U.S. patent application number 12/732532 was filed with the patent office on 2010-07-15 for methods for improving braze joints utilizing gold/copper/nickel brazing alloys.
Invention is credited to David Edwin Budinger, Kazim Ozbaysal.
Application Number | 20100176119 12/732532 |
Document ID | / |
Family ID | 41400602 |
Filed Date | 2010-07-15 |
United States Patent
Application |
20100176119 |
Kind Code |
A1 |
Ozbaysal; Kazim ; et
al. |
July 15, 2010 |
METHODS FOR IMPROVING BRAZE JOINTS UTILIZING GOLD/COPPER/NICKEL
BRAZING ALLOYS
Abstract
A method to improve the impact resistance of a braze joint
between a tungsten/carbide/cobalt substrate and a substrate
including titanium or alloy thereof includes utilizing a brazing
material including gold, nickel, and copper present in respective
amounts to improve the ductility of the braze joint.
Inventors: |
Ozbaysal; Kazim;
(Cincinnati, OH) ; Budinger; David Edwin;
(Loveland, OH) |
Correspondence
Address: |
GENERAL ELECTRIC COMPANY
GE AVIATION, ONE NEUMANN WAY MD F16
CINCINNATI
OH
45215
US
|
Family ID: |
41400602 |
Appl. No.: |
12/732532 |
Filed: |
March 26, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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11930858 |
Oct 31, 2007 |
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12732532 |
|
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11236953 |
Sep 28, 2005 |
7328832 |
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11930858 |
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Current U.S.
Class: |
219/615 ;
228/101; 228/119; 228/248.1; 228/252; 228/256 |
Current CPC
Class: |
C22C 1/0425 20130101;
B22F 7/08 20130101; B32B 15/01 20130101; B22F 5/009 20130101; C22C
14/00 20130101; C22C 5/02 20130101; Y10T 428/12 20150115; B23K
35/3013 20130101; C22C 1/0466 20130101; Y10T 428/12806 20150115;
C22C 9/00 20130101; B32B 15/016 20130101; B22F 7/064 20130101 |
Class at
Publication: |
219/615 ;
228/101; 228/256; 228/248.1; 228/252; 228/119 |
International
Class: |
B23K 1/002 20060101
B23K001/002; B23K 1/20 20060101 B23K001/20; B23K 31/02 20060101
B23K031/02 |
Claims
1. A method of improving the impact resistance of a braze joint
between a midspan shroud of a fan or compressor blade for a gas
turbine engine and a wear pad brazed thereto, the method
comprising: brazing the wear pad to the midspan shroud with a
brazing material including: about 40 to about 60 wt % gold; about 5
to about 16 wt % nickel; about 35 to about 55 wt % copper; wherein
the gold, nickel, and copper are present in respective amounts to
provide the brazing material with a post-braze hardness of between
about 450 and about 600 KHN, and the braze joint with an impact
resistance of greater than about 0.60 Joules.
2. The method according to claim 1 further comprising: providing
the midspan shroud, wherein the midspan shroud includes a face for
receiving the wear pad; providing the wear pad; and disposing the
brazing material between the wear pad and the face to provide a
brazing assembly.
3. The method according to claim 2 wherein the brazing material is
in a form selected from a homogeneous alloy form, a powder form, or
a layered form.
4. The method according to claim 3 wherein the brazing material is
in the layered form, and wherein the method includes: positioning a
layer consisting essentially of a copper foil between a layer of
nickel-containing foil and a layer of gold-containing foil.
5. The method according to claim 2 wherein providing the midspan
shroud includes: providing a midspan shroud requiring repair due to
a damaged wear pad; and removing the damaged wear pad.
6. The method according to claim 5 wherein the damaged wear pad is
removed chemically, mechanically, or a combination of chemically
and mechanically.
7. The method according to claim 2 further comprising: subjecting
the brazing assembly to an induction heating process for a duration
of at least about 1 minute and less than 10 minutes at braze
temperatures of less than about 1900.degree. F. (about 1038.degree.
C.).
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a Divisional Application of application
Ser. No. 11/930,858, filed Oct. 31, 2007, which is a
Continuation-in-Part of application Ser. No. 11/236,953, filed Sep.
28, 2005, now U.S. Pat. No. 7,328,832, each of which is
incorporated herein by reference in its entirety.
TECHNICAL FIELD
[0002] Embodiments herein relate generally to methods for improving
braze joints, and more particularly to improving braze joints
between titanium alloy substrates and tungsten/carbide/cobalt
(WC--Co) wear pads by utilizing gold/copper/nickel brazing
alloys.
BACKGROUND OF THE INVENTION
[0003] In a gas turbine engine, air is pressurized in a compression
module during operation. The air channeled through the compression
module is mixed with fuel in a combustor and ignited, generating
hot combustion gases which flow through turbine stages that extract
energy therefrom for powering the fan and compressor rotors and
generating engine thrust to propel an aircraft in flight or to
power a load, such as an electrical generator.
[0004] The compression system includes a rotor assembly comprising
a plurality of rotor blades extending radially outward from a disk.
More specifically, each rotor blade has a dovetail which engages
with the disk, a platform forming a part of the flow path, and an
airfoil extending radially from the platform to a tip. The platform
may be made integral to the blade or, alternatively, made
separately.
[0005] In some designs, the rotor blade, especially those in a fan
rotor and the front stages of a multistage compression system, have
a pair of circumferentially extending shrouds on the airfoil, one
projecting from the pressure surface and one projecting from the
suction surface. The shrouds are located at a radial location
between the blade dovetail and the blade tip. In some other
designs, the shrouds may be located at the tip of the blade
airfoil. During normal operation of the compression system, the
blades twist and the shrouds on adjacent blades contact with each
other, forming a shroud ring that provides support to the blades.
During engine operation, the shroud ring resists vibration and
twisting of the blades. The term "midspan shroud" is used herein to
refer to all supports on fan and compression system blades that
contact with each other during operation, and includes all supports
located anywhere on the span of the blade, including supports at
the tip of the blade. The "midspan shrouds" as used herein, may be
located anywhere along the blade span, not just at the midpoint of
the span.
[0006] During certain abnormal events, such as a bird impact, other
foreign object impact, or stalls during engine operation, the
normal contact between the shrouds of adjacent blades is disturbed.
The contact forces become high and misaligned due to the impacts
and the shrouds become disengaged fully or partially. This is
called "shingling" of the blades. Shingling causes significant wear
and tear damage on the midspan shrouds. When the speed of the
compressor rotor drops, the shingled blades may rebound, causing
further wear and tear on the shrouds.
[0007] Fan or compressor blades sometimes have wear pads brazed on
the contact faces of the midspan shrouds. Wear pads have been used
on blades to address the wear problem. For example, some compressor
blades contain a brazed-on WC--Co wear pad to reduce wear between
two rubbing midspan shrouds.
[0008] The blades may comprise titanium or alloys thereof (i.e., Ti
6Al-4V and/or Ti 8Al-1V-1 Mo alloys) having beta transus
temperatures at or slightly above 1800.degree. F. (about
982.degree. C.). The wear pads are conventionally brazed to the
titanium blade using a titanium-copper-nickel (TiCuNi) alloy braze
foils. Diffusion occurs between TiCuNi braze foil and WC--Co wear
pad during high temperature braze. Titanium forms brittle compounds
with the alloying elements of the wear pad in the braze joint. As a
result, the braze joint provides a high hardness (about 1200 KHN)
W--Co--Ti--Cu--Ni alloy. The braze interface exhibits cracking at
impact energies as low as 0.30 Joules, and the wear pad may be
liberated from the substrate at the brittle braze interface at an
impact energy of about 0.60 Joules.
[0009] Industrially available braze alloys have been unable to meet
the demands for high ductility and low cost necessary for aircraft
engine applications. Accordingly, there is a need for lower cost,
high ductility, impact resistant brazing alloys for brazing WC--Co
substrates to titanium or titanium alloy substrates. In particular,
there is a need for brazing alloys for brazing WC--Co materials to
titanium and titanium alloys without forming a brittle braze
interface.
BRIEF DESCRIPTION OF THE INVENTION
[0010] The above-mentioned need or needs may be met by exemplary
embodiments which provide brazing materials that provide high
ductility (i.e., low hardness), sufficient wettability to the
substrates, and can be brazed without harming the substrates.
[0011] An exemplary embodiment includes a method of improving the
impact resistance of a braze joint between a midspan shroud of a
fan or compressor blade for a gas turbine engine and a wear pad
brazed thereto. The method includes brazing the wear pad to the
midspan shroud with a brazing material comprising about 40 to about
60 wt % gold, about 5 to about 16 wt % nickel, and about 35 to
about 55 wt % copper wherein the gold, nickel, and copper, are
present in respective amounts to provide the brazing material with
a post-braze hardness of between about 450 and about 600 KHN, and
the braze joint with an impact resistance of greater than about
0.60 Joules.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the concluding
part of the specification. The invention, however, may be best
understood by reference to the following description taken in
conjunction with the accompanying drawing figures in which:
[0013] FIG. 1 is a perspective view of an exemplary compressor
blade having a midspan shroud.
[0014] FIG. 2 is a partial perspective view showing an exemplary
midspan shroud-wear pad assembly.
[0015] FIG. 3 is a cross-sectional view of the midspan shroud-wear
pad assembly taken through 3-3 of FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0016] Referring to the drawings wherein identical reference
numerals denote the same elements throughout the various views,
FIG. 1 shows an exemplary compressor blade 10 having an airfoil 11,
dovetail 12, a platform 14, and a midspan shroud 16 extending from
the suction side 17 of the airfoil 11. The midspan shroud 16
includes a contact face 18. It will be appreciated by those with
skill in the art that a similar midspan shroud extends from the
pressure side of the airfoil. It will further be appreciated by
those with skill in the art that blade 10 as shown is identified as
a compressor blade, although the descriptions set forth herein are
equally applicable to fan blades.
[0017] In fan and compressor rotor assemblies, the blades are
arranged in the circumferential direction around a disk. During
engine operation, the blades airfoils twist, and the midspan shroud
on the suction side of a blade comes into contact with the midspan
shroud on the pressure side of the adjacent blade. The shrouds,
when thus engaged with each other, form a stiff ring supporting the
blades to prevent vibration. As the engine shuts down the shrouds
disengage. As the engines operate through many cycles, the contact
faces of the shrouds are subjected to significant wear and
tear.
[0018] FIG. 2 illustrates an exemplary midspan shroud-wear pad
assembly 20. In the assembly, a wear pad 22 is shown attached to
contact face 18 of the midspan shroud 16. Wear pads are used with
midspan shrouds 16 to address the wear problem addressed above. For
example, some compressor blades made from titanium or alloys
thereof may include a brazed-on WC--Co wear pad to prevent adhesive
wear between two contacting midspan shrouds.
[0019] FIG. 3 illustrates a braze joint 24 at the interface between
a midspan shroud 16 and wear pad 22. Braze joint 24 comprises a
brazing material 26 that, after brazing, provides an improvement in
impact resistance of the braze joint 24 as compared to known prior
art braze joints.
[0020] Embodiments disclosed here and are directed to brazing
materials for brazing a first substrate, such as a WC--Co wear pad
22, to a second substrate, such as a midspan shroud comprising
titanium or alloys thereof. Exemplary brazing materials include
gold (about 40 to about 60 wt %), nickel (about 5 to about 16 wt
%), and copper (about 35 to about 55 wt %).
[0021] In an exemplary embodiment, the substrates are brazed under
brazing conditions to prevent damage to the mechanical properties
of the substrates. In an exemplary embodiment, the brazing
temperature is generally not greater than about 1800.degree. F.
(about 982.degree. C.), which is generally below the beta transus
temperatures of the titanium alloy substrate. In exemplary
embodiments, the brazing materials disclosed herein may include a
nickel content sufficient to ensure wetting to both WC--Co and
titanium substrates, a copper content that is sufficiently high to
ensure ductility for impact resistance, and gold content that is
reasonably low to ensure adequate cost. Further, the brazing
materials disclosed herein are able to braze the first and second
substrates using a rapid induction heating process. In an exemplary
embodiment, brazing occurs at temperatures below about 1800.degree.
F. (about 982.degree. C.) at braze times of from about 1 to about
10 minutes. In an exemplary embodiment, the braze time may be from
about 1 minute to about 3 minutes. The induction heating may occur
under vacuum of about 10.sup.-4 to about 10.sup.-5 Torr. In an
exemplary embodiment, the rapid braze process may allow braze
temperatures to be as high as about 1900.degree. F. (about
1038.degree. C.) without damaging the substrates.
[0022] In an exemplary embodiment, the weight percentages of gold,
nickel, and copper in the brazing material may be selected based
upon the intended use of the brazing alloy. In particular, the
weight percentages may be selected such that the resulting brazing
alloy has a high impact resistance and high ductility (i.e., low
hardness) after brazing and brazing temperatures below the beta
transus temperature of the substrate such that the mechanical
properties of the substrate are not negatively affected, for
example, by way of phase transitions by high brazing temperatures.
It is contemplated that exemplary embodiments disclosed herein may
be brazed at temperatures of up to about 1900.degree. F.
(1038.degree. C.) without negatively impacting the substrates.
[0023] In an exemplary embodiment the brazing material may include
about 40 to about 60% by weight gold, about 5 to about 16% by
weight nickel, and about 35 to about 55% by weight copper.
[0024] In an exemplary embodiment, the brazing material may include
from about 45 to about 49% by weight gold, about 9 to about 11% by
weight nickel, and about 35 to about 55% by weight copper.
[0025] In an exemplary embodiment, the brazing material may include
from about 40 to about 60% by weight gold, about 9 to about 16% by
weight nickel, and about 40 to about 55% by weight copper.
[0026] In an exemplary embodiment, the brazing material may include
from about 45 to about 49 weight % gold, about 9 to about 11 weight
% nickel and about 41 to about 55 weight % copper.
[0027] In an exemplary embodiment, the brazing material may consist
of about 47 weight % gold, about 10 weight % nickel, and about 43
weight % copper.
[0028] In an exemplary embodiment, the gold, nickel, and copper are
present in amounts such that the brazing material has a post-braze
hardness of between 450 and 600 KHN. In an exemplary embodiment,
the post-braze hardness may be between about 550 to about 570 KHN.
In an exemplary embodiment, the copper content may be between about
40 and about 60 weight %. In an exemplary embodiment, the copper
content may be between about 41 to about 55 weight %.
[0029] In an exemplary embodiment, nickel is present in an amount
sufficient to provide wetting to the first and second substrates
during induction heating. In an exemplary embodiment, the duration
of the induction heating process is at least about one minute. In
an exemplary embodiment, the induction heating process is not
greater than about 10 minutes. In an exemplary embodiment, the
braze temperature is not greater than about 1800.degree. F.
(982.degree. C.). In an exemplary embodiment, the braze temperature
is between about 1750.degree. F. (about 954.degree. C.) to about
1800.degree. F. (982.degree. C.). In other exemplary embodiments,
the braze temperature may be up to about 1900.degree. F.
(1038.degree. C.). In other exemplary embodiments, the braze
temperature may be between about 1750.degree. F. (about 954.degree.
C.) to about 1900.degree. F. (1038.degree. C.).
[0030] The brazing materials disclosed herein may be provided in
various forms. For example, the brazing materials may be provided
as homogenous compositions including gold, nickel, and copper. In
other exemplary embodiments, the brazing materials may be provided
as powders. In other exemplary embodiments, the brazing alloys may
be provided as layered or laminated films or foils.
[0031] In a powdered form, the brazing alloys may be provided as
mixtures of gold, nickel, and copper, and/or powders of alloys of
one or more of gold, nickel, and copper, wherein the metals are
present in the appropriate quantities. In an exemplary embodiment,
the powders may form a homogeneous alloy upon being heated to the
appropriate brazing temperature. For example, an exemplary brazing
material may be provided as a dispersion of copper powder,
gold/copper/nickel powder, gold/nickel powder or mixtures thereof
as appropriate.
[0032] In a layered form, the gold, nickel, copper may be provided
in separate layers, thereby providing homogeneous alloys upon being
heated to the appropriate brazing temperature. For example, a
brazing alloy may be provided as a laminated film or a layered
material. In an exemplary embodiment, the brazing material may
comprise a layer of copper foil positioned between layers of
gold/nickel foil. Any combination of layers may be utilized to
provide the alloying metals in the appropriate quantities. In other
exemplary embodiments, the brazing material may be provided as
layered or laminated films or foils.
[0033] In the layered form, the metals or alloys of the
gold/nickel/copper brazing material may be provided in separate
layers that provide a substantially homogeneous alloy during the
brazing process. Those skilled in the art will appreciate that
various arrangements and numbers of layers and various combinations
of metals and/or alloys are within the scope of this disclosure.
The layered material may be used in a flat (i.e., planar)
configuration, or may be rolled or otherwise shaped prior to
brazing.
[0034] An exemplary embodiment includes a brazing assembly
comprising a tungsten/carbide/cobalt (WC--Co) substrate, a titanium
or titanium alloy substrate, and a brazing material disposed
between the substrates. An exemplary brazing material includes 40
to about 60 percent by weight gold, about 5 to about 16 percent by
weight nickel, and about 35 to about 55 percent by weight
copper.
[0035] An exemplary embodiment comprises an article including a
first substrate comprising tungsten/carbide/cobalt material, a
second substrate comprising titanium or alloys thereof, and a braze
joint at the interface of the first substrate and the second
substrate. The braze joint is formed from an exemplary brazing
material including about 40 to about 60 percent by weight gold,
about 5 to about 16 percent by weight nickel, about 35 to about 55
percent by weight copper.
Example 1
[0036] A brazing material is prepared by positioning a copper foil
between two layers of gold/nickel braze foil. The thickness of each
layer was selected such that the resulting material included about
47 wt % gold, about 10 wt % nickel, and about 43 wt % copper with
respect to the total weight of the layered material. The resulting
material had a brazing temperature of about 1775.degree. F. (about
968.degree. C.).
Example 2
[0037] A brazing material was prepared by positioning a copper foil
between two layers of gold/nickel braze foil. The thickness of each
layer was selected such that the resulting material included about
53 wt % gold, about 11 wt % nickel and about 36 wt % copper with
respect to the total weigh of the layered material. The resulting
layered material has a brazing temperature of about 1795.degree. F.
(about 979.degree. C.).
Example 3
[0038] The brazing material of Example 1 was rolled up and
positioned between a WC--Co (2-10% cobalt) wear pad and a titanium
alloy (90 wt % Ti, 6 wt % Al and 4 wt % V) midspan shroud and the
assembly was raised to a temperature of about 1800.degree. F. (by
way of induction heating) for about 10 minutes under vacuum (about
10.sup.-4 Torr). After the assembly was allowed to cool, the braze
joint was determined to have a hardness of about 550 KHN.
Example 4
[0039] The brazing material of Example 2 was rolled up and
positioned between a WC--Co (2-10% cobalt) wear pad and a titanium
alloy (90 wt % Ti, 6 wt % Al and 4 wt % V) midspan shroud and the
assembly was raised to a temperature of about 1800.degree. F. (by
way of induction heating) for about 10 minutes under vacuum (about
10.sup.-4 Torr). After the assembly was allowed to cool, the braze
joint was determined to have a hardness of about 570 KHN.
Example 5
[0040] An exemplary gold/nickel/copper brazing material as
disclosed herein was employed to braze a WC--Co wear pad to the
midspan shroud (e.g., 16) of an airfoil (e.g., 11). The braze
temperature reached about 1885.degree. F. (about 1029.degree. C.)
at some locations. A cut-up inspection of the airfoil showed no
damage from the brazing process to the body of the airfoil.
[0041] Accordingly, the gold/nickel/copper brazing alloys disclosed
herein are ductile and impact resistant with respect to
titanium/nickel/copper brazing alloys and exhibit excellent wetting
when used to join various WC--Co material to various titanium
alloys.
[0042] In an exemplary embodiment, a method for improving the
impact resistance of a braze joint 24 between a first substrate
(i.e., wear pad 22) and a second substrate. (i.e., midspan shroud
16) includes providing a brazing assembly including the first
substrate the second substrate and a brazing material disposed
therebetween. Any of the aforementioned exemplary brazing materials
26 may be utilized. In particular, the wear pad 22 may be brazed to
the contact surface 18 of the midspan shroud. In an exemplary
embodiment, the brazing material comprises gold, nickel, and copper
in respective amounts such that, after brazing, the braze joint 24
has a hardness of between about 450 and 600 KHN and an impact
resistance of greater than about 0.60 Joules. The brazing material
may be provided in any of the aforementioned forms, including
layered, powdered, or homogeneous forms.
[0043] In an exemplary method, providing a midspan shroud includes
providing a midspan shroud requiring repair due to a damaged wear
pad. In an exemplary method, the damaged wear pad is removed by
mechanical, chemical or a combination of mechanical and chemical
methods. For example, the midspan shroud of a blade may be
subjected to a grinding process to remove the worn wear pad and
prior braze material. Alternately, the worn wear pad may be
chemically removed. If necessary, the midspan shroud may be
subjected to further processes in preparation for brazing on a new
wear pad (i.e., material build up, machining to specifications, and
the like).
[0044] An exemplary method further includes brazing the first
substrate to the second substrate. In an exemplary method, an
induction heating process is utilized for brazing. The brazing
assembly (i.e., midspan shroud 16, brazing material 26, wear pad
22) may be placed into a vacuum chamber. The midspan shroud 16 may
be placed into an induction coil. AC current passing through the
coil generates a magnetic field in the midspan shroud, generating
eddy currents in the shroud to rapidly increase the temperature to
the brazing range. In exemplary embodiments, the brazing
temperature is between about 1750.degree. F. (about 954.degree. C.)
to about 1800.degree. F. (982.degree. C.). Duration for the braze
may be about 1-3 minutes. In other exemplary embodiments, the braze
temperature may be as high as about 1900.degree. F. (about
1038.degree. C.). An exemplary braze duration may be up to about 10
minutes. In an exemplary embodiment, the braze duration is at least
about 1 minute. In an exemplary embodiment, the brazing is
accomplished under vacuum of about 10.sup.-4 to about 10.sup.-5
Torr.
[0045] With reference to FIGS. 1-3, an exemplary embodiment
comprises an article including at least one braze joint. The
article may be a fan or compressor blade 10. The blade 10 may
include a midspan shroud-wear pad assembly 20. The wear pad 22 is
attached to contact face 18 of the midspan shroud through the braze
joint 24. Braze joint 24 is formed from any of the exemplary
brazing materials disclosed herein. The braze joint 24 exhibits
increased ductility (decreased hardness) and thus provides improved
impact resistance.
[0046] Exemplary embodiments include a braze assembly illustrated
in FIG. 3. An exemplary braze assembly includes a first substrate,
such as wear pad 22 which may comprise WC--Co. The exemplary braze
assembly includes brazing material 26 disposed between the first
and second substrates. An exemplary brazing material comprises
about 40 to about 60 percent by weight gold, about 5 to about 16
percent by weight nickel, and about 35 to about 55 percent by
weight copper. Other exemplary brazing materials disclosed here may
be used in the braze assembly.
[0047] Thus, embodiments disclosed herein provide braze assemblies,
brazing materials, methods of improving the impact resistance of a
brazed joint, and brazed articles. The brazing materials disclosed
herein provide post-braze joints having increased ductility. The
gold/nickel/copper brazing materials disclosed herein provide good
wetting when brazing WC--Co substrates to titanium or alloys
thereof under brazing conditions to minimize or prevent damage to
the substrates. For example, the brazing temperature may be less
than about 1800.degree. F. (982.degree. C.) during induction
heating of less than about 10 minutes. In other exemplary
embodiments, rapid induction heating may allow for increased braze
temperatures of up to about 1900.degree. F. (about 1038.degree.
C.).
[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 make and use the invention. 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 languages
of the claims.
* * * * *