Air purifier FIELD

[0001] The present invention relates to air purifiers, and more particularly to air purifiers with an electrostatic precipitator.

BACKGROUND

[0002] An electrostatic precipitator (ESP), or an electrostatic air purifier, is a device that removes fine particles, like dust and smoke, from a flowing gas by electrostatic attraction. ESPs ionize, or electrically charge, particles as incoming air is drawn over an electronic cell. The charged particles are then attracted to and trapped by collector plates that are grounded or positively/negatively charged. The trapped particles stick to the plates until they are removed.

[0003] Collector plates are usually formed as an assembly of parallel conductive plates or nested cylinders. The collector plates are typically made of metal, for example stainless steel or aluminium. While stainless steel plates are very corrosion and heat resistant, they are also rather heavy, which is not desirable in house-hold devices, and expensive. Aluminium plates are lighter but more sensitive to humidity and corrosion.

[0004] Depending on the method by which particulates are removed from the collector plates, electrostatic precipitators may be divided into two categories: dry and wet. The dry variant is the most abundantly used, basic form of an ESP. In industrial- scale dry ESPs the removal of accumulated dust can be accomplished by using rappers: the dirt and dust is shaken loose by vibration.

[0005] In wet precipitators, a continuous supply of water is used for forming a wet layer on the surfaces of the collector plates to remove the dirt therefrom. [0006] In household electrostatic air purifiers, which are of the dry type but without any rapper or vibration technology, the accumulated dirt must be removed for example by manually cleaning the plates with regular intervals. If the plates are not cleaned regularly, the purification efficiency drops. Typically, cleaning is accomplished by removing the plate assembly, soaking it to a cleansing solution for several hours, rinsing with water, and allowing to dry. Washing the plate assembly in a dishwasher has also been recommended by manufacturers. Alternatively, the user may replace the collector assembly with a new assembly.

[0007] Air purifiers comprising an electrostatic collector have been described for example in the following publications:

[0008] DE 3927569 Al describes a dry electrostatic precipitator with collector plates made from polypropylene containing carbon as a conducting filler material. Ionization electrodes extend between grounded collector plates, which form a honeycomb matrix.

[0009] US 2003/0061934 Al describes an air cleaning device with conventional metallic collection surfaces. Instead of washing the surfaces, they are replaced with the help of a protective covering bag.

SUMMARY OF THE INVENTION

[0010] There is a need for developing an improved air purifier based on an electrostatic precipitator, which is lightweight and requires minimal maintenance and replacement of parts.

[0011] There is a further need for increasing the lifetime and chemical resistance of the collector plates of air purifiers.

[0012] There is a further need for increasing the versatility of air purifiers comprising an electrostatic collector and to adapt them for receiving and treating contaminated air from various household and industrial sources.

[0013] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0014] According to an aspect of the present invention, there is provided an air purifier comprising a housing, said housing exhibiting in a cascade: an ionization chamber arranged for charging impurity particles in the incoming air; and electrostatic collector plates located after the ionization chamber in the direction of air flow during purification and arranged for trapping the charged impurity particles; wherein the electrostatic collector plates are made of an electrically conducting plastic material, and every other electrostatic collector plate is charged and the other electrostatic collector plates are grounded or oppositely charged.

[0015] According to a second aspect of the present invention, there is provided an air cleaner comprising an elongated housing, said housing having an inlet for air to be cleaned and an outlet for the cleaned air, and further exhibiting in a cascade a first zone connected to the inlet and arranged for charging impurity particles in the air to be cleaned; and a second zone connected to the outlet and arranged for trapping the charged impurity particles. Advantageously, the first zone is an ionization chamber, and the second zone is a collector plate assembly, wherein the collector plates are made of an electrically conducting plastic material, and every other electrostatic collector plate is charged and the other electrostatic collector plates are grounded or oppositely charged.

[0016] According to a third aspect of the present invention, there is provided use of the air purifier for treating air comprising alkaline, acidic or corrosive impurities.

[0017] According to a fourth aspect of the present invention, there is provided use of an ozone compatible, electrically conducting plastic material as the material of an electrostatic collector surface of an air purifier.

[0018] According to a fifth aspect of the present invention, there is provided an air purifier comprising a housing, said housing exhibiting: an ionizer arranged for charging impurity particles in the incoming air; and a charged or grounded electrostatic collector surface arranged for trapping the charged impurity particles; wherein the electrostatic collector surface is made of an electrically conducting polymer composite material comprising an ozone compatible plastic material and an electrically conducting filler.

[0019] More specifically, the present invention is characterized by what is stated in the characterizing parts of the independent claims. [0020] The invention provides considerable advantages. The collector plates, and the whole purifier, are lighter, which makes it easier for the user to move or lift the device, which is particularly relevant during house-hold use.

[0021] A plastic material can be more freely shaped and the manufacturing costs are lower. For example, it is possible to design plate shapes and geometries that differ from the typically employed stack of rectangular, flat plates. [0022] A further advantage is that the collector plates according to the present invention are more corrosion-resistant than the currently used aluminium plates, and therefore they are suitable for treating air that contains acidic or alkaline impurities, such as air from industrial processes. [0023] A further advantage is that the collector plates can be equipped with a replaceable coating, which facilitates cleaning of the plates.

BRIEF DESCRIPTION OF THE DRAWINGS

[0024] FIGURE 1 illustrates schematically an example apparatus capable of supporting at least some embodiments of the present invention, and

[0025] FIGURES 2 A to 2D show different embodiments of electrostatic collector plates according to the present invention.

EMBODIMENTS

[0026] The invention provides an air purifier with an improved electrostatic collector structure. The collector comprises one or more plates that are made of an electrically conducting plastic material.

[0027] In the present context, the term "electrically conducting" refers to a material that can be classified either as a semiconductor or a metal.

[0028] In the present context, the term "evenly spaced plates" refers to an arrangement of plates where the distance between adjacent plates is essentially constant across their whole surface area and the same for all adjacent plates. The plates can be flat or they can be bent or curved as long as they all have approximately similar shape to keep the distance between adjacent plates constant.

[0029] In the present context, the term "every other electrostatic collector plate" refers to "every second electrostatic collector plate" or "every alternate electrostatic collector plate".

[0030] In the present context, the term "generalized cylinder" refers to a cylinder shape the cross-section of which can be any closed or open curve. [0031] In the present context, the term "spiral-wound plate" refers to a plate that has been wound to a spiral so that the cross-section of the wound plate is a curve that winds around a fixed center point at a continuously increasing distance from the point.

[0032] In the present invention, we have surprisingly observed that at least some of the drawbacks of the known electrostatic precipitators can be overcome by making the collector plates of an electrically conducting plastic material.

[0033] In one embodiment, the air purifier is a household air purifier. In a household air purifier, the air flow during purification is typically in the range 50 to 1000 m ³ /h, for example 50 to 400 m ³ /h. The impurities that are present in the air in a household environment include dust from textiles, sand dust, soot, hair, greasy particles, and/or microbes.

[0034] In another embodiment, the air purifier is an industrial-scale air purifier. In an industrial-scale air purifier, the air flow during purification is typically more than 400 m ³ /h, for example 1 000 to 500 000 m ³ /h. The impurities that are present in contaminated air in industrial environments include acidic and alkaline impurities, and corrosive gases.

[0035] According to one embodiment of the present invention, Fig. 1 shows an air purifier with a housing 11 enclosing an inner space with a vertical central axis when in use. Incoming air, i.e. air to be purified, is introduced to the purifier from below, in parallel with the vertical central axis. The air is first arranged to flow through an ionization chamber 12, which contains a tube with ionization needles 13. In this embodiment, the upward flow of air is established by means of an axial fan 18. In the ionization chamber 12, small impurity particles (with diameters less than about 100 nm) become charged and thrown against the side walls of the chamber 12. Larger particles (with diameters greater than about 100 nm) also become charged, but they are conducted further upwards, until the electrostatic collector 14, which traps them. The electrostatic collector 14 comprises charged and/or grounded conductive collector plates, such as plates 15 and 16. The purified air exits after having flown through the inner space in the vertical direction, for example through holes in a top part of the housing 11.

[0036] In the embodiment of Fig. 2, the air purifier comprises an integrated washing system in the form of washing nozzles 20 located above the electrostatic collector plates, which nozzles are arranged for spraying a cleansing solution onto the electrostatic collector plates.

[0037] In some embodiments, the air purifier comprises a washing system as described in the Finnish patent application No. 20165186. In such embodiments, the air purifier comprises a housing with an essentially vertical central axis when in operation.

[0038] In other embodiments, the air purifier does not comprise any integrated washing system. In such embodiments, the orientation of the air purifier can be chosen freely, and the central axis of the housing need not be vertical. The central axis can be vertical, horizontal or anything in between. [0039] In some embodiments, the dispensing of the cleansing solution can be done either by utilizing gravitational force or by applying pressure.

[0040] The washing system can be arranged to be activated by the user. The air purifier preferably indicates the need for collector plate cleaning at regular intervals.

[0041] In one embodiment, after activation, the nozzles 20 spray a cleansing solution onto the plates for a pre-determined period of time. The cleansing solution flows downwards through the plate assembly and through the ionization chamber, and finally into a reservoir in the bottom of the purifier. The washed plates and the ionization chamber are dried by means of the axial fan 18. The fan 18 is capable of two-mode action: a purification mode of aspirating air to be purified upwards through the ionization chamber and subsequently through the electrostatic collector plates, and a drying mode of blowing air in the opposite direction, i.e. downwards. The drying mode can be automatically activated for a pre-determined period of time after the spraying has been completed.

[0042] The used cleansing solution can be directed to a container located in the bottom of the purifier, or it can be pumped to a remote container, or it can be directed to drainage.

[0043] In one embodiment, the fan system is located within the inner space of the air purifier, for example above the collector plates, or between the collector plates and the ionization chamber, or before the ionization chamber. The fan system is easier to keep clean if it is located above the collector plates, thus avoiding contact with used cleansing solution. To reduce noise, it is advantageous to position the fan system inside the housing of the air purifier, surrounded by other components of the purifier, for example between the collector plates and the ionization chamber.

[0044] In one embodiment, the fan system comprises an axial fan that is capable of aspirating air in one direction, i.e. upwards, and of blowing air in the opposite direction, i.e. downwards, by changing the rotation direction of its propeller.

[0045] In one embodiment, the fan system comprises a first fan arranged for aspirating air in the purification mode and a second fan arranged for blowing air in the drying mode, and wherein the first fan is inactive during the drying mode and the second fan is inactive in the purification mode. In this embodiment, the first and the second fan can be independently selected from the following: an axial- flow fan, a centrifugal fan, a cross-flow fan.

[0046] The flow rate of the incoming air during purification is for example 50 to

1000 m ³ /h, preferably 50 to 400 m ³ /h, more preferably 60 to 300 m ³ /h, most preferably 100 to 200 m ³ /h. [0047] The flow rate to the opposite direction during the drying mode is preferably equal to or smaller than the flow rate during the purification mode, for example 20 to 400 m ³ /h, preferably 30 to 100 m ³ /h.

[0048] In one embodiment, the air to be blown in the drying mode is heated by means of an electrical heating element in order to speed up drying. [0049] The preparation and supply of a suitable cleansing solution can be accomplished in many ways. In one embodiment the air purifier has an integrated container into which a ready-to-use cleansing solution is poured before activating the washing system. In another embodiment, only water is poured into the integrated container, and the purifier is arranged to add a suitable amount of a liquid or solid cleansing agent (e.g. in the form of solid tablets or powders) to the water from a separate integrated container that preferably is dimensioned for serving several washing rounds. In yet another embodiment, the purifier is connected by hoses to an external water supply (e.g. a tap) that provides water to the integrated container. In this embodiment, user efforts are minimized once the purifier has been installed. [0050] Suitable cleansing solutions include aqueous solutions of surfactants, aqueous solutions of dishwasher detergents, aqueous solutions of non-foaming detergents and aqueous solutions of sodium hydroxide.

[0051] Figs. 2A to 2D illustrate different embodiments of electrostatic collector plates according to the present invention.

[0052] In Fig. 2A, the collector plates consist of nested cylinders which have a cross-section of a circle. The air coming from the ionization chamber contains charged particles, which are attracted by oppositely charged collector plates. Every other collector plate is positively or negatively charged while the other plates are grounded. In some embodiments, every other collector plate is positively charged while the other plates are negatively charged.

[0053] The central part 23a of the collector is blocked and air cannot enter there.

Thus, air is forced to flow between the collector plates, and charged impurity particles are effectively trapped. [0054] Figs. 2B to 2D show other possible geometries for the collector plates. In

Fig. 2B the collector plates are nested cylinders which have cross-sections varying from a circle to a round-cornered square.

[0055] In Fig. 2C the collector plates are nested cylinders which have an oval cross- section, resembling the shape of a racing track. [0056] In Fig. 2D the collector plates consist of two nested spiral- wound plates 21,

22.

[0057] Preferably, the electrostatic collector plates comprise nested generalized cylinders, or alternatively the electrostatic collector plates comprise nested spiral-wound plates. [0058] According to some embodiments, the nested spiral-wound plates have a cross-section which is one of the following: Archimedean spiral, Euler spiral, Fermat's spiral, logarithmic spiral, involute circle. [0059] According to some embodiments, the collector plates comprise plates that have been wound around a central axis to a generalized cylinder shape having a cross- section of an open curve.

[0060] According to some embodiments, the collector plates comprise a stack of parallel, flat plates.

[0061] In each of the embodiments shown in Figs. 2A - 2D, the central part 23a,

23b, 23c, 23d of the cylindrical or spiral-formed collector assembly is empty. Preferably, air is prevented from flowing through the central part by blocking it. In this way, air flows only between the nested plates, which maximizes the contact between charged impurity particles and the collector surfaces. However, in other embodiments, it is possible to leave the central part unblocked, if the air flow rate through the purifier needs to be higher.

[0062] In one embodiment, one or more of the electrostatic collector plates have a cross-section of a circle, an oval, an ellipse or a round-cornered polygon.

[0063] In one embodiment, the air purifier comprises a collector consisting of only one grounded or charged collector plate or surface. Preferably, the collector surface is cylindrical, surrounds an ionizer tube, and made of a conducting polymer composite material comprising a plastic material and a metal filler. Typically, the plastic material is ozone compatible and has a Cole-Parmer ozone compatibility rating A or B.

[0064] In one embodiment, the collector assembly includes at least two plates, for example 3 to 50 plates. The number of plates can be odd or even.

[0065] In one embodiment, the washing system comprises nozzles that are movable with regard to the electrostatic collector plates.

[0066] In one embodiment, the washing system comprises one or more spray arms that are rotatable around the vertical central axis of the electrostatic collector plates. Washing efficiency can be optimized by having cylinder-shaped nested collector plates and rotating spray arms above the plates.

[0067] Preferably, the washing system is automated and integrated to the air purifier, and its use does not necessitate demounting of the collector assembly. [0068] In one embodiment, the air purifier comprises two washing systems, a first washing system above the electrostatic collector plates and a second washing system above the ionization chamber. In this way it is possible to effectively clean both the plates and the ionization chamber, either simultaneously or by first cleaning the plates and then the ionization chamber.

[0069] In one embodiment, every other electrostatic collector plate is either negatively or positively charged, and the other electrostatic collector plates are grounded.

[0070] In one embodiment, the electrostatic collector plates are configured in a stack of first electrostatic collector plates and second electrostatic collector plates, whereby a stack of plates is provided in which each first electrostatic collector plate is alternated with a second electrostatic collector plate; each first electrostatic collector plate has a charge; and each second electrostatic collector plate is grounded or has a charge opposite to the charge on each first electrostatic collector plate. The air containing charged impurity particles flows between the plates. The direction of air flow is thus lateral, i.e. parallel to the plates. The plates can have a planar shape or a generalized cylinder shape.

[0071] It is possible to use only two electrostatic collector plates, wherein one of the plates has a charge and the other plate is grounded or has an opposite charge.

[0072] In one embodiment, the electrostatic collector plates do not have any sharp corners or edges. Sharp edges could lead to generation of ozone, which is not desirable, particularly in a household environment.

[0073] In one embodiment, the electrostatic field between the electrostatic collector plates is at least 3 kV/cm, preferably at least 4 kV/cm.

[0074] In one embodiment, the distance between the electrostatic collector plates is for example from 2 mm to 150 mm, preferably from about 3 mm to about 30 mm, more preferably from 4 mm to 10 mm. The spacing of the plates is fixed by isolated bars or combs.

[0075] In the embodiment of Fig. 2, the air purifier further comprises an active carbon filter 17 located above the collector plates, between the nozzles 20 and the fan 18. The active carbon filter is used for ozone removal, which is highly desired in household air purification applications. Since active carbon filters are particularly sensitive to water and humidity, the nozzles and the collector plates must be located below the active carbon filter. In this way, during the drying mode, the fan 18 is able to blow air in such a direction (downwards) that any humidity or water droplets will not be conducted from the collector plates towards the active carbon filter 17 but to the opposite direction, towards the ionization chamber 12.

[0076] In one embodiment, the housing comprises in a cascade: the ionization chamber; the electrostatic collector plates; the washing system; an active carbon filter.

[0077] In another embodiment, the housing comprises in a cascade: the ionization chamber; the electrostatic collector plates; an active carbon filter. [0078] In the embodiment of Fig. 2, the ionization chamber 12 comprises an ionizer with ionizing needles 13 attached to a tube located in the middle of the ionization chamber 12. Needle-formed ionizers are advantageous because the volume where ozone might be generated is smaller. Preferably, the ionization chamber is separate from the collector plates in the sense that the tube does not extend up to or in between the collector plates. [0079] The material of the collector plates may be any suitable electrically conducting plastic material, for example a conducting polymer composite or an electrically conductive polymer.

[0080] In a preferred embodiment, the collector plates are made of a conducting polymer composite material comprising or consisting of a plastic material and an electrically conducting filler. The electrically conducting filler may be a metal. The filler may be in the form of powder, particles, aggregates, droplets, ribbons, wires or fibers. For example, the metal may be stainless steel.

[0081] The conducting polymer composite material preferably comprises 1 to 30 wt-

% of an electrically conducting filler, more preferably 5 to 15 wt-%, typically about 10 to 12 wt-%.

[0082] In some embodiments, the collector plates are made of an intrinsically conducting polymer, such as polyfluorenes, polyphenylenes, polypyrenes, polyazulenes, polynaphthalenes, polypyrroles, polycarbazoles, polyindoles, polyazepines, polyanilines, polythiophenes, poly(3,4-ethylenedioxythiophene), poly(p-phenylene sulphide), polyacetylenes, poly(p-phenylene vinylene). [0083] Ionization may result in the generation of minor concentrations of ozone inside the air purifier. Preferably, the plastic material comprises an ozone compatible plastic material. Most preferably, the plastic material has Cole-Parmer A rating (excellent) or B rating (good) with regard to ozone compatibility. The Chemical Compatibility Database by Cole-Parmer Instrument Company, LLC (Vernon Hills, IL 60061 United States) is available at https://www.coleparmer.com/chemical-resistance. Ratings of chemical behaviour listed in the database apply at a 48-hr exposure period. The different ratings have the following meanings: A rating - Excellent; B rating - Good: minor effect, slight corrosion, or discoloration; C rating - Fair: moderate effect, not recommended for continuous use, softening or loss of strength, and swelling may occur; D rating - severe effect: not recommended for any use.

[0084] It follows that it is not preferable to use for example polypropylene or polyamide as the plastic material, as they have ozone compatibility C rating (Fair).

[0085] In one embodiment, the plastic material comprises or consists of an ozone compatible plastic material, such as polycarbonate (PC), acrylonitrile butadiene styrene (ABS), chlorinated polyvinylchloride (CPVC), cross-linked polyethylene (PEX), high density polyethylene (HDPE), low density polyethylene (LDPE), polyetheretherketone (PEEK), polyacrylate, polyvinylchloride (PVC), polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE) or any combination of them, wherein the plastic material has a Cole-Parmer ozone compatibility rating A or B.

[0086] Polycarbonate is particularly advantageous as the plastic material, because it has a Cole-Parmer A rating for ozone compatibility, high tensile strength, and excellent mo ldability/ formability .

[0087] In one embodiment, the plastic material to be used in the conducting polymer composite material comprises a styrenic polymer, such as polystyrene (PS), expandable polystyrene (EPS), acrylonitrile butadiene styrene copolymer (ABS), or styrene acrylonitrile copolymer (SAN). Styrenic polymers are particularly lightweight and easy to process. ABS provides good resistance to heat and chemicals. A mixture of ABS and polycarbonate (PC) is particularly well suited for injection moulding and thus for manufacturing of electrostatic collector plates. [0088] Preferably, the plastic material is a thermoplastic. The advantage is that thermoplastics have a low density and a high formability. They can be formed for example by injection moulding, thermo forming, blow moulding and rotational moulding.

[0089] In some embodiments, the material of the collector plates has a conductivity of at least 0.01 S/cm, typically at least 50 kS/cm, for example at least 100 kS/cm.

[0090] Preferably, the conducting polymer composite material has a volume resistivity less than 100 ohm. cm, more preferably less than 10 ohm. cm, most preferably less than 1 ohm. cm.

[0091] Preferably, the conducting polymer composite material has a surface resistance less than 1E4 ohm, more preferably less than 1E3 ohm, most preferably less than 1E2 ohm.

[0092] In one embodiment, the conducting polymer composite material contains PC,

ABS or a combination thereof, and at least 5 wt-%, preferably at least 10 wt-% stainless steel fibers or particles. [0093] In one embodiment, the conducting polymer composite material comprises a mixture of ABS and PC as the plastic material and at least 10 wt-% stainless steel fibers or particles as the electrically conducting filler. Preferably, the composite material has volume resistivity less than 100 ohm. cm and surface resistance less than 1E4 ohm. An exemplary composite material is EMI 2561 FR supplied by RTP Company (Winona, Minnesota 55987 USA, https://www.rtpcompany.com/).

[0094] In one embodiment, the conducting polymer composite material comprises a mixture of ABS and PC as the plastic material and at least 15 wt-% stainless steel fibers or particles as the electrically conducting filler. Preferably, the composite material has volume resistivity less than 1E1 ohm. cm and surface resistance less than 1E4 ohm. An exemplary composite material is EMI 2562 FR supplied by RTP Company.

[0095] In one embodiment, the conducting polymer composite material comprises

PC as the plastic material and at least 8 wt-% stainless steel fibers or particles as the electrically conducting filler. Preferably, the composite material has volume resistivity less than 100 ohm. cm and surface resistance less than 1E4 ohm. An exemplary composite material is EMI 330 D FR supplied by RTP Company. [0096] In one embodiment, the conducting polymer composite material comprises

PC as the plastic material and at least 12 wt-% stainless steel fibers or particles as the electrically conducting filler. Preferably, the composite material has volume resistivity less than 1 ohm. cm and surface resistance less than 1E3 ohm. An exemplary composite material is EMI 330 F FR supplied by RTP Company.

[0097] In one embodiment, the conducting polymer composite material comprises

ABS as the plastic material and at least 15 wt-% stainless steel fibers or particles as the electrically conducting filler. Preferably, the composite material has volume resistivity less than 1 ohm. cm and surface resistance less than 1E3 ohm. An exemplary composite material is EMI 662 supplied by RTP Company.

[0098] In one embodiment, the conducting polymer composite material comprises an ether-based thermoplastic polyurethane elastomer (abbreviated TPUR or TPU) as the plastic material and at least 10 wt-% of an electrically conducting filler. Preferably, the composite material has a volume resistivity in the range from 1E1 to 1E2 ohm. cm and a surface resistivity in the range from 1E3 to 1E4 ohm/sq. An exemplary composite material is EMI 1262 T-80A supplied by the RTP Company.

[0099] Ether-based TPUR or TPU is mainly based on tetrahydrofuran (THF) ethers.

[00100] In one embodiment, walls of the ionization chamber and/or the ionizer tube are/is made of an electrically conducting plastic material. [00101] In one embodiment, each of the collector plates has a replaceable plastic surface coating or film. The coating can be made of the same or different material as the collector plate itself. The coating must be electrically conducting. Preferably, the coating is made of an electrically conducting plastic material and the collector plate is made of metal. When dirt has accumulated, the coating can be removed and replaced with a clean one. In this embodiment, the number of collector plates is small, for example less than 10, preferably 1 to 4.

[00102] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting. [00103] Reference throughout this specification to one embodiment or an embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[00104] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and example of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[00105] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In this description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[00106] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below. [00107] The verbs "to comprise" and "to include" are used in this document as open limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[00108] At least some embodiments of the present invention find industrial application in the field of household air purifiers.

ACRONYMS LIST ABS Acrylonitrile Butadiene Styrene

CPVC chlorinated PVC

PEX cross-linked polyethylene

HDPE high density polyethylene

LDPE low density polyethylene PEEK polyetheretherketone

PA polyamide

PC polycarbonate

PE polyethylene

PVC polyvinylchloride

PVDF polyvinylidene fluoride (Kynar)

PTFE polytetrafluoroethylene

TPUR and TPU ether-based thermoplastic polyurethane elastomer

PS polystyrene

EPS expandable polystyrene SAN styrene acrylonitrile copolymer

THF tetrahydrofuran

REFERENCE SIGNS LIST

CITATION LIST

Patent Literature

DE 3927569 Al

US 2003/0061934 Al