Electrostatic filter unit for air purification equipment and air purification equipment

Abstract

The invention relates to an electrostatic filter unit for an air purification device, wherein the filter unit (2) comprises an ionization unit (100) and a separation unit (170) having at least two deposition electrodes (17, 19). The electrostatic filter unit is characterized in that the at least two deposition electrodes (17, 19) are air-permeable and the filter unit (2) has at least one protective element for at least one of the elements of the ionization unit (100). In addition, the invention relates to an air purification device (1) having at least one filter unit according to the invention.

Description

Technical Field

[0001] The invention relates to a filter unit for an air cleaning device, in particular a smoke extractor, and to an air cleaning device having at least one filter unit. Background Art

[0002] Air cleaning equipment can be, for example, an air purifier for filtering indoor air, an equipment for filtering the air sucked in the passenger compartment in the automotive industry, or a smoke exhaust device for the kitchen, which smoke exhaust device is, for example, a range hood. It is known in these air cleaning equipments that liquid and solid dirt and odors are filtered out from the steam and smoke formed in the polluted air or cooking. Mechanical filters are mostly used for this purpose. As mechanical filters, for example, metal plate filters, perforated plate filters, baffle filters that can also be called eddy flow filters, edge suction filters and porous foam media are used. All of these mentioned filter media are filtered according to mechanical separation mechanisms such as diffusion effect, blocking effect and decisive inertial effect.

[0003] In the case of separation based on inertial effects, the particles, due to their inertia, cannot follow the flow lines of the gas (air) around individual filter fibers, expanded metal layers, porous media or the like and collide with them as a result. Due to the dominant inertial effect, the probability of particles hitting individual fibers of the filter medium (corresponding to the overall separation efficiency) increases with increasing particle velocity of the filter medium, increasing particle diameter, increasing filter packing density and filter density in the flow direction, and decreasing filter fiber diameter.

[0004] A disadvantage of these filter units is that particularly high inflow velocities must be achieved in order to ensure a satisfactory filter efficiency for particle diameters greater than 1 μm.

[0005] Furthermore, for example, DE 2146288 A discloses a range hood in which an electrostatic filter unit is used. In such a range hood, the electrostatic filter unit consists of a plate-shaped separation electrode and a counter electrode and a linear ionization electrode. The plate-shaped separation electrode and the counter electrode are connected to each other by conductive tabs and arranged in such a way that the air entering the filter element first flows into the separation electrode with the linear ionization element located therebetween and then into the upwardly biased counter electrode. The separation electrode is fastened to the housing of the range hood by a partition wall. Furthermore, a high-voltage device is arranged in the housing of the range hood near the intake port, which is connected to the electrodes of the filter unit.

[0006] A disadvantage of such filter units is that they require a relatively large installation space and at the same time present a risk for the user. Summary of the invention

[0007] The invention is therefore based on the object of creating a concept by means of which, with a simple design, a sufficient filter efficiency can be reliably ensured and yet a safe use can be ensured.

[0008] According to a first aspect, the object is thus achieved by an electrostatic filter unit for an air purification device, wherein the filter unit comprises an ionization unit and a separation unit with at least two deposition electrodes. The electrostatic filter unit is characterized in that the at least two deposition electrodes are air-permeable and the filter unit has at least one protective element for at least one of the elements of the ionization unit.

[0009] The electrostatic filter unit is also referred to as a filter unit or an electrostatic filter hereinafter. The filter unit has an ionization unit and a separation unit. The ionization unit can also be referred to as an ionization zone and the separation unit can be referred to as a separation zone. In order to be able to electrostatically separate particles in the air, these particles must first be electrostatically charged (ionized). For this purpose, the ionization unit works. The separation unit is connected after the ionization unit in the flow direction. The ionization unit preferably has at least one ionization electrode and at least one counter electrode. The ionization electrode is loaded with a voltage, preferably a high voltage. When the polluted air flows through the ionization unit, solid and liquid particles are electrostatically charged by means of an ionization electrode, which can also be referred to as a discharge electrode, by means of a corona discharge. The ionization electrode, which can be represented as a linear ionization electrode, is preferably arranged between two plate-shaped counter electrodes in the ionization unit. This is necessary because the particles usually have no charge in their original state or have insufficient charge for efficient electrostatic separation. The goal of the ionization unit is to electrically charge the particles of each individual particle until its maximum electrical saturation charge.

[0010] The separation unit comprises at least two deposition electrodes. The at least two deposition electrodes are preferably arranged parallel to each other. The at least two deposition electrodes are at a high voltage and thus form an electric field relative to each other. In this case, at least one deposition electrode is a negative deposition electrode and at least one deposition electrode is a positive deposition electrode. In this case, the magnitude or value of the electric field strength depends decisively on the potential, that is to say the value of the voltage in kV, the distance between the positive deposition electrode and the negative deposition electrode relative to each other, and the geometry of the deposition electrodes.

[0011] The air escaping from the ionization unit with the electrically charged particles flows into the separation unit. Due to the electric field formed there between the deposition electrodes, the particles are separated at the deposition electrodes and thus filtered out of the air.

[0012] In order to ionize particles from the air and also for the separation of these particles, a high voltage of several thousand volts is required, whereby not only positive high voltage but also negative high voltage can be used. In order to generate / produce this necessary high voltage, a high voltage transformer is used, which can also be referred to as a high voltage generator, a high voltage power supply. Such a high voltage transformer supplies the ionization zone and the separation zone of the electrostatic filter box with high voltage or electrical energy. Here, the high voltage transformer is preferably implemented in an electrostatic filter unit, which can also be referred to as a filter module or a filter box. The electrostatic filter module / filter box is preferably arranged in the air intake area of ​​the smoke exhaust device in order to protect the components placed behind it from the influence of cooking smoke / aerosol / dirt. However, such a filter device can also be optionally arranged in the air outlet area in the smoke exhaust device or arranged along the air flow guide between the inlet area and the outlet area of ​​the smoke exhaust device.

[0013] According to the present invention, the deposition electrode is permeable. The deposition electrode can be made of a permeable material or a non-permeable material with at least one air permeable port. In the first case, the deposition electrode is also referred to as a porous deposition electrode. All deposition electrodes can be made of the same permeable material. However, under the framework of the present invention, different deposition electrodes are made of different materials. The advantage of using a permeable material for the deposition electrode is that, on the one hand, it is easy to manufacture an electrostatic filter because the required permeability is given by the material itself. On the other hand, in the case of a permeable material, the openings in the material have a small size, which can ensure efficient separation of particles based on a mechanical separation effect. According to this embodiment in which the deposition electrode is made of a non-permeable material with at least one air permeable port, it is also feasible that only some of the deposition electrodes, such as only the positive deposition electrode or only the negative deposition electrode, are made of this material, and correspondingly the other deposition electrodes are made of a permeable material. In addition, it is also feasible that, for example, only the first, that is, the deposition electrode facing the ionization unit is made of a non-permeable material with a air permeable port. The non-permeable material can be a plate, for example. The air permeability openings can be holes, for example, which are punched or introduced into the sheet material in another way. In particular, the air-impermeable material with the air permeability openings can be a metal sheet.

[0014] Thus, the material of the at least one deposition electrode can be, for example, expanded metal, wire mesh, fiber material, nonwoven, perforated sheet, sintered plastic or foam material.

[0015] This results in a number of advantages. On the one hand, the air flow can not only flow along the deposition electrodes as in the prior art, but can also flow through these deposition electrodes. Due to the air permeability of the deposition electrodes, these deposition electrodes can therefore be used as mechanical filters. Since the separation unit of the ionization unit is placed behind in the flow direction, the particles contained in the air enter the separation unit in an electrically charged state. Therefore, the separation of the particles at the deposition electrodes is obtained not only by a mechanical filtering effect but also by a charge-induced, that is, electrostatic filtering effect.

[0016] Typical mechanical filters have the following properties: Due to the dominant inertial effect, the filtration efficiency for particles with a diameter of >1 μm increases with increasing flow velocity. In the case of purely electrostatic filters, the filtration efficiency increases with decreasing flow velocity, since the residence time of the particles in the ionization and separation zones is increased. The combination according to the invention effectively utilizes the advantages of both the mechanical and the electrostatic filtration mechanisms.

[0017] Furthermore, for typical electrostatic filters, the filtration efficiency depends significantly on the values ​​of the ionization voltage and the separation voltage. If the electronic high-voltage component fails (voltage failure) or the electronic high-voltage component fails due to a short circuit, there is no longer any filtration effect. On the contrary, in the case of the present invention, the mechanical filtration mechanism or the filtration effect is still maintained. Therefore, there is no complete failure of the overall filtration performance.

[0018] Finally, due to the gas permeability of the deposition electrode, the particles can be at least partially retained in the pores or other gas permeable openings of the deposition electrode.

[0019] According to the invention, the electrostatic filter unit has at least one protective element for at least one of the elements of the ionization unit. In the sense of the invention, the following element or device is called a protective element, which protects the user from direct or indirect contact with one of the elements of the ionization unit and / or protects the elements of the ionization unit from mechanical damage.

[0020] By providing at least one such protective element, the electrostatic filter unit can be operated at high pressure and thus achieve an increase in the filter efficiency and protect the user and the filter unit.

[0021] According to one embodiment, the protective element is a protective element that resists the action of forces. In this embodiment, the protective element can preferably be a flat element that is arranged in front of the ionization unit in the flow direction. Here, the protective element is gas-permeable.

[0022] Additionally or alternatively, the protective element can be a shielding element for electrical shielding. In particular, the ionization unit and the separation unit can be shielded.

[0023] According to a preferred embodiment, the protective element is designed as an intervention protection device, which has at least one layer and is connected in front of the ionization unit in the flow direction. By connecting the protective element in front of the ionization unit in the flow direction, it is possible to ensure not only physical access to the ionization unit by the user but also electrical shielding of the ionization unit relative to the user. The intervention protection device is preferably dimensioned so that the side of the ionization unit facing the flow direction is completely shielded by the layers of the intervention protection device.

[0024] According to a preferred embodiment, at least one layer of the intervention protection device is designed as a prefilter. A layer is referred to as a prefilter, which is used to filter relatively large dirt and dust particles, in particular with a diameter d hyd >=1 μm. By designing the protective element as a prefilter, in addition to preventing user intervention in the ionization unit and preferably electrically shielding the ionization unit and the separation unit, the filter efficiency of the electrostatic filter unit can also be increased. The prefilter consists of expanded metal, perforated sheet metal, wire mesh, welded grid or warp-woven wire grid.

[0025] According to one embodiment, the intrusion protection device has at least one protective layer and a spacer element in addition to the prefilter. The spacer element is arranged between the prefilter and the protective layer. The protective layer is preferably a layer which is the first layer of the intrusion protection device in the flow direction. The protective layer can be made of an electrically conductive material, in particular a metal, or of an electrically insulating material, in particular a plastic.

[0026] According to one embodiment, the protection element is at least partially composed of a surface impedance R <= 10 11 The prefilter is preferably composed of such a material. By using such a material, it is possible to at least conduct away the voltage present in the prefilter.

[0027] According to another embodiment, at least one protective element is embodied as at least one component of a housing for the ionization unit. In particular, the protective element in this embodiment is preferably embodied as at least one component of an insulating housing of the ionization unit. In this embodiment, the protective element is preferably composed of an insulating material. By providing an insulating protective element, it is possible in particular to accommodate voltage-impinging elements of the ionization unit in such a way that these elements cannot be reached by a user.

[0028] According to one embodiment, the filter unit has a high-voltage transformer, and the high-voltage transformer is integrated in one of the housing parts. This prevents a user from accessing the high-voltage transformer. In addition, the design of the air purification device can be simplified by integrating the high-voltage transformer into the filter unit, since such an air purification device only has to have lines and contact points for the low voltage.

[0029] According to a preferred embodiment, the filter unit has a protective element which is designed as a prefilter and the prefilter is connected to the return line of the secondary side of the high-voltage transformer.

[0030] According to one embodiment, the electrostatic filter unit has a filter frame, and the filter frame is connected to a return line on the secondary side of the high-voltage transformer.

[0031] According to one embodiment, the deposition electrode is in a state perpendicular to the flow direction of air through the ionization unit. The flow direction of air through the ionization unit is preferably parallel to one or more counter electrodes of the ionization unit. Therefore, the deposition electrode is preferably transverse and in particular perpendicular to one or more counter electrodes of the ionization unit.

[0032] By such an orientation of the air-permeable deposition electrode, the air flow entering the separation unit can be guided completely through the deposition electrode. The filtration efficiency is thus further increased. In addition, by such an orientation of the deposition electrode, the required installation space for the filter unit can be minimized. In contrast to filter units, in which the deposition electrode is parallel to the air flow and preferably to one or more counter-electrodes of the ionization unit, the height or length of this embodiment of the filter unit according to the invention is smaller, since the deposition electrode is in a transverse position in this direction.

[0033] According to one embodiment, the deposition electrodes abut against each other. In typical electrostatic filters with plate or tubular separators in the separation unit, relatively significantly more space is required for the electrostatic filter as a whole and in particular for the separation zone. In the filter unit according to the invention, the deposition electrodes are gas-permeable. Preferably, the deposition electrodes are in the form of gas-permeable plates or layers. Therefore, even in the case of a plurality of deposition electrodes placed one on top of the other, the total height of the stacked structure of the deposition electrodes is small. In addition, due to the small spacing of the deposition electrodes relative to each other, the particles separated / filtered between the individual gas-permeable deposition electrodes can be retained between the deposition electrodes due to capillary action. Therefore, according to the separation zone of the invention, these particles can be stored in the separation zone itself in addition to the storage device.

[0034] The order of the deposition electrodes in the separation unit can be freely selected according to the invention. Thus, for example, a positive deposition electrode can be arranged at the side of the separation unit that faces the ionization unit and through which the air enters the separation unit, and then a negative deposition electrode and a positive deposition electrode can be arranged alternately. Alternatively, however, a negative deposition electrode can also be arranged as the first deposition electrode at the side facing the ionization unit and then positive and negative deposition electrodes can be arranged alternately.

[0035] However, according to another embodiment, it is also possible that at least two deposition electrodes adjacent to each other have the same polarity. Thus, for example, two or more negative deposition electrodes can be arranged between two positive deposition electrodes.

[0036] According to a preferred embodiment, at least one of the deposition electrodes has an insulating coating. The insulating coating should be able to be applied to the deposition electrodes by means of powder coating, dip coating or other coating processes. Preferably, the respective deposition electrode is completely electrically insulated, wherein the insulating coating is omitted at the electrical contact points that are respectively required for applying voltage to the deposition electrode.

[0037] As a result, electrical short circuits and the voltage disturbances associated therewith can be avoided between the individual deposition electrodes which are alternately subjected to voltage.

[0038] According to the invention, all deposition electrodes of the separation unit can be provided with an insulating coating. Preferably, however, only the positive deposition electrode is electrically insulated. The particles are charged in the ionization unit. If the positively charged particles strike the negative deposition electrode, then the particles should also be able to release their charge again, because otherwise the electric field between the layers would weaken over time. However, by providing the positive deposition electrode with an insulating coating in the embodiment mentioned, an electrical short circuit between the positive deposition electrode and the negative deposition electrode can be prevented even in the case of a small spacing or abutment between the deposition electrodes.

[0039] According to a further aspect, the invention relates to an air cleaning device having at least one electrostatic filter unit according to the invention.

[0040] The advantages and features described with respect to the electrostatic filter unit apply correspondingly to the air purification device, as far as applicable, and vice versa.

[0041] The air cleaning device can be, for example, an air purifier for filtering indoor air, a device for filtering air sucked into a passenger compartment in the automotive industry, or a smoke extraction device for a kitchen. The air cleaning device can have a plurality of electrostatic filter units according to the invention. At least one electrostatic filter unit is preferably arranged at the intake side of the air cleaning device. However, within the framework of the present invention, it is also possible to provide at least one electrostatic filter unit at the outlet side of the air cleaning device as an additional solution or alternative.

[0042] According to one specific embodiment, the air cleaning device is embodied as a range hood, and the range hood has at least one contact point for making contact with the high-voltage transformer of the filter unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention is described in more detail below with reference to the accompanying drawings, in which:

[0044] Figure 1 A schematic perspective view of an embodiment of an air purification device according to the present invention is shown;

[0045] Figure 2 shows a schematic exploded view of an embodiment of an electrostatic filter unit according to the present invention;

[0046] Figure 3 Shown according to Figure 2 A schematic exploded view of an intervention device of an electrostatic filtration unit;

[0047] Figure 4 Shown according to Figure 2 A schematic exploded view of an ionization unit of an electrostatic filtration unit;

[0048] Figure 5 Shown according to Figure 2 A schematic exploded view of a separation unit of an electrostatic filtration unit;

[0049] Figure 6a and 6b Shown according to Figure 2 A schematic perspective view of an embodiment of a deposition electrode of an electrostatic filtration unit;

[0050] Figure 7 A schematic cross-sectional view showing an embodiment of a deposition electrode of an electrostatic filtration unit according to the present invention;

[0051] Figure 8a and 8b A schematic cross-sectional view showing a further embodiment of a deposition electrode of an electrostatic filtration unit according to the invention;

[0052] Fig. 9A schematic diagram showing the wiring of an embodiment of an electrostatic filtration unit according to the present invention; and

[0053] Fig.10 A schematic diagram shows the filter efficiency of an electrostatic filter unit according to the invention in comparison with an expanded metal filter. DETAILED DESCRIPTION

[0054] exist Figure 1 , an embodiment of an air cleaning device 1 according to the present invention is shown. In the embodiment shown, the air cleaning device 1 is a range hood. An inlet is formed in the front side of the air cleaning device 1, in which two electrostatic filter units 2 are arranged in the embodiment shown. However, it is also possible within the framework of the present invention to arrange only one or more than two electrostatic filter units 2 in the inlet. An air outlet sleeve 3 for air escape from the air cleaning device 1 is provided on the upper side of the air cleaning device. In the embodiment shown, the inlet and therefore the electrostatic filter unit 2 are in a vertical state. However, it is also possible within the framework of the present invention that the inlet and therefore the electrostatic filter unit 2 are in any adjustment angle between the vertical state and the horizontal state. The electrostatic filter unit 2 has a box shape in the embodiment shown. The electrostatic filter unit 2 is therefore also called a filter box. In particular, the electrostatic filter unit 2 has a width and a length that are respectively greater than the depth. Here, the dimension along the main flow direction is called the depth, which is in the horizontal in the embodiment shown. The main flow direction is indicated in the figure by a block arrow. The electrostatic filter unit 2 completely covers the inlet. Therefore, all air flowing into the air purification device 1 is guided through the electrostatic filter unit 2. During operation of the air purification device, the polluted air flows through the large filter surface of the electrostatic filter unit 2 and is removed by the filter by means of the electrostatic filtration mechanism and also the mechanical filtration mechanism. hyd Liquid and solid dirt / particles with a hydraulic diameter of >=0.001 μm. If the electrostatic filter unit 2 has reached its saturation with dirt, it can be removed from the air purification device and cleaned in a dishwasher or manually by hand with water and detergent.

[0055] exist Figure 2 A schematic exploded view of an embodiment of an electrostatic filter unit 2 according to the present invention is shown. In the embodiment shown, the electrostatic filter unit 2 consists of a filter frame 40, an intervention protection device 60, an ionization unit 100 and a separation unit (170). These individual functional components of the electrostatic filter unit 2 each have a flat shape or a defined surface. The filter frame 40 in the embodiment shown consists of two parts. Figure 2The components shown as lower components are referred to below as filter frame front side 4 and the components shown as upper components are referred to as filter frame rear side 5. In order to produce or to assemble the electrostatic filter unit 2, the intervention protection device 60, the ionization unit 100 and the separation unit 170 can be placed in the filter frame front side 4 and then closed with the filter frame rear side 5.

[0056] exist Figure 3 , an embodiment of the intervention protection device 60 is shown in an exploded view. The intervention protection device 60 constitutes a protection element according to the present invention. In the embodiment shown, the intervention protection device 60 consists of three individual parts. In particular, the intervention protection device 60 consists of a protective layer 6, a spacer element intervention protection structure 7 and a filter layer of a pre-filter part 8, which is also referred to as a pre-filter in the following text. The individual parts of the intervention protection device 60 each have a flat shape or a layer shape. The first layer, which constitutes the actual protective layer 6, protects the individual parts of the intervention protection device 60 placed behind it and the structural components of the electrostatic filter unit 2 from inappropriate forces from the outside. In addition, the protective layer 6 can contribute to the appearance of the entire filter box as a design element. The protective layer 6 can be made of an electrically conductive material, in particular metal, or of an electrically insulating material, in particular plastic.

[0057] In addition to mechanical protection against force action, the intrusion protection device 60 can also be used as an electrical protection element. In particular, the filter layer for the pre-filter 8 is used as an electrical protection element. On the one hand, the filter layer for the pre-filter 8 is used as a filter for relatively large dirt and dust particles, especially with a diameter of d hyd >=1 μm particles pre-filter. On the other hand, the filter layer of the pre-filter 8 is also used as an electrical shield. Here, the shielding by the filter layer of the pre-filter 8 is carried out according to the principle of the Faraday cage. In particular, the ionization unit 100 and the separation unit 170 located behind the filter layer of the pre-filter 8 in the flow direction are shielded by this filter layer. In particular, the filter layer of the pre-filter 8 causes that the external suction area, that is, the area located in front of the electrostatic filter unit 2 in the flow direction, maintains a zero field due to the static and quasi-static electric field of the ionization unit and prevents the electric induction caused by this to the outside, especially outside the protective layer 6. The undesirable static loading of the protective layer 6 is thus prevented. The filter layer of the pre-filter 8 is preferably composed of an air-permeable conductive or antistatic material. The filter layer of the pre-filter can be made of conductive plastic, for example. However, the filter layer of the pre-filter 8 can also be composed of a metal plate mesh, a punched plate, a wire mesh, a welded grid or a warp-woven wire grid, for example. The filter layer of the pre-filter 8 preferably has a surface impedance R <= 10 11 In the embodiment shown, the filter layer of the pre-filter 8 consists of only one layer. However, it is also possible within the scope of the present invention that the filter layer of the pre-filter 8 consists of more than one layer.

[0058] A further layer of an intrusion protection device 60 is arranged between the filter layer of the prefilter 8 and the protective layer 6. This layer is called a spacer element intrusion protection structure 7 and serves to hold the filter layer of the prefilter 8 and the protective layer 6 at a defined distance relative to each other.

[0059] exist Figure 4 1 shows an embodiment of an ionization unit 100 of an electrostatic filter unit 2 in an exploded view. In the embodiment shown, the ionization unit 100 comprises an inner frame 9, two insulating housing parts 10, 11, a counter electrode 15 and an ionization element 16 which can also be referred to as a discharge electrode. In addition, a spacer 12 is provided in the embodiment shown, which holds the counter electrodes 15 at a distance relative to each other. In addition, the ionization unit 100 in the embodiment shown comprises a high-voltage transformer 14 and a high-voltage busbar 13.

[0060] The insulating housing parts 10 and 11 are inserted into the inner frame 9. The insulating housing parts 10, 11 each have a rectangular rod shape and are inserted into the inner frame 9 at opposite ends, in particular longitudinal ends. The insulating housing parts 10, 11 each have a contact opening at one side, into which the ionization element 16 is guided. The insulating housing parts 10 and 11 are introduced into the inner frame 9 in such a way that the contact openings face each other. Thus, the ionization element 16, which can be in the form of a wire, can be clamped between the insulating housing parts 10, 11. In the embodiment shown, the counter-electrode 15, which is formed by a plate, is inserted into the inner frame 9 and preferably also into the insulating housing parts 10, 11. In addition, a spacer 12 is arranged, by which the counter-electrodes 15 are held at a distance relative to each other over their entire length. The insulating housing parts 10, 11 are preferably composed of an electrically insulating material and preferably have a surface impedance R>=10 11 The insulating housing parts 10 , 11 preferably consist of ceramic or plastic.

[0061] In one of the insulating housing parts 10, 11, in the embodiment shown, an installation space is additionally provided in the insulating housing part 11. The installation space is provided with a high-voltage transformer 14, a high-voltage busbar 13 and various wiring elements and contacts (not shown) which are necessary for the electrical contacting of the individual parts concerned. The ionizing element 16 is then fastened between the insulating housing parts 10, 11 and in particular between the high-voltage busbar 13 of the insulating housing part 11 and the insulating housing part 10.

[0062] exist Figure 5An embodiment of a separation unit 170 of an electrostatic filter unit 2 is shown in FIG. The separation unit 170 is constructed by a negative deposition electrode 17, a spacer element separation unit 18 and a positive deposition electrode 19. The spacer element 18 holds the positive deposition electrode 19 and the negative deposition electrode 17 at a predetermined distance relative to each other. A high voltage of U > 1 kV DC (direct current) is preferably applied to the positive deposition electrode 19. Preferably, the positive deposition electrode 19 is completely electrically insulated with an electrically insulating cover layer except for the contact points 20 in order to prevent discharge sparks and short circuits. For the insulation of the positive deposition electrode 19, the positive deposition electrode can be coated. Functional powder layers, vortex sintering, sol-gel, dip coating, emulsion or painting are considered coating methods. As a base material or matrix for the positive deposition electrode 19, an electrically conductive material, in particular a metal, is preferably used. Particularly preferably, as a matrix for the positive deposition electrode 19, a Figure 6a and Figure 6b The materials shown in Figure 6a In an embodiment, the substrate is a perforated sheet or expanded metal and according to Figure 6b Appears as a welded grid.

[0063] As an alternative to the metal for the substrate on which the electrode 19 is deposited, it is also possible to consider a substrate having a surface resistance R <= 10 11 Ohmic conductive or antistatic plastic.

[0064] The negative deposition electrode 17 is also a gas-permeable medium. The negative deposition electrode 17 is also made of a conductive material, such as metal, or an antistatic material, such as a material having a surface resistance R <= 10 11 Ohmic plastic composition. For the negative deposition electrode 17, for example expanded metal, punched sheet, wire mesh, welded grid, woven wire grid and plastic mesh can be used.

[0065] exist Figure 7 An alternative embodiment of the deposition electrodes 17, 19 of the separation unit 170 is shown in FIG. Figure 7 In the embodiment shown in , the negative deposition electrode 17 consists of a single piece which is arranged in a serpentine or corrugated manner between the positive deposition electrodes 19. This embodiment has the advantage that the individual negative deposition electrodes 17 do not have to be individually electrically contacted with each other by contacts or other means.

[0066] exist Figure 8a and Figure 8b1 shows a further embodiment of the deposition electrodes of the separation unit 170. In this embodiment, the deposition electrodes 17, 19 each have a pleated or corrugated structure. These measures are used to reduce the pressure loss Delta p [Pa] when the filter medium (of the separation unit 170) flows through, and to increase the filter efficiency under generally unchanged boundary conditions, on the one hand. In particular, the area of ​​the deposition electrodes 17, 19 can be increased with the same width and length of the filter frame 40.

[0067] In each of these embodiments of the deposition electrodes 17 , 19 , the deposition electrodes can each consist of a single layer. Alternatively, however, the positive deposition electrode 19 can be constructed from a plurality of layers with n>=1. This also applies to the negative deposition electrode 17 .

[0068] The number of positive deposition electrodes 19 per filter module corresponds to >= 1. The number of negative deposition electrodes 17 per filter module also corresponds to >= 1. Spacer elements 18 can be used to improve the filtration efficiency. Alternatively, these spacer elements can also be omitted, and the positive and negative deposition electrodes 17, 19 can be stacked directly on top of each other. However, the spacer elements 18 cause a performance improvement in the filtration efficiency.

[0069] Preferably, the sequence of the positive and negative deposition electrodes 17, 19 is as in Figure 5 In the flow direction, the first and last deposition electrodes can be either positive deposition electrodes or negative deposition electrodes. This means that the first layer or the first electrode can be positive or negative, and the last layer or the last electrode can also be positive or negative.

[0070] exist Fig. 9 The electrical wiring of the electrostatic filter unit 2 is schematically shown in . The electrical power supply with low voltage (<=50 V AC; <=120 V DC) or low voltage (<=1000 V AC; <=1500 V DC) is realized via the contact points or connections of the low voltage 26 on the primary side of the high-voltage transformer 14.

[0071] The power supply is carried out via contact elements (not shown) between each individual electrostatic filter unit 2 and the smoke extraction device or air purification device 1. The electrical contact is ideally made between the support surface of the filter frame rear side 5 and the air purification device 1 in the area of ​​the air inlet. The support surface of the filter frame rear side 5 is the support surface of the filter frame rear side 5. Figure 2 Alternatively, the electrical contact interface can be realized at any desired location on the outer surface of the filter frame elements 4 and 5 .

[0072] On the secondary side, a high-voltage line 24 with U>1 kV DC is connected via the high-voltage busbar 13 (see Figure 4 ) is connected to the ionization element 16 and further to all positive deposition electrodes 19. The return line 23 on the secondary side is connected to all counter-electrodes 15 and to one or more negative deposition electrodes 17. The filter frame front side 4, the filter frame rear side 5 and the filter layers of the pre-filter 8 are also connected to the return line 23 and are at the same potential.

[0073] exist Fig.10 For particle size range 0.3 ≤ d hyd <=3 μm shows the filter efficiency of a metal mesh filter for an average flow velocity c<1 m / s and shows the filter efficiency of an embodiment of the electrostatic filter unit 2 according to the invention. As can be read from the graph, the electrostatic filter unit 2 according to the invention has a significantly better filter efficiency than a typical metal mesh filter of a smoke extractor.

[0074] The present invention has a number of advantages.

[0075] Preferably, the surface impedance R≤10 11 The ohmic, completely surrounding conductive or antistatic housing, which serves as an electrical shield, protects the user / customer and his environment from electrical hazards. All individual components subject to high voltage are completely encapsulated by conductive or antistatic elements due to this structural design. Electrostatic charging of the outermost individual components, in particular the filter frame and the insertion guard, which can be directly touched by the consumer, is prevented.

[0076] Due to the invention having at least one protective element, an electrostatic filter mechanism can be used without causing danger to the user. In this way, compared to typical range hood grease filters, in particular for low flow velocities c<2 m / s, a filter having a hydraulic diameter d hydSignificantly better filtration efficiency for liquid and solid particles <100 μm. The improved filtration efficiency is achieved in particular in embodiments of electrostatic filter units in which porous deposition electrodes are used and thus the diffusion effect, blocking effect and mass inertia effect of the electrostatic filtration mechanism are superimposed on the mechanical separation mechanism that otherwise acts. Due to the significantly better filtration efficiency, especially at low flow velocities c<2 m / s, the downstream elements of the smoke extractor (fan, housing, odor filter) remain free of oil and dirt accumulation. In particular for circulating smoke extractors, which in the direction of flow represent an odor filter (activated carbon or zeolite filter) connected downstream of a grease filter, the service life (lifetime) of the circulating filter remains longer or is thus extended, since the circulating filter in this case does not become contaminated by the finest particles and thus become clogged. In contrast to typical grease filters of smoke extractors, such electrostatic filter cartridges have a significantly lower pressure loss Delta p at the same filtration efficiency.

[0077] By providing a protective element according to the invention, which can be, for example, an insulating housing part, a high-voltage carrier can be introduced into the electrostatic filter unit without this high-voltage carrier being dangerous to the user. Since the electrostatic filter unit can also be supplied with electrical energy from the air cleaning device via contacts with low voltage (<=50 V AC; <=120 V DC) or low voltage (<=1000 V AC; <=1500 V DC), the electrical risk for the user / consumer is also reduced.

[0078] Finally, the solution of preferably using a gas-permeable "porous" deposition electrode instead of a plate group (the plate group corresponds to the structure of a typical electronic filter for separation) reduces the complexity and cost point of the entire system, because fewer individual parts are used. By using a gas-permeable (porous) insulating deposition electrode, a fine electrostatic field with a high electric field strength is generated. Compared to a typical plate-type electronic filter according to the Penney principle, a high separation capacity can be achieved with a very small construction space. The invention makes it possible to use this high electric field strength without endangering the user.

[0079] Furthermore, in contrast to typical electronic filters with plate separators, which due to their structural form have only a low storage capacity, a greater storage capacity is provided by using a permeable deposition electrode. In the case of typical electronic filters with plate separators, the filtered / separated particles accumulate on the surface of the airtight separation plate. With a greater accumulation of particles, the retention capacity of this surface is exhausted. This leads to the detachment of the filtered / separated particles. These particles are then carried away again, for example, by an air flow. By using a permeable / porous deposition electrode, a storage structure or a storage structure is obtained. The detachment of already separated particles is greatly reduced.

[0080] Finally, due to the preferably provided electrically insulating coating of the positive deposition electrode, it is possible to place the electrodes directly one above the other without the electric field collapsing due to leakage currents and discharge sparks between the positive and negative deposition electrodes. The electrostatic filter unit thus has a better leakage current stability.

[0081] List of reference numerals:

[0082] 1. Air purification equipment

[0083] 2 Electrostatic filtration unit

[0084] 3. Air outlet sleeve of air purification equipment

[0085] 40 Filter Framework

[0086] 4 Filter frame front

[0087] 5 Filter frame rear side

[0088] 60 Protection elements

[0089] 6. Protective layer

[0090] 7 Spacer element intervention protection structure

[0091] 8 Filter layer of pre-filter

[0092] 9 Inner frame

[0093] 100 Ionization Unit

[0094] 10 Insulating housing parts

[0095] 11 Insulating housing parts including the inserting space

[0096] 12 Spacer

[0097] 13 High voltage busbar

[0098] 14 High Voltage Transformer

[0099] 15 Paired Electrode

[0100] 16 Ionization element / discharge electrode

[0101] 170 Separation Unit

[0102] 17 Negative deposition electrode

[0103] 18 Spacer element separation unit

[0104] 19 Positive deposition electrode

[0105] 20 Contact of deposited electrode

[0106] 23 Return line to secondary side / connector of negative deposition electrode

[0107] 24 High voltage connector / high voltage wire on the secondary side

[0108] 26 Low voltage connector

[0109] Dhyd = hydraulic diameter.

Claims

1. A range hood having at least one electrostatic filter unit, wherein: The filter unit (2) comprises an ionization unit (100) and a separation unit (170) having at least two deposition electrodes (17, 19), characterized in that the at least two deposition electrodes (17, 19) are gas-permeable and the filter unit (2) has at least one protective element for at least one of the elements of the ionization unit (100), wherein the protective element (60) is a shielding element and / or a protective element for resisting force, wherein at least one protective element (60) is an intervention protection device having at least one layer and being connected in the flow direction before the ionization unit (100), wherein at least one layer is a prefilter (8), wherein the intervention protection device has at least one protective layer (6) and a spacer element (7), and wherein the spacer element (7) is arranged between the protective layer (6) and the prefilter (8).

2. The range hood according to claim 1, characterized in that: The protection element (60) is at least partially composed of a 11 The ohmic surface impedance of the conductive or antistatic components.

3. The range hood according to claim 1 or 2, wherein: At least one protective element (60) is embodied as at least one housing part (10, 11) of a housing for the ionization unit (100).

4. The range hood according to claim 3, wherein: The filter unit (2) has a high-voltage transformer (14), and the high-voltage transformer (14) is integrated in one of the housing parts (10, 11).

5. The range hood according to claim 4, characterized in that: The prefilter (8) is connected to the return line of the secondary side of the high-voltage transformer (14).

6. The range hood according to claim 5, characterized in that: The electrostatic filter unit (2) has a filter frame (40), and the filter frame (40) is connected to the return line of the secondary side of the high-voltage transformer (14).

7. The range hood according to claim 1 or 2, wherein: The deposition electrodes (17, 19) are in a state perpendicular to the flow direction of air passing through the ionization unit (100).

8. The range hood according to claim 1 or 2, wherein: At least one of the deposition electrodes (17, 19) has an insulating coating.

9. The range hood according to claim 1 or 2, wherein: The positive deposition electrode (19) has an insulating coating.

10. The range hood according to claim 1 or 2, wherein: The range hood has at least one contact point for making contact with a high-voltage transformer (14) of the filter unit (2).

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