Fire detector with multi-level response

• US 6,057,549 A
• Filed: 05/30/1997
• Issued: 05/02/2000
• Est. Priority Date: 07/31/1996
• Status: Expired due to Term

• Current Assignee: Honeywell International Inc.
• Original Assignee: The Fire Sentry Corp. (Honeywell International Inc.)
• Inventors: Castleman, David A.
• Primary Examiner(s): Westin, Edward P.
• Assistant Examiner(s): HANIG, RICHARD E
• Application Number:
  US08/866,024
• Time in Patent Office: 1,068 Days
• Field of Search: 250/339.15, 250/339.14, 250/292.1, 250/554, 340/578
• US Class Current: 250/339.15
• CPC Class Codes: G08B 17/12 Actuation by presence of radiation or particles, e.g. of infrared radiation or of ions
• CPC Class Codes: G08B 25/002 Generating a prealarm to the central station
• CPC Class Codes: G08B 29/22 Provisions facilitating manual calibration, e.g. input or output provisions for testing; Holding of intermittent values to permit measurement
• CPC Class Codes: G08B 29/24 Self-calibration, e.g. compensating for environmental drift or ageing of components

Abstract

A process and system for flame detection includes a microprocessor-controlled detector with at least three sensors. A wide band infrared sensor is used as the primary detector, with near band and visible band sensors serving to detect false-alarm energy from nonfire sources. Digital signal processing is used to analyze sensed data and discriminate against false alarms. A multistage alarm system can be provided, which is selectively triggered by the microprocessor. Spectral recording and analysis of prefire data is provided for. The detector can be housed in an enclosed, sealed, removable, plastic housing that may include an integral plastic window lens.

Claims

1. A fire detection and response system, comprising:

means for detecting, over a wideband infrared spectrum, energy emitted by a fire;

means for calculating a change in wideband infrared energy emitted by said fire with respect to a measured baseline that varies gradually over time;

means for determining whether the change in wideband infrared energy emitted by the fire is above a first energy threshold;

means for determining whether the change in wideband infrared energy emitted by the fire is above a second energy threshold;

means for initiating a first response when the chance in wideband infrared energy emitted by the fire is above the first energy threshold; and

means for initiating a second response when the change in wideband infrared energy emitted by the fire is above the second energy threshold.

2. A fire detection and response system as in claim 1 wherein the first response is activation of audio and visual alarms.

3. A fire detection and response system as in claim 2 wherein the first energy threshold is about 3 kilowatts.

4. A fire detection and response system as in claim 2 wherein the second response is release of at least one fire suppression agent to extinguish the fire.

5. A fire detection and response system as in claim 4 wherein the second energy threshold is about 13 kilowatts.

6. A fire detection and response system as in claim 4 wherein at least one suppression agent is selected from the group consisting of water, water mist, carbon dioxide and halon.

7. A fire detection and response system as in claim 1 further comprising means for discriminating between fire and non-fire events.

8. A fire detection and response system as in claim 1 further comprising:

means for determining whether the energy output of the fire is above a third energy threshold; and

means for initiating a third response when the energy output of the fire is above the third energy threshold.

9. A fire detector and response system as in claim 8 wherein the first response is audio and visual alarms, the second response is electric shut down of a source of the fire and the third response is release of at least one suppression agent to extinguish the fire.

10. A fire detection and response system as in claim 1 wherein said means for detecting energy emitted by the fire comprises a wideband infrared wavelength detector that detects at least fifty percent of total energy from a fire and has a wavelength detection range of about 700-3500 nanometers.

11. A fire detector and response system as in claim 10 wherein said wideband infrared wavelength detector comprises a sensor selected from the group consisting of a quantum photodetector, a pyroelectric sensor and a thermopile sensor.

12. A fire detector and response system as in claim 10 wherein said wideband infrared wavelength detector comprises a lead sulphate detector.

18. A fire detection and response system as in claim 1, wherein said means for deriving a change in wideband infrared energy emitted by said fire with respect to a measured baseline that varies gradually over time comprises

a wideband infrared energy sensor;

a first lowpass filter connected to said wideband infrared energy sensor;

a second lowpass filter connected to said wideband infrared energy sensor, said second lowpass filter having a higher cutoff frequency than said first lowpass filter; and

a subtractor connected to an output of said first lowpass filter and to an output of said second lowpass filter.

19. A fire detection and response system as in claim 1, further comprising

means for detecting, over a nearband infrared spectrum, energy emitted by said fire;

and

means for calculating a change in nearband infrared energy emitted by said fire with respect to a measured baseline of nearband infrared energy that varies gradually over time;

wherein said means for calculating a change in wideband infrared energy emitted by said fire with respect to a measured baseline that varies gradually over time comprises means for subtracting said change in nearband infrared energy from energy detected by said means for detecting, over a wideband infrared spectrum, energy emitted by said fire.

20. A fire detection and response system as in claim 1, further comprising

means for detecting, over a visible energy spectrum, energy emitted by said fire;

and

means for calculating a change in visible energy emitted by said fire with respect to a measured baseline of visible energy that varies gradually over time;

wherein said means for calculating a change in wideband infrared energy emitted by said fire with respect to said measured baseline that varies gradually over time comprises means for subtracting said change in visible energy from energy detected by said means for detecting, over said wideband infrared spectrum, energy emitted by said fire.

21. A fire detection and response system as in claim 20, wherein said means for calculating said change in visible energy emitted by said fire with respect to said measured baseline of visible energy that varies gradually over time comprises

a visible energy sensor;

a first lowpass filter connected to said visible energy sensor;

a second lowpass filter connected to said visible energy sensor, said second lowpass filter having a higher cutoff frequency than said first lowpass filter;

a peak detector connected to an output of said second lowpass filter; and

a subtractor connected to an output of said first lowpass filter and to an output of said peak detector.

22. A fire detection and response system as in claim 21, wherein said peak detector prevents a sudden dropoff in ambient visible energy from causing a corresponding sudden dropoff in said calculated change in visible energy emitted by said fire.

13. A method of detecting and suppressing a fire, comprising the steps of:

detecting, over a wideband infrared spectrum, energy emitted by a fire;

calculating a change in wideband infrared energy emitted by said fire with respect to a measured baseline which varies gradually over time;

activating a first response if the change in wideband infrared energy emitted by said fire is above a first predetermined energy output level; and

activating a second response if the change in wideband infrared energy emitted by said fire is above a second predetermined energy output level.

14. A method as in claim 13 wherein the first predetermined energy output level is about 3 kilowatts.

15. A method as in claim 13 wherein the second predetermined energy output level is about 13 kilowatts.

16. A method as in claim 13 further comprising the step of:

activating a third response if the energy output level of the fire is above a third predetermined energy output level.

17. A method as in claim 13 wherein the first response is an alarm and the second response is release of at least one suppression agent.

23. A fire detection and response system, comprising:

means for detecting, over a wideband infrared spectrum, energy emitted by a fire;

means for calculating a change in wideband infrared energy emitted by said fire with respect to a measured baseline that varies gradually over time;

means for determining whether the change in wideband infrared energy emitted by the fire is above a predetermined energy threshold;

means for initiating a first response when the change in wideband infrared energy emitted by the fire is above said predetermined energy threshold; and

means for initiating a second response when the change in wideband infrared energy emitted by the fire is above said predetermined energy threshold after a first predetermined time period elapses following a previous determination that the energy output of the fire is above said predetermined energy threshold.

24. A fire detection and response system as in claim 23 wherein the first response is activation of audio and visual alarms.

25. A fire detection and response system as in claim 24 wherein the second response is release of at least one fire suppression agent to extinguish the fire.

26. A fire detection and response system as in claim 25 wherein at least one suppression agent is selected from the group consisting of water, water mist, carbon dioxide and halon.

27. A fire detection and response system as in claim 23 further comprising means for discriminating between fire and non-fire events.

28. A fire detection and response system as in claim 23 further comprising:

means for initiating a third response when the change in wideband infrared energy emitted by the fire is above said predetermined energy threshold after a second predetermined time period elapses following the previous determination that the energy output of the fire is above said predetermined energy threshold.

29. A fire detector and response system as in claim 28 wherein the first response is audio and visual alarms, the second response is electric shut down of a source of the fire and the third response is release of at least one suppression agent to extinguish the fire.

30. A fire detection and response system as in claim 23 wherein the means for detecting energy emitted by the fire comprises a wideband infrared wavelength detector that detects at least fifty percent of total energy from a fire and has a wavelength detection range of about 700-3500 nanometers.

31. A fire detector and response system as in claim 30 wherein said wideband infrared wavelength detector comprises a sensor selected from the group consisting of a quantum photodetector, a pyroelectric sensor and a thermopile sensor.

32. A fire detector and response system as in claim 31 wherein said wideband infrared wavelength detector comprises a lead sulphate detector.

33. A method of detecting and suppressing a fire, comprising the steps of:

detecting, over a wideband infrared spectrum, energy emitted by a fire;

calculating a change in wideband infrared energy emitted by said fire with respect to a measured baseline which varies gradually over time;

activating a first response if the change in wideband infrared energy emitted by the fire is above a predetermined energy output level; and

activating a second response if the change in wideband infrared energy emitted by the fire is above the predetermined energy output level after a first predetermined time period elapses following a first determination that the energy emitted by the fire is above the predetermined energy threshold.

34. A method as in claim 33 wherein the first response is audio and visual alarms and the second response is release of at least one suppression agent to extinguish the fire.

35. A method as in claim 33 further comprising the step of:

activating a third response if the energy emitted by the fire is above the predetermined energy output level after a second predetermined time period elapses following the first determination that the energy emitted by the fire is above the predetermined energy threshold.

36. A method as in claim 35 wherein the first response is an alarm, the second response is electrical shut down of a source of the fire and the third response is release of at least one suppression agent.

37. A fire detector, comprising:

a wideband infrared energy sensing system for detecting radiant energy from a radiant energy source;

a filtering network connected to said wideband infrared energy sensing system, said filtering network outputting a measured radiant energy release rate of said radiant energy source; and

a processor connected to said filtering network, said processor classifying said radiant energy source based upon the measured radiant energy release rate and initiating a response selected according to the classification of said radiant energy source.

38. The fire detector of claim 37, wherein radiant energy continues to be detected by said wideband infrared energy sensing system after initiation of said response, and wherein said processor suspends said response upon a sudden dropoff in the measured radiant energy release rate of said radiant energy source.

39. The fire detector of claim 37, wherein said wideband infrared energy sensing system comprises a wideband infrared energy detector, and wherein said filtering network comprises

a first lowpass filter connected to said wideband infrared energy detector, said first lowpass filter outputting a wideband infrared energy baseline that varies gradually over time;

a second lowpass filter connected to said wideband infrared energy detector, said second lowpass filter having a higher cutoff frequency than said first lowpass filter; and

a subtractor having inputs connected to said wideband infrared energy baseline and to an output of said second lowpass filter.

40. The fire detector of claim 39, wherein said wideband infrared energy sensing system comprises a nearband infrared energy detector, and wherein said filtering network comprises

a third lowpass filter connected to said nearband infrared energy detector, said third lowpass filter outputting a nearband infrared energy baseline that varies gradually over time;

a fourth lowpass filter connected to said nearband infrared energy detector, said fourth lowpass filter having a higher cutoff frequency than said third lowpass filter;

a second subtractor, said second subtractor having inputs connected to said nearband infrared energy baseline and to an output of said fourth lowpass filter; and

means for algebraically combining the outputs of said first subtractor and said second subtractor to generate said measured radiant energy release rate.

41. The fire detector of claim 39, further comprising a visible energy detector connected to said filtering network, wherein said filtering network comprises

means for calculating a change in visible energy emitted by said radiant energy source with respect to a measured baseline of visible energy that varies gradually over time;

and

means for subtracting said change in visible energy from radiant energy detected by said wideband infrared energy sensing system.

42. The fire detector of claim 41, wherein said means for calculating said change in visible energy emitted by said fire with respect to said measured baseline of visible energy that varies gradually over time comprises

a first lowpass filter connected to said visible energy sensor;

a second lowpass filter connected to said visible energy sensor, said second lowpass filter having a higher cutoff frequency than said first lowpass filter;

a peak detector connected to an output of said second lowpass filter; and

a subtractor connected to an output of said first lowpass filter and to an output of said peak detector.

43. The fire detector of claim 42, wherein said peak detector prevents a sudden dropoff in visible energy from causing a corresponding sudden dropoff in the measured radiant energy release rate of said radiant energy source.

44. A method of fire detection and response, comprising the steps of:

detecting, over a wideband infrared spectrum, radiant energy output from a radiant energy source;

calculating a radiant energy release rate of the radiant energy source;

classifying the radiant energy source in one of a plurality of size categories according to the calculated radiant energy release rate;

selecting, from a plurality of available responses, a response correlated to the size category of the radiant energy source; and

initiating said response.

45. The method of fire detection and response of claim 44, further comprising the step of preventing a response to said fire source when detected visible energy coincides with detected wideband infrared energy.

46. The method of fire detection and response of claim 44, further comprising the steps of

continuing to detect, over a wideband infrared spectrum, radiant energy output from said radiant energy source after initiation of said response;

and

suspending said response upon a sudden dropoff in the calculated radiant energy release rate of said radiant energy source.

47. The method of fire detection and response of claim 44, wherein said step of detecting, over a wideband infrared spectrum, radiant energy output from said radiant energy source comprises the step of receiving radiant energy from said radiant energy source on a wideband infrared energy detector and generating a wideband infrared energy signal in response thereto, and wherein said step of calculating the radiant energy release rate of the radiant energy source comprises the steps of

generating, from said wideband infrared energy signal, a wideband infrared energy baseline that varies gradually over time;

low pass filtering said wideband infrared energy signal, thereby generating a filtered wideband infrared energy signal; and

calculating a difference between said filtered wideband infrared energy signal and said wideband infrared energy baseline, thereby generating a wideband infrared energy difference signal.

48. The method of fire detection and response of claim 47, wherein said step of detecting over a wideband infrared spectrum, radiant energy output from said radiant energy source comprises the step of detecting radiant energy from said radiant energy source over a nearband infrared spectrum and generating a nearband infrared energy signal in response thereto, and wherein said step of calculating the radiant energy release rate of the radiant energy source further comprises the steps of

generating, from said nearband infrared energy signal, a nearband infrared energy baseline that varies gradually over time;

low pass filtering nearband infrared energy signal, thereby generating a filtered nearband infrared energy signal;

calculating a difference between said filtered nearband infrared energy signal and said nearband infrared energy baseline, thereby generating a nearband infrared energy difference signal; and

algebraically combining said nearband infrared energy difference signal with said wideband infrared energy difference signal to generate said calculated radiant energy release rate.

49. The method of fire detection and response of claim 48, further comprising the step of detecting visible energy from said radiant energy source, wherein said step of calculating the radiant energy release rate of the radiant energy source further comprises the steps of

calculating a change in visible energy emitted by said radiant energy source with respect to a measured baseline of visible energy that varies gradually over time;

and

subtracting said change in visible energy from radiant energy detected by said wideband infrared energy detector.