Smoke detector

• US 20050173638A1
• Filed: 03/15/2003
• Published: 08/11/2005
• Est. Priority Date: 05/27/2002
• Status: Active Grant

• Current Assignee: Kidde Ip Holdings Limited
• Original Assignee: Kidde Ip Holdings Limited
• Inventors: Powell, Brian David
• Granted Patent: US 7,483,139 B2
• Time in Patent Office: Days
• US Class Current: 250/341.100
• CPC Class Codes: G01N 21/0303 Optical path conditioning in cuvettes, e.g. windows; adapted optical elements or systems; path modifying or adjustment G01N21/031 - G01N21/15 take precedence
• CPC Class Codes: G01N 21/534 by measuring transmission alone, i.e. determining opacity
• CPC Class Codes: G01N 2201/065 Integrating spheres
• CPC Class Codes: G08B 17/103 using a light emitting and receiving device
• 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 29/183 Single detectors using dual technologies G08B13/1672, G08B13/2448, G08B13/2494 take precedence

Abstract

A smoke detector (1) has a spherical chamber (2) including a plurality of holes (15,17) for allowing smoke and other particles to enter the chamber. The majority of the internal surface (3) of the chamber (2) is covered with a high reflectivity Lambertian surface, that is a material that scatters incident light equally in all directions and at all wavelengths. The remaining portion of the internal surface (3) is coated with a light absorbing material (13) such as a matt black coating. A scatter sensor (9) is directed towards the absorbing coating (3), and an integrating detector (5) is configured to detect radiation directly from the entire Lambertian surface. A first LED (19) emits blue light into the chamber (2), and a second LED (21) emits infrared light into the chamber. Processing means (23, 25 and 27) are provided to analyse the signals from the detectors (5,9), including means for discriminating between signals from the sensors indicative of different frequencies of received radiation. The processing means can distinguish between different smoke types, such as white/grey smoke and black smoke, and can also distinguish between smoke and other particles.

Claims

1. A particle detector including:

a chamber having a substantially high reflectivity substantially Lambertian surface and for receiving particles,

radiation emitting means for emitting radiation into the chamber, and

radiation detecting means for detecting the effect of the particles on the radiation within the chamber,

wherein the radiation detecting means is primarily for detecting absorption of the radiation by the particles, and

wherein the radiation detecting means has a wide viewing angle to receive radiation directly from a substantial portion of the high reflectivity Lambertian surface.

2. A detector according to claim 1, wherein the particles include smoke particles.

3. A detector according to claim 1, wherein the high reflectivity Lambertian surface is a majority of the chamber surface.

4. A particle detector according to claim 3, wherein the high reflectivity Lambertian surface covers at least 80% of the chamber surface.

5. A particle detector according to claim 1, including a second radiation detecting means primarily for detecting scattering of radiation by the particles.

6. A detector according to claim 1, including a second radiation emitting means for emitting radiation into the chamber, the second radiation emitting means emitting radiation having a wavelength or wavelengths different from the wavelength or wavelengths of the radiation emitted by the first-mentioned radiation emitting means.

7. A detector according to claim 6, wherein the first-mentioned radiation emitting means emits blue light and the second radiation emitting means emits infrared radiation.

8. A detector according to claim 1, wherein the chamber includes a radiation absorbing surface.

9. A detector according to claim 8, wherein the radiation absorbing surface is black.

10. A detector according to claim 8, wherein the chamber includes holes for allowing the admission of particles, at least one of the holes being in the radiation absorbing surface.

11. A detector according to claim 8, wherein the first-mentioned radiation detecting means is located at the radiation absorbing surface.

12. A detector according to claim 8, wherein the second radiation detecting means is sensitive substantially only to radiation in a path between the second radiation detecting means and the radiation absorbing surface.

13. A detector according to claim 6, including means for processing signals from the or each radiation detecting means to obtain data indicative of the detected radiation emitted by each of the radiation emitting means.

14. A detector according to claim 13, wherein the data is obtained by frequency division multiplexing.

15. A detector according to claim 13, wherein the data is obtained by time division multiplexing.

16. A detector according to claim 13, wherein the two radiation emitting means are driven at different frequencies and the processing means includes lock-in amplifiers operative at the different frequencies and for receiving the output of the detecting means.

17. A detector according claim 1, wherein the or each radiation emitting means is positioned arbitrarily with respect to the or each radiation detecting means.

18. A detector according to claim 1, wherein the or each radiation emitting means has a beam spread of between about + or −

10° and

about + or −

15°

.

19. A detector according to claim 2, including a second radiation detecting means primarily for detecting scattering of radiation by the particles, and processing means for analysing data from the two radiation detecting means to determine characteristics of the smoke particles in the chamber.

20. A detector according to claim 2, including a second radiation detecting means primarily for detecting scattering of radiation by the particles, and processing means for analysing the data from the two radiation detecting means to determine whether smoke particles or other particles are present in the chamber.

21. A detector according to claim 1, wherein the first-mentioned radiation detecting means and the chamber are configured such that the first-mentioned radiation detecting means has a direct view of substantially the entire chamber.

22. A detector according to claim 1, wherein the chamber is ellipsoidal.

23. A detector according to claim 1, wherein the chamber is spherical.

24. A detector according to claim 1, wherein the chamber is an integrating sphere.

25. A detector according to claim 6, including at least one further radiation emitting means, in addition to the first and second radiation emitting means the further radiation means emitting radiation having a wavelength or wavelengths different from the wavelength or wavelengths of the first or second radiation emitting means.

26. A particle detector according to claim 1, wherein the Lambertian surface reflects greater than 90% of said radiation.

27. A particle detecting method including the steps of providing a chamber having a substantially high reflectivity substantially Lambertian surface and for receiving particles,

emitting radiation into the chamber, and

detecting the effect of the particles on the radiation within the chamber;

wherein the step of detecting radiation includes detecting the absorption of radiation by receiving radiation directly from a substantial portion of the high reflectivity Lambertian surface.

28. A method according to claim 27, wherein the particles are smoke particles.

29. A method according to claim 27, wherein the step of detecting radiation further includes the step of detecting the scattering of radiation.

30. A method according to claim 27, wherein the step of emitting radiation includes the steps of emitting radiation at two different wavelengths or wavelength ranges.

31. A method according to claim 30, wherein one of said wavelengths or wavelength ranges corresponds to that of blue light and the other of the wavelengths or wavelength ranges corresponds to that of infrared radiation.

32. A method according to claim 30, including the step of analysing the detected radiation to obtain data indicative of the radiation received at each of the wavelengths or wavelength ranges.

33. A method according to claim 32, including the step of deriving from said data signals indicative of the type of particles within the chamber.

34. A method according to claim 33, including the step of deriving signals indicative of whether or not the particles are smoke particles.

35. A method according to claim 30, including the step of emitting radiation of at least a further wavelength or wavelength range, different to said two wavelengths or wavelength ranges.

36. A method according to claim 27, wherein the Lambertian surface reflects greater than 90% of said radiation.