U.S. patent application number 11/334545 was filed with the patent office on 2006-06-22 for piezoelectric actuator and pump using same.
This patent application is currently assigned to PAR Technologies, LLC. Invention is credited to W. Joe East.
Application Number | 20060131530 11/334545 |
Document ID | / |
Family ID | 33029647 |
Filed Date | 2006-06-22 |
United States Patent
Application |
20060131530 |
Kind Code |
A1 |
East; W. Joe |
June 22, 2006 |
Piezoelectric actuator and pump using same
Abstract
Thin chamber diaphragm-operated fluid handling devices,
including thin chamber pumps and thin chamber valves, facilitate
device compactness and, in some configurations, self-priming.
Diaphragm actuators of the thin chamber devices either comprise or
are driven by piezoelectric materials. The thinness of the chamber,
in a direction parallel to diaphragm movement, is in some
embodiments determined by the size of a perimeter seal member which
sits on a floor of a device cavity, and upon which a perimeter
(e.g. circumferential or peripheral portion) of the diaphragm
actuator sits. The diaphragm actuator is typically retained in a
device body between the floor seal member and another seal member
between which the perimeter of the actuator is sandwiched. The
devices have an input port and an output port.
Inventors: |
East; W. Joe; (Grafton,
VA) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
901 NORTH GLEBE ROAD, 11TH FLOOR
ARLINGTON
VA
22203
US
|
Assignee: |
PAR Technologies, LLC
Hampton
VA
|
Family ID: |
33029647 |
Appl. No.: |
11/334545 |
Filed: |
January 19, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10388589 |
Mar 17, 2003 |
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11334545 |
Jan 19, 2006 |
|
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PCT/US01/28947 |
Sep 14, 2001 |
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10388589 |
Mar 17, 2003 |
|
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60233248 |
Sep 18, 2000 |
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Current U.S.
Class: |
251/129.06 |
Current CPC
Class: |
F16K 31/006 20130101;
F16K 31/005 20130101; F04B 43/046 20130101 |
Class at
Publication: |
251/129.06 |
International
Class: |
F16K 31/02 20060101
F16K031/02 |
Claims
1. (canceled)
2. (canceled)
3. (canceled)
4. (canceled)
5. (canceled)
6. (canceled)
7. (canceled)
8. (canceled)
9. (canceled)
10. (canceled)
11. (canceled)
12. (canceled)
13. (canceled)
14. (canceled)
15. (canceled)
16. (canceled)
17. (canceled)
18. (canceled)
19. (canceled)
20. (canceled)
21. (canceled)
22. A valve comprising: a body for at least partially defining a
valve chamber including an interior floor, the valve chamber having
an inlet port and an outlet port provided on the interior floor,
one of the inlet port and the outlet port being a controlled port;
at least one piezoelectric actuator provided in the valve chamber,
the piezoelectric actuator comprising a piezoelectric element
having a fluid-contacting layer adhered thereto; a valve chamber
spacer member provided around the interior floor; a port sealing
gasket provided around a mouth of the controlled port; the
piezoelectric actuator being operable by selective application of
an electric field to a first state and a second state, in the first
state the fluid-contacting layer of the piezoelectric actuator
being positioned against the port sealing gasket of the controlled
port to prevent transmission of fluid between the valve chamber and
the controlled port, in the second state the fluid-contacting layer
of the piezoelectric actuator being positioned away from the port
sealing gasket of the controlled port to permit transmission of
between the valve chamber and the controlled port; a thickness of
the valve chamber being uniformly essentially a thickness of the
valve chamber spacer member and chosen to facilitate self-priming
of the valve.
23. The apparatus of claim 22, wherein the fluid-contacting layer
of the piezoelectric actuator is a stainless steel membrane.
24. The apparatus of claim 22, wherein in the first state the
piezoelectric actuator has no electromagnetic field applied
thereto, and wherein in the second state the piezoelectric actuator
has an electromagnetic field applied thereto.
25. The apparatus of claim 22, wherein when the controlled port is
open fluid travels between the controlled port and the valve
chamber in a direction essentially perpendicular to a plane of the
fluid-contacting layer.
26. The apparatus of claim 22, wherein the port sealing gasket for
the controlled port is provided on a wall of the valve chamber.
27. The apparatus of claim 22, wherein the port sealing gasket has
essentially a same thickness as the valve chamber spacer
member.
28. A diaphragm pump comprising: a body for at least partially
defining a pumping chamber and an inlet port for the pumping
chamber; a diaphragm which, in conjunction with application of an
electric field to a piezoelectric material, acts upon a fluid in
the pumping chamber; a wicking material situated in at least one of
the pumping chamber and the inlet port, the wicking material
facilitating priming of the pump with a liquid by capillary
action.
29. The apparatus of claim 28, wherein the wicking material is a
micro fiber fabric or a wicking foam material.
30. (canceled)
31. The apparatus of claim 28, wherein the wicking material is
situated in the pumping chamber but is not compressed by movement
of the diaphragm.
32. The apparatus of claim 28, wherein the wicking material is
situated in the pumping chamber and is shaped essentially as a
disk.
33. The apparatus of claim 28, wherein the wicking material extends
through the inlet port.
34. The apparatus of claim 28, wherein the wicking material is
situated both in the pumping chamber and in the inlet port.
35. The apparatus of claim 28, wherein the wicking material is
situated in the pumping chamber and is shaped essentially as a
disk.
36. The apparatus of claim 35, wherein the disk has a first hole
aligned with the inlet port and a second hole aligned with the
outlet port.
37. The apparatus of claim 36, wherein a channel connects the first
hole and the second hole.
38. The apparatus of claim 28, further comprising a sealing member
which extends around an inner periphery of the pumping chamber and
which defines a height of the pumping chamber between the
piezoelectric actuator when unactuated and the body.
39. A method of self-priming a diaphragm pump, the diaphragm pump
comprising a body for at least partially defining a pumping chamber
and a diaphragm which is actuated by selective application of an
electric field to a piezoelectric material to act upon a liquid in
the pumping chamber; the method comprising: putting a wicking
material in one of the pumping chamber and an inlet port of the
pumping chamber; putting a wicking material into a vessel;
inserting a first end of the vessel into the pumping chamber so
that the wicking material in the vessel contacts the wicking
material in the pump; inserting a second end of the vessel into a
liquid; actuating the diaphragm to facilitate priming of the pump
with the liquid by capillary action.
40. (canceled)
41. (canceled)
42. (canceled)
43. A diaphragm pump comprising: a body for at least partially
defining a pumping chamber, the pumping chamber having a pumping
chamber first lateral portion, a pumping chamber second lateral
portion, an inlet port, and an outlet port; a first diaphragm
which, in conjunction with application of an electric field to a
first piezoelectric element, acts upon a fluid in the pumping
chamber first lateral portion; a second diaphragm which, in
conjunction with application of an electric field to a second
piezoelectric element, acts upon a fluid in the pumping chamber
second lateral portion; a driver circuit which actuates the first
diaphragm and the second diaphragm.
44. The apparatus of claim 43, wherein the driver circuit actuates
the first diaphragm and the second diaphragm whereby in a deformed
state the first diaphragm and the second diaphragm simultaneously
draw fluid into the pumping chamber first lateral portion and the
pumping chamber second lateral portion, respectively.
45. The apparatus of claim 43, wherein the pumping chamber further
has a pumping chamber central portion, and wherein the pumping
chamber first lateral portion communicates with the pumping chamber
central portion through a first window and the pumping chamber
second lateral portion communicates with the pumping chamber
central portion through a second window.
46. The apparatus of claim 45, wherein the pumping chamber first
lateral portion and the pumping chamber first lateral portion both
have a disk shape with the pumping chamber first lateral portion
lying in a first plane and the pumping chamber second lateral
portion lying in a second plane which is parallel to the first
plane, wherein a projection of a circumference of the first pumping
chamber on the first plane is a circle, and wherein a projection of
a circumference of the first window on the first plane is a ellipse
having an axis which when extended forms a chord of the circle.
47. The apparatus of claim 45, wherein at least one of the first
window and the second window has an elliptical shape.
48. The apparatus of claim 43, further comprising a diverter which
diverts fluid introduced by the inlet port toward the pumping
chamber first lateral portion and toward the pumping chamber second
lateral portion.
49. The apparatus of claim 48, wherein the pumping chamber has a
pumping chamber central portion; the pumping chamber first lateral
portion communicates with the pumping chamber central portion
through a first window and the pumping chamber second lateral
portion communicates with the pumping chamber central portion
through a second window, the diverter has a diverter first edge
proximate the first window and a diverter second edge proximate the
second window, and the first diaphragm draws fluid around the
diverter first edge from the inlet port to the outlet port and the
second diaphragm draws fluid around the diverter second edge from
the inlet port to the outlet port.
50. The apparatus of claim 49, wherein the first diaphragm lies in
a first plane and the second diaphragm lies in a second plane,
wherein in a third plane which is perpendicular to the first plane
and the second plane the diverter strut has a quadrilateral
cross-sectional shape, and wherein in the third plane two corners
of the quadrilateral are aligned with a fluid flow axis of the
inlet port and the outlet port.
51. The apparatus of claim 49, wherein the first diaphragm lies in
a first plane and the second diaphragm lies in a second plane,
wherein in a third plane which is perpendicular to the first plane
and the second plane the diverter has a quadrilateral
cross-sectional shape, and wherein in the third plane two corners
of the quadrilateral are aligned with a fluid flow axis of the
inlet port and the outlet port.
52. The apparatus of claim 48, wherein: the pumping chamber first
lateral portion communicates with the inlet port through a pumping
chamber first lateral portion first window; the pumping chamber
first lateral portion communicates with the outlet port through a
pumping chamber first lateral portion second window; the pumping
chamber second lateral portion communicates with the inlet port
through a pumping chamber second lateral portion first window; the
pumping chamber second lateral portion communicates with the outlet
port through a pumping chamber second lateral portion second
window.
53. The apparatus of claim 52, wherein the diverter has a first
wall which is essentially parallel to a plane of the first
diaphragm when unactuated and a second wall which is essentially
parallel to a plane of the second diaphragm when unactuated.
54. The apparatus of claim 52, wherein: the first diaphragm draws
fluid through the pumping chamber first lateral portion first
window, into the pumping chamber first lateral portion, and out the
pumping chamber first lateral portion second window toward the
outlet port; and the second diaphragm draws fluid through the
pumping chamber second lateral portion first window, into the
pumping chamber second lateral portion, and out the pumping chamber
second lateral portion second window toward the outlet port.
55. The apparatus of claim 43, wherein the pumping chamber first
lateral portion and the pumping chamber first lateral portion both
have a disk shape with the pumping chamber first lateral portion
lying in a first plane and the pumping chamber second lateral
portion lying in a second plane which is parallel to the first
plane, wherein a projection of a fluid flow axis of the inlet port
and the outlet port on a circumference of the pumping chamber first
lateral portion in the first plane forms a chord with respect to
the circumference.
56. The apparatus of claim 43, further comprising: a first sealing
member which extends around a periphery of the pumping chamber
first lateral portion and which defines a height of the pumping
chamber first lateral portion between the first diaphragm when
unactuated and the body; and a second sealing member which extends
around a periphery of the pumping chamber second lateral portion
and which defines a height of the pumping chamber second lateral
portion between the second diaphragm when unactuated and the
body.
57. The apparatus of claim 56, wherein the first sealing member and
the second sealing member are O-rings.
58. The apparatus of claim 56, wherein the first sealing member and
the second sealing member are essentially flat gaskets.
59. The apparatus of claim 56, wherein the height of at least one
of the pumping chamber first lateral portion and the pumping
chamber second lateral portion is 20 mils or less.
60. The apparatus of claim 56, wherein the height of at least one
of the pumping chamber first lateral portion and the pumping
chamber second lateral portion is 10 mils.
61. A diaphragm pump comprising: a body for at least partially
defining a pumping chamber, the pumping chamber having an inlet
port and an outlet port; a diaphragm which, in conjunction with
application of an electromagnetic field to a piezoelectric element,
acts upon a fluid in the pumping chamber; a flapper valve situated
in one of the inlet port and the outlet port, the flapper valve
comprising a thin wafer having an arcuate cut therein.
62. The apparatus of claim 61, wherein the thin wafer is a circular
wafer.
63. The apparatus of claim 61, wherein the thin wafer is a silicon
wafer.
64. The apparatus of claim 61, wherein the thin wafer has a
thickness of about 0.002 inch.
65. The apparatus of claim 61, wherein the arcuate cut is a
substantially U-shaped cut.
66. The apparatus of claim 61, further comprising a retainer member
which holds the flapper valve in place relative to the one of the
inlet port and the outlet port.
67. The apparatus of claim 61, wherein the flapper valve has a
modulus which forces the flapper valve to close after action of the
diaphragm has filled the pumping chamber, but which also causes
automatic closure of the flapper valve without requiring pressure
of the diaphragm.
68. (canceled)
69. (canceled)
70. (canceled)
71. (canceled)
Description
[0001] This application claims the benefit and priority of U.S.
Provisional Patent Application No. 60/233,248 filed 18 Sep. 2000,
and is a divisional of U.S. patent application Ser. No. 10/388,589
filed Mar. 17, 2003, which is a continuation-in-part of PCT patent
application PCT/US01/28947 filed 14 Sep. 2001, all of which are
incorporated by reference herein in their entirety.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention is in the field of the manufacture of
ferroelectric actuators and miniature diaphragm pumps using these
actuators as the prime mover. In the best mode the actuators are
piezoelectric.
[0004] 2. Related Art and Other Considerations
[0005] Certain prior art for this invention may be grouped as
follows:
[0006] U.S. Pat. Nos. 5,471,721, 5,632,841, 5,849,125, 6,162,313,
6,042,345, 6,060,811, and 6,071,087 showing either prestressing of
piezoelectric actuators, or dome-shaped piezoelectric actuators, or
both. This prior art is generally inapposite because the present
invention does not use a prestressed or dome-shaped piezoelectric
actuator.
[0007] U.S. Pat. Nos. 6,179,584, 6,213,735, 5,271,724, 5,759,015,
5,876,187, 6,227,809 showing so-called micropumps. Such pumps
generally pump only a drop of fluid at a time because of the small
forces and low Reynolds numbers involved, this prior art is
generally inapposite.
[0008] U.S. Pat. Nos. 4,034,780, 4,095,615 showing flapper valves.
These are flappers mounted on a separate hinge. No prior art was
found showing a flex valve with a miniature pump.
[0009] U.S. Pat. Nos. 5,084,345, 4,859,530, 3,936,342, 5,049,421
showing use of polyimide adhesives for various purposes, including
bonding metals and other materials to film.
[0010] U.S. Pat. Nos. 4,939,405, 5,945,768 showing electrical
driver circuits for piezoelectric actuators,
[0011] U.S. Pat. Nos. 6,227,824, 6,033,191, 6,109,889, German WO
87/07218 showing various kinds of pumps incorporating piezoelectric
actuators.
BRIEF SUMMARY
[0012] Thin chamber diaphragm-operated fluid handling devices,
including thin chamber pumps and thin chamber valves, facilitate
device compactness and, in some configurations, self-priming.
Diaphragm actuators of the thin chamber devices either comprise or
are driven by piezoelectric materials. The thinness of the chamber,
in a direction parallel to diaphragm movement, is in some
embodiments determined by the size of a perimeter seal member which
sits on a floor of a device cavity, and upon which a perimeter
(e.g. circumferential or peripheral portion) of the diaphragm
actuator sits. The diaphragm actuator is typically retained in a
device body between the floor seal member and another seal member
between which the perimeter of the actuator is sandwiched. The
devices have an input port and an output port.
[0013] In one embodiment, a thin chamber valve has a port seal
member seated on the floor of the device cavity and around a mouth
of a controlled one of the input port and the output port. The port
seal member has a thickness comparable to the perimeter seal member
which defines the thinness of the valve chamber. Upon selective
energization and de-energization, the actuator opens and closes the
controlled port by respectively uncovering and covering the port
seal member.
[0014] Thin chamber devices having dual chambers are also provided,
with each of the dual chamber portions being at least partially
defined by a respective actuator whose perimeter sits upon a
chamber thinness-defining seal member or gasket. Dual chamber
devices thus have two chamber lateral portions. Typically a central
wall divides the two opposing chamber lateral portions, with an
inlet port and an outlet port extending into peripheral end
portions of the central wall. The inlet and outlet ports
communicate with one or more chamber central portions, with
transmission of fluid between the central chamber portions
occurring through certain windows. A diverter portion of the
central wall influences the configuration of the windows and flow
of fluid between the ports and the dual chamber lateral portions.
Differing shapes or configurations of diverters are provided. The
diaphragm actuators for the dual chamber are simultaneously driven
or actuated so that both chamber portions simultaneously drawn in,
then expel, fluid.
[0015] Implementations of some embodiments of thin chamber pumps
utilize a wicking material situated for, e.g., the purpose of
facilitating priming of the pump with a liquid by capillary action.
In one implementation, the wicking material is situated either to
fully or partially occupy in the pumping chamber. Instead of or in
addition to a pump having wicking material in its pumping chamber,
the inlet port of a pump may also contain wicking material. Such
wicking material can either fully or partially occupy the inlet
port. In the implementations in which wicking material occupies at
least some of the pumping chamber and at least some of the inlet
port, the wicking materials may be integral or separately formed
but positioned for physical contact. The wicking material is
preferably a microfiber fabric or wicking foam material. The
wicking material situated in the pump chamber may have various
features such as holes aligned with ports of the pump, or even
channels interconnecting such holes. A self-priming method is also
provided for a pump having wicking material.
[0016] A unique flapper valve is provided for optional use with
thin chamber devices. The flapper valve comprises a thin wafer
(e.g., a circular silicon wafer) having a cut therein. The shape of
the cut (e.g., U-shaped) defines a flexible flapper which responds
to movement of the diaphragm for opening and closing the flapper
valve.
[0017] In some embodiments a valve chamber has an elastomeric wall.
A piezoelectric element of the valve is operable in a first state
to configure the elastomeric wall to a first position and to close
a controlled port, and in a second state to configure the
elastomeric wall to a second position and to open the controlled
port. The entire valve chamber may be elastomeric, and may be
integrally formed. The piezoelectric member is external to the
valve chamber and acts through an actuator rod on the valve
chamber. The piezoelectric member is thus not contacted by fluid in
the valve chamber.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing and other objects, features, and advantages
will be apparent from the following more particular description of
preferred embodiments as illustrated in the accompanying drawings
in which reference characters refer to the same parts throughout
the various views. The drawings are not necessarily to scale,
emphasis instead being placed upon illustrating the principles of
the invention.
[0019] FIG. 1 is a perspective view of the pump according to an
embodiment of the invention.
[0020] FIG. 2 is a sectional view of the pump along line 2-2 of
FIG. 1.
[0021] FIG. 3 is a sectional view of the press used to make the
piezoelectric actuators of the invention.
[0022] FIG. 4 shows the driver circuit for the piezoelectric
actuator used with the pump.
[0023] FIG. 5 is a partially diagrammatic view showing an
alternative embodiment of the invention in which the pump chamber
is reduced in size.
[0024] FIG. 6 is a partially diagrammatic view showing another
alternative embodiment of a pump in which the inlet and outlet are
perpendicular to the plane of the actuator.
[0025] FIG. 7A and FIG. 7B are schematic cross sectional front
views showing a thin chamber valve having a piezoelectric actuator,
FIG. 7A showing de-energization of the piezoelectric actuator and
FIG. 7B showing energization of the piezoelectric actuator.
[0026] FIG. 8A is a schematic cross sectional front view of a thin
chamber pump according to an example embodiment; FIG. 8B is a top
view of the pump of FIG. 8A taken along the line 8B.
[0027] FIG. 9A is a schematic cross sectional front view of a thin
chamber pump according to another example embodiment; FIG. 9B is a
cross sectional top view of the pump of FIG. 9A taken along the
line 9B.
[0028] FIG. 10A is a schematic cross sectional front view of a thin
chamber pump according to another example embodiment; FIG. 10B is a
cross sectional top view of the pump of FIG. 10A taken along the
line 10B; FIG. 10C is a cross sectional side view of the pump of
FIG. 10A taken along the line 10C.
[0029] FIG. 11A is a schematic cross sectional front view of a
first example embodiment of a thin chamber pump which uses a
wicking material; FIG. 11B is a schematic cross sectional front
view of another example embodiment of a thin chamber pump which
uses a wicking material; FIG. 11C is a schematic cross sectional
front view of yet another example embodiment of a thin chamber pump
which uses a wicking material.
[0030] FIG. 12A-FIG. 12D are top views of a differing embodiments
of wicking material usable with the pump of FIG. 11A.
[0031] FIG. 13-1 through FIG. 13-5 are schematic front views
illustrating certain basic, representative steps of a method of
self-priming a pump such the pump of FIG. 11A.
[0032] FIG. 14A is a schematic cross sectional front view of a thin
chamber pump according to an example embodiment.
[0033] FIG. 14B is top view of a flapper valve included in the pump
of FIG. 14A.
[0034] FIG. 14C is a diagrammatic perspective view of an open
flapper valve included in the pump of FIG. 14A.
[0035] FIG. 15A is a front view of a valve according to an example
embodiment showing a piezoelectric actuator in a first position;
FIG. 15A is a front view of the valve of FIG. 15A showing the
piezoelectric actuator in a second position; FIG. 15C is a top view
of the valve of FIG. 15A; FIG. 15D is a bottom view of the valve of
FIG. 15A; and FIG. 15E is a dual chamber valve variation of the
valve of FIG. 15A.
DETAILED DESCRIPTION
[0036] In the following description, for purposes of explanation
and not limitation, specific details are set forth such as
particular compositions, processes, techniques, etc. in order to
provide a thorough understanding of the present invention. However,
it will be apparent to those skilled in the art that the present
invention may be practiced in other embodiments that depart from
these specific details. In other instances, detailed descriptions
of well-known ingredients, steps, or operations are omitted so as
not to obscure the description of the present invention with
unnecessary detail.
[0037] FIG. 1 shows how the piezoelectric actuator of the present
invention may be used in a miniature diaphragm pump. The pump 10 is
generally in the form of a circular short cylinder. It includes the
pump body 12, piezoelectric actuator 14, pump cover 16 and
piezoelectric actuator electronic driver circuit 18. The pump body
12 has lugs 20 for mounting the pump to any substrate. Inlet 22 and
outlet 24 are part of the pump body 12 though they could be
separate pieces otherwise fastened to the pump body. The pump cover
16 is essentially the same diameter and of the same material as the
pump body 12. The material would ordinarily be of a standard
plastic such as acetal[DELRIN.RTM.], PVC, or PC, or of a metal such
as stainless steel or brass. These are preferable since they can be
easily machined or thermally formed. The cover 16 may be fastened
to the pump body 12 by any means such as by a fast-curing adhesive
while the pump body 12 and cover 16 are under compression such as
by clamping. The pump cover has an opening 26 for venting the space
above the actuator 14.
[0038] The dimensions of the pump depend on the particular
application. In the best mode the pump body 12 is about 40 mm [1.5
inch] in diameter. A pump chamber 30 is formed in the center of the
pump body 12, for example by molding or machining. The pump chamber
30 is about 28 mm [1.125 inch] in diameter or about 3 mm [1/8 inch]
less in diameter than the diameter of the piezoelectric actuator
14. The chamber 30 is about 6 mm [0.25 inch] deep. A seat 32 about
3 mm [0.125 inch] wide and about 2 mm [0.070 inch] deep is provided
in the pump body 12 at the top of the pump chamber 30. As shown in
FIG. 2 the piezoelectric actuator 14 is mounted on the seat 32 to
form the diaphragm in the top of the pump chamber 30.
[0039] To assemble the pump a sealing washer 34 the same diameter
as the piezoelectric actuator is put on the seat 32 to seal the
pump chamber when the piezoelectric actuator 14 is put in place.
The sealing washer 34 may be of a relatively soft material such as
Buna-N or silicon rubber to account for any irregularities in the
mating surfaces and ensure a good seal between the actuator 14 and
the pump body 12. Once the piezoelectric actuator 14 is in place an
O-ring seal 36 is placed on top of the piezoelectric actuator 14 to
hold the piezoelectric actuator 14 in place and seal it from the
cover 16. The cover 16 of the same outside diameter as the pump
body 12 base but only about 1/8 inch thick is then put in place.
Sealing washer 34 and O-ring seal 36 are referred to collectively
as the pump seals, even though they both have the additional
function of fixing the actuator 14 in place with respect to the
pump body 12. The cover 16 is then fastened to the body 12 while
under compression, for example by adhesive under clamping pressure,
to seal the piezoelectric actuator 14 to the body 12 and fix the
actuator 14 in place to allow pumping action.
[0040] The process for making the piezoelectric actuator 14
generally is as follows:
[0041] A piezoelectric wafer 38 formed of a polycrystailine
ferroelectric material such as PZT5A available from Morgan Electro
Ceramics is obtained. As the name implies this material is actually
a ceramic. It is processed into the high displacement piezoelectric
actuator 14 by laminating the piezoelectric wafer 38 between a
metal substrate layer 40 and an outer metal layer 42 as shown in
FIG. 2, where the thicknesses of the three layers and the adhesive
between them are exaggerated for clarity. The bonding agent 41
between the layers 38 and 40 is a polyimide adhesive. This
lamination process does several things: It ruggedizes the
piezoelectric actuator 14 because the metal layers keep the
piezoelectric from fracturing during high displacement. It permits
higher voltage due to the relatively high dielectric constant of
the polyimide adhesive, thereby allowing up to about twice the
displacement of a conventional piezoelectric. Being laminated
between metal layers using a high performance polyimide adhesive
makes the piezoelectric actuator highly resistant to shock and
vibrations. With this invention piezoelectric actuator devices can
be used in environments as hot as a continuous 2000C, compared to
only 115.degree. C. for a conventional piezoelectric. The
significant increase in temperature is due to the polyimide
adhesive used in the bonding process which is unaffected by
temperatures up to 200.degree. C. Epoxy adhesives used in
conventional piezoelectrics normally can withstand temperatures up
to only 115.degree. C. This increase in operating temperature would
allow the pumps of this invention to be used in a variety of pump
applications, even pumping boiling water continuously.
[0042] The piezoelectric wafers 38 are available from the vendor
mentioned in various shapes and thicknesses. For the invention
circular wafers 25 mm [1.00 inch] in diameter and 0.2 mm [0.008
inch] thick were found to be optimum. Square wafers were tried but
did not give maximum displacement. In general the thinner the
wafer, the greater the displacement at a given voltage, but the
lower the force. The 0.2 mm [8-mil] thickness gives the best flow
rate for the diameter of the wafer.
[0043] In the best mode stainless steel 0.1 mm [0.004 inch] thick
is used for the substrate layer 40, the layer in contact with the
pumped liquid. Stainless steel is chosen for its compatibility with
many liquids, including water, its fatigue resistance, its
electrical conductivity and its ready availability at low cost.
Aluminum 0.05 mm [0.001 inch] thick is used for the outer layer 42
primarily for its electrical conductivity in transmitting the
actuating voltage to the piezoelectric wafer 38 across its surface,
but also for its robustness and ready availability at low cost.
[0044] The diameter of the piezoelectric wafer 38 being about 25 mm
[1 inch] as noted above, the diameter of the substrate layer 40 is
about 40 mm [1.25 inch]. The setback of the wafer 38 from the edge
of the substrate layer 40 is an important feature of some
embodiments which seek higher actuator displacement and thus higher
flow. This leaves a rim that serves as a clamping surface for the
actuator assembly. This means that the entire piezoelectric wafer
38 is free and relatively unconstrained, except insofar as it is
bonded to the substrate 40 and the outer layer 42. This allows
maximum displacement of the actuator 14, ensuring maximum flow of
liquid through the pump.
[0045] The diameter of the outer layer 42 is smaller than the
diameter of the wafer 38. This setback of the outer layer 42 from
the edge of the wafer 38 is done to prevent arcing over of the
driving voltage from the outer layer 42 to the substrate layer
40.
[0046] Other materials and thicknesses may be used for the
enclosing layers 40 and 42 as long as they meet the requirements
noted.
[0047] Of special note is that the piezoelectric actuator of the
invention is flat. In much of the prior art the actuator is
dome-shaped, it being supposed that this shape is necessary for
maximum displacement of the actuator and therefore maximum capacity
of the pump for a given size actuator. Special molds and methods
are proliferated to produce the shapes of the actuator considered
necessary, or to produce a prestress in the actuator that is
supposed to increase its displacement. Our tests of the invention
have shown, however, that a dome shape is not necessary, and that
the flat actuator has a higher pumping capacity for a given size
than any known pump in the prior art. As such the actuator is much
simpler to produce in large quantities, as the following will
demonstrate. The flat shape also means that the pump may be smaller
for a given application. A flat actuator is also inherently easier
to mount in any given application than a dome shaped actuator would
be. Furthermore, pumps using the actuator have been shown to have
sufficiently long life for numerous applications.
[0048] The process for making the piezoelectric actuator 14
specifically is as follows:
[0049] 1. The piezoelectric wafer 38 and enclosing layers 40 and 42
are cleaned using a solvent that does not leave a residue, such as
ethanol or acetone. All oil, grease, dust and fingerprints must be
removed to ensure a good bond.
[0050] 2. The piezoelectric wafer 38 is then coated on both sides
with a thin layer 41, not more than 0.1 mm [0.005 inch], of a high
performance polyimide gel adhesive such as that available from
Ranbar Inc. The gel should contain a minimum of 25% solids to allow
sufficient material for a good bond after the solvent is driven
off.
[0051] 3. The piezoelectric wafer 38 is then placed under a
standard heat lamp for about 5 minutes to remove most of the
solvent from the gel and start the polyimide gel polymerization
process. Both sides of the piezoelectric must be cured under the
heat lamp since both sides are to be bonded to metal.
[0052] 4. Once the adhesive is dry to the touch, the piezoelectric
wafer 38 is then placed between the substrate layer 40 and the
outer layer 42.
[0053] 5. The assembly is placed in a special press. This press was
developed specifically for making piezoelectric actuators 14 and
provides uniform temperature and pressure to ensure a good bond
between the three components of the actuator. Referring to the best
mode shown in FIG. 3 the press comprises two 300 mm [12 inch]square
by 6 mm [1/4inch] thick plates of aluminum 101 held together with
thumbscrews 102, four on each edge. To ensure uniform pressure
while in the press, the bottom plate 101 of the press is covered
with a sheet of low cost polyimide film 104 such as Upilex
available from Ube Industries Ltd. The piezoelectric actuators 38
are placed on the film and a sheet of high temperature, 4 mm [1/8
inch] thick rubber 106 is placed over the piezoelectric actuators.
The rubber on top and the film on bottom cushion the piezoelectric
actuators 38 providing even distribution of pressure when the press
is taken to temperature. Of course other dimensions of the press
plates are possible.
[0054] 6. Once the piezoelectric actuators are placed in the press
the thumb screws 102 are made finger tight.
[0055] 7. The press is then placed in a standard convection oven
for thirty minutes at about 200.degree. C.
[0056] 8. The press is removed from the oven, allowed to cool to a
safe temperature, and the actuators 14 removed from the press.
[0057] The press 100 is the result of an effort to develop a low
cost, rapid process for manufacturing piezoelectric actuators. The
press takes advantage of the thermal expansion of the aluminum
plates 101 which creates the necessary pressure to cause the
polyimide adhesive to bond to the piezoelectric wafer 38 and metal
layers 40, 42 while it is at curing temperature. The press can be
put into the oven, and taken out, while the oven is at temperature
thereby allowing continuous operation during the manufacturing
process. The abrupt change in temperature does not affect the
piezoelectric actuators 14 since they will remain under pressure
even while the press is removed from the oven and allowed to assume
room temperature.
[0058] Of special note is that this press process is one of further
driving off the solvent and curing the polyimide at a relatively
low temperature. Prior art processes for making similar
piezoelectric actuators require the mold/press to be taken to much
higher temperatures, high enough to melt the polyimide adhesive.
Furthermore, since such high temperatures depole the piezoelectric
ceramic, it is necessary to pole it again at the end of the
process. The present invention eliminates this step altogether,
thus contributing to the lower cost of manufacturing the
piezoelectric actuators.
[0059] Using these simple methods and hardware it is possible to
manufacture hundreds of thousands of piezoelectric actuators 14 per
month, or even more, depending on the scale of the operation
desired.
[0060] The principle of the piezoelectric actuator pump 10 is the
same as for any diaphragm pump. Normally the diaphragm in a
diaphragm pump is operated by a cam or a pushrod connected to a
motor or engine. This is not the case in the piezoelectric actuator
pump 10. The piezoelectric actuator 14 acts as the diaphragm and
moves when a pulsed electric field is imposed across the
piezoelectric wafer 38 by means of the enclosing layers 40 and 42.
This varying electric field causes the piezoelectric actuator 14 to
expand and contract. As the actuator 14 expands, with its edge
constrained, it assumes a slight dome shape as the center of the
actuator moves away from the pump chamber 30. This draws liquid
into the pump chamber 30 through the inlet 22. When the
piezoelectric actuator 14 contracts it moves toward the liquid,
forcing it out of the pump chamber 30 through outlet 24.
[0061] One of the problems with prior art piezoelectric actuators
has been the voltage necessary to drive the piezoelectric. To
provide power to the piezoelectric actuator pump 10 the electrical
driver 18 shown in FIG. 4 was invented that converts the voltage
from any six volt d.c. power source to an alternating current of
over 200 volts peak-to-peak. This voltage is sufficient in the
preferred embodiment to drive a piezoelectric actuator to attain
the pumping rates noted above. In the circuit in FIG. 4 point A is
connected to the substrate layer 40 while point B is connected to
the outer layer 42.
[0062] Piezoelectric actuators perform better when the peak-to-peak
voltage is not evenly balanced. They respond better to a positive
voltage than the same negative voltage. Thus the circuit 18 has
been designed to produce alternating current with the voltage
offset to 150 volts positive and 50 volts negative. This is
sufficient voltage for the piezoelectric actuator to make a very
efficient pump. While a sinusoidal wave will work, at the lower
frequencies and voltages, a square wave makes the piezoelectric
more efficient. Values of the circuit components in FIG. 4 are as
follows: TABLE-US-00001 R1 - 8 to 20 M.OMEGA. R2 - 8 to 20 M.OMEGA.
R3 - 680 K.OMEGA. R4 - 1 M.OMEGA. C1 - 0.1 .mu.F C2 - 0.1 .mu.F C3
- 0.1 .mu.F[200 v] C4 - 0.47 .mu.F[200] L1 - 680 .mu.H D1 - BAS21
diode
[0063] U1 is an IMP 528 chip designated an electroluminescent lamp
driver. In this circuit, with the other components, it serves to
shape the pulses and amplify them to the 200 volt peak-to-peak
value needed to drive the piezoelectric actuator 14. The values of
R1 and R2 are chosen to vary the frequency of the output between
about 35 Hz and about 85 Hz, depending on the particular
application. It should be understood that the IMP 528 is just one
example of electroluminescent lamp driver that can be utilized as
or part of a drive circuit for the pumps and valves herein
described. Moreover, other types of drive circuits, e.g.,
micro-controller or microprocessor-based drive circuits can also be
utilized.
[0064] This circuit is composed of miniaturized components so it
may be contained in a box 302 approximately 25 mm [1 inch] square
by 6 mm [.+-.4 inch] deep. It has only eleven off-the-shelf surface
mount components. The box 302 may be mounted anywhere in proximity
to the pump 10. In the best mode it is mounted on top of the pump,
as shown in FIGS. 1 and 2, for example by an appropriate adhesive.
Leads 15 run from the driver circuit 18 and are fastened to spring
loaded contacts 304 such as those sold by the ECT Company under the
trademark POGO.RTM.. These contacts 304 are mounted in a box 306 on
top of pump cover 16 and project through the pump cover 16 to make
contact with the two layers 40 and 42. This small driver circuit
eliminates the need for the large power supplies and transformers
used in prior art piezoelectric applications. Alternatively the
leads 15 could be run through an opening in the cover 16 and
fastened electrically to the layers 40 and 42, as by soldering.
O-ring 36 is soft enough to accommodate the soldered point on the
substrate layer 42.
[0065] Several conventional types of one-way valves were evaluated
as inlet and outlet valves for the piezoelectric actuator pump 10.
All had various drawbacks including bulk and poor response to the
dynamic behavior of the piezoelectric actuator 14. An inline flex
valve 200 was invented that is well adapted to the action of the
piezoelectric actuator 14 as shown in FIG. 2. The working element
of the flex valve is an elliptical disk 202 of polyimide film about
0.05 mm [0.002 inch] thick. The disk 202 is the same size and shape
as the end of a short piece of rigid tube 204 formed at about a
45.degree. angle to the axis of the rigid tube 204. The inside
diameter of the rigid tube 204 is the same as the inside diameter
of the inlet 22 or outlet 24 of the pump body 12. Rigid tube 204 is
captured in the end of the flexible system conduit 206 which slips
over the inlet/outlet 22,24 and carries the system liquid, as shown
in FIG. 2. Valve disk 202 is attached to the nether end of the
slanted surface at the point designated 203 by any sufficient means
such as by adhesive or thermal bonding. A similar flex valve 200
may be placed in the outlet 24. Both disks 202 of both valves would
point in the same direction downstream. However, it was found in
operating the pump 10 that it would pump at full capacity with no
valve at all in the outlet. It is postulated that the liquid in the
inlet circuit, even with the inlet valve partially open, provides
enough inertia to act as a closed inlet valve. At least for some
embodiments, operation with only the inlet valve is considered to
be the best mode.
[0066] This flex valve 200 is of absolute minimum bulk. The mass of
the disk 202 is also about as light as it could possibly be so it
reacts rapidly to the action of the actuator 14. When it is open it
presents virtually no resistance to the system flow. Mounted at the
45.degree. angle, it has to move through an angle of only
45.degree. to fully open, whereas if it were mounted perpendicular
to the flow it would have to move through an angle twice as large.
It is of extreme simplicity and low cost of materials and
fabrication. Also no part of the valve 200 projects into pump
chamber 30. This minimizes the volume of pump chamber 30 which
helps make the pump self-priming and increases its efficiency.
Further contributing to these characteristics is that the flex
valve 200 is biased closed when the pump is not operating.
[0067] FIGS. 5 and 6 show alternative embodiments of the pump of
the invention. The pump in FIG. 5 is essentially the same as that
of FIG. 2 except that the pump chamber 30 is reduced in thickness
to that of the sealing washer 34. This improves the self-priming
ability of the pump. The pump in FIG. 6 also has a minimally thick
pump chamber 30. Further, the inlet 22 and outlet 24 are
perpendicular to the plane of the actuator 14, a configuration that
may be more convenient in some applications.
[0068] In yet another embodiment, not shown, the bottom of the pump
body comprises a piezoelectric actuator 14 arranged identically but
as a mirror image of the piezoelectric actuator 14 just described,
with the substrate layers 40 facing each other across the pump
chamber 30.
[0069] In still another embodiment, not shown, two of the pumps
above described are mounted side by side in one pump body. The
actuator; seals; inlets and outlets, with one-way valve in the
inlets only; pump covers; and drivers are positioned in one or more
of the configurations described above. In a preferred form of this
embodiment, the drivers are in series electrically, with the pumps
operating in parallel fluidwise in the system in which they are
deployed.
[0070] FIG. 7A and FIG. 7B show a valve 710 which resembles pump 10
of FIG. 5 in having a thin chamber 730. A piezoelectric actuator
714 is provided to at least partially define valve chamber 730. As
in the manner previously described, the piezoelectric actuator 714
comprises an essentially planar piezoelectric element (such as
piezoelectric wafer 38) having an essentially planar
fluid-contacting layer (e.g., metal substrate layer 40) adhered
thereto. As with the piezoelectric actuators for all embodiments
described herein, the piezoelectric actuator 714 can be fabricated
with a piezoelectric element which is sandwiched (e.g., by
polyimide adhesive) between a metal substrate layer and an outer
metal layer. In each of the embodiments described herein, the
layers of the piezoelectric actuators can be configured in either
of two possible configuration modes. In a configuration first mode,
already described with respect to FIG. 2, for example, the metal
substrate layer can have a diameter larger than the other layers
comprising the piezoelectric actuator to provide, e.g., the setback
which is useful for clamping the metal substrate layer only, and
thereby achieving higher displacement and flow. In a second
configuration mode, illustrated previously by FIG. 5 and FIG. 6 and
also by FIG. 7A and FIG. 7B and some other embodiments, the layers
comprising the piezoelectric actuator can have essentially the same
diameter, thereby providing a shorter moment of force and thus a
higher pumping pressure. Regardless of how illustrated or
described, it should be understood that each embodiment is
susceptible to either mode of piezoelectric actuator
configuration.
[0071] The valve 710 has a body 12 for at least partially defining
the valve chamber 730. The valve chamber 730 has an inlet port 22
and an outlet port 24. One of the inlet port 22 and the outlet port
24 is considered a "controlled" port. In the non-limiting example
herein described, the inlet 22 is preferably designated as the
controlled port.
[0072] As in the FIG. 5 embodiment, the piezoelectric actuator 714
of valve 710 has its circumference resting on valve chamber sealing
washer 34, also known as a valve chamber perimeter gasket. The
periphery of the floor (or bottom wall) of the valve chamber 730 is
the seat 32 upon which valve chamber sealing washer 34 is
positioned. In FIG. 7A and FIG. 7B, however, a port sealing gasket
737 is situated on the floor of valve chamber 730 around a mouth
723 of the controlled port, e.g., inlet 22. The port sealing gasket
737 has an interior diameter which approximates the diameter of
mouth 723 of inlet 22. The outer diameter of port sealing gasket
737 is, of course, larger than its interior diameter, but smaller
than the interior diameter of the valve chamber sealing washer 34.
The thickness of port sealing gasket 737 is approximately the same
thickness as the thickness of valve chamber sealing washer 34.
[0073] As in the case for actuators for other embodiments described
herein, the piezoelectric actuator 714 of valve 710 of FIG. 7A and
FIG. 7B is preferably fabricated generally in the manner described
above. The piezoelectric actuator 714 is connected to a driver
circuit 718. The driver circuit 718 can be, for example, of the
type previously described.
[0074] The piezoelectric actuator 714 of valve 710 of FIG. 7A and
FIG. 7B performs a valving function. In particular, in the state
shown in FIG. 7A, no power is applied to the driver circuit 718, so
that no electromagnetic field is applied to piezoelectric actuator
714. In the de-energized state of FIG. 7A, a bottom or
fluid-contacting surface of the piezoelectric actuator 714 rests
against the port sealing gasket 737, thereby preventing fluid from
entering from port 22 into valve chamber 730. That is, the
de-energized piezoelectric actuator 714 impedes flow into the
chamber 730, thereby acting as a valve. The metal substrate layer
40 of the piezoelectric actuator 714 actually sits on the port
sealing gasket 737 to stop liquid from entering from inlet 22 into
chamber 730. The metal substrate layer 40 is preferably a membrane
of stainless steel or other element having a suitably high
coefficient of thermal expansion, such as aluminum, beryllium,
brass, or copper, for example.
[0075] On the other hand, when voltage is applied to driver circuit
718, the piezoelectric actuator 714 is in an energized state (e.g.,
has an electromagnetic field applied thereto) and moves away or
deflects from the port sealing gasket 737 essentially in the manner
shown in FIG. 7B. When the piezoelectric actuator 714 is moved away
from port sealing gasket 737, fluid is then able to flow from inlet
22 into valve chamber 730, and then out of valve chamber 730 via
the outlet 24 in the manner depicted by arrows 725 in FIG. 7B.
[0076] In the quiescent state in which no power is applied to
driver circuit 718, the piezoelectric actuator 714 closes inlet 22
and thus the valve. But when a proper voltage (e.g., 3VDC to 16
VDC) is applied to driver circuit 718, the piezoelectric actuator
714 is actuated and moves away from port sealing gasket 737,
allowing fluid to move through valve chamber 30 and thus through
the valve 710.
[0077] The valve 710 of FIG. 7A and FIG. 7B thus employs
piezoelectric actuator 714 rather than a solenoid to control fluid
flow. The valve 710 employs a ruggedized piezoelectric actuator 714
and driver circuit 718 which provides the necessary displacement
for piezoelectric actuator 714 to function as a valve. Yet the
orientation of inlet port 22 and outlet port 24 relative to body 12
may vary.
[0078] In the FIG. 7A and FIG. 7B embodiment, when the controlled
port (e.g., inlet 22) is open, fluid travels between the controlled
port and the valve chamber 730 in a direction essentially
perpendicular to a plane of the fluid-contacting layer of
piezoelectric actuator 714. The particular configuration of the
valve 710 of FIG. 7A and FIG. 7B is similar to that of pump 10 of
FIG. 5 in having the orientation of inlet 22 and outlet 24 be
parallel to the plane of actuator 714. It should be understood,
however, that for the valve 710 the inlet and outlet can be
oriented in the manner of FIG. 6 as well.
[0079] In the embodiment of FIG. 7A and FIG. 7B, the piezoelectric
actuator 714 covers the controlled port (illustrated as inlet 22 in
FIG. 7A and FIG. 7B). The other port (e.g., the outlet 24 in FIG.
7A and FIG. 7B) can have, but is not required to have, its own
valve. That is, the non-controlled port can have a valve such as an
inline flex valve 200 previously described, or a miniature check
valve. In the embodiment of FIG. 7A and FIG. 7B, there is only one
controlled port, i.e., only one port having a port sealing gasket,
and preferably the controlled port is the inlet port. While it
would be possible, in another embodiment, to have the port sealing
gasket on the outlet port instead of the inlet port, placement of
the port sealing gasket at the outlet port can present
complications, particularly in exiting of fluid from the
chamber.
[0080] In one example implementation, the piezoelectric actuator
714 rests upon a valve chamber sealing washer 34 which is 0.020
inch thick and which extends around the periphery of valve chamber
30. The port sealing gasket 737 has the same thickness (0.020 inch
thick) as its sits on inlet 22. The mouth 23 of inlet 22 and the
mouth of outlet 24 both have diameters of about one eight inch
(0.125 inch).
[0081] Depending on the size of the valve 710, the input voltage
available to driver circuit 718, and the pressure and viscosity of
the fluid, the valve 710 can handle flows in a range from
microliters per minute up to twenty milliliters per minute. Due to
its small size, simple manufacturable design, flow rates, and low
current draw, the valve 710 has useful employment in diverse
products.
[0082] As with other embodiments herein described, the driver
circuit 718 can be the same or similar to the drive circuit
previously described with reference to FIG. 4, or some other
suitable electroluminescent lamp driver, or a micro-controller or
micro-processor-based circuit.
[0083] Another thin chamber device is illustrated in FIG. 8A and
FIG. 8B. The device of FIG. 8A and FIG. 8B is a pump 810 which
resembles the valve of FIG. 7A and FIG. 7B to the extent, e.g.,
that a piezoelectric actuator rests upon a chamber sealing washer
which defines the thickness of the chamber. In particular,
piezoelectric actuator 814 rests upon a pump chamber sealing washer
34. In an example implementation of the pump 810, the pump chamber
sealing washer 34 has a thickness of approximately 10 mils. Such a
small thickness makes the pump 810 self-priming. For the same
example implementation, other dimensions D1-D4 as shown in FIG. 8A
are follows: D1=1.00 inch; D2=0.156 inch; D3=0.250 inch; D4=0.187
inch. The pump 810 can be as thick as 0.625 inch and still be
self-priming.
[0084] It will be noted that the embodiments of FIG. 8A, FIG. 9A,
and FIG. 10A happen to be illustrated with the piezoelectric
actuators 814, 914, and 1014, respectively, being fabricated in
accordance with a first actuator configuration mode. In other
words, the metal substrate layers of the piezoelectric actuators
814, 914, and 1014 have a larger diameter than other layers, with
the metal substrate layers serving, e.g., as a clamping layer. But
as previously indicated, it should be understood that the
piezoelectric actuators of these and other embodiments can
alternately also be fabricated in the second mode of actuator
configuration with two or more layers having a same diameter,
particularly when higher pressure is desirable.
[0085] FIG. 9A and FIG. 9B shows a variation of the thin chamber
pump of FIG. 8A, particularly example pump 910. The pump 910 has
body 912 which includes body base 913. The body base 913 has a
generally disk shape with a diameter L I. A rim 970 of body base
913 has a greater thickness in an axial direction than does a
central wall 972 of body base 913. In FIG. 9A, the axial direction
is taken in the plane of the paper to be perpendicular to diameter
L1. The greater thickness of rim 970 of body base 913 creates two
lateral cavities 974A, 974B on opposing sides of central wall 972.
A first pump cover 916A which comprises pump body 912 substantially
closes the lateral cavity 974A, while a second pump cover 916B
substantially closes the lateral cavity 974B.
[0086] The pump body 912 together with two piezoelectric actuators
914A, 914B, define a pumping chamber. The pumping chamber has a
pumping chamber first lateral portion 930A bounded in the lateral
cavity 974A by piezoelectric actuator 914A, as well as a pumping
chamber second lateral portion 930B bounded in the lateral cavity
974B by piezoelectric actuator 914B. In addition, the pumping
chamber comprises two pumping chamber central portions 930C which
extend axially through central wall 972 to interconnect the pumping
chamber first lateral portion 930A and the pumping chamber second
lateral portion 930B.
[0087] A first of the pumping chamber central portions 930C
communicates with inlet port 922; a second of the pumping chamber
central portions 930C communicates with outlet port 924. Both inlet
port 922 and outlet port 924 extend in a radial direction into the
central wall 972 of body base 913 in aligned fashion, as depicted
in FIG. 9B. One or both of inlet port 922 and outlet port 924 has a
valve, such as the slanted inline flex valve 200 previously
described. Use of the slanted inline flex valve 200 allows higher
pump flows due to the higher displacement that results from using
the dual piezoelectric actuators 914. Other types of valves, such
as check valves, may alternatively be employed.
[0088] Each lateral portion of the pumping chamber thus has two
windows, an input window and an output window, through which fluid
travels. The pumping chamber first lateral portion 930A
communicates with the inlet port 922 through a pumping chamber
first lateral portion first window 976A-I; the pumping chamber
first lateral portion 930A communicates with the outlet port 924
through a pumping chamber first lateral portion second window
976A-O. The pumping chamber second lateral portion 930B
communicates with the inlet port 922 through a pumping chamber
second lateral portion first window 976B-I; the pumping chamber
second lateral portion 930B communicates with the outlet port 924
through a pumping chamber second lateral portion second window
976B-O.
[0089] The first piezoelectric actuator 914A, when experiencing
application of an electric field, acts upon fluid in the pumping
chamber first lateral portion 930A. The second piezoelectric
actuator 914B, in conjunction with application of the electric
field, acts upon fluid in the pumping chamber second lateral
portion 930B. A driver circuit 918 actuates the first piezoelectric
actuator 914A and the second piezoelectric actuator 914B whereby in
a deformed state the first piezoelectric actuator 914A and the
second piezoelectric actuator 914B simultaneously draw fluid into
the pumping chamber first lateral portion 930A and the pumping
chamber second lateral portion 930B, respectively.
[0090] A portion of the central wall 972 of body base 913 between
the two pumping chamber central portions 930C acts as a diverter
978 to divert fluid introduced by the inlet port 922 toward the
pumping chamber first lateral portion 930A and toward the pumping
chamber second lateral portion 930B. The diverter 978 has a first
wall 980A and a second wall 980B, both of which are essentially
parallel to a plane of the piezoelectric actuators when the
piezoelectric actuators are unactuated.
[0091] In operation, when actuated the first piezoelectric actuator
914A draws fluid through the pumping chamber first lateral portion
first window 976A-I, into the pumping chamber first lateral portion
930A, and out the pumping chamber first lateral portion second
window 976A-O toward the outlet port 924. Similarly and essentially
simultaneously, the second piezoelectric actuator 914B draws fluid
through the pumping chamber second lateral portion first window
976B-I, into the pumping chamber second lateral portion 930B, and
out the pumping chamber second lateral portion second window 976B-O
toward the outlet port 924.
[0092] As in various preceding embodiments, a first sealing member
934A extends around a periphery of the pumping chamber first
lateral portion 930A to define a height of the pumping chamber
first lateral portion 930A (between the first piezoelectric
actuator 914A when unactuated and the body 912). Similarly, a
second sealing member 934B extends around a periphery of the
pumping chamber second lateral portion 930B and defines a height of
the pumping chamber second lateral portion 930B (between the second
piezoelectric actuator 914B when unactuated and the body 912). In
the particular embodiment shown, the thickness of the pumping
chamber lateral portions 930A and 930B in an axial direction is
defined by a thickness of pumping chamber sealing washers 934A and
934B, respectively. Each of the pumping chamber sealing washers 934
can be, for example, an essentially flat gasket. In view of the
thickness of the pumping chamber sealing washers 934, the height or
thickness of each of the pumping chamber first lateral portion 930A
and the pumping chamber second lateral portion 930B is 20 mils or
less, and preferably on the order of 10 mils. Each piezoelectric
actuator 914 is retained within its respective lateral cavity 974
by having a peripheral portion of the piezoelectric actuator 914
sandwiched between the pumping chamber sealing washer 934 and
another sealing member, such as an O-ring seal 936.
[0093] For an example implementation of the embodiment shown, the
lengths L1-L4 have the respective values: L1=1.125 inch; L2=0.156
inch; L3=0.250 inch; L4=0.156 inch. If required, the inlet port 922
and outlet port 924 can be modified to make the pump even thinner
(e.g., to make L3 even smaller).
[0094] The fact that the thicknesses of the pumping chamber first
lateral portions 930 is 20 mils or less advantageously renders the
pump self-priming.
[0095] FIG. 10A, FIG. 10B, and FIG. 10C show another variation of
the thin chamber pump of FIG. 8, particularly pump 1010. The pump
1010 has body 1012 which includes body base 1013. The body base
1013, also being of a disk shape, is generally thicker in the axial
direction than body base 913 in order to accommodate a differing
diverter shape and window configuration. In particular, each
lateral portion 1030A, 1030B of the pumping chamber of the FIG.
10A-FIG. 10C embodiment has one window toward the diverter 1078 and
the pumping chamber central portions. The pumping chamber first
lateral portion 1030A communicates with the inlet port 1022, the
outlet port 1024, and the pumping chamber central portions through
a pumping chamber first lateral portion window 1076A. Likewise, the
pumping chamber second lateral portion 1030B communicates with the
inlet port 1022, the outlet port 1024, and the pumping chamber
central portions through a pumping chamber second lateral portion
window 1076B.
[0096] In the FIG. 10A-FIG. 10C embodiment, the first window 1076A
and the second window 1076B both preferably have an elliptical
shape, as shown in FIG. 10B. The pumping chamber first lateral
portion 1030A and the pumping chamber second lateral portion 1030B
both have a disk shape and lie in respective first and second
planes, the first and second planes being parallel planes. A
projection of a circumference of the first pumping chamber 1030A on
the first plane is a circle. A projection of a circumference of the
first window 1076A on the first plane is a ellipse having an axis
1082 which, when extended, forms a chord of the circle.
[0097] The function of the diverter 1078 is to divert fluid
introduced by the inlet port toward the pumping chamber first
lateral portion 1030A and toward the pumping chamber second lateral
portion 1030B. The diverter has a diverter first edge 1084A
proximate the first window 1076A and a diverter second edge 1084B
proximate the second window 1076B. The first piezoelectric actuator
1014A draws fluid around the diverter first edge 1084A from the
inlet port 1022 to the outlet port 1024. Likewise, the second
piezoelectric actuator 1014B draws fluid around the diverter first
edge 1084B from the inlet port 1022 to the outlet port 1024.
[0098] When unactuated, the first piezoelectric actuator 1014A lies
in a first plane and the second piezoelectric actuator 1014A lies
in a second plane. In a third plane which is perpendicular to the
first plane and the second plane, the diverter strut 1078 has a
quadrilateral cross-sectional shape. In particular, in the third
plane two corners 10861 and 10890 of the quadrilateral are aligned
with a fluid flow axis 1088 of the inlet port 1022 and the outlet
port 1024.
[0099] As in the preceding embodiment, a first sealing member 1034A
extends around a periphery of the pumping chamber first lateral
portion 1030A to define a height of the pumping chamber first
lateral portion 1030A between the first piezoelectric actuator
1014A when unactuated and the body 1012. Similarly, a second
sealing member 1034B extends around a periphery of the pumping
chamber second lateral portion 1030B and defines a height of the
pumping chamber second lateral portion 1030B between the second
piezoelectric actuator 1014B when unactuated and the body 1012. In
the particular embodiment shown, the thickness of the pumping
chamber lateral portions 1030A and 1030B in an axial direction is
defined by a thickness of pumping chamber sealing washers 1034A and
1034B, respectively. Each of the pumping chamber sealing washers
1034 can be, for example, an essentially flat gasket. In view of
the thickness of the pumping chamber sealing washers 1034, the
height or thickness of each of the pumping chamber first lateral
portion 1030A and the pumping chamber second lateral portion 1030B
is 20 mils or less, and preferably on the order of 10 mils. Each
piezoelectric actuator 1014 is retained within its respective
lateral cavity 1074 by having a peripheral portion of the
piezoelectric actuator 1014 sandwiched between the pumping chamber
sealing washer 1034 and another sealing member, such as an O-ring
seal 1036.
[0100] As in other embodiments, the fact that the thicknesses of
the pumping chamber first lateral portions 1030 is 20 mils or less
advantageously renders the pump self-priming.
[0101] The pump 1010 thus has dual piezoelectric actuators 1014.
The pump 1010 is capable of pumping liquids, having a viscosity
approximating that of water, at a rate of over one liter per
minute. The pump housing or pump body has two working chambers
(e.g., 1030A and 1030B) on opposite sides of the pump, with a
piezoelectric actuator 1014 for each chamber working in opposition
to each other. The inlet and outlet of the fluid is through the
center of the pump 1010. Due to the amount of fluid that the
piezoelectric actuators 1014 can pump together, the inlet port 1022
and the outlet port 1024 must be of sufficient interior diameter
(ID) to meet the needs of the piezoelectric actuators 1014. For the
size described in the example implementation, the inlet port 1022
and the outlet port 1024 have diameters of about one quarter inch
(0.25 inch) ID. The chambers 1030A and 1030B are connected in the
center of the pump so that the fluid drawn in by the piezoelectric
actuators 1014 to their respective chambers 1030 is taken from the
same intake port. When the fluid is compressed, the fluid exits the
pumping chambers into a common outlet port 1024. This technique of
using a common inlet port 1022 and a common outlet port 1024 makes
the pump extremely efficient, and makes it appear as if a single
piezoelectric actuator is pumping the fluid. Flows, depending on
voltage and frequency of the driver circuit 1018, can be as high as
1.3 liters per minute.
[0102] Thus, as with some other embodiments described herein, the
pump 1010 uses two piezoelectric actuators 1014. In one mode of
operation, the two piezoelectric actuators 1014 can be operated
in-phase with one another, e.g., with both actuators working
simultaneously to draw fluid into the pump 1010 and then to squeeze
the fluid out of pump 1010 from its individual chambers 1030. In
other modes, the two piezoelectric actuators 1014 can be operated
out of phase, or in a different phase relationship.
[0103] The inlet port 1022 and outlet port 1024 and preferably both
equipped with valves. While valves of various types may be utilized
for these ports, usage of the slant inline flex valve 200 enhances
efficiency of the pump 1010. Unlike the normal check valve which is
normally either open or closed, the slant inline flex valve 200
responds to the needs of the piezoelectric actuators 1014. The
inline flex valve 200 is biased closed and allows only the amount
of fluid to enter the pumping chamber 1030 as demanded by its
respective piezoelectric actuator 1014. Since the inline flex valve
200 is biased closed, it does not have to be closed by the
piezoelectric actuator 1014. As soon as fluid enters the pumping
chamber 1030 as commanded by the respective piezoelectric actuator
1014, the inline flex valve 200 automatically closes. The automatic
closing is a function of the flexing membrane of the piezoelectric
actuator 1014 and thus does not require energy from the
piezoelectric actuator 1014 to close. The pump 1010 is
approximately ten percent more efficient when using only one inline
flex valve 200 (on the inlet port 1022) than when using two inline
flex valves 200 (one on inlet port 1022 and one on outlet port
1024). However, when two inline flex valves 200 are used, the pump
1010 can be self-priming since employment of the two valves may
create a sufficient vacuum to draw fluid into the chamber.
[0104] FIG. 11A, FIG. 11B, and FIG. 11C show representative
implementations of three other embodiments of thin chamber pumps,
particularly pumps 1110A of FIG. 11A, pump 1110B of FIG. 11B, and
pump 1110C of FIG. 11C. Each of pump 1110A, pump 110B, and pump
1110C has a body 1112 comprising a body base 1113 and pump cover
1116. The body base 1113 has a cavity 1174 which accommodates a
disk-shaped piezoelectric actuator 1114. The piezoelectric actuator
1114 can be fabricated according to either the first mode of
actuator configuration or the second mode of actuator
configuration, as previously discussed. A rim of piezoelectric
actuator 1114 sits on pumping chamber sealing member 1134 in cavity
1174. A sealing member 1136 retains piezoelectric actuator 1114 in
cavity 1174 between sealing member 1134 and pump cover 1116. A
pumping chamber 1130 is defined between piezoelectric actuator 1114
and pump body base 1113. The pumping chamber 1130 has an inlet port
1122 and an outlet port 1124. The sealing member 1134, which
extends around an inner periphery of the pumping chamber 1130,
defines a height of pumping chamber 1130 between the piezoelectric
actuator 1114 (when unactuated) and the body 1113.
[0105] The pump 1110A of FIG. 10A, pump 1110B of FIG. 10B, and the
pump 1110C of FIG. 10C utilize a wicking material for, e.g., the
purpose of facilitating priming of the pump with a liquid by
capillary action. In the pump 1110A of FIG. 10A, a wicking material
1190 is situated either to fully or partially occupy the pumping
chamber 1130. In an embodiment in which the wicking material 1190
essentially fills the pumping chamber 1130, the wicking material
1190 has substantially the shape of the pumping chamber 1130.
[0106] For example, in an embodiment in which pumping chamber 1130
and piezoelectric actuator 1114 are essentially disk-shaped, the
wicking material 1190 is also shaped essentially as a disk. In an
example such implementation, the piezoelectric actuator 1114 (and
hence the wicking material 1190) has a diameter of one inch or
less.
[0107] It is not necessary that the wicking material 1190 fill the
pumping chamber 1130, as other configurations and shapes of wicking
material 1190 which occupy less than the maximum capacity of
pumping chamber 1130 are also possible. Preferably, however, the
wicking material 1190 is situated in pumping chamber 1130 to
overlie or contact the inlet port 1122, and (in some embodiments)
possibly the outlet port 1124 as well.
[0108] In one example embodiment, the wicking material is a micro
fiber fabric or a wicking foam material, examples of which are well
known. Although the wicking material 1190 may or may not fill the
pumping chamber 1130, the wicking material 1190 is preferably not
compressed by movement of piezoelectric actuator 1114. It will be
appreciated, particularly in view of previously described
embodiments, that the piezoelectric actuator 1114, in conjunction
with application of an electric field to a piezoelectric material,
acts upon a liquid in pumping chamber 1130.
[0109] The wicking material 1190 may have various features which
facilitate its wicking operation or operation of pump 1110 in
general. In contrast to the essentially continuous or featureless
wicking material 1190(A) shown in FIG. 12A, the wicking material
1190(B) of FIG. 12B has a first hole 1194BI which, when the wicking
material 1190B is inserted in pumping chamber 1130, is aligned with
inlet port 1122. Moreover, wicking material 190(B) has second hole
1194BO which is aligned with the outlet port 1124.
[0110] The wicking material 1190(C) of FIG. 12C also has holes
1194CI and 1194CO, with the holes 1194CI and hole 1194CO being
connected by a channel 1196C which extends along a line from a
center of hole 1194CI to a center of hole 1194CO. The channel 1196C
of wicking material 1190(C) is a rather narrow slit. The wicking
material 1190(D) of FIG. 12D, on the other hand, has two holes
holes 1194DI and 1194DO which communicate via a wider channel
1196D.
[0111] Instead of or in addition to a pump having wicking material
(such as wicking material 1190) in its pumping chamber, the inlet
port 1122 of a pump may also contain wicking material. Such wicking
material can either fully or partially occupy the inlet port. For
example, pump 1110B of FIG. 11B illustrates wicking material 1192
situated in inlet port 1122. The wicking material in the inlet port
can be of considerable length, even longer than a tube or the like
connected to the inlet port, so long as the vertical draw of the
wicking material is sufficient to accomplish the desired capillary
action. FIG. 11C illustrates pump 1110C having both wicking
material 1190 in the pumping chamber 1130 and wicking material 1192
situated in inlet port 1122. In the embodiment of FIG. 11C, the
wicking material 1192 may be integral with wicking material 1190,
or (more likely) separately formed but positioned in inlet port
1122 for physical contact with wicking material 1190 in pumping
chamber 1130.
[0112] The pumps 1110A, 1110B, and 1110C are thus miniature
piezoelectric diaphragm pumps which are self-priming. These pumps
are very small, in one example implementation having measurements
M1 through M7 has shown in FIG. 11A, FIG. 11B, and FIG. 11C (with
all measurements in inches) M1=0.625; M2=0.060; M3=0.125; M4=0.50;
M5=0.250; M6=0.03; M7=0.81.
[0113] As used herein, "self priming" means that a pump can start
pumping liquid without having mechanically to draw water into the
pumping chamber. In order to self-prime, the diaphragm must create
a vacuum in the pumping chamber to pull water into the pump. To
create the vacuum, the diaphragm must expand and compress the air
in the pumping chamber to displace the air and create a vacuum to
pull fluid into the pump and start pumping liquid. Traditionally, a
piezoelectric pump with a diaphragm smaller than one inch is
incapable of creating sufficient diaphragm displacement to be
self-priming.
[0114] The example pumps 1110A, 1110B, 1110C (collectively
referenced as pump 1110), and variations thereof, can be operated
in accordance with techniques which get liquid into the pumping
chamber 1130, thereby reducing air in the pump and allowing the
pump to self prime. FIG. 13-1 through FIG. 13-5 illustrate certain
basic, representative steps of a method of self-priming a pump such
as pump 1110 of FIG. 11A.
[0115] As a first step, the wicking material is inserted into the
pumping chamber. This first step is depicted in FIG. 13-1, which
shows wicking material 1190 in pumping chamber 1130. Note that the
particular implementation shown in FIG. 13-1, unlike that of FIG.
1B and FIG. 1C, does not have wicking material 1192 in inlet port
1122. Yet techniques suitable for pumps of FIG. 11B and FIG. 11C
are understandable also from the present description. Although any
wicking material can be used, micro fiber fabric or wicking foam
material is preferred. These materials are known for their wicking
capability through capillary action of the liquid. The wicking
material 1190 may fill all or part of the pumping chamber 1130, but
in either case in a manner so that the wicking material 1190 will
not be compressed by movement of piezoelectric actuator 1114.
[0116] Either subsequently or previously to the first step, as a
second step a wicking material 1390 is also inserted into a vessel
112 such as a tube or hose (see FIG. 13-2) Optimally, the vessel
110 has an internal diameter of less than one eight inch, and the
wicking material 1390 is the same material as wicking material
1190. For wicking material 1390, a micro fiber material is
preferred to wicking foam. The wicking material 1390 must not be
compressed in vessel 112 in order not to impede or hamper the
wicking (capillary) action.
[0117] Then, as a third basic step, a first end of the vessel 112
is inserted into or situated proximate the pumping chamber so that
the wicking material 1390 in the vessel 112 contacts the wicking
material 1190 in the pumping chamber 1130 (see FIG. 13-3). For
example, the vessel 112 may be inserted into inlet port 1122 so
that the first end of the vessel 112 contacts the wicking material
1190 in pumping chamber 1130. It is important that the wicking
material 1390 in the vessel 112 actually physically contacts or
touches the wicking material 1190 in pumping chamber 1130. Such
contact enables the liquid being wicked up the vessel 112 to be
transferred to wicking material 1190 in pumping chamber 1130.
[0118] As a fourth basic step, the second end of the vessel 112 is
then inserted into a liquid, such as liquid in liquid reservoir 114
(see FIG. 13-4). Immersion or contact of the second end of vessel
112 with the liquid facilitates the capillary action performed by
wicking material 1390 and wicking material 1190. Of course, if the
pump is provided with wicking material such as wicking material
1192 of the FIG. 11B or FIG. 11C implementation, and such wicking
material is sufficient long to extend into liquid reservoir 114,
the wicking material 1192 may be utilized in lieu of the wicking
material 1390 illustrated for the pump 1110A of the FIG. 11A
implementation.
[0119] For the fifth basic step, the pump 1110 is turned on so that
piezoelectric actuator 1114 is actuated (see FIG. 13-5). Turning on
the pump 1110 starts movement of piezoelectric actuator 1114, as
indicated by arrow 116 in FIG. 13-5. Further, the wicking action
draws liquid into pumping chamber 1130, as shown by arrow 118. When
the amount of liquid drawn into pumping chamber 1130 by capillary
action displaces sufficient air in pumping chamber 1130 for the
pump 1110 to overcome the expansion and contraction of air, the
pump 1110 will start pumping regularly.
[0120] Yet another thin chamber device is illustrated in FIG. 14A.
The device of FIG. 14A is a diaphragm pump 1410 which comprises
body 1412 for at least partially defining a shallow cylindrical
pumping chamber 1430. The pumping chamber 1430 has an inlet port
1422 and an outlet port 1424. In the particular implementation
shown in FIG. 11, the body 1412 has a body base 1413 and a body
cover 1416.
[0121] The pump 1410 has a diaphragm 1414 situated in the pumping
chamber 1430. In similar manner as piezoelectric actuator 714 above
described, the diaphragm 1414 sits on sealing washer 34 (known in
the FIG. 14A embodiment as pumping chamber sealing washer 34). The
circular periphery of diaphragm 1414 is sandwiched between pumping
chamber sealing washer 34 and O-ring seal 36.
[0122] The diaphragm 1414 acts upon a fluid in the pumping chamber
1430. Preferably action of the diaphragm 1414 is in response to
application of an electromagnetic field to a piezoelectric element.
The piezoelectric element may actually comprise the diaphragm 1414
(in the manner of piezoelectric wafer 38 comprising actuator 14 in
FIG. 2, for example). Alternatively, the diaphragm 1414 may be
mechanically connected to a piezoelectric member which moves, and
which thereby causes the diaphragm 1414 to move, in response to
application of the electromagnetic field. For example, see the
mechanical connection in FIG. 15A.
[0123] At least one, and preferably both, of inlet port 1422 and
outlet port 1424 of the pump 1410 of FIG. 14A is provided with a
flapper valve 1450. Each flapper valve 1450 is a thin wafer,
preferably circular in shape (see FIG. 14B), having an arcuate cut
1452 formed therein.
[0124] For inlet port 1422, flapper valve 1450 is situated in a
recessed seat 1454 provided on a chamber-facing surface of body
base 1413. For outlet port 1424, flapper valve 1450 is situated in
a recessed seat 1456 on a chamber-opposing face of body base 1413.
The flapper valves 1450 are held in place in their respective
recessed seats 1454 by a retainer element 1457 which is pressed
into place around the edges of the flapper valve 1450. Preferably,
the retainer element 1457 is circular.
[0125] Preferably each flapper valve 1450 is a thin silicon wafer.
In one implementation, the flapper valve 1450 has a diameter of
about 0.37 inch and a thickness of about 0.002 inch. As shown in
FIG. 14B, the arcuate cut 1452 is a substantially U-shaped cut. In
the illustrated implementation, the arcuate cut 1452 extends along
0.25 inch of the diameter of flapper valve 1450. The arcuate cut
1452 serves to form a flexible flapper 1458 which is shaped
somewhat as a peninsula in the interior of flapper valve 1450. The
flapper 1458 of flapper valve 1450 has a modulus which forces the
flapper valve 1450 to close after the piezoelectric element has
functioned to fill the chamber 1430, but which also causes
automatic closure of valve 1450 without requiring the pressure of
the piezoelectric element for the closure. For example, considering
a flapper valve 1450 installed in inlet port 1422, when the
diaphragm 1414 moves to draw fluid into pumping chamber 1430 in the
direction depicted by arrow 1460 in FIG. 14C, the flexible flapper
1458 flexes or moves also in the direction of arrow 1460.
Conversely, considering the flapper valve 1450 in outlet port 1424,
when the diaphragm 1414 is actuated to drive fluid out of diaphragm
1414 in the direction depicted by arrow 1464, the flexible flapper
1458 of the flapper valve 1450 in outlet port 1424 also flexes in
the direction of arrow 1462.
[0126] The flapper valve 1450 is particularly beneficial for
replacing metal check valves or the like in small pumps.
Advantageously, the thin flapper valve 1450 facilitates overall a
thinner pump. Whereas conventional metal check valves have a
thickness on the order of about 0.093 inch, the flapper valve 1450
has a thickness of about 0.002 inch. In the illustrated
implementation, such small thickness for flapper valve 1450 means
that the pump 1410 can have an overall thickness (in the direction
of arrow 1460) as small as 0.125 inch. As such, the pump 1410 is
particularly advantageous for use in fuel cells, fountains and
cooling solutions as well as drug infusion pumps in the medical
industry, or in any environment in which small but accurate flows
are required. The entire pump 1410 can be either molded in
ceramics, injection molded in plastic or milled in metal or
plastic.
[0127] FIG. 15A, FIG. 15B, FIG. 15C, and FIG. 15D show a valve 1510
which has a valve housing 1512. In the example illustrated
embodiment, the valve housing 1512 happens to be essentially
rectangular in shape. Internal to valve housing 1512 is a valve
chamber 1530.
[0128] The valve chamber 1530 has at least one elastomeric wall
1530W. Preferably, all walls of valve chamber 1530 are of
elastomeric composition. More preferably, the entire valve chamber
1530 comprises a unitary elastomeric part. It is advantageous that
the elastomer be a solvent resistant elastomer.
[0129] The valve chamber 1530 has both an inlet port 1522 and an
outlet port 1524. At least one of the inlet port 1522 and the
outlet port 1524 is considered to be a "controlled port". In the
specific example implementation shown in FIG. 15A-FIG. 15D, the
outlet port 1524 is considered to be the controlled port for
reasons explained below.
[0130] Within valve housing 1512 but external to valve chamber 1530
is a piezoelectric actuator element 1514, e.g., a piezoelectric
bimorph. The piezoelectric actuator 1514 is operable in a first
state to configure the elastomeric wall 1530W of the valve chamber
1530 to a first position (illustrated in FIG. 15A) to close the
controlled port (e.g., outlet port 1524). The piezoelectric
actuator 1514 is also operable in a second state to configure the
elastomeric wall 1530W of valve chamber 1530 to a second position
(illustrated in FIG. 15B) to open the controlled port.
[0131] In the illustrated example implementation, the piezoelectric
actuator 1514 is a cantilever-shaped piezoelectric element. The
piezoelectric actuator 1514 has an essentially stationary proximal
end and a distal end which is connected to the elastomeric wall
1530W of the valve chamber 1530. An actuator rod 1598 connects the
distal end of piezoelectric actuator 1514 to the elastomeric wall
1530W of valve chamber 1530. In particular, actuator rod 1598 has a
distal end which extends through the elastomeric wall and
terminates in an actuator head 1599. When the piezoelectric
actuator 1514 is in the first position, the actuator head 1599
closes the controlled port (e.g., outlet port 1524).
[0132] The valve housing 1512 thus substantially encases the valve
chamber 1530 and piezoelectric actuator 1514, with the inlet port
1522 and the outlet port 1524 also being formed in valve housing
1512. The piezoelectric actuator 1514 is connected to an
unillustrated drive circuit by leads DCL. The drive circuit is
external to valve housing 1512. Preferably only the valve chamber
1530 isolates the piezoelectric actuator 1514 from fluid in valve
chamber 1530, so that the piezoelectric actuator 1514 is never wet.
In an example implementation of valve chamber 1530, each of the
measurements N1, N2, and N3 shown in FIG. 15A-FIG. 15D are 0.5
inch.
[0133] FIG. 15E shows a dual chambered valve 1510E which is a
variation of the valve 1510 of FIG. 15A-FIG. 15D. The valve 1510E
has a winged piezoelectric actuator 1514E which has a central
mounting at center support 150 and two winged actuator levers. The
valve 1510E has two valve chambers, notably valve chamber 1530E(1)
and valve chamber 1530E(2). The measurements J1-J3 of the valve
1510E (in inches) are as follows: J1=0.5; J2=0.750; J3=0.125. In
the dual chambered, winged-actuator configuration of FIG. 15E, both
winged halves of piezoelectric actuator 1514E are actuated at the
same time using the same voltage input. This effectively doubles
the efficiency of valve 1510E by allowing two separate fluid
sources to be controlled at the same time.
[0134] The valve 1510 and valve 1510E allow the pumping volume
within valve chamber 1530 to be full of fluid and pressurized at
all time to facilitate opening and closing of the valves. The
actuator head 1599 is configured to fit flush against the orifice
of the controlled port (e.g., outlet port 1524). In the first
position shown in FIG. 15A, the actuator head 1599 stops fluid from
exiting the outlet port 1524, thus stopping liquid from entering
the inlet port 1522. Advantageously, the piezoelectric actuator
1514 lies flat, making the valves thin in the N1 dimension as shown
in FIG. 15A and FIG. 15D. The fact that the piezoelectric actuator
1514 is hermetically sealed with respect to the contents of the
valve chamber 1530 extends the life of piezoelectric actuator 1514,
since the piezoelectric actuator 1514 is not exposed to humidity
and contaminates.
[0135] This invention has particular application for water cooling
of the CPU in computers but may have wider applications wherever a
very small pump relatively high flow rate and minimum power
consumption is needed to move liquids at very low cost. The
piezoelectric actuator by itself can have very many other
applications, such as speakers, audible alarms, automotive sensors,
sound generators for active noise cancellation, and
accelerometers.
[0136] While the invention has been described in connection with
what is presently considered to be the most practical and preferred
embodiment, it is to be understood that the invention is not to be
limited to the disclosed embodiment, but on the contrary, is
intended to cover various modifications and equivalent arrangements
included within the spirit and scope of the appended claims. For
example, the driving circuit for the piezoelectric actuator may be
situated outside a device body, such as in the manner illustrated
in various drawings. Alternatively, the drive circuit can be on a
circuit board or the like situation in a cavity defined by the
device body and a lid, for example.
* * * * *