CLEANING SYSTEM FOR A SMOKE DETECTOR

Abstract

An optical smoke detector 1 includes an ultrasonic transducer 4 configured to cause oscillations in its housing 2 so as to dislodge accumulated particulate matter from the walls of a sensor chamber or a labyrinth of the smoke detector 1. Additionally or alternatively, the ultrasonic transducer 4 may be configured to cause oscillations that dislodge accumulated particulate matter from a light source or a light receiver of the smoke detector 1.

Claims

1. An optical smoke detector comprising an ultrasonic transducer configured to cause oscillations to dislodge accumulated particulate matter from at least one component of the smoke detector.

2. An optical smoke detector according to claim 1, comprising a housing having walls that define a sensor chamber and a labyrinth, wherein the at least one component of the smoke detector includes one or more of the walls that at least partially defining the sensor chamber or the labyrinth.

3. An optical smoke detector according to claim 1, wherein the smoke detector is configured to periodically activate the ultrasonic transducer.

4. An optical smoke detector according to claim 1, wherein the smoke detector is configured to activate the ultrasonic transducer in response to a detected or estimated degree of fouling exceeding a threshold value.

5. An optical smoke detector according to claim 4, wherein the degree of fouling is estimated based on a level of light detected when the sensor chamber does not contain smoke.

6. An optical smoke detector according to claim 1, comprising a light source configured to illuminate a gas within the sensor chamber, and a light detector configured to detect light from the light source that has been scattered by smoke within the sensor chamber.

7. An optical smoke detector according to claim 6, wherein the light source is a light-emitting diode.

8. An optical smoke detector according to claim 6, wherein the at least one component includes one or both of the light source and the light detector.

9. A method of cleaning an optical smoke detector comprising generating oscillations using ultrasonic vibrations to dislodge accumulated particulate matter from at least one component of the smoke detector.

10. A method according to claim 9, wherein the at least one component includes at least one wall of a housing of the smoke detector that defines part of a sensor chamber or a labyrinth of the smoke detector.

11. A method according to claim 9, wherein the component includes one or both of a light source and a light detector of the smoke detector.

12. A method according to any of claim 9, comprising generating the oscillations periodically.

13. A method according to claim 9, comprising generating the oscillations in response to a detected or estimated degree of fouling exceeding a threshold value.

Description

DRAWING DESCRIPTION

[0022] FIG. 1 depicts a smoke detector in an example embodiment.

DETAILED DESCRIPTION

[0023] An optical smoke detector 1 is shown in FIG. 1.

[0024] The smoke detector 1 comprises a housing 2 that defines a sensor chamber and a labyrinth. The housing 2 in this embodiment is formed from a plastic material in two parts that can be disassembled from one another. The labyrinth fluidly connects the sensor chamber to an ambient environment surrounding the smoke detector 1, so as to permit air to move freely between the sensor chamber and the ambient environment. However, the labyrinth is configured to prevent light from the external environment from entering the sensor chamber, i.e. such that there is no unimpeded straight-line path between the ambient environment and the sensor chamber.

[0025] The smoke detector 1 further comprises a controller 3, a light source and a light detector. The controller 3 may be an integrated within the housing 2, or may be external to the housing, for example as part of a centralised controller. The light source in this embodiment comprises an LED and is configured to emit light in the infra-red spectrum (wavelengths of 700 nm to 1 mm). The light detector in this embodiment comprises a photodiode receptor sensitive to at least the light emitted by the light source.

[0026] The light source is configured to emit a beam of light into the sensor chamber, and the light detector is configured to detect light from the beam of light scattered within the sensor chamber. However, the light source and light detector are configured such that light from the light source cannot directly hit the light detector. For example, the housing 2 may comprise a wall between the light source and the light detector that blocks direct transmission of light between the light source and the light detector.

[0027] The internal walls of the sensor chamber are either formed from or coated with a black material, so as to minimise reflection of light by the walls from the emitter to the detector.

[0028] The controller 3 is configured to cause the light source to emit a pulsed, light beam into the sensor chamber and to detect how much light is received by the light detector. When no smoke is present within the sensor chamber, the light beam is absorbed by the black material. When smoke is present within the chamber, the beam is scattered by the smoke particles. The degree of scattering is proportional to the quantity of smoke within the sensor chamber. Thus, the controller 3 can measure the quantity of smoke present within the sensor chamber.

[0029] Over time, various contaminants in the air, such as dust, soot from combustion engines, and other pollutants will accumulate on the walls of the labyrinth and the sensor chamber. These increase the amount of light reflected by the walls, which means that external light may reflect into the chamber via the walls of the labyrinth or that light from the light source may reflect off of the walls of the sensor chamber. Thus light may be detected by the light detector, even when no smoke is present within the sensor chamber.

[0030] The controller 3 of the smoke detector 1 comprises a compensation algorithm that automatically compensates for this type of fouling. The compensation algorithm may monitor base levels of light over an extended period of time, and determine a degree of fouling based on this level. The compensation algorithm may alter a sensitivity of the smoke detector 1 based on the degree of fouling.

[0031] The smoke detector 1 is further provided with an ultrasonic transducer 4. The ultrasonic transducer is configured to cause oscillations in the housing 2, and particularly in the walls of the sensor chamber and/or the labyrinth. The purpose of these oscillations is to dislodge accumulated particles fouling these walls.

[0032] The ultrasonic transducer 4 is activated by the controller 3 of the smoke detector 1. It may be actuated periodically. For example, the transducer 4 may be activated monthly, weekly, daily, or based upon any other periodic cycle. Alternatively, or additionally, it may be actuated based on an estimated or detected degree of fouling, such as determined by the compensation algorithm.

[0033] By automatically cleaning the smoke detector 1, manual maintenance can be reduced as the smoke detector 1 can remove a degree of fouling automatically. Indeed, in some embodiments, the compensation algorithm may no longer be required and thus may be omitted. By using ultrasonic vibrations, the cleaning of the smoke detector 1 will not disturb nearby people.

[0034] Whilst it is primarily envisaged that the ultrasonic transducer 4 will be used to dislodge accumulated particulate matter from the walls of the housing 2, in other embodiments the ultrasonic transducer 4 may be used to dislodge accumulated particulate matter from any component within the smoke detector 1 that requires cleaning. For example, the ultrasonic transducer 4 may be configured to generate oscillations to dislodge accumulated particulate matter from the light sensor and/or the light detector.

[0035] Whilst the ultrasonic transducer 4 has been described within the context of an optical smoke detector 1 having a housing, the principles discussed herein may be applied to a chamberless optical smoke detector. Chamberless optical smoke detectors operate on the same light-scattering principle as the described smoke detector 1, but have no sensor chamber and instead include additional sensors to automatically compensate for the presence of ambient light. In the context of a chamberless optical smoke detector, the ultrasonic transducer 4 may be arragned to dislodge accumulated particulate matter from the light sensor and/or light emitter, which are particularly prone to fouling due to the absence of a housing.

[0036] Furthermore, whilst the ultrasonic transducer 4 has been described within the context of a light-scattering optical smoke detector 1, it may also be employed for cleaning other types of optical smoke detectors, such as an optical beam smoke detector, which operates based on a principle of light obscuration (either by absorption or scattering of the light). In yet further examples, ultrasonic transducers may be used as described above to clean other types of smoke detector.