Smoke detecting apparatus capable of detecting both smoke fine particles

• US 5,477,218 A
• Filed: 12/23/1993
• Issued: 12/19/1995
• Est. Priority Date: 01/07/1993
• Status: Expired due to Term

• Current Assignee: Hochiki Kabushiki Kaisha
• Original Assignee: Hochiki Kabushiki Kaisha
• Inventors: Manmoto, Atsushi, Yamauchi, Yukio
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Lefkowitz, Edward
• Application Number:
  US08/173,628
• Time in Patent Office: 726 Days
• Field of Search: 340/628, 340/629, 340/630, 250/574, 250/485.1, 356/43, 356/51
• US Class Current: 340/630
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/113 Constructional details

Abstract

A light emitting device for projecting a light beam onto a monitor area, and a light receiving device, arranged so that a light beam is not directly received by the device, for receiving diffused light caused as a result of fine particles, such as dust, or smoke caused by a fire, entering the monitor area, are provided. Also, an amplifying device for amplifying an output from the light receiving device, and a counting device for counting the output from the amplifying device in units of time are provided. In addition, a computing device for computing an average value or an integrated value of the output from the amplifying device in units of time, and a determining device for determining the level of contamination of the monitor area on the basis of the count value of the counting device and for determining the level of the fire on the basis of the average value or the integrated value computed by the computing device, are provided. As a result, a smoke detecting apparatus consisting of a single unit capable of detecting both smoke and fine particles can be provided, the apparatus detecting a fire on the basis of an environmental abnormality.

Claims

1. A smoke detecting apparatus capable of detecting both smoke and fine particles in a monitoring area, comprising:

light emitting means for projecting a light beam onto said monitoring area;

light receiving means with an output located at a position where a light beam projected from said light emitting means is not directly received, said light receiving means receiving scattered light caused by fine particles including dust and smoke caused by fire entering said monitoring area;

amplifying means for amplifying said output from said light receiving means, said amplifying means having an output that may exceed a predetermined level a number of times;

counting means for counting the number of times that said output from said amplifying means has exceeded said predetermined level as a function of time for detecting said fine particles, said predetermined level being exceeded when fine particles are present in said monitoring area and said predetermined level being not exceeded when fine particles are not present in said monitoring area so that presence of fine particles is detected;

computing means for computing an average value of the output from said amplifying means as a function of time to detect said smoke; and

determining means for determining a contamination level of said monitoring area dependent on a count counted by said counting means and determining characteristics of a fire as a function of said average value computed by said computing means when smoke density is high and the count counted by said counting means reaches a saturation point at which further counting cannot be carried out and emitting an alarm dependent on a result determined by said determining means.

2. A smoke detecting apparatus according to claim 1, wherein said light emitting means is formed of a halogen lamp.

3. A smoke detecting apparatus according to claim 1, comprising:

a pump for supplying air of the space to be monitored to said monitor area; and

flow rate detecting means for detecting the flow rate of air in said monitor area.

4. A smoke detecting apparatus according to claim 3, wherein said flow rate detecting means is a flowmeter.

5. A smoke detecting apparatus according to claim 3, wherein said flow rate detecting means is a flow velocity meter.

6. A smoke detecting apparatus according to claim 3, wherein said flow-rate detecting means is a pressure gauge.

7. A smoke detecting apparatus according to claim 3, wherein said pump is controlled on the basis of a detected value of said flow rate detecting means so that the amount of air supplied to said monitor area is maintained to be a constant amount.

8. A smoke detecting apparatus according to claim 3, wherein said output of said light receiving means is updated on the basis of the value detected by said flow rate detecting means.

9. A smoke detecting apparatus according to claim 3, wherein said monitor area is cleaned at predetermined time intervals.

10. A smoke detecting apparatus according to claim 9, wherein said cleaning is performed by supplying clean air to the monitor area.

11. A smoke detecting apparatus according to claim 9, wherein, after said monitor area is cleaned, fine particles in the monitor area are detected.

12. A smoke detecting apparatus according to claim 1, wherein said parts comprise said light emitting means.

13. A smoke detecting apparatus according to claim 1 wherein when the amount of light emission of said light emitting means and light receiving sensitivity of said light receiving means is varied due to its deterioration or contamination, the amount of light emission of said light emitting means and light receiving sensitivity of said light receiving means is corrected.

14. A smoke detecting apparatus according to claim 1, wherein when the amount of light emission of said light emitting means and light receiving sensitivity of said light receiving means is varied due to its deterioration or contamination, an alarm is issued.

15. A smoke detecting apparatus according to claim 13, wherein a second light receiving means is disposed in the vicinity of said light emitting means so that when the amount of light received by the second light receiving means varies, an output of said light emitting means is corrected.

16. A smoke detecting apparatus according to claim 14, wherein a second light receiving means is disposed in the vicinity of said light emitting means so that when the amount of light received by the second light receiving means falls below a predetermined value, an alarm is issued.

17. A smoke detecting apparatus according to claim 14, wherein a second light receiving means is disposed in the vicinity of said light emitting means, a third light receiving means is disposed at a position where it faces said light emitting means and a light beam from said light emitting means directly enters said third light receiving means, so that the amount of light received by said second light receiving means is compared with the amount of light received by said third light receiving means and when the difference between them is a predetermined value or more, an alarm is issued.

18. A smoke detecting apparatus according to claim 13, wherein a second light receiving means,is disposed at a position where a light beam is directly projected onto said light receiving means, so that a test beam of a fixed amount is projected from said second light emitting means, so that the amount of the test beam is detected to correct the sensitivity of said light receiving means.

19. A smoke detecting apparatus as defined in claim 1, comprising:

drive means for driving said light emitting means; and

light switching means for switching a signal input to said drive means so that light can be emitted from said light emitting means.

20. A smoke detecting apparatus as defined in claim 1, comprising:

a light chopper disposed on the front side of said light emitting means so that light is emitted from said light emitting means;

drive means for driving said light emitting means; and

light switching means for switching a signal input to said drive means.

21. A smoke detecting apparatus as defined in claim 1, including means for recording the time during which predetermined parts of said smoke detecting apparatus are operative and in use, and an alarm for indicating replacement of parts at predetermined time intervals.

22. A smoke detecting apparatus according to claim 13, including means for detecting a value of current consumption of said light emitting means and emitting an alarm when the current value falls below a predetermined value.

23. A smoke detecting apparatus according to claim 14, wherein a second light emitting means is disposed at a position where a light beam is projected directly onto said light receiving means, and a test beam of a fixed intensity is projected from said second light emitting means to said light receiving means, and means for issuing an alarm when the intensity of the test beam is a predetermined value or less.

24. A smoke detecting apparatus as defined in claim 1, wherein said predetermined value computed by said computing means is an average value.

25. A smoke detecting apparatus as defined in claim 1, wherein said predetermined value computed by said computing means is an integrated value.

26. A smoke detecting apparatus as defined in claim 1, wherein said light emitting means comprises a laser diode.

27. A smoke detecting apparatus as defined in claim 19, wherein said light comprises pulsed light.

28. A smoke detecting apparatus as defined in claim 19, wherein said light is continuous light.

29. A smoke detecting apparatus capable of detecting both smoke and fine particles in a monitoring area, comprising:

light emitting means for projecting a light beam onto said monitoring area;

light receiving means with an output located at a position where a light beam projected from said light emitting means is not directly received, said light receiving means receiving scattered light caused by fine particles including dust and smoke caused by fire entering said monitoring area;

amplifying means for amplifying said output from said light receiving means and having an output for each predetermined level corresponding to a diameter of said fine particles;

frequency computing means for differentiating the output from said amplifying means for each predetermined level corresponding to a diameter of said fine particles and counting as a function of time the predetermined levels from said output of said amplifying means over a fixed time period and computing a frequency distribution of said output of said amplifying means;

storing means for prestoring the frequency distribution of the output of said light receiving means for each of said levels when smoke particles enter said monitoring area and for prestoring the frequency distribution of all other particles corresponding to a diameter for each of said levels when other fine particles enter said monitoring area; and

determining means for comparing the frequency distribution computed by said frequency computing means with that stored in said storing means and distinguishing between smoke and other fine particles, and emitting an alarm dependent on a result determined by said determining means.

30. A smoke detecting apparatus according to claim 29, wherein said determining means lowers a fire determination level when said determining means distinguishes smoke.