Smoke detectors particularly ducted smoke detectors

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.

1 . A point detector for detection of particles suspended in a fluid, the point detector comprising light source(s) adapted to provide at least a first polarized illumination and a second polarized 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 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 a majority of light received by the sensor is the light scattered off particles within the detection zone.  
   
   
       2 . A point detector for detection of particles suspended in a fluid, the point detector comprising 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 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, and a majority of light received by the sensor is the light scattered off particles within the detection zone.    
   
   
       3 . The point detector as claimed in  claim 2 , wherein the first and second illuminations are disposed substantially opposite to an area of particle detection, and the body portion is configured substantially axially similar.  
   
   
       4 . A smoke detector comprising the point detector as claimed in  claim 2 .  
   
   
       5 . The point detector as claimed in  claim 2 , wherein substantially all of the light received by the sensor is the light scattered off particles within the detection zone.  
   
   
       6 . A point detector for detection of particles, the point 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, at least one light receiving sensor mounted in the body to receive scattered light from the detection zone, the light projectors being adapted to project light into the detection zone, wherein the projected light includes pulses of differing wavelength, polarization and/or angle impinging upon smoke and dust particles entering the detection zone and creating 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, wherein a majority of light received by the sensor is scattered light created by the projected light impinging upon smoke and dust particles entering the detection zone.  
   
   
       7 . A point detector for detecting particles comprising: 
 at least two light sources for projecting light of differing wavelength, polarization and/or angle; and    at least one sensor for receiving scattered light, wherein the scattered light is produced by the projected light impinging upon particles, said sensor providing a signal representing at least one of particle concentration, particle size and particle range, wherein a majority of light received by the sensor is the scattered light produced by the projected light impinging upon the particles.    
   
   
       8 . The point detector as claimed in  claim 7 , wherein substantially all of the light received by the sensor is the scattered light produced by the projected light impinging upon the particles.  
   
   
       9 . An aspirated detector for detection of particles suspended in a fluid, the aspirated detector comprising light source(s) adapted to provide at least a first polarized illumination and a second polarized 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 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 a majority of light received by the sensor is the light scattered off particles within the detection zone.  
   
   
       10 . An aspirated detector for detection of particles suspended in a fluid, the aspirated detector comprising 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 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, and a majority of light received by the sensor is the light scattered off particles within the detection zone.    
   
   
       11 . The aspirated detector as claimed in  claim 10 , wherein the first and second illuminations are disposed substantially opposite to an area of particle detection, and the body portion is configured substantially axially similar.  
   
   
       12 . A smoke detector comprising the aspirated detector as claimed in  claim 10 .  
   
   
       13 . The aspirated detector as claimed in  claim 10 , wherein substantially all of the light received by the sensor is the light scattered off particles within the detection zone.  
   
   
       14 . An aspirated detector for detection of particles, the aspirated 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, at least one light receiving sensor mounted in the body to receive scattered light from the detection zone, the light projectors being adapted to project light into the detection zone, wherein the projected light includes pulses of differing wavelength, polarization and/or angle impinging upon smoke and dust particles entering the detection zone and creating 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, wherein a majority of light received by the sensor is scattered light created by the projected light impinging upon smoke and dust particles entering the detection zone.  
   
   
       15 . An aspirated detector for detecting particles comprising: 
 at least two light sources for projecting light of differing wavelength, polarization and/or angle; and    at least one sensor for receiving scattered light, wherein the scattered light is produced by the projected light impinging upon particles, said sensor providing a signal representing at least one of particle concentration, particle size and particle range, wherein a majority of light received by the sensor is the scattered light produced by the projected light impinging upon the particles.    
   
   
       16 . The aspirated detector as claimed in  claim 15 , wherein substantially all of the light received by the sensor is the scattered light produced by the projected light impinging upon the particles.  
   
   
       17 . A method of detecting particles comprising: projecting light of differing wavelength, polarization and/or angle from at least two light sources, wherein the light from each light source is projected at different angles; receiving scattered light produced by the projected light from the at least two light sources impinging upon particles by at least one sensor, wherein a majority of light received by the sensor is the scattered light produced by the projected light from the at least two light sources impinging upon particles; and generating a signal representing at least one of particle concentration, particle size and particle range based on the received scattered light.  
   
   
       18 . A device for detection of particles suspended in a fluid, the device comprising light source(s) adapted to provide at least a first polarized illumination and a second polarized illumination, wherein the light from each light source is projected at different angles, 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 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 substantially all of the light received by the sensor is the light scattered off particles within the detection zone.  
   
   
       19 . A device for detection of particles suspended in a fluid, the device comprising light source(s) adapted to provide at least a first polarized illumination and a second polarized 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 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 a majority of light received by the sensor is the light scattered off particles within the detection zone, and the first and second illuminations are provided at different angles relative to an axis of the detection zone.  
   
   
       20 . A device for detection of particles suspended in a fluid, the device comprising 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 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, and a majority of light received by the sensor is the light scattered off particles within the detection zone, the first and second illuminations provided at different angles relative to an axis of the detection zone.    
   
   
       21 . The device as claimed in  claim 20 , wherein the first and second illuminations are disposed substantially opposite to an area of particle detection, and the body portion is configured substantially axially similar.  
   
   
       22 . A smoke detector comprising the particle detection device as claimed in  claim 20 .  
   
   
       23 . The device as claimed in  claim 20 , wherein substantially all of the light received by the sensor is the light scattered off particles within the detection zone.  
   
   
       24 . 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, at least one light receiving sensor mounted in the body to receive scattered light from the detection zone, the light projectors being adapted to project light into the detection zone, wherein the projected light includes pulses of differing wavelength, polarization and/or angle impinging upon smoke and dust particles entering the detection zone and creating 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, wherein a majority of light received by the sensor is scattered light created by the projected light impinging upon smoke and dust particles entering the detection zone, and the at least two light projectors projecting light at different angles relative to an axis of the detection zone.  
   
   
       25 . A device for detecting particles comprising: 
 at least two light sources for projecting light of differing wavelength, polarization and/or angle; and    at least one sensor for receiving scattered light, wherein the scattered light is produced by the projected light impinging upon particles, said sensor providing a signal representing at least one of particle concentration, particle size and particle range, wherein a majority of light received by the sensor is the scattered light produced by the projected light impinging upon the particles, and the at least two light projectors projecting light at different angles relative to an axis of a detection zone.    
   
   
       26 . The device as claimed in  claim 25 , wherein substantially all of the light received by the sensor is the scattered light produced by the projected light impinging upon the particles.  
   
   
       27 . A method of detecting particles comprising: 
 projecting light of differing wavelength, polarization and/or angle from at least two light sources;    receiving scattered light produced by the projected light from the at least two light sources impinging upon particles by at least one sensor, wherein a majority of light received by the sensor is the scattered light produced by the projected light from the at least two light sources impinging upon particles; and    generating a signal representing at least one of particle concentration, particle size and particle range based on the received scattered light, wherein the projected light from at least two light sources is provided at different angles relative to an axis of a detection zone.