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 pump body having pump walls substantially cylindrical in shape and having a side wall closed by two end walls for containing a fluid;
an actuator disposed between the two end walls and being a first portion of a common end wall forming a first cavity and a second cavity, each cavity having a height (h) and a radius (r), wherein a ratio of the radius (r) to the height (h) is greater than about 1.2, the actuator operatively associated with a central portion of the common end walls and adapted to cause an oscillatory motion of the common end walls at a frequency (f), thereby generating radial pressure oscillations of the fluid within both the first cavity and the second cavity;
an isolator extending from the periphery of the actuator to the side wall as a second portion of the common wall and flexibly supporting the actuator;
a first aperture disposed at a location in the end wall associated with the first cavity and extending through the pump wall;
a second aperture disposed at another location in the end wall associated with the first cavity and extending through the pump wall;
a first valve disposed in one of the first and second apertures to enable the fluid to flow through the first cavity in one direction when in use;
a third aperture disposed at a location in the end wall associated with the second cavity and extending through the pump wall; and
a second valve disposed in the third aperture to enable the fluid to flow through the second cavity in both directions when in use.
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 the first valve is a flap valve.
4. The pump of claim 1 , wherein the second valve comprises two flap valves.
5. The pump according to claim 1 , wherein the 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 the 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 the differential pressure of the fluid outside the flap valve.
6. The pump of claim 1 , wherein the first cavity and second cavity are configured for a parallel pumping operation.
7. The pump of claim 1 , wherein the first cavity and a second cavity are configured for a series pumping operation.
8. The pump of claim 1 , wherein the actuator comprises a first piezoelectric disc and either a steel disc or a second piezoelectric disc.
9. The pump of claim 8 , wherein the isolator is bonded between the first piezoelectric disc and either the steel disc or the second piezoelectric disc.
10. The pump of claim 1 , wherein isolator is ring-shaped.
11. The pump of claim 1 , wherein the actuator is disc-shaped.
12. The pump of claim 1 , wherein the actuator has a diameter less than the diameter of the first cavity and a second cavity.
13. The pump of claim 1 , wherein the sidewall extends continuously between the end walls that form the first cavity and the second cavity.
14. 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.
15. The pump of claim 1 , wherein the isolator includes a plastic layer and one or more metal layers.
16. The pump of claim 1 , wherein the isolator has a thickness between about 10 microns and about 200 microns.
17. The pump of claim 1 , wherein the ratio r/h is greater than about 20.
18. The pump of claim 1 , wherein the combined volume of the first cavity and the second cavity is less than about 10 ml.
19. The pump of claim 1 , wherein the 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.
20. The pump of claim 1 , wherein the lowest resonant frequency of, radial fluid pressure oscillations in the first cavity and the second cavity is greater than about 500 Hz when in use.
21. The pump of claim 1 , wherein the motion of the end walls is mode-shape matched to the pressure oscillation in the first cavity and the second cavity.
22. The pump of claim 1 , 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 the center of the end wall associated with the first cavity.
23. The pump of claim 1 , wherein the ratio h 2 /r is greater than 10 −7 meters.