U.S. patent application number 09/220310 was filed with the patent office on 2001-08-16 for piezoelectric micropump.
Invention is credited to BOUTON, CHAD E., PETERS, RICHARD D., ZIMLICH JR., WILLIAM C..
Application Number | 20010014286 09/220310 |
Document ID | / |
Family ID | 22823034 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010014286 |
Kind Code |
A1 |
PETERS, RICHARD D. ; et
al. |
August 16, 2001 |
PIEZOELECTRIC MICROPUMP
Abstract
A piezoelectric micropump is disclosed for pumping fluid from a
container to a delivery point in low volumes and at controlled flow
rates. The pumping action is created by movement of two or three
diaphragms. The movement of each diaphragm is caused by expansion
and contraction of an attached piezoelectric actuator. Coordination
of the movement of the diaphragms creates unidirectional flow of
the fluid. The piezoelectric actuators are cantilevered between the
pump body and the diaphragms to provide greater deflection of the
diaphragms. The piezoelectric actuators preferably are
piezoelectric bimorphs such that the diaphragms can function as
both seals and pumps.
Inventors: |
PETERS, RICHARD D.;
(GAHANNA, OH) ; BOUTON, CHAD E.; (DUBLIN, OH)
; ZIMLICH JR., WILLIAM C.; (DUBLIN, OH) |
Correspondence
Address: |
INTELLECTUAL PROPERTY DEPARTMENT
PORTER WRIGHT MORRIS & ARTHUR
28TH FLOOR
41 SOUTH HIGH STREET
COLUMBUS
OH
432156194
|
Family ID: |
22823034 |
Appl. No.: |
09/220310 |
Filed: |
December 23, 1998 |
Current U.S.
Class: |
417/53 ; 417/322;
417/413.2 |
Current CPC
Class: |
F04B 43/046
20130101 |
Class at
Publication: |
417/53 ;
417/413.2; 417/322 |
International
Class: |
F04B 001/00; F04B
017/00; F04B 035/00 |
Claims
We claim:
1. A micropump for pumping a fluid from a fluid container to a
delivery point, comprising: a pump body, said pump body having a
passageway therethrough from said fluid container to said delivery
point, said pump body having first, second, and third cavities
intersecting with said passageway; a first diaphragm covering said
first cavity, said first diaphragm opening and closing said
passageway as said first diaphragm is raised and lowered; a first
diaphragm clamp for securing said first diaphragm to said pump
body; a first cantilevered piezoelectric actuator for raising and
lowering said first diaphragm, said first cantilevered
piezoelectric actuator having a first end and second end, said
first end being operatively connected to said first diaphragm; a
first actuator clamp for securing said second end of said first
cantilevered piezoelectric actuator to said pump body; a second
diaphragm covering said second cavity, said second diaphragm
opening and closing said passageway as said second diaphragm is
raised and lowered; a second diaphragm clamp for securing said
second diaphragm to said pump body; a second cantilevered
piezoelectric actuator for raising and lowering said second
diaphragm, said second cantilevered piezoelectric actuator having a
first end and second end, said first end being operatively
connected to said second diaphragm; a second actuator clamp for
securing said second end of said second cantilevered piezoelectric
actuator to said pump body; a third diaphragm covering said third
cavity, said third diaphragm opening and closing said passageway as
said third diaphragm is raised and lowered, said third diaphragm
being clamped to said pump body by said first diaphragm clamp; a
third cantilevered piezoelectric actuator for raising and lowering
said third diaphragm, said third cantilevered piezoelectric
actuator having a first end and second end, said first end being
operatively connected to said third diaphragm, said second end of
said third cantilevered piezoelectric actuator being clamped to
said pump body by said first actuator clamp; and, an electronic
control circuit for supplying voltages to said first, second, and
third cantilevered piezoelectric actuators for raising and lowering
said first, second, and third diaphragms, thereby promoting a flow
of said fluid through said passageway.
2. The micropump of claim 1 wherein said pump body has a first side
and a second side, said first and third cavities being on said
first side of said pump body and said second cavity being on said
second side of said pump body.
3. A micropump for pumping a fluid from a fluid container to a
delivery point, comprising: a pump body, said pump body having a
passageway therethrough from said fluid container to said delivery
point, said pump body having first and second cavities intersecting
with said passageway; a first diaphragm covering said first cavity,
said first diaphragm opening and closing said passageway as said
first diaphragm is raised and lowered; a first piezoelectric
actuator for raising and lowering said first diaphragm, said first
piezoelectric actuator having a first end and second end, said
first end being operatively connected to said first diaphragm; a
second diaphragm covering said second cavity, said second diaphragm
opening and closing said passageway as said second diaphragm is
raised and lowered; securing means for securing said first and
second diaphragms to said pump body; a second piezoelectric
actuator for raising and lowering said second diaphragm, said
second piezoelectric actuator having a first end and second end,
said first end being operatively connected to said second
diaphragm; cantilever securing means for securing said second end
of said first piezoelectric actuator and said second end of said
second piezoelectric actuator to said pump body in a cantilever
manner; and, electrical means for applying voltages to said first
and second piezoelectric actuators causing said first and second
piezoelectric actuators to raise and lower said first and second
diaphragms.
4. The micropump of claim 3 wherein said pump body has a third
cavity intersecting with said passageway, said micropump further
comprising: a third diaphragm covering said third cavity, said
third diaphragm opening and closing said passageway as said third
diaphragm is raised and lowered, said third diaphragm being clamped
to said pump body by said securing means; a third piezoelectric
actuator for raising and lowering said third diaphragm, said third
piezoelectric actuator having a first end and second end, said
first end being operatively connected to said third diaphragm, said
second end of said third piezoelectric actuator being clamped to
said pump body by said cantilever securing means in a cantilever
manner, said electrical means applying a voltage to said third
piezoelectric actuator causing said third piezoelectric actuator to
raise and lower said third diaphragms.
5. The micropump of claim 4 wherein said pump body has a first side
and a second side, said first and third cavities being on said
first side of said pump body and said second cavity being on said
second side of said pump body.
6. The micropump of claim 4 wherein said first, second, and third
piezoelectric actuators each comprise: a first layer of
piezoelectric material; a second layer of piezoelectric material;
and a shim separating said first and second layers.
7. The micropump of claim 6 wherein said piezoelectric material is
class 5H lead zirconate titanate.
8. The micropump of claim 6 wherein said shim is brass.
9. The micropump of claim 6 wherein said shim is a carbon fiber
composite.
10. The micropump of claim 5 wherein said securing means comprises:
a first diaphragm clamp for securing said first and third
diaphragms to said pump body; and, a second diaphragm clamp for
securing said second diaphragm to said pump body.
11. The micropump of claim 5 wherein said securing means comprises:
a clamp for securing said first, second, and third diaphragms to
said pump body.
12. The micropump of claim 11 wherein said cantilever securing
means comprises said clamp.
13. The micropump of claim 5 wherein said cantilever securing means
comprises: a first actuator clamp for securing said second end of
said first piezoelectric actuator and said second end of said third
piezoelectric actuator to said pump body; and, a second actuator
clamp for securing said second end of said second piezoelectric
actuator to said pump body.
14. The micropump of claim 14 wherein said first and second
actuator clamps are integral with said pump body.
15. The micropump of claim 6 wherein said electrical means
comprises: an electronic control circuit for supplying a voltage to
said first, second, and third piezoelectric actuators for raising
and lowering said first, second, and third diaphragms, thereby
promoting a flow of said fluid through said passageway.
16. The micropump of claim 15 wherein said electronic control
circuit further comprises: means for gradually applying voltages to
said first and second layers of each of said first, second, and
third piezoelectric actuators.
17. A micropump for pumping a fluid from a fluid container to a
delivery point, comprising: a pump body, said pump body having a
passageway therethrough from said fluid container to said delivery
point, said pump body having first and second cavities intersecting
with said passageway; first pumping means for opening and closing
said passageway at said first cavity and creating a vacuum for
promoting the flow of said fluid through said passageway; a first
piezoelectric actuator for actuating said first pumping means;
second pumping means for opening and closing said passageway at
said second cavity and creating a vacuum for promoting the flow of
said fluid through said passageway; a second piezoelectric actuator
for actuating said second pumping means; electrical means for
applying voltages to said first and second piezoelectric actuators
causing said first and second piezoelectric actuators to actuate
said first and second pumping means.
18. The micropump of claim 17 wherein said pump body has a third
cavity intersecting with said passageway, said micropump further
comprising: third pumping means for opening and closing said
passageway at said third cavity and creating a vacuum for promoting
the flow of said fluid through said passageway; a third
piezoelectric actuator for actuating said third pumping means; and,
electrical means for applying a voltage to said third piezoelectric
actuator causing said third piezoelectric actuator to actuate said
third pumping means.
19. The micropump of claim 18 wherein said first pumping means
comprises a first piston engageable with said first cavity.
20. The micropump of claim 19 wherein said second pumping means
comprises a second piston engageable with said second cavity.
21. The micropump of claim 20 wherein said third pumping means
comprises a third piston engageable with said third cavity.
22. The micropump of claim 18 wherein said first pumping means
comprises a first diaphragm engageable with said first cavity.
23. The micropump of claim 22 wherein said second pumping means
comprises a second diaphragm engageable with said second
cavity.
24. The micropump of claim 23 wherein said third pumping means
comprises a third diaphragm engageable with said third cavity.
25. The micropump of claim 17, further including an open container
in communication with the passageway.
26. The micropump of claim 17, further including a closed, sealed
container in communication with the passageway.
27. A method of pumping a fluid from a container to a delivery
point through a micropump, said micropump comprising a pump body
having a passageway therethrough and first and second cavities
intersecting said passageway, first and second diaphragms covering
said first and second cavities, and first and second piezoelectric
actuators mounted in a cantilever manner attached to said first and
second diaphragms to raise and lower said first and second
diaphragms, said method comprising the steps of: actuating said
first piezoelectric actuator to raise said first diaphragm, thereby
allowing fluid to flow through said passageway from said container
to said first cavity; actuating said second piezoelectric actuator
to raise said second diaphragm and actuating said first
piezoelectric actuator to lower said first diaphragm, thereby
allowing fluid to flow through said passageway from said first
cavity to said second cavity; and actuating said second
piezoelectric actuator to lower said second diaphragm, thereby
allowing fluid to flow through said passageway toward said delivery
point.
28. The method of claim 27 wherein said pump body has a third
cavity intersecting said passageway and said micropump further
comprises a third diaphragm covering said third cavity and a third
piezoelectric actuator for raising and lowering said third
diaphragm, said method further comprising the steps of: actuating
said third piezoelectric actuator to raise said third diaphragm
while actuating said second piezoelectric actuator to lower said
second diaphragm, thereby allowing fluid to flow through said
passageway from said second cavity to said third cavity; and,
actuating said third piezoelectric actuator to lower said third
diaphragm, thereby allowing fluid to flow through said passageway
toward said delivery point.
29. A micropump for pumping a fluid from a fluid container to a
delivery point, comprising: a pump body, said pump body having a
passageway therethrough from the fluid container to the delivery
point, said pump body having first and second cavities intersecting
with said passageway; a first diaphragm covering said first cavity,
said first diaphragm opening and closing said passageway as said
first diaphragm is raised and lowered; a first piezoelectric
actuator having a first end and second end, said first end being
operatively connected to said first diaphragm and said second end
being connected to said pump body to define a cantilever support
for said first diaphragm; a second diaphragm covering said second
cavity, said second diaphragm opening and closing said passageway
as said second diaphragm is raised and lowered; a second
piezoelectric actuator having a first end and second end, said
first end being operatively connected to said second diaphragm and
said second end being connected to said pump body to define a
cantilever support for said first second; and, a power supply for
selectively applying voltages to each of said first and second
piezoelectric actuators causing said first and second piezoelectric
actuators to raise and lower the corresponding diaphragms.
30. The micropump of claim 29 wherein said piezoelectric actuators
are piezoelectric bimorphs.
31. The micropump of claim 29 wherein actuation of said first and
second diaphragms controls both pumping and valving.
32. A micropump for pumping a fluid from a fluid container to a
delivery point, comprising: a pump body, said pump body having a
passageway therethrough from the fluid container to the delivery
point, said pump body having first and second cavities intersecting
with said passageway; a first diaphragm covering said first cavity,
said first diaphragm opening and closing said passageway as said
first diaphragm is raised and lowered; a first piezoelectric
bimorph actuator having a first end and second end, said first end
being operatively connected to said first diaphragm and said second
end being connected to said pump body; a second diaphragm covering
said second cavity, said second diaphragm opening and closing said
passageway as said second diaphragm is raised and lowered; a second
piezoelectric bimorph actuator having a first end and second end,
said first end being operatively connected to said second diaphragm
and said second end being connected to said pump body; and, a power
supply for selectively applying voltages to each of said first and
second piezoelectric actuators, wherein application of a voltage to
said first piezoelectric actuator displaces said first diaphragm to
define a first reservoir in said first cavity and draw fluid from
said container through said inlet and into said first reservoir and
application of an opposing voltage to said first piezoelectric
actuator displaces said first diaphragm in an opposite direction to
force fluid in said first reservoir into said passageway downstream
of said first diaphragm and seal said first cavity.
33. The micropump of claim 32 wherein application of a voltage to
said second piezoelectric actuator displaces said second diaphragm
to define a second reservoir in said second cavity and draw fluid
from said passageway downstream of said first reservoir into said
second reservoir and application of an opposing voltage to said
second piezoelectric actuator displaces said second diaphragm in an
opposite direction to force fluid in said second reservoir into
said passageway downstream of said second reservoir and seal said
second cavity.
34. The micropump of claim 32, further comprising: means for
purging said passageway of fluid after the fluid is pumped from
said fluid container to said delivery point.
35. The micropump of claim 29 wherein said power supply applies
gradually increasing and decreasing voltages to said first and
second piezoelectric actuators.
36. The micropump of claim 33 wherein said power supply applies
gradually increasing and decreasing voltages to said first and
second piezoelectric actuators.
37. The method of claim 27, further comprising the step of: purging
fluid from said passageway.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of Invention
[0002] This invention pertains to the art of methods and
apparatuses for pumping fluid from a container to a delivery point
in low volumes and at controlled flow rates, and more specifically
to methods and apparatuses for using a piezoelectric driven pump to
control the delivery of a fluid, such as a pharmaceutical solution
or suspension, from a container to a delivery point.
[0003] 2. Description of the Related Art
[0004] Numerous fluidics applications in such areas as medicine,
chemistry, and environmental testing exist on a small scale for
reasons of sample size, reagent costs, or portability.
Cost-effective fluidics components, including pumps, that are
capable and reliable are required for such small scale systems.
Current pump designs are typically based on valves that open and
close. Such valves tend to be direct applications of designs that
work in macroscopic apparatuses, but are not necessarily the best
choice for microapplications. These apparatuses require valve seats
or other types of sealing and antiseizure mechanisms, and typically
are limited to fully-opened clearances that are relatively
small.
[0005] A number of micropumps exist for delivering small amounts of
a fluid to a delivery point. Some of the pumps include a
piezoelectric element, which changes its dimensions when it is
stressed electrically by a voltage. U.S. Pat. No. 4,938,742 to
Smits describes a micropump with piezoelectric valves. These valves
contain a diaphragm covered by a single layer of piezoelectric
material, which limits the control and deflection possibilities of
the valves.
[0006] U.S. Pat. No. 5,611,676 to Ooumi et al. shows the use of a
cantilevered piezoelectric bimorph. A piezoelectric bimorph has two
layers of a piezoelectric material separated by a shim. The
application of an electric field across the two layers of the
bimorph causes one layer to expand while the other contracts. The
net result is a curvature much greater that the length or thickness
deformation of the individual layers. However, the micropump of
Ooumi et al. uses the piezoelectric bimorphs only as single
function seals for opening and closing openings or as single
function pumps, not as multifunctional seals and pumps.
[0007] The present invention contemplates a new and improved
piezoelectric micropump that is simple in design, effective in use
and compact. The new and improved piezoelectric micropump provides
increased fluid flow rates with low power consumption. It overcomes
the foregoing difficulties and others while providing better and
more advantageous overall results.
SUMMARY OF THE INVENTION
[0008] In accordance with the present invention, a new and improved
piezoelectric micropump is provided that pumps fluid from a
container to a delivery point in small and precise amounts or at
controlled flow rates.
[0009] According to one aspect of the present invention, a
micropump for pumping a fluid from a fluid container to a delivery
point is disclosed that includes a pump body. A passageway extends
through the pump body from the fluid container to the delivery
point. The pump body has first, second, and third cavities
intersecting with the passageway. A first diaphragm covers the
first cavity and opens and closes the passageway as the first
diaphragm is raised and lowered. A first diaphragm clamp secures
the first diaphragm to the pump body. A first cantilevered
piezoelectric actuator raises and lowers the first diaphragm. The
first cantilevered piezoelectric actuator has a first end and
second end, the first end being operatively connected to the first
diaphragm. A first actuator clamp secures the second end of the
first cantilevered piezoelectric actuator to the pump body. A
second diaphragm covers the second cavity and opens and closes the
passageway as the second diaphragm is raised and lowered. A second
diaphragm clamp secures the second diaphragm to the pump body. A
second cantilevered piezoelectric actuator raises and lowers the
second diaphragm. The second cantilevered piezoelectric actuator
has a first end and second end, the first end being operatively
connected to the second diaphragm. A second actuator clamp secures
the second end of the second cantilevered piezoelectric actuator to
the pump body. A third diaphragm covers the third cavity. The third
diaphragm opens and closes the passageway as the third diaphragm is
raised and lowered. The third diaphragm is secured to the pump body
by the first diaphragm clamp. A third cantilevered piezoelectric
actuator raises and lowers the third diaphragm. The third
cantilevered piezoelectric actuator has a first end and second end,
the first end being operatively connected to the third diaphragm,
the second end of the third cantilevered piezoelectric actuator
being secured to the pump body by the first actuator clamp. An
electronic control circuit supplies voltages to the first, second,
and third cantilevered piezoelectric actuators for raising and
lowering the first, second, and third diaphragms at predetermined
intervals, thereby promoting a flow of the fluid through the
passageway.
[0010] According to another aspect of the present invention, a
micropump for pumping a fluid from a fluid container to a delivery
point is disclosed which includes a pump body having a passageway
therethrough from the fluid container to the delivery point. The
pump body has first and second cavities intersecting with the
passageway. A first diaphragm covers the first cavity. The first
piezoelectric actuator has a first end and second end, the first
end being operatively connected to the first diaphragm. The first
diaphragm opens and closes the passageway as the first diaphragm is
raised and lowered in response to a first piezoelectric actuator. A
second diaphragm covers the second cavity. The second diaphragm
opens and closes the passageway as the second diaphragm is raised
and lowered. A securing apparatus secures the first and second
diaphragms to the pump body. A second piezoelectric actuator raises
and lowers the second diaphragm. The second piezoelectric actuator
has a first end and second end, the first end being operatively
connected to the second diaphragm. The second ends of the first and
second piezoelectric actuators are secured to the pump body with
the first ends of the actuators being cantilevered from the pump
body. An electrical apparatus applies voltages to the first and
second piezoelectric actuators causing the first and second
piezoelectric actuators to raise and lower the first and second
diaphragms at predetermined intervals.
[0011] According to another aspect of the present invention, the
micropump pump body has a third cavity intersecting with the
passageway. The micropump further includes a third diaphragm
covering the third cavity. The third diaphragm opens and closes the
passageway as the third diaphragm is raised and lowered. The third
diaphragm is secured to the pump body by the securing apparatus. A
third piezoelectric actuator raises and lowers the third diaphragm.
The third piezoelectric actuator has a first end and second end,
the first end being operatively connected to the third diaphragm.
The second end of the third piezoelectric actuator is secured to
the pump body by the cantilever securing apparatus. The electrical
apparatus applies a voltage to the third piezoelectric actuator
causing the third piezoelectric actuator to raise and lower the
third diaphragm.
[0012] According to another aspect of the present invention, a
micropump for pumping a fluid from a fluid container to a delivery
point is disclosed which includes a pump body. The pump body has a
passageway therethrough from the fluid container to the delivery
point. The pump body has first and second cavities intersecting
with the passageway. A first pumping apparatus opens and closes the
passageway at the first cavity and creates a vacuum for promoting
the flow of the fluid through the passageway A first piezoelectric
actuator actuates the first pumping apparatus. A second pumping
apparatus opens and closes the passageway at the second cavity and
creates a vacuum for promoting the flow of the fluid through the
passageway. A second piezoelectric actuator actuates the second
pumping apparatus. An electrical apparatus applies voltages to the
first and second piezoelectric actuators causing the first and
second piezoelectric actuators to actuate the first and second
pumping apparatuses.
[0013] According to another aspect of the present invention, the
pump body has a third cavity intersecting with the passageway. The
micropump further includes a third pumping apparatus that opens and
closes the passageway at the third cavity and creates a vacuum for
promoting the flow of the fluid through the passageway. A third
piezoelectric actuator actuates the third pumping apparatus. The
electrical apparatus applies a voltage to the third piezoelectric
actuator causing the third piezoelectric actuator to actuate the
third pumping apparatus.
[0014] According to another aspect of the present invention, a
micropump for pumping a fluid from a fluid container to a delivery
point is disclosed. The micropump has a pump body having a
passageway therethrough from the fluid container to the delivery
point and first and second cavities intersecting with the
passageway. The micropump includes first and second diaphragms
covering the first and second cavities, respectively. The micropump
further includes first and second piezoelectric actuators each
having a first end and second end. The first ends of the actuators
are operatively connected to the corresponding diaphragms and the
second ends are connected to the pump body to define cantilever
supports for the diaphragms. The pump also includes a power supply
for selectively applying voltages to each of the first and second
piezoelectric actuators, causing said first and second
piezoelectric actuators to raise and lower the corresponding
diaphragms. The first and second diaphragms each open and close the
passageway as they are raised and lowered by the piezoelectric
actuators.
[0015] The piezoelectric actuators in the above-described micropump
may be piezoelectric bimorphs. In such a pump, the actuation of the
first and second diaphragms controls both pumping and valving.
[0016] According to another aspect of the invention, a micropump
for pumping a fluid from a fluid container to a delivery point is
disclosed. The micropump has a pump body having a passageway
therethrough from the fluid container to the delivery point and
first and second cavities intersecting with the passageway. The
micropump includes first and second diaphragms covering the first
and second cavities, respectively. The micropump further includes
first and second piezoelectric bimorphs each having first and
second ends. The first ends are operatively connected to the first
and second diaphragms, respectively, and the second ends are
connected to the pump body. The micropump also includes a power
supply for selectively applying voltages to each of the first and
second piezoelectric actuators to raise and lower the corresponding
diaphragms. The first and second diaphragms each open and close the
passageway as they are raised and lowered by the piezoelectric
actuators. Application of a voltage to the first piezoelectric
actuator displaces the first diaphragm to define a first reservoir
in the first cavity and draw fluid from the container through the
inlet and into the first reservoir and application of an opposing
voltage to the first piezoelectric actuator displaces the first
diaphragm in an opposite direction to force fluid in the first
reservoir into the passageway downstream from the first reservoir
and seal the first cavity.
[0017] According to yet another aspect of the invention,
application of a voltage to the second piezoelectric actuator in
the above-described micropump displaces the second diaphragm to
define a second reservoir in the second cavity and draw fluid from
the passageway downstream of the first reservoir into the second
reservoir and application of an opposing voltage to the second
piezoelectric actuator displaces the second diaphragm in an
opposite direction to force fluid in the second reservoir into the
passageway downstream from the second reservoir and seal the second
cavity.
[0018] According to another aspect of the present invention, a
method of pumping a fluid from a container to a delivery point
through a micropump is disclosed. The micropump includes a pump
body having a passageway therethrough and first and second cavities
intersecting the passageway, first and second diaphragms covering
the first and second cavities, and first and second piezoelectric
actuators cantilevered between the pump body and the first and
second diaphragms to raise and lower the first and second
diaphragms. The method includes the steps of actuating the first
piezoelectric actuator to raise the first diaphragm, thereby
allowing fluid to flow through the passageway from the container to
the first cavity; actuating the second piezoelectric actuator to
raise the second diaphragm and actuating the first piezoelectric
actuator to lower the first diaphragm, thereby allowing fluid to
flow through the passageway from the first cavity to the second
cavity; and actuating the second piezoelectric actuator to lower
the second diaphragm, thereby allowing fluid to flow through the
passageway toward the delivery point.
[0019] According to another aspect of the present invention, the
pump body has a third cavity intersecting the passageway and the
micropump further includes a third diaphragm covering the third
cavity and a third piezoelectric actuator for raising and lowering
the third diaphragm. The method further includes the steps of
actuating the third piezoelectric actuator to raise the third
diaphragm while actuating the second piezoelectric actuator to
lower the second diaphragm, thereby allowing fluid to flow through
the passageway from the second cavity to the third cavity; and
actuating the third piezoelectric actuator to lower the third
diaphragm, thereby allowing fluid to flow through the passageway
toward the delivery point.
[0020] One advantage of the present invention is that the micropump
controls the flow of precise amounts of fluid, which is
particularly advantageous for pharmaceuticals and other fluids to
be dispensed in precise amounts or at controlled rates.
[0021] Another advantage of the present invention is that each of
the piezoelectric actuator and diaphragm assemblies acts both a
gate for the passageway of the micropump and a pump promoting the
flow of the fluid through the micropump.
[0022] Another advantage of the present invention is that the flow
rate of fluid may be controlled by varying the level of voltage
applied to the piezoelectric actuators, thereby controlling the
amount of deflection and the level to which the diaphragms are
raised.
[0023] Another advantage of the present invention is that the flow
rate of fluid may be controlled by varying the frequency of the
pumping cycle of the piezoelectric actuators.
[0024] Another advantage of the present invention is that the
gradual application of an increasing or decreasing voltage to the
piezoelectric actuators stabilizes the flow of fluid through the
micropump.
[0025] Another advantage of the present invention is that
cantilevering the piezoelectric actuators between the pump body and
the diaphragms provides increased deflection of the diaphragms
compared with piezoelectric circular disks to maximize fluid flow
while controlling power consumption.
[0026] Still other benefits and advantages of the invention will
become apparent to those skilled in the art to which it pertains
upon a reading and understanding of the following detailed
specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] The invention may take physical form in certain parts and
arrangement of parts, a preferred embodiment of which will be
described in detail in this specification and illustrated in the
accompanying drawings which form a part hereof and wherein:
[0028] FIG. 1 is a perspective view of a piezoelectric
micropump;
[0029] FIG. 2 is an exploded view of the piezoelectric micropump of
FIG. 1;
[0030] FIG. 3 is a cross-sectional view of the piezoelectric
micropump of FIG. 1 taken along line 3-3;
[0031] FIG. 4 is a side perspective view of a piezoelectric
actuator;
[0032] FIGS. 5A-5E are schematic drawings illustrating the pumping
cycle of the piezoelectric micropump;
[0033] FIG. 6 is a graph of the waveforms of an electrical control
circuit for an embodiment of the piezoelectric micropump;
[0034] FIG. 7 is a side view of an alternate embodiment of the
piezoelectric micropump with two diaphragms; and, FIG. 8 is a
perspective view of an alternate embodiment of the piezoelectric
micropump featuring means for purging the passageway of fluid.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0035] Referring now to the drawings which are shown only for
purposes of illustrating a preferred embodiment of the invention
and not for purposes of limiting the same, FIG. 1 is a perspective
view of a micropump 10 for delivering precise amounts of a fluid
from a container 14 to a delivery point 18. The micropump 10
includes a pump body 22. In a preferred embodiment, the pump body
22 is preferably made of molded or machined plastic such as
Delrin.
[0036] For pharmaceutical or other applications, the pump body 22
may be made from an antimicrobial material or provided with an
antimicrobial coating. The antimicrobial material and coating
should be nonleaching. The pump body 22 and other components
preferably are compatible with sterilization techniques so the
micropump 10 may be packaged sterile.
[0037] With continuing reference to FIG. 1, FIG. 2 shows an
exploded view of the micropump 10. Within the pump body 22 is a
passageway 26. The passageway 26 preferably is molded or machined
into the pump body 22 and is physically compatible with the fluids
to be pumped including liquid solutions and microsuspensions. The
passageway 26 and all other pump surfaces that come into contact
with fluids are chemically compatible with the fluids to be pumped.
The passageway 26 runs from an inlet 30 to which the container 14
is interchangeably connected, through the pump body 22, to an
outlet 32, shown in FIG. 3, and the delivery point 18.
[0038] As shown in FIG. 3, which is a cross-sectional view taken
along line 3-3 of FIG. 1, with continuing reference to FIGS. 1 and
2, the passageway 26 runs from inlet 30 to outlet 32 through the
pump body 22 in a preferably zig-zag fashion The passageway 26 is
intersected by and opened at three passageway cavities 34, 36, 38.
These cavities 34, 36, 38 preferably are covered by nonleaching,
elastomeric diaphragms 40, 42, 44. The diaphragms 40, 42, 44
preferably are made of silicone disks and may have a thickness of
approximately 0.005 inch and a diameter of approximately 12 mm in a
pump capable of pumping in the range of about 10-100
microliters/sec. When the diaphragms 40, 42, 44 are tightly secured
against the pump body 22 in the cavities 34, 36, 38, the passageway
26 is closed at each of the cavities 34, 36, 38. When a diaphragm
40, 42, 44 is pulled away from its cavities 34, 36, 38, the
corresponding portion of the passageway 26 is opened.
[0039] With continued reference to FIGS. 1, 2, and 3, the
piezoelectric actuators 46, 48, 50 are attached to the diaphragms
40, 42, 44 at first ends 64, 66, 68, respectively. In the preferred
embodiment, a silicone adhesive or other compatible adhesive is
used to attach the diaphragms 40, 42, 44 to the piezoelectric
actuators 46, 48, 50. However, any suitable method of attachment
may be used. For example, the diaphragms 40, 42, 44 may be provided
with slots that receive the first ends of the piezoelectric
actuators 46, 48, 50 or the diaphragms 40, 42, 44 and piezoelectric
actuators 46, 48, 50 may be molded to form an integral piece.
[0040] The piezoelectric actuators 46, 48, 50 may be mounted to the
pump body 22 by actuator clamps 78, 80. In one embodiment of the
present invention, actuator clamps 78, 80 are pieces designed
separately from pump body 22. However, actuator clamps 78, 80 may
also be formed integrally with pump body 22. The clamping of the
second ends 70, 72, 74 of the piezoelectric actuators 46, 48, 50 to
the pump body 22 creates a cantilever system of mounting. The
cantilever system of mounting and the use of piezoelectric bimorphs
are preferred for the piezoelectric actuators 46, 48, 50 to
maximize the piezoelectric deflection achieved with a given applied
voltage. When voltages are applied to the piezoelectric actuators
46, 48, 50, the second ends 70, 72, 74 remain stationary while the
first ends 64, 66, 68 are displaced relative to the pump body 22,
thereby raising and lowering the diaphragms 40,42,44. Deflecting
one of the diaphragms 40, 42, 44 opens the corresponding portion of
the passageway 26 that runs through the pump body 22. In the
preferred embodiment, the diaphragms 40, 42, 44 are further held in
contact with the pump body 22 in the cavities 34, 36, 38 by
diaphragm clamps 84, 86.
[0041] The piezoelectric actuators 46, 48, 50 are preferably
piezoelectric bimorph actuators. FIG. 4 is a detailed view of one
of the piezoelectric actuators 46. The piezoelectric actuator 46
preferably contains two layers of piezoelectric ceramic 54, 56
separated by a shim 60 preferably made of brass or an appropriate
carbon fiber material. The application of an electric field across
the two layers of piezoelectric ceramic material 54, 56 causes one
layer of piezoelectric ceramic 54 to expand while the other layer
of piezoelectric ceramic 56 contracts. The net result is a
curvature of much greater than the length or thickness definition
of the individual piezoelectric ceramic members 54, 56. The
piezoelectric actuator 46 in a pump capable of pumping in the range
of about 10-100 microliters per second may have a width of
approximately 0.075 inch and a cantilevered length of approximately
1.0 inch. The preferred piezoelectric ceramics 54, 56 are lead
zirconate titanate, class 5H. Class 5A piezoceramics may also be
used, but require higher voltages to achieve motion similar to
class 5H piezoceramics. Use of piezoelectric bimorphs enables the
diaphragms 40, 42, 44 to function as both seals and pumps.
Displacement of one of the diaphragms 40, 42, 44 in one direction
opens the corresponding cavity 34,36,38 to form a reservoir for
fluid. Displacement of the diaphragm 40, 42, 44 in the opposite
direction forces fluid out of the reservoir and the cavity 34, 36,
38.
[0042] With continuing reference to FIGS. 1, 2, and 3, FIGS. 5A
through 5E show the pumping cycle of the micropump 10. Each
diaphragm 40, 42, 44 is independently controlled by a piezoelectric
actuator 46, 48, 50. During the pumping cycle, the piezoelectric
actuators 46, 48, 50 cooperate to move the fluid in a
unidirectional flow from the container 14 to the delivery point 18.
The unidirectional flow and the sealing action of the diaphragms
40, 42, 44 maintain the integrity of the fluid.
[0043] When the micropump 10 is at rest, as shown in FIG. 5A, each
of the diaphragms 40, 42, 44 is in its lowered position against the
cavities 34, 36, 38, thereby closing passageway 26 at each of the
cavities 34, 36, 38. In the first step of operation, as shown in
FIG. 5B, the first diaphragm 40 is deflected or raised by applying
a voltage to piezoelectric actuator 46, thereby displacing the
first end 64 of the piezoelectric actuator 46. Raising diaphragm 40
creates a vacuum within the passageway 26 in cavity 34, thereby
drawing fluid from the container 14 through the inlet 30 into a
reservoir created in cavity 34 by the raised diaphragm 40. As used
herein, "raising" a diaphragm means moving the diaphragm to an open
or unsealed position although this movement need not be in an
upward direction. Similarly, "lowering" a diaphragm means moving
the diaphragm to a closed or sealed position although this movement
need not be in a downward direction.
[0044] In FIG. 5C, step two of the pumping cycle is shown. A
voltage is applied to piezoelectric actuator 48 to raise diaphragm
42, creating a vacuum in the passageway 26 at cavity 36. At the
same time, an opposing voltage is applied to piezoelectric actuator
46, causing the first end 64 to lower diaphragm 40. The vacuum
created by diaphragm 42 in cavity 36 and the lowering of diaphragm
40 causes a flow of the fluid from the reservoir created in cavity
34 to a reservoir created in cavity 36.
[0045] FIG. 5D shows the next step in the pumping cycle. A voltage
is applied to piezoelectric actuator 50, causing the first end 68
of piezoelectric actuator 50 to raise diaphragm 44, creating a
vacuum in cavity 38. Simultaneously, an opposing voltage is applied
to piezoelectric actuator 48, causing first end 66 of piezoelectric
actuator 48 to lower diaphragm 42 into the reservoir. The vacuum
created by raising diaphragm 44 and the lowering of diaphragm 42
pushes fluid through passageway 26 to cavity 38.
[0046] FIG. 5E shows the final step of the pumping cycle. An
opposing voltage is applied to piezoelectric actuator 50, lowering
first end 68 of piezoelectric actuator 50 and lowering diaphragm
44. The lowering of diaphragm 44 forces the fluid from the
reservoir created in cavity 38 through the passageway 26 and outlet
32 to the delivery point 18.
[0047] FIG. 6 shows a graph of the application of voltages to the
piezoelectric actuators 46, 48, 50 during a theoretical operation
of the micropump 10 to pump water. The graph designated 1 shows the
voltage applied to the first piezoelectric actuator 46. The graph
designated 2 shows the voltage applied to the second piezoelectric
actuator 48. The graph designated 3 shows the voltage applied to
the third piezoelectric actuator 50. All three graphs 1, 2, 3 are
shown together with time along the x-axis. Each of the voltages is
applied in a gradually increasing manner as shown in the graphs 1,
2, 3 to prevent vibration of the actuators and audible noise during
operation of the micropump 10 and to promote even flow through the
passageway 26. The application of voltages to the piezoelectric
actuators 46,48,50 is controlled by a control circuit 88,
represented in FIG. 1, which is well known to those skilled in the
art of electronics. The peak of graph 1 corresponds approximately
to the step of the pumping cycle illustrated in FIG. 5B. The peak
of graph 2 corresponds approximately to the step of the pumping
cycle illustrated in FIG. 5C. The peak of graph 3 corresponds
approximately to the step of the pumping cycle illustrated in FIG.
5D. The gradual increase in the voltage and the timing of the
actuation of the various actuators helps to control unidirectional
flow and minimize backflow. The wave forms and timing may vary
depending on the fluid to be pumped and the desired fluid
output.
[0048] In the preferred embodiment, the maximum voltage applied to
the piezoelectric actuators 46, 48, 50 is 120 volts. If batteries
are used to supply power to the piezoelectric actuators 46, 48, 50,
the voltages of typical batteries must be stepped up by the control
circuit 88 to provide sufficient voltages to create the
piezoelectric effect in the piezoelectric actuators 46, 48, 50. In
the preferred embodiment, the voltages are applied through leads
90, 92, as shown in FIG. 1, that are attached to the piezoelectric
actuators 46, 48, 50. However, any other suitable method of
supplying the voltages to the piezoelectric actuators 46, 48, 50
may be used, including, but not limited to, the use of electrically
conductive strips or other suitable materials.
[0049] The flow rate of fluid through the micropump 10 may be
controlled by one of three methods or a combination of methods. The
first, and preferred, method for controlling the flow rate of fluid
through the micropump 10 is by increasing or decreasing the
frequency of the pumping cycle. The frequency of the pumping cycle
may be controlled by programming the control circuit 88 to speed up
or slow down the application of voltages to the piezoelectric
actuators 46, 48, 50.
[0050] The second method of controlling the flow rate of fluid
through the micropump 10 is to control the level of voltage applied
to the piezoelectric actuators 46, 48, 50. Applying a low voltage
to the piezoelectric actuators 46,48,50 reduces the amount of
deflection of the piezoelectric actuators 46, 48, 50, thereby
limiting the height to which the diaphragms 40, 42, 44 are raised.
The displacement of the diaphragms 40, 42, 44 in turn limits the
vacuum created in the cavities 34, 36, 38 during the pumping cycle.
The smaller the vacuums, the smaller the amounts of fluid drawn
from the container 14 and moved through the pump 10.
[0051] The third method of controlling the flow rate of fluid
through the micropump 10 is by controlling the diameter of the
passageway 26. The greater the diameter of the passageway 26, the
greater the amount of fluid that will flow through the micropump
10.
[0052] In the preferred embodiment of the invention, the flow rate
of fluid through the micropump 10 is between about 10 microliters
per second and 100 microliters per second. The precise motion of
the piezoelectric actuators 46, 48, 50 provides tight tolerance at
low flow rates. The use of multiple diaphragm cycles per dose
provides tight tolerance at low volumes.
[0053] The container 14 may be an open reservoir as shown in FIG.
1, or the container 14 may be a sealed, collapsible container. If
an open reservoir is used, the micropump 10 must be maintained in a
generally upright orientation with the container 14 on top of the
pump body 22. If a sealed, collapsible container is used, the
micropump 10 may be used in a variety of orientations. However, the
present model of the micropump 10 continues to work best when
oriented with the container 14 on top of the pump body 22 even when
a sealed, collapsible container is used. A change in orientation,
along with the change in gravitational effects and head pressure
that accompany the change in orientation, may affect the flow rate
of fluid through the micropump 10.
[0054] FIG. 7 shows an alternate embodiment of the invention in
which the micropump 10' features a pump body 22' with two cavities
34', 36' that are covered by two diaphragms 40', 42'. The two
diaphragms 40', 42' are attached to two piezoelectric actuators
46', 48' that raise and lower the diaphragms 40', 42'. The
micropump 10 of FIG. 7 is operational and works in the same manner
as micropump 10, but the micropump 10 with three diaphragms 40, 42,
44, as shown in FIGS. 1, 2, and 3, is preferred because it offers
more control. The micropump 10' is also more susceptible to head
pressure from the container 14' than the micropump 10 because the
passageway 26' is completely open as fluid flows from the first
cavity 34' to the second cavity 36'. Use of a fluid container under
positive pressure with micropump 10' may overcome this problem.
[0055] The micropump 10 may include a purge feature to clear
residual fluid from the passageway 26 after operation of the
micropump 10. Purging the micropump 10 of fluid may be desirable to
prevent microbial growth within the passageway 26, particularly
near the outlet 32, or to prevent the buildup of residue within the
passageway 26. As described below, the purge feature may include a
apparatus for introducing a puring medium and causing the purging
medium to travel through the passageway 26.
[0056] FIG. 8 shows an embodiment of the present invention
incorporating means for purging the passageway 26" of fluid after
operation of the micropump 10". The purge feature includes an inlet
31" for introducing a purging medium to the passageway 26". The
pump body 22" has a passageway 26" running from an inlet 30" to an
outlet 32". The passageway 26" is intersected by three passageway
cavities 34", 36", 38". These cavities 34", 36", 38" preferably are
covered by elastomeric diaphragms 40", 42", 44". The second and
third diaphragms 42", 44" are each controlled by piezoelectric
actuators 48", 50" as described above. A second inlet 31" is also
located within pump body 22" to the first cavity 34". A diaphragm
40" covers the first cavity 34". A first piezoelectric actuator 46"
raises and lowers the diaphragm 40" over the portion of the
passageway 26" leading to inlet 30" and a second piezoelectric
actuator 47" raises and lowers the diaphragm 40" over the second
inlet 31" and the portion of the passageway 26" that continues
toward the second cavity 36". During operation of the micropump
10", piezoelectric actuators 46", 48", 50" raise and lower
diaphragms 40", 42", 44" as described in the previous
embodiments.
[0057] Purging may be accomplished by introducing a purging medium,
which may be filtered air, water, a cleansing fluid, or any other
suitable material, into the micropump 10" through inlet 31" upon
completion of the pumping cycle. During purging, piezoelectric
actuator 46" seals the passageway 26" leading to the inlet 30".
Three methods may be employed to move the purging medium through
the passageway 26". First, the purging medium may be introduced
through the second inlet 31" and pumped through the micropump 10"
in the manner described above with the exception that piezoelectric
actuator 47" raises and lowers diaphragm 40" in place of
piezoelectric actuator 46". Second, the purging medium may be
supplied under pressure through the second inlet 31" while
actuators 47", 48", 50" hold the diaphragms 40", 42", 44" open,
thereby allowing the purging medium to blow through the passageway
26". Third, each of the diaphragms 40", 42", 44" may be held open
by actuators 47", 48", 50", thereby allowing the purging medium to
enter through inlet 31" and pass through the passageway 26" as a
mechanism (not shown) at the outlet 32" pulls the purging medium
therethrough. This mechanism may, for example, be an
electrohydrodynamic spraying apparatus. While one method and
apparatus for introducing a purging medium to the micropump 10" has
been disclosed, it is understood that other methods and apparatuses
for introducing purging media at or near the inlet 30" or first
diaphragm 40" that is pumped, pushed, or pulled through the
micropump 10" may be used.
[0058] In yet another embodiment of the present invention, the
diaphragms 40,42,44 may be replaced by pistons or other pumping
apparatuses that move within the cavities 34, 36, 38 to induce
fluid flow.
[0059] The preferred embodiments have been described, hereinabove.
It will be apparent to those skilled in the art that the above
methods may incorporate changes and modifications without departing
from the general scope of this invention. It is intended to include
all such modifications and alterations in so far as they come
within the scope of the appended claims or the equivalents
thereof
[0060] Having thus described the invention, it is now claimed:
* * * * *