SE1950823A1

SE1950823A1 - Air purification device

Info

Publication number: SE1950823A1
Application number: SE1950823A
Authority: SE
Inventors: Attila Fodor; Emil Helin; Lars Wettre; Lena Nilevi
Original assignee: Cabinair Sweden Ab
Priority date: 2019-06-28
Filing date: 2019-06-28
Publication date: 2020-12-29
Also published as: CN114258324B; WO2020263171A1; EP3990191A4; SE544046C2; CN114258324A; EP3990191A1

Abstract

An air purification device for separating airborne particles from a flow of air is disclosed. The air purification device comprises an emitter electrode, and a filter medium arranged to attract at least a subset of the airborne particles. The filter medium comprises a conductive material. Furthermore, the emitter electrode and the filter medium comprising the conductive material are so arranged as to produce an ionizing volume for charging airborne particles present in the flow of air.

Description

AIR PURIFICATION DEVICE TECHNICAL FIELD The present disclosure relates to the field of air purification. More particularly the presentdisclosure relates to an air purification device for separating airborne particles from a flow of air.

BACKGROUND Within many different technical fields, like for example different types of vehicles or buildingsair filtration systems are used to ensure the desired air quality within the cabin or building or other closed space. lonizing filtering systems are frequently used since they provide efficient cleaning of airborneparticles. The ionizing filtering system comprises an ionizer (or ionizing unit) that is configuredto produce an ionizing volume for electrically charging particles in the air such that the particles adhere to a filter medium arranged downstream the air flow path. |ons can be produced in several ways but one frequently used arrangement comprises anemitter electrode and a collector electrode, for example a corona tip surrounded by a collectorelectrode which could be connected to ground, such that ions are produced in a volumesurrounding the emitter electrode, i.e. the corona tip, when a high voltage is applied over theemitter electrode and the collector electrode. The volume in which ions are produced is referredto as ionizing volume and the emitter and collector electrodes are preferably arranged such thatthe ionizing volume spans the flow path. When particles pass through the ionizing volume atleast a portion of the particles are charged. The charged particles then adhere to the filter medium downstream the air flow path.

When providing ionizing filtering systems in vehicles or in buildings, there are severalparameters to be taken into account, such as a need for a sufficient size of a ionizing volume,i.e. a volume where airborne particles are charged by means of an ion field, that the space fordifferent systems and components may be limited or otherwise restricted in shape, that the effect of the electromagnetic emissions from an ionizing filtering system may affect other 2components, and that the possibility to adapt the further equipment and arrangements islimited, that adding further arrangement in a flow of air will affect the flow of air, etc. Hence,there is consequently a need for an ionizing arrangement that provides a suitable trade-off between different limiting pa ra meters.

SUMMARY An object of the present disclosure is to provide an air purification device which seeks tomitigate, alleviate, or eliminate one or more of the above-identified deficiencies in the art and disadvantages singly or in any combination.This object is obtained by an air purification device ofthe independent claim.

According to an aspect, an air purification device for separating airborne particles from a flowof air is provided. The air purification device comprises an emitter unit comprising an emitterelectrode, and a filter medium arranged to attract at least a subset of the airborne particles.The filter medium comprises a conductive material. Furthermore, the emitter electrode and thefilter medium comprising the conductive material are so arranged as to produce an ionizing volume for charging airborne particles present in the flow of air.

Prior art air purification devices including an ionizing unit and a filter medium generally havethe ionizing unit and the filter medium at a distance from each other. lt has been surprisinglyfound that an ionizing unit and a filter medium may be arranged adjacent to one another andthat a sufficient ionizing volume, i.e. a volume where airborne particles are charged by meansof an ion field, may still be produced for charging airborne particle to an extent that enhancesan air purification device in relation to an air purification device without any ionization unit. Theinventors have further realised that a collector electrode of the ionizing unit can be integrated in the filter medium by providing a filter medium comprising a conductive material.

By providing the filter medium comprising a conductive material and thus arranging the filtermedium to act as a collector electrode, an air purification device may be provided having thesame combined size as the size of a separate filter medium in an arrangement without anionizing unit, but where the air purification device has an enhanced reduction of particles froman air flow when in use as compared to the separate filter medium. Furthermore, more evenly distributed fields over the entire filter surface will be achieved. 3The terms ”ionizing unit” and ”ionizer” are used herein to denote a combination of an emitter electrode and a collector electrode (or sender electrode and receiver electrode).

That the filter medium attracts at least a subset of the charged airborne particles means thatthe at least a subset of the charged airborne particles are entrapped in the filter medium such that they are not in the flow of air after the filter medium.

The term ”filter medium” is used herein to denote a natural or synthetic material or amanufactured article used for filtration which have a porous structure permeable to gases, andwhich would entrap at least a subset of airborne particles even if they and/or the airborne particles are not charged.

By air flow is meant the flow of air that passes through the device in use. The air flow may beactively generated in that it is driven by a fan or other such air displacement means, or it maybe passive in that it is generated by way of the air being directed through the filter while avehicle comprising such a device is being driven. The air flow may also be driven by a vehicle's air conditioning system.

There are many ways of achieving a filter medium comprising a conductive material. However,the filter medium comprising a conductive material should preferably be such that an additional pressure drop resulting from the conductive material should be kept low. ln embodiments, the conductive material may form an integral part ofthe filter medium, suchas a carbon filter layer or the like. The conductive material may also be added as a conductiveparticle media, e.g. by spraying or by other means providing conductive particles on a surfaceof within the filter media. A further alternative is to add a mesh of a conductive material, suchas a metal mesh, to the filter medium, either on the surface of or in-between layers of the filter media. ln embodiments, the filter medium comprising the conductive material is connected toelectrical ground or to another electric potential different from the electric potential of the emitter.

By connecting the filter medium comprising a conductive material connected to electricalground or to another electric potential different from the electric potential of the emitter, airborne particles charged in an ionizing volume produced by the air purification device, will 4more likely be trapped by the filter medium. Furthermore, once a charged particle is trapped inthe filter material, the charge of the particle will be neutralised. Hence, a risk of the filtermedium becoming charged by the charged particles and hence not attract or even repel the cha rged pa rticles is avoided. ln embodiments, the emitter electrode and filter medium comprising the conductive materialare preferably arranged at distance within 10-100 millimetres, and even more preferablyarranged at distance within 12-30 millimetres. The distance is preferably measured from aportion of the emitter electrode closest to a portion of the filter medium comprising the conductive material. ln embodiments, the emitter electrode and filter medium comprising the conductive materialare so arranged that an ionizing volume is produced in a direction away from the filter mediumwhen the air purification device is in use. This enables charging of airborne particles in an airflow which first passes through the ionizing volume directed away from the filter medium andthen through the filter medium in which at least a subset of the charged airborne particles areattracted. The emitter electrode may hence be arranged close to the filter medium comprisingthe conductive material in order to provide a emitter unit and filter medium combination withas small as possible total distance from a topmost portion of the emitter unit to a bottommostportion the filter medium, whilst maintaining an as large as possible distance from a topmost to a bottommost portion the filter medium, i.e. a thickness of the filter medium. ln further embodiments, the emitter electrode and the filter media comprising the conductivematerial are so arranged that an ionizing volume is produced which is adapted to a portion of aventilation system contiguous to a position in which the air purification device is intended to be arranged. ln embodiments, the emitter electrode comprises one or more corona discharge points,wherein at least a subset of said corona discharge point is directed away from the filter medium.By pointing at least a portion of the one or more corona discharge points away from the filtermedium, an ionizing volume is produced in a direction away from the filter medium when theair purification device is in use. This enables charging of airborne particles in an air flow whichfirst passes through the ionizing volume directed away from the filter medium and then through the filter medium in which at least a subset ofthe charged airborne particles are attracted. The 5emitter electrode may hence be arranged close to the filter medium in order to provide emitterelectrode and filter medium combination with as small as possible total distance from a topmostportion ofthe emitter electrode to a bottommost portion the filter medium, whilst maintainingan as large as possible distance from a topmost to a bottommost portion the filter medium, i.e. a thickness of the filter medium.

The corona generated on application of a voltage to the emitter may be positive or negative.The voltage applied to the emitter electrode may be between -10 and 10kV DC, more preferablybetween -7 and 7 kV DC.

Corona discharge points directed away from the filter medium does not only encompass coronadischarge points directed perpendicular away from the filter medium but alternativearrangements with smaller angles, such as 45° or the like which also produce an ionizing volumein a direction away from the filter medium, i.e. the ionizing volume situated before the filter medium in relation to a flow of air when the device is in use, are also encompassed. ln embodiments, the emitter electrode comprises a plurality of corona discharge points. Byprovision of a plurality of corona discharge points, an ionizing volume may be produced with alower voltage applied to the plurality of corona discharge points when the air purification deviceis in use, which is sufficient for charging airborne particle to an extent similar to an air purification device with only one corona discharge point applied with a higher voltage.

The plurality of corona discharge points could for example be a plurality of tips, carbon brushes etc. to produce points where a density of an electrical field is sufficient to produce a corona.

The plurality of corona discharge points may be arranged on a single emitter electrode in whichcase they are electrically connected to one another. However, it is also possible for there toexist a plurality of emitter electrodes which are electrically separate from one another, butwhich work together to generate an ion field in use. For example, it is possible for there to be apair of emitter electrodes, electrically apart from one another, but each comprises a plurality ofcorona discharge points. ln such an embodiment it is possible for the corona discharge pointson separate emitter electrodes to point in the same direction or substantially opposite directions. 6Similarly, it is possible for the filter comprising the conducting material to form a single,grounded collector electrode for corona discharge points. However, it is also possible for the filter comprising the conducting material to be divided into a plurality of collector electrodes. ln embodiments, the filter media comprising the conductive material is arranged such that saidplurality of corona discharge points ofthe emitter electrode are at a substantially same distancefrom respective portions of filter medium comprising the conductive material. This enablesproduction of a substantially uniform ionizing volume when the air purification device is in use, thereby providing substantially uniform charging of airborne particles in the ionizing volume. ln further embodiments, the emitter electrode is an elongated structure and said plurality ofcoronal discharge points are distributed along a length of the emitter electrode, the collectorelectrode is an elongated structure, and the emitter electrode and the collector electrode arearranged substantially parallel to one another. This enables production of a substantiallyuniform ionizing volume when the air purification device is in use, thereby providing substantially uniform charging of airborne particles in the ionizing volume. ln embodiments, the emitter electrode is a flattened and elongated structure arranged suchthat it is flattened in a plane substantially parallel to the flow of air. The emitter electrode beingflattened in a plane substantially parallel to the flow of air when the air purification device is inuse, enables a reduction of influence of the emitter electrode on the flow of air. The emitterelectrode may include one or more corona discharge points, and at least a subset ofthe one ormore corona discharge points may be arranged on an edge of the emitter electrode such thatthe at least a subset of the plurality of corona discharge points is directed away from the filter medium. ln embodiments, the air purification device comprises two or more emitter units comprising emitter electrodes. ln embodiments, the emitter unit further comprises an emitter carrier for holding the emitterelectrode and for electrically isolating the emitter electrode from the filter medium comprising the conductive material. 7ln further embodiments, the emitter unit is flexibly connected to the filter medium so as toallow for deformation of the filter medium whilst the emitter unit is attached to the filter medium. ln embodiments, the air purification device further comprises a power supply, a first connectorconnecting the power supply to the emitter electrode, and a second connector connecting the power supply to the filter medium comprising the conductive material. ln embodiments, the second connector connecting the power supply to the filter mediumcomprising the conductive material, may be a fastener for fastening a housing comprising thepower supply to a wall of a box or frame in which the filter medium comprising the conductivematerial is arranged when the air purification device is in use. The fastener may be electricallyconnected to electrical ground or to a voltage different from a voltage supplied to the emitterelectrode when the air purification device is in use. The fastener may further be electricallyconnected to the conductive material of the filter medium when the air purification device is in USS. ln embodiments, the box or frame has the shape of a rectangle or square with one corner cutof and the housing has the shape of a triangle adapted to be fastened to a wall of the housing52 at the cut off corner, such that the combined housing and box or frame has the shape of a complete rectangle or square, respectively.

BRIEF DESCRIPTION OF THE DRAWINGS The foregoing will be apparent from the following more particular description of the exampleembodiments, as illustrated in the accompanying drawings in which like reference charactersrefer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the example embodiments.

Figure 1 is a simplified cross section view of embodiments of an air purification device of the present disclosure.

Figure 2 is a perspective view of an emitter electrode of a first type which can be used in embodiments of an air purification device of the present disclosure. 8Figure 3 is a perspective view of an emitter electrode of a second type which can be used in embodiments of an air purification device ofthe present disclosure.

Figures 4a-d are an example configuration of and details of an air purification device according to the present disclosure.

DETAILED DESCRIPTION Aspects of the present disclosure will be described more fully hereinafter with reference to theaccompanying drawings. The device disclosed herein can, however, be realized in manydifferent forms and should not be construed as being limited to the aspects set forth herein.

Like numbers in the drawings refer to like elements throughout.

The terminology used herein is for the purpose of describing particular aspects of the disclosureonly, and is not intended to limit the invention. As used herein, the singular forms "a", "an" and"the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.

Figure 1 is a simplified cross section view of an embodiment of an air purification device 10 ofthe present disclosure. The air purification device 10 comprises an emitter unit 12 comprisingan emitter electrode 14 and an emitter carrier 16. The emitter electrode 14 of the embodimenthas arranged thereon one or more (a plurality of) corona discharging points 20 in electricalcontact with the emitter electrode. The air purification device 10 further comprises a filtermedium 22 comprising a conductive material. The emitter electrode 14 and the filter medium22 comprising the conductive material are arranged for charging airborne particles present in aflow of air 18 when the air purification device 10 is in use. This is done by generation of coronaon the one or more corona discharging points 20 by application of a positive or negative voltageto the emitter electrode 14. The voltage applied to the emitter electrode 14 may be between -10 and 10 kV DC, and more preferably between -7 and 7 kV DC. The filter medium 22 comprisingthe conductive material may for example be connected to electrical ground or the oppositevoltage in relation to the emitter electrode 14. The filter medium 22 comprising the conductivematerial is further arranged to attract at least a subset of the charged airborne particles in theflow of air 18. The emitter unit 12 comprising the emitter electrode 14 and the filter medium 22 comprising the conductive material are arranged adjacent to one another with the emitter 9carrier 16 isolating the emitter electrode 14 from the filter medium 22 comprising theconductive material. They are further preferably arranged such that the emitter electrode 14and the filter medium 22 comprising the conductive material are at a distance within 10-100millimetres, and more preferably arranged at distance within 12-30 millimetres. The distance ismeasured from a portion of the emitter electrode 14 closest to a portion of the filter medium22 comprising the conductive material. The distance is for example adapted such that the riskof arcs being produced between the emitter electrode 14 and the filter medium 22 comprisingthe conductive material is minimized. The filter medium 22 is arranged after the emitter unit in the flow of air 18.

There are many ways of achieving the filter medium 22 comprising the conductive material.However, the filter medium comprising the conductive material should preferably be such that an additional pressure drop resulting from the conductive material should be kept low.

The conductive material may form an integral part of the filter medium, such as a carbon filterlayer or the like including activated carbon. The conductive material may also be added as aconductive particle media, e.g. by spraying or by other means providing conductive particles ona surface of within the filter media. A further alternative is to add a mesh of a conductivematerial, such as a metal mesh, to the filter medium, either on the surface of or in-between layers of the filter media. ln the air purification device 10, the emitter unit 12 comprising the emitter electrode 14 andthe filter medium 22 comprising the conductive material are preferably arranged so as to reducea total distance from a topmost portion ofthe emitter unit 12 to a bottommost portion the filtermedium 22. However, it would also possible for at least a portion of the emitter unit 12 to bearranged in recesses into the filter medium 22. For example, at least a portion of the emitterunit 12 could be arranged in recesses into the filter medium 22 comprising the conductive material.

The one or more corona discharge points 20 are directed away from the filter medium 22 toproduce an ionizing volume in a direction away from the filter medium 22 when the airpurification device is in use. Corona discharge points 20 directed away from the filter medium22 does not only encompass corona discharge points 20 directed perpendicular away from the filter medium 22 but alternative arrangements with smaller angles, such as 45° or the like which also produce an ionizing volume in a direction away from the filter medium 22, i.e. the ionizingvolume situated before the filter medium 22 in relation to the flow of air 18 when the device 10 is in use, are also encompassed.

The one or more corona discharge points 20 could for example be a plurality of tips as shown inFigure 1. ln alternative, carbon brushes or other means can be used to produce points where a density of an electrical field is sufficient to produce a corona.

Figure 2 is a perspective view of an emitter electrode 14 of a first type which can be used inembodiments of an air purification device of the present disclosure, such as the air purificationdevice 10 disclosed in figure 1. The emitter electrode 14 includes a plurality of corona dischargepoints 20. The plurality of corona discharge points are arranged in the same direction and maywhen arranged in an air purification device be directed away from the filter medium.Embodiments are however envisaged where at least one or more of the plurality of discharge points 20 are directed in another direction.

The plurality of corona discharge points 20 could for example be a plurality of tips as shown infigure 2. ln alternative, carbon brushes or other means can be used to produce points where a density of an electrical field is sufficient to produce a corona. ln alternative to the blade 14 and tips 20 both being vertical as disclosed in figure 2, the blade14 may be horizontal and the tips 20 may be bent with an angle, such as 45-70°, upwards from the edge of the horizontal blade 14.

Figure 3 is a perspective view of an emitter electrode 34 of a second type which can be used inembodiments of an air purification device ofthe present disclosure, such as the air purificationdevice 10 disclosed in figure 1. The emitter electrode 34 is of a cylindrical shape and may for example be formed using a copper wire.

Figure 4a is an example configuration of an air purification device 40 according to the presentdisclosure. An emitter unit 42 of the air purification device 40 comprises an emitter electrode44 and an emitter carrier 46 and a filter medium 22 comprising a conducting material. Theemitter carrier 46 is arranged for holding the emitter electrode 44 and for isolating the emitterelectrode 44 from the filter medium 22 comprising the conductive material. The emitter carrier 46 is made of a non-conductive material, such as non-conductive plastic. The emitter electrode 1144 has arranged thereon a plurality of corona discharging points in electrical contact with theemitter electrode 44. The filter medium 22 comprising a conducting material is arranged in aframe or box 50. The air purification device 40 further comprises a housing 52 comprising apower supply (not shown) and further electronics (not shown) for operating the air purificationdevice 40. The emitter electrode 44 and the filter medium 22 comprising the conductingmaterial are arranged for charging airborne particles present in a flow of air when the airpurification device 40 is in use. This is done by generation of corona on the plurality of coronadischarging points of the emitter electrode 44 by application of a positive or negative voltage tothe emitter electrode 44. The voltage is applied by the power supply (not shown) in the housing52 via an electric connector, such as a power cable 54 as shown in figure 4a. The voltage appliedto the emitter electrode 44 may be between -10 and 10 kV DC, and more preferably between - 7 and 7 kV DC.

The filter medium 22 comprising the conductive material may for example be connected toelectrical ground or the opposite voltage in relation to the emitter electrode 44, such that apotential difference is produced between the emitter electrode 44 and the filter medium 22comprising the conductive material. The filter medium 22 comprising the conductive material isfurther arranged to attract at least a subset of the charged airborne particles in a flow of air.The emitter unit 42 comprising the emitter electrode 44 and the filter medium 22 comprisingthe conductive material are arranged adjacent to one another with the emitter carrier 46isolating the emitter electrode 44 from the filter medium 22 comprising the conductivematerial. They are further preferably arranged such that the emitter electrode 44 and the filtermedium 22 comprising the conductive material are at a distance within 10-100 millimetres, andmore preferably arranged at distance within 12-30 millimetres. The distance is measured froma portion of the emitter electrode 44 closest to a portion of the filter medium 22 comprising theconductive material. The distance is for example adapted such that the risk of arcs beingproduced between the emitter electrode 44 and the filter medium 22 comprising the conductive material is minimized.

The air purification device 40 may be designed such that the frame or box 50 has the same sizeand shape as a standard filter box comprising a filter media normally placed in a filtercompartment of a vehicle. Hence, the air purification device 40 can replace the standard filter box without the need for any adaptation of the actual filter compartment. ln use, a flow of air 12is directed from above the emitter electrode 44 and towards the filter medium 22, i.e. firstpassing through an ionizing volume produced by the emitter electrode 44 and the filter medium22 comprising the conductive material, and then through the filter medium 22. The ionizingvolume can be produced such that is adapted to a portion of a ventilation system contiguousand upstream to the filter compartment. This can be done by adaptation of the emitterelectrode 42, the corona discharge tips 20 and the filter medium 22 comprising the conductivematerial. By such adaptation, the time and distance travelled by airborne particles in the flowof air in the ionizing volume can be prolonged in order to increase the portion/percentage ofparticles being charged and hence the number of particles attracted to the filter medium andremoved from the flow of air before entering the space after the filter medium, e.g. a cabin of a vehicle the air purification device is arranged in. ln use, the air purification device 40 is arranged such that the emitter unit 42 comprising theemitter electrode 44, and the filter medium 22 comprising the conductive material are arrangedadjacent to one another. More specifically, the emitter electrode 44 and the filter medium 22are arranged so as to reduce a total distance from a topmost portion of the emitter unit 42, to a bottommost portion the filter medium 22.

Even though figure 4a shows an air purification device 40 including one emitter unit 42comprising one emitter electrode 44, it is understood that the air purification device 40 can beprovided with two or more emitter units 42 comprising emitter electrodes 44. The number ofemitter units 42 and the arrangement ofthem depends on the ionization volume to be formedand is further in some cases a trade of between enabling a large ionization volume and maintaining a low pressure drop through the air purification device 40.

Figure 4b is a first detail of the air purification device 40 of figure 4a. A portion of the filtermedium 22 comprising the conductive material is show together with a portion of the emitterunit 42 comprising the emitter electrode 44 and the emitter carrier 46. On the emitter electrodethe corona discharging points in the form of tips (pins) 20 are arranged and directed away fromthe filter medium 22 comprising the conductive material. Between each tip 20, protrusions 56on the emitter carrier 46 are arranged. The protrusions 56 are made of a non-conductivematerial, such as non-conductive plastic. Such protrusions 56 are advantageous in order to protect a person handling the air purification device 40, e.g. when installing it, from getting in 13contact with the corona discharging points 20 as they are generally sharp and may cause cuts and may also be damaged themselves by becoming bent or less sharp.

The emitter unit 42 further comprises attachment parts 58. The attachment parts 58 arearranged such that they attach to the filter medium 22 comprising the conductive material. Theattachment parts 58 are preferably movably arranged on the emitter carrier 46 such that, if thefilter medium 22 is deformed to an extent, e.g. by bending along pleats of the filter medium,the attachment parts 58 can keep the emitter ca rrier 46 attached to the filter medium 22, whilstat the same time be moved in relation to the emitter carrier 46 to accommodate thedeformation of the filter medium 22. The attachment parts 58 are preferably arranged in a wayso that they allow free positioning on filter regardless relative positioning of pleats of the filtermedium 22 and such that they provide easy and secure mounting on filter. The attachment parts58 should further be arranged to ensure positioning of emitter unit 42 substantiallyperpendicular to pleats. This is preferable in order to keep a low pressure drop and highutilisation of filter area. As shown in figure 4b, the attachment parts 58 may be slidably arrangedon a rod 60 ofthe emitter carrier 46. lf an attachment part 58 is clipped onto a pleat ofthe filtermedium 22 and the filter medium 22 is deformed by bending along the pleat onto which theattachment part 58 is clipped, the attachment part 58 may slide along the rod 60 toaccommodate the movement of the pleat onto which the attachment part is clipped.Furthermore, having the attachment parts 58 in the form of clips slidably arranged on rods 60,each attachment part 58 can be easily and securely clipped onto a pleat ofthe filter medium 22by sliding the attachment part 58 in line with a position of a corresponding pleat of the filtermedium 22. ln order to enable such adaptation of the position of the attachment parts 58, thelength of each rod 60 should be longer than the distance between two pleats of the filter medium 22.

The emitter electrode 44 may for example consist of a blade parallel with the filter medium 22with the tips 20 on one edge of the blade and bent upwards away from the filter medium 22.This allows for flat cost effective manufacturing. Furthermore, the emitter electrode 44 maythus bend with the filter medium 22 when mounted on the emitter carrier to enable a desireddirection of the tips 20 in relation to the filter medium. The flat blade parallel with the filter medium 22 also allows for a low design of the overall combination of the emitter unit 42 and 14the filter medium 22 comprising the conductive material. Additionally, since the tips 20 are directed away from the filter medium, they can be made short to further enable a low design.

Figure 4c is a second detail of the air purification device 40 of figure 4a. The housing 52comprising the power supply (not shown) and further electronics (not shown) for operating theair purification device is attached to a wall of the frame or box 50 by means of a fastener 62.The fastener 52 is be electrically connected to electrical ground or to a voltage different from avoltage supplied to the emitter electrode when the air purification device is in use. The fastener62 is further electrically connected to the conductive material of the filter medium 22 when the air purification device is in use.

As seen in figure 4a, the box or frame 50 has the shape of a rectangle with one corner cut ofand the housing 52 has the shape of a triangle adapted to be fastened to a wall of the housing52 at the cut off corner, such that the combined housing 52 and box or frame 50 has the shapeof a complete rectangle. Even though the housing 52 has the shape of a triangle, the housing 52and box or frame 50 may have other shapes. Using a cut off corner of the box or frame 50 and a triangular housing 52 has been selecting to simplify manufacturing of the filter.

Figure 4d shows the housing 52 and the fastener 62 when detached from the box or frame. Thefastener, e.g. made of metal, is a clip which is attached to the housing and arranged to be clippedonto a wall of the box or frame. The fastener 62 includes a first flat portion attached to ahorizontal wall of the housing 52 and a second portion parallel with the first portion includinghooks 64 with optional rolled tips. The hooks 64 with the optional rolled tips are arranged toslide into to pockets (pleats) of the filter to come in electrical contact with the conductivematerial of the filter medium. The conductive material of the filter medium may for example bea carbon filter layer including activated carbon, a conductive material disposed on the surface of a layer of the filter medium or a conductive mesh.

On the housing 52 is also a protrusion 66 including a hole 68. The hole 68 allows a power cableand/or a light guide to pass from inside the box or frame 50 and/or the housing 52. Theprotrusion 66 may be part of a fastener for secure fastening and positioning of the housing 52 and/or the entire box or frame 50 and to ensure air tightness. lt should be noted that the word ”comprising” does not necessarily exclude the presence ofother elements or steps than those listed and the words ”a” or ”an” preceding an element donot exclude the presence of a plurality of such elements. lt should further be noted that anyreference signs do not limit the scope of the claims, that the example embodiments may beimplemented at least in part by means of both hardware and software, and that several H ll ”means , units” or ”devices” may be represented by the same item of hardware. ln the drawings and specification, there have been disclosed exemplary embodiments.However, many variations and modifications can be made to these embodiments. Accordingly,although specific terms are employed, they are used in a generic and descriptive sense only andnot for purposes of limitation, the scope of the embodiments being defined by the following claims.

Claims

16CLAll\/IS

1. Air purification device for separating airborne particles from a flow of air, the airpurification device comprising: an emitter unit comprising an emitter electrode; and a filter medium arranged to attract at least a subset of the airborne particles, wherein the filter medium comprises a conductive material, and wherein the emitter electrode and the filter medium comprising the conductive materialare so arranged as to produce an ionizing volume for charging airborne particles present in the flow of air.

2. Air purification device according to claim 1, wherein the conductive material is one of a sheet of activated carbon, conductive particle media, and a conductive mesh.

3. Air purification device according to any one of claims 1 and 2, wherein the filter medium comprising the conductive material is connected to electrical ground.

4. Air purification device according to any one of claims 1-3, wherein the emitter electrode and filter medium are arranged at distance within 10-100 millimetres.

5. Air purification device according to any one of claims 1-3, wherein the emitter electrode and filter medium are arranged at distance within 12-30 millimetres.

6. Air purification device according to any one of claims 1-5, wherein the emitter electrode comprises one or more corona discharge points.

7. Air purification device according to claim 6, wherein said one or more corona discharge points are directed away from the filter medium.

8. Air purification device according to any one of claims 6 and 7, wherein the emitterelectrode is an elongated structure and said plurality of coronal discharge points are distributed along a length ofthe emitter electrode. 17

9. Air purification device according to any one of claims 1-8, wherein the emitter unitfurther comprises an emitter carrier for holding the emitter electrode and for electrically isolating the emitter electrode from the filter medium comprising the conductive material.

10. Air purification device according to any one of claims 1-9, wherein the emitter unit isflexibly connected to the filter medium so as to allow for deformation ofthe filter medium whilst the emitter unit being attached to the filter medium.

11. Air purification device according to any one of claims 1-10, further comprising:a power supply,a first connector connecting the power supply to the emitter electrode; anda second connector connecting the power supply to the filter medium comprising the conductive material.