U.S. patent application number 13/459874 was filed with the patent office on 2013-10-31 for fan blade.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is Scott Roger FINN, Prakash Kashiram JADHAV, Nicholas Joseph KRAY, Dong-Jin SHIM, Vikash Kumar SINHA, Li ZHENG. Invention is credited to Scott Roger FINN, Prakash Kashiram JADHAV, Nicholas Joseph KRAY, Dong-Jin SHIM, Vikash Kumar SINHA, Li ZHENG.
Application Number | 20130287588 13/459874 |
Document ID | / |
Family ID | 49477454 |
Filed Date | 2013-10-31 |
United States Patent
Application |
20130287588 |
Kind Code |
A1 |
SHIM; Dong-Jin ; et
al. |
October 31, 2013 |
FAN BLADE
Abstract
A fan blade for a turbine system includes a root portion
connectable to a rotating member of a turbine system and airfoil
portion having a morphable portion on an edge of the airfoil
portion. The morphable portion includes a plurality of layers
aligned unsymmetrically relative to each other in a thickness
direction and changes in shape in response to a change in a speed
of the airfoil portion.
Inventors: |
SHIM; Dong-Jin; (Cohoes,
NY) ; FINN; Scott Roger; (Niskayuna, NY) ;
KRAY; Nicholas Joseph; (Mason, OH) ; SINHA; Vikash
Kumar; (Hyderabad, IN) ; JADHAV; Prakash
Kashiram; (Bangalore, IN) ; ZHENG; Li; (Troy,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SHIM; Dong-Jin
FINN; Scott Roger
KRAY; Nicholas Joseph
SINHA; Vikash Kumar
JADHAV; Prakash Kashiram
ZHENG; Li |
Cohoes
Niskayuna
Mason
Hyderabad
Bangalore
Troy |
NY
NY
OH
NY |
US
US
US
IN
IN
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
49477454 |
Appl. No.: |
13/459874 |
Filed: |
April 30, 2012 |
Current U.S.
Class: |
416/240 |
Current CPC
Class: |
F04D 29/382 20130101;
F04D 29/324 20130101; F04D 29/388 20130101 |
Class at
Publication: |
416/240 |
International
Class: |
F04D 29/38 20060101
F04D029/38 |
Claims
1. A fan blade for a turbine system comprising: a root portion
connectable to a rotating member of a turbine system; an airfoil
portion having a morphable portion on an edge of said airfoil
portion and a non-morphable remainder of said airfoil portion, said
morphable portion comprising a plurality of layers aligned
unsymmetrically relative to each other in a thickness direction,
said morphable portion changing shape in response to a change in a
rotational speed of said airfoil portion.
2. The blade of claim 1 wherein said edge comprises at least one of
a leading edge and a trailing edge of said airfoil portion.
3. The blade of claim 1 wherein said morphable portion is less
rigid than said remainder of said airfoil portion.
4. The blade of claim 1 wherein said morphable portion comprises a
different material relative to said remainder of said airfoil
portion.
5. The blade of claim 1 wherein said morphable portion comprises a
material of a different density relative to said remainder of said
airfoil portion.
6. The blade of claim 1 wherein said plurality of layers is aligned
unsymmetrically relative to a center line in the thickness
direction of at least one of said morphable portion and said
remainder of said air foil portion.
7. The blade of claim 1 wherein said plurality of layers comprises
a plurality of morphable portion layers of materials arranged
differently relative to a plurality of remainder layers of said
remainder of said air foil portion.
8. The blade of claim 7 wherein a first morphable portion layer of
said plurality of morphable portion layers and a first remainder
layer of said plurality of remainder layers are longitudinally
aligned at different angles relative to each other.
9. The blade of claim 1 wherein said morphable portion and said
remainder of said airfoil portion comprise unsymmetrical
laminations relative to each other.
10. The blade of claim 1 wherein a first layer of said plurality of
layers comprises a different material relative to a second layer of
said plurality of layers.
11. The blade of claim 1 wherein a first layer of said plurality of
layers comprises a different material relative to a second layer of
said remainder.
12. The blade of claim 1 wherein the change in rotational speed
comprises an increase in rotational speed and the airfoil portion
is configured to change shape from a more curved C-shape to a less
curved C-shape in response to the increased rotational speed.
13. A method for use in operating a turbine; rotating a rotor
connected to a plurality of fan blades; and changing a speed of the
rotor to cause a change in a shape of a morphable portion on an
edge of an airfoil portion of a first fan blade of the plurality of
fan blades wherein the morphable portion is formed by a plurality
of layers aligned unsymmetrically relative to each other in a
thickness direction.
14. The method of claim 13 wherein the edge comprises at least one
of a leading edge and trailing edge of the airfoil portion.
15. The method of claim 13 wherein the morphable portion comprises
a different material relative to a remainder of the airfoil
portion.
16. The method of claim 13 wherein the plurality of layers is
aligned unsymmetrically relative to a center line in a thickness
direction of at least one of the morphable portion and a remainder
of the air foil portion.
17. The method of claim 13 wherein a first morphable portion layer
of the plurality of morphable portion layers and a first remainder
layer of the plurality of remainder layers are longitudinally
aligned at different angles relative to each other.
18. The blade of claim 13 wherein the change in shape of the
morphable portion comprises a change in shape from a more curved
C-shape to a less curved C-shape in response to the change in speed
being an increase in the speed.
19. A fan blade for a turbine system comprising: a root portion
connectable to a rotating member of a turbine system; an airfoil
portion having a shape changing portion on an edge of said airfoil
portion and a remainder, said shape changing portion comprising a
different weight distribution relative to said remainder, said
shape changing portion changing shape in response to a change in a
rotational speed of said airfoil portion.
20. The blade of claim 19 wherein said edge comprises at least one
of a leading edge and a trailing edge of said airfoil portion.
21. The blade of claim 19 wherein said shape changing portion is
less rigid than said remainder of said airfoil portion.
22. The blade of claim 19 wherein said shape changing portion
comprises a material of a different density relative to a second
material of said remainder of said airfoil portion.
Description
BACKGROUND
[0001] This disclosure relates, in general, to gas turbine engines
and in particular to fan blades for turbines of such turbine
engines.
[0002] At least one known gas turbine engine assembly includes a
fan assembly that is mounted upstream from a core gas turbine
engine. During operation, airflow discharged from the fan assembly
is channeled downstream to the core gas turbine engine where the
airflow is further compressed. The compressed airflow is then
channeled into a combustor, mixed with fuel, and ignited to
generate hot combustion gases. The combustion gases are then
channeled to a turbine which extracts energy from the combustion
gases for powering the compressor, as well as producing useful work
to propel an aircraft in flight.
[0003] The referenced fan blade assemblies may include fan blades
having root portions which are connected to a rotor such that the
rotor rotates in response to gases being directed toward the fan
blades. In typical currently used fan blades, an airfoil shape of a
fan blade is designed to yield optimum performance at a single
operating or flight cycle point, which may be highly inefficient at
other design points of importance. For example, such a blade design
may be more efficient at one rotating speed relative to
another.
[0004] There are also examples of prior fan blades including those
that have mid chord regions that change in shape from a C-shaped
cross-section to an S-shaped cross-section by an unsymmetric
arrangement of fibers subjected to in-plane loads during operation.
Such blades are constructed to bend at the mid-chord region of the
blade to move from the C-shape to the S-shape.
[0005] There is a continuing need for blades which provide for more
efficient operation of a turbine system of which they are a
part.
SUMMARY
[0006] The present system provides, in one aspect, a fan blade for
a turbine system which includes a root portion connectable to a
rotating member of a turbine system and airfoil portion having a
morphable portion on an edge of the airfoil portion. The morphable
portion includes a plurality of layers aligned unsymmetrically
relative to each other in a thickness direction and changes in
shape in response to a change in a speed of the airfoil
portion.
[0007] The present technique provides, in a second aspect, a method
for use in operating a turbine including rotating a rotor connected
to a plurality of fan blades and changing a speed of the rotor to
cause a change in a shape of a morphable portion on an edge of an
airfoil of a first fan blade of the plurality of fan blades. The
morphable portion is formed by a plurality of layers aligned
unsymmetrically relative to each other in a thickness
direction.
[0008] The present system provides, in a third aspect, a fan blade
for a turbine system which includes a root portion connectable to a
rotating member of a turbine system. An airfoil portion has a shape
changing portion on an edge of the airfoil portion and a remainder.
The shape changing portion includes a different weight distribution
relative to the remainder. The shape changing portion changes shape
in response to a change in a rotational speed of the airfoil
portion.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
features, and advantages of the invention will be readily
understood from the following detailed description of preferred
embodiments taken in conjunction with the accompanying drawings in
which:
[0010] FIG. 1 is a schematic illustration of a gas turbine engine
assembly in accordance with one embodiment;
[0011] FIG. 2 is a left side elevational view of a fan blade of the
system according to one embodiment of the system;
[0012] FIG. 3 is a right side elevational view of the fan blade of
FIG. 2;
[0013] FIG. 4 is a left side perspective view of the fan blade of
FIG. 2;
[0014] FIG. 5 is a right side perspective view of the fan blade of
FIG. 2;
[0015] FIG. 6 is a front end perspective view of the fan blade of
FIG. 2;
[0016] FIG. 7 is a front end perspective view of the fan blade of
FIG. 2;
[0017] FIG. 8 is a cross-sectional view of a tip of the fan blade
of FIG. 2; and
[0018] FIG. 9 is a close-up view of a trailing edge of the fan
blade of FIG. 3;
[0019] FIG. 10 is a side cross-sectional view of a morphable
portion of the fan blade of FIG. 2;
[0020] FIG. 11 is a side cross-sectional view of a non-morphable
portion of the fan blade of FIG. 2;
[0021] FIG. 12 is a left side perspective view of another
embodiment of a fan blade according to the present invention;
[0022] FIG. 13 is a left side perspective view of another
embodiment of a fan blade according to the present invention;
[0023] FIG. 14 is a left side perspective view of another
embodiment of a fan blade according to the present invention;
[0024] FIG. 15 is a left side perspective view of another
embodiment of a fan blade according to the present invention;
[0025] FIG. 16 is a left side perspective view of another
embodiment of a fan blade according to the present invention;
[0026] FIG. 17 is a left side perspective view of another
embodiment of a fan blade according to the present invention;
and
[0027] FIG. 18 is a cross-sectional view of another embodiment of a
tip of a fan blade in accordance with the present invention.
DETAILED DESCRIPTION
[0028] In accordance with the principles of the present system and
techniques, turbine blade systems for use in gas turbine engines
for aircraft engines are provided.
[0029] FIG. 1 is a schematic illustration of an exemplary gas
turbine engine assembly 10 having a longitudinal axis 11. Gas
turbine engine assembly 10 includes a fan assembly 12 and a core
gas turbine engine 13. Core gas turbine engine 13 includes a high
pressure compressor 14, a combustor 16, and a high pressure turbine
30. In the exemplary embodiment, gas turbine engine assembly 10
also includes a low pressure turbine 131, and a multi-stage booster
compressor 22.
[0030] Fan assembly 12 includes a plurality of fan blades 24
extending radially outward from a rotor disk 26. Gas turbine engine
assembly 10 has an intake side 28 and an exhaust side 18. Fan
assembly 12, booster 22, and turbine 131 are coupled together by a
first rotor shaft 31, and compressor 14 and turbine 30 are coupled
together by a second rotor shaft 32. In operation, air flows
through fan assembly 12 and a first portion of the airflow is
channeled through booster 22. The compressed air that is discharged
from booster 22 is channeled through compressor 14 wherein the
airflow is further compressed and delivered to combustor 16. Hot
products of combustion (not shown in FIG. 1) from combustor 16 are
utilized to drive turbines 30 and 131, and turbine 131 is utilized
to drive fan assembly 12 and booster 22 by way of shaft 31.
[0031] A first blade 140 of plurality of fan blades 24 is depicted
in FIGS. 2-9 with a leading edge 150 and a trailing edge 160.
Leading edge 150 is at a frontmost portion of the blade as it
rotates while trailing edge 160 is at a rearmost point, as will be
understood by one of ordinary skill in the art. Blade 140 may also
include a root portion 170 and an airfoil portion 180 as depicted
in FIGS. 2-7. Root portion 170 may be configured (e.g., shaped and
dimensioned) to be received in a cavity of rotor disk 26 to allow a
connection of the blade to the rotor. A mid-chord region 181 may be
located about midway between root portion 170 and an outer edge 101
as depicted in FIGS. 2-7. Although only blade 140 is described in
detail herein the remaining blades may be similar or identical to
blade 140 and blade 140 is described in detail only for ease of
explanation.
[0032] Blade 140 in one embodiment is a composite fan blade
constructed as a solid, hollow internal cavity or filled internal
cavity with a low density material. In one example blade 140
includes a morphable portion 100, located on the trailing edge of
airfoil portion 180 at or near outer edge 101, which is configured
to change in shape based on the speed the blade is moving during
operation and thus the surface pressure applied by its immediate
environment (e.g., gases in the area of fan assembly 12) and
centrifugal forces due to the rotation. FIG. 8 depicts one example
of a change in shape of morphable portion 100 wherein the dotted
line shows a first shape while the solid line shows a second shape
thereof due to increased rotational speed /or increased air or gas
surface pressure against blade 140. FIG. 9 is a close-up view of
the trailing edge of the fan blade in FIG. 8 which shows a change
in shape according to an angle .theta..
[0033] The change of the shape of morphable portion 100 relative to
remainder 110 allows for the airfoil shape to be optimized at two
or more operating cycle points thereby increasing the aerodynamic
efficiency of the fan (i.e., plurality of fan blades 20 connected
to rotor disk 26), which in turn lowers the specific fuel
consumption of the gas turbine engine. For example, morphable
portion 100 may have a first shape at a low or cruising speed
(e.g., 2291 rpm) and a changed shape at a higher speed present
(e.g., 2655 rpm at maximum takeoff conditions). For example, in a
chordwise cross-section, an initial shape may be singly curved with
a relatively high curvature while the morphed shape is singly
curved with a relatively low curvature.
[0034] Laminated structures using composite materials may be used
to construct fan blades (e.g., blade 140) exhibiting various
coupling behaviors such as bending and twisting deflections in the
direction perpendicular to the loading in the presence of in-plane
and bending loads. Such coupling properties of laminated composite
structures may be used to change an airfoil shape (e.g., of blade
140). By tailoring the ply layup in the composite structure both in
terms of unsymmetric and/or multi-material ply orientations and the
region where these ply orientations occur, the airfoil shape can be
morphed (e.g., morphable portion 100) as a function of a
centrifugal force which is a function of the rotational speed of
the fan blade (e.g., of blade 140). The centrifugal force provides
an in-plane load that may cause a fan blade with a coupling
behavior to change its shape. Also, the bending load induced by the
centrifugal force (or in-plane load) when the fan blade (e.g.,
blade 140) rotates takes on a significant role in morphing the
airfoil. Therefore, the initial shape of the airfoil in the
spanwise direction prior to changing its shape may be optimized in
addition to the unsymmetric ply layup.
[0035] Further, the airfoil shape change (e.g., change in shape of
blade 140) can be achieved by tailoring the ply layup in the
composite fan blade (e.g., in morphable portion 100) laminated
structure through one or a combination of the following methods: 1)
unsymmetric ply layup through a thickness of a laminated structure,
2) a ply layup using two or more distinct materials, i.e.,
multi-material laminated structure, and 3) intentionally changing
the weight distribution at various locations of the fan blade. A
region or regions of the fan blade or the entire fan blade may be
designed in this manner to achieve a desired airfoil shape
change.
[0036] Blade 140 may be formed by the application/or lamination of
a plurality of continuous, unidirectional fiber reinforced matrix
material layers. The orientation of each layer or ply is typically
defined as the direction of the continuous, unidirectional fibers.
For example, blade 140 may be formed of carbon fibers, glass
fibers, boron fibers, or a combination of these materials.
[0037] Morphable portion 100 may be formed of a plurality of layers
whose ply orientations are unsymmetrical through the thickness of
the blade while the remainder 110 of blade 140, e.g., all of blade
140 except morphable portion 100, may be formed of a plurality of
layers whose ply orientations are symmetrical through the thickness
of the blade. Such symmetry and unsymmetry through the thickness of
the blade may be about an imaginary center line of the thickness of
the blade such that an equal distribution of material of the blade
is present between such center line and the corresponding outer
surface of the blade in the case of a symmetric arrangement. In
contrast, in the case of an unsymmetric arrangement, a different
amount of material may be present between such a center line and
the corresponding outer surface of the blade on one side of such
center line. Thus, the layers of morphable portion 100 in a
thickness direction may be arranged differently (e.g., layer(s) of
the morphable portion may be longitudinally aligned at an angle
relative to each other). Further, the individual layers of
morphable portion 100 and remainder 110 could be formed of a same
material or the different layers could be formed of a mix of the
same and/or different materials in the thickness direction.
[0038] In one example depicted in FIG. 10, morphable portion 100
may be unsymmetrical and may include a first layer 200, a second
layer 210, a third layer 220, a fourth layer 230, a fifth layer
240, a sixth layer 250, a seventh layer 260, and an eighth layer
270 in a thickness direction. The layers may be aligned at various
angles relative to each other. For example, first layer 200 and
sixth layer 250 may both have their fibers longitudinally aligned
at 0.degree. relative to each other while third layer 220 and
seventh layer 260 may be longitudinally aligned at 0.degree.
relative to each other. These aligned pairs of layers may further
be longitudinally aligned with each other and/or the other layers,
or the pairs of layers may be misaligned relative to such other
layers or pairs of layers. The remaining layers (i.e., 210, 230,
240 and 270) may be aligned relative to each other at a 0 degree
angle or may be aligned at various angles relative to each other
and the layers described above. The total of these layers of
morphable portion 100 taken together are arranged to allow the
morphing of morphable portion 100 as described above.
[0039] In contrast to the unsymmetrical alignment of layers in FIG.
10, FIG. 11 depicts a symmetrical lay up or alignment of layers of
remainder 110. In particular, remainder 110 may include a first
layer 280, a second layer 290, a third layer 300, a fourth layer
310, a fifth layer 320, a sixth layer 330, a seventh layer 340, and
an eighth layer 350 in a thickness direction. An imaginary center
line may be present between third layer 310 and fourth layer 320.
The layers of remainder 110 may have its fibers longitudinally
aligned symmetrically to one another about the center line. For
example, first layer 280 may be aligned at 0 degrees relative to
eighth layer 350, second layer 290 may be aligned at 0 degrees
relative to seventh layer 340, third layer 300 may be aligned at 0
degrees relative to sixth layer 310. Fourth layer 310 may be
aligned at 0 degrees relative to fifth layer 320. These pairs of
layers may also be aligned or misaligned relative to each
other.
[0040] Further, adjacent layers of morphable portion 100 and
remainder 110 could abut one another and could have longitudinal
fibers aligned relative to each other or such adjacent portions
could be misaligned relative to each other. Such alignment and/or
misalignment could be present through the thickness of the layers
of the morphable portion and remainder abutting each other.
[0041] Further, the layers of morphable portion 100 and remainder
110 could be aligned in any number of ways to allow morphable
portion 100 to change its shape based on the centrifugal force
applied thereto due to the rotation thereof and surface pressure
thereto (e.g., pressure due to the gas surrounding portion 100).
Also, morphable portion 100 and/or remainder 110 could have various
layers aligned or misaligned relative to one another within such
morphable portion and/or remainder 110 to provide a change in shape
or resistance to such a change as desired. Moreover, the layers of
morphable portion 100 and remainder 110 could have varying
thicknesses to provide such a desired change in shape. Also, the
ratio of the surface area and/or volume of morphable portion 100
and remainder 110 may also be controlled to provide a desired
performance of blade 140 in response to a rotating speed thereof
and surface pressure thereto.
[0042] The initial shape of an airfoil (e.g., airfoil portion 180)
prior to changing shape may be optimized such that the bending
loads (or moments) are favorable to induce morphing of a fan blade
(e.g., blade 140). Unsymmetric ply layups including multi-material
systems and varying weight distributions may be optimized such that
in-plane load from centrifugal forces due to blade (e.g., blade
140) rotation and the induced bending moments drive the initial
airfoil shape (e.g., blade 140 thereof) to change. In a chordwise
cross-section, an initial shape of a blade (e.g., blade 140) may be
singly curved with a relatively high curvature while the morphed
shape is singly curved with a relatively low curvature.
[0043] Further, as described, blade 140 may change shape from a
more curved C-shape to a less curved C-shape in response to an
increased rotational speed. The shape change occurs in trailing
edge region of the blade or in both the leading and trailing edge
regions of the blade and not at the mid-chord region of the blade.
An example of such a trailing edge is depicted in FIG. 8 while an
example of a shape change in a leading and trailing edge is
depicted in FIG. 18.
[0044] It would be understood by one of ordinary skill in the art
that a fan blade (e.g., fan blade 140 and any of fan blades 24)
could include a morphable portion (e.g., morphable portion 100) at
various locations including the leading and trailing edges of the
blades at various radial locations relative to a root connectable
to a rotor of a fan assembly, (e.g., fan assembly 12). FIGS. 15-17
depict blades 500, 510 and 520 with morphable portions of various
sizes. For example, a first morphable portion 505 may be of a first
size while a third morphable portion 515 may be at an outer extent
of the size of such a morphable portion while a second morphable
portion 507 may be larger than first morphable portion 505 and
smaller than third morphable portion 515. In order to induce a
change in shape from a more curved C-shape to a less curved C-shape
in the trailing edge region, the morphable portion(s) may extend
from an outer edge (e.g., outer edge 101) in the chord direction
toward, but not reaching, a mid chord region along a trailing edge
(e.g., trailing edge 160) or a leading edge (e.g., leading edge
150) of a fan blade (e.g., blade 140), for example. In the span
direction, the morphable portion(s) may extend from the outer blade
tip edge toward, but not reaching the mid span region. In a further
example, morphable portion 505 could be 3 inches by 8 inches,
morphable portion 507 could be 7 inches by 17 inches, and morphable
portion 515 could be 12 inches by 18 inches.
[0045] In another example, a fan blade may be formed of materials
having different densities or rigidities to provide a desired
change in shape to the blade in response to the centrifugal force
(or in-plane load) when the fan blade rotates. Further, the weight
distribution of the blade could be manipulated otherwise to provide
a desired shape change and performance in operation. Such changes
in density, materials, or weight distribution could be done in
various portions (e.g., shape changing portions) which could be
located at a leading edge, trailing edge or at other locations on a
blade. Examples of blades with portions of different weigh
distributions are depicted in FIGS. 12-14. A first blade 400 may
include a weighted portion 410 on a leading edge of the blade at or
near outer edge 101 while a second blade 420 may include a weighted
portion 430 on a trailing blade edge of the blade at or near outer
edge 101. Further, a third blade 440 may include a weighted portion
450 in a mid-portion of the blade at or near outer edge 101. Such
weighted portions may be more or less dense or otherwise have
different weights relative to surrounding portions (e.g., a
remainder) of the blade of which they are a part. As described
above relative to blade 140, blades 410, 420, and 430 could change
shape in a manner depicted in FIGS. 8 and 18.
[0046] It is to be understood that the above description is
intended to be illustrative, and not restrictive. For example, the
above-described embodiments (and/or aspects thereof) may be used in
combination with each other. In addition, many modifications may be
made to adapt a particular situation or material to the teachings
of the various embodiments without departing from their scope.
While the dimensions and types of materials described herein are
intended to define the parameters of the various embodiments, they
are by no means limiting and are merely exemplary. Many other
embodiments will be apparent to those of skill in the art upon
reviewing the above description. The scope of the various
embodiments should, therefore, be determined with reference to the
appended claims, along with the full scope of equivalents to which
such claims are entitled. In the appended claims, the terms
"including" and "in which" are used as the plain-English
equivalents of the respective terms "comprising" and "wherein."
Moreover, in the following claims, the terms "first," "second," and
"third," etc. are used merely as labels, and are not intended to
impose numerical requirements on their objects. Further, the
limitations of the following claims are not written in
means-plus-function format and are not intended to be interpreted
based on 35 U.S.C. .sctn.112, sixth paragraph, unless and until
such claim limitations expressly use the phrase "means for"
followed by a statement of function void of further structure. It
is to be understood that not necessarily all such objects or
advantages described above may be achieved in accordance with any
particular embodiment. Thus, for example, those skilled in the art
will recognize that the systems and techniques described herein may
be embodied or carried out in a manner that achieves or optimizes
one advantage or group of advantages as taught herein without
necessarily achieving other objects or advantages as may be taught
or suggested herein.
[0047] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description, but is only limited by the scope of the appended
claims.
[0048] This written description uses examples to disclose the
invention, including the best mode, and also to enable any person
skilled in the art to practice the invention, including making and
using any devices or systems and performing any incorporated
methods. The patentable scope of the invention is defined by the
claims, and may include other examples that occur to those skilled
in the art. Such other examples are intended to be within the scope
of the claims if they have structural elements that do not differ
from the literal language of the claims, or if they include
equivalent structural elements with insubstantial differences from
the literal language of the claims.
* * * * *