WO1993006462A1 - Smoke and particle detector - Google Patents

Smoke and particle detector Download PDF

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Publication number
WO1993006462A1
WO1993006462A1 PCT/GB1992/001709 GB9201709W WO9306462A1 WO 1993006462 A1 WO1993006462 A1 WO 1993006462A1 GB 9201709 W GB9201709 W GB 9201709W WO 9306462 A1 WO9306462 A1 WO 9306462A1
Authority
WO
WIPO (PCT)
Prior art keywords
sensor
flow path
smoke
chamber
light
Prior art date
Application number
PCT/GB1992/001709
Other languages
French (fr)
Inventor
Peter Varney
F. John James
David Nicholas Ball
Original Assignee
Kidde-Graviner Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Kidde-Graviner Limited filed Critical Kidde-Graviner Limited
Priority to EP92919493A priority Critical patent/EP0604502A1/en
Publication of WO1993006462A1 publication Critical patent/WO1993006462A1/en

Links

Classifications

    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/103—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device
    • G08B17/107—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using a light emitting and receiving device for detecting light-scattering due to smoke
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B17/00—Fire alarms; Alarms responsive to explosion
    • G08B17/10—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means
    • G08B17/11—Actuation by presence of smoke or gases, e.g. automatic alarm devices for analysing flowing fluid materials by the use of optical means using an ionisation chamber for detecting smoke or gas
    • G08B17/113—Constructional details
    • G—PHYSICS
    • G08—SIGNALLING
    • G08B—SIGNALLING OR CALLING SYSTEMS; ORDER TELEGRAPHS; ALARM SYSTEMS
    • G08B29/00—Checking or monitoring of signalling or alarm systems; Prevention or correction of operating errors, e.g. preventing unauthorised operation
    • G08B29/18—Prevention or correction of operating errors
    • G08B29/20—Calibration, including self-calibrating arrangements
    • G08B29/24—Self-calibration, e.g. compensating for environmental drift or ageing of components

Definitions

  • the invention relates to smoke and particle detectors.
  • a detector of smoke or other particles in a gaseous medium comprising means defining a flow path for the gaseous medium, a source emitting a beam of electromagnetic radiation, a sensor for the electromagnetic radiation and producing a corresponding output, the source being so mounted in relation to the sensor and in relation to the flow path that the said beam has a first part which intersects the flow path but substantially cannot reach the sensor except when scattered by smoke or other particles in the gaseous medium in the flow path and a second part which is directed towards the sensor, and electromagnetic radiation blocking means juxtaposed with the second part of the beam and switchable between a first setting in which it blocks the second part of the beam so as to enable the sensor to produce an output dependent on the scattered radiation and thus the presence of the smoke or particles, and a second setting in which it permits the second part of the beam to reach the sensor whereby the latter produced an output dependent on factors other than smoke or particles in the flow path, characterised in that the second part of the beam is clear of the flow path.
  • a method of detecting smoke or other particles in a gaseous medium comprising the steps of defining a flow path for the gaseous medium, emitting a beam of electromagnetic radiation in a predetermined emission direction, sensing electromagnetic radiation arriving along a predetermined arrival direction, the beam having a first part which intersects the flow path but cannot travel along the arrival direction except when scattered by smoke or other particles in the gaseous medium in the flow path and a second part which is directed along the arrival direction, and selectively blocking the second part so as to enable sensing of any radiation scattered into the arrival direction by the presence of the smoke or particles and thus the production of an output dependent thereon, the second part of the beam when unblocked producing an output dependent on factors other than smoke or particles in the flow path, characterised in that the second part of the beam is clear of the flow path.
  • Figure 1 is a cross-section through one of the detectors; and Figure 2 is a cross-section through another of the detectors.
  • the detector of Figure 1 comprises a casing 10 made of suitable solid material, such as plastics or metal, defining a hollow chamber 12.
  • the chamber 12 has inlet and exit passageways (not shown) defining a flow path across the chamber and through which a gaseous medium, for example air, which may carry smoke or other particles to be detected, may be passed through the chamber.
  • a gaseous medium for example air, which may carry smoke or other particles to be detected
  • the flow path for the gaseous medium is indicated diagrammatically at 14, though it will be appreciated that the gaseous medium may not in practice flow in such a well-defined way.
  • the gaseous medium may be caused to flow along the path 14 by means of a pump or blower, or may diffuse along the path.
  • a light source 16 is mounted, this being an electrically energised light source of any suitable type. It is arranged to produce a beam directed across the chamber 12 and indicated generally at 18, the beam 18 intersecting the flow path 14.
  • a light sensor 20 is mounted, this being of any suitable type capable of detecting the light from the light source 16 and producing a corresponding electrical signal.
  • the detector incorporates a bore 22 in one wall of the chamber 12 in which is slidably mounted a solid plunger 24, the plunger having a portion 26 extending into the hollow chamber 12 and a portion 28 extending into an actuating unit 30.
  • the actuator unit 30 can move the plunger 24 into and out of the chamber 12.
  • the Figure shows the plunger 24 in its limit position in the chamber 12.
  • the plunger 24 is in the position illustrated. In this position, the plunger 24 prevents any of the light in the beam 18 from directly reaching the light sensor 20 along the straight line path indicated at
  • the senor 20 will receive substantially no light from the source 16. In order to prevent any light from being reflected by the wall of the chamber 12 towards the sensor
  • all internal surfaces of the chamber are painted matt black.
  • the geometry of the chamber may be designed such that any minimal amount of light that is reflected from the chamber wall is reflected, or multiply reflected away from the sensor 20. If any smoke or other particles are present within the gaseous medium in the flow path 14, however, these will scatter some of the light in the light beam 18 and some of this scattered light will be scattered towards and sensed by the sensor 20, thus producing an electrical output indicating the presence of the smoke or other particles.
  • the light source 16 may be caused to produce light modulated at a particular frequency. Any of this light which is scattered by smoke or particles in the flow path 14 will produce an electrical output from the sensor 20 which is correspondingly modulated and can thus be detected and distinguished, such as by filtering or phase discrimination, from stray light from other sources.
  • the light beam 18 from the light sensor is designed such that some of the light from the source is directed along this path 32 and will consequently reach the light sensor when the plunger is withdrawn in this way.
  • the light sensor will produce a resultant output, and the level of this output, in comparison with a predetermined datum, will be a measure of the total degradation in performance (due to the factors previously mentioned) .
  • the degradation in performance can be monitored. If it becomes excessive (if the degradation, as measured by the reduction in the output of the sensor 20, exceeds a predetermined value), compensating steps may be taken; for example, the light output of the source 16 may be increased. This may be done manually or automatically.
  • the plunger 24 is moved back to the position illustrated.
  • the plunger 24 can be moved into the degradation-testing position under manual control or (preferably) automatically at predetermined instances.
  • the plunger 24 is moved into and out of the position illustrated by the actuating unit 30 which may take any suitable form.
  • the actuating unit 30 may take any suitable form.
  • it may comprise a solenoid which can be electrically energised so as to attract and repel the plunger 24 and thus move it between its two positions.
  • it could be pneumatically operated.
  • Another possible form could incorporate an electric motor connected to move the plunger 24 by means of a crank or a cam and cam follower arrangement.
  • a non-mechanical arrangement could be used for controlling the direct light path 32, such as some suitable electrical device which can be switched, by means of an electrical or other non-mechanical signal, between a light obscuring and a light transmitting setting.
  • items corresponding to Figure 1 are similarly referenced.
  • the surfaces defining or mainly defining the walls of the chamber 12 are arranged as two parabolas, a first parabola 36 and a second parabola 38.
  • Parabola 36 has its focus at 40, that is, at the point (or substantially at the point) from which the light is emitted.
  • the parabola 36 is arranged so that the emitted light is projected forwardly and, except for the direct path 32, away from the sensor 20 but intersecting the flow path 14.
  • Parabola 38 has its focus at 42. Focus 42 is obscured from the light source 16 by the parabola 36. Any light striking the surface of the parabola will therefore be reflected to the focus 42 - and thus will be directed away from the sensor 20 (this assumes, of course, that there are no imperfections in the surface of the parabola) .
  • light includes other suitable electromagnetic radiation.

Abstract

A smoke detector has a chamber (12) through which air or another gaseous medium in which smoke or other particles to be detected flows along a flow path (14). A light source (16) emits light into the chamber and a light sensor (20) receives light from the chamber. The light source (16) emits a first part (18) of its light towards the flow path (14) and but not towards the field of view of the sensor (20), and a second part (32) of its light directly towards the field of view of the sensor (20). As light obscuring plunger (24) normally blocks such direct light (32) from the sensor (20) which can thus only respond to light from the source (16) when it is scattered by smoke or other particles in the flow path (14), thus producing an output dependent on such particles. Periodically, however, the plunger (24) is withdrawn so that the sensor (20) produces an output dependent directly on the light from the source (16), on any obscuration of the source or the sensor, or their respective windows, or on any other factor degrading the operations of the source or the sensor. The latter output can be used to adjust the magnitude of the light emitted by the source (16) to compensate.

Description

SMOKE AND PARTICLE DETECTOR
The invention relates to smoke and particle detectors.
According to the invention, there is provided a detector of smoke or other particles in a gaseous medium, comprising means defining a flow path for the gaseous medium, a source emitting a beam of electromagnetic radiation, a sensor for the electromagnetic radiation and producing a corresponding output, the source being so mounted in relation to the sensor and in relation to the flow path that the said beam has a first part which intersects the flow path but substantially cannot reach the sensor except when scattered by smoke or other particles in the gaseous medium in the flow path and a second part which is directed towards the sensor, and electromagnetic radiation blocking means juxtaposed with the second part of the beam and switchable between a first setting in which it blocks the second part of the beam so as to enable the sensor to produce an output dependent on the scattered radiation and thus the presence of the smoke or particles, and a second setting in which it permits the second part of the beam to reach the sensor whereby the latter produced an output dependent on factors other than smoke or particles in the flow path, characterised in that the second part of the beam is clear of the flow path. According to the invention, there is further provided a method of detecting smoke or other particles in a gaseous medium, comprising the steps of defining a flow path for the gaseous medium, emitting a beam of electromagnetic radiation in a predetermined emission direction, sensing electromagnetic radiation arriving along a predetermined arrival direction, the beam having a first part which intersects the flow path but cannot travel along the arrival direction except when scattered by smoke or other particles in the gaseous medium in the flow path and a second part which is directed along the arrival direction, and selectively blocking the second part so as to enable sensing of any radiation scattered into the arrival direction by the presence of the smoke or particles and thus the production of an output dependent thereon, the second part of the beam when unblocked producing an output dependent on factors other than smoke or particles in the flow path, characterised in that the second part of the beam is clear of the flow path.
Smoke and particle detectors embodying the invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawing in which:
Figure 1 is a cross-section through one of the detectors; and Figure 2 is a cross-section through another of the detectors.
The detector of Figure 1 comprises a casing 10 made of suitable solid material, such as plastics or metal, defining a hollow chamber 12. The chamber 12 has inlet and exit passageways (not shown) defining a flow path across the chamber and through which a gaseous medium, for example air, which may carry smoke or other particles to be detected, may be passed through the chamber. The flow path for the gaseous medium is indicated diagrammatically at 14, though it will be appreciated that the gaseous medium may not in practice flow in such a well-defined way. The gaseous medium may be caused to flow along the path 14 by means of a pump or blower, or may diffuse along the path.
At one side of the chamber, a light source 16 is mounted, this being an electrically energised light source of any suitable type. It is arranged to produce a beam directed across the chamber 12 and indicated generally at 18, the beam 18 intersecting the flow path 14.
On the opposite side of the chamber 10 a light sensor 20 is mounted, this being of any suitable type capable of detecting the light from the light source 16 and producing a corresponding electrical signal.
In addition, the detector incorporates a bore 22 in one wall of the chamber 12 in which is slidably mounted a solid plunger 24, the plunger having a portion 26 extending into the hollow chamber 12 and a portion 28 extending into an actuating unit 30. In a manner to be described, the actuator unit 30 can move the plunger 24 into and out of the chamber 12. The Figure shows the plunger 24 in its limit position in the chamber 12.
During normal operation, the plunger 24 is in the position illustrated. In this position, the plunger 24 prevents any of the light in the beam 18 from directly reaching the light sensor 20 along the straight line path indicated at
32. Therefore, in the absence of any smoke or other particles in the gaseous medium in the flow path 14, the sensor 20 will receive substantially no light from the source 16. In order to prevent any light from being reflected by the wall of the chamber 12 towards the sensor
20, all internal surfaces of the chamber are painted matt black. Furthermore, the geometry of the chamber may be designed such that any minimal amount of light that is reflected from the chamber wall is reflected, or multiply reflected away from the sensor 20. If any smoke or other particles are present within the gaseous medium in the flow path 14, however, these will scatter some of the light in the light beam 18 and some of this scattered light will be scattered towards and sensed by the sensor 20, thus producing an electrical output indicating the presence of the smoke or other particles.
In order to increase the efficiency of operation and to prevent the sensor 20 from producing a false smoke alarm in response to stray light from other sources, the light source 16 may be caused to produce light modulated at a particular frequency. Any of this light which is scattered by smoke or particles in the flow path 14 will produce an electrical output from the sensor 20 which is correspondingly modulated and can thus be detected and distinguished, such as by filtering or phase discrimination, from stray light from other sources.
Over a period of time, various factors may operate to degrade the relationship between the electrical output of the sensor 20 and the amount of smoke or other particles present in the gaseous medium in the flow path 14. For example, contamination from dirt or other deposits (such as from the gaseous medium in the flow path 14) may become present on the surface of the light source 16 and/or the sensor 20, or on windows covering them. Such contamination will reduce the overall sensitivity of the detector. Furthermore, ageing of the light source and/or light sensor will change the output of the sensor 20, as will other defects in them or their associated circuitry. In order to test for any such degradation in performance, the plunger 24 is momentarily withdrawn from the chamber 12 so as to open the direct path 32 between the light source 16 and the light sensor 20. The light beam 18 from the light sensor is designed such that some of the light from the source is directed along this path 32 and will consequently reach the light sensor when the plunger is withdrawn in this way. The light sensor will produce a resultant output, and the level of this output, in comparison with a predetermined datum, will be a measure of the total degradation in performance (due to the factors previously mentioned) .
In this way, the degradation in performance can be monitored. If it becomes excessive (if the degradation, as measured by the reduction in the output of the sensor 20, exceeds a predetermined value), compensating steps may be taken; for example, the light output of the source 16 may be increased. This may be done manually or automatically.
After completion of the degradation test, the plunger 24 is moved back to the position illustrated.
The plunger 24 can be moved into the degradation-testing position under manual control or (preferably) automatically at predetermined instances.
The plunger 24 is moved into and out of the position illustrated by the actuating unit 30 which may take any suitable form. For example, it may comprise a solenoid which can be electrically energised so as to attract and repel the plunger 24 and thus move it between its two positions. Instead, for example, it could be pneumatically operated. Another possible form could incorporate an electric motor connected to move the plunger 24 by means of a crank or a cam and cam follower arrangement.
Instead of the plunger 24, a mechanical shutter arrangement could be used which would alternately block and open the direct light path 32.
However, a non-mechanical arrangement could be used for controlling the direct light path 32, such as some suitable electrical device which can be switched, by means of an electrical or other non-mechanical signal, between a light obscuring and a light transmitting setting. In Figure 2, items corresponding to Figure 1 are similarly referenced.
In the detector of Figure 2, the surfaces defining or mainly defining the walls of the chamber 12 are arranged as two parabolas, a first parabola 36 and a second parabola 38. Parabola 36 has its focus at 40, that is, at the point (or substantially at the point) from which the light is emitted. The parabola 36 is arranged so that the emitted light is projected forwardly and, except for the direct path 32, away from the sensor 20 but intersecting the flow path 14.
Parabola 38 has its focus at 42. Focus 42 is obscured from the light source 16 by the parabola 36. Any light striking the surface of the parabola will therefore be reflected to the focus 42 - and thus will be directed away from the sensor 20 (this assumes, of course, that there are no imperfections in the surface of the parabola) .
The operation of the detector of Figure 2 is otherwise the same as that of Figure 1.
In this specification and its claims, "light" includes other suitable electromagnetic radiation.
1439S

Claims

1. A detector of smoke or other particles in a gaseous medium, comprising means defining a flow path (14) for the gaseous medium, a source (16) emitting a beam (18,32) of electromagnetic radiation, a sensor (20) for the electromagnetic radiation and producing a corresponding output, the source (16) being so mounted in relation to the sensor (20) and in relation to the flow path (14) that the said beam has a first part (18) which intersects the flow path (14) but substantially cannot reach the sensor (20) except when scattered by smoke or other particles in the gaseous medium in the flow path and a second part (32) which is directed towards the sensor (20), and electromagnetic radiation blocking means juxtaposed with the second part (32) of the beam and switchable between a first setting in which it blocks the second part (32) of the beam so as to enable the sensor (20) to produce an output dependent on the scattered radiation and thus the presence of the smoke or particles, and a second setting in which it permits the second part (32) of the beam to reach the sensor (20) whereby the latter produced an output dependent on factors other than smoke or particles in the flow path, characterised in that the second part (32) of the beam is clear of the flow path (14).
2. A detector according to claim 1, characterised by a housing (10) defining an interior chamber (12) and in that the source (16) and the sensor (20) are mounted on opposite sides of the chamber (12) so that the said beam (18,32) is directed across the interior of the chamber (12), the second part of the beam (32) being directed rectilinearly across the interior of the chamber (12), the flow path (14) being directed through the interior of the chamber (12) transversely to the beam (18,32) and clear of the second part (32) thereof.
3. A detector according to claim 2, characterised in that the surface defining the interior of the chamber (12) is at least in part of parabolic shape (38) having its focus (42) positioned out of the line of sight of the sensor (20) so that light striking this part of the surface is reflected to the said focus (42) and thus away from the sensor (20) .
4. A detector according to claim 2 or 3, characterised in that the surface of the interior of the chamber (12) is at least in part of parabolic shape (36) having its focus (40) substantially placed at the position of emission of the beam (18,32) .
5. A detector according to any one of claims 2 to 4, characterised in that the blocking means (24) comprises a radiation blocking member (24) movably mounted in the housing (10) between a first position which corresponds to the first setting and in which it protrudes into the interior of the chamber (12) so as to block the second part (32) of the beam but to be clear of the first part (18) thereof and a second position which corresponds to the second setting and in which it is clear of the first and second parts (18,32) of the beam.
6. A detector according to claim 5, characterised in that the blocking member (24) is substantially clear of the interior of the chamber (12) in the second position.
7. A detector according to claim 5 or 6, characterised in that the blocking means (24) is moved electromagnetically between its two positions.
8. A detector according to any one of claims 1 to 4, characterised in that the blocking means comprises means positioned in the second part (32) of the beam and switchable between the two said settings.
9. A detector according to claim 8, characterised in that the blocking means is switchable between the two said settings by means of an externally applied non-mechanical signal.
10. A detector according to any preceding claim, characterised by means responsive to the output produced by the sensor (20) when the blocking means (24) is in its second setting for adjusting the emission of the source (16) so as to tend to bring that output of the sensor (20) to a predetermined value.
11. A detector according to any preceding claim, characterised by means for modulating the emission of the source (16) in a predetermined manner, and by processing means responsive only to corresponding modulation in an output signal of the sensor (20) and thereby to produce the said output.
12. A method of detecting smoke or other particles in a gaseous medium, comprising the steps of defining a flow path (14) for the gaseous medium, emitting a beam (18,32) of electromagnetic radiation in a predetermined emission direction, sensing electromagnetic radiation arriving along a predetermined arrival direction, the beam having a first part (18) which intersects the flow path (14) but cannot travel along the arrival direction except when scattered by smoke or other particles in the gaseous medium in the flow path (14) and a second part (32) which is directed along the arrival direction, and selectively blocking the second part (32) so as to enable sensing of any radiation scattered into the arrival direction by the presence of the smoke or particles and thus the production of an output dependent thereon, the second part (32) of the beam when unblocked producing an output dependent on factors other than smoke or particles in the flow path, characterised in that the second part (32) of the beam is clear of the flow path (14).
1439S
PCT/GB1992/001709 1991-09-18 1992-09-17 Smoke and particle detector WO1993006462A1 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
EP92919493A EP0604502A1 (en) 1991-09-18 1992-09-17 Smoke and particle detector

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB9119942A GB2259761B (en) 1991-09-18 1991-09-18 Smoke and particle detector
GB9119942.2 1991-09-18

Publications (1)

Publication Number Publication Date
WO1993006462A1 true WO1993006462A1 (en) 1993-04-01

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ID=10701613

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1992/001709 WO1993006462A1 (en) 1991-09-18 1992-09-17 Smoke and particle detector

Country Status (3)

Country Link
EP (1) EP0604502A1 (en)
GB (1) GB2259761B (en)
WO (1) WO1993006462A1 (en)

Cited By (2)

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EP3131073A1 (en) * 2015-08-13 2017-02-15 Siemens Schweiz AG Smoke detection unit having light emitting diodes and photoreceiver, and with an led chip in the light emitting diode and photosensor for determining an aging level and/or a light current compensation value, and light emitting diode
CN110296959A (en) * 2008-06-10 2019-10-01 爱克斯崔里斯科技有限公司 Detection of particles

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EP0733894B1 (en) * 1995-03-24 2003-05-07 Nohmi Bosai Ltd. Sensor for detecting fine particles such as smoke
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EP1855259A1 (en) * 2006-05-08 2007-11-14 Siemens Schweiz AG Fire detecor
US7876217B2 (en) * 2008-02-15 2011-01-25 Infineon Technologies Ag Apparatus and method for secure sensing
EP3539104B1 (en) 2016-11-11 2022-06-08 Carrier Corporation High sensitivity fiber optic based detection
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EP3539105A1 (en) * 2016-11-11 2019-09-18 Carrier Corporation High sensitivity fiber optic based detection
US10957176B2 (en) 2016-11-11 2021-03-23 Carrier Corporation High sensitivity fiber optic based detection
US11127270B2 (en) 2016-11-11 2021-09-21 Carrier Corporation High sensitivity fiber optic based detection

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Publication number Priority date Publication date Assignee Title
CN110296959A (en) * 2008-06-10 2019-10-01 爱克斯崔里斯科技有限公司 Detection of particles
CN110296959B (en) * 2008-06-10 2022-05-03 嘉睿特热系统有限公司 Particle detection
EP3131073A1 (en) * 2015-08-13 2017-02-15 Siemens Schweiz AG Smoke detection unit having light emitting diodes and photoreceiver, and with an led chip in the light emitting diode and photosensor for determining an aging level and/or a light current compensation value, and light emitting diode
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US9666049B2 (en) 2015-08-13 2017-05-30 Siemens Schweiz Ag Smoke detection unit with light-emitting diode and photo-detector, and with an LED chip arranged in the light-emitting diode and with a photosensor for determining a degree of aging and/or a compensation value for a light current, as well as a light-emitting diode
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Also Published As

Publication number Publication date
GB2259761B (en) 1995-04-05
GB2259761A (en) 1993-03-24
GB9119942D0 (en) 1991-10-30
EP0604502A1 (en) 1994-07-06

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