U.S. patent application number 14/733645 was filed with the patent office on 2015-10-08 for horizontal plate microbial support media.
The applicant listed for this patent is Advanced Bio Energy Development LLC. Invention is credited to John S. Reitzel, William C. Stewart.
Application Number | 20150284670 14/733645 |
Document ID | / |
Family ID | 41610749 |
Filed Date | 2015-10-08 |
United States Patent
Application |
20150284670 |
Kind Code |
A1 |
Reitzel; John S. ; et
al. |
October 8, 2015 |
Horizontal Plate Microbial Support Media
Abstract
A horizontal plate microbial support media. The horizontal plate
microbial support media having a plurality of frustum shaped
protuberances extending there-from, the frustum shapes having a
hole in their upper base for allowing fluid to flow there-through.
These media plates able to be stacked for use in a bioreactor.
Inventors: |
Reitzel; John S.;
(Brookfield, VT) ; Stewart; William C.; (Caldwell,
ID) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Advanced Bio Energy Development LLC |
Boise |
ID |
US |
|
|
Family ID: |
41610749 |
Appl. No.: |
14/733645 |
Filed: |
June 8, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13056869 |
Jan 31, 2011 |
9068156 |
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PCT/US09/52407 |
Jul 31, 2009 |
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14733645 |
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61085244 |
Jul 31, 2008 |
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Current U.S.
Class: |
435/305.1 |
Current CPC
Class: |
C12M 25/06 20130101;
C12N 11/14 20130101; C02F 3/101 20130101; C12M 23/34 20130101; Y02W
10/10 20150501; C12M 27/22 20130101; C12M 27/18 20130101; Y02W
10/15 20150501; C12M 25/02 20130101 |
International
Class: |
C12M 1/00 20060101
C12M001/00; C12M 1/12 20060101 C12M001/12 |
Claims
1-20. (canceled)
21. A microbial support media system for an upward flow microbial
digestion system, comprising: a plurality of horizontal microbial
support media plates in a vertical stack, each of the plurality of
horizontal microbial support media plates having a plurality of
protuberances extending upward to an upper end, the upper end of
each of the plurality of protuberances having an opening for
allowing the upward flow of a liquid to pass through, the
horizontal microbial support media plates in the vertical stack are
disposed in such a way that protuberances of adjacent horizontal
microbial support media plates are offset a predetermined distance
from one another; a plurality of upward flow splitting features
formed by the plurality of protuberances of the plurality of
horizontal microbial support media plates in the vertical stack,
the plurality of upward flow splitting features configured to split
the upward flow of the liquid; and a plurality of upward flow
remixing features formed by the plurality of protuberances of the
plurality of horizontal microbial support media plates in the
vertical stack, the plurality of upward flow remixing features
configured to remix the flow of liquid split by the plurality of
upward flow splitting features.
22. The microbial, support media system of claim 21, wherein the
plurality of upward flow splitting features are configured to ace
as a first attachment sire for a first biofilm.
23. The microbial support media system of claim 22, wherein the
first biofilm is comprised mainly of methane producing
microorganisms.
24. The microbial support media system, of claim 22, wherein the
plurality of upward flow splitting features are configured to act
as an impingement surface for the liquid flowing upward such that
the liquid contacts the first biofilm.
25. The microbial support media system of claim 24, wherein the
liquid is as an upward flowing carrier liquid for suspended and
colloidal solids.
26. The microbial support media system of claim 25, wherein the
first biofilm captures suspended and colloidal solids from the
liquid for digestions.
27. The microbial support media system of claim 26, wherein the
first biofilm captures upward flowing carbon dioxide (CO.sub.2) and
hydrogen (H.sub.2).
28. The microbial support media system of claim 27, wherein the
carbon dioxide (CO.sub.2) and hydrogen (H.sub.2) are released in
hydrolysis and acidogenesis reactions.
29. The microbial support media system of claim 22, wherein the
plurality of upward flow remixing features are configured to
provide a second attachment sire for a second biofilm.
30. The microbial support media system of churn 29, wherein the
second biofilm is comprised mainly of hydrolysis bacteria and
acidogenesis bacteria.
31. The microbial support media system of claim 24, further
comprising biofilm attachment projections extending downward irons
the impingement surface of the upward flow splitting feature.
32. The microbial support media system of claim 31, wherein the
biofilm attachment projections are configured to act as a third
attachment site for the first biofilm.
33. A horizontal plate microbial support media for an upward flow
microbial digestion system, the horizontal plate microbial support
media configured to be disposed, within a stack of similarly
configured horizontal plates in a staggered layout, the horizontal
plate microbial support media comprising. an upper surface and a
lower surface; a plurality of protuberances, each of the
protuberances having a base and an upward end, each of the
protuberances extending upward from the upper and lower surfaces at
the base to the upward end in such a way that the base of each of
the protuberances is wider than the upward end, each upward end
having an opening for allowing the upward flow of a liquid to pass
through; an upward flow splitting feature formed on the lower
surface of the horizontal plate microbial support media by adjacent
portions of at least two protuberances, the upward flow splitting
features configured to split the flow of liquid prior to the liquid
flowing upward through the opening; and an upward flow remixing
feature formed at least in part on the upper surface of the
horizontal plate microbial support media by the adjacent portions
of the at least two protuberances, the upward flow remixing feature
configured to remix at least a portion of the flow of the liquid
split by the upward flow splitting feature after the liquid has
passed through the opening.
34. The horizontal plate microbial support media of claim 33,
wherein the upward flow splitting feature is configured to act as a
first attachment site for a first biofilm, wherein the upward flow
remixing feature is configured to provide a second attachment site
for a second biofilm.
35. The horizontal plate microbial support media of claim 34,
wherein the upward flow splitting feature is configured to act as
an impingement surface for the liquid flowing upward such that the
liquid contacts the first biofilm.
36. The horizontal plate microbial support media of claim 35,
further comprising biofilm attachment projections extending
downward from the impingement surface of the upward flow splitting
feature, wherein the biofilm attachment projections are configured
to act as a third attachment site for the first biofilm.
37. A microbial support: media system for an upward flow microbial
digestion system, comprising: a plurality of horizontal microbial
support media plates in a vertical stack, each of the plurality of
horizontal microbial support media plates having a plurality of
protuberances extending upward to an upper end, the upper end of
each of the plurality of protuberances having an opening for
allowing the upward flow of a liquid to pass through, the
horizontal microbial support media plates in the vertical stack are
disposed in such a way that protuberances of adjacent horizontal
microbial support media plates are offset a predetermined distance
from one another; a plurality of upward flow splitting features
formed by the plurality of protuberances of the plurality of
horizontal microbial support media plates in the vertical stack,
the plurality of upward flow splitting features configured to split
the upward flow of the liquid, the plurality of upward flow
splinting features are configured to act as impingement surfaces
for the liquid flowing upward; a plurality of upward flow remixing
features formed by the plurality of protuberances of the plurality
of horizontal microbial support media plates in the vertical stack,
the plurality of upward flow remixing features configured to remix
the flow of liquid split by the plurality of upward flow splitting
features; and a plurality of biofilm attachment projections
extending downward from the impingement surfaces of the plurality
of upward flow splitting features, the plurality of biofilm
attachment projections configured to act as first attachment sites
tor a first biofilm.
38. The microbial support media system of claim 37, wherein the
first biofilm is comprised mainly of methane producing
microorganisms.
39. The microbial support media system of claim 37, wherein the
plurality of upward flow remixing features are configured to
provide second attachment sites for a second biofilm.
40. The microbial support media system of claim 39, wherein the
second biofilm is comprised mainly of hydrolysis bacteria and
acidogenesis bacteria.
Description
BACKGROUND
[0001] In nature, microbial communities in fluid environments
attach to solid substrates (e.g., rocks, sand granules) to form
biofilms. Biofilms are aggregations of microorganisms attached to a
submerged surface, affording a protective matrix for complex
community interactions. These biofilms also increase the resistance
of microbes to environmental perturbations (e.g., temperature
changes, toxins).
[0002] In engineered bioreactors, permanent fixed surfaces (aka
"biological attachment surfaces" and "microbial support media") are
commonly provided as attachment sites for development of biofilms.
Such engineered bioreactors include those used in water and
wastewater treatment facilities, toxic waste remediation processes,
pharmaceutical and chemical manufacturing processes, and renewable
fuel production.
[0003] Operational advantages to the use of such microbial support
media include: (1) increased system stability and reliability; (2)
increased microbial productivity; (3) decreased reactor size
requirements; (4) minimization of microbial loss when product is
removed from the reactor; and (5) significantly greater resistance
to environmental stresses such as temperature or pH fluctuations
and exposure to toxins.
[0004] Types of Microbial Support Media. There are two broad
classifications of microbial support media commonly used in
industry, namely (1) "Random Media" and (2) "Modular Media."
[0005] Random Media (also known as "Dumped Media") comprises
individual pieces of media which are randomly placed into a
bioreactor. Random Media can comprise a wide variety of material
including, but not limited to, lava rock chunks and various shapes
of synthetic media (e.g., perforated balls, saddles, pall
rings).
[0006] There are a number of problems inherent in the use of Random
Media as a microbial support media, including: (1) Random Media can
have an inconsistent pore space between individual microbial
support media pieces, thereby resulting in uneven hydraulic flow
through the microbial support media, increased backpressure and
reduced substrate contact with the attached biofilm; (2) Random
Media typically has relatively low specific surface area for
microbial attachment; and (3) due to its configuration, uneven
biomass buildup can occur in Random Media, this buildup resulting
in a long-term increase in pore blockage and hydraulic short
circuiting.
[0007] Modular Media (also knows as "Sheet Media") typically
comprises formed sheets, usually made of PVC plastic, which are
joined together. There are two main types of modular media, namely,
simple vertical tubes and vertical cross-flow tubes. In vertical
cross-flow tubes, the tubes intersect at opposite angles (e.g.,
sixty degrees), thereby increasing mixing. Both types of modular
media were developed originally for air systems. In biological
applications, they are currently used primarily in down-flow
aerobic trickling filter systems for wastewater treatment.
[0008] Modular media poses a number of problems, particularly when
applied to upflow anaerobic reactors, namely that (1) the tubular
media has poor mixing characteristics and tends to be susceptible
to aperture blockage due to biomass buildup, particularly at the
interface where modules are stacked, and (2) the cross flow media
has good mixing characteristics in high fluid velocity situations
such as down-flow trickling filters, however, in the low upward
fluid velocities characteristic of anaerobic reactors, laminar flow
occurs, reduced mixing characteristics occurs, and reduced contact
of substrate with the attached biofilm occurs.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 is a perspective view of a first embodiment of the
present invention.
[0010] FIG. 2 is a plan view of the embodiment of FIG. 1.
[0011] FIG. 3A is a partial, side view of a forty-five degree
angled protrusion.
[0012] FIG. 3B is a partial, side view of a sixty degree angled
protrusion.
[0013] FIG. 4 is a perspective view of two of the sheets of FIG. 1
shown in a stacked, spaced configuration.
[0014] FIG. 5 is a partial, side representation of flow through of
a first configuration.
[0015] FIG. 6 is a partial, side representation of flow through of
a second configuration.
[0016] FIG. 7 is a partial, side representation of flow through of
a third configuration.
[0017] FIG. 8 is a partial, side representation of flow through of
a fourth configuration.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] While the invention is susceptible of various modifications
and alternative constructions, certain illustrated embodiments
thereof have been shown in the drawings and will be described below
in detail. It should be understood, however, that there is no
intention to limit the invention to the specific form disclosed,
but, on the contrary, the invention is to cover all modifications,
alternative constructions, and equivalents falling within the
spirit and scope of the invention as defined in the claims.
[0019] In the following description and in the figures, like
elements are identified with like reference numerals. The use of
"e.g.," "etc," and "or" indicates non-exclusive alternatives
without limitation unless otherwise noted. The use of "including"
means "including, but not limited to," unless otherwise noted.
[0020] The present invention is a horizontal plate microbial
support media (also referred to herein as the "support media" and
as a "filter plate"). The support media was specifically designed
to optimize both the hydraulic and biological functionality of
upflow anaerobic processes.
[0021] The support media is preferably thermoformed or stamped from
suitable material (e.g., a polyvinyl chloride (PVC) sheet, a
polypropylene (PP) sheet, a metal sheet) such as the sheet 20 shown
in FIGS. 1 and 2. The thickness used can be varied based upon the
application.
[0022] The support media 20 preferably provided on a generally
rectangular, generally planar sheet having a first end edge 70 and
a second end edge 72 at respective opposing longitudinal ends
thereof defining a width of the support media 20 there-between, a
first side edge 74 and a second side edge 76 at respective opposing
lateral ends thereof defining a length of the support media 20
there-between, where the sides and ends defining a top surface 78
and a bottom surface 80.
[0023] It is preferred that a plurality of protuberances 30 be
formed extending from one or more of the top or bottom surfaces,
preferably from the top surface 78. It is preferred that
protuberances be generally equidistantly spaced apart.
[0024] The protuberances 30 can be any number of shapes, but are
preferably shaped like a frustum, having a bottom plane (bottom
base) defined by the top surface 78 (or the bottom surface 80) of
the support media 20 and a top plane 50 (top base) spaced
there-from. The frustum having at least one face 40 extending
between the top base and bottom base. Preferred frustum shapes
include oval frustums and frustums having three or more sides
(e.g., hexagonal frustums, heptagonal frustums, octagonal
frustums). A right, hexagonal frustum (as shown in the Figures)
being the most preferred. Other frustum shapes are also
possible.
[0025] In the preferred embodiment, the faces 40 intersect the
bottom base 22 at a 20.degree. to 80.degree. angle, with 45.degree.
to 60.degree. being more preferred. A face angle (A1) of
45.degree., as shown in FIG. 3A, is preferred where solids loading
is low for final effluent polishing to increase surface area per
unit volume. FIG. 3B showing a 60.degree. face angle (A2).
[0026] The height of the protuberances 30 (distance between the two
frustum bases) can be varied based upon the application. Preferred
heights include from 1.00 inch (2.54 cm) to 12.00 inches (30.48 cm)
or more.
[0027] It is preferred that an elongate or oval hole (passageway)
56 be defined in the top base 50 for allowing fluid communication
with overlaying horizontal sheets.
[0028] Preferably, at least one sheet hole 24 be defined through
the sheet 20 adjacent and/or in between the protuberances 30. The
sheet holes allow any solids or sludge which may build up at the
base of the protuberances to be removed by reversing the flow in
the reactor (from upward flow to downward flow) for a period of
time. This step may need to be done occasionally to prevention of
any blockage due to excessive buildup of solids on the horizontal
flat sheet portion between the protuberances.
[0029] A staggered layout is preferred, this staggered layout
allowing individual sheets 20 of the present invention to be
stacked into modules (for use in a reactor vessel) by rotating
certain of the sheets (for instance, every other sheet) in the
stack. For instance, in one configuration, every other sheet could
be rotated 180 degrees. Having a staggered layout, the sheets would
not nest when so rotated and would form a vertical structure (as
shown in FIG. 4), the "stacked formation." However, when
manufactured, shipped and stored, the sheets can be stacked in a
nested fashion, saving space (the "nested formation").
[0030] FIG. 4 showing a first sheet 20 stacked upon a second sheet
20'. In this configuration, the first sheet 20 is identical to the
second sheet 20', however the first sheet 20 has been rotated in
the plane of the bottom base 180 degrees. The second sheet (support
media) 20' preferably provided on a generally rectangular,
generally planar sheet having a first end edge 70' and a second end
edge 72' at respective opposing longitudinal ends thereof defining
a width of the support media 20' there-between, a first side edge
74' and a second side edge 76' at respective opposing lateral ends
thereof defining a length of the support media 20' there-between,
where the sides and ends defining a top surface 78' and a bottom
surface 80'. The second sheet 20' having protuberances 30' which
support the underside of the first sheet. The figure also showing a
plurality of sheet holes 24' in the second sheet.
[0031] It is preferred, but not necessary, that when in the stacked
formation an adhesive or other means of joining the sheets together
(e.g., sonic welding, fasteners, glue) permanently or
semi-permanently could be utilized. In such a configuration, the
media is self-supporting (it does not rely on reactor vessel walls
for support or produce lateral forces against the reactor vessel
walls). Again, such a staggered configuration allows the media
sheets to be stacked tightly for compact shipping, yet allows them
to be easily assembled on the job site without special tools.
[0032] FIGS. 5-8 show various partial cross-sectional views
representing what the hydraulic flows in stacked configurations
could look like. FIG. 5, shows potential hydraulic attributes
present. In that figure, an upper sheet is stacked upon a lower
sheet, these stacked sheets forming individual cells which impose
flow splitting 61 and remixing 60 at low upflow velocities found in
anaerobic reactors. This significantly reduces and/or eliminates
potential channeling effects. As can be seen in FIG. 6, such a
design also imposes impingement against upper surface of media
sheets prior to flow splitting and remixing.
[0033] Biologically, the support media 20 provides a stable
attachment site for biofilm development, minimizing washout (loss
of microorganisms) and maximizing process stability. The flow
splitting, mixing, remixing, and flow impingement at the upper
media surface, characteristic of the design, ensures even
distribution of substrate throughout the reactor volume and
maximizes contact with the biologically active media surfaces (as
is illustrated in FIGS. 5 and 6).
[0034] The enforced impingement of liquid at the upper media
surface, which insures contact with the microbial biofilm attached
to this surface (FIG. 6), accelerates capture, agglomeration, and
removal of suspended and colloidal solids from the upflowing
carrier fluid. As these agglomerated solids build up, they drop off
the upper surface 62 to the lower surface 63 (shown in FIG. 6)
where further digestion takes place.
[0035] The enforced impingement of product against the upper media
surface also increases contact and entrapment with rising gases
such as carbon dioxide (CO.sub.2) and hydrogen (H.sub.2) released
in the hydrolysis and acidogenesis reactions of anaerobic
digestion. Conversion of these gases by the methane (CH.sub.4)
producing microorganisms attached to the upper surface of a media
cell is enhanced producing a higher BTU biogas in that it contains
more methane (CH.sub.4) and less carbon dioxide (CO.sub.2).
[0036] The enforced impingement of product against the upper media
surface also increases contact of soluble low-molecular weight
organics (e.g., acetate) released in the acidogenesis phase
reactions of methane production. Conversion of these organics by
the methane producing microorganisms attached to the upper surface
of a media cell is enhanced, producing larger quantities of methane
(CH.sub.4) gas.
[0037] The provision of an upper and lower attachment surface
permits the establishment of a multi-phased biological system
within the media. For example, solids digestion takes place on the
lower surface of a cell, while the capture and digestion of the
soluble end products of the solids digestion takes place by the
biofilm attached to the upper layer of the media. This reduces
potential competitive interactions between the two communities.
This multi-phased mechanism is particularly important in protecting
methane (CH.sub.4) producing microorganisms (attached to the upper
surface) from competition with the more robust hydrolysis and
acidogenesis bacteria on the lower digestive surface.
[0038] The horizontal plate design also permits roughing (e.g.,
sandblasting, spraying on a coating) of upper surface to improve
adhesion of biofilm and/or addition of elongate stalactite-like
biofilm attachment projections 64 on upper surface of media to
increase surface area for biofilm attachment, as is illustrated in
FIG. 7.
[0039] The provision of edges 65 at the openings of the media
induces accelerated and heavy growth of biofilm at these edges in
response to food availability thus increasing specific biological
activity, as is illustrated in FIG. 8.
[0040] Media Countercurrent Flow Application for Ethanol,
Pharmaceuticals and Other Applications. In many biotechnology
manufacturing operations, gases (e.g., carbon dioxide (CO.sub.2),
hydrogen (H.sub.2)) are formed as waste products or metabolic
by-products. These gases, as their concentration increases, can
impede biological production of the desired product due to
inhibitory effects. To alleviate this effect, the Horizontal Plate
Microbial Support Media can be used in a countercurrent flow
application in which the liquid stream carrying the food material
and resultant product flows in a downward direction in a reactor
packed with the media. The microorganisms performing the
transformation will then be found at highest concentrations on the
lower surface of the media. Inhibitory gases, such as carbon
dioxide (CO.sub.2), will rise upward against this liquid flow.
These gases will primarily contact the upper surface of the media
sheets, protecting the active biofilm on the lower surface from
full contact with these inhibitory gases.
[0041] In cases where such countercurrent flow is desirable, the
media can be modified to increase biofilm formation and surface
area by roughing the lower surface (e.g. sandblasting, spraying on
a coating) and/or addition of elongate stalagmite-like biofilm
attachment projections (as opposed to the stalactite like biofilm
attachment projections 64 shown on the upper surface of a cell in
FIG. 7) on the lower surface of the media to increase surface area
for biofilm attachment. Other liquid downward flow applications in
which countercurrent flow of a liquid and a gas can be applied
include aerobic and anaerobic reactors such as wastewater trickling
filters, air pollution trickling filters and various pharmaceutical
and other biotechnology manufacturing reactors.
[0042] The basic media design approach can also be applied as media
in cooling towers, mist eliminators, tube or plate settlers,
biofilter trickling filters, wastewater trickling filters, aerobic
submerged media wastewater treatment reactors, ethanol production
reactors, and pharmaceutical product reactors, among other
applications.
[0043] A first example embodiment. A filter medium for allowing a
flow of a liquid there-through, said medium comprising: a vertical
stack of adjacent generally rectangular sheets having a first end
edge and a second end edge at respective opposing lateral ends, a
first side edge and a second side edge at respective opposing
longitudinal ends, said sides and ends defining a top surface and a
bottom surface, said sheets having a plurality of frustum-shaped
protuberances extending from said top surface, said frustum-shape
having a bottom base defined by the top surface of the sheet and a
top base spaced there-from, the frustum having at least one face
extending between the top base and bottom base, wherein said at
least one face intersects the bottom base at a 45.degree. to
60.degree. angle, said top base further comprising a passageway
defined there-through; wherein adjacently stacked sheets are
arranged so as to create non-linear flow paths.
[0044] A second example embodiment. A generally rectangular,
generally planar filter plate, said plate comprising: a sheet
having a first end edge and a second end edge at respective
opposing longitudinal ends, a first side edge and a second side
edge at respective opposing lateral ends, said sides and ends
defining a top surface and a bottom surface; and a plurality of
frustum-shaped protuberances extending from said top surface, said
frustum-shape having a bottom base defined by the top surface of
the sheet and a top base spaced therefrom, the frustum having at
least three faces extending between the top base and bottom base,
wherein said faces intersect the bottom base at a 45.degree. to
60.degree. angle, said top base further comprising a passageway
defined there-through.
[0045] A third example embodiment. First and second generally
identical filter plates, said filter plates configured for
stacking, each of said filter plates comprising: a generally
rectangular, generally planar sheet having a first end edge and a
second end edge at respective opposing longitudinal ends, a first
side edge and a second side edge at respective opposing lateral
ends, said sides and ends defining a top surface and a bottom
surface, a plurality of frustum-shaped protuberances extending from
said top surface, each of said frustum-shaped protuberances having
generally matching frustum-shaped recesses formed in said bottom
surface, said frustum-shape protuberance having a bottom base
defined by the top surface of the sheet and a top base spaced
there-from, the frustum having at least three faces extending
between the top base and bottom base, wherein said faces intersect
the bottom base at a 45.degree. to 60.degree. angle, said top base
further comprising a passageway defined there-through; wherein said
first filter plate and said second filter plate are configured to
stack together in a nesting configuration with the frustum-shaped
protuberances of the first filter plate being received into the
frustum-shaped recesses of said second filter plate; wherein said
first filter plate can be rotated so that said first filter plate
and said second filter plate are configured to stack together in a
vertically spaced configuration wherein said first filter plate's
top bases contact said second filter plate's bottom surface thereby
spacing said first filter plate apart from said second filter plate
.
[0046] While there is shown and described the present preferred
embodiment of the invention, it is to be distinctly understood that
this invention is not limited thereto but may be variously embodied
to practice within the scope of the following claims. From the
foregoing description, it will be apparent that various changes may
be made without departing from the spirit and scope of the
invention as defined by the following claims.
[0047] The purpose of the Abstract is to enable the public, and
especially the scientists, engineers, and practitioners in the art
who are not familiar with patent or legal terms or phraseology, to
determine quickly from a cursory inspection, the nature and essence
of the technical disclosure of the application. The Abstract is
neither intended to define the invention of the application, which
is measured by the claims, nor is it intended to be limiting as to
the scope of the invention in any way.
[0048] Still other features and advantages of the claimed invention
will become readily apparent to those skilled in this art from the
following detailed description describing preferred embodiments of
the invention, simply by way of illustration of the best mode
contemplated by carrying out my invention. As will be realized, the
invention is capable of modification in various obvious respects
all without departing from the invention. Accordingly, the drawings
and description of the preferred embodiments are to be regarded as
illustrative in nature, and not as restrictive in nature.
* * * * *