United States Patent
`Higsonetal.
`
`1:5
`
`[11] Patent Number:
`[45]
`Date of Patent:
`
`4,976,259
`Dec. 11, 1990
`
`[54]
`
`[75]
`
`ULTRASONIC NEBULIZER
`
`Inventors:
`
`James R. Higson, Santa Barbara;
`David A. D’Alfonso, Goleta; Robert
`R. Walls, Santa Barbara,all of Calif.
`
`[73]
`
`Assignee:
`
`Mountain Medical Equipment, Inc.,
`Denver, Colo.
`
`[21]
`
`[22]
`
`Appl. No.:
`Filed:
`
`266,823
`
`Nov.2, 1988
`
`[63]
`
`[51]
`[52]
`
`[58]
`
`[56]
`
`Related U.S. Application Data
`Continuation-in-part of Ser. No. 944,203, Dec. 22,
`1986, abandoned.
`
`Unt, CLS oo. ceceecesessessetsccercetssscesssseees A61M 11/00
`US. Cl, esesecsscsssescseeseveees 128/200.18; 128/200.16;
`128/200.14; 238/107.1
`Field of Search................::000 128/200.14, 200.16,
`128/200.18; 239/102.1, 102.2
`References Cited
`U.S. PATENT DOCUMENTS
`
`3/1969 Scarpa ....escsersserercsecreeeseeres 259/1
`3,433,461
`3,774,602 11/1973 Edwards ...cssssesereesere 128/194
`
`8/1974 Buchet al. vss 239/102.2
`3,828,773
`
`1/1975 Harris et al. csccscecesenven 128/194
`3,861,386
`2/1975 Denton.........
`239/102.2
`3,866,831
`3,989,042 11/1976 Mitsui et ale scsccccssssessen 128/194
`4,001,650
`1/1977 Romain vvecscsscsceseusess 317/41
`4,094,317
`6/1978 Wasmich ssssssssssscsssssssen 128/194
`4,109,863
`8/1978 Olsonet al.....
`239/102
`4,113,809
`9/1978 ~- Abair etal.
`. 261/81
`4,646,967
`3/1987 Geithman. ...........eee 239/102.2
`
`
`
`
`
`Primary Examiner-—Randall L. Green
`Assistant Examiner—K. M.Reichle
`Attorney, Agent, or Firm—JohbnE.Reilly
`
`[57]
`
`ABSTRACT
`
`An ultrasonic nebulizer is of the type having a piezo-
`electric transducer communicating with a fluid reser-
`voir and is characterized by having a protective cover
`of a predetermined wavelength which is superimposed
`on the transducer, an elastomeric boot in surrounding
`relation to the coverto preventfluid loss from the inter-
`face between the cover and transducer, and an oil cou-
`pling medium is disposed in the interface for coupling
`the ultrasonic energy from the transducerto the cover.
`
`10 Claims, 6 Drawing Sheets
`
`
`
`
`
`10
`
`PRIOR ART
`
`DPpe|
`
` 0
`
`INTLit
`TTDIMIM MEM
`
`
`Petitioner Puzhen - Ex. 1014, p. 001
`
`Petitioner Puzhen - Ex. 1014, p. 001
`
`

`

`US. Patent
`
`Dec. 11, 1990
`
`Sheet 1 of 6
`
`4,976,259
`
`LUVYOldd
`
`gbud
`
`Petitioner Puzhen - Ex. 1014, p. 002
`
`Petitioner Puzhen - Ex. 1014, p. 002
`
`
`

`

`US. Patent
`
`Dee. 11, 1990
`
`Sheet 2 of 6
`
`4,976,259
`
`94
`
`90
`
`92
`
`86
`
`ao
`
`
`
`
`
`
`
`ioRSgoeNGal Y
`°6
`.Fug. 8
`
`60
`
`58 52
`
`54
`
`\64
`
`\66
`
`58
`
`
`
`Petitioner Puzhen - Ex. 1014, p. 003
`
`Petitioner Puzhen - Ex. 1014, p. 003
`
`

`

`US. Patent
`
`Dec. 11, 1990
`
` LLLLLELLLLLLLLLLLLELLLLELELLLLLLLLLLLLLL
`
`
`SARA,
`.O04
`
`
`0&
`
`7,
`
`89
`
`LUVYOldd
`
`
`
`LLLLLELLLLLLLLLLLLLLLLo
`
`
`Sheet 3 of 6
`
`4,976,259
`
`OP
`
`
`
`
`
`Petitioner Puzhen - Ex. 1014, p. 004
`
`Petitioner Puzhen - Ex. 1014, p. 004
`
`
`
`

`

`Sheet 4 of6
`
`4,976,259
`
`US. Patent
`
`Dec.11, 1990
`
`
`
`Petitioner Puzhen - Ex. 1014, p. 005
`
`Petitioner Puzhen - Ex. 1014, p. 005
`
`

`

`US. Patent
`
`Dec. 11, 1990
`
`Sheet 5 of 6
`
`4,976,259
`
`Pug.
`
`10
`
`PRIOR ART
`
`LAA
`
`
`
`LLLLLLLLLLLL
`
`Pug. 7
`
`Petitioner
`
`Puzhen- Ex. 1014, p. 006
`
`Petitioner Puzhen - Ex. 1014, p. 006
`
`
`

`

`
`
`US.Patent—Dee. 11, 1990 Sheet 6 of 6 4,976,259
`
`
`
`160
`|
`sa |
`
`feAS cI
`i52
`
`
`
`
`
`
`
` =3 Sa
`
`
`Es
`
`
`
`
`
`eo
`
` RSS}
`
`
`Petitioner Puzhen - Ex. 1014, p. 007
`
`Petitioner Puzhen - Ex. 1014, p. 007
`
`

`

`4,976,259
`
`1
`
`ULTRASONIC NEBULIZER
`
`CROSS REFERENCE TO RELATED
`APPLICATIONS
`
`This is a continuation-in-part application of Ser. No.
`944,203, filed Dec. 22, 1986, now abandoned by James
`R. Higson et al, and assigned to the assignee of the
`present invention. This invention relates to medical
`devices for the inhalation of medication and, morepar-
`ticularly, to a novel and improved nebulizer which is
`specifically adapted for use in the inhalation of medica-
`tion but having useful application on other devices em-
`ploying a piezoelectric crystal for ultrasonic stimulation
`and excitation such as emulsifiers, cleaners and thelike.
`
`BACKGROUND AND FIELD OF THE
`INVENTION
`
`Pulmonary drug delivery systems, commonly re-
`ferred to medically as nebulizers, come in various
`forms. These, in turn can be broken downinto various
`sub-groups. For example, the atomizer type of device
`uses the venturi principle of air passing across a pipe or
`orifice to draw liquid medication from a storage recepti-
`cal and atomizeit into small particles. Such devices can
`be operated by squeezing a bulb or with a pressurized
`container.
`When ultrasonic energy of the right frequency and
`poweris applied to a liquid, a very fine particle mist is
`released from the surface. At the frequency required to
`convert liquids, such as, water to a mist, the ultrasonic
`energy can be produced by electrically exciting a
`piezoelectric-material, such as, lead zirconate titonate,
`and mechanically coupling that material to the liquid.
`Of the total energy which enters a system of this type,
`some is converted to heat in the piezoelectric material,
`some may be converted to heat in the liquid, and the
`remainder is consumedat the liquid surface in the pro-
`cess of breaking away particles to form the mist.
`In a medical application, this process is called nebuli-
`zation and is used to convert medication to a mist for
`inhalation in the treatment.of respiratory disease. In
`orderto do this most effectively, the medication should
`be nebulized into particles or droplets of a particular
`size range and, as a general rule, the smaller the parti-
`cles the better the penetration of the particles into the
`lungs and the bronchial passageways.
`Earlier versions of ultrasonic nebulizers were in-
`tendedfor use primarily in the home or medical facility
`- environment. However, miniaturization and the avail-
`ability of small, highly efficient, rechargeable battery
`packs makeit highly desirable to provide portable ultra-
`sonic nebulizers which can be hand-carried and used as
`required in the treatment of respiratory disease.
`In the past, ultrasonic nebulizers which have em-
`ployed a piezoelectric material have encountered nu-
`merous problems, among which is the tendency of the
`material to rapidly degrade owing to the generation of
`heat, cavitation of the liquid caused by the high acoustic
`energy level, and chemical attack of the surface by
`medications and cleaning agents. Each time that acous-
`tic energy crosses from one material to another, someis
`passed and someis reflected. Any material positioned
`between the transducerand the liquid for-protecting the
`surface should possess high energy transmission effi-
`ciency and low energy reflection back to the trans-
`ducer. It has been found that this condition can be cre-
`ated by providing a thin coating or plating of approxi-
`
`20
`
`35
`
`40
`
`45
`
`55
`
`60
`
`65
`
`2
`mately 1/100 W,such as, teflon, polyimide or gold, or
`providing a cover having a thickness of W/2 or a multi-
`ple thereof, such as, W, 3W/2, 2W attachedto the trans-
`ducer surface where ¢Weo is the wavelength of the
`excitation signal. Glass is a preferred material for such a
`cover because it presents an easily cleaned and durable
`surface to the liquid and can tolerate high temperatures.
`Nevertheless, a coupling agent is required to bridge the
`air gap between the two surfaces. In U.S. Pat. No.
`4,109,863 to Olson et al, it was proposed to employ
`adhesives for this purpose. However, high temperatures
`tend to weaken the bondof the adhesive and cause poor
`acoustic coupling and increased reflected energy. Olson
`et al proposed to solve the problem of high tempera-
`tures at the transducer surface by circulating a cooling
`water over the transducer and glass, but this methodis
`not feasible for a portable handheld device and has the
`additional undesirable effect of acoustically damping
`the back side of the transducer and thus reducing the
`efficiency of the nebulizer system.
`Wehavefoundit desirable to employ oil of the cor-
`rect viscosity and temperature capability as a coupling
`agent. The oil tends to migrate toward the high energy
`density center of the transducer/glass interface and
`occurs even after high temperatures have forced some
`of the oil to the periphery. In order to overcome any
`tendency ofthe oil film to be too thin, causing reduced
`nebulization, the gap between the protective cover and
`the transducer surface must be so shaped as to provide
`an optimum oil film thickness thereacross which will
`avoid regularly generated reflections. Also it is impor-
`tant to contain the oil so that gravity and capillary
`forces do not carry it away from thegap during periods
`ofinactivity. Accordinglyit is important that the oil be
`confined or sealed in such a wayas to assure thatit will
`migrate towards the center of the gap when energyis
`applied. Moreover, another problem associated with
`the use of oil as a coupling agent is the presence of
`entrapped gas which, when released during operation,
`may displace the oil and uncouple the glass cover. It is
`therefore desirable to minimize the amountof entrapped
`gas present in the oil in the process of assembling the
`elements of the nebulizer and to make provision for
`accumulation of any entrapped gas which may escape
`from the transducer surface during its life.
`Amongvarious other prior art techniques, U.S. Pat.
`No.3,433,461 to Scarpa employs a piezoelectric crystal
`bonded to a support layer. Both the crystal and the
`support layer were chosen to be one-half wavelength in
`thickness and bonded together with an adhesive to form
`a composite structure one wavelength in thickness. This
`structure is supported aroundits periphery and contains
`a thin web between the vibrating center and supported
`periphery to prevent support structure loading whichis
`counter productive to efficient high energy vibration.
`Other patents of interest are U.S. Pat. No. 4,094,317 to
`Wasnich and U.S.Pat. No. 3,861,386 to Harris where an
`acoustic wave form is shaped to perform ultrasonic
`nebulization of the liquid andtoisolate the liquid from
`the piezoelectric crystal and prevent dry operation of
`the device.
`
`SUMMARY OF THE INVENTION
`
`It is therefore an object of the present invention to
`provide for a novel and improved ultrasonic nebulizer
`whichis capable ofefficient acoustical coupling of en-
`ergy from a piezoelectric crystal into the medication
`
`Petitioner Puzhen - Ex. 1014, p. 008
`
`Petitioner Puzhen - Ex. 1014, p. 008
`
`

`

`4,976,259
`
`4
`mined wavelength superimposed on the transducer, the
`cover member and transducer having generally planar
`confronting surfaces and a common interface therebe-
`tween, annular sealing means in outer surrounding rela-
`tion to the cover member to prevent the loss of fluid
`from the interface, and oil coupling meansin the inter-
`face for coupling the ultrasonic energy from the trans-
`ducer to the cover member. Most desirably the trans-
`ducer is a piezoelectric crystal having a top electrode
`extending down the sides and wrapping around the
`bottom edge and a bottom disc electrode of substan-
`tially smaller diameter than the diameter of the piezo-
`electric crystal whereby the electrical contact to the
`bottom of the piezoelectric crystal thereof is adjacent to
`the center thereof.
`
`3
`being nebulized without significant attenuation and
`wherein the crystal itself is protected from undesired
`early destruction.
`Another object of the present invention is to provide
`in an ultrasonic nebulizer for a novel and approved
`piezoelectric transducer and wherein the means for
`acoustically coupling the ultrasonic energy from the
`piezoelectric element to a face plate is a liquid; and
`further wherein the gap formed betweenthe face plate
`and piezoelectric element is so formed that the energy
`transfer is maximized and heating minimized so as to
`avoid the necessity for external means of cooling.
`A further object of the present invention is to provide
`in an ultrasonic nebulizer for a novel and improved
`method and means for mounting a piezoelectric crystal
`and protective cover and face plate which will maintain
`an optimum gap between the elements notwithstanding
`pressure increases created by thermal expansion of the
`coupling fluid; and further wherein the mounting means
`will act as a reservoir for the coupling fluid and retain
`any entrapped gases therein so as to prevent decay of
`the coupling efficiency otherwise resulting from gas
`build up.
`It is an additional object of the present invention to
`provide for a method of assembly of a piezoelectric
`crystal
`in an ultrasonic nebulizer
`to minimize the
`amount of entrapped gases in a coupling fluid between
`the crystal and face plate and to effectively seal the
`crystal and the face plate along with the coupling fluid
`for most efficient energy transfer between the crystal
`and the face plate.
`It is still an additional object of the present invention
`to provide for a novel and improved nebulizer which
`will maximize the isolation and removal of optimum
`size particles for inhalation by the user as well as to
`more effectively collect and renebulize larger particles
`in such a way as to minimize clogging or impaction of
`the particles.
`In accordance with the present invention, the forego-
`ing objectives have been attained in an assembly having
`a cavity therein for holding a liquid medication to be
`nebulized by a piezoelectric crystal disposed in commu-
`nication with the cavity and separated from medication
`contained in the cavity by a thin cover of a material
`having characteristics for allowing it to match acousti-
`cal impedances withoutsignificant attenuation, such as,
`those possessed by glass,
`the crystal being disposed
`adjacent to the cover; a thin film of an energy-coupling
`fluid interposed between the cover and the surface of
`the crystal; and, sealing means for the cover and the
`surface of the crystal for preventing loss of fluid from
`between the cover and the surface of the crystal.
`In one embodiment, the cavity has a hole in the bot-
`tom thereof communicating with the surface of the
`crystal; and, the cover comprises a sheet of glass, or the
`like, disposed over the surface of the crystal.
`In a second embodiment, the cavity has a hole in the
`bottom thereof communicating with the surface of the
`crystal; and, the cover comprises the bottom ofa uni-
`tary bowlinsert of a glass-like material inserted into the
`cavity. In a third embodiment, the bowl unit is of uni-
`tary construction and the cover comprises the bottom
`of the cavity which is formed therein.
`In a preferred apparatus for the ultrasonic nebuliza-
`tion of fluids wherein a piezoelectric transduceris dis-
`posed in communication with a reservoir for nebulizing
`liquid medication in the reservoir,
`the improvement
`comprises a protective cover member of a predeter-
`
`20
`
`25
`
`40
`
`45
`
`50
`
`DESCRIPTION OF THE DRAWINGS
`
`FIG.1 is a partially exploded, simplified, cutaway
`drawing of a prior art ultrasonic nebulizer;
`FIG.2 is a drawing ofthe prior art nebulizer of FIG.
`1 shown assembled and showing its manner of opera-
`tion;
`FIG.3 is an enlarged, detailed, cutaway drawing of
`the bowl portion of a nebulizer according to the present
`invention in a first embodiment thereof;
`FIG. 4 is a simplified cutaway drawing through a
`piezoelectric crystal as employedin prior art ultrasonic
`nebulizers showing the mannerof vibrational propaga-
`tion therethrough;
`FIG. 5 is a simplified cutaway drawing through a
`piezoelectric crystal as employedin the ultrasonic nebu-
`lizer of the present invention with its protective cover-
`ing and showing the mannerofvibrational propagation
`therethrough; -
`FIG. 6 is an enlarged, detailed, cutaway drawing of
`the bowl portion of a nebulizer according to the present
`invention in a second embodimentthereof;
`FIG. 7 is an enlarged, detailed, cutaway drawing of
`the bowl portion of a nebulizer according to the present
`invention in a third embodiment thereof;
`FIG.8 is a simplified cutaway drawing through a
`prior art vibrational surface specially shaped to direct
`the energy waves toward the center thereof;
`FIG. 9 is a simplified cutaway drawing through a
`prior art composite structure for a piezoelectric crystal
`wherein the crystal is adhesively attachedto a vibrating
`support structure and the virbating portion is decoupled
`from the actual support area;
`FIG. 10 is a simplified cutaway through a prior art
`structure wherein the liquid to be nebulized is contained
`in a separate container;
`FIG. 11 is a sectional view of a preferred form of
`portable nebulizer unit in accordance with the present
`invention;
`FIG.12 is a detailed view in section of the piezoelec-
`tric transducer assembly; and
`FIG. 13 is a bottom view of the preferred form of
`crystal employed in accordance withthe present inven-
`tion.
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`65
`
`Asa setting for the present invention, prior art nebu-
`lizers, such as, that generally indicated at 10 in FIG. 1 in
`exploded view, comprise a power pack 12 containing
`batteries, not shown,
`if it
`is a portable unit, or are
`adapted to be plugged into a wall outlet in the case of
`non-portable units. The power pack 12 is connected by
`
`Petitioner Puzhen - Ex. 1014, p. 009
`
`Petitioner Puzhen - Ex. 1014, p. 009
`
`

`

`4,976,259
`
`5
`powercable 14 to the nebulizing unit 16. The nebulizing
`unit 16, in turn, comprises a bowl portion 18 over which
`a cover 20 is adapted to be positioned. The cover 20 has
`a mouthpiece mounting tube 22 through the sidewalls
`thereof into which mouthpiece 24 can be pressfit. For
`ease of manufacture and assembly, the bowl portion 18,
`cover 20, tube 22 and mouthpiece 24 are usually cylin-
`drical in cross section. The same components are also
`typically made of high impactplastic for light weight,
`ease of cleaning, and non-contamination. The bowl
`portion 18 contains a bowl-shaped cavity 26 in the top
`thereof into which the liquid medication 28 (see FIG.2)
`is poured. A piezoelectric crystal 30 is positioned under
`the cavity 26 and the bottom of the cavity 26 has a
`circular hole 32 therein communicating with the top of
`the piezoelectric crystal 30. To activate the unit, the
`button 34 on the top of the power pack 12 is depressed,
`causing the piezoelectric crystal 30 to have power ap-
`plied thereto. That, in turn, causes the crystal 30 to
`vibrate at ultrasonic frequency and nebulize a portion of
`the liquid medication disposed within the hole 32 and on
`top of the surface of the piezoelectric crystal 30. The
`atomized droplets 36 produced are inhaled through the
`mouthpiece 24 in combination withair, indicated by the
`arrows38, which is drawn in through the entry pipe 40
`in the top of the cover 20 provided for that purpose.
`Suchprior art devices made and operating according
`to the foregoing description work adequately for their
`intended purpose with a major shortcoming that the
`piezoelectric crystal is rapidly destroyed in the process.
`This, of course, requires frequent and costly repair or
`replacement of the bow] portion 18. One problem with
`using a bare crystal is that the plated electrode thereof
`is attacked by someofthe cleaning solutions(e.g., vine-
`gar). Another problem arises because of the wide differ-
`ence between the acoustical
`impedances of a water
`based liquid (i.e., the medication to be nebulized) and
`air. If the acoustical impedances are properly matched,
`then the acoustical energy is radiated; if not, a majority
`of the energy is reflected back into the crystal. When
`the energy is reflected back,it is in a very small region
`and produces high localized temperatures. These high
`temperatures tend to cause the crystal material, along
`with its plated electrode,
`to rapidly degrade. When
`there is medicine present, a good acoustical impedance
`match exists and there is good nebulization. When the
`medicine is not present or exists in only a thin layer, a
`poor acoustical impedance match exists, causing very
`destructive conditions for the crystal. When the bare
`crystal fails due to the acoustical impedance mismatch,
`the high energy densities locate in the interface between
`the plated electrode and the piezo crystal itself. This
`develops thermal gradients which, in turn, cause the
`plating to develop pin holes therethrough. Once the pin
`holes appear, the plating quickly degrades as the medi-
`cine seeps in. Additionally, cavitation effects accelerate
`the destruction once the holes appear.
`Attempts at coating the piezoelectric crystal have
`met with little or no success to date. Either the ultra-
`sonic vibration of the crystal is not coupled into the
`covering, or poorly coupled, such that nebulization is
`inefficient or nonexistent; or, the coating is simply de-
`stroyed in the same manner, followed shortly thereafter
`by the crystal itself. For example, with a coating, such
`as, Teflon or a high temperature polyimide as previ-
`ously employedin the art, the same impedance problem
`is encountered; except, it is complicated by the coating
`having its own characteristic acoustic impedance as
`
`15
`
`20
`
`25
`
`30
`
`35
`
`45
`
`50
`
`60
`
`65
`
`6
`well. Now, the energy is concentrated in the interface
`between the electrode and the coating. Subsequently,
`the coating sees the high energy densities and associated
`thermal gradients. Failure is quite similar to the bare
`crystal. Small bubblesfirst begin to appear in the center
`of the assembly, i.e., the most active portion. Once a
`bubble appears, the assembly quickly degrades in the
`manner described above.
`In the prior art structure of FIG. 9, the piezoelectric
`crystal 88 is bonded to a support layer 90 which actually
`contacts the liquid. Both the crystal 88 and the support
`layer 90 were chosen to be one-half wavelength in
`thickness and then bonded together with an adhesive 92
`to form a composite structure 86 one wavelength in
`thickness. The composite structure 86 is supported
`aboutits periphery and contains a thin web 94 between
`the vibrating center portion and the supported periph-
`ery 96 to prevent support structure loading thereof
`which is counterproductive to efficient high energy
`vibration.
`Asdepicted in FIG.8, a vibrating surface is shown on
`whichthe liquid to be nebulized is in contact in order to
`focus the energy waves towardsthe centerofthe liquid
`in a concentrated energy area. Thus, for example, the
`vibrating surface 98 in FIG.8 is in the form of a Fresnel
`lens, which aims or directs the vibrational energy,indi-
`cated by the dotted lines 100, towards a plane passing
`through the center.
`A second technique is shown in simplified form in
`FIG. 10 and comprises placing the liquid to be nebu-
`lized 102 in a smail container 104 having a thin, vibrat-
`able bottom surface 106 and placing the small container
`104 in a large container 108 filled with liquid 110 (such
`as water) and having the piezoelectric crystal 30 at the
`bottom thereof. In this manner, the crystal 30 is always
`liquid-covered. When the crystal 30 is vibrated,
`the
`energy wavestravel through the liquid 110 in the large
`container 108 and strike the bottom surface 106 of the
`small container 104, causing it to vibrate an amount
`sufficient to nebulize the liquid 102 and cause the drop-
`lets 112.
`_
`°
`.
`The improved bowlportion ofan ultrasonic nebulizer
`similar to the prior art nebulizer of FIGS. 1 and 2 and
`modified according to the present invention is shown in
`detail in FIG. 3 and labelled therein as 18’. It is designed
`to be used in conjunction with a power pack 12 and
`cover 20, as previously described with respect to FIGS.
`1 and 2, and in the interest of simplicity and the avoid-
`ing of redundancy in the description and drawings,
`those portions will not be shownor described hereinaf-
`ter.
`
`to a piezoelectric crystal con-
`The improvement
`structed assembly of the present invention as used in a
`nebulizer, for example, includes a protective covering
`for the piezoelectric crystal and a revised construction
`ofthe crystal itself. As best seen in the detailed cutaway
`view of FIG.3, the piezoelectric crystal 30’ of the pres-
`ent invention in the first embodiment thereof has a pro-
`tective pyrex glass covering 42 disposed over the sur-
`face thereof and under the hole 32 in the bottom of the
`cavity 26. As an indication of the sizes involved in the
`apparatus being described, in a tested embodiment of
`this embodiment whichis to be commercially manufac-
`tured and sold by the assignee of this application, the
`piezoelectric crystal 30’ is 0.77 inches in diameter and
`the glass covering 42 is 0.61 inches in diameter. The
`glass covering 42 is one-half wavelength of the crystal’s
`frequency in thickness, which was found to give pre-
`
`Petitioner Puzhen - Ex. 1014, p. 010
`
`Petitioner Puzhen - Ex. 1014, p. 010
`
`

`

`4,976,259
`
`7
`ferred coupling to the medication 28 shownin FIG.2.
`Since the frequency being employedis about 1.65 MHz,
`the thickness of the glass covering 42 is approximately
`0.064 inches. It should be noted at this point that while
`the tested example being described here employsa pro-
`tective pyrex glass covering, other materials known to
`those skilled in the art could, of course, be employed.
`For example, certain plastics and ceramic materials
`would undoubtedly make good substitutes. Likewise,
`while a circular disc is shown and preferred for ease of
`manufacture, other shapes could, of course, be used and
`the term “disc” is not to be construed as a limitation, but
`rather, a term of convenience only.
`Employing a glass covering over the piezoelectric
`crystal bonded by adhesive would not improve greatly
`over the prior art approaches mentioned above and
`would suffer from the same problems. Such approach
`was initially tried by the applicants herein with the
`expected results, or lack thereof. Primarily, there is a
`major loss of acoustic coupling of the ultrasonic energy
`into the glass cover as the adhesive bond deteriorates.
`Oneof the possible solutions to the non-coupling prob-
`lem which was tried was the use ofa thin film of com-
`monly available fluids, such as, water as a coupling fluid
`between the surface of the crystal 30’ and the glass 42.
`While, initially, these fluids would cause coupling of the
`energy into the glass cover 42, these common coupling
`fluids were quickly destroyed in operation, resulting in
`failure of the unit by loss of acoustic coupling of the
`energy. Extensive testing finally lead to the discovery
`of certain fluids which, underinfluence of the ultrasonic
`vibration, acted exactly contrary to the other, normally
`thought of, coupling fluids, which had disintegrated in
`use; that is, while the other, non-useful fluids had mi-
`grated to the edges of the glass 42 and crystal 30’ and
`away from the central active zone of vibrational trans-
`fer,
`the workable coupling fluids discovered by the
`applicants herein tended to migrate to the center under
`vibrational stimulation and, thereby, effect maximum
`energy transfer from the crystal 30’ into the glass cover
`42. Again, it is worthy of note at this point that while
`fluids of a particular type and exhibiting particular cou-
`pling characteristics are described hereinafter by way of
`example,
`those skilled in the art will recognize and
`appreciate that there are other materials, which could
`be easily overlooked in the broad classification of “flu-
`ids”, which could be substituted as the coupling fluid.
`Wherethe term “fluid”is used in the descriptions herein
`and in the claims appendedhereto,it is the applicants’
`intent that it be considered in its broadest sense as in-
`cluding other coupling fluids possessing the necessary
`qualities and characteristics as set forth in detail herein-
`after. As to some of the fluids which were tested and
`found to be unsuitable, some were quickly destroyed
`while others were not. When destruction was immedi-
`ate, i.e., in less than ten uses, no amount of time was
`enough to recover the ability to effectively pass the
`ultrasonic energy into the medicine bowl. Such fluids
`included silicone as well as Teflon-based oils and
`greases. Other fluids failed because of migration out
`from under the glass. This resulted in excessively long
`“warm up” times to produce nebulization, which al-
`lowed the fluid to go to the center of activity and for
`electrical conduction through the film of oil between
`the brass connector ring and the wrap-around elec-
`trode. The “oil” fluids ultimately employed by the ap-
`plicants as a film between the crystal and its closely
`adjacent, spaced, protective cover have the property of
`
`10
`
`20
`
`25
`
`30
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`8
`being “self protecting and self healing”; that is, when
`destructive conditions appear,theoil film will move out
`of the most active (and destructive) areas. After the
`detrimental conditions haveleft; i.e., there is medicine
`in the bowl and a good impedance match,
`the oil
`“pumps”itself back into the necessary areas to allow
`good acoustic coupling.
`Thecritical properties of acoustic coupling fluids
`which are appropriate include—viscosity, viscosity
`breakdown, temperature stability, acoustic impedance,
`chemical stability, and molecular composition. These
`properties will now be addressed individually.
`Viscosity: Through empirical analysis, the applicants
`herein were able to determine the workable limits of
`viscosity. Bounding the low endis the ability to manu-
`facture the assembly. If the fluid is too thin (under 1
`centistoke at 100° C. foroil), it is very difficult to inti-
`mately join the crystal and the glass without excessive
`air entrapping itself (enough to significantly decrease
`life or couple effectively). On the high end (above 100
`centistoke at 100° C. for oil), the fluid still passes the
`acoustical energy; but, attenuation becomessignificant.
`The higher viscosity fluids tested produced lowerout-
`put as comparedto thefluid viscosities. It is desirable
`for the fluid to have a viscosity curve whichis as flat as
`possible. This provides uniformity as the temperature of
`the system changes. The preferred viscosity range is
`between 4 and 10 centistoke at 100° C. for an oil cou-
`pling. In this range, there were no detectable differ-
`ences in either coupling orlife.
`Viscosity Breakdown: Because of the high energy
`densities of the reflected acoustic wave when imped-
`ances are mismatched(i.e., air only, no medicine) corre-
`sponding high temperatures are found in the interface
`between the crystal and the glass containing the fluid.
`To maintain the desired viscosity range and reasonable
`life, the fluid should not undergo permanent changesin
`viscosity when exposed to the high temperature and
`energy densities involved.
`Temperature Stability: As previously mentioned, the
`fluid is subject
`to very high temperature gradients.
`Therefore, the fluid needs to have high operating tem-
`perature limits as well as a reasonably flat viscosity
`curve. Temperature requirements are met if the flash
`point is above 200° C. and there is no viscosity break-
`downafter repeated thermal cycling.
`Acoustic Impedance: The fluid must also have an
`acoustic impedance whichis acceptable to the assembly
`system at
`the desired frequency without significant
`attenuation. Ideal
`impedance matching between the
`crystal and coveris difficult to attain; however, through
`empirical testing, the applicants were able to determine
`that the window of acceptability was fairly large in a
`given family of fluids.
`Chemical Stability: Some ofthe fluids tested failed to
`pass the acoustic energy after a limited numberofuses.
`It is hypothesized that the high energy densities and
`thermal gradients caused the fluids to change chemical
`composition. Therefore,
`the fluid needs to maintain
`chemical composition when exposed to high tempera-
`ture and energy densities. Synthetic oils appear to have
`the ability to take the harsh conditions and maintain
`their initial properties.
`Molecular Composition: Some of the fluids which
`met the abovecriteriastill failed to pass enough acous-
`tic energy to be effective. The applicants’ best guess in
`this regard is that the molecular composition is such -
`
`Petitioner Puzhen - Ex. 1014, p. 011
`
`Petitioner Puzhen - Ex. 1014, p. 011
`
`

`

`4,976,259
`
`9
`that these fluids’ molecular composition outweighed the
`characteristics of the above properties.
`Preferred Fluid: The fluid preferred by applicants, as
`a group, is synthetic oil based. The preferred embodi-
`ment as presently employed by the applicants in the
`commercial embodiments of the present invention is an
`8 centistoke (at 100° C.) Polyalphaolefin base oil.
`While the discovery of a workable class offluids to
`effect coupling was a major breakthroughin the devel-
`opmentof a long-lasting ultrasonic nebulizer,it, in turn,
`created new problemsto be solved in the overall design
`of the bowl portion 18’. Because of the close spacing
`employed between the glass cover and the crystal, one
`of the problem phenomena wascapillary action of the
`fluid during periods of non-use; that is, the fluid simply
`moved to the outer edges of the glass and was lost due
`to capillary action. There are also transition periods
`whenthe unit is turning on and off. During these times,
`the assembly is attempting tostabilize to th