Fire detection system with programmed sensitivity changes

• US 4,388,616 A
• Filed: 03/05/1981
• Issued: 06/14/1983
• Est. Priority Date: 03/19/1980
• Status: Expired due to Fees

• Current Assignee: Hochiki Corporation
• Original Assignee: Hochiki Corporation
• Inventors: Machida, Haruchika
• Primary Examiner(s): Swann, III, Glen R.
• Application Number:
  US06/240,646
• Time in Patent Office: 831 Days
• Field of Search: 340/628, 340/629, 340/587, 340/501, 169/61, 169/60, 169/56, 169/23
• US Class Current: 340/587
• CPC Class Codes: G08B 17/00 Fire alarms; Alarms responsive to explosion
• CPC Class Codes: G08B 25/04 using a single signalling line, e.g. in a closed loop

Abstract

In a fire detection system having at least one fire sensor, a receiver including a power source connected to the fire sensor for supplying a power source voltage to the fire sensor and a receiving relay for receiving a fire detection signal from the fire sensor, and at least one power/signal line for coupling the fire sensor to the receiver, the receiver comprises a timer for producing a clock signal over the time of day and command means for providing predetermined detection sensitivity change commands of the fire sensor which are programmed according to the time of day in response to the clock signal from the timer, and the fire sensor comprises sensitivity change control means for changing the detection sensitivity of the fire sensor in response to the detection sensitivity change command from the command means. The fire detection sensitivity of the fire sensor is varied in accordance with predictive fire damage conditions predetermined in view of the activities of people during the time of day. The system can realize an early discovery of fire to minimize the fire damage.

Claims

1. A fire detection system, comprising:

at least one fire sensor having a changeable detection sensitivity for producing a fire detection signal and including sensitivity change control means for changing the detection sensitivity in response to any one of a plurality of predetermined detection sensitivity change commands;

a receiver including a timer for producing a clock signal corresponding to the time of day, command means for providing the predetermined detection sensitivity change commands in response to the clock signal, said change commands being programmed according to the time of day, a power source connected to said fire sensor for supplying a power source voltage to said fire sensor, and a receiving relay for receiving the fire detection signal;

at least one power/signal line for coupling said fire sensor to said receiver; and

,

wherein said command means includes a computer having a read only memory for storing a detection sensitivity pattern programmed according to the time of day, said computer reading out from said read only memory, in response to said clock signal from said timer, present a detection sensitivity signal, converting means for converting said present detection sensitivity signal to a frequency signal, and at least one first capacitor inserted between said converting means and said at least one power/signal line, and said fire sensor further includes a low-pass filter and a second capacitor which are connected to said power/signal line, a smoke sensing portion and a fire judging section to both of which a power source voltage derived from said low-pass filter is applied and a switching element for producing said fire detection signal, said frequency signal being supplied through said second capacitor to said sensitivity change control means, and a sensitivity change control signal derived from said sensitivity change control means and an output signal from said smoke sensing portion are supplied to said fire judging section, so that the switching of said switching element is controlled by the output signal from said fire judging section.

2. A fire detection system as claimed in claim 1, wherein said detection sensitivity signal derived from said computer is in the form of a digital signal, said converting means includes a D/A converter for converting said digital signal to an analog voltage and a V-F converter for converting said analog voltage to said frequency signal, said sensitivity change control means has an F-V converter for converting said frequency signal into a voltage signal, said fire judging section has an operational amplifier, and said switching element is a thyristor having a gate connected to the output terminal of said operational amplifies and an anode and a cathode which are connected to said low-pass filter.

3. A fire detection system as claimed in claim 1, further comprising an interlock enabling relay which operates when said present detection sensitivity signal produced from said command means exceeds a predetermined value, and a fire alarm relay which operates when said receiving relay operates, whereby a fire extinguishing installation is operated when said fire alarm relay operates under a condition that said interlock enabling relay operates.

4. A fire detection system as claimed in claim 1, wherein two types of sensitivity patterns for a weekday and a holiday are written in said read only memory.

5. A fire detection system, comprising:

at least one fire sensor having a changeable detection sensitivity for producing a fire detection signal and including sensitivity change control means for changing the detection sensitivity in response to any one of a plurality of predetermined detection sensitivity change commands;

a receiver including a timer for producing a clock signal corresponding to the time of day, command means for providing the predetermined detection sensitivity change commands in response to the clock signal, said change commands being programmed according to the time of day, a power source connected to said fire sensor for supplying a power source voltage to said fire sensor, and a receiving relay for receiving the fire detection signal;

at least one power/signal line for coupling said fire sensor to said receiver; and

,

wherein a plurality of fire sensors are provided corresponding to a plurality of fire sensing systems, respectively, said command means includes a computer having a read only memory for storing a plurality of detection sensitivity patterns programmed according to the time of day corresponding to said plurality of fire sensing systems, said computer reading out from said read only memory, in response to said clock signal from said timer, present detection sensitivity signals corresponding to the respective fire sensing systems, converting means for converting said detection sensitivity signals to frequency signals, respectively, and a plurality of first capacitors connected respectively between said converting means and a plurality of power/signal lines corresponding to said fire sensing systems, and each of said fire sensors includes a low-pass filter and a second capacitor which are connected to said power/signal line, a smoke sensing portion and a fire judging section, to both of which a power source voltage derived from said low-pass filter is applied, and a switching element for producing said fire detection signal, said frequency signal being supplied through said second capacitor to said sensitivity change control means, and a sensitivity change control signal derived from said sensitivity change control means and an output signal from said smoke sensing portion are supplied to said fire judging section, so that the switching of said switching element is controlled by the output signal from said fire judging section.

6. A fire detection system as claimed in claim 5, further comprising an interlock enabling relay which operates when said present detection sensitivity signals produced from said command means exceed a predetermined value, and a fire alarm relay which operates when said receiving relay operates, whereby a fire extinguishing installation is operated when said fire alarm relay operates under a condition that said interlock enabling relay operates.

7. A fire detection system, comprising:

at least one fire sensor having a changeable detection sensitivity for producing a fire detection signal and including sensitivity change control means for changing the detection sensitivity in response to any one of a plurality of predetermined detection sensitivity change commands;

a receiver including a timer for producing a clock signal corresponding to the time of day, command means for providing the predetermined detection sensitivity change commands in response to the clock signal, said change commands being programmed according to the time of day, a power source connected to said fire sensor for supplying a power source voltage to said fire sensor, and a receiving relay for receiving the fire detection signal;

at least one power/signal line for coupling said fire sensor to said receiver; and

,

wherein a plurality of fire sensors are provided corresponding to a plurality of fire sensing systems, respectively, said command means includes a computer having a read only memory for storing a detection sensitivity pattern programmed according to the time of day, said computer reading out from said read only memory, in response to said clock signal from said timer, present detection sensitivity signals corresponding to the respective fire sensing systems, converting means for converting said present detection sensitivity signals to frequency signals, and first capacitors connected between said converting means and a plurality of power/signal lines corresponding to said fire sensing systems, and each of said fire sensors includes a low-pass filter and a second capacitor which are connected to said power/signal lines, a smoke sensing portion and a fire judging section, to both of which a power source voltage derived from said low-pass filter is applied, and a switching element for producing said fire detection signal, said frequency signal being supplied through said second capacitor to said sensitivity change control means, and a sensitivity change control signal derived from said sensitivity change control means and an output signal from said smoke sensing portion are supplied to said fire judging section, so that the switching of said switching element is controlled by the output signal from said fire judging section.

8. A fire detection system as claimed in claim 7, further comprising an interlock enabling relay which operates when said present detection sensitivity signal produced from said command means exceeds a predetermined value, and a fire alarm relay which operates when said receiving relay operates, whereby a fire extinguishing installation is operated when said fire alarm relay operates under a condition that said interlock enabling relay operates.

9. A fire detection system, comprising:

at least one fire sensor having a changeable detection sensitivity for producing a fire detection signal and including sensitivity change control means for changing the detection sensitivity in response to any one of a plurality of predetermined detection sensitivity change commands;

a receiver including a timer for producing a clock signal corresponding to the time of day, command means for providing the predetermined detection sensitivity change commands in response to the clock signal, said change commands being programmed according to the time of day, a power source connected to said fire sensor for supplying a power source voltage to said fire sensor, and a receiving relay for receiving the fire detection signal;

at least one power/signal line for coupling said fire sensor to said receiver; and

,

wherein said command means includes a computer having a read only memory for storing at least one detection sensitivity pattern programmed according to the time of day, said computer reading out from said read only memory, in response to said clock signal from said timer, at least one present detection sensitivity signal, and power source voltage control means for changing the power source voltage derived from said power source in response to said present detection sensitivity signal to supply the changed power source voltage to said receiving relay and said fire sensor, said sensor includes a low-pass filter connected to said at least one power/signal line, and a smoke sensing portion, a fire judging section, a constant voltage circuit and a switching element for producing said fire detecting signal to which the power source voltage from said low-pass filter is applied, a sensed output signal from said smoke sensing portion and a reference level from said constant voltage circuit being supplied to said fire judging section, so that the switching of said switching element is controlled by the output signal from said fire judging section.

10. A fire detection system as claimed in claim 9, wherein said power source voltage control means is a transistor having a base receiving the present detection sensitivity signal and a collector and an emitter which are inserted between said power source and said receiving relay.

11. A fire detection system as claimed in claim 9, further comprising an interlock enabling relay which operates when said at least one present detection sensitivity signal produced from said command means exceeds a predetermined value, and a fire alarm relay which operates when said receiving relay operates, whereby a fire extinguishing installation is operated when said fire alarm relay operates under a condition that said interlock enabling relay operates.

12. A fire detection system, comprising:

at least one fire sensor having a changeable detection sensitivity for producing a fire detection signal and including sensitivity change control means for changing the detection sensitivity in response to any one of a plurality of predetermined detection sensitivity change commands;

a receiver including a timer for producing a clock signal corresponding to the time of day, command means for providing the predetermined detection sensitivity change commands in response to the clock signal, said change commands being programmed according to the time of day, a power source connected to said fire sensor for supplying a power source voltage to said fire sensor, and a receiving relay for receiving the fire detection signal;

at least one power/signal line for coupling said fire sensor to said receiver; and

,

further comprising an interlock enabling relay which operates when said at least one predetermined sensitivity change command produced from said command means exceeds a predetermined value, and a fire alarm relay which operates when said receiving relay operates, whereby a fire extinguishing installation is operated when said fire alarm relay operates under a condition that said interlock enabling relay operates.