Light-attenuation type fire detector assembly

• US 4,675,661 A
• Filed: 12/12/1985
• Issued: 06/23/1987
• Est. Priority Date: 12/18/1984
• Status: Expired due to Fees

• Current Assignee: Hochiki Kabushiki Kaisha
• Original Assignee: Hochiki Kabushiki Kaisha
• Inventors: Ishii, Hiromitsu
• Primary Examiner(s): Rowland, James L.
• Assistant Examiner(s): Myer, Daniel
• Application Number:
  US06/807,979
• Time in Patent Office: 558 Days
• Field of Search: 340/628, 340/629, 340/630, 250/573, 250/574, 250/575, 250/565, 356/438, 356/439
• US Class Current: 340/630
• CPC Class Codes: G01J 2001/1636 one detector directly monitoring the source, e.g. also impulse time controlling
• CPC Class Codes: G01N 21/534 by measuring transmission alone, i.e. determining opacity
• CPC Class Codes: G01N 2201/062 LED's
• CPC Class Codes: G01N 2201/0696 Pulsed
• CPC Class Codes: G08B 17/103 using a light emitting and receiving device

Abstract

A light-attenuation type fire detector assembly of the present invention comprises a light emission drive section including a light emitter for radiating light having an intensity corresponding to an input signal level; a smoke detecting section including a light receiver which directly receives the light radiated from the light emission drive section and is adapted to output a detection signal corresponding to the received light amount of the light receiver; a smoke amount computing section for computing the amount of smoke based on the detection signal from the smoke detecting section; a delay circuit for retarding input of the detection signal from the smoke detecting section to the light emission drive section for a predetermined time; and a control section for repeating the operations of the light emission drive section, the smoke detecting section and the delay circuit and generating a control signal after a predetermined period of time has been passed or a predetermined times of operation has been done to drive the smoke amount computing section, and wherein the amount of smoke is computed during a time when said smoke amount computing section is driven based on the smoke detection signal input to said smoke amount computing section to detect if there is attenuation in the radiated light due to smoke between the light emitter and the light receiver.

Claims

1. A light-attenuation type fire detector assembly which comprises a light emission drive section including a light emitter for radiating light having an intensity corresponding to an input signal level;

a smoke detecting section including a light receiver which directly receives the light radiated from the light emission drive drive section and outpus a detection signal corresponding to the intensity of the light received by the light receiver;

a smoke amount computing section for computing the amount of smoke based on the detection signal from the smoke detecting section;

a delay circuit for retarding input of the detection signal from the smoke detecting section to the light emission drive section for a predetermined time; and

a control section for causing repeated operation of the light emission drive section, the smoke detecting section and the delay circuit, and generating a control signal after a predetermined period of time during which a predetermined number of such operations have been repeated;

the amount of smoke computed by said smoke amount computing section being based on the smoke detection signal input to said smoke amount computing section, such signal signifying the attenuation in the light received by the light receiver due to smoke between the light emitter and the light receiver.

2. A light-attenuation type fire detector assembly according to claim 1, wherein said control section includes a threshold level discriminating means which outputs a fire alarm signal when the detecting signal from the fire detecting section exceeds a predetermined threshold level corresponding to occurrence of fire in the smoke detecting section.

3. A light-attenuation type fire detector assembly according to claim 1, wherein said control section includes a threshold level discriminating means which transmits a drive signal to said smoke amount computing section when there occurs, in the detection signal from the smoke detecting section, a change exceeding a predetermined threshold level within said predetermined period of time.

4. A light-attenuation type fire detector assembly according to claim 1, wherein said delay circuit comprises a capacitor which is charged according to the received light amount and a switching means for discharging the charge stored in the capacitor.

5. A light-attenuation type fire detector assembly according to claim 1, wherein said delay ciruit comprises a first capacitor which is charged according to the received light amount;

a first switching means for discharging the charge stores in said first capacitor after said predetermined period of time has passed;

a second capacitor which is charged by the charge discharged from said first capacitor; and

a second switching means which discharges the charge stored in said second capacitor by switching and actuates the light emitter to radiate light.

6. A light-attenuation type fire detector assembly according to claim 5, wherein said second switching means comprises a square wave generating circuit.

7. A light-attenuation type fire detector assembly according to claim 5, comprising at least two pairs of light emitters and light receivers.

8. A light-attenuation type fire detector assembly according to claim 1, which further comprises an analog display section for displaying an analog indication of the amount of smoke in response to the detection signal from said smoke detecting section.

9. A light-attenuation type fire detector assembly according to claim 1, which further comprises another light receiver for receiving the light radiated from the light emitter through a smoke-free path and a compensation circuit in the light emission drive section for compensating for dirt on the light emitter and for temperature changes by using the intensity of the light received by said second light receiver as a reference value.

10. A light-attenuation type fire detector assembly according to claim 1, comprising at least two pairs of light emitters and light receivers.

11. A light-attenuation type fire detector assembly which comprises a light emission drive section including a light emitter for radiating light having an intensity corresponding to an input signal level;

a smoke detecting section including a light receiver which directly receives the light radiated from the light emission drive section and outputs a detection signal corresponding to the intensity of the light received by the light receiver;

a delay circuit for retarding input of the detection signal from the smoke detecting section to the light emission drive section for a predetermined time; and

a control section for causing a predetermined number of repeated operations of the light emission drive section, the smoke detecting section and the delay circuit;

the detection of the attenuation in the radiated light due to smoke between the light emitter and the light receiver being based on the detection signal produced by the light receiver after said predetermined number of operations of the light emission drive section, the smoke detecting section and the delay circuit have been completed.

12. A light-attenuation type fire detector assembly according to claim 11, wherein said delay circuit comprises a capacitor which is charged according to the received light amount and a switching means for discharging the charge stored in the capacitor.

13. A light-attenuation type fire detector assembly according to claim 11, wherein said delay circuit comprises a first capacitor which is charged according to the received light amount;

a first switching means for discharging the charge stored in said first capacitor after said predetermined period of time has passed;

a second capacitor which is charged by the charge discharged from said first capacitor; and

a second switching means which discharges the charge stored in said second capacitor by switching and actuates the light emitter to radiate light.

14. A light-attenuation type fire detector assembly according to claim 13, wherein said second switching means comprises a square wave generating circuit.

15. A light-attenuation type fire detector assembly according to claim 13, comprising at least two pairs of light emitters and light receivers.

16. A light-attenuation type fire detector assembly according to claim 11, which further comprises an analog display section for displaying an analog indication of the amount of smoke in response to the detection signal from said smoke detecting section.

17. A light-attenuation type fire detector assembly according to claim 11, which further comprises another light receiver for receiving the light radiated from the light emitter through a smoke-free path and a compensation circuit in the light emission drive section for compensating for dirt on the light emitter and for temperature changes by using the intensity of the light received by said second light receiver as a reference value.

18. A light-attenuation type fire detector assembly according to claim 11, comprising at least two pairs of light emitters and light receivers.