U.S. patent application number 16/783541 was filed with the patent office on 2020-06-04 for composite rivet blank and installation thereof.
The applicant listed for this patent is BOMBARDIER INC.. Invention is credited to Didier HOSTE, Louis LABERGE LEBEL, Alain LANDRY, Paul TRUDEAU.
Application Number | 20200171758 16/783541 |
Document ID | / |
Family ID | 52811159 |
Filed Date | 2020-06-04 |
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United States Patent
Application |
20200171758 |
Kind Code |
A1 |
TRUDEAU; Paul ; et
al. |
June 4, 2020 |
COMPOSITE RIVET BLANK AND INSTALLATION THEREOF
Abstract
Composite fasteners, associated blanks and also methods and
apparatus for the installation of such fasteners are disclosed. An
exemplary composite rivet disclosed comprises an elongated body
including braided reinforcement fibers embedded inside the body and
supported in a matrix material. Also disclosed are structural
assemblies comprising composite fasteners and panels or other parts
comprising composite and/or other materials.
Inventors: |
TRUDEAU; Paul; (Guelph,
CA) ; LABERGE LEBEL; Louis; (Montreal, CA) ;
HOSTE; Didier; (Mascouche, CA) ; LANDRY; Alain;
(Beaconsfield, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BOMBARDIER INC. |
Dorval |
|
CA |
|
|
Family ID: |
52811159 |
Appl. No.: |
16/783541 |
Filed: |
February 6, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15123084 |
Sep 1, 2016 |
10589468 |
|
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PCT/IB2015/051651 |
Mar 6, 2015 |
|
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16783541 |
|
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61949449 |
Mar 7, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
B29K 2101/12 20130101;
B29C 70/24 20130101; B29K 2071/00 20130101; B29K 2081/06 20130101;
B29K 2079/085 20130101; B29K 2081/04 20130101; B29K 2077/00
20130101; B29C 66/21 20130101; B29K 2309/08 20130101; B29C 66/71
20130101; B29C 66/81423 20130101; B29C 66/71 20130101; B21J 15/147
20130101; B29C 66/81431 20130101; B29C 65/601 20130101; B29L
2031/3085 20130101; B29L 2031/3082 20130101; B29C 65/32 20130101;
B29C 66/43 20130101; B29C 70/845 20130101; B29L 2031/3002 20130101;
B29C 66/1122 20130101; F16B 19/06 20130101; B29C 66/83221 20130101;
B29C 65/7841 20130101; B29C 66/8242 20130101; B29K 2995/0077
20130101; B29C 66/7212 20130101; B29C 66/71 20130101; F16B 5/00
20130101; B29C 65/18 20130101; F16B 5/04 20130101; B29C 70/462
20130101; B29K 2995/0027 20130101; B29C 65/30 20130101; B29C
66/7212 20130101; B29K 2105/06 20130101; B29L 2031/3088 20130101;
B29C 65/605 20130101; B29C 66/71 20130101; B29C 66/7422 20130101;
B29C 66/721 20130101; B29C 66/71 20130101; B29C 66/81811 20130101;
B29C 66/72141 20130101; B29C 66/8181 20130101; B29C 66/71 20130101;
B29C 66/8223 20130101; B29C 66/81812 20130101; B29K 2307/04
20130101 |
International
Class: |
B29C 65/60 20060101
B29C065/60; B29C 65/18 20060101 B29C065/18; B29C 65/32 20060101
B29C065/32; B29C 65/78 20060101 B29C065/78; B29C 65/00 20060101
B29C065/00; F16B 5/04 20060101 F16B005/04; F16B 19/06 20060101
F16B019/06; B21J 15/14 20060101 B21J015/14; B29C 70/84 20060101
B29C070/84; B29C 70/24 20060101 B29C070/24 |
Claims
1.-45. (canceled)
46. An apparatus for installing a composite rivet, the apparatus
comprising: a first finishing member configured to be positioned on
a first side of a part into which a composite rivet blank has been
inserted and finish a first end of the blank by applying pressure
to the first end of the blank; a second finishing member configured
to be positioned on a second side of a part into which the blank
has been positioned and finish a second end of the blank by
applying pressure to the second end of the blank; and a heating
element configured to heat the blank to a temperature sufficient to
permit thermoforming of the first end and second end of the blank
via the first finishing member and the second finishing member.
47. The apparatus as defined in claim 46, wherein the heating
element is configured to heat the blank when the blank is outside
of the part.
48. The apparatus as defined in claim 46, wherein the heating
element is thermally coupled to at least one of the first finishing
member and the second finishing member to cause heating of the
blank via the at least one of the first finishing member and the
second finishing member.
49. The apparatus as defined in claim 46, wherein at least one of
the first finishing member and second finishing member comprises a
fiber anchoring feature configured to at least partially control
deformation of reinforcement fibers in the blank during
thermoforming of the at least one associated first end and second
end of the blank.
50. The apparatus as defined in claim 49, wherein the fiber
anchoring feature comprises a recess.
51. The apparatus as defined in claim 46, wherein at least one of
the first finishing member and the second finishing member is
thermally coupled to an active cooling device.
52. The apparatus as defined in claim 46, wherein the first
finishing member comprises a ram disposed inside a sleeve where the
sleeve is movable relative to the ram.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This International PCT Patent Application relies for
priority on U.S. Provisional Patent Application Ser. No. 61/949,449
filed on Mar. 7, 2014, the entire content of which is incorporated
herein by reference.
TECHNICAL FIELD
[0002] The disclosure relates generally to composite materials and
more particularly to composite fasteners useful in fastening parts
comprising composite or other materials.
BACKGROUND OF THE ART
[0003] Fiber-reinforced polymeric resin composite materials are
becoming more widely used in aircraft structures due to their
strength to weight characteristics. Current fastening methods for
securing composite parts together can require relatively
complicated tooling and procedures. For example, titanium fasteners
have been used to secure composite parts but such fasteners are
relatively expensive. Also, due to the material and mechanical
properties of composite materials, the use of titanium rivets
requires advanced drilling techniques to avoid or minimize stress
concentrations in the composite parts. Alternatively, the use of
aluminum rivets may not be appropriate for securing parts made of
composite materials due to compatibility issues that may result in
galvanic corrosion between the aluminum and carbon in the composite
material.
[0004] For aircraft applications, the use of electrically
conductive metallic fasteners in composite materials with a very
low electrical conductivity can also cause some concerns associated
with electromagnetic interference (EMI) and lightning strike
protection.
[0005] Improvement is therefore desirable.
SUMMARY
[0006] The disclosure describes composite fasteners, associated
blanks and also methods and apparatus for the installation of such
fasteners. Also disclosed are structural assemblies comprising such
fasteners and panels or other parts comprising composite and/or
other materials. The fasteners and associated blanks disclosed
herein may be used in aircraft, automotive and/or other
applications.
[0007] In one aspect, the disclosure describes a composite rivet
blank where the blank comprises an elongated body having an axis
and a length along the axis where the body comprises braided
reinforcement fibers embedded inside the body and supported in a
matrix material.
[0008] The braided reinforcement fibers may extend the length of
the body.
[0009] The body may have a substantially uniform transverse
cross-section along its length.
[0010] The matrix material may comprise a thermoplastic.
[0011] For example, the matrix material may comprise any one of:
nylon, polyetherimide (PEI), polyethersulfone (PES), polyphenylene
sulfide (PPS), polyetheretherketone (PEEK) and
polyetherketoneketone (PEKK).
[0012] The fibers may comprise carbon.
[0013] The fibers may comprise glass.
[0014] In some embodiments, at least some of the fibers may be
oriented at an inclination angle between 15 degrees and 30 degrees
from the axis of the body.
[0015] In some embodiments, at least some of the fibers may be
oriented at an inclination angle of about 20 degrees.
[0016] The volume fraction of reinforcement fibers in the body may
be between 55% and 63%.
[0017] The volume fraction of reinforcement fibers in the body may
be about 60%.
[0018] The body may comprise one of a pultruded rod and a
compression molded rod.
[0019] The fibers may be arranged in a biaxial braid.
[0020] In another aspect, the disclosure describes a composite
fastener blank. The blank comprises an elongated body having a
longitudinal axis and a length along the axis, the body having a
substantially uniform transverse cross-section along its length,
the body comprising continuous reinforcement fibers embedded inside
the body and extending the length of the body, the reinforcement
fibers being supported in a matrix material and at least part of
the reinforcement fibers within the length of the body extend in a
direction non-parallel to the axis of the body.
[0021] The matrix material may comprise a thermoplastic.
[0022] For example, the matrix material may comprise any one of:
nylon, polyetherimide (PEI), polyethersulfone (PES), polyphenylene
sulfide (PPS), polyetheretherketone (PEEK) and
polyetherketoneketone (PEKK).
[0023] The fibers may comprise carbon.
[0024] The fibers may comprise glass.
[0025] The fibers may be braided.
[0026] The fibers may be arranged in a biaxial braid.
[0027] In some embodiments, at least some of the fibers may be
oriented at an inclination angle between 15 degrees and 30 degrees
from the longitudinal axis of the body.
[0028] In some embodiments, at least some of the fibers may be
oriented at an inclination angle of about 20 degrees.
[0029] The volume fraction of reinforcement fibers in the body may
be between 55% and 63%.
[0030] The volume fraction of reinforcement fibers in the body may
be about 60%.
[0031] The body may comprise one of a pultruded rod and a
compression molded rod.
[0032] In another aspect, the disclosure describes a composite
structural assembly. The structural assembly comprises:
[0033] a first part having a first hole formed therein;
[0034] a second part having a second hole formed therein, the first
part and the second part being positioned relative to each other so
that the first hole is at least partially aligned with the second
hole; and
[0035] a composite rivet securing the first part and the second
part together via the first hole and the second hole, the composite
rivet comprising a body having braided reinforcement fibers
embedded inside the body and supported in a matrix material.
[0036] The rivet may comprise a first finished end engaged with the
first part and a second finished end engaged with the second part,
at least one of the finished ends comprising a fiber anchoring
artifact used to at least partially control the deformation of the
fibers during thermoforming of the at least one of the finished
ends.
[0037] The matrix material may comprise a thermoplastic.
[0038] The fibers may comprise carbon.
[0039] The fibers may comprise glass.
[0040] The fibers may be arranged in a biaxial braid.
[0041] In another aspect, the disclosure describes another
composite structural assembly. The structural assembly
comprises:
[0042] a first part having a first hole formed therein;
[0043] a second part having a second hole formed therein, the first
part and the second part being positioned relative to each other so
that the first hole is at least partially aligned with the second
hole; and
[0044] a composite rivet securing the first part and the second
part together via the first hole and the second hole, the composite
rivet comprising a blank as disclosed herein with a first finished
end engaged with the first part and a second finished end engaged
with the second part.
[0045] In another aspect, the disclosure describes an aircraft
comprising one or more of the structural assemblies disclosed
herein.
[0046] In another aspect, the disclosure describes a composite
rivet. The rivet comprises: a body having braided reinforcement
fibers embedded inside the body and supported in a matrix material,
the body comprising a first finished end for engaging a first part
and a second finished end for engaging a second part.
[0047] In some embodiments, at least one of the finished ends may
comprise a fiber anchoring artifact used to at least partially
control the deformation of the fibers during finishing of the at
least one of the finished ends.
[0048] The matrix material may comprise a thermoplastic.
[0049] The fibers may comprise carbon.
[0050] The fibers may comprise glass.
[0051] The fibers may be arranged in a biaxial braid.
[0052] In another aspect, the disclosure describes a method for
installing a composite rivet. The method comprises:
[0053] inserting a composite rivet blank into a hole in a part;
[0054] after insertion of the blank into the hole: [0055] finishing
a first end of the blank by thermoforming the first end of the
blank; and [0056] finishing a second end of the blank opposite the
first end by thermoforming the second end of the blank.
[0057] Finishing the first end of the blank may comprise anchoring
part of the first end of the blank to at least partially control
the deformation of reinforcement fibers embedded inside the
blank.
[0058] Finishing the second end of the blank may comprise anchoring
part of the second end of the blank to at least partially control
the deformation of the fibers embedded in the blank.
[0059] In some embodiments, the method may comprise heating the
blank, before inserting the blank into the hole, to a temperature
sufficient to permit the finishing of the first end and the second
end.
[0060] In some embodiments, the method may comprise heating the
blank, after inserting the blank into the hole, to a temperature
sufficient to permit the finishing of the first end and the second
end.
[0061] Finishing the second end may comprise deforming the second
end to fill a countersink in the part and finishing the first end
may comprise bucking the first end.
[0062] In a further aspect, the disclosure describes an apparatus
for installing a composite rivet. The apparatus comprises:
[0063] a first finishing member configured to be positioned on a
first side of a part into which a composite rivet blank has been
inserted and finish a first end of the blank by applying pressure
to the first end of the blank;
[0064] a second finishing member configured to be positioned on a
second side of a part into which the blank has been positioned and
finish a second end of the blank by applying pressure to the second
end of the blank; and
[0065] a heating element configured to heat the blank to a
temperature sufficient to permit thermoforming of the first end and
second end of the blank via the first finishing member and the
second finishing member.
[0066] The heating element may be configured to heat the blank when
the blank is outside of the part.
[0067] The heating element may be thermally coupled to at least one
of the first finishing member and the second finishing member to
cause heating of the blank via the at least one of the first
finishing member and the second finishing member.
[0068] In some embodiments, at least one of the first finishing
member and second finishing member may comprise a fiber anchoring
feature configured to at least partially control deformation of
reinforcement fibers in the blank during thermoforming of the at
least one associated first end and second end of the blank.
[0069] The fiber anchoring feature may comprise a recess.
[0070] In some embodiments, at least one of the first finishing
member and the second finishing member is thermally coupled to an
active cooling device.
[0071] The first finishing member may comprise a ram disposed
inside a sleeve where the sleeve is movable relative to the
ram.
[0072] Further details of these and other aspects of the subject
matter of this application will be apparent from the detailed
description and drawings included below.
DESCRIPTION OF THE DRAWINGS
[0073] Reference is now made to the accompanying drawings, in
which:
[0074] FIG. 1A is a schematic perspective view of an exemplary
composite rivet blank;
[0075] FIG. 1B is a schematic representation of an exemplary braid
structure of yarns of reinforcement fibers that may be embedded
inside the blank of FIG. 1A;
[0076] FIG. 2A is a schematic perspective view of an exemplary
braid structure of yarns of reinforcement fibers that may be used
to produce the blank of FIG. 1A;
[0077] FIG. 2B is a schematic perspective view of the braid
structure of FIG. 2A in a compressed state;
[0078] FIG. 3 is a schematic elevation view of another exemplary
braid structure of yarns of reinforcement fibers that may be used
to produce the blank of FIG. 1A;
[0079] FIGS. 4A-4D schematically illustrate an exemplary method for
installing the blank of FIG. 1 using an installation apparatus
according to one embodiment;
[0080] FIGS. 5A-5C schematically illustrate another exemplary
method for installing the blank of FIG. 1 using another
installation apparatus according to another embodiment;
[0081] FIG. 6 is a cross-sectional view of a structural assembly
comprising a rivet formed using the blank of FIG. 1;
[0082] FIG. 7 is a cross-sectional view of finishing members of the
installation apparatus of FIGS. 5A-5C;
[0083] FIG. 8 is a top plan view of another exemplary installation
apparatus according to another embodiment;
[0084] FIGS. 9A-9D schematically illustrate another exemplary
method for installing the blank of FIG. 1 using the installation
apparatus of FIG. 8; and
[0085] FIG. 10 schematically illustrates another exemplary method
for installing the blank of FIG. 1 using different types of
finishing members.
DETAILED DESCRIPTION
[0086] Aspects of various embodiments are described through
reference to the drawings.
[0087] The present disclosure relates to fasteners comprising
composite materials. In various embodiments, the present disclosure
discloses composite fasteners, associated blanks and also methods
and apparatus for the installation of such fasteners. The present
disclosure also discloses structures that incorporate such
composite fasteners. The fasteners and associated blanks disclosed
herein may be used to secure parts together including parts
comprising composite materials. The fasteners and associated blanks
disclosed herein may be used to secure parts together including
parts comprising metallic material(s) (e.g., aluminum). The
fasteners and associated blanks disclosed herein may also be used
in hybrid structures comprising metallic and composite materials.
Accordingly, the fasteners and associated blanks disclosed herein
may be used in aircraft, automotive and/or other applications. In
some embodiments, the fasteners disclosed herein may alleviate, at
least in part, some concerns associated with conventional metallic
fasteners used in composite parts with respect to electromagnetic
interference shielding and electrostatic discharge inside aircraft
and/or galvanic corrosion of dissimilar materials.
[0088] FIG. 1A is a schematic perspective view of an exemplary
composite fastener (e.g., rivet) blank 10 (referred hereinafter as
"blank 10"). As explained further below, blank 10 may be a
precursor to a suitable fastener for securing two or more parts
together. Even though the structure of the fastener obtained from
blank 10 may be different from conventional metallic rivets, the
function of the fastener obtained with blank 10 may, in some
embodiments, have similarities to that of conventional rivets and
accordingly may be referred as a "rivet" in the present
application. However, the term "rivet" is not intended to limit the
structure or function of the fasteners or blanks disclosed
herein.
[0089] Blank 10 may comprise elongated body 12 having longitudinal
axis A and length L. Body 12 may have a generally cylindrical
shape. For example, body 12 may have a generally circular
transverse cross-section but body 12 could also have other
cross-sectional shapes. In various embodiments, body 12 may have a
substantially uniform cross-section along length L but body 12
could also have a cross-sectional shape and/or size that varies
along its length L.
[0090] Body 12 may comprise a consolidation of reinforcement fibers
in the form of yarns 14 embedded in a suitable matrix material 16.
Body 12 may be produced by known or other pultrusion or compression
molding processes or other suitable manufacturing process(es). For
example, a suitable pultrusion process may be used to form a
continuous pultruded rod of desired diameter and structure from
which a plurality of blanks 10 of desired length may be cut.
Alternatively, body 12 may comprise a compression molded rod.
Accordingly, yarns 14 comprising reinforcement fibers may be
embedded inside body 12 and supported by matrix material 16. Matrix
material 16 (e.g., the second phase of blank 10) may serve to hold
the reinforcement fibers together in the desired shape, protect the
reinforcement fibers and distribute loads through the reinforcement
fibers. Ends of yarns 14 are shown at end 12A of blank 10 of FIG.
1A. During the pultrusion process, each yarn 14 brought together to
consolidate blank 10 may comprise a plurality of reinforcement
fibers as well as a plurality of filaments of matrix material 16
that are commingled. Alternatively or in addition, one or more of
yarns 14 may comprise reinforcement fibers that are powder coated
or otherwise impregnated with matrix material 16 prior to being
consolidated. During pultrusion or other consolidation process(es),
matrix material 16 may be at least partially melted and compressed
together with yarns 14 so as to form a consolidated (e.g.,
thermoformed) rod of desired diameter and composition from which
one or more blanks 10 may be cut.
[0091] In various embodiments, matrix material 16 may comprise a
suitable thermoplastic or other thermo-formable material(s). For
example, matrix material 16 may comprise one or more of the
following: Nylon such as polyamide, polyetherimide (PEI),
polyethersulfone (PES), polyphenylene sulfide (PPS),
polyetheretherketone (PEEK) and polyetherketoneketone (PEKK). While
the exemplary embodiments described and shown in the present
disclosure are mainly directed to the use of thermo-formable
materials such as thermoplastics, other types of materials may be
suitable for use as matrix material 16. In some embodiments, matrix
material 16 in blank 10 may, for example, include a thermosetting
material such as a B-staged thermoset resin which may be softened
by the application of heat and formed accordingly during
installation of blank 10. In some embodiments, matrix material 16
may, for example, include an epoxy resin that is curable by
exposure to ultraviolet (UV) light so that an exemplary blank 10
comprising a UV-curable resin may be positioned and shaped as
desired for installation and subsequently cured with the
application of UV light. The use of glass or other material(s) that
is/are at least partially transparent to UV light as a material for
reinforcement fibers used in yarns 14 may facilitate the curing of
a UV-curable matrix material by permitting at least some UV light
to penetrate the matrix material 16 more effectively via the
reinforcement fibers.
[0092] Reinforcement fibers used in yarns 14 may, for example,
comprise any suitable material typically used in the reinforcement
of composite materials or other suitable material. In various
embodiments, reinforcement fibers may comprise inorganic materials
including glass or carbon filaments. For example, reinforcement
fibers may comprise S-2 glass fibers and/or E-glass fibers. Yarns
14 may not necessarily comprise reinforcement fibers of all the
same material. For example, each yarn 14 may comprise reinforcement
fibers of different materials to achieve desired material and
mechanical properties. In some embodiments, different yarns 14 may
comprise reinforcement fibers of different materials. In some
embodiments, the reinforcement fibers may be continuous or be
discontinuous and optionally of different lengths.
[0093] The material of reinforcement fibers, size of reinforcement
fibers, number of reinforcement fibers per yarn 14 and number of
yarns 14 in blank 10 may be selected based on the specific
application and desired properties for the fastener obtained from
blank 10. For example, the specific structure of blank 10 may be
selected based on factors such as size constraints, environmental
and operating conditions, and the types and magnitudes of loads
expected to be supported by the fastener. For example, in some
embodiments, it may be appropriate to use yarns that each have
about 12,000 carbon fibers of 6 .mu.m (0.00024 inch) in diameter.
For example, in order to produce a blank of about 4.75 mm (0.1875
inch) in diameter, 20 yarns of such carbon fibers may be used to
form a pultruded rod from which blank 10 may be cut. Prior to
pultrusion, such yarns 14 may also comprise thermoplastic filaments
of about 20 .mu.m (0.00079 inch) in diameter that are commingled
with the reinforcement fibers so that the thermoplastic may form
matrix material 16 after pultrusion.
[0094] The volume fraction of reinforcement fibers to matrix
material 16 in blank 10 may also be selected based on the specific
application. For example, in some embodiments, the volume fraction
of reinforcement fibers in body 12 may be around 60%. In some
embodiments, the volume fraction of reinforcement fibers in body 12
may be between about 55% and about 63%. In some embodiments, a
suitable range for the volume fraction of reinforcement fibers in
body 12 may be between about 30% and about 70%. In some
embodiments, a suitable range for the volume fraction of
reinforcement fibers in body 12 may be between about 50% and about
60%.
[0095] Yarns 14, and hence reinforcement fibers, may be supported
by matrix material 16 and embedded inside of body 12. Each yarn 14
may comprise a grouping of reinforcement fibers generally following
a common path and extending between first end 12A and second end
12B of body 12. In various embodiments, yarns 14 and hence the
reinforcement fibers may extend continuously along the entire
length L of body 12. Yarns 14 may be disposed at various radial
distances from a core region (e.g., from axis A) of body 12 so that
the reinforcement fibers may be disposed at various positions
throughout the cross-section of body 12. For example, one or more
yarns 14 may be disposed near or at a core region of body and/or
near or at an outer region of body 12. In some embodiments, one or
more of yarns 14 could follow respective paths extending between
diametrically opposed surface portions of blank 10 while crossing
axis A of blank 10. In some embodiments, one or more yarns 14 may
also be disposed near or on an outer surface of body 12. For
example, in addition to or instead of having yarns 14 embedded
inside of body 12, one or more yarns 14 could also be disposed over
(i.e., wrapped around) an outer surface of body 12.
[0096] FIG. 1B is a schematic representation of an exemplary braid
structure 20 of yarns 14 that may be embedded inside blank 10. FIG.
1B may illustrate yarns 14 in region 1B shown in FIG. 1A. In
various embodiments, at least some of yarns 14 may follow a path
where at least part of the path has an orientation that is
non-parallel to axis A of body 12. For example, yarns 14 may extend
between first end 12A of body 12 and second end 12B of body 12 in a
helical manner or along other directions that are divergent from
axis A. In various embodiments, two or more yarns 14 may be braided
together along at least a portion of length L of body 12. For
example, a plurality of yarns 14 may be braided together at a
desired inclination angle (e.g., braid angle) .alpha. that is
measured from axis A. While blank 10 may comprise one or more yarns
14 or portions thereof that are non-parallel to axis A, blank 10
may also comprise one or more yarns 14 that are substantially
parallel to axis A. For example, in some embodiments, blank 10 may
comprise a combination of braided yarns 14 and unidirectional yarns
14.
[0097] The inclination angle .alpha. of yarns 14 may be selected
based on the specific application and loads that the fastener is
expected to withstand. For example, a relatively small inclination
angle .alpha. (e.g., a shown in FIG. 1B) where yarns 14 are closer
to being parallel to axis A may provide a higher tensile strength
and stiffness from the fastener formed from blank 10.
Alternatively, a relatively larger inclination angle (e.g., as
shown in FIG. 2) may provide a higher hoop strength and stiffness
from the fastener formed from blank 10. In some embodiments, blank
10 could comprise a combination of yarns 14 at small inclination
angle(s) and yarns 14 at larger inclination angles depending on the
properties desired. Accordingly, it may be possible to tailor the
mechanical properties of a fastener produced from blank 10 to some
extent by selecting one or more inclination angles for the
reinforcement fibers. For some applications, an inclination angle
of about 20 degrees may be suitable. In some embodiments, one or
more inclination angles between about 15 degrees and about 30
degrees may be suitable. In some embodiments, one or more
inclination angles between about 5 degrees and about 95 degrees may
be suitable.
[0098] FIG. 2A is a schematic perspective view of an exemplary
braid structure 22 of yarns 14 of reinforcement fibers that may be
used to produce blank 10. As shown, braid structure 22 may have a
biaxial and tubular configuration but other known or other types of
braid structures such as one or more tri-axial braids,
3-dimensional braids, unidirectional fibers and/or randomly
oriented fibers could also be used in some applications. For
example, other braid structures resembling a shoe lace or a rope
may be used in some embodiments. Braid structure 22 may be used for
the pultrusion of blank 10 as explained above.
[0099] FIG. 2B is a schematic perspective view of braid structure
22 in a compressed state. Biaxial braids such as shown in FIG. 2A
may be able to deform when they are tensed or compressed along
their length as shown in FIG. 2B without causing significant damage
to the reinforcement fibers. For example, like a Chinese finger
trap, the diameter of braid structure 22 may decrease when braid
structure 22 is tensed or elongated, or, the diameter of braid
structure 22 may increase when braid structure 22 is compressed.
When the diameter of braid structure 22 increases or decreases as
braid structure 22 is tensed or compressed, yarns 14 may rotate at
cross-over points without causing significant buckling of the
reinforcement fibers. In some applications, this phenomenon may be
advantageous because, as explained below, when blank 10 is
installed by being compressed into a hole, the diameter of braid
structure 22 may increase until it becomes in contact with the hole
wall and may also conform to hole features such as a countersink or
other irregularities in the hole. Accordingly, in some
applications, the use of blank 10 may not require the high
precision drilling techniques that can be required when using
titanium rivets. Also, in some applications, the use of blank 10
may not require the use of sealant between the produced rivet and
the part into which the rivet is formed.
[0100] FIG. 3 is a schematic view of another exemplary braid
structure 24 of yarns 14 of reinforcement fibers that may be used
to produce blank 10. Braid structure 24 may be used for the
pultrusion of blank 10 as explained above. Braid structure 24 may
comprise a plurality of nested tubular biaxial braids 24A, 24B and
24C. Other braid structures than those shown herein could be used
for the pultrusion of blank 10. Combinations of different braid
structures could also be used in the same blank 10. For example,
nested (e.g., concentric) braids 24A, 24B and 24C could have the
same or different structural parameters (e.g., size and type of
reinforcement fibers, size and number of yarns, inclination angles,
braiding structures, etc.)
[0101] FIGS. 4A-4D schematically illustrate a method for installing
a composite rivet using blank 10. As mentioned above, blank 10 may
be used to secure two or more parts together. For example, as shown
in FIGS. 4A-4D, blank 10 may be used to secure two overlapping
panels 26, 28 (e.g., lap joint). One or more of panels 26, 28 may
comprise a composite material with which the materials of blank 10
may be compatible. Alternatively or in addition, one or more of
panels 26, 28 may comprise a metallic material such as aluminum.
For example, a blank 10 comprising glass reinforcing fibers may be
suitable for fastening aluminum parts (e.g., aircraft skins)
together. Panels 26, 28 may, for example, comprise aircraft
structural parts such as fuselage or wing components of a
fixed-wing aircraft or a helicopter. However, blank 10 could also
be used to secure other types of parts. In some applications, blank
10 could also be used to at least partially fill a hole in a part
while not necessarily securing two parts together. The composition
of blank 10 may be selected so that it may be compatible with the
materials of panels 26, 28. For example, blank 10 made of composite
materials may be suitable for securing panels 26, 28 comprising the
same or compatible materials so that the risk of galvanic corrosion
may be reduced or avoided.
[0102] As illustrated in FIGS. 4A-4D, a method for installing a
composite rivet using blank 10 may comprise: inserting blank 10
into a hole extending in one or more of panels 26, 28; and, after
insertion of blank 10 into the hole: finishing first end 12A of
blank 10 by thermoforming first end 12A of blank 10; and finishing
second end 12B of blank 10 opposite first end 12A by thermoforming
second end 12B of blank 10. The hole extending in one or more of
panels 26, 28 may be a hole that extends completely through the one
or more panels 26, 28. For example, when blank 10 is used to fill a
hole in a single panel, the hole may extend through the single
panel. Alternatively, when blank 10 is used to secure panel 26 and
panel 28 together, the hole may comprise a first through hole
disposed in panel 26 and a second through hole disposed in panel 28
where the first and second through holes are at least partially
aligned together to permit passage of blank 10 therethrough.
[0103] FIGS. 4A-4D also show apparatus 34 for installing rivet 32
using blank 10. Apparatus 34 may comprise finishing members
including first ram 36 for finishing first end 12A of blank 10 and
second ram 38 for finishing second end 12B of blank 10. While
apparatus 34 shows the use of two rams 36, 38, some embodiments of
apparatus 34 could have only one movable ram 36 and ram 38 could be
replaced with a stationary support member against which blank 10
could be pushed and also having a shape suitable for finishing
second end 12B of blank 10. Rams 36, 38 may each be movably
disposed in respective thermal insulators 40. Thermal insulators 40
may each have an annular shape and comprise a ceramic material or
other suitable material with a relatively low thermal conductivity.
In some embodiments, thermal insulators 40 may have the form of
ceramic bushings. Opposing insulators 40 may be used to apply
pressure on the lap joint between panel 26 and panel 28 during the
installation of blank 10.
[0104] In FIG. 4A, blank 10 has been inserted into holes formed in
panel 26 and also in panel 28. As explained below, blank 10 could
be heated prior to insertion into the holes or could be at ambient
temperature when inserted into the holes. Once inserted, first end
12A and second end 12B of blank 10 may be finished by
thermoforming. For example, both ends 12a and 12B of blank 10 may
be finished substantially simultaneously or one at a time using
first ram 36 and second ram 38 respectively. First and second rams
36, 38 may be used to apply both heat and pressure to first and
second ends 12A, 12B respectively in order to carry out the
thermoforming of blank 10. FIG. 4 shows both first and second rams
36, 38 as being initially at a relatively cold (e.g., ambient)
temperatures.
[0105] In FIG. 4B, pressure may be applied by first ram 36 and
second ram 38 so as to compress blank 10. Heat may also be applied
to first ram 36 and/or second ram 38. The combination of heat and a
compressive force being applied to first end 12A of blank 10 via
first ram 36 may cause softening and/or melting of matrix material
16 of blank 10 and may cause deformation (i.e., thermoforming) of
first end 12A of blank 10. The deformation of first end 12A may
cause first end 12A to conform to the shape of the hole and also to
a first finishing cavity such as a countersink defined by first ram
36, panel 26 and associated insulator 40.
[0106] In FIG. 4C, heat may also be applied to second ram 38 in
order to finish (e.g., buck) second end 12B of blank 10. The
combination of heat and a compressive force being applied to second
end 12B of blank 10 via second ram 38 may cause softening and/or
melting of matrix material 16 of blank 10 and may cause deformation
of second end 12B of blank 10. The deformation (i.e.,
thermoforming) of second end 12B may cause second end 12B to
conform to the shape of the hole and also to a second finishing
cavity defined by second ram 38, panel 28 and associated insulator
40.
[0107] In FIG. 4D, first and second ends 12A, 12B of blank 10 have
been finished (e.g., thermoformed) into first finished end 32A and
second finished end 32B respectively. In other words, blank 10 has
been transformed into composite rivet 32. First finished end 32A
may be engaged with panel 26 and second finished end 32B may be
engaged with panel 28 so as to secure panel 26 and panel 28
together. FIG. 4D also shows both first ram 36 and second ram 38
being cold (i.e., at a temperature lower than that required for
thermoforming of blank 10). For example, one or both of first ram
36 and second ram 38 may be actively cooled in order to remove heat
from composite rivet 32 and accelerate the solidification of
composite rivet 32 after thermoforming. One or both of first ram 36
and second ram 38 may be cooled using a suitable cooling fluid such
as air or other suitable fluid. Once composite rivet 32 has cooled
to a desired temperature or solidification state, ram 36,
insulators 40 and ram 38 may be removed from panels 26 and 28 and
apparatus 34 may be moved to another location to re-start the
process of installing another composite rivet 32 using another
blank 10.
[0108] FIGS. 5A-5C schematically illustrate another exemplary
method for installing blank 10 using another installation apparatus
42. Apparatus 34 of FIGS. 4A-4D and apparatus 42 of FIGS. 5A-5C may
share some similarities so like elements have been identified using
like reference numerals in the present disclosure. Using apparatus
42, blank 10 may be heated while outside of panels 26 and 28 prior
to being inserted into first hole 26A and second hole 28A formed in
panel 26 and panel 28 respectively. The heating of blank 10 while
outside of panels 26 and 28 may limit an amount of heat transferred
to panels 26 and 28. Accordingly, apparatus 42 may comprise heater
44 disposed inside of insulator 40. Heater 44 may comprise an
electric heater having an annular configuration and suitable for
heating blank 10 to a temperature permitting thermoforming of blank
10. For example, heater 44 may comprise an electric resistance
heater or be part of an induction heating unit. Insulator 40 may
prevent some of the heat from heater 44 from getting transferred
into panel 26. Apparatus 42 may also comprise first ram 36 for
pushing blank 10 into holes 26A, 28A after blank 10 has been heated
to a temperature suitable for thermoforming. Instead of second ram
38 of apparatus 34, apparatus 42 may comprise stationary support
member 46 which may have a function analogous to a bucking bar for
finishing second end 12B of blank 10. Apparatus 42 may also
comprise forming ring 48 that may be in direct contact with panel
26 and may assist in finishing (e.g., thermoforming) first end 12A
of blank 10. One or more suitable cooling devices 50 may be
thermally coupled to first ram 36 and support member 46.
Alternatively, a common cooling device 50 may be thermally coupled
to both first ram 36 and support member 46.
[0109] FIG. 5A shows ram 36 being retracted and blank 10 being
heated by heater 44 prior to insertion into holes 26A, 28A through
panel 26 and panel 28.
[0110] FIG. 5B shows ram 36 being advanced toward support member 46
and exerting a downward force on blank 10 to thereby cause
deformation of blank 10, which has been heated to a temperature to
permit thermoforming. Under the pressure exerted by ram 36, blank
10 may deform and fill the cavity defined by hole 28A and support
member 46 in order to form second finished end 32B of composite
rivet 32 (shown in FIGS. 5C and 6). As shown in FIG. 5B, hole 28A
may comprise a countersink which may get filled by blank 10. Blank
10 may also deform outwardly to fill holes 26A and 28A.
[0111] FIG. 5C illustrates the forming of first finished end 32A of
composite rivet 32. Once second finished end 32B has been formed,
insulator 40 may be retracted (i.e., raised) by some distance so
that ram 36, insulator 40, panel 26 and forming ring 48 may define
a cavity which may be filled by blank 10 while ram 36 applies
pressure on blank 10. Accordingly, pressure exerted by ram 36 may
be maintained while insulator 40 is partially retracted so that the
defined cavity may be filled in order to form first finished end
32A of composite rivet 32. For example, even though insulator 40
may be retracted, pressure on panels 26 and 28 may still be
maintained via support member 46 and forming ring 48. Accordingly,
in some embodiments, there may always be a pressure exerted on the
lap joint between panels 26 and 28 throughout the process of
installing rivet 32. Cooling device(s) 50 may draw heat from ram 36
and support member 46 in order to promote cooling and
solidification of composite rivet 32. Once composite rivet 32 has
cooled to a desired temperature or solidification state, ram 36,
insulator 40, forming ring 48 and support member 46 may be removed
from panels 26 and 28 and apparatus 42 may be moved to another
location to re-start the process of installing another composite
rivet 32 using another blank 10.
[0112] FIG. 6 is a cross-sectional view of structural assembly 30.
For example, structural assembly 30 may comprise, panel 26 having a
first hole formed therein; panel 28 having a second hole formed
therein; and composite rivet 32 (i.e., formed from blank 10)
securing panel 26 and panel 28 together via the first hole and the
second hole. Panel 26 and panel 28 may be positioned relative to
each other so that the first hole is at least partially aligned
with the second hole. Also composite rivet 32 may comprise a body
having braided reinforcement fibers embedded in the body and
supported in a matrix material 16 as described above. Composite
rivet 32 may also comprise first finished end 32A engaged with
panel 26 and second finished end 32B engaged with panel 28. In some
embodiments, at least one of finished ends 32A, 32B may comprise
fiber anchoring artifact 52 which, as explained below, may be used
to at least partially control the deformation of the reinforcement
fibers inside of composite rivet 32 during thermoforming of the at
least one of the finished ends 32A, 32B. As shown in FIG. 6, fiber
anchoring artifacts 52 may comprise a protrusion extending from
each of first finished end 32A and second finished end 32B but
other configurations of fiber anchoring artifacts 52 may also be
suitable.
[0113] FIG. 7 is a cross-sectional view of finishing members of
installation apparatus 42 without showing structural assembly 30
therebetween. The relative positions of ram 36, insulator 40 and
support member 46 correspond to those shown in FIG. 5C during the
thermoforming of first finished end 32A. As shown in FIG. 7, the
lower extremity of ram 36 is at distance T above the lower
extremity of insulator 40 when blank 10 is thermoformed and first
finished end 32A of composite rivet 32 is formed. The recess
defined by the distance T between ram 36 and the lower end of
insulator 40 serves as a fiber anchoring feature 54 in order to at
least partially control the deformation of reinforcement fibers
embedded inside of blank 10 during the thermoforming of blank 10. A
similar fiber anchoring feature 54 (e.g., recess) may also be
defined in support member 46. The presence of fiber anchoring
features 54 may result in corresponding fiber anchoring artifacts
52 being formed on first finished end 32A and on second finished
end 32B of composite rivet 32.
[0114] During the compression of blank 10 and the thermoforming of
first finished end 32A and second finished end 32B, fiber anchoring
features 54 may receive and at least partially anchor the ends of
yarns 14 and prevent the ends of yarns 14 from being deflected in
random and unpredictable directions, which could otherwise occur if
finishing members (e.g., ram 36, insulating member 40 and support
member 46) did not provide any form of anchoring or guidance of the
reinforcement fibers during thermoforming. In some embodiments, the
use of fiber anchoring features 54 may provide some control over
the deformation of the reinforcement fibers especially in first and
second finished ends 32A, 32B and thereby improves the
repeatability and predictability of the thermoforming and also of
the mechanical properties of composite rivet 32.
[0115] FIG. 8 is a top plan view of another exemplary installation
apparatus 60 according to another embodiment. Apparatus 60 and
apparatus 34 and 42 described above may share some similarities so
like elements have been identified using like reference numerals in
the present disclosure. Apparatus 34, 42 and 60 or parts thereof
may be supported by one or more operators during operation or could
be supported by suitable structure (e.g., jig). Apparatus 60 may
comprise first frame 62 that may be configured to be positioned on
a first side of structural assembly 30, and, second frame 64 that
may be configured to be positioned on a second (e.g., opposite)
side of structural assembly 30. First frame 62 and second frame 64
may be urged toward one another via one or more clamps 66 or other
suitable structure or operator(s) of apparatus 60. The urging of
first frame 62 and second frame 64 towards each other may cause a
compressive force to be exerted on structural assembly 30 via
insulators 40 disposed on opposite sides of structural assembly
30.
[0116] Second ram 38 may be associated with and supported by second
frame 64 and may be configured to be actuated via wheel 68. The
turning of wheel 68 may cause advancement and retraction of second
ram 38 via suitable threaded engagement (not shown). The use of
wheel 68 to actuate second ram 38 may provide suitable position
control of second ram 38. Other means of actuation of second ram 38
may be used to control the position of second ram 38. Heater 44 may
also be associated with second frame 64 so that blank 10 may be
heated by heater 44 prior to insertion into holes formed in panels
26, 28 of structural assembly 30.
[0117] First ram 36 may be associated with and supported by first
frame 62 and may be configured to be actuated via actuator 70. For
example, first ram 36 may be coupled to actuator 70 via one or more
set screws. Actuator 70 may comprise one or more pneumatic
cylinders or other hydraulic actuator(s) configured to maintain a
desired force applied by first ram 36 and thereby maintain a
desired pressure on blank 10 during installation of blank 10. Other
means of actuation could be used to control the force applied by
first ram 36. Accordingly, in some embodiments, second ram 38 may
be position-controlled and first ram 36 may be
force-controlled.
[0118] First ram 36 may be disposed inside of sleeve 72. Sleeve 72
may be movable relative to first ram 36 and also movable relative
to insulator 40. Sleeve 72 may extend into associated insulator 40
and also be coupled to or uncoupled from locking plate 74. Sleeve
72 may be rotatable about its longitudinal axis using handle 76 in
order to either lock sleeve 72 with locking plate 74 or unlock
sleeve 72 from locking plate 74. For example, locking plate 74 may
be rigidly fastened to frame 62 via suitable fasteners or be
integral to first frame 62. Locking plate 74 may also comprise a
locking feature which may be used to lock sleeve 72 in its first
(i.e., locked) position as shown in FIGS. 9A and 9B. For example,
the locking feature on locking plate 74 may cooperate with a
corresponding locking feature on sleeve 72 in order to prevent
retraction of sleeve 72 when sleeve 72 is at a first orientation
(e.g., when handle 76 is lowered as shown in FIGS. 9A and 9B) and
permit retraction of sleeve 72 when sleeve 72 is at a second
orientation (e.g., when handle 76 is raised as shown in FIGS. 9C
and 9D). Any other suitable structure secured to or integral with
frame 62 could be used to lock and unlock sleeve 72.
[0119] Accordingly sleeve 72 may be movable relative to first ram
36 via handle 76. Also, during initial advancement of first ram 36
toward structural assembly 30 via actuator 70, first ram 36 may be
advanced relative to sleeve 72 until pusher 80 makes contact with
catch 82. Pusher 80 may be secured to actuator 70 and be advanced
together with first ram 36. Catch 82 may be secured to or integral
with sleeve 72. For example, catch 82 may comprise a portion of
sleeve 72 having an increased outer diameter. Accordingly, once
pusher 80 makes contact with catch 82 advancement force from
actuator 70 may be transmitted to both first ram 36 and sleeve 72
so that first ram 36 and sleeve 72 may be urged toward structural
assembly 30 and cooperate in the thermoforming of blank 10.
[0120] Spring 84 may be disposed between catch 82 and bushing 78.
Accordingly, when actuator 70 urges sleeve 72 toward structural
assembly 30 via pusher 80 and catch 82, actuator 70 may also cause
compression of spring 84. However, when sleeve 72 is rotated to its
second (i.e., unlocked) position by the raising of handle 76,
spring 84 may assist the retraction of sleeve 72 by urging (catch
82 of) sleeve 72 away from structural assembly 30 in the absence of
a counteracting force being exerted on catch 82 by actuator 70 via
pusher 80.
[0121] First fitting 86 may be secured to first frame 62 to permit
the introduction of a cooling fluid such as air inside first frame
62 to actively cool first ram 36 and sleeve 72. Similarly, second
fitting 88 may be secured to second frame 64 to permit the
introduction of a cooling fluid such as air inside second frame 64
to actively cool second ram 38 and heater 44.
[0122] FIGS. 9A-9D schematically illustrate another exemplary
method for installing blank 10 using installation apparatus 60.
Steps of installing blank 10 are sequentially shown in FIGS. 9A-9D.
FIGS. 9A-9D only show portions of apparatus 60 near panels 26 and
28 to illustrate the installation of blank 10. Using apparatus 60,
blank 10 may be heated while outside of panels 26 and 28 prior to
being inserted in panels 26 and 28. Accordingly, blank 10 may be
heated by heater 44 while second ram 38 is retracted. Once blank 10
has been heated to a temperature suitable for thermoforming, second
ram 38 may be advanced so as to push blank 10 through the holes
formed in panels 26 and 28 as shown in FIG. 9A while relatively
little to no pressure is applied by first ram 36 and first ram 36
is therefore permitted to retract to accommodate the insertion of
blank 10. In some embodiments, first ram 36 may already be
retracted when blank 10 is initially inserted through panels 26 and
28.
[0123] FIG. 9A shows second ram 38 in a fully extended position. As
explained above in relation to apparatus 42, second ram 38 may be
positioned at a distance short of the surface of insulator 40 which
is in contact with panel 28 so as to define a recess that may serve
as a fiber anchoring feature (similar to feature 54 shown in FIG.
7). At this stage, sleeve 72 may be in its first (i.e., locked)
position and fully extended against panel 26 as indicated by the
lowered position of handle 76.
[0124] FIG. 9B shows the finishing of second finished end 32B of
composite rivet 32. While blank 10 is still at a temperature
suitable for thermoforming, second ram 38 is in its extended
position and sleeve 72 is in its fully extended position against
panel 26, first ram 36 may be extended by the application of a
suitable force by actuator 70. The extension of first ram 36 may
cause the blank 10 to fill the cavity (e.g., countersink) defined
by panel 28, second ram 38 and associated insulator 40 and thereby
produce second finished end 32B of composite rivet 32.
[0125] FIG. 9C shows the unlocking and retraction of sleeve 72 away
from panel 26 after second finished end 32B has been thermoformed
and in preparation for the finishing of first finished end 32A
shown in FIG. 9D. The retraction of sleeve 72 may be achieved by
rotating sleeve 72 to its second (i.e., unlocked) position by
raising handle 76 and then manually retracting sleeve 72 away from
panel 26 via handle 76. The rotation and retraction of sleeve 72
could be conducted manually by an operator or a suitable actuator
could be provided as part of apparatus 60 to conduct the rotation
and retraction of sleeve 72.
[0126] FIG. 9D shows the forming of composite rivet 32 by producing
(e.g., bucking) first finished end 32A. As explained above, during
the final portion of the stroke of first ram 36, both sleeve 72 and
first ram 36 are advanced together by actuator 70. As shown in FIG.
9D, the leading end of first ram 36 may be behind the leading end
of sleeve 72 so that a fiber anchoring feature (e.g., such recess
54 shown in FIG. 7) may be produced. The pressure applied to blank
10 by first ram 36 and sleeve 72 may cause blank 10 to fill the
cavity defined by first ram 36, sleeve 72, panel 26 and associated
insulator 40 in order to produce first finished end 32A of
composite rivet 32. Once first finished end 32A has been produced,
portions of apparatus 60 may be actively cooled to accelerate the
cooling and solidification of composite rivet 32. For example, a
source of air or other cooling fluid may be used to actively cool
first ram 36, sleeve 72, second ram 38 and heater 44. Once
composite rivet 32 has cooled to a desired temperature or
solidification state, apparatus 60 may be moved to another location
to re-start the process of installing another composite rivet 32
using another blank 10 on the same panels 26 and 28 or on different
parts.
[0127] FIG. 10 schematically illustrates another exemplary method
for installing blank 10 using different types of end finishing
members. FIG. 10 illustrates different stages of installation from
left to right of FIG. 10. Starting on the left of FIG. 10, blank 10
may be inserted through first hole 26A formed in panel 26 and
second hole 28A formed in panel 28A. Then, first and second rams
36, 38 (i.e., end finishing members) may be used to compress blank
10 into holes 26A and 28A and produce finished ends 32A and 32B of
composite rivet 32. One or both of first and second rams 36, 38 may
be heated in order to cause thermoforming of blank 10.
Alternatively or in addition, blank 10 may be heated to a suitable
thermoforming temperature prior to being inserted into holes 26A
and 28A. One or both of first and second rams 36, 38 may have a
hemispherical shape so as to produce corresponding hemispherical
finished ends 32A and 32B on composite rivet 32. On the right side
of FIG. 10, another embodiment of first ram 36 is shown as having a
flat face for compressing blank 10 into a countersink formed in
panel 26. In any case, first finished end 32A may be engaged with
panel 26 and second finished end 32B may be engaged with panel
28.
[0128] The above description is meant to be exemplary only, and one
skilled in the relevant arts will recognize that changes may be
made to the embodiments described without departing from the scope
of the invention disclosed. The present disclosure may be embodied
in other specific forms without departing from the subject matter
of the claims. Also, while the blanks, fasteners, assemblies,
apparatus and methods disclosed and shown herein may comprise a
specific number of elements or steps, the blanks, fasteners,
assemblies, apparatus and methods could be modified to include
additional or fewer of such elements or steps. The present
disclosure is also intended to cover and embrace all suitable
changes in technology. Modifications which fall within the scope of
the present invention will be apparent to those skilled in the art,
in light of a review of this disclosure, and such modifications are
intended to fall within the appended claims.
* * * * *