Note: Descriptions are shown in the official language in which they were submitted.
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INVENTORS: JEFF BUSBY, MATT BOYD, DAVID SCHMIDT
TITLE: A SPACER AND GASKET ASSEMBLY FOR USE ON AN AIRCRAFT
ASSIGNEE: AVIATION DEVICES & ELECTRONIC COMPONENTS, L.L.C.
This continuation-in-part application claims priority to, benefit of, and
incorporates
herein by reference, US Patent Application Serial No. 14/264,216, filed
4/29/2014; which
claims the benefit of US Patent Application Serial No. 13/793,533, filed
3/11/2013; and
US Provisional Application Serial No. 61/669,957, filed 7/10/2012. All of the
foregoing
are incorporated by reference.
FIELD OF THE INVENTION
[01] Multi-component aircraft assemblies and, more particularly, to a
spacer and gasket
assembly for an interposition under compression between a static structure of
an aircraft
and a removable structure of an aircraft.
BACKGROUND OF THE INVENTION
[02] The use of gaskets for environmental sealing in aircraft, especially
the outside of an
aircraft, has some unique challenges. In its lifetime, an aircraft will
undergo environmental
extremes, pressures ranging from those typically found at sea level to the
extremely air
pressures found at 40,000-50,000 feet. Temperature ranges are also subject to
extremes,
as are humidity conditions and pressure differentials across a gasket.
[03] Given such a radical and extreme environment, environmental seals,
such as
gaskets and gasket assemblies, especially those adapted for use on an aircraft
exterior,
must often have unique properties. Furthermore, the gaskets sometimes must be
adapted
to be conductive or nonconductive between the pieces that they join, depending
upon their
application. Furthermore, potential reactivity with the aircraft structures to
which they
engage is yet another consideration.
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SUMMARY OF THE INVENTIONS
[04] In one embodiment, a spacer and gasket assembly for receipt between a
static
structure having an outer and inner surface and fastener holes therethrough
and a
removable structure having a base with fastener holes and an upper surface and
a lower
surface, the static structure and removable structure typically being engaged
through a
multiplicity of fasteners adapted to apply a compression on the gasket between
the static
structure and the removable structure, the spacer and gasket assembly. The
assembly
comprises a substantially non-compressible spacer adapted for receipt between
the static
structure, and the removable structure having a spacer thickness; and a
compressible
gasket having a sticky, deformable, flowable (under compression) elastomeric
body
(sometimes a gel) and a skeleton, substantially enclosed with the body. The
spacer and the
gasket are placed between the static structure and the removable structure and
the
fasteners torqued to a preselected value or until the spacer "bottoms" out
against the
skeleton and the faying surfaces of the static and removable structures, where
a spike in
torque resistance will be encountered.
[05] A spacer and gasket assembly for receipt between a static structure
having a
surface and fastener holes therethrough and a removable structure having a
surface with
fastener holes, the spacer and gasket assembly comprising: a substantially non-
compressible spacer having a spacer thickness; and a gasket having a sticky,
deformable,
pliable, elastomeric body, the gasket having an uncompressed gasket thickness
greater
than the spacer thickness; and a multiplicity of fasteners having a shaft with
a shaft
diameter, the fasteners adapted to apply a compression on the spacer and the
gasket
between the static structure and the removable structure; wherein a sticky,
elastomeric gel,
applied at the time the fasteners are entrained, coats at least part of some
of the multiplicity
of fasteners.
[06] In one embodiment of the invention set forth in the preceding
paragraph, the gasket
includes a skeleton and the spacer and the gasket are stacked such that upon
compression,
the spacer is encapsulated in the elastomeric body. The gasket may include a
skeleton and
the spacer and the gasket may be placed side-by-side. The body of the gasket
may be
comprised of a cured polyurethane and may be tabular shape. The gasket may
include
fastener holes. It's compressed thickness is typically, in one embodiment,
about 40 to 80%
of its uncompressed thickness.
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[07] A spacer and gasket assembly for receipt between a static structure
having a
surface and fastener holes therethrough and a removable structure having a
surface with
fastener holes, the static structure and removable structure being engaged
through a
multiplicity of fasteners, the fasteners adapted to apply a compression
between the static
structure and the removable structure, the static structure and the removeable
structure
having opposed, generally flat, facing surfaces, the spacer and gasket
assembly
comprising: a substantially non-compressible spacer adapted for receipt
between the static
structure and the removable structure, the spacer having a spacer thickness;
and a gasket
having a sticky, deformable, pliable, elastomeric body without a skeleton, the
gasket having
an uncompressed gasket thickness; wherein spacer and the gasket are adapted to
be
placed under compression between the facing surfaces of the static structure
and the
removable structure.
[08] A spacer and gasket assembly for receipt between a static structure
having a
surface and fastener holes therethrough and a removable structure having a
surface with
fastener holes, the static structure and removable structure being engaged
through a
multiplicity of fasteners, the fasteners adapted to apply a compression on the
gasket
between the static structure and the removable structure, the static structure
and the
removable structure having opposed, generally flat, facing surfaces, the
spacer and gasket
assembly comprising: a substantially non-compressible spacer adapted for
receipt between
the static structure and the removable structure, the spacer having a spacer
thickness; and
a gasket having a sticky, deformable, pliable, elastomeric body with an
embedded skeleton,
the gasket having an uncompressed gasket thickness; wherein spacer and the
gasket are
adapted to be placed under compression between the facing surfaces of the
static structure
and the removable structure; and wherein the gasket is a tape.
[09] The tape of the invention of the preceding paragraph may include, in one
embodiment, a skin on one of an upper or lower surface thereof. The
elastomeric body may
be a gel. The gasket may include cutouts and the cutouts may have spacing that
matches a
spacing of the fastener holes of the removable structure. The cutouts may
extend through
the skeleton of the gasket so as to receive the spacer under compression
without
compressing the skeleton. The cutouts may extend through the skin. The spacers
may be
washers and may be located around at least some of the fastener holes.
[10] A gasket for use between a first and a second part, the parts having
facing surfaces
under compression with multiple fasteners having multiple fastener holes, the
fastener holes
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having a fastener hole spacing, wherein at least one of the parts has spacers
on a facing
wall thereof, integral with the part and around at least some of the fastener
holes, the gasket
comprising: a tape having a sticky, pliable, elastomeric body, the tape for
placement
between the facing surfaces under compression.
[11] The tape of the invention of the preceding paragraph may include a
skeleton
encapsulated in the body. The tape may have multiple cutouts and they may
extend
through the skeleton and may have a spacing matching the fastener spacing. The
tape may
have a skin on the upper or lower surface thereof. In one embodiment, the
first and second
parts are an aircraft floorboard and a support member for receiving the
aircraft floorboard.
The spacers may be integral with the facing wall of the floorboard and the
skin may contact
the support member.
[12] A spacer and gasket assembly for receipt between a static structure
having a
surface and fastener holes therethrough and a removable structure having a
perimeter
shape with fastener holes and a surface: a substantially non-compressible
spacer
comprising linear members conforming to the perimeter shape of the removable
structure,
adapted for receipt between the static structure and the removable structure
the spacer
having a spacer thickness; and a gasket having a sticky, deformable,
elastomeric body, the
gasket having an uncompressed gasket thickness greater than the spacer
thickness;
wherein the gasket and spacer are dimensioned for receipt between the static
and
removable structure, and wherein the spacer is dimensioned for embedment into
the body
of the gasket.
[13] The gasket a set forth in the preceding paragraph may have a skeleton
which may
be made of cured polyurethane gel and may be tabular.
[14] A spacer and gasket assembly for receipt between a static structure
having a
surface and fastener holes therethrough and a removable structure having a
surface and
fastener holes and with a multiplicity of fasteners engaging the two
structures under
compression: a gasket having a sticky, deformable, elastomeric body, the
gasket having an
uncompressed gasket thickness; a multiplicity of substantially non-
compressible, discreet,
cylindrical shaped spacers dimensioned for receipt between the static
structure and the
removable structure and proximate the fastener holes, the spacer having a
spacer thickness
thinner than the gasket; and wherein spacer and the gasket are dimensioned to
be placed
substantially between the surfaces of the static structure and the removable
structure.
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[15] The gasket of the preceding paragraph may include a skeleton and the
spacer and
the gasket may be stacked or side-by-side. The body may be comprised of cured
polyurethane gel and may be tabular.
[16] A spacer and gasket assembly for receipt between a metallic static
structure having
a surface and fastener holes therethrough and a metallic removable structure
having a
surface with fastener holes, and a multiplicity of fasteners, the fasteners to
apply a
compression between the static structure and the removable structure, the
static structure
and the removable structure having opposed, typically flat, facing surfaces; a
substantially
non-compressible metallic spacer adapted for receipt between the static
structure and the
removable structure having a spacer thickness; and a gasket having a sticky,
deformable,
elastomeric body, and a metallic skeleton embedded therein, the gasket having
an
uncompressed gasket thickness greater than the spacer thickness; wherein
spacer and the
gasket are adapted to be placed substantially between the facing surfaces of
the static
structure and the removable structure, under compression.
[17] The spacer and the gasket described in the preceding paragraph may be
stacked or
side-by-side. The body may be made of cured polyurethane gel and may be
tabular. The
fastener holes may be a diameter that is about equal to a greater than the
shaft diameter of
the fasteners.
[18] A floorboard and support member assembly comprising: a floorboard with an
upper
surface and an at least partly flat lower surface; a support member having a
flat upper
surface for receiving the lower surface of the floorboard; wherein the
floorboard and the
support surface have multiple fastener holes, the fastener holes of each
having matching
spacing for alignment of the floorboard with the support surface; a gasket
tape having a
sticky, deformable, pliable body and a skeleton; and, multiple discreet
spacers; wherein the
floorboard and support member hold the gasket tape and spacers under
compression
therebetween through the use of multiple fasteners engaging the floorboard and
support
member.
[19] The floorboard and support member assembly of the preceding paragraph may
include multiple discrete spacers integral with the floorboard lower surface.
The spacers
may be multiple discrete spacers, which may or may not surround the holes of
the
floorboard. The gasket tape may include the skin on one surface thereof and
the skin may
be against the body of the gasket and against the support member upper surface
when the
floorboard and support members under compression. The tape may have holes cut
through
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the skeleton and at least partly into the body of the gasket, the holes
dimension for receipt
of the spacers. The spacers may or may not be integral with floorboard or
support surface.
[20] A method of assembling a floor of an aircraft having multiple floor
supporting
members, the floor supporting members having a flat upper surface with
multiple fastener
holes therethrough, the method comprising the steps of: providing multiple
floorboards,
each with a flat underside and multiple fastener holes therethrough, the holes
having a hole
spacing matching a hole spacing of the floor supporting members; providing a
tape having a
sticky, pliable, elastomeric body, a skeleton and a skin on one of an upper or
lower surface
of the body, the tape having a tape thickness; providing multiple spacers, the
spacers
having a spacer thickness that is less than the tape thickness of the body of
the tape;
placing the tape and fasteners between the floorboards and the support member
such that
the fastener holes of each align; inserting fasteners through the fastener
holes; and
torqueing down the fasteners until a spike in torque resistance is
encountered.
BRIEF DESCRIPTION OF THE DRAWINGS
[21] Fig. 1 is an exploded perspective view of Applicants' spacer and
gasket assembly as
used on an aircraft between a static structure and a removable structure.
[22] Fig. 1A is a perspective view of a washer for use with the present
invention.
[23] Figs. 2 and 3 are cross-sectional views of Applicants' spacer and
gasket assembly
between a removable structure and a static structure on an aircraft body; Fig.
2 before
compression; Fig. 3 after compression.
[24] Figs. 4 and 5 are alternate preferred embodiments of Applicants'
spacer and gasket
assembly.
[25] Figs. 6, 7, and 8 are exploded perspective and side elevation cross-
sections of an
alternate preferred embodiment of Applicants' spacer and gasket assembly. Fig.
7 before
compression; Fig. 8 following compression.
[26] Figs. 9A, 98, and 9C illustrate cross-sections of the stacked washer
in cross-
sectional side view, uncompressed, partially compressed, fully compressed.
[27] Fig. 10 illustrates a cross-sectional view of a procedure for
installing any of the
embodiments of Applicant's spacer and gasket assembly, wherein a wet seal of
uncured
polyurethane gel mix is applied on or about the fastener or fastener hole
junction prior to
installation of the fastener through the workpiece into the static structure.
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[28] Figs. 11A and 11B illustrate in perspective views, a spacer and gasket
assembly in
which the spacers are embedded in the body of the gasket, such that the
assembly is a
unitary one-piece assembly.
[29] Figs. 12A and 12B are top and side views of another embodiment of the
spacer and
gasket assembly.
[30] Figs. 13A and 13B are top and side views of another embodiment of the
spacer and
gasket assembly.
[31] Fig. 14 is a top view of another embodiment of the spacer and gasket
assembly.
[32] Figs. 15A, 15B, and 15C illustrate an alternate preferred embodiment
of a parts
assembly using a spacer and gasket assembly.
[33] Figs. 16A, 16B, and 16C illustrate an additional alternate preferred
embodiment of a
parts assembly using a spacer and gasket assembly.
[34] Figs. 17A and 17B include an alternate embodiment of a spacer and gasket
assembly for use with a floorboard assembly.
[35] Fig. 18 is an alternate embodiment of an integral spacer.
[36] Fig. 19A and 19B illustrate a preferred embodiment of a spacer and
gasket
assembly used with a floorboard assembly.
[37] Fig. 20 is a method of assembly a floorboard assembly.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[38] Figs. 1-5 illustrate an embodiment of Applicants' spacer and gasket
assembly 10,
seen in an embodiment to include a spacer 12 or other mechanical stop, such as
a washer,
and a gasket 14 for interposition in a stacked or side-by-side arrangement
between a
removable workpiece 28 and a static structure 30.
[39] A multiplicity of fasteners 32 may be provided for engaging the removable
workpiece
28 and static structure 30, the fasteners typically including a shaft 34 with
a threaded portion
thereon, the shaft having a head 36 at one end, such as a hex head, for
engaging a drive
tool, such as a torque wrench. Shaft 34 is adapted to engage a nut 38, such as
a blind nut
or captured nut 38, as illustrated in Fig. 1, the nut typically part of the
static structure.
[40] Removable workpiece 28 may, in one embodiment (see Fig. 1), be an
aircraft
antenna for removable receipt against a gasket 14 and a spacer 12 for
attachment to static
structure 30 which, in a preferred embodiment, may be the outer fuselage of an
aircraft
body. Thus, a parts assembly is disclosed, the various parts for use with
Applicant's various
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embodiments of Applicant's spacer and gasket assembly. Removable workpiece 28
may
include a base 40, which may be tabular, with a flat upper surface 40a and a
flat lower
surface 40b. Lower surface 40b may be planer or slightly curved and may
conform in shape
to outer surface 30a of static structure 30. For example, if outer surface 30a
is flat, lower
surface 40b may be adapted to conform to the flat outer surface 30a of the
static structure
and may be flat also. If there is a slight curve to outer surface 30a, lower
surface 40b may
match the curve of outer surface 30a of the static structure.
[41] Removable workpiece 28 may include an extended member 42, such as the fin
of an
antenna, the antenna for receipt or transmission of RF or other signals from
an aircraft.
Removable workpiece 28 may also include a multiplicity of fastener receiving
holes 44, the
holes with a diameter of Wpd (workpiece diameter). Moreover, the removable
workpiece
may have an outer perimeter 46.
[42] Static structure 30 may include an access port 48, such as in one
embodiment, an
access port 48 for electrically conductive cables engaging an antenna
electrically to the
interior of an aircraft. Outer surface 30a may represent the skin of an
aircraft and inner
surface 30b may represent the underside thereof. Fastener holes 50 may be
provided in
the static structure for receipt of fasteners 32 therethrough, the fastener
holes having a
diameter of Shd, which is typically equal to diameter Wphd, which is, just
slightly larger than
the diameter of the shaft of the fastener that is carried in holes 44/50.
[43] Gasket 14 may include a body 16 of any suitable compressible and
deformable
medium, and, in one embodiment, a skeleton 18, the skeleton may be
electrically
conductive or non-conductive and may be woven or non-woven and, in one
embodiment,
may be woven fiberglass (i.e., non-conductive) and in another embodiment may
be woven
aluminum wire (or other suitable electrical conductor, i.e., conductive).
Skeleton 18 may be
crushable; that is, under some compression, such as about 150-250 psi, may
flatten out or
otherwise deform. In one specific embodiment, skeleton 18 is a woven
fiberglass member.
[44] Typically, a crushable skeleton will be one that will undergo
permanent deformation
under compression between a workpiece, such as an aircraft antenna and a base,
such as
the wing skin or fuselage of an aircraft. In one embodiment, there may be
permanent
deformation or set, so that when pressure is released, there will be very
little rebound of the
fibers of the crushed skeleton. In one embodiment, the crushable skeleton is
woven. In one
embodiment of woven skeletons, the skeleton may be metallic, such as an 18 x
18 strands
per inch woven mesh (17 mil strand diameter), aluminum fabric available from
Cleveland
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Wire Cloth, Cleveland, Ohio. In another embodiment, the crushable skeleton may
be a non-
metallic fabric, such as a woven fiberglass fabric. One such fabric is
available from Phifer,
Tuscaloosa, Alabama, Part No. 3021975, which provides a woven fiberglass non-
metallic
screen. In yet another embodiment, the skeleton may be a metal foam, such as
Duocel
reticulated aluminum foam available from ERG Aerospace.
[45] Typically, the body is coherent and integral with so as to encapsulate
the skeleton
for those embodiments using a skeleton. Typically, the skeleton is not a solid
sheet, but one
with many holes or pores. The gasket body material, for example, polyurethane,
will flow
(during the manufacturing of the gasket), uncured, through the pores like many
tiny arms
and hook up with other arms of elastomer running through the holes, such as to
provide, on
curing, a coherent, integrated skeleton, elastomeric gasket.
[46] In a preferred embodiment, gasket 14 may be an Avdec product, for
example, Part
Nos. AG8430000-88, AG723000-28 or AG822000-14. Some of these gasket bodies and
skeleton combinations are disclosed in the following Avdec patents
incorporated herein by
reference: 6,530,577; 6,695,320; and 7,229,516.
[47] Figs. 2 and 3 illustrate that the spacer 12 may lay stacked in a pre-
compression
state above the upper surface of the gasket, prior to compression (Fig. 2).
Compression is
accomplished by rotation of fastener head 36 against non-movable nut 38, which
compression may be achieved with a torque wrench to preselected values.
[48] A comparison of Fig. 2 to Fig. 3 will illustrate that under
compression, gasket 14 will
deform, with the body at least flowable and deformable by displacement of the
spacer
thereinto. However, it is also seen that, in one embodiment, preselected
torque limits will be
reached before all of the elastomer between the lower surface of the washer
and the base is
squeezed out. That is to say, in one embodiment, there is typically a gap
between the lower
surface of the spacer and the upper surface of the static structure that
leaves some
elastomer and some skeletal material (typically crushed) therebetween. If the
skeletal
material is a woven metallic mesh, it typically engages both the underside of
the antenna
(moveable piece) and outer surface of the aircraft fuselage (static) usually
but not
necessarily also in the non-crushed areas.
[49] One of the uses of Applicants' gasket and spacer assembly is to
eliminate the re-
torque requirements when standard elastomeric gaskets, used without spacers,
are
tightened between a removable workpiece and a static structure. In the prior
art, the
deformable and flowable nature of the body of the gaskets caused (after an
initial torque to
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a preselected value) a drop in the released torque after a period of time, for
example, about
15 to 60 minutes. That is to say, prior art gaskets for properly seating the
gasket between
the removable workpiece and static structure required re-torqueing (back up to
a preselect
value) after a period of time. This is likely due to the set of the
elastomeric body,
deformation taking place over a period of time under compression, which would
require re-
torqueing of fasteners 32.
[50] Applicants' use of a novel spacer and gasket assembly provides a
substantially
incompressible mechanical stop, such as washer or, in the embodiments set
forth in Figs. 4
and 5, plates 24 (with flat top and flat bottom surfaces against the pieces
under
compression) or spheres 26 (or any suitable configuration), Figs. 12A and 12B,
shaped to
body, and Fig. 14 disc or cylinder (flat top and bottom surfaces). In one
embodiment, the
incompressible members may have flat top and bottom surfaces for generally
flush contact
with the moveable workpiece and stationary or base member. On the other hand,
the top
and bottom surfaces of the incompressible spaces, including conductive metal
spaces, may
have spikes or pointed projections extending therefrom for good electrical
contact between
the two pieces. Such substantially non-compressible members, when stacked with
relation
to the deformable body of the gasket, including, typically, a compressible
skeleton, will
provide a substantial mechanical block, such that initial torqueing of the
fasteners to a
preselected value will not result in a substantial drop (overtime) in such
preselected value.
Therefore, re-torqueing may be eliminated.
[51] In Figs. 1-3, the mechanical stop or spacer is seen to be configured
as a washer,
that is, a generally cylindrical body having flat upper and flat lower
surfaces, and having a
thickness Tw, an outer perimeter 20, and an inner perimeter 22. The diameter
of the inner
cutout of the washer is designated Whd.
[52] In a preferred embodiment, the spacers are stacked (placed on top of
the gasket)
(see Figs. 2 and 3), and spacer thickness Tw may be nominally 0.03" or in the
range of
about 0.01" and 0.07". Gasket thickness may be nominally about 0.045" or in
the range of
about 0.015" and 0.120". The hardness of the elastomer body may, in one
embodiment, be
in the range given in the previous AVDEC patents and a skeleton may be woven
fiberglass.
[53] Turning to Figs. 6 and 7, it may be seen that an alternate preferred
embodiment of
Applicants' spacer and gasket assembly may be used, wherein the mechanical
stops,
instead of being stacked on top (or bottom) of the gasket and compressed
thereinto, will lay
adjacent, in side-by-side fashion, to the gasket (see Figs. 6 and 10, for
example), and, in
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one embodiment, between the lower surface of the antenna and upper surface of
the
fuselage or between an aircraft floorboard and a floorboard support (see Figs.
15C and
16C). The gasket may be typically about 45 mil (range 15 to 80 mil) thicker
than the
substantially incompressible mechanical stop and deformation of the body will
be
occasioned during the initial torqueing of fasteners 38.
[54] Gap A, Fig. 2, is seen to be typically in the range of about 25 mil to
200 mil; that is,
the gap generated by uncompressed stacked spacer and gasket assembly. Fig. 3
illustrates
gap B smaller, the washer being compressed into the body of the gasket, which
gap may be
in the range of about 10 mil to 120 mil, which will typically represent
sufficient torque on
fasteners 38 to be within aircraft specifications and not require re-torque
(typical aircraft
antenna mounted to aircraft outer surface, metallic or non-metallic skeleton).
[55] Fig. 2 illustrates an embodiment providing a slight cutback or
undercut of the outer
perimeter of the gasket with respect to the outer perimeter of the workpiece.
This
indentation is typically sized that, under compression as seen in Fig. 3, the
deformation of
the elastomer and its subsequent push outward will bring the outer edge of the
gasket,
when under compression, to about or just beyond the outer edge of removable
workpiece
28. This undercut may be in the range of about 50 mil to 250 mil.
[56] Figs. 9A, 9B, and 9C illustrate a number of features of embodiments of
Applicants'
parts assembly and spacer and gasket assembly. Fig. 9A shows a stacked version
uncompressed with the washer laying atop the body of the gasket, the body of
the gasket
laying on the static member and the top piece being a workpiece, in this case,
the antenna
of an aircraft. However, under close examination, it may be seen that a hole
52 pre-cut in
the gasket for the passage of the fastener therethrough is slightly undercut
in one preferred
embodiment. The term "undercut" means that the diameter of the hole (typically
cylindrical)
is equal to or slightly less than the diameter of the shaft of the fastener
that is passing
through the hole. This will allow some drag on the sticky elastomeric gel as
it clings to the
shaft of the fastener as the fastener passes through the gasket and into the
static structure.
This also helps ensure that when the gasket is tightened down and squeeze-out
occurs
(Figs. 9B and 9C) that that squeeze-out will be of sufficient volume to fill
in and around the
gasket holes and some into the fastener holes in the base and/or workpiece. It
is
disadvantageous for too much air to be around the fastener holes. In other
embodiments,
the fastener hole in the gasket is about equal to or slightly larger (overcut)
when compared
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to the fastener diameter. In yet other embodiments, Figs. 10, 15B, and 16B, a
wet seal may
be provided during parts assembly.
[57] In one embodiment, Applicants' various assemblies illustrated and
described herein
are used on parts engaging the surfaces of an aircraft. As a result, there is
sometimes a
substantial pressure difference as between the aircraft exterior and the
aircraft interior, for
example, when the aircraft is at cruise altitude. That pressure difference is
typically great as
the aircraft climbs to altitude. Moreover, the pressure differences cycle, as
do temperature
differences. It may be quite cold at a cruising altitude of 40,000 feet and
the air pressure
quite low. As a result, one of the objects of Applicants' assembly is to
sufficiently fill voids or
air pockets which might trap gas and moisture when the aircraft is exposed to
thermal and
pressure cycles. It has been found that undercutting the gasket around the
fastener holes
appears to help achieve these benefits. The undercut may be in the order of
magnitude of
about 1 5-1 00 mil in one embodiment. Also, it has been found that
"overcutting" the inner
diameter of the washer is also beneficial, the overcutting of the washer
refers to the inner
diameter of the washer being larger than the fastener shaft passing through.
This overcut
may be in the magnitude of about 1 5-1 00 mil in one embodiment.
[58] In Figs. 5 and 6, it is seen that hole 44 diameter Hd in the removable
workpiece is
typically just slightly larger than the shaft 34 of fastener 32, as is known
in the art. Ghd is
gasket hole diameter 52 and is, in one embodiment, sufficient to receive the
spacer
therethrough for the cutout embodiments where the spacer is adjacent to the
gasket, rather
than sandwiched or stacked with the gasket.
[59] It is seen in Figs. 9B and 9C that, as the workpiece is torqued down,
gasket body 16
has sufficient flowability to deform responsive to the washer being pushed
into the body.
Some of the gasket body material, typically cured polyurethane gel, will be
pushed inward
and help fill the void left by the gap between the spacer and the fastener and
some will be
pressed up against the inner facing wall of the workpiece and the outer facing
wall of the
static structure.
[60] In Fig. 9C, it is seen that, when sufficient torque is placed on the
fastener that the
lower surface of the spacer will contact the upper surface of the skeleton and
press it
against the upper surface of the base or static structure 30. In the process
of torqueing
down the fastener, this can actually be felt (rotational resistance force of
the fastener
increases) and passing this point typically crushes the fibers of the woven or
other
crushable skeleton (which may, like the spacer, be metallic) against one
another to cause
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skeletal deformation. This typically ensures that a sufficiently tight seal is
made from the
workpiece through the spacer and skeleton to the static structure.
[61] In another embodiment, as illustrated in Fig. 6 (adjacent spacers),
the holes may be
overcut, so that the washer is not pressed into the gel body. In one form of
this particular
embodiment, a metallic skeleton may be used. In one embodiment of such a
configuration,
if a metallic skeleton is used, for example, for an EMI application where
conductivity is
desired between the static piece or base and the moveable piece, then the
washer may be
either metallic or non-metallic and is slightly thinner than the precrushed
thickness of the
metallic skeleton. By sizing the skeleton and washer in such a fashion in the
overcut
(adjacent spaces) application, it will help ensure that there is some crushing
of the metallic
skeleton, so as to ensure good contact and conductivity before the hard stop
or mechanical
stop of the underside of the moveable piece against the washer is achieved.
[62] In one embodiment of the various parts and the spacer and gasket
configurations
illustrated herein, the gasket (pre-compression) is about 45 mil thick with an
encapsulated
about 13 mil skeleton and about a 31 mil thick nylon (or other suitable)
washer. Typically,
the washer will be driven into the skeleton so as to at least partially crush
the skeleton.
[63] The fastener shafts, in one embodiment, may be typically sized between
about .164
inch to .250 inch diameter. The tape or gasket is typically flexible and
tabular (generally flat
top and bottom, thickness much less than width and length) and the area may
range, in one
embodiment, from about 25 square inches to about 100 square inches. The number
of
fasteners between the moveable workpiece and the static base may range, in one
embodiment, from 4 to 10. The clamping pressure, in one embodiment, may be
about 150
to 450 psi (or substantially to a crushed skeleton). In another embodiment,
the range is
about 150 to 350 psi (to a crushed skeleton). In one embodiment, nylon washers
may be
used and the gasket may be slightly undersized, typically, in the range of
about 1/64 inch to
1/32 inch undersized or undercut, for a tight interference fit with the shaft
of the fastener.
[64] Fig. 10 illustrates the application of an uncured ("wet"), sticky,
resilient polyurethane
101 on or about fastener 32 and/or the spacer 12 and/or the hole in spacer and
gasket
assembly 10. Fig. 10 illustrates that uncured polyurethane (or other suitable
curable,
injectable two-part mix sealant) 101 may be applied with an applicator 100
having a nozzle
101a. Nozzle 101a typically mixes the two parts of the sealant, in one
embodiment, a polyol
102 and an isocynate 104, which will mix in the nozzle and flow into and
adhere in and
around fastener 32, and the hole in the gasket. It will typically flow at
least partway or all the
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way through the hole in the spacer and gasket assembly and the hole (if there
is one) in
spacer 12 and typically, at least partially, into static structure 30. As the
polyurethane is
uncured in the applied state, it has a consistency somewhat similar to thick
but sticky, slow
flowing motor oil and will stick to, as well as flow about and coat, the space
between the
fastener and the gasket, the shaft of the fastener, and the blind nut or a
captured nut to
which the fastener may be attached. In one embodiment, uncured polyurethane
mix 101 is
applied at the time of placing the removable structure 28 onto the gasket,
which is on the
static structure 30, such that the fastener is fastened down before the mix
fully cures. The
details of polyurethane 101 may be found in the patents incorporated herein by
reference.
By applying the pre-cured mix to the fastener and the fastener area, as well
as the hole,
through static structure 30 and spacer and gasket assembly 10, a more complete
environmental seal is typically provided. This will help inhibit corrosion.
[65] Figs. 11A and 11B illustrate that Applicant's spacer and gasket
assembly 10 may
include spacers 12 that are, during the manufacturing of the gasket, molded
into and
become integral with body 16. Moreover, body 16 may be gel only, such as
polyurethane
gel and, in one embodiment, not have a skeleton at all (see Fig. 11B). For
example, Fig.
11A illustrates uncured mix 101 being applied to a mold 106 wherein, prior to
curing or
before squeezing the uncured mix 101 (into the mold), the spacers may be
placed in the
mold. Either way, when the polyurethane mix cures, with or without the
skeleton, the entire
assembly may be lifted out of the mold and used with an aircraft antenna,
floorboards or
other suitable structure. The mold may first be lined with release paper (not
shown), for
ease of removal of the gasket after the mix cures. In any of the embodiments
shown, the
thickness of the spacer 12 in relation to body 16 may be such that they are
about the same
or the spacer is less in thickness (in one embodiment, about 40-80% of the
precompressed
thickness of the body).
[66] Figs. 12A and 12B illustrate an alternate embodiment of Applicant's
spacer and
gasket assembly 10, one in which the spacer 12 is embedded in the resilient
gel gasket
body 16 with or without skeleton. In the illustrated embodiment, the
substantially
incompressible spacer (under typical psi ranges found between the static
assembly and the
moveable workpiece, in an aircraft, for example), which is embedded is seen to
include
members 12a that substantially conform to the outer perimeter of the gasket.
These may be
linear members, that may be along the edge of the gasket or set back, but
conform to the
shape of the edge. In one embodiment, perimeter conforming members 12a are set
back
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from the perimeter in the order of magnitude of about 20 to 250 mil, for
example. Figs. 12A
and 12B also show that, in addition to perimeter conforming members, the
spacers may
include fastener hole branches 12b that branch off from the perimeter
conforming members
to substantially surround the fastener holes. These perimeter members may
provide
support substantially around a fastener, but spaced back somewhat from the
spacer hole.
In some embodiments, there may be a combination of the linear member spacer
illustrated
in Figs. 12A and 12B, and the discrete spacers of the other embodiments. A
skeleton may
or may not be used. As with the other embodiments, the spacers may be metallic
or non-
metallic. In Fig. 12B, it is seen that gasket body 16 may substantially embed
spacer 12.
[67] A manufacturing process for the assembly is illustrated. See Figs. 11A
and 11B.
The embedded spacers 12 may be laid into uncured mix 101 before it cures in a
mold 106
configured to the required perimeter shape of the gasket. The embedded spacer
may be
laid in first and the uncured mix built up around it, or layered in multiple
steps, i.e., thin layer
of mix is first cured, then spacer laid on top and additional gel added and
allowed to cure.
[68] Figs. 13A, 13B, and 14 show how spacers 12 may be placed in relation
to fastener
holes 44 in body 16. As set forth hereinabove, the spacer and gasket assembly
may have,
in one embodiment, such as Figs. 1, 2, 3 above, spacers which encircle the
fasteners. In
other embodiments, they may lay adjacent the fastener holes. For example, in
Figs. 4 and
5, there are spacers 24 (flat top and bottom)/26 (spherical) within about one
to three
fastener diameters from the fastener to help spread the mechanical stop and
minimize
flexing of the body of the workpiece. As in the previous embodiments of the
spacer and
gasket assembly, spacers in Figs. 10-14 may be embedded during manufacturing
or may be
stacked during assembly of the workpiece, or placed in holes 44 in the gasket,
the cutouts
or holes 44 shaped to receive the spacers. The spacer holes may be made during
manufacturing by die cut. The cutouts for spacers may form in the same manner
as cutouts
for fastener holes. Fastener holes through the skeleton may be made with a
sharp, pointed
tool such as an awl, on-site during installation.
[69] In Figs. 13A and 13B, it is seen that spacers 12 here discrete, may be
placed about
equidistant along a line between adjacent fasteners or fastener holes 44.
These spacers
may be configured in any shape set forth herein or in any suitable shape. They
may be
placed in such positions and used, in one embodiment, with the fastener
encircling spacers
(washers) as seen, for example, in Fig. 6. In another embodiment, the spacers
may be
used without the washers. Fig. 13B illustrates an embodiment in which skeletal
member 18,
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either metallic or non-metallic, and either woven or unwoven, may be placed
closer to or
adjacent one of the top or bottom surfaces of the body of the gasket rather
than centered.
This may provide selective adhesion with the parts which compress the gasket
to make
subsequent release easier.
[70] Fig. 14 illustrates that in one embodiment, spacer 12 in any shape
disclosed herein,
discreet, linear, disc or cylindrical, spherical, tabular, washer, etc., may
be placed adjacent
on either side of a fastener hole, typically about one or in the range of
about 2 to about 5
fastener diameters, to provide a mechanical stop on either side of fastener
hole 44 and
adjacent an outer perimeter edge of the gasket. It is seen that each of the
fastener holes
have a pair of spacers and, in one embodiment, are configured diagonally, with
respect to
the corner of gasket 14 to either side of the fastener hole.
[71] Figs. 15A, 15B, and 15C illustrate an alternate preferred embodiment
if a spacer and
gasket assembly 10, in this case for use with a floorboard assembly 200 or
other suitable
environment. Floorboard 203, such as aluminum floorboard for an aircraft, is
provided with
an integral or built in, typically cylindrical, integral spacer 204. It may be
machined into the
floorboard when the floorboard is manufactured, or provided separately and
attached by an
adhesive or welding or any other suitable means. Fastener hole 206 is provided
through
integral spacer 204 for receipt of a fastener 32 therethrough. A multiplicity
of built-in or
integral spacers 204 may be provided, in a pattern that will match holes in a
support
member 210 for receipt of the floorboard thereon. In one embodiment, the
support member
may be a carbon fiber or composite upright member of an aircraft. In one
embodiment, a
spacer gasket assembly 10 comprising a cured polyurethane gel tape 212 with
spacer holes
214 cut through is provided. Holes 214 are cut in a diameter sufficient to
receive spacers
such that the spacer will contact the top of support surface 210 when
compression is
applied an act as a stop, with applicant's gasket tape, providing an
environmental seal to the
facing surfaces of the two parts providing the compression.
[72] Thus, Applicant's spacer and gasket assembly 10 may include a gasket in
the form
of a tape 212 having a gel body 16 as set forth elsewhere in these
specifications and,
optionally, skeleton 18 (see Fig. 15C). Applying torque to fastener 32 will
bring floorboard
203, more specifically, lower surface of integral spacer 206 (or washer, not
shown) into
contact with the top surface of support member 210.
[73] Applicant's tape, in one embodiment, may be HT 3000, HT 3000 RT or HT
3935,
available from AvDec, 1810 Mony St., Fort Worth, Texas 76102. Tape 212 is a
form of a
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gasket, functionally assisting with providing of an environmental seal with
providing the
compression on the gasket. It also provides some resistance to compression, as
does the
spacer, more greatly so when the parts contact the spacer. However, being a
tape, it is
usually cut to fit, lengthwise, at the worksite, but used in the width
provided typically
between about 1/2" and 4" inches. Non-tape gaskets, on the other hand,
typically are precut
to the footprint of a workpiece or supplied in 24" wide sheets. In one
embodiment, a non-
sticky (to the floorboard), film 212a (such as PTFE) is applied to body 16 in
the
manufacturing of the tape. Film 212a is sticky to body 212b, but not to any of
the parts
under compression or workpieces. A single-sided sticky means there is one film
layer or
skin 212a on the surface of the tape or gasket. In one application, a single-
sided sticky is
used between the two parts (floorboard 203 and support 210), in one embodiment
with the
non-sticky side up (see Fig. 15B) and, in another embodiment (Figs. 17A and
17B), with film
212bdown and sticky side up. Having the non-sticky side up makes removal of
the
floorboard relatively straightforward. The gel body being sticky will not be
in contact with the
underside of the floorboard in Figs. 15B and 15C, but provides a good
environmental seal
to block moisture and contaminants when sticking to the support surface. The
sticky side
may be placed against the workpiece when ingress of potential contaminants may
be a
problem. The non-sticky side may be placed against the workpiece for which a
"clean"
removal is desired in one embodiment the support member (Fig. 17A), in another
the
floorboard (Fig. 15B).
[74] Figs. 16A, 16B, and 160 illustrate yet another gasket and spacer
assembly 10,
similar to that in Figs. 15A, 15B, and 15C (using tape), except that loose
(non-integral)
spacers 12 are used to place in the tape cutout holes 214. Again, this may be
used with the
floorboard assembly 200. Optionally the uncured two-part mix 101 may be
applied (see Fig.
16B), to provide a wet seal, which, when cured will help hold the
washer/spacer 12 in place
during removal of the floorboard and provide a good environmental seal.
[75] Figs. 17A and 17B illustrate a floorboard assembly 200 comprising a
floorboard 203
with a gasket and spacer assembly 10 therebetween. In this embodiment, the
gasket is in
the form of a polyurethane gel tape 212 and the spacers integral to the
floorboard. The gel
tape has a skin or film 212a, such as PTFE, but the sticky side is "up"
against the underside
of floorboard 203. This puts the non-sticky film "down" against the support
210, which may
be composite and the floorboard aluminum. There will be a clean release from
support 210.
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Fig. 18 illustrates an alternate embodiment of an integral spacer 204 that is
not around hole
206 in floorboard 203.
[76] Figures 19A and 19B illustrate a method of assembling loose spacers 12
on
floorboard 203, so that the loose spacers 12 are affixed to the floorboard
before the
floorboard is placed on support member 210. This method involves placing the
floorboard
flat with the underside of the floorboard up as in Fig. 19A. The spacers, here
in front of
washers for encircling holes 206 of the floorboard (but any of the spacer
shapes may be
used) are laid on one or more of the holes just before the tape is placed,
sticky side down,
down over them. A first washer and a subsequent second and third washer may be
placed
down against the holes in the floorboard. The edge of the tape is laid down at
the edge of
the floorboard and over the first washer, then against the floorboard
underside then over the
second washer, etc. The tape is sticky side to the floorboard underside and
therefore will
surround and hold the washer in place and against the floorboard. Even after
the floorboard
is turned right side up (Fig. 19B). After the tape is laid down along the hole
path, while the
washers are placed manually about the holes, the tape is cut to length at the
end of the line
of holes or floorboard. The floorboard is then inverted (right side up).
However, since the
tape is holding the washers in place against the underside of the floorboard
the washers will
stay in place (Fig. 19B).
[77] After the floorboard is placed against the upper surface of the support
in a manner
which aligns the holes in the floorboard with the holes in the support, and
awl 216 or other
pointed tool is driven through the hole in the floorboard through the hole in
the washer
through the skeleton of the tape, if there is one and through the skin. See
Fig. 20. The skin
is against the upper surface of support member 210 and is usually tough. In
puncturing the
skin with an awl the subsequent insertion of the fastener (see Fig. 19B) is
easily
accomplished. Moreover, when one removes the floorboard it easily removes off
the
support member because the non-sticky skin is against the support surface, and
all the
washers are held in place by the sticky tape 212.
[78] A method of assembling a floor of an aircraft having multiple floor
supporting
members 210 is provided. The floor supporting members have a flat upper
surface with
multiple fastener holes. A tape, in one embodiment having a sticky pliable gel
body 212b
with a skeleton embedded therein and a skin 212a on one of an upper or lower
surface of
the body is provided. The tape has a tape thickness. Multiple spacers are
provided. The
spacers having a spacer thickness that is typically less than the tape
thickness. The tape
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and fasteners are placed together between the floorboards and the support
members such
that the fastener holes of the floorboards and the support members align.
Fasteners are
then inserted through the fastener holes and torqued down. They are typically
torqued
down such that the gel of the body is squeezed out above and below the spacers
and, if
there is a skeleton above or below the fasteners, they will flatten out the
skeleton. At this
point, there will be a sudden sharp increase in the resistance force on the
torquing
instrument, such as a torque wrench. The spacers alone or the spaces in
combination with
a skeleton, which may be crushed, provide a mechanical stop between the
floorboard in the
support member. While almost all of the deformable gel is squeezed out there
is still a very
thin layer that provides a good environmental seal, but is not thick enough to
take a set over
a period of time which set would require a retorque of the fasteners. The
thickness of the
gel when this torque spike is sensed or measured is likely less than one or
two mil.
[79] Although the invention has been described with reference to a specific
embodiment,
this description is not meant to be construed in a limiting sense. On the
contrary, various
modifications of the disclosed embodiments will become apparent to those
skilled in the art
upon reference to the description of the invention. The invention is not
limited to a process
having all the steps described in the preferred embodiments. There may be
utility in utilizing
a process with more limited steps as defined in the claims. Individual
technical features of
the illustrated embodiments are not limited to use in those embodiments, and
may where
suitable, be used with any embodiment falling within the scope of the claims.
It is therefore
contemplated that the appended claims will cover such modifications,
alternatives, and
equivalents that fall within the true spirit and scope of the invention.
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