Smoke detector

• US 6,326,897 B2
• Filed: 03/12/2001
• Issued: 12/04/2001
• Est. Priority Date: 12/08/1999
• Status: Expired due to Term

• Current Assignee: Gentex Corporation
• Original Assignee: Gentex Corporation
• Inventors: Pattok, Greg R., Kadwell, Brian J.
• Primary Examiner(s): Lieu, Julie
• Application Number:
  US09/804,543
• Publication Number:
  US 20010020899A1
• Time in Patent Office: 267 Days
• Field of Search: 340/628, 340/630, 340/514, 356/338, 356/342, 250/573, 250/574, 250/575
• 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
• CPC Class Codes: G08B 17/125 by using a video camera to detect fire or smoke
• CPC Class Codes: G08B 29/043 of fire detection circuits

Abstract

A smoke detector includes a housing defining a dark chamber admitting test atmosphere. A light receiver is disposed within the chamber. A scatter emitter is positioned within the chamber such that light strikes the receiver when reflected off particles suspended in the test atmosphere. An obscuration emitter is positioned within the chamber such that light emitted is directed to the receiver unless obstructed by particles suspended in the test atmosphere. A smoke detect signal is generated responsive to a measurement made responsive to the scatter emitter and/or the obscuration emitter.

Claims

1. A particle detector, comprising:

a housing defining a dark chamber, the chamber admitting test atmosphere;

a scatter emitter/receiver combination disposed within the chamber, the scatter emitter positioned such that any portion of the light emitted by the scatter emitter that is reflected off of particles suspended in the atmosphere and received is proportional to the amount of high reflectivity particles present in the atmosphere;

an obscuration emitter/receiver combination disposed within the chamber, the obscuration emitter positioned such that any portion of the light emitted by the obscuration emitter that is received is inversely proportional to the amount of low reflectivity particles present in the atmosphere; and

a controller coupled to the scatter emitter/receiver combination and the obscuration emitter/receiver combination, the controller using the amount of particles sensed by the obscuration emitter/receiver combination to alter the sensitivity of the scatter emitter/receiver combination.

2. The particle detector of claim 1, wherein the scatter emitter/receiver combination and the obscuration emitter/receiver combination share a common receiver.

3. The particle detector of claim 1, wherein the controller is also configured to change a particle detector sensor cycle when a high reflectivity particle level crosses an initial scatter emitter threshold, and wherein the rate of the particle detector sensor cycle determines the frequency with which at least one of the scatter emitter and obscuration emitter emits light.

4. The particle detector of claim 3, wherein the controller causes the obscuration emitter to generate light only after the high reflectivity particle level crosses the initial scatter emitter threshold.

5. The particle detector of claim 4, wherein a scatter emitter alarm threshold is modified to occur at a lower high reflectivity particle level when an obscuration emitter threshold is exceeded thus altering the sensitivity of the scatter emitter/receiver combination.

6. The particle detector of claim 3, wherein the controller determines the high reflectivity particle level by calculating an initial scatter ratio whose numerator is related to a scatter conduction current provided by the receiver of the scatter emitter/receiver combination in response to light from the scatter emitter and whose denominator is related to a scatter dark current provided by the receiver of the scatter emitter/receiver combination in response to no light from the scatter emitter.

7. The particle detector of claim 6, wherein the controller compensates for changing environmental conditions and degraded performance of the particle detector by altering a scatter reference ratio that is used to provide a normalized scatter ratio that replaces the initial scatter ratio, wherein the normalized scatter ratio is used to determine the high reflectivity particle level, and wherein the scatter reference ratio corresponds to a no particle scatter ratio that is occasionally updated under a no particle condition.

8. The particle detector of claim 7, wherein the controller determines the low reflectivity particle level by calculating a percentage change in obscuration from one particle detector sensor cycle to another particle detector sensor cycle, and wherein a detected obscuration is related to a difference between a conduction time in which an obscuration conduction current is provided by the receiver of the obscuration emitter/receiver combination in response to light from the obscuration emitter and an obscuration dark time in which a dark current is provided by the receiver of the obscuration emitter/receiver combination in response to no light from the obscuration emitter.

9. The particle detector of claim 8, wherein the controller compensates for changing environmental conditions and degraded performance of the particle detector by setting an obscuration reference, and wherein the obscuration reference is utilized as a base for later determinations of percentage change in obscuration.

10. The particle detector of claim 9, wherein the obscuration reference is set when the scatter measurement crosses the initial scatter emitter threshold.

11. A smoke detector, comprising:

a housing defining a dark chamber, the chamber admitting test atmosphere;

a scatter emitter/receiver combination disposed within the chamber, the scatter emitter positioned such that any portion of the light emitted by the scatter emitter that is reflected off of particles suspended in the atmosphere and received is proportional to the amount of gray smoke present in the atmosphere;

an obscuration emitter/receiver combination disposed within the chamber, the obscuration emitter positioned such that any portion of the light emitted by the obscuration emitter that is received is inversely proportional to the amount of black smoke present in the atmosphere; and

a controller coupled to the scatter emitter/receiver combination and the obscuration emitter/receiver combination, the controller using the amount of smoke sensed by the obscuration emitter/receiver combination to alter the sensitivity of the scatter emitter/receiver combination.

12. The smoke detector of claim 11, wherein the scatter emitter/receiver combination and the obscuration emitter/receiver combination share a common receiver.

13. The smoke detector of claim 11, wherein the controller is also configured to change a smoke detector sensor cycle when a gray smoke level crosses an initial scatter emitter threshold, and wherein the rate of the smoke detector sensor cycle determines the frequency with which at least one of the scatter emitter and obscuration emitter emits light.

14. The smoke detector of claim 13, wherein the controller causes the obscuration emitter to generate light only after the gray smoke level crosses the initial scatter emitter threshold.

15. The smoke detector of claim 14, wherein a scatter emitter alarm threshold is modified to occur at a lower gray smoke level when an obscuration emitter threshold is exceeded thus altering the sensitivity of the scatter emitter/receiver combination.

16. The smoke detector of claim 13, wherein the controller determines the gray smoke level by calculating an initial scatter ratio whose numerator is related to a scatter conduction current provided by the receiver of the scatter emitter/receiver combination in response to light from the scatter emitter and whose denominator is related to a scatter dark current provided by the receiver of the scatter emitter/receiver combination in response to no light from the scatter emitter.

17. The smoke detector of claim 16, wherein the controller compensates for changing environmental conditions and degraded performance of the smoke detector by altering a scatter reference ratio that is used to provide a normalized scatter ratio that replaces the initial scatter ratio, wherein the normalized scatter ratio is used to determine the gray smoke level, and wherein the scatter reference ratio corresponds to a no smoke scatter ratio that is occasionally updated under a no smoke condition.

18. The smoke detector of claim 17, wherein the controller determines the black smoke level by calculating a percentage change in obscuration from one smoke detector sensor cycle to another smoke detector sensor cycle, and wherein a detected obscuration is related to a difference between a conduction time in which an obscuration conduction current is provided by the receiver of the obscuration emitter/receiver combination in response to light from the obscuration emitter and an obscuration dark time in which a dark current is provided by the receiver of the obscuration emitter/receiver combination in response to no light from the obscuration emitter.

19. The smoke detector of claim 18, wherein the controller compensates for changing environmental conditions and degraded performance of the smoke detector by setting an obscuration reference, and wherein the obscuration reference is utilized as a base for later determinations of percentage change in obscuration.

20. The smoke detector of claim 19, wherein the obscuration reference is set when the scatter measurement crosses the initial scatter emitter threshold.

21. A particle detector, comprising:

a housing defining a dark chamber, the chamber admitting test atmosphere;

at least one receiver disposed within the chamber;

a first emitter disposed within the chamber, where a received portion of the light emitted by the first emitter is proportional to the amount of high reflectivity particles present in the atmosphere;

a second emitter disposed within the chamber, where a received portion of the light emitted by the second emitter is inversely proportional to the amount of low reflectivity particles present in the atmosphere; and

a controller coupled to the first emitter, the second emitter and the at least one receiver, the controller using the amount of particles sensed using one of the first and second emitters to alter an alarm threshold of the remaining emitter.

22. The particle detector of claim 21, wherein the controller is also configured to change a particle detector sensor cycle when a high reflectivity particle level crosses an initial first emitter threshold, and wherein the rate of the particle detector sensor cycle determines the frequency with which at least one of the first and second emitters emits light.

23. The particle detector of claim 22, wherein the controller causes the second emitter to generate light only after the high reflectivity particle level crosses the initial first emitter threshold.

24. The particle detector of claim 23, wherein a first emitter alarm threshold is modified to occur at a lower high reflectivity particle level when a second emitter threshold is exceeded.

25. The particle detector of claim 22, wherein the controller determines the high reflectivity particle level by calculating an initial first emitter ratio whose numerator is related to a first emitter conduction current provided by the receiver in response to light from the first emitter and whose denominator is related to a first emitter dark current provided by the receiver in response to no light from the first emitter.

26. The particle detector of claim 25, wherein the controller compensates for changing environmental conditions and degraded performance of the particle detector by altering a first emitter reference ratio that is used to provide a normalized first emitter ratio that replaces the initial first emitter ratio, wherein the normalized first emitter ratio is used to determine the high reflectivity particle level, and wherein the first emitter reference ratio corresponds to a no particle first emitter ratio that is occasionally updated under a no particle condition.

27. The particle detector of claim 26, wherein the controller determines the low reflectivity particle level by calculating a percentage change in obscuration from one particle detector sensor cycle to another particle detector sensor cycle, and wherein a detected obscuration is related to a difference between a conduction time in which a second emitter conduction current is provided by the receiver in response to light from the second emitter and a second emitter dark time in which a dark current is provided by the receiver in response to no light from the second emitter.

28. The particle detector of claim 27, wherein the controller compensates for changing environmental conditions and degraded performance of the particle detector by setting an obscuration reference, and wherein the obscuration reference is utilized as a base for later determinations of percentage change in obscuration.

29. The particle detector of claim 28, wherein the obscuration reference is set when the first emitter measurement crosses the initial first emitter threshold.