WO1999038621A1

WO1999038621A1 - Method of piezoelectrically atomising and pumping fluids and piezoelectric fluid atomising and pumping device

Info

Publication number: WO1999038621A1
Application number: PCT/DK1999/000045
Authority: WO
Inventors: Karl Astrup Holm
Original assignee: Danmist Aps
Priority date: 1998-01-28
Filing date: 1999-01-28
Publication date: 1999-08-05
Also published as: AU2610099A

Abstract

A fluid atomising device having a fluid source (77) for supplying fluid to a container (80) where a pumping effect is achieved by the expansion of the volume of a portion of a piezoelectric stacked actuator (83) inside the container (80). The pumping effect pumps a portion of fluid to the space between the stacked piezoelectric actuator (83) and a second stacked piezoelectric actuator (86). Expansion of the actuators (83 and 86) results in the surface thereof facing each other impacting the portion of fluid located in said space thereby atomising the fluid into very small droplets.

Description

1

Method of piezoelectrically atomising and pumping fluids and piezoelectric fluid atomising and pumping device

The present invention relates to a method of atomising fluids by placing a portion of fluid between two pressing surfaces and displacing at least one of said surfaces towards the other surface until the portion of fluid is impacted by at least a portion of each surface such that the fluid is pressed out from between the surfaces to the surroundings with a velocity sufficient to atomise at least part of the portion of fluid.

A method of the type indicate is disclosed in publications WO 94/25176 and WO 96/14163. The pressing surfaces are displaced towards each other by means such as springs, cam mechanisms, solenoid coils and like mechanical means.

Although such displacement means are relatively effective for many applications, for applications where many sequential displacements are required per second, the displacement mechanisms disclosed may be subject to a high degree of wear and also require a relatively large input of energy while developing frictional heat that may tend to evaporate the fluid before atomisation can take place.

A main object of the invention is to provide a method of atomising fluids requiring relatively small energy input, requiring relatively small space and not being subject to wear and development of frictional heat.

According to the invention this object is achieved by the method comprising the steps of:

- providing a first surface and a second surface spaced from one another,

- providing at least one first body having piezoelectric properties and being arranged and adapted for displacement of at least one of said surfaces towards the other surface when said first body is subjected to an electrical voltage,

- locating a portion of fluid between the first and second surfaces, and

- applying an electrical voltage to the at least one first body such that the at least one of said surfaces is displaced towards the other surface until the portion of fluid is impacted by at least a portion of each surface such that the fluid is pressed out from between the surfaces to the surroundings with a velocity sufficient to atomise at least part of the portion of fluid. Particularly in connection with relatively small amounts of fluid to be atomised for each atomising stroke of the pressing surfaces this method is particularly useful and requires very little energy input so that a standard alkaline battery is sufficient to supply power for many applications. The necessary forces for atomising according to this method do not give rise to appreciable wear and development of frictional heat. Furthermore, the space requirements are relatively modest.

The piezoelectric elements and principles required for implementing the method according to the invention are well known as for instance described in the publication "Piezoelectric Technology Data for Designers" published by Morgan Matroc Inc., Vemitron Division, this publication as well as any US Patents issued to this company hereby being incorporated herein by reference.

Although many different shapes of the piezoelectric body may be utilized just as the connection between the body and the surface or surfaces to be displaced may be direct or indirect, in the currently preferred embodiment of the method according to the invention the at least one surface is a surface of the at least one first body.

Hereby, the most efficient utilization of the piezoelectric deformations and forces is obtained as no other masses have to be displaced by the piezoelectric effect.

Preferably, the material of the at least first body is a piezoelectric ceramic material and/or a piezoelectric crystal.

Although many ways of locating the fluid portion in the atomising region are conceivable, for instance by pulsed jet or dripping, in the currently preferred embodiment, the portion of fluid is located between the first and second surfaces by a pumping means, preferably a piezoelectric pumping means.

By using a piezoelectric pumping means, the advantages of low energy needs, small space requirements and little wear are obtained also for this element of the method. Although many well known types of piezoelectric pumps may be used, in the currently preferred embodiment of the method, the piezoelectric pumping means comprises the at least first body.

Hereby a particularly compact and inexpensive method is obtained where the same body is utilized for atomising and for pumping.

In the currently preferred embodiment of the method according to the invention, the method further comprises the steps of: - providing control means for synchronising the pumping action of the pumping means with the displacement of the at least one of said surfaces towards the other surface, - sequentially displacing the at least one of said surfaces towards the other surface and away from said other surface, and - sequentially pumping a fluid portion to the region between said surfaces for each said displacement such that the fluid portion is impacted by the said two surfaces.

Hereby, a particularly efficient, automatic method is obtained by means of which a steady stream of atomised droplets is obtained in a well controlled manner.

In the currently preferred embodiment of the method according to the invention, at least a portion of the at least first body is arranged within a container completely filled with the fluid to be atomised such that the piezoelectric deformation of said body by application of said electrical voltage causes the volume of the portion of the body within the container to increase.

Hereby, a particularly compact, reliable, precise and efficient pumping effect and thereby atomisation is achieved. This is particularly important in applications where the amount of atomised fluid produced must be constant and well determined.

In many applications it is necessary to atomise two or more fluids either simultaneously or sequentially for achieving the desired result and for such applications the method according to the invention may advantageously comprise the additional step of locating a portion of at least one additional fluid between the first and second surfaces either simultaneously or sequentially.

According to the invention, the fluid or fluids may comprise a pharmaceutical substance for the therapeutic treatment of asthma, diabetes and the like or the fluid or fluids may selected from a group of fluids comprising bactericides, herbicides, pesticides, fire control substances, cleaning substances, perfumes, deodorants, conservating substances, coating substances, diesel, gasoline and the like.

The invention further relates to a method of pumping a fluid and comprising the steps of:

- providing a body having piezoelectric properties and arranged such that at least a portion of the body is located within a container completely filled with the fluid, and - applying an electrical voltage to the body such that the piezoelectric deformation of the body causes the volume of the portion of the body within the container to increase.

Hereby, a particularly compact, reliable, low energy and precise pumping effect may be obtained, particularly for small pumping rates.

Moreover, the invention relates to a method of administering two or more substances by inhalation and comprising the steps of:

- providing an inhaling device comprising two or more sources of substance, each source having a substance dispensing means,

- providing entraining means for entraining the pharmaceutic substances dispensed from each substance source in a gas flow emanating from the inhalation device, and

- activating the dispensing means of said substance sources in a pre-determined sequence.

In the currently preferred embodiment of the method according to the invention, when the two or more pharmaceutic substances are fluids, the method comprises the further steps of: a.- providing the inhaling device with a first surface and a second surface spaced from one another, b.- providing at least one first body having piezoelectric properties and being arranged and adapted for displacement of at least one of said surfaces towards the other surface when said first body is subjected to an electrical voltage, c- locating a portion of a first fluid between the first and second surfaces, d.- applying an electrical voltage to the at least one first body such that the at least one of said surfaces is displaced towards the other surface until the portion of first fluid is impacted by at least a portion of each surface such that the first fluid is pressed out from between the surfaces to the surroundings with a velocity sufficient to atomise at least part of the portion of first fluid, and e.- repeating steps c-d with a portion of a further fluid.

In another aspect, the invention relates to a fluid atomising device comprising:

- a first pressing surface and a second pressing surface spaced from one another,

- fluid dispensing means for dispensing a portion of fluid to a location between said two pressing surfaces,

- at least one body having piezoelectric properties and being arranged and adapted for displacement of at least one of said pressing surfaces towards the other pressing surface to an atomisation position for both surfaces adjacent one another when said body is subjected to an electrical voltage, and

- electrical means for applying the electrical voltage to the at least one body.

In the currently preferred embodiment of the device according to the invention, the at least one of said pressing surfaces is a surface of the at least one body.

Advantageously, the first pressing surface is a surface of a first body having piezoelectric properties and the second pressing surface is a surface of a second body having piezoelectric properties, the electrical means comprising means for applying an electrical tension to each of the first and second bodies.

Hereby, the piezoelectric deformations and forces available for atomising are enhanced.

In the currently preferred embodiment of the invention, the at least one first body comprises two or more discrete sub-bodies of a piezoelectric material arranged such that the individual piezoelectric deformations of the sub-bodies upon application of an electrical voltage to each of said sub-bodies are substantially added to achieve a resulting piezoelectric deformation of the at least one body for displacing the corresponding pressing surface.

In the currently preferred embodiment of the device according to the invention, the device further comprises a fluid pumping means, preferably a piezoelectric pumping means, and fluid conduit means communicating the fluid pumping means with the atomising region between said pressing surfaces and with a source of fluid, and the piezoelectric pumping means comprises the at least one body.

Preferably, the device according to the invention further comprises control means for synchronising the pumping action of the pumping means with the displacement of the at least one of said pressing surfaces towards the other pressing surface.

In the currently preferred embodiment of the device according to the invention, at least a portion of the at least first body is arranged within a container completely filled with the fluid to be atomised, and the fluid dispensing means comprise a fluid flow passage extending through the at least one body from an inlet aperture to an outlet aperture, the outlet aperture being located at the pressing surface of the at least one body.

In a special embodiment of the device according to the invention for special applications, the device further comprises two or more sources of different fluids, and the dispensing means are adapted for sequentially and/or simultaneously dispensing a portion of each fluid to the atomising region between said pressing surfaces.

The invention further relates to a piezoelectric fluid pump comprising a body having piezoelectric properties, electrical means for applying an electrical voltage to the body, a container for the fluid to be pumped, inlet means for supplying fluid to the container such that it constantly is totally filled with the fluid, the body being arranged such that at least a portion of the body is located within the container, and the piezoelectric properties of the body being such that application of the electrical voltage to the body causes a piezoelectric deformation of the body resulting in an increase of the volume of said portion of the body within the container.

Finally, the invention also relates to an inhalation device for administering two or more substances to a person by inhalation and comprising:

- two or more sources of different substances, each source having a substance dispensing means,

- entraining means for entraining the substances dispensed from each substance source in a gas flow emanating from the inhalation device, and

- activating means for activating the dispensing means of said substance sources in a pre-determined sequence.

In the currently preferred embodiment of the device according to the invention, the two or more substances are fluids, the device further comprising:

- fluid dispensing means for dispensing a portion of each fluid to a location between said two pressing surfaces,

- at least one body having piezoelectric properties and being arranged and adapted for displacement of at least one of said pressing surfaces towards the other pressing surface to an atomisation position for both surfaces adjacent one another when said body is subjected to an electrical voltage, and - electrical means for applying the electrical voltage to the at least one body.

In the following the method and device according to the invention will be further explained in connection with various embodiments shown by way of example in the attached drawings where:

Figs. 1-12 are diagrammatic illustrations of different embodiments of a piezoelectric atomising device according to the invention,

Fig. 13 is a diagrammatic cross sectional view of four sequential stages in the operation of an atomising device according to the invention designed for enhancing the spatial distribution of the atomised fluid,

Fig. 14 is a diagrammatic cross sectional view of three stages in the operation of a piezoelectric pump according to the invention,

Fig. 15 is a diagrammatic cross sectional view of an atomising device incorporating piezoelectric pumping means according to the invention,

Figs 16 and 17 are diagrammatic cross sectional views of two stages in the operation of an atomising device according to the invention incorporating piezoelectric pumping means according to the invention,

Fig. 18 shows an elevational partly sectional view of a medicinal atomising device according to the invention for use for inhaling therapeutic substances,

Figs 19 and 20 show enlarged scale partly sectional views of details of the device shown in Fig. 18,

Figs 21-23 show elevational partly sectional views of alternative embodiments of medicinal atomising devices according to the invention,

Figs 24 and 25 respectively show an elevational and partly sectional view of an array of piezoelectric atomising devices according to the invention arranged in a room and a partly sectional enlarged scale view of part of the array, and

Fig. 26 illustrates schematically a control diagram of an atomising device according to the invention.

Referring now to Fig. 1 showing a diagrammatic cross sectional and corresponding end view of a first embodiment of an atomising device according to the invention, a stationary plate 1 of any suitable rigid material such as a plastic material or steel is connected to a second plate 2 of such material by means of a rod 4 extending through a bore 5 in a substantially cylindrical piezoelectric body 3. An annular surface 6 of the piezoelectric body 3 faces an annular surface 7 of the second plate 2.

Not shown electrical connections are provided for applying a preferably alternating electrical voltage to the body 3 such that an expansion and contraction of the body 3 in the direction of the arrows R1 is obtained. The length of the rod 4 relative to the axial length of the body 3 when not subjected to the electrical voltage is chosen such that said surfaces will substantially abut each other in the expanded condition of the body 3.

Any portion of fluid arranged between the surfaces 6 and 7 will be atomised by being impacted by the surfaces and squeezed out to the periphery of the surfaces to the surroundings with a velocity sufficient to atomise the fluid as indicated by the reference numeral 8.

The circular plate 2 may also be made of a piezoelectric material, and not shown electrical connections may be provided for causing expansion and contraction of the plate 2 in the direction of the arrows R1 such that by synchronizing the expan- sion and contraction of the plate 2 and the body 3, a larger maximum distance between the surfaces 6 and 7 is allowed while still allowing abutment of the surfaces in the expanded state of the body 3 and plate 2.

The portion of fluid to be atomised may be placed between the surfaces 6 and 7 prior to the squeezing action thereof in many suitable ways, for instance by providing a channel through either the body 3 and communicating with the interior of the bore 5 or through the plate 2 and communicating with the surface 7. Suitable pumping means may be provided for dispensing the portions of fluid for each stroke 10

of the atomising surfaces 6 and 7.

In case fluid is supplied to the space defined by the bore 5 and the rod 4, a pumping action will be obtained by the expansion and contraction of the body 3 causing a change in the volume of said space that will cause portions of fluid to be pumped through the space to the surface 6, particularly if a non-return valve is arranged in the channel through the body 3 or in a conduit leading from a fluid source to the channel so as to avoid return of fluid during the pumping action described above. A non-return valve may advantageously be arranged is said space adjacent the outlet thereof to the surface 6 to avoid return flow of part of the fluid portion during atomising abutment of the surfaces 6 and 7.

The arrangement of flow conduits, valves, fluid pump and control equipment therefor will be dealt with more in detail below in connection with the discussion of the embodiments shown in Figs 18-20.

The principle of utilizing the piezoelectric expansion and contraction of one or more bodies to bring two surfaces into mutual abutment may be utilized in connection with many different geometrical and mechanical configurations whereof some will be explained in connection with Figs 2-12.

In Fig. 2 showing a diagrammatical cross sectional and corresponding end view of a second embodiment of an atomising device according to the invention, a fixed circular plate 9 attached to a cylindrical rod 10 is also attached to a piezoelectrical cylindrical body 11 having a bore 12 enveloping the rod 10 and forming a space between the opposed cylindrical surfaces of the rod 10 and boring 12.

When electrical alternating voltage is applied to the body 11 causing alternating contraction and expansion in the direction of the arrows R2 and R3, the opposed surfaces of the bore 12 and the rod 10 will respectively alternately abut one another and be spaced from one another and thereby atomise portions of fluid sequentially arranged between said surfaces as indicated by the reference numeral 13. 11

The expansion of the body 11 in the direction of the arrows R2and R3 will entail a corresponding increase of the volume of the space between the surfaces of the bore 12 and the rod 10 thereby fluid may be sucked into the space from a fluid conduit for instance in the form of a channel through the plate 9 or partly through the rod 10 and therefore a separate pump may be dispensed with. A non-return valve is preferably arranged in the fluid conduit to avoid return flow of the fluid between said surfaces during the atomising contraction of the body 11.

In this case the rod 10 may also be made of a piezoelectric material such that the piezoelectric deformations of the rod 10 and the body 11 cooperate to bring about the atomising abutment of the surfaces and the fluid pumping expansion of the volume of the space between said surfaces.

Referring now to Fig. 3, a fixed plate 14 is attached to a rod 15 attached to a plate 16 and two piezoelectric bodies 17 and 18 are arranged between the said plates such that piezoelectric deformation of said bodies in the direction of the arrows R4 and R5 causes atomising abutment of the mutually facing surfaces of said bodies and fluid flow pumping action in the space between the rod 15 and the body 17 in a manner as described in connection with the embodiment in Fig. 1.

In the embodiments shown in Figs. 1-3 the bodies, plates and rods are shown as having circular cylindrical cross sectional configurations. Obviously the cross sections may be polygonal as long as congruent abutting surfaces are formed for the fluid atomisation.

In Fig. 4 an embodiment having conical atomising surfaces is shown. A cylindrical piezoelectric body 18 having a conical tapered bore 18a for receiving a conical piezoelectric body 19 having a surface 19a facing the surface of the bore 18a.

Piezoelectric contraction and expansion of the bodies 18 and 19 in the direction of the arrows R6, R7 and R8 will cause atomisation of a fluid arranged between the bodies as indicated by the numeral 20 thus creating an annular spray of atomised 12

fluid particles.

In Fig. 5 an embodiment utilizing a so-called "end-supported, center driven Bender Bimorph" (trade name of Morgan Matroc Inc., Vernitron Division) piezoelectric elongate rectangular body 21 fixedly supported at points 21a near the ends thereof flexes piezoelectrically at the center in the direction of the arrows R9 such that a plate 25 attached to the body 21 by means of a rod 24 is displaced to and fro in the direction of the arrows R9 relative to a cylindrical body 22 attached to the body 21 by means of rods 23 such that a fluid portion arranged between the mutually facing surfaces of the plate 25 and the body 22 is atomised as indicated at 26.

In Fig. 6 a fixedly arranged plate 27 is attached to a rod 28 attached to a plate 29. A cylindrical body 30 is attached to a cylindrical piezoelectric body 31. Piezoelectric deformation of the body 31 in the directions of arrows R10 will cause the mutually facing surfaces of plate 29 and body 30 to atomise a fluid portion arranged therebetween as indicated at 32.

In Fig. 7 a piezoelectric rod 33 is arranged between two end surfaces of a generally U-shaped rod 34. Piezoelectric deformation of the rod 33 in the directions of arrows R11 will cause atomisation of fluid portions arranged between the mutually facing end surfaces of the rod 33 and the rod 34 as shown at 35 and 36.

Figs. 8-12 illustrate embodiments utilizing spherical surfaces in various ways.

In Fig. 8, a block 37 is provided with a semi-spherical hollow 38 for fixedly receiving a semi-spherical shell 39 of a piezoelectrical material arranged for piezoelectrical deformation in the direction of the arrows R12 and R13, i.e. radially. The inner surface of the shell 39 faces the outer surface of a sphere 40 fixedly attached to the block 37 by means of a rod 41. Piezoelectric deformation of the shell 39 causes atomisation of a fluid portion arranged between said surfaces as indicated at 42.

In Fig. 9 a piezoelectric sphere 43 is fixedly attached to a plate 44 fixedly attached to a rod 45 fixedly attached to a spherically hollowed out block 46 such that 13

piezoelectric deformation of the sphere 44 will atomise fluid portions arranged between the lower sphere surface and the hollow surface as indicated at 47.

Figs. 10-12 illustrate variations of the embodiment of Fig. 9 utilizing a solid semi - sphere 48, a spherical shell 49 and a semi-spherical shell 50, respectively.

Obviously, the surfaces of the spherical body and spherical hollow may be replaced by mutually congruent surfaces of cones, ellipsoids, cylinders and so on. The abutting surfaces may also be a small portion of a sphere, ellipsoid, cone and so on.

Dotted lines 51 in Figs. 8 and 10-12 indicate an advantageous sharpening of the exit edges of the atomising surfaces by removing the portions of the sphere or block outside the dotted lines such that the atomised droplets may escape freely and not adhere to the surface of the sphere or block. This feature is also advantageous in that it seems to promote formation of smaller droplets in the atomised fluid.

Shallow flow channels may be machined in the atomising surfaces radiating from the centre towards the free edges thereof to promote the formation of thin radially extending fluid threads or streams thereby controlling the fluid flow outwards to said edges, a flow that takes place under a pressure of several hundred Bar.

Referring now to Fig. 13, two piezoelectric bodies 52 and 53 are arranged for abutting the mutually facing surfaces thereof to atomise portions of fluid sequentially positioned between same as discussed above. So as to distribute the atomised fluid spatially so as to reduce agglomeration of droplets by collision between previously and posteriorly formed droplets, the atomisation position of the mutually facing surfaces is displaced up and down while the atomisation takes place by subjecting the lower body 52 to a varying electrical voltage such that the level of the atomising surface 52a thereof is at different heights above the base surface by deforming the body 52 in the directions of the arrows R12.

Simultaneously, the body 53 is subjected to a varying electrical voltage superimposed on the alternating voltage for the atomising contractions and expansions 14

described above such that said body is deformed in the direction of the arrows R13 such that the surface 53a moves from an atomising position abutting the surface 52a and a fluid introduction position spaced therefrom while also altering the mean height of the surface 53a above the base 54 in synchronization with the corresponding height variation of the surface 52a.

Hereby, the atomisation height of the surfaces 52a and 53a above the base 54 is displaced up and down such that the droplets formed in sequential atomising strokes have less tendency to collide and agglomerate as a result of the enhanced spatial distribution of the droplets formed in sequential atomisation strokes of the surfaces 52a and 53a.

In all the embodiments described above the fluid to be atomised is supplied to the region between the atomisation surfaces through a channel extending through one or both of the bodies comprising the atomisation surface or surfaces and ending in one or more apertures on said surface or surfaces. The fluid may be supplied to the surfaces by active pumping by any suitable pumping means or by capillary effect as usually the volume of the individual fluid portions to be atomised is small, for instance 0.1-0.2 microlitres.

In the embodiment shown in Fig. 9, the sphere 43 may have an internal cavity and contain fluid in the cavity, the fluid being squeezed out to the region between the atomising surface through channels communicating the cavity with said region during the piezoelectric contraction of the sphere 43. This could also be the case for the spherical bodies in Figs. 10-12.

In Fig. 9 the sphere 43 could also consist of an outer spherical shell enveloping an inner concentric sphere and defining a fluid space therebetween communicating with the atomising surface through apertures in the outer shell. The piezoelectric deformation of the inner sphere relative to the piezoelectric deformation of the outer shell could be synchronized and dimensioned such that a pumping effect is achieved thereby and a non-return affect may be achieved by the inner sphere occluding the apertures during the atomisation abutment of the atomising surfaces. 15

The fluid may also be pumped to the atomisation region by means of a piezoelectric pump, for instance as shown in Fig. 14.

Referring now to Fig. 14, three stages in the operation of a piezoelectric pump according to the invention are shown. Three piezoelectric bodies 54, 55 and 56 are arranged in a row in a fluid conduit 57. In the uppermost stage, the bodies 54 and 55 are fully piezoelectrically contracted while the body 56 is fully piezoelectrically expanded such that the body 56 fully occludes the fluid conduit 57 as the entire edge of the body 56 abuts the interior surface of the conduit 57. Fluid can freely flow past the body 54 as indicated by the arrow R14.

In the middle stage, the body 54 is fully expanded so as to totally occlude the conduit 57. The body 55 is still fully contracted, and the body 56 is now also fully contracted. Thus the body 54 functions as a non-return valve.

In the lowermost stage, the pumping stage, the body 54 is still fully expanded and the body 56 is also fully expanded while the body 55 now also is fully expanded in a manner achieving a larger overall volume of the body 55 in the conduit 57. Hereby, fluid is displaced past the body 56 in the direction of the arrow R15. The cycle is then repeated whereby a portion of fluid corresponding to the piezoelectric volume increase of the body 55 is pumped through the conduit 57 in the direction of the arrows.

The body 55 is preferably a shell having a considerable cavity such that an appreciable overall volume variation may be achieved piezoelectrically. Certain solid ceramic piezoelectric bodies also achieve an overall volume variation, eg. as described in the publication "Piezoelectric Technology Data for Designers" published by Morgan Matroc Inc., Vernitron Division.

Referring now to Fig. 15, a plate 58 is attached to a rod 59 extending through a bore in a body 60 having an atomisation surface facing an atomisation surface of the plate 58. The rod 59 is provided with piezoelectric bodies 61 and 62 fixedly 16

attached thereto. The plate 58 and the rod 59 are connected to not shown reciprocating means for moving the plate 59 to and fro in the direction of the arrows R16 for atomising fluid between said surfaces as shown at 63. The reciprocating means may be of any suitable type including piezoelectric means.

The piezoelectric bodies 61 and 62 function as a pump means for pumping fluid portions to the atomising region between said atomising surfaces in the direction of the arrows R17.

When the plate 58 moves away from the body 60, the body 61 is piezoelectrically expanded to occlude the bore in the body 60 and the body 62 is in its contracted state allowing fluid to be pumped into the atomising region. When the plate 58 moves towards the body 60 for atomising the fluid therebetween, the body 62 is piezoelectrically expanded occluding the bore and functioning as a non-return valve while the body 61 is in its contracted state. Hereby, the reciprocating motion of the plate 58 and rod 59 together with the synchronized piezoelectrical deformation of the bodies 61 and 62 functions as a pump and non-return valve for sequentially locating a portion of fluid between the atomising surfaces.

Referring now to Figs. 16-17, a body 64 that may be piezoelectric as shown or of any other suitable rigid material and a piezoelectric body 65 are alignedly arranged between two fixed frame means 66 and 67. The body 65 is partly inserted in a fluid container 68 through an aperture 69. A sealing means 69 such as an elastic membrane or an O-ring is arranged between the body 65 and the edge of the aperture 69 such that no fluid from the container 68 can leak past the sealing means. The container 68 is provided with an inlet aperture 71 for admitting fluid in the direction of the arrow R18 through a non-return valve 72 under a pressure sufficient to ensure that the container always is totally filled with fluid.

A fluid flow channel 73 extends through the body 65 for fluid flow from the container 68 to the atomising surface 74 of the body 65. An optional non-return valve 75 is arranged in the channel 73. 17

In operation, application of suitable electrical alternating voltage to the two bodies 64 and 65 will cause atomising reciprocating movement of the two surfaces as described above. In the contracted state of the body 65 shown in Fig. 17 the volume of the part of the body 65 immersed in the fluid in the container is larger than in the expanded state shown in Fig. 16. Hereby, a portion 76 of the fluid is forced out of the container 68 through the channel 73 as the non-return valve 72 does not allow any of the displaced fluid volume to flow back through the aperture 71. The portion of liquid is thereafter atomised as indicated at 77 in Fig., 16 when the bodies 64 and 65 move to the piezoelectrically expanded state thereof.

The non-return valve 75 prevents the fluid portion 76 from flowing back into the channel 73 during movement of the body 65 from the contracted to the expanded state thereof. Depending on the amount of fluid 76 pumped in each atomising stroke and on the configuration of the atomising surfaces as well as the distribution of the fluid portion 76 on the surface 74, a sufficient amount of fluid will remain on the surface 74 even though the non-return valve is dispensed with.

It should be noted that the pumping device according to the invention shown in Figs. 16-17 may obviously also be utilized in any other pumping application, particularly where relatively small rates of fluid flow are desired.

The flow rate of the pumping device may be altered by altering the intensity and frequency of the electrical alternating voltage applied as well as the depth of immersion of the body 65 in the container 68.

Naturally, the outlet for pumped fluid does not necessarily have to be through the body 68 but may be through any aperture leading out of the container 68.

For suitable shapes and sizes of the container and the flow outlet, the distance from flow outlet to the body 65 relative to the distance of the inlet outlet from said body as well as the frequency and intensity of the applied electrical alternating voltage it may be acceptable to also dispense with the non-return valve 72. 18

Referring now to Figs. 18-20, a medicinal inhaler housing 76 is provided with a medicinal dispensing container 77 with an activating push button 78 and an outlet nozzle 79 having a built in non-return valve. The fluid to be atomised is dispensed from the nozzle 79 in a manner well known in the art.

The outlet nozzle 79 communicates with a fluid container 80 equivalent to the fluid container 68 of Figs. 16-17 through an aperture 81 such that the container 80 at all times is kept completely filled with fluid at the pressure of the fluid in the container 77.

A piezoelectric body 83 equivalent to the body 65 in Fig. 16 is immersed in the fluid in the container, an O-ring 82 preventing leakage of fluid between the container wall and the body 81. The body 83 is for instance a piezoelectric multilayer (stacked) ceramic actuator type 711/3/xxxx/10 from Morgan Matroc Limited, Wrexham, UK and is provided with a bore 84 in which a rod 85 is arranged. The rod 85 extends into a second piezoelectric body 86, for instance a piezoelectric multilayer actuator type 711/3/xxxx/07 from the same company. The rod 85 is attached to a plate 87 of steel by means of a screw 88. The rod 85 is provided with a longitudinal bore 89 communicating with a bore 90 communicating with the interior of the container 80. A non-return valve 91 of the rubber sleeve type is arranged in the bore 89, and outlet apertures 92 for fluid flow from the bore 89 to the atomising surface 93 are provided at the end of the bore 89. Resilient seals 94 are provided between the rod 85 and the interior surface of the bore 84 to prevent fluid from penetrating the interior of the stacked piezoelectric actuators 83 and 86.

An electric battery 95 for powering the device is arranged in the housing 76 and electrically connected to a printed circuit 96 for controlling the various functions of the atomiser. A transformer 97 connected to the printed circuit 96 supplies the pulsed voltage to the actuators 83 and 86 through an electrical conduit 98.

A vane type circuit breaker 99 is arranged in an air flow passage through the housing 76 for activating the atomising function by contacting a contact 100 when air is sucked through the air flow passage by a patient sucking air through the 19

passage by means of a mouthpiece in the direction of the arrows R19 and R20.

In use, a patient sucks air through the mouthpiece 101 after depressing the push button 78 whereby medicinal fluid is released through the nozzle 79 into the con- tainer 80 while the circuit breaker 99 contacts the contact 100 so as to initiate the atomising deformations of the actuators 83 and 86 and the pumping action of the actuator 83 as described above in connection with Figs. 16 and 17.

When utilizing the atomising device for medicinal fluids it is typically required that the amount of medicine atomised be around 25 microlitres per second, so a frequency of the alternating voltage applied of 250 Hz and a volume of each portion of fluid of approx. 0.1 microlitres per atomisation stroke will be chosen. These values may obviously vary according to the frequency chosen, the required rate of medicine administration by inhalation and so on. The portion of fluid on the pressing surface will typically have a diameter of approx. 1 -2mm.

The embodiment described above is currently preferred, but many different designs are possible as regards the piezoelectric elements, the pumping elements and so on without departing from the scope of the invention as defined in the appended claims.

Referring now to Fig. 21, the atomising device shown is identical to the one shown in Fig. 18 except that the pumping function for supplying portions of fluid to the atomising region between the piezoelectric actuators 83 and 86 is carried out by a piezoelectric pump 102 electrically controlled through a further electrical conduit 103. The pump 102 is for instance a Plastic Micropump supplied by Micro Montage, Soest, Holland.

In connection with treatment of asthma patients it is often desirable to supply two different inhaled substances sequentially such as a bronchio dilator followed by a steroid type therapeutic substance.

Currently it is necessary to utilize two separate inhalers giving rise to various 20

practical problems resulting in non-compliance with the therapeutic program.

Referring now to Fig. 22, a medical atomising device similar in function and configuration to the one shown in Figs. 18 and 21 comprises two containers 110 and 111 for two different medicinal fluids and arranged on a revolving disc 112 rotatably arranged on a pivot 113. The nozzle of the container 110 connects to a flow conduit 114 communicating with a pump mechanism 114a communicating with a flow channel 114b while the nozzle of the container 111 connects with a flow conduit 115 communicating with a pump mechanism 115a communicating with a flow channel 115b when the revolving disc 112 is rotated to bring the container 111 into the operative position thereof instead of the situation shown in Fig. 22 where the container 110 is in the operative position thereof.

In use, a patient will activate the push button of container 110 and inhale air through the inhaler first and thereafter rotate the disc 112 to bring the container 111 into the operative position thereof, whereafter the patient will depress the push button for container 111 and again inhale air through the inhaler thereby administering two separate substances sequentially with the same inhaler.

Although the inventive principle of providing two different inhalation substance sources in one single inhaler is particularly practical in connection with piezoelectric atomising devices it is also useful in connection with other inhalation substance dispensing devices as for instance two different aerosol containers or an aerosol container and a powder dispenser of the type well known in the art.

Referring now to Fig. 23, a variation of the double inhaler in Fig. 22 is shown where the two containers 110 and 111 are fixedly arranged side-by-side, the same elements having the same reference numerals as in Fig. 22. In this case the patient simply activates the two push buttons sequentially for administering the two dif- ferent inhalation substances sequentially.

Obviously, the above principle may be utilized to atomise a mixture of two or more fluids by delivering a portion of each fluid to the atomisation region simultaneously 21

or sequentially for each atomisation stroke.

In many applications it is desirable to produce a fog of very fine droplets for either wide distribution or concentrated distribution. For instance it is very useful for application of bactericides in food processing or storage facilities, agricultural field herbicides or insecticides, fire extinguishing liquid fog application and so on.

In such applications the energy requirements, reliability, space constraints, simplicity and costs are important factors.

By utilizing the piezoelectric atomisation according to the invention in such applications most of the above factors are optimized because of the low energy requirements, reliability, small space requirements, simplicity and low costs of the piezoelectric atomisation according to the invention.

Referring now to Figs. 24-25, a room 120 in for instance a meat storage or processing facility is provided with an array of piezoelectric atomising devices 121 arranged in a series of elongate frames 122 suspended immediately below the ceiling 123 of the room 120.

The atomising devices 121 are of the type shown in Figs. 16-17 with a bactericidal fluid being supplied through a conduit 124 from a pumping, power supply and control station 125. Ventilators 126 arranged adjacent each atomising device 121 distribute the atomised fluid droplets over the entire volume of air in the room by blowing the droplets out of the housing 127 of each device 121 through apertures 128 in each housing 127.

Hereby, a well distributed fog of small droplets of bactericide is created for preserving the food products in the room 120 in a simple, reliable, low energy and relatively inexpensive manner.

Obviously, the number and location of the atomising devices may be modified in many ways, and the dispersion of the atomised droplets formed may be carried out 22

by any suitable means such as for instance jets of compressed air, movement of the atomising devices relative to the surroundings and so on.

It will be obvious to those skilled in art to apply the above principle to other applications requiring a well distributed or concentrated fog of small droplets. For concentrated applications such as for fire fighting or herbicidal field spraying, the fog produced by several piezoelectrical atomising devices according to the invention may be collected in a single concentrated stream of air or gas instead of being widely dispersed as in Figs. 24-25.

The important feature of being able to produce very fine droplets with a small device requiring relatively small energy sources and requiring very little maintenance possibilitates the application of the principle of piezoelectric atomisation according to the invention to many diverse technological fields requiring distribution of a substance in small droplets. It will be obvious to those skilled in the art in different technological fields requiring such distribution to apply the principles of the invention. Among other technological fields not dealt with above are the fields of internal combustion with gasoline and diesel, perfumes, deodorants, room humidifiers, air conditioning, surface and textile cleaning, surface protection, surface coating and so on.

Referring finally to Fig. 26 illustrating schematically a control circuit for the atomising device in Fig. 21 , a pulse generator 140 supplies alternating pulsed voltage to a pulse amplifier 141 connected through a time delay circuit 142 to a fluid pump, for instance a piezoelectric pump. The pulse amplifier 141 is connected to the individual piezoelectrical elements forming part of two stacked piezoelectric amplifiers 144 and 145 in manner well known to those skilled in the art. By choosing the pulse frequency and time delay in a suitable manner a simple control of the sequential supply of fluid portions for atomisiation synchronized with the atomising strokes or pie- zoelectric deformations of the bodies 144 and 145 is obtained.

Claims

23CLAIMS

1. A method of atomising fluids comprising the steps of:

- providing a first surface and a second surface spaced from one another,

- locating a portion of fluid between the first and second surfaces,

- applying an electrical voltage to the at least one first body such that the at least one of said surfaces is displaced towards the other surface until the portion of fluid is impacted by at least a portion of each surface such that the fluid is pressed out from between the surfaces to the surroundings with a velocity sufficient to atomise at least part of the portion of fluid.

2. A method according to claim 1 , wherein the at least one surface is a surface of the at least one first body.

3. A method according to claim 1 or 2, wherein the material of the at least first body is a piezoelectric ceramic material and/or a piezoelectric crystal.

4. A method according to any of the preceding claims, wherein the portion of fluid is located between the first and second surfaces by a pumping means, preferably a piezoelectric pumping means.

5. A method according to claim 5, wherein the piezoelectric pumping means comprises the at least first body.

6. A method according to claim 4 or 5, wherein the method further comprises the steps of: 24

- providing control means for synchronising the pumping action of the pumping means with the displacement of the at least one of said surfaces towards the other surface,

- sequentially displacing the at least one of said surfaces towards the other surface and away from said other surface, and

- sequentially pumping a fluid portion to the region between said surfaces for each said displacement such that the fluid portion is impacted by the said two surfaces.

7. A method according to claim 5 or claim 6 as dependent on claim 5, wherein at least a portion of the at least first body is arranged within a container completely filled with the fluid to be atomised such that the piezoelectric deformation of said body by application of said electrical voltage causes the volume of the portion of the body within the container to increase.

8. A method according to any of the preceding claims and comprising the addi- tional step of locating a portion of at least one additional fluid between the first and second surfaces either simultaneously or sequentially

9. A method according to any of the preceding claims, wherein the fluid or fluids comprise a pharmaceutical substance for the therapeutic treatment of asthma, diabetes and the like.

10. A method according to any of the preceding claims, wherein the fluid or fluids are selected from a group of fluids comprising bactericides, herbicides, pesticides, fire control substances, cleaning substances, perfumes, deodorants, conservating substances, coating substances, diesel, gasoline and the like.

11. A method of pumping a fluid and comprising the steps of: 25

- providing a body having piezoelectric properties and arranged such that at least a portion of the body is located within a container completely filled with the fluid, and

- applying an electrical voltage to the body such that the piezoelectric deformation of the body causes the volume of the portion of the body within the container to increase.

12. A method of administering two or more pharmaceutic substances by inhalation and comprising the steps of:

- providing an inhaling device comprising two or more sources of pharmaceutic substance, each source having a substance dispensing means,

- providing means for entraining the pharmaceutic substances dispensed from each substance source in a gas flow emanating from the inhalation device,

13. A method according to claim 12, wherein the two or more pharmaceutic substances are fluids, the method comprising the further steps of:

a.- providing the inhaling device with a first surface and a second surface spaced from one another,

b.- providing at least one first body having piezoelectric properties and being arranged and adapted for displacement of at least one of said surfaces towards the other surface when said first body is subjected to an electrical voltage,

c- locating a portion of a first fluid between the first and second surfaces,

d.- applying an electrical voltage to the at least one first body such that the at least one of said surfaces is displaced towards the other surface until the portion of first 26

fluid is impacted by at least a portion of each surface such that the first fluid is pressed out from between the surfaces to the surroundings with a velocity sufficient to atomise at least part of the portion of first fluid, and

e.- repeating steps c-d with a portion of a further fluid.

14. A fluid atomising device comprising:

15. A device according to claim 14, wherein the at least one of said pressing surfaces is a surface of the at least one body.

16. A device according to claim 14 or 15, wherein the first pressing surface is a surface of a first body having piezoelectric properties and the second pressing surface is a surface of a second body having piezoelectric properties, the electrical means comprising means for applying an electrical voltage to each of the first and second bodies.

17. A device according to any of the claims 14-16, wherein the material of the at least first body is a piezoelectric ceramic material and/or a piezoelectric crystal.

18. A device according to any of the claims 14-17, wherein the at least one first 27

body comprises two or more discrete sub-bodies of a piezoelectric material arranged such that the individual piezoelectric deformations of the sub-bodies upon application of an electrical voltage to each of said sub-bodies are substantially added to achieve a resulting piezoelectric deformation of the at least one body for displacing the corresponding pressing surface.

19. A device according to any of the claims 14-18 and further comprising a fluid pumping means, preferably a piezoelectric pumping means, and fluid conduit means communicating the fluid pumping means with the atomising region between said pressing surfaces and with a source of fluid.

20. A device according to claim 19, wherein the piezoelectric pumping means comprises the at least one body.

21. A device according to claim 19 or 20, wherein the device further comprises control means for synchronising the pumping action of the pumping means with the displacement of the at least one of said pressing surfaces towards the other pressing surface.

22. A method according to claim 20 or claim 21 as dependent on claim 20, wherein at least a portion of the at least first body is arranged within a container completely filled with the fluid to be atomised.

23. A device according to any of the claims 14-22, wherein the fluid dispensing means comprise a fluid flow passage extending through the at least one body from an inlet aperture to an outlet aperture, the outlet aperture being located at the pressing surface of the at least one body.

24. A device according to any of the claims 14-23, wherein the device further comprises two or more sources of different fluids, and the dispensing means are adapted for sequentially and/or simultaneously dispensing a portion of each fluid to the atomising region between said pressing surfaces. 28

25. A piezoelectric fluid pump comprising a body having piezoelectric properties, electrical means for applying an electrical voltage to the body, a container for the fluid to be pumped, inlet means for supplying fluid to the container such that it constantly is totally filled with the fluid, the body being arranged such that at least a portion of the body is located within the container, and the piezoelectric properties of the body being such that application of the electrical voltage to the body causes a piezoelectric deformation of the body resulting in an increase of the volume of said portion of the body within the container.

26. An inhalation device for administering two or more substances to a person by inhalation and comprising:

27. A device according to claim 26, wherein the two or more substances are fluids, the device further comprising:

- at least one body having piezoelectric properties and being arranged and adapted for displacement of at least one of said pressing surfaces towards the other pressing surface to an atomisation position for both surfaces adjacent one another when said body is subjected to an electrical voltage, and 29