Methods and apparatus for controlling piezoelectric vibration

• US 6,546,927 B2
• Filed: 03/13/2001
• Issued: 04/15/2003
• Est. Priority Date: 03/13/2001
• Status: Expired due to Term

• Current Assignee: Stamford Devices Limited
• Original Assignee: Aerogen, Inc. (Nektar Therapeutics)
• Inventors: Litherland, Craig, Behzadian, Kamran, Klimowicz, Michael, Burnside, Rob
• Primary Examiner(s): Lewis, Aaron J.
• Assistant Examiner(s): MITCHELL, TEENA KAY
• Application Number:
  US09/805,498
• Publication Number:
  US 20020129813A1
• Time in Patent Office: 763 Days
• Field of Search: 128/200.14, 128/200.16, 128/200.18, 128/200.23, 128/202.25, 128/203.12, 128/203.15, 128/203.27, 239/3, 239/690, 239/706
• US Class Current: 128/200.16
• 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: B05B 12/081 responsive to the weight of a reservoir or container for liquid or other fluent material; responsive to level or volume of liquid or other fluent material in a reservoir or container
• CPC Class Codes: B05B 15/14 Arrangements for preventing or controlling structural damage to spraying apparatus or its outlets, e.g. for breaking at desired places; Arrangements for handling or replacing damaged parts
• CPC Class Codes: B05B 17/0646 Vibrating plates, i.e. plates being directly subjected to the vibrations, e.g. having a piezoelectric transducer attached thereto
• CPC Class Codes: B05B 17/0669 Excitation frequencies
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for

Abstract

A method for aerosolizing a liquid comprises providing an aerosol generator having a plate with a plurality of apertures and a piezoelectric element to vibrate the plate. Liquid is supplied to the plate, and the piezoelectric element is energized to vibrate the plate at an initial frequency. The energy level is adjusted to vibrate the plate at its instantaneous resonant frequency during aerosolization of the liquid.

Claims

1. A method for aerosolizing a liquid, comprising:

providing an aerosol generator comprising a plate having a plurality of apertures therein and a piezoelectric element disposed to vibrate the plate;

supplying a liquid to the plate;

energizing the piezoelectric element to vibrate the plate at an initial frequency;

adjusting energization of the piezoelectric element to vibrate the plate at a desired frequency during aerosolization of the liquid through the plurality of apertures;

energizing the piezoelectric element at to vibrate the plate at its resonant frequency at a first power level prior to supplying the liquid to the plate; and

increasing power level to a second power level when liquid is supplied to the plate.

2. A method according to claim 1, wherein the adjusting step comprises:

detecting a first value of an electrical characteristic of the piezoelectric element at the initial frequency;

energizing the piezoelectric element to vibrate the plate at a second frequency, the initial and second frequencies differing from each other by a predetermined amount;

detecting a second value of the electrical characteristic of the piezo electric element at the second frequency; and

comparing the first and second values of the electrical characteristics.

3. A method according to claim 2, wherein the electrical characteristic is selected from the group consisting of voltage, current and phase difference between voltage and current in the piezoelectric element.

4. A method according to claim 2, further comprising:

energizing the piezoelectric element at a third frequency, the second and third frequencies differing from each other by an amount dependent upon the comparison between the first and second values of the electrical characteristic.

5. A method according to claim 4, wherein the amount is substantially equal to the predetermined amount when the first and second values of the electrical characteristic are substantially equal.

6. A method according to claim 4, wherein the amount is less than the predetermined amount when the first and second values of the electrical characteristic are substantially unequal.

7. A method according to claim 6, wherein the amount differs from the predetermined amount in inverse proportion to a difference between the first and second values of the electrical characteristic.

8. A method according to claim 4, further comprising:

detecting a third value of the electrical characteristic of the piezoelectric element at the third frequency;

comparing the second and third values of the electrical characteristic; and

energizing the piezoelectric element at a fourth frequency, the third and fourth frequencies differing from each other by an amount dependent upon the comparison between the second and third values of the electrical characteristic.

9. A method according to claim 8, wherein the steps of detecting, comparing, and energizing are iterativley repeated.

10. A method according to claim 1, further comprising comparing a parameter indicative of instantaneous resonant frequency with a predetermined range of values.

11. A method according to claim 10, further comprising providing an indication when the parameter falls outside the predetermined range of values.

12. A method according to claim 1, wherein adjusting energization of the piezoelectric element is controlled by a phased locked loop circuit.

13. A method according to claim 1, wherein the desired frequency is the instantaneous resonant frequency of the plate.

14. A method according to claim 1, wherein the desired frequency is an anti-resonant frequency of the piezoelectric plate.

15. A method for aerosolizing a liquid, comprising:

providing an aerosol generator comprising a plate having a plurality of apertures therein and a piezoelectric element disposed to vibrate the plate;

supplying a liquid to the plate;

energizing the piezoelectric element to vibrate the plate at an initial frequency;

adjusting energization of the piezoelectric element to vibrate the plate at a desired frequency during aerosolization of the liquid through the plurality of apertures; and

monitoring a parameter indicative of instantaneous resonant frequency to detect any rapid change in instantaneous resonant frequency.

16. A method according to claim 15, further comprising:

reducing energy to the piezoelectric element upon detection of a rapid change in instantaneous resonant frequency, wherein back puff is reduced.

17. A method according to claim 15, further comprising:

providing an indication upon detection of a rapid increase in instantaneous resonant frequency.

18. A method according to claim 17, wherein the indication is an end of dose indication.

19. A method according to claim 15, further comprising:

reducing energization of the piezoelectric element upon detection of a rapid increase in instantaneous resonant frequency.

20. A method according to claim 15, wherein the parameter monitored is an impedance of the piezoelectric element.

21. A method according to claim 15, further comprising:

energizing the piezoelectric element at to vibrate the plate at a resonant frequency at a first power level prior to supplying the liquid to the plate.

22. A method according to claim 21, further comprising:

increasing power level to a second power level when liquid is supplied to the plate.

23. A method of controlling piezoelectric vibration in an apparatus comprising a piezoelectric vibrating element and a vibratable structure to which the piezoelectric vibrating element is attached, the method comprising:

energizing the piezoelectric vibrating element to vibrate the vibratable structure at a first frequency;

detecting a first value of an electrical characteristic of the piezoelectric vibrating element at the first frequency;

energizing the piezoelectric vibratable element to vibrate the vibratable structure at a second frequency, the first and second frequencies differing from each other by a predetermined amount;

detecting a second value of the electrical characteristic of the piezoelectric vibrating element at the second frequency;

comparing the first and second values of the electrical characteristic; and

energizing the piezoelectric element at a third frequency, the second and third frequencies differing from each other by a variable amount dependent upon the comparison made between the first and second values of the electrical characteristic.

24. A method according to claim 23, wherein the electrical characteristic is selected from the group consisting of voltage, current and phase difference between voltage and current in the piezoelectric vibrating element.

25. A method according to claim 24, wherein the variable amount is substantially equal to the predetermined amount when the first and second values of the electrical characteristic are substantially equal.

26. A method according to claim 25, wherein the variable amount is less than the predetermined amount when the first and second values of the electrical characteristic are substantially unequal.

27. A method according to claim 26, wherein the variable amount differs from the predetermined amount in inverse proportion to a difference between the first and second values of the electrical characteristic.

28. A method according to claim 23, further comprising:

detecting a third value of the electrical characteristic of the piezoelectric vibrating element at the third frequency;

comparing the second and third values of the electrical characteristic; and

energizing the piezoelectric vibrating element at a fourth frequency, the third and fourth frequencies differing from each other by an amount dependent upon the comparison made between the second and third values of the electrical characteristic.

29. A method according to claim 23, wherein the apparatus comprises a piezoelectric structure.

30. A method according to claim 23, further comprising supplying a liquid to the vibratable structure.

31. A method of determining degradation of a piezoelectric vibration device, the method comprising:

at a first time, determining a first resonant frequency of the a piezoelectric vibration device;

at a second time, determining a second resonant frequency of the a piezoelectric vibration device; and

comparing the first and second resonant frequencies to determine a difference, wherein the difference indicates degradation in the piezoelectric vibration device, wherein the degradation in the piezoelectric vibration device includes a crack in the piezoelectric vibration device;

wherein the first and the second resonant frequencies are determined when the piezoelectric vibration device is not loaded with fluid.

32. A method of determining degradation of a piezoelectric vibration device, the method comprising:

at a first time, determining a first resonant frequency of the a piezo electric vibration device;

at a second time, determining a second resonant frequency of the a piezoelectric vibration device; and

comparing the first and second resonant frequencies to determine a difference, wherein the difference indicates degradation in the piezoelectric vibration device, wherein the degradation in the piezoelectric vibration device includes a clog in the piezoelectric vibration device.

33. A method according to claim 32, wherein the first and the second resonant frequencies are determined when the piezoelectric vibration device is not loaded with fluid.

34. A method according to claim 32, wherein the degradation in the piezoelectric vibration device includes a crack in the piezoelectric vibration device.

35. A method for aerosolizing a liquid, comprising:

providing an aerosol generator comprising a plate having a plurality of apertures therein and a piezoelectric element disposed to vibrate the plate;

supplying a liquid to the plate;

energizing the piezoelectric element to vibrate the plate at an initial frequency;

adjusting energization of the piezoelectric element to vibrate the plate at a desired frequency during aerosolization of the liquid through the plurality of apertures;

and comparing a parameter indicative of an instantaneous resonant frequency with a predetermined range of values.

36. A method for aerosolizing a liquid, comprising:

providing an aerosol generator comprising a plate having a plurality of apertures therein and a piezoelectric element disposed to vibrate the plate;

supplying a liquid to the plate;

energizing the piezoelectric element to vibrate the plate at an initial frequency;

adjusting energization of the piezo electric element to vibrate the plate at a desired frequency during aerosolization of the liquid through the plurality of apertures, the desired frequency being an instantanteous frequency of the plate.

37. A method of aerosolizing a fluid for inhalation, comprising:

providing an aerosolizing device having an aerosolizing element, the aerosolizing element being vibrated to aerosolize a fluid, the aerosolizing device having a mouthpiece through which a user inhales aerosolized fluid;

vibrating the aerosolizing element at a resonant frequency;

measuring a first parameter related to the resonant frequency of the aerosolizing element during the vibrating step;

delivering a volume of the fluid to the aerosolizing element;

aerosolizing the fluid by vibrating the aerosolizing element, the aerosolized fluid being delivered to the user through the mouthpiece;

measuring a second parameter related to the resonant frequency after initiating the aerosolizing step; and

determining when the volume of fluid has been delivered by comparing the first and second parameters.

38. The method of claim 37, wherein:

the measuring steps are carried out with the first and second parameters each being a parameter selected from the group of parameters consisting of frequency and impedance.

39. The method of claim 37, wherein:

the measuring step for the first parameter is carried out before the delivering step.

40. The method of claim 37, further comprising the step of:

vibrating the aerosolizing element after the delivering step at a power such that liquid is not aerosolized by the vibrating element.

41. The method of claim 37, wherein:

the vibrating step is carried out with the aerosolizing element not being loaded with fluid.