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WO1990001997A1 - Generateur electronique a aerosol - Google Patents

Generateur electronique a aerosol Download PDF

Info

Publication number
WO1990001997A1
WO1990001997A1 PCT/GB1989/000944 GB8900944W WO9001997A1 WO 1990001997 A1 WO1990001997 A1 WO 1990001997A1 GB 8900944 W GB8900944 W GB 8900944W WO 9001997 A1 WO9001997 A1 WO 9001997A1
Authority
WO
WIPO (PCT)
Prior art keywords
cavity
aerosol generator
exit
transducer assembly
orifices
Prior art date
Application number
PCT/GB1989/000944
Other languages
English (en)
Inventor
Borge Riis Jensen
Original Assignee
P.A. Consulting Services Limited
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by P.A. Consulting Services Limited filed Critical P.A. Consulting Services Limited
Publication of WO1990001997A1 publication Critical patent/WO1990001997A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05B—SPRAYING APPARATUS; ATOMISING APPARATUS; NOZZLES
    • B05B17/00—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups
    • B05B17/04—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods
    • B05B17/06—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations
    • B05B17/0607—Apparatus for spraying or atomising liquids or other fluent materials, not covered by the preceding groups operating with special methods using ultrasonic or other kinds of vibrations generated by electrical means, e.g. piezoelectric transducers

Definitions

  • the present invention relates to an aerosol generator and more particularly to a low cost electronic aerosol generator.
  • Aerosol generators are used in numerous applications for dispensing of liquids, such as perfumes, pharmaceuticals insecticide, paints etc.
  • the most common principle used for generation of these aerosols is to force the liquid, using a drive gas such as freon, through a nozzle. This causes the liquid to break-up into individual droplets thus generating the aerosol.
  • an electrically controlled aerosol generator in the form of a droplet generator similar to those used for ink-jet printing.
  • the formation of individual droplets is controlled precisely by an electrical voltage pulse.
  • One system uses a piezoelectric device to compress the ink contained in a cavity. The compression of the ink in the cavity generates a pressure pulse, which travels towards a nozzle opening. If the amplitude of the pressure pulse is sufficiently high a droplet will be ejected from the nozzle. Once the oscillations of the ink in the cavity, caused by reflections of the pressure pulse, have died out, a new voltage pulse can be applied to the piezoelectric device and a new droplet ejected. It is possible to eject droplets at a frequency of a few kHz with these systems.
  • the present invention provides an aerosol generator comprising a reservoir for fluid to be dispersed and an exit cavity communicating with the reservoir, the exit cavity having a plurality of exit orifices and being coupled to a piezoelectric transducer assembly arranged to induce variations in pressure in the exit cavity, and a control circuit for driving the piezoelectric transducer assembly at one of its resonant frequencies.
  • the exit cavity and piezoelectric transducer assembly effectively act as a pump ejecting liquid droplets at the resonant frequency of the transducer assembly.
  • By operating at resonance and by using a large number of small exit orifices it is ensured that a high volume of liquid is ejected at high frequency resulting in efficient aerosol generation.
  • Typical operating frequencies are in the range 10-200 kHz, depending on the construction of the transducer assembly and the liquid-to be ejected.
  • the fluid pressure variations at the orifices caused by vibrations of the transducer assembly should be maximised. If the exit cavity is not appropriately constructed, the vibrations of the transducer assembly could merely cause turbulence at the exit orifices which is not sufficient to achieve droplet ejection.
  • the distance between the transducer assembly and the exit orifices is chosen to be very short to avoid acoustic vibrations in the liquid.
  • the distance between the transducer assembly and the exit orifices should be small relative to the wavelength of sound in the liquid to be dispersed. With such an arrangement acoustic vibrations are minimised and vibrations of the transducer assembly result directly in pressure variations at the exit orifices.
  • the exit cavity is constructed as a resonant cavity tuned to the resonant frequency of the transducer assembly whereby resonant standing waves are generated with a pressure antinode at a wall portion of the cavity.
  • the exit orifices are provided at this wall portion. The result is a high pressure variation at the exit orifices which results in synchronous ejection of droplets from the individual orifices. In this way it is possible to generate an aerosol consisting of several streams of droplets. With the generator tuned to eject droplets at resonance, the required electrical energy input is very low and the electronic drive circuit can be kept very simple.
  • the cavity is preferably a cylindrical tubular member closed at one end by a plate in which the exit orifices are formed and at the other end by the piezoelectric transducer assembly.
  • the tubular member will be very short; for the second embodiment the length of the tubular member will be selected to generate the required mode of oscillation.
  • Figure 1 shows a schematic drawing of a first embodiment of the invention
  • Figure 2 shows a more detailed drawing of the resonating pipe assembly of Figure 1;
  • Figure 3 shows a more detailed circuit diagram of the preferred drive electronics for the embodiment of Figure 1; and Figure 4, shows a schematic drawing of a second embodiment of the invention.
  • the aerosol generator consists an exit cavity in the form of a pipe section 1, typically of a round cross section, closed at one end by an orifice plate 2 and at the other end by a piezoelectric transducer assembly 3.
  • the pipe section 1 is connected via a filling tube 4, to a fluid reservoir 5, containing the liquid to be atomised.
  • the piezoelectric transducer 3, is electrically connected to an' oscillator circuit 6, including a battery 7 and a switch 8.
  • the piezoelectric transducer assembly 3 When the switch 8 is activated, the piezoelectric transducer assembly 3 is energized by the oscillator circuit 6 and caused to vibrate at its resonance frequency, and generate pressure waves in the liquid in the pipe section 1.
  • the length of the pipe 1 is chosen such that, a strong pressure oscillation within the liquid can be created due to resonating standing pressure waves.
  • an approximate antinode of a standing pressure wave can be generated at the orifice plate 2.
  • the orifice plate 2 is a thin plate, containing a multiple number of small orifices. The liquid will by capillary forces be drawn into each orifice, and form a meniscus on the outer surface of the orifice plate 2.
  • the reservoir 5 is preferably of a collapsible type, which compensates for the liquid volume which has been ejected.
  • the reservoir has side walls 5a formed as a bellows arrangement which collapses as the volume of fluid in the reservoir decreases.
  • the reservoir may simply comprise a collapsible bag.
  • FIG. 2 shows the resonating pipe assembly in more detail.
  • the preferred piezoelectric transducer assembly is a flexure construction, consisting of a round diaphragm, having a diameter D, onto which has been bonded a thin piezoelectric ceramic element 10.
  • the piezoelectric element 10 When the piezoelectric element 10 is activated with a voltage across its thickness, it will expand or contract, causing the diaphragm 9 to deflect inwards or outwards.
  • the mechanical resonance frequency, F r of this flexure element can be approximated as:
  • the length L of the pipe section 1 is chosen such that when the transducer assembly 3 vibrates at its resonance frequency, a resonating standing wave pattern is generated in the pipe section, resulting. approximately in a pressure antinode at the orifice plate 2 and a pressure node at the transducer 3.
  • the length L of the pipe can approximately be determined from the following expression: c
  • the orifice plate 2 is preferably produced by electroforming or chemical milling processes, allowing a multiple number of precise defined orifices to be implemented at low cost. Suitable dimensions for the orifices would be 20 jum diameter in a plate 40 ⁇ thick.
  • FIG 3 shows the diagram of a preferred electronic drive circuit for the aerosol generator.
  • the transducer oscillates in a self- excited mode reflecting the resonances of both the transducer and the pipe section.
  • the piezoelectric ceramic element 11 has three electrodes. It is an important aspect of the overall design, that at resonance the transducer impedance is at a minimum, when the correct standing wave pattern is generated in the pipe section 1. This allows the oscillator circuit to compensate automatically for changes in the resonance frequency due to temperature effects, or mechanical tolerances on the components.
  • this electronic drive circuit with other functions such as automatic dispensing at programmed time intervals, or a timer to give an exact dose every time the device is activated.
  • FIG. 4 The most important difference between the arrangements of Figures 1 and 4 is that in Figure 4 the resonating pipe has been replaced by a cavity 102.
  • Cavity 102 is preferably a circular pipe section closed at one end by an orifice plate 102 and at the other end by a piezoelectric transducer assembly 103.
  • the distance between the transducer assembly 3 and the orifice plate 2 is short in comparison to the wavelength of sound in the fluid to be dispensed.
  • the transducer assembly may be the same as that described above in relation to Figure 3.
  • the length L of the cavity may suitably be about 1mm.
  • the piezoelectric transducer assembly when a switch 108 is activated, the piezoelectric transducer assembly is energised by an oscillator circuit 106 to vibrate at its resonant frequency.
  • the oscillator circuit 106 is powered by a battery 107.
  • the reservoir 105 illustrated in Figure 4 comprises a collapsible bag but it could equally well comprise a bellows arrangement of the type shown in Figure 1.

Landscapes

  • Special Spraying Apparatus (AREA)

Abstract

Un générateur à aérosol comprend un réservoir (5) contenant du liquide à distribuer, ainsi qu'une cavité (1) de sortie comportant une pluralité d'orifices de sortie formés dans une plaque (2) à orifices. La cavité (1) est accouplée à un ensemble (3) à transducteur piézoélectrique agencé pour provoquer des variations de pression dans la cavité de sortie. Un cicuit de commande fait fonctionner l'ensemble à transducteur à sa fréquence résonante de sorte que des gouttelettes sont chassées simultanément des orifices à cette fréquence pour former un aérosol.
PCT/GB1989/000944 1988-08-16 1989-08-16 Generateur electronique a aerosol WO1990001997A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
GB888819473A GB8819473D0 (en) 1988-08-16 1988-08-16 Electronic aerosol generator
GB8819473.3 1988-08-16

Publications (1)

Publication Number Publication Date
WO1990001997A1 true WO1990001997A1 (fr) 1990-03-08

Family

ID=10642219

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/GB1989/000944 WO1990001997A1 (fr) 1988-08-16 1989-08-16 Generateur electronique a aerosol

Country Status (2)

Country Link
GB (1) GB8819473D0 (fr)
WO (1) WO1990001997A1 (fr)

Cited By (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991016997A1 (fr) * 1990-05-09 1991-11-14 Siemens Aktiengesellschaft Vaporisateur a ultrasons pour laque capillaire
EP0666053A1 (fr) * 1994-02-03 1995-08-09 AEG Hausgeräte GmbH Appareil d'entretien de sols
US5666977A (en) * 1993-06-10 1997-09-16 Philip Morris Incorporated Electrical smoking article using liquid tobacco flavor medium delivery system
EP0923957A1 (fr) * 1997-11-19 1999-06-23 Microflow Engineering SA Nébuliseur de goutelettes pour un Inhalateur thérapeutique
US6405934B1 (en) 1998-12-01 2002-06-18 Microflow Engineering Sa Optimized liquid droplet spray device for an inhaler suitable for respiratory therapies
WO2003066229A1 (fr) * 2002-02-07 2003-08-14 Brezhnev Vyacheslav Nikolaevic Procede de production d'aerosols/cavites-bulles de resonance
US7776241B2 (en) 2003-12-23 2010-08-17 Niro A/S Method and apparatus for producing micro particles

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2512743A (en) * 1946-04-01 1950-06-27 Rca Corp Jet sprayer actuated by supersonic waves
EP0049636A1 (fr) * 1980-10-06 1982-04-14 Matsushita Electric Industrial Co., Ltd. Pulvérisateur électrique de liquide
GB2099710A (en) * 1981-06-06 1982-12-15 Rowenta Werke Gmbh Inhalant device for an ultrasonic inhaler
JPS59199074A (ja) * 1983-04-26 1984-11-12 Matsushita Electric Ind Co Ltd 霧化装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2512743A (en) * 1946-04-01 1950-06-27 Rca Corp Jet sprayer actuated by supersonic waves
EP0049636A1 (fr) * 1980-10-06 1982-04-14 Matsushita Electric Industrial Co., Ltd. Pulvérisateur électrique de liquide
GB2099710A (en) * 1981-06-06 1982-12-15 Rowenta Werke Gmbh Inhalant device for an ultrasonic inhaler
JPS59199074A (ja) * 1983-04-26 1984-11-12 Matsushita Electric Ind Co Ltd 霧化装置

Non-Patent Citations (2)

* Cited by examiner, † Cited by third party
Title
PATENT ABSTRACTS OF JAPAN, Vol. 9, No. 66 (C-271) (1789), 26 March 1985; & JP-A-59199074 (Matsushita Denki Sangyo K.K.) 12 November 1984 *
Review of Scientific Instruments, Vol. 58, No. 7, July 1987, American Institute of Physics (New York, N.Y., US) N. ASHGRIZ et al.: " Development of a Controlled Spray Generator", pages 1291-1296 *

Cited By (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO1991016997A1 (fr) * 1990-05-09 1991-11-14 Siemens Aktiengesellschaft Vaporisateur a ultrasons pour laque capillaire
US5666977A (en) * 1993-06-10 1997-09-16 Philip Morris Incorporated Electrical smoking article using liquid tobacco flavor medium delivery system
EP0666053A1 (fr) * 1994-02-03 1995-08-09 AEG Hausgeräte GmbH Appareil d'entretien de sols
EP0923957A1 (fr) * 1997-11-19 1999-06-23 Microflow Engineering SA Nébuliseur de goutelettes pour un Inhalateur thérapeutique
US6196219B1 (en) 1997-11-19 2001-03-06 Microflow Engineering Sa Liquid droplet spray device for an inhaler suitable for respiratory therapies
EP1129741A2 (fr) 1997-11-19 2001-09-05 Microflow Engineering SA Dispositif de pulvérisation pour inhalateur
EP1149602A2 (fr) 1997-11-19 2001-10-31 Microflow Engineering SA Atomiseur pour un inhalateur adapté à des thérapies respiratoires
EP1149602A3 (fr) * 1997-11-19 2003-12-10 Microflow Engineering SA Atomiseur pour un inhalateur adapté à des thérapies respiratoires
EP1129741A3 (fr) * 1997-11-19 2003-12-10 Microflow Engineering SA Dispositif de pulvérisation pour inhalateur
US6405934B1 (en) 1998-12-01 2002-06-18 Microflow Engineering Sa Optimized liquid droplet spray device for an inhaler suitable for respiratory therapies
WO2003066229A1 (fr) * 2002-02-07 2003-08-14 Brezhnev Vyacheslav Nikolaevic Procede de production d'aerosols/cavites-bulles de resonance
US7776241B2 (en) 2003-12-23 2010-08-17 Niro A/S Method and apparatus for producing micro particles

Also Published As

Publication number Publication date
GB8819473D0 (en) 1988-09-21

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