Nebulizer

• US 20030192532A1
• Filed: 04/12/2002
• Published: 10/16/2003
• Est. Priority Date: 04/12/2002
• Status: Abandoned Application

• Current Assignee: Hopkins, Andrew David
• Original Assignee: Hopkins, Andrew David
• Inventors: Hopkins, Andrew David
• Application Number:
  US10/121,237
• Publication Number:
  US 20030192532A1
• Time in Patent Office: Days
• US Class Current: 128/200.14
• CPC Class Codes: A61M 11/005 using ultrasonics spraying or atomising liquids using ultrasonic vibrations in general B05B17/06
• CPC Class Codes: A61M 15/0085 using ultrasonics spraying or atomising liquids using ultrasonic vibrations in general B05B17/06
• CPC Class Codes: A61M 2206/16 Rotating swirling helical flow, e.g. by tangential inflows
• CPC Class Codes: A61M 2206/18 Coaxial flows, e.g. one flow within another

Abstract

The present invention relates to a nebulizer comprising an electrically energizable ultrasonic transducer having an oscillation frequency dependent current and voltage characteristic exhibiting the occurrence of a minimum magnitude of current through the transducer at an anti-resonance frequency of the transducer, the voltage across the transducer increasing with an increase in frequency within a range of frequencies including said anti-resonance frequency. The nebulizer further comprises a transducer drive system for generating a drive signal for energising the transducer, the drive system comprising oscillation frequency control means operable to maintain the frequency of the drive signal at a specific frequency within said range of frequencies by reference to the variation of both current through the transducer and voltage across the transducer with a change of frequency within the said frequency range. The transducer is arranged to receive said drive signal and to cause physical vibrations in fluid to be nebulized when energised by said drive signal. A transducer having a simple automatic frequency tuning system is thereby provided.

Claims

1. A nebulizer comprising:

an electrically energizable ultrasonic transducer having an oscillation frequency dependent current and voltage characteristic exhibiting the occurrence of a minimum magnitude of current through the transducer at an anti-resonance frequency of the transducer, the voltage across the transducer increasing with an increase in frequency within a range of frequencies including said anti-resonance frequency;

a transducer drive system for generating a drive signal for energizing the transducer, the drive system comprising oscillation frequency control means operable to maintain the frequency of the drive signal at a specific frequency within said range of frequencies by reference to the variation of both current through the transducer and voltage across the transducer with a change of frequency within the said frequency range, the transducer being arranged to receive said drive signal and to cause physical vibrations in fluid to be nebulized when energized by said drive signal.

2. A nebulizer as claimed in claim 1, wherein the oscillation frequency control means maintains the frequency of the drive signal at a magnitude at which the variation with frequency of a function of current through the transducer is zero.

3. A nebulizer as claimed in claim 2, wherein the function of current is such that the relationship of said function with frequency is identical to that of current through the transducer with frequency.

4. A nebulizer as claimed in claim 2, wherein the function of current has a zero variation with frequency at a frequency magnitude other than the anti-resonance frequency of the transducer.

5. A nebulizer as claimed in claim 4, wherein the function of current has a zero variation with frequency at a frequency magnitude at which the yield of fluid nebulized by the transducer is substantially maximized.

6. A nebulizer as claimed in claim 1, wherein the oscillation frequency control means comprises a comparator for determining the direction of change with frequency of the function of current through the transducer.

7. A nebulizer as claimed in claim 6, wherein the oscillation frequency control means comprises a comparator for determining the direction of change with frequency of voltage across the transducer.

8. A nebulizer as claimed in claim 7, wherein outputs from the two comparators are applied to an exclusive OR gate for determination of the frequency magnitude at which the function of current has a zero variation with frequency.

9. A nebulizer comprising means for inducing a swirling motion in nebulized fluid about a swirl axis as said nebulized fluid is extracted from the nebulizer, the angular velocity of the swirling fluid being sufficient to result in undesirably large nebulized particles moving in a direction offset to the direction of swirl and thereby away from the swirl axis.

10. A nebulizer as claimed in claim 9, wherein the means for inducing includes at least one vane.

11. A nebulizer as claimed in claim 9, wherein the at least one vane includes a radius of curvature which decreases in a direction towards the swirl axis.

12. A nebulizer comprising a demand prediction system which determines a period of a cyclical demand for nebulized fluid by monitoring fluid flow with detection means so as to determine the start of consecutive demand cycles and compensating for lag between the actual start of a demand cycle and the detected start of said cycle by calculating the start of a next demand cycle as being a length of time from the detected start of a current demand cycle where said length of time is equal to the determined period less a fixed length of time.

13. A nebulizer as claimed in claim 12, wherein the system includes means for determining when demand has ceased.

14. A nebulizer as claimed in claim 13, wherein the means for determining includes a calculation based on breathing rate.