Cleaning device and method using acoustic transducer

Abstract

The invention provides an apparatus (1) for cleaning a surface, the apparatus (1) comprising: a body defining a cavity (10a), the body (10a) terminating in a distal end (12), the distal end being adapted, in use, to be located adjacent to a surface (2) to be cleaned so that the surface (2) to be cleaned forms an end wall of a chamber (11) comprising the cavity (10a); at least one cleaning liquid inlet (14) for allowing cleaning liquid to flow into the chamber (11); a baffle located in or at the end of the cavity (10a); (16), the partition dividing the chamber (11) into a first part (11a) and a second part (11b), the second part (11b) being in fluid communication with the surface (2) to be cleaned in use; and an acoustic transducer connected to the first part of the chamber (11) for introducing acoustic energy into the chamber (11); wherein the partition is adapted to allow the acoustic energy to pass through it from the first part (11a) of the chamber (11) to the second part (11b) of the chamber (11), thereby allowing pressure fluctuations to be generated at the surface (2) to be cleaned. The present invention also provides a method for cleaning a surface (2).

Description

[0001] Description of the case

[0002] This invention patent application is a divisional patent application.

[0003] The original application of this divisional patent application is an invention patent application with an international application date of May 13, 2016, an international application number of PCT / EP2016 / 060911, a Chinese national application number of 201680041121.8, and an invention name of “Cleaning device and method using an acoustic transducer”. Technical Field

[0004] The present invention relates to a cleaning device and to a method of cleaning a surface. Background Art

[0005] Many surfaces (including floors, walls, ceilings, vehicle surfaces and other panels) need to be cleaned periodically. Known surface cleaning devices and methods often provide unsatisfactory cleaning performance and leave a large amount of cleaning liquid on the surface being cleaned and in the surrounding area. Known surface cleaning devices and methods are often also inefficient, using a large amount of cleaning liquid and energy. When cleaning cracks, cracks and small holes in other flat surfaces, known surface cleaning devices and methods are often less effective than required.

[0006] Ultrasonic cleaning is used in some industries to clean items. Items that need to be cleaned by ultrasonic cleaning are usually placed in an ultrasonic bath filled with a cleaning liquid and exposed to ultrasonic waves to achieve cleaning. However, conventional ultrasonic cleaning equipment is not suitable for cleaning many types of surfaces (including floors, walls, ceilings, vehicle surfaces and other panels) and in any case is often plagued by the above-mentioned shortcomings.

[0007] The present invention provides a cleaning device and method for cleaning a surface which overcomes the above-mentioned disadvantages. Summary of the invention

[0008] A first aspect of the invention provides an apparatus for cleaning a surface, comprising: a body defining a cavity, the body terminating in a distal end, the distal end being adapted, in use, to be in the vicinity of a surface to be cleaned so that the surface to be cleaned forms an end wall of a chamber comprising the cavity; at least one cleaning liquid inlet for allowing the cleaning liquid to flow into the chamber; a baffle located in or at the end of the cavity, the baffle dividing the chamber into a first part and a second part, the second part being fluidically connected to the surface to be cleaned in use; and an acoustic transducer connected to the first part of the chamber to introduce acoustic energy into the chamber; wherein the baffle is adapted to allow acoustic energy to pass through it from the first part of the chamber to the second part of the chamber, thereby allowing pressure fluctuations to be generated at the surface to be cleaned.

[0009] The distal end of the body is the end of the body which, in use, is arranged closest to the surface to be cleaned.

[0010] The device of the first aspect of the present invention allows acoustic energy to be delivered to the surface to be cleaned to provide effective and efficient cleaning to the surface, particularly by activating bubbles at or near the surface to be cleaned to achieve cleaning. The activation of the bubbles preferably includes using acoustic energy to cause non-inertial motion of the bubbles at the surface to be cleaned. The non-inertial motion of the bubbles can also be generated at a distance from the surface to be cleaned. Depending on the pressure amplitude generated by the device, the activation of the bubbles can also include using acoustic energy to cause inertial cavitation of the bubbles at the surface to be cleaned and / or at a distance from the surface to be cleaned. Inertial cavitation at the surface to be cleaned allows particularly effective cleaning for solid surfaces, but can be avoided in some applications, particularly when cleaning more delicate surfaces.

[0011] The second portion of the chamber may be partially or completely located outside the cavity disposed in the body, or alternatively mainly (or even completely) located inside the cavity disposed in the body. For example, in some embodiments where the partition is located at the distal end of the body or on the distal end of the body (as discussed below), the second portion of the chamber may be completely outside the cavity disposed in the body. In other embodiments where the partition is set back from the distal end of the body and the distal end of the body is spaced apart from the surface to be cleaned during use, at least a portion of the second portion of the chamber may be located inside the cavity disposed in the body, and the remainder may be located between the distal end of the body and the surface to be cleaned. In other embodiments where the partition is set back from the distal end of the body and the distal end of the body is directly located on the surface to be cleaned during use, substantially all of the second portion of the chamber may be located inside the cavity in the body. In this case, the volume of the chamber is substantially the same as the volume of the cavity.

[0012] It should be noted that while the distal end of the body is typically spaced apart from the surface to be cleaned during use, with or without a skirt extending between the body and the surface to be cleaned, in some embodiments the distal end of the chamber itself is arranged to directly engage the surface to be cleaned during use.

[0013] When the equipment is arranged on the surface to be cleaned or adjacent to the surface to be cleaned and the surface to be cleaned forms the end wall of the chamber, the acoustic transducer can be operable to produce acoustic resonance in the chamber in use, and the sound pressure antinode is formed on the surface to be cleaned or adjacent to the surface to be cleaned. The sound pressure antinode is formed near the surface to be cleaned or the surface, so that efficient energy transfer can be carried out from the sound transmitter to the surface to be cleaned, thereby minimizing the power requirement of the cleaning equipment, and minimizing the heat of the transducer. When the surface to be cleaned acts as an acoustic rigid boundary or an approximate acoustic rigid boundary, the sound pressure antinode can be produced at the surface to be cleaned, so that it does not reflect the sound pressure wave substantially without phase change. The example of the suitable surface that is suitable for utilizing the equipment to clean includes concrete, metal, plastic and ceramic.

[0014] The body (and chamber) may be in the form of a cylinder or prism, for example, that is circular, oval, triangular, square, rectangular, pentagonal, hexagonal, etc. The cylinder or prism may have any number of sides.

[0015] The cross-section of the body and / or chamber may be constant along the length of the body (in use in a direction perpendicular to the surface to be cleaned), or alternatively may vary along the length of the body. The body (and chamber) may be, for example, in the form of a truncated cone, or a truncated pyramid, or a straight or curved horn, or a hemisphere or another form of dome. Other shapes are also feasible.

[0016] The diameter or lateral width (in use in a direction parallel to the surface to be cleaned) of the body (and chamber) may be in the range 5mm to 1m, or 10mm to 150mm, or 20mm to 100mm. Other dimensions are also possible.

[0017] The length of the chamber (in use in a direction perpendicular to the surface to be cleaned) can be in the following ranges: 10 mm to 140 mm, or 20 mm to 120 mm, or 60 mm to 100 mm. Other sizes are also possible. In a particularly preferred embodiment, the length is 100 mm. It should be noted that in embodiments where the skirt extends outwardly from the distal end of the body, the length of the body may be less than the length of the chamber.

[0018] The body may be formed from, for example, metal or a polymer material such as an acrylic material.

[0019] In a preferred embodiment of the present invention, the body has a rectangular or square cross-section and is formed from a polymer material.

[0020] In some preferred embodiments of the present invention, the body has a regular external shape, such as a rectangular or square cross section, or any other prism shape, so that a plurality of bodies can be assembled together in a mutually adjacent or inlaid form to form a linear or two-dimensional array of the plurality of bodies. Correspondingly, a linear or two-dimensional array of a plurality of mutually adjacent or inlaid chambers is provided, each chamber being connected to a corresponding acoustic transducer. This array can provide a device for cleaning a surface, the device can have an overall shape and size that matches the surface to be cleaned, such as a linear array for cleaning elongated linear surfaces or a two-dimensional array for cleaning a large surface area. This provides a more efficient single device for cleaning a surface, the single device having a plurality of adjacent chambers defined by a corresponding body, each chamber having acoustic energy introduced therein by a corresponding acoustic transducer. Each chamber / acoustic transducer assembly is constructed to provide high quality or optimized cleaning for the surface to be cleaned, and the array provides an enlarged composite cleaning device to improve cleaning efficiency.

[0021] The partition may include a diaphragm. The diaphragm may be substantially sealed relative to the body around a periphery of the diaphragm.

[0022] The diaphragm can be formed of a material that is substantially impedance matched to the cleaning liquid. The diaphragm can thereby promote the generation of an acoustic field in the second portion of the chamber and thereby generate higher pressure fluctuations on the surface to be cleaned. For example, the diaphragm can be formed of a Rho-C rubber that is substantially impedance matched to water. The thickness of the Rho-C diaphragm can be in the range of 0.5mm to 10mm, but more preferably in the range of 1-2mm. Alternatively, the diaphragm can be formed of another rubber that is substantially impedance matched to the intended cleaning liquid. The impedance-matched diaphragm can generally be located anywhere in the chamber, including at a location where an acoustic pressure antinode or acoustic pressure node is formed during use (although it is preferred that the diaphragm be arranged at or near the distal end of the body). Preferably, the material of the diaphragm is selected so that the reflection coefficient between the diaphragm and the cleaning liquid is as close to zero as possible.

[0023] The diaphragm can be thin enough so that it does not significantly reduce the sound passing through it from the first part of the chamber to the second part of the chamber in use. The diaphragm can therefore be substantially non-invasive relative to the sound field, and can promote the generation of the sound field in the second part of the chamber, and thus generate higher pressure fluctuations on the surface to be cleaned. For example, the thickness of the diaphragm can be in the range of 5 to 100 microns, typically in the range of 5 to 20 microns, or in the range of 8 to 15 microns, or approximately 10 microns. For example, the diaphragm can include stainless steel or other metal sheets with a thickness of 10 microns. If the diaphragm is thin enough so that it does not significantly reduce the sound passing through it in use, the diaphragm does not need to be formed by a material that is substantially impedance matched with the cleaning liquid (as described above) or by a material having a specific acoustic property to match the sound field at its position in use (as described below).

[0024] The diaphragm may be formed of a material having specific acoustic properties to match the acoustic field at its location in use. The diaphragm may therefore be substantially non-intrusive with respect to the acoustic field and may facilitate the generation of an acoustic field in the second part of the chamber and thereby generate higher pressure fluctuations at the surface to be cleaned. For example, the diaphragm may comprise a thin metal wall which substantially coincides with an acoustic pressure antinode in the chamber when the device is in use. For example, consider a cubic chamber with rigid walls having internal dimensions of 100 mm x 100 mm and a height of H = 100 mm for cleaning horizontal surfaces. If the speed of sound in the cleaning liquid is c = 1500 m / s, then at 30 kHz there is a 3D resonant mode of the form (α, β, γ) = (0, 0, 4), where γ is the number of acoustic pressure nodes contained within the container in the vertical direction and where α and β are the number of acoustic pressure nodes in each of the horizontal directions. In this mode, an acoustic pressure antinode is formed at x = 25 mm above the surface to be cleaned and therefore the thin metal diaphragm may be arranged accordingly (see Figure 8 ). It should be noted that the speed of sound in the cleaning liquid may not be constant but may be altered by a bubble group that is generated in the cleaning liquid or introduced into the cleaning liquid during use. The diaphragm position may be determined taking into account any changes in the speed of sound in the cleaning liquid caused by the bubble group during use. The diaphragm may alternatively be arranged at a location that does not coincide with the acoustic pressure antinode, although arranging the metal wall at another location results in reduced efficiency.

[0025] The diaphragm may include reinforcement, for example in the form of reinforcement bars or ribs. The reinforcement may be formed from the same material as the diaphragm itself, or alternatively may include a material different from the material forming the main part of the diaphragm.

[0026] The partition may include an interface between the acoustic energy transmission material located in the first part of the chamber, wherein the acoustic energy transmission material includes a material different from the cleaning liquid and its acoustic impedance is similar to the acoustic impedance of the cleaning liquid. The acoustic energy transmission material may, for example, include a solid or gel material, the acoustic impedance of which is similar to the acoustic impedance of the cleaning liquid. The acoustic energy transmission material may, for example, include agar gel or gelatin. The interface may be a simple interface, or alternatively may include a wall or diaphragm, which is formed by a material different from the acoustic energy transmission material. In some embodiments of the first part of the acoustic energy transmission material filled chamber, the cleaning liquid may only be present in the second part of the chamber in use. However, in other embodiments, the first part of the chamber may be only partially filled with the acoustic energy transmission material, and the cleaning liquid may also be present in the first part of the chamber.

[0027] The diaphragm may include an acoustic lens that focuses the acoustic energy on the surface to be cleaned in use. Focusing the acoustic energy on the surface to be cleaned enables efficient energy transfer from the acoustic transmitter to the surface to be cleaned with the heating of the tiny transducer.

[0028] The lens may be a biconcave lens formed of a material having a sound velocity greater than that of the cleaning liquid, such as (poly)methyl methacrylate (PMMA) or a plastic having a sound velocity greater than that of water. Alternatively, the lens may take any other form that allows the acoustic energy to be focused on the surface to be cleaned.

[0029] The lens can act as a partition and divide the chamber into a first part and a second part, and in use, the cleaning liquid and / or the acoustic energy transmission material is located in the first part of the chamber. Alternatively, in addition to the diaphragm or interface as described above, the lens can be included in the cleaning device. At least one hole can be formed through the lens to allow the cleaning liquid to flow from the first part of the chamber into the second part of the chamber at any desired flow ratio and / or flow rate, or alternatively a gap can be provided between the lens and the side wall of the body.

[0030] Cleaning devices including lenses in place of or in addition to the above-described diaphragms or interfaces may be particularly useful for cleaning surfaces that do not provide rigid boundaries or nearly rigid boundaries (e.g., carpets) because such cleaning devices do not require resonance to be generated within the room in order to provide efficient cleaning (as described below).

[0031] Cleaning equipment can include multiple acoustic transducers, which are positioned and oriented indoors so that the acoustic energy produced by the multiple transducers in use converges on the surface to be cleaned. The multiple acoustic transducers can be, for example, arranged in an array across the dome of the room, or alternatively arranged on multiple angled surfaces forming the top of the room. Each acoustic transducer can be oriented and positioned to face a common point. As described above, this cleaning equipment can include a diaphragm. Alternatively or additionally, as described above, this cleaning equipment can include an acoustic lens. The multiple acoustic transducers can be operated to produce focusing or beam pointing effects by phase delay.

[0032] The partition may be located at or near the distal end of the body. For example, where the partition is a membrane, the membrane may be located above the distal end of the body. Alternatively, the partition may be located directly adjacent to the distal end of the body, or set back from the distal end of the body, for example, the distance set back may be in the range of 1 mm to 60 mm, or 2 mm to 40 mm, or 5 mm to 10 mm. Placing the partition at or near the distal end of the body may advantageously reduce the rate at which the cleaning liquid leaks out of the device.

[0033] The cleaning liquid inlet may be arranged so that the cleaning liquid flows into the first part of the chamber, the cleaning liquid inlet being fluidly connected to the cavity at a location inside the partition. In this case, the cleaning liquid passes through or bypasses the partition before contacting the surface to be cleaned. Alternatively (or additionally), the cleaning liquid inlet may be arranged so that the cleaning liquid flows into the second part of the cavity, the cleaning liquid inlet being fluidly connected to the cavity at a location outside the partition.

[0034] The partition can be suitable for allowing cleaning liquid to flow through it from the first part of the chamber into the second part of the chamber in use. The partition can, for example, include one or more holes or small holes or other porous areas, and the cleaning liquid can flow through the holes or small holes or other porous areas from the first part of the chamber into the second part of the chamber in use. Any number of holes can be used in any configuration or position on the partition. By using the partition to separate the cleaning liquid in the first part of the chamber from the second part of the chamber and only allowing a part of the cleaning liquid to flow through, the delivery of the cleaning liquid to the surface to be cleaned can be controlled. In some embodiments of the present invention, a plurality of holes are arranged to extend through the partition so as to allow the cleaning liquid to flow from the first part of the chamber into the second part of the chamber, and the plurality of holes can be arranged in a regular or irregular array. It has been found that the arrangement of the array of such holes provides enhanced cleaning of the surface. It has been found that for a given volume flow rate (e.g., liters per minute) of the cleaning liquid through the hole, the surface to be cleaned or the partition is enhanced to clean by a plurality of smaller holes compared to a larger hole.

[0035] The flow rate of the cleaning liquid through the partition entering the second part of the chamber from the first part of the chamber can be controlled or selected to provide enhanced cleaning, for example, the cleaning effect can be enhanced at a faster flow rate (similar to a higher speed liquid jet rather than a low speed liquid flow, particularly if the jet is directed to the surface to be cleaned). If the supply of liquid to the first part of the chamber is directed downward, for example to the diaphragm (if the hole is above the diaphragm), the cleaning effect can also be enhanced. In addition, in addition to the first part of the liquid flowing into the chamber or replacing the first part of the liquid flowing into the chamber, the liquid flow can be introduced into the second part of the chamber. Under higher flow speeds and if the flow is directed downward to the surface to be cleaned, this liquid supply directly to the second part of the chamber can provide enhanced cleaning. Typically, the flow velocity of the liquid flow entering the second part of the chamber or directly entering the second part of the chamber and optionally directed to the surface to be cleaned is from 0.25 to 5 meters per second, for example from 0.5 to 2 meters per second, for example about 1 meter per second.

[0036] The cleaning liquid inlet may be fluidly connected to the cavity at a location between the diaphragm and the distal end of the body. In this case, the cleaning liquid is delivered directly to the second portion of the chamber and the diaphragm may be impermeable to the cleaning liquid. The first portion of the chamber may be filled with a separate body of liquid or alternatively have some other acoustic energy transmission material as described above.

[0037] The apparatus may comprise a plurality of cleaning liquid inlets fluidly connected to the first and / or second portion of the chamber and to the inlet manifold.

[0038] The device may include a skirt arranged around the distal end of the body, the skirt being suitable for keeping the cleaning liquid in the second part of the chamber in contact with the surface to be cleaned. The skirt may include a wall extending around the opening at the distal end of the body. The skirt may reduce the residual cleaning liquid on the surface to be cleaned after cleaning, for example leaving only as much liquid as can be expected based on a household mop. The cleaning liquid inlet may be formed in the skirt, in which case the cleaning liquid is directly delivered to the second part of the chamber and the partition may be impermeable to the cleaning liquid. The skirt may, for example, extend outwardly from the distal end of the body, and the extension distance may be in the range of 3mm to 10mm. For example, if the skirt extends 5mm from the distal end of the body and the partition retreats 5mm from the distal end of the body, the distance between the end of the partition and the skirt will be 10mm. The skirt may be formed by rubber. However, in all embodiments, a separated skirt is not necessary.

[0039] The apparatus may include a wet / dry vacuum device that is used to remove excess cleaning liquid from the surface to be cleaned. The wet / dry vacuum device will also be used to remove loose contaminants from the surface after cleaning.

[0040] The device may include a clean liquid outlet for the clean liquid to flow out of the chamber. The clean liquid outlet is preferably fluidly connected to the first part of the chamber. The device may include a plurality of clean liquid outlets, which are fluidly connected to the first and / or second part of the chamber and are fluidly connected to the outlet header. The device may be arranged to remove the clean liquid from the chamber through the outlet and return the clean liquid to the reservoir, from which the clean liquid is supplied to the chamber.

[0041] The device may include sound insulation in the inlet and / or outlet to prevent sound from traveling out of the chamber.

[0042] The device may include a liquid conditioning unit adapted to remove bubbles from the cleaning liquid supplied to the chamber. The liquid conditioning unit may, for example, include at least one of a settling container, a physical grid, a microporous material (e.g., a porous open-cell foam or sponge), and a cyclone chamber. The liquid conditioning unit may significantly reduce the number of bubbles present in the cleaning liquid entering the chamber, which would otherwise weaken the sound field. The liquid conditioning unit may be arranged upstream of the cleaning liquid inlet to remove bubbles from the cleaning liquid before the cleaning liquid is supplied to the chamber.

[0043] The cleaning device may include a bubble generator suitable for generating or releasing bubbles in a cleaning liquid. The bubble generator may, for example, include: an acoustic transducer for introducing acoustic energy into the chamber or one or more additional transducers for generating bubble cavitation; or a pair or more pairs of electrodes for generating bubbles using electrolysis; or a venturi system; or a bubble injection system including one or more bubble injection needles. The electrode may be in the form of a wire, a plate, a grid, or a curved surface. The electrode may be disposed in or attached to a partition. The electrode may be arranged in a hole or pore or porous region adjacent to the partition so that the flow of the cleaning liquid through the hole or pore or porous region is used to disperse the bubbles generated by the electrode, and the attenuation of the acoustic energy is minimized. An ion-conducting membrane may be arranged between the electrodes to promote electrolytic bubble generation, particularly when the ionic conductivity of the cleaning liquid is low.

[0044] The radius of the bubbles generated by the bubble generator may be in the following ranges: 0.1 to 150 microns, or 1 to 100 microns, or 10 to 50 microns. The bubbles preferably have a resonant size or less. For example, for bubbles in water driven at 40 kHz, the radius of the bubbles may be in the range of 30 to 75 microns.

[0045] The bubble generator may be arranged to introduce bubbles into the cleaning liquid upstream of the cleaning liquid inlet and / or in the first part of the chamber and / or at the partition and / or in the second part of the chamber. Introducing bubbles into the cleaning liquid only at the partition and / or in the second part of the chamber may reduce the acoustic attenuation in the first part of the chamber and ensure a sufficient bubble concentration at the surface to be cleaned.

[0046] The baffles may be constructed or treated to reduce or avoid the baffles acting to capture bubbles in the chamber, such as bubbles that rise in the liquid below the baffle to contact the lower surface of the baffle and / or bubbles that form and / or grow on the upper surface of the baffle or bubbles that are pushed downward on the upper surface. Either or both of the upper and lower surfaces of the baffles may be constructed or treated to be hydrophilic, such as by treatment with one or more hydrophilic chemicals or by plasma treatment of the surface to introduce oxygen-containing polar groups onto or into the surface of the baffle. In some embodiments, the flow of fluid through the chamber is controlled to at least partially clear bubbles from the upper and / or lower surfaces of the baffles.

[0047] When the cleaning liquid is aqueous, such a hydrophilic surface of the partition may be advantageous for bubble capture. However, in some embodiments of the present invention, the cleaning liquid may be non-aqueous, such as may be a hydrophobic oil. Non-aqueous cleaning liquids may be preferred when the surface to be cleaned has previously been in contact with a non-aqueous liquid (e.g., oil). When a hydrophobic cleaning liquid is used, either or both of the upper and lower surfaces of the partition may be constructed or treated to be hydrophobic so as to reduce or avoid the partition from acting to capture bubbles in the chamber.

[0048] The bubble generator can use positive feedback to allow a mode to be excited when the bubble group changes the speed of sound in the clean liquid. For example, in the case where the drive frequency is lower than the particular mode frequency for the bubble-free liquid but close enough to produce cavitation, cavitation occurs and the bubble group increases, causing the speed of sound in the liquid to decrease. This decrease in the speed of sound in turn increases cavitation and further reduces the speed of sound in the liquid until the mode frequency in the chamber reaches the transducer frequency.

[0049] The apparatus may comprise a first controller for the bubble generator, the first controller being adapted to control the bubble generator to generate or release pulses of bubbles.

[0050] The device may comprise a second controller for the acoustic transducer, which is adapted to control the acoustic transducer to generate pulses of acoustic energy. This may be achieved, for example, by intermittently switching the acoustic transducer on and off, or alternatively by providing amplitude or frequency tuning.

[0051] The first controller and the second controller can be coordinated so that the pulses of bubbles and the pulses of acoustic energy are generated in a mutually controlled time relationship. For example, the pulses of bubbles and the pulses of acoustic energy can be timed to impact the surface to be cleaned substantially simultaneously. The use of such a mutually controlled time relationship can allow efficient cleaning with reduced bubble requirements so that acoustic attenuation in the chamber is minimized.

[0052] The apparatus may include a tuner for providing amplitude or frequency tuning of the pulses of acoustic energy.

[0053] The acoustic transducer may be suitable for being driven at a frequency in the range of 20kHz to 10MHz. For example, the acoustic transducer may be suitable for being driven at a frequency in the range of 20kHz to 500kHz, or 20kHz to 200kHz, or 20kHz to 50kHz. In two preferred embodiments, the frequency is 20kHz or 40kHz. In another preferred embodiment, the acoustic transducer is suitable for being driven at a frequency in the range of at least 50kHz, preferably at least 60kHz and more preferably from 60 to 140kHz. Depending on the intended application, other frequencies are also feasible, for example as low as 1Hz in special cases.

[0054] Acoustic energy pulses can be controlled to enhance the removal of bubbles from the chamber. It has been found that, although the acoustic energy is closed, bubbles can leave the chamber cavity and rise toward the vent. Therefore, the closing time between each acoustic energy pulse can help remove bubbles from the chamber, which may otherwise weaken the sound field and reduce cleaning. When the acoustic energy is turned on, some bubbles are prevented from leaving the chamber and rising by the Bjerknes force, and therefore the closing time between each acoustic energy pulse can help flow and buoyancy to remove bubbles. Another advantage of the acoustic energy pulse effect is that at the beginning of subsequent pulses, there are many frequencies (as shown in the Fourier transform of the beginning of the pulse) in the time window near the beginning of that pulse. It has been found that for a short period of time after each pulse starts, the size of the bubble away from the resonance in the sound field can respond to some energy present at the beginning of the pulse. Therefore, for example, it has been found that the beginning of the pulse can provide a small impetus or "recoil" for the large bubbles that adhere to the surface (i.e., floor) or partition / diaphragm to be cleaned, and the impetus or "recoil" can knock out bubbles from the surface or partition / diaphragm. It has therefore been found that by pulsing the sound field (particularly with a pulse waveform having a sudden start such as a square wave), some of the undesirable bubbles (particularly large bubbles) attached to the floor or partition / diaphragm can be expelled, thereby improving the cleaning efficiency of the device.

[0055] The walls of the chamber may be formed of an acoustically rigid material or a pressure-releasing material. Acoustically rigid materials are preferred in order to maximize the area cleaned by the device to the edge of the chamber. The material may be metal, for example. Alternatively, a transparent plastic, glass or acrylic material may be selected in order to allow inspection of the chamber during use.

[0056] The equipment can also include an erosion or accelerator introduction system to introduce one or more erosion or accelerators. The erosion or accelerator can include, for example, ozone, chlorine and / or hydrogen peroxide. The erosion or accelerator can be added in the equipment by injection and / or by electrochemical generation. The erosion or accelerator can be added or generated at the partition and / or in the second chamber to achieve high concentrations in the vicinity of the surface to be cleaned. Alternatively, the erosion or accelerator can be added or generated at the liquid conditioning unit.

[0057] The device may include a chemically active agent introduction system to introduce one or more chemically active agents. The chemically active agent may include, for example, a detergent, a surfactant and / or a bactericide. The surfactant may enhance control of bubble diameter by reducing the likelihood of bubble merging.

[0058] The distal end of the body may be substantially flat. The device may therefore be particularly suitable for cleaning substantially flat surfaces. Alternatively, the distal end of the body may have some other shape suitable for cleaning surfaces having a corresponding shape. The device may be provided with castors in order to position the device relative to the surface to be cleaned.

[0059] The acoustic transducer may be arranged in or on the top wall of the body opposite the distal end of the body. However, the acoustic transducer need not be directly opposite the surface to be cleaned and may alternatively be arranged in or on the side wall of the body.

[0060] The device may include a plurality of acoustic transducers. The acoustic transducers may be arranged in or on the top wall of the body and one or both of the side walls of the body. The acoustic transducers may be operated by phase delay, for example to produce a focusing or beam pointing effect.

[0061] The surface cleaning assembly may comprise a plurality of devices according to the first aspect of the invention. The surface cleaning assembly may comprise a plurality of devices, for example, arranged in one or more rows or arranged in a circle. In a given time when a single assembly is operated alone, such a surface cleaning assembly may be able to clean a larger area of ​​the surface to be cleaned.

[0062] Where multiple devices are included in a surface cleaning assembly, it may be advantageous to use a square or rectangular body to allow the bodies to be arranged side by side with minimal space between the individual devices.

[0063] The body of at least one device may share a common side wall with the body of at least one other device. This arrangement can reduce the space between corresponding chambers formed by adjacent devices, thereby allowing more consistent cleaning. This arrangement can also reduce the weight and material cost of the surface cleaning assembly.

[0064] A plurality of devices may be supplied with cleaning liquid in parallel. Alternatively, a plurality of devices may be connected in series, with one or more cleaning liquid outlets of one or more devices being fluidly connected to one or more cleaning liquid inlets of one or more other devices, so that cleaning liquid is delivered in series from each device to an adjacent device.

[0065] In the case where one or more devices share a common side wall with one or more adjacent devices, one or more of the common side walls may include one or more holes or vents to allow cleaning liquid to pass between adjacent cleaning devices. This arrangement can reduce the need for pipes between adjacent multiple devices connected in series.

[0066] A single common skirt may be shared by multiple adjacent cleaning devices.

[0067] A second aspect of the present invention provides a method for cleaning a surface, the method comprising the following steps: a) providing an apparatus comprising a body defining a cavity and a partition located in or at an end of the cavity; b) arranging a distal end of the apparatus near a surface to be cleaned so that the surface to be cleaned forms an end wall of a chamber including the cavity, the partition dividing the chamber into a first part and a second part, the second part of the chamber being fluidically connected to the surface to be cleaned; c) supplying a cleaning liquid to the second part of the chamber so that the cleaning liquid engages the surface to be cleaned; d) introducing acoustic energy into the chamber using an acoustic transducer; and e) causing the acoustic energy to pass from the first part of the chamber through the partition to the second part of the chamber, thereby generating pressure fluctuations on the surface to be cleaned.

[0068] The method may include generating an acoustic resonance within the chamber. Since the surface to be cleaned forms the end wall of the chamber, for surfaces with an acoustic impedance significantly higher than that of the cleaning liquid or acoustically rigid surface, this allows a stronger resonant structure to be achieved and the cleaning will be more efficient. However, cleaning of other surfaces is also possible, since the walls of the body enable the mode to be generated, even if the surface to be cleaned is not acoustically rigid.

[0069] The method may include forming an acoustic pressure antinode at or near the surface to be cleaned. It is generally preferred that the acoustic pressure antinode is formed at the surface to be cleaned. However, in some cases, the acoustic pressure antinode may be spaced apart from the surface to be cleaned, for example, by 1 / 8 of a wavelength, particularly when cleaning an uneven surface (e.g., a surface including ridges, notches or other discontinuities).

[0070] The method may comprise focusing the acoustic energy onto the surface to be cleaned using a diaphragm, the diaphragm comprising a lens. Where a lens is used to focus the acoustic energy, the surface to be cleaned need not have any particular acoustic properties.

[0071] A cleaning liquid may be supplied into the first portion of the chamber, and the method may include allowing the cleaning liquid to flow through the barrier from the first portion of the chamber into the second portion of the chamber.

[0072] The method may include removing bubbles from the cleaning liquid supplied to the chamber using a liquid conditioning unit.

[0073] The method may include generating bubbles using a bubble generator or releasing the bubbles into the cleaning liquid.

[0074] The method may include controlling, using a first controller, a bubble generator to generate or release pulses of bubbles into the cleaning liquid.

[0075] The method may include coordinating a first controller and a second controller for controlling the acoustic transducer to generate the pulse of acoustic energy such that the pulse of bubbles and the pulse of acoustic energy are generated in a controlled time relationship to each other.

[0076] The pulse of bubbles and the pulse of acoustic energy may impact the surface substantially simultaneously.

[0077] The method may include controlling the acoustic energy to induce non-inertial bubble motion at the surface to be cleaned.

[0078] The method may include controlling the acoustic energy to induce inertial cavitation of bubbles at the surface to be cleaned and / or at a distance from the surface to be cleaned.

[0079] The method may include controlling the acoustic energy to generate surface waves and / or microflows in the bubble.

[0080] The method may include using tuned acoustic energy to induce non-inertial bubble motion and / or inertial cavitation and / or generate surface waves and / or micro-streaming.

[0081] The method may include causing bubbles to enter a cavity, recess or pore formed in the surface to be cleaned. The bubbles may be driven toward and into the cavity, recess or pore by acoustic energy.

[0082] The method may include exciting the surface of the bubble using acoustic energy while the bubble is in the cavity, recess or aperture.

[0083] The method may comprise using water as the cleaning liquid.The water may optionally comprise one or more corrosive or dissolving agents or chemically active agents as described above.

[0084] The method may comprise maintaining the distal end of the body at a distance of 5 mm to 8 mm from the surface to be cleaned.

[0085] The method of the second aspect of the invention may be performed using an apparatus comprising any of the features described above in relation to the first aspect of the invention. The method of the second aspect may also include further steps using any of the features described above in relation to the first aspect of the invention.

[0086] A third aspect of the present invention provides a method for cleaning a surface (e.g., a ship hull) immersed in an underwater environment. The method comprises the following steps: a) providing an apparatus comprising a body defining a cavity; b) arranging a distal end of the apparatus near a surface to be cleaned so that the surface to be cleaned forms an end wall of a chamber comprising the cavity, the surface to be cleaned being immersed in the underwater environment; c) supplying a cleaning liquid to the chamber so that the cleaning liquid engages the surface to be cleaned; d) introducing acoustic energy into the chamber using an acoustic transducer; e) passing the acoustic energy through the chamber to generate pressure fluctuations at the surface to be cleaned.

[0087] When the surface to be cleaned is immersed in an underwater environment, the baffle of the apparatus of the first aspect of the present invention can be omitted. In addition to omitting the baffle, the method of the third aspect of the present invention can be performed using an apparatus including any of the features described above with respect to the first aspect of the present invention. The method of the third aspect can also include additional steps using any of the features described above with respect to the first aspect of the present invention.

[0088] Acoustic cavitation occurs when bubbles surrounded by liquid change volume under the action of a changing pressure field. The bubble volume change is oscillatory, but sometimes can last less than one oscillation. Inertial cavitation occurs when the movement and collapse of bubbles are dominated by the inertia of the influx of liquid. During inertial cavitation, high-speed liquid jets and shock waves can be generated by rapid bubble involution. Inertial cavitation can lead to various effects, including free radical generation, sonoluminescence, and sonochemical effects. In contrast, during non-inertial bubble motion, the perturbation of the bubble gas pressure (rather than the liquid inertia) controls the dynamics of the pulsation. Non-inertial bubble motion and non-inertial cavitation include a series of phenomena, including the generation of surface waves on the bubble wall, micro-flow fluid flow in a clean liquid and / or shear in a clean liquid, radiation force (especially primary and secondary Bjerknes force) effects, acoustically driven bubble splitting and merging, bubble motion under acoustic radiation force, and spherical pulsations with amplitudes insufficient to produce effects associated with inertial collapse.

[0089] Inertial and / or non-inertial properties can be controlled, for example, by changing the zero-to-peak pressure amplitude. For water with 20kHz ultrasound in normal room conditions of temperature and pressure, a zero-to-peak pressure amplitude below approximately 120kPa produces non-inertial properties. For zero-to-peak pressure amplitudes greater than approximately 120kPa, inertial properties are produced for some bubbles (depending on the bubble size) in normal room conditions of temperature and pressure, and non-inertial properties are produced for other bubbles at the same time. At the minimum acoustic pressure amplitude at which inertial cavitation can be produced in the liquid, only bubbles of the optimal size are subject to inertial cavitation. However, as the zero-to-peak pressure amplitude increases, the range of bubble sizes subject to inertial cavitation increases, and thereby the number of bubbles subject to inertial cavitation increases. In this way, depending on the range of ultrasonic frequencies and bubble sizes, non-inertial bubble motion and / or inertial cavitation can be produced by the device. Inertial properties can also be promoted by reducing the drive frequency and by optimizing the bubble size for inertial properties. BRIEF DESCRIPTION OF THE DRAWINGS

[0090] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings in which:

[0091] Figure 1 An apparatus for cleaning a surface according to a first embodiment of the present invention is shown;

[0092] Figure 2 Shown in use Figure 1 the interface between the device and the surface;

[0093] FIG. 3 illustrates various arrangements of chambers and chambers that may be used in different embodiments of the present invention;

[0094] Figure 4 An alternative apparatus for cleaning a surface according to a second embodiment of the present invention is shown;

[0095] Figure 5 Another alternative embodiment for cleaning a surface according to the third embodiment of the present invention is shown;

[0096] Figure 6 A cleaning assembly comprising a plurality of devices according to a fourth embodiment of the present invention is shown;

[0097] Figure 7 A cleaning device according to a fifth embodiment of the present invention is shown; and

[0098] Figure 8 The γ=4 mode in an apparatus for cleaning a surface according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0099] Figure 1A cleaning device 1 according to the invention is shown. The device 1 comprises a metal or polymer (e.g. acrylic) body 10 in the form of a circular, square or rectangular cylinder defining a cavity 10a. The body 10 terminates in a flat distal end 12, such as Figure 1 , the flat distal end is held in use adjacent to a flat surface 2 to be cleaned (the surface). When the body 10 is held such that the distal end 12 of the body 10 is adjacent to the surface 2, the surface 2 forms an end wall of a chamber 11, the chamber 11 comprising a cavity 10a formed within the body 10 and a further area extending between the distal end 12 of the body 10 and the surface 2. (Other possible arrangements of cavities and chambers that may be used for different embodiments of the present invention are described below with reference to Figure 5 The body 10 is provided with castors 13 for positioning the device 1 relative to a surface 2.

[0100] The device 1 further comprises a cleaning liquid inlet 14 through which cleaning liquid, such as water, can be supplied from the cleaning liquid reservoir 3 to the chamber 10a, and a cleaning liquid outlet 15 through which cleaning liquid can be removed from the chamber 10a and returned to the cleaning liquid reservoir 3.

[0101] The device 1 further comprises a partition 16 located at the end of the cavity 10a (and at the distal end 12 of the body 10). When the device 1 is arranged such that the distal end 12 of the body 10 is adjacent to the surface 2 to be cleaned and the surface forms the end wall of the chamber 11 comprising the cavity 10a (e.g. Figure 1 ), the partition divides the chamber 11 into a first portion 11a and a second portion 11b. The first portion 11a of the chamber 11 is bounded by: a top wall 10b or end wall of the body 10, which is opposite the distal end 12; the partition 16; and a side wall 10c of the body 10, which extends between the top wall 10b and the partition 16. The second portion 11b of the chamber 11 is bounded by: the partition 16; the surface 2; and a flexible skirt 17, such as a rubber skirt, which extends between the body 10 and the surface 2. Figure 1 In the embodiment shown in FIG, the baffle 16 is located at the distal end 12 of the body 10 and thus the second portion 11b of the chamber 11 is located completely outside the body 10, but other possible arrangements are discussed below with reference to FIG 3. As described below, when the device is in the use position, the second portion 11b of the chamber is in fluid communication with the surface 2 so that the cleaning liquid in the second portion 11b of the chamber 11 can directly engage the surface 2 and achieve cleaning.

[0102] The diaphragm 16 is a thin plate or membrane formed of a material that is substantially impedance matched to the cleaning liquid. Where the cleaning liquid is water, a Rho-C rubber diaphragm having an acoustic impedance of approximately 1,500,000 Rayls may be used, although other materials having other acoustic impedances may be used depending on the intended cleaning liquid. The diaphragm 16 is sealed about its periphery relative to the body 10 and is substantially impermeable to water except for a 0.9 mm diameter hole 16a formed through the diaphragm that provides fluid communication between the first portion 11a of the chamber 11 and the second portion 11b of the chamber 11.

[0103] Both the cleaning liquid inlet 14 and the cleaning liquid outlet 15 are located inside the partition 16 so that cleaning liquid is delivered to and removed from the first part 11 a of the chamber 11 .

[0104] The acoustic transducer 18 is mounted on the top wall 10b of the body 10 and is arranged to introduce acoustic energy into the chamber 11. The acoustic transducer 18 is controlled by a controller 19 and can be driven at a frequency of 20kHz to 20MHz. The tuner allows the amplitude or frequency of the pulse of acoustic energy to be tuned. Sound insulation (not shown) in the cleaning liquid inlet 14 and the cleaning liquid outlet 15 prevents sound from propagating out of the chamber 11.

[0105] When the device 1 is arranged on or adjacent to the surface 2 to be cleaned (e.g. Figure 1 ) and the chamber 11 is filled with a cleaning liquid, the acoustic transducer 18 can be operated in use to generate an acoustic resonance in the chamber 11, wherein an acoustic pressure antinode is formed at or adjacent to the surface 2.

[0106] The liquid conditioning unit 20 is located upstream of the cleaning liquid inlet 14 and is adapted to remove bubbles from the cleaning liquid supplied to the chamber 11 (eg by a physical grid) to significantly reduce the number of bubbles present in the cleaning liquid entering the chamber 11 which would otherwise attenuate the acoustic field.

[0107] The bubble generator 21 includes an electrode in the form of a wire that is built into the partition 16 for generating bubbles in the cleaning liquid. The bubble generator is controlled by a controller 22 and generates bubbles with a radius in the range of 0.1 to 100 microns. The bubble generator controller 22 can be operated with timed pulses to generate bubbles.

[0108] The etchant or dissolving agent introduction system 23 can be used to introduce one or more etchants or dissolving agents (e.g., ozone, chlorine and / or hydrogen peroxide) into the first portion 11a of the chamber 11b. The chemically active agent introduction system 24 can be used to introduce one or more chemically active agents (e.g., detergents, surfactants and / or bactericides) into the cleaning liquid.

[0109] The operation of the device will now be described.

[0110] In use, the apparatus is arranged on a surface 2 to be cleaned, with the body 10 held by the castors 13 so that the distal end 12 and the baffle 16 are spaced approximately 5 mm to 8 mm from the surface and the surface 2 forms the end wall of a chamber 11 comprising the cavity 10a. Water (or another cleaning liquid) is treated by the liquid conditioning unit 20 to remove air bubbles and is supplied to the first part 11a of the chamber 11 through the cleaning liquid inlet 14. The water fills the first part 11a of the chamber 11 and is also allowed to flow into the second part 11b of the chamber 11 through the hole 16a in the baffle 16. The skirt 17 holds the water in the second part 11b of the chamber 11 and in contact with the surface 2. In one mode of operation, the water may be supplied at a rate of 1 to 2 dm 3 / min is supplied through the inlet 14, and water is supplied at a rate of 1 to 5 cm 3 / s flows through the hole 16a.

[0111] When the chamber 11 is filled with water, the ultrasonic transducer 18 is used to introduce acoustic energy into the chamber 11. The diaphragm 16, which is formed of a material that is substantially impedance matched to the cleaning liquid, allows the acoustic energy to pass through it from the first portion 11a of the chamber 11 into the second portion 11b of the chamber 11, such as Figure 2 , and a strong acoustic field is generated in the lower part 11a of the chamber 11. The surface 2 forms an acoustically rigid end wall of the chamber 11, and an acoustic resonance is generated in the chamber 11, wherein an acoustic pressure antinode is formed at or near the surface 2. In this way, pressure fluctuations are generated at the surface 2. (The device can also be used to clean surfaces that are not acoustically rigid, because the walls of the body 10 enable a mode to be generated even if the surface to be cleaned is not acoustically rigid. However, for non-rigid surfaces, cleaning is less efficient.)

[0112] like Figure 2 As shown in FIG. 1 , the bubble generator 21 is operated to generate bubbles 50 in the second portion 11b of the chamber 11. The bubbles are driven by the acoustic field in the chamber 11 towards the surface.

[0113] The acoustic transducer 18 may be operated to control acoustic energy in the chamber 11 to induce non-inertial bubble motion at the surface 2. The acoustic transducer may be operated, for example, at a frequency of 20 kHz with a zero to peak pressure amplitude well below 120 kPa, for example 90 kPa.

[0114] By controlling the acoustic energy to induce non-inertial bubble motion at the surface 2, the apparatus 1 provides enhanced cleaning of the surface without subjecting the surface to stress and possible damage that may result from inertial cavitation.

[0115] Alternatively, or in addition, the acoustic transducer 18 may be operated to control the acoustic energy in the chamber 11 to induce inertial cavitation of bubbles at the surface 2 and / or at a distance from the surface 2. By controlling the acoustic energy to induce inertial cavitation of bubbles at the surface 2 and / or at a distance from the surface 2, the apparatus 1 may provide enhanced cleaning for harder surfaces. The acoustic transducer may be operated, for example, at a frequency of 20 kHz, with a zero to peak pressure amplitude well above 120 kPa, for example 250 kPa.

[0116] As the zero to peak pressure amplitude increases, the range of bubble sizes subject to inertial cavitation increases and thus the number of bubbles subject to inertial cavitation increases. In this way, depending on the ultrasonic frequency and the range of bubble sizes, non-inertial bubble motion and / or inertial cavitation can be produced by the device.

[0117] Alternatively, or in addition, the acoustic transducer 18 may be operable to control acoustic energy in the chamber 11 to generate surface waves and / or micro-flows in the bubbles.

[0118] Surface waves can be controlled by varying the zero to peak pressure amplitude and / or the ultrasonic frequency and / or the bubble size. In general, the closer the bubble is to its pulsating resonant size, the lower the threshold acoustic pressure required to excite Faraday waves (and other related waves).

[0119] The acoustic field may be continuous or alternatively amplitude tuned or frequency tuned, and the cleaning operation may include using the tuned acoustic energy to induce non-inertial bubble motion and / or inertial cavitation and / or generate surface waves and / or micro-streaming.

[0120] Where the surface 2 comprises a cavity, the cleaning operation may comprise passing the bubble into the cavity, recess or aperture formed in the surface 2 and exciting the surface of the bubble using acoustic energy whilst the bubble is in the cavity, recess or aperture.

[0121] In one mode of operation, the bubble generator controller 22 can be used to control the bubble generator 21 to generate pulses of bubbles, rather than continuously. The acoustic transducer controller 19 can be used to control the acoustic transducer 18 to generate pulses of acoustic energy. The pulses of bubbles and the pulses of acoustic energy can be generated in a controlled time relationship with each other, for example to impact the surface substantially simultaneously. In this way, the transducer can be operated more efficiently by generating only pulsed acoustic energy and by reducing the attenuation caused by bubbles.

[0122] The wet / dry vacuum 25 is operated to remove excess water, as well as any expelled contaminants. The skirt 17 substantially holds the water within the second portion 11b of the chamber 11 and prevents water from substantially leaking out of the device. The device 1 thus leaves only as much liquid as would be expected from a household mop. As water leaks out of the second portion 11b of the chamber 11 under the skirt 17 and is removed by the wet / dry vacuum 23, it is replenished as water continues to flow from the first portion 11a of the chamber 11 into the second portion 11b of the chamber 11 through the apertures 16a.

[0123] The device 1 may be moved across the surface 2 to clean a larger area, or alternatively remain stationary in a single location to provide spot cleaning.

[0124] In reference Figure 1 In the depicted embodiment, the partition 16 is located at the distal end of the cavity 10a and thus the first portion 11a of the chamber 11 is completely located within the cavity 10a and the second portion 11b of the chamber 11 is completely located outside the cavity 10a. Figure 3a However, in an alternative embodiment, the partition 16 may be retracted from the distal end of the cavity 10a so that a portion of the second portion 11b of the chamber 11 is located within the cavity 10a, as shown in FIG. Figure 3b In another alternative embodiment, the skirt may be omitted and the distal end 12 of the body 10 may be substantially directly located on the surface, so that substantially all of the second portion 11b of the chamber 11 is located within the cavity 10a, as shown in FIG. Figure 3c as shown in .

[0125] In reference Figure 1 In the depicted embodiment, the diaphragm 16 is formed of a material that is substantially impedance matched to the cleaning liquid to allow acoustic energy to efficiently pass through it from the first portion 11a of the chamber 11 into the second portion 11b of the chamber 11 to produce a strong acoustic field in the second portion 11b of the chamber 11. However, in an alternative embodiment, the diaphragm 16 may alternatively (or additionally) be sufficiently thin so that it does not significantly attenuate the sound passing through it from the first portion 11a of the chamber 11 to the second portion 11b of the chamber 11 in use. In this way, the diaphragm 16 may be substantially non-intrusive with respect to the acoustic field and may promote the generation of an acoustic field in the second portion 11b of the chamber 11, and thereby promote the generation of higher pressure fluctuations at the surface 2. In another alternative embodiment, the diaphragm 16 may be formed of a material having particular acoustic properties that matches the acoustic field at its location in use (e.g., the diaphragm may include a thin metal wall that substantially coincides with an acoustic pressure antinode in the chamber when the device is in use), and thereby be substantially non-intrusive with respect to the acoustic field. In each case, the baffle 16 is adapted to allow efficient energy transfer from the acoustic transducer 18 to the surface 2 with minimal transducer heating.

[0126] In reference Figure 1 In the depicted embodiment, cleaning liquid is supplied into the first portion 11a of the chamber 11 and is allowed to flow through the apertures 16a formed in the partition 16 to the second portion 11b of the chamber 11. However, in an alternative embodiment, water (or other cleaning liquid) may instead be supplied directly to the second portion 11b of the chamber 11, such as Figure 4 In such an embodiment, the first portion 11a of the chamber 11 may alternatively be filled with a different acoustic energy conducting material 100, such as a gel, such as Figure 4 In such an embodiment, the partition may simply be in the form of an interface between the acoustically conductive material 100 and the second portion 11b of the chamber 11. The acoustically conductive material should have an acoustic impedance similar to that of the cleaning liquid to achieve the above-described Figure 1 The efficient operation of the device described in the device. Those skilled in the art will understand that the above Figure 1 The features described in the embodiments can also be applied to Figure 4 The embodiment shown in FIG.

[0127] In another alternative embodiment, the baffle may be in the form of an acoustic lens which, in use, focuses acoustic energy introduced into the chamber 11 by the acoustic transducer 18 onto the surface 2, such as Figure 5 . Focusing the acoustic energy on the surface to be cleaned allows efficient energy transfer from the acoustic transducer 18 to the surface 2 to be cleaned with minimal transducer heating. Cleaning devices that include lenses instead of (or in addition to) the diaphragms or interfaces described above may be particularly useful for cleaning surfaces that do not provide rigid boundaries or nearly rigid boundaries, such as carpets, because such cleaning devices do not require resonance to be generated in the room in order to provide efficient cleaning (as described above). Those skilled in the art will appreciate that the above description of Figure 1 and 4 The features described in the embodiments can also be used for Figure 5 For example, the cleaning liquid may be introduced into a first portion 11a of the chamber 11 formed between the top wall of the body and the lens, or into a second portion 11b of the chamber 11 formed between the lens and the surface on which the device is placed. In addition, the first portion 11a of the chamber 11 may be filled with a cleaning liquid (e.g., Figure 1 ), or alternatively filled with a different acoustically conductive material, such as a gel (as in Figure 4 in the embodiment of FIG. 1 ).

[0128] The surface cleaning arrangement 1000 may comprise a plurality of cleaning devices 1 as described above, for example Figure 6The plurality of cleaning devices need not be identical. In some embodiments, the surface cleaning arrangement 1000 may include a batch of devices of the first embodiment, the second embodiment, and / or the third embodiment, which are together in a single array. Figure 6 In the embodiment shown in , the two cleaning devices located farthest to the right share a common side wall. In other embodiments, the cleaning devices may each be formed with at least one side wall shared with at least one adjacent cleaning device.

[0129] Figure 7 Another alternative embodiment is shown in which the cleaning apparatus comprises a hemispherical or dome-shaped body 10 and chambers 11a, 11b, and a plurality of acoustic transducers 18 forming an array arranged across the dome of the chamber so that the acoustic energy produced by the acoustic transducers is focused on the surface 2 to be cleaned in use. In this embodiment, similar to the embodiment of Figure 1 The embodiment described herein has a diaphragm in which the diaphragm 16 is arranged in a dome-shaped chamber.

[0130] In one embodiment, the lateral width of the body 10 and chamber 11 (in a direction parallel to the surface to be cleaned) can be significantly greater than the length of the chamber 11 (in a direction perpendicular to the surface 2 to be cleaned). With this width / length aspect ratio, the top wall 10b of the body 10 on which the acoustic transducer 18 is mounted (i.e., the top wall 10b of the body 10 facing and away from the surface 2 to be cleaned) can act as an acoustic baffle that is substantially acoustically rigid to the transducer 18. The transducer 18 can be mounted on the outer face of the top wall 10b, away from the chamber 11, or located in a close-fitting hole provided in the top wall 10b, so that the top wall 10b surrounds the transducer 18, thereby forming an acoustic baffle. When the distance between the transducer 18 and the surface 2 to be cleaned is small, additional cleaning can be caused by the contribution of the direct acoustic field from the transducer 18, which increases in magnitude near the transducer 18 and is superimposed on the resonant mode in the chamber 11.

[0131] In various embodiments of the method of the present invention, the surface 2 to be cleaned is exposed to the atmosphere. At least during the step of introducing acoustic energy into the chamber 11 with the acoustic transducer 18 and the step of passing the acoustic energy through the partition 16 from the first part 11a of the chamber 11 to the second part 11b of the chamber 11, the device can slide translationally on the surface 2 to be cleaned, thereby generating pressure fluctuations on the surface 2 to be cleaned, thereby providing a continuous cleaning action on the surface area of ​​the surface 2 that is greater than the area of ​​the distal end 12 of the device 1. The cleaning liquid that engages the surface 2 to be cleaned can be used to lubricate the translational sliding action of the distal end 12 on the surface 2 to be cleaned at least during these steps.

[0132] Alternatively, in other embodiments of the method of the present invention, the surface 2 to be cleaned is immersed in an underwater environment (optionally a ship's hull), for example, to clean biofouling from an external hull surface. Moreover, at least during the step of introducing acoustic energy into the chamber 11 with the acoustic transducer 18 and the step of passing the acoustic energy through the diaphragm 16 from the first part 11a of the chamber 11 to the second part 11b of the chamber 11, the device can slide translationally on the surface 2 to be cleaned, thereby generating pressure fluctuations on the surface 2 to be cleaned, thereby providing a continuous cleaning action on a surface area of ​​the surface 2 that is greater than the area of ​​the distal end 12 of the device 1. In these embodiments, water in the underwater environment and / or a cleaning liquid engaging the surface to be cleaned can be used to lubricate the translational sliding action of the distal end 12 on the surface 2 to be cleaned, at least during these steps. In addition, when the surface 2 to be cleaned is immersed in the underwater environment, the diaphragm 16 can be omitted, and the chamber 11 is a single undivided chamber containing the cleaning liquid.

[0133] Various other modifications of the invention will be apparent to those skilled in the art and are included within the scope of the invention as defined by the appended claims.

Claims

1. A device for treating a surface, the device comprising: a body defining a cavity, the body terminating in a distal end portion adapted to be positioned adjacent a surface to be treated such that the surface to be treated forms an end wall of a chamber comprising the cavity; at least one liquid inlet for flowing a process liquid into the chamber; a partition located in the cavity, the partition dividing the chamber into a first portion and a second portion separated from each other, wherein the at least one liquid inlet is arranged to introduce a treatment liquid into the first portion of the chamber, the second portion of the chamber being in fluid communication with the surface to be treated, wherein the partition is 1-60 mm away from the distal end of the body so that a portion of the second portion of the chamber is located in the cavity; an acoustic transducer adapted to introduce acoustic energy into the first portion of the chamber; a bubble generator configured to generate bubbles at the partition and / or in the second portion of the chamber such that the bubbles are configured to be driven toward the surface to be treated, wherein the diaphragm is adapted to allow acoustic energy to pass through it from the first part of the chamber to the second part of the chamber, thereby allowing pressure fluctuations to be generated at the surface to be treated, wherein the partition includes at least one hole extending through the partition to allow process liquid to flow from the first portion of the chamber into the second portion of the chamber; and A skirt is provided around the distal end of the body and is adapted to retain treatment liquid in the second portion of the chamber and in contact with the surface to be treated.

2. The device according to claim 1, wherein: The at least one hole comprises a plurality of holes arranged in an array.

3. The device according to claim 1, wherein: The at least one hole is disposed between the acoustic transducer and a distal end of the body.

4. The device according to claim 1, wherein: The separator includes a diaphragm.

5. The device according to claim 4, wherein: The diaphragm is formed of a material that is substantially impedance matched to the process liquid.

6. The device according to claim 4, wherein: The diaphragm is thin enough that it does not significantly attenuate sound passing through it from the first portion of the chamber to the second portion of the chamber.

7. The device according to claim 4, wherein: The diaphragm is formed from a material having specific acoustic properties to match the acoustic field at the location of the diaphragm.

8. The apparatus of claim 1, further comprising a liquid conditioning unit adapted to remove air bubbles from the process liquid supplied to the chamber.

9. A device for treating a surface, the device comprising: a body defining a cavity, the body terminating in a distal end portion adapted to be positioned adjacent a surface to be treated such that the surface to be treated forms an end wall of a chamber comprising the cavity; at least one liquid inlet for flowing a process liquid into the chamber; a baffle disposed within the cavity, the baffle dividing the chamber into a first portion and a second portion separated from each other, wherein the at least one liquid inlet is configured to introduce a treatment liquid into the first portion of the chamber, the second portion being in fluid communication with the surface to be treated, wherein the baffle is disposed between the acoustic transducer and a distal end of the body and spaced from the acoustic transducer, and wherein the baffle is spaced from the distal end of the body such that a portion of the second portion of the chamber is located within the cavity; an acoustic transducer adapted to introduce acoustic energy into the first portion of the chamber; a bubble generator configured to generate bubbles at the partition and / or in the second portion of the chamber such that the bubbles are configured to be driven toward the surface to be treated, wherein the diaphragm is adapted to allow acoustic energy to pass therethrough from the first portion of the chamber to the second portion of the chamber, thereby allowing pressure fluctuations to be generated at the surface to be treated, and wherein the partition includes at least one hole extending through the partition to allow process liquid to flow from the first portion of the chamber into the second portion of the chamber; and A skirt is provided around the distal end of the body and is adapted to retain treatment liquid in the second portion of the chamber and in contact with the surface to be treated.

10. The device according to claim 9, wherein: The at least one hole comprises a plurality of holes arranged in an array.

11. The device according to claim 9, wherein: The at least one hole is disposed between the acoustic transducer and a distal end of the body.

12. The device according to claim 9, wherein: The separator includes a diaphragm.

13. The apparatus of claim 9, further comprising a liquid conditioning unit adapted to remove air bubbles from the process liquid supplied to the chamber.

14. An apparatus for treating a surface, the apparatus comprising: a body defining a cavity, the body terminating in a distal end portion adapted to be positioned adjacent a surface to be treated such that the surface to be treated forms an end wall of a chamber comprising the cavity; at least one liquid inlet for flowing a process liquid into the chamber; a baffle located within the cavity, the baffle dividing the chamber into a first portion and a second portion separated from each other, wherein the at least one liquid inlet is arranged to introduce a treatment liquid into the first portion of the chamber, the second portion being in fluid communication with the surface to be treated, wherein the baffle is spaced from a distal end of the body such that a portion of the second portion of the chamber is located within the cavity; an acoustic transducer adapted to introduce acoustic energy into the first portion of the chamber; a bubble generator configured to generate bubbles at the partition and / or in the second portion of the chamber such that the bubbles are configured to be driven toward the surface to be treated, wherein the baffle is disposed between the acoustic transducer and a distal end of the body, and wherein the baffle includes at least one aperture disposed between the acoustic transducer and the distal end of the body, the at least one aperture extending through the baffle to allow process liquid to flow from a first portion of the chamber into a second portion of the chamber; and wherein the diaphragm is adapted to allow acoustic energy to pass therethrough from the first portion of the chamber to the second portion of the chamber, thereby allowing pressure fluctuations to be generated at the surface to be treated; and A skirt is provided around the distal end of the body and is adapted to retain treatment liquid in the second portion of the chamber and in contact with the surface to be treated.

15. The device according to claim 14, wherein: The at least one hole comprises a plurality of holes arranged in an array.

16. The apparatus according to claim 14, wherein: The separator includes a diaphragm.

17. The apparatus according to claim 16, wherein: The diaphragm is formed of a material that is substantially impedance matched to the process liquid.

18. The apparatus according to claim 16, wherein: The diaphragm is thin enough that it does not significantly attenuate sound passing through it from the first portion of the chamber to the second portion of the chamber.

19. The apparatus according to claim 16, wherein: The diaphragm is formed from a material having specific acoustic properties to match the acoustic field at the location of the diaphragm.

20. The apparatus of claim 14, further comprising a liquid conditioning unit adapted to remove air bubbles from the process liquid supplied to the chamber.

21. An apparatus for treating a surface, the apparatus comprising: a body defining a cavity, the body terminating in a distal end portion adapted to be positioned adjacent a surface to be treated such that the surface to be treated forms an end wall of a chamber including the cavity, wherein the chamber is configured to contain a treatment liquid; an acoustic transducer adapted to direct acoustic energy into the chamber, through the treatment liquid, and to the surface to be treated; a partition located within the cavity, the partition dividing the chamber into a first portion and a second portion separated from each other, the second portion being in fluid communication with the surface to be treated, wherein the partition is spaced from the distal end of the body so that a portion of the second portion of the chamber is located within the cavity; a bubble generator configured to generate bubbles at the partition and / or in the second portion of the chamber such that the bubbles are configured to be driven toward the surface to be treated, at least one treatment liquid inlet located near the distal end of the body, the at least one treatment liquid inlet adapted to introduce a treatment liquid into the first portion of the chamber; and a liquid conditioning unit located upstream of the at least one treatment liquid inlet, the liquid conditioning unit being adapted to remove air bubbles from the treatment liquid supplied to the chamber through the at least one treatment liquid inlet, and wherein the partition includes at least one hole extending through the partition to allow process liquid to flow from the first portion of the chamber into the second portion of the chamber; and A skirt is provided around the distal end of the body and is adapted to retain treatment liquid in the second portion of the chamber and in contact with the surface to be treated.

22. The apparatus according to claim 21, wherein When the apparatus is arranged so that the surface to be treated forms an end wall of the chamber, the acoustic transducer is adapted to produce an acoustic resonance in the chamber and has an acoustic frequency and a spacing from the distal end such that the acoustic transducer is arranged to form an acoustic pressure antinode at or near the surface to be treated.

23. The apparatus of claim 22, wherein: The acoustic frequency of the acoustic transducer and the spacing from the distal end are adapted so that only one acoustic pressure antinode is formed in the chamber, the location of which is at or adjacent to the surface to be treated.

24. The apparatus of claim 21, wherein: The liquid conditioning unit has a liquid output connected to a liquid input of each of the at least one process liquid inlet.

25. The apparatus of claim 21, wherein: The liquid conditioning unit comprises a microporous material adapted to remove air bubbles from the process liquid.

26. An apparatus for cleaning a surface, the apparatus comprising: a body defining a cavity, the body terminating in a distal end portion adapted, in use, to be located adjacent a surface to be cleaned such that the surface to be cleaned forms an end wall of a chamber comprising the cavity; at least one cleaning liquid inlet for flowing cleaning liquid into the chamber; a baffle located at or adjacent an end of the cavity, the baffle dividing the chamber into a first portion and a second portion separated from each other, wherein the at least one liquid inlet is arranged to introduce treatment liquid into the first portion of the chamber, the second portion being in fluid communication with the surface to be cleaned in use, wherein the baffle is spaced from a distal end of the body such that a portion of the second portion of the chamber is located within the cavity; an acoustic transducer coupled to the first portion of the chamber to introduce acoustic energy into the chamber; a bubble generator configured to generate bubbles at the partition and / or in the second portion of the chamber such that the bubbles are configured to be driven toward the surface to be treated, wherein the diaphragm is adapted to allow acoustic energy to pass therethrough from the first portion of the chamber to the second portion of the chamber, thereby allowing pressure fluctuations to be generated at the surface to be cleaned, and wherein the partition includes at least one aperture extending through the partition to allow cleaning liquid to flow from the first portion of the chamber into the second portion of the chamber; and A skirt is provided around the distal end of the body and is adapted to retain treatment liquid in the second portion of the chamber and in contact with the surface to be treated.

27. An apparatus comprising: a body defining a cavity, the body terminating in a distal end portion adapted, in use, to be located adjacent a surface to be cleaned such that the surface to be cleaned forms an end wall of a chamber comprising the cavity; at least one cleaning liquid inlet for flowing cleaning liquid into the chamber; a baffle located at or adjacent an end of the cavity, the baffle dividing the chamber into a first portion and a second portion separated from each other, wherein the at least one liquid inlet is arranged to introduce treatment liquid into the first portion of the chamber, the second portion being in fluid communication with the surface to be cleaned in use, wherein the baffle is spaced from a distal end of the body such that a portion of the second portion of the chamber is located within the cavity; an acoustic transducer coupled to the first portion of the chamber to introduce acoustic energy into the chamber; a bubble generator configured to generate bubbles at the partition and / or in the second portion of the chamber such that the bubbles are configured to be driven toward the surface to be treated, wherein the baffle is adapted to allow acoustic energy to pass therethrough from a first portion of the chamber to a second portion of the chamber, thereby allowing pressure fluctuations to be generated at the surface to be cleaned, and wherein the baffle is constructed or treated to reduce or avoid the baffle acting to trap gas bubbles in the chamber, and wherein the partition includes at least one aperture extending through the partition to allow cleaning liquid to flow from the first portion of the chamber into the second portion of the chamber; and A skirt is provided around the distal end of the body and is adapted to retain treatment liquid in the second portion of the chamber and in contact with the surface to be treated.

28. The apparatus according to any one of claims 1 to 27, wherein: The bubble generator and the acoustic transducer are configured such that the acoustic energy can induce inertial or non-inertial cavitation in the bubbles at or above the surface to be cleaned.

29. A method for cleaning a surface, the method comprising the steps of: a) providing an apparatus comprising a body defining a cavity, a baffle located within an end of the cavity, and a skirt disposed around a distal end of the body; b) arranging the distal end of the body adjacent a surface to be cleaned so that the surface to be cleaned forms an end wall of a chamber comprising the cavity, the partition dividing the chamber into a first portion and a second portion separated from each other, wherein the partition is spaced from the distal end of the body so that part of the second portion of the chamber is located within the cavity, and wherein at least one liquid inlet is arranged to introduce a treatment liquid into the first portion of the chamber, the second portion of the chamber being in fluid communication with the surface to be cleaned; c) supplying cleaning liquid to the second portion of the chamber so that the cleaning liquid engages the surface to be cleaned, the skirt retaining the treatment liquid in the second portion of the chamber and in contact with the surface to be cleaned, and using a bubble generator to generate or release bubbles at the baffle and / or in the second portion of the chamber so that the bubbles enter the cleaning liquid; d) introducing acoustic energy into the chamber using an acoustic transducer; e) passing acoustic energy through the baffle from the first portion of the chamber to the second portion of the chamber, thereby generating pressure fluctuations at the surface to be cleaned; and Wherein the partition includes at least one aperture extending through the partition to allow cleaning liquid to flow from the first portion of the chamber into the second portion of the chamber.

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