FIELD OF THE INVENTION

The present disclosure relates to the field of air treatment apparatuses involving air purifying apparatuses. More generally, the present invention relates to home appliances that are arranged for treatment of ambient air in buildings, so as to improve a sense of well-being of the present residents.

More particularly, the disclosure relates to a filtering device for an air treatment apparatus that enhances a purifying performance. Further, in some specific embodiments, the disclosure relates to a filtering device that is also capable of moisturizing the treatment air that passes the air treatment apparatus.

BACKGROUND OF THE INVENTION

CN 101590268 A discloses a vertical indoor air ultraviolet lamp purifying/humidifying apparatus, comprising a housing that comprises, seen from top to bottom, a filter chamber, a sterilization chamber, and a revolving wheel humidification chamber, wherein a layer of filter material is provided in the filter chamber, wherein an ultraviolet lamp is provided in the sterilization chamber, wherein an annular revolving humidification wheel is provided in the humidification chamber, wherein the humidification wheel is made from a porous material, wherein a bottom of the humidification wheel is arranged to be immersed in a water tub, and wherein an interior space of the humidification wheel is coupled with an air inlet of the apparatus.

Air treatment apparatuses may be used in housing areas, but also in working areas, including offices, workshops, shops, etc. So-called single-purpose air purifying apparatuses are available on the market. An air purifying apparatus is a device which is arranged to remove small particles and gaseous contaminants from the ambient air in a room. These devices are commonly considered as being beneficial to allergy sufferers and asthmatics, and at reducing or eliminating second-hand tobacco smoke. Further field of application may be envisaged.

Those appliances may be regarded as domestic appliances that improve the quality of the room air in buildings. Air purifying apparatuses may utilize, for instance, a set of filters to clean the room air. Further, air quality sensors may be provided. A ventilating unit may be provided that generates an air flow through the appliances.

Indoor air purification is an important topic for human health because nowadays people generally spend more than 80% of their time in houses, offices, and cars. Indoor air pollutants mainly comprise three groups: particulate matter, volatile organic compounds (so-called VOCs), and microorganisms. Exposure to VOCs may cause adverse health effects like irritation of the eyes, skin and respiratory tract, and also may lead to more serious diseases including cancer and leukaemia.

Among the various toxic gaseous compounds, formaldehyde has been identified as a particular issue. Formaldehyde is toxic, allergenic and carcinogenic. High concentration formaldehyde has far-reaching impact on human respiratory, nervous and immune systems. Long term exposure to indoor air even containing a few parts per million of formaldehyde may cause various adverse health threats. Even worse, unlike many other indoor VOCs that can be effectively removed by porous sorbent media via physical adsorption (e.g. granular activated carbon, etc.), formaldehyde cannot be satisfactorily removed by pure sorbent media due to its high vapour pressure (3883 mmHg [2078 in H ₂ 0] at 25°C) and relatively low boiling point (-19.3 ° C [-2.74 ° F]).

A supposed main source of indoor formaldehyde is widespread unregulated use of low-cost building and decoration materials containing formaldehyde-based resins. Normally, sufficient natural ventilation of ambient indoor air with outdoor is an adequate method to remove indoor formaldehyde. But it becomes less desirable and thus employed when the outdoor air is polluted or the outdoor temperature is uncomfortable. Furthermore, many people tend to minimize natural ventilation for night time sleeping.

Therefore, there is a certain need to develop efficient and environmentally friendly approaches for removal of formaldehyde. Several approaches have been proposed and developed for formaldehyde removal to satisfy environmental regulations, health regulations, etc. In general, those approaches may include physical adsorption, chemisorption, photo-catalytic oxidation, thermal catalytic oxidation, plasma technology, and biological/ botanical filtration.

However, the removal of indoor formaldehyde is still a challenging issue due to the limited adsorption capacity, high energy consumption, high temperature required, byproduct formation, low efficiency, etc. Among these approaches, chemisorption is currently believed to be an effective and promising method for indoor formaldehyde removal. The main reasons for this are considerable performance in practical applications and reasonable costs. In the content of this approach, air purifier filters are often impregnated with chemical agents to react with formaldehyde. The chemicals for formaldehyde removal are mostly organic amines. The chemical reaction of formaldehyde and amines, converts the

formaldehyde into a non- volatile compound and thus removes the pollutant from the air.

Considering other indoor gaseous pollutants, such as acidic gases or alkaline gases, corresponding alkaline or acidic chemical regents can be used as functional chemicals for their removal.

Therefore, the above described exemplary case of application for air treatment apparatuses shall not be understood in a limiting sense.

It has been observed that the air cleaning or air purifying performance often can be improved by moisturizing and/or wetting the filters with a liquid treatment agent. However, controlling a moisturizing process and a resulting air purifying/humidification procedure poses several challenges.

US 2,767,638 discloses an air conditioner for vehicles. The device contains a splashing and spraying wheel for moistening the filter with water from a reservoir in the device.

JP 2005282980A discloses a humidifier in which water from a water tank is dropped on a humidifying structure using rotating dippers. JP 2005282980A does not disclose the removal of a target pollutant from air.

SUMMARY OF THE INVENTION

It is an object of the present disclosure to provide filtering device for an air treatment apparatus and a corresponding air treatment apparatus that enable an improved air treatment performance, particularly an improved filter/purifying performance. Preferably, the filtering device enhances an air cleaning capability of the apparatus. Further, it is desirable to provide a filtering device that may be attached in an air tight fashion to a treatment air inlet. More preferably, the filtering device allows for an improved control of an impregnation state of a filter material which involves a control of a degree of purification and humidification.

It is a further object to present a corresponding method of operating an air treatment apparatus which facilitates a filter impregnation procedure and which preferably involves a control mechanism for the impregnation level of the filter material.

In a first aspect of the present disclosure there is presented a filtering device for an air treatment apparatus, the filtering device comprising:

a supply tray for providing a treatment liquid, a filter unit, and

a feeding unit at least partially encompassing the filter unit,

wherein the feeding unit is actuable to supply the filter unit with the treatment liquid from the supply tray, wherein the feeding unit is operable to moisten or wet the filter unit with the treatment liquid, wherein the filter unit is fixed, and wherein the feeding unit is movable.

This aspect is based on the insight that gaps or even cracks through which air may escape without passing through the filter may be avoided when the filter unit, particularly a filter element thereof, is tightly attached and/or arranged in a sealed fashion. This may particularly apply to a connection between the filter unit and a ventilating unit that supplies the filter unit with a flow of to-be-treated air. For example, the filter unit is connectable to the ventilating unit and the filter unit is arranged in a sealed fashion such that a flow of to-be-treated air generated by the ventilating unit passes through the filter unit without leakage.

A further advantage of the above arrangement is that by controlling a movement speed of the feeding unit, a supply rate of the treatment liquid which is transferred to the filter unit may be easily controlled. This in contrast to US 2,767,638 which uses a splashing and spraying wheel to moisten the filter. The apparatus disclosed in US 2,767,638 does not allow accurate and easy control of the supply rate of the treatment liquid to the filter unit leading to less efficient filtration. Thus, it is an advantage of the invention that by at least partially encompassing the filter unit with the feeding unit, a liquid can be provided to the filter unit in an easy and controllable fashion using dripping/dropping of the liquid on the filter unit. As the moistening of the filter unit can be controlled more accurately, this leads to a better or more accurate purification performance of the device.

As used herein, the feeding unit, at least a feeding cage/wheel thereof, is arranged to be moved with respect to the filter unit. Hence, the feeding unit may be arranged as a conveyor that entrains a fraction of the treatment liquid from the supply tray so as to transfer this fraction to the filter unit. The feeding unit may be also referred to as wetting unit and/or moisturizing unit. The air treatment apparatus may be also referred to as air purifying apparatus. The air treatment apparatus may be also operated in a humidifying mode which involves a humidification of treated air. Hence, in certain embodiments, the air treatment apparatus may be also referred to as air combined purifying/humidifying apparatus.

The feeding unit at least partially surrounds the filter unit. The filter unit may be also referred to as fixed filter unit. By contrast, the feeding unit may be also referred to as movable filter unit. As the filter unit is not arranged to be moved, a sealed attachment of the filter unit is enabled. This prevents undesired bypass air flow involving air that does not pass through the filter unit. Hence, the overall air purification performance may be improved.

As the filtering device is further provided with the feeding unit, also the non- movable filter unit may be impregnated and/or soaked with the treatment liquid.

A further advantage is that, irrespective of the humidity of the inlet air, a remarkable air purification performance is achieved so dry air may be humidified accordingly.

In an exemplary embodiment, the filter unit is fixed, wherein the feeding unit is movable, and wherein the feeding unit is operable to moisten or wet the filter unit with the treatment liquid.

In other words, the filter unit, particularly a filter material from which a filter element is formed, may be poured with the treatment liquid when the feeding unit is moved with respect to the filter unit. In certain embodiments, the feeding unit is arranged as a rotatable feeding unit. Hence, at least a part of the feeding unit is arranged to be rotated.

Preferably, a portion of the feeding unit that encompasses/surrounds the filter unit is arranged to be rotated about the filter unit when the feeding unit is actuated. Further, in certain embodiments, there is no direct contact between a movable component of the feeding unit and the filter unit. Rather, when the feeding unit is actuated, drops of the treatment liquid may drip/drop from the feeding unit and absorbed by the filter material of the filter unit. A further advantage is that an excess treatment liquid will fall back into that tray. Hence, consumption of the treatment liquid is low.

In alternative embodiments, a spray is generated by the feeding unit which is at least partially absorbed by the filter material of the filter unit.

In a further exemplary embodiment, the feeding unit comprises at least one trough that entrains, at a bottom zone, a fraction of the treatment liquid from the supply tray and that dispenses, at a top zone, the treatment liquid towards the filter unit, when the feeding unit is activated.

The feeding unit may comprise a corresponding feeding cage or feeding wheel. The movable component of the feeding unit may be also referred to as paddle-wheel, bucket- wheel or scoop-wheel. Preferably, a plurality of troughs is provided, wherein respective troughs are angularly offset at an outer circumference of the wheel.

The bottom zone may be also referred to as entrainment zone. The top zone may be also referred to as drop zone. In a further exemplary embodiment, the feeding unit comprises a rotatable feeding wheel that surrounds at least a portion of the filter unit and that is provided with a plurality of angularly staggered troughs.

In other words, the troughs may be evenly or unevenly distributed along the circumferential extension of the feeding wheel. The feeding wheel may be arranged as a cage-shaped wheel having a hollow interior in which the filter element of the filter unit is provided. Further, at the circumference of the feeding wheel, the troughs may be arranged for fluid entrainment and/or dispensing.

The feeding wheel may be provided with a wheel frame which has a number of horizontally extending troughs on its circumference. The wheel frame surrounds the outer surface of the drum-shaped filter element. When the wheel frame rotates, the troughs take up the treatment liquid (typically a chemical solution) from the tray which is placed below the filter and drop the treatment liquid to the filter element. Therefore, the filter is kept wet which facilitates or promotes the chemical reaction between components of the filter element and pollutant gases. Thus, the filter element of the filter unit, or the filter element of the filter unit, is configured to remove a target pollutant from air when air is propagated through the unit or the element.

In a further exemplary embodiment, the feeding unit comprises a feeding drive, and wherein the feeding drive is operable to adjust a movement speed of the feeding unit and thus to control a supply rate of the treatment liquid to the filter unit.

In certain embodiments, the feeding drive is operable to adjust a speed of rotation of a feeding wheel or feeding cage of the feeding unit. There is no feed for a pump for supplying the filter element with the treatment liquid.

In a further exemplary embodiment, the filter unit is placed above a fill level in the supply tray and wherein the feeding unit is at least partially immersed in the treatment liquid, when the supply tray is filled up to the fill level.

The filter unit as such is not in direct contact with the treatment liquid stored in the supply tray. Between the filter unit and the supply tray, the feeding unit, at least the feeding wheel thereof, is provided. The at least one trough of the feeding unit dips in the treatment liquid provided in the supply tray when the feeding unit is moved. Hence, a bottom end of the supply wheel is immersed in the treatment liquid when the supply tray is filled with the treatment liquid up to the defined fill level.

In a further exemplary embodiment, the filter unit comprises a filter element that is provided with an inlet opening and a cavity defined by a circumferential wall and a closed opposite end, and wherein the inlet opening is arranged to be coupled with an outlet opening of a ventilating unit in a sealed fashion.

In a further exemplary embodiment, the filter unit comprises a filter element that is provided with an inlet opening and a cavity defined by a circumferential wall and a closed opposite end.

The filter element may be arranged as a cylindrical filter element. The filter element may be also referred to as filter cartridge. Preferably, in the vicinity of the inlet opening, the filter element is attached to an outlet of the ventilator in an airtight fashion.

Hence, the filter element is preferably flange-mounted to an outlet of the ventilator in a sealed fashion. Consequently, a sealed fluid line between the outlet of the ventilator and the inlet opening of the filter element of the filter unit is provided. This reduces or prevents a potential air leakage/bypass flow.

In a further exemplary embodiment, the filter element is arranged in a pot-like or cartridge fashion, wherein the circumferential wall and a closed end that is opposite to the inlet opening define an interior of the filter element, wherein the filter element comprises a gas permeable filter material.

For instance, the filter element may be shaped in a cylindrical fashion, wherein also the feeding unit, particularly the feeding wheel thereof, is arranged in a cylindrical fashion, and wherein the feeding wheel is arranged in a fashion radially offset from the filter element. In other words, an outer diameter of the filter element is smaller than an inner diameter of the feeding wheel.

A further advantage of the cartridge arrangement of the filter element is that a large filter surface is provided as the circumferential wall and a frontal end of the filter element may be used for filtering the air passing therethrough.

The filter element may be arranged as a non-rotatable drum filter having an open front end into which air carrying pollutions flows, a closed rear end longitudinally opposite said front end, and a cylindrical section extending between said front and rear ends. Said front end, said rear end and said extending section define an interior area of said drum filter. Said open front end covers the whole passage of air flow, thus all of the inlet air is led into the interior of the drum filter from the open front end and, after passing the filter material, output from the closed rear end and the cylindrical extending section.

In a further exemplary embodiment, the filter element comprises a filter material that is a hydrophilic substrate material. Hence, the filter element may be arranged as a hydrophilic carrier permeable for gas flow which is made from hydrophilic materials, e.g. from ceramics, polymer, paper, etc. The filter element may be also referred to as drum filter. The filter element may be formed in a corrugated fashion featuring a plurality of open air channels.

In a further exemplary embodiment, the filtering device further comprises a control unit that is operable to control the feeding unit to control a supply rate of the treatment liquid. Humidity can be controlled in a desired appropriate range just by controlling the speed/rotation status of the rotary wheel frame. In certain embodiments, the feeding unit can be activated and deactivated. In certain refined embodiments, further characteristics of the feeding unit's movement may be controlled, e.g. movement speed, rotation speed, etc.

In a further exemplary embodiment, the treatment liquid is a water based liquid and comprises a chemical air purifying solution.

For instance, if formaldehyde is the target pollutant, the solution may contain tris-hydroxymethyl-amino-methane as a functional formaldehyde scrubbing agent, potassium bicarbonate as an alkaline agent and potassium formate as a humectant. Depending on the type of the target pollutant(s), other compositions and chemical formulations may be utilized.

In certain embodiments, when the treatment liquid contains exclusively water or almost entirely water the apparatus may be operated in a humidification mode rather than in a (chemisorption based) air purifying mode.

In a further exemplary embodiment, the filtering device further comprises a replenishment indicator for at least one of the treatment liquid, water for preparing the treatment liquid, chemical ingredients for preparing the treatment liquid, and a combination thereof. In certain embodiments, there is no need for a considerably frequent and expensive filter change. Rather, the user only needs to replace the relatively cheap chemical solution from time to time.

In a further exemplary embodiment, the filtering device further comprises a reservoir for the treatment liquid, wherein a tank of the reservoir and the supply tray are operatively coupled for refilling the supply tray.

By way of example, a refill valve may be provided between a tank of the reservoir and the supply tray. Hence, a fill level in the supply tray may be maintained or restored. Depending on the capacity of the reservoir, a certain operation time may be ensured.

The tank of the reservoir may be arranged as a water tank. The tank may be removable which facilitates a water refilling procedure. When the tank contains water, a concentrate of the chemical solution may be provided in the tray which is diluted by the water from the tank. Ingredient chemicals for the treatment liquid initially may be provided in the form of powder or a concentrated solution. As the tank is primarily provided for water supply, the tank as such is not in direct contact with the chemicals which further facilitates the refill procedure.

In a further aspect of the present disclosure there is provided an air treatment apparatus, the apparatus comprising:

a housing portion,

a filtering device in accordance with at least one embodiment as discussed herein, and

a ventilating unit that sucks inlet air and that blows treatment air towards the filter unit.

The air treatment apparatus may be particularly arranged as an air purifying apparatus. The air treatment apparatus may take the form of a home appliance or a household appliance.

In a further aspect of the present disclosure there is presented a method of operating an air treatment apparatus, the method comprising the following steps:

providing a supply tray for providing a treatment liquid,

providing a filter unit for air treatment,

providing a feeding unit at least partially encompassing the filter unit, moving the feeding unit independently from the filter unit to supply the filter unit with the treatment liquid from the supply tray, and

blowing treatment air into the impregnated filter unit, e.g. blowing treatment air into the impregnated filter unit in a sealed fashion such that all treatment air passes through the impregnated filter unit without leakage.

Preferably, the method can make use of the air treatment apparatus and/or the filtering device in accordance with at least one embodiment as described herein.

In an exemplary embodiment of the operating method, there is further provided the step of controlling a speed of rotation or a speed of movement of the feeding unit to control a level of humidification of the treatment air.

Exemplary embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed method has similar and/or identical preferred embodiments as the claimed device and/or apparatus and as defined in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. In the following drawings

Fig. 1 shows a simplified schematic side view of an exemplary embodiment of an air treatment apparatus that implements a filtering device;

Fig. 2 shows a detailed cross-sectional frontal view of a filter unit and a feeding unit of the filtering device of the air treatment apparatus illustrated in Fig. 1; and

Fig. 3 shows a schematic block diagram illustrating several steps of an exemplary embodiment of a method of operating an air treatment apparatus in accordance with the present disclosure.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows in a schematic, simplified view an exemplary embodiment of an air treatment apparatus that is designated by reference numeral 10. The apparatus 10 is arranged as an air purifying apparatus. Further, the apparatus 10 may be operable to humidify treatment air. Hence, in at least some embodiments, the apparatus 10 may be also referred to as a combined purifying/humidifying apparatus.

The apparatus 10 comprises a housing 12. The housing 12 may implement a unibody design. However, in at least some embodiments, at least some components of the apparatus 10 may be arranged as separate components. Hence, in accordance with these embodiments, the apparatus 10 may implement a distributed design.

The housing 12 typically comprises at least one inlet grille and at least one outlet grille for the respective to-be-treated air flow. Further, operator controls, power connectors, etc. may be provided. Further, service/replenishment covers and/or connectors may be arranged at the housing 12.

The apparatus 10 as such may be arranged as a mobile apparatus, e.g. provided with wheels, rolls, etc. Hence, a mobile apparatus 10 may be moved (rolled or lifted and carried) through a building.

In alternative embodiments, the apparatus 10 is arranged as a stationary apparatus. The stationary apparatus may be arranged at a fixed installation place in a building.

The air treatment apparatus 10 comprises a filtering device 14. Further, a ventilating unit 16 is provided that blows to-be-treated air towards and into the filtering device 14. The filtering device 14 comprises a filter unit 18 and a so-called feeding unit 20. Further, the air treatment apparatus 10 comprises a reservoir 22 for a treatment liquid.

The apparatus 10 may be operated via a control unit 24 comprising control elements, for instance a user interface, indicators, display elements, etc.

The ventilating unit 16 is arranged to suck in inlet air, refer to an arrow 28.

The inlet air 28 is pressurized and propelled towards the filter unit 18. Hence, the ventilating unit 16 comprises at least one fan 30 which is arranged between an inlet 32 and an outlet 34 of the ventilating unit 16. The filtering device 14 is sealingly coupled with the ventilating unit 16. For instance, the filter unit 18 is attached to a connecting wall 38 between the ventilating unit 16 and the filtering device 14. Via a passage 40 between the fan 30 of the ventilating unit 16 and the filter unit 18, treatment air may be blown into the filter unit 18 for air treatment purposes.

A motor for the fan 30 of the ventilating unit 16 is indicated in Fig. 1 by reference numeral 36. The motor 36 rotates the fan 30 so as to suck, pressurize and blow the to-be-treated air towards the filter unit 18. A respective ventilator outlet air flow is indicated by an arrow that is designated by reference numeral 42 in Fig. 1.

As the filter unit 18 is coupled with the ventilating unit 16, particularly an outlet 34 thereof, no relative movement between the filter unit 18 and a connecting wall 38 in which an air flow passage 40 is formed is present. In other words, the filter unit 18 may be referred to as a fixed (non-movable) filter unit 18.

The filter unit 18 comprises a filter element 44 which may be also referred to as filter cartridge. The filter element 44 is arranged in a cartridge or pot-like/cup-like fashion. The filter element 44 comprises a circumferential wall 46. At a first end of the

circumferential wall 46, an inlet opening 48 is provided. The inlet opening 48 of the filter element 44 matches the passage 40 or the outlet 34 of the ventilating unit 16.

At an end thereof that is opposite to the inlet opening 48, the filter element 44 comprises a closed end 50. The circumferential wall 46 and the closed end 50 of the filter element 44 define and delimit an interior space. As a consequence, a large air-permeable treatment surface may be provided by the filter element 44 which enhanced the filter performance. The purified air may axially and/or radially escape from the filter element 44.

The circumferential wall 46 and a respective wall that forms the closed end (frontal end wall) 50 contain or are preferably substantially made from a filter material 52. Preferably, the filter material 52 is a gas-permeable filter material. The filter material 52 may be regarded as an air-purifying filter material. Consequently, purified air (refer to the arrow 54 in Fig. 1) may pass through and escape from the filter element 44.

As no gap and no relative movement is provided between the ventilating unit 16 and the filter element 44 of the filter unit 18, a likelihood of a presence of an air leakage between the filter element 44 and the ventilating unit 16 is greatly reduced or, more preferably, entirely prevented.

It has been observed that the filter performance of the filter unit 18 may be enhanced by moisturizing and/or wetting the filter unit 18, particularly the filter material 52 of the filter element 44 thereof. Further, it would be advantageous if the air treatment apparatus 10 would be also capable of humidifying the treatment air.

In this context, filtering devices have been proposed which are arranged in a movable fashion so as to impregnate or moisten the filter material in a continuous or intermediate fashion. However, as in accordance with these approaches the filter element has to be moved with respect to the ventilating unit, at least a small gap has to be provided where relative movement is present. At least a certain fraction of the treatment air may thus escape through this gap. Hence, the filter performance is degraded and the air purifying function is considerably compromised.

In accordance with the present disclosure, no air leakage between the ventilating unit 16 and the filter unit 18 may occur as the filter element 44 of the filter unit 18 is sealingly coupled with an outlet 34 of the ventilating unit 16.

The feeding unit 20 is provided for supplying the filter unit 18 with a treatment liquid (reference numeral 76). The feeding unit 20 comprises a feeding wheel 56 which is movably arranged at/in the housing 12. In exemplary embodiments, the feeding wheel 56 is arranged to be rotated about the filter element 44 of the filter unit 18. In this context, further reference is made to Fig. 2, illustrating a cross-sectional partial frontal view of the filter unit 18 and the feeding unit 20.

It can be seen from Fig. 1 and Fig. 2 that the feeding unit 20 comprises a plurality of troughs 58. In the frontal view of Fig. 2, eight troughs 58-1, 58-2, 58-3, 58-4, 58- 5, 58-6, 58-7 and 58-8 are provided which are angularly distributed at the circumference of the feeding unit 20, particularly of the feeding wheel 56 thereof. Needless to say, also varying numbers of troughs 58 may be present at the feeding wheel in further embodiments.

The feeding wheel 56 may be also referred to as feeding cage. The feeding wheel 56 is arranged in a circular/cylindrical fashion and encompasses the filter element 44 of the filter unit 18. The feeding wheel 56 is arranged to be moved about a rotation axis 60. Hence, a main elongation axis of the filter element 44 and the feeding wheel 56 is a horizontal axis, at least in the embodiment illustrated in connection with Fig. 1 and Fig. 2. A movement direction of the feeding unit 20 is indicated in Fig. 2 by a curved arrow designated by reference numeral 62.

In the side view of Fig. 1, a feeding drive 64 for the feeding unit 20 is provided. The feeding drive 64 may comprise a motor that operates/actuates the feeding wheel 56.

The air treatment apparatus 10 further comprises a supply tray 70. The tray 70 may be assigned to the reservoir 22. The reservoir 22 further comprises a tank 72. The tray 70 and the tank 72 are operatively coupled. For instance, a refill valve 74 is arranged between the tray 70 and the tank 72 for refilling the tray 70. In Fig. 1, a fill level of the tank 72 is indicated by reference numeral 78. A fill level of the tray 70 is indicated by reference numeral 80. At the tray 70, a fill level sensor 84 for the tray 70 is provided. Further, a fill level sensor 82 for the tank 72 is provided. Hence, the refill valve 74 may be operated so as to maintain a defined fill level in the tray 70.

In certain embodiments, the tank 72 is removably arranged in/at the housing 12 of the apparatus 10 which facilitates a refill procedure.

In certain embodiments, in the tank 72, a water-based treatment liquid 76 is stored. The treatment liquid 76 flows, via the refill valve 74, in the tray 70. Via the troughs 58, the treatment liquid 76 is entrained from the tray 70 and, eventually, transferred to the filter element 44 when the feeding wheel 56 of the feeding unit 20 is moved.

In certain embodiments, in the tank 72, water is stored. In the tray 70 the treatment liquid 76 is provided in a concentrated form. Hence, the water from the tank 72 may refill the tray 70 which involves a dilution of the concentrated treatment liquid 76 in the tray 70. An advantage of this approach is that the tank 72 is not in direct contact with the chemicals of the treatment liquid 76.

As can be best seen in Fig. 2, the filter element 44 of the filter unit 18 is placed above a fill level 80 of the treatment liquid 76 in the tray 70. In other words, a lowermost point of the filter material 52 of the filter element 44 is elevated with respect to the fill level 80. The filter element 44 is vertically spaced away from the fill level 80.

By contrast, a bottom portion of the feeding wheel 56 of the feeding unit 20 is at least partially immersed in the treatment liquid 76 when the tray 70 is filled up to a desired fill level 80. Hence, when the feeding wheel 56 is rotated, the troughs dip into the tray (reference numeral 58-1) and entrain a small fraction of the treatment liquid 76 (reference numerals 58-2 and 58-3). When the rotation of the feeding wheel 56 is continued, the treatment liquid is dispensed from the troughs (reference numerals 58-4 and 58-5), refer also to the drips/drops 98 shown in Fig. 2 for illustrative purposes. Hence, the filter material 52 of the filter element 44 is constantly supplied with the treatment liquid 76 when the feeding unit 20 is actuated. An excess fraction of the treatment liquid 76 falls back into the tray 70.

Further, emptied troughs (reference numerals 58-6, 58-7 and 58-8) return to the tray 70.

Depending on an actual state of operation and a speed of rotation, a supply rate of the treatment liquid 76 may be controlled. As a consequence, the air treatment process may be controlled. For instance, a moisturizing process and/or an air purification process may be implemented and controlled in this way.

The feeding wheel 56 may be also referred to as scoop-wheel, paddle-wheel or bucket-wheel. Hence, the troughs 58 may be arranged as paddles, buckets and/or scoops. A plurality of troughs 58 may be arranged at an outer circumference of the feeding wheel 56 at a defined angular offset.

As indicated in Fig. 2 by a radial arrow 54, the treatment air passes the impregnated filter material 52 and is thus purified and/or humidified.

Due to the fixed, non-movable arrangement of the filter element 44 of the filter unit 18, air leakages are avoided. Due to the movable feeding unit 20, a defined impregnation of the filter material 52 with the treatment liquid 56 is enabled. As an impregnation rate is basically dependent on a rotation speed of the feeding wheel 56, the supply rate of the treatment liquid 76 to the filter element 54 and thus a humidification rate is easily controllable.

Again, reference is made to Fig. 1, illustrating a general overall layout of an exemplary arrangement of an air treatment apparatus 10 in accordance with the present disclosure.

As indicated above, a control unit 24 is provided. The control unit 24 may be arranged as a central control unit that controls the ventilating unit 16, the feeding unit 20 and further components of the apparatus 10. However, in alternative embodiments, separate (distributed) control units 24 may be provided.

So as to control a supply rate of the treatment liquid 76 to the filter element 44, the control unit 24 may operate and control the feeding drive 64 so as to set a speed of rotation of the feeding wheel 56. Further, the control unit 24 may control the motor 34 of the ventilating unit 16.

In addition, the control unit 24 may be operatively coupled with at least one of the fill level sensor 82 of the tank 72 and the fill level sensor 84 of the tray 70. Particularly, the control unit 24 may operate the refill valve 74 so as to ensure that the fill level 80 of the treatment liquid 76 in the tray 70 is reached and maintained.

Further, the control unit 24 may indicate that a replenishment of the liquid in the tank 72 is required. To this end, at least one replenishment indicator 94 may be provided. The same may apply to the replenishment of the chemicals that form the treatment liquid in a water-solved state. Further indicators, control elements, user interfaces, displays, etc. may be present. For instance, an exemplary operator control is indicated in Fig. 1 by reference numeral 96. Operator controls may include, but are not limited to, dials, buttons, keys, switches, knobs, sensor pads, LEDs, touchscreens, etc.

At the apparatus 10, at least one output/outlet sensor 90 may be provided. In certain embodiments, the sensor 90 is arranged as an air quality sensor. In certain

embodiments, the sensor is arranged as a humidity sensor. Needless to say, also combined sensors and/or a set of sensors 90 may be provided.

The sensor(s) 90 may detect a level of humidification of the output air stream (reference numeral 54). Further, the sensor(s) 90 may detect a degree of purification. Hence, a signal provided by the sensor 90 may be used to adapt a supply rate of the treatment liquid 76 accordingly by adjusting a movement speed of the feeding drive 64. For example, apparatus 10 may comprise a controller that is configured to adjust the movement speed of the feeding drive based on the output signal of the sensor(s) 90.

In one embodiment, the filter element 44 which may be arranged as a drum filter that is positioned above the tray 70 at an appropriate height so that no part of the filter element 44 will directly contact the treatment liquid 76 (chemical solution) in the tray 70. The filter element 44 is arranged in a horizontal fashion.

In certain embodiments, the filter element 44 may be made from various air- permeable materials and made in various structures. For instance, the filter element 44 is primarily made of hydrophilic materials e.g. paper, polymer, ceramics, or a mixture thereof. Further, the filter element 44 is preferably constructed in a porous structure that provides a great contact surface area which results in relatively low pressure drop. In certain

embodiments, a preferred pore diameter is between 0.5 to 5 mm. To eliminate air flow leakage/bypassing, the filter element 44 is coupled with the ventilating unit 16 in an air-tight fashion. For instance, a connection wall 38 between the filter element 44 and the ventilating unit 16 may be provided, wherein the passage 40 for the treatment air is formed in the connection wall 38. The filter element 44 is sealingly attached to the connection wall 38.

In certain embodiments, the reservoir 22 has two major parts: a tray 70 and a tank 72. The tank 72 holds water and releases it as required via the refill valve 74 into the tray 70. The tank 72 may be removable by the user to add fresh water, if necessary. When the feeding wheel 56 rotates, the chemical solution in the tray 70 is continuously consumed because of water evaporation resulting from the air flow through the filter element 44. When the fill level 80 in the tray 70 drops below a certain level, fresh water from the tank 72 may be automatically introduced into the tray 70 through the refill valve 74.

The treatment liquid 76 contains water and chemical agents. The chemical agents may contain a main active component which may react with targeted gaseous pollutant(s) to form non-volatile and non-hazardous products, and one or more assistants.

For instance, formaldehyde undergoes a condensation reaction with organic amines to form non- volatile compounds, thus formaldehyde is removed from the air. In one embodiment, the chemical tris-hydroxymethyl-aminomethane (Tris, (CH ₂ OH) ₃ C-NH ₂ ) is identified as the formaldehyde-binding agent which is no more than 25% w/w (mass fraction) in the solution and potassium bicarbonate is used as the assistant which is no more than 33% w/w (mass fraction) in the solution. When air passes through the filter element 44, pollutants such as formaldehyde will react with the active compounds on/in the filter element 44.

The control unit 24 is arranged to indicate that a refilling of the reservoir 22 or a replenishment of the chemical solution based on which the treatment liquid 76 is provided is necessary. For instance, when the solution level in the tray 70 is below a pre-set level, the reminder may be sent via LEDs or sound notification. The reminder to replenish the chemical solution may be obtained by counting the total amount of air flow that has passed through the filter element 44. If the appliance 10 is equipped with pollutant sensors upstream and downstream of the filter element 44, the sensors 90 can be used to indicate the need to replace the chemical solution in the filter. When even after a certain rotation of the feeding wheel 56 the pollutant removal efficiency remains too low, a replenishment of the chemical solution may be advised.

Reference is made to Fig. 3 illustrating an exemplary block diagram that represents an exemplary embodiment of a method of operating an air treatment apparatus. The method involves a step S10 involving a provision of a filter unit for an air treatment procedure. Further, a step S12 is present which involves a provision of a supply tray for providing a treatment liquid. A further step S14 involves a provision of a feeding unit that is arranged to at least partially encompass the filter unit, particularly a filter element thereof.

The filter unit provided in the step S10 is arranged as a fixed filter unit i.e. non-movable or non-rotatable. Rather, the feeding unit comprises a feeding element which may be arranged as a feeding cage or a feeding wheel which is movable with respect to the filter element of the filter unit. In certain embodiments, the feeding unit is provided with at least one trough or bucket. The feeding unit is arranged in such a way that, when the feeding unit is moved, the at least one trough or bucket dips into the treatment liquid contained in the supply tray and entrains a fraction thereof which eventually can be transferred to the filter unit. The filter unit as such is not in direct contact with the reservoir treatment liquid that is contained in the supply tray.

In a subsequent step SI 6, the feeding unit is actuated at a defined speed of movement/speed of rotation. As a consequence, a transfer of the treatment liquid at a defined supply rate from the supply tray to the filter unit is established. Hence, the filter unit is at least partially impregnated with the treatment liquid.

In a further step SI 8, a ventilating unit of the air treatment apparatus is operated so as to blow treatment air into the filter unit. Hence, the treatment air is purified and/or humidified when it passes through the filter material of the filter unit. As the filter unit is arranged as a fixed filter unit, an undesired bypass flow of the treatment air may be avoided.

In a further step S20, a sensing operation is performed. To this end, at least one of an air quality sensor and/or an air humidity sensor may be provided. A signal provided from the sensor may be used to adjust a movement speed of the feeding unit which eventually results in an adapted supply rate, refer to the feedback arrow between the step S20 and the step SI 6.

Eventually, at a step S22, an outlet air stream of treated air is provided.

Depending on a current operation mode, the outlet air stream may involve humidified air and/or purified air. A level of humidification and/or a level of purification may be controlled by controlling the supply rate of the treatment liquid. Further, the supply rate may be adapted to a present throughput of air which may be controlled by controlling a ventilating unit of the air treatment apparatus. Further, the supply rate may be adapted to a present humidification state of the passing air.

Further exemplary embodiments of the method may be envisaged. In certain embodiments, when the user takes an air purifying apparatus into operation for the first time, extra chemicals are provided, form instance in the form of powder or solution. In an initial set-up, the user puts the chemicals into the tray and adds water into the tank of the reservoir. Hence, the treatment liquid is formed. Then the apparatus is ready for the air treatment procedure.

Further, when the appliance is operated, sensors may detect and monitor at least one of filter efficiency, relative humidity of inlet air, relative humidity of outlet air, a liquid level in the tray, a liquid level in the tank, etc.

When deviations from a defined range and/or minimum value for a state variable are detected, the control unit alerts the user to take respective measures. This may involve water replenishment, replenishment of the chemicals, etc. For instance, decreasing filter efficiency may indicate that the chemicals need to be replenished.

When the user replenishes the water and the chemicals accordingly, the apparatus is refitted and may be operated again.

In certain embodiments, the apparatus also may be primarily used as a humidifier when there is just water in the reservoir. In certain alternative embodiments, if no humidification is needed, the control unit may simply stop the feeding wheel rotating when the filter element is sufficiently impregnated and loaded with the treatment liquid (chemical solution). In this mode, the apparatus will be primarily operated for air cleaning/purification.

Generally, the removal performance and humidification efficiency depends on several parameters such as air flow rate, air/filter contact surface, treatment time, chemical concentration, temperature, initial pollutant concentration, inlet air humidification, etc. Many of those parameters can be optimized/controlled to achieve the desired purifying/humidifying result.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.