U.S. patent application number 14/488648 was filed with the patent office on 2015-03-19 for split fluidic diaphragm.
This patent application is currently assigned to Aavid Thermalloy, LLC. The applicant listed for this patent is Aavid Thermalloy, LLC. Invention is credited to Timothy Swain Lucas.
Application Number | 20150078934 14/488648 |
Document ID | / |
Family ID | 51628480 |
Filed Date | 2015-03-19 |
United States Patent
Application |
20150078934 |
Kind Code |
A1 |
Lucas; Timothy Swain |
March 19, 2015 |
SPLIT FLUIDIC DIAPHRAGM
Abstract
A diaphragm for a fluid mover, such as a synthetic jet device
includes separate, concentric substrate sections. The substrate
sections may be joined together by a resilient material at a
junction between the sections, and the sections may include
intermeshed cantilever tabs. The substrate sections may be joined
to resist pressure-induced ballooning or similar deformation, yet
allow for relatively large axial deformation.
Inventors: |
Lucas; Timothy Swain;
(Richmond, VA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Aavid Thermalloy, LLC |
Laconia |
NH |
US |
|
|
Assignee: |
Aavid Thermalloy, LLC
Laconia
NH
|
Family ID: |
51628480 |
Appl. No.: |
14/488648 |
Filed: |
September 17, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61879298 |
Sep 18, 2013 |
|
|
|
Current U.S.
Class: |
417/413.1 |
Current CPC
Class: |
F16J 3/02 20130101; F04B
43/0054 20130101; F04B 45/04 20130101; F04B 43/02 20130101; F04B
43/04 20130101 |
Class at
Publication: |
417/413.1 |
International
Class: |
F04B 43/00 20060101
F04B043/00; F04B 43/04 20060101 F04B043/04 |
Claims
1. A fluid mover comprising: a chamber having an outlet opening; a
fluidic diaphragm having a portion movable in the chamber to cause
fluid to move at the outlet opening, the fluidic diaphragm
including two or more diaphragm substrate sections including first
and second diaphragm substrate sections having cantilever tabs that
are joined together by a resilient junction material, the
cantilever tabs of the first and second diaphragm substrate
sections being at least partially intermeshed such that one or more
cantilever tabs of the first diaphragm substrate section is
positioned between two cantilever tabs of the second diaphragm
substrate section; and an actuator coupled to the fluidic diaphragm
to move the portion of the fluidic diaphragm in the chamber.
2. The fluid mover of claim 1, wherein the fluidic diaphragm is
flat, has a center, and the cantilever tabs have portions that
extend radially relative to the center.
3. The fluid mover of claim 1, wherein the cantilever tabs of each
diaphragm section form a directionally alternating and length-wise
over lapping array of cantilever tabs that define a primary flexing
portion of the diaphragm and wherein the alternating cantilever
tabs provide mutual support of each of their adjacent cantilever
tabs.
4. The fluid mover of claim 1, wherein the resilient junction
material includes an overmolding layer that bonds the cantilever
tabs of the first and second diaphragm substrate sections
together.
5. The fluid mover of claim 1, wherein the first and second
diaphragm substrate sections are concentric with the first
diaphragm substrate section located inside of the second diaphragm
substrate section.
6. The fluid mover of claim 5, wherein the cantilever tabs of the
first diaphragm substrate section extend radially outwardly from a
main body of the first diaphragm substrate section and the
cantilever tabs of the second diaphragm substrate section extend
radially inwardly from the second diaphragm substrate section.
7. The fluid mover of claim 6, wherein the cantilever tabs of the
first and second diaphragm substrate sections are interdigitated
such that the cantilever tabs of the first diaphragm substrate
section are each positioned between a respective pair of cantilever
tabs of the second diaphragm substrate section.
8. The fluid mover of claim 1, wherein the first and second
diaphragm substrate sections each have a main body and the
cantilever tabs each have a triangular shape that extends from the
main body of the corresponding diaphragm substrate section.
9. The fluid mover of claim 1, wherein the diaphragm substrate
sections are formed of a sheet metal.
10. The fluid mover of claim 1, wherein the resilient junction
material includes a rubber.
11. The fluid mover of claim 1, wherein the resilient junction
material is positioned in gaps between adjacent cantilever
tabs.
12. The fluid mover of claim 11, wherein the resilient junction
material is positioned over a top or bottom surface of cantilever
tabs of the fluidic diaphragm.
13. The fluid mover of claim 1, wherein the first and second
diaphragm substrate sections, including the cantilever tabs, are
flat and arranged in a common plane.
14. The fluid mover of claim 1, wherein the fluidic diaphragm is
arranged for vibratory movement in the chamber in which a portion
of the fluidic diaphragm moves at a frequency of 0.1 Hz to 1 kHz or
more.
15. The fluid mover of claim 1, wherein the fluidic diaphragm has a
periphery which is fixed relative to the chamber, and the actuator
is arranged to move portions of the fluidic diaphragm located
inward of the periphery relative to the chamber.
16. A fluid mover comprising: a chamber having an outlet opening; a
fluidic diaphragm having a portion movable in the chamber to cause
fluid to move at the outlet opening, the fluidic diaphragm
including first and second diaphragm substrate sections that are
flat and concentric such that the first diaphragm substrate section
is located inside of the second diaphragm substrate section, the
first and second diaphragm substrate sections being joined together
by a resilient junction material; and an actuator coupled to the
fluidic diaphragm to move the portion of the fluidic diaphragm in
the chamber.
17. The fluid mover of claim 16, wherein the first diaphragm
substrate section has portions that extend radially outwardly and
the second diaphragm substrate section has portions that extend
radially inwardly, the radially outwardly and radially inwardly
extending portions being interleaved such that one or more
outwardly extending portions of the first diaphragm substrate
section is positioned between two inwardly extending portions of
the second diaphragm substrate section.
18. The fluid mover of claim 16, wherein the fluidic diaphragm has
a spring stiffness in relation to pressure deformation that is 34
to 64 times greater than a spring stiffness of the fluidic
diaphragm in relation to axial displacement.
19. A fluidic diaphragm comprising: first and second diaphragm
substrate sections that are flat and concentric such that the first
diaphragm substrate section is located inside of the second
diaphragm substrate section, the first and second diaphragm
substrate sections being joined together by a resilient junction
material.
20. The fluidic diaphragm of claim 19, wherein the first and second
diaphragm substrate sections each have cantilever tabs that are
joined together by the resilient junction material and are at least
partially intermeshed such that one or more cantilever tabs of the
first diaphragm substrate section is positioned between two
cantilever tabs of the second diaphragm substrate section.
21. The fluidic diaphragm of claim 19, wherein the first and second
diaphragm substrate sections have cantilever tabs that are joined
together by the resilient junction material.
22. The fluidic diaphragm of claim 21, wherein the fluidic
diaphragm is flat, has a center, and the cantilever tabs have
portions that extend radially relative to the center.
23. The fluidic diaphragm of claim 21, wherein the cantilever tabs
of each diaphragm section form a directionally alternating and
length-wise over lapping array of cantilever tabs that define a
primary flexing portion of the diaphragm and wherein the
alternating cantilever tabs provide mutual support of each of their
adjacent cantilever tabs.
24. The fluidic diaphragm of claim 21, wherein the resilient
junction material includes an overmolding layer that bonds the
cantilever tabs of the first and second diaphragm substrate
sections together.
25. The fluidic diaphragm of claim 21, wherein the cantilever tabs
of the first diaphragm substrate section extend radially outwardly
from a main body of the first diaphragm substrate section and the
cantilever tabs of the second diaphragm substrate section extend
radially inwardly from the second diaphragm substrate section.
26. The fluidic diaphragm of claim 21, wherein the cantilever tabs
of the first and second diaphragm substrate sections are
interdigitated such that the cantilever tabs of the first diaphragm
substrate section are each positioned between a respective pair of
cantilever tabs of the second diaphragm substrate section.
27. The fluidic diaphragm of claim 21, wherein the first and second
diaphragm substrate sections each have a main body and the
cantilever tabs each have a triangular shape that extends from the
main body of the corresponding diaphragm substrate section.
28. The fluidic diaphragm of claim 19, wherein the diaphragm
substrate sections are formed of a sheet metal, and the resilient
junction material includes a rubber.
29. The fluidic diaphragm of claim 21, wherein the resilient
junction material is positioned in gaps between adjacent cantilever
tabs.
30. The fluidic diaphragm of claim 29, wherein the resilient
junction material is positioned over a top or bottom surface of
cantilever tabs of the fluidic diaphragm.
31. The fluidic diaphragm of claim 19, wherein the fluidic
diaphragm is arranged for vibratory movement in a chamber in which
a portion of the fluidic diaphragm moves at a frequency of 0.1 Hz
to 1 kHz or more.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of U.S. Provisional
Application No. 61/879,298, filed Sep. 18, 2013, which is hereby
incorporated by reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1) Field of Invention
[0003] This invention relates generally to diaphragms for the
pumping of fluids in positive displacement pumping devices,
otherwise known as fluid movers, such as liquid pumps, gas
compressors and synthetic jets and in general to the transfer of
energy to fluids.
[0004] 2) Description of Related Art
[0005] When compared to rotary, piston, centrifugal and other
pumping approaches, diaphragms provide a lower profile means for
creating a cyclic positive displacement for small fluid movers such
as pumps, compressors and synthetic jets. It is an advantage for
all sizes of fluid movers to increase their pumping power density
as defined by pumping power divided by the fluid mover size. To
increase pumping power requires an increase in either displacement
per stroke or pressure lift or both. A common limitation of
diaphragms is that they do not provide large volumetric
displacements due to their small strokes which are limited by the
bending and tensile stresses of the diaphragm materials such as
metals or plastics. If more resilient or stretchable materials such
as common elastomers are used that permit larger strokes, then the
diaphragm will typically flex during a stroke in response to
increasing pressure, thus preventing larger pressure lifts and
preventing higher power densities.
[0006] One particular diaphragm issue for miniature fluid movers
pertains to high power synthetic jets. Synthetic jets can provide
significant energy savings when used for cooling high power density
and high power dissipation electronics products such as for example
servers, computers, routers, laptops, HBLEDs and military
electronics. U.S. Pat. No. 8,272,851 and PCT application
PCT/US2011/055196 describe various arrangements for synthetic jet
systems and other fluid mover systems, and are both hereby
incorporated by reference in their entirety.
SUMMARY OF THE INVENTION
[0007] However, the compression chamber of a synthetic jet actuator
must provide relatively large strokes and high dynamic pressures in
order to drive large, multi-port manifolds while at the same time
the actuator must be small enough to fit within many
space-constrained products. Conventional diaphragm technologies
that are stiff enough to create large fluid pressures, such as
those that use a single piece metal diaphragm, cannot provide the
required volume displacement to drive multi-port manifolds.
Conversely, elastomeric diaphragms that are flexible enough to
provide large displacements cannot create high dynamic pressures
needed for some applications. These same limitations of
conventional diaphragms also make it difficult to downsize other
fluid movers such as liquid pumps and gas compressors without
significant loss of pumping power performance.
[0008] There is therefore a need for positive displacement
diaphragms that are compliant with respect to relatively large
axial strokes, but at the same time are stiff enough to create
relatively large dynamic pressures, thereby enabling increased
pumping power density for miniature fluid movers including
synthetic jets, liquid pumps and gas compressors.
[0009] Aspects of the invention provide a diaphragm for a fluid
mover, such as a synthetic jet generator, that is suitably
compliant to accommodate relatively large axial strokes and
volumetric displacements, but is suitably stiff to create
relatively large dynamic pressures. For example, in one embodiment,
a diaphragm substrate includes two or more separate substrate
sections which are connected to each other by a resilient material
junction (such as an elastomeric over molding). Each diaphragm
substrate section, which may be formed from a metal sheet, may
include a plurality of cantilever tabs that are closely adjacent
to, and are intermeshed with, counter facing cantilever tabs of the
other diaphragm section. For example, the cantilever tabs may
extend like fingers from each diaphragm substrate section and
intermesh with the finger-like tabs of the adjoining diaphragm
substrate section. The counter facing tabs are bonded together by
the resilient material in such a way that they must follow a nearly
identical displacement distribution as the diaphragm is moved. Once
bonded together, the counter facing tabs work synergistically so as
to respond very differently to axial diaphragm displacements as
opposed to pressure deformation, whereby the cantilever tabs
present a low spring stiffness (spring k rate) to axial
displacements with acceptable material stress levels and conversely
present a much higher spring stiffness to pressure deformations
resulting in very small pressure deformations. The reason that
different spring k rates occur is that axial displacement and
pressure deformation encounter very different cantilever end
constraints. The resilient elastomeric connection between the
diaphragm sections may serve to connect the finger-like tabs
together, allowing the cantilever tabs to support each other in
bending, and yet allow the tabs to move or slip relative to each
other in the plane of the diaphragm, thereby relieving large
in-plane stresses that can occur if the diaphragm substrate
sections were to bend while being unable to move or slip relative
to each other. As such, the diaphragm may accommodate relatively
large axial deflections, but since adjoining cantilever tabs of the
two diaphragm sections may support each other in bending and slip
relative to each other, the diaphragm may remain relatively stiff.
That is, once coupled by the elastomeric over molding or other
resilient junction material, the adjoining cantilever tabs may work
synergistically together to provide a diaphragm that: (1) allows
large axial displacements (i.e., in directions transverse to the
plane of the diaphragm) without excessive stresses which enables
large volumetric displacements in a low-profile small-footprint
diaphragm assembly, (2) presents a high stiffness in resistance to
fluid pressure induced deformation of the diaphragm to minimize
ballooning or yielding of the flexing cantilever section which
enables the diaphragm to create large cyclic pressures, and (3)
provides a diaphragm design capable of providing a wide range of
axial spring k values that can enable the resonant operation of
fluid movers at commercially desirable frequencies.
[0010] In one aspect of the invention, a fluid mover includes a
chamber having an outlet opening, and a fluidic diaphragm having a
portion movable in the chamber to cause fluid to move at the outlet
opening. The fluidic diaphragm may include two or more diaphragm
substrate sections including first and second diaphragm substrate
sections having cantilever tabs that are joined together by a
resilient junction material. The cantilever tabs of the first and
second diaphragm substrate sections may be at least partially
intermeshed such that one or more cantilever tabs of the first
diaphragm substrate section is positioned between two cantilever
tabs of the second diaphragm substrate section. An actuator may be
coupled to the fluidic diaphragm to move the portion of the fluidic
diaphragm in the chamber.
[0011] In another aspect of the invention a fluid mover includes a
chamber having an outlet opening, and a fluidic diaphragm having a
portion movable in the chamber to cause fluid to move at the outlet
opening. The fluidic diaphragm may include first and second
diaphragm substrate sections that are flat and concentric such that
the first diaphragm substrate section is located inside of the
second diaphragm substrate section, and the first and second
diaphragm substrate sections may be joined together by a resilient
junction material. An actuator may be coupled to the fluidic
diaphragm to move the portion of the fluidic diaphragm in the
chamber.
[0012] In some embodiments, the fluidic diaphragm is flat, has a
center, and has cantilever tabs with portions that extend radially
relative to the center. The cantilever tabs of each diaphragm
section may form a directionally alternating and length-wise
overlapping array of cantilever tabs that define a primary flexing
portion of the diaphragm, and alternating cantilever tabs may
provide mutual support of each of their adjacent cantilever tabs.
For example, the cantilever tabs of the first and second diaphragm
substrate sections may be interdigitated such that the cantilever
tabs of the first diaphragm substrate section are each positioned
between a respective pair of cantilever tabs of the second
diaphragm substrate section. The cantilever tabs of the first
diaphragm substrate section may extend radially outwardly from a
main body of the first diaphragm substrate section, and the
cantilever tabs of the second diaphragm substrate section may
extend radially inwardly from the second diaphragm substrate
section. The cantilever tabs may have a variety of different
shapes, such as a triangular shape that extends from a main body of
the corresponding diaphragm substrate section.
[0013] In some embodiments, the resilient junction material may
include an overmolding layer that bonds the cantilever tabs of the
first and second diaphragm substrate sections together, e.g., the
resilient junction material may be injection molded over and around
portions of the cantilever tabs. The resilient junction material
may be positioned in gaps between adjacent cantilever tabs, and/or
over a top or bottom surface of cantilever tabs of the fluidic
diaphragm.
[0014] In some embodiments, the fluidic diaphragm may have a
periphery which is fixed relative to the chamber, and the actuator
may be arranged to move portions of the fluidic diaphragm located
inward of the periphery relative to the chamber.
[0015] In some arrangements, the fluidic diaphragm may have a
spring stiffness in relation to pressure deformation that is 34 to
64 times greater than a spring stiffness of the fluidic diaphragm
in relation to axial displacement.
[0016] It should also be noted that aspects of the invention
include a fluidic diaphragm configured as described herein, and
need not be coupled with an actuator and/or positioned in a chamber
of a fluid mover.
[0017] These and other aspects of the invention will be apparent
from the following description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The accompanying drawings, which are incorporated in and
form a part of the specification, illustrate select embodiments of
the present invention and, together with the description, serve to
explain the principles of the inventions. In the drawings:
[0019] FIG. 1 shows a sectional view of a fluid mover in an
illustrative embodiment;
[0020] FIG. 2 shows a top view of a diaphragm of the fluid mover of
FIG. 1 in accordance with an embodiment of the invention;
[0021] FIG. 3 shows the outer of two diaphragm substrate sections
of the FIG. 2 embodiment;
[0022] FIG. 4 shows the inner of two diaphragm substrate sections
of the FIG. 2 embodiment;
[0023] FIG. 5 shows the diaphragm of FIG. 2 with a two-sided
elastomeric over molding resiliently connecting the two diaphragm
substrate sections;
[0024] FIG. 6 shows how the counter facing cantilever tabs of the
two diaphragm section are constrained by the resilient over molding
(not shown) to bend with the same displacement distribution;
[0025] FIG. 7 shows a sectional view of a pump or compressor fluid
mover with a diaphragm undergoing pressure deformation or (aka
ballooning);
[0026] FIG. 8 illustrates beam deflection for a free end, fixed end
beam;
[0027] FIG. 9 illustrates beam deflection for a free end, simply
supported beam;
[0028] FIG. 10 illustrates beam deflection for a fixed end, fixed
end beam;
[0029] FIG. 11 illustrates another embodiment in which each
cantilever tab has a narrow, distal extension that is supported at
an opposing diaphragm clamp circle;
[0030] FIG. 12 illustrates another embodiment of a diaphragm having
three diaphragm substrate sections;
[0031] FIG. 13 illustrates a diaphragm with a non axi-symmetric
arrangement, e.g., having a rectangular shape; and
[0032] FIG. 14 shows a resilient junction material in the form of
an elastomeric over molding with ribs to provide additional support
while minimizing cyclic elastomeric damping.
DETAILED DESCRIPTION
[0033] Aspects of the invention are not limited in application to
the details of construction and the arrangement of components set
forth in the following description or illustrated in the drawings.
Other embodiments may be employed and aspects of the invention may
be practiced or be carried out in various ways. Also, aspects of
the invention may be used alone or in any suitable combination with
each other. Thus, the phraseology and terminology used herein is
for the purpose of description and should not be regarded as
limiting.
[0034] FIG. 1 shows a sectional view of a fluid mover 4 in an
illustrative embodiment that includes a chamber 6 having an
internal volume in which a diaphragm 2 and actuator 12 are located.
In this embodiment, the internal volume of the chamber 1 above the
diaphragm 2 is closed except for an opening 8 located in a top wall
of the chamber 6. (The opening 8 may be located in other places,
such as a sidewall of the chamber 6, if desired, and in some
embodiments such as liquid pumps and gas compressors, two or more
openings may be provided and these openings may also include valves
to enable fluid compression and/or one-directional flow). The
diaphragm 2 is controllable to move cyclically in the chamber 6 so
that air or other fluid is alternately drawn into the opening 8 and
then driven out of the opening 8 in the direction of an arrow 10.
As is known to those of skill in the art and described in more
detail in U.S. Pat. No. 8,272,851, this air movement at the opening
3 can cause the formation of a series of air pulses and vortex
rings that move away from the opening 8 in the direction of the
arrow 10 so that a synthetic jet is created. Movement of the
diaphragm 2 is caused by the actuator 12, which may be a voice
coil, piezoelectric, magnetostrictive, capacitive, variable
reluctance, solenoid or other electromagnetic, mechanical
concentric or other drive. Details regarding diaphragm actuators
are provided in U.S. Pat. No. 8,272,851 and PCT application
PCT/US2011/055196 as well. In short, the diaphragm 2 may be moved
by any suitable actuator as aspects of the invention are not
limited in this regard.
[0035] Operation of the actuator 12 may be controlled by a
controller 14 (e.g., including a suitably programmed general
purpose computer or other data processing device) that receives
control information (e.g., from one or more sensors, user input
devices, etc.) and correspondingly controls operation of the
actuator 4 and/or other fluid mover components. The controller 14
may include any suitable components to perform desired control,
communication and/or other functions. For example, the controller
14 may include one or more general purpose computers, a network of
computers, one or more microprocessors or PICs, etc., for
performing data processing functions, one or more memories for
storing data and/or operating instructions (e.g., including
volatile and/or non-volatile memories such as optical disks and
disk drives, semiconductor memory, magnetic tape or disk memories,
and so on), communication buses or other communication devices for
wired or wireless communication (e.g., including various wires,
switches, connectors, Ethernet communication devices, WLAN
communication devices, and so on), software or other
computer-executable instructions (e.g., including instructions for
carrying out functions related to controlling the actuator 12, and
other components), a power supply or other power source (such as a
plug for mating with an electrical outlet, batteries, transformers,
etc.), relays, other switching devices and/or drive circuitry for
driving the actuator 12, mechanical linkages, one or more sensors
or data input devices (such as a sensor to detect movement and/or
position of the diaphragm 2 and/or temperature of a device being
cooled by a jet stream created by the fluid mover 4, user-operated
buttons or switches, and interface to receive control instructions
from another device, and so on), user data input devices (such as
buttons, dials, knobs, a keyboard, a touch screen or other),
information display devices (such as an LCD display, indicator
lights, a printer, etc.), and/or other components for providing
desired input/output and control functions. In short, the
controller 14 may include any suitable components to perform
desired control and communication functions for the fluid mover 4
or for other fluid movers such as liquid pumps, gas compressors or
acoustic pumps and compressors.
[0036] In accordance with an aspect of the invention, the fluid
mover may include a fluidic diaphragm that includes first and
second diaphragm substrate sections that are flat, separate from
each other, and concentric such that the first diaphragm substrate
section is located inside of the second diaphragm substrate
section. The diaphragm substrate sections may have portions that
are intermeshed with each other and that are joined by a resilient
junction material so that the diaphragm substrate sections can
support each other in bending, yet move or slip relative to each
other in the plane of the diaphragm.
[0037] In another aspect of the invention, the diaphragm may
include two or more diaphragm substrate sections arranged so that
the diaphragm substrate sections have counter facing cantilever
tabs that are joined together by a resilient junction material. In
some embodiments, the cantilever tabs of the diaphragm substrate
sections may be at least partially intermeshed such that one or
more cantilever tabs of a diaphragm substrate section is positioned
between two cantilever tabs of another diaphragm substrate section.
In some embodiments, the diaphragm substrate sections may be
separated from each other by a gap and be joined together by a
resilient junction material so that the diaphragm formed is thereby
sealed and made capable of moving fluid and has desired pumping
power and volume displacement characteristics. In addition, such an
arrangement may allow for the diaphragm to have a desired axial
spring stiffness so that the diaphragm can serve as a spring in a
fluid mover having a spring-mass resonance thereby allowing the
fluid mover to be operated at a desired resonant frequency and
relatively high efficiency. That is, it is typically more efficient
to drive a fluid mover at or near its spring-mass resonant
frequency and aspects of the invention may allow for a diaphragm to
be constructed that provides the spring stiffness required for a
desired resonant frequency. For example cantilever tab shape, size
thickness or other characteristics may be defined to provide the
diaphragm with desired spring stiffness.
[0038] FIG. 2 shows a top view of an illustrative diaphragm that
may be used in the fluid mover 4 of FIG. 1 and has first and second
diaphragm substrate sections 2a, 2b. When assembled as a diaphragm
2 as shown in FIG. 2, the two diaphragm substrate sections 2a, 2b
may be flat, concentric, lie in a common plane, and be separated by
a gap or slot 16. The diaphragm substrate sections 2a, 2b (which
are shown individually in FIGS. 3 and 4) may be formed as a flat
sheet, e.g., cut from a metal sheet such as a steel. The diaphragm
design of FIG. 2 has an outer diameter of 2.650 in and a thickness
of 0.003 in, but a wide range of other diameters, thicknesses and
cantilever tab dimensions can be chosen to meet the needs of
specific application requirements. (While the first diaphragm
substrate section 2a is shown having a central hole, e.g., to
facilitate attachment of the section 2a to an actuator 12, the
central hole is not necessarily required.) As noted above, the
diaphragm substrate sections 2a, 2b may have cantilever tabs 18
that are intermeshed so that at least one cantilever tab 18 of one
section 2a, 2b is located between two cantilever tabs 18 of the
other diaphragm substrate section 2a, 2b. In this embodiment, the
cantilever tabs 18 are interdigitated so that each cantilever tab
18 of one diaphragm substrate section 2a, 2b is positioned between
a pair of cantilever tabs 18 of the other diaphragm substrate
section 2a, 2b, but other interleaving or intermeshing arrangements
are possible. For example, two or more cantilever tabs 18 of one
diaphragm substrate section 2a, 2b may be located between a pair of
cantilever tabs 18 of the other diaphragm substrate section 2a, 2b.
Other variations are possible.
[0039] In accordance with another aspect of the invention, the two
or more diaphragm substrate sections may be separated from each
other (e.g., by a gap 16), yet be attached to each other by a
resilient junction material. The resilient junction material may
fill the gap 16 between the diaphragm substrate sections 2a, 2b
and/or be arranged on a top and/or bottom side of the diaphragm
substrate sections 2a, 2b. The resilient junction material may be
positioned only in the area of the cantilever tabs 18 or may be
arranged on other portions of the diaphragm substrate sections 2a,
2b. In the illustrative embodiment as shown in FIG. 5, the
diaphragm substrate sections 2a, 2b are joined by a resilient
junction material 24 that is arranged in the gap 16 between the
diaphragm substrate sections 2a, 2b, as well as being arranged as a
layer on top and bottom surfaces of the diaphragm substrate
sections 2a, 2b. In this embodiment, the resilient junction
material 24 is formed as an over molding of a rubber or other
resilient material (e.g., by injection molding a rubber from top
and bottom sides of the diaphragm 2), but other arrangements are
possible. For example, a sheet of rubber or other suitable material
may be adhered to the top and/or bottom surface of the diaphragm 2
with or without resilient material being located in the gap 16 or
resilient material can be located in gap 16 without being adhered
to the top and bottom surface of diaphragm 2. Alternatively, the
clearance between sections 2a, 2b can be removed so that the gap 16
is eliminated with the edges of sections 2a, 2b being in contact or
in some cases overlapping.
[0040] Once sections 2a, 2b of diaphragm 2 are coupled together by
the resilient junction material, diaphragm 2 exhibits unique
characteristics that enable large volumetric displacements while
resisting pressure deformation. The respective axial deformation
and pressure deformation characteristics in one illustrative
embodiment are described as follows.
[0041] Axial Deformation
[0042] In operation, section 2b of diaphragm 2 may be rigidly
clamped along clamp circle 22 (e.g., between portions of the
housing of the fluid mover 4 as suggested in FIG. 1) and section 2a
may be clamped along clamp circle 20 (e.g., between portions of a
reciprocating clamp 11 as shown in FIG. 1). When clamped in this
manner, only cantilever tabs 18 bend when reciprocating clamp 11 is
displaced from its rest position relative to the housing of the
fluid mover 4.
[0043] Resilient junction material 24 of FIG. 5 constrains the
counter facing tabs 18 of sections 2a, 2b to bend with a similar
displacement distribution y(r), where y is the displacement from
the diaphragm's rest plane at a radial distance r from the clamp
circle 22. FIG. 6 illustrates how the cantilever tabs of sections
2a, 2b follow a same displacement distribution, where the resilient
junction material 24 is not shown to more clearly illustrate the
bending of tabs 18. The cantilever bending modes shown in FIG. 6
were generated using finite element software where the model
included a rubber over molding material 24 shown in FIG. 5.
[0044] The resilient junction material 24 allows some slip between
counter facing cantilever tabs 18 of sections 2a, 2b and this
slippage relieves the displacement-induced stresses that would
otherwise occur in a one-piece diaphragm. Consequently, much larger
displacements can be achieved with peak stresses being low enough
to provide long life. A further advantage of diaphragm 2 of FIG. 5
is that it provides an effective piston area that is larger than a
clamped one-piece diaphragm. For diaphragm 2 of FIG. 5, the
diameter of clamp circle 20 is 2/3 the diameter of clamp circle 22
and the effective piston diameter of diaphragm 2 is the average of
the diameters of clamp circles 20 and 22. This diameter yields an
effective piston area that is 70% of a piston having a diameter
equal to clamp circle 22. By comparison, a simple metal disk
clamped at clamp circle 22 would have an effective piston area of
only 30% of a piston having a diameter equal to clamp circle 22. A
larger effective piston area provides proportionately larger
volumetric displacement for a given diaphragm stroke, and this is a
significant advantage when miniaturizing fluid movers without
losing pumping performance. Effective piston areas higher than 70%
can be achieved simply by using more cantilever tabs of reduced
length, which would allow the diameter of clamp circle 20 to be
increased.
[0045] Pressure Deformation
[0046] While the axial diaphragm deformations described above
provide the volumetric displacements needed to do fluid pumping
work, that volumetric displacement can be reduced by pressure
deformations, thereby reducing the pumping work done. FIG. 7
illustrates a case of diaphragm pressure deformation that would
reduce the pumping work done by the diaphragm 2. In FIG. 7, a
diaphragm 28 is clamped into fluid mover 26, which in this case is
a pump or compressor having outlet port 30 and inlet port 32 with
respective valves 34 and 36. If the unsupported span 29 of
diaphragm 28 is too compliant, then when plunger 38 moves upward
thereby moving the diaphragm 28 upward and increasing the fluid
pressure in chamber 40, the unsupported span 28 will deform or
balloon as shown in FIG. 7. This ballooning relieves the pressure
within chamber 40 and the ballooning volume of unsupported span 28
subtracts from the displaced volume created by the stroke of
diaphragm 28 in the absence of ballooning. Consequently, both
pressure and volumetric displacement are reduced which in turn
reduces pumping power. To more clearly illustrate the ballooning
effect, the fluid mover 26 of FIG. 7 shows the diaphragm at its
rest position. During operation, the ballooning deformation is
superimposed on the axial deformation, but otherwise has the same
disadvantageous effect described above.
[0047] Aspects of the invention minimize pressure deformation of
the diaphragm thereby maximizing pumping power. In order to
minimize pressure deformation while still enabling comparatively
large axial strokes with low related material stress, the diaphragm
design in accordance with aspects of the invention creates a very
high stiffness which acts only against pressure deformation, while
presenting a much lower stiffness to the desired axial
displacements. Since the cantilever tabs are beams in the
analytical sense, some insight can be provided into how the
diaphragm can present a lower spring stiffness to axial deformation
and a higher spring stiffness to pressure deformation by looking at
the beam deflection equations for end constraint conditions that
resemble these two types of deformation. Here these equations are
used to calculate a comparative spring stiffness constant k, for
the two cases. The comparison is intended to approximate the ratio
of the spring k values, but not to find their absolute values. For
each case the cantilever geometry is assumed identical and only the
end constraints are changed, which allows the relative comparisons
(i.e. k ratio) to be found. Also, making spring k comparisons
requires that point loads are used in each case.
[0048] Solving for k from the equation F=kx, where is F is the
applied force, k is the spring constant and x is the spring
displacement, gives k=F/x.
[0049] FIG. 8 schematically illustrates beam bending for a
cantilever with a fixed end, a free end and point load at W. This
case most closely resembles the bending mode of a cantilever tab
when the diaphragm undergoes an axial deformation (displacement).
When the perimeter of diaphragm 2 is clamped and the center portion
is displaced, the stiffness contributed by a single cantilever is
represented by letting a=0 in max deflection equation. Beam
equations for bending as shown in FIG. 8 are provided in Table 1
below (reproduced from Roark's Formulas for Stress and Strain,
2.sup.nd Edition, page 189).
TABLE-US-00001 TABLE 1 R A = 0 M A = 0 .theta. A = w ( l - a ) 2 2
EI ##EQU00001## Max M = M.sub.B; max possible value = -Wl when a =
0 y A = - w 6 EI ( 2 l 3 - 3 l 2 a + a 3 ) ##EQU00002## Max .theta.
= .theta. A ; max possible value = w l 2 2 EI when a = 0
##EQU00003## R.sub.B = W M.sub.B = -W(l - a) Max y = y A ; max
possible value = w l 3 3 EI when a = 0 ##EQU00004## .theta..sub.B =
0 y.sub.B = 0
[0050] FIG. 9 schematically illustrates beam bending for a
cantilever beam that is simply supported at its free end (the free
end can slide and rotate) and with a point load at W. FIG. 10
schematically illustrates beam bending for a beam that is fixed at
both ends and with a point load at W. These bending modes most
closely resemble the bending of a cantilever in response to
pressure deformation of the diaphragm, and FIG. 10 illustrates
bending in response to pressure-induced ballooning as in FIG. 7.
Beam equations for bending as shown in FIGS. 9 and 10 are provided
in Tables 2 and 3 below (reproduced from Roark's Formulas for
Stress and Strain, 2.sup.nd Edition, page 190).
TABLE-US-00002 TABLE 2 R A = w 2 l 3 ( l - a ) 2 ( 2 l + a ) M A =
0 ##EQU00005## Max + M = Wa 2 l 3 ( l - a ) 2 ( 2 l + a ) at x = a
; max possible value = 0.174 W l when a = 0.3661 ##EQU00006##
.theta. A = - w a 4 EIl ( l - a ) 2 y A = 0 ##EQU00007## Max - M =
M B ; max possible value = - 0.1924 W l when a = 0.5773 l
##EQU00008## R B = wa 2 l 3 ( 3 l 2 - a ) 2 .theta. B = 0
##EQU00009## Max y = - wa 6 EI ( l - a ) 2 ( a 2 l + a ) 1 / 2 at x
= l ( a 2 l + a ) 1 / 2 when a > 0.414 l ##EQU00010## M B = - wa
2 l 2 ( l 2 - a 2 ) y B = 0 ##EQU00011## Max y = - wa ( l 2 - a 2 )
3 3 EI ( 3 l 2 - a 2 ) 2 at x = l ( l 2 + a 2 ) 3 l 2 - a 2 when a
< 0.414 l ; max possible y = - 0.0098 ##EQU00012## wl 3 EI when
x = a = 0.414 l ##EQU00013##
TABLE-US-00003 TABLE 3 R A = w l 3 ( l - a ) 2 ( l + 2 a )
##EQU00014## Max + M = 2 wa 2 l 3 ( l - a ) 2 at x = a ; max
possible value = wl 8 when a = l 2 ##EQU00015## M A = - wa l 2 ( l
- a ) 2 ##EQU00016## Max - M = M A if a < 1 2 ; max possible
value = - 0.1481 Wl when a = l 3 ##EQU00017## .theta..sub.A = 0
y.sub.A = 0 Max y = - 2 w ( l - a ) 3 a 3 3 EI ( l + 2 a ) 2 at x =
2 al l + 2 a if a > l 2 ; max possible value = - wl 3 192 EI
when x = a = l 2 ##EQU00018## R B = - wa 2 l 3 ( 3 l - 2 a )
##EQU00019## M B = - wa 2 l 2 ( l - a ) ##EQU00020## .theta..sub.B
= 0 y.sub.B = 0
[0051] However, in the subject invention the resilient junction
material constrains the counter facing cantilever tabs to follow a
nearly identical deflection curve, so it is clear that the
supported end of the tabs is not free to rotate and not completely
free to slip. That is, the resilient junction material allows some
slippage between the counter facing cantilever tabs, but since the
counter facing tabs are constrained to a nearly identical
deflection curve and bonded to each other, the slippage that could
otherwise occur is reduced. Consequently, the spring k value
related to pressure deformation of the subject diaphragm is likely
to lie somewhere between the k value of the bending mode of FIG. 9
and the k value of the bending mode of FIG. 10.
[0052] To make the axial spring k vs. pressure spring k comparison,
the max deflection equation for the bending modes of FIGS. 8-10 is
solved for k which then provides equations for k.sub.a, k.sub.c and
k.sub.d, where k.sub.a, corresponds to the bending mode of FIG. 8,
k.sub.c corresponds to the bending mode of FIG. 9, and k.sub.d
corresponds to the bending mode of FIG. 10. For bending modes for
FIGS. 9 and 10, the load is applied at midpoint along the
cantilever's length L (i.e. a=L/2). The resulting ratios are
k.sub.c/k.sub.a=34 and k.sub.d/k.sub.a=64. Consequently, the spring
k which resists pressure deformation is somewhere between 34 to 64
times higher than the spring k that resists axial
displacements.
[0053] In general, stiffness is a trend-wise indicator of a beam's
stress at a given deflection (i.e., a higher stiffness will be
accompanied by a higher stress for a given beam deflection). From
the above beam analysis it can be seen that embodiments in
accordance with aspects of the invention successfully provide a
single set of cantilever springs that respond very differently to
axial diaphragm displacements and pressure deformation, whereby
axial displacements are accompanied by a lower spring k rate that
enables axial displacements within acceptable material stress
levels and pressure deflections are minimized by a much higher
spring k rate that resists ballooning and yet both spring k values
are created by the same cantilever springs. The different spring k
rates occur because the single set of cantilever springs can
present one unique set of beam end constraints to the axial
deflections and a second unique set of beam end constraints to
ballooning deflections.
[0054] For clarity of illustration, the beam deflection cases of
FIGS. 9 and 10 show a load being applied while the diaphragm is at
its rest position (i.e. no axial deflection), while in an operating
oscillating diaphragm pressure deformation would be superimposed on
an axial deformation. In other words, the actual deformation curve
of the cantilevers would include the superposition of axial
deflection and pressure deformation. Nevertheless, the diaphragm's
unique characteristics described previously hold for either the
stationary or dynamic case.
[0055] The diaphragm design represented in FIGS. 2-6 was designed
using FEA software and was then built and tested. Diaphragm
specifications were: spring steel substrate thickness of 0.003 in,
steel substrate outer diameter 2.650 in, cantilever dimensions were
exactly as shown in FIGS. 2-6, the resilient junction material was
0.020 in thick 40A durometer silicone which was injection molded
from both sides of the diaphragm and the gap between inner and
outer diaphragm pieces was 0.020 in. This diaphragm could provide
0.25 in axial strokes with a stress safety factor of 2 (yield
divided by peak), and a spring stiffness k for axial displacements
of 10,440N/m.
[0056] The FEA model was also used to find the spring stiffness k
that resists pressure deformation. In this model both the center
and perimeter of the diaphragm were constrained so that only the
cantilever tabs could move in response to an applied pressure of 25
psi. For this test the ballooning displacement (i.e., distance from
the diaphragm plane to the peak of the pressure deformation of the
cantilever tabs) was 0.014 in, with a corresponding ballooning
metal stress safety factor of 4.4. To calculate the spring
stiffness, the load was found by multiplying the applied pressure
by the area of the cantilever tabs (i.e., the area bounded by the
two clamp circles 20 and 22). The resulting force of 88.8N results
in a spring k of 250,000 N/m which is a factor of 60.times. higher
than the axial k value.
[0057] While in the embodiment of FIG. 2 the distal ends of the
cantilever tabs 18 were not rigidly connected to a clamp plate 11
or to a housing of the fluid mover 4, the diaphragm 2 may be
configured in other ways. For example, the diaphragm 2 of FIG. 11
is arranged to have the distal end of each cantilever tab 18 extend
beyond the opposite clamp line 42, 44 so that the distal ends of
the cantilever tabs 18 may be directly supported by the opposing
clamp plate 11 or housing. Such an arrangement may provide for a
stiffer diaphragm 2 that relies less on the junction material 24
for interconnecting cantilever tabs 18 to each other at their
distal ends. Note that the cantilever tab distal ends need not be
secured at the opposing clamp line in such a way that the distal
ends are prevented from sliding movement relative to the clamp
line. Instead, the distal ends may be permitted to slide by virtue
of the junction material in the plane of the diaphragm at the
opposing clamp line as in the FIG. 11 embodiment yet have axial
force of the clamp plate 11 or housing applied more directly to the
distal end.
[0058] Other diaphragm configurations are possible, and variations
may provide for different diaphragm operating characteristics. For
example, the diaphragm 2 shown in FIG. 12 includes three diaphragm
substrate sections 2a, 2b, 2c which all have counter-facing
cantilever tabs 18. When the diaphragm 2 is over molded or
otherwise provided with a junction material 24, the counter-facing
cantilever tabs 18 of the diaphragm substrate sections 2a, 2b, 2c
function in much the same manner and provide at least some of the
same advantages of the diaphragm arrangement of FIG. 2. This
approach could be extended to include any suitable number of
diaphragm substrate sections and will be appreciated by those of
skill in the art.
[0059] While embodiments above have a diaphragm with a circular
shape, aspects of the invention are not limited in this regard.
Instead, a diaphragm may have any suitable shape, such as
rectangular (as shown in FIG. 13 for example), triangular, oval,
pentagonal, etc. The diaphragm 2 of FIG. 13 also illustrates that
cantilever tabs 18 in a diaphragm need not all have the same shape
and/or size, but rather may vary as desired. In addition, the
aspect ratio of cantilever tabs 18 may vary as desired, e.g., along
their length, width or in other ways.
[0060] As mentioned above, the junction material 24 may function to
help transmit force from one cantilever tab 6 to another adjacent
cantilever tab 6 and so constrain the counter facing cantilever
tabs to a nearly identical displacement distribution. As such, the
junction material 24 may be arranged to help transmit force more
efficiently and/or reliably. For example, a diaphragm 2 shown in
FIG. 14 is arranged like that in FIG. 5, except that the resilient
junction material 24 includes one or more concentric ribs 46 that
are formed to provide additional mechanical support to the
counter-facing cantilever tabs 18 to help keep the tabs 18 in the
same displacement distribution. However, some radial stretching of
the junction material 24 may still occur with diaphragm
displacement and damping may increase with increasing thickness
and/or durometer of the junction material 24. The ribs 46 in FIG.
14 may provide support for the cantilever tabs 18 while allowing
for radial stretching to occur in the thinner portions of junction
material between the ribs 46 to minimize cyclic damping energy
losses. Other rib geometries could be used such as honey comb,
etc.
[0061] Many improvements and/or other changes to the embodiments
described above will occur to those skilled in the art. For
example, the embodiments above mostly include isosceles
triangle-shaped cantilever tabs. Many other cantilever tab shapes
can used within the scope of the present invention including, for
example, sawtooth, "T" shaped, "I" shaped, trapezoid-shaped,
claw-shaped, or hooked tabs. In general, there are many
counter-facing cantilever tab shapes with widths, thicknesses
and/or moments of inertia that become progressively smaller when
traversing from clamped or base end to the tip or distal end, and
any of these may be employed. The spacing or gap 16 between the
diaphragm sections need not be constant along its extent but may
vary as required by various cantilever tab shapes. To improve
elastomeric-to-diaphragm bonding, flow through holes could be added
to the diaphragm sections to allow the junction material and/or
adhesive to flow through from both sides during the injection
molding or other bonding process. Diaphragm substrate materials
could be metal, plastic or any material that meets the design
requirements of a given application. In some applications a single
one-sided over molding layer could be used.
[0062] Applications for the diaphragm of the present invention can
be found wherever energy is transferred to fluids by means of
positive volumetric displacement. Applications include, for
example, fluid movers such as pumps, compressors and synthetic
jets; applying fluidic energy to fluid filled acoustic resonators
for applications such as acoustic compressors or thermoacoustic
engines, buzzers and as speaker cone elements in sound
reproduction.
[0063] The embodiments provided herein are not intended to be
exhaustive or to limit the invention to a precise form disclosed,
and many modifications and variations are possible in light of the
above teachings. The embodiments were chosen and described in order
to best explain the principles of the invention and its practical
application to thereby enable others skilled in the art to best
utilize the invention in various embodiments and with various
modifications as are suited to the particular use contemplated.
Although the above description contains many specifications, these
should not be construed as limitations on the scope of the
invention, but rather as an exemplification of alternative
embodiments thereof.
[0064] The indefinite articles "a" and "an," as used herein in the
specification and in the claims, unless clearly indicated to the
contrary, should be understood to mean "at least one."
[0065] The phrase "and/or," as used herein in the specification and
in the claims, should be understood to mean "either or both" of the
elements so conjoined, i.e., elements that are conjunctively
present in some cases and disjunctively present in other cases.
Multiple elements listed with "and/or" should be construed in the
same fashion, i.e., "one or more" of the elements so conjoined.
Other elements may optionally be present other than the elements
specifically identified by the "and/or" clause, whether related or
unrelated to those elements specifically identified.
[0066] The use of "including," "comprising," "having,"
"containing," "involving," and/or variations thereof herein, is
meant to encompass the items listed thereafter and equivalents
thereof as well as additional items.
[0067] It should also be understood that, unless clearly indicated
to the contrary, in any methods claimed herein that include more
than one step or act, the order of the steps or acts of the method
is not necessarily limited to the order in which the steps or acts
of the method are recited.
[0068] While aspects of the invention have been described with
reference to various illustrative embodiments, such aspects are not
limited to the embodiments described. Thus, it is evident that many
alternatives, modifications, and variations of the embodiments
described will be apparent to those skilled in the art.
Accordingly, embodiments as set forth herein are intended to be
illustrative, not limiting. Various changes may be made without
departing from the spirit of aspects of the invention.
* * * * *