U.S. patent application number 14/695649 was filed with the patent office on 2016-10-27 for composite seals for turbomachinery.
This patent application is currently assigned to GENERAL ELECTRIC COMPANY. The applicant listed for this patent is GENERAL ELECTRIC COMPANY. Invention is credited to Anthony MARIN, Neelesh Nandkumar SARAWATE, Edip SEVINCER, Venkat Subramanian VENKATARAMANI.
Application Number | 20160312633 14/695649 |
Document ID | / |
Family ID | 57110577 |
Filed Date | 2016-10-27 |
United States Patent
Application |
20160312633 |
Kind Code |
A1 |
SEVINCER; Edip ; et
al. |
October 27, 2016 |
COMPOSITE SEALS FOR TURBOMACHINERY
Abstract
The present application provides composite seals for reducing
leakages between adjacent components of turbomachinery. The
composite seals may include a metallic shim, a metallic support
structure and a ceramic, glass or enamel coating. The shim and the
support structure may be bonded or fused together. The support
structure may include internal voids or gaps, and the coating may
be applied to the shim and the support structure such that the
coating is provided within the voids or gaps of the support
structure, between portions of the support structure and the shim,
and substantially over the outer surface of the support structure.
The support structure may thereby provide a mechanical attachment
between the shim and the coating. In use, the coating provides
thermal and/or chemical insulation to the metallic shim and the
support structure of the seal.
Inventors: |
SEVINCER; Edip; (Watervliet,
NY) ; SARAWATE; Neelesh Nandkumar; (Niskayuna,
NY) ; MARIN; Anthony; (Saratoga Springs, NY) ;
VENKATARAMANI; Venkat Subramanian; (Clifton Park,
NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GENERAL ELECTRIC COMPANY |
Schenectady |
NY |
US |
|
|
Assignee: |
GENERAL ELECTRIC COMPANY
Schenectady
NY
|
Family ID: |
57110577 |
Appl. No.: |
14/695649 |
Filed: |
April 24, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F01D 11/003 20130101;
F05D 2300/6033 20130101; F01D 25/005 20130101; F01D 11/005
20130101; F05D 2300/6012 20130101 |
International
Class: |
F01D 11/00 20060101
F01D011/00; F01D 25/00 20060101 F01D025/00 |
Claims
1. A seal assembly for positioning within a seal slot formed at
least partially by adjacent turbomachinery components to seal a gap
extending between the components, the seal assembly comprising: a
metallic shim including a sealing surface and a support surface; a
porous metallic support structure bonded to the support surface of
the metallic shim; and a ceramic, glass or enamel coating extending
over and within the porous metallic support structure such that the
coating substantially covers the support surface side of the
metallic shim and the support structure, and wherein portions of
the coating are positioned between the support surface of the
metallic shim and portions of the metallic support structure.
2. The seal assembly of claim 1, wherein portions of the coating
are positioned between the support surface of the metallic shim and
portions of the metallic support structure in a direction extending
away from the support surface to mechanically couple the coating to
the metallic shim via the metallic support structure.
3. The seal assembly of claim 2, wherein the direction extending
away from the support surface is substantially normal to the
support surface.
4. The seal assembly of claim 1, wherein the metallic shim is a
substantially solid metallic shim.
5. The seal assembly of claim 1, wherein the coating is chemically
bonded to the support structure.
6. The seal assembly of claim 1, wherein at least one of the
support surface of the metallic shim and the metallic support
structure includes a protective outer coating configured to prevent
oxidation of the respective metallic component.
7. The seal assembly of claim 1, wherein the metallic support
structure is diffusion bonded to the metallic shim via at least one
braze.
8. The seal assembly of claim 1, wherein the metallic support
structure is a mesh structure.
9. The seal assembly of claim 1, wherein portions of the coating
are positioned between the support surface of the metallic shim and
portions of the metallic support structure that are bonded to the
support surface of the metallic shim.
10. The seal assembly of claim 1, wherein portions of the coating
are positioned between the support surface of the metallic shim and
portions of the metallic support structure that are not bonded to
the support surface of the metallic shim.
11. The seal assembly of claim 10, wherein the portions of the
metallic support structure that are not bonded to the support
surface of the metallic shim extend from or are coupled to portions
of the metallic support structure that are bonded to the support
surface of the metallic shim.
12. The seal assembly of claim 1, wherein the coating is bonded to
at least one of the support surface of the shim and the support
structure.
13. The seal assembly of claim 1, further comprising: a second
porous metallic support structure bonded to the sealing surface of
the shim; and a second ceramic, glass or enamel coating extending
over and within the second porous metallic support structure such
that the second coating substantially covers the sealing surface
side of the metallic shim and the second support structure, and
wherein portions of the second coating are positioned between the
sealing surface of the metallic shim and portions of the second
metallic support structure.
14. A method of forming a seal assembly for use within a seal slot
formed at least partially by adjacent turbomachinery components to
seal a gap extending between the components, the method comprising:
bonding at least one portion of a porous metallic support structure
to a metallic shim; applying ceramic, glass or enamel coating
material to the porous metallic support structure such that the
coating material overlies the support surface side of the metallic
shim and the support structure, and includes portions that are
positioned between the support surface of the metallic shim and
portions of the metallic support structure; and densifying the
ceramic, glass or enamel coating material to form a ceramic, glass
or enamel coating mechanically fixed to the metallic shim via the
metallic support structure.
15. The method of claim 14, wherein bonding at least one portion of
the metallic support structure to the support surface of the
metallic shim includes diffusion bonding at least one portion of
the metallic support structure to the support surface of the
metallic shim.
16. The method of claim 14, wherein applying ceramic, glass or
enamel coating material to the porous metallic support structure
comprises applying a high viscosity castable ceramic composition by
screen printing or toweling.
17. The method of claim 16, further comprising removing a portion
of the ceramic composition applied to the support structure via a
doctor blade, and wherein densifying the ceramic composition
comprises curing and heat treating the applied ceramic
composition.
18. The method of claim 14, wherein applying ceramic, glass or
enamel coating material to the porous metallic support structure
comprises applying a glass or enamel based composition in a
paintable form by painting, dip coating or spray coating.
19. The method of claim 18, wherein densifying the glass or enamel
based composition comprises drying and heat treating the applied
glass or enamel based composition.
20. A turbomachine comprising: a first turbine component and a
second turbine component adjacent the first turbine component, the
first and second turbine components forming at least a portion of a
seal slot extending across a gap between the turbine components;
and a seal positioned within the seal slot of the first and second
turbine components and extending across the gap therebetween, the
seal comprising: a metallic shim including a sealing surface and a
support surface; a porous metallic support structure bonded to the
support surface of the metallic shim; and a ceramic, glass or
enamel coating provided on and within the metallic support
structure such that the coating substantially covers the support
surface side of the metallic shim and the support structure, and
portions of the coating are positioned between the support surface
of the metallic shim and portions of the metallic support
structure.
21. The turbomachine of claim 20, wherein the ceramic, glass or
enamel coating of the seal is positioned against a first side of
the seal slot that is collectively formed by a first side of the
first turbine component and a first side of the second turbine
component.
22. The turbomachine of claim 20, wherein the metallic shim is a
substantially solid metallic shim, and the porous metallic support
structure is a metallic mesh structure.
23. The turbomachine of claim 20, wherein portions of the coating
are positioned between the support surface of the metallic shim and
portions of the metallic support structure in a direction extending
substantially normal to the support surface to mechanically couple
the coating to the metallic shim via the metallic support
structure.
Description
BACKGROUND OF THE INVENTION
[0001] The present application relates generally to seals for
reducing leakage, and more particularly to seals configured to
operate within a seal slot to reduce leakage between adjacent
stationary components of turbomachinery.
[0002] Leakage of hot combustion gases and/or cooling flows between
turbomachinery components generally causes reduced power output and
lower efficiency. For example, hot combustion gases may be
contained within a turbine by providing pressurized compressor air
around a hot gas path. Typically, leakage of high pressure cooling
flows between adjacent turbine components (such as stator shrouds,
nozzles, and diaphragms, inner shell casing components, and rotor
components) into the hot gas path leads to reduced efficiency and
requires an increase in burn temperature, and a decrease in engine
gas turbine efficiency to maintain a desired power level as
compared to an environment void of such leakage. Turbine efficiency
thus can be improved by reducing or eliminating leakage between
turbine components.
[0003] Traditionally, leakage between turbine component junctions
is treated with metallic seals positioned in the seal slots formed
between the turbine components, such as stator components. Seal
slots typically extend across the junctions between components such
that metallic seals positioned therein block or otherwise inhibit
leakage through the junctions. However, preventing leakage between
turbine component junctions with metallic slot seals positioned in
seal slots in the turbine components is complicated by the
relatively high temperatures produced in modern turbomachinery. Due
to the introduction of new materials, such as ceramic-matrix
composite (CMC) turbine components, that allow turbines to operate
at higher temperatures (e.g., over 1,500 degrees Celsius) relative
to traditional turbines, conventional metallic turbine slot seals
for use in seal slots may not be adequate.
[0004] Preventing leakage between turbine component junctions with
metallic seals is further complicated by the fact that the seal
slots of turbine components are formed by corresponding slot
portions in adjacent components (a seal positioned therein thereby
extending across a junction between components). Misalignment
between these adjacent components, such as resulting from thermal
expansion, manufacturing, assembly and/or installation limitations,
etc., produces an irregular seal slot contact surface that may vary
in configuration, shape and/or magnitude over time. Such
irregularities in the seal slot contact surface allow for leakage
across a slot seal positioned within the seal slot if the seal does
not flex, deform or otherwise account for such irregularities.
Unfortunately, many conventional metallic shims that account for
such irregular seal slot contact surfaces due to misalignment of
adjacent turbine components may not adequately withstand increases
in operating temperatures of turbines.
[0005] Accordingly, composite turbomachinery component junction
seals configured for use in typical turbine seal slots that
withstand the increasingly higher operating temperatures of
turbines and conform to irregularities in the seal slot contact
surface would be desirable.
SUMMARY OF THE INVENTION
[0006] In a first aspect, the present disclosure provides a seal
assembly for positioning within a seal slot formed at least
partially by adjacent turbomachinery components to seal a gap
extending between the components. The seal assembly includes a
metallic shim, a porous metallic support structure, and a ceramic,
glass or enamel coating. The metallic shim includes a sealing
surface and a support surface. The porous metallic support
structure is bonded to the support surface of the metallic shim.
The ceramic, glass or enamel coating extends over and within the
porous metallic support structure such that the coating
substantially covers the support surface side of the metallic shim
and the support structure. Portions of the coating are positioned
between the support surface of the metallic shim and portions of
the metallic support structure.
[0007] In some embodiments, portions of the coating may be
positioned between the support surface of the metallic shim and
portions of the metallic support structure in a direction extending
away from the support surface to mechanically couple the coating to
the metallic shim via the metallic support structure. In some such
embodiments, the direction extending away from the support surface
may be substantially normal to the support surface.
[0008] In some embodiments, the metallic shim may be a
substantially solid metallic shim. In some embodiments, the coating
may be chemically bonded to the support structure. In some
embodiments, at least one of the support surface of the metallic
shim and the metallic support structure may include a protective
outer coating configured to prevent oxidation of the respective
metallic component. In some embodiments, the metallic support
structure may be diffusion bonded to the metallic shim via at least
one braze. In some embodiments, the metallic support structure may
be a mesh structure. In some embodiments, portions of the coating
may be positioned between the support surface of the metallic shim
and portions of the metallic support structure that are bonded to
the support surface of the metallic shim.
[0009] In some embodiments, portions of the coating may be
positioned between the support surface of the metallic shim and
portions of the metallic support structure that are not bonded to
the support surface of the metallic shim. In some such embodiments,
portions of the metallic support structure that are not bonded to
the support surface of the metallic shim may extend from or are
coupled to portions of the metallic support structure that are
bonded to the support surface of the metallic shim.
[0010] In some embodiments, the coating may be bonded to at least
one of the support surface of the shim and the support structure.
In some embodiments, the seal assembly may further include a second
porous metallic support structure bonded to the sealing surface of
the shim, and a second ceramic, glass or enamel coating extending
over and within the second porous metallic support structure such
that the second coating substantially covers the sealing surface
side of the metallic shim and the second support structure, and
portions of the second coating may be positioned between the
sealing surface of the metallic shim and portions of the second
metallic support structure.
[0011] In another aspect, the present disclosure provides a method
of forming a seal assembly for use within a seal slot formed at
least partially by adjacent turbomachinery components to seal a gap
extending between the components. The method includes bonding at
least one portion of a porous metallic support structure to a
metallic shim. The method further includes applying ceramic, glass
or enamel coating material to the porous metallic support structure
such that the coating material overlies the support surface side of
the metallic shim and the support structure, and includes portions
that are positioned between the support surface of the metallic
shim and portions of the metallic support structure. The method
also includes densifying the ceramic, glass or enamel coating
material to form a ceramic, glass or enamel coating mechanically
fixed to the metallic shim via the metallic support structure.
[0012] In some embodiments, bonding at least one portion of the
metallic support structure to the support surface of the metallic
shim may include diffusion bonding at least one portion of the
metallic support structure to the support surface of the metallic
shim. In some embodiments, applying ceramic, glass or enamel
coating material to the porous metallic support structure may
comprise applying a high viscosity castable ceramic composition by
screen printing or toweling. In some such embodiments, the method
may further include removing a portion of the ceramic composition
applied to the support structure via a doctor blade, and wherein
densifying the ceramic composition comprises curing and heat
treating the applied ceramic composition. In some embodiments,
applying ceramic, glass or enamel coating material to the porous
metallic support structure may comprise applying a glass or enamel
based composition in a paintable form by painting, dip coating or
spray coating. In some such embodiments, densifying the glass or
enamel based composition may comprise drying and heat treating the
applied glass or enamel based composition.
[0013] In another aspect, the present disclosure provides a
turbomachine that includes a first turbine component and a second
turbine component adjacent the first turbine component, the first
and second turbine components forming at least a portion of a seal
slot extending across a gap between the turbine components. The
turbomachine further includes a seal positioned within the seal
slot of the first and second turbine components and extending
across the gap therebetween. The seal comprises a metallic shim, a
porous metallic support structure, and a ceramic, glass or enamel
coating. The metallic shim includes a sealing surface and a support
surface. The porous metallic support structure is bonded to the
support surface of the metallic shim. The ceramic, glass or enamel
coating is provided on and within the metallic support structure
such that the coating substantially covers the support surface side
of the metallic shim and the support structure, and portions of the
coating are positioned between the support surface of the metallic
shim and portions of the metallic support structure.
[0014] In some embodiments, the ceramic, glass or enamel coating of
the seal may be positioned against a first side of the seal slot
that is collectively formed by a first side of the first turbine
component and a first side of the second turbine component. In some
embodiments, the metallic shim is a substantially solid metallic
shim, and the porous metallic support structure is a metallic mesh
structure. In some embodiments, portions of the coating may be
positioned between the support surface of the metallic shim and
portions of the metallic support structure in a direction extending
substantially normal to the support surface to mechanically couple
the coating to the metallic shim via the metallic support
structure.
[0015] These and other objects, features and advantages of this
disclosure will become apparent from the following detailed
description of the various aspects of the disclosure taken in
conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a cross-sectional view of a portion of a first
exemplary slot seal assembly according to the present
disclosure;
[0017] FIG. 2 is a perspective view of the exemplary slot seal of
FIG. 1 partially assembled to illustrate the arrangement of the
shim, support structure and coating portions;
[0018] FIG. 3 is a perspective view of the shim and support
structure sub-assembly of the exemplary slot seal of FIG. 1;
[0019] FIG. 4 is an enlarged perspective view of a portion of the
shim and support structure sub-assembly of FIG. 3;
[0020] FIG. 5 is an enlarged cross-sectional view of a portion of
the shim and support structure sub-assembly of FIG. 4;
[0021] FIG. 6 is a side cross-sectional view of an exemplary slot
seal assembly positioned within a seal slot to seal an exemplary
junction between turbine components; and
[0022] FIG. 7 is a side cross-sectional view of an exemplary slot
seal assembly.
DETAILED DESCRIPTION
[0023] When introducing elements of various embodiments of the
present invention, the articles "a," "an," "the," and "said" are
intended to mean that there are one or more of the elements. The
terms "comprising," "including," and "having" are intended to be
inclusive and mean that there may be additional elements other than
the listed elements. Any examples of operating parameters are not
exclusive of other parameters of the disclosed embodiments.
Components, aspects, features, configurations, arrangements, uses
and the like described, illustrated or otherwise disclosed herein
with respect to any particular seal embodiment may similarly be
applied to any other seal embodiment disclosed herein.
[0024] Composite turbomachinery component junction seals configured
for use in turbine seal slots (e.g., composite turbine slot seals),
and methods of manufacturing and using same, according to the
present disclosure are configured to withstand the relatively high
operating temperatures of turbines including CMC components and/or
conform to irregularities in the seal slot contact surface. In
particular, the composite slot seals are configured to
substantially prevent chemical interaction and substantially limit
thermal interaction of metallic components of the composite slot
seals with the hot gas flow/leakage and/or the seal slot itself. In
this way, the composite slot seals provided herein allow for use in
high temperature turbine applications. In addition to high
temperature operation, the composite slot seals of the present
disclosure are configured to conform to irregularities on the seal
slot contact surface to decrease leakage due to seal slot surface
misalignment and/or roughness.
[0025] As shown in FIGS. 1-5, the exemplary seal 10 may be a seal
assembly including at least one shim or plate 12, at least one
support structure or layer 14 and at least one coating or coating
layer 16 coupled to one another. The shim 12 may be effective in
substantially preventing the passage of substances therethrough.
For example, the shim 12 may be substantially solid or otherwise
substantially impervious to at least one of gases, liquids and
solids at pressures and temperatures produced in turbo machinery.
However, the shim 12 may also provide flexibility at pressures and
temperatures produced in turbomachinery to accommodate skews or
offsets in slot surfaces in the thickness T1 direction. In one
embodiment, the shim 12 is a substantially solid plate-like
metallic member. In some such embodiments the shim 12 may be a high
temperature metallic alloy or super alloy. For example, in some
embodiments the shim 12 (and/or the support structure 14) may be
made from stainless steel or a nickel based alloy (at least in
part), such as nickel molybdenum chromium alloy, Haynes 214, or
Haynes 214 with an aluminum oxide coating. In some embodiments, the
shim 12 may be made of a metal with a melting temperature of at
least 1,500 degrees Fahrenheit, and more preferably at least 1800
degrees Fahrenheit. In some embodiments, the shim 12 may be made of
a metal with a melting temperature of at least 2,200 degrees
Fahrenheit.
[0026] An exterior sealing surface or side 22 of the shim 12 that
substantially opposes the support structure 14, as shown in FIGS.
1-5, may be substantially planar (in a neutral state). As explained
further below, the exterior sealing surface 22 of the shim 12 may
be configured to engage or interact with a cooling high pressure
air flow flowing through at least one gap or joint between at least
first and second components forming a seal slot (at least in part)
so that the seal 10 is forced or pressed against sealing surfaces
of the first and second components in the seal slot to
substantially prevent gases, liquids and/or solids from migrating
through the gap or joint. As such, at least one of the shim 12 and
the coating 16 (or the shim 12 and the coating 16 acting in
concert) may be substantially impervious to liquids, gases and/or
solids at pressures experienced in turbomachinery such that the
seal 10 provides at least a low leakage rate past the seal
slot.
[0027] As shown in FIGS. 1-5 the support structure 14 may be
coupled to a support surface or side 24 of the shim 12 that
substantially opposes the sealing surface 22. In some embodiments
the support structure 14 may be metallic, such as metallic material
with the characteristics described above with respect to the shim
12. The shim 12 and the support structure 14 may be formed of the
same or substantially similar metallic material, and thereby
include the same or substantially similar coefficient of thermal
expansion (hereinafter CTE). However, the shim 12 and the support
structure 14 need not be formed of the same or substantially
similar material, or include the same or substantially the same
CTE. It is preferable, however, that the shim 12 and the support
structure 14 be configured such that any difference in CTE
therebetween does not fracture, break or otherwise render a
diffusion bond therebetween, as described further below,
ineffective due to cyclic thermal loading of the seal 10 during use
in turbomachinery. As such, the CTE of the shim 12 and the CTE of
the support structure 14 may differ only to such an extent that the
diffusion bond between the shim 12 and the support structure 14 is
not rendered ineffective by cyclic thermal loading of the seal 10
during use in turbomachinery. Stated differently, the material of
the shim 12 and the support structure 14 (or any other factor
affecting CTE) may differ, but the shim 12 and the support
structure 14 may be configured such that a diffusion bond
therebetween is not damaged or rendered ineffective when the seal
10 is subjected to cyclic thermal loading when utilized in a seal
slot of a turbine.
[0028] The support structure 14 may be a support structure, member
or assembly that is capable of chemically bonding or fusing (e.g.,
via a diffusion bond) to the support surface 24 of the shim 12, and
capable of securely mechanically coupling or affixing with the
coating 16 (which is chemically bonded to the shim 12). In this
way, the coating 16 may be securely mechanically coupled or affixed
to the shim 12 via the support structure 14. For example, the
support structure 14 may be a substantially porous metallic
structure (as opposed to the substantially non-porous shim 12) that
includes cavities or voids for holding portions of the coating 16
therein. The term "porous" is used herein, with respect to the
support structure 14, to describe a structure, member(s) or
mechanism than includes pores, channels, voids, gaps, cavities or
other interior spaces that, individually and/or collectively, allow
the coating 16 to extend into the support structure 14 from the top
or outer surface of the support structure 14 in a direction
extending towards the shim 12 and that at least some portions of
the coating 16 are positioned between the sealing surface 24 of the
shim 12 and at least a portion of the support structure 14 in a
direction extending at least generally away from the sealing
surface 24 of the shim 12, such as substantially normal to the
sealing surface 24 of the shim 12. In some embodiments, the support
structure 14 may be a porous metallic mesh, lattice, honeycomb or
woven-type structure with interlocked, interwoven or intermingled
members, fibers or portions, as shown in FIGS. 1-5.
[0029] As shown in FIGS. 1-5, at least some portions of the support
structure 14 (e.g., portions of metallic mesh members or fibers)
may be fused or bonded with the support surface 24 of the shim 12.
In some embodiments, however, other portions of the support
structure 14 may be spaced from the support surface 24 of the shim
12 (i.e., not fused or bonded to the shim 12). For example, a
metallic mesh-type support structure 14 may include metallic
members or fibers that include first portions that are fused or
bonded to the support surface 24 of the shim 12 and second portions
that are not bonded or fused to the shim 12 and, potentially,
spaced from the support surface 24 of the shim 12. In this way,
only a fraction or portion of the support structure 14 may be
bonded or fused to the shim 12, with the remaining fraction or
portion of the support structure 14 being coupled to (e.g.,
mechanically attached) or extending from the bonded or fused
portion.
[0030] The shim 12 and at least a portion of the support structure
14 may be bonded or fused to each other such that their attachment
is capable of effectively withstanding the temperature, pressure
and other conditions experienced in a seal slot of a turbine. For
example, the shim 12 and at least a portion of the support
structure 14 may be bonded or fused in such a manner that creates a
solid state chemical bond therebetween. In some embodiments, the
shim 12 and at least a portion of the support structure 14 may be
solid state welded to each other, such as via diffusion bonding. In
some embodiments, the shim 12 and the support structure 14 may be
diffusion bonded to each other by at least one high temperature
braze.
[0031] The shim 12 and/or the support structure 14 of the shim 10
may include one or more protective coating (not shown) applied or
positioned over or on an exterior surface thereof. For example, at
least a portion of the outer surface of the shim 12, such as the
sealing surface 22 or the support surface 24, and/or at least a
portion of the outer surface of the support structure 14 may
include at least one protective coating or layer. Stated
differently, at least a portion of the outer surface of the shim 12
(e.g., the support surface 24) and/or the support structure 14 may
be defined by a protective coating overlying the underlying
metallic component (i.e., the metallic shim 12 or the metallic
support structure 14). As such, the portion or portions of the shim
12 and/or the support structure 14 which are diffusion bonded to
each other may include the protective coating or layer. For example
the support structure 14 may be bonded to protective coating
overlying on the shim 12 and forming the support surface 24. The
protective coating(s) of the metallic shim 12 and/or the metallic
support structure 14 may be configured to substantially prevent or
retard oxidation of the underlying metallic component. In some
embodiments, the protective coating(s) of the metallic shim 12
and/or the metallic support structure 14 may include or
substantially comprise an oxide, such as chromium oxide or alumina
oxide.
[0032] With the shim 12 and at least a portion of the support
structure 14 bonded or fused to each other, the at least one
coating 16 may be applied to the seal 10 to protect the shim 12 and
support structure 14. As shown in FIGS. 1 and 2, the coating 16 may
be applied to the seal 10 such that the coating 16 substantially
covers or overlies at least the support structure 14 and the
support surface 24 of the shim 12 (i.e., the coating extends over
and into the support structure 14 of the seal 10 and thereby over
the support surface 24 of the shim 12). The coating 16 may
substantially fill the pores or voids of the support structure 14,
and may be substantially non-porous (as opposed to the support
structure 14). In some embodiments, the coating 16 may also cover
or overlie the support surface 24 side and the side edges of the
seal 10 such that the sealing surface 22 side of the seal 10 is the
only side or edge of the seal 10 not covered by, or contains, the
coating 16.
[0033] The coating 16 may be one or more coating material that
is/are effective in substantially preventing chemical interaction
and substantially limiting thermal interaction of at least the
metallic shim 12 (and, potentially, the support structure 14) when
the seal 10 is utilized in a seal slot of a turbine, such as a seal
slot formed by components of a high temperature gas turbine, such
as stator components. As explained further below, the coating 16 on
the support structure 14 may be configured to sealingly engage
first and second sealing surfaces of first and second components
that form a seal slot to substantially prevent gases, liquids
and/or solids from migrating through a gap or joint between the
first and second components. In this way, the coating 16 may be
effective in substantially preventing silicide formation,
oxidation, thermal creep and/or wear of at least the metallic shim
12 (and, potentially, the support structure 14) during use of the
seal 10 in such a seal slot of a turbine. Stated differently, the
coating 16 allows for metallic-based seals, such as the seal 10
with the one or more metallic shim 12 (and, potentially, the
support structure 14), to be utilized in high temperature gas
turbine applications. In some embodiments, the coating 16 may be a
ceramic, glass or enamel material that is effective in protecting
(e.g., preventing or reducing oxidation, silicide formation,
thermal creep, wear, etc.) at least the metallic shim 12 and/or the
support structure 14.
[0034] In some embodiments, the coating 16 may be formed of a
crystalline, glassy or glass ceramic composite. In some such
embodiments, the coating 16 may include metal oxides, nitrides or
oxynitrides. For example, the coating 16 may include stabilized or
unstabilized zirconia, alumina, titania, alkaline earth and/or rare
earth zirconates, titanates, aluminates, tantalates and niobates,
tungstates, molybdates, silicates borates, phosphates, silicon
nitride, silicon carbide, intermetallic compounds such as MAX phase
materials (Ti2AlC) and combinations thereof. In some embodiments,
the coating 16 may be formed of a high temperature porceain enamel
composition. For example, the coating 16 may include alkali/alkali
earth alumino boro phosphor silicate glasses and fillers. The
coating 16 (whether a ceramic, glass or enamel material) may
include the required high temperature melt and flow properties to
provide optimum stability and compliance at the operating
conditions of the seal 10.
[0035] In some embodiments, the coating 16 (and/or the protective
coating described herein) may be formed on the metallic shim 12
(and/or the metallic support structure 14) by, at least in part,
the diffusion of selected species into, and/or reaction with, the
metallic shim 12 (and/or the metallic support structure 14) to form
metal silicide(s) and/or at least one oxide layer on the metallic
shim 12 (and/or the metallic support structure 14). The metal
silicide(s) formed by the diffusion/reaction of the selected
species and the metallic shim 12 (and/or the metallic support
structure 14) may be resistant to oxidation. The one or more oxide
layer formed by the diffusion/reaction of the selected species and
the metallic shim 12 (and/or the metallic support structure 14) may
include negligible oxygen diffusion capacity therethrough, thus
protecting the metallic shim 12 (and/or the metallic support
structure 14). For example, Si may be utilized and diffused into,
and/or reacted with, the metallic shim 12 (and/or the metallic
support structure 14). In some embodiments, the selected species
for forming the metal silicide(s) and/or the at least one oxide
layer may include Al, Si, B, alloys thereof, or combinations
thereof. In some embodiments, the metallic shim 12 (and/or the
metallic support structure 14) may be formed of or include a
refractory metal, such as Mo, W, alloys thereof, or combinations
thereof, and the refractory metal shim 12 (and/or support structure
14) may include a silicide layer and/or an alumina protective layer
as at least a portion of the coating 16. In some embodiments, the
metal silicide(s) and/or the at least one oxide layer may be formed
by reaction with a packed bed of the selected species (e.g., in a
powder or like form) and the metallic shim 12 (and/or the metallic
support structure 14) at high temperatures (i.e., a pack
siliciding/oxide layer method). In other embodiments, the metal
silicide(s) and/or the at least one oxide layer on the metallic
shim 12 (and/or the metallic support structure 14) may be formed
through one or more coating of the selected species (e.g., metallic
elements/alloys) through vapor phase deposition (e.g., chemical
vapor deposition (CVD) or physical vapor deposition (PVD)),
followed by chemical and/or heat treatment.
[0036] In some ceramic coating 16 embodiments, the ceramic coating
16 may be formed from a high viscosity castable composition, such
as a castable cement (e.g., COTRONICS 904 or 989). The high
viscosity castable composition may be applied on the bonded shim 12
and the support structure 14 by screen printing or toweling. After
the castable composition of the coating 16 is applied to the bonded
shim 12 and the support structure 14, excess coating 16 material
may be removed by doctor blading to a desired or required thickness
on the seal 10 (e.g., a particular amount of coating castable
composition on the top or above the outer surface of the support
structure 14). The applied and bladed "green" coating may be
further processed to densify and chemically bond to the coating 16
material to the bonded shim 12 and the support structure 14 by
curing and heat treating. The curing may set the coating 16
material, and the heat treating may densify the coating 16 material
to a closed porosity state to, ultimately, form the coating 16 on
the bonded shim 12 and the support structure 14. As noted above,
the coating 14 may be bonded to the metallic shim 12 itself or to a
protective coating overlying the metallic shim 12.
[0037] In some glass or enamel coating 16 embodiments, the coating
16 may be formed from glass or enamel based compositions in a
paintable form. The paintable form glass or enamel based
compositions may include a relatively low viscosity that allows the
glass or enamel based compositions to be painted on the bonded shim
12 and the support structure 14, or the bonded shim 12 and the
support structure 14 may be dip or spray coated with the glass or
enamel based compositions. In some embodiments, the glass or enamel
based compositions may include a solvent or the like to decrease
the viscosity of the compositions. After the glass or enamel based
compositions are applied to the bonded shim 12 and the support
structure 14, the compositions may be dried, such as to remove
solvents from the applied compositions. After drying of the applied
glass or enamel based compositions on the bonded shim 12 and the
support structure 14, the compositions may be heat treated to form
a coating 16 of a substantially dense, smooth, glassy coating that
is chemically bonded and mechanically coupled to the shim 12 and
the support structure 14.
[0038] In some alternative embodiments, the coating 16 composition
may be formulated as precursor. For example, the coating 16
composition be formed of a gellable sol from precursor slats such
as nitrates, carboxylates, alkoxides with a certain fraction added
as fillers. The gellable sol may be applied to bonded shim 12 and
the support structure 14 to form the coating 16 by any of the
aforementioned processes.
[0039] As discussed above, the coating 16 (whether it be ceramic,
glass or an enamel) may be applied to the metallic shim 12 and the
metallic support structure 14 such that the coating 16 is, at least
initially, chemically bonded or coupled directly to the metallic
shim 12 (e.g., over or on the support surface 24 of the metallic
shim 12) and/or the metallic support structure 14. As also noted
above, the metallic shim 12 and/or metallic support structure 14
may include a protective coating. In some such embodiments, the
coating 16 may be chemically bonded to the protective coating
(thereby indirectly chemically bonded to the metallic shim 12
and/or metallic support structure 14).
[0040] The coating 16 may substantially fill voids of the support
structure 14 (including any or spaces between the support structure
14 and the shim 12, as explained further below) and extend over the
top or outer surface of the support structure 14 (to thereby cover
the support surface 22 of the shim 12). As explained further below,
the support structure 14 may be chemically bonded to the shim 12
and configured to mechanically couple with the coating 16. In this
way, the coating 16, which is effective in thermally and chemically
insulating the metallic shim 12, may be at least initially both
chemically bonded and mechanically fixed to the metallic shim 12
and the metallic support structure 14.
[0041] In order for the coating 16 to continuously or reliably
provide protection to at least the metallic shim 12 (and,
potentially, the metallic support structure 14), the support
structure 14 may be effective in maintaining the attachment or
coverage of the coating 16 over the metallic shim 12--such as
sides, edges or portions of at least the metallic shim 12 that may
be exposed to during use of the seal 10 in a seal slot of a
turbine. For example, the chemical bond or coupling between a
ceramic or glass coating 16 and the metallic shim 12 and metallic
support structure 14 (or a protective coating thereon) may not
withstand the thermal cycling of the shim 12 (occurring during use
of the shim 12, for example) due to the thermal mismatch between
the ceramic or glass coating 16 and the metallic shim 12 and
metallic support structure 14. As shown in FIGS. 1 and 2 and
explained above, the metallic support structure 14 may be bonded or
fused to the metallic shim 12 and the coating 14 may be provided at
least throughout or within voids of the support structure 14. More
specifically, however, the coating 14 may also extend or be
positioned, at least partially, between the shim 12 and portions of
the support structure 14 in a direction extending at least
generally away from the sealing surface 22 of the shim 12. In some
embodiments, the coating 14 may be positioned, at least partially,
between the shim 12 and the individual members, fibers or portions
of the support structure 14 (or portions thereof) in a direction
extending substantially normal to the support surface 24 of the
shim 12. The coating 14 thereby may be provided or extend
substantially about fibers, members or portions of the support
structure 14 (but for the portions thereof that are fused or bonded
to the shim 12). In this way, because at least some of the fibers,
members or portions of the support structure 14 are bonded or fused
to the metallic shim 12 and portions of the coating 14 are
positioned between the shim 12 and portions of the support
structure 14, the support structure 14 provides a mechanical
attachment of the coating 14 to the metallic shim 12 that prevents
the coating 14 from detaching or decoupling from the shim 12. For
example, if the chemical bond between the coating 16 and the
metallic shim 12 and/or the metallic support structure 14 (or a
protective coating thereon) fails due to thermal mismatch
therebetween, the positioning of the coating 16 substantially about
the fibers, members or portions of the support structure 14 (e.g.,
over the outer surface of the support surface 24 and between
portions of the support surface 24 and the shim 12) provides a
mechanical attachment that prevents the coating 16 from becoming
detached or decoupled from the metallic shim 12 (via the metallic
support structure 14).
[0042] As noted above, portions of the coating 14 may be positioned
between the metallic shim 12 and portions of the support structure
14 that are spaced from the metallic shim 12 (e.g., portions that
are not bonded or fused to the metallic shim 12, but rather extend
from, or are coupled to, portions that are that are bonded or fused
to the metallic shim 12). Portions of the coating 14 may also be
positioned between the metallic shim 12 and portions of the support
structure 14 that are bonded or fused to the metallic shim 12. As
shown in FIGS. 1 and 5, for example, the fibers, members or
portions of the support structure 14 that are bonded or fused to
the metallic shim 12 may include or define a shape that provides or
forms a space or void 26 between the fibers, members or portions of
the support structure 14 and the support surface 24 of the shim 12.
In the exemplary illustrated embodiment in FIGS. 1, 4 and 5, the
fibers, members or portions of the support structure 14 that are
bonded or fused to the support surface 24 of the shim 12 are
substantially circular in cross-section such that a space or void
26 is formed between the respective fibers, members or portions of
the support structure 14 and the support surface 24 of the shim 12.
Other configurations of the support structure 14 that form such a
space or void 26 between the support surface or side 24 of the shim
12 and the support structure 14 (when bonded) may be utilized. In
this way, the shape or configuration of the fibers, members or
portions of the support structure 14 may allow the coating 14 to be
positioned between bonded portions of the support structure 14 and
the sealing surface or side 24 of the shim 12 (e.g., in a direction
extending generally away from, or substantially normal to, the
sealing surface 24).
[0043] FIG. 6 illustrates a cross-sectional view of an exemplary
slot seal assembly 110 positioned within an exemplary seal slot to
seal an exemplary junction between turbine components, such as
stator components. The exemplary slot seal assembly 110 is
substantially similar to the exemplary slot seal assembly 10 of
FIGS. 1-5 described above, and therefore like reference numerals
preceded with "1" are used to indicate like aspects or functions,
and the description above directed to such aspects or functions
(and the alternative embodiments thereof) equally applies to the
exemplary slot seal assembly 110. Specifically, FIG. 6 shows a
cross-section of a portion of an exemplary turbomachine including
an exemplary first turbine component 142, an adjacent exemplary
second turbine component 144, and an exemplary composite slot seal
110 installed in the seal slot formed by the first and second
components 142, 144. The first and second turbine components 142,
144 may be first and second stator components, such as first and
second nozzles of first and second stators, respectively. In other
embodiments, the first and second components 142, 144 may be any
other adjacent turbomachinery components, such as stationary or
translating and/or rotating (i.e., moving) turbine components.
Stated differently, the exemplary composite slot seals 10, 110
described herein may be configured for, or used with, any number or
type of turbomachinery components requiring a seal to reduce
leakage between the components.
[0044] The cross-section of the exemplary components 142, 144 and
exemplary composite slot seal 110 illustrated in FIG. 6 is taken
along a width of the structures, thereby illustrating an exemplary
width and thickness/height of the structures. It is noted that the
relative width, thickness and cross-sectional shape of the
structures illustrated in FIG. 6 is exemplary, and the structures
may include any other relative width, thickness and cross-sectional
shape. Further, the length of the structures (extending in-out of
the page of FIG. 6) may be any length, and the shape and
configuration of the structures in the length direction may be any
shape or configuration. It is also noted that although only two
exemplary turbine components 142, 144 forming one seal slot is
shown, a plurality of components may form a plurality of seal slots
that are in communication with one another. For example, a
plurality of turbine components may be circumferentially arranged
such that seal slots formed thereby are also circumferentially
arranged and in communication with one another. In such
embodiments, the slot seals 10, 110, 210 according to the present
disclosure may be configured to span a plurality of seal slots to
seal a plurality of gaps or junctions and thereby reduce leakage
between a plurality of turbine components.
[0045] As shown in FIG. 6, the first and second adjacent turbine
components 142, 144 may be spaced from one another such that a
junction, gap or pathway 190 extends between the first and second
adjacent components 142, 144, such as stators. Such a junction 190
may thereby allow flow, such as airflow, between the first and
second turbine components 142, 144. In some configurations, the
first and second turbine components 142, 144 may be positioned
between a first airflow 150, such as a cooling airflow, and a
second airflow 160, such as hot combustion airflow. It is noted
that the term "airflow" is used herein to describe the movement of
any material or composition, or combination of materials or
compositions, translating through the junction 190 between the
first and second turbine components 142, 144.
[0046] To accept a seal that spans across the junction 190, and
thereby block or otherwise cutoff the junction 190, the first and
second adjacent components 142, 144 may each include a slot, as
shown in FIG. 6. In the exemplary illustrated embodiment, the first
component 142 includes a first seal slot 170 and the second
component includes a second seal slot 180. The first and second
seal slots 170, 180 may have any size, shape, or configuration
capable of accepting a seal therein. For example, as shown in the
illustrated exemplary embodiment in FIG. 6, the first and second
seal slots 170, 180 may be substantially similar to one another and
positioned in a mirrored relationship to define together a net slot
or cavity that extends from within the first component 142, across
the junction 190, and into the second component 144. In this
manner, the pair of first and second seal slots 170, 180 may
jointly form a cavity or seal slot to support opposing portions of
a seal such that the seal 110 passes through the junction 190
extending between the adjacent components 142, 144.
[0047] In some arrangements wherein the first and second turbine
components 142, 144 are adjacent, the first and second seal slots
170, 180 may be configured such that they are substantially aligned
(e.g., in a mirrored or symmetric relationship). However, due to
manufacturing and assembly limitations and/or variations, as well
as thermal expansion, movement and the like during use, the first
and second seal slots 170, 180 may be skewed, twisted, angled or
otherwise misaligned. In other scenarios, the first and second seal
slots 170, 180 may remain in a mirrored or symmetric relationship,
but the relative positioning of the first and second seal slots
170, 180 may change (such as from use, wear or operating
conditions). The term "misaligned" is used herein to encompass any
scenario wherein seal slots have changed relative positions or
orientations as compared to a nominal or initial position or
configuration.
[0048] With respect to the exemplary first and second seal slots
170, 180 of the exemplary first and second turbine components 142,
144 and the exemplary seal 110 of FIG. 6, in a misaligned
configuration (not shown) the exemplary seal 110 is preferably
flexible to account for the misalignment and maintain sealing
contact of the coating 116 with the first and second seal slots
170, 180 to effectively cut off or eliminate the junction 190
extending between the first and second turbine components 142, 144
to thereby reduce or prevent the first and second airflows 150, 160
from interacting. More particularly, as shown in FIG. 6 the first
and second airflows 150, 160 may interact with the junction 190
such that the first airflow 150 is a "driving" airflow that acts
against the exterior sealing surface 122 of the shim 112 of the
seal 110 to force the coating 116 of the seal 110 against first
side surfaces 135, 145 of the first and second seal slots 170, 180,
respectively. In such scenarios, the seal 110 (and/or coating 166)
may be preferably sufficiently flexible to deform (e.g.,
elastically) as a result of the forces applied by the first airflow
150 (e.g., above that applied by the second airflow 160) to account
for any misalignment between the first and second seal slots 170,
180, but sufficiently stiff to resist being "folded" or otherwise
"pushed" into the junction 190. Stated differently, in such a
scenario, the exemplary seal 110 may be preferably sufficiently
flexible, but yet sufficiently stiff, to maintain sealing
engagement of the coating 116 of the shim 112 with the first side
surfaces 135, 145 via the forces of the first airflow 150. For
example, the metallic shim 112, metallic support structure 114, and
the coating 116 may be configured to conform to irregularities on
the seal slot contact surfaces 135, 145 during use of the turbine.
In some such embodiments, the coating 116 may be a glass insulating
coating with a transition temperature (Tg) similar to that of the
operating temperatures of the turbine/seal 110 so that the glass
coating 116 becomes soft or deformable at operating temperatures to
facilitate deformation an contouring of at least the coating 116 to
the first side surfaces 135, 145. In addition to being sufficiently
flexible (in all directions) to effectively seal the junction 190
in misalignment scenarios, as described above, the exemplary seal
110 may preferably be sufficiently stiff to satisfy assembly
requirements.
[0049] The size of the seal 110 may be any size, but may be
dependent upon, or at least related to, the components 142, 144 in
which the seal 110 is installed. The thickness T1 of the exemplary
seal 110 may be less than the thickness T2 of the first and second
seal slots 170, 180, and thereby the thickness T2 of the net slot
created by the first and second seal slots 170, 180 when the first
and second adjacent components 142, 144 are assembled. In some
embodiments, the thickness T1 of the exemplary seal 110 may
preferably be within the range of about 0.01 inches to about 1/4
inches, and more preferably within the range of about 0.05 inches
to about 0.1 inches. Similarly, the width W1 of the seal 110 may be
less than the width W2 of the net slot created by the first and
second slots 170, 180 of the first and second components 142, 144,
respectively, and the gap 190 between the components 142, 144 when
the components 142, 144 are installed adjacent to one another. In
some embodiments, the width W1 of the exemplary seal 110 may
preferably be within the range of about 0.125 inches to about 0.75
inches.
[0050] As shown in the illustrated embodiment in FIG. 6, for
example, the seal 110 may be positioned and arranged within the
seal slot (i.e., the first and second seal slots 170, 180) such
that the first or cooling airflow 150 acts against the exterior
sealing surface 122 of the shim 112 to force the coating 116
against the first side surfaces 135, 145 of the first and second
seal slots 170, 180. Due to the impervious nature of the shim 112
and/or the coating 116, the seal 110 thereby prevent the cooling
airflow 150 from migrating through the gap 190 and into the second
or hot combustion airflow 160. Further, the coating 116 protects
the metallic shim 112 from the high temperatures of the combustion
airflow 160. In this way, at least the shape and configuration of
the exterior or sealing surface of the coating 116 of the seal 110
(e.g., the surface that interacts with the exemplary first side
surfaces 135, 145 or other sealing surfaces of the exemplary first
and second seal slots 170, 180) may be related to the shape and
configuration of the slots 142, 144 in which the seal 110 is
installed. Stated differently, the shape and configuration of at
least the exterior or sealing surface of the coating 116 of the
seal 110, such as the contour, surface texture, etc., may be
configured to ensure sealing engagement with the first and second
seal slots 170, 180 in which the seal 110 is installed. For
example, in the illustrated example in FIG. 6, the exterior or
sealing surface of the coating 116 of the seal 110 may be
substantially smooth and planar to substantially abut or otherwise
substantially engage the substantially planar first side surfaces
135, 145 of the first and second seal slots 170, 180 to effectively
prevent or reduce leakage of the first airflow 150 between the seal
assembly 110 and the first side surfaces 135, 145 of the first and
second seal slots 170, 180 and, ultimately, into the second or hot
combustion airflow 160 (and to also protect the metallic shim 12
from the high temperatures of the hot combustion airflow 160). In
some alternative embodiments (not shown), the shape and
configuration of at least the exterior or sealing surface of the
coating 116 of the seal 110 may be shaped or configured differently
than that of the corresponding sealing surfaces of the first and
second seal slots 170, 180 (such as the exemplary first side
surfaces 135, 145 of the first and second seal slots 170, 180
illustrated in FIG. 6).
[0051] FIG. 7 illustrates a cross-sectional view of another
exemplary slot seal assembly 210 according to the present
disclosure. The exemplary slot seal assembly 210 is substantially
similar to the exemplary slot seal assemblies 10 and 110 of FIGS.
1-6 described above, and therefore like reference numerals preceded
with "2" are used to indicate like aspects or functions, and the
description above directed to such aspects or functions (and the
alternative embodiments thereof) equally applies to the exemplary
slot seal assembly 210. As shown in FIG. 7, slot seal assembly 210
differs from seal assemblies 10 and 110 in that the seal 210 is
symmetrical in the thickness direction. As such, seal assembly 210
provides for ease of installation or assembly of the seal 210 in a
turbine seal slot as the seal 210 does not need to be particularly
oriented in the thickness direction.
[0052] As shown in FIG. 7, both the sealing surface 222 and the
support surface 224 sides of the metallic shim 12 include a
metallic support structure 214 bonded thereto. In some embodiments
(not shown), the support structure may 214 may extend over one or
more side edges of the metallic shim 212 and onto the sealing
surface 222 and the support surface 224. Similarly, both the
support structure 214 bonded to the sealing surface 222 and the
support structure 214 bonded to the support surface 224 of the
metallic shim 212 include the coating 216 applied thereto. In some
embodiments (not shown), the coating 216 may extend over one or
more side edges of the metallic shim 212 and onto/into the support
structure 214 bonded to the sealing surface 222 and the support
structure 214 bonded to the support surface 224. The coating 216
applied on and in the support structure 214 that is bonded to the
sealing surface or side 222 of the shim 210 may insulate or protect
the sealing surface side 22 of the shim 212 (such as from the
cooling airflow 150 discussed above with respect to FIG. 6).
[0053] The seal assemblies disclosed herein provide low leakage
rate similar to that possible with tradition slot seals, such as
solid metal shim seals, while eliminating the silicide formation,
oxidation, thermal creep and/or increased wear concerns when
applied to modern high temperature turbomachinery. Moreover, the
seal assemblies disclosed herein may be less susceptible to
manufacturing variations as compared to existing seals. The seal
assemblies disclosed herein thus reduce leakage with low
manufacturing and operational risks, and are applicable in both OEM
and retrofit applications.
[0054] It is to be understood that the above description is
intended to be illustrative, and not restrictive. Numerous changes
and modifications may be made herein by one of ordinary skill in
the art without departing from the general spirit and scope of the
invention as defined by the following claims and the equivalents
thereof. 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. Also,
the term "operably connected" is used herein to refer to both
connections resulting from separate, distinct components being
directly or indirectly coupled and components being integrally
formed (i.e., monolithic). 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.
[0055] 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 disclosure
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.
[0056] 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.
* * * * *