JP2831181B2 - Anti-theft device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anti-theft device for protecting a product from shoplifting by attaching an anti-theft device to a display in a store.

[0002]

2. Description of the Related Art In a record store, an anti-theft device as shown in FIG. 5 is used to protect a CD record of a product from shoplifting.

The anti-theft device main body 4 (hereinafter referred to as the main body) including a battery 1, a buzzer 2 driven by the battery 1, and a receiving circuit 3 is bent in a U-shape with a back plate 5. A transparent acrylic plate 6 is attached with a double-sided adhesive tape or the like, and a case-containing CD record 7 is inserted into a storage portion formed by the main body 4, the back plate 5, and the acrylic plate 6. .

[0004] In this state, a CD record is displayed in the store, and a customer who wants to purchase takes it to the cash register with the main body 4 attached, and a clerk uses a jig to generate an alarm. It is used in a sales form in which the CD record 7 stored in the storage section is taken out and handed to the customer after the state is not set.

When the CD record 7 is taken out without using a jig, the main body 4 operates to generate an alarm. Also, without removing the CD record 7 from the storage section,
If the user tries to take the CD record out of the store with the mark, the reception circuit 3 detects a signal radiated from the transmitter only near the entrance of the store and generates an alarm.

The signal frequency radiated from the transmitter is V
An electromagnetic wave in the HF region or the UHF region is used, and the tuning frequency of the receiving circuit 3 corresponds to the signal frequency radiated from the transmitter in the VHF region or the UHF region.
The region is set to a single frequency.

[0007]

When the receiving circuit 3 is manufactured, an adjustment must be performed so that its tuning frequency is exactly tuned to the transmitting frequency of the transmitter.

However, even if the tuning frequency of the receiving circuit 3 is exactly adjusted to the transmitting frequency of the transmitter, the receiving circuit 3 may be subjected to the temperature of the use environment or an external shock when receiving.
The tuning frequency set in the HF area or the UHF area may be greatly deviated.
There are malfunctions such that no alarm is generated even if the record is taken out of the store, or a false alarm is likely to be generated by an external radio wave.

Another problem is that electromagnetic waves radiated from the transmitter in the VHF or UHF range tend to cause malfunctions in other devices. SUMMARY OF THE INVENTION It is an object of the present invention to provide an anti-theft device which has a larger margin of variation of a tuning frequency of a receiving circuit than a conventional one, and which is hardly affected by electromagnetic waves radiated from a transmitter to other devices.

[0010]

According to a first aspect of the present invention, there is provided an anti-theft device including an alarm device for generating an alarm and a receiving circuit for receiving an external signal and operating the alarm device. A transmitter that radiates a signal to a specific area, wherein the transmitter includes sweep means for changing a transmission frequency of the transmitter with time by sweeping a frequency band including a tuning frequency of the reception circuit. And the sweeping pattern of the sweep means is a repetitive pattern in which the frequency is gradually increased from the lower limit frequency to the upper limit frequency, and when the upper limit frequency is reached, the frequency is gradually reduced toward the lower limit frequency. And

[0011]

According to a second aspect of the present invention, there is provided an anti-theft device having a built-in alarm device for generating an alarm and a receiving circuit for receiving an external signal and operating the alarm device; And a radiating transmitter.
The frequency of the electromagnetic wave radiated by the transmitter and the tuning frequency of the receiving circuit are set to 30 KHz or less corresponding to a voice range, and the transmitter sweeps a frequency band including the tuning frequency of the receiving circuit to time. A sweep means for changing the transmission frequency of the transmitter is provided, and the sweep pattern of the sweep means is gradually increased in frequency from the lower limit frequency to the upper limit frequency. It is characterized by a repetitive pattern in which the frequency is gradually lowered.

[0013]

According to the first aspect of the present invention, the transmission frequency of the transmitter is not a single frequency, but is changed by the action of the sweep means. When the transmission frequency of the transmitter matches the tuning frequency of the circuit, the alarm means generates an alarm. And the sweeping pattern of the sweep means is a repetition pattern in which the frequency is gradually increased from the lower limit frequency to the upper limit frequency and reaches the upper limit frequency, and then the frequency is gradually reduced toward the lower limit frequency. Even if the reception frequency of the main body is shifted near the lower limit frequency or near the upper limit frequency of the sweep means,
The signal of the transmitter can be detected stably.

[0014]

According to the second aspect of the present invention, the transmitting frequency of the transmitter and the tuning frequency of the receiving circuit of the anti-theft device are set to 30 KHz or less corresponding to the voice range, and the transmitting frequency of the transmitter is not a single frequency. The sweep pattern of the sweep means is changed by the action of the sweep means, and the frequency is gradually increased from the lower limit frequency to the upper limit frequency, and when the upper limit frequency is reached, the frequency is gradually reduced toward the lower limit frequency. Since the repetition pattern is used, the signal of the transmitter can be stably detected even when the reception frequency of the anti-theft device deviates near the lower limit frequency or the upper limit frequency of the sweep means.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. It is to be noted that components having the same functions as those in FIG. 5 showing a conventional example are denoted by the same reference numerals.

The transmitter 8 of the anti-theft device according to the present invention is shown in FIG.
As shown in FIG. 4, a sweep oscillation circuit 9 is used as a signal source as sweep means. The output signal of the sweep oscillation circuit 9 repeatedly outputs a triangular wave whose output voltage changes over time as shown in FIG. FIG.
Shows a specific circuit diagram thereof, and is output via the buffer 10.

The output signal of the sweep oscillation circuit 9 is a voltage minus
Frequency converter [Model number AD65 manufactured by Analog Devices, Inc.]
4] is converted into a rectangular wave having a repetition cycle corresponding to the input voltage by 11 and is converted into a JK flip-flop [digital IC
A signal which is input to the power amplifying unit 13 via the output control unit 12 constituted by the model number 4027] and whose frequency is swept according to the output signal of the sweep oscillation circuit 9 is transmitted from the loop coil type antenna 14 to the store. Radiated near entrance.

An infrared pyroelectric sensor 16 is connected to a terminal 15 of the output control section 12 to detect the approach of a person, and a monostable multivibrator is detected by detecting that a person has approached the entrance of the store. [Digital IC Model No. 4536] By operating 18, the signal on the output side of the voltage-frequency converter 11 is amplified by the power amplifier for a specified time after the sensor 16 detects the approach of a person.
Enter in 13. When a signal is continuously radiated from the antenna 14 regardless of the approach of a person, the switch 17 is switched.

The tuning frequency of the receiving circuit 3 of the main body 4 is set near the center frequency of the output frequency of the transmitter 8 which is being swept. With this configuration, even if the tuning frequency of the receiving circuit 3 fluctuates during use, the output frequency of the transmitter 8 is swept.
, The buzzer 2 as an alarm means can be sounded.

When an electromagnetic wave in the VHF region or the UHF region is used as the electromagnetic wave radiated from the antenna 14 of the above-described embodiment, the tuning frequency of the receiving circuit 3 is also changed to the antenna 14.
Is set to a single frequency in the VHF region or the UHF region corresponding to the signal frequency radiated from. In this case, the tuning frequency of the receiving circuit 3 is liable to fluctuate due to disturbance, but since the output frequency of the transmitter 8 is swept as described above, the margin of the receiving circuit 3 against the fluctuation of the receiving frequency is improved, and the stability is improved. Operation can be realized.

When the output frequency of the transmitter 8 is swept by using an electromagnetic wave of 30 KHz or less corresponding to a voice region as the electromagnetic wave radiated from the antenna 14, a margin for the fluctuation of the tuning frequency of the receiving circuit is obtained. Is further improved, and more stable operation can be expected. In this case, malfunction of the receiving circuit 3 due to external noise is extremely unlikely to occur, and no malfunction is caused to other devices. In addition, there is no need for a compensating means for preventing the occurrence of false alarms or malfunctions in other devices, so that there is an advantage that the anti-theft device main body 4 can be downsized.

In the present invention, as shown in FIG. 2, when the voltage gradually increases from the lower limit voltage value to the upper limit voltage value and reaches the upper limit voltage value, then the repetitive voltage gradually decreases toward the lower limit voltage value. Since the VF converter 11 is driven by the waveform, the frequency change of the signal transmitted from the antenna 14 gradually increases from the lower limit frequency to the upper limit frequency, and reaches the upper limit frequency. A signal having a repetitive pattern of gradually lowering the frequency is generated. For comparison with this, see JP-A-2-81200.
A case is considered in which a transmission signal is swept by a saw-tooth wave control signal as disclosed in Japanese Patent Application Laid-Open Publication No. H11-209,036. In this case, the transmission signal gradually increases from the lower limit frequency to the upper limit frequency, and when it reaches the upper limit frequency, at the next instant, it changes to the lower limit frequency at a stretch, and then gradually increases toward the upper limit frequency. A pattern signal is generated. Assuming that the sweep speeds from the lower limit frequency to the upper limit frequency of the two sweep patterns are the same, for example, considering the case where the reception frequency of the anti-theft device main unit 4 is shifted near the upper limit frequency, By using a sweep pattern, the time width of the output signal in the tuning circuit of the anti-theft device main body 4 can be reduced by the output signal in the tuning circuit of the anti-theft device main body 4 when the sweep pattern disclosed in Japanese Patent Laid-Open No. 2-81200 is adopted. The time width can be twice as long as the time width of the anti-theft device 4, and the signal of the transmitter 8 can be received stably by the anti-theft device 4, and the reliability is improved.

According to the first aspect of the present invention, the transmitter has sweep means for sweeping the frequency band including the tuning frequency of the receiving circuit of the anti-theft device and changing the transmission frequency of the transmitter with time. And the sweep pattern of the sweep means is a repetitive pattern in which the frequency is gradually increased from the lower limit frequency toward the upper limit frequency and reaches the upper limit frequency, and then the frequency is gradually reduced toward the lower limit frequency. As compared with the case where the transmission signal is swept by the control signal of the sawtooth wave, the time width of the output signal in the tuning circuit of the anti-theft device can be made wider, and the reception frequency of the anti-theft device can be swept. Even if the frequency deviates near the lower limit frequency or near the upper limit frequency, the signal of the transmitter can be received stably, and the reliability of the antitheft device To improve.

[0025]

According to the configuration of claim 2, in addition to the configuration of claim 1, since the frequency of the transmission signal of the transmitter is set to 30 KHz or less, it is unlikely to cause malfunction to other devices.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an anti-theft device and a transmitter constituting an anti-theft device of the present invention.

FIG. 2 is an output waveform diagram of a sweep oscillation circuit of the device.

FIG. 3 is a circuit configuration diagram of a sweep oscillation circuit of the device.

FIG. 4 is a circuit configuration diagram of the transmitter.

FIG. 5 is an external perspective view of the antitheft device main body.

[Explanation of symbols]

 2 Buzzer (alarm means) 3 Receiving circuit 4 Anti-theft device 8 Transmitter 9 Sweep oscillation circuit [Sweep means] 11 Voltage-frequency converter 13 Power amplifier 14 Antenna

────────────────────────────────────────────────── ─── Continuing on the front page (72) Kohei Miyata 2-35 Jinmucho, Yao-shi, Osaka Inside the Kubota Kuhoji Plant (72) Inventor Hiroshi Matsushima 3-1-29-1 Yawatadori, Chuo-ku, Kobe-shi, Hyogo Prefecture No. Shinwa Kogyo Co., Ltd. (56) References JP-A-2-81200 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G08B 13/00-13/24

Claims (2)

(57) [Claims] 1. An anti-theft device having a built-in alarm means for generating an alarm, a receiving circuit for receiving an external signal and operating the alarm means, and a transmitter for radiating a signal to a specific area. The transmitter includes sweep means for changing a transmission frequency of the transmitter with time by sweeping a frequency band including a tuning frequency of the reception circuit , and
The frequency of the sweep pattern of the sweep means
From the wave number to the upper limit frequency, gradually increase to the upper limit frequency
, Then gradually increase the frequency toward the lower frequency limit.
Anti-theft device with a repetitive pattern of lowering . 2. Alarm means for generating an alarm and an external signal
And a receiving circuit for receiving the signal and operating the alarm means
Radiates signals to a specific area with the anti-theft device itself
And a transmitter, the frequency of the electromagnetic wave radiated by the transmitter.
The wave number and the tuning frequency of the receiving circuit
30 KHz or less, and the transmitter
Sweeps the frequency band including the tuning frequency of the
Sweep means to change the transmitter frequency of the transmitter.
The sweep pattern of the sweep means
Gradually increase from the lower frequency to the upper frequency.
Once the limit frequency is reached,
Anti-theft device with a repetitive pattern that lowers the frequency .