Surgery – Liquid medicament atomizer or sprayer – Ultrasonic
Patent
1994-05-10
1996-09-03
Burr, Edgar S.
Surgery
Liquid medicament atomizer or sprayer
Ultrasonic
12820014, 12820312, A61M 1100
Patent
active
055514162
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a nebuliser such as an ultrasonic device used to generate a fine mist of therapeutic fluid which can be inhaled by a patient undergoing treatment. The invention further relates to a control system for optimising preset characteristics of the nebuliser.
It is known to produce a nebulised medicament using an ultrasonic transducer which may be an electrically driven piezo-electric crystal. The transducer produces a mechanical vibration which is transferred to a liquid body of medicament. Typically, the vibration may be in the ultrasonic range of the order of 1-2 megahertz. This vibration can cause cavitation, or violent motion, at the liquid surface and thereby generates a mist. It is known that an optimum mist particle size for efficient transfer of the drug to a patients lungs is of the order of 1 to 6 micrometers. It is also known that such nebulisers, or mist creators, have a variety of applications such as distributing cleaning agents in otherwise inaccessible locations and for facial massage or similar cosmetic/dermatological treatments. Also, whilst the words medicament and therapeutic drug are used it is to be understood that water can be inhaled in treatment of health disorders and is therefore included in the meaning of these words.
Several known techniques of nebulising a liquid are disclosed in U.S. Pat. No. 3,387,607 (Gauthier) which uses a transfer fluid to relay the ultrasonic vibration from the transducer to the drug. Gauthier teaches of a technique of focusing the ultrasonic compressional wave to optimise the density of mist created above the liquid body of drug. Density of nebulised fluid is also optimised by Gauthier by setting the transducer drive frequency near, but preferably slightly above its resonant frequency.
A nebuliser control system is disclosed in U.S. Pat. No. 4,319,155 (Omron) which controls the ultrasonic transducer output level using a variable pulse oscillating circuit. Omron varies the output level between two states, effectively "nebulisation on" and "nebulisation off" states, the mark/space ratio of the power signal thereby determines the quantity of nebulised fluid and therefore enables control of the rate of treatment.
A further known nebuliser is disclosed in European patent 174862 (Varian) which uses a method of sweeping through the third harmonic resonant frequency of about 3 MHz compared to the fundamental resonant frequency of about 1 MHz of a piezo-electric crystal. Additionally, the voltage across the crystal is pulsed on and off at a much lower frequency. EP 174862 does not disclose a method of locking onto an operating frequency but rather the crystal is cooled to maintain a constant resonant frequency.
Known devices do not disclose a technique of minimising the current drawn by the transducer drive circuitry. It is not known to drive an ultrasonic transducer at its anti-resonant frequency and optimise nebulisation and drive circuit power consumption in this state. It is not known to periodically scan a range of frequencies and lock onto an anti-resonant frequency thereby to compensate for variation in the anti-resonant frequency of a piezo-electric crystal during operation due, for example, to variation in physical conditions such as temperature. Accordingly, the present invention seeks to avoid or at least mitigate these and other problems of the prior art.
One aspect of the invention provides a nebuliser comprising a piezo-electric crystal transducer which converts an electrical drive signal into mechanical vibration to nebulise a liquid in mechanical contact with said transducer and a transducer drive system which causes said transducer to vibrate at or near its anti-resonant frequency and to maintain vibration at this frequency. The anti-resonant frequency being defined as the crystal frequency characterised by a maximum or elevated electrical impedance.
A feature of this aspect of the invention provides a nebuliser wherein said drive system comprises a nebuliser wherein the drive system comprises: drive signal such as to maintain
REFERENCES:
patent: 3804329 (1974-04-01), Martner
patent: 3866831 (1975-02-01), Denton
patent: 3989042 (1976-11-01), Mitsui et al.
patent: 4281484 (1981-08-01), Massa
patent: 4316580 (1982-02-01), Bodai
patent: 4318062 (1982-03-01), Mitsui et al.
patent: 4336509 (1982-06-01), Bernitz
patent: 4703213 (1987-10-01), Gasler
patent: 4823042 (1989-04-01), Coffey et al.
patent: 4939402 (1990-07-01), Hirayama et al.
patent: 4976259 (1990-12-01), Higson et al.
patent: 5216338 (1993-06-01), Wilson
Patent Abstracts of Japan, vol. 4, No. 180 12, Dec. 1980.
Patent Abstracts of Japan, vol. 12, No. 221 23, Jun. 1988.
Hopkins Andrew D.
Stimpson Philip G.
Burr Edgar S.
Deane, Jr. William J.
Evans Richard W.
Johnston Michael G.
Medix Limited
LandOfFree
Nebuliser and nebuliser control system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Nebuliser and nebuliser control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Nebuliser and nebuliser control system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1945003