Patent Application
20200156113
Improvement for integrating a transducer with a folded resonator.
The use of ultrasonic vibration to atomize fluids is a well-established technology (see Frederick, J., Ultrasonic Engineering, Wiley 1965, pp 152-55. Methods of Experimental Physics, Vol. 19, pp. 333-6, Academic Press, 1981). Liquids introduced onto a surface vibrating at an ultrasonic frequency can be subjected to very large accelerating forces that surpass their cohesive tensile strength and surface tension, resulting in the formation of droplets that separate from the parent body of fluid and leave the surface, possessing acceleration imparted by the surface's motion. As an example, consider a 100 micron thick film of water placed on a surface vibrating sinusoidally at 40 kHz with an amplitude of 10 microns. The film is subject to an acceleration of about 630,000 meters per second per second or 64,000 times that of gravity. The tensile stress in the film is its density multiplied by the product of the film thickness and the acceleration, which for 40 kHz vibration of an amplitude of 10 microns is 63 kPa which is above the tensile strength of tap water. The water separates into droplets that are propelled away from the surface, forming a stream of vapor. This phenomenon forms the basis of operation of ultrasonic humidifiers and nebulizers as well as fuel injectors.
It is known that ultrasonic atomization is a sensitive function not only of the fluid's tensile strength but also of its surface tension and, particularly, viscosity. Of interest here is the development of compact ultrasonic atomizers that are able to vaporize fluids, including those having viscosities and surface tensions substantially greater than that of water and that have a simple construction and compact geometry. For example, certain medicines can be efficaciously and conveniently administered in vapor form but are resistant to vaporization by ultrasonic nebulizers that are effective with water. It has been shown that such fluids must be subject to significantly greater amplitudes of ultrasonic motion at any given frequency than are necessary using water to experience atomization.
Ultrasonic humidifiers typically use piezo-electric disks vibrating in resonance to generate motion. Ultrasonic nebulizers may use disks or bimorphs attached to a metal diaphragm to perform the same function. However, neither arrangement generates motion sufficient to atomize fluids having viscosities ten times or more larger than that of water. U.S. Pat. No. 9,533,323B2 discloses the use of a conventional Langevin transducer to produce ultrasonic motions larger than are available from aqueous humidifiers and nebulizers. The structures shown in that patent, however, contain many separate parts in an elaborate assembly not having the same economy in manufacture, use and servicing as that afforded by a simple construction.
The present invention introduces such refinements. In its preferred embodiments, the present invention has several aspects or facets that can be used independently, although they are preferably employed together to optimize their benefits. All of the foregoing operational principles and advantages of the present invention will be more fully appreciated upon consideration of the following detailed description, with reference to the drawings.
This invention presents at least one preferred embodiment for a vibrating piezoelectric atomizer for atomizing a liquid comprising: a piezoelectric transducer tubular body, having a length, a first end defining an opening, a second end and connected electrodes to a power source; the second end of the piezoelectric transducer tubular body is connected to a horn; the horn is dimensioned to be a half wavelength resonator; the horn is folded and located alongside the piezoelectric transducer tubular body; a metallic disk is connected to the horn near the first end of the piezoelectric transducer tubular body; whereby by applying an alternating voltage from a battery across the connected electrodes of the piezoelectric transducer tubular body, the piezoelectric transducer tubular body is excited into a resonant vibration when frequency of excitation equals to half wavelength resonant frequency of the piezoelectric transducer tubular body's length and vibrates in synchronism and is communicated to the metallic disk to atomize the liquid. The metallic disk is perforated or has at least one hole and a plastic cover with perforations. The horn can lie within or outside the piezoelectric transducer tubular body. A wick can transfer the liquid to the metallic disk. The piezoelectric transducer tubular body can have an inside surface and an outside wall; the electrical contacts can be coupled to the inner surface and outside wall; the power source can be a battery.
A vibrating piezoelectric atomizer for atomizing a liquid comprising: a piezoelectric tube having a length, a first end and a second end and electrodes, which are connected to a power source; a resonator; a first endcap and a second endcap engage the first end and the second end of the piezoelectric tube and the resonator; a metallic disk (perforated or has at least one hole or a plastic cover with perforations) is connected to one of the endcaps near the first end of the piezoelectric tube; whereby by applying an alternating voltage across electrodes of the piezoelectric tube, the piezoelectric tube is excited into a resonant vibration when frequency of excitation equals to half wavelength resonant frequency of the piezoelectric tube's length and vibrates in synchronism and is communicated to the metallic disk to atomize the liquid.
The second resonator can be a mass-spring-mass mechanical oscillator with the casing being the spring and the caps being the masses; a wick transfers the liquid to the metallic disk′ the piezo body has an inside surface and an outside wall; the electrical contacts are coupled to the inner surface and outside wall. There can be use of right-hand and left-hand threads, which ensure that the tightening process does not introduce torsion to the piezo tube. The resonator can lie approximately at a center portion of the length of the piezoelectric tube and where there is very little vibratory motion.
A fluid is placed on the upper surface of the disk or communicated to the lower surface of a perforated disk, via a wick; the fluid will be atomized into an aerosol once the assembly is excited into resonance.
Similarly, fluid is placed on the upper surface of the disk or communicated to the lower surface of a perforated disk, via a wick; the fluid will be atomized into an aerosol once the assembly is excited into resonance.
In the embodiment in group
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The piezo-electric tube is excited into resonant vibration along its length by impressing an alternating voltage across its electrodes having a frequency equal to its length expansion and contraction resonance. While the excitation through the wall thickness of the tube does produce diametrical expansion and contraction, Poisson coupling produces expansion and contraction of the tube's length which, when the frequency of excitation equals the half wavelength resonant frequency of the tube's length, lengthwise dynamic displacement of the tube's faces occurs.
The horn is designed to have an extensional resonant frequency approximately that of the tube so that both vibrate in synchronism. While the vibration of the tube, (S1), is equal and opposite in direction at its opposite ends, the horn, receiving the tube's vibration at its end attached to the tube, produces a much greater amplitude (S0), at its other end (which is connected to the thin perforated metal disk).
The end of the horn that is not fastened to the tube is attached to a thin perforated metal disk. The motion of the horn at this junction is communicated to the disk. Although a stepped horn is shown in the drawings (
Following conventional and established art, a cylindrically shaped wick, one end of which is placed in the fluid, is in contact with the underside of the disk, as it is placed in the hollow passage through the horn. The wick brings fluid, contained in a well, to the underside of horn through capillary action, and the vibration atomizes the fluid, which leaves the disk through the perforations.
Additional embodiments of the invention are shown in the second group of
With the caps held stationary, the casing is turned by applying a wrench to keyed slots in the casing (not shown) to compress the caps against the tube, forming an acoustic joint between the tube and the caps and hence the casing itself. Use of right-hand and left-hand threads ensures that the tightening process does not introduce torsion to the piezo tube. Such torsion, if present, can precipitate fracture of the tube during the tightening process.
Bonded to the upper cap is a titanium disk whose center portion may contain perforations. The bonding mechanism may be high strength epoxy or the disk may be welded to the upper cap using electron beam or laser welding equipment. When the assembly is excited into resonance by applying an alternating voltage of the appropriate frequency to the electrodes of the tube through the wires shown, the disk is also excited into flexural resonance whose up and down motion is particularly acute at its center portion. Fluid applied to the upper surface of the disk or via a fluid carrying wick inserted into the tubular cavity of the casing and reaching the underside of a perforated disk will be atomized into an aerosol appropriate for inhalation.
Aside from the bonding of the disk to the Upper Cap, the joints between the Upper and Lower Caps and the surfaces of the piezo tube may also be bonded using high strength epoxy adhesive. This bonding process is accomplished before pre-stressing is applied to the assembly. Such bonds serve to improve the integrity of the acoustic joints which couple the two resonators and ensure the communication of vibration between Piezo tube and the casing and end caps.
A region located approximately at the center length of the Piezo Tube provides a surface useful for mounting the transducer in an enclosure. In this region, there is very little vibratory motion, permitting the use of elastomeric material to fixate the assembly within an outer rigid housing and thereby electrically insulating the voltages present on the surface of the tube and preventing contact of the driving voltage from being communicated to the housing.
In this variation, rather than being enclosed by the piezo tube, the casing or transducer horn surrounds the piezo tube. Access to the tube's electrodes is provided again by wires that are routed through a small hole in the casing. In this construction, the disk is sandwiched between the Cap and the Piezo tube and, as such, when the caps are held stationary and casing turned, the disk is clamped during pre-stressing which provides additional acoustical coupling between the two resonators and the disk itself, but the disk again can be bonded to the Upper Cap and to the Piezo tube. As in
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The casing contains a flange to permit mounting the folded transducer into an enclosure. Vibratory motion is minimized at this location, permitting the use of elastomeric fixation using 0 rings or other compliant means.
Detailed embodiments of the present invention are disclosed; however, the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms; specific structural and functional details disclosed are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. The title, headings, terms and phrases used are not intended to limit the subject matter or scope; but rather, to provide an understandable description of the invention. The invention is composed of several sub-parts that serve a portion of the total functionality of the invention independently and contribute to system level functionality when combined with other parts of the invention. The terms “a” or “an” are defined as: one or more than one. The term “plurality” is defined as: two or more than two. The term “another” is defined as: at least a second or more. The terms “including” and/or “having” are defined as comprising (i.e., open language). The term “coupled” is defined as connected, although not necessarily directly, and not necessarily mechanically.
Any element in a claim that does not explicitly state “means for” performing a specific function, or “step for” performing a specific function, is not be interpreted as a “means” or “step” clause as specified in 35 U.S.C. Sec. 112, Paragraph 6. In particular, the use of “step of” in the claims herein is not intended to invoke the provisions of 35 U.S.C. Sec. 112, Paragraph 6.
All publications, patents, patent applications and Internet website addresses mentioned in this specification are incorporated by reference to the same extent as if each individual publication, patent, or patent application was specifically and individually indicated to be incorporated by reference;
U.S. Pat. Nos. 3,283,182; 4,425,115; 4,526,571; 4,750,488; 4,930,512; 5,167,619; 5,221,282; 5,811,909; 6,086,369; 7,762,979; 9,962,183; US Publ. Appl. 2010/0044460; U.S. Pat. No. 6,278,218; EP0933138A2; US Publ. Appl. 20150151058A1; U.S. Pat. Nos. 5,152,456A; 6,539,937B1; U.S. Publ. Appl. 2017/0197041; U.S. Publ. Appl. 2017/0120284; U.S. Publ. Appl. 2004/0047485; U.S. Publ. Appl. 2008/0128527; U.S. Pat. Nos. 10,335,754; 10,272,404; 8,610,334.
This application claims the benefit of U.S. Provisional Patent Appl. No. 62/767,547, filed on Nov. 15, 2018; U.S. Provisional Patent Appl. No. 62/895,862, filed on Sep. 4, 2019; and U.S. Provisional Patent Appl. No. 62/907,443, filed on Sep. 27, 2019, which are all incorporated by reference in entirety. This application is also related to U.S. Provisional Appl. 62/314,380, filed on Mar. 28, 2016 and 62/343,086, filed May 30, 2016; U.S. patent application Ser. No. 15/004,920, filed on Jan. 23, 2016 and PCT/US2016/014646, filed on Jan. 23, 2016; U.S. Provisional No. 62/106,852, filed on Jan. 23, 2015 and 62/142,464, filed on Apr. 2, 2015; all listed applications are incorporated by reference in entirety.
| Number | Date | Country | |
|---|---|---|---|
| 62767547 | Nov 2018 | US | |
| 62895862 | Sep 2019 | US | |
| 62907443 | Sep 2019 | US |
