Patent Application
20070175502
1. Field of the Invention
The present invention relates to devices, systems, and processes using acoustic energy for cleaning or surface-alteration.
2. Description of Related Art
By far the most widely used systems utilizing acoustic energy for cleaning are immersion systems employing ultrasonic transducers. Items to be cleaned are immersed in a liquid filled tank, usually with a cleaning enhancing agent such as a solvent, detergent, wetting-agent or cavitation-agent added, and ultrasonic energy is transmitted into the liquid tank from at least one transducer mounted thereon. There are numerous commercially available systems that utilize this technology including ones made by Branson, Crest and many others. Typically, these systems operate in the 15-70 KiloHertz (KHz) range and most commonly in the 15-30 KHz frequency range at sufficient power to drive steady cavitation, which is known to serve as the primary energetic cleaning (or treating) mechanism. Such systems and their ultrasonic output are never used on human skin, as any such significant cavitation would cause skin damage of a mechanical and thermal nature as well as pain. On the other hand, such systems are frequently used on non-living inanimate mechanical, electronic and optical parts, components, materials etc., which are insensitive to limited or even unlimited cavitation. The point is that cavitation is the primary industrial acoustical cleaning or treating mechanism for inanimate surfaces, but it is not regarded as safe for human skin use as reflected by federal regulations of the Food And Drug Administration (FDA) in the United States. The skin is a very sensitive organ and is easily damaged by cavitation phenomenon even on its surface.
Another type of system using acoustic energy for cleaning excites a tip of a tool with sonic energy and the vibrating mechanical tip is placed in direct physical contact with the item to be cleaned. An example is tooth-cleaning devices that involve ultrasonic excitation of a tooth-contacting water-flushed tip. These are the ultrasonic descaling devices utilized by a dentist for cleaning teeth. They primarily cavitate plaque and other hard tooth coatings and are not aimed at gum tissues, which are very sensitive.
Hydraulically pressure-pulsed products with pulsatile water flow, such as tooth and gum cleaners found in many modern home bathrooms, are not sonic cleaning devices; they are pulsating flow devices wherein the flow velocity equals the pulse velocity. There is no significant acoustical energy delivered by these devices nor is there any cavitation occurring.
EP 00645987B1 to Harrel discloses a descaler utilizing an ultrasonically excited scraper tip and a liquid flush. EP 00649292B1 to Bock discloses an ultrasonically energized brush used in the direct contact mode. Both of these use the acoustics to attack tooth coatings and plaques. The scraper surely cavitates and the brush might cavitate under some conditions. Again, any significant cavitation-exposure of the gums would both be painful and damaging. Note that in the above devices, the acoustic cavitation, if any, is produced directly on or at the enamel tooth surface to be cleaned by a mechanical exciter physically deliverable to that surface.
We have cited these ultrasonic references first as they are cleaning references and cleaning is a major use for our invention herein. However, as will be seen, we deliver disruptive cleaning energy in a different manner.
There are systems which (transmit/receive or pulse/echo) couple very low bidirectional acoustic energy through a short liquid stream or film to an object for non-destructive testing (NDT), but these are very low-power mapping or imaging systems in which disrupting or cavitating the object to which the liquid stream is coupled is to be absolutely entirely avoided. Such NDT systems have been known for 30 years or more. These systems use sonic echoes to analyze the object and take great pains in their design and operation to avoid any disruptive action at all. They are not cleaning systems and in fact are used to detect rather than remove contaminants. An example of an acoustic NDT system that contemplates delivery of acoustic energy to a test site via a liquid stream is found in U.S. Pat. No. 4,507,969 to Djordjevic. Note that cavitation phenomenon, if allowed, would not only damage the workpiece but also introduce un-wanted acoustic harmonics into the received echo signals. NDT imaging is therefore done at acoustic power levels far lower than that required to cavitate. Generally, such NDT systems use as short a coupling water plume as possible, as every surface ripple and bubble in the plume introduces acoustic confounding noise to the NDT process. Typically, such gravity-fed plumes are a fraction of an inch to a couple of inches long maximum and utilize essentially pure water to minimize attenuation and bubble content. Pressurized water is not used, as the flow rate needs to only be high enough to assure coupling and it is normally desired that the coupling water be conserved and not have to be cleaned up.
There is also a system disclosed in U.S. Pat. No. 5,013,241 to Von Gutfield, which claims to utilize an ultrasonically energized liquid stream to clean a tooth upon which the stream was blindly directed by a user. This device was neither clinically nor commercially successful because the design of the device ignored prior art that teaches that powers of even a few watts/cm2 cause severe pain and undesirable sensations (as well as cellular damage) to the sensitive gums in real human applications. No cleaning agents were disclosed by Von Gutfield as being necessary or desirable for adding to the liquid stream. Also, the Von Gutfield ultrasonic transducer was not liquid cooled nor air-backed, thus limiting the power level and efficiency at which it could operate. The Von Gutfield disclosure did not teach the use of high power ultrasonic energy and in fact tried to keep the energy low enough to avoid admitted discomfort, which also meant that the cleaning action was rendered relatively ineffective. Had Von Gutfield used high power in the range contemplated by the device disclosed and claimed in the instant application, Von Gutfield's transducer would have overheated and failed, as well as caused severe disabling pain and serious gum damage to the patient due to cavitation. The Von Gutfield device cannot merely be scaled up or used in multiple numbers to anticipate the device disclosed and claimed in the instant application. It would not produce the result that the instant invention accomplishes, which is the rapid cleaning of objects over a relatively large area of their surface (or subsurface, interstices etc if permeable). The instant invention most preferably accomplishes this result by using an elongated energy generator that couples high-powered acoustic energy into a liquid stream(s) that is(are) directable onto an object to be cleaned. Liquid cooling of the acoustic energy source and the use of additive cleaning-enhancing or other surface-alteration agents are desirable for high efficiency operation and are not disclosed by Von Gutfield. Furthermore, multi-step processes such as cleaning and rinsing are also not therein disclosed or suggested. Immersion systems do not use flowing-liquid transducer cooling and none have contemplated their use in connection with a liquid stream that is delivering substantial acoustic cleaning energy to a distant non-immersed object. Immersion systems are effective for cleaning items that can be put into their tanks, but impractical for on-site field cleaning of large objects that cannot be easily moved into or even fit into a tank. The Von Gutfield device was designed for spot cleaning of live teeth in situ and cannot deliver sufficient power or a large enough acoustically energized liquid stream for effective use in industrial-type cleaning. The very fact that no commercial versions of the Von Gutfield invention have ever been made, despite its desirability, argues against its obviousness. There is no limit to the size of an object that can be cleaned by the instant invention, yet the prior art deals with large objects by making larger and larger immersion tanks. Pressure washers of the type that typically use piston or diaphragm pumps to deliver water blast cleaning through a nozzle at pressures upwards of 1000 psi are useful, but not nearly as effective as the instant invention, which can actually clean any portion of an object that the acoustically energized liquid can contact, including backsides, interstices, and other areas that are treated far less effectively by mere pressure blasts directed from a distal point. High-pressure jet washers do not utilize ultrasonics and thus are still subject to fluid boundary-thickness effects.
Additional patent references are included below. These provide detailed disclosures as to how ultrasound or ultrasonically produced bubbles or added bubbles can be used to enhance the cleaning of objects in cavitation-based ultrasonic immersion tanks.
U.S. Pat. No. 5,156,687 to Ushio teaches ultrasonic wet-surface pretreatments for the painting of polymers. U.S. Pat. No. 5,143,750 to Yamagata teaches oxidation removal and polishing of work surfaces using ultrasonic wet processes. EP 01036889A1 to Shinbara teaches bubble-loading of liquids to enhance cleaning in the presence of ultrasonics. None of these teaches or suggests water-jet or plume delivered high-energy ultrasound for cleaning or treating.
Finally, we have a class of devices in the prior art designed to deliver medical therapies to subdermal tissues or organs in living beings. The authors have developed products in this arena of therapeutic or surgical ultrasound. Frequently seen such applications include the noninvasive and invasive acousto-thermal ablation of cancerous tissues. If cavitation is also or instead employed, it is because mechanical tissue destruction is desired. Such destruction, given the presence of cavitation, is un-avoidable both on the macroscopic scale and on the microscopic cellular or genetic scale. So we again emphasize that the delivery of cavitation ultrasound to surface or at-depth tissues is not practiced if one desires to avoid tissue damage.
U.S. Pat. No. 6,450,979 B1 to Miwa teaches the ultrasonic exposure of subdermal fat cells in a human body for the purpose of depletion of their adipocytes fat-content. Note how carefully Miwa focuses, properly so, on avoiding cavitation in the patient. Note also how carefully Miwa avoids any significant heating (by any mechanism) of the patient's tissues. The point to be taken here is that Miwa's treatment, in industrial terms, is a very-low power ultrasound treatment as well as a non-cavitation treatment unlike virtually all industrial treatments and is not useful as an industrial treatment.
Thus, when Miwa suggests passing his therapeutic ultrasonic energy through a water stream or array of water jets (
Further, we note explicitly in Miwa's apparatus, such as that in
So the prior art fails to teach a means to deliver high-power acoustical cleaning or treating energy through a liquid stream in a manner wherein: a) the transducer is not thermally damaged, b) wherein interfering reflections do not degrade the passing acoustical energy, c) wherein cavitation in the streaming device does not damage the streaming device and its orifice(s), d) wherein acoustical cavitation can be driven at a distal location along the stream (if it is desired), or e) wherein cavitation, treatment or cleaning agents are delivered into or to the stream. Further, none of the prior art teaches the use of f) acoustical echoes passed along such a stream to monitor or assess a parameter such as attenuation, detergent-content or a workpiece-distance for such a cleaning or treating process. Finally, none of the prior art teaches g) the manipulation of the shape of the stream(s) or jet(s) to enhance acoustical waveguiding or acoustical amplification phenomenon such that distal cavitation can be accomplished.
The instant invention preferably utilizes extended streams or plumes (fractions of a meter or at least several centimeters long), laterally-extended plumes or films of liquid or utilizes arrays of smaller streams with overlapping treating action that have not been suggested by the above art and that would cause severe multi-path signal propagation problems for the prior NDT art. The prior art low-flow approach would not allow for a meter-length plume to be formed at any significant angle to gravity or the vertical using water. We also have discovered that separate adjacent impacting plumes or streams can provide a work surface interstream cleaning effect due to acoustic propagation laterally on the work surface within the liquid meniscus between impinging streams, something not disclosed or suggested by the prior art. Our optional use of bubbling or bubble constituents in a flowing jet of liquid intended to deliver acoustic energy to a workpiece is counter-intuitive. We find that low to moderate amounts of bubble volumetric percentage makeup in the plume add more stable and/or transient cavitation acoustics action than they cost in terms of increased attenuation. At some point a high enough (suds-like) concentration of bubbles will deliver virtually no acoustic cleaning action. Thus, there is a workable middle ground. Furthermore, even non-bubbling additives increase attenuation, but we again realize that the added detergent effects outweigh the attenuation effects at least for low to moderate concentrations. These are counter-intuitive improvements from purely the acoustics-manipulation point of view.
Because we can operate at moderate to high power (because of our unique preferred transducer liquid cooling and efficiency-enhancing air-backing and matching layer(s) of our transducers) and we can also optionally get additional beneficial stable and/or transient cavitation effects from modest levels of bubbles, we can afford to lose some acoustic energy to attenuation and scattering losses in the plume. So we can tolerate a variable-shaped plume and even plumes containing surface-ripples, defects and turbulence, if necessary. The toleration of turbulence or undulating surface shapes in a liquid waveguide is totally contrary to all the prior art. In NDT it introduces chaotic signal noise thus very, very low flow, low velocity laminar streams are utilized in NDT. In dental applications, it would involve very high flows introducing further considerable uncomfortable sensations and mouth flooding even with oral aspiration. In general, we utilize a somewhat acoustically lossy flowing liquid waveguide contrary to all prior NDT and dental teaching. Uniquely, our plume waveguide can flow quickly if desired, such as to direct it sideways or to provide impacting water pressure at the impact zone.
Thus, a need exists for a system and method for an acoustically enhanced liquid cleaning or treating approach that does not depend upon immersion of the object to be cleaned and can utilize multi-component liquids, workpiece-cavitation as desired, and medium to high-power without transducer overheating, internal cavitation or damaging internal reflections. There is also a need for a system that can effectively clean in shielded or obstructed areas where the cleaning effect of high velocity liquid blasts is decreased. It is also desirable that such a system be capable of being used in hand held or fixed mount devices and which also can be automatically or manually directed towards objects to be cleaned.
The present invention combines a liquid cooled, preferably elongated, acoustic energy source capable of moderate to high power operation, a liquid stream(s) into which acoustic energy is coupled with the stream(s) being directable onto and or into a target object for delivering acoustic cleaning energy and associated liquids thereto. The acoustic energy source is preferably air-backed and acoustically impedance matched with a matching layer, such that the treating or cleaning acoustic energy is efficiently propagated forward toward the workpiece. Some cooling is provided for the transducer at least by passing plume liquid and possibly also or instead by additional conductive or convective measures as is convenient.
In one embodiment of the invention, an apparatus for treating or cleaning a workpiece is provided that utilizes acoustic energy carried to the workpiece through at least one flowable stream directed at or upon said workpiece. The apparatus comprises
In another embodiment of the invention, an apparatus for treating or cleaning a workpiece or object is provided that utilizes acoustic energy carried to the workpiece through two or more flowable streams or plumes substantially commonly directed at or upon a workpiece or site thereon for at least a period. The apparatus comprises
I. Definitions.
The following definitions are put forward not as an exhaustive all-inclusive interpretation of words used, but as an aid in understanding the words as used herein.
Liquid: Any flowable material or media that can be poured, expelled or otherwise extracted under a pressure gradient, gravity, by surface-tension, capillary-action or acoustic-streaming pressures. A liquid may contain any or all of additional additive or materials such as detergents, bubbles, abrasives, ice, etc. The liquid may also contain solids in other physical-phase forms of itself (ice particles, steam, vapor bubbles). The liquid may have any number of phases and may comprise a solution, mixture, emulsion, paste, cream, gel, foam, suspension, etc. Typically, at least one treatment substep will involve an additive or agent being placed into or used with the liquid, such as a detergent or wax.
Plume, film or stream: A volume of liquid that is substantially transportable to a workpiece from an emission orifice(s). May be continuous at a given moment (connecting the orifice and workpiece) or discontinuous at a given moment (disconnected from one or both of the orifice or workpiece at a given moment). Typically, flowed by gravity and/or pressure but in some cases flowable using acoustic-streaming or capillary-action surface-tension forces.
Acoustics: Acoustic, sonic or vibratory energy which is injected, coupled into or produced within an emitted liquid plume, film or stream in any manner, at least some of which arrives at the workpiece before total attenuation occurs. Frequencies will typically be chosen in the range from 1 KHz to tens of MHz. Energy may be single frequency, multi-frequency, variable frequency, alternating frequency, broadband frequency, CW, pulsed, chirped, etc.
Bubble: Any stable or transient void or vapor bubble in a liquid, regardless of how it was formed or when it was formed. Stable oscillating bubbles can be driven with low acoustic power, whereas transient bubbles require high acoustic power. Bubbles may be in the stream and/or in the wetted or impacted film upon the work surface. Preformed bubbles may be injected or solid or gaseous nuclei typically smaller than the in-situ seeded bubbles may be employed. Also, included in the definition of bubble is any particulate which itself contains a gas or air.
Transducer: Any device that can convert a first energy type into acoustic, sonic or vibrational energy. Typically, the first energy type is electrical, electromagnetic or electrostatic energy. Transducers may be of any type including single-element, multielement, arrays, mechanically focused, acoustically lensed, mechanically unfocused, mechanically collimated, mechanically defocused, mechanically scanned, electronically scanned, etc. Multiple different transducers may be used in one or more plumes or films or two or more transducers may simultaneously be operated with different acoustic parameters.
Multi-step process: Any workpiece cleaning or treatment process wherein at least one operative parameter or constituent is changed during the total overall process-even if it is merely altered between on and off or between two fixed values. The parameter may be a liquid flow, an additive concentration, a plume shape-change (e.g., film to spray), an acoustic power, a temperature, a flow rate, etc. A typical multi-step process would be an acoustic clean followed by a rinse.
Attenuation: A measure of the time it takes for acoustic waves to decay from 90% of their initial value to 10% of their initial value. Typically, with a few exceptions, attenuation rates rise with frequency and the addition of additives including bubbles.
Water: Typically, untreated faucet or well water, treated or softened municipal water, or filtered water of any type. May be provided from domestic or industrial plumbing, from a user-reservoir or tank, from a hose, from a tanker-truck or a deionized water system. Water particularly for cleaning is beneficially treated to remove potential residues such as carbonates or particulates.
Disruptive: Altering or changing a property of an object or its surface. Used to distinguish the aggressive cleaning action of our acoustically energized liquid streams from the deliberately delicate non-disruptive acoustically energized liquids streams of the NDT prior art. We note that disruption may take place on the surface of the workpiece most commonly, but we also anticipate the ingress into the workpiece of some liquid, additive, and acoustical energy such that sub-surface regions may also be disrupted or altered. A good example of this would be the inventive disruption of a permeable material for at least several cell-dimensions distance below the exposed surface.
Target surface: The site to which the acoustically energized liquid or flowable stream is directed. The surface can include materials that are impermeable, permeable, or any combination of properties that affect the interaction of the liquid and the object that it impacts. The target surface may be below, adjacent beside or even above the device. In many applications, such as cleaning or treating permeable fabric from roll-to-roll, the wetting and cleaning action will take place through the entire fabric thickness-perhaps with some or all used liquid leaking through the fabric-despite the cleaning wand being on just one side of the fabric web.
While operating in the cavitational mode, the invention may be used, for example, for wound-cleaning or debridement. In this special human or animal case, surface-damage is actually desired to remove scab and other undesired tissue and exudates.
Further, while operating in either the cavitational or non-cavitational modes, one may utilize the apparatus to enhance the permeability of the skin or to treat burns, for example.
Both of these examples are of surface-driven processes not taught by the prior art using our type of apparatus and method.
II. Acoustic Cleaning System.
Pressure waves P1 (vertically directed) and/or P2 (angularly directed) from the transducers are coupled into the liquid plume 3 through acoustically-transparent membrane 7. Membrane 7 could, for example, be a very thin stainless steel foil or a copper-foil that would have acceptably low acoustic losses, a hermetic nature, and serve as an electrical ground electrode if desired. Transducers 5 and 6 are the second and third transducers (with piezo electric elements 5b and 6b respectively) in the extended row and are coupled to the liquid through their respective matching layers 5a and 6a and membrane 7. The acoustics oriented reader will realize that the membrane may also be sandwiched between the matching layers and PZT exciters (arrangement not shown) or one may even utilize the membrane material itself as a matching layer. Further, one may sacrifice coupling efficiency and omit the matching layer. Item 8c is the deformed liquid stream 3 as it impacts the surface 2a to be cleaned or otherwise treated or altered. Item 9 illustrates a transient defect (hole) in the otherwise substantially continuous film or stream 3. Transient defects such as hole 9 do not substantially impact the effectiveness of the cleaning as the acoustic energy from at least one transducer will propagate around the defect and the acoustic shadow of the defect will likely move in the X-axis as well. In fact, the present inventors include an embodiment wherein controlled bubbles or microbubbles are purposefully formed in or injected into the plume to serve as cavitation sites. In some cases, injected additives or agents, even of a solid nature, may serve as cavitation nuclei. An air cavity or “air-backing” 10 is shown surrounding the backs of transducers 4, 5, and 6 in the array. The use of air on the backside of the transducers minimizes backwards acoustic propagation, thus enhancing the acoustic efficiency of selectively delivering acoustic energy in the forward direction of the liquid. However, this makes liquid cooling of the transducer using the plume liquid highly desirable. The acoustic pressure waves formed by the interaction of the transducers and the liquid that flows past them produces pressure waves 12 shown in vector-format as P1 and P2 in the film 3. F1 is the liquid flow vector in the downwards-moving film of liquid 3. F2 and F3 illustrate the split lateral flow vectors of F1, after it impacts the surface 2a and is typically redirected. P2 illustrates pressure waves angled sideways in the X- and Z-plane as by phase-delayed firing of two transducers 5 and 6 (beam-forming) or as by angled propagation from a single transducer 4, 5 or 6. V1 is the translational velocity (if any) of the wand 1 in the Y-axis and VY is the velocity of the film 3 in the Y-axis. At a given instant, these may have somewhat different values. T1, is a local thickness of free film 3. T2 is a local thickness of the film on surface 2a near the point of impact. D is the approximate film length or working-distance in the Z-axis and we specifically note that because the film 3 curves to an angle theta (θ), that the actual curved film 3 length is somewhat longer than D. Theta is the angle of film impact (shown to be about 20 to 30 degrees in
Typically used liquid additives (agents) would include items such as detergents, soaps, emulsifiers, solvents, surfactants, antimicrobials, sterilants, biocides, wetting agents, surface-tension adjusters, pH adjusters, bubbles or bubbling particulates as cavitation agents, etchants, passivations or other workpiece coatings. They could also include insecticides, antifungicides, antibacterials, antivirals, oxidizers such as hydrogen peroxide, antiseptics, chemical etchants, primers, paints, polishes, waxes, ultraviolet barriers, sealants, stains, other decorative finishes or even abrasives. Additives may act on their own or may react with other additives or with the workpiece surface being treated. Most implementations will utilize a carrier liquid such as water or a solvent (possibly with additive(s) in it), but the invention may alternatively utilize a material or media possibly defined above as an “additive” alone instead. Water will be the typical plume liquid utilized and that water may be preconditioned as by heating, cooling, additive mixing, degassing, gasifying, water-softening, filtering or pH adjustment. The plume liquid(s) or additives may also be recirculated or refiltered in any convenient manner. Additives can be introduced directly into the acoustically energized liquid film 3 at any number of points before impact or in an alternative approach they could be delivered to the surface 2a from a different source or delivered separately to mix with the acoustically energized liquid. We note that in some applications water may not be used and instead a solvent, for example, is used. Alternatively, the wand 1 may emit nothing but the “additive” or agent with no dilution or buffering. We simply note that water is expected to be a common base-liquid or sole emitted liquid, as it is inexpensive and readily available and, if desired, can easily be filtered and recirculated.
By delivering the acoustically energized liquid in discrete and physically separated volumes or packets (not shown) further enhanced cleaning action and/or conservation of dispensed liquids or additives may be obtained. Even though the packets or stream-segments are not directly coupled to the transducers, once they leave or detach from the orifice 11 (they become non-bridging and separated, at least temporarily), they still contain internally propagating and reflecting acoustic pressure waves which, if they reach the surface 2a before their energy has decayed or attenuated too far, can still deliver enough energy to the surface to perform a useful cleaning (or treating) action. Since acoustical energy dissipates quickly, this approach may require a very high velocity water plume and a shorter working distance D. In cleaning of contamination that has resilient components, sometimes a period of time without liquid impact will allow a spring-back action to occur, which will place certain previously bent-over contaminants in a better position or attitude for cleaning by the impact of a subsequently delivered acoustically energized liquid globule or “packet”. Furthermore, the impact of each separate stream-segment, packet or globule involves more disruptive energy than an equivalent unbroken single segment. Pulsatile continuous flow (pressure-varying wherein the pressure waves travel approximately at the stream velocity) may be even better for this situation, since it permits a direct coupling of the transducers to the liquid during the entire transit from the orifice 11 to the surface 2a and even beyond that point. It is a simple matter to produce isolated-globule or pulsatile continuous flow liquid using pumps, electrically controllable valves or many other well known techniques.
The device of the instant invention can be used in multi-step operations where wash and rinse cycles are used or an active or passive drying cycle is introduced. The liquid (and/or additives or agents if any) may be filtered and or recirculated and can be alternately applied to the surface 2a with and without acoustic energy coupled into it. They might also be delivered into the plume 3 or onto the workpiece 2, as by deposition from an ambient surrounding the plume 3. The width-taper of orifice 11 causes an amplification effect that is sometimes beneficial but is not essential to the operation of the device. We note further in
Multi-step cleaning or treating processes are contemplated herein such as:
Operation of the device of the present invention is relatively straight forward. The transducer(s) excitation mode is preferably CW (continuous wave) or CW pulsed and can employ swept frequencies or multiple or single discrete frequencies and/or harmonics as is known in the acoustic arts. We can emit single or multiple different frequencies or even broadband spectrums from a given transducer or from neighboring transducers, and these frequencies can be mixed and even beam-formed using phased array techniques known to the acoustic arts. One may also or instead use wave-shaping or wave-biasing in known art manners to suppress or enhance cavitation (acoustical formation of bubbles) if that is desired. We utilize, optionally, one or both of stable cavitation and transient cavitation, the two known types, wherein we enhance cavitation for some processes. Stable cavitation typically involves bubbles that oscillate between finite non-zero sizes. Such oscillation requires little acoustic energy, given a seed-bubble is provided in the form of a microbubble or dissolved gas that precipitates out of solution. Transient cavitation involves total cyclic collapse of the bubble and is a process requiring large acoustic input energy as the bubble is ripped from solid fluid every wave-cycle. Such cavitation can also cause physical erosion or pitting or the workpiece if desired. Transient bubbles require no seeding at all, although surface-tension reducing agents, dissolved gases, and injected microbubbles, for example, enhance the known effect. However, such transient cavitation is energy-consuming and can be damaging to a workpiece or painful to a human subject. On the other hand, desirable surface-altering processes are frequently means of controlled uniform damage such as grit-blasting, paint-stripping and sanding. Thus, such surface damage may be part of a useful surface-process such as abrasion or physiochemical etching. When stable or transient cavitation occurs, some bubbles are acoustically excited into oscillation wherein microstreaming flow occurs around the bubble periphery, thus enhancing the cleaning action of the liquid stream particularly adjacent the work surfaces where such bubbles tend to loiter and energetically collapse. Again, these are acoustically-known cavitation effects. Within the scope of the invention is certainly the formation and/or delivery of cavitation bubbles to the workpiece to enhance our inventive cleaning and treating processes. However, we further include in that scope that such cavitation bubbles or nuclei therefore may be formed or injected at any point before workpiece arrival, such as in the plume or in the apparatus head itself. We anticipate that for the higher plume flow velocities that a single cavitation event will take place over a physical traveled distance in the plume and it is thus possible to have cavitation events begin in the plume before finishing (imploding) at or within useful range of the workpiece. Thus, we anticipate that, particularly for higher plume velocities, a plume cavitation event might transpire through a range of plume locations-ideally with the cavitational collapse taking place at or on the substrate surface 2a.
The operative liquid, for example water, is preferably cleansed of particulates, carbonates, solids and other filterable or easily extractable contaminants with an accompanying filter or known filtration-bed means, which may itself be disposable or cleanable. Contaminants that can be removed from the workpiece or from the plume fluid medium by chemical treatment can be treated by chemical processors that are incorporated as a part of the liquid treatment subsystem. The direction of acoustic waves, such as P2 and P1, may be implemented as by operating a multiplicity of transducers as a phased array (steering) or by orienting the transducers or using concave or other specially shaped transducers or other known means of focusing (mechanical focusing not depicted), steering or shaping acoustic wavefronts. Although not needed in prior art industrial cleaning ultrasonic-immersion processes, one or more transducers may be utilized herein in pulse-echo configuration to deduce parameters of interest such as dimensions (e.g. workpiece distance D) and/or workpiece shapes and/or attenuation of plume 3. PZT transducers can be used to alternately “transmit” or “listen”, as is well known. Included in the scope of our invention is the use of pulse-echo or CW-CW echo techniques, for example, wherein ultrasound passed down the beam is passed again up the beam. Also included in the scope of our invention is the passive detection of cavitation anywhere that it occurs. For a pulse-echo approach, at least some reflected acoustic energy can be sensed coming back up a continuous film or stream 3 for at least one of the purposes of: sensing the degree of film or stream continuity or attenuation, flow-velocity, additive-content, sensing of a tool to work-surface distance, sensing of a velocity of an effluent of the tool, or sensing an angle of impingement of a film or stream upon a work-surface. These functions can be performed by circuits, sensors, methods and algorithms well known in the pulse-echo acoustic art. Also included in our inventive scope is the use of prior known pitch-catch arrangements wherein the acoustic transmitter and receiver are separate.
Fluid or flowable-media (liquids, gases etc.) manifolds such as 8a may deliver water, detergents, wetting agents, surface-tension controlling agents, gas or vapor bubbles, micro bubble media, solvents, abrasive particulates, workpiece coatings or any agent that can enhance a desired surface alteration (or coating) operation such as cleaning, abrading, conversion, etching, priming, polishing or even drying. We include in the scope of the invention the practice of electrochemical conversion such as anodization wherein an electrode and current path may be utilized, perhaps using an electrolyte as the plume fluid. The operation of wand 1 may alternate between wash, rinse or dry and can optionally be arranged to deliver air, even heated air, through the orifice 11 to enhance drying. Included in the scope of the invention is the use of orifice 11 or additional coaligned or nearby orifices or nozzles to also deliver gaseous or vapor materials which do not necessarily carry acoustic energy for cleaning or treatment steps. Chunks or globules of non-bridging plume film (not shown) or isolated substreams (isolated from one or both of the wand or work surface at at least one point in time) may be used instead of a continuously bridging film as shown in
Film (flowable media) 3 may comprise a slurry formed of materials such as ice particles, microballoons, beads or by other particles or extended molecules. The additive or filler material might even be reusable. The wand 1 may be oscillated or stepped, rotated or twisted. The work substrate 2 may instead or also be translated/rotated. The overall dimension of wand 1 may be from micromechanical (micronsized) to meters if not tens of meters. The operative frequency may be beneficially chosen or dynamically controlled to have a controlled ratio to a dimension such as T or D and may be of the frequencies normally used in commercially available immersion ultrasound cleaning tanks. Relating an operational frequency to a dimension for acoustic propagation, resonance or amplification purposes is widely known in the acoustic art. The present Inventors expect that the inventive system will typically operate in the 10-150 Khz range for cavitating and non-cavitating applications and all the way up into the megahertz regimes or above for non-cavitating applications. Waveguides are known in the art to operate best when the propagating wavelength(s) have certain preferable known ratios to the waveguide cross-section in particular, as well as to the waveguide length. Flow F1 is preferably at least partly laminar but turbulent flows F1 which have low average duty-cycle (transient) propagation-path defects (e.g., defect 9) are also useable in our device because we do not care if the acoustic attributes of the shape-varying jet 3 cause some active or passive acoustic noise or transient masking. Still, on average, despite transient defects 9 and jet 3 shape-changes, we deliver high enough average acoustic power to cavitate if desired. The acoustically inclined will recognize this condition as a mechanical index or Ml=1 or above. The wand 1 performs a disruptive process upon the substrate 2 and changes the substrate in some manner as opposed to the NDT systems, which strive to avoid any disruption or change in the object to which the acoustically energized liquid is directed. The emanated liquid/mixture/solution (or constituent thereof may or may not have a constituent that remains with the substrate 2. For example, if the process is a coating process, then some part of the emanated material would either be deposited permanently or would cause a surface-altering process to take place (e.g., etching, conversion-coating, or paint-coating).
It was realized by inventors that when the three streams impact in region 13 upon the surface 2a (sometimes referred to a “work surface”) that ultrasonic energy (as well as fluidic flow kinetic energy) is redirected to fill the interplume gaps shown having a wetted meniscus radius R. So we have downward flows FA, FB, Fc combining and causing work surface flows of the types FD and FE shown. Thereby originally downwards directed acoustic energy can be, at least in part, redirected laterally or normally into the surface 2a itself. This allows us to “alter” a surface 2a area larger and more contiguous than the isolated gapped impinging streams 3a, 3b, 3c would seem to support. Again note that each of or any of the streams 3a, 3b, 3c could be tapered to cause acoustic amplification (not shown). The invention does not require use of the shown overlapping impact meniscuses; however, they allow avoidance of untreated strips of work surface between jet-plume impact areas.
The inventors have found that as long as the pitch (spacing) of the adjacent plumes is not hugely greater than the plume diameter d1, then effective cleaning can be achieved even between plumes due to the (overlapping) meniscus of radius R that wells around the plume impact points and the above lateral acoustic propagation in that meniscus overlap region. This welled wetted (non-zero thickness) mound or overlap region is capable of passing ultrasonic energy within itself such that all wetted regions of the work surface at least in the wetted region 13 are effectively cleaned. Within plume 3c, we further depict ultrasonic waves passing straight down the plume as P1A as well as additional or alternative waves P2A passing along that plume via some reflections from the plumes water/air boundary. Passing waves may or may not undergo reflection, refraction or mode changes depending on the exact plume geometries, surface shapes, ultrasonic frequencies and materials. As with the apparatus of
The present inventors note that it is quite easy to establish a large stand-off dimension D in
Referring again to
One may have more than one row of plumes than the one shown in
We include in the scope of the invention a plume diameter d or thickness t (or any other dimension or angle) being adjustable as by user-mechanical adjustment, automatic adjustment, or substitution of parts. We also include in the scope of the invention the surrounding of one or more plumes with a flowing or static material (such as enveloping blown air) which encourages the plumes not to break down or become unstable or which favorably changes their shape, angle, velocity or concentration of an agent(s). In the example of blown air, one could easily intersperse (not shown) air-jets between our water plumes to accomplish this. One could also have concentric jets co-axial or collinear with the plume jet or orifice(s) (not shown). Also included in the scope of the invention is the use of catchments, shields or drains utilized to at least one of a) recycle a liquid or constituent thereof, b) prevent a liquid or constituent thereof from migrating (particularly in an airborne aerosol manner or floor-puddling manner) away from the worksite or work surface for any reason.
Additional specific processes to be performed by the inventive device might, for example, also be any of the following:
In the case of a high-rise window washing application, human operators may be safety-beneficially displaced and the system may incorporate at least vertical plume scanning means. Transducer arrays are typically extended as described, comprising at least one row of elements or one “equivalent” row even if straight rows are not employed. Individual transducer elements may optionally be operator replaceable. Typically, an average length of a plume (whether straight or curved as by gravity or wand/surface motion) will have a length to average thickness (or diameter) ratio of 1.5:1 to 10,000 to 1, more preferably from 2.0:1 to 1,000:1, and most preferably from about 2.0:1 to 300:1. Typically, the liquid/acoustic wand array itself will have a length/width ratio between 2:1 to 1,000:1, more preferably between 5:1 to 500:1 and most preferably between 8:1 and 100:1. Typically, if multiple plumes/streams are used, their average pitch to average diameter ratio measured at the impact zone on the work-surface would be between 2:1 and 50:1, more preferably from 2.5:1 to 10:1, and most preferably between approximately 3:1 and approximately 5:1. Typically, acoustic transducer arrangements utilized will operate at at least one frequency in the KHz to a few-MHz range. Plume additives may also be utilized that favorably stabilize the plume from breakup, such as surface-tension reducers, for example. These might also do double-duty to support workpiece processing. One may also choose acoustic operating conditions that enhance the stability of the plume(s). An extended transducer array (which may comprise many abutted or overlapped transducers or one really long transducer) may be straight, curved, circular, polygonal, etc. Fluid effluent may be emitted from such an array at variable angles vs. time or variable angles versus position on the array. Flow rates may vary with time, with process substep, with substep progress or degree-of-completion, with acoustic emission, etc. Acoustic parameters may vary with flow and with specific orifice or specific transducer. Automatic and/or manual control of one or more of these parameters is anticipated in various embodiments. Liquids or additives dispatched from a plume may undergo phase changes such as the evaporation of a solvent or the sublimation of dry ice or supercritical CO2 liquid.
The apparatus may be powered (at least acoustically) by an external electrical power cord, by a battery/fuel-cell pack or even by compressed gas or fluid whose forced flow causes purposeful resonation. A typical acoustic duty-cycle would have the acoustic power on a total of 25%-75% of the time allowing downtime or off-time of 75-25%, possibly for additional cooling, pulse/echo measurements, if any, or rinsing. On-time would typically comprise CW pulses, each CW pulse having multiple waveforms, typically tens of waveforms if not hundreds or thousands. Alternatively, rather than one or more fixed-frequency CW signals, one may utilize chirped or broad-band pulses alone or strung together in extended bursts.
We specifically note that, particularly in the case of CW operation, one preferably utilizes air-backed transducers (item 10 of
Our liquid (more accurately “flowable”) effluent may be heated or cooled as beneficial to the work surface process, step or substep being performed. At least one of the substeps will cause a useful work surface or work-article alteration. Our acoustic pulses may be purposely asymmetric in the known manner in order to suppress cavitation if that is desired. They may alternatively be symmetric and undistorted to enhance cavitation if that is desired. One or more of our substeps may include a spray or aerosol of liquid, particularly the non-acoustic steps. Such a spray or aerosol might be powered by the same transducers and/or by other known pressurized atomizers or nebulizers. A typical spray application would be a rinse or a deposition. The apparatus may include sliders, rollers or other distance-sensors that monitor and/or otherwise physically maintain a desired plume length and/or angle as the workpiece translates and/or rotates relative to it.
III. Acoustic Cleaning System of the Present Invention.
We have taught above that in several preferred modes of operation of our surface treatment or cleaning device, we would arrange for our ultrasonic jet or plume to deliver one or both of acoustical cavitating-action or acoustical non-cavitating action to the work surface or object. Now we provide further detailed arrangements and methods to do one or both of those, separately, sequentially or simultaneously.
Moving now to our
Note that downward fluid flow is indicated by flow vector F and that the flow F impacts upon the substrate 27 with a meniscus 28 forming on the fluid 30 surface. It will be appreciated that we have already taught that the fluid flow F may be gravity-fed or may be pressurized above ambient pressure with any static, ramped, oscillating, pulsed or varying pressurization scheme desired.
Practitioners of the acoustic arts for medical imaging will be aware that one can make transducers which have a movable (or distributed) focus in the Z-axis in any one or more of several manners.
A mechanically focused transducer, as shown in
Acousticians from medical imaging fields will also be aware that one can achieve a movable focus that is movable electronically or electrically. Electronic movement can be implemented by having transducer 23 comprise an annular array transducer with at least some if not all of the ring elements in the array fired with a phase-delay relative to others. This is called electronic beam forming. An advantage of beam forming is electronic movement of the focus (vertically in this example) or laterally and vertically in phased-array acoustic imaging. We discussed above the use of lateral beam scanning as well, such as scanning an acoustic beam inside or upon a plume surface.
Beam forming, regardless of how it is done, gives the user an acoustic amplification factor at the focus compared to at the transducer 23a face in terms of acoustic-intensity. It is a desirable thing to have if one wishes to selectively cavitate or to have higher power-density (even non-cavitation power density) at a distal location such as at remote points 21 and/or 22.
Another method of moving the focus electrically is to have a curved-face transducer 23/23a such that the thickness of the transducer is variable across a width such as across W. By driving the transducer at a higher frequency, one may selectively excite only the thinner transducer regions (such as inside width W1). Alternatively, by driving the transducer at a lower frequency, only the outboard thicker edges of the transducer 23 can be driven. Of course, if the radii or directivity of these portions of surface 23a are different, then the beam is also focused at different locations when this takes place.
We have shown an aperture or orifice plate 29 in
Included in the scope of our invention is the integration of the orifice plate with the transducer 23 (not shown in
We stress that by focus we do not restrict that to a point focus; rather, the focus may instead be a line focus, a curvilinear focus, or a laterally and/or vertically moving focus, for example. It may also be a distributed focus, as mentioned earlier.
For a handheld cleaning device, for example, it would be preferable to have either a distributed focus or a movable focus wherein the moving is such that the focus is maintained at or near the work surface despite a variable throw-distance of the plume as the user's hand moves.
Thus, we already included in the scope of our invention the use of, for example, pulse-echo detection of a transducer/work surface distance such that the device may optionally electronically adjust the focus to be at the surface 27 despite movement of transducer 23.
Moving now to
The essential aspect of
Again, we have depicted the device of
Again, the major advantage of the
Before proceeding to the next Figure, we shall reinforce and add detail for some prior comments regarding cavitation. We taught above that cavitation involves the formation of microbubbles in the liquid. These bubbles can take two general forms, ones that last for only one pressure cycle and ones that last for many pressure cycles. Further, it is known that when cavitation microbubbles form at, upon or near surfaces (work surface 27 for example) those bubbles emit directional fluid jets as they collapse, and it is these jets that can cause erosion and pitting of even hard surfaces. These phenomena are well understood in ultrasonic immersion containers.
Understanding these phenomena, the present inventors specifically anticipate that we will have one or both types of cavitation phenomenon in devices we design to utilize cavitational mechanisms. For example, we may have multicycle cavitation bubbles formed in the falling (jetted) plume. We may also have single-cycle cavitation events in the plume. Further, particularly with distal acoustic intensities being arranged to be higher than transducer-near-field intensities (
We explicitly note that we can have cavitational bubbles or microbubbles that form in the plume but that get delivered to the surface, whereupon they can contribute to our energetic cleaning or treating processes. Some or all of these microbubbles may be nonjetting while in the plume but become jetting when delivered to the surface. We note that the velocity of the plume determines how much closer a cavitation event gets to surface 27 before it expires or dies out. So we anticipate, in various embodiments of the invention, arrangements wherein the plume velocity is selected, at least in part, to maximize delivered cavitational events to the surface. Thus, some applications might utilize very fast plumes or streams close to, equal to or even faster than sonic velocities in water. In such a manner, one might also gain benefit from the known benefits of treating or cleaning using near-sonic or supersonic liquid streams.
A second competing mechanism that could prevent distal cavitation is the acoustic lossiness and scatter in the beam (plume). It is possible to squelch the ability of the plume to deliver acoustical energy to surface.27 if massive cavitation or microbubbling is happening near the face of the transducer or in the mid-beam regions. By “microbubbling” we mean gas-dissolution, whether or not it is acoustically aided or pressure-drop aided as it passes into or along the plume. Such microbubbles become cavitational seeds for one or both of free-space cavitational oscillations or surface-centric jetting cavitation. Thus, such microbubbles, whether cavitating or not, could limit power delivery to the work surface 27. Excess addition of agents could also cause so much attenuation that cavitation at the surface becomes impossible.
Moving now to
Acousticians will be aware of two phenomena as follows. The first phenomenon is called streaming-pressure and it is the effect of propagating acoustics in liquids to drag or pump the liquid. Streaming pressures, for high-intensity ultrasound, are high enough to jet water feet in height. The second phenomenon is called radiation-pressure and in particular we mean acoustic radiation pressure upon particles suspended (or carried) in the liquid. That radiation pressure typically attempts to push the solid particle through the liquid.
In cases of a viscous liquid with particles in it, one has both forces working. The particles are directly pushed because of the acoustic radiation pressure, but they drag the liquid along with them due to the liquid viscosity. Secondly, and independently to a substantial degree for low particle densities, we also have the acoustic beam pushing the liquid itself directly.
In
The plume 31e from transducer/orifice set 23e/29e is shown as having a velocity Ve and a flow Fe, an upper diameter d1 and a lower distal diameter d2. Like-wise we see the plume 31f from transducer/orifice set 23f/29f having velocity Vf and flow Ff with similar diameters, and the plume 31g from transducer/orifice set 23g/29g with velocity Vg and flow Fg and similar diameters. Note that we have depicted a phantom work surface 27 at a throw-distance or working-distance of D3. The outer liquid/air surfaces or interfaces of the three plumes 31e-31g are depicted as 28e, 28f, and 28g, accordingly.
The first plume 31e, assuming all the plumes are round or generally cylindrical in nature along the Z-axis, is depicted, at least over distance D3, as having a diameter d1 and d2, which does not hugely change as it falls or is propelled through distance D3. Fluidics practitioners will be well-aware that Rayleigh instabilities will, at some distance D3, cause any such plume to become disfigured, non-uniform, and break up into droplets or globules due to surface-tension driven forces. However, it is known that measures that can help keep the plume together for larger distances D3 include, for example, using a more viscous liquid, using laminar flow conditions, or using high velocities with a properly shaped orifice, using or causing low-surface tensions in the fluid, and minimizing drag with the ambient.
Moving now to the second plume 31f of
Moving now to the third and rightmost plume 31g in
One reason for pointing out these nodes is that the present inventors expect that these nodes, in one or both of their moving or stationary states, will stabilize the plume with respect to Rayleigh instabilities. This phenomenon is exceedingly attractive if it allows for longer throw-distances or reduced fluid consumption.
The present inventors wish to reemphasize at least two types of cleaning or treating mechanisms deliverable by the invention. The first is cavitational. The second is non-cavitational. It is known that acoustic waves passing relatively parallel to a dirtied surface can, by liquid-phase motions alone, scrub off such microparticles. This has been commonly deemed the (non-cavitating) immersion “megasonic” effect in the semiconductor industry and has been utilized to immersion-clean semiconductor wafers and glass micromasks for decades now. Using our invention herein, we can deliver similar megasonic-style cleaning action without the prior art required immersion of the workpiece. We can do this two ways. The first way is to impact the work surface 27 at a small almost tangential angle with our streams or plumes. The second way is to allow impacting acoustical energy to be redirected or mode-converted from essentially work surface-nonparallel plumes (i.e. they have some angle with the work surface, say a few degrees or more). Mode conversion is a known phenomenon that has critical angles that can be calculated. Further, depending on the work surface material and surface features, the work surface may itself encourage such mode conversion and/or redirection of acoustical energy. We include in the scope of our invention mode conversions wherein the starting mode is in the plume and the resulting mode is either in the plume or injected into the workpiece. Further, the acoustic modes in the plume may be injected into the workpiece material as a known function of impedance-differences and angle of incidence. Previously, we described how the meniscus shapes at the plume impact points on the work surface can spread and/or redirect treatment ultrasound.
Note also that for an inventive multi-stream or multi-plume device, we may also mechanically move or scan one or more orifices relative to one or more transducers. This option could also encompass having fewer transducers than orifices or having only one transducer serving several orifices. Obviously, one could scan either the transducer(s) or orifices(s) relative to the other and/or relative to a workpiece. We have shown the simplest plume arrangements herein, but it will be noted that any useful 1-D, 2-D or 3-D plume geometries may be practiced, including those that emit plumes and/or ultrasound in or along one, two or more directions or radii or that scan or sweep through one or more angles. The device may have one or more transducers that emit substantially all or most of their acoustic energy through one or more orifices (shown) or may have transducer(s) which either have some of their acoustic output masked (as by plate 29 or orifice 29b-29g, for example) or as by having an orifice occasionally scanned in front of said transducer whereupon the acoustics are unmasked. The invention utilizes defined streams or plumes that are most easily formed using an orifice or aperture. However, we do not limit the scope of the invention to requiring an orifice. An example of a no-orifice implementation would be wherein the stream is created emanating from a fluid pool using only acoustical energy, in a manner known to those researching new ways of inkjet and biojet printing.
We have shown the flowing plume and ultrasound energy having a substantially uninterrupted path from transducer to workpiece, perhaps except for some losses in the plume due to, for example, additives or bubbles or modal changes/amplification. Alternatively, one may have, for example, a metal screen over the orifice and have the plume and ultrasound pass through it. This is particularly possible in cases wherein the acoustic wavelength in the liquid is longer than the pitch or spacing of the screen features. Such a screen, for example, could be used to electrically charge the plume or to carry plume electrical current in an eletroconversion or electroplating process.
We have previously mentioned the use of various frequencies with the invention. Two particular likely scenarios include higher frequencies in the megahertz range for our megasonic (non-cavitational) approach and lower frequencies in the tens or hundreds of kilohertz range for our cavitational approach. Specifically included in the scope of the invention is the use of one or more transducers which, alone or together, offer multi-frequency operation. By “multi-frequency” we mean either or both of simultaneous operation or sequential operation. Such transducers frequently are broadband in nature and have one or more acoustic and one or more electronic matching layers and networks respectively. If one is trying to cavitate, it is frequently attractive to operate in continuous wave mode (CW mode) to initiate and sustain cavitation-particularly at the lower frequencies of tens to hundreds of kilohertz.
Care should be taken, if appropriate, to make sure that the device has no irritating audible tones such as might be emanating from the transducer or from its power supply. Such tones may be primary, sub-harmonic or super-harmonic tones, but will most often be sub-harmonic or primary tones or frequencies. Such tones, in manners known to the acoustic industrial equipment art, may be damped out physically or electronically or may be avoided entirely by a different choice of primary operating frequency or as by real-time variation of the operating frequency.
The present inventors anticipate that the treating/cleaning apparatus, depending on application, may be operated from a fixed or moving mounting, or perhaps both. As an example, in a carwash, the car is moved on a floor chain such that the inventive apparatus, particularly if it has a laterally extended plume, may not need to be moved relative to the building frame. The same argument can be made for a glazing-cleaning apparatus that goes up and down the outside of skyscrapers to clean the windows. Such devices could easily be automatic and not require direct hands-on manual operation or intervention. On the other hand, if the workpiece is not itself passed by the inventive apparatus as by translation or rotation, then one may elect to physically scan the apparatus, in at least one dimension, direction or axis, across or around the workpiece. The present inventors give as an example of this an apparatus used to clean a large stationary irregularly shaped object such as a fighter jet on an aircraft carrier. We also include in the inventive scope the use of robots to scan either or both of the inventive apparatus and/or the workpiece.
The present inventors anticipate applications wherein, if the liquid plume is not serving a waveguide function, then measures to keep the beam in the flow plume if one or both of them move or are moved might be necessary for large movements. Along these lines, we include in the scope of the invention acoustic beams that are aligned or realigned to their plume and/or plumes that are aligned or realigned to their acoustic beams. Knowledge of the orientation or positioning of one of those allows the second to be aligned to it, perhaps even in real time for scanning systems. Thus, for example, we may have optical or video sensors determine plume geometry/orientation and have that information fed to the acoustic emitter such that it be steered in the same direction. Alternatively, one may slew the acoustic beam mechanically or electronically and have the movable plume follow accordingly, given the pointing information. We had earlier mentioned using the acoustic beam itself to sense a parameter of the plume or workpiece. We hereby now explicitly include in that acoustic sensing of a plume parameter related to beam geometry, positioning or pointing. Typically, such detected information would be utilized in a feedback loop.
We emphasize that by “scan” we mean that, ultimately, at least one plume is moved relative to a workpiece, regardless of whether the apparatus, the plume or the workpiece is actually moved or how it is moved.
Another attractive application for the invention is in a vehicle or carwash wherein one desires to clean the inside of complex wheels, particularly “mag” wheels or spoked wheels. This application may utilize a side-shooting implementation of the apparatus
IV. Additional Considerations.
For the sheet-shaped or 2-D (flat or curvilinear) plume, a focused or phased-array transducer may be used to steer within the self-limiting thickness confines of that plane (and preferably also get our amplification/summation). This could be just one generally flat sheet or plume, but it is still in the spirit of amplification/summation. In the thin thickness dimension of the plane, it is most likely that the plume plane acts as a waveguide in that thickness direction only.
Agents may be added, such as detergents, solvents, coatings, etchants, plating solutions, microbubbles, microbubble nuclei (evolved gas content), abrasives, and the like for aiding in the cleaning.
The plume/stream velocity can have any value of zero or greater, positive or negative (e.g., upward or downward). This includes subsonic, near-sonic and sonic in the limit.
A variety of applications of the acoustic cleaning system disclosed herein are possible, including, without limitation, cleaning buildings, glass, masonry, facades, equipment, components, tools, vehicles, animals, people, graffiti, as well as conversion coating such as anodization, which may utilize a biased, charged or electrically conductive fluid, electroless plating, electroplating, toxic cleanup, painting, stripping, abrading, degreasing, etching, and the like.
The plume temperature may be favorably manipulated to enhance treatment
The workpiece may be human or animal, but one would not necessarily cavitate in that case unless one wants to destroy/remove tissue as for wound cleaning, skin-layer stripping, etc. Some medical applications may not require cavitation, such as one which injects ultrasound for subsurface beneficial or therapeutic heating/
Two or more impinging streams may be joined to form a bridging meniscus, thereby aiding the treatment of between-stream gaps.
While the invention has been described in detail with reference to preferred embodiments thereof, it will be apparent to one skilled in the art that various changes can be made, and equivalents employed, without departing from the scope of the invention. Specific examples of the invention described herein are not exclusive of other applicable structures and methods.
The present application claims priority from provisional application Ser. No. 60/786,861, filed Mar. 28, 2006. The present application is also a continuation-in-part of application Ser. No. 11/193,958, filed on Jul. 28, 2005, entitled “Apparatus and Method for Delivering Acoustic Energy Through a Liquid Stream to a Target Object for Disruptive Surface Cleaning or Treating Effects”, filed in the names of the present Applicants (“prior application”). That application, which is incorporated herein by reference, claims priority based on provisional application Ser. No. 60/592,593, filed Jul. 30, 2004.
| Number | Date | Country | |
|---|---|---|---|
| 60786861 | Mar 2006 | US | |
| 60592593 | Jul 2004 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11193958 | Jul 2005 | US |
| Child | 11729567 | Mar 2007 | US |
