U.S. patent application number 15/952646 was filed with the patent office on 2018-08-16 for structural capacitor and method for making the same.
The applicant listed for this patent is U.S. Army Research Laboratory. Invention is credited to Daniel M. Baechle, Daniel J. O'Brien, Eric D. Wetzel, Oleg B. Yurchak.
Application Number | 20180233290 15/952646 |
Document ID | / |
Family ID | 56799073 |
Filed Date | 2018-08-16 |
United States Patent
Application |
20180233290 |
Kind Code |
A1 |
Baechle; Daniel M. ; et
al. |
August 16, 2018 |
STRUCTURAL CAPACITOR AND METHOD FOR MAKING THE SAME
Abstract
A structural capacitor having a plurality of planar dielectric
layers and a plurality of positive and negative electrodes with the
positive and negative electrodes alternating between each
dielectric layer. First and second spaced apart holes are provided
through each dielectric layer as well as the electrodes so that the
first holes in the electrodes register with the first holes in the
dielectric layer and likewise for the second holes. The capacitor
is formed by stacking the dielectric layers and electrodes on two
spaced apart alignment pins with a positive alignment pin extending
through the first holes and a negative alignment pin extending
through the second holes in the dielectric layers and electrodes.
These alignment pins maintain layer alignment during subsequent
thermal and pressure processing to bond together the dielectric and
electrode layers into an integral structural material. After
processing, the alignment pins are removed and replaced with
electrode pins, where the positive electrode pin is in electrical
contact only with the positive electrodes and the negative
electrode pin is in electrical contact only with the negative
electrodes. The electrode pins are used for subsequent electrical
and mechanical connectorization to the structural capacitor.
Inventors: |
Baechle; Daniel M.;
(Rosedale, MD) ; O'Brien; Daniel J.; (Hydes,
MD) ; Wetzel; Eric D.; (Baltimore, MD) ;
Yurchak; Oleg B.; (Montgomery Village, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
U.S. Army Research Laboratory |
Adelphi |
MD |
US |
|
|
Family ID: |
56799073 |
Appl. No.: |
15/952646 |
Filed: |
April 13, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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14633616 |
Feb 27, 2015 |
9959974 |
|
|
15952646 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01G 4/16 20130101; H01G
4/30 20130101; H01G 4/232 20130101; H01G 4/18 20130101; H01G 4/203
20130101 |
International
Class: |
H01G 4/30 20060101
H01G004/30; H01G 4/20 20060101 H01G004/20; H01G 4/232 20060101
H01G004/232; H01G 4/18 20060101 H01G004/18; H01G 4/16 20060101
H01G004/16 |
Goverment Interests
GOVERNMENT INTEREST
[0001] The invention described herein may be manufactured, used,
and licensed by or for the United States Government.
Claims
1. A structural capacitor comprising: a plurality of planar
structural dielectric layers, each structural layer having at least
a first and a second spaced apart alignment holes extending from a
top of each layer to a bottom of each layer, a plurality of planar
positive electrodes and a plurality of planer negative electrodes,
each electrode having at least a first and a second spaced apart
alignment holes extending from a top and to a bottom of each
electrode, said positive electrodes having an electrically
conductive portion in electrical contact with said first hole but
not said second hole and said negative electrodes having an
electrically conductive portion in electrical contact with said
second hole but not said first hole, a positive electrode pin and a
negative electrode pin, a stack having a plurality of dielectric
layers and alternating positive and negative electrodes stacked
upon each other so that said positive electrode pin extends through
said first holes in said dielectric layers and electrodes and so
that said negative electrode pin extends through said second holes
in said dielectric layers and electrodes.
2. The structural capacitor as defined in claim 1 wherein said
stack is sandwiched between a top plate and a bottom plate during
manufacture of the structural capacitor.
3. The structural capacitor as defined in claim 1 wherein said
dielectric layers each comprise a fiber reinforced polymer.
4. The structural capacitor as defined in claim 3 wherein said
polymer comprises an epoxy polymer.
5. The structural capacitor as defined in claim 3 wherein said
fiber comprises an interwoven mesh.
6. The structural capacitor as defined in claim 3 wherein said
fiber comprises a glass fiber.
7. The structural capacitor as defined in claim 1 wherein said
electrode pins are electrically conductive.
8. The structural capacitor as defined in claim 1 and comprising an
electrically conductive fill material in said first and second
alignment holes.
9. The structural capacitor as defined in claim 8 wherein said fill
material fills a space between said electrode pins and said
stack.
10. The structural capacitor as defined in claim 1, where the
electrodes comprise metallized paper, metallized polymer film, or
metallized fiber-reinforced polymer composite sheet.
11. The structural capacitor as defined in claim 10, where the
metallization consists of Al, Zn, or Al--Zn alloy.
12. A method of constructing a structural capacitor comprising the
steps of: forming a plurality of dielectric layers, each layer
having a first and a second spaced apart alignment holes extending
between a top and a bottom of each dielectric layer, forming a
plurality of planar electrically conductive positive and negative
electrodes, each electrode having a first and a second spaced apart
alignment holes extending between a top and a bottom of each
electrode, said positive electrodes having an electrically
conductive portion in electrical contact with said first hole but
not said second hole and said negative electrodes having an
electrically conductive portion in electrical contact with said
second hole but not said first hole, arranging a positive alignment
pin and a negative alignment pin in a spaced apart and parallel
relationship, creating a stack having a plurality of dielectric
layers and alternating positive and negative electrodes stacked
upon each other so that said positive alignment pin extends through
said first holes in said dielectric layers and electrodes and so
that said negative alignment pin extends through said second holes
in said dielectric layers and electrodes.
13. The method as defined in claim 12 and comprising the step of
sandwiching said stack between a top plate and a bottom plate.
14. The method as defined in claim 12 wherein said dielectric
layers each comprise a fiber reinforced polymer.
15. The method as defined in claim 14 wherein said polymer
comprises an epoxy polymer.
16. The structural capacitor as defined in claim 14 wherein said
fiber comprises an interwoven mesh.
17. The method as defined in claim 14 wherein said fiber comprises
a glass fiber.
18. The method as defined in claim 12 and comprising the step of
removing the structural capacitor from the top plate, bottom plate,
and alignment pins, and then placing electrically conductive
electrode pins into said first and second alignment holes alignment
holes.
19. The method as defined in claim 18 and comprising the step of
placing an electrically conductive fill material in said first and
second alignment holes.
20. The method as defined in claim 19 wherein said fill material
fills a space between said electrode pins and said stack.
Description
BACKGROUND OF THE INVENTION
I. Field of the Invention
[0002] The present invention relates generally to capacitors and,
more particularly, to a structural capacitor.
II. Description of Related Art
[0003] In many situations it is desirable to create electrical
capacitors that can not only store electrical energy, but also
simultaneously carry mechanical loads. For example, in military
applications, the storage and release of electrical pulsed power is
useful in many different applications, such as electromagnetic rail
guns, electromagnetic armor, short-pulse high-energy lasers, and
the like. Cylindrically wound thin-film capacitors are one
technology used to store and release electrical energy.
[0004] There have been conventional pulsed power platforms that
include components which carry structural loads. For example,
continuous fiber-reinforced, polymer-matrix composite materials
have been used to create strong, stiff, and lightweight structures,
such as vehicle frames and ballistic armor panels.
[0005] Gains in overall platform efficiency are possible by
creating a laminated composite material that can both carry
mechanical loads as well as store and release electrical energy.
The previously known designs include metallized polymer film
electrodes that are interleaved between glass fiber-reinforced
epoxy composite plies with the resulting stack of materials
processed together to integrally bond the components together.
[0006] In order to form such laminated structural capacitors, the
previously known methods include enveloping the materials in an
evacuated bag so that the stack of laminated materials is subjected
to atmospheric pressure. The bag with the contained stack is then
placed in an autoclave, hot press, or convection oven to bond the
layers together.
[0007] These previously known methods, however, have only been
effective to form structural laminated capacitors for a limited
number of layers, e.g. no more than about five dielectric layers,
since the layers are not laterally confined while being constructed
or bonded together. Rather, under the compaction pressure, the
layers of material move laterally and lose their relative alignment
with each other.
[0008] Alignment, however, is the key to both structural and
electrical operation since the alignment and relative position of
the layers determines both the laminate stiffness and strength as
well as the energy density and capacitance of the capacitor. In
some cases, the lateral shifting of the layers may result in
misalignment of electrodes so that opposing electrodes are in
direct contact with each other. This, in turn, shorts the capacitor
rendering it inoperable.
[0009] Other methods, such as closed molds and adhesive tape, have
also been tried to limit lateral movement of the layers when
constructing and bonding the layers of the structural capacitor
together. These previously known attempts, however, have not proven
successful except for only a limited number of layers of the
capacitor. The limited number of capacitor layers, in turn, limits
not only the structural strength of the capacitor, but also the
capacitance and amount of energy which can be stored by the
capacitor.
SUMMARY OF THE PRESENT INVENTION
[0010] The present invention provides a structural capacitor and
method for making the structural capacitor which overcomes the
above mentioned disadvantages of the previously known devices and
methods.
[0011] In brief, the structural capacitor of the present invention
includes a plurality of planar structural dielectric layers. Each
layer has at least a first and a second spaced apart alignment hole
which extends from a top and to a bottom of each layer.
[0012] A plurality of planar positive electrodes and a plurality of
planar negative electrodes are then provided. Each electrode,
furthermore, includes at least a first and second spaced apart
alignment hole extending from a top and to a bottom of each
electrode. The positive electrodes have an electrically conductive
portion in electrical contact with the first hole but not the
second hole while the negative electrodes have an electrically
conductive portion in electrical contact with the second hole, but
not the first hole. In one embodiment, the electrodes consist of a
thin metallization layer on the surface of a paper support layer.
In another embodiment, the electrodes consist of a thin
metallization layer on the surface of a polymer film.
[0013] In order to construct the structural capacitor, a positive
alignment pin and a negative alignment pin are arranged in a spaced
apart and parallel relationship so that the first alignment pin
registers with the first holes in the dielectric layers and the
electrodes while the negative alignment pin registers with the
second holes in the dielectric layers and electrodes. The alignment
pins maintain the alignment of the dielectric layers and electrodes
relative to each other and enable the stacking of multiple layers
for the capacitor while maintaining the alignment of the layers and
electrodes relative to each other.
[0014] After the desired number of dielectric layers and electrodes
are stacked upon the alignment pins, the layers are sandwiched
between a top plate and a bottom plate using conventional fasteners
which engage the alignment pins. The resulting structure is then
bonded together in any conventional fashion, such as a convection
oven, hot press, and the like.
BRIEF DESCRIPTION OF THE DRAWING
[0015] A better understanding of the present invention will be had
upon reference to the following detailed description when read in
conjunction with the accompanying drawing, wherein like reference
characters refer to like parts throughout the several views, and in
which:
[0016] FIG. 1 is a top plan view illustrating a preferred
embodiment of the present invention;
[0017] FIG. 2 is an exploded sectional view taken substantially
along line 2-2 in FIG. 1 and enlarged for clarity;
[0018] FIG. 3 is a cross-sectional view of the structural capacitor
during its assembly;
[0019] FIG. 4 is a view similar to FIG. 3, but illustrating the
completion of the stacking of the structural capacitor components
sandwiched between top and bottom compression plates;
[0020] FIG. 5 is a view similar to FIG. 4, but illustrating the
structural capacitor components enveloped in a vacuum bag;
[0021] FIG. 6 is a view similar to FIG. 4, but illustrating a
modification thereof; and
[0022] FIG. 7 shows the final structural capacitor after removal
from the compression plates and vacuum bag, and insertion of
electrical pins.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0023] With reference first to FIGS. 1 and 2, an exemplary
structural capacitor 20 in accordance with the present invention is
illustrated. The structural capacitor 20 is illustrated in FIG. 1
as being generally rectangular or square in shape. However, the
structural capacitor 20 may be formed in any shape desired without
deviation from the spirit or scope of the invention.
[0024] Still referring to FIGS. 1 and 2, the structural capacitor
includes a plurality of dielectric layers 22. These dielectric
layers 22 are preferably formed from a polymer, such as an epoxy
polymer. In order to enhance the structural strength of the
dielectric layers 22, the dielectric layers 22 are preferably
reinforced with fibers 24 such as glass fibers. The fibers 24 are
preferably formed in an interwoven mesh as shown in FIG. 2.
[0025] A first alignment hole 26 and a spaced apart second
alignment hole 28 are provided between a top surface 30 and a
bottom surface 32 of each dielectric layer. These alignment holes
26 and 28, furthermore, are at the same position for each of the
dielectric layers 22.
[0026] Referring now particularly to FIG. 2, the capacitor 20
comprises a plurality of positive electrodes 34 as well as a
plurality of negative electrodes 36. The positive electrodes 34
each have a pair of spaced apart alignment holes 38 and 40,
respectively, while, similarly, the negative electrodes 36 have a
first and second alignment hole 42 and 44, respectively. The first
alignment holes 38 and 42 in the positive and negative electrodes
34 and 36, respectively, are aligned with the first alignment holes
26 in the dielectric layers 30. Similarly, the second alignment
holes 40 and 44 in the positive and negative electrodes 34 and 36,
respectively, are aligned with the second alignment holes 28 in the
dielectric layers 22.
[0027] Although the electrodes may take many forms, in a preferred
embodiment, each electrode 34 and 36 includes a paper separator 46
having a conductive film 48 formed on at least a portion of one
side of the paper separator 46.
[0028] Still referring to FIG. 2, the conductive film 48 on the
positive electrodes 34 extends around and is in contact with the
first alignment holes 38 in the positive electrode 34, but not the
second alignment hole 40 in the positive electrode 34. Conversely,
the conductive film 48 on the negative electrode 36 extends around
and is in contact with the second alignment hole 44, but not the
first alignment hole 42.
[0029] With reference now to FIGS. 2 and 3, in order to construct
the structural capacitor 20, a positive alignment pin 50 and a
negative alignment pin 52 are mounted to a bottom compression plate
54 so that the alignment pins 50 and 52 are spaced apart and
parallel to each other. The dielectric layers 22 and alternating
positive 34 and negative electrodes 36 are then sequentially
stacked upon the alignment pins 50 and 52 with the alignment pin 52
extending through the first holes in the dielectric layers 22 and
electrodes 34 and 36, and the negative alignment pin 52 extending
through the second holes in the dielectric layers 22 and positive
and negative electrodes 34 and 36. After a plurality of dielectric
layers 22 and electrodes 34 and 36 have been stacked upon the
alignment pins 50 and 52, a top compression plate 56 is positioned
over the upper ends of the alignment pins 50 and 52 thus
sandwiching the layers and electrodes together as shown in FIG.
4.
[0030] With reference now to FIG. 5, in order to bond the
dielectric layers 22 and electrodes 34 and 36 together, a vacuum
bag 58 preferably envelopes the dielectric capacitor 20 as well as
the bottom plate 54 and top plate 56. The vacuum bag 58 containing
the dielectric capacitor is then placed in a convection oven, hot
press, or the like in order to bond the dielectric layers 22 and
electrodes 34 and 36 together.
[0031] With reference now to FIG. 6, in order to ensure a sound
electrical contact between the alignment pins 50 and 52 and their
associated electrodes 34 and 36, an elongated bus strip 60 extends
around the first alignment pin 50 and is in electrical contact with
the positive electrodes. Similarly, a negative bus strip 62 is
provided around the second alignment pin 52 and is in electrical
contact with the negative electrodes.
[0032] With reference now to FIG. 7, to complete the structural
capacitor, the bonded dielectric and electrode layers are removed
from the compression plates and alignment pins and through the
alignment holes are placed a positive electrode pin 70 and negative
electrode pin 72. A conductive fill material 64 may be inserted
around the first electrode pin 70 to enhance the electrical contact
between the first electrode pin 70 and the positive electrodes.
Similarly, fill material 64 is inserted around the second electrode
pin 72 to enhance the electrical contact between the second
electrode pin 72 and the negative electrodes. The fill material 64
may comprise metal solder, metal-laden polymer such as a conductive
epoxy, a conductive paint such as silver paint, and/or the
like.
[0033] As shown in FIG. 7, the electrode pins 70 and 72 protrude
outwardly from one side, e.g. the top, of the structural capacitor
20. These electrode pins 70 and 72 may be externally threaded for
convenient connection to electrical cables. Alternatively, the
threaded electrode pins 70 and 72 may be used in conjunction with
mechanical fasteners, such as nuts, to mechanically integrate the
structural capacitor 20 with its associated device.
[0034] From the foregoing, it can be seen that the present
invention provides a simple yet effective structural capacitor
which may contain many layers of dielectric material and electrodes
without fear of misalignment of its layers. Having described our
invention, however, many modifications thereto will become apparent
to those skilled in the art to which it pertains without deviation
from the spirit of the invention as defined by the scope of the
appended claims.
* * * * *