Outer flap elastic seal assembly

An elastic seal includes a longitudinally extending elastomeric seal member with a continuous sealing surface and a longitudinally extending structural support member having at least one section with fingers extending transversely from the section with slots between the fingers. Each of the fingers is entirely embedded within the elastomeric seal member near the continuous elastomeric sealing surface. The fingers are preferably articulated downward in a direction normal to the sealing surface and together with the rest of the support member are preferably made of a spring material such as a flexible material such as a springy sheet metal. The elastomeric seal and structural members may be continuous bands with continuous metallic band with the fingers extending transversely from the metallic band. The continuous metallic and elastomeric bands may be annular, rectangular, ellipsoid, or have some other shaped cross-section.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates generally to sealing devices for providing a close 
seal between a stationary member and a member pivotal in relation thereto 
and, more particularly, with respect to aircraft gas turbine engines, 
between engine ducts and outer flaps of vectorable or non-vectorable 
exhaust nozzles. 
2. Discussion of the Background Art 
Exhaust nozzles for military aircraft gas turbine engines typically include 
outer flaps which define the outer wetted surface of exhaust nozzle and is 
exposed to the airstream flowing past the aircraft. The outer flaps are 
usually hinged to an outer engine casing. Typical types of exhaust nozzles 
include axisymmetrical vectorable and nonvectorable and two dimensional. 
Vectorable nozzles generally employ divergent flaps to turn or vector the 
exhaust flow and thrust of the gas turbine engine powering the aircraft. 
Two dimensional nozzles have been devised which employ relatively flat 
flaps to direct the pitch or yaw direction of the engine's thrust. Hauer, 
in U.S. Pat. No. 4,994,660 incorporated herein by reference, discloses an 
Axisymmetric Vectoring Nozzle (i.e., General Electric's AVEN.RTM. nozzle) 
that provides a means for vectoring the thrust of an axisymmetric 
convergent/divergent nozzle by universally pivoting the divergent flaps of 
the nozzle in an asymmetric fashion or in other words pivoting the 
divergent flaps in radial and tangential directions with respect to the 
unvectored nozzle centerline. Wood et al., in U.S. Pat. No. 5,485,959 
incorporated herein by reference, discloses a thermal shield for the 
Axisymmetric Vectoring Nozzle with outer flaps and seals. 
Hot pressurized nozzle flow is contained by convergent and divergent flaps 
and seals (in the case of axisymmetric nozzles) wherein the divergent 
flaps and seals are pivotally connected to the nozzle throat in a manner 
permitting pivotal movement and axial translation of the exhaust nozzle 
exit. Outer flaps pivotally connected to an exhaust casing of the engine 
and outer seals (when used) supported by and disposed the outer flaps are 
used to surround the nozzle's convergent and divergent flaps and seals as 
demonstrated in U.S. Pat. No. 4,128,208 by Ryan et al., entitled "Exhaust 
Nozzle Flap Seal Arrangement" assigned to the same assignee as the present 
invention. The outer flaps and seals are convergent in shape in the aft 
direction and are designed to provide an aerodynamically smooth surface 
around the nozzle to prevent adverse aerodynamic conditions that might 
otherwise arise. Because of the convergent shape, airflow along the outer 
flaps and seals are prone to separation which causes a highly undesirable 
increase in boat-tail drag on the nozzle, engine and ultimately the 
aircraft. Therefore, it is highly desirable to forestall separation as far 
aft on the outer flaps as possible and to eliminate separation along the 
flaps, if possible. 
The hot pressurized nozzle flow tends to leak out of the nozzle flow path 
and into a nozzle bay formed between the convergent and divergent flaps 
and seals and the outer flaps. This pressurizes the bay which then leaks 
relatively high pressure airflow between the engine casing and the outer 
flaps and seals where the outer flaps are pivotally connected to the 
exhaust casing of the engine by hinges. The leakage from the bay can cause 
the boundary layer along the outer flaps and seals to trip from laminar to 
turbulent flow and, in turn, to cause the airflow along the outer flaps 
and seals to separate, thus, bringing about the unwanted increase in 
boat-tail drag. The separation can cause other undesirable effects 
relating to aerodynamic flow instabilities caused by the flow separation. 
U.S. Pat. No. 4,022,948 discloses resiliently coated metallic finger seals 
having two overlapping metallic seal members fixed at one set of ends with 
fingers extending backward at another set of ends encapsulated with 
resilient coating material. The slits between the fingers are offset 
between fingers so that resilient coating material cannot extend 
continuously between coatings over the upper and lower fingers. The 
resilient coating extends almost to the end of the slits but doesn't form 
an elastic seal entirely around the fingers. The problem of leakage is 
compounded by the strong aerodynamic forces acting along the interface 
between the engine casing and the outer flaps and seals and because the 
outer flaps and seals are pivoted with respect the engine casing. 
The present invention overcomes these problems by providing an elastic seal 
which functions like a rubber band to keep the elastic seal tightly but 
resiliently against sealed elements. The elastic seal has at least one 
embodiment that can be used between the engine casing and the outer flaps 
and seals and which can be used for axisymmetric vectoring and 
non-vectoring nozzles and for two dimensional vectoring and non-vectoring 
nozzles. These features and advantages will become more readily apparent 
in the following description when taken in conjunction with the appended 
drawings. 
SUMMARY OF THE INVENTION 
The present invention provides an elastic seal which includes a 
longitudinally extending elastomeric seal member with a continuous sealing 
surface and a longitudinally extending structural support member having at 
least one section with fingers extending transversely from the section 
with slots between the fingers. Each of the fingers are entirely embedded 
within the elastomeric seal member near the continuous sealing surface. 
The fingers are preferably articulated downward in a direction normal to 
the sealing surface and together with the rest of the support member are 
preferably made of a flexible material such as a springy sheet metal. 
In one particular embodiment of the invention, the elastomeric seal member 
is an elastomeric band and the structural member includes a preferably 
continuous metallic band with the fingers extending transversely from the 
metallic band. The continuous metallic and elastomeric bands may be 
annular, rectangular, ellipsoid, or have some other shaped cross-section. 
Another embodiment particularly useful for rectangular seals and for two 
dimensional (2D) nozzles, provides peripherally extending portions of the 
inner metallic member around corners of the seal having no fingers. Yet, 
another embodiment particularly useful for seals and nozzles having angled 
or rounded corners, such as ellipsoidal, provides peripherally extending 
portions of the inner metallic member around corners of the seal with no 
slots. The support member may be segmented having at least two metallic 
segments (more than two may also be useful) of a metallic segmented band. 
The present invention also provides a seal assembly having a relatively 
fixed first periphery around a first component, a second periphery around 
a second component disposed in relatively movable relationship with 
respect to the first component, a gap between the components, a seal, as 
disclosed above, disposed across the gap in sealing engagement with sealed 
surfaces of the components. The seal assembly may include a rotatable 
relationship between one of the sealed surfaces against the continuous 
inner sealing surface of the continuous elastomeric band of the seal. 
One more particular embodiment includes an annular ring connected in force 
transmitting relationship to a gas turbine engine nozzle casing annularly 
disposed about a nozzle axis such that the first periphery is 
circumscribed around the annular ring, and the second periphery is 
circumscribed around outer nozzle elements. The outer nozzle elements are 
circumferentially disposed about the nozzle axis and are either outer 
flaps pivotally connected to the ring or outer flaps pivotally connected 
to the ring with outer seals interdigitated between the outer flaps and 
the second periphery and the metallic and elastomeric bands are annular. 
The annular ring may be fixedly connected to the gas turbine engine nozzle 
casing with the first periphery circumscribed around a nozzle fairing 
attached to the annular ring. The annular ring may be movable with respect 
to the gas turbine engine nozzle casing with the first periphery 
circumscribed around a nozzle fairing attached to the annular ring. The 
annular ring may be translatable with respect to the gas turbine engine 
nozzle casing and/or tiltable with respect to the gas turbine engine 
nozzle casing. The outer nozzle elements may each have an end that is 
curved at a radius of curvature which extends from the outer flaps to an 
axis of rotation about which the outer flaps are pivotally connected to 
the ring. 
ADVANTAGES 
The present invention has many advantages over seals disclosed in the prior 
art. The present invention provides a more complete seal and seal assembly 
that can better seal all around a periphery, particularly between 
relatively movable gas turbine engine nozzle components such as between 
rings attached to a nozzle casing and outer flaps or outer flaps and 
seals. The seal can better seal gaps between vectored axisymmetric nozzle 
outer flaps and rings they are attached to in both vectored and unvectored 
attitudes. This provides better control of airflow over the outer elements 
on the outside of the nozzle. Another advantage is that seals of the 
present invention can be constructed to accommodate symmetric as well as 
non-symmetric, fixed shapes and somewhat variable shapes, and rounded, 
linear and squared shapes of components to be sealed. The present 
invention can be used in new designs and retrofits and is relatively 
inexpensive to construct.

DETAILED DESCRIPTION 
Referring now to the drawing, there is schematically illustrated in FIG. 1 
an exhaust section 10 of a gas turbine engine includes, in serial flow 
relationship, a fixed area duct or more particularly an engine casing 11, 
including an afterburner liner 12, and a convergent/divergent symmetric 
variable area exhaust nozzle 14 of the type commonly found in military gas 
turbine engines such as the General Electric F110 engine used in the F-16 
aircraft. Nozzle 14 as shown is of the convergent/divergent type, though 
the present invention is not intended to be limited to such a structure, 
and includes in serial flow relationship a convergent section 16, a throat 
18 and a divergent section 20. The convergent section 16 includes a 
plurality of convergent flaps 24 circumferentially disposed about an 
engine centerline 8 and overlapping convergent seals (not shown) disposed 
between and in sealing engagement with radially inward facing surfaces of 
circumferentially adjacent ones of the convergent flaps 24. The convergent 
flaps 24 are pivotally attached at their forward ends to casing 11 by 
first pivotal or clevis joints 28. Similarly, the divergent section 20 
includes a plurality of divergent flaps 25 circumferentially disposed 
about the engine centerline 8 and overlapping divergent seals (not shown) 
are disposed between and in sealing engagement with radially inward facing 
surfaces of circumferentially adjacent ones of the divergent flaps 25. The 
convergent flaps 24 are pivotally attached at their forward ends to casing 
11 by first pivotal or clevis joints 28. The convergent and divergent 
flaps 24 and 25, respectively, are pivotally attached to each other at 
their adjacent ends 27 at the throat 18 of the nozzle 14. 
The variable area exhaust nozzle 14 includes at an outer periphery 31 a 
plurality of circumferentially spaced outer flaps 34 having their forward 
end 36 hinged on a circumferentially extending common circle 38 about 
engine centerline 8 in such a way as to collectively define a continuous 
downstream converging frustum of a cone when the nozzle is in the closed 
position. The outer flaps 34 overlap each other in an iris type 
arrangement to provide a continuous frustum of a cone in an open as well 
as closed position. 
Some exhaust nozzles such as that disclosed in U.S. Pat. No. 4,128,208, 
entitled "Exhaust Nozzle Flap Seal Arrangement", have non-overlapping 
outer flaps which form a discontinuous frustum of a cone when in the open 
position, the discontinuity being pie-shaped in form. In order to offset 
the aerodynamic effect of these discontinuities, a plurality of outer 
seals (not shown) are placed in close relationship with the inner sides of 
the outer flaps 34, with an outer seal being placed between each pair of 
outer flaps so as to effectively seal off the discontinuities whenever the 
nozzle is not in the fully closed position. 
The outer flaps 34 or the combination of outer flaps and the outer seals 
define part of an outer flow path 39 of the nozzle 14. The outer flow path 
39 has a frusto-conical shape often called a boattail which is subject to 
separation and all of the adverse effects associated to separation 
discussed above. The common circle 38 defines an annular gap 41 or 
interval around the nozzle 14 along where the forward ends 36 of the outer 
flaps are hinged to an annular ring 42 that is fixedly attached to the 
engine casing 11 in force transmitting relationship by a conical web 44. 
The annular ring 42 may be part of a nozzle fairing 35 as illustrated in 
FIGS. 1 and 2. Annularly disposed between the outer flaps 34 and the 
convergent section 16, throat 18 and divergent section 20 is a nozzle bay 
46 which contains pressurized air that can leak through the gap 41 and 
cause airflow into and normal to the outer flow path 39 which can 
precipitate separation at or directly downstream of the gap. 
Variations of a nozzle throat area A8 and/or a nozzle exit area A9 are 
generally controlled by either a crew command or automatically by an 
electronic controller in accordance with engine performance requirements 
and are generally accomplished by hydraulic means illustrated by a 
plurality of hydraulic nozzle actuators 50 which are disposed around the 
engine casing 11 and having a casing end 52 connected by a mounting ring 
56 to the casing which tends to fix the radial position of the nozzle 
actuators. A rod end 58 of the nozzle actuator 50 is connected by a bolt 
59 to a clevis 60 which extends from a fixed diameter actuation ring 62. 
Each of the divergent flaps are connected to the annular ring 42 by way of 
the secondary drive links 64. The annular gap 41 is sealed all around the 
nozzle 14 by a elastic seal 70 in accordance with a first embodiment of 
the present invention. The present invention provides a seal assembly 71 
with the elastic seal 70 disposed around the periphery of and in sealing 
engagement with the engine casing 11 or the nozzle fairing 35 and outer 
flaps 34. The elastic seal 70 is annular and continuous in this embodiment 
as illustrated in FIG. 3 but may, for particular applications, be 
segmented into annular segments which when assembled form an annular 
elastic seal 70. 
Referring to FIGS. 2-4, the annular gap 41 is sealed all around the nozzle 
14 by the elastic seal 70 of the present invention which includes a 
longitudinally extending elastomeric seal member 72 with a continuous 
sealing surface 74 and a preferably metallic longitudinally extending 
structural support member 76 having at least one longitudinally extending 
section 78 with fingers 80 extending transversely from the section and 
slots 82 between the fingers. Each of the fingers 80 is entirely embedded 
within and covered entirely by the elastomeric seal member 72 near the 
continuous sealing surface 74. The fingers 80 are preferably articulated 
downward 84 in a direction N normal to the sealing surface 74 and, 
preferably, together with the rest of the support member are preferably 
made of a flexible material such as a springy sheet metal. The articulated 
fingers 80 further urge the sealing surface 74 into contact and better 
sealing engagement with the outer flaps 34. The elastomeric seal member 72 
may be made of fluoroelastic material such as a Viton.TM. elastomer, a 
trademarked artificial or man made rubber material made by the DuPont 
company and a wear and/or lubricating coating is also preferably used over 
at least the elastomeric sealing surface 74. 
Referring again to FIG. 2, each of the outer flaps 34 preferably have a 
curved end 37 that is curved at a radius of curvature R which extends from 
the outer flaps to an axis of rotation 33 about which the outer flaps are 
pivotally connected to the ring 42. This enhances sealing between the 
continuous sealing surface 74 and the curved ends 37 of the outer flaps 34 
or any rotatable or pivotal element that the elastic seal of the present 
invention may be used with. The fingers 80 and slots 82 in between allow 
for localized sealing which is particularly useful when the boat-tail 
angles 86, generally the acute angles between the outer flaps 34 tangency 
and the nozzle or engine centerline 8, change during the adjustment of 
A8/A9 or when the throat area A8 is varied. This is also true of 2D 
nozzles 14A such as the one illustrated in FIGS. 7 and 7A. The 
articulation of the fingers 80 better help the fingers act as springs to 
urge the sealing surface 74 into contact and better sealing engagement 
with the outer flaps 34. 
The elastic seal 70, illustrated in greater detail in FIG. 4, has each of 
the fingers 80 entirely embedded within the elastomeric seal member 72 
such that the elastomeric material of the elastomeric seal member fills 
the slots 82 between the fingers, thus, forming structural walls 83 that 
structurally connect upper and lower longitudinally extending elastomeric 
band portions 91 and 93, respectively, of the elastomeric seal member. 
This also forms a compartment 85 around the fingers 80 which allows the 
fingers to locally direct the sealing and to locally accommodate surface 
irregularities of the surface being sealed. This provides an integrated 
band that allows the elastomeric seal member 72 to provide the sealing 
function and the support member 76 help urge the sealing surface 74 into 
sealing engagement so that the elastic seal 70 operates similar to a 
rubber band. The elastic seal 70 is preferably undersized so that the 
elastomeric member 72 must be stretched over the outer flaps 34 providing 
a tight uniform seal. 
The fingers 80 and slots 82 may be designed to accommodate different types 
of design goals and geometries. Finger widths WF and slot widths WS and 
finger and slot lengths L may be designed to promote better localized 
sealing. Longer more narrow fingers will accommodate a greater amount of 
out of plane variance such as that encountered by outer flaps 34 and outer 
seals of axisymmetric vectoring nozzles 14B such as those disclosed in 
U.S. Pat. Nos. 4,994,660 and 5,485,959, and as illustrated in FIG. 5. Note 
that when the nozzle is in the vectored position as shown in FIG. 5 a top 
boat-tail angle AT is greater than a bottom boat-tail angle AB and the 
seal accommodates the circumferential variation as well as the out of 
plane (that normal to the plane of FIG. 5) variation. The fingers 80 are 
preferably articulated downward in a direction N normal to the sealing 
surface 74 so as to help direct the elastomeric force produced by the 
elastomeric seal member 72 in a desired direction to better promote 
sealing engagement with the outer flaps 34, or whatever element and 
surface the elastic seal 70 is sealing. The elastomeric seal member 72 
provides the primary sealing force and the fingers 80 help provide sealing 
force and also provide stability and accommodation of surface 
irregularities. The outer flaps 34 are hinged to an annular vectoring ring 
43 which is actuated and attached to the engine casing 11 in force 
transmitting relationship by vectoring actuators 47. The annular vectoring 
ring 43 is translatable with respect to the gas turbine engine nozzle 
casing 11 and tiltable with respect to the gas turbine engine nozzle 
casing and about the engine centerline 8. The outer nozzle elements, the 
outer flaps 34 and outer seals, each preferably have one of the curved 
ends 37 that is curved at the radius of curvature R which extends from the 
outer flaps to the axis of rotation 33 about which the outer flaps are 
pivotally connected to the vectoring ring 43. 
FIG. 10 illustrates a variation or alternate embodiment of elastic seal 70 
in which the metallic fingers are not covered on their metallic bottom 
surface 73 by the elastomeric seal member 72 the continuous sealing 
surface 74 and part of the bottom surface 73 of the metallic fingers 
contact and seal the outer flaps 34. The elastic seal 70 illustrated 
herein still retains the benefits afforded by the walls 83 which 
structurally connects the upper and lower longitudinally extending 
elastomeric band portions 91 and 93, respectively, though, the fingers 80 
are not entirely embedded within the elastomeric seal member 72. The 
elastomeric material of the elastomeric seal member 72 fills the slots 82 
between the fingers, thus, allowing the walls 83 to connect an area of the 
elastomeric seal member 72 containing the sealing surface 74 to be 
structurally tied to the upper band portion 93 and to form the compartment 
85 around the fingers 80. This variation may be used in many of the 
applications disclosed in this patent as well as others contemplated by 
this patent. 
FIG. 6 illustrates a linear elastic seal 70A, in accordance with a third 
embodiment of the present invention, which includes a longitudinally 
extending linear elastomeric seal member 72 with a continuous sealing 
surface 74 and a preferably metallic longitudinally extending linear 
structural support member 76 having at least one longitudinally extending 
section 78 with fingers 80 extending transversely from the section and 
slots 82 between the fingers. Each of the fingers 80 is entirely embedded 
within the elastomeric seal member 72 near the continuous sealing surface 
74. 
The elastic seal 70 is preferably a continuous band with the elastomeric 
seal member 72 and the inner structural support member 76 being continuous 
bands that may be annular, rectangular, square, or otherwise shaped. FIGS. 
7 and 7A illustrate a 2D nozzle having a rectangular or more particularly 
a continuous band square shaped elastic seal 70B with continuous band 
square shaped elastomeric seal member and inner structural support members 
72 and 76, respectively. Peripherally extending portions 90 of the inner 
structural support member 76 around squared corners 92 of the square 
shaped elastic seal 70B preferably have no fingers 80 to better 
accommodate the 2D pivoting of the outer flaps 34. 
FIG. 8 illustrates an ellipsoidally shaped elastic seal 70C particularly 
useful for elastic seals and nozzles having angled or rounded corners 94. 
The ellipsoidally shaped elastic seal 70C provides peripherally extending 
portions 90 of the inner structural support member 76 around the angled or 
rounded corners 94 of the ellipsoidally shaped elastic seal 70C with no 
slots 82. Instead the angled or rounded corners 94 of the ellipsoidally 
shaped elastic seal 70C have bent fingers 98 that are bent around the 
corners of the ellipsoidally shaped elastic seal. 
FIG. 9 illustrates the use of the seal 70 and the seal assembly 71 of the 
present invention for sealing the gap 41 between the engine casing 11 and 
an aircraft structure such as a skin 100. 
The foregoing descriptive embodiments of the invention have been presented 
for the purpose of describing and illustrating the invention. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed and obviously many modifications and variations are possible in 
light of the above teachings. While the preferred embodiment of the 
invention has been described fully in order to explain its principles, it 
is understood that various modifications or alterations may be made to the 
preferred embodiment without departing from the scope of the invention as 
set forth in the appended claims.