Field of the invention

The invention relates to passenger cabin air filters systems, or more generally to a gas cleaning device comprising a filter cartridge with a filter medium and at least a first filter terminal for providing an electrical contact to first duct terminal of a duct. The duct may further comprise a duct wall enclosing a duct volume with an upstream gas inlet and a downstream gas outlet, as well as a filter support. The filter support may removably support the filter cartridge in the duct volume in between of the gas inlet and the gas outlet. The gas cleaning device may further comprise a gas ionizer for ionizing at least a portion of a gas stream through the duct. The gas ionizer may comprise at least a first ionizer electrode and a second ionizer electrode, a first ionizer terminal and a second ionizer terminal. The first ionizer terminal may be electrically connected to the first electrode and the second ionizer terminal is electrically connected to the second electrode.

Description of the related art

Passenger cabin air filters systems remove pollutants from the ambient air and provide the cleaned air to the interior of a passenger cabin of a vehicle. Essentially the same technology may be used in other fields, e.g., for building ventilation.

Usually "filtration" references to removal of particulate matter from a gas stream by a sieving the gas stream using fibrous filter - the sieve. Cleaning the air based on sieving alone requires balancing between the size of the smallest particles to be held back in the sieve and the pressure drop of the sieving element - the fibrous filter medium. Removing particulate matter from a gas stream by filtration appears to be a result of a number of effects including interception, diffusion, inertial impaction. It has been suggested to improve particle removal from a gas stream using electrostatic forces by means of electret filters. The particle removal of these electret filters, however, appears to fade with increasing deposition of the fibers with particles. To address this drawback, it has been suggested to apply an external electrical field across the filter medium by locating the filter medium as a dielectric medium between two air permeable electrodes. Even non-charged submicron sized particles can be effectively removed from the gas stream using this technique. This technique referred to as active field polarized media air cleaning, which is to be distinguished from electrostatic precipitation and passive electrostatic filters (electret filters).

These active field polarized media gas cleaners usually have a gas filter housing with a receptacle for a gas filter and a high-voltage (HV) source being connected to the electrodes of the gas filter. Once the service life of the gas filter is reached it is removed from the housing and replaced by another one. The housing hence has at least two electrical contacts for removably contacting corresponding electrical contacts of the gas filter, thereby enabling to provide an electrical connection of the gas filter with the HV-source.

US 2007/0199450 Al suggest an air filter having two air permeable ground electrodes and an air permeable HV electrode in between of these. Between each ground electrode and the HV electrode is a dielectric filter medium. The HV-field between the electrodes polarizes both, the particles as well as the fibers of the dielectric.

While these active field polarized media air cleaners allow to efficiently remove even sub-micron particles, air-ionization enables to sterilize air as well as to remove odors on a molecular scale. Air-ionization requires, depending on the distance of the electrode about 5kV and typically -depending on the size of the air- ionizer - a current of a few lOpA to 10mA. Corona discharge air cleaners are an example of air-ionizers. Industry scale gas ionizer may have correspondingly larger currents.

WO2020/263171A1 suggests using a conductive filter medium of a filter cartridge as an electrode of a gas ionizer. Attached to the upstream side of the filter element are a number of isolating supports for emitter electrodes having tips pointing in the upstream direction. About 7-10kV are provided to the emitter electrodes, while the filter medium is grounded. The voltage between the filter medium and the emitter electrodes results in a corona discharge which contributes to particle removal from a gas flow though the filter element. A power supply is directly attached to the filter cartridge and is removed with the filter cartridge when replacing the filter cartridge. The power supply may then be removed from the used filter cartridge and may be attached mechanically to a support structure of the new filter cartridge. Further, the output terminals of the power supply are to be connected via a cable with the emitter electrodes of the gas ionizer. The ground electrode is embedded in the center of the filter medium and may be e.g., an activated charcoal layer of the filter medium or a layer of carbon fibers. This ground electrode layer is contacted by pinching a needle through the plied filter medium. The needle is connected by a wire with the ground connector of the power source.

US2019/160475A1 suggest an electrostatic air filter having a reduced ozone and nitrogen oxide emission. The electrostatic air filter comprises an air flow channel with an inlet having an ion generator comprising corona electrodes and cumulative electrodes. The corona electrodes and the cumulative electrodes are electrically connected to each other, while the cumulative electrodes are insulated from the corona electrodes, so that corona discharge occurs between the corona electrodes and the cumulative electrodes. The corona discharge causes ioniza- tion of contaminant particles present in the air flowing through the channel. Contaminant particles are separated downstream with an input electrode and an output electrode. The air flows through the two electrodes to the channel outlet. The electric field strength in the space between the input electrode and the output electrode is directed opposite to the electric field strength in the space between the ion generator and the input electrode.

KR 2020/0057523 addresses the problem of sparking in electric filters by suggesting an ionization unit including a discharge electrode to which a positive voltage is applied and a facing electrode plate to which a negative voltage is applied.

Dust is ionized by these electrodes and collected by a dust collecting unit with a positive electrode plate disposed on the rear side of the ionization unit and a negative electrode plate configured to collect the dust ionized while passing through the ionization unit. The positive electrode plate and the negative electrode plate are alternately stacked while being vertically spaced from each other. The electrode plates include a metal plate and an insulation layer for protecting the electrode plates from contact with moisture.

JP H06 91199A relates to an electro-osmic dehydration method of sludge in which the sludge is heated prior to electro-osmotic dehydration.

Summary of the invention

The problem to be solved by the invention is to reduce waste, ease used filter recycling and to increase operational safety of a gas cleaning device with a gas ionizer.

Solutions of the problem are described in the independent claims. The dependent claims relate to further improvements of the invention.

For example, a solution may be a cabin air cleaner or more generally a gas cleaning device as well as its components, be it in combination or as such. The gas cleaning device may comprise an optional filter cartridge. The filter cartridge may have a filter medium and at least a first filter terminal and/or a second filter terminal. Each of the filter terminals may be used to connect the filter cartridge to a power source. To connect in this context means as usual to provide an electrical connection between the filter terminals and the corresponding connectors of the power source.

The filter medium may preferably comprise a capacitor with at least a first filter electrode and a second filter electrode. At least one of the filter electrodes may be electrically connected to a corresponding filter terminal. A dielectric medium may be located in between of the first filter electrode and the second filter electrode. For example, the first filter terminal may be electrically connected ("connected" for short) to the first filter electrode and/or the second filter terminal may be connected to the second filter electrode. Via the first filter terminal and/or the second filter terminal the filter electrodes may be connected to a power source, but other means to connect the first electrode and/or the second electrode to an output port of the power source may be used as well.

As usual, the at least one filter medium is permeable for a fluid (e.g., a gas, in particular air), but not for particles above a given particle size. Thus, the filter medium can be considered as a sieve.

The gas cleaning device may further comprise a duct. The duct may be defined by and/or comprise a duct wall. The duct wall may enclose a duct volume with an upstream gas inlet and a downstream gas outlet. Thus, as usual a gas stream to be cleaned may enter the gas inlet flow, through the duct and leave the duct via the gas outlet. The gas inlet can thus be considered as an upstream end and the gas outlet can be considered as a downstream end of the duct.

The duct may further comprise a filter support, wherein the filter support is configured to removably support the filter cartridge in the duct volume in between of the gas inlet and the gas outlet in an operation position. In other words, gas flowing from the gas inlet passes the filter medium prior to leaving the duct via the gas outlet. For example, the filter support can be a tray configured to receive the filter cartridge and maintain it in the position in between of the gas inlet and the gas outlet during normal operation of the gas cleaning device.

Removably means that the filter cartridge is movable from an "inserted position" which can as well be referred to as the operating position to a removed a so called "non-inserted" position. In other words, the filter cartridge is preferably configured to be moved between the inserted position and the non-inserted position. In the non-inserted position, the filter cartridge may but does not need to be supported by the filter support.

Generally, one may assume, that in the inserted position gas flowing through the duct passes the filter cartridge's filter medium, preferably, the entire gas flow passes the filter medium. However, in some applications a bypassing gas flow can be accepted and/or not avoided and/or may even be required. In other words, in the inserted position, the filter cartridge is preferably configured to provide a first percentage of a given gas flow through the duct through the filter element of the filter cartridge, whereas in the non-inserted position the filter cartridge is configured to filter none or only a reduced second portion of the gas flow through the duct. The second portion being filtered corresponds hence to a lower percentage than the first percentage. Lower percentage may for example mean a significantly lower percentage, which can be considered as equal or less than 50% of the first gas flow. In a preferred example the filter cartridge is fully removed from the duct, in case it is in its non-inserted position.

The duct may further comprise a first duct terminal and/or a second duct terminal. In case a filter cartridge is inserted into the filter support, the first duct terminal may contact the first filter terminal and/or the second duct terminal may contact the second filter terminal. Thus, a voltage can be provided to the filter cartridge via at least one of the filter terminals. Only to avoid ambiguities, "is inserted" describes a state in which the insertion of the filter cartridge into the filter support is completed. One could as well say, that in case a filter cartridge has been inserted into the filter support, the first duct terminal may contact the first filter terminal and/or the second duct terminal may contact the second filter terminal. If the filter has been removed, i.e. the filter cartridge is not inserted, the first duct terminal may not contact the first filter terminal and/or the second duct terminal may not contact the second filter terminal. Thus, in the state of non-insertion of the filter cartridge in the filter support, i.e., in the state of removal, the first duct terminal is electrically disconnected from the first filter terminal and/or the second duct terminal is electrically disconnected from the second filter terminal.

The gas cleaning device may further comprise a gas ionizer. The gas ionizer may comprise at least a first ionizer electrode and a second ionizer electrode, a first ionizer terminal and a second ionizer terminal, wherein first ionizer terminal is preferably electrically connected to the first electrode and the second ionizer terminal is preferably electrically connected to the second electrode. Thus, by applying a corresponding voltage to the first ionizer terminal and/or the second ionizer terminal, a corona discharge can be observed. Such corona discharge occurs, if the electrical field in the vicinity of an ionizer electrode exceeds the dialectical strength of the fluid (e.g., a gas) gas in the duct volume, which fluid may preferably be air. Typical voltages for air cleaning by corona discharge are in the range of a couple kV (e.g., 2 to 12 kV, typical 3 to 7kV) depending on the design of the ionizer electrodes.

Corona discharge in air produces Ozone (O ₃ ). However, O ₃ is considered to cause irritations of mucous and respiratory tissues of passengers in the passenger cabin. Accordingly, the ionizer electrodes are preferably upstream of the filter cartridge, as by this sequencing of the ionizer electrodes and the filter cartridge O ₃ is at least mostly converted to O ₂ when passing the filter medium. For example, if activated charcoal and/or a polymer and/or carbon fibers are/is comprised in the filter medium, the O ₃ concentration in the air flow is significantly reduced while passing the filter cartridge.

The gas ionizer is preferably located upstream of the filter element. For example gas ionizer may be supported in the duct, as well. In another example, the gas ionizer may be located in or define a separate conduit, which separate conduit is preferably in fluid communication with the upstream facing side of the filter element. Only for simplicity, herein we assume that such separate conduit and optional valves for controlling the gas flow are a part of the duct.

The duct may as well mechanically support the gas ionizer. Alternatively, gas ionizer may be supported by other components. For example, the gas ionizer may be supported by brackets, that may e.g. extend via at least one hole of the duct and which may themselves be supported by a support structure, like e.g. a base, a chassis, a flooring, a ceiling, a wall, a door leaf, or the like. For the operation of the gas cleaning device the way of attachment is not important and it may be adapted as suited best by the corresponding use or location of use of the gas cleaning device.

Preferably, the filter cartridge, if inserted in the filter support, provides for an electrical connection between the first duct terminal and the first ionizer terminal and/or for an electrical connection between the second duct terminal and the second ionizer terminal. Thus, if the filter cartridge is removed, gas ionizer is disconnected from the power source. As apparent, the at least two ports or connectors of the power source may be connected to the first duct terminal and/or the second duct terminal. In a preferred example, the at least one, preferably two power source ports (terminal) is/are provided by each by one or more duct terminal(s).

The first electrical connection may be provided by a first filter conductor of the filter cartridge contacting the first duct terminal and the first ionizer terminal. In this sense, if the filter cartridge has been inserted the first ionizer terminal may be contacted via the first filter terminal with the first duct terminal. The wording "via the first filter terminal" shall not exclude additional means of conduction in the electrical path between the first filter terminal and the first ionizer terminal. For example, the first ionizer terminal may contact a contact surface of any conducting element being electrically connected with the first filter terminal. The conducting element being contacted may be a part of the filter cartridge and/or a part of the duct or of any other element of the gas cleaning device, provided the first filter terminal is connected in series in between the first duct terminal and the first ionizer terminal and thus the first ionizer electrode.

The second electrical connection may be provided by a second filter conductor of the filter cartridge contacting the second duct terminal and the second ionizer terminal. In this sense, if the filter cartridge has been inserted the second ionizer terminal may be contacted via the first filter terminal with the first duct terminal. The wording "via the second filter terminal" shall not exclude additional means of conduction in the electrical path between the second filter terminal and the second ionizer terminal. For example, the second ionizer terminal may contact a second contact surface of second conductor being electrically connected with the second filter terminal. The conducting element being contacted by the second ionizer terminal may be a part of the filter cartridge and/or a part of the duct or of any other element of the gas cleaning device, provided the second filter terminal is connected in series in between the second duct terminal and the second ionizer terminal and thus the second ionizer electrode. In both cases, removing the filter cartridge interrupts the connection of the duct terminal(s) with their corresponding ionizer terminal. The risk of unintendedly releasing O ₃ via the duct gas outlet, e.g., into a passenger cabin of a vehicle or a bureau or living room or any other volume where humans or animals may be present is thus mitigated, as the electrical connection between the gas ionizer and the power source is interrupted is the filter is removed. Only to clarify, to ensure the function of interrupting the current through the ionizer, it is sufficient if one of the first ionizer terminal and the second ionizer terminal is electrically connected via the corresponding filter terminal with the corresponding duct terminal. The respective other ionizer terminal may be connected directly to the corresponding port of the high voltage source, where "directly" means in this sentence in any way that does not include the corresponding filter terminal.

In a preferred example, the first duct terminal contacts the first filter terminal. Further, it is preferred that the first ionizer terminal is electrically connected with the first duct terminal via the first filter terminal. It is particularly preferred, if the first duct terminal contacts the first filter terminal while the first ionizer terminal contacts the first filter terminal. Similarly, it is preferred if the second duct terminal contacts the second filter terminal and the second ionizer terminal is electrically connected with the second duct terminal via the second filter terminal. Removing the filter cartridge automatically disconnects at least one of the first and second ionizer terminals from the power source.

It is particularly preferred if the first duct terminal contacts the first filter terminal while (i.e., only when) the first ionizer terminal contacts the first filter terminal and/or if the second duct terminal contacts the second filter terminal while the second ionizer terminal contacts the second filter terminal. In any of the three possibilities, the voltage drop across the filter cartridge is reduced. This contributes directly to lower operating costs as well as to lower installation costs, as the high voltage source being connected to the first duct terminal and/or the second duct terminal for providing the electrical power to the gas ionizer can be dimensioned accordingly smaller.

For example, a first surface section of the first filter terminal may electrically contact the first duct terminal and a second surface section of the first filter terminal my electrically contact the first ionizer terminal. Similarly, a first surface section of the second filter terminal may electrically contact the second duct terminal and a second surface section of the second filter terminal may electrically contacts the second ionizer terminal.

In any of the above sketched examples, removing the filter cartridge from the filter support provides a situation in which the first duct terminal does not contact the first filter terminal and accordingly the first ionizer terminal is electrically disconnected from at least the first duct terminal and/or in which the second duct terminal does not contact the second filter terminal and accordingly the second ionizer terminal is electrically disconnected from at least the second duct terminal.

As already sketched above, it is preferred, if the filter element further comprises a first polarization electrode, a second polarization electrode and a second filter terminal, wherein the first filter terminal is electrically connected with the first polarization electrode and the second filter terminal is electrically connected with the second polarization electrode. If the filter cartridge is inserted in the filter support, the second filter terminal preferably contacts the second duct terminal.

The second filter terminal as well as the second duct terminal can be omitted, e.g., by providing a direct connection of the second polarization electrode with a corresponding port (e.g. a ground terminal) of the power source. In a preferred example, the first filter terminal may be electrically connected via a first resistance to a branching point. Further, the second filter terminal may be electrically connected via a second resistance to the same branching point. The first polarizing electrode may be electrically connected to the branching point as well, and the second polarizing electrode may be electrically connected to the second filter terminal. This allows to adjust the voltage across the polarization electrodes by adjusting the ratio of the first and the second resistor and hence to adapt them to the dimensions and the material of the filter medium in between of the filter electrodes. Thus, the polarization voltage can be adjusted to a particular filter medium, without any necessity to adjust the voltage being provided by the power source via at least the first duct terminal. This allows to adjust e.g., the filter medium to different environmental conditions. For example, in a humid climate one may want to use a different filter than in dry and dusty climates. This change of the filter layout may require a change of the polarization voltage, which can be obtained by simply adjusting the first and the second resistors, which may be comprised in or by the filter cartridge. Further, a single high voltage power source providing a single voltage can be used to power the gas ionizer as well as the gas polarizer.

For example, the first filter terminal and/or the second filter terminal may be made of, consist of, or comprise(s) a conducting polymer and/or a conducting ceramic and/or a conducting compound. The resistors and connections between the first filter terminal and the first polarizing electrode and/or the second filter terminal may be made of the same material. These materials are not considered to be electro-scrap and can thus be recycled or deposited like usual garbage. If the terminals, resistors or the like would be typical electronic parts, being e.g., mounted to a printed circuit board, more resources would be required, and recycling would be more difficult and this expensive. As already apparent, it is preferred, if the first filter terminal and/or the first resistor and/or the second filter terminal and/or the second resistor and/or the branching point are unitary. These parts may be manufactured as single piece that may be attached to a support structure of the filter cartridge. For example, this single piece may be attached to a side wall of the filter cartridge. For example, the optional side wall of the filter cartridge may define at least one narrow facing side of the filter cartridge and may be configured to close a gap between the duct wall and the filter cartridge.

The first filter terminal and/or the second filter terminal may have at least a first sprue and/or a second sprue. The first sprue may contact the first duct terminal and/or the second sprue may contact the second duct terminal. This allows to reduce the contact resistance between the mutually contacting terminals, as conducting polymers and/or a conducting ceramic and/or a conducting compound often show a reduced resistivity in their core compared to the resistivity in the outer regions (i.e., in the vicinity of the 'normal' shell surface). At the sprue location, the core reaches the shell surface and is hence contactable, i.e., in this area the contact resistivity is reduced.

In addition or alternatively, the first duct terminal and/or the second duct terminal and/or the first ionizer terminal first and/or the second ionizer terminal are/is a blade being inserted into the first filter terminal and/or the second filter terminal, respectively. The blade may thus cut through the outer layer of the first filter terminal and/or of the second filter terminal and thereby contact a core section of the terminal. Such contact is particularly safe and reliable and provides a particularly low contact resistance.

In a preferred example, at least one of the first filter terminal, the second filter terminal, the first duct terminal and the second duct terminal is and/or com- prises an electrically conducting pin, wherein the pin is contacted by the corresponding terminal of the respective other entity. The electrically conducting pin may be accommodated by a first recess or a second recess, respectively, of the duct or the filter terminal, respectively, and the recess may optionally be delimited by a non-conducting recess wall. The corresponding terminal of the other entity may contact the pin inside of the recess. To make it more vivid, if the pin is the first filter terminal, it may be referred to as first filter pin. In this case, the recess may be formed by the duct, e.g., by the duct wall and/or it may be a part of the filter support. The first filter terminal may thus engage into the recess at least with a distal portion of the first filter pin and while being engaged, the first filter pin may contact the first duct terminal. The recess wall may thus mechanically support the first filter pin and/or provide a shock-proof protection of the duct terminal in case the filter cartridge is deinstalled, e.g., during maintenance. The first ionizer terminal may preferably contact a proximal portion of the first filter pin. In case the electrically conducting pin is the second filter terminal, one simply has to replace first by second in the previous five sentences. Proximal means a portion of the pin being closer to the filter medium that the end of the pin that contacts the corresponding duct terminal.

As apparent, the from the above paragraph, the electrically connecting pin may be comprised by the filter cartridge and may be contacted inside the recess by the first duct terminal. In this case it is preferred, if the distance between the first duct terminal and the first ionizer terminal and/or the distance between the first duct terminal and a filter cartridge facing edge of the recess wall is greater than the distance between the first ionizer electrode and the second ionizer electrode. Each of these measures increases intrinsic safety: By these choices of the distances, it can be avoided that sparking between the first ionizer terminal and the first duct terminal occurs, if the filter cartridge is not installed and for any reason (e.g., a defective switch, a software error, ...) the power source is not switched off as it should be. Further, the risk of an electrical shock of maintenance personal replacing a filter cartridge is reduced.

The gas cleaning device may comprise a power source, as well referred to as high voltage source, herein. The high voltage source has a first source terminal and a second source terminal. The high voltage source may have a voltage source housing. The voltage source housing may be attached to and/or at least in part integrated in the duct. For example, a portion of the duct wall may as well be a part of the power source housing and/or the power source housing may be attached to the duct wall. A first source terminal may be electrically connected to and/or identical with the first duct terminal and optionally a second source terminal may be electrically connected to the second duct terminal and/or be identical with the second duct terminal. For example, the first duct terminal may be connected to a high voltage output terminal (i.e., the first source terminal) of the power source and the second duct terminal may be connected to a ground terminal (i.e., the second source terminal) of the power source or vice versa. The power source and/or the duct may have additional terminals. None of these terminals is necessarily a ground terminal, but at least one of these may be.

Another solution of the above sketched problems is provided by a method for connecting (and/or disconnecting) a first ionizer terminal of a gas ionizer to a first duct terminal of a gas duct of a gas cleaning device, wherein a first filter terminal is electrically connected (and/or disconnected) to the duct terminal and at the same time connected (and/or disconnected) to the first ionizer terminal. Preferably said connecting and disconnecting is obtained by contacting and releasing the previously provided contact, respectively.

The method can for example be performed by assembling the gas cleaning device as described above and/or in the figures by electrically connecting the first filter terminal to the first duct terminal by inserting the filter cartridge into the filter support and disconnecting by removing the filter cartridge from the filter support.

Only to avoid any confusion it is recalled that the term "terminal”, as usual, denotes a point, in practice piece with a contact surface, at which a conductor from a component, device or network comes to an end (see e.g. https://en.wikipe- dia.o rminal , dated May 19, 2022). In an alternative, one may say that a terminal is an electrical contact. Examples for a terminal are a male pin type connectors and/or a corresponding female sleeve type connectors and/or a simple contact pad.

Herein contacting two pieces means to provide an electrical contact between these two pieces by bringing them in direct contact. A connection in is an electrical connection, i.e., two electrically conducting pieces that are connected are contacted with each other indirectly or directly. An indirect connection may be provided e.g., by an electrical conductor that contacts both pieces. In case of a direct connection the two electrically conducting pieces contact each other.

Herein, a conductor is an electrical conductor (e.g., a metal), it may of course have a resistivity. A conductor distinguishes from an isolator in that an isolator has a band gap AE between the fermi energy E -and the conduction band, wherein the band gap is greater than the kpT E » kpT), T is the operating temperature and kp the Boltzman constant. Semiconductors (AE « k p _T ) shall be considered as conductors. In short, during normal operation, a conductor is electrically conducting, and an isolator is not.

Herein, the term conductive polymer and/or conductive ceramics encompasses not only polymers and/or ceramics being conductors or semiconductors, but as well compound materials based on a matrix of non-conducting polymers and/or non-conducting ceramic materials into which a conductive material, e.g., metal fibers and/or carbon fibers and/or graphite or the like have been integrated. The conducting compound hence may have a non-conductive matrix into which conductive fibers have been embedded and the conductivity of the compound can hence be attributed to the conductive fibers (which may as well be filaments, particles, beads or the like), being for example randomly distributed in the matrix. Of course, non-conducting fibers may as well be embedded in a conducing matrix. In both cases, the compound material is able to conduct a current.

Description of Drawings

In the following the invention will be described by way of example, without limitation of the general inventive concept, on examples of embodiment with reference to the drawings.

Figure 1 shows a perspective sectional view of a gas filter device.

Figure 2 shows a gas filter cartridge and a gas ionizer of the gas filter device of FIG. 1.

Figure 3 shows the gas filter cartridge and the gas ionizer of FIG. 1 with a power source in a top view.

Figure 3A shows detail C of FIG. 3.

Figure 3B shows detail D of FIG. 3.

Figure 4 shows a sectional view along the plane A-A of detail D of FIG. 3B.

Figure 5 shows a sectional view along the plane B-B of detail C of FIG. 3A.

Figure 6 shows a sketch of a filter medium and the connection of the filter electrodes with the corresponding terminals.

FIG. 1 shows an example gas cleaning device 1 in perspective sectional view. The gas cleaning device 1 has a duct 100 with a duct wall 110. Only as an example, the duct wall 110 may comprise a front wall 111, a rear wall 113 and two side walls 112. One of the two side walls 112 has been removed in FIG. 1 for illustrative purposes, only. The duct wall 110 has an upstream facing end surface 3 and a downstream facing end surface 4. The inner rim of the upstream facing end surface 3 delimits an inlet gas opening and the inner rim of the downstream facing end surface 4 delimits an outlet gas opening.

The duct 100 may comprise or form a filter support that may accommodate a filter cartridge 200. The filter cartridge 200 has a filter medium 220. Preferably, the filter medium 220 is a part of a capacitor or even preferred forms a capacitor. For example, the filter medium 220 may comprise a first polarizing electrode 221 and a second polarizing electrode 222. In between of these two polarizing electrodes 221,222 may be a dielectric medium 223 (see FIG. 6). The first polarizing electrodes 221 may be a first filter layer 221 and the second polarizing electrode 222 may be a second filter layer 222.

As can be seen in FIG. 2, the filter cartridge 200 may comprise an electrical module 240. The electrical module 240 may be made of or comprise a conductive polymer string and/or a conducting ceramic string and/or a conducting compound is attached to a filter cartridge 200. Preferably, the electrical module 240 is a unitary piece. The filter cartridge 200 may further comprise a first filter terminal 231 being connected with the first filter layer 221 and a second filter terminal 232 being connected with the second filter layer 222. As depicted, the electrical module 240 may comprises the first terminal 231 and the second filter terminal 232 and may as well comprise conductors connecting the first filter terminal 231 with the first filter layer 221 and the second filter terminal 232 with the second filter layer 222. Preferably, the first filter terminal 231 is connected via a first portion of the electrical module 240 (a first resistor Rl) with a branching point BR. Further, the branching point BR may preferably be connected via a second portion R2 of the electrical module 241 with the second filter terminal 232. The branching point BR may be further connected via a third portion R3 of the electrical module, i.e., via a third resistor R3 with the first filter layer 221. Further, the second filter terminal 232 may preferably be connected by a fourth portion R4 of the module 240 to the second filter layer 222 as shown (see as well FIG. 6).

Upstream of the filter cartridge 200 may be a gas ionizer 300 (see FIG. 1 to 3). The gas ionizer 300 is preferably supported by the duct 100 as well, but it can of course as well be supported and/or attached to other parts. The gas ionizer 300 may in a particularly preferred example, be supported independently from the filter cartridge 200, but again it is noted that this independence is not required, although it simplifies maintenance. Supported independently means in this context that if the filter cartridge 200 is removed, e.g., shifted out of the support (tray), the gas ionizer 300 may stay in place.

The gas ionizer 300 may have one or more first ionizer electrodes 321 (regardless of the number, briefly: first ionizer electrodes 321) and one or more second ionizer electrodes 322 (regardless of the number, briefly: second ionizer electrodes 322). The first ionizer electrodes 321 may be electrically connected via a conductor with a first ionizer terminal 331. Similarly, the second ionizer electrodes 322 may be electrically connected via a conductor with a second ionizer terminal 332. As can be seen, i.a., in FIG. 2, the first ionizer terminal 331 may preferably contact directly the first filter terminal 231 and/or the second ionizer terminal 332 may preferably contact directly the second filter terminal 232. As can be seen in this example, the at least one, preferably both ionizer terminals 321, 322 may preferably contact a peripheral surface of the corresponding filter terminal 231, 232, preferably directly. As shown in the depicted examples, it is preferred if at least one (shown: both) of the first filter terminal 231 and the second filter terminal 232 are first and second pins 231, 232 with longitudinal axes 2311, 2322 that extend parallel to the direction of movement when inserting or removing the filter cartridge 200 into or out of, respectively, the duct 200. In this example the direction of movement is indicated by a double headed arrow 9 (see FIG. 1). Only to rephrase it, the first and the second filter terminals 231, 232 may have the shape of first and a second pin 231, 232.

As can be seen best in FIG. 2, the filter cartridge 200 may have a front filter medium support 211 and/or a rear filter medium support 213. The electrical module 240 is preferably attached at least in part to the front filter medium support 211 and/or the rear filter medium support 213. The front filter medium support 211 and/or a rear filter medium support 213 are preferably made of in isolating material like, e.g., cardboard, wood, isolating plastics, etc.

Further, the gas cleaning device 1 may comprise a power source 400 (see FIG. 1 and 3). The power source 400 may provide a high voltage (for example 5kV, more generally 3 to 7kV even more generally 1-lOkV, depending on the distance of the ionizer electrodes) to a pair of duct terminals 131, 132, which are visible in FIG. 1, 4 and 5, respectively. As will be explained in more detail below, the first ionizer terminal 321 is preferably connected by and/or via the first filter terminal 212 with the first duct terminal 121 and hence to the power source 400. Similarly, the second ionizer terminal 322 may be connected by and/or via the second filter terminal 222 with the second duct terminal 122. Thus, if one removes the filter cartridge 200 from the duct, the gas ionizer 300 is disconnected from the power source 400 and it is avoided that O ₃ can be produced that would enter a passenger cabin if no filter cartridge were installed.

In FIG. 3 a top view (i.e., the viewing direction is parallel with the gas flow direction 2 in FIG. 1) of the filter cartridge 200, the gas ionizer 300 and the power supply 400 is shown. The duct walls have been omitted in the FIGs. 4 and 5 for illustrative purposes. In FIG. 3A and 3B, showing the details C and D of FIG. 3, two sections, namely A-A and B-B are indicated. Section plane A-A extends through the first filter terminal 231 and section plane B-B extends through the second filter terminal 232. The corresponding sectional views are shown in FIGs. 4 and 5, respectively.

As can be seen in FIGs. 2 and 4, the first duct terminal 131 may be a conducting protrusion being located in a first recess 161 (see Fig. 4) of the duct 100. As shown in FIG. 4, the power source housing may provide a portion of the duct wall 110 or may in part be unitary with at least a portion of the duct wall 110. The first recess 161 is delimited by a recess wall and the first duct terminal 131 may protrude through the bottom of the recess wall. In a preferred example, the first duct terminal 131 may comprise a conducting elastic element, e.g., a spring, that is preferably compressed if the first filter terminal 131 is inserted into its final location in the first recess 161 to thereby ensure a reliable electric contact between the first duct terminal 131 and the first filter terminal 231. In the final position of the first filter terminal 231, as depicted, the first filter terminal 231 engages into the first recess 161 to thereby contact the duct terminal 131. As can be seen in FIG. 4, the first ionizer terminal 331 may be pressed against the housing wall by a shoulder of the first filter terminal 231. Thereby, the contact between the first filter terminal 231 and the first ionizer terminal 331 is particularly good. In addition or alternatively, at least one of the first ionizer terminal 331 and the first duct terminal 131 may be a blade that cuts into the first filter terminal 231.

FIG. 5 shows a very similar setup of the second duct terminal 132, the second filter terminal 232, and the second ionizer terminal 332. The second duct terminal 132 may be a conducting protrusion being located in a second recess 162 of the duct 100. As shown, the power source housing may provide a portion of the duct wall or may in part be unitary with at least a portion of the duct wall 110. The second recess 162 is delimited by a recess wall and the second duct terminal 132 may protrude through the bottom of the second recess wall. In a preferred example, the second duct terminal 132 may comprise a conducting elastic element, e.g. a spring, that is preferably compressed if the second filter terminal 132 is inserted into its final location in the second recess 162 to thereby ensure a reliable electric contact between the second duct terminal 132 and the second filter terminal 232. In the final position of the second filter terminal 232, as depicted, the second filter terminal 232 may engage into the second recess 162 to thereby contact the second duct terminal 132. As can be seen in FIG. 5, the second ionizer terminal 332 may be pressed against the housing wall by a shoulder of the first filter terminal 232. Thereby, the contact between the second filter terminal 232 and the second ionizer terminal 332 is particularly good. In addition or alternatively, at least one of the second ionizer terminal 332 and the second duct terminal 132 may be a blade that cuts into the second filter terminal 232.

As can be seen in FIGs. 2 and 6, the filter medium 220 may comprise one or more plied sheets 221, 222, 223, but this is only a preferred example. Other types and shapes of filter media 220 may be used as well. The filter medium 220 may preferably comprise at least three layers: two polarizing electrode layers 221, 222 and a dielectric layer 223 in between of the electrode layers 221, 222. Each of the polarizing electrode layers 221, 222 may thus be considered as an electrode 221, 222 of a capacitor 220, wherein the dielectric layer 223 is the capacitor's dielectric 223 in between of the two polarizing electrodes 221, 222 (FIG. 6). The filter medium 220 may thus be and/or comprise and/or form a capacitor. List of reference numerals

1 gas cleaning device

2 flow direction

3 upstream facing side / upstream facing end surface 3

4 downstream facing side / downstream, facing end surface

100 duct / gas filter housing

110 duct wall / housing wall

111 front side wall / front wall

112 side wall

113 rear side wall / rear wall

131 first duct terminal/ protrusion (optional)

132 second duct terminal/ protrusion (optional)

161 first recess (optional)

162 second recess (optional)

200 filter cartridge

220 filter medium / capacitor (optional)

221 first polarizing electrode / first conductive filter layer

222 second polarizing electrode/ second conductive filter layer

223 dielectric medium (optional)

231 first filter terminal / first pin (optional)

2311 first terminal axis

232 second filter terminal / second pin (optional)

2311 second terminal axis

240 electrical module (optional)

300 gas ionizer (optional) 321 first ionizer electrode (optional)

322 second ionizer electrode (optional)

331 first ionizer terminal (optional)

332 second ionizer terminal (optional)

400 power source / high voltage source

R1 resistance/resistor between the branching point BR and the first filter terminal 231

R2 resistance/resistor between the branching point BR and the second filter terminal 232.

R3 resistance/resistor between the branching point BR and the first polarizing electrode 221

R4 resistance/resistor between the branching point BR and the second polarizing electrode 222

BR branching point