Liquid spray apparatus and method

• US 5,823,428 A
• Filed: 05/16/1996
• Issued: 10/20/1998
• Est. Priority Date: 06/23/1994
• Status: Expired due to Term

• Current Assignee: TTP Group Plc
• Original Assignee: The Technology Partnership PLC (TTP Group Ltd.)
• Inventors: Sant, Andrew Jonathan, Humberstone, Victor Carey
• Primary Examiner(s): WELDON, KEVIN P
• Application Number:
  US08/646,271
• Time in Patent Office: 887 Days
• Field of Search: 239/596, 239/601, 239/4, 239/102.2, 239/558, 347/47, 347/68
• US Class Current: 239/4
• 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 17/0684 Wicks or the like
• CPC Class Codes: B41J 2202/15 Moving nozzle or nozzle plate

Abstract

A method of and apparatus for atomizing a liquid are disclosed, in which a liquid is caused to pass through tapered perforations (50) in a vibrating membrane (5) in the direction from that side of the membrane (5) at which the perforations (50) have a smaller cross-sectional area to that side of the membrane (5) at which the perforations (50) have a larger cross-sectional area.

Claims

1. A liquid droplet spray device comprising:

a perforate membrane having first face and a second face and first perforations;

an actuator, for vibrating the membrane; and

means for supplying liquid to the first face of the membrane, wherein

the first perforations in the membrane have a reverse taper, namely a larger cross-sectional area at the second face of the membrane from which liquid droplets emerge than the first face of the membrane.

2. A device according to claim 1, further including a liquid reservoir for containing the liquid at a reduced pressure at the liquid contacting first face.

3. A device according to claim 2, wherein the reduced pressure lies in the range of about zero to about a pressure determined by the liquid which is sufficient to draw air from the second face through the first perforations and through the fluid.

4. A device according to claim 1, wherein the perforations, on that face of the membrane away from which liquid droplets emerge, are not touching.

5. A device according to claim 1, wherein the actuator is a piezoelectric actuator.

6. A device according to claim 5, wherein the piezoelectric actuator is adapted to operate in the bending mode.

7. A device according to claim 1, wherein the means for supplying liquid to a surface of the membrane comprises a capillary feed mechanism.

8. A device according claim 1, wherein the means for supplying liquid to a surface of the membrane comprises a bubble-generator feed mechanism.

9. A device according to claim 1, wherein the perforations have a reverse taper.

10. A device according to claim 9, wherein the membrane further includes second perforations having a taper opposite the taper of the first perforations.

11. A device according to claim 10, wherein the second perforations are disposed around the outside of the first perforations.

12. A device according to claim 10, wherein second perforations supply liquid to the second face of the membrane.

13. A device according to claim 1, wherein the diameter of each perforation is about 1 capillary wavelength.

14. A device according to claim 1, wherein the actuator is arranged to vibrate said membrane such that the following relation is satisfied:

##EQU3## where;

φ

=the diameter of the tapered perforation at a selected point between the front and the rear face of the membrane

n=an integer

λ

_c =the wavelength of capillary waves in the liquid

σ

=fluid surface tension (at frequency f)

ρ

=fluid density

f=an operating frequency of the actuator.

15. A device according to claim 1, wherein the actuator is arranged to vibrate said membrane in a frequency range of about 20 kHz to about 7 MHz.

16. A method of atomising a liquid in which a liquid is caused to pass through tapered first perforations in a vibrating membrane in the direction from a first side of the membrane at which the first perforations have a smaller cross-sectional area to a second side of the membrane at which the first perforations have a larger cross-sectional area.

17. A method according to claim 16, further including establishing a reduced pressure in the liquid opposing the passage of the liquid through the first perforations from the first side to the second side.

18. A method according to claim 17, wherein the reduced pressure lies in the range of about zero to about a pressure determined by the liquid which is sufficient to draw air the first perforations of the membrane and through the fluid.

19. A method according to claim 16, wherein the actuator is a piezoelectric actuator and is caused to operate in the bending mode.

20. A method according to claim 16, wherein the liquid is supplied to the first dose of the membrane through a capillary feed mechanism.

21. A method according to claim 16, wherein the liquid is supplied to the first face of the membrane through a bubble-generator feed mechanism.

22. A method according to claim 16, wherein the liquid is supplied to the second face of said membrane from which liquid droplets emerge.

23. A method according to claim 16, wherein the liquid is supplied to the first face of said membrane.

24. A method according to claim 16, wherein the actuator causes said membrane to vibrate such that the following relation is satisfied:

##EQU4## where;

φ

=the diameter of the tapered perforation at a selected point between the front and the rear face of the membrane

n=an integer

λ

_c =the wavelength of capillary waves in the liquid

σ

=fluid surface tension (at frequency f)

ρ

=fluid density

f=an operating frequency of the membrane.

25. A method according to claim 16, wherein the membrane is vibrated at a frequency in the range of about 20 kHz to about 7 MHz.

26. A liquid droplet spray device comprising:

a perforate membrane having first face and a second face away from which droplets emerge;

an actuator, for vibrating the membrane; and

means for supplying liquid to at least one of the first and second faces of the membrane, wherein

perforations in the membrane have a reverse taper, namely a larger cross-sectional area at the second face of the membrane than the first face of the membrane.

27. The liquid droplet spray device of claim 26, wherein the droplets emerge from a liquid meniscus formed on at least one of the first face and the second face.