U.S. patent application number 13/493064 was filed with the patent office on 2012-10-04 for scalable high pressure compressor variable vane acuation arm.
This patent application is currently assigned to United Technologies Corporation. Invention is credited to Daniel W. Major, Bernard W. Pudvah.
Application Number | 20120251297 13/493064 |
Document ID | / |
Family ID | 41363955 |
Filed Date | 2012-10-04 |
United States Patent
Application |
20120251297 |
Kind Code |
A1 |
Major; Daniel W. ; et
al. |
October 4, 2012 |
SCALABLE HIGH PRESSURE COMPRESSOR VARIABLE VANE ACUATION ARM
Abstract
A variable vane arm has a hook portion comprising a radially
inner leg connected to a radially outer leg by an arcuate
connection, and an actuation lever extending from the hook portion.
The hook portion and actuation lever are formed from a singular
piece of material.
Inventors: |
Major; Daniel W.;
(Middletown, CT) ; Pudvah; Bernard W.; (Portland,
CT) |
Assignee: |
United Technologies
Corporation
Hartford
CT
|
Family ID: |
41363955 |
Appl. No.: |
13/493064 |
Filed: |
June 11, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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12251560 |
Oct 15, 2008 |
8215902 |
|
|
13493064 |
|
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Current U.S.
Class: |
415/148 ;
29/889.2 |
Current CPC
Class: |
Y02T 50/672 20130101;
F01D 17/162 20130101; Y10T 29/49323 20150115; Y02T 50/60 20130101;
F04D 29/563 20130101; Y10T 29/4932 20150115 |
Class at
Publication: |
415/148 ;
29/889.2 |
International
Class: |
F01D 9/04 20060101
F01D009/04; B23P 15/00 20060101 B23P015/00 |
Claims
1. A variable vane arm, comprising: a hook portion for attaching
the vane arm to the outer trunnion of a vane, comprising a radially
inner leg connected to a radially outer leg by an arcuate
connection; and an actuation lever extending from the hook portion,
the actuation lever containing an aperture for the reception of a
fastener to connect the actuation lever to an actuation mechanism;
wherein the hook portion and actuation lever are formed from a
singular piece of material.
2. The variable vane arm of claim 1 further comprising: a bend
between the hook portion and actuation lever.
3. The variable vane arm of claim 1 wherein the radially inner leg
contains a first aperture and the radially outer leg contain a
second aperture.
4. The variable vane arm of claim 3 wherein the first and second
apertures are collinear.
5. The variable vane arm of claim 4 wherein the first aperture
contains different dimensions that the second aperture.
6. The variable vane arm of claim 3 wherein the first aperture and
the second aperture each contain different dimensions a radially
inner surface than a radially outer surface.
7. The variable vane arm of claim 3 wherein the radially inner leg
contains a cut out portion adjacent one edge.
8. The variable vane arm of claim 3 wherein the radially outer leg
contains a third aperture between the second aperture and the
arcuate support.
9. A method comprising: cutting a blank from a sheet of material;
bending the blank in a first position to create a vane arm having a
hook portion with two generally parallel legs, and an actuation
lever extending from the hook portion; providing a fixture designed
to be placed between the two generally parallel legs to support the
vane arm during additional fabrication; machining a first aperture
through a first generally parallel leg; and machining a second
aperture through the second generally parallel leg, the first
aperture and the second aperture being collinear about an axis.
10. The method of claim 7 further comprising: fabricating a cut out
adjacent an edge of the first generally parallel leg.
11. The method of claim 9 further comprising: bending the vane arm
in a second position.
12. The method of claim 9 further comprising: fabricating an
aperture in the blank adjacent an end opposite of the hook
portion.
13. The method of claim 9 further comprising: connecting a vane to
the vane arm.
14. The method of claim 13 further comprising: connecting the vane
arm to a sync ring.
15. The method of claim 13 further comprising: rotating the vane
arm about a radial axis by moving the sync ring with an actuation
system.
Description
CROSS-REFERENCE TO RELATED APPLICATION(S)
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/251,560 filed Oct. 15, 2008.
BACKGROUND
[0002] Gas turbine engines are widely applied machines for
generating power or thrust. Most typically, they are employed on
modern aircraft to provide the propulsion necessary for flight.
They may also be used onboard such aircraft for power generation in
an APU (Auxiliary Power Unit) capacity to provide for onboard
heating, cooling, and ventilation, as well as operational power and
lighting systems onboard the aircraft within the cockpit, passenger
cabin, and the like. They may also be used in land based
applications for generation of electrical power or mechanical
horsepower in myriad vehicles and pieces of machinery.
[0003] In a typical gas turbine engine, three main sections are
provided, namely, a compressor section, a combustion section, and a
turbine section. Within the compressor section, ambient air is
ingested, highly compressed, and directed through a downstream
diffuser into the combustion section. Within the combustion
section, the highly compressed air is mixed with fuel within an
annular combustion chamber and burned at extremely high
temperatures, generating massive levels of heat energy. Moreover,
as opposed to internal combustion engines, wherein the ignition of
the fuel is intermittent every two or four strokes of the engine,
ignition within a gas turbine engine is continuous, thereby
increasing the high power levels attainable by the engine.
[0004] From the combustion section, the extremely hot combustion
gases are directed to the turbine section downstream of the
combustion chamber. As both the turbine section and the compressor
section are mounted on the same shaft assembly, rotation of the
turbine blades, upon contact with the rapidly expanding and hot
combustion gases, causes the shaft to which they are mounted to
rotate and in turn causes the compressor blades, also mounted to
the shaft, to rotate and thus complete the engine cycle. The
discharge of the rapidly expanding hot gases at high velocities
from the turbine causes the engine to generate the aforementioned
thrust needed for aircraft operation.
[0005] Typical compressors and turbines include a plurality of
blades mounted on the rotor or central shaft of the engine, and a
plurality of vanes on an inner engine casing, sometimes referred to
as a stator. Within the compressor section, the compression ratio
achievable by modern day gas turbine engines is in excess of 40:1.
Such compressors can also rotate in excess of 1,000 miles/hr. and
ingest in excess of 2,600 lbs/air/sec. These attributes, when
combined with the continuous flow and ignition of fuel indicated
above, can result in the engine generating in excess of 250,000 hp,
with exhaust gases exiting the engine at speeds in excess of 1,000
miles/hr, thereby enabling commercial aircraft to cruise at the
slightly less than supersonic speeds at which modern travelers have
become accustomed, and military aircraft to travel at Mach speeds
necessary in modern warfare.
[0006] However, in order for such engines to operate optimally, the
vanes of the compressor section, those extending both from the
rotor and the engine casing, must be accurately dimensioned and
mounted to ensure the incoming air is compressed as needed and does
not simply flow axially through the engine. Moreover, it is often
necessary for some of the vanes, typically those mounted on the
engine casing, to be movable about a longitudinal axis. More
specifically, such vanes are typically provided with a mounting
stem or trunnion for connection to a vane arm. The vane arm is
mounted so as to be rotatable and is connected to an actuator, such
as a motor or other power source within the aircraft, so as to
enable the vanes to rotate when the vane arm rotates.
[0007] In light of the above, one of ordinary skill in the art will
readily understand that the mounting structure of the vane arm must
be sufficiently robust to withstand the significant forces
generated by the compressor section during not only normal
operation, but when the engine experiences surge or other
transients as well.
[0008] With prior art vane designs, vanes are typically mounted
within vane arms using a retention device often referred to as a
claw. In other words, the vane arm includes first and second
appendages which wrap around the vane trunnion and insert into
grooves or slots provided within the vane trunnion. A threaded
fastener such as a bolt is then inserted through the vane arm and
into the vane trunnion to provide additional attachment. Such a
design provides a dual retention feature in that the claws are able
to retain the vane in the event that the preload provided by the
fastener is lost or when the entire fastener itself becomes
dislodged from the vane arm. However, such a design is limited in
the load conditions under which it can operate in that the claw
arms tend to spread or cam away from the trunnion under high loads
thereby causing the assembly to lose its capability for driving the
vane to the correct angular orientation.
[0009] In another prior art design, it has therefore been known to
provide a vane arm that drives the vane using an interference fit
between the trunnion and the vane arm, with a loose fit being
provided between another portion of the trunnion and a surge slot
of the vane arm. Accordingly, when the vane arm assembly is placed
under high loads and the interference fit begins to be lost due to
deformation of the vane arm, the deformation causes the loose
fitting area between the vane arm and trunnion to tighten, thereby
providing a secondary mechanism for driving the vane under higher
loads. While such a design is effective in this regard, it does not
provide dual retention features in the event of fastener or
fastener preload loss, and it requires relatively heavy materials
at added expense.
[0010] It is also known in the prior art to provide a vane arm that
has a dual retention capability to ensure that vanes of the gas
turbine engine remain connected to the vane arm even under surge
loads or when the fastener is lost. This is accomplished with a
variable vane arm with a surge slot to facilitate rotation of the
vane even when the vane is operating under surge or otherwise
excessively high pressure conditions. Such a system and design is
effective for dual retention, but does again require relatively
heavy materials and added expense in manufacturing.
[0011] Within the context of aircraft, it is also important to
understand that weight is always at a premium. The lighter the
material is, the lighter the engine, and the lighter the engine,
the lighter the aircraft will be. This directly translates into
less fuel consumption and lower costs of operation. Designers have
therefore been required to select materials which are sufficiently
robust to withstand the aforementioned loads, while minimizing the
weight being added to the aircraft. A still further complicating
factor is that of cost. Quite often the materials which are
sufficiently robust to withstand the loads encountered by the
engine and still meet certain weight requirements, come at costs
which make them unacceptable. Alternatively, they come at a cost
which makes the overall engine cost more than is desirable.
[0012] In light of the foregoing, it can therefore be seen that a
need exists for a vane arm mounting structure with improved
retention capabilities even in the situation where fastener preload
or the entire fastener are lost, and which can provide a mechanism
by which the vane can be driven during both normal loads and
surging. Moreover, it would be beneficial if such a design were to
be provided wherein relatively inexpensive and light weight
materials could be used in the place of materials which have
traditionally been required.
SUMMARY
[0013] In one embodiment, a variable vane arm has a hook portion
comprising a radially inner leg connected to a radially outer leg
by an arcuate connection, and an actuation lever extending from the
hook portion. The hook portion and actuation lever are formed from
a singular piece of material.
[0014] In another embodiment, a vane arm assembly is disclosed that
contains a vane arm having a hook portion having a radially inner
leg connected to a radially outer leg by an arcuate connection and
an actuation lever extending from the hook portion. A spacer
capable of being inserted into the hook portion of the vane arm, a
locking mechanism attached to the radially outer side of the hook,
and a fastener for securing the assembly to a vane are also
provided to complete the assembly.
[0015] In a different embodiment, a gas turbine engine has a
compressor section, a combustion section; and a turbine section.
The compressor section contains a plurality of vanes connected to a
plurality of vane arms, each vane arm having a hook portion having
a radially inner leg connected to a radially outer leg by an
arcuate connection, and an actuation lever extending from the hook
portion.
[0016] In yet another embodiment, a method of fabricating a vane
arm is disclosed. A blank is cut from a sheet of material, and then
bent in a first position to create a hook portion with two
generally parallel legs. A fixture designed to be placed between
the two generally parallel legs to support the vane arm during
additional fabrication is provided. Then, a first aperture through
a first generally parallel leg, and a second aperture through the
second generally parallel leg are machined in the vane arm. The
first aperture and the second aperture are collinear about a common
axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 shows a schematic of a gas turbine engine in which
variable vane arm assemblies are used.
[0018] FIG. 2 shows a high pressure compressor section of the gas
turbine engine of FIG. 1 showing the interaction between variable
stator vanes and a high pressure compressor (HPC) front case.
[0019] FIG. 3 shows a perspective view of a variable vane arm
assembly.
[0020] FIG. 4 shows a perspective view of the variable vane
assembly of FIG. 3 with a vane arm having a pin and spacer attached
thereto.
[0021] FIG. 5 shows a cross-sectional view of a variable vane arm
assembly.
[0022] FIG. 6 shows a perspective view of a fixture and tooling for
manufacturing vane arms.
DETAILED DESCRIPTION
[0023] FIG. 1 shows a schematic gas turbine engine 10, in which a
vane segment with an integral inner air seal can be used. Gas
turbine engine 10 comprises fan 12, low pressure compressor (LPC)
14, high pressure compressor (HPC) 16, combustor section 18, high
pressure turbine (HPT) 20 and low pressure turbine (LPT) 22, which
are each concentrically disposed around longitudinal engine
centerline CL. Fan 12 is enclosed at its outer diameter within fan
case 23A. Likewise, the other engine components are correspondingly
enclosed at their outer diameters within various engine casings,
including LPC case 23B, HPC case 23C, HPT case 23D and LPT case 23E
such that an air flow path is formed around centerline CL.
[0024] Inlet air A enters engine 10 and it is divided into streams
of primary air AP and secondary air AS after it passes through fan
12. Fan 12 is rotated by low pressure turbine 22 through shaft 24
to accelerate secondary air AS (also known as bypass air) through
exit guide vanes 26, thereby producing a major portion of the
thrust output of engine 10. Shaft 24 is supported within engine 10
at ball bearing 25A, ball bearing 25B and roller bearing 25C.
Primary air AP (also known as gas path air) is directed first into
low pressure compressor (LPC) 14 and then into high pressure
compressor (HPC) 16. LPC 14 and HPC 16 work together to
incrementally step up the pressure of primary air AP. HPC 16 is
rotated by HPT 20 through shaft 28 to provide compressed air to
combustor section 18. Shaft 28 is supported within engine 10 at
bearing 25D and bearing 25E. The compressed air is delivered to
combustors 18A and 18B, along with fuel through injectors 30A and
30B, such that a combustion process can be carried out to produce
the high energy gases necessary to turn turbines 20 and 22. Primary
air AP continues through gas turbine engine 10 whereby it is
typically passed through an exhaust nozzle to further produce
thrust.
[0025] In order to expand the performance range of engine 10,
variable stator vanes are used in high pressure compressor 16. For
example, HPC 16 comprises variable vanes 32A and 32B, which are
stationary and extend radially inward from fan case 23C. Blades 34A
and 34B, which rotate with HPC 16 on shaft 28, are positioned
adjacent vanes 32A and 32B. Vanes 32A and 32B form part of an array
of vane stages arranged circumferentially around the engine
centerline between HPC case 23C and an inner diameter vane shroud.
Blades 34A and 34B sequentially push primary air AP past vanes 32A
and 32B within HPC 16 to increase the pressure of primary air AP.
Vanes 32A and 32B rotate about their radial axis to adjust the
incidence of the air AP onto subsequent blades, including blade
34B, during different operation modes, or speeds, of engine 10. In
order to ensure optimal operation of engine 10, it is preferable
that vanes 32A and 32B are able to rotate freely about their axis
within HPC case 23C and the inner diameter vane shroud.
[0026] FIG. 2 shows the sequential arrangement of the various
stages of high pressure compressor 16 about centerline CL of gas
turbine engine 10. For the embodiment of engine 10 shown, HPC 16 is
divided into stages S5 through S15, with LPC 14 of FIG. 1
comprising stages S1 through S4. Vanes 32A and 32B and blades 34A
and 34B comprise stages S6 and S7 of HPC 16, respectively. The
variable vanes rotate between HPC case 23C and a plurality of inner
diameter vane shrouds. Specifically, vanes 32A and 32B rotate
between HPC outer shroud 36, which is a component of case 23C, and
HPC inner shrouds 38A and 38B, respectively. In order to rotate
vanes 32A, 32B within outer shroud 36, vanes 32A, 32B are connected
to synchronization rings 40A and 40B, respectively, through a
plurality of vane sync arms 42. Sync rings 40A, 40B are connected
to, for example, a hydraulic actuator to adjust the pitch of vanes
32A, 32B such that airflow through HPC 16 is optimized for
different operating levels of engine 10. In order that vanes 32A,
32B rotate freely within outer shroud 36 and inner shrouds 38A,
38B, vanes 32A, 32B include inner and outer diameter trunnions.
[0027] When rotation of one of vanes 32A, 32B is desired,
corresponding vane arm 42A, 42B to which the particular vane 32A,
32B is mounted is rotated. To provide the motive force needed for
such rotation each vane arm 42A, 42B is connected to an actuator.
Energization of the actuator causes movement of a linkage or
similar structure, which in turn causes movement of sync ring 40A,
40B extending circumferentially around the engine casing 23. As
each vane arm 42, 42B is pivotally connected to sync ring 40A, 40B,
movement of sync ring 40A, 40B causes movement of vane arms 42A,
42B, and thus vanes 32A, 32B. Any number of different actuators and
drive mechanisms may be employed, including, but not limited to,
motors, gears, pulleys, linear actuators, solenoids, screw-drives,
and the like. In addition, a number of synchronization rings (as
represented by 40A, 40B) corresponding to the number of vane stages
may be provided, with two rings and stages being depicted in FIG.
2.
[0028] FIG. 3 is a perspective view of the components of a vane arm
assembly 50 for connecting to outer trunnion 52 of vane 32. FIG. 4
shows a perspective view of variable vane arm assembly 50 of FIG. 3
with vane arm 42 having pin 100 and spacer 56 attached thereto.
Vane arm 50 assembly is comprised of vane arm 42, spacer 56,
locking mechanism 58, and nut 59. Nut 59 is a conventional threaded
nut, such as a locking hex nut, that will screw onto threaded
portion of vane trunnion 52 to secure vane assembly. As illustrated
in the cross-sectional view of vane arm assembly 50 in FIG. 5,
outer trunnion 52 is the top portion of vane 32, and contains
cylindrical portion 52a and threaded portion 52b connected by
joining portion 52c. Joining portion 52c may be a tapered shank,
and may contain a mistake proofing feature, such as a nonlinear
side, to assure proper orientation of vane 32 with respect to vane
arm assembly 50. Outer trunnion 52 may contain a shelf 52d on
cylindrical portion 52a, which may act as a stop for vane arm 42 in
some embodiments.
[0029] Locking mechanism 58 secures spacer 56 in position with
respect to vane arm 42. In the embodiment illustrated, locking
mechanism 58 contains a generally planer portion 60 with an
aperture 62, and tab 64. Locking mechanism 58 is constructed from a
light weight metal, carbon graphite, composite, polymer, or similar
materials. Tab 64 is a generally rectangular extension that is
generally perpendicular to planer portion 60. Tab 64 is fabricated
by bending a portion of a planer portion 60. In an alternate
embodiment, tab 64 may be a small rod or strip of material secured
to planer portion 60 such as by welding or a similar fusion
process. Planer portion 60 is a washer with aperture 62 for the
reception of the outer threaded portion 66 of trunnion 52 of vane
32. In the embodiment illustrated, planer portion 60 is comprised
of circular portion 68, connecting portion 70, and locating members
72, 74. Circular portion 68 may be either centrally located or
axially offset from center, and contains aperture 62 and acts as a
normal flat or locking washer would. Connecting portion 70 extends
from circular portion 68 and provides the attachment surface for
tab portion. Locating members 72, 74 extend from circular 68. In
the embodiment illustrated, two locating members 72, 74 extend at
approximately ninety degrees from on another, and will extend past
the perimeter of nut 59 when vane assembly is assembled. Locating
members 72, 74 may be designed to contain various surfaces to align
or act as reference points with respect to other engine hardware
and components.
[0030] Spacer 56 is constructed from a light weight metal, carbon
graphite, composites, or similar materials, and may be fabricated,
such as by machining, from a larger piece of material. This helps
reduce the overall weight of the vane arm assembly 50. Spacer has a
rectangular prism shape with an extension 76 from one side. Spacer
56 is a precision piece that is designed to be placed between
radially inner leg 80 and radially outer leg 82 of hook 84 of vane
arm 42 that will provide support for hook 84 of vane arm 42, and
attachment and guide means for other components of vane arm
assembly 50.
[0031] In the embodiment illustrated, spacer 56 is of a length
approximately equal that of the length of generally parallel
surfaces of radially inner leg and radially outer leg 82 of hook
84. Extension 76 is sized to mate with the cut-out 86 of vane arm
extension, i.e., being of a length and depth that allows the
surfaces of extension 76 to be generally flush with cut-out area 86
and linear surfaces of radially inner leg 80 and radially outer leg
82 of hook 84. Extension 76 is illustrated as a rectangular prism,
although other geometries may be utilized. Various dimensions of
spacer 56, including extension 76, may be oversized to allow for an
interference fit with vane arm 42. In an alternate embodiment, a
bonding agent may be used between spacer 56 and vane arm 42 to keep
the parts in place with respect to on another after installation.
An interference fit or bonding eliminates the need for additional
components, such as fasteners, for assembling vane arm assembly
50.
[0032] Spacer 56 contains aperture 88 for the reception of outer
threaded portion 66 of trunnion 52 of vane 32. In the embodiment
illustrated, the diameter of aperture 88 is equal to the largest
cross-sectional dimension of trunnion stem 52. Aperture 88 extends
through the body of spacer 56. In alternate embodiments, aperture
88 is of a cross sectional area that allows for insertion of
trunnion stem joining portion 52c through spacer 56 and vane arm
42. Aperture 88 may be over-sized compared to the cross-sectional
area of trunnion stem 52 to reduce weight of spacer 56.
[0033] Spacer 56 may have a portion of material removed adjacent
extension to form recesses 90, 92. The geometry of recesses 90, 92,
including cross-sectional area and shape, may vary. Recesses 90, 92
provide a space for air flow, as well as reduce the weight of
spacer 56.
[0034] Vane arm 42 has hook 84 and actuation lever 94. Hook 84 is
attached adjacent actuation lever 94, and both parts are fabricated
from a singular piece of material such as a light weight, high
tensile metal or alloy, or composite. Vane arm 42 is constructed
from standard sheet stock materials, thus reducing weight and
cost.
[0035] Actuation lever 94 is comprised of a generally flat strip of
material. End 96 opposite hook 84 is illustrated as rounded, but
may be a different geometry such as square. Actuation lever 94
contains an aperture 98 adjacent end 96. Aperture 98 facilitates
attachment of actuation lever 94 to sync ring 40A, 40B and thus the
actuator for providing rotational movement of vane arm 42 (see FIG.
2). Any type of bolt, fastener, or linkage may be employed in this
capacity with pin 100 being depicted to enable pivotal movement
with the synchronization ring of the vane case.
[0036] Vane arm 42 may contain an angle or bend 102 to facilitate
spacing and connection of vane arm assembly 50 with other adjacent
engine components. Bend 102 positions actuation lever 94 with
respect to hook 84. In the embodiment illustrated, bend 102 is
between actuation lever 102 and hook 94, although in other
embodiments bend 102 may be contained within actuation lever 94 of
vane arm 42. Similarly, bend 102 is shown to be spacing actuation
lever 94 radially outward of hook 84, but in other embodiments
actuation lever 94 may be radially inward of the radially outward
surface of hook 84. In yet another embodiment, vane arm 42 contains
no angle or bend and actuation lever 94 is collinear with radially
outer leg 82 of hook 84.
[0037] Hook 84 contains radially outer leg 82 joined to radially
inner leg 80 through support 104. Support 104 is a semicircular or
arcuate bend in vane arm 42, and positions radially outer leg 82
and radially inner leg 84 so that the two are generally parallel.
Hook 84 is formed from a singular piece of material.
[0038] End 106 of radially outer leg 82 opposite support is
connected to bend 102. Radially outer leg 82 contains aperture 108
adjacent bend. Aperture 108 receives tab 64 of locking mechanism 58
to secure locking mechanism 58 in place with respect to vane arm
42. Spacer 56 may also contain tab reception aperture (not
illustrated), which provides a position for the insertion of tab 64
of locking mechanism 58 to locate vane arm assembly 50 components
with respected to one another. The tab reception aperture of spacer
56 and aperture 108 are collinear about a radial axis, but need not
be the same size or geometry in cross-section. Tab reception
aperture need not extend through the entire body of spacer 56.
[0039] Radially outer leg 82 contains second aperture 110, which
has two generally parallel sides 112, 114, linear side 116, and
non-linear side 118. Aperture 110 is for the reception of stem 52
of vane 32. Non-linear side 118 acts as a fool-proofing mechanism
during installation of vane arm assembly 50, assuring that vane 32
is properly set with respect to vane arm 42. In other embodiments,
aperture 110 may contain other fool-proofing geometries, such as a
trapezoidal opening. Aperture 110 is illustrated as being centrally
located, but may be closer to support 104 than to bend 102.
[0040] Radially inner leg 80 contains aperture 120. Aperture 120
contains the same opening geometry and is collinear with aperture
110 in radially outer leg 82. This allows for the insertion of stem
52 of vane 32. In an alternate embodiment, a portion of outer
trunnion stem 52 is tapered, resulting in different cross-sectional
areas of apertures 110, 120, and within each aperture 110 or 120
from its radially inner edge to its respective radially outer edge.
Such a geometry assures full contact of the side surfaces of
apertures 110, 120 with joining portion 52c (see FIG. 5). Such
continuous contact eliminates wear-based backlash or hysteresis of
the vane arm assembly 50.
[0041] Radially inner leg 80 also contains cutout 86 for the
reception of extension of spacer. As illustrated, cutout has three
linear surfaces 124, 126, and 128 separated by arcs 130, 132.
During fabrication, two holes are drilled through radially inner
leg, and then linear surfaces 124, 126, 128 are fabricated. The
presence of arcs 130, 132 allows for alignment of spacer 56, weight
reduction of the part, and provides a fluid path for allowing air
to contact and be directed by recesses 90, 92 of spacer 56.
[0042] The disclosed design of vane arm 42 greatly reduces
manufacturing costs associated with the part. First, blanks are cut
from sheet stock. Next, the blank is bent utilizing known bending
methods, such as a break press. Vane arm 42 is designed so that
hook 84 contains an inner radius R (see FIG. 4) that extends
forward of actuation lever 94, and thus allows for the minimization
of width W (see FIG. 5) of vane arm 42 without compromising
structural integrity of the part. A narrower width W accommodates
tight spatial constraints between adjacent vanes 32.
[0043] FIG. 6 illustrates fixture 134 supporting several vane arms
42. Fixture 134 contains a series of slots 136 on top side 138 to
receive radially outer leg 80 and position vane arm 42 within
fixture 134. Fixture 134 is designed to allow vane arm 42 to slide
over until contacting support 104 of vane arm 42. In the embodiment
illustrated, apertures are formed within stem support with an EDM
(electro-discharge machine) tool 140. Tool 140 is shaped to create
an aperture that allows for the foolproofing shape previously
discussed. Similarly, tool 140 may be provided with a taper 142,
profiling that of the outer trunnion stem of vane 32 as illustrated
in FIG. 5.
[0044] Fixture 134 may contain aperture 144 corresponding to
apertures 110,120, and thus tool 140 is used to create apertures in
vane arm 42. In an alternated embodiment, fixture 134 is disposable
tooling and the EDM tooling cuts an aperture 144 through fixture as
well as radially inner leg 80 and radially outer leg 82 of vane arm
42. In this embodiment, vane arm 42 is first cut from a base piece
of material. The arm is then bent, and positioned on fixture 134,
and finally all apertures 110, 120, and 98 and other associated
features (cut out 86) are cut. Apertures 110, 120 are started by
drilling circular holes 146,148 to create a discharge path for
debris from tool 140. Tool 140 then cuts aperture 110, including
two generally parallel sides 112, 114, linear side 116, and
non-linear side 118. Similarly, tool 140 will then cut aperture 120
in radial outer leg 82.
[0045] In an alternate embodiment, vane arm 42 is cut from a piece
of material. Apertures 98 and 108 are then drilled. Cut out 86 is
then fabricated by first drilling two holes 130, 132, and then
removing material leaving linear surfaces 124, 126, 128, such as by
machining. After completion of these features, vane arm 42 is bent
to create support 104, and also bend 102.
[0046] In an alternate embodiment, vane arm 42 and corresponding
110, 120 and 98 apertures are formed prior to bending of vane arm
42, such as by stamping, laser or plasma cutting, or drilling and
machining of the flat pattern into a sheet of material. Vane arm 42
is then bent to create hook 84, and optionally bend 102. Care
should be taken in the bending process to assure that apertures
110, 120 in the radially inner leg 80 and radially outer leg 82 of
vane arm 42 align after the flat pattern is bent. In yet another
embodiment, a combination of machining and drilling is done both
prior to and after bending.
[0047] After fabrication, vane arm 42 and associated vane arm
assembly components may be installed into engine 10. Spacer 56 is
placed in hook 84. Locking mechanism 60 is then placed on the
radially outer surface of hook 84. Apertures 110, 120 of hook 84,
aperture 88 in spacer 56, and aperture 62 in locking mechanism 62
are aligned to be collinear about a radially extending axis. In
some embodiments, extension 76 of spacer 56 is secured to cutout 86
in vane arm 42 through an interference fit. Further, in some
embodiments, tab 64 of locking mechanism 60 extends into aperture
108 of vane arm 42, and optionally into an aperture in spacer 56.
This locates and further secures vane arm 42, spacer 56, and
locking mechanism 60 with respect to each other. Outer trunnion 52
is then inserted into this sub-assembly, and is secured to vane arm
assembly 50 via fastener 59. Next, actuation lever 94 is positioned
so that fastener 100 may be inserted into aperture 98 to connect
vane arm assembly 50 to sync ring 40.
[0048] The disclosed design of a vane arm and vane arm assembly has
several advantages. The fabrication of the vane arm utilizes
existing machinery without requiring expensive tooling, thus
reducing costs. Similarly, fabricating the vane arm from stock
material, such as cutting blanks from sheets, saves on material
costs over existing designs.
[0049] The design of the vane arm assembly allows for several
different ways of reducing weight of the components (vane arm,
spacer, and locking mechanism) without sacrificing structural
integrity. This is important because added weight to an engine
reduces the efficiency of the engine and any corresponding machine
(i.e., aircraft) by requiring greater fuel consumption. The design
of the hook with a small radius reduces the size of the vane
assembly. Further, the spacer with the hook of the vane arm adds
strength, which allows for a narrower vane arm. This prevents
interference with adjacent parts, and also can be translated into
additional vanes for the engine stage if desired. Although the vane
arm may contain a smaller area adjacent the trunnion than existing
vane arms, this can be compensated by placing a bend in the vane
arm. This assures that the vane arm is still capable of being
connected to both the vane and the sync ring, and thus allows for
retrofitting on existing engines.
[0050] Although the present invention has been described with
reference to preferred embodiments, workers skilled in the art will
recognize that changes may be made in form and detail without
departing from the spirit and scope of the invention.
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