U.S. patent application number 10/158391 was filed with the patent office on 2003-01-16 for formed membrane and method of making.
Invention is credited to June, Matthew R., Murray, Michael C., Quick, Nathaniel R..
Application Number | 20030012676 10/158391 |
Document ID | / |
Family ID | 23132097 |
Filed Date | 2003-01-16 |
United States Patent
Application |
20030012676 |
Kind Code |
A1 |
Quick, Nathaniel R. ; et
al. |
January 16, 2003 |
Formed membrane and method of making
Abstract
An improved formed membrane and process of making is disclosed
comprising the deposition of fine metallic fibers onto a formed
substrate. The deposited fine fibers accumulate on the formed
substrate to form a formed layer of membrane material.
Catalytically active particles can be dispersed with the fine
fibers. A nonporous mask can be applied to a portion of the formed
substrate. The formed layer of membrane material is sintered for
forming the formed membrane.
Inventors: |
Quick, Nathaniel R.; (Lake
Mary, FL) ; Murray, Michael C.; (Eustis, FL) ;
June, Matthew R.; (Daytona Beach, FL) |
Correspondence
Address: |
KNOBBE MARTENS OLSON & BEAR LLP
2040 MAIN STREET
FOURTEENTH FLOOR
IRVINE
CA
92614
US
|
Family ID: |
23132097 |
Appl. No.: |
10/158391 |
Filed: |
May 28, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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60294148 |
May 29, 2001 |
|
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Current U.S.
Class: |
419/4 |
Current CPC
Class: |
B01D 39/2044 20130101;
B22F 7/002 20130101; B22F 3/002 20130101; B01D 39/2048
20130101 |
Class at
Publication: |
419/4 |
International
Class: |
B22F 007/04 |
Claims
What is claimed is:
1. A process of making a formed membrane from a multiplicity of
fine metallic fibers, comprising: suspending the multiplicity of
fine metallic fibers within a liquid binder; depositing the
multiplicity of fine fibers onto a formed substrate to form a
formed layer of membrane material; and sintering the formed layer
of membrane material for sinter bonding the fine fibers to adjacent
fine fibers to form the formed membrane.
2. A process of making a formed membrane as set forth in claim 1,
further comprising dispersing a catalytically active material into
the multiplicity of fine metallic fibers.
3. A process of making a formed membrane as set forth in claim 1,
further comprising applying a nonporous mask to a portion of the
formed substrate.
4. A process of making a formed membrane as set forth in claim 1,
wherein the fine fibers are made by a metallic wire drawing
process.
5. A process of making a formed membrane as set forth in claim 1,
wherein the liquid binder is a curable polymeric material.
6. A process of making a formed membrane as set forth in claim 1,
wherein the fine fibers are deposited onto a formed porous
substrate comprising a mesh material.
7. A process of making a formed membrane as set forth in claim 1,
wherein the fine fibers are deposited onto a formed porous
substrate comprising a ceramic material.
8. A process of making a formed membrane as set forth in claim 1,
further comprising removing the formed layer of membrane material
from the porous substrate.
9. A process of making a formed membrane as set forth in claim 1,
further comprising: heating the formed layer of membrane material
for a time sufficient for adhering the fine fibers to adjacent fine
fibers; and removing the formed layer of membrane material from the
porous substrate prior to sintering the formed layer of membrane
material.
10. A process of making a formed membrane as set forth in claim 1,
wherein sintering the formed layer of membrane material comprises
sintering the layer of membrane material and the formed substrate
for a time sufficient for sinter bonding the fine fibers to
adjacent fine fibers.
11. A process of making a formed membrane as set forth in claim 1,
wherein sintering the formed layer of membrane material comprises
sintering the layer of membrane material for a time sufficient for
forming a substantially rigid formed membrane.
12. A process of making a formed membrane as set forth in claim 1,
wherein sintering the formed layer of membrane material comprises
sintering the layer of membrane material and the substrate for a
time sufficient for sinter bonding the fine fibers to adjacent fine
fibers and for sinter bonding fine fibers to the porous
substrate.
13. A process of making a formed membrane from a multiplicity of
fine fibers, comprising: forming a substrate into a desired shape
for forming a formed porous substrate; suspending the multiplicity
of fine fibers within a liquid binder; depositing the fine fibers
onto the formed substrate to form a formed layer of membrane
material; and sintering the formed layer of membrane material for
sinter bonding the fine fibers to adjacent fine fibers to form the
formed membrane.
14. A process of making a formed membrane as set forth in claim 13,
wherein the liquid binder is a curable liquid binder.
15. A process of making a formed membrane as set forth in claim 13,
further comprising applying a pressure to the liquid binder for
depositing the fine metallic fibers onto the formed porous
substrate.
16. A process of making a formed membrane as set forth in claim 15,
wherein the pressure is a mechanical pressure.
17. A process of making a formed membrane as set forth in claim 16,
wherein the mechanical pressure is applied with a piston.
18. A process of making a formed membrane as set forth in claim 17,
wherein the piston a hydraulically operated piston.
19. A process of making a formed membrane as set forth in claim 13,
further comprising: heating the formed layer of membrane material
for a time sufficient for adhering the fine fibers to adjacent fine
fibers; and removing the formed layer of membrane material from the
formed porous substrate prior to the process of sintering the
formed layer of membrane material.
20. A process of making a composite formed membrane from a
multiplicity of fine fibers, comprising: forming a substrate into a
desired shape for forming a formed substrate; suspending a
multiplicity of first fibers within a liquid binder; depositing the
first fibers onto the formed substrate to form a first formed layer
of membrane material; suspending a multiplicity of second fibers
within a liquid binder; depositing the second fibers onto the first
formed layer of membrane material to form a composite formed layer
of membrane material; and sintering the composite formed layer of
membrane material for sinter bonding the fibers to adjacent fibers
to form the formed membrane.
21. A process of making a formed membrane as set forth in claim 20,
wherein the second fibers are of a different size than the first
fibers.
22. A process of making a formed membrane as set forth in claim 20,
wherein the second fibers are of a different material than the
first fibers.
23. A process of making a formed membrane from a multiplicity of
fine metallic fibers, comprising: forming a porous substrate into a
desired shape for forming a formed substrate; suspending the
multiplicity of fine fibers within a liquid binder; applying a
pressure to the liquid binder for forcing the liquid binder through
the porous substrate for depositing the fine metallic fibers onto
the porous substrate to form a formed layer of membrane material;
and sintering the composite formed layer of membrane material for
sinter bonding the fibers to adjacent fibers to form a
substantially rigid formed membrane.
24. A process of making a composite formed membrane from a
multiplicity of fine fibers, comprising: forming a porous substrate
into a desired shape for forming a formed substrate; suspending a
multiplicity of first fibers within a liquid binder; applying a
pressure to the liquid binder for forcing the liquid binder through
the porous substrate for depositing the first fibers onto the
porous substrate to form a first formed layer of membrane material;
suspending a multiplicity of second fibers within a liquid binder;
applying a pressure to the liquid binder for forcing the liquid
binder through the first formed layer of membrane material and the
porous substrate for depositing the second fibers onto the first
formed layer of membrane material to form a composite formed layer
of membrane material; and sintering the composite formed layer of
membrane material for sinter bonding the fibers to adjacent fibers
to form a substantially rigid formed membrane having overlaying
layers of the first and second fibers.
25. A process of making a formed membrane as set forth in claim 24,
wherein the second fibers are of a different size than the first
fibers.
26. A process of making a formed membrane as set forth in claim 24,
wherein the second fibers are of a different material than the
first fibers.
27. A process of making a formed membrane from a multiplicity of
fine fibers, comprising: forming a porous substrate into a desired
shape for forming a formed substrate; applying a nonporous mask to
a portion of the formed substrate; suspending a multiplicity of
first fibers within a liquid binder; applying a pressure to the
liquid binder for forcing the liquid binder through the porous
substrate for depositing the first fibers onto the porous substrate
to form a first formed layer of membrane material; removing the
nonporous mask from the formed substrate; suspending a multiplicity
of second fibers within a liquid binder; applying a pressure to the
liquid binder for forcing the liquid binder through the previously
masked portion of the porous substrate for depositing the second
fibers onto the previously masked portion of the porous substrate;
and sintering the first and second formed layers of membrane
material for sinter bonding the fibers to adjacent fibers to form a
substantially rigid formed membrane having first and second
fibers.
28. A process of making a formed membrane as set forth in claim 27,
wherein the second fibers are of a different size than the first
fibers.
29. A process of making a formed membrane as set forth in claim 27,
wherein the second fibers are of a different material than the
first fibers.
30. A formed membrane formed from a multiplicity of fine fibers,
comprising: a formed layer of membrane material formed from a
multiplicity of fine fibers; and a sinter bond for bonding said
multiplicity of fine fibers to adjacent fine fibers of said formed
layer of membrane material for forming a substantially rigid formed
membrane.
31. A formed membrane formed from a multiplicity of fine fibers as
set forth in claim 30, wherein said fine fibers comprise fine
metallic fibers.
32. A formed membrane formed from a multiplicity of fine fibers as
set forth in claim 30, wherein said fine metallic fibers have a
diameter between 0.001 and 100 microns.
33. A formed membrane formed from a multiplicity of fine fibers as
set forth in claim 30, wherein said multiplicity of fine fibers are
formed in a wire drawing process.
34. A formed membrane formed from a multiplicity of fine fibers as
set forth in claim 30, wherein said formed layer of membrane
material is supported by a porous substrate.
35. A formed composite membrane formed from a multiplicity of fine
fibers, comprising: a first formed layer of membrane material
formed from a multiplicity of first fine fibers; a second formed
layer of membrane material formed from a multiplicity of second
fine fibers; and sinter bonds for bonding said multiplicity of
first fine fibers to adjacent first fine fibers of said first
formed layer of membrane material, for bonding said multiplicity of
second fine fibers to adjacent second fine fibers of said second
formed layer of membrane material, and for bonding said first
formed layer of membrane material to said second formed layer of
membrane material for forming a substantially rigid formed
composite membrane.
36. A formed composite membrane formed from a multiplicity of fine
fibers as set forth in claim 35, wherein said second formed layer
of membrane material overlies said first formed layer of membrane
material.
37. A formed composite membrane formed from a multiplicity of fine
fibers as set forth in claim 35, wherein said second formed layer
of membrane material is located adjacent to said first formed layer
of membrane material.
Description
[0001] The benefit under 35 U.S.C. .sctn.119(e) of U.S. provisional
application entitled PREFORMED MEMBRANE AND METHOD OF MAKING,
Serial No. 60/294,148, filed May 29, 2001, is hereby claimed and
the disclosure thereof is hereby incorporated by reference in its
entirety.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates to membranes and more particularly to
an improved formed membrane and a method of making the same.
[0004] 2. Description of the Related Art
[0005] Metal filters have long been used for a variety of
applications. For example, porous stainless steel filters prepared
from sintered metal particulate, e.g., stainless steel powder, have
found use in a variety of processes where high pressure drops are
acceptable and in applications where relatively fine filtration
capability must be combined with mechanical strength, resistance to
high temperatures and/or resistance to chemical attack. Such
applications include high temperature, high pressure, corrosive
process gas filtration (solid-gas filtration), gas-gas separation,
hydraulic/liquid filtration, gas burners, heat exchangers,
electrodes, structural components requiring light weight and other
non-filtration components requiring porosity. Still another use of
such filters is in the filtration of molten resin used in the
manufacture of polymeric films and fibers as, for example,
polyester film.
[0006] One form of commercially available metal filters in
cylindrical form is typically prepared from sheet material which is
formed into a cylindrical shape and then longitudinally welded.
Another form of metal fiber media filters and membranes are
fabricated by processing a web structure; sintering these
structures to form a media or membrane, forming these structures
mechanically into shapes, then assembling the finished structure by
welding the seam in the media and welding solid end-caps onto the
open ends. Unfortunately, this method of manufacture results in a
structure sensitive to rapid temperature change; uneven heating and
cooling can ultimately result in cracking and failure of the
structure adjacent the seam weld. Other drawbacks to such welded
structures are solid endcaps and the welded seam reduce the
effective surface area of the component and create non-uniform blow
back characteristics and the inability to make relatively small
diameter structures. For example, at one-half inch diameter, the
welded seam occupies a significant portion of the overall surface
available for filtration, limiting the onstream filter life for a
given cycle.
SUMMARY OF THE INVENTION
[0007] One embodiment of the invention is a process of making a
formed membrane from a multiplicity of fine metallic fibers. The
process includes suspending the multiplicity of fine metallic
fibers within a liquid binder, depositing the multiplicity of fine
fibers onto a formed substrate to form a formed layer of membrane
material, and sintering the formed layer of membrane material for
sinter bonding the fine fibers to adjacent fine fibers to form the
formed membrane.
[0008] Another embodiment of the invention is a process of making a
composite formed membrane from a multiplicity of fine fibers. The
process includes forming a substrate into a desired shape for
forming a formed substrate, suspending a multiplicity of first
fibers within a liquid binder, depositing the first fibers onto the
formed substrate to form a first formed layer of membrane material.
The process further includes suspending a multiplicity of second
fibers within a liquid binder, depositing the second fibers onto
the first formed layer of membrane material to form a composite
formed layer of membrane material, and sintering the composite
formed layer of membrane material for sinter bonding the fibers to
adjacent fibers to form the formed membrane. In one embodiment, the
second fibers are of a different size than the first fibers. In
another embodiment, the second fibers are of a different material
than the first fibers.
[0009] Another embodiment of the invention is a process of making a
formed membrane from a multiplicity of fine metallic fibers. The
process includes forming a porous substrate into a desired shape
for forming a formed substrate, suspending the multiplicity of fine
fibers within a liquid binder, applying a pressure to the liquid
binder for forcing the liquid binder through the porous substrate
for depositing the fine metallic fibers onto the porous substrate
to form a formed layer of membrane material, and sintering the
composite formed layer of membrane material for sinter bonding the
fibers to adjacent fibers to form a substantially rigid formed
membrane.
[0010] Another embodiment of the invention is a formed membrane
formed from a multiplicity of fine fibers. The membrane includes a
formed layer of membrane material formed from a multiplicity of
fine fibers, and sinter bonds for bonding the multiplicity of fine
fibers to adjacent fine fibers of the formed layer of membrane
material for forming a substantially rigid formed membrane.
[0011] Another embodiment of the invention is a process of making a
formed membrane from a multiplicity of fine fibers. The process
includes forming a porous substrate into a desired shape for
forming a formed substrate, applying a nonporous mask to a portion
of the formed substrate, suspending a multiplicity of first fibers
within a liquid binder, applying a pressure to the liquid binder
for forcing the liquid binder through the porous substrate for
depositing the first fibers onto the porous substrate to form a
first formed layer of membrane material, and removing the nonporous
mask from the formed substrate. The process further includes
suspending a multiplicity of second fibers within a liquid binder
applying a pressure to the liquid binder for forcing the liquid
binder through the previously masked portion of the porous
substrate for depositing the second fibers onto the previously
masked portion of the porous substrate, and sintering the first and
second formed layers of membrane material for sinter bonding the
fibers to adjacent fibers to form a substantially rigid formed
membrane having first and second fibers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1A is a block diagram illustrating a first process of
forming a formed membrane, shown in FIGS. 2-5.
[0013] FIG. 1B is a block diagram illustrating a second process of
forming a formed membrane, shown in FIGS. 6-11.
[0014] FIG. 1C is a block diagram illustrating a third process of
forming a formed membrane, shown in FIGS. 12-19.
[0015] FIG. 1D is a block diagram illustrating a fourth process of
forming a formed membrane, shown in FIGS. 20-25.
[0016] FIG. 2 is a side view illustrating an initial process of
depositing fine fibers onto a formed porous substrate for forming a
formed layer of membrane material.
[0017] FIG. 3 is a side view similar to FIG. 2 illustrating the
continued process of depositing fine fibers onto the porous
substrate for forming the formed layer of membrane material.
[0018] FIG. 4 is a side view illustrating the sintering of the
formed layer of membrane material to form a formed membrane.
[0019] FIG. 5 is a magnified view of a portion of FIG. 4.
[0020] FIG. 6 is a side view illustrating an initial process of
depositing first fine fibers onto a porous substrate for forming a
first formed layer of membrane material.
[0021] FIG. 7 is a side view similar to FIG. 6 illustrating the
continued process of depositing first fine fibers onto the porous
substrate for forming the first formed layer of membrane
material.
[0022] FIG. 8 is a side view similar to FIG. 7 illustrating the
initial process of depositing the second fine fibers onto the first
formed layer of membrane material for forming a second formed layer
of membrane material.
[0023] FIG. 9 is a side view similar to FIG. 8 illustrating the
continued process of depositing the second fine fibers onto the
first formed layer of membrane material for forming the second
formed layer of membrane material.
[0024] FIG. 10 is a side view illustrating the sintering of the
first and second formed layers of membrane material to form a
composite formed membrane.
[0025] FIG. 11 is a magnified view of a portion of FIG. 10.
[0026] FIG. 12 is a side view illustrating the application of a
nonporous mask to a portion of the formed substrate.
[0027] FIG. 13 is a side view illustrating an initial process of
depositing first fine fibers onto a porous substrate for forming a
first formed layer of membrane material.
[0028] FIG. 14 is a side view similar to FIG. 13 illustrating the
continued process of depositing first fine fibers onto the porous
substrate for forming the first formed layer of membrane
material.
[0029] FIG. 15 is a side view similar to FIG. 14 illustrating the
removal of the nonporous mask from the formed substrate.
[0030] FIG. 16 is a side view similar to FIG. 15 illustrating the
initial process of depositing second fine fibers onto the porous
substrate within void formed in the first formed layer of membrane
material by the nonporous mask.
[0031] FIG. 17 is a side view similar to FIG. 16 illustrating the
continued process of depositing the second fine fibers onto the
porous substrate within void formed in the first formed layer of
membrane material by the nonporous mask.
[0032] FIG. 18 is a side view illustrating the sintering of the
first and second formed layers of membrane material to form a
composite formed membrane.
[0033] FIG. 19 is a magnified view of a portion of FIG. 18.
[0034] FIG. 20 is a side view illustrating an initial process of
depositing fine fibers onto a formed porous substrate for forming a
formed layer of membrane material.
[0035] FIG. 21 is a side view similar to FIG. 20 illustrating the
continued process of depositing fine fibers onto the porous
substrate for forming the formed layer of membrane material.
[0036] FIG. 22 illustrates the removal of the formed porous
substrate and the formed layer of membrane material.
[0037] FIG. 23 illustrates the separation of the formed layer of
membrane material from the formed porous substrate.
[0038] FIG. 24 is a side view of the formed layer of membrane
material of the present invention. and
[0039] FIG. 25 is a top view of FIG. 24.
DETAILED DESCRIPTION OF THE INVENTION
[0040] A detailed description of an embodiment of the invention is
provided below. While the invention is described in conjunction
with that preferred embodiment, it should be understood that the
invention is not limited to any one embodiment. On the contrary,
the scope of the invention is limited only by the appended claims
and the invention encompasses numerous alternatives, modifications
and equivalents. For the purpose of example, numerous specific
details are set forth in the following description in order to
provide a thorough understanding of the invention. The invention
may be practiced according to the claims without some or all of
these specific details.
[0041] FIG. 1A is a block diagram illustrating a first process 5 of
forming a formed membrane 10 with fine fibers 20. The first process
5 will be explained with reference to the formation of the formed
membrane 10 shown in FIGS. 2-5. FIG. 1A illustrates a process step
11 of forming a formed porous substrate 25. The step of forming the
formed substrate 25 includes forming the substrate 25 into a
desired shape for forming a formed membrane 10 with fine fibers
20.
[0042] FIG. 2 illustrates the porous substrate 25 for forming the
formed membrane 10. The formed substrate 25 is made from a porous
substrate material and is formed in a desired shape to provide a
pattern for the final shape of the formed membrane 10. In one
embodiment of the invention, the porous substrate 25 is shown
formed from a metallic mesh screen in a desired shape for the
formed membrane 10. In the alternative, the porous substrate 25 may
be formed from a porous ceramic material in a desired shape for the
formed membrane 10.
[0043] In one embodiment of the invention, the formed substrate 25
is formed into the shape of a gas burner for a gas boiler, a gas
turbine or the like. Although the formed substrate 25 has been
shown in the shape of a gas burner, it should be understood that
the formed substrate 25 may be formed in any suitable shape for
providing a pattern for the final shape of the formed membrane
10.
[0044] FIG. 1A illustrates a process step 12 of depositing fine
fibers 20 onto the formed substrate 25. The fine fibers 20
accumulate on the formed substrate 25 to form a layer of membrane
material 30 of the fine fibers 20.
[0045] FIG. 2 is a side view illustrating the process step 11 of
depositing the fine fibers 20 onto the formed porous substrate 25.
In one embodiment, the process step 11 of depositing the fine
fibers 20 onto the formed substrate 25 is accomplished within a
pressure vessel 50. The pressure vessel 50 comprises a container 52
having sidewalls 54 and a base 56. A piston 58 is slidably mounted
within the container 52. The formed porous substrate 25 is
connected in fluid tight communication with a fluid outlet 57
defined within the base 56 of the container 52. The container 52
includes a drain valve 59 for draining a liquid from the container
52.
[0046] The fine metallic fibers 20 are suspended in a liquid binder
26. Preferably, the fine metallic fibers are metallic fibers formed
by a wire drawing process and have a diameter between 0.001 microns
and 100 microns. Preferably, the fine metallic fibers 20 have a
diameter between 0.1 and 10 microns, and more preferably between
0.5 and 3 microns. One suitable method of drawing fine metallic
fibers is explained in U.S. Pat. No. 6,112,395 entitled PROCESS OF
MAKING FINE AND ULTRA FINE METALLIC FIBERS, the disclosure of which
is hereby incorporated by reference in its entirety. Another method
of providing fine metallic fibers using a laser is explained in
U.S. Patent Application Publication No. 20020043091 entitled
APPARATUS AND METHOD FOR DRAWING CONTINUOUS FIBER, the disclosure
of which is hereby incorporated by reference in its entirety. The
liquid binder 26 is a curable polymeric material such as an acrylic
or any other suitable binder material. However, one skilled in that
art will understand that the liquid binder 26 may be of any
suitable type depending on the type of the fine metallic fibers 20
used to form the tubular membrane 10. The multiplicity of fine
metallic fibers 20 are suspended within the liquid binder 26 and
placed within the pressure vessel 50 to overlay the porous
substrate 25.
[0047] In one embodiment, the fine metallic fibers can be made from
stainless steel. In other embodiments, the metallic fibers can be
made from FeCrAl, 17-4PH or other corrosion resistant metals. The
metallic fibers can also be made from of a catalytically active
material. In an alternative embodiment, the metallic fibers include
fibers made from a base metal clad with a catalytic metal on the
surface. For example, the fiber can have a base of 300 series
stainless steel with a platinum surface. Other catalytic metals,
such as cobalt, nickel and the like, can also be used.
[0048] FIG. 3 illustrates a layer of membrane material 30 of the
fine fibers 20 onto the porous substrate 25 formed when
substantially all of the liquid binder 26 has passed through the
fluid outlet 57 defined within the base 56. A pressure is applied
to the liquid binder 26 for forcing the liquid binder 26 through
the porous substrate 25 for depositing the fine fibers 20 onto the
formed porous substrate 25. In one embodiment, the pressure applied
to the liquid binder 26 is a mechanical pressure applied by the
piston 58 against the liquid binder 26 as shown by the arrow. In
the alternative, a gas pressure (not shown) may be applied to the
liquid binder 26 for forcing the liquid binder 26 through the
porous substrate 25 for depositing the fine fibers 20 onto the
porous substrate 25. In still a further alternative, a vacuum
applied to the fluid outlet 57 defined in the porous base 56 of the
pressure vessel 50 enables atmospheric pressure to force the liquid
binder 26 through the porous substrate 25.
[0049] As explained above, the layer of membrane material 30 is
formed in the shape of the formed porous substrate 25. Initially,
the liquid binder 26 migrates through the formed porous substrate
25 in accordance with the shape and the flow characteristics of the
container 52. After a partial accumulation of the fine fibers 20
onto the surface of the formed porous substrate 25, the liquid
binder 26 migrates preferentially through the areas of least
accumulation of the fine fibers 20 onto the surface of the formed
porous substrate 25. This pressure wet lay process results in a
substantially uniform porosity to the layer of membrane material
30.
[0050] The thickness and the porosity of the layer of membrane
material 30 of the fine fibers 20 may be preselected by controlling
various parameters during the process step 12 of depositing fine
fibers 20 onto the formed substrate 25. These various parameters
include the control of the volume of the liquid binder 26, the
density of the fine fibers 20 within the liquid binder 26, the rate
of movement of the piston 58, the pressure applied to the piston 58
and the flow rate of the liquid binder 26 through the formed porous
substrate 25.
[0051] FIG. 3 illustrates a substantial portion of the liquid
binder 26 passing through the fluid outlet 57. The multiplicity of
fine fibers 20 accumulate on the formed porous substrate 25 for
forming the layer of membrane material 30. After the liquid binder
26 has passed through the formed porous substrate 25, the formed
porous substrate 25 supports the layer of membrane material 30 of
the fine fibers 20 coated with the remainder of the liquid binder
26. The layer of membrane material 30 of the fine fibers 20
supported by the formed porous substrate 25 is removed from the
pressure vessel 50.
[0052] In one embodiment of the invention, the layer of membrane
material 30 of the fine fibers 20 remains on the formed porous
substrate 25. In an alternative embodiment of the invention, the
layer of membrane material 30 of the fine fibers 20 is removed from
the formed porous substrate 25. The liquid binder 26 maintains the
integrity of the layer of membrane material 30 of the fine fibers
20 after removal from the formed porous substrate 25.
[0053] The layer of membrane material 30 of the fine fibers 20 is
allowed to dry or cure either in an atmospheric condition or in a
drying oven or the like. The cured liquid binder 26 maintains the
integrity of the layer of membrane material 30 of the fine fibers
20.
[0054] In still a further alternative embodiment of the invention,
the layer of membrane material 30 of the fine fibers 20 may be
heated in an oven prior to removal from the formed porous substrate
25. The layer of membrane material 30 is heated for a time and
temperature sufficient to liberate the cured liquid binder 26 from
the fine fibers 20. In one embodiment, the layer of membrane
material 30 of the fine fibers 20 is heated for a time sufficient
for the fine fibers 20 to adhere to an adjacent fine fiber 20 to
form a flexible layer of membrane material 30. The flexible layer
of membrane material 30 facilitates the removal of the layer of
membrane material 30 from the formed porous substrate 25.
[0055] In one example, heating the layer of membrane material 30
made of stainless steel fibers 20 having a diameter of 2.0 microns
at temperature 212 degrees Fahrenheit for a period of 20 hours
within an air atmosphere provides a suitable flexible layer of
membrane material 30.
[0056] In one embodiment, a catalytically active material can be
dispersed with the fine fibers 20. The catalytically active
material can be dispersed into the fine metallic fibers 20 before
the fibers 20 are deposited onto the porous substrate 25.
Alternately, a catalyically active material can be injected into
the pores of the membrane material 30. The catalytically active
material may be injected or dispersed by an air injection lay
process or a wet lay injection process. In addition, the
catalytically active material may be injected and dispersed by a
pasting process.
[0057] FIG. 1A illustrates a process step 13 of sintering the layer
of membrane material 30 of the fine fibers 20 to form the formed
membrane 10. The sintering of the layer of membrane material 30 of
the fine fibers 20 transforms the layer of membrane material 30
into a substantially rigid formed membrane 10.
[0058] FIG. 4 is a side view illustrating the process step 13 of
sintering of the layer of membrane material 30 of the fine fibers
20 to form the formed membrane 10. In one embodiment, the layer of
membrane material 30 of the fine fibers 20 is passed through a
sintering chamber 60. The sintering chamber 60 includes an upper
and a lower heater 61 and 62. The sintering chamber 60 may contain
a specialized atmosphere such as an inert atmosphere or a reducing
atmosphere depending upon the type of fine fibers 20 used for
making the formed membrane 10 of the present invention.
Furthermore, the process step 13 of sintering the layer of membrane
material 30 may take place as a continuous process or as a batch
process as should be well known to those skilled in the art.
[0059] The process step 13 of sintering the layer of membrane
material 30 utilizes a higher temperature than the heating of
membrane material 30 previously set forth. In one embodiment, the
layer of membrane material 30 is heated for time sufficient for the
fine fibers 20 to sinter bond with adjacent fine fibers 20. The
sinter bond between adjacent fine fibers 20 provides a
substantially rigid formed membrane 10. In one example, a rigid
formed membrane 10 made of stainless steel fibers 20 having a
diameter of 2.0 microns is sintered at a temperature of 1750
degrees Fahrenheit for a period of one hour within a partial
hydrogen atmosphere to provide a suitable formed membrane 10. The
membrane 10 can be heated at a temperature between 1300 and 2150
degrees Fahrenheit, with the lower sintering temperatures used with
smaller fibers. One skilled in the art will understand that other
methods of sintering can be used such as induction sintering and
infrared sintering such as is taught in U.S. Pat. No. 6,200,523
entitled APPARATUS AND METHOD OF SINTERING ELEMENTS BY INFRARED
HEATING, the disclosure of which is hereby incorporated by
reference in its entirety.
[0060] FIG. 5 is a magnified sectional view of a portion of FIG. 4
illustrating the sidewall of the formed membrane 10. In one
embodiment, the formed membrane 10 comprises the formed porous
substrate 25 sinter bonded to support the layer of membrane
material 30. The formed porous substrate 25 may be provided with a
mounting ferrule (not shown) for mounting the formed membrane
10.
[0061] FIG. 1B is a block diagram illustrating a second process 105
of forming a formed membrane 110 with first and second fine fibers
121 and 122. The second process 105 will be explained with the
reference to the formation of the formed membrane 110 shown in
FIGS. 6-11.
[0062] FIG. 1B illustrates a process step 111 of forming a formed
substrate 125. The formed substrate 125 is formed into a desired
shape for forming a formed membrane 110 with first and second fine
fibers 121 and 122. The first and second fine fibers 121 and 122
can be made from stainless steel. In other embodiments, the
metallic fibers can be made from FeCrAl, 17-4PH or other corrosion
resistant metals. The metallic fibers can also be made from of a
catalytically active material. In an alternative embodiment, the
metallic fibers include fibers made from a base metal clad with a
catalytic metal on the surface. For example, the fiber can have a
base of 300 series stainless steel with a platinum surface. Other
catalytic metals, such as Cobalt, Nickel and the like, can also be
used.
[0063] FIG. 6 illustrates a porous substrate 125 in a desired shape
for forming a formed membrane 110 with first and second fine fibers
121 and 122. The porous substrate 125 is shown formed from a porous
ceramic material but the porous substrate 125 may be formed from a
metallic mesh screen as previously set forth. Although the formed
substrate 125 has been shown in the shape of a gas burner, it
should be understood that the formed substrate 125 may be formed in
any suitable shape for providing a pattern for the final shape of
the formed membrane 110.
[0064] FIG. 1B illustrates a process step 112 of depositing first
fine fibers 121 onto the formed substrate 125 to form a first layer
of membrane material 131 of the first fine fibers 121.
[0065] FIG. 6 is a side view illustrating the process step 112 of
depositing the first fine fibers 121 onto the formed porous
substrate 125. The process step 112 of depositing the first fine
fibers 121 onto the formed substrate 125 is accomplished within a
pressure vessel 50 as described previously. Catalytically active
material can be dispersed with the fine fibers as previously set
forth.
[0066] FIG. 7 is a side view similar to FIG. 6 illustrating the
process step 112 of depositing the first fine fibers 121 onto the
porous substrate 125. The pressure applied to the liquid binder 126
forces the liquid binder 126 through the formed porous substrate
125 for depositing the first fine fibers 121 onto the formed porous
substrate 125.
[0067] The process step 112 of depositing the first fine fibers 121
onto the porous substrate 125 is terminated after an appropriate
thickness of the first layer of membrane material 131 of the first
fine fibers 121 is deposited onto the formed porous substrate 125.
The remaining liquid binder 126 and first fine fibers 121 not
deposited onto the porous substrate 125 are removed from the
container 50 through the outlet valve 59.
[0068] FIG. 1B illustrates a process step 113 of depositing the
second fine fibers 122 onto the first layer of membrane material
131. The second fine fibers 122 are deposited onto the first layer
of membrane material 131 in a manner similar to the process step
112 of depositing first fine fibers 121 on the formed substrate
125. The second fine fibers 122 accumulate on the first layer of
membrane material 131 to form a second layer of membrane material
132 of the second fine fibers 122.
[0069] FIG. 8 is a side view illustrating an initial process 113 of
depositing the second fine fibers 122 onto the first layer of
membrane material 131. The process step 113 of depositing the
second fine fibers 122 onto the first layer of membrane material
131 is accomplished within a pressure vessel 50 as described
previously.
[0070] FIG. 9 is a side view similar to FIG. 8 illustrating the
continued process step 113 of depositing the second fine fibers 122
onto the first layer of membrane material 131. The pressure applied
to the liquid binder 126 forces the liquid binder 126 through the
first layer of membrane material 131 and through the formed porous
substrate 125 for depositing the second fine fibers 122 onto the
first layer of membrane material 131.
[0071] The process step 113 of depositing the second fine fibers
122 onto the first layer of membrane material 131 is terminated
after an appropriate thickness of the second layer of membrane
material 132 is deposited onto the first layer of membrane material
131 to form a composite membrane material 133. The composite
membrane material 133 may remain on the formed porous substrate 125
or may be removed from the formed porous substrate 125 as set forth
previously.
[0072] Preferably, the first fine fibers 121 are different from the
second fine fibers 122. In one embodiment, the first fine fibers
121 have a different fiber diameter or thickness than the second
fine fibers 122. In another embodiment, the first fine fibers 121
are made from a different material than the second fine fibers
122.
[0073] FIG. 1B illustrates a process step 114 of sintering the
composite layer of membrane material 133 of the first and second
fine fibers 121 and 122 to form the formed membrane 110. The
sintering of the composite layer of membrane material 133 of the
first and second fine fibers 121 and 122 transforms the composite
layer of membrane material 133 into a substantially rigid formed
membrane 110.
[0074] FIG. 10 is a side view illustrating the process step 114 of
sintering the composite layer of membrane material 133 of the first
and second fine fibers 121 and 122 to form the formed membrane 110.
In one embodiment, the composite layer of membrane material 133 is
passed through the sintering chamber 60 as described previously.
After the sintering process the first and second layers of the
membrane material 131 and 132 are bonded into the composite
membrane 133.
[0075] FIG. 11 is a magnified sectional view of a portion of FIG.
10 illustrating the sidewall of the formed membrane 110. In one
embodiment, the formed membrane 110 comprises the composite layer
of membrane material 133. The first layer of membrane material 131
is supporting the second layer of membrane material 132. The first
layer of membrane material 131 may be provided with a mounting
ferrule for mounting the formed membrane 110.
[0076] FIG. 1C is a block diagram illustrating a third process 205
of forming a formed membrane 210 with first and second fine fibers
221 and 222. The third process 205 will be explained with reference
to the formation of the formed membrane 210 shown in FIGS.
12-19.
[0077] FIG. 1C illustrates a process step 211 of forming a formed
substrate 225. The formed substrate 225 is formed into a desired
shape for forming a formed membrane 210 with the first and second
fine fibers 221 and 222.
[0078] FIG. 12 illustrates a porous substrate 225 into a desired
shape for forming a formed membrane 210 with first and second fine
fibers 221 and 222. The porous substrate 225 is shown formed from a
metallic mesh screen. Catalytically active material can be
dispersed with the fine fibers as previously set forth.
[0079] FIG. 1C illustrates the process step 212 of applying a
nonporous mask 241 to selected portions of the formed substrate
225. The nonporous mask 241 may be made of any suitable material
such as a polymeric material, a metallic material or the like.
[0080] FIG. 12 illustrates a porous substrate 225 with the
nonporous mask 241 secured to selected portions of the formed
substrate 225. In one embodiment, the nonporous mask 241 comprised
a flexible polymeric material having a suitable adhesive for
securing to the formed substrate 225. It should be appreciated by
those skilled in the art that many other types of materials may be
used for the nonporous mask 241.
[0081] FIG. 1C illustrates a process step 213 of depositing first
time fibers 221 onto the formed substrate 225. The first fine
fibers 221 are deposited onto the formed substrate 225. The first
fine fibers 221 accumulate on the formed substrate 225 to form a
first layer of membrane material 231 of the first fine fibers
221.
[0082] FIG. 13 is a side view illustrating an initial process 213
of depositing the first fine fibers 221 onto a formed porous
substrate 225. The process step 213 of depositing the first fine
fibers 221 onto the formed substrate 225 is accomplished within the
pressure vessel 50 as described previously.
[0083] The nonporous mask 241 blocks the flow of the liquid binder
226 through the formed substrate 225 at the selected portions of
the formed substrate 225. The nonporous mask 241 inhibits the
deposition of the first fine fibers 221 onto the selected portions
of the formed substrate 225.
[0084] FIG. 14 is a side view similar to FIG. 13 illustrating the
continued process step 213 of depositing the first fine fibers 221
onto the porous substrate 225. The pressure applied to the liquid
binder 226 forces the liquid binder 226 through the formed porous
substrate 225 for depositing the first fine fibers 221 onto the
formed porous substrate 225. The nonporous mask 241 blocks the flow
of the liquid binder 226 through the formed substrate 225 at the
selected portions of the formed substrate 225.
[0085] The process step 213 of depositing the first fine fibers 221
onto the porous substrate 225 is terminated after an appropriate
thickness of the first layer of membrane material 231 of the first
fine fibers 221 is deposited onto the formed porous substrate 225.
The remaining liquid binder 226 and first fine fibers 221 are
removed from the container 50 through the outlet valve 59.
[0086] FIG. 1C illustrates a process step 214 of removing the
nonporous mask 241 from the selected portions of the formed
substrate 225. After removal of the nonporous mask 241, the formed
substrate 225 is exposed at the selected portions of the formed
substrate 225.
[0087] FIG. 15 illustrates a porous substrate 225 with the
nonporous mask 241 removed to expose the selected portions of the
formed substrate 225. The nonporous mask 241 may be readily removed
from the selected portions of the formed substrate 225 when an
adhesive is used to secure the nonporous mask 241 to the formed
substrate 225. A strong adhesive is not needed since the pressure
applied to the liquid binder 226 assists the adhesive in
maintaining the position of the nonporous mask 241 on the formed
substrate 225.
[0088] FIG. 1C illustrates a process step 215 of depositing second
fine fibers 222 onto the selected portions of the formed substrate
225 and subsequently onto the first layer of membrane material 231
of the first fine fibers 221. Initially, the second fine fibers 222
are preferentially deposited onto the selected portions of the
formed substrate 225. The second fine fibers 222 accumulate at the
selected portions of the formed substrate 225 to form a second
layer of membrane material 232 of the second fine fibers 222.
Thereafter, the second fine fibers 222 are deposited onto the first
layer of membrane material 231 of the first fine fibers 221 to form
a second layer of membrane material 232.
[0089] FIG. 16 is a side view illustrating an initial process 215
of depositing the second fine fibers 222 onto the selected portions
of the formed substrate 225. The process step 215 of depositing the
second fine fibers 222 onto the selected portions of the formed
substrate 225 is accomplished within the pressure vessel 50 as
described previously.
[0090] FIG. 17 is a side view similar to FIG. 16 illustrating the
continued process step 215 of depositing the second fine fibers 222
onto the selected portions of the formed substrate 225 and
subsequently onto the first layer of membrane material 231 of the
first fine fibers 221. The pressure applied to the liquid binder
126 forces the liquid binder 126 through the previously masked
portion 241 of the formed porous substrate 225 for depositing the
second fibers 222 onto the previously masked 241 of the porous
substrate 225. The second fine fibers 222 are preferentially
deposited onto the previously masked portions 241 of the formed
substrate 225. Thereafter, the second fine fibers 222 are deposited
onto the first layer of membrane material 231 of the first fine
fibers 221 to form a second layer of membrane material 232.
[0091] The process step 215 of depositing the second fibers 222
onto the first layer of membrane material 231 is terminated after
an appropriate thickness of the second layer of membrane material
232 is deposited onto the first layer of membrane material 231 to
form a composite membrane material 233. The composite membrane
material 233 may remain on the formed porous substrate 225 or may
be removed from the formed porous substrate 225 as set forth
previously.
[0092] Preferably, the first fibers 221 are different from the
second fibers 222. In one embodiment, the first fibers 221 have a
different fiber diameter or thickness than the second fibers 222.
In another embodiment, the first fibers 221 are made from a
different material than the second fibers 222.
[0093] FIG. 1C illustrates a process step 216 of sintering the
composite layer of membrane material 233 of the first and second
fine fibers 221 and 222 to form the formed membrane 210. The
sintering of the composite layer of membrane material 233 of the
first and second fine fibers 221 and 222 transforms the composite
layer of membrane material 233 into a substantially rigid formed
membrane 210.
[0094] FIG. 18 is a side view illustrating the process step 216 of
sintering of the composite layer of membrane material 233 of the
first and second fibers 221 and 222 to form the formed membrane
210. In one embodiment, the composite layer of membrane material
233 is passed through the sintering chamber 60 as described
previously. After the sintering process, the first and second
layers of the membrane material 231 and 232 are bonded into the
composite membrane 233.
[0095] FIG. 19 is a magnified section view of a portion of FIG. 18
illustrating the sidewall of the formed membrane 210. In one
embodiment, the formed membrane 210 comprises the composite layer
of membrane material 233 comprising the first and second layers of
the membrane material 231 and 232. The first layer membrane of the
material 231 overlays all of the formed substrate 225 except the
masked portions 241. The second layer of the membrane material 232
overlays the masked portions 241 and overlays the first layer of
the membrane material 231.
[0096] FIG. 1C illustrates alternative process steps 214A and 215A
for the third process 205 of forming a formed membrane 210 with
first and second fine fibers 221 and 222. The alternative third
process 205 will be explained with reference to the formation of
the formed membrane 210A shown in FIGS. 16A-19A.
[0097] FIG. 1C illustrates the alternate process step 214A of
applying a second nonporous mask 241 to the first layer of membrane
material 231A of the first fine fibers 221. The second nonporous
mask 242 may be made of any suitable material such as a polymeric
material, a metallic material or the like as set forth
previously.
[0098] FIG. 1C illustrates the process step 215 of depositing
second fine fibers 222 onto only the selected portions of the
formed substrate 225. The second fine fibers 222 are deposited only
onto the selected portions of the formed substrate 225 to form a
second layer of membrane material 232A of the second fine fibers
222.
[0099] FIG. 16A is a side view illustrating an initial process 215
of depositing the second fine fibers 222 only onto the selected
portions of the formed substrate 225. The process step 215 of
depositing the second fine fibers 222 onto the selected portions of
the formed substrate 225 is accomplished within the pressure vessel
50 as described previously. Catalytically active material can be
dispersed with the fine fibers as previously set forth.
[0100] FIG. 17A is a side view similar to FIG. 16A illustrating the
continued process step 215 of depositing the second fine fibers 222
onto only the selected portions of the formed substrate 225. The
pressure applied to the liquid binder 126 forces the liquid binder
126 through the previously masked portion 241 of the formed porous
substrate 225 for depositing the second fibers 222 only onto the
previously masked portion 241 of the porous substrate 225. The
second nonporous mask 242 overlays the first layer of membrane
material 231A of the first fine fibers 221 and prevents the
accumulation of the second fine fibers 222 onto the first layer of
membrane material 231A.
[0101] The process step 215 of depositing the second fibers 222 is
terminated after an appropriate thickness of the second layer of
membrane material 232 is deposited onto the previously masked
portion 241 to form a composite membrane material 233A.
[0102] FIG. 1C illustrates then alternate process step 215A of
removing the second nonporous mask 242 from the first layer of
membrane material 231A. The second nonporous mask 242 may be
readily removed from the first layer of membrane material 231A as
previously described.
[0103] FIG. 18A is a side view illustrating the process step 216 of
sintering of the composite layer of membrane material 233A of the
first and second fibers 221 and 222 to form the formed membrane
210A. In one embodiment, the composite layer of membrane material
233A is passed through the sintering chamber 60 as described
previously. After the sintering process, the first and second
layers of the membrane material 231A and 232A are bonded into the
composite membrane 233A.
[0104] FIG. 19A is a magnified sectional view of a portion of FIG.
18 illustrating the sidewall of the formed membrane 210A. In one
embodiment, the formed membrane 210A comprises the composite layer
of membrane material 233A comprising the first and second layers of
the membrane material 231A and 232A. The first layer membrane of
the material 231A overlays the formed substrate 225 except the
masked portions 241. The second layer of the membrane material 232A
overlays only the masked portions 241.
[0105] FIG. 1D is a block diagram illustrating a fifth process 305
of forming a formed membrane 310 with fine fibers 320. The fifth
process 305 will be explained with reference to the formation of
the formed membrane 310 shown in FIGS. 20-25. FIG. 1D illustrates a
process step 311 of forming a formed substrate 325 into a desired
shape for forming a formed membrane 310 with fine fibers 320.
[0106] FIG. 20 illustrates a porous substrate 325 for forming a
formed membrane 310 with fine fibers 320. In one embodiment of the
invention, the porous substrate 325 is shown having a cylindrical
shape defining an inner cylindrical surface 329. Preferably, the
porous substrate 325 is formed from a porous ceramic material.
[0107] FIG. 1D illustrates a process step 312 of depositing fine
fibers 320 onto the formed substrate 325. The fine fibers 320
accumulate on the formed substrate 325 to form a layer of membrane
material 330 of the fine fibers 320.
[0108] FIG. 20 is a side view illustrating an initial process 312
of depositing the fine fibers 320 onto a formed porous substrate
325. A pressure vessel 350 comprises a container 352 having
sidewalls 354 and a base 356. A piston 358 is slidably mounted
within the container 352. The sidewalls 354 includes a porous
sidewall portion 357. The formed substrate 325 is connected in
fluid tight communication with the porous sidewall portion 357 of
the container 352.
[0109] In one embodiment of the invention, the fine fibers 320 are
suspended in a liquid binder 326. The liquid binder 326 may be of
any suitable type depending on the type of the fine fibers 320 used
to form the formed membrane 310.
[0110] FIG. 21 is a side view similar to FIG. 20 illustrating the
continued process step 312 of depositing the fine fibers 320 onto
the porous substrate 325. A pressure is applied to the liquid
binder 326 for forcing the liquid binder 326 through the formed
porous substrate 325 for depositing the fine fibers 320 onto the
formed porous substrate 325. The fine fibers 320 are deposited on
the inner cylindrical surface 329 of the formed porous substrate
325. The multiplicity of fine fibers 320 accumulate on the inner
cylindrical surface 329 of the formed porous substrate 325 for
forming the layer of membrane material 30.
[0111] FIG. 1D illustrates the process step 313 of shrinking the
layer of membrane material 330. After the liquid binder 326 has
passed through the formed porous substrate 325, the formed porous
substrate 325 supports the layer of membrane material 330 of the
fine fibers 320. The formed porous substrate 325 and the layer of
membrane material 330 of the fine fibers 320 are removed from the
pressure vessel 350.
[0112] FIG. 22 illustrates removal of the formed porous substrate
325 and the layer of membrane material 330 of the fine fibers 320
from the pressure vessel 350. The layer of membrane material 330 of
the fine fibers 320 is supported by the formed porous substrate
325.
[0113] FIG. 23 illustrates the separation of the layer of membrane
material 330 of the fine fibers 320 from the formed porous
substrate 325. The layer of membrane material 330 of the fine
fibers 320 is allowed to dry or cure on the formed porous substrate
325 either in an atmospheric condition or in a drying oven or the
like. As the layer of membrane material 330 of the fine fibers 320
is allowed to dry or cure, the layer of membrane material 330
shrinks and separates from the formed porous substrate 325.
[0114] FIGS. 24 and 25 illustrate the layer of membrane material
330 of the fine fibers 320 removed from the formed porous substrate
325. The layer of membrane material 330 is sintered in a manner
similar to the sintering as set forth previously.
[0115] The process of the present invention has many applications
and uses as should be appreciated by those skilled in the art. The
following is a small list of applications and uses of the present
invention, but this should not be construed to be a complete or
exhaustive list of applications and uses.
[0116] The present invention may be used in burners for natural gas
turbine electricity generating plants, mantels for propane lanterns
and for other gas burners such as propane and the like. The burners
may be shaped for providing shaped burner surfaces. The present
invention may be used in filters such as air conditioning filters,
fuel filters and the like. The present invention may be used as a
support for catalytic converters or skeleton for filters made from
otherwise weak fibers. The present invention may be used as a
substrate for a catalyst. The present invention may be used as
diffusers and electrical electrodes for electrochemical operations,
batteries, fuel cells and the like. The present invention may be
used in heat exchangers and the like.
[0117] Specific blocks, sections, devices, functions and modules
have been set forth. However, a skilled technologist will recognize
that there are many ways to partition the system of the invention,
and that there are many parts, components, modules or functions
that may be substituted for those listed above. While the above
detailed description has shown, described, and pointed out
fundamental novel features of the invention as applied to various
embodiments, it will be understood that various omissions and
substitutions and changes in the form and details of the system
illustrated may be made by those skilled in the art, without
departing from the intent of the invention.
* * * * *