Disc pump with advanced actuator
A two-cavity pump having a single valve in one cavity and a bidirectional valve in another cavity is disclosed. The pump has a side wall closed by two end walls for containing a fluid. An actuator is disposed between the two end walls and functions as a portion of a common end wall of the two cavities. The actuator causes an oscillatory motion of the common end walls to generate radial pressure oscillations of the fluid within both cavities. An isolator flexibly supports the actuator. The first cavity includes the single valve disposed in one of a first and second aperture in the end wall to enable fluid flow in one direction. The second cavity includes the bidirectional valve disposed in one of a third and fourth aperture in the end wall to enable fluid flow in both directions.
1. A pump comprising:
a side wall substantially cylindrical in shape;
a first end wall and a second end wall closing the side wall for containing a fluid;
an actuator disposed between the first end wall and the second end wall;
an isolator extending from a periphery of the actuator to the side wall;
a first cavity adjacent the first end wall;
a second cavity adjacent the second end wall;
a first aperture disposed in the first end wall;
a second aperture disposed in the first end wall;
a first valve disposed in either one of the first aperture and the second aperture;
a third aperture disposed in the second end wall; and
a second valve disposed in the third aperture and configured to enable fluid to flow through the second cavity in both directions;
wherein the actuator is adapted to cause an oscillatory motion of the actuator to generate radial pressure oscillations of the fluid within the first cavity and the second cavity.
2. The pump of claim 1 , wherein the radial pressure oscillations include at least one annular pressure node in response to a drive signal being applied to the actuator.
3. The pump of claim 1 , wherein a frequency of the oscillatory motion is equal to the lowest resonant frequency of radial pressure oscillations in the first cavity and the second cavity when in use.
4. The pump of claim 1 , wherein the first aperture and the second aperture extend through the first end wall.
5. The pump of claim 1 , wherein the third aperture extends through the second end wall.
6. The pump of claim 1 , wherein the first valve is a flap valve.
7. The pump of claim 1 , wherein the second valve comprises two flap valves.
8. The pump according to claim 1 , wherein at least one of the first valve and the second valve is a flap valve comprising:
a first plate having first apertures extending generally perpendicular through the first plate;
a second plate having first apertures extending generally perpendicular through the second plate, the first apertures being substantially offset from the first apertures of the first plate;
a sidewall disposed between the first and second plate, the sidewall being closed around a perimeter of the first and second plates to form a cavity between the first and second plates in fluid communication with the first apertures of the first and the second plates; and
a flap disposed and moveable between the first and second plates, the flap having apertures substantially offset from the first apertures of the first plate and substantially aligned with the first apertures of the second plate;
whereby the flap is motivated between the first and second plates in response to a change in direction of a differential pressure of the fluid outside the flap valve.
9. The pump of claim 1 , wherein the first cavity and second cavity are configured for a parallel pumping operation.
10. The pump of claim 1 , wherein the first cavity and a second cavity are configured for a series pumping operation.
11. The pump of claim 1 , wherein the actuator comprises a first piezoelectric disc and either a steel disc or a second piezoelectric disc.
12. The pump of claim 11 , wherein the isolator is bonded between the first piezoelectric disc and either the steel disc or the second piezoelectric disc.
13. The pump of claim 1 , wherein isolator is ring-shaped.
14. The pump of claim 1 , wherein the actuator is disc-shaped.
15. The pump of claim 1 , wherein the actuator has a diameter less than the diameter of the first cavity and a second cavity.
16. The pump of claim 1 , wherein the side wall extends continuously between the first end wall and the second end wall.
17. The pump of claim 1 , further comprising a recess in the side wall for slidably receiving the isolator whereby the isolator is free to move within the recess when the actuator vibrates.
18. The pump of claim 1 , wherein the isolator includes a plastic layer and one or more metal layers.
19. The pump of claim 1 , wherein the isolator has a thickness between about 10 microns and about 200 microns.
20. The pump of claim 1 , wherein a combined volume of the first cavity and the second cavity is less than about 10 ml.
21. The pump of claim 1 , wherein the actuator oscillatory motion is mode-shape matched to the radial pressure oscillations in the first cavity and the second cavity.
22. The pump of claim 1 , wherein each cavity has a height (h) and a radius (r), wherein a ratio of the radius (r) to the height (h) is greater than about 1.2 and less than about 50.
23. The pump of claim 22 , wherein each cavity has a height (h) and a radius (r), wherein a ratio of the radius (r) to the height (h) is greater than about 20 and less than about 50.
24. The pump of claim 22 , wherein a one of the first aperture and the second aperture that does not contain the first valve is located at a distance of 0.63r plus or minus 0.2r from a center of the first end wall.
25. The pump of claim 22 , wherein a ratio
h
2
r
is greater than 10 −7 meters and less than about 10 −3 meters.