Smoke detectors particularly ducted smoke detectors

• US 20030011770A1
• Filed: 08/09/2002
• Published: 01/16/2003
• Est. Priority Date: 02/10/2000
• Status: Active Grant

• Current Assignee: Siemens Schweiz AG (Siemens AG)
• Original Assignee: Martin Terence Cole
• Inventors: Cole, Martin Terence
• Granted Patent: US 7,075,646 B2
• Time in Patent Office: Days
• US Class Current: 356/338
• CPC Class Codes: G01N 2021/4711 Multiangle measurement
• CPC Class Codes: G01N 2021/4733 Discriminating different types of scatterers
• CPC Class Codes: G01N 2021/4792 Polarisation of scatter light
• CPC Class Codes: G01N 21/53 within a flowing fluid, e.g. smoke
• CPC Class Codes: G08B 17/107 for detecting light-scattering due to smoke
• CPC Class Codes: G08B 17/113 Constructional details

Abstract

The present invention relates to the detection of particles suspended in fluid particularly smoke detectors suitable for mounting on ducting for the early detection of smoke created by unwanted pyrolysis or combustion of materials in a protected area or fire zone to which the duct is connected. The present invention provides alternately illuminating a detection zone with one of either a first or a second illumination. The improvement embodied in the current invention is the ability to retain sensitivity to a wide range of particle sizes and also to discriminate between different kinds of smoke or dust according to particle size, whilst also achieving relatively long service life, small size, light weight and low cost.

Claims

1. A device for the detection of particles suspended in a fluid, the device including light source(s) adapted to provide at least a first polarised illumination and a second polarised illumination, a particle detection zone through which a stream of sample fluid is adapted to flow, logic means adapted to alternately illuminate the detection zone with either the first or second illumination, sensor means for reception of light scattered off particles within the detection zone and output means to provide an indication of a predetermined condition in the detection zone.

2. A device as claimed in claim 1, wherein at least one of the polarised first and second illumination is provided by light from the light source(s) being projected through polarising filters, each with a different relative polarisation.

3. A device as claimed in claim 1 wherein at least one of the polarised first and second illumination is provided by a source of light having different polarisation.

4. A device as claimed in claim 3, wherein the source of light having different polarisation is a laser diodes set to different polarisation and/or wavelength.

5. A particle detection device as claimed in any one of claims 1 to 4, wherein the light source(s) includes at least 2 light sources, the components of the device are mechanically fixed in position, the first and second illuminations are independently radiated, the first and second illuminations are of different polarisation, the first and second illuminations are provided from different positions, and/or the first and second illuminations are of different wavelength such as one of short wavelength light and the other of long wavelength light.

24. A smoke detector including the particle detection device as claimed in any one of claims 1 to 9.

38. A probe adapted to be installed in a conduit, such as a duct through which a fluid may flow, the probe being adapted to communicate fluidly with a device, detector or detection unit as claimed in any one of claims 1 to 25 or 37, the probe including

a first portion adapted to be inserted into the conduit,

the first portion having an inlet for receiving an upstream fluid flow, and an outlet portion having an outlet for outputting a downstream flow,

the inlet and outlet portions each having a channel which curved to enable a change of direction of the fluid flow within the probe whilst substantially minimising flow resistance.

6. A device for the detection of particles suspended in a fluid, the device including a body portion, light source(s) adapted to provide at least a first illumination and a second illumination, a particle detection zone through which a stream of sample fluid is adapted to flow, logic means adapted to alternately illuminate the detection zone with either the first or second illumination, sensor means for reception of light scattered off particles within the detection zone and output means to provide an indication of a predetermined condition in the detection zone, wherein

the body portion is configured from two substantially similar halves.

7. A device as claimed in claim 6, wherein the first and second illuminations are disposed substantially opposite an area of particle detection.

8. A device as claimed in claim 7, wherein the body portion is configured substantially axially similar.

9. A particle detector having a body, at least two light projectors mounted within the body for projecting light into a detection zone adapted to receive an air sample, as few as one light receiving sensor mounted in the body to receive scattered light from the zone, the light projectors being adapted to project light into the detection zone, the arrangement being such that the projected light in pulses of differing wavelength, polarisation and/or angle impinging upon the smoke and dust particles entering the detection zone will create scattered light indicative of a range of smoke particle sizes and/or the existence of dust particles, said sensor upon receiving at least some of said scattered light being adapted to provide a signal which upon analysis enables the determination of particle concentration and particle size and/or range.

10. In a particle detector including:

a body having an inlet through which sample(s) of fluid, including air, can be provided, and output means for indicating an alarm condition,

a particle detection unit having a source of light, and a particle size discrimination means, wherein;

the alarm condition is provided by determining over a predetermined period of time a change in the concentration of selected particle size(s).

11. A detection unit as claimed in claim 10, wherein the particle size discrimination means detects the presence of relatively large particle size(s).

12. A detection unit as claimed in claim 10 or 11, wherein an alarm condition indicative of pyrolysis is provided upon determining a relatively slow increase in large particles.

13. A detection unit as claimed in claim 10, wherein the particle size discrimination means detects the presence of relatively small particle size(s).

14. A detection unit as claimed in claim 10 or 13, wherein an alarm condition indicative of a flaming fire is provided upon determining a relatively rapid increase in small particles.

15. A detection unit as claimed in claim 14, wherein an alarm condition indicative of an accelerant being used is provided upon determining that prior to the rapid increase in small particles, there was a small, if any, period of pyrolysis.

16. A detection unit as claimed in claim 10, wherein the particle size discrimination means is used to determine airborne dust content.

17. A detection unit as claimed in any one of claims 10 to 15, wherein a separate alarm output is provided for any one of, or any combination of, the alarm conditions.

18. A detection unit as claimed in any one of claims 10 or 17, wherein the particle size discrimination means includes a first light source for detecting relatively small particle size(s) and a second light source for detecting relatively large particle size(s).

19. A detection unit as claimed in claim 18, wherein the first and second light source are alternatively active.

20. A detection unit as claimed in any one of claims 10 to 19, wherein the particle size discrimination unit utilises a relatively short wavelength of light and a relatively long wavelength of light to detect particle size.

21. A detection unit as claimed in any one of claims 10 to 19, wherein the particle size discrimination unit utilises a light of horizontal polarisation and a light of vertical polarisation to detect particle size.

22. A smoke detector including the detection unit as claimed in any one of claims 10 to 21.

23. A dust detector including the detection unit as claimed in any one of claims 10 to 21.

25. A smoke detector including the detection unit as claimed in any one of claims 10 to 21 which discriminates against dust to avoid false fire alarms.

27. A method as claimed in claim 26, wherein the particle size(s) and/or particle range(s) determined are relatively large particle size(s) and/or range(s).

28. A method as claimed in claim 26 or 27, wherein an alarm condition indicative of pyrolysis is provided upon determining a relatively slow increase in large particle size(s) and/or range(s).

29. A method as claimed in claim 26, wherein the particle size(s) and/or range(s) determined are relatively small particle size(s) and/or range(s).

30. A method as claimed in claim 26 or 29, wherein an alarm condition indicative of a flaming fire is provided upon determining a relatively rapid increase in small particle size(s) and/or range(s).

31. A method as claimed in claim 30, wherein an alarm condition indicative of an accelerant being used is provided upon determining that prior to the rapid increase in small particle size(s) and/or range(s), there was a small, if any, period of pyrolysis.

32. A method as claimed in claim 26, wherein airborne dust content is determined in order to reduce false alarms.

33. A method as claimed in any one of claims 28, 30 or 31, wherein a separate alarm output is provided for any one of, or any combination of, the alarm conditions.

35. A method as claimed in claim 34, wherein in determining particle size(s) and/or range(s), the first and second light source are alternatively active.

26. A method of detecting an alarm condition for a pyrolysis, smouldering and/or smoke event, the method including the steps of:

a. providing a sample of fluid,

b. impinging upon the fluid sample, light emanating from a source of light,

c. determining, using the emanating light, particle size(s) and I or particle range(s),

d. determining over a predetermined period of time whether the number or concentration of selected particle size(s) and/or particle range(s) has changed,

e. providing an alarm if the determination of step d falls within selected criteria.

34. A method as claimed in any one of claims 26 to 33, wherein in determining the particle size(s) and/or particle range(s), a first light source for detecting a first range and/or relatively small particle size(s) and a second light source for detecting a second and/or relatively large particle size(s) is used.

36. A method as claimed in any one of claims 26 to 35, wherein in determining the particle size(s) and/or range(s), a relatively short wavelength of light and a relatively long wavelength of light is used.

37. A particle and/or smoke detector operatively adapted to detect an alarm condition in accordance with the method of any one of claims 26 to 36.