U.S. patent application number 16/100954 was filed with the patent office on 2018-12-06 for method of fabricating space satellite tank components utilizing additive manufacturing and spin forming.
The applicant listed for this patent is Keystone Engineering Company. Invention is credited to Ian Ballinger, Wayne H. Tuttle.
Application Number | 20180347756 16/100954 |
Document ID | / |
Family ID | 57683977 |
Filed Date | 2018-12-06 |
United States Patent
Application |
20180347756 |
Kind Code |
A1 |
Ballinger; Ian ; et
al. |
December 6, 2018 |
METHOD OF FABRICATING SPACE SATELLITE TANK COMPONENTS UTILIZING
ADDITIVE MANUFACTURING AND SPIN FORMING
Abstract
A thin wall spinformed metallic tank shell includes a first
region with a first thickness and at least one second region with a
second thickness greater than the first thickness including
structural features formed by an additive manufacturing process,
where the features are added outside and inside of the metallic
tank shell and can include: polar bosses added to one or both
external polar regions of a spherical section of the tank; mounting
tabs on a circumferential skirt of the tank; mounting rings
containing threaded holes attached to the interior or exterior
surface of the tank; mounting trunnions attached to the external
surface of the tank; propellant management devices attached to the
interior surface of the tank; structural reinforcement vanes and
ribs attached to the inside surface of the tank; and brackets
and/or shelves attached to the inside surface of the tank.
Inventors: |
Ballinger; Ian; (Anaheim
Hills, CA) ; Tuttle; Wayne H.; (Torrance,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Keystone Engineering Company |
Long Beach |
CA |
US |
|
|
Family ID: |
57683977 |
Appl. No.: |
16/100954 |
Filed: |
August 10, 2018 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15196636 |
Jun 29, 2016 |
10088103 |
|
|
16100954 |
|
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|
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62187414 |
Jul 1, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B22F 2005/005 20130101;
F17C 2203/012 20130101; B22F 2998/10 20130101; B23K 9/048 20130101;
F17C 2203/0639 20130101; F17C 2270/0186 20130101; B23K 15/0086
20130101; B23K 2101/12 20180801; Y02P 10/25 20151101; F17C 2260/01
20130101; F17C 2209/21 20130101; B21D 22/16 20130101; F17C 1/14
20130101; F17C 2203/0646 20130101; B23K 9/046 20130101; B23K 9/167
20130101; B33Y 10/00 20141201; B22F 3/1055 20130101; B23K 26/342
20151001; B22F 7/08 20130101; B23K 2103/04 20180801; B22F 5/10
20130101; Y02P 10/295 20151101; F17C 2203/0636 20130101; B33Y 80/00
20141201; F17C 1/08 20130101; B23K 2103/14 20180801; B23K 9/1093
20130101; B23K 2103/10 20180801; B23P 15/00 20130101; B21D 51/18
20130101; F17C 2201/0128 20130101; B22F 2998/10 20130101; B21D
22/16 20130101; B22F 3/1055 20130101 |
International
Class: |
F17C 1/08 20060101
F17C001/08; B22F 7/08 20060101 B22F007/08; B23K 26/342 20140101
B23K026/342; B23K 15/00 20060101 B23K015/00; F17C 1/14 20060101
F17C001/14; B23K 9/04 20060101 B23K009/04; B23K 9/167 20060101
B23K009/167; B23K 9/10 20060101 B23K009/10; B21D 22/16 20060101
B21D022/16; B21D 51/18 20060101 B21D051/18; B22F 3/105 20060101
B22F003/105 |
Claims
1. A thin wall spinformed metallic tank shell comprising: a first
region with a first thickness; and at least one second region with
a second thickness greater than the first thickness including
structural features formed by an additive manufacturing process,
wherein the structural features comprise at least one of: (a) polar
bosses added to one or both external polar regions of a spherical
section of the tank; (b) mounting tabs on a circumferential skirt
of the tank; (c) mounting rings containing threaded holes attached
to the interior or exterior surface of the tank; (d) mounting
trunnions attached to the external surface of the tank; (e)
propellant management devices (PMD) attached to the interior
surface of the tank; (f) structural reinforcement vanes and ribs
attached to the inside surface of the tank; and (g) brackets and/or
shelves attached to the inside surface of the tank.
2. The metallic tank shell of claim 1, wherein the structural
features are formed from a metal comprising one or more of
aluminum, titanium, steel, and alloys thereof.
3. The metallic tank shell of claim 2, wherein the metal comprises
6061, 2219, 2014 aluminum alloys and CP Ti, Ti-6Al-4V,
Ti-15V-3Cr-3Sn-3Al titanium alloys.
4. The metallic tank shell of claim 1, wherein the additive
manufacturing process comprises powder based and wire based direct
metal deposition processes.
5. The metallic tank shell of claim 4, wherein powder based direct
metal deposition comprises at least one of laser engineered net
shaping (LENS), direct metal laser sintering (DMLS), selected laser
melting, laser powder injection, and direct metal deposition
(DMD).
6. The metallic tank shell of claim 4, wherein wire based direct
metal deposition comprises at least one of wire feed laser
deposition, electron beam additive manufacturing (EBAM), hot wire
gas tungsten arc welding (HW-GTAW), and ion fusion formation (IFF).
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a divisional of U.S. application Ser.
No. 15/196,636 filed Jun. 29, 2016 for "Method of Fabricating Space
Satellite Tank Components Utilizing Combinations of Additive
Manufacturing and Spinforming" by I. Ballinger and W. Tuttle, which
in turn claimed the benefit of U.S. Provisional Application No.
62/187,414 filed Jul. 1, 2015 for "Method of Fabricating Space
Satellite Tank Components Utilizing Combinations of Additive
Manufacturing and Spinforming" by I. Ballinger and W. Tuttle, both
of which are hereby incorporated by reference in their
entirety.
BACKGROUND
[0002] In the design and manufacture of satellite propellant and
pressurant tank shells there are two main driving characteristics.
These are weight and mounting configuration. The weight, or total
mass of the finished item is controlled through the use of
lightweight high-strength materials to minimize the thickness of
the material while still meeting the operating pressure
requirements. This generally drives the designs toward spherical
tanks with thin membrane thicknesses or cylindrical tanks with
hemispherical ends. These tanks are attached to the spacecraft
structure such that the mechanical loads from the mass of the tank
and its contents are transferred to the frame of the satellite.
This requires that the attachment points are thicker than the
nominal thickness of a tank that only must carry its low pressure
loads.
[0003] In addition there is often the need to mount surface tension
propellant management devices or other fluid expulsion devices such
as bladders or bellows inside the tank. There also might be needs
for local stiffening rings for stabilization of the pressure shell
for vacuum conditions or high external buckling loads.
[0004] To solve this issue, designers typically provide thick
section attachment points at selective locations such as at polar
bosses, skirts at the circumference of the tank, or bosses attached
to the sides of the tanks. These attachment features drive the
initial material thickness of the raw materials from which the
tanks are fabricated. To illustrate this consider a typical tank
used for propellants of a GPS space satellite.
[0005] The raw material for the domes of such tanks are often
forgings with sufficient thickness that an integral circumferential
attachment ring can be machined from the parent material. The added
thickness of the forging significantly increases the material cost.
Additionally the increased material thickness significantly
increases the fabrication cost as additional machining time and
operations are required to remove the thicker material in the
locations where it is not required. To reduce these inefficiencies,
some designs utilize thinner domes welded to attachment rings
fabricated from forgings, thereby reducing the total amount of
material removal required, but increasing the fabrication costs and
overall mass by producing and joining the welded ring to the tank
components.
[0006] Another method of reducing the cost of manufacturing these
tanks is the use of spinformed domes in lieu of forgings. The
spinformed domes take advantage of the ability to spinform domes
from thinner sheet metals, thereby reducing the amount of waste
material at the "machine blank" stage, but the thinner sheet cannot
generally accommodate the thicker attachment points except at the
polar bosses. To generate the thickness required for attachment
bosses, generally a thicker sheet is used and contours are machined
in the part before spinforming, or a thinner sheet is locally
reinforced through techniques such as inertia friction welding bar
stock onto the sheet at the boss locations. But it is generally not
possible to fabricate circumferential attachments on domes made
from spinformed processes without adding welded attachment rings
fabricated from forgings.
[0007] Therefore, there is a need for a method of fabricating space
satellite tank components that is capable of producing physical and
mechanical material characteristics in complex shapes with minimal
excess material to be removed in subsequent machining
operations.
SUMMARY
[0008] A method of forming a thick wall section on a specific
region of a thin wall spinformed metallic tank shell includes
forming a thin wall metallic tank shell blank by spinforming a
metal sheet over a mandrel and removing the tank shell blank from
the mandrel. The method further includes mounting the blank in an
additive manufacturing system and adding metallic structural
features to the tank shell according to a 3D model stored in memory
in the additive manufacturing system.
[0009] In an embodiment a thin wall spinformed metallic tank shell
includes a first region with a first thickness and at least one
second region with a second thickness greater than the first
thickness. The second region contains useful structural features
formed by an additive manufacturing process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a schematic illustration of a propellant tank.
[0011] FIG. 2 is a schematic illustration of a wire feed laser
deposition direct metal deposition process.
[0012] FIG. 3 is a schematic illustration of a powder based direct
metal deposition process.
[0013] FIG. 4 is a schematic illustration of a polar boss formed on
a spinformed tank shell.
[0014] FIG. 5 is a schematic illustration of a mounting ring formed
on a spinformed tank shell.
[0015] FIG. 6 is a schematic illustration of a trunnion formed on a
spinformed tank shell.
[0016] FIG. 7 is a schematic illustration of a mounting tab formed
on a spinformed tank shell.
[0017] FIG. 8A is a schematic illustration of a mounting support
formed on the interior of a spinformed tank shell.
[0018] FIG. 8B is a propellant management device that can mount on
the support in FIG. 8A.
[0019] FIG. 9 is a diagram showing the fabrication steps of
metallic structural features added to spinformed tank shells by
additive manufacturing.
[0020] FIG. 10 is an illustration of a structural feature formed on
a spinformed tank shell by wire feed laser deposition.
DETAILED DESCRIPTION
[0021] One method to resolve the fabrication inefficiencies
addressed above is the use of additive manufacturing (AM) to
produce the tank components with reduced waste material. This is
accomplished by molten metal deposition onto a substrate using
techniques similar to welding, wherein material is additively
applied layer by layer. An example method is the use of an electron
beam welding system with a filler wire feeder to deposit weld metal
onto a substrate and then continue to deposit weld metal until the
complete part is fabricated. To achieve material quality and
mechanical properties similar to plate or forged metals, the parts
are protected from atmospheric reactions through the use of a
vacuum environment. Additionally, the thermal management of the
process has significant effects on the material's metallurgical
structure and mechanical properties. Because the part is being
created in a vacuum from molten metal, the entire part is subjected
to significant exposure to high temperatures during the material
deposition. Thermal expansion of the material being deposited
causes the part size to vary during deposition. Thermal input to
the process is provided from the electron beam and thermal output
is provided through conduction into the previously deposited
portion of the fabrication plus radiation, causing significant heat
buildup during deposition. Thus, the part shape during fabrication
is determined based on the final part sizing at its use temperature
as well as the thermal buildup during fabrication. Depending on
part size, configuration, and quality activities, it may be
desirable to interrupt deposition periodically. During these
interruptions the part's thermal condition and physical size
changes, increasing the complexity of subsequent deposition
activities. Similarly, the addition of local attachment features
causes a change in the thermal profile of the part being fabricated
and therefore the physical size and mechanical properties of the
fabricated component.
[0022] The present invention is a method of fabricating space
satellite tank components utilizing a combination of mandrel-based
spinforming and additive manufacturing (AM). Initially the part (a
dome is used for illustrative purposes, although other components
such as cylinders are shown to be equally applicable to the process
described) is produced from thin sheet metal. Unlike prior art, the
locations of polar bosses or other tank attachment features are not
required to be at final part thickness. Instead the thickness at
these locations is driven by fabrication convenience and best shop
practices.
[0023] After the part is spinformed the thickness of attachment
locations are locally increased through additive manufacturing
techniques. These may include, but are not limited to laser
consolidation of powdered metal, and addition of wire utilizing
conventional weld metal buildup processes such as gas tungsten arc,
plasma arc, laser beam, electron beam, and others known in the art.
The spinforming process provides a surface that can mate to thermal
control tooling (heat sink devices, for example) to minimize
thermal distortion of the dome during the additive manufacturing
activities. This eliminates the negative thermal effects to the
base material, or substrate (material at the location of
instantaneous additive manufacturing processing). Examples of the
work would include buildup of polar bosses on tanks and creation of
mounting tabs and circumferential mounting features.
[0024] The process can also be used to generate features on the
interior surfaces of spinformed domes for the purpose of mounting
or supporting internal components such as propellant management
devices (PMD), or for structural purposes such as reinforcement
ribs. Mandrel-based spinforming does not typically allow the
generation of raised features on the part's interior surface since
the inner mold line of the part is in intimate contact with the
outer surface of the mandrel during forming operations. Removal of
the formed part from the mandrel at the conclusion of spinforming
necessitates that the mandrel not create concavities or locally
convex internal features. Utilizing additive manufacturing to build
up features on the interior of spinformed tank components enables
the use of thin spinformed domes without the need for complex
milling of interior cavities from thicker materials.
[0025] Similar to the illustration using domes provided above, it
will be apparent to one skilled in the art that parts of
cylindrical, conical, or other shapes can be fabricated on internal
mandrels and subsequently have internal and external features
applied through additive manufacturing.
[0026] An example of a space satellite propellant tank is shown in
FIG. 1. Tank 10 comprises domes 12 and 14 separated by cylindrical
section 16 joined to domes 12 and 14 by circumferential welds 18
and 20 respectively. Skirt 22 is attached to tank 10 and contains
tabs 24 for securing the tank to the frame of the satellite.
Fixtures 26 and 28 provide propellant ingress and outlet
respectively to the system. According to the invention, individual
tabs 24 may be formed by additive manufacturing on tank 10 thereby
eliminating the weight of skirt 22.
[0027] Three general classes of additive manufacturing for
depositing metal on a substrate are powder based layer by layer,
powder based direct metal deposition, and wire based direct metal
deposition. Powder based layer by layer fabrication of metal
structures is not suitable for forming individual metallic
structures on the uneven surfaces encountered on internal and
external satellite tank features. Powder based and wire based
direct metal deposition of metallic structural features are
suitable processes for the present invention. In both processes,
metal is fed to a localized molten pool on a substrate created by a
focused energy beam traversing the substrate. As the molten pool
solidifies the added metal forms a three dimensional structure
according to a computer model stored in the memory of the direct
metal deposition system. Closed loop feedback control systems
managing the energy beam, traverse rate, metal feed rate,
atmosphere control, and other parameters known in the art allow
fully dense additively manufactured near net shapes of a wide
variety of alloys.
[0028] An exemplary wire feed additive manufacturing (AM) system is
shown in FIG. 2. Wire feed AM system 30 comprises high powered
layer system 32, laser beam 34, wire feed system 36, wire 38,
shielding gas cloud 40, deposit 42, and substrate 44. Laser system
32, wire feed system 36 and gas cloud 40 are indicated moving in
the direction of arrow A during a build. Although both powder feed
and wire feed direct metal composite systems can form the
structural features of the invention on tank components, a wire
feed system is preferable for the present invention.
[0029] A schematic representation of an exemplary powder based
direct metal deposition additive manufacturing system is shown in
FIG. 3. Powder based laser deposition system 50 comprises nozzle
52, high power laser beam 54, powder feed channels 56, powder 58,
shielding gas channels 60, shielding gas 62, direct metal deposit
64, and substrate 66. Nozzle 52 containing laser beam 54, powder
feed channels 56, and shielding gas channels 60 is indicated moving
in the direction of arrow B during a build. Examples of powder
based direct metal deposition known in the art include at least
laser engineered net shaping (LENS), direct metal laser sintering
(DMLS), selected laser melting (SLM), laser powder injection, and
direct metal deposition (DMD). Examples of wire based direct metal
deposition known in the art include at least wire feed laser
deposition, electron beam additive manufacturing (EBAM), hot wire
gas tungsten arc melting (HW-GTAW), and ion fusion formation
(IFF).
[0030] An example of a structural feature added to a spinformed
satellite tank shell is shown in FIG. 4. The feature is a polar
boss formed on a spherical section of a tank. Polar boss feature 70
comprises tank shell 72, transition region 74, and boss (or
locating pin) 76. Prior art methods of forming polar boss 70 would
be to remove materials surrounding the feature by machining an
initial casting or forging (i.e. subtractive manufacture). Cost and
material savings are substantial.
[0031] Another example of a structural feature added to a
spinformed satellite tank is the mounting ring shown in FIG. 5.
According to the invention, the ring can be formed in place by
additive manufacturing. Mounting ring feature 80 comprises tank
shell 82, mounting ring 84, and threaded holes 86 for attaching
external features to tank shell 82. Cost and material savings by
not having to machine mounting ring 80 from a casting or forging
blank are substantial.
[0032] A third example of an external structural feature added to a
spinformed satellite tank shell is a trunnion for supporting the
tank shell shown in FIG. 6. Trunnion feature 90, preferably formed
by additive manufacturing, comprises spinformed tank shell 92, boss
94, and pin 96. Cost and material savings by forming trunnion 90 by
additive manufacturing instead of machining the feature from an
initial casting or forging blank are substantial.
[0033] A fourth example of an external structural feature added to
a spinformed satellite tank shell by additive manufacturing is
shown in FIG. 7. FIG. 7 shows mounting tab feature 100 comprising
spinformed tank shell 102, circumferential rib 104, and mounting
tab 106. The cost and material savings due to forming
circumferential rib 104 and mounting tab 106 by additive
manufacturing instead of machining the feature from a blank forging
or casting are substantial.
[0034] An example of an internal structural feature added to a
spinformed satellite tank shell by additive manufacturing is shown
in FIG. 8A. Propellant management device (PMD) mounting feature 110
comprises tank shell 112 and mounting ring 114. An exemplary PMD is
shown in FIG. 8B. PMD 116 comprises vanes 118 attached to sump
feature 120 for collecting propellant and directing it to a drain
under sump 120. PMD 116 may be mounted on mounting ring 114 by
securing the bottom of sump 120 to mounting ring 114.
[0035] Method 130 of forming structural features on thin wall
metallic satellite tank shells is shown in FIG. 9. The first step
is to procure metal sheet (step 132). Satellite tank shells may be
aluminum, titanium, steel, and alloys thereof. In an embodiment,
the tank shells may be 6061, 2219, and 2014 aluminum alloys and
CPTi, Ti-6Al-4V, Ti-15V-3Cr-3Sn-3Al titanium alloys. Initial
thickness of the metal sheet may be from 0.125 in. (0.318 cm) to
0.5 in. (1.27 cm). The metal sheet may be mounted on a mandrel to
initiate spinforming (step 134). The sheet may then be spinformed
to form a tank shell typically at an elevated temperature (step
136). The spinformed tank shell may then be removed from the
mandrel and the outer surface is stripped using machining or
abrasive removal methods (step 138). The tank shell may then be
mounted in an additive manufacturing (AM) system in preparation for
deposition of metallic structural features on the spinformed tank
shell (step 140). Preferable AM processes for adding structural
features to the tank shell may be powder based and wire based
direct metal deposition. Powder based direct metal deposition
systems for the present invention include, but are not limited to,
laser engineered net shaping (LENS), direct metal laser sintering
(DMLS), selected laser melting (SLM), laser powder injection, and
direct metal deposition (DMD). Wire based direct metal deposition
systems for the present invention include, but are not limited to,
wire feed laser deposition, electron beam additive manufacturing
(EBAM), hot wire gas tungsten arc welding (HW-GTAW), and ion fusion
formation. A preferred direct metal deposition process for the
present invention is wire feed laser deposition. In the next step,
the metallic structural feature is deposited on the tank shell wall
(step 142). As discussed above, metallic structural features of the
invention include, but are not limited to, polar bosses, mounting
rings, trunnions, mounting tabs, and others known and not known in
the art. In the present invention, the structural features may be
added to the outside and inside of the tank shell. In the last
step, the metallic features are machined to final dimensions (step
144).
[0036] FIG. 10 is an illustration of structural feature 150 on
spinformed metallic tank shell 152 formed by wire feed laser
deposition. Both structural feature 130 and spinformed metallic
tank shell 132 are CPTi. The feature is in the form of a ledge or
shelf. Striations on the feature are due to the forming process and
in practice, would be removed when the feature is machined to final
dimensions.
DISCUSSION OF POSSIBLE EMBODIMENTS
[0037] The following are nonexclusive descriptions of possible
embodiments of the present invention.
[0038] A method of forming metallic structural features in a
specific region of a thin wall spinformed metallic tank shell may
include: forming a thin wall metallic tank shell blank by
spinforming a metal sheet over a mandrel; removing the tank shell
blank from the mandrel; mounting the blank in an additive
manufacturing system; and adding the metallic structural features
to the tank shell according to a 3D model stored in memory in the
additive manufacturing system.
[0039] The method of the preceding paragraph can optionally
include, additionally and/or alternatively any, one or more of the
following features, configurations and/or additional
components:
[0040] The thickness of the metal sheet may be from about 0.125 in.
(0.318 cm) to about 0.5 in. (1.27 cm).
[0041] The features may be added outside and inside of the metallic
tank shell.
[0042] The features added to the outside of the tank shell may be
at least one of ribs, bosses, brackets, and shelves.
[0043] The features added to the inside of the tank shell may be at
least one of ribs, shelves, and mounting structures for propellant
management devices (PMD).
[0044] The metallic structural features may be composed of one or
more of aluminum, titanium, steel, and alloys thereof.
[0045] The structural features may be composed of one or more 6061,
2219, 2014 aluminum alloys, and CP Ti, Ti-6Al-4V,
Ti-15V-3Cr-3Sn-3Al titanium alloys.
[0046] The additive manufacturing system may be configured to
perform powder based and wire based direct metal deposition
processes.
[0047] The powder based direct metal deposition may be at least one
of laser engineered net shaping (LENS), direct metal laser
sintering (DMLS), selected laser melting, laser powder injection,
and direct metal deposition (DMD).
[0048] The wire based direct metal deposition may be at least one
of wire feed laser deposition, electron beam additive manufacturing
(EBAM), hot wire gas tungsten arc welding (HW-GTAW), and ion fusion
formation (IFF).
[0049] A thin wall spinformed metallic tank shell may include: a
first region with a first thickness; at least one second region
with a second thickness greater than the first thickness including
structural features formed by an additive manufacturing
process.
[0050] The thin wall spinformed metallic tank shell of the
preceding paragraph can optionally include, additionally and/or
alternatively any, one or more of the following features,
configurations, and/or additional components:
[0051] The structural features may be on the outside or inside of
the tank shell.
[0052] The structural features on the outside of the tank shell may
be at least one of ribs, bosses, brackets, and shelves.
[0053] The structural features on the inside of the tank shell may
be at least one of ribs, shelves, and mounting structures for
propellant management devices (PMD).
[0054] The structural features may be formed from a metal
comprising one or more of aluminum, titanium, steel, and alloys
thereof.
[0055] The metal may be 6061, 2219, 2014 aluminum alloys and CP Ti,
Ti-6Al-4V, Ti-15V-3Cr-3Sn-3Al titanium alloys.
[0056] The additive manufacturing process may be a powder based and
wire based direct metal deposition process.
[0057] The powder based direct metal deposition may include at
least one of laser engineered net shaping (LENS), direct metal
laser sintering (DMLS), selected laser melting, laser powder
injection, and direct metal deposition (DMD).
[0058] The wire based direct metal deposition may include one of
wire feed laser deposition, electron beam additive manufacturing
(EBAM), hot wire gas tungsten arc welding (HW-GTAW), and ion fusion
formation (IFF).
[0059] While the invention has been described with reference to an
exemplary embodiment(s), it will be understood by those skilled in
the art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment(s) disclosed, but that the invention will
include all embodiments falling within the scope of the appended
claims.
* * * * *