An air treatment apparatus, and a method of cleaning a filter of an air treatment apparatus

Abstract

An air treatment apparatus 10 comprising a filter 26 with first and second sides (40, 42 - figure 12) and a UV-C source 22 arranged to direct light onto both sides of the filter 26. Also defines a met

Description

The invention relates to an air treatment apparatus, and a method of cleaning a filter of an air treatment apparatus. Some known air treatment apparatus have a primary air treatment means such as a HEPA filter or a UV-C filter, and a pre-filter arranged before the primary air treatment means so as to remove dust, debris and larger particulates from the air before the air reaches the primary air treatment means, so as to increase the operational efficiency of the primary air treatment means. However, a pre-filter can accumulate particles, and become a health and safety risk itself. Various methods of cleaning the pre-filter are known. However, the known methods of cleaning the pre-filter have drawbacks. US8007574B2 discloses a wall mounted air conditioning unit. 1 The unit 1 has an air filter 5 arranged behind an air suction inlet 210. To prevent dust build-up on the air filter 5, a mechanical filter cleaning assembly 300 uses brushes to sweep dust from at least part of both sides of the filter 5. A small ultraviolet (UV) lamp 410 in the ultraviolet irradiation unit 400, is positioned on the side of the air filter 5 remote from the air suction inlet 210, and is directed towards the air filter 5. A reflector 230 is positioned on the side of the air filter 5 remote from the UV lamp 410. UV light must pass through the material of the air filter 5, and any particulate build-up, to be reflected by reflector 230 and irradiate the second side of the air filter 5 adjacent the air suction inlet 210. The UV light source 410 ensures particles trapped by the primary air cleaning method, the air filter 5, are not biologically hazardous through human contact / exposure. The UV light source 410 is not designed to irradiate all air that passes through the unit. US20060057020A1 discloses an air cleaning apparatus 51 having a chamber 52 with a filter (or a pre-filter in the context of the other filter, the HEP A filter, in this apparatus) 55 across an inlet at the base of the chamber 52, and a HEPA filter 56 across its outlet at the top of the chamber. A plurality of UV-C lamps 54 are located within the chamber 52 between the filter 55 and the HEPA filter 56. This layout means both filters are irradiated upon their internally facing surfaces, and may not penetrate to outer surfaces of such filters. The author of US20060057020A1 suggests that use of a filter material with a certain degree of UV-C transmissibility would help irradiate the whole filter. However, it is also acknowledged by the author that the types of particulate materials that are captured by such a filter are not typically UV-C transparent. Germicidal UV-C has a wavelength of 253.4 nanometres, It does not penetrate anywhere near as well as visible light wavelengths, as discussed in more detail later in this application. As the filter 55 gets dirty, it will block more of the light from reaching the dirty side of the filter. As such, UV transmission would be ineffective on a dirty filter (which has a greater requirement to be sanitised), whereas UV transmission may only be effective on a clean filter (which has less of a requirement to be sanitised). US5225167A discloses a room air sterilizer 10. Air enters the return air grille 16, flows through an expandable sleeve section 17 and through a prefilter 18. Facing this pre-filter 18 is an UV sterilizer lamp 19. The UV lamp 19 projects UV light onto the side of the pre-filter 18 nearest the return air grille 16, i.e. the dirtier side of the pre-filter 18. Air is then channelled by a fan 20 through a fan baffle 21 towards an outflow port 22 comprising a large curved HEPA filter 23 designed to trap airborne particulate matter. Another UV sterilizer lamp 25 irradiates an inside surface of the HEPA filter 23. The room air sterilizer 10 does not disclose the radiation penetrating pre-filter 18 or HEPA filter 23, so as to ensure both sides of the filters are cleaned. The UV lamps 19 and 25 are additional components with respect to the primary sanitising mechanism system, the HEPA filter 23, that require significant power. Increasing the intensity of the UV lamps 19 and 25 so that more of it penetrates a given filter, so as to effectively clean both sides of the filter, can place an unacceptable power demand on a room air sterilizer 10. Moreover, UV transmission would be ineffective on a dirty filter. Due to its position, the UV sterilizer lamp 19 is exposed to dust, potentially reducing its longevity and effectiveness. US5891399 discloses a cleaning arrangement 1 in which air is drawn into a housing means 2 through a perforated grate 10 and a pre-filter 3. The outlet (cleaner) side of the pre-filter 3 is irradiated by UV radiation sources [4n] as it passes through a main chamber of the housing means 2. Once through this reactor section, the air passes through a fan 5 and a post-filter 6, preferably a bioclimatic filter, and finally outlet air 13 passes through a filter grid 14. The casing 2 of the cleaning arrangement 1 can be opened mechanically when a room is unoccupied to provide a dosage of UV Sterilisation to surfaces and air outside the device. Again, the UV radiation sources 4n only irradiating one side of each filter, leading to the same drawbacks. An aim of the present invention is to provide an improved, or at least an alternative, air treatment apparatus. According to a first embodiment of the invention there is provided an air treatment apparatus in accordance with Claim 1. In that way, UVC light is directed from the UVC source to both sides of the filter in a relatively unobstructed manner. A different, separate, aim of the present invention is to provide an improved, or at least an alternative, method of cleaning a filter of an air treatment apparatus. According to a second embodiment of the invention there is provided a method of cleaning a filter of an air treatment apparatus in accordance with Claim 11. Other optional and preferred features of an embodiment of the invention are set out in the dependent claims and / or the description, below. It will be appreciated that the features of each of the independent claims can be combined in any complimentary manner with one or more features of another independent claim, any one or more of the dependent claims, and / or with one or more features of the description, where such a combination of features would provide a working embodiment of the invention. A pre-filter for an air treatment apparatus, an air treatment apparatus, and a method of cleaning a pre-filter of an air treatment apparatus in accordance with the embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which, Figure 1 is a perspective view of an UV-C air treatment apparatus in accordance with the invention, Figure 2 is a perspective view of part of an UV-C air treatment apparatus in accordance with the invention, Figure 3 is a perspective view, partially in cut away, of a lower part of an UV-C air treatment apparatus in accordance with the invention, Figure 4 is a schematic front view of the UV-C air treatment apparatus of Figure 2, taken in the direction of arrow IV in Figure 2, Figure 5 is a schematic side view of the UV-C air treatment apparatus of Figure 2, viewed in cross section at line V-V in Figure 4, Figure 6 is a schematic top view of the UV-C air treatment apparatus of Figure 2, viewed in cross section at line VI-VI in Figure 4, Figure 7 is a schematic perspective view of a fan, Figure 8 to 10 show air flow paths, Figure 8 is a perspective view of the UV-C air treatment apparatus of Figure 2, showing air flow paths, Figure 9 shows the air flow paths through the UV-C air treatment apparatus of Figure 6, Figure 10 shows the air flow paths through the UV-C air treatment apparatus of Figure 5, Figure 11 shows a light reflection path through the UV-C air treatment apparatus of Figure 6, Figure 12 shows light reflection paths through the UV-C air treatment apparatus of Figure 6, Figure 1 shows an air treatment apparatus 10. The air treatment apparatus 10 comprises an outer casing 12 and a vent grille 14. Referring to Figures 2, 5 and 6, the outer casing 12 has six sides, a top 12A, a base 12B, a first side 12C, a second side 12D, a front side 12E, and a rear side 12F. The outer casing 12 comprises air inlet vents 16 in the first side 12C and the second side 12D, as shown in Figures 3 and 6. The outer casing 12 also comprises air exit vents 18 in the top 12A as shown in Figure 2. Referring to Figures 3 to 6, air treatment apparatus 10 comprises a primary air sanitising mechanism in the form of a reflective aluminium reactor 20 within the outer casing 12, and a plurality of UV Lamps 22 are arranged within the reactor 20. A wall of the reactor 20 has a small window 24. The window 24 is made of a material that allows UV-C radiation transmission, but that also is not degraded by UV radiation, whilst blocking airflow. Quartz glass is used in one preferred embodiment because it is an excellent transmitter of UV-C radiation. Most glasses are not. In other preferred embodiments, several alternatives can be used, e.g. fused silica. The air treatment apparatus 10 comprises a pre-filter 26 arranged within the casing 12 to minimise dust accumulation in the reactor 20. The pre-filter 26 is a pleated g4 type disposable dust pre-filter 26. The pleats increase the overall surface area of the pre-filter 26 for the available filter installation size, increasing its lifespan. Moreover, the pleats of the prefilter 26 are oriented vertically so as to reduce the surface geometry of the pre-filter obstructing light paths from the quartz window 24. Whilst a g4 type filter is used in this embodiment, because it is the preferred pre-filter type in many applications due to its low cost and simple replacement, in other embodiments, the air treatment apparatus 10 could use a wide variety of filter materials, including washable materials, or materials capable of removing finer airborne particles for example. The air treatment apparatus 10 comprises baffle plates 28, adjacent each air inlet vent 16, that prevent UV-C radiation from escaping the air inlet vents 16. The air treatment apparatus 10 comprises reflectors 30, positioned on both sides of the window 24, to direct light passing through the window towards the near side of the prefilter 26 (i.e. the upstream side, which in an untreated pre-filter would be the dirtier side). The air treatment apparatus 10 comprises a fan 32 arranged downstream of the prefilter 26, and upstream of the reactor 20. Air can only reach the reactor 20 by passing through the fan 32. The fan 32 can have light reflective surfaces. Conveniently, the fan 32 can be a backward curved fan, which optimises the direction of air flow through the fan. Figure 7 shows a 32 fan that can be employed. The side of the fan 32 pointing uppermost in Figure 7 is configured to face the front side 12E of the casing 12. It is preferable that reflected light from the reactor 20 has a direct line of sight of front side 12E of the casing 12 through fan 32. Without a direct line of sight, the power reaching the prefilter 26 would be significantly reduced by both of the following factors: Power loss over distance. Without a direct route the distance the radiation travels is increased. Power loss on reflection. Each reflection required to transmit the radiation reduces its power. On some low reflectivity surfaces such as fan blades this reduction could be greater than 90° o per reflection. Avoiding these power losses through the use of direct line of sight light paths with minimum reflections is therefore desirable. The inner surface if the front side 12E of the casing 12 is reflective so as to reflect light escaping through the fan back onto the downstream side of the prefilter 26. The air treatment apparatus 10 comprises a suitable baffle arrangement 34, shown purely schematically for conciseness, for restricting light from the reactor 20 from escaping through the exit vents 18. In use, referring to Figures 8 and 9, air is drawn in through inlet vents 16, and flows around baffling plates 28, through the prefilter 26, as shown by the arrows. After the air passes through the pre-filter 26, it is drawn through the fan 32 into the main reactor chamber 20, as shown by the arrows. Referring to Figure 10, once the air has passed through the reactor 20, it exits through the exit vents 18, as shown by the arrows. The baffle arrangement 34 ensures UV-C light escape is kept to safe levels. Importantly, referring to Figure 11, the small quartz glass window 24 allows a small constant dose of radiation to escape the main reactor 20 and to be directed, via the reflectors 30 onto the upstream side 40 of the prefilter 26, as shown by rays. Also importantly, referring to Figure 12, a small dose of UV-C radiation is able to escape through the fan 32, and that radiation is then channelled to the downstream side 42 of the pre-filter 26 by means of the reflective surface of the front side 12E of the casing 12, as shown by rays. The arrangement provided by the air treatment apparatus 10 of the invention ensures both faces 40, 42 of the pre-filter 26 receive a constant, low dosage of UV-C radiation, as shown in Figure 12, thereby reducing any potential build-up of harmful micro-organisms; thus making the changing of said filter 26 a safer manual operation. The type of fan 32 used in the air treatment apparatus 10 should as a minimum allow direct line of sight from the reactor internal surfaces through the impeller of the fan 32, to the reflective surface on the inside of the casing on the clean side of the filter. It should be noted that many bacteria are capable of surviving on surfaces for periods greater than 2 months when left untreated. For example, E-Coli strains can survive on dry inanimate surfaces for up to 16 months (A. Kramer, I. Schwebke and G. Kampf, "How long do nosocomial pathogens persist on inanimate surfaces? A systematic review", BMC Infectious Diseases, vol. 6, no. 1, 2006. Available at 10.1186 / 1471-2334-6-130, and https: / / www.ncbi.nlm.nih.gov / pmc / articles / PMC1564025 / ). Therefore, the dosages of radiation to both sides of the pre-filter 26 should be appropriate. In one embodiment, in use, the UV-C radiation energy that reaches the upstream side 40 of the pre-filter 26 is a minimum dose of 16J / m2 over a time period of 1 hour, and the UV-C radiation that reaches the downstream side 42 of the pre-filter is a minimum dose of 16J / m2 over a time period of 1 hour. In other embodiments, the downstream side 42 of the pre-filter receives a greater dose of UV-C than the upstream side 40. The above mentioned dosages meet the required dosage to achieve a safe 90% inactivation level of any potential bacteria on the surface 40 of the filter 26 within 1 hour., according to page 75 of Kowalski’s UGI Handbook (W. Kowalski, Ultraviolet Germicidal Irradiation Handbook. Berlin: Springer Berlin, 2014, p. 75. Also at https: / / books.google.co .uk / books?id=ReqUM XNGioC&lpg=PR9&ots=2LNbdzTR7a&dq=kowalski %20uv%20surface&lr&pg=PR4#v=onepage&q&f=false). An advantage of the air treatment apparatus 10 is that as debris lands on upstream side 40 of the pre-filter 26 that upstream side 40 is exposed to radiation from the UV-C source arranged on the same side of the pre-filter, even if dirt on the pre-filter has blocked UV-C from passing through the pre-filter. In known devices that are reliant on UV-C passing through a filter from the clean side to the dirty side, from the moment the device is first turned on, and as the filter accumulates dust and debris, the UV-C power that passes through (if it passes through at all in the first place) will start to reduce. The rate of this reduction will be dependent on the filter material / source power / source location, dust make up, dust levels and filter maintenance. In the air treatment apparatus 10, by directly releasing UV-C light from the reactor 20 through the quartz glass window 24, onto the upstream (dirtier) side 40 of the filter 26, as time passes, each new layer of debris is directly exposed to UV-C light without the risk of the UV-C to the surface 40 being blocked by the debris itself, or reduced by the preceding debris. Thus, the level of UV-C energy reaching new debris on the filter 26 will be relatively constant at the design level of the specific air treatment apparatus 10 mentioned above. It is advantageous that performance does not degrade as the upstream side of the filter 26 as it is covered by debris in use. This feature of the invention is important when a pre-filter 26 reaches the end of its life, when therefore the pre-filter 26 is due to be handled. It should be noted that, in practice, filter maintenance is very frequently neglected until the air treatment apparatus begins to underperform, at which point even optimally designed systems (if they exist) that rely on filter transparency may no longer be effectively sanitising new debris that lands on the filter. It should be appreciated that UV-C light in the germicidal range is unable to penetrate 0.1mm of the outer layer of human skin cells, as this short wavelength is very easily absorbed and converted into energy, (hence its germicidal effects). By analogy, even a very fine layer of dust on a filter will reduce its ability for the wavelengths of UV-C light to pass through it. Although the specific depth at which UV-C light is blocked completely on a given filter would be extremely difficult to quantify, there will be an increasing reduction as dust / debris levels increase. The longer the wavelength the greater the ability to pass through materials, which is why visible light may still penetrate. Another advantage of the air treatment apparatus 10 is that because it does not rely on UVC light passing through the pre-filter 26, so a range of materials can be employed to make the pre-filter. The range of materials may have different UV-C absorption values. In one embodiment, a material that is impermissible to UV-C may be employed. A wide range of types and sizes of fan 32 can be used to channel UV-C light from the course through the fan to the downstream side 42 of the pre-filter 26. The type of fan 32 in Figure 7 is just one example. The key point is that UV-C light can pass from the source through the fan 32 to the downstream side of the pre-filter when the vanes of the fan are rotating during operation. The light reflecting surfaces of the interior of the fan can help to maximise this incident light. The interior of the casing of the fan 32 can be made from the same reflective aluminium surfaces as the reactor 20. The invention also relates to a method of cleaning a filter of an air treatment apparatus 10 with one or more steps that correspond to one or more features of the air treatment apparatus 10. 5 In another embodiment the primary means of treating air that passes through the apparatus can be a HEPA filter. In another embodiment, not shown for conciseness, the filter has a gap or window in the air filtering material, and the UV-C light source is arranged to direct UVC light through the gap 10 or window in the filter. In such a case, baffles, reflectors or other means can be used to minimise UV-C escaping the apparatus. In the embodiment shown, the air treatment apparatus 10 is portable. The dimensions of the air treatment apparatus 10 may have a height of about 80 cm to 1 m, a width of about 40 cm to 50 15 cm, and a depth of about 40 cm to 50 cm. Also, the air treatment apparatus 10 has wheels or rollers 100, as shown in Figure 1. In other embodiments, not shown, the air treatment apparatus 10 can be fixed.

Claims

1. An air treatment apparatus comprising a UV-C light source and an air filter to remove dust and the like from the air that passes through it, the filter having a first side for unfiltered air and a second side for filtered air, the UV-C light source is arranged in a casing for UV-C treating air, characterised in that the casing comprises a casing window made of a material that allows UV-C radiation transmission, but that also is not degraded by UV-C radiation, whilst blocking airflow, the same UV-C light source is arranged to direct UV-C light to both the first side and the second side of the filter, and the apparatus is arranged to direct UV-C light through the casing window to one side of the filter.

2. An air treatment apparatus according to Claim 1, characterised in that the UVC light to both the first side and the second side of the filter is unobstructed by the air filtering material of the filter.

3. An air treatment apparatus according to Claim 1, characterised in that the UV-C light source is arranged to direct UVC light around the filter.

4. An air treatment apparatus according to Claim 3, characterised in that air filtering material of the filter has a filter gap or filter window, and the UV-C light source is arranged to direct UVC light through the filter gap or filter window.

5. An air treatment apparatus according to any preceding claim, characterised in that the apparatus is arranged to direct UVC light through the casing window to an upstream i.e. dirty side of the filter.

6. An air treatment apparatus according to any preceding claim, characterised in that the apparatus comprises a fan, and the apparatus is arranged to direct UVC light from the source through a fan to one side of the filter, preferably a downstream side of the filter.

7. An air treatment apparatus according to Claim 6, characterised in that the fan has a UV-C light reflective surface.

8. An air treatment apparatus according to Claim 6 or 7, characterised in that the UV source is arranged after the fan in terms of air flow path.

9. An air treatment apparatus according to any preceding claim, characterised in that the UV source is arranged after the filter in terms of air flow path.

10. An air treatment apparatus according to any preceding claim, characterised in that the UV-C light source is the primary means of treating, by sanitizing, the air that passes through the air treatment apparatus, and the filter is a pre-filter upstream of the UV-C light source.

11. A method of cleaning a filter of an air treatment apparatus, the method comprising the steps of, providing an air treatment apparatus comprising a UV-C light source arranged in a casing for UV-C treating air, the casing comprises a casing window made of a material that allows UV-C radiation transmission, but that also is not degraded by UV-C radiation, whilst blocking airflow, the air treatment apparatus also comprising a filter, the filter having a first side and a second side, characterised by arranging the UV-C light source to direct UVC lightto both the first side and the second side of the filter and through the casing window to one side of the filter.12 11 24

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