US3861386A

US3861386A - Ultrasonic nebulizer

Info

Publication number: US3861386A
Application number: US145043A
Authority: US
Inventors: Raleigh J Harris; Allan E Peck
Original assignee: Misto and Gen Equipment Co
Current assignee: Misto and Gen Equipment Co; Timeter Instrument Corp
Priority date: 1966-01-12
Filing date: 1971-05-19
Publication date: 1975-01-21
Anticipated expiration: 1992-01-21
Also published as: DE1575050A1; CH477885A

Abstract

An ultrasonic nebulizer having a transducer at an end of a liquid receiving nebulizer chamber, for generating ultrasonic waves in the liquid in the chamber, which waves are concentrated substantially at the surface of such liquid. The ultrasonic waves cause extremely rapid formation and collapse of cavitities in the liquid which upon encountering the liquid surface produce aerosol adjacent such surface.

Description

United States Patent Harris et al.

ULTRASONIC NEBULIZER Inventors: Raleigh J. Harris; Allan E. Peck,

both of Oakland, Calif.

Assignee: Misto & Gen Equipment Co.,

Oakland, Calif.

Filed: May 19, 1971 Appl. No.: 145,043

Related U.S. Application Data Continuation of Ser. No. 777,986, Nov. 6, 1968, which is a continuation of Ser. No. 552,332, Jan. 12, 1966, abandoned.

[56] References Cited UNITED STATES PATENTS 3,387,607 6/1968 Gauthier et a1. 128/173 R Primary Examiner-Williarn E. Kamm Attorney, Agent, or Firm-Townsend and Townsend [57] ABSTRACT An ultrasonic nebulizer having a transducer at an end of a liquid receiving nebulizer chamber, for generating ultrasonic waves in the liquid in the chamber, which waves are concentrated substantially at the surface of such liquid. The ultrasonic waves cause extremely U.S. Cl. 128/194, 239/338 id f ti and collapse of Cavitities in the liquid Int. Cl A61m 11/04 which upon encountering the liquid surfac'3 produce Field of Search 128/173, 194; 239/102, aerosol adjacent Such Surface- 4 Claims, 7 Drawing Figures 7 I401: H07: I 108 85 105 a g 99 {I06 |o4-; 17m? Patented Jan. 21, 1975 7 3,861,386

2 Sheets-Sheet 1 l 'INVENTORS 7 I3 BY /ALLAN E. PECK RfiLEIGH J. HARRIS 26%, 77/9444, Jada MM ATTORNEYS Paiehted Jan. 21, 1975 2 Sheets-Sheet 2 INVENTORS ALLAN E. PECK RALEIGH J. HARRIS fi k, aw xww ATTORNEYS ULTRASONIC NEBULIZER CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of application Ser. No. 777,986, of Raleigh J. Harris and Allan E. Peck, filed Nov. 6, 1968, which is a continuation of abandoned application Ser. No. 522,332, of Raleigh J. Harris and Allan E. Peck, filed Jan. 21, 1966.

BACKGROUND OF THE INVENTION This invention relates generally to liquid nebulizing or aerosolizing and more particularly to a nebulizing apparatus in which ultrasonic waves are transmitted through a liquid to generate an aerosol.

In the treatment of respiratory diseases, techniques are employed which involve the inhalation by the patient of aerosols. Conditions accompanying many respiratory diseases are respiratory congestion and inadequate expulsion by the patient of secretions from the lungs, and it has been found that a water or saline aerosol introduced into the lungs assists in correcting these. It is conventional practice to directly introduce a medicine, such as relaxant for the treatment of asthma, into the respiratory system in aerosol form; and as a diagnostic technique the analysis of sputa specimens coughed up after the deposit of aerosol in the lungs provides more representative information than may be obtained from a biopsy.

Conventional nebulizers for aerosol generation utilized in inhalation thereapy include a supply of liquid and a supply of breathable gas under pressure. A liquid discharge nozzle and gas discharge nozzle are arranged so that a stream of the gas is discharged past the discharging liquid to provide a mixture of gas and nebulized liquid which is breathed by the patient. This type of nebulizer requires an air compressor or other source of gas under pressure and is quite limited in its maximum output, which necessitates the use of multiple nebulizers for higher output applications. Deepest penetration of aerosols into the respiratory system is accomplished with minimum aerosol particle size and maximum particle uniformity, and the above described conventional type of nebulizers frequently do not pro duce particles of this character.

SUMMARY OF THE INVENTION The above-noted and other disadvantages associated with conventional nebulizers are avoided by the use of the nebulizer of the present invention in which aerosol is generated by transmitting ultrasonic waves through the liquid to be nebulized, such waves emanating from an ultrasonically vibrating element acoustically connected to the liquid.

Accordingly, it is an object of the present invention to provide an apparatus for generating aerosol from a liquid by means of ultrasonic waves.

It is another object of this invention to provide an improved nebulizer for generating aerosols for medical application, at a higher output than heretofore practically attainable, which aerosols have smaller and more uniform particle size than heretofore.

It is yet another object of this invention to provide an improved nebulizer in which portions which contact the nebulized liquid are not adversely affected by such contact and are readily sterilizable.

It is a further object of this invention to provide an ultrasonic nebulizer in which nebulization occurs more efficiently than heretofore.

It is a still further object of this invention to provide an improved nebulizer which is effectively prevented from suffering damage when left in an operating condition for a long period of time with an inadequate supply of liquid to be nebulized.

An additional object of the invention is to provide a novel vial for liquid medicine for use in an ultrasonic nebulizer and in which a measured quantity of such medicine may be contained for shipment and storage.

This invention possesses other objects and features of advantage, which with the foregoing, will be set forth in the following description of preferred forms of the invention which are illustrated in the drawings accompanying and forming part of this specification. It is to be understood, however, that variations in the showing made by said drawings and description may be adopted within the scope of the invention as set forth in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 is a perspective view of one form of ultrasonic nebulizer embodying the present invention, showing the major components thereof.

FIG. 2 is a vertical sectional view of the nebulizer assembly of the present invention taken substantially along line 2-2 of FIG. 1, and in slightly enlarged scale relative thereto.

FIG. 3 is a side elevational view, partly broken away, of the nebulizer and liquid supply assemblies as seen generally from line 33 of FIG. 1.

FIG. 4 is an enlarged perspective view of the lower portion of the nebulizer assembly of FIG. 1 broken away to illustrate the transducer and transducer mounting structure.

FIG. 5 is an exploded perspective view of the upper portion of the nebulizer assembly of FIG. 1, on an enlarged scale relative thereto, and particularly illustrating the baffle and baffle enclosure.

FIG. 6 is a side elevational view of a modified form of the lower portion of the nebulizer assembly of FIG. 1, partly broken away, and enlarged relative thereto, utilizing a vial containing a predetermined volume of liquid medicine to be nebulized instead of the liquid supply assembly of FIGS. 1 and 3.

FIG. 7 is a perspective view of a vial for liquid medicine adapted for use with the ultrasonic nebulizer of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In detail, a preferred embodiment of the present invention (FIG. 1) comprises three major components; an ultrasonic wave generator or oscillator l, a nebulizer assembly 2, and a liquid supply reservoir 3.

Oscillator 1 includes a housing 4 in which is a chassis or base 12 for carrying the electronic components of a conventional ultrasonic generator circuit and a blower unit 13. Housing 4 comprises a pair of

side walls

5, 6, top 7, base wall 8 and end wall 9. At the front end of housing 4 is a panel 15 which is recessed slightly from the front edges of

walls

5, 6, 7, 8. Chassis l2 and panel 15 are removably secured to

walls

5, 6 of housing 4 by screws 16. When panel 15 and chassis 12 are secured to walls 5, 6 (FIG. 1) the components carried by the chassis are within protective housing 4, but are also ventillated through openings 11 in said walls. Upon removal of screws 16, panel 15 and chassis 12 may together be readily removed through the open end of housing 4 for access to the enclosed components. Elongated recessed portion 17 at each side of panel 15 facilitates gripping the panel with the fingers for removal thereof and provides added openings for ventillation.

Rigidly secured to the inside surface of panel 15 proximate each top corner thereof is a horizontally, laterally, outwardly projecting arm 18 (FIG. 1) formed of an inner bar portion 19 riveted or screwed to panel 15 and an outer horizontal end ring 22 having a forward section which is vertically slotted as at 23. Arms 18 are provided for mounting nebulizer assembly 2 and liquid supply reservoir 3 hereinafter described in detail, and slots 23 facilitate their mounting as will become clear. The forward edge of

walls

5, 6 are notched at 24, 25 respectively, to accommodate bar portions 19. Housing 4, chassis l2 and panel 15 may all be of suitably rigid aluminum sheet material, or other material, noting that the material of panel 15 must be of sufficient thickness to enable said panel to support arms 18 and nebulizer assembly 2 and liquid supply reservoir 3. Nebulizer assembly 2 (FIGS. 1 and 2) is generally elongated and cylindrical and at its base has a circular cylindrical cap 26 of conductive material and including a central axis recess 27, FIG. 2, extending downwardly from the flat upper surface 28 of said cap. A bore 29 extends radially from one side of cap 26 to intersect recess 27 and includes an enlarged outer portion 32 providing an outwardly facing shoulder 33. Received within

bores

29, 32 is a conventional electrical cable connector 34, one electrical connection of which is a conductive sheath 35 in bore 29, with an annular flange 36 engaged shoulder 33. The other electrical connection of connector 34 is a central pin 37 insulated from sheath 35 by coaxial insulating layer 38, and with connector 34 positioned as described, the inner end of pin 37 extends to substantially the center of recess 27. Connector 34 is secured within

bores

29, 32 by an allen screw 39 threaded into cap 26 for bearing against sheath 35.

A cylindrical cup member 42 (FIGS. 2, 4) formed of a plastic or other nonconductive material rests on upper surface 28 of cap 26 and includes a flat circular base 43 bounded by an upstanding rim 44, with said base having a central circular opening 45 extending through a depending boss 46 which projects into recess 27 A generally flat circular disc 47 of a thin conductive sheet material rests on base 43 and is dimpled centrally so as to provide a slight projection 48 which extends downwardly through opening 45. A light compression spring 49 extends vertically between the inner end of pin 37 and disc 47 and is centered in boss 46 by projection 48. The length of spring 49 in the extended position is greater than the distance between pin 37 and disc 47 so that the disc is urged upwardly thereby under relatively slight pressure.

A ring 52 of a conductive material rests on cap 26 in surrounding engagement with cup member 42 and has an inwardly directed annular flange 53, FIG. 2, at its upper end providing a downwardly facing shoulder 54 which overlies the top edge of rim 44 and terminates radially inwardly of such top edge.

Cap 26, cup member 42, disc 47 and associated structure together provide a mounting for a disc transducer 55, such as a piezoelectric ceramic crystal (FIGS. 2, 4) which is seated on disc 47. Transducer 55 is of the type which when excited by electrical energy converts the same into mechanical wave energy, and it is therefore suitably resiliently mounted between disc 47 which is yieldably urged upwardly by spring 49, and an O-ring 56 of conductive material, disposed peripherally of the transducer upper surface and partially compressed between said surface and shoulder 54.

Radio frequency electrical energy is impressed upon transducer 55 through an electrical circuit to one electrical contact at its lower surface and the other at its upper surface. Such circuit is completed from pin 37 through spring 49 and disc 47, all of which are insulated from cap 26, to the underside of transducer 55, and from the upper side of said transducer through 0- ring 56, ring 52, cap 26 and to the outer sheath of connector 34. The two electrical connections of connector 34 are electrically connected to the output of ultrasonic oscillator l.

The oscillator wave generator 1 is preferably of the type commonly used in radio work and capable of producing a tuned, high-power electromagnetic wave of radio frequency. For purposes of this invention, generator 1 preferably puts out electromagnetic energy at approximately 15 watts to vibrate transducer crystal 55 at 1.4 megacycles.

Housing 4 (FIG. 1) also includes on its front panel 15 and connected in the wave generator circuit a power switch 109, indicator light 112, fuse holder 113 and the connector 114 to which a power cable 115 is connected. When switch 109 is moved to the on position, the output of generator 1 is applied to transducer 55 through two-wire cable 115, one wire of which is connected to sheath 35 and the other of which is connected to pin 37. Switch 109 also activates blower unit 13.

An elongated, cylindrical, open-ended tube 57 (FIG. 2) of plastic or other nonconductive material is formed with a circular recess at its lower end, providing a downwardly directed annular flange 58 and a downwardly facing shoulder 59, which receives the upper end of ring 52. A plurality of screws 62 (only oneof which is shown in FIG. 2) extending through cap 26 and ring 52 into threaded engagement with the bottom end of tube 57 secure the transducer mounting in place. An O-ring seal 64 seated in a recess 65 adjacent shoulder 59 is compressed against the upper surface of flange 53 of ring 52 thereby rendering the joint between said ring and tube 57 liquid tight.

Above transducer 55, tube 57 provides a chamber in which liquid is to be nebulized in the form of a circular central axial bore 67 of the lower portion of which is the same diameter as the opening bounded by flange 53 of ring 52, which is slightly less than the outside diameter of transducer 55. The upper portion of bore 67 is of substantially larger diameter providing between said portions and generally centrally of tube 57 an upwardly slanting shoulder 68, an upwardly facing horizontal shoulder 72, and a horizontal step 73. Said step positions upper wall portion 74 outwardly of the lower portion of tube 57 and provides an external, downwardly directed shoulder 66 for engagement by ring 22 (FIGS. 1-3) for supporting the same. A radially inwardly directed flange 75 at the upper end of wall portion 74 has a downwardly slanting upper surface 76, and extends inwardly to the same inside diameter as the inner wall portion above shoulder 72.

A second cylindrical open-ended tube 77, preferably of a transparent plastic or similar transparent material, has an outside diameter substantially equal to the inside diameter of flange 75 and the wall portion above shoulder 72, and a wall thickness equal to the width of said shoulder. Tube 77 is thus insertable into tube 57 with its outside surface in engagement with flange 75 and the wall portion at step 73 and with its bottom end resting on shoulder 72. When tube 77 is inserted in this manner, it forms a larger diameter continuation of bore 67 and is of sufficient length to project upwardly from the upper end of outer tube 57 to an upper end 78 formed with external threads 79.

Threadedly secured on said upper end 78 and communicating with tube 77 is a cylindrical baffle enclosure 82 (FIGS. 2, 5), having for such purpose internal threads 83 on its lower end complementary with threads 79. A baffle member 84 is received in enclosure 82, and a cap 85 closes the upper end thereof.

Above the lower threaded portion, the cylindrical wall of enclosure 82 includes a relatively thick wall portion 86 extending to the upper surface of a transverse web 87. A generally radial port 88 in wall portion 86 is directed angularly downwardly toward and communicates with the interior of enclosure 82.

A vertically extending deflector or baffle plate 89 depends from the underside of web 87 centrally of enclosure 82 to divide the interior of said enclosure below web 87 and the upper portion of tube 77 into two substantially semi-cylindrical portions. The side edges of plate 89 are notched at 92 (FIG. 5) to receive the inwardly projecting sides of wall portion 86. Plate 89 is secured in position by being wedged against the curved inner sides of wall portion 86 by screw 94, threaded radially through wall portion 86 into engagement with the surface of said plate.

At the side of plate 89 adjacent port 88, web 87 is provided with a relatively small aperture 95, and at the other side of said plate substantially all of web 87 is cut away to provide a generally segmentally-shaped aperture 96 (FIG. 5). The enclosure wall portion 97 above web 87 is formed with an internal, upwardly facing shoulder 98 spaced upwardly from web 87.

Baffle member 84 (FIGS. 2, 5) includes a central cylindrical body 99, projecting radially from which and equally axially spaced therealong are three relatively thin segmentally shaped fins 102, each having a straight edge 103 adjacent the periphery of body 99 and a sharpened circular edge 104 concentric with said body. The diameter of curved edges 104 of fins 102 is substantially the same as and that of cylindrical body 99 is approximately one-half of the inside diameter of wall portion 97 above shoulder 98 so that member 84 fits in enclosure 82 with curved edges 104 positioned substantially against wall 97 and the lowermost fin 102 resting on shoulder 98. When baffle member 84 is correctly positioned, straight edge 103 of the lowermost fin 102 is parallel with the upper edge of plate 89 and disposed over aperture 95, and the curved portion 104 of said lowermost fin extends in spaced, covering relation to segmental aperture 96. It will be noted that the curved portion 104 of the central fin 102 is diametrically opposed to the curved portions of the upper and lower fins, thereby providing a tortuous passageway from aperture 96 past baffle member 84 to the upper end of enclosure 82.

Cap fits in sealing relation to the upper end of enclosure 82 by means of an O-ring 105 received in a recess 106 in the cap. A chamber 107 opening downwardly of cap 85 has an inner wall surface converging upwardly toward and communicating with an upwardly opening central outlet port 108. All of the components of the baffle structure are preferably formed of a plastic or other noncorrodible and sterilizablc material.

A hose 116 is connected at one end to the output of blower 13 in housing 4 (FIG. I) and at the other end to a fitting 117 in port 88 (FIG. 2) to conduct an air stream from blower 13 into the upper end of tube 77 on the side of baffle plate 89 opposite aperture 96.

To obtain aerosol of maximum particle uniformity and optimum nebulizing efficiency with respect to the rate of aerosol generation, it is necessary to provide a continuous supply of liquid to the interior of tube 57 and to maintain the level of such liquid substantially constant. Liquid to be nebulized is supplied to the inte rior of bore 67 from supply reservoir 3 (FIGS. 1 and 3) which includes an inverted jar 119 across the bottom open end of which is sealingly secured a closure member 122 (FIG. 3) by a ring cap 123 threaded onto said bottom end.

An annular gasket 124 is bonded to the periphery of the upper surface of closure member 122, and a central, generally circular block 125 (FIGS. 1 and 3) depends from the underside thereof and is received in ring portion 22 of the left-hand arm 18. Extending vertically upwardlly from closure member 122 into the interior ofjar 119 is an open-ended tube 126 bent in the form of an elongated inverted U. One threaded end 127 projects through closure member 122 and block 125, is secured thereto by nuts 128, and is open to the atmosphere. The opposite end 129 terminates inwardly of closure member 122 and is likewise threaded. End 129 threadedly receives a hollow sleeve 132 having a threaded axial bore 133 and a pair of opposed manually graspable flat surfaces, so that said sleeve may be readily rotated on end 129 to vary the elevation of the lower open end 139 of sleeve 132 above closure 122. A small threaded opening 134 through closure member 122 and block 125 receives a hose fitting 135. Recesses 136 are formed in block 125 to accommodate fitting and the lower nut 128.

Supply liquid is conducted from reservoir 3 into the interior of bore 67 (FIG. 3) through flexible conduit or tube 137 connected at the inlet end to fitting 135 and at the outlet end to a fitting 138 (FIGS. 2, 3) in the lower portion of tube 57, and is prevented from leaking from the interior of bore 67 by O-

rings

56, 64. Fitting 138 includes a check valve to permit flow of liquid one way only, i.e., into the interior of said bore.

The level of liquid in bore 67 is maintained constant as the liquid is supplied thereto, and such level is even with the lower end 139 of sleeve 132 for reasons presently to be explained. Arms 18 respectively support nebulizer assembly 2 and liquid supply reservoir 3 so that sleeve 132 is adjustable to be positioned with lower end 139 on a level with shoulder 72 of tube 57.

Initially jar 119 is filled with supply liquid and placed on arm 18 so that the upper surface of said liquid is substantially above sleeve 132. End 139 is in communication with the atmosphere through tube 126, and when the liquid system is in static equilibrium the liquid in jar 119 at the level of sleeve end 139 is at atmospheric pressure, with the pressure of the liquid and air thereabove less than atmospheric and the pressure of the liquid therebelow greater than atmospheric. The liquid system initially and continuously seeks a state of static equilibrium in which the surface of the liquid in base 67, which surface is always at atmospheric pressure, rises to the level of sleeve end 139. As the liquid in bore 67 is dissipated through nebulization, any tendency for the surface thereof to drop is resisted since such a drop to below the level of sleeve end 139 creates a pressure differential wherein the liquid at end 139, being above the surface of the liquid in bore 67 is at less than atmospheric pressure. To eliminate such differential, liquid is supplied from jar l 19 to the interior of bore 67, while simultaneously air is introduced into said jar through tube 126 to displace the supplied liquid; so that the surface of the liquid in bore 67 is maintained at the level of sleeve end 139. When the liquid in jar 119 drops below the level of sleeve end 139, the liquid in bore 67 is at a corresponding level.

In operation, the oscillator circuit is initially connected to a current source, jar 119 is filled with supply liquid which may be water, saline solution or other liquid; nebulizer assembly 2 and liquid supply reservoir 3 are mounted on arms 18, with cable 115, tube 137, connector 34 and fitting 138 being passed through slots 23, and the liquid system therein permitted to come to a state of equilibrium. Power switch 109 is then moved to the on position, whereupon ultrasonic oscillation of transducer 55 by application of electrical energy from generator 1, and actuation of blower unit 13 are initiated. as indicated by illumination of pilot light 112. By varying the power supplied to transducer 55, the amplitude of oscillation thereof may be regulated to thereby provide one form of control of the rate of aerosol generation of the nebulizer.

When transducer 55, previously described as a disc of piezoelectric crystal, is excited by electromechanical energy at ultrasonic frequency, its faces move with respect to each other axially of the disc, i.e., oscillate, at a corresponding frequency. The amplitude of oscillation produced by a given amount of incident energy is markedly greater at the resonant frequency of the crystal, and it is therefore preferable to drive the crystal at such resonant frequency, normally indicated as its rated frequency.

When one of the oscillating faces is in contact with a body of liquid, ultrasonic waves are transmitted therefrom through the liquid. Also, a pressure drop in the liquid occurs at the crystal face, which causes the formation and collapse of cavities or bubbles at an extremely high rate. These bubbles stream toward the surface of the liquid and encounter the interface between the liquid and air, resulting in the production of fine mist or aerosol adjacent the liquid surface.

In the present nebulizer aerosol particle size uniformity and rate of aerosol generation are maximized by concentrating the beam of ultrasonic waves at the point where it intersects the liquid surface and focusing the stream of bubbles to a focal point substantially at such liquid surface. The desired concentration of the ultrasonic beam is accomplished in a beam concentrating chamber defined by the wall surface of bore 67 and the adjacent face of transducer 55, which chamber is filled with liquid to be nebulized.

Bore 67 is of a uniform diameter from its end adjacent transducer 55 to substantially its upper opposite end at which is an enlarged diameter portion. The diameter of the uniform portion of bore 67 is related to the diameter of transducer 55 and is approximately equal to but slightly less than such diameter. It is desirable that the bore diameter be relatively small so that the reflective character of the solid material is utilized to confine and highly concentrate the ultrasonic beam. However, a practical minimum bore diameter should not be significantly less than that of the transducer since solid material overlying the transmitting face of the transducer in the path of the transmitted waves absorbs a portion of the transmitted energy to decrease nebulizing efficiency, though the nebulizer is not thereby rendered totally inoperative. In the present nebulizer, peripheral contact between tube 57 and transducer 55 is necessary for effecting a liquid tight seal.

After the diameter of the uniform portion of the bore and the resulting focal point of the convergent bubble stream in the liquid to be nebulized are determined, the length of such portion is fixed so that the focal point occurs in the enlarged upper portion of the bore substantially at shoulder 72. This is the optimum level for the liquid in bore 67 and the level at which such liquid is automatically maintained in the present nebulizer by supply reservoir 3 and the above-described liquid level regulating structure.

In the illustrated apparatus, transducer 55 is a disc of piezoelectric ceramic, which may be of the barium titanate type, approximately seven-eighths inch in diameter, and tube 57 is nylon and formed with bore 67 which has a lower portion of a uniform diameter of eleven-sixteenths inch along a length of approximately one and five-eighths inches, and an upper enlarged diameter portion extending axially an additional onefourth inch to shoulder 72. When transducer 55 is excited at 1.4 megacycles by generator 1 of approximately 15 watts output, optimum aerosol generating efficiency occurs with the liquid surface substantially on a level with shoulder 72, to generate aerosol at a rate of approximately 2 cc. per minute.

Ultrasonic beams can alternatively be made to converge by utilizing a concavely curved crystal, but a curved crystal is considerably more expensive than a flat one.

When the nebulizer is operating, the liquid in chamber 67 is continuously dissipating; but the liquid surface is maintained at the optimum level until the reserve in supply jar 119 drops below such level. As the liquid in bore 67 drops below this level, the efficiency of nebulization decreases markedly. In the apparatus illustrated in FIG. 2, it requires a period of several hours to exhaust all the liquid by nebulization after the liquid surface drops from the desired level. Therefore, if the apparatus is inadvertently left in an operating condition with an inadequate liquid supply, changes are great that the condition will be discovered and corrected long before all the liquid is exhausted and damage done to the apparatus through overheating.

The air stream from blower unit 13, as indicated by arrow 142 (FIG. 2), carries the aerosol from tube 77 upwardly past baffles 103 which trap out any gross particles and through port 108 and a hose I40 and mask or other suitable conduit to the patient. The stream from blower 13, having a relatively slight flow rate, discharges from fitting 117, impinges against plate 89, passes downwardly along the near face of said plate and around the lower end thereof to pick up the mist generated in bore 67, then upwardly with said mist along the opposite face of said plate, and through baffle enclosure 82 and port 108. The flow rate of air from blower 13 may be regulated as best suits the particular application. Oxygen or other breathable gas under pressure may be utilized as the aerosol carrier instead of the air stream, or the patient may draw the aerosol in by inhalation. In the treatment of particular diseases, specific gas carriers may be called for, but it should be noted that compressed gas or an air stream is not essential to the nebulizing process.

Aerosol particle size is further reduced to maximize uniformity by the use of the baffle structure. With the baffle in the instant apparatus, the maximum size of particles discharged from port 108 is under microns.

The aerosol is carried upwardly through aperture 96 and follows a tortuous path, indicated by arrow 143 (FIG. 5) along both faces of fins 102, then past cham her 107 and through port 108. Particles which are heavier than desired impinge against the underside of fins 103 and other obstructing surfaces and condense, and the condensation drains along wall 97 and finally through aperture 95. The lighter particles pass through the baffle structure without contacting any of the baffle surface.

Parts of the apparatus which are in contact with the liquid or aerosol are easily separable, e.g., tube 77, member 84 and cap 85 are each separable from enclosure 82; and of a sterilizable and non-corrodible material.

If it is desired to administer a relatively small and carefully measured dosage of medicine in aerosol form, the nebulizing apparatus may be modified as illustrated in FIGS. 6 and 7. In FIG. 7, a vial 144 for liquid medicine which may be utilized in place of tube 77 is shown. Vial 144 includes a cylindrical wall 145, of the same diameter as tube 77, having a threaded end on which is screwed a cap 146. The opposite end is closed by an end wall or diaphragm 147 having a central hemispherical depression or bowl 148 projecting axially outwardly therefrom. A label 149 or other means is provided for carrying information identifying the medicine and relating to proper dosage, etc. Medicine may thus be stored and transported in vial 144 just as with conventional vials.

With cap 146 removed, vial 144 may be inserted in tube 57 (FIG. 6) with diaphragm 147 resting on shoulder 72, and baffle enclosure 82 is threaded onto the upper end thereof in place of said cap. In the modified embodiment, a measured amount of liquid medicine in vial 144 is nebulized rather than liquid in bore 67, so that no continuous liquid supply is required. Liquid supply assembly 3 is disconnected and, instead, the lower portion of chamber 67 is initially filled with liquid to the level of shoulder 72. If chamber 67 is inadvertently filled above shoulder 72, flange 75 prevents spillage of the displaced liquid when vial 144 is inserted.

With vial 144 in place, the liquid in chamber 67 below wall 147 is substantially sealed in such space so that it cannot be nebulized; and within the vial there is, 6

pressed upon diaphragm 147, causing said diaphragm to vibrate ultrasonically. Vibrations impinging on rounded depression 148 are focused thereby a small fraction of an inch above diaphragm 147 so that the focal point occurs substantially on a level with the upper surface of the medicine. Projection 148 accomplishes sufficient focusing of the ultrasonic waves so that the medicine will continue to be rapidly nebulized as it is dissipated until it is completely exhausted. The medicinal aerosol may be carried by air or other breathable gas in the manner previously described.

We claim:

1. A nebulizer, comprising:

a. a generally vertically elongated nebulizer chamber having a closed bottom end and an outlet at its upper end, for receiving therein liquid with the upper surface of said liquid a predetermined level above said bottom end;

b. an electromechanical transducer supported at said bottom end with a surface thereof acoustically connected to the liquid in said chamber;

c. means for exciting said transducer for causing it to generate ultrasonic waves; and

. means defining an ultrasonic beam concentrating chamber for concentrating said waves at said predetermined leve] including a portion of said nebulizer chamber of substantially circular interior cross-section extending vertically from said transducer substantially to said predetermined level, said interior cross-section being of uniform diameter between points immediately above said transducer and immediately below said predetermined level, the distance between said points being at least twice the length of said uniform diameter.

2. A nebulizer comprising:

b. an electromechanical transducer of generally fiat form supported at said bottom end and including a planar surface acoustically connected to the liquid in said chamber;

d. means for concentrating said waves at said predetermined level including a portion of said nebulizer chamber of substantially circular interior crosssection extending vertically from said transducer substantially to said predetermined level, said interior cross-section being of uniform diameter between points immediately above said planar surface of said transducer and immediately below said predetermined level, the distance between said points being'at least twice the length of said uniform diameter.

3. The nebulizer of claim 2, including:

e. a separable, elongated vial for liquid insertable into the upper end of said chamber with a bottom wall substantially at said predetermined level;

f. said bottom wall including a downwardly extending central depression curved for concentrating said waves at substantially said bottom wall and upper surface of the liquid in said vial.

4. In a device for ultrasonic nebulization of liquid, in-

cluding a generally vertically elongated nebulizer lar interior cross-section extending from said planar surface substantially to said predetermined level, said interior cross-section being of uniform diameter between points immediately above said planar surface of said transducer and immediately below said predetermined level, said points being spaced apart a distance at least twice the length of said uniform diameter.

Claims

1. A nebulizer, comprising: a. a generally vertically elongated nebulizer chamber having a closed bottom end and an outlet at its upper end, for receiving therein liquid with the upper surface of said liquid a predetermined level above said bottom end; b. an electromechanical transducer supported at said bottom end with a surface thereof acoustically connected to the liquid in said chamber; c. means for exciting said transducer for causing it to generate ultrasonic waves; and d. means defining an ultrasonic beam concentrating chamber for concentrating said waves at said predetermined level including a portion of said nebulizer chamber of substantially circular interior cross-section extending vertically from said transducer substantially to said predetermined level, said interior cross-section being of uniform diameter between points immediately above said transducer and immediately below said predetermined level, the distance between said points being at least twice the length of said uniform diameter.

2. A nebulizer comprising: a. a generally vertically elongated nebulizer chamber having a closed bottom end and an outlet at its upper end, for receiving therein liquid with the upper surface of said liquid a predetermined level above said bottom end; b. an electromechanical transducer of generally flat form supported at said bottom end and including a planar surface acoustically connected to the liquid in said chamber; c. means for exciting said transducer for causing it to generate ultrasonic waves; and d. means for concentrating said waves at said predetermined level including a portion of said nebulizer chamber of substantially circular interior cross-section extending vertically from said transducer substantially to said predetermined level, said interior cross-section being of uniform diameter between points immediately above said planar surface of said transducer and immediately below said predetermined level, the distance between said points being at least twice the length of said uniform diameter.

3. The nebulizer of claim 2, including: e. a separable, elongated vial for liquid insertable into the upper end of said chamber with a bottom wall substantially at said predetermined level; f. said bottom wall including a downwardly extending central depression curved for concentrating said waves at substantially said bottom wall and upper surface of the liquid in said vial.

4. In a device for ultrasonic nebulization of liquid, including a generally vertically elongated nebulizer chamber having a closed bottom end and an outlet at its upper end, receiving therein said liquid with an upper surface a predetermined level above said bottom end, a generally flat electromechanical transducer at said bottom end having a planar surface in acoustical contact with said liquid and means for causing said transducer to generate ultrasonic waves in said liquid, means for concentrating said waves at said predetermined level, comprising: a. a nebulizer chamber portion of substantially circular interior cross-section extending from said planar surface substantially to said predetermined level, said interior crosssection being of uniform diameter between points immediately above said planar surface of said transducer and immediately below said predetermined level, said points being spaced apart a distance at least twice the length of said uniform diameter.