FIELD OF THE INVENTION
The present invention relates to thrust reversers for jet engines,
and more particularly, to anti-deployment mechanisms for thrust reversers.
BACKGROUND OF THE INVENTION
Jet aircraft, such as commercial passenger and military aircraft,
utilize thrust reversers on the aircraft's jet engines to reduce the aircraft's
speed after landing. One type of thrust reverser used in modern jet aircraft is
the cascade type, described in more detail in U.S. 5,448,884. For ease of reference,
the description of the cascade type of thrust reverser is substantially reproduced
Referring first to FIG. 1, there is shown a conventional aircraft
nacelle indicated at 18 which includes a jet engine, such as a Pratt & Whitney
PW4000, indicated at 20 (shown in hidden lines) supported by a strut 22 on a wing
24 (only a portion of which is shown). The nacelle 18 includes a nose cowl 26,
a fan cowl 27, a thrust reverser sleeve 28, a core cowl 30 and nozzle exhaust 32.
Although some of these components are made up of two mirror image parts split vertically
in a clamshell arrangement, each component will be referred to herein as being
As shown in more detail in FIGS. 2 and 3, the thrust reverser system
includes an inner duct (fan duct cowl) 36 and outer sleeve 28. The sleeve 28 translates
in an aft direction indicated by an arrow identified by a number 42 in FIG. 2,
and a forward direction indicated by an arrow identified by a number 44. When the
thrust reverser is deployed, the translating sleeve 28 moves aft from a "stowed"
position shown in FIG. 1 to a "deployed" position shown in FIG. 2. In this process,
cascade vanes 46 (FIG. 2) mounted to a thrust reverser support structure are uncovered.
Vanes 46 are slanted in a forward direction so that during thrust reverser operation,
fan air from the engine is redirected forward through the vanes (indicated by arrows
47) to aid in decelerating the airplane.
Air driven aft by the engine fan flows along an annular duct 48 (FIGs.
2 & 3) formed by the fan duct cowl 36 and core duct cowl 30. Movement of the
sleeve 28 in the aft direction, causes blocker doors 50 to pivot from their stowed
positions (shown in FIG. 3) to their deployed positions (shown in FIG. 2) where
the doors are positioned to block rearward movement of the air through duct 48.
In this manner all rearward movement of the engine fan air is redirected forward
through the cascade vanes 46.
Movement of the sleeve 28 is guided along a pair of parallel tracks
mounted to the top and bottom of the fan duct cowl 36 in a fore and aft direction.
The sleeve 28 is moved between the stowed and deployed positions by means of a
number of hydraulic actuators indicated at 54 (FIG. 3), each having an actuator
rod 56 which is connected to the sleeve 28. More specifically, as shown in FIGS.
5 and 6, each actuator 54 is connected to a structural torque box 57 via a gimbal
mount 61 thereby allowing the actuator to accommodate lateral variances in sleeve
motion. As shown in FIG. 4, the actuator rod 56 is located inside the aerodynamic
surface of sleeve 28 and is connected to the sleeve 28 by a ball joint 68. The
ball joint 68 is accessible by removing a panel 70 which is bolted to the exterior
surface of the sleeve 28.
In operation, when the thrust reverser is commanded by the pilot
to the deployed position, each actuator rod 56 (FIG. 5) extends in the aft direction.
Conversely, when the thrust reverser is commanded by the pilot to move to the stowed
position, each actuator rod 56 retracts in the forward direction. In an exemplary
embodiment, the actuator 54 is a thrust reverser actuator currently installed on
Boeing 767 airplanes.
As shown in FIG. 7, each actuator 54 includes a double acting piston
72 which is extended in the rightward direction (with reference to FIG. 7) by hydraulic
pressure acting against a face 74 of the piston 72. Retraction of the piston 72
and the thrust reverser sleeve therewith is accomplished by relieving hydraulic
pressure from the piston face 74, so that hydraulic pressure acting against an
opposing face 76 of the piston causes it to move in the leftward direction. The
piston 72 is connected to the actuator rod 56 which in turn is connected to the
thrust reverser sleeve 28 in the manner described previously.
In the exemplary embodiment, each thrust reverser sleeve is driven
by three of the actuators 54 (FIG. 3). It is important that each actuator 54 extend
and retract the sleeve at the same rate to avoid causing the sleeve to bind along
the tracks 51. To accomplish this, operation of each of the three actuators 54
is synchronized by means of an interconnecting synchronizing shaft 80. The sync
shaft 80 (FIGS. 5 and 6) is a tube having a stationary outer sleeve and an internal
rotating flexible shaft 81 which synchronizes motion of the three actuators. The
outer sleeve of the sync shaft 80 is connected to the actuator 54 by a swivel coupling
In order to explain this synchronizing operation in greater detail,
reference is made to the section view of the actuator 54 in FIG. 7. As shown, the
piston 72 is connected via a non-rotating threaded drive nut 84 to a rotating
Acme screw 86. As piston 72 translates the drive nut 84 moves with it. Translating
movement of the drive nut 84 along the Acme screw 86 causes the Acme screw to rotate
thereby converting translational movement into rotational movement. Synchronizing
operation is further accomplished by a worm gear 90 (FIG. 6) located inside the
actuator housing which engages a spur gear 94 which in turn is mounted to the end
of the Acme screw 86. Furthermore, the internal sync shaft 81 has a splined end
tip which is positioned inside a slot (not shown) in the right end of the worm
Referring again to FIG. 7, extension and retraction of the thrust
reverser sleeve results in rotation of the Acme screw 86 and rotary gear 94 therewith.
This causes rotation of the worm gear 90 in a manner that a high torque and low
rotational speed input from the Acme screw 86 is converted by the worm gear 90
to a low torque and high rotational speed output to the sync shaft. In the event
one of the actuators 54 attempts to move the thrust reverser sleeve at a different
rate than the other actuators, their rates are equalized via the common sync shaft
and through the respective worm gears, spur gears and Acme screws of the actuators.
This results in uniform translation of the thrust reverser sleeve.
In order to allow the thrust reverser sleeve 28 to be moved between
the stowed and deployed positions for maintenance purposes while the airplane is
on the ground, a manual drive clutch mechanism 96 shown in FIG. 6 is attached to
the left end of the actuator. The manual drive clutch 96 includes a socket (not
shown) for receiving a square drive tool (also not shown) in its left end 95. The
manual drive clutch 96 is connected by a female coupling 97 to a threaded male
connector 98 at the left end of the actuator. The drive clutch 96 includes a drive
shaft 99 (FIG. 10) having a square-ended tip which extends in a rightward direction
from the clutch and which fits inside an end slot 100 (FIG. 5) of the actuator
worm gear 90.
In operation, when the square drive tool is inserted into the manual
drive clutch in a rightward direction, the clutch is engaged thereby allowing the
square drive tool to drive the worm gear 90 (FIG. 6), which in turn drives the
spur gear 94, Acme screw 86 to translate the thrust reverser sleeve.
With reference to FIGS. 8 - 11, mechanical lock 104 is connected
to the actuator 54 in place of the drive clutch 96. In turn, the drive clutch 96
is connected to the left end of the mechanical lock 104. Like elements described
previously will be identified in FIGS. 8 through 11 by like numerals.
The purpose of the mechanical lock 104 is to prevent uncommanded
translation of the thrust reverser sleeve. The mechanical lock 104 includes a cylindrical
housing 106 (FIG. 10) having an internal cylindrical passageway 108. Axially aligned
with the centerline of the passageway 108 is a cylindrical shaft 110 having an
eight-pointed splined slot 112 at its left end for receiving therein the splined
end tip 99 Of the clutch mechanism 96 described previously. At the right end of
the shaft 110 is a splined tip 113 which is inserted in the socket 100 (FIG. 5)
of the actuator worm gear 90. Mounted centrally on the center shaft 110 (FIGS.
9 and 10) is a lock wheel 114 having a cylindrical outer surface 116.
Extending from the locking wheel surface 116 at equally spaced intervals
are four square teeth 118 (FIG. 11) whose rotational path is blocked by a locking
pin 120 when the device is de-energized and the locking pin is in a down/locking
position shown in FIGS. 10 and 11. More particularly, the locking pin 120 extends
through an opening 122 in the upper wall of the housing 106. It should be appreciated
that the direction of the shear force created by the rotation of the locking wheel
114 and shaft 110 therewith is orthogonal to the locking/unlocking movement of
the locking pin thereby minimizing the forces required to extend and retract the
locking pin 120.
In operation, when the locking pin 120 is in the down/locking position
it prevents rotational movement of the shaft 110 thereby preventing rotation of
the worm 90 (FIG. 9), worm gear 94, and the Acme screw 86. This, in turn, prevents
translational movement-of the drive nut 84 (FIG. 7), the piston 72 and the thrust
reverser sleeve 28 therewith, thereby preventing thrust reverser sleeve motion.
Movement of the locking pin 120 (FIG. 10) between the locked position
and an unlocked position (where the pin 120 is above and clear of the teeth 118)
is controlled by an electrically operated solenoid 124 through which the upper
end of the locking pin 120 extends. Electrical control is initiated at the cockpit
(not shown) via conventional airplane thrust reverser control circuits and is transmitted
by electrical wires 125 to the solenoid 124. Control of the solenoid may be accomplished
in a conventional manner. It should be appreciated that other means for controlling
movement of the locking pin 120, such as hydraulic or electrohydraulic means, may
Thrust reversers include various anti-deployment mechanisms to prevent
in-flight deployment, such as locking actuators, non-locking actuators, synchronization
shaft locks (sync lock), and auto-restow systems. Thrust reversers presently used
on Boeing aircraft have three levels of locking means. For example, thrust reversers
used on wide body aircraft illustratively have two locking actuators per nacelle
and one sync lock per nacelle. Thrust reversers used on narrow body aircraft illustratively
have one locking actuator per nacelle, one sync lock per nacelle, and an auto-restow
system per nacelle.
SUMMARY OF THE INVENTION
It is an object of this invention to link the synchronization
systems of the thrust reverser actuation systems of the two sides of the thrust
reverser so that anti-deployment mechanisms used for each of the thrust reverser
actuation systems can provide one or more of the redundant anti-deployment mechanisms
for the other thrust reverser actuation system.
A synchronization cross-feed system for a thrust reverser having
at least first and second sides. Each side of the thrust reverser has a thrust
reverser actuation system having a plurality of actuators. The actuators in each
thrust reverser actuation system are synchronized by a synchronization system.
A synchronization cross-feed system couples the synchronization systems of the
thrust reverser actuation systems of the first and second sides of the thrust reverser
allowing an anti-deployment mechanisms of each thrust reverser actuation system
to serve as one or more of the redundant anti-deployment mechanisms for other the
thrust reverser actuation system.
In an embodiment, the synchronization cross-feed systems has first
and second coupling assemblies that are removably coupled to each other so that
they decouple from each other when the thrust reverser sides are opened to allow
the thrust reverser sides to be opened.
In an embodiment, the first and second coupling assemblies have engagement
teeth that mate with each other when the thrust reverser sides are closed.
In an embodiment, the engagement teeth of the first coupling assembly
is disposed on a telescopic coupling shaft that is spring loaded by a spring in
the first coupling assembly that forces telescopic coupling shaft toward the second
In an embodiment, the first and second coupling assemblies have shafts
that are coupled to respective actuators of the thrust reverser actuation systems
of the first and second thrust reverser sides.
Further areas of applicability of the present invention will become
apparent from the detailed description provided hereinafter. It should be understood
that the detailed description and specific examples, while indicating the preferred
embodiment of the invention, are intended for purposes of illustration only and
are not intended to limit the scope of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention will become more fully understood from the
detailed description and the accompanying drawings, wherein:
FIG. 1 is a side view of a conventional nacelle and strut;
FIG. 2 is a side view of a conventional thrust reverser system;
FIG. 3 is an isometric view of a conventional thrust reverser system;
FIG. 4 is a partial view of a conventional thrust reverser sleeve
showing an access port located on the sleeve;
FIG. 5 is an isometric view of a conventional thrust reverser actuator;
FIG. 6 is a side view of the conventional thrust reverser actuator
shown in FIG. 5;
FIG. 7 is side sectional view of the thrust reverser actuator shown
in FIGS. 5 and 6;
FIG. 8 is an isometric view of a thrust reverser actuator employing
a prior-art mechanical synchronization shaft lock;
FIG. 9 is a side view of the thrust reverser actuator and mechanical
lock shown in FIG. 8;
FIG. 10 is a side sectional view of the mechanical lock of FIG. 8;
FIG. 11 is a partial end sectional view of the mechanical lock of
FIG. 12 is a cross-section of a thrust reverser having the synchronization
cross-feed system of the invention;
FIG. 13 is a side view of the synchronization cross-feed system of
the invention in an open position;
FIG. 14 is a sectional view taken along the line 14 - 14 of FIG.
FIG. 15 is a sectional view taken along the line 15 - 15 of FIG.
FIG. 16 is a side view of the synchronization cross-feed system of
the invention in a closed position; and
FIG. 17 is a side view of a ninety degree mechanical drive mechanism.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The following description of the preferred embodiment(s) is merely
exemplary in nature and is in no way intended to limit the invention, its application,
Referring to FIGs. 12 - 16, a synchronization cross-feed system 200
in accordance with the invention is described. Elements common to FIGs. 1 - 11
will be identified with the same reference numerals. Specifically referring to
FIG. 12, a cross-section of a thrust reverser 202, looking aft, is shown with synchronization
cross-feed system 200 spanning a lower bifurcation area 204 of thrust reverser
202 and linking thrust reverser actuation systems 206 of left and right sides 203,
205, (as oriented in FIG. 12) of thrust reverser 202. Each thrust reverser actuation
system 206 can illustratively be the thrust reverser actuation system described
with reference to FIGs. 1 - 11.
Specifically referring to FIGs. 13 - 16, synchronization cross-feed
system 200 is shown in greater detail. Synchronization cross-feed system 200 has
left and right coupling assemblies 212, 213 (as oriented in Figs. 13 - 16) having
housings 208, 209 supporting respective bearing assemblies 210. Left coupling assembly
212 has a telescopic coupling shaft 214 slidably coupled to a synchronization shaft
coupling 216 affixed to an end of a synchronization shaft 218. Right coupling assembly
213 has a fixed coupling 220 coupled to an end of a synchronization shaft 224.
Synchronization shaft coupling 216 and fixed coupling 220 are generally cylindrical,
having bores in distal ends 219, 221 in which respective ends of synchronization
shafts 218, 224 are received. Distal ends 219 and 221 are machined as double square
ends and the ends of synchronization shafts 218, 224 that are received in the double
square machined ends 219, 221 are illustratively swaged into squares. It should
be understood that right coupling assembly 213 could have the telescopic coupling
shaft 214 and the left coupling assembly 212 could have the fixed coupling 220.
Synchronization shaft coupling 216 and fixed coupling 220 illustratively
include a threaded portion 226, 228, respectively, and shoulders 230, 232, respectively.
A threaded bearing retainer 234 is threaded onto threaded portion 226 of synchronization
shaft coupling 216 to retain bearing 236 of the bearing assembly 210 on left coupling
assembly 212 against shoulder 230 to retain bearing 236 in place. Similarly, a
second bearing retainer 234 is threaded onto threaded portion 228 of fixed coupling
220 retain bearing 236 of bearing assembly 210 on right coupling assembly 213 in
Left coupling assembly 212 further includes a pin 238 radially extending
through synchronization shaft coupling 216 that holds a bearing retainer 240 in
place. Bearing retainer 240 holds bearing 242 of bearing assembly 210 in left coupling
assembly 212 in place.
Telescopic coupling shaft 214 includes wheel 244 having engagement
teeth 246 extending radially outwardly around a proximal facing side 245 and extending
axially therefrom toward fixed coupling 220. Wheel 244 also has tapered engagement
nose 248 extending axially from the center of proximal facing side 245 toward fixed
coupling 220. Wheel 244 and engagement teeth 246 are shown in more detail in FIG.
14. Wheel 244 further includes a cylindrical shaft 250 that extends from a distal
facing side 247 of wheel 244 over synchronization shaft coupling 216 and is slidably
secured thereon by a pin 252. A proximal end 254 of synchronization shaft coupling
216 has a spring receiving bore 256 therein that receives a spring 258 that extends
within cylindrical shaft 250 of telescopic coupling shaft 214 to a spring receiving
recess 259 in distal facing side 247 of wheel 244. Housing 208 of left coupling
assembly 212 has a radially outwardly extending flange 262 at a proximal end 260.
Flange 262 is secured to a fixed element of the thrust reverser, such as a torque
box 57 of the left side of thrust reverser 202, to secure left coupling assembly
212 in place.
Fixed coupling 220 has a bore 266 therein that opens at a proximal
end 264 of fixed coupling 220. Proximal end 264 has engagement teeth 268 around
the opening of bore 266. Engagement teeth 268 extend axially toward telescopic
coupling shaft 214. Engagement teeth 268 preferably angle outwardly from bore 266
to facilitate reception of tapered nose 248 into bore 266 when synchronization
cross-feed system 200 is in its engaged position where coupling assembly 212 mates
with right coupling assembly 213, as shown in FIG. 16. A bearing 270 of bearing
assembly 210 of right coupling assembly 213 is disposed around fixed coupling 220
in a recess 272 therein and is received in a recess 274 in housing 209. Housing
209 includes a flange 276 secured to fixed element of thrust reverser 202, such
as a torque box 57 of the right side of the thrust reverser 202, to secure right
coupling assembly 213 in place.
In operation, left coupling assembly 212 mates with right coupling
assembly 213 when thrust reverser sleeves 28 are in their operational positions
(stowed or deployed). In this regard, the right and left sides of thrust reverser
202 are in proximity to each other such that telescopic coupling shaft 214 has
been urged into fixed coupling 220 such that engagement teeth 246 of left coupling
assembly 212 engage engagement teeth 268 of right coupling assembly 213. Cylindrical
shaft 250 of telescopic coupling shaft 214 is urged into synchronization shaft
coupling 216, compressing spring 262, which urges telescopic coupling shaft 214
into fixed coupling 220. Telescopic coupling shaft 214 in cooperation with spring
262 allows for some movement between the halves of thrust reverser 202 without
damaging synchronization cross-feed system 200 yet maintains the engagement of
coupling assemblies 212 and 213. Further, since coupling assemblies 212 and 213
are held together only by the force of spring 262, they decouple from each other
when the left and right sides 203,205 of thrust reverser 202 are opened for maintenance,
thus allowing the left and right sides 203, 205 of thrust reverser 202 to be opened
Synchronization shafts 218, 224 are coupled to translation actuators
54 of left and right sides of thrust reverser 202 in the same fashion as described
above with reference to synchronization shaft 80 and translation actuators 54 and
illustratively couples to a translation actuator 54 in lieu of manual drive clutch
mechanism 96, thus coupling to the synchronization system (synchronization shaft
80 and associated components) of the thrust reverser actuation system. In this
regard, a manual drive mechanism, such as manual drive mechanism 300 (FIG. 17),
would be added to thrust reverser 202 in place of manual drive clutch mechanism
96. Alternatively, manual drive clutch mechanism 96 would be appropriately modified
to permit the respective synchronization shaft 218, 224 to couple to the translation
actuator 54. In another embodiment, mechanical lock 104 would be appropriately
modified to permit the respective synchronization shafts 218, 224 to mate to mechanical
lock 104 and thus to the synchronization system of the thrust reverser actuation
With reference to FIG. 17, mechanical drive mechanism 300 has a housing
301 in which a spring loaded drive pin 302 is mounted. Drive pin 302 has a square
hole 304 in its top to receive a square driver. Drive pin 302 has a bevel gear
306 at a lower end 308 (as oriented in FIG. 17). A shaft 310 extends transversely
through housing 301 at a lower end 312 thereof. Shaft 310 has a bevel gear 314
mounted thereon that mates with bevel gear 306 on drive pin 302 when drive pin
302 is depressed. A left end 316 (as oriented in FIG. 17) of shaft 310 is squared
to mate with the double squared hole in a translation actuator, such as actuator
54. Left end 316 of shaft 310 could also be formed to have a double squared hole
to mate with a shaft, such as synchronization shaft 218 or 224, for "in-line" installation.
A right end 318 of shaft 310 has a double squared hole to receive a squared end
of a shaft, such as synchronization shaft 218 or synchronization shaft 224. Right
end 318 of shaft 310 is affixed to cylindrical shaft 321 which is supported within
housing 301 by a pair of bearings 322. Housing 301 further has attachment fittings
320, such as B-nut fittings, surrounding left end 316 and right end 318 of shaft
The description of the invention is merely exemplary in nature and,
thus, variations that do not depart from the gist of the invention are intended
to be within the scope of the invention. Such variations are not to be regarded
as a departure from the spirit and scope of the invention.