GB2620007A

GB2620007A - Optical detection devices

Info

Publication number: GB2620007A
Application number: GB2305944.7A
Authority: GB
Inventors: Mark Wheatcroft Peter
Original assignee: AVANSYS LLP
Current assignee: AVANSYS LLP
Priority date: 2022-04-28
Filing date: 2023-04-24
Publication date: 2023-12-27
Also published as: GB202206168D0; GB202305944D0

Abstract

A cleaning system for an optical detection or viewing device (11, fig. 4) which has a lens or window (12, fig. 5) which must be kept clean to enable the device to visually detect a predetermined operating or environmental condition or view a scene. The system has a housing (16, fig. 5) with a front cover 15 with an aperture (13, fig. 5) through which the device operates via the lens or window. The front cover also incorporates a series of jets 17 disposed around the aperture through which a stream of compressed air is supplied to each jet via a system of spiralling passages 18a-18h built into the front cover and inclined relative to periphery of the lens or window to provide an even distribution of swirling air flow down and across the lens or window to clean unwanted detritus therefrom which might otherwise accumulate and render the device ineffective. The front cover is of a multi-layer construction with the spiralling passages and jets formed in the rear of one of the layers of the front cover and being sealed by a further layer of the front cover extending over the rear of this one layer. The system may include feedback means connected to a fire alarm system.

Description

OPTICAL DETECTION DEVICES

This invention relates to optical devices and, in particular, to arrangements for cleaning such devices to ensure their correct and continued operation.

Although the invention will be described below in relation to a fire alarm system it will be appreciated that the invention is applicable to a wide range of applications where an optical device is located in an environment where the device is likely to be negatively impacted by dust or other detritus which will impede its operation.

One area of use for the present invention is for the detection of fire in recycling and waste disposal plants which are very dusty and dirty environments, but they also carry high risk of fire and automatic fire detection means are essential to provide early warning of fire.

One method of automatic fire detection involves the use of optical flame/radiant energy or video-based fire detectors. These detection devices are located behind lenses or window which must be kept clean in order to maintain a clear sight of the target area and therefore effective detection. The lenses or windows may be recessed from the front face of the device to, for example, retain the lens or window in position and protect it from damage.

Fire detectors are life safety devices and must have their constructions certified by the relevant authorities which is an expensive and lengthy process. Unless cleaning features are incorporated in the design prior to certification, any cleaning device or system must be able to be fitted to the detector without requiring any modification to the detector itself and in such a manner that the operation of the detector is in no way impeded and the entire surface of the lens or window, whether recessed or otherwise, is cleaned with a high degree of effectiveness consistent with the critical nature of the function of the detector.

Although various air cleaning devices for optical detection devices are in existence which use an air nozzle mounted such that a jet of compressed air may be released through the nozzle onto the lens of the detection device to clean the lens, these arrangements are not practical in the application described for one or more of the following reasons: 1 the air cleaning device will obstruct the view of the detection device thereby impeding its operation, 2 the design features of the air cleaning device would need to form an integral part of the design of the detection device itself, whereas no changes to the certified design of the device are possible, and 3 the cleaning effect produced at the surface of the lens would not produce an adequate cleaning effect across the whole surface of the lens or window, especially if the lens or window is recessed.

These existing devices also incorporate no feedback means to provide evidence that the detection device is in a functional condition.

The existing devices also do not incorporate control means whereby the flow of air may be controlled by electrical impulses all contained within a neat compact housing.

The invention is also applicable to cleaning the lens of devices in the form of cameras used in, for example, a monitoring or surveillance system.

It is therefore an object of the present invention to provide a cleaning system for an optical detection or viewing device which addresses the above difficulties and can be retro fitted to a detecting or viewing device without requiring any modifications to the device itself.

Thus according to the present invention there is provided a cleaning system for an optical detection or viewing device which has a lens or window which must be kept clean to enable the device to visually detect a predetermined operating or environmental condition or view a scene, the system having a housing with a front cover with an aperture through which the device operates via the lens or window, the front cover also incorporating a series of jets disposed around the aperture through which a stream of compressed air is supplied to each jet via a system of spiralling passages built into the front cover and inclined relative to the periphery of the lens or window to provide an even distribution of swirling air flow directed down and across the face of the lens or window to clean unwanted detritus therefrom which might otherwise accumulate and render the device ineffective, the front cover being of a multi-layer construction with the spiralling passages and jets formed in the rear of one of the layers of the front cover and being sealed by a further layer of the front cover extending over the rear of said one layer.

The above cleaning system can be used with a standard certified detecting or viewing device without requiring any modification of the device itself. It is also particularly effective in cleaning lenses or windows which are recessed within the front of the housing.

Air at atmospheric pressure may be mixed with the compressed air prior to entering the spiralling passages to amplify the airflow further adding to the effectiveness of the swirling action of the air while at the same time requiring a minimal volume of compressed air.

An electrically operated air flow control valve may be provided to control the supply of compressed air into a supply chamber formed in the front cover, the compressed air flowing from the supply chamber into a main passage prior to entering the spiralling passages and thus drawing the atmospheric air into the main passage and thus into the spiralling passages.

The system may be provided with a feedback means whereby operation of the system can be monitored and any failure of the air supply is indicated.

The feedback means may utilise a compressed air pressure level sensor or air flow rate sensor which operates to provide a signal indicative as to whether the cleaning system has operated.

The air flow control valve and for the air pressure or air flow rate sensors may be mounted on the rear of the front cover.

The feedback means may be connected to a fire alarm system such that defects in operation of the cleaning system can be centrally enunciated by the fire alarm system.

The electrical signal to the air control valve may be derived via an interface connected to the fire alarm system, the fire alarm system being programmed to issue electrical signals to control the frequency and timing of the electrical signal to the air control valve and hence the cleaning operations.

The inside of the front cover may carry a locating formation which cooperates with the device to ensure that the device is correctly aligned and located with respect to the aperture and air jets of the system.

The aperture may have outer edges which are chamfered to ensure that the field of view of the device is not obstructed by the cover.

The housing may contain the optical device, air jets and passages, feedback device and interfacing for a fire alarm system and may be installed in its operational position by the means of a single fixing bracket.

The feedback means may have a visual indicator of the operation of the air jets.

The invention also provides a fire alarm system in which a fire detection device has a lens or window cleaned by a cleaning system as described above.

The invention further provides a monitoring or surveillance system in which a camera has a lens or window cleaned by a cleaning system as described above.

The invention also provides a cleaning system for an optical detection or viewing device which has a lens or window which must be kept clean to enable the device to visually detect a predetermined operating or environmental condition or view a scene, the system having a housing with a front cover with an aperture through which the device operates via the lens or window, the front cover also incorporating a series of jets disposed around the aperture through which a stream of compressed air is supplied to each jet via a system of spiralling passages built into the front cover and inclined relative to the periphery of the lens or window to provide an even distribution of swirling air flow across the lens or window to clean unwanted detritus therefrom which might otherwise accumulate and render the device ineffective, the aperture in the front cover having outer edges which are chamfered to ensure that the field of view of the device through the aperture is not obstructed by the cover.

The invention further provides a cleaning system for an optical detection or viewing device which has a lens or window which must be kept clean to enable the device to visually detect a predetermined operating or environmental condition or view a scene, the system having a housing with a front cover with an aperture through which the device operates via the lens or window, the front cover also incorporating a series of jets disposed around the aperture through which a stream of compressed air is supplied to each jet via a system of spiralling passages inclined relative to the periphery of the lens or window to provide an even distribution of swirling air directed down and across the face of the lens or window to clean unwanted detritus therefrom which might otherwise accumulate and render the device ineffective, The present invention will now be described, by way of example only with reference to the accompanying drawings in which:-Figure 1 shows a front view of a housing of a cleaning system in accordance with the present invention for an optical detecting or viewing device; Figure 2 shows a rear perspective view of the housing of Figure 1; Figure 3 shows an end view in the direction of arrow X of Figure 1; Figure 4 shows a front view of the housing of Figure 1 with its front cover removed; Figure 5 shows a section on the line A-A of Figure 1; Figure 5a shows on a larger scale the detail of the bottom left-hand corner of Figure 5; Figure 6 shows a section on the line B-B of Figure 3 showing the internal air passages of the cleaning system; Figure 7 shows on a larger scale the air jet detail on the left-hand side of the detection window of Figure 5; Figure 8 shows a simplified diagram of the interconnection of the main components of the cleaning system; Figure 9 shows a perspective partly exploded view of the cleaning system showing the sandwich construction of the housing front cover; Figure 10 shows details of the air jet construction surrounding the aperture in the front cover, and Figure 11 shows a rear exploded view of the front cover which supports an air flow control valve and an air pressure sensor.

Referring to the drawings, Figure 5 shows a cross section through a cleaning system 10 in accordance with the present invention for a flame detection device 11 shown in outline section only. Typically, such detection devices operate in the infrared or ultraviolet spectrum and are designed to detect a spark or a characteristic flicker of a flame and provide automatic detection of fire in environments where common types of smoke detector would be prone to unacceptably high rates of false alarm.

The detection device 11 has a window 12 and views its operating scene through an aperture 13 in a front cover 15 of a housing 16. As can be seen from Figures 5 and 10 the viewing angle V of the detection device is 90 degrees and it is important that this viewing angle is not obstructed. This is ensured by the chamfered outer edge 13a of aperture 13 (see Figure 7). In accordance with the present invention the window 12 is provided with a controlled stream of compressed air channelled across the face of the window through a series of jets 17 disposed around the periphery of the aperture 13 (see Figure 10) to provide a swirling action of the air across the window 12 to clean unwanted detritus which might otherwise accumulate and render the device ineffective.

The air jets 17 are each provided with compressed air via a respective curved spiralling passage 18a to 18h of the form shown in Figure 6. The individual spiralling passages 18a to 18h are fed by a main passage 19 supplied with compressed air via a supply chamber 20 which is connected with an external supply of compressed air as will be described below. The curvature and cross-section of passages 19 and 18a to 18h is chosen to ensure a balanced supply of compressed air to jets 17 so that the required swirling action of the air across window 12 is achieved.

These passages 19, 18a to 18h, jets 17 and supply chamber 20 are milled or otherwise formed in the inner surface of front cover 15 which has a multi-layer sandwich construction as shown in Figure 5A which shows on a larger scale the lower left-hand corner of Figure 5. The passages 18a to 18h formed in cover 15 are sealed by a thinner inner plate 15b and an intermediate sealing gasket or adhesive layer 15c (see Figures 9 and 11). A further outer decal layer 15d is applied to cover 15. The cover 15 is secured in position on flanges 16c of the housing 16 by fixings 16d.

The jets 17 direct their air flow at an angle R, typically 15 degrees to the perpendicular to the periphery of the aperture 13. The jets are also directed downwardly towards the window 12 at an angle D (see Figure 7) typically 24 degrees. This downward direction of the air jets is achieved by angled surfaces 17a which deflect the air travelling towards each jet 17 prior to the air emerging from the jet. Air jets 17 are thus able to provide the required swirling action of the air (see arrows Z in Figure 6) across the window 12 to clean unwanted detritus which might otherwise accumulate and render the device ineffective without the front cover 15 encroaching on the 90 degree viewing angle of the device 11.

The passages cut or otherwise formed into the inner surface of the front plate 15 are also connected with atmospheric air supply passages 21 which emerge through the front cover 15 via slots 22. An air pressure or air flow rate sensor 50 carried on the inside of inner plate 15b is connected with a passage 23 connected to supply chamber 20 as will be described in more detail below.

Air at atmospheric pressure is drawn into the cleaning system via slots 22 and passages 21 by the compressed air supplied to chamber 20 so that the airflow supplied to passages 19, 18a to 18h and jets 17 is amplified thus further adding to the effectiveness of what is a 360-degree evenly distributed swirling action across window 12 while at the same time requiring a minimal volume of compressed air.

The rear of housing 16 has provision for an external compressed air connection supplied from, for example, an external compressed air feed, which passes through gland 24 in the housing is connected within housing 16 to an air flow control valve 25 supported from the rear of front cover 15 using fixing holes 15e (see Figures 6 and 11) and which delivers compressed air to supply chamber 20 when valve 25 is opened by a solenoid 26 which is carried by and controls valve 25.

External electrical cable glands 27 are provided on housing 16 via which the electrical cable connections to device 11 and solenoid 26 are provided and various input and output signals are passed to and from the components of the cleaning system.

As shown in Figure 4, the interior of the housing 16 is divided into two sections flame detector chamber 16a and wiring chamber 16b with the detection device 11 mounted in one section 16a via fixing studs 11g and an external interface block 28 and connector block 29 which are mounted on a DIN rail 30 secured in section 16b.

The cleaning system of the present invention is connected to an external control and monitoring unit such as the fire alarm system (see item 36 in Figure 8) which provides control signals to Interface block 28 and flame detector/camera device 11. The system is also connected externally to a 24-volt source 35 via line 34. Cable glands 27 allow cables to enter wiring chamber 16b while maintaining the environmental integrity of the enclosure.

Solenoid valve 25 is connected to 24-volt source 35 via line 34 via interface block 28 and via control line 37. Interface block 28 is operated at predetermined intervals by an external control and monitoring unit such as the fire alarm system to operate the solenoid of air control valve 25 via connector block 29 to provide the air blast to clean window 12 via jets 17.

Pressure sensor 50 mounted on the rear of front cover 15 via fixing holes 15f monitors pressure in passage 23 connected with supply chamber 20 and its output is fed to interface block 28 via feedback line 38. Air pressure in passage 23 indicates that valve 25 is open and this is relayed via interface block 28 so that the operation of the cleaning system can be centrally enunciated by an external control and monitoring unit such as a fire alarm system.

Similarly, in an alternative configuration, the pressure sensor 50 may be replaced by a flow rate sensor inserted between supply chamber 20 and main passage 19 which provides feedback indication that there is positive air flow through air jets 17. This alternative air flow rate sensor is also connected to the external fire alarm system via interface block 28 so that the operation of the cleaning system can be centrally enunciated.

By connecting both input and output elements of the system through interface block 28 which in turn connects to fire alarm system 36 or other external control and monitoring unit it is thereby possible for correct functioning of the air jet cleaning system to be monitored externally.

The front of cover is provided with LED lights 41 one of which is illuminated when a fire is detected by device 11 and one of which indicates that the cleaning system is powered on and functioning.

To ensure that the jets 17 are correctly aligned with and located relative to the window 12 when the front cover is secured in position on the housing 16 the inside of the front cover is provided with an annular locating formation 40 which cooperates with the annular raised portion lla of the device 11 surrounding the window to ensure correct alignment.

As can be seen from Figures 2, 3, and 5 the housing 16 can be conveniently mounted in its operating position via a single bracket 31 for pivoting about horizontal and vertical axes.

Figure 8 shows a simplified diagram of the interconnection of the main components of the cleaning system. The window 12 of detecting device 11 is supplied with pressurised air from a source of pressurised air 32 via external connector 24 and air line 33 which includes solenoid-controlled valve via 25, air flow or pressure sensor 50 and jets 17.

The solenoid valve 25 is opened to clean the window by a signal from the connected alarm system 36 via interface block 28 and control line 37 at predetermined intervals. Any flame sensing signal from detecting device 11 is notified to system 36 via line 39.

As will be appreciated, although the detection device and associate cleaning system has been described above as being connected with an external fire alarm system, this being the appropriate set up for larger systems where multiple detection devices and cleaning systems can conveniently be connected to a single external alarm system, the cleaning system could be applied to a single detection device and cleaning system with the housing 16 housing the main control function which issues the signals to initiate cleaning of the detector and processes the signals coming from the system to initiate the appropriate alarm signals from an audible and/or visual warning device housed in or on the housing.

Also, as 1 previously indicated, the invention is applicable to cleaning the lens of an optical device in the form of a camera used in, for example, a monitoring or surveillance system.

As will be clear from the above, the cleaning system of the present invention can be used with existing certified detecting or viewing devices without requiring any modification of the device itself and in such a manner that it does not interfere with the field of view of the device even when the device has, for example, an annular raised portion 11a within which the window 12 is recessed. The cleaning system provides air flow across window 12 despite the raised portion lla of the device 11 (see Figure 7) which surrounds the window.

Claims

CLAIMS1. A cleaning system for an optical detection or viewing device which has a lens or window which must be kept clean to enable the device to visually detect a predetermined operating or environmental condition or view a scene, the system having a housing with a front cover with an aperture through which the device operates via the lens or window, the front cover also incorporating a series of jets disposed around the aperture through which a stream of compressed air is supplied to each jet via a system of spiralling passages built into the front cover and inclined relative to periphery of the lens or window to provide an even distribution of swirling air flow directed down and across the face of the lens or window to clean unwanted detritus therefrom which might otherwise accumulate and render the device ineffective, the front cover being of a multi-layer construction with the spiralling passages and jets formed in the rear of one of the layers of the front cover and being sealed by a further layer of the front cover extending over the rear of said one layer.
2 A system according to claim 1 in which air at atmospheric pressure is mixed with the compressed air prior to entering the spiralling passages to amplify the airflow further adding to the effectiveness of the swirling action of the air while at the same time requiring a minimal volume of compressed air.
3 A system according to claim 2 in which an electrically operated air flow control valve is provided to control the supply of compressed air into a supply chamber formed in the front cover, the compressed air flowing from the supply chamber into a main passage prior to entering the spiralling passages and thus drawing the atmospheric air into the main passage and thus into the spiralling passages.
4 A system according to any one of claims 1 to 4 provided with a feedback means whereby operation of the system can be monitored and any failure of the air supply is indicated.
A system according to claim 4 in which the feedback means utilises a compressed air pressure level sensor or air flow rate sensor which operates to provide a signal indicative as to whether the cleaning system has operated.
6. A system according to claim 3 and 5 in which the air flow control valve and /or the air pressure or air flow rate sensors are mounted on the rear of the front cover.
7 A system according to claims 4 or 5 in which the feedback means is connected to a fire alarm system such that defects in operation of the cleaning system can be centrally enunciated by the fire alarm system.
8 A system according to claims 3 and 7 in which the electrical signal to the air control valve is derived via an interface connected to the fire alarm system, the fire alarm system being programmed to issue electrical signals to control the frequency and timing of the electrical signal to the air control and hence the cleaning operations.
9 A system according to any one of claims 1 to 8 in which the inside of the front cover carries a locating formation which cooperates with the device to ensure that the device is correctly aligned and located with respect to the aperture and air jets of the system.
10.A system according to ay one of claims 1 to 9 in which the aperture has outer edges which are chamfered to ensure that the field of view of the device through the aperture is not obstructed by the cover.
11.A system according to any one of claims 1 to 10 in which the housing contains the optical device, air jets and passages, feedback device and interfacing for a fire alarm system and can be installed in its operational position by the means of a single fixing bracket.
12.A system according to claim 4 in which the feedback means has a visual indicator of the operation of the air jets.
13.A fire alarm system in which a fire detection device has a lens or window cleaned by a cleaning system according to any one of claims 1 to 12.
14.A monitoring or surveillance system in which a camera has a lens or window cleaned by a cleaning system according to any one of claims 1 to 12.
15.A cleaning system for an optical detection or viewing device which has a lens or window which must be kept clean to enable the device to visually detect a predetermined operating or environmental condition or view a scene, the system having a housing with a front cover with an aperture through which the device operates via the lens or window, the front cover also incorporating a series of jets disposed around the aperture through which a stream of compressed air is supplied to each jet via a system of spiralling passages built into the front cover and inclined relative to periphery of the lens or window to provide an even distribution of swirling air flow across the lens or window to clean unwanted detritus therefrom which might otherwise accumulate and render the device ineffective, the aperture in the front cover having outer edges which are chamfered to ensure that the field of view of the device through the aperture is not obstructed by the cover.