by a buzzer drive circuit 115 of the alarm drive unit 104.

There are two buzzer drive signal outputs, both of which are pulse outputs between the power supply and the ground which are substantially equal to the resonance frequency of the piezoelectric buzzer 117 of the alarm means 105, and one output is an inverted output of the other output. Has become. The buzzer drive signal is sent from the buzzer drive circuit 115 to the push-pull circuit 1
16 is output. The push-pull circuit 116 is connected to the first PNP transistor 118 and the second
NPN transistor 121 or second PNP transistor 119 and first NPN transistor 120 are alternately turned on.

[0008] The piezoelectric buzzer 117 of the alarm means 105 oscillates by the output of the push-pull circuit 116 and emits an alarm sound.

Such an anti-theft device is required to have a detection function and an alarm function for a destruction by the impact on the anti-theft device 101 in the store in order to prevent the article 1 from being taken out of the store illegally. ing.

[0010]

However, the anti-theft device 101 having such a conventional configuration does not have a detection function and an alarm function for vandalism due to an impact.
Regarding the act of destroying the anti-theft device 101 attached to the article 1 in the store and taking it out of the store, the alarm means 105 of the anti-theft device 101 could not issue an alarm and notify the clerk.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an anti-theft device which issues an alarm when a strong impact is applied.

[0012]

In order to achieve this object, an anti-theft device according to the present invention has a configuration in which a piezoelectric buzzer is used as alarm means and a receiving coil and a piezoelectric buzzer are connected in series.

[0013] Accordingly, it is possible to provide an anti-theft device that issues an alarm when a strong impact is applied.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is a receiving means for receiving an electromagnetic wave transmitted from a monitoring antenna and including a receiving coil in its element, and connected to and connected to the receiving means. A detection unit that determines whether the input signal is an electromagnetic wave transmitted from the monitoring antenna; an alarm driving unit connected to the detection unit; and an alarm unit connected to an output of the alarm driving unit. ,
A piezoelectric buzzer is used as the alarming means, and the receiving coil and the piezoelectric buzzer are connected in series to form an anti-theft device.When an external shock is applied to the anti-theft device, the piezoelectric buzzer receives an impact. The induced electric signal is inputted to the detecting means via the receiving means, thereby detecting that an impact is applied from the outside of the anti-theft device, and issuing an alarm from the piezoelectric buzzer via the alarm driving means. it can.

According to a second aspect of the present invention, there is provided the anti-theft device according to the first aspect, wherein a voltage control circuit for limiting a voltage value of an input signal is provided at an input of the detecting means. Even if an excessive electric signal is generated, the detection means is not destroyed.

According to a third aspect of the present invention, in the voltage control circuit, two zener diodes are formed by a series connection having anodes connected to each other, and the series connection is connected in parallel with the piezoelectric buzzer. The anti-theft device according to the second aspect of the present invention has a simple structure, and can realize a small-sized and low-cost anti-theft device.

According to a fourth aspect of the present invention, there is provided the anti-theft device according to the first aspect, further comprising a signal adjusting means for adjusting a change amount of a signal intensity of an electric signal induced by the piezoelectric buzzer. Since the amount of change in the signal strength of the electric signal induced in the piezoelectric buzzer can be adjusted according to the strength of the shock, the strength of the shock for issuing an alarm can be adjusted.

According to a fifth aspect of the present invention, there is provided the signal adjusting means,
5. The anti-theft device according to claim 4, wherein a resistor is inserted between the push-pull circuit forming a part of the alarm driving means and the piezoelectric buzzer, and has a simple structure, a small size and a low price. It can be an anti-theft device.

According to a sixth aspect of the present invention, a capacitor is connected in parallel with the piezoelectric buzzer to form a parallel connection, and the series resonance frequency formed by the parallel connection and the receiving coil is determined by the alarm driving means. The anti-theft device according to claim 1, wherein the voltage is applied to both ends of the piezoelectric buzzer when the receiving coil resonates with the oscillation frequency of the alarm driving means, so that the alarm sound is generated. Can be bigger.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an anti-theft support system according to the present invention, which comprises a monitoring antenna 10 and an anti-theft device 11. The anti-theft device 1
As for 1, the detailed circuit is also included.

In FIG. 1, 1 is an article, 10 is a monitoring antenna, and 11 is an anti-theft device. The anti-theft device 11 is composed of more detailed elements. That is,
Reference numeral 12 denotes a receiving unit, 13 denotes a detecting unit, 14 denotes an alarm driving unit, and 15 denotes an alarm unit, each of which is configured as shown by a dotted line.

Next, each element constituting the anti-theft device 11 will be described. The receiving means 12 includes the receiving coil 3
1 and a resonance capacitor 32, and the reception coil 31 and the resonance capacitor 32 are connected in parallel to form an LC parallel resonance circuit. The resonance frequency of this LC parallel resonance circuit is
The frequency is set to be substantially equal to the frequency of the electromagnetic wave transmitted from the monitoring antenna 10.

The detecting means 13 comprises a filter capacitor 33 and a detecting circuit section 34. One end of the filter capacitor 33 is connected to the receiving means 12 and the alarm means 15, and the other end is connected to the detection circuit section 34.
The output of the detection circuit unit 34 is connected to the alarm drive unit 14.

The alarm drive means 14 comprises a buzzer drive circuit 35 and a push-pull circuit 36. The output of the detection circuit section 34 is connected to a buzzer drive circuit 35.
The two outputs of the buzzer drive circuit 35 are the push-pull circuit 3
6 is connected.

The push-pull circuit 36 includes a first PNP transistor 50, a second PNP transistor 51, and a first PNP transistor 51.
NPN transistor 52, second NPN transistor 53 and first adjusting resistor 54, second adjusting resistor 55,
It is constituted by a third adjustment resistor 56 and a fourth adjustment resistor 57. First PNP transistor 50, first NPN
A drive circuit including a transistor 52, a first adjustment resistor 54, and a second adjustment resistor 55, and a drive circuit including a second PNP transistor 51, a second NPN transistor 53, a third adjustment resistor 56, and a fourth adjustment resistor 57. The drive circuits form a pair and have the same circuit configuration.

One output of the buzzer driving circuit 35 is a first PNP transistor 50 and a first NPN transistor 5.
2 base. The power supply is connected to the emitter of the first PNP transistor 50, and the collector is connected to the first PNP transistor 50.
Of the first N through the adjustment resistor 54 and the second adjustment resistor 55.
Connected to the collector of PN transistor 52. The emitter of the first NPN transistor 52 is grounded.
The paired drive circuits have the same circuit configuration.
A drive signal is extracted from a connection point between the first adjustment resistor 54 and the second adjustment resistor 55, and the third adjustment resistor 56 and the fourth adjustment resistor 57 are received via the receiving unit 12 and the alarm unit 15.
Connected to the connection point.

The alarm means 15 comprises a piezoelectric buzzer 37, an adjusting capacitor 38, and a voltage control circuit 39.
The voltage control circuit 39 forms a series connection in which two Zener diodes have their anodes connected to each other. The piezoelectric buzzer 37, the adjusting capacitor 38, and the voltage control circuit 39 are connected in parallel.

The operation of the anti-theft device configured as described above will be described below. First, as shown first, the anti-theft device 11 is attached to the article 1. Examples of the attachment method include a method of winding the anti-theft device 11 around the article 1 with a tape, a method of attaching a double-sided adhesive tape to the attachment surface of the anti-theft device 11, and attaching the article to the article 1.

On the other hand, a monitoring antenna 10 installed at an outlet of a store, for example, an outlet of a retail store, transmits an electromagnetic wave of a specific frequency to a predetermined area.

Now, when an attempt is made to break the main body of the anti-theft device 11 attached to the article 1 in the store by applying an impact, an electric signal is generated in the piezoelectric buzzer 37 by a piezoelectric action. The amplitude of this electric signal is limited by the voltage control circuit 39, and is substantially equal to the sum of the Zener voltages of the two Zener diodes. The relationship between the strength of the shock applied to the main body of the anti-theft device 11 and the amplitude of the electric signal generated in the piezoelectric buzzer 37 is determined by the first adjustment resistor 54, the second adjustment resistor 55, and the third adjustment resistor. 56, and can be adjusted by the fourth adjustment resistor 57.

Since the piezoelectric buzzer 37 is connected to the connection line between the receiving means 12 and the detecting means 13, the piezoelectric buzzer 37
Only the AC component of the electric signal generated in step (1) is extracted by a filter capacitor 33 built in the detection means 13 and input to the detection circuit section 34. The detection circuit unit 34 determines whether the input signal is an electric signal generated by the piezoelectric buzzer 37 or whether the input signal is an electromagnetic wave of a specific frequency transmitted from the monitoring antenna 10. The detection circuit unit 34 determines that the input signal is an electric signal generated by the piezoelectric buzzer 37,
When it is determined that the amplitude of the input signal is equal to or greater than the specified value for issuing an alarm, the output signal is turned on and the buzzer drive circuit 35 incorporated in the alarm drive unit 14 is activated.

The power is supplied to the buzzer drive circuit 35 when the output of the detection means 13 is turned on, and a buzzer drive signal is generated. There are two outputs of the buzzer drive signal, one is a rectangular wave output between the power supply and the ground, and the other is an inverted output of the rectangular wave output. The frequency of this rectangular wave output is substantially equal to the resonance frequency of the piezoelectric buzzer 37.

The buzzer drive signal is sent from the buzzer drive circuit 35 to the first PNP transistor 5 of the push-pull circuit 36.
0 and output to the first NPN transistor 52.
When the buzzer drive signal is on, that is, at the power supply level, the first
PNP transistor 50 is turned off, and first NPN transistor 52 is turned on. On the other hand, the second PN
P transistor 51 and second NPN transistor 5
3 includes a first PNP transistor 50 and a first N
Since the inverted signal of the buzzer drive signal output to the PN transistor 52 is output, the output is off, that is, at the ground level, the second PNP transistor 51 is turned on, and the second NPN transistor 53 is turned off. As a result, current flows in the directions of the second PNP transistor 51, the third adjustment resistor 56, the piezoelectric buzzer 37, the receiving means 12, the second adjustment resistor 55, and the first NPN transistor 52. Similarly, the first PNP transistor 5
When the buzzer drive signal output to 0 and the first NPN transistor 52 is off, that is, at the ground level, the first PNP transistor 50, the first adjustment resistor 54, the receiving means 12, the piezoelectric buzzer 37, the fourth adjustment The current flows in the direction of the resistor 57 and the second NPN transistor 53. As described above, since the piezoelectric buzzer 37 is bidirectionally energized by the buzzer drive signal substantially equal to the resonance frequency of the piezoelectric buzzer 37, the piezoelectric buzzer 37 oscillates and emits an alarm sound.

At this time, the combined capacitance of the parallel connection body composed of the piezoelectric buzzer 37 and the adjusting capacitor 38 and the receiving coil 31
Form an LC series resonance circuit. Since the resonance frequency of the LC series resonance circuit is substantially equal to the oscillation frequency of the alarm driving means 14, the resonance occurs when an alarm is issued. Since the voltage applied to both ends of the piezoelectric buzzer 37 is boosted by this resonance, the sound pressure of the alarm sound by the alarm means 15 is higher than when driven by the power supply voltage.

Further, when the article 1 with the anti-theft device 11 attached is taken out from the exit, the electromagnetic wave of a specific frequency transmitted from the monitoring antenna 10 is
L formed by the receiving coil 31 and the resonance capacitor 32 of the receiving means 12 built in the antitheft device 11
The signal is received by the C parallel resonance circuit, and the received signal is
Only the AC component is extracted by a built-in filter capacitor 33 and input to the detection circuit unit 34. The detection circuit unit 34 determines whether the input signal is an electric signal generated by the piezoelectric buzzer 37 or whether the input signal is an electromagnetic wave of a specific frequency transmitted from the monitoring antenna 10. If the detection circuit unit 34 determines that the received signal is a transmission signal from the monitoring antenna 10, it turns on the output signal and activates the buzzer drive circuit 35 built in the alarm drive unit 14. Hereinafter, the same operation as when an impact is applied to the anti-theft device 11 to generate an alarm sound is performed.

As described above, according to the present embodiment, as shown in FIG. 1, the receiving means 12 which receives the electromagnetic wave transmitted from the monitoring antenna 10 and includes the receiving coil 31 in its components, A detection unit 13 connected to the monitoring unit 12 and determining whether or not the input signal is an electromagnetic wave transmitted from the monitoring antenna 10;
3 and an alarm means 15 connected to the output of the alarm drive means 14. The piezoelectric buzzer 37 is used as the alarm means 15, and the receiving coil 31 and the piezoelectric buzzer 37 are connected in series. With the connected structure, when a shock is applied to the anti-theft device 11 from the outside, an electric signal induced by the shock by the piezoelectric buzzer 37 is input to the detecting means 13 via the receiving means 12, There is an effect that it is possible to detect that an external impact is applied to the anti-theft device 11 and to issue an alarm by the alarm drive unit 14 and the alarm unit 15.

Further, since the voltage control circuit for limiting the voltage value of the input signal is provided at the input of the detecting means 13, an effect that an excessive electric signal is generated in the piezoelectric buzzer due to a strong impact and the detecting means is not destroyed. There is.

Further, the voltage control circuit 39 has a configuration in which two zener diodes are formed by a series connection with anodes connected to each other, and this series connection is connected in parallel with the piezoelectric buzzer 37. There is an effect that the structure is simple, small, and inexpensive.

Further, by providing a signal adjusting means for adjusting the amount of change in the signal intensity of the electric signal induced by the piezoelectric buzzer 37, the piezoelectric buzzer 37 induced by the impact intensity changes. Since the amount of change in the signal strength of the electric signal can be adjusted, there is an effect that the strength of the shock for issuing an alarm can be adjusted.

Further, the signal adjusting means includes an alarm driving means 1
By using a configuration in which an adjustment resistor is inserted between the push-pull circuit 36 that forms part of the block 4 and the piezoelectric buzzer 37, the structure is simple, and the size and cost can be reduced. There is.

Further, an adjusting capacitor 38 is connected in parallel to the piezoelectric buzzer 37 to form a parallel connection, and the series resonance frequency formed by the parallel connection and the receiving coil 31 is used as the oscillation frequency of the alarm driving means 14. , The receiving coil 31 resonates with the oscillation frequency of the alarm driving means 14 so that the piezoelectric buzzer 37
Since the voltage applied to both ends increases, the alarm sound is increased.

[0042]

As described above, according to the present invention, since the piezoelectric buzzer is used as the alarm means and the receiving coil and the piezoelectric buzzer are connected in series, an external impact is applied to the anti-theft device. When an electric signal induced by an impact on the piezoelectric buzzer is inputted to the detecting means via the receiving means, it is detected that an impact is applied from outside the anti-theft device, and the piezoelectric signal is outputted via the alarm driving means. An alarm can be issued from a buzzer.

[Brief description of the drawings]

FIG. 1 is a block diagram of an anti-theft support system including a detailed circuit of an anti-theft device according to an embodiment of the present invention;

FIG. 2 is a block diagram of an anti-theft support system including a detailed circuit of a conventional anti-theft device;

[Explanation of symbols]

 Reference Signs List 10 monitoring antenna 11 anti-theft device 12 receiving means 13 detecting means 14 alarm driving means 15 alarm means 37 piezoelectric buzzer

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5C084 AA03 AA09 BB31 CC35 DD79 GG71 5C087 AA02 AA32 AA42 DD05 DD11 EE07 EE14

Claims (6)

[Claims] 1. A receiving means for receiving an electromagnetic wave transmitted from a monitoring antenna and including a receiving coil in its element, and whether the input signal is connected to the receiving means and the input signal is an electromagnetic wave transmitted from the monitoring antenna. Detecting means for judging whether or not, an alarm driving means connected to the detecting means, an alarm means connected to the output of the alarm driving means, using a piezoelectric buzzer as the alarm means and the receiving coil An anti-theft device in which the piezoelectric buzzer is connected in series. 2. The anti-theft device according to claim 1, wherein a voltage control circuit for limiting a voltage value of the input signal is provided at an input of the detecting means. 3. The anti-theft system according to claim 2, wherein the voltage control circuit is formed by connecting two Zener diodes in series with an anode connected to each other, and connecting the series connected body in parallel with the piezoelectric buzzer. apparatus. 4. The anti-theft device according to claim 1, further comprising a signal adjusting means for adjusting an amount of change in the signal intensity of the electric signal induced by the piezoelectric buzzer. 5. The anti-theft device according to claim 4, wherein the signal adjusting means includes a resistor inserted between the push-pull circuit forming a part of the alarm driving means and the piezoelectric buzzer. 6. A method in which a capacitor is connected in parallel with the piezoelectric buzzer to form a parallel connection, and a series resonance frequency formed by the parallel connection and the receiving coil is substantially equal to the oscillation frequency of the alarm driving means. Item 7. The anti-theft device according to Item 1.