U.S. patent application number 09/834390 was filed with the patent office on 2002-02-21 for compliant electrical contacts for fuel cell use.
Invention is credited to Arikara, Muralidharan P., Bawden, Lawrence R. JR., Franklin, Jerrold E., Mettler, Eric S..
Application Number | 20020022382 09/834390 |
Document ID | / |
Family ID | 26920569 |
Filed Date | 2002-02-21 |
United States Patent
Application |
20020022382 |
Kind Code |
A1 |
Franklin, Jerrold E. ; et
al. |
February 21, 2002 |
Compliant electrical contacts for fuel cell use
Abstract
This invention concerns improvements in fuel cell fabrication.
Arrays of independent acting compliant electrical contacts are
incorporated within a fuel cell which improve fuel cell Bi Polar
Separator Plate (bipolar separator plate) which improve fuel cell
operation by creating uniform and intimate electrical contact with
the adjacent membrane electrode assembly (Membrane electrode
assembly). These compliant electrical contacts provide substantial
uniform internal pressure distribution and substantially uniform
electrical contact. In one embodiment, the array of compliant
electrical contacts are in the form of a plurality of metal springs
of various configurations which are electrically and mechanical
contacted to a conducting base plate. In another embodiment the
array of compliant electrical contacts are in the form of a
plurality of small metal pins or rods which are electrically and
mechanically contacted to a conducting base plate.
Inventors: |
Franklin, Jerrold E.;
(Sacramento, CA) ; Mettler, Eric S.; (Cameron
Park, CA) ; Arikara, Muralidharan P.; (Folsom,
CA) ; Bawden, Lawrence R. JR.; (El Dorado Hills,
CA) |
Correspondence
Address: |
Howard M. Peters
PETERS, VERNY, JONES & BIKSA, LLP
Suite 6
385 Sherman Avenue
Palo Alto
CA
94306
US
|
Family ID: |
26920569 |
Appl. No.: |
09/834390 |
Filed: |
April 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60226471 |
Aug 18, 2000 |
|
|
|
Current U.S.
Class: |
439/66 |
Current CPC
Class: |
H01M 8/0297 20130101;
H01M 8/0206 20130101; H01M 8/0271 20130101; H01M 50/183 20210101;
H01M 8/2457 20160201; H01M 8/241 20130101; H01M 8/2483 20160201;
Y02E 60/50 20130101; H01M 8/0247 20130101; Y02E 60/10 20130101;
H01M 8/026 20130101 |
Class at
Publication: |
439/66 |
International
Class: |
H05K 001/00 |
Claims
We claim:
1. An array of independently acting compliant electrical contacts
within a fuel cell electrode which improve fuel cell operation and
performance by providing substantially increased and optimized
surface area for increased electrical contact between the compliant
contact attached to the conducting plate and bipolar separator
plate and membrane electrode assembly, substantial uniform internal
compressive loads and distribution resulting from the independent
action of the compliant electrical contacts when the fuel cell
stack is compressed.
2. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of inverted V shaped metal springs
or other configurations as described herein which are electrically
contacted and connected mechanically, metallurgically or
combinations thereof to a conducting base plate or bipolar
separator plate.
3. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of inverted V shaped metal arch
springs having a cantilevered portion which are electrically
contacted and connected mechanically, metallurgically or
combinations thereof to a conducting base plate or bipolar
separator plate.
4. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of inverted rounded metal arch
springs having a cantilevered portion which are electrically
contacted and connected mechanically, metallurgically or
combinations thereof to a conducting base plate or bipolar
separator plate.
5. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of inverted flat contact surface
shaped metal arch springs having a cantilevered portion which are
electrically contacted and connected mechanically, metallurgically
or combinations thereof to a conducting base plate or bipolar
separator plate.
6. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of omega shaped metal springs with
multiple deflection areas and multiple contact areas and which are
electrically contacted and connected mechanically, metallurgically
or combinations thereof to a conducting base plate or bipolar
separator plate.
7. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of omega shaped metal springs with
multiple deflection areas and multiple contact areas, in strip
form, and which are electrically contacted and connected
mechanically, metallurgically or combinations thereof to a
conducting base plate or bipolar separator plate.
8. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of "S" shaped springs with right
angle contact area with multiple deflection areas and having a flat
area and which are electrically contacted and connected
mechanically, metallurgically or combinations thereof to a
conducting base plate or bipolar separator plate.
9. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of "S" shaped springs with radiused
right angle contact area, and interlocking and alignment/locating
features with multiple deflection areas, and having a flat area and
which are electrically contacted and connected mechanically,
metallurgically or combinations thereof to a conducting base plate
or bipolar separator plate.
10. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of "S" shaped springs with radiused
right angle contact area, and interlocking and alignment/locating
features with multiple deflection areas, in strip form, and having
a flat area and which are electrically contacted and connected
mechanically, metallurgically or combinations thereof to a
conducting base plate or bipolar separator plate.
11. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of "Z" shaped springs with right
angle contact area, and right angle mounting area, with multiple
deflection areas and which are electrically contacted and connected
mechanically, metallurgically or combinations thereof to a
conducting base plate or bipolar separator plate.
12. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of modified omega shaped springs
with multiple deflection areas and a slight break in the top curve
crating a slight peak and which are electrically contacted and
connected mechanically, metallurgically or combinations thereof to
a conducting base plate or bipolar separator plate.
13. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of modified omega shaped metal
springs with multiple deflection areas and a slight break in the
top curve crating a slight peak, in strip form and which are
electrically contacted and connected mechanically, metallurgically
or combinations thereof to a conducting base plate or bipolar
separator plate.
14. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of modified omega shaped metal
springs with multiple deflection areas and a smooth crown in the
top curve leaving no peak and which are electrically contacted and
connected mechanically, metallurgically or combinations thereof to
a conducting base plate or bipolar separator plate.
15. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of modified omega shaped metal
springs with multiple deflection areas and a smooth crown in the
curve leaving no peak, in strip form and which are electrically
contacted and connected mechanically, metallurgically or
combinations thereof to a conducting base plate or bipolar
separator plate.
16. The array of claim 1 individually or in strip form, wherein the
strips form ventilated horizontal channels or passages to aid in
air/oxygen flow to the fuel cell membrane and aid in the operation
of the fuel cell.
17. The array of claim 1 individually or in strip form, wherein the
strips form vertical ventilated channels or passageways (chimneys)
to aid in air/oxygen flow to the fuel cell membrane and aid the
operation of the fuel cell.
18. The array of claim 1 and all of its embodiments, wherein the
combination of the compliant electrical contacts and the conducting
base plate and bipolar separator plate create a uniform thermal
gradient for stable fuel cell operation and increased life.
19. The array of claim 1 wherein the compressive forces developed
by the individual springs withing the cell that are accommodated by
the compliant electrical contacts is usually between about 0.10 lb
and 50 lb per spring leaf or finger depending on the configuration
as described herein.
20. The array in claim 1 wherein the compliant electrical contacts
range in cross section from 0.030 in. to 3.00 in., but are not
limited by size or shape.
21. The array of claim 1 wherein the spacing between compliant
electrical contacts range from 0.005 in. to 2.0 in., but are not
limited by size or shape.
22. The array in claim 1 wherein the compliant electrical contacts
range in length (across the fuel cell plate from 0.10 in. to 100.0
in., but are not limited by size or shape.
23. The conductive plates and bipolar separator plates that the
array in claim 1 attach to are as small as 1/4 in..times.1/4 in.
for very small, light, portable devices such as video cameras,
movie cameras, etc. to large sizes 3 to 30 square meters required
for homes, businesses, large buildings, or small cities.
24. The array of claim 1 wherein the compliant electrical contacts
are in the form of a plurality of small metal pins which are
electrically contacted and connected mechanically, metallurgically
or combinations thereof to a conducting base plate or bipolar
separator plate.
25. The array of claim 1 wherein the plurality of compliant
electrical contacts form a regular patterned arrangement having a
substantially uniform distance between contact points (surfaces).
In another aspect, the pluralities of compliant electrical contacts
(metal springs) have an irregular patterned arrangement and
substantially non-uniform distance between contact points
(surfaces).
26. The array of claim 24 wherein the tips of the small metal pins
in to contact the adjacent electrode have a head similar to a nail
head.
27. The array of claim 24 wherein the plurality of metal pins form
a regular patterned arrangement having a substantially uniform
distance between pins.
28. The compliant electrical contacts of claim 24 are selected from
those shown in FIGS. 5, 6, 7, 8, 9A to 9O or 10.
29. The array of claim 1 wherein the bipolar separator plates are
selected from, very thin, very flexible metal bipolar separator
plates (about 0.001 to 0.500 in. thick).
30. The compliant electrical contacts (springs) wherein the
thickness of the shaped metal strip is between about 0.001 in. and
0.090 in.
31. The individual compliant electrical contact wherein the width
of the shaped metal strip is between about 0.020 in. and 1.0
in.
32. The compliant electrical contact of claim 24 wherein the height
of the configures metal strip from base to electrical contact
point(s) surface is between about 0.010 in. and 2.0 in., but not to
be limited by size or shape.
33. The array of claim 24 wherein the compliant electrical contacts
are comprised of alloys of iron, copper, gold, silver, platinum,
aluminum, nickel, chromium, and combinations thereof.
34. The array of claim 24 wherein compliant electrical contacts are
electrically, mechanically and/or metallurgically contacted and
connected to the conducting plate or bipolar separator plate via
soldering, brazing, welding, conductive adhesives, riveting,
bolting, crimping or other metallurgical or mechanical method of
attachment.
35. The array of claim 24 wherein the blank for the compliant
electrical contacts are fabricated by etching, machining, stamping,
fine blanking, coining, die cutting, extruding, laser cutting,
hydro-forming, electro discharge machining, or other suitable
method of fabrication.
36. The array of claim 24 wherein the compliant electrical contacts
are formed into the various shapes and configurations described
herein by etching, machining, stamping, fine blanking, coining,
dies cutting, extruding, laser cutting, hydro-forming, electro
discharge machining or other suitable method of fabrication or
forming.
37. The conductive plates which the array of claim 24 are connected
to are fabricated by etching, stamping, machining, fine blanking,
coining, die cutting, extruding, laser cutting, roll forming,
hydro-forming or other suitable method of fabrication.
Description
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. Ser. No.
60/226,471, filed Aug. 18, 2000 which is incorporated herein by
reference in its entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention concerns compliant electrical contacts for
fuel cell use to create, adjust and distribute internal forces and
loads to optimize contact area to increase fuel cell performance.
In a number of embodiments, an array of metal springs of different
shapes and configurations contact the adjacent electrode. In
another embodiment, a series of electrical contact points similar
to a "bed of nails" is used to adjust forces and pressure.
[0004] 2. Description of the Related Art
[0005] Fuel cells are energy conversion devices that use hydrogen,
the most abundant fuel on earth, and oxygen from the air, to create
electricity through a chemical conversion process, without
combustion and without harmful emissions. The voltage and current
output depends on the number of cells in the stack, total active
surface area and efficiency. The basic process, for a single cell,
is shown in FIG. 1.
[0006] Traditional fuel cell stacks 1, see FIG. 2, are made of many
individual cells 2, see FIG. 3, which are stacked together. The
ability to achieve the required gas and liquid sealing and to
maintain intimate electrical contact has traditionally been
accomplished with the use of relatively thick and heavy "end
plates" (3, 4) with the fuel cell stack 5 held together by heavy
tie-rods or bolts 6 and nuts 7 (or other fasteners) in a
"filter-press" type of arrangement, see FIGS. 2 and 4. Disassembly
and analysis of fuel cell stacks built by traditional and other
methods reveals evidence of incomplete electrical contact between
bipolar separator plates (BSPs) 8 and the membrane electrode
assembly (MEAs) 9, which results in poor electrical conduction,
lower cell performance, often along with evidence of gas and liquid
leakage.
[0007] The traditional method of assembly of Proton Exchange
Membrane (PEM) fuel cells requires several parallel and serial
mechanical processes that must be accomplished simultaneously for
each individual cell, see FIG. 3.
[0008] 1. The Membrane Electrode Assembly (MEA) 9 must be sealed to
the Bipolar Separator Plates (BSPs) 8 at each plate/MEA interface,
via a gasket 10A and 10B.
[0009] 2. The fuel, oxidizer and coolant manifolds 11, 11A and 11B
are all required to be sealed at the same time during fabrication
as the MEA is sealed to the BSP.
[0010] 3. The BSPs 8 must be in intimate electrical contact with
the electrode assembly 9, across its entire surface area, at all
times for optimum performance.
[0011] As the traditional fuel cell stack 1 is assembled, each
individual cell (layer) 2 must seal, manage gasses and liquid,
produce power and conduct current. Each cell relies on all the
other cells for these functions. Additionally, all seals and
electrical contacts must be made concurrently at the time of
assembly of the stack, see FIGS. 2 and 3.
[0012] The assembly of a traditional PEM cell stack which comprises
a plurality of PEM cells each having many separate gaskets which
must be fitted to or formed on the various components is
labor-intensive, costly and in a manner generally unsuited to high
volume manufacture due to the multitude of parts and assembly steps
required.
[0013] performance, along with evidence of gas and liquid
leakage.
[0014] The traditional method of assembly of Proton Exchange
Membrane (PEM) fuel cells requires several parallel mechanical
processes that must be accomplished simultaneously for each
individual cell, see FIG. 3.
[0015] The traditional construction method does not allow for
testing or evaluation of the individual cells before they are
assembled into the stack. If there is leakage or a performance
problem with a single cell or group of cells in an assembled stack,
then the entire stack has to be disassembled to correct the
problem. This is very expensive and time consuming.
[0016] Some patents of interest are listed below.
[0017] R. G. Spear et al. in U.S. Pat. No. 5,683,828, assigned to H
Power Corporation disclose metal platelet fuel cells production and
operation methods.
[0018] R. G. Spear et al. in U.S. Pat. No. 5,858,567, assigned to H
Power Corporation discloses fuel cells employing integrated fluid
management platelet technology.
[0019] R. G. Spear, et al. in U.S. Pat. No. 5,863,671, assigned to
H Power Corporation discloses plastic platelet fuel cells employing
integrated fluid management.
[0020] R. G. Spear, et al. in U.S. Pat. No. 6,051,331 assigned to H
Power Corporation discloses fuel cell platelet separators having
coordinate features.
[0021] These four U.S. patents describe conventional fuel cell
assembly.
[0022] W. A. Fuglevand et al. in U.S. Pat. No. 6,030,718, assigned
to Avista Corporation describes a proton exchange membrane fuel
cell power system. In the figures of this patent, particularly its
FIG. 12 and following, component 202 is described as a biasing
assembly, as a plurality of metal wave springs which cooperate with
the cathode cover and is able to impart force to the adjacent
pressure transfer assembly 203 by means of a rigid pressure
distribution assembly 204.
[0023] Other art of general interest includes, for example: U.S.
Pat. No. 5,338,621; European Patent 446,680; U.S. Pat. No.
5,328,779; U.S. Pat. No. 5,084,364; U.S. Pat. No. 4,445,994; U.S.
Pat. No. 5,976,727; U.S. Pat. No. 5,470,671; U.S. Pat. No.
5,176,966; and U.S. Pat. No. 5,945,232;
[0024] All of the references, patents, standards, etc. cited in
this application are incorporated by reference in their
entirety.
[0025] It is apparent from the above discussion that existing fuel
cell technology can be mostly improved with modification in the
design and fabrication of components and assembly of the units. The
present invention of compliant electrical contacts provides such an
improvement for a fuel cell.
SUMMARY OF THE INVENTION
[0026] The present invention concerns an array of compliant
electrical contacts within a fuel cell electrode which improve fuel
cell operation providing substantially and uniform internal load
distribution to effect uniform electrical contact across the
conductive surface.
[0027] In another aspect the array of compliant electrical contacts
are in the form of a plurality of inverted V, Z, S or omega shaped
independent metal springs which are electrically, mechanically,
metallurgically or combinations theory contacted and connected to a
conducting base plate or BSP.
[0028] In another aspect the plurality of metal springs have a
regular patterned arrangement having substantially uniform distance
between contact points or surfaces.
[0029] In another aspect, the plurality of metal springs have an
irregular patterned arrangement and substantially non uniform
distance between contact points or surfaces.
[0030] In another aspect, the array of compliant electrical
contacts are in the form of a plurality of small metal pins which
are electrically and mechanically contacted to a conducting base
plate.
[0031] In another aspect, the tips of the small metal pins which
are in to contact with the adjacent electrode have a head similar
to a nail head.
[0032] In another aspect, in the array the plurality of metal pins
form an irregular arrangement or a regular patterned arrangement
having a substantially uniform distance between pins.
[0033] In another aspect, the compliant electrical contacts are
comprised of alloys of iron, copper, gold, silver, platinum,
aluminum, nickel, chromium, and combinations thereof.
BRIEF DESCRIPTION OF THE FIGURES
[0034] FIG. 1 is a schematic representation of the basic
conventional fuel cell process. It shows the extracted hydrogen
ions which combine with oxygen across a PEM membrane to produce
electrical power.
[0035] FIG. 2 is a schematic representation of the conventional PEM
fuel cell stack of electrodes compressed together with heavy end
plates and tie rod bolts.
[0036] FIG. 3 is a schematic representation of an exploded view of
a conventional PEM single cell of a fuel cell assembly.
[0037] FIG. 4 is a schematic representation of an exploded view of
a conventional PEM fuel cell stack of electrodes showing the
arrangement of the internal and external parts.
[0038] FIG. 5 is a schematic representation of the compliant
electrical contacts with the array of cantilevered inverted
V-shaped thin metal spring.
[0039] FIG. 5A is a schematic representation of the obverse
integrated and modular bipolar separator plate (BSP), membrane
electrode assembly (MEA) and manifold.
[0040] FIG. 6 is a schematic crossectional representation of the
compliant electrical contacts with the array of cantilevered
inverted V-shaped springs shown contacting the adjacent MEA.
[0041] FIG. 7 is a photographic representation of the compliant
electrical contacts and array of inverted V-shaped cantilevered
springs.
[0042] FIG. 8 is a photographic representation of an end view of
the compliant electrical contacts of FIG. 7.
[0043] FIGS. 9A, 9B, 9C, 9D, 9E, 9F, 9G, 9H, 9I, 9J, 9K, 9L, 9M, 9N
and 9P are each schematic or isometric or cross sectional
representations of various types of compliant electrical
contacts.
[0044] FIG. 9A is an inverted V-shape.
[0045] FIG. 9B is a circular portion of an arc.
[0046] FIG. 9C is a right angle contact.
[0047] FIG. 9D is a rounded inverted V-shape.
[0048] FIG. 9E is an omega shape, with multiple deflection areas
and multiple contact areas.
[0049] FIG. 9F is an array of the omega shape in strip form.
[0050] FIG. 9G is a "S" shape with a right angle contact.
[0051] FIG. 9H is in an S shape in strip form.
[0052] FIG. 9I is in an S shape with a radiused contact point and
interlocking and alignment/locating features.
[0053] FIG. 9J is a S with interlocking and locating features, in
strip form.
[0054] FIG. 9K is a Z form with right angle contact area.
[0055] FIG. 9L is a Z in strip form.
[0056] FIG. 9M is a modified omega shape similar to FIG. 9E showing
two versions.
[0057] FIG. 9N has the support feet pointing inward FIG. 9M has the
support feet pointing outward.
[0058] FIG. 9P is a modified omega design, similar to FIG. 9E,
without the crown or point in the top arch.
[0059] In all cases, regardless of spring shape, the contact areas
of the springs maximize the physical contact to the MEA and
facilitate electrical conduction, and reduce electrical
resistance.
[0060] FIG. 10 is a schematic cross sectional representation of the
"bed of nails" as the compliant electrical contacts. The array of
contact points (48) contact the adjacent MEA.
[0061] FIG. 11 is a photograph of the current embodiment showing
the array of the modified omega design of FIG. 9P attached to the
bipolar separator plate and with the multi manifold
arrangement.
[0062] FIG. 12 is an edge view of the spring/plate/manifold
configuration shown in FIG. 11. This shows the array of springs
attached to the bipolar separator plate.
[0063] FIG. 13 shows an uncompressed stack of bipolar separator
plates, manifolds and springs.
[0064] FIG. 14 shows the same parts as in FIG. 13 in the compressed
state with the springs making contact with the adjacent cell.
DETAILED DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
[0065] Definitions:
[0066] As described herein:
[0067] "Bed of nails" refers to a configuration of compliant
electrode contacts of vertical thin metal rods which accommodate
forces and loads in an operating fuel cell usualy the top (exposed)
end of the rod is larger than the shaft (for better electrical
contact).
[0068] "BSP" refers to bipolar separator plates.
[0069] "Compliant electrode contact" refers to a spring-like
adjusting electrical contact which create the loads and pressures
of an operating fuel cell which maintain constant electrical
contact.
[0070] "MEA" refers to the membrane electrode assembly.
[0071] "PEM" refers to proton exchange membrane--a component of a
fuel cell.
[0072] In one embodiment, the compliant contacts are an array of
individual metal strips which have been folded to produce an
inverted V configuration. This is shown in FIGS. 5-8 and 9D. One
side of the inverted V-shape is connected mechanically and
electrically to a conducting base. The points of the inverted V
configuration provide electrical and mechanical contact to the
electrode. As each individual folded strip contacts the electrode,
it adjusts to the variation in cell spacing and maintains uniform
electrical contact with the MEA.
[0073] Compliant Electrical Contacts
[0074] As stated above, traditional fuel cell design has relied on
the "filter press" type of fabrication and assembly, see FIG. 2,
i.e., end-plates and tie-rods, to create suitable electrical
contact between the MEA and adjacent BSP. These designs have not
made use of other, more standardized forms of electrical contact
such as (1) metallurgical, by methods such as welding, soldering or
brazing, (2) mechanically such as fastened with bolts, screws,
cams, etc., and (3) spring contacts such as battery clips or wall
plugs. As a method of decoupling the electrical contacts, spring
loaded electrical contacts of the present invention are a novel
solution and add mechanical compliance.
[0075] The present fuel cell uses thin metal plate BSPs in which
the reactant gas flow patterns are integrated. Each BSP is
independently held in intimate contact with the MEA via independent
acting compliant spring electrical contacts and do not require the
heavy end plates, tie rods and the massive compressive forces
required of traditional fuel cell stacks to achieve contact and
conductance.
[0076] Conventional fuel cell design is followed up to a certain
point. See U.S. Pat. No. 6,030,718 and the other U.S. patents
listed on pages 2 and 3 above. One of skill in the art with these
incorporated-by-reference U.S. patents will have the basic design
to fabricate a conventional fuel cell. With the text and figures
provided herein, one of skill in the art is enabled to fabricate
the present invention. In the creation of the compliant electrical
contacts of the present invention within the cell, the following
additional methodology is followed.
[0077] With reference to FIG. 5A the present fuel cell design 50
uses a single thin metal plate BSP onto which the MEA and reactant
manifolds 51A, 51B and 51D are assembled into modular units prior
to being incorporated into a complete fuel cell unit (stack). These
fuel cell modules are comprised of a single BSP, which may contain
a reactant flow pattern, the MEA with or without an incorporated
diffusion layer, separate diffusion layers if needed, an adhesive
or an adhesive backed gasket, the reactant manifolds 51A and 51B
and the manifold seals or adhesives. Other features in FIG. 5A
include on the obverse adhesive or gasket by the hole 52, reactant
passageway 53, 53A and 53B, edge seal 54, inactive border 55 and
active membrane 56.
[0078] Compliant electrical contact is achieved in the subject fuel
cell design by use of springs and contact points. In the spring
design a large array of individual springs are attached to each BSP
each of which makes intimate contact with the MEA attached to the
adjacent BSP, see FIG. 5 and SA. When these springs are compressed,
continuous electrical contact is assured between the adjacent BSPs
through the MEAS, FIG. 6. FIGS. 7 and 8 are photographs of one
array of inverted V-shaped compliant electrical contacts.
[0079] The compliant electrical contacts can take a number of
forms. All units are flexible. For example, FIGS. 7 and 8 to 9 show
a rounded contact point which is in an inverted V-shape. Other
shapes include the following:
[0080] FIG. 9A which shows a sharp inverted V-shape 10 having a
cantilevered portion 11 which is mechanically contacted at area 12
to a base plate 13.
[0081] FIG. 9B shows a round metal arc 14 as contact having a
cantilevered portion 15 which is contacted at area 12 to a base
plate 13.
[0082] FIG. 9C shows a flat surface 16 as the contact having a
cantilevered portion 15 which is contacted at area 12 to base plate
13.
[0083] FIG. 9D shows a rounded, inverted "V" form 17 having a
cantilevered portion 15 which is contacted at area 12 to base plate
13.
[0084] FIG. 9E shows a modified omega shape 21, with multiple
deflection areas and multiple contact areas. One or both flat
portions 22A and 22B are connected to a base plate.
[0085] FIG. 9F is an array 23 of the modified omega shape in strip
form 18 which are connected to the base plate 24A and 24B.
[0086] FIG. 9G is a "S" shape 25 with right angle contact 26 having
a flat area 27 to connect to a base plate.
[0087] FIG. 9H is an array of "S"-shape 26 of FIG. 9G, wherein the
array of S-shape contacts are connected to a base plate 28.
[0088] FIG. 9I is a "S" shape 29 with radiused contact point 30 and
interlocking and alignment/locating features. The "S" shape is
connected to base 31.
[0089] Figure J is an array of the S-shape 32 in strip form
connected to base 33.
[0090] FIG. 9K is a "Z" form 34 with right angle contact area 35.
The Z-shape is connected to a base 36.
[0091] FIG. 9L is an array 37 of the Z-shape of FIG. 9K which is
connected to base 38.
[0092] The compliant electrical contact approach (springs) is not
limited by size or shape of the application. The springs are
usually between 0.020" and 2" high. The forces (e.g. tension) in
the spring portion, within the cell that are accommodated by the
compliant electrical contacts is usually between about 0.10 lb and
10 lb per spring leaf depending on the configuration as described
herein. The plates are as small as 1/4".times.1/4" (for very small,
light, portable devices such as video cameras, movie cameras, etc.)
to the large sizes required for homes, businesses, large buildings,
or even small cities.
[0093] FIG. 9M is a modified omega configuration similar to FIG. 9E
has two versions, FIG. 9M with the support feet pointing inward and
FIG. 9N with the support feet pointing outward. The modified omega
has a slight break in the curve at the top 42. One or both flat
portions 43A and 43B are mechanically (e.g. soldered) and
electrically attached to a conducting base plate and can point
either inward or outward.
[0094] FIG. 9P is a modified omega configuration shown in an array
45 similar to FIGS. 9E and 9F. The modified omega has no break in
the curve at the top 46. One or both flat portions 47A and 47B are
mechanically and electrically attached to a conducting base
plate.
[0095] The compliant electrical contact approach (springs) is not
limited by size or shape of the application. The springs are
usually between 0.020" and 2" high. The forces (e.g. tension) in
the spring portion, within the cell that are accommodated by the
compliant electrical contacts is usually between about 0.10 lb and
50 lb per spring leaf depending on the configuration as described
herein. For example, when the spring strip has a thickness of 0.004
inches, and is deflected (compressed 0.040 inches, 0.84 pounds
force is created. The plates are as small as 1/4".times.1/4" (for
very small, light, portable devices such as video cameras, movie
cameras, etc.) to the large sizes required for homes, businesses,
large buildings, or even small cities.
[0096] In the contact points design, very thin, very flexible metal
BSPs (0.001-0.500 inch thick) with numerous metal contact pins (48)
with heads (49) which are optionally larger than the diameter of
the pins are used to effect the contact, FIG. 10. Each pin is
attached to the metal BSP. The head of the pin is the electrical
contact surface and mechanical support for the adjacent MEA. The
individual BSPs do not have springs. The springs are located on
each end of the stack or in the center of the stack, pushing the
thin flexible metal BSPs to create compliant electrical
contacts.
[0097] These methods does not rely on perfectly flat BSPs and the
heavy and bulky endplates and tie-rods of the conventional fuel
cell art.
[0098] A variety of materials are used for such contacts. Gold
plate is the obvious choice due to its resistance to the high
humidity atmosphere associated with fuel cell operation and its
corrosion resistance. Spring-loaded contacts fabricated from
stainless steel (without gold plating) were used to demonstrate the
technology with significant performance improvement over expected
results.
[0099] In the preferred embodiment, FIG. 9N, a modified omega
configuration compliant electrical contacts, in strip or array form
45, without crown or break at top 46, are orientated vertically on
the thin metal conductive plate and bipolar separator plate. The
contact portion of the 0.004 in. thick compliant contact (springs)
has essentially flat surfaces that are approximately 0.100 in. by
0.400 in. Each compliant contact is separated from the other by
0.050 in. The strip or individual springs are approximately 0.200
in. high. Each individual contact exerts approximately 2.5 pounds
of spring force, when compressed .0.030 to 0.040 inches in the fuel
cell stack.
[0100] The one preferred embodiment, FIGS. 11 and 12, shows the
array of FIG. 9N attached to the bipolar separator plate along with
the attached manifolds. In the relaxed condition, the crowns of the
spring contacts extend above the level of the manifolds. FIG. 13
shows a stack of the plates in the relaxed spring condition. When
compressed, in FIG. 14, the spring arrays are compressed and the
individual springs contact the neighboring cell with the result of
a positive electrical contact with its neighbor. Each spring acts
independently from the adjacent spring of the arrays and therefore
compensates for any variation in fabrication or assembly.
[0101] The preferred method of fabrication is to stamp or coin the
metal conducting plates, stamp the spring or compliant contact
blank and form the compliant contact to shape by stamping. The
compliant contact(s) are then attached to the conducting plate via
pre-applied solder paste and soldered using conventional electronic
circuit board manufacturing equipment and techniques. This
embodiment provides a uniform thermal gradient, especially when the
compliant electrical contacts are oriented vertically in the fuel
cell stack. This configuration creates a chimney effect and
increasing the amount of air (oxygen) to the membrane. The heated
air, due to the chimney effect, carries the excess heat away. This
is an usually desirable feature.
[0102] While only a few embodiments of the invention have been
shown and described herein, it will become apparent to those
skilled in the art that various modifications and changes can be
made in the compliant electrical contacts and applications to
provide long-term substantially uniform or nonuniform spacing
between electrodes and consistent electrical contact of electrodes
in a fully functioning fuel cell device without departing from the
spirit and scope of the present invention. All such modifications
and changes coming within the scope of the appended claims are
intended to be carried out thereby.
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