Communications: electrical – Condition responsive indicating system – Specific condition
Reexamination Certificate
2001-04-02
2003-03-11
Mullen, Thomas (Department: 2632)
Communications: electrical
Condition responsive indicating system
Specific condition
C340S693300
Reexamination Certificate
active
06531961
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to antitheft systems for protecting merchandise on display in stores from unlawful acts such as shoplifting, and more particularly to an antitheft system which comprises a signal transmitter incorporated, for example, in an antitheft gate for producing an alarm activating signal, and a self-sounding alarm unit attached to a commodity or like article to be protected from theft and adapted to generate sound in response to the alarm activating signal received from the signal transmitter.
BACKGROUND OF THE INVENTION
FIG. 9
shows an antitheft system conventionally used in stores wherein commodities such as compact disk cassettes and magnetic tape cassettes are on display for sale, to protect these articles from shoplifting or like illegal acts.
The antitheft system comprises an antitheft gate
2
installed in the vicinity of an exit
5
of the store, and an alarm unit
4
attached to a commodity
6
. The antitheft gate
2
has a circuit board
21
and a transmitting antenna (not shown) which are incorporated therein. The circuit board
21
is provided with a transmitting circuit for producing an alarm activating signal for the alarm unit
4
.
With reference to
FIG. 10
, the alarm unit
4
comprises a buzzer
41
, circuit board
42
, battery (not shown), etc. which are housed in a casing
40
. The casing
40
has a surface provided with sound emitting holes
43
and an alarm actuating switch piece
44
projecting therefrom. The buzzer
41
has its operation controlled by the circuit board
42
and is adapted to produce an alarm when the unit
4
is removed from the commodity
6
or when the unit
4
passes by the antitheft gate
2
.
The commodity
6
is placed on display in the store, with the alarm unit
4
attached thereto. When selling the commodity to the customer, the clerk holds the buzzer
41
out of operation by sending a specified signal to the circuit board
42
of the alarm unit
4
from a nullifying device (not shown), then removes the unit
4
from the commodity
6
and hands the commodity
6
to the customer in exchange for money.
If the customer wrongfully removes the alarm unit
4
from the commodity
6
, the switch piece
44
is turned off to actuate the buzzer
41
. Further if the customer acts to unlawfully bring the commodity
6
out of the store along with the alarm unit
4
, the circuit board
42
of the alarm unit
4
receives an alarm activating signal from the transmitting antenna of the antitheft gate
2
to turn on the buzzer
41
.
FIG. 11
shows the electrical construction of the alarm unit
4
.
The alarm unit
4
has a receiving antenna
46
comprising a coil and a capacitor and connected to a control circuit
48
via a signal amplification circuit
47
. The aforementioned battery (primary battery)
45
is connected to the signal amplification circuit
47
and the control circuit
48
. These circuits
47
,
48
are energized by the primary battery
45
to operate as specified. The control circuit
48
is provided with the alarm actuating switch piece
44
and has the buzzer
41
connected thereto.
The receiving antenna
46
receives a signal, which is fed to the amplification circuit
47
for amplification and then fed to the control circuit
48
. The control circuit
48
judges whether the signal fed from the amplification circuit
47
is an alarm activating signal from the antitheft gate
2
, and gives a drive command to the buzzer
41
if the signal is the activating signal. The control circuit
48
further detects opening of the alarm actuating switch piece
44
when it is turned off, giving a drive command to the buzzer
41
. Thus, the buzzer
41
goes on in response to the drive command given by the control circuit
48
.
With the alarm unit
4
of the type described, the primary battery
45
incorporated therein is replaced when the life of the battery
45
terminated. The alarm unit
4
is usually attached to each commodity in the store, and many alarm units
4
are in use. It is therefore likely that the primary batteries of many alarm units
4
need to be replaced at the same time. The replacement of batteries of many alarm units
4
is very cumbersome and costly. It is accordingly required to suppress the power consumption of the alarm unit
4
to the greatest possible extent.
However, the conventional alarm unit
4
is so adapted that whenever electromagnetic waves from one source or another are received by the receiving antenna
46
, the control circuit
48
judges whether the waves are an alarm activating signal from the antitheft gate
2
. When a commodity having the alarm unit
4
attached thereto is on display as positioned, for example, in the vicinity of an inverter fluorescent lamp, the electromagnetic waves emitted by the lamp at all times are received by the antenna
46
, permitting the control circuit
48
to continuously perform the signal judging operation, hence the problem of wasting electric power to shorten the battery life. The life of the primary battery
45
is about 3 to about 5 years when the alarm unit
4
is not exposed to the electromagnetic waves from the inverter fluorescent lamp, whereas the life becomes shortened to 1 to 2 weeks if the unit
4
is held exposed to noise signals.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an antitheft system comprising an alarm unit which is adapted to suppress the shortening of battery life due to useless power consumption.
The present invention provides an antitheft system comprising an alarm unit attachable to an article to be protected from theft, and a signal transmitter for transmitting an alarm activating signal to the alarm unit, the alarm unit comprising:
receiving means for receiving signals from outside,
alarm means for producing an alarm in response to an alarming command,
nullifying means operable in response to a nullifying command to nullify the signal received by the receiving means for a predetermined period of time subsequent to the reception of the nullifying command, and
control means operable upon reception of the received signal from the receiving means to judge whether the received signal is the alarm activating signal and give the alarming command to the alarm means when the signal is the alarm activating signal or give the nullifying command to the nullifying means when the signal is not the alarm activating signal.
In the case where the antitheft system of the invention is installed in a store, the commodities to be protected against theft are placed on a display counter, with the alarm unit attached to each commodity, while the signal transmitter is disposed in an warning area in the vicinity of the exit of the store.
The receiving means of the alarm unit in this state is likely to receive external noise signals, such as electromagnetic waves being emitted by electric lamps. At this time, the control means judges whether the received signal is an alarm activating signal. Upon finding that the received signal is not the alarm activating signal, the control means gives a nullifying command to the nullifying means, which in turn nullifies the received signal for a predetermined period of time subsequent to the reception of the signal. This period of time is such that will cause no trouble to the operation of the alarm unit to be described below, e.g., 200 msec. Consequently, the control means is forced to cease the signal judging operation for the predetermined period of time despite the reception of signals by the receiving means. Accordingly, if the display counter is positioned in the vicinity of an inverter fluorescent lamp, the receiving means will receive the electromagnetic waves being emitted by the fluorescent lamp at all time, while the control means performs the signal judging operation intermittently.
If the customer passes through the warning area in the vicinity of the store exit in an attempt to wrongfully bring a commodity out of the store, the receiving means of the alarm unit attached to the commodity will receive an alarm activating signal from the signal
Mullen Thomas
Rader & Fishman & Grauer, PLLC
Sanyo Electric Co,. Ltd.
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