Mist generating device

Abstract

The invention relates to a mist generating device for generating an aerosol from a liquid. The mist generating device includes at least one chamber (102-116) in which an aerosol is generated. Each chamber (102-116) includes a chamber housing including a bottom portion and a sidewall extending from the bottom portion to a top portion of the chamber (102-116); an ultrasonic transducer (122-136) arranged at the bottom; and a filter element (502, 504) arranged at the top of the chamber (102-116). In operation of the mist generating device (100), the chambers (102-116) are at least partially filled with a liquid to a filling level (802) such that at least the ultrasonic emitting surfaces (804, 806) of the ultrasonic transducers (122-136) are submerged in the liquid. The chamber (102-116) has a directed gas inlet (808, 810) at the sidewall configured to direct a gas flow introduced into the chamber (102-116) in a direction substantially parallel (812, 814) to a surface of the liquid in the chamber (102-116) and substantially along the sidewall. The filter element (502, 504) includes a plurality of guide surfaces (702) configured to direct an airflow out of the chamber (102-116) in a direction substantially perpendicular (828, 830) to a surface of the liquid in the chamber (102-116).

Description

Technical Field

[0001] The present application relates to a mist-generating device for generating an aerosol from a liquid. The mist-generating device comprises at least one chamber in which the aerosol is generated by an ultrasonic transducer. Background Art

[0002] A mist generator, also known as a fog machine, mist generator or simply a mister, is a device used to create a dreamy or mysterious atmosphere in a live performance or space. It typically produces an extremely fine mist similar to a fog machine, but at a lower temperature and with less emissions. Its main function is to scatter light in a different way, reflecting light from the source back into the audience or room, creating a more significant visual impact and sense of depth. Many popular shows and clubs use mist machines to enhance the atmosphere and emphasize certain elements of their production. Misting can also be used to filter out any bright colors and shapes, making them more subtle.

[0003] A mist machine can draw an air stream from the atmosphere and then pass it through a vaporizer, which vaporizes a liquid or atomizing solution stored in the machine's reservoir. The air then disperses the atomizing solution into a vaporized mist of tiny droplets, which is then blown into the air. There are a variety of technologies used to vaporize the liquid in a mist machine. These technologies include atomizing and spraying the liquid into the air through a spray pump. There are also ultrasonic and thermal methods, which rely on sound and temperature, respectively, to vaporize the liquid. Ultrasonic mist machines use a transducer immersed in the liquid to vaporize the liquid and create a mist. Ultrasonic mist machines can generate their effects with less noise than other technologies.

[0004] Generally speaking, two immiscible substances can be easily mixed together using ultrasound. Such a mixture is usually called a colloid or dispersion. If the mixture consists of small droplets, it is called an aerosol (or mist) if these droplets are dispersed in a gas, and an emulsion if they are in another liquid.

[0005] One of the main applications of ultrasonic dispersion is the atomization of liquids, i.e. the generation of aerosols. For this purpose, ultrasonic waves arriving from below the liquid surface can be used. If the intensity of the sound waves is high enough, a spray of droplets or mist emerges from the surface as a side effect of the formation of an ultrasonic fountain. It is worth noting that the aerosol generated is monodisperse, i.e. the size of the droplets is almost uniform. The formation of this mist is not a thermal process, but rather by exciting capillary waves at the liquid surface, which propel the droplets into the air.

[0006] For the generation of capillary waves, the propagation of surface waves on a liquid can be considered. If the surface is subjected to a harmonic disturbance with a certain angular frequency, a potential flow will be generated in the liquid, which describes a surface wave propagating in the horizontal direction, whose amplitude decreases with increasing depth in the liquid (i.e. in the vertical downward direction). This will produce a combination of gravitational waves and capillary waves. Assuming that the liquid as a whole moves up and down in a sinusoidal manner, it will experience an alternating acceleration superimposed on the gravitational acceleration. This modulation of gravitational acceleration can be achieved by ultrasonic waves propagating to the surface. The waves generated have a sinusoidally varying restoring force and certain inherent instabilities, which lead to the spontaneous excitation of standing capillary waves. At low acoustic intensities, the capillary waves are sinusoidal. As the ultrasonic amplitude increases, the amplitude of the capillary waves also increases, and due to nonlinearity, their shape deviates more and more from the sine wave. Finally, at high amplitudes, droplets are pushed out from the wave crest, resulting in atomization of the liquid. The size of the droplets may be uniform, because their diameter is expected to be a certain fraction of the capillary wavelength. Ultrasonic waves can be generated by piezoelectric ceramic transducers operating at 0.5-2 MHz and produce particularly high acoustic intensities at the surface of the liquid. For example, droplet diameters of 2 µm can be achieved at an ultrasonic frequency of 1.8 MHz.

[0007] Critical aspects of mist generating device design may relate to high quality and consistency of the generated mist, liquid consumption, cooling of the ultrasound transducer, cooling of the liquid, control of bacterial growth in the liquid, and robustness of the mist generating device during operation and transportation. Summary of the invention

[0008] In view of the above, there is a need for improvements in mist generating devices to address at least some of the above aspects.

[0009] According to the present application, this need is met by the features defined in the independent claim. The dependent claims define embodiments.

[0010] A mist generating device for generating an aerosol from a liquid includes at least one chamber in which the aerosol is generated. For example, the mist generating device may include two to twenty chambers, depending on the amount of mist to be generated in a given time period and the size or volume of the venue. The chambers may be arranged in an array or matrix. In various examples, eight chambers may be arranged in an array of four by two chambers. Thus, a compact design of the mist generating device may be achieved for ease of installation and transportation.

[0011] Each chamber of at least one chamber comprises a chamber housing. The chamber housing has a bottom and a side wall extending from the bottom to the top of the chamber. For example, each chamber can have a cubic shape. At the bottom of each chamber, an ultrasonic transducer is arranged. At the top of each chamber, a filter element is arranged. In operation of the mist generating device, the chamber is at least partially filled with liquid to a certain filling level so that at least the ultrasonic emitting surface of the ultrasonic transducer is immersed in the liquid. The ultrasonic emitting surface of the ultrasonic transducer can be arranged horizontally, that is, substantially parallel to the surface of the liquid in the chamber, or the ultrasonic emitting surface of the ultrasonic transducer can be inclined relative to the surface of the liquid in the chamber, for example at an angle between 15 degrees and 22 degrees.

[0012] Each chamber has a directional gas inlet at the side wall, which is configured to direct the gas flow introduced into the chamber in a direction substantially parallel to the surface of the liquid in the chamber and substantially along the side wall (i.e. parallel to or tangential to the side wall). Thus, a circulating flow of gas in a plane and parallel to the surface of the liquid in the chamber can be achieved.

[0013] The filter element has a plurality of guide surfaces configured to direct the gas flow out of the chamber in a direction substantially perpendicular to the surface of the liquid in the chamber. Circulating the gas above the surface of the liquid and then directing the gas vertically out of the chamber can help to continuously generate a uniform aerosol. In particular, the discharge of larger droplets may be prohibited. A high-quality, continuous mist can be produced.

[0014] In various examples, each of the plurality of guide surfaces of the filter has a first surface portion extending perpendicular to the surface of the liquid in the chamber and a second surface portion extending at an angle from the first surface portion toward the surface of the liquid in the chamber. For example, the second surface portion may extend downward from the first surface portion at an angle in the range of 90 to 110 degrees, preferably 100 degrees. The first surface portion and the second surface portion may have similar sizes. For example, the extension length of the second surface portion away from the first surface portion may be in the range of 20% to 150% of the extension length of the first surface portion perpendicular to the surface of the liquid in the chamber. In some examples, the extension length of the second surface portion away from the first surface portion may be the same as the extension length of the first surface portion perpendicular to the surface of the liquid in the chamber. The angled guide surface can separate large droplets (e.g., droplets with a diameter greater than 2 or 3 μm) from the aerosol, and can reliably return the separated large droplets to the liquid for reuse. The slightly downwardly inclined second surface portion helps the separated large droplets to return quickly to the liquid and prevents the filter from clogging. Liquid consumption can be reduced.

[0015] The first surface portion and the second surface portion can each be planar. The second surface portion can extend from the edge of the first surface portion. The first surface portions of a plurality of guide surfaces can be arranged parallel to each other and have a gap therebetween. The width of the gap can be several millimeters, such as 2 to 10 mm, preferably 3 to 5 mm. In addition or as an alternative, the second surface portions of a plurality of guide surfaces can be arranged parallel to each other. A gap can be set between the second surface portions. The width of these gaps can be several millimeters, such as 2 to 5 mm. For example, the inclined guide surfaces can be arranged in a staggered manner, spaced apart from each other, to achieve a compact design of the filter. The airflow of the circulation above the surface of the liquid in the chamber is received by the second surface portion, and is directed upwardly out of the filter along the angled connection between the second surface portion and the first surface portion in a vertical direction. A uniform and dense aerosol can be obtained.

[0016] According to various examples, the mist generating device includes a reservoir or tank for liquid and a pump connected between the reservoir and the chamber for pumping the liquid from the reservoir to the chamber. In addition, a return pipe may be included, which connects the liquid outlet of each of the chambers to the reservoir. The liquid outlet may be located at a liquid level corresponding to the filling level. During operation of the mist generating device, the pump may pump the liquid from the reservoir into the chamber. When the liquid level of the liquid in the chamber reaches the liquid level of the liquid outlet, the liquid may flow back into the reservoir through the liquid outlet and the return pipe. In this way, the liquid level can be automatically maintained at the liquid level of the liquid outlet without the need for an additional liquid level sensor. In addition, the liquid is continuously circulated so that the liquid heated by the ultrasonic transducer in the chamber is continuously replaced by cold liquid from the reservoir. In this way, both the ultrasonic transducer and the fluid can be cooled.

[0017] In some examples, the mist generating device comprises two or more chambers. In this case, each chamber may have a separate liquid outlet. The filling level in each chamber can be automatically maintained without providing any additional liquid level sensors.

[0018] In some further examples, the mist generating device comprises a plurality of groups of chambers. Each group of chambers is fluidly separated from the other groups of chambers. For example, the mist generating device comprises four groups of two chambers. Each group of chambers has a separate liquid outlet. The fill level in each group of chambers can be automatically maintained without providing any additional liquid level sensors. This modular chamber design allows the mist generating device to operate in an arrangement that is not precisely aligned, for example, up to + / - 15 degrees from horizontal in the pitch direction and up to + / - 5 degrees in the roll direction.

[0019] In various examples, a sensor (such as an optical liquid sensor) can be provided in the return conduit to monitor the return flow of liquid from the chamber to the reservoir. The liquid circulation can be monitored and a warning can be output in the event of a failure. The cause of the failure may be that the reservoir is empty, the pipeline is blocked, the pump fails, or the mist generating device is incorrectly arranged, such as in an overly tilted position. In some examples, an additional pump can be provided in the return conduit for pumping liquid from the chamber into the reservoir. The additional pump can be controlled based on the sensor value from the sensor. The additional pump can make the arrangement of the return conduit and the reservoir relative to the chamber more flexible. For example, even if the filling level of the liquid in the parts of the return conduit or the reservoir is higher than the liquid level of the liquid outlet of the chamber, the additional pump can also allow the liquid to be pumped from the chamber into the reservoir.

[0020] The mist generating device may also include an ultraviolet light source for irradiating the liquid with ultraviolet light. For example, an ultraviolet light source may be provided in the reservoir to emit ultraviolet light into the liquid in the reservoir. In another example, the ultraviolet light source may be disposed in a return conduit to emit ultraviolet light into the liquid flowing through the return conduit. When the gas passes through the filter along the surface of the liquid in the chamber, ambient air is drawn into the mist generating device by the fan, and this air may contaminate the liquid with organic matter in the air, thereby causing the growth of fungi and bacteria in the reservoir, conduit, pump and / or chamber. The liquid may be irradiated with ultraviolet light to prevent the growth of such fungi and bacteria.

[0021] According to various examples, the reservoir may be provided with a filling inlet for filling and refilling liquid into the reservoir. The reservoir may be configured so that it provides liquid level control to ensure that the predefined volume in the reservoir is not filled with liquid via the filling inlet. Therefore, although the predefined volume of the reservoir is not currently filled with liquid, the configuration of the reservoir prohibits filling the predefined volume via the filling inlet. The predefined volume may be considered as a "hidden volume" that is not available for liquid from the perspective of a user or an operator who fills or refills the reservoir. For example, the filling inlet of the reservoir may include a vertical tube extending downward in the reservoir. The valve device may control the ventilation of the "hidden volume". The valve device may be controlled by the control circuit of the mist generating device. In some examples, a valve ball may be provided at the lower end of the vertical tube. When the liquid level exceeds the lower end of the tube, the valve ball closes the tube so that no more liquid can be hidden in the reservoir, even though there is an unfilled volume space along the vertical tube.

[0022] The predefined "hidden volume" may correspond to the sum of the volumes of liquid in the plurality of chambers during operation of the mist generating device. The mist generating device may include a control circuit configured to operate the pump in reverse to pump liquid from the chamber back into the reservoir. Since the configuration of the reservoir ensures that the operator cannot fill the predefined "hidden volume" via the filling inlet, it can be ensured that the reservoir provides sufficient volume to receive liquid from the chamber. The liquid may be pumped back from the chamber to the reservoir for transport of the mist generating device to ensure that no liquid in the chamber will leak from the mist generating device during transport even if the mist generating device is tilted or inverted. The control circuit may include an electrical energy storage device, such as a rechargeable battery or a supercapacitor, for operating the pump in reverse using electrical energy from the electrical energy storage device when a disconnection of the external power supply is detected. Thus, when the mist generating device is turned off or disconnected from the power supply, the chamber is automatically emptied so that the mist generating device is ready for transport.

[0023] In various examples, the mist generating device includes an additive tank and a mixing device connected to the additive tank and the reservoir. The mixing device is configured to add the additive or concentrate contained in the additive tank to the liquid in the reservoir. Ethylene glycol or glycerol can be used as an additive to be mixed with tap water. The concentration of the additive in the tap water can be in the range of 5% to 10%, for example 8%. Therefore, only a small amount of additive needs to be transported to the site, and tap water may be easily available locally. As described above, by circulating the liquid through the chamber and the reservoir, good mixing of the additive and the tap water can be achieved.

[0024] In various examples, the ultrasonic transducer is driven by a control circuit using an electrical signal having a sinusoidal waveform. For example, each ultrasonic transducer of a plurality of chambers can be driven individually or a group of ultrasonic transducers can be driven collectively. Each ultrasonic transducer can be controlled by a control circuit to be in parallel resonance. For example, an ultrasonic transducer can represent the inductance of an LC circuit and can be operated at or near the resonant frequency of the LC circuit. In this way, energy-saving operation of the ultrasonic transducer can be achieved. The sinusoidal waveform used to drive the ultrasonic transducer can be further tuned in response to an electrical noise signal determined at the current driving the ultrasonic transducer to maintain the ultrasonic transducer in parallel resonance.

[0025] If the mist generating device comprises two or more chambers, the control circuit may control the operation of the two or more ultrasonic transducers to balance the operation time of the ultrasonic transducers. For example, depending on the desired mist output, not all chambers need to be active at the same time. To balance the operation time in these cases, the control circuit may turn the ultrasonic transducers on and off according to a predefined scheme, wherein, during a first time period, a first group of ultrasonic transducers is activated and the other transducers are deactivated, during a second time period, a second group of ultrasonic transducers is activated and the other transducers are deactivated, during a third time period, a third group of ultrasonic transducers is activated and the other transducers are deactivated, and so on, until each ultrasonic transducer is activated at least once, and then the scheme is repeated. In this way, uniform wear of the ultrasonic transducers can be achieved.

[0026] The features explained above and the features described below can be used not only in the respectively explicitly stated combination but also in other combinations or alone, without departing from the scope of protection of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be described more fully below with reference to the accompanying drawings, in which embodiments of the present invention are shown. However, the present invention should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided to make this disclosure more comprehensive and complete and to fully convey the scope of the present invention to those skilled in the art. The same numbers throughout the text represent the same elements.

[0028] Figure 1 schematically illustrates an isometric view of a mist generating device according to one of the various embodiments;

[0029] Figure 2 Schematically shows Figure 1 Additional isometric views of the mist generating device in;

[0030] Figure 3 Schematically shows Figure 1 A side view of a mist generating device;

[0031] Figure 4 Schematically shows Figure 1 Another side view of the mist generating device;

[0032] Figure 5 Schematically shows Figure 1 An isometric view of a pair of chambers of a mist generating device;

[0033] Figure 6 Schematically shows Figure 5 An exploded isometric view of a pair of chambers;

[0034] Figure 7Schematically shows Figure 5 A top view of a pair of chambers;

[0035] Figure 8 Schematically shows Figure 5 A cross-sectional view of a pair of chambers;

[0036] Fig. 9 Schematically shows Figure 1 Control architecture and fluid control of a mist generating device;

[0037] Fig.10 Shows Figure 1 Method steps performed by a control circuit of a mist generating device;

[0038] Fig.11 schematically illustrates a perspective view of a reservoir according to one of the various embodiments;

[0039] Fig.12 Schematically shows Fig.11 Top view of the storage tank;

[0040] Fig.13 Schematically shows Fig.11 A cross-sectional view of a storage device;

[0041] Fig.14 A water tank according to one of several embodiments is schematically illustrated. DETAILED DESCRIPTION

[0042] In conjunction with the description of the more detailed explanation of the exemplary embodiments below in conjunction with the accompanying drawings, the nature, features and advantages of the present invention described above and the modes for achieving them will become clearer and more clearly understood. For the purpose of simplicity and illustration, the present invention is described mainly with reference to the exemplary embodiments of the present invention. In the following description, many specific details are set forth to provide a thorough understanding of the present invention. However, it is apparent to those of ordinary skill in the art that the present invention can be practiced without being limited to these specific details. In this description, well-known methods and structures are not described in detail to avoid unnecessarily obscuring the present invention.

[0043] Figure 1 and Figure 2 Isometric views of the mist-generating device 100 from different directions are schematically shown. Figure 3 and Figure 4 1 and 2 show side views of the mist generating device 100 from different directions. In operation, the mist generating device 100 can generate an aerosol from a liquid. The liquid can be provided in a reservoir, which is located in a Figures 1 to 4 Not shown and will be combined below Fig. 9The mist generating device 100 comprises a plurality of chambers. The mist generating device 100 may have any number of chambers, for example in the range of 1 to 20. Figures 1 to 4 The mist generating device 100 shown has eight chambers arranged in pairs, that is, the eight chambers are arranged in a matrix of 4×2 chambers. Figure 1 In FIG. 1 , only five of the eight chambers are visible, namely, chambers 102, 104, 106, 108, and 110 are visible, while chambers 112, 114, and 116 are not visible. Figure 4 In the side view of FIG. 1 , chambers 102 and 116 are visible. Each pair of chambers, namely chamber pair 102 / 116, chamber pair 104 / 114, chamber pair 106 / 112, and chamber pair 108 / 110, can have substantially the same structure. Each chamber pair is arranged in a row. At the bottom of each chamber, a corresponding ultrasonic transducer 122-136 is arranged. Again, in Figure 1 Only transducers 122, 124, 126, 128 and 130 of chambers 102, 104, 106, 108 and 110 are visible, and Figure 4 In FIG. 1 , transducers 122 and 136 of chambers 102 and 116 are visible.

[0044] In operation of the mist generating device 100, each chamber 102-116 is filled with liquid from a reservoir so that the ultrasound emitting surface of the transducer 122-136 is immersed in the liquid. When the ultrasound transducer is driven, for example with a sinusoidal waveform in the range of 1 to 2 MHz, droplets are generated on the surface of the liquid in the chamber 102-116.

[0045] At one end of the row of chamber pairs, a fan 140 is arranged, which blows ambient air into the chamber 102-116, as will be described in more detail below. The droplets generated in the chamber 102-116 are received by the air flow from the fan 140 and are blown out together with the air at the upper end of each chamber 102-116, as will be described in more detail below. Therefore, aerosol is generated in the chamber 102-116 and discharged from the chamber 102-116. The cover 150 is arranged above the upper end of the chamber 102-116. The cover 150 forms a passage. At one end 152 of the cover 150, another fan 160 is provided, which is used to blow ambient air into the passage. Aerosol combines with the ambient air from another fan 160 to form a mist, which is discharged at the other end 154 of the cover 150.

[0046] Figure 5 An isometric view of a chamber pair (e.g., chamber pair 108 / 110) is schematically shown. As described above, respective ultrasound transducers 128 and 130 are arranged at the bottom side of each chamber 108, 110. The chambers 108, 110 are open at the top side, see Figure 6 1. A corresponding filter element 502, 504 is provided at the top side of each chamber. In addition, an inlet structure 506 is provided for directing the airflow from the fan 140 into each chamber 108, 110. Figure 7 As shown in the top view of the chamber pair 108 / 110 in FIG. 1 , each filter element 502, 504 is provided with a plurality of guide surfaces 702. In addition, as shown in FIG. Figure 7 As shown, a liquid inlet 704 and a liquid outlet 706 are provided in the chamber pair 108 / 110 .

[0047] Figure 8 Shown along Figure 7 802. In operation of the mist generating device 100, liquid is pumped into the chambers 108, 110 via the liquid inlet 704. The liquid may be a mixture of water and an additive, such as glycerol or ethylene glycol, for example 5% to 15% by weight or volume. The liquid outlet 706 is located at a higher level than the liquid inlet 704. When the liquid level in the chambers 108, 110 reaches the desired filling level 802, any excess liquid may flow out of the chambers 108, 110 via the liquid outlet 706. Therefore, no specific sensor detection is required to control the level of the liquid in the chambers 108, 110. When the filling level 802 is reached, the ultrasound emitting surfaces 804, 806 of the ultrasonic transducers 128 and 130 are immersed in the liquid. In operation of the ultrasonic transducers 128 and 130, droplets separated from the liquid surface are generated above the filling level 802.

[0048] Further in operation, air from the fan 140 is introduced into each chamber 108, 110 via the inlet structure 506. The inlet structure 506 provides each chamber 108, 110 with a respective gas inlet 808 and 810 that introduces air from the fan 140 in a horizontal direction (i.e., parallel to the surface of the liquid in the chamber) along the sidewalls of the chambers 108, 110 (e.g., along the sidewalls extending outward from the center between the pair of chambers 108 / 110) to above the fill level 802. Figure 8 As shown, in chamber 108, air may be directed horizontally to the right in the direction of arrow 812, and in chamber 110, air may be directed horizontally to the left in the direction of arrow 814. Then, within each chamber 108, 110, the airflow may begin to circulate in a horizontal plane within the respective chamber 108, 110, as shown by arrows 816 and 818. The circulating air may pick up droplets from the liquid, thereby generating an aerosol. The circulating aerosol may rise within the chamber 108, 110 to the respective filter 502, 504, see arrows 820 and 822.

[0049] Each filter 502, 504 has a plurality of guide surfaces 702 or baffles. Figure 8 In the example shown, each filter 502, 504 has five guide surfaces 702. However, the filters 502, 504 may have any other number of guide surfaces, for example in the range of 3 to 10. Each guide surface 702 has a first surface portion 824 in the vertical direction (i.e. perpendicular to the filling level 802), and a second surface portion 826 extending from the lower edge of the first surface portion 824 in the transverse direction, so that the angle between the first surface portion 824 and the second surface portion 826 is in the range of 90 to 110 degrees, for example. Figure 8 In the example shown, the first surface portion 824 and the second surface portion 826 include an angle of approximately 100 degrees, such that the second surface portion 826 is tilted slightly downwardly by 10 degrees relative to horizontal.

[0050] The five guide surfaces 702 are separated from each other, that is, there is a gap between every two adjacent guide surfaces 702. The width of the gap can be several millimeters, for example, in the range of 2 to 10 millimeters, such as 3 or 5 millimeters. The first surface portions 824 of the guide surfaces 702 can be parallel to each other. Similarly, the second surface portions 826 can be parallel to each other. The guide surfaces 702 can be as shown in FIG. Figure 8 The stacking or staggering shown means that a portion of the first surface portion 824 of one guide surface 702 partially overlaps the first surface portion 824 of an adjacent guide surface 702 and / or a portion of the second surface portion 826 of one guide surface 702 partially overlaps the second surface portion of an adjacent guide surface 702 .

[0051] The rising circulating aerosol enters the gap between the second surface portions 826 and is deflected in the vertical direction by the first surface portion 824, and then leaves the filters 502, 504 in the vertical direction, as shown by arrows 828 and 830. Due to the deflection within the filters 502, 504, droplets having a diameter greater than a desired diameter (e.g., 1 to 2 microns) may collide with the guide surface 702, and then they may flow back to the liquid in the chambers 108, 110 along the first surface portion 824 and the second surface portion 826 under the action of gravity. As a result, a uniform aerosol is obtained at the outlet of the filters 502, 504, and the liquid having droplets of an undesirable size can be reused.

[0052] like Figure 8As depicted, the ultrasonic emitting surfaces 804, 806 of the transducers 128, 130 are tilted relative to the horizontal (i.e., relative to the surface of the liquid). It has been found that tilting the ultrasonic emitting surfaces 804, 806 at an angle in the range of 15 to 22 degrees, preferably at an angle of 18 degrees, can effectively generate droplets. In addition, the droplets of the ultrasonic fountain generated by the ultrasonic transducers 128, 130 may fly upward toward the upper wall portions 832, 834 of the inlet structure 506. Larger droplets may collide with these upper wall portions 832, 834 and may flow back downward for reuse, while smaller droplets are pulled with the airflow 808-822. This can prevent the formation of larger droplets. In addition, larger droplets can be further separated by guiding the airflow along the first surface portion 826 and the second surface portion 824. The aerosol generated in the chambers 102-116 is discharged by the corresponding filters into the channel provided by the cover 150 and blown out by the fan 160, as described above in conjunction with Figure 1 discussed.

[0053] Fig. 9 Schematically illustrated are further components of the mist generating device 100. As shown, the mist generating device 100 includes a plurality of pairs of chambers (e.g., chamber pair 108 / 110 and chamber pair 106 / 112), a reservoir 902 for a liquid, a control circuit 904, a plurality of fill pumps 906, 908 (e.g., one fill pump for each chamber pair), a return line pump 910, a liquid sensor 912, an ultraviolet light source 914, and an electrical energy storage device 916, such as a rechargeable battery or a power capacitor.

[0054] The control circuit 904 may include, for example, control logic based on analog and / or digital circuits. The control circuit 904 may include a power amplifier for driving the ultrasonic transducers 122-136. The control circuit 904 may include a separate power amplifier for each ultrasonic transducer 122-136 or may drive a group or all of the ultrasonic transducers 122-136 with a single power amplifier. The control logic 904 may be based on a combination of a microprocessor or a digital signal processor with a computer program and a memory for storing computer programs and data. One or more power amplifiers may drive the ultrasonic transducers 122-136 at a frequency in the range of 1 to 2 MHz and may be tuned with a resolution of several kHz, for example, with a resolution of 3 kHz. In order to solve electromagnetic compatibility (EMC) problems, the drive waveform may be a sine wave. Shielded transducer installation may facilitate maintenance and reduce electromagnetic compatibility (EMC) problems.

[0055] As depicted, the control circuit 904 is coupled to the ultrasonic transducers 122-136, the pumps 906-910, the liquid sensor 912, the ultraviolet light source 914, and the valve arrangement 918 at the reservoir 902. The operation of the mist generating device 100 under the control of the control circuit 904 may proceed as follows, see Fig.10 .

[0056] When the mist generating device 100 is installed at a venue, for example, at the stage of a theater or concert hall, the reservoir 902 can be filled with liquid via the filling inlet 920. At this time, the control circuit 904 can set the valve device 918 to a first mode, wherein the valve device 918 allows air to flow into the reservoir 902, but does not allow air to escape from the reservoir 902 (step 1002). The filling inlet 920 includes a pipe extending downward in the reservoir 902, so that the reservoir 902 can only be filled to a filling level 922, and a certain volume 924 remains unfilled and cannot be filled because the air in the volume 924 cannot escape when the valve device 918 is in the first mode. Since this volume is not visible to the operator of the mist generating device 100, it is also referred to as a "hidden volume" here. However, when the filling inlet 920 is closed with a lid, liquid can be taken out of the reservoir 902 without generating negative pressure because the valve device 918 allows air to flow into the reservoir 902. The volume of the reservoir 902 may be several liters, for example 3 liters, excluding hidden volume.

[0057] Then, the operator can turn on the mist generating device 100. The control circuit controls the filling pump 906 to pump liquid from the reservoir 902 to the chambers 108 and 110. See step 1004. Once the chambers 108 and 110 are filled to the desired filling level 802, any excess liquid will be discharged through the liquid outlet 706 of the chamber pair 108 / 110 and refluxed to the reservoir 902. In addition, and in the same manner, the control circuit 904 controls the filling pump 908 to pump liquid from the reservoir 902 to the chambers 106 and 112. The remaining chamber pairs 104 / 114 and 102 / 116 can be filled with additional (not shown) filling pumps. This scheme can be extended to any number of chambers or chamber pairs. In particular, this scheme can also be applied to chambers that are not arranged in pairs, but rather to separate chambers with separate liquid inlets and liquid outlets. Any excess liquid from the chamber pair can be discharged back to the reservoir 902 through the reflux conduit 926. A return line 926 may be provided with a return line pump 910 to facilitate return of liquid to the reservoir 902. In addition, the return line 926 may be provided with a liquid sensor 912 that indicates whether liquid is flowing through the return line 926. If the liquid sensor 912 indicates liquid flow in step 1006, it may be assumed that at least some of the chambers have been filled to the desired fill level 802 without any further sensor detection in the chambers. The pump may be a low noise diaphragm pump and / or a peristaltic pump to achieve low noise operation.

[0058] Once the chamber is securely filled with liquid, the ultrasonic transducers 122-136 can be activated to generate droplets, resulting in an aerosol in the chamber and outputting a mist. See step 1008. As the liquid is continuously circulated from the reservoir 902 through the chambers 102-116 and back to the reservoir 902, the ultrasonic transducers 122-136 can be cooled by the large amount of liquid. Overheating of the ultrasonic transducers 122-136 can be avoided. The low temperature of the liquid can be maintained.

[0059] The wear algorithm can distribute the operating time to all available ultrasonic transducers. For example, some ultrasonic transducers may be temporarily turned off while other transducers are still working. The wear algorithm can change which ultrasonic transducers are turned off to achieve an even distribution of operating time for all ultrasonic transducers.

[0060] The control circuit 904 can control each ultrasonic transducer 122-136 individually, that is, a corresponding amplifier can be provided for each ultrasonic transducer. The amplifier can use a "push-pull" driver with current feeding. Piezoelectric transducers generally have an acoustic resonance and a crystal / mechanical resonance. For example, each amplifier can be controlled by feedback of the noise of the current from the specified ultrasonic transducer to keep the transducer in parallel resonance, for example to allow efficient operation. The noise may be generated by the random nature of the water flow in the fountain from which the water droplets emerge. This may cause changes in the load on the amplifier, which can be measured as noise in the range of 1 to 10kHz. This can be observed when the transducer surface is very dirty, and a fountain will still be generated, but no droplets will be generated because the ultrasound is not coupled with the liquid. It has been found that the peak of the signal is not actually the best point for mist generation. The maximum mist output can be achieved at several kilohertz below the measured peak resonance. The wear leveling algorithm can spread the working time across all available transducers regardless of the output level.

[0061] In the storage 902, the ultraviolet light source 914 can be controlled by the control circuit 904 to emit ultraviolet light into the liquid for disinfection and sanitation control. The ultraviolet light source 914 can emit ultraviolet light with a wavelength of about 280 nm. Again, as the liquid circulates continuously, all the liquid is continuously disinfected.

[0062] although Fig. 9 906 , but the mist generating device 100 may include a mixing device for automatically adding a concentrate or additive (e.g., ethylene glycol) to the liquid in the reservoir 902. In this case, the reservoir 902 can be filled with tap water. The amount of tap water filled into the water tank 902 can be measured at the inlet 920 or input by the operator via a user interface. Then, the appropriate amount of concentrate or additive is automatically added to the liquid, for example, by a pump or under the control of a valve or venturi injector in a pipe between the reservoir 902 and the pump 906. As the liquid continues to circulate, the concentrate or additive mixes with the tap water so that a liquid with a uniform concentration of the concentrate or additive is obtained. The tap water can be treated with polyphosphate crystals to prevent scale from forming on the surfaces of the chambers 102-116 and the reservoir 902.

[0063] When the mist generating device 100 is turned off or disconnected from the power supply (step 1010), the control circuit 904 can control the valve device 918 to operate in the second mode using the energy from the energy storage device 916, see step 1012. In the second mode, the valve device 918 allows air to escape from the reservoir 902 to the outside. At the same time, the control circuit 904 can control the filling pumps 906, 908 to pump in the reverse direction using the energy from the energy storage device 916. See step 1014. Therefore, the liquid from the chambers 102-116 is pumped back into the reservoir 902. The hidden volume 924 is configured to be large enough to accommodate the liquid from all chambers 102-116. For example, the chambers 102 to 116 can be configured so that each chamber contains 50 to 200 milliliters when filled to the filling level 802. For example, each chamber pair can be configured so that when it is filled to the filling level 802, it contains 175 ml, and the corresponding hidden volume 924 can be at least 700 ml to cover the volume of the four chamber pairs. The filling pumps 906, 908 can be controlled to pump in reverse for a sufficient period of time to ensure that all chambers 102-116 are emptied. Then, the control circuit 904 can turn off the filling pumps 906, 908, and the valve device 918 can be controlled to operate in the first mode so that the reservoir 902 is completely sealed from the outside. See step 1016. In this state, the mist generating device 100 can be transported even in an inclined position without leaking any liquid from the reservoir 902 or any chamber 102-116.

[0064] The liquid circulation system including pumps 906, 908, 912 can be used to transfer liquid via corresponding valve devices ( Fig. 9 100 is a device that is used to clean the system. The system may be operated by a user (not shown) to introduce a cleaning solution from a separate reservoir or tank for automatic system cleaning. This may be done automatically upon operator request or upon detection that the mist generating device 100 is turned off.

[0065] The above storage 902 is only an example. Figures 11 to 13 A further exemplary reservoir 1102 is described. The reservoir 1102 may be used in the same manner as the reservoir 902 in the mist-generating device 100. Fig.11 shows a perspective view of the storage 1102, Fig.12 A top view of the reservoir 1102 is shown, and Fig.13 Shown along Fig.12 A cross-sectional view of the reservoir 1102 is shown in section AA.

[0066] The reservoir 1102 has a filling inlet 920, through which water and concentrate for generating the mist can be filled into the reservoir 1102. The filling inlet 920 can be connected to an external water tank having a volume of, for example, 5 to 10 liters, for example, via a corresponding water pump. Fig.14 An exemplary water tank 1400 is shown. The filling inlet 920 may also be connected to a concentrate tank having a volume of, for example, several hundred milliliters (eg, 300 to 800 milliliters), for example, via a corresponding concentrate pump. Both the water pump and the concentrate pump may be controlled by the control circuit 904 .

[0067] The reservoir 1102 has a fluid connector 1106 that can be connected to the chambers 106-116, for example, via pumps 906, 908 to the chamber pair, such as Fig. 9 The reservoir 1102 has a return liquid connector 1108 that can be connected to the liquid outlet 706 of the chamber 106 - 116 , for example, via the return line 926 , the return line pump 910 , and the liquid sensor 912 .

[0068] The reservoir 1102 may be provided with liquid level sensors 1110 and 1112. The liquid level sensor 1110 may be used to prevent the reservoir 1102 from being filled with the water tank and the concentrate tank to a level above the fill level 922. The liquid level sensor 1112 may be used to prevent liquid from flowing back from the chambers 106-116 to above the overflow level 1114. When the reservoir 1102 is filled to the overflow level 1114, its total capacity may be, for example, one liter. Several hundred milliliters (e.g., 200 to 400 milliliters) may be required to fill the reservoir 1102 to the fill level 922. In combination with the above Fig. 9 The predefined “hidden” volume 924 in question corresponds to the volume between the fill level 922 and the overflow level 1114 .

[0069] Although in Figures 11 to 13 Although not shown, an ultraviolet light source may be disposed in the reservoir 1102 and may be controlled by the control circuit 904 to emit ultraviolet light into the liquid for disinfection and sanitation control.

[0070] Fig.14Details of the water tank 1400 are shown. The water tank 1400 may include a hollow body 1402, a lid 1406, and a filter 1408. The volume of the hollow body 1402 may be, for example, in the range of 5 to 10 liters, for example, the volume of the hollow body may be 6 liters. The hollow body has a filling opening 1404, which may be closed by the lid 1406. The filter 1408 is disposed on the lower side of the lid 1406. The outlet connector 1410 is disposed on the upper side of the lid 1406. The outlet connector 1410 may be connected to the filling inlet 920 of the reservoir 1102 by a pump. When the lid 1406 and the filter 1408 are removed, the hollow body 1402 of the water tank 1400 may be filled with tap water. The filter 1408 at the lid 1406 is then inserted into the filling opening 1404, and the lid 1406 is fixed to the filling opening 1404, for example, by threads disposed on the filling opening 1404 and the lid 1406. Tap water may be drawn from the hollow body 1402, with the water passing through the filter 1408. Using tap water may be problematic because scale may leave a white coating on the inside of the components of the mist generating device 102 (e.g., on the inside of the reservoir 902 and chambers 102-116). By using polyphosphates disposed in the filter 1408, scale formation may be at least partially avoided. The filter 1408 may be a replenishable filter. Fig.14 As shown, the filter can be located in the neck of the water tank 1400. As the water drawn from the hollow body 1402 passes through the filter 1408, small amounts of polyphosphates very slowly dissolve in the water stream and change the reaction of the calcium in the water. Thus, the mist generating device 102 can operate using tap water rather than deionized water.

[0071] When the mist generating device 100 including the reservoir 1102 is installed at a site, the filling inlet 920 may be connected to a water tank (e.g., the outlet connector 1410 of the water tank 1400) via a water pump and to a concentrate tank via a concentrate pump. The mist generating device 100 may be turned on, and the control circuit 904 may activate the water pump and the concentrate pump to pump water and concentrate into the reservoir 1102 until the filling level 922 is reached. During further operation of the mist generating device 100, the control circuit 904 may continuously monitor the filling level using the level sensor 1110, and may activate the water pump and the concentrate pump to pump water and concentrate into the reservoir 1102 to reach the filling level 922 when necessary.

[0072] The operator can then control the control circuit 904 to start generating mist. The control circuit controls the fill pump 906 to pump liquid from the reservoir 1102 into the chambers 108 and 110. Once the chambers 108 and 110 are filled to the desired fill level 802, any excess liquid is discharged through the liquid outlet 706 of the chamber pair 108 / 110 and flows back into the reservoir 1102. In addition, and in the same manner, the control circuit 904 controls the fill pump 908 to pump liquid from the reservoir 902 into the chambers 106 and 112. The remaining chamber pairs 104 / 114 and 102 / 116 can be filled with additional fill pumps. Any excess liquid from the chamber pairs can be discharged back into the reservoir 1102 through the return conduit 926 and the return liquid connector 1108.

[0073] Once the chamber is securely filled with liquid, the ultrasonic transducers 122-136 can be activated to generate droplets, resulting in an aerosol in the chamber and outputting a mist. During mist generation, the control circuit 904 can continuously monitor the fill level using the liquid level sensor 1110, and can activate the water pump and the concentrate pump to pump water and concentrate into the reservoir 1102 to maintain the fill level 922.

[0074] When the mist generating device 100 is turned off or disconnected from the power supply, the control circuit 904 can control the filling pumps 906, 908 to pump in the reverse direction using energy from the energy storage device 916. In this way, the liquid from the chambers 102-116 is pumped back into the reservoir 1102. The hidden volume 924 is configured to be large enough to accommodate the liquid from all chambers 102-116. The filling pumps 906, 908 can be controlled to pump in the reverse direction for a sufficient period of time to ensure that all chambers 102-116 are emptied. The control circuit 904 can then turn off the filling pumps 906, 908. In this state, the mist generating device 100 can be transported even in a tilted position without leaking any liquid from the reservoir 902 or any chamber 102-116.

[0075] In general, all terms used in this article should be interpreted according to their ordinary meaning in the relevant technical field, unless a different meaning is explicitly given and / or implied in the context of its use. Unless otherwise explicitly stated, all references to elements, equipment, parts, devices, steps, etc. should be openly interpreted as referring to at least one instance of elements, equipment, parts, devices, steps, etc. The steps of any method disclosed herein do not need to be performed in the exact order disclosed, unless a certain step is explicitly described as being after or before another step, and / or implying that a certain step must be after or before another step. Where appropriate, any feature of any embodiment disclosed herein can be applied to any other embodiment. Similarly, any advantage of any embodiment can be applied to any other embodiment, and vice versa. Through the specification, other purposes, features and advantages of the attached embodiments will become apparent. As used herein, the term "configured to" means being set, organized, adjusted or arranged to operate in a specific way; the term is synonymous with "designed to". As used herein, the term "substantially" means almost or substantially, but not necessarily completely; the term covers and takes into account mechanical or component value tolerances, measurement errors, random variations and similar sources of inaccuracy.

[0076] Of course, the present invention can also be implemented in ways other than those specifically described herein without departing from the basic features of the present invention. The embodiments disclosed herein should be considered illustrative rather than restrictive in all respects, and all modifications within the meaning and equivalent scope of the appended claims are intended to be included therein.

[0077] The following examples define features that may be implemented in a mist generating device:

[0078] Example 1: A mist generating device for generating an aerosol from a liquid, the mist generating device comprising at least one chamber in which the aerosol is generated, wherein each chamber of the at least one chamber comprises:

[0079] - a chamber housing comprising a bottom and side walls extending from the bottom to the top of the chamber,

[0080] - an ultrasonic transducer arranged at the bottom, and

[0081] - a filter element mounted at the top of the chamber,

[0082] wherein in operation of the mist generating device, the chamber is at least partially filled with the liquid to a filling level such that at least the ultrasound emitting surface of the ultrasound transducer is immersed in the liquid,

[0083] wherein the chamber has a directional gas inlet at the side wall, the directional gas inlet being configured to direct a gas flow introduced into the chamber in a direction substantially parallel to a surface of the liquid in the chamber and substantially along the side wall,

[0084] Wherein the filter element comprises a plurality of guide surfaces configured to direct the gas flow out of the chamber in a direction substantially perpendicular to the surface of the liquid in the chamber.

[0085] Example 2: A mist generating device according to Example 1, wherein each of the plurality of guide surfaces has a first surface portion extending perpendicular to the surface of the liquid in the chamber and a second surface portion extending at an angle from the first surface portion toward the surface of the liquid in the chamber.

[0086] Example 3: A mist-generating device according to example 2, wherein the second surface portion extends downwardly from the first surface portion at an angle in the range of 90 degrees to 110 degrees, preferably at 100 degrees.

[0087] Example 4: A mist generating device according to Example 2 or Example 3, wherein an extension length of the second surface portion away from the first surface portion is in the range of 20% to 150%, preferably 100%, of an extension length of the first surface portion perpendicular to the surface of the liquid in the chamber.

[0088] Example 5: The mist generating device according to any one of Examples 2 to 4, wherein the first surface portions of the plurality of guide surfaces are arranged parallel to each other, and / or

[0089] The second surface portions of the plurality of guide surfaces are arranged parallel to each other.

[0090] Example 6: A mist-generating device according to any one of Examples 2 to 5, wherein the first surface portion and the second surface portion are each planar.

[0091] Example 7: A mist-generating device according to any one of Examples 2 to 6, wherein the second surface portion extends from an edge of the first surface portion.

[0092] Example 8: A mist generating device for generating an aerosol from a liquid, the mist generating device comprising

[0093] - at least one chamber in which the aerosol is generated, wherein each of the at least one chamber comprises an ultrasonic transducer,

[0094] - a reservoir for said liquid,

[0095] - a pump coupled between the reservoir and the chamber for pumping the liquid from the reservoir into the chamber, and

[0096] - a return line connecting the liquid outlet of the chamber and the reservoir,

[0097] Wherein the liquid outlet is arranged at a level corresponding to the filling level.

[0098] Example 9: A mist-generating device according to Example 8, wherein the mist-generating device comprises at least two chambers, wherein each of the at least two chambers has a separate liquid outlet.

[0099] Example 10. The mist-generating device of Example 8, wherein the mist-generating device comprises a plurality of groups of chambers, wherein each group of chambers is fluidly separated from the other groups of chambers, wherein each group of chambers has a separate liquid outlet.

[0100] Example 11. A mist generating device according to Example 10, wherein each group of chambers comprises two chambers.

[0101] Example 12. A mist-generating device according to any one of Examples 8 to 11, wherein the return conduit comprises a sensor for monitoring a return flow of the liquid from the chamber to the reservoir.

[0102] Example 13. A mist-generating device according to example 12, wherein the return conduit comprises a further pump for pumping the liquid from the chamber into the reservoir.

[0103] Example 14. A mist generating device according to example 13, wherein the further pump is controlled in dependence on a sensor value from the sensor.

[0104] Example 15. The mist generating device of any one of Examples 8 to 14, wherein the mist generating device further comprises an ultraviolet light source that emits ultraviolet light toward the liquid in the reservoir.

[0105] Example 16: A mist generating device for generating an aerosol from a liquid, the mist generating device comprising

[0106] - at least one chamber in which the aerosol is generated, wherein each of the at least one chamber comprises an ultrasonic transducer,

[0107] - a reservoir for said liquid, and

[0108] - a pump coupled between the reservoir and the chamber for pumping the liquid from the reservoir into the chamber,

[0109] Wherein a filling inlet of the reservoir for filling the liquid into the reservoir has a level control to ensure that a predefined volume within the reservoir cannot be filled with the liquid via the filling inlet.

[0110] Example 17. The mist-generating device of Example 16, wherein the predefined volume corresponds to a sum of volumes of the liquid in the plurality of chambers during operation of the mist-generating device.

[0111] Example 18. A mist generating device according to any of Examples 16 or 17, wherein the mist generating device comprises a control circuit configured to operate the pump in reverse to pump the liquid from the chamber into the reservoir.

[0112] Example 19. A mist generating device according to example 18, wherein the control circuit comprises an electrical energy storage device for operating the pump in the reverse direction using electrical energy from the electrical energy storage device upon detecting that the external power supply is turned off.

[0113] Example 20. A mist generating device according to any one of Examples 8 to 19, wherein the mist generating device comprises an additive tank and a mixing device coupled to the additive tank and the reservoir, wherein the mixing device is configured to add an additive contained in the additive tank to the liquid in the reservoir.

[0114] Example 21. A mist generating device according to any of the preceding examples, wherein the ultrasound emitting surface of the ultrasound transducer is inclined between 15 degrees and 22 degrees relative to the surface of the liquid in the chamber.

[0115] Example 22. A mist-generating device according to any of the preceding examples, wherein the mist-generating device comprises eight chambers arranged in an array of four by two chambers.

[0116] Example 23. A mist generating device according to any of the preceding examples, wherein the ultrasonic transducer is driven by a control circuit using an electrical signal having a sinusoidal waveform.

[0117] Example 24. A mist-generating device according to any preceding example, wherein the mist-generating device comprises at least two chambers, wherein a control circuit controls the operation of the ultrasonic transducers of the at least two chambers to balance the operation time of the ultrasonic transducers.

[0118] Example 25. A mist generating device according to any of the preceding examples, wherein the ultrasonic transducer is controlled by a control circuit in parallel resonance.

[0119] Example 26. A mist generating device according to any of the preceding examples, wherein the ultrasonic transducer is controlled by a control circuit based on an electrical noise signal determined at a current driving the ultrasonic transducer.

Claims

1. A mist generating device for generating an aerosol from a liquid, the mist generating device (100) comprising at least one chamber (102-116) in which the aerosol is generated, wherein each chamber (102-116) of the at least one chamber (102-116) comprises: - a chamber housing comprising a bottom and side walls extending from the bottom to the top of the chamber (102-116), - an ultrasonic transducer (122-136) arranged at the bottom, and - a filter element (502, 504) arranged at the top of the chamber (102-116), wherein in operation of the mist generating device (100), the chamber (102-116) is at least partially filled with the liquid to a filling level (802) such that at least the ultrasound emitting surfaces (804, 806) of the ultrasound transducers (122-136) are immersed in the liquid, wherein the chamber (102-116) has a directional gas inlet (808, 810) at the side wall, the directional gas inlet being configured to direct a gas flow introduced into the chamber (102-116) in a direction substantially parallel (812, 814) to a surface of the liquid in the chamber (102-116) and substantially along the side wall, The filter element (502, 504) comprises a plurality of guide surfaces (702) configured to direct the airflow out of the chamber (102-116) in a direction substantially perpendicular (828, 830) to the surface of the liquid in the chamber (102-116).

2. The mist generating device according to claim 1, wherein each of the plurality of guide surfaces (702) has a first surface portion (824) extending perpendicular to the surface of the liquid in the chamber (102-116) and a second surface portion (826) extending at an angle from the first surface portion (824) toward the surface of the liquid in the chamber (102-116).

3. The mist-generating device according to claim 2, wherein the second surface portion (826) extends downwardly from the first surface portion (824) at an angle in the range of 90 to 110 degrees, preferably at 100 degrees.

4. The mist generating device according to claim 2, wherein the first surface portions (824) of the plurality of guide surfaces (702) are arranged parallel to each other, and / or The second surface portions (826) of the plurality of guide surfaces (702) are arranged parallel to each other.

5. The mist generating device according to claim 1, wherein the mist generating device (100) further comprises: - a reservoir (902, 1102) for said liquid, - a pump (906, 908) coupled between the reservoir (902, 1102) and the chamber (102-116) for pumping the liquid from the reservoir (902, 1102) into the chamber (102-116), and - a return line (926) connecting the liquid outlet (706) of the chamber (102-116) and the reservoir (902, 1102), The liquid outlet (706) is arranged at a level corresponding to the filling level (802).

6. The mist-generating device according to claim 5, wherein the mist-generating device (100) comprises at least two chambers, wherein each of the at least two chambers has a separate liquid outlet.

7. The mist generating device according to claim 5, wherein the mist generating device (100) comprises a plurality of groups of chambers (102 / 116, 104 / 114, 106 / 112, 108 / 110), wherein each group of chambers is fluidly separated from the other groups of chambers, and wherein each group of chambers has a separate liquid outlet (706).

8. The mist-generating device of claim 5, wherein the return conduit (926) comprises a sensor (912) for monitoring a return flow of the liquid from the chamber (102-116) to the reservoir (902, 1102).

9. The mist-generating device according to claim 5, wherein the return conduit (926) comprises a further pump (910) for pumping the liquid from the chamber (102-116) into the reservoir (902, 1102).

10. The mist-generating device according to claim 5, wherein the mist-generating device (100) further comprises an ultraviolet light source (914) emitting ultraviolet light toward the liquid in the reservoir (902, 1102).

11. The mist generating device according to claim 5, wherein a filling inlet (920) of the reservoir (902, 1102) for filling the liquid into the reservoir (902, 1102) has a liquid level control to ensure that a predefined volume (924) within the reservoir (902, 1102) cannot be filled with the liquid via the filling inlet (920).

12. The mist generating device of claim 5, wherein the mist generating device (100) comprises a control circuit (904) configured to operate the pump (906, 908) in reverse to pump the liquid from the chamber (102-116) into the reservoir (902, 1102).

13. The mist generating device according to claim 12, wherein the control circuit (904) includes an energy storage device (916) for operating the pump (906, 908) in the reverse direction using electrical energy from the energy storage device (916) when it is detected that the external power supply is turned off.

14. The mist generating device according to claim 5, wherein the mist generating device (100) comprises an additive tank and a mixing device connected to the additive tank and the reservoir (902, 1102), wherein the mixing device is configured to add the additive contained in the additive tank to the liquid in the reservoir (902, 1102).

15. The mist generating device according to claim 1, wherein the ultrasonic transducer (122-136) is controlled by a control circuit (904) using an electrical signal having a sinusoidal waveform and / or in parallel resonance and / or based on an electrical noise signal determined at a current driving the ultrasonic transducer (122-136).

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