Fire detection system

Claim 2

A fire detection system having at least one fire sensor, a receiver including a power source connected to said fire sensor for supplying a power source voltage to said fire sensor and a receiving relay for receiving a fire detection signal from said fire sensor, and at least one power/signal line for coupling said fire sensor to said reciever, said fire detection system comprising in said receiver a timer for producing a clock signal over the time of day and commanding means for providing at least one predetermined detection sensitivity change command of said fire sensor which is varied according to the time of day in response to said clock signal from said timer, and in said fire sensor sensitivity change control means for changing the detection sensitivity of said fire sensor in response to said detection sensitivity change command from said commanding means.

Claim 3

A fire detection system as claimed in claim 1, wherein said commanding means includes a computer having a read only memory for storing a detection sensitivity pattern predetermined according to the time of day, said computer reading out a present detection sensitivity from said read only memory in response to said clock signal from said timer to produce a present 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 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 the sensitivity change control signal derived from said sensitivity change control means and the 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.

Claim 4

A fire detection system as claimed in claim 1, wherein a plurality of fire sensors are provided corresponding to a plurality of fire sensing systems, respectively, said commanding means includes a computer having a read only memory for storing a plurality of detection sensitivity patterns predetermined according to the time of day corresponding to said plurality of fire sensing systems, said computer reading out present detection sensitivities from said read only memory in response to said clock signal from said timer to produce 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 the sensitivity change control signal derived from said sensitivity change control means and the 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.

Claim 5

A fire detection system as claimed in claim 1, wherein a plurality of fire sensors are provided corresponding to a plurality of fire sensing systems, respectively, said commanding means includes a computer having a read only memory for storing a detection sensitivity pattern predetermined according to the time of day, said computer reading out a present detection sensitivity from said read only memory in response to said clock signal from said timer to produce 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 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 the sensitivity change control signal derived from said sensitivity change control means and the 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.

Claim 6

A fire detection system as claimed in any one of claims 2,3 and 4, wherein said detection sensitivity 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 signal to said frequency signal, said sensitivity change control means has an F - V converter for converting said frequency signal to 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 amplifire and an anode and a cathode which are connected to said low-pass filter.

Claim 7

A fire detection system as claimed in claim 1, wherein said commanding means includes a computer having a read only memory for storing at least one detection sensitivity pattern predetermined according to the time of day, said computer reading out a present detection sensitivity from said read only memory in response to said clock signal from said timer to produce 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, the 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.

Claim 8

A fire detection system as claimed in claim 6, 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.

Claim 9

A fire detection system as claimed in claim 1, further comprising an interlock enabling relay which operates when said at least one predetermined sensitivity change command produced from said commanding means exceeds a predetermined value,-and a fire alarm relay which operates when any one of 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.

Claim 10

A fire detection system as claimed in claim 2, further comprising an interlock enabling relay which operates when said present detection sensitivity signal produced from said commanding means exceeds a predetermined value, and a fire alarm relay which operates when any one of 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.

Claim 11

A fire detection system as claimed in claim 3, further comprising an interlock enabling relay which operates when said present detection sensitivity signals produced from said commanding means exceeds a predetermined value, and a fire alarm relay which operates when any one of 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.

Claim 12

A fire detection system as claimed in claim 4, further comprising an interlock enabling relay which operates when said present detection sensitivity signals produced from said commanding means exceeds a predetermined value, and a fire alarm relay which operates when any one of 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.

Claim 13

A fire detection system as claimed in claim 6, further comprising an interlock enabling relay which operates when said at least one present detection sensitivity signal produced from said commanding means exceeds a predetermined value, and a fire alarm.,relay which operates when any one of 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.

Claim 14

A fire detection system as claimed in any one of claims 2 to 7 and 9 to 12, wherein two types of sensitivity patterns for weekday and holiday are written in said read only memory.

Claim 15

A fire detection system comprising a fire sensor (Sal) and means (4,6a,14,12) for changing the sensitivity of the fire sensor (Sal), the system being characterised by a timer (2) to which said sensitivity changing means (4,6a,14,12) is responsive so that the sensitivity of the fire sensor (Sal) is varied in a predetermined manner in accordance with the time of day.

Claim 16

A fire detection system comprising a fire sensor (Sal) and means (4,6a,14,12) for changing the sensitivity of the fire sensor (Sal), the system being characterised by a timer (2) to which said sensitivity changing means (4,6a,14,12) is responsive so that the sensitivity of the fire sensor (Sal) is varied in a predetermined manner in accordance with the time of day.