Abstract:
An actuator assembly includes a rotatable first shaft, a second shaft, and a ball screw mechanism. The second shaft is telescopically received in and extensible relative to the first shaft. The second shaft is rotatable with the first shaft and is connected to and drives the ball screw mechanism.

Description:
BACKGROUND 
       [0001]    Jet engines typically include movable parts, which can be moved outward or retracted at various times through a flight. These movable parts are typically moved through actuation mechanisms of various types. 
         [0002]    The thrust reverser system of an engine may include a number of such movable parts. Generally a thrust reverser system includes two thrust reverser cowls. The thrust reverser cowls are actuated independently, and are located on each side of the engine, one on the right side and one on the left side. Each thrust reverser cowl assembly further may include a variable area fan nozzle (“VAFN”) cowl which needs to be able to move with the thrust reverser cowl, and further be able to translate beyond the movements with the thrust reverser cowl. This is sometimes done by attaching a gearbox and motor assembly to the thrust reverser cowl assembly translating frame. Such an assembly adds weight to the engine. 
       SUMMARY 
       [0003]    An actuator assembly includes a rotatable first shaft, a second shaft, and a ball screw mechanism. The second shaft is telescopically received in and extensible relative to the first shaft. The second shaft is rotatable with the first shaft and is connected to and drives the ball screw mechanism. 
         [0004]    In one embodiment, the actuator assembly is mounted to the nacelle of an engine. The gas turbine engine includes a thrust reverser cowl that is movable between a first position and a second position and a variable area fan nozzle cowl movable with the thrust reverser cowl and further movable beyond the thrust reverser cowl. In one embodiment, a gearbox and the first shaft are mounted to a stationary portion of the nacelle and the second shaft is connected to and is movable with the thrust reverser cowl. The ball screw mechanism is connected to and drives the variable area fan nozzle cowl to move the variable area fan nozzle cowl relative to the thrust reverser cowl. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0005]      FIG. 1A  is a side view of an actuator assembly mounted to a nacelle of an engine along with an external position sensor where the thrust reverser cowl and the VAFN cowl closed. 
           [0006]      FIG. 1B  is a side view of the actuation system of  FIG. 1A  with the thrust reverser cowl open and the VAFN cowl open. 
           [0007]      FIG. 2  is a perspective view of one embodiment of the actuator assembly which includes a gearbox, an outer shaft, and a ball screw mechanism. 
           [0008]      FIG. 2A  is a perspective view of the actuator assembly of  FIG. 2  with portions of the ball screw mechanism and the outer shaft removed to show an inner shaft. 
           [0009]      FIG. 3A  is a partial sectional view of another embodiment of the actuator assembly that utilizes a position sensor disposed the inner and outer shafts. 
           [0010]      FIG. 3B  is perspective view of the actuator assembly of  FIG. 3A  with the gearbox removed to reveal a worm gear assembly and a linear variable differential transformer. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]      FIG. 1A  shows an actuator assembly  14  mounted to a nacelle  12  of an engine  10  where a thrust reverser cowl  18  and a VAFN cowl  20  are in a closed or stowed position.  FIG. 1B  shows the actuator assembly  14  extended with thrust reverser cowl  18  and VAFN cowl  20  in an open or deployed position. The embodiment of the actuator assembly  14  shown in  FIGS. 1A and 1B  includes a first outer shaft  22 , a ball screw mechanism  24 , and a gearbox  28 . In  FIG. 1B , a second inner shaft  26  is extended from outer shaft  22  and translates with thrust reverser cowl  18 .  FIGS. 1A and 1B  additionally illustrate a position sensor  16  disposed external to actuator assembly  14  and a thrust reverser actuation system  30  that comprises a separate actuator from actuator assembly  14 . 
         [0012]    As shown in  FIGS. 1A and 1B , actuator assembly  14  is mounted to nacelle  12  and extends generally parallel to a position sensor  16  such as a linear variable differential transformer (“LVDT”). Position sensor  16  determines the position of inner shaft  26  and ball screw mechanism  24  in order to determine the position of thrust reverser cowl  18  and VAFN cowl  20  for control purposes. In the embodiment shown, outer shaft  22  is mounted to a stator portion of nacelle  12  and is free to rotate relative thereto when driven. 
         [0013]    Inner shaft  26  is mounted to and is translatable with thrust reverser cowl  18  and is capable of rotational movement with respect thereto. As shown in  FIG. 1A , inner shaft  26  is telescopically housed within outer shaft  22  when thrust reverser cowl  18  is in the stowed position. In the embodiment shown in  FIGS. 1A and 1B , inner shaft  26  is connected to outer shaft  22  by spline connection. The spline connection allows inner shaft  26  to rotate with outer shaft  22  while allowing inner shaft  26  to translate and extend relative to outer shaft  22  with movement of thrust reverser cowl  18 . In the embodiment shown, thrust reverser cowl  18  is actuated and moved to and from the stowed and deployed positions ( FIGS. 1A and 1B ) by thrust reverser cowl actuation system  30 . Thus, thrust reverser actuation system  30  operates as a different system independent of actuator assembly  14  for VAFN cowl  20 . Actuator assembly  14  must accommodate movement of thrust reverser cowl  18  while operating to move VAFN cowl  20  to and from the stowed and deployed positions. 
         [0014]    A distal end of inner shaft  26  is connected directly to ball screw mechanism  24 . Ball screw mechanism  24  is mounted to VAFN cowl  20  and is driven by rotation of inner shaft  26  to translate and extend or retract VAFN cowl  20  relative to thrust reverser cowl  18 . Gearbox  28  is mounted to the stator portion of nacelle adjacent the distal portion of outer shaft  22 . Gearbox  28  is connected by flex shaft or similar device to a hydraulic motor drive or an electric motor drive as further described in United States Patent Application Publication 2009/0013664A1, which is incorporated herein by reference. Gearbox  28  operates to transfer torque from flex shaft to outer shaft  22 . In turn, outer shaft  22  transfers torque to inner shaft  26  by aforementioned spline connection and inner shaft  22  transfers drive torque to ball screw mechanism  24  to move VAFN cowl  18 . 
         [0015]    Actuator assembly  14  allows VAFN cowl  20  to move with thrust reverser cowl  18  and additionally to have VAFN cowl  20  be driven from an actuator mounted to a stator part such as nacelle  12 . This results in a more efficient, lighter weight, and simpler differential movement actuation system than prior art systems. Some past systems attempted to overcome challenges associated with being able to actuate the VAFN cowl while still allowing it to move with the thrust reverser cowl by attaching the actuation system to the thrust reverser cowl. This resulted in the thrust reverser cowl being much less efficient, having to carry the additional weight of the actuation system. Past systems presented challenges in accommodating the translating electrical wires (which provide the motor with electricity to run). Other systems would drive the VAFN cowl from the fixed structure, but would coordinate the actuation with the actuation of the thrust reverser cowl, resulting in a need to monitor and actuate multiple systems in concert. This presented challenges requiring the actuation systems be monitored closely to ensure they were both working and working together so no parts would be damaged if one was not working. These systems also required more power as both actuation systems had to be working for any type of movement. The actuation system of the current invention overcomes the challenges of past systems by actuating the VAFN cowl from a fixed surface and allowing the shaft to be driven by a drive unit but to also move freely through the drive unit when the VAFN cowl is moving with the thrust reverser cowl. 
         [0016]      FIGS. 2 and 2A  show actuator assembly  14  where thrust reverser cowl  18  ( FIG. 1A ) and VAFN cowl  20  ( FIG. 1A ) are stowed (i.e. in a closed position).  FIG. 2A  shows a distal end of actuator assembly  14  with portions of the ball screw mechanism  24  and the outer shaft  22  removed to show inner shaft  26  and other components. In addition to outer shaft  22 , ball screw mechanism  24 , inner shaft  26  and gearbox  28 , actuator assembly  14  includes a first bearing support  32 , a second bearing support  34 , and a coupling  36 . Ball screw mechanism  24  includes a ball screw  38 , a ball nut  40 , and gimbal mounts  42 . 
         [0017]    As shown in  FIG. 2A , first bearing support  32  includes bearings  44 . Second bearing support  34  includes bearings  46 . Coupling  36  includes a clevis pin  48 . Ball nut  40  includes balls  50  and recirculation tubes  52 . Inner shaft  26  includes splines  54 . 
         [0018]    As shown in  FIG. 2 , gearbox  28  is mounted to and supports outer shaft  22  at a proximal end. Outer shaft  22  is supported near a distal end by first bearing support  32 . First bearing support  32  includes a flange connection with holes allowing first bearing support  32  to be connected to stator nacelle  12  ( FIGS. 1A and 1B ) by fasteners or other means. As shown in  FIG. 2A , first bearing support  32  includes internal bearings  44  which allow outer shaft  22  to rotate relative to stator nacelle  12 . 
         [0019]    Second bearing support  34  is disposed distal to first bearing support  32  adjacent ball screw mechanism  24 . Similar to first bearing support  32 , second bearing support includes bearings  46 , which allow inner shaft  26  and ball screw  38  to rotate relative to thrust reverser cowl  18  ( FIGS. 1A and 1B ). Second bearing support  34  is mounted to thrust reverser cowl  18  ( FIGS. 1A and 1B ) by fasteners or other known means. 
         [0020]    Ball screw  38  extends from and is supported by second bearing support  34 . Ball screw  38  is connected to inner shaft  26  by coupling  36 . In the embodiment shown, coupling  36  utilizes a clevis pin  48  ( FIG. 2A ), in other embodiments connection of the inner shaft  26  and ball screw  38  can be accomplished by other known connections such as a universal joint. In operation, ball screw  38  is driven by inner shaft  26 . 
         [0021]    The construction and operation of ball screw mechanism  24  is known in the art, and therefore, will not be described in detail. As discussed previously, ball screw  38  is driven and comprises a threaded shaft. The threaded shaft provides a helical raceway for balls  50  ( FIG. 2A ). Balls  50  ( FIG. 2A ) are disposed between ball nut  40  and ball screw  38  and allow ball nut  40  to translate relative to ball screw  38  ( FIG. 2A ). Balls  50  ( FIG. 2A ) are captured within ball nut  40  and are recycled as ball nut  40  translates. In the embodiment shown, balls  50  ( FIG. 2A ) are recycled through redundant recycling tubes  52  ( FIG. 2A ) as ball nut  40  translates relative to ball screw  38 . 
         [0022]    In the embodiment shown, gimbal mounts  42  are connected to ball nut  40 . Gimbal mounts  42  connect to suitable mounting features of VAFN cowl  20  ( FIGS. 1A and 1B ). Thus, linear translation of ball nut  40  is transferred to open and close VAFN cowl  20  ( FIGS. 1A and 1B ). 
         [0023]    As illustrated in  FIG. 2A , inner shaft  26  includes splines  54  and outer shaft  22  includes cooperating mating splines (not shown). During operation, splines  54  allow torque and rotation to be transferred between outer shaft  22  and inner shaft  26  while allowing inner shaft  26  to translate relative to outer shaft  22  with the movement of thrust reverser cowl  18  ( FIG. 1B ), which is moved by separate thrust reverser actuation system  30  ( FIGS. 1A and 1B ). Ball screw  38  is connected to and driven by inner shaft  26 . Rotation of ball screw  38  causes linear translation of ball nut  40  to open and close VAFN cowl  20  ( FIGS. 1A and 1B ). 
         [0024]      FIG. 3A  shows a partial sectional view of another embodiment of actuator assembly  14  with portions of gearbox  28 , outer shaft  22 , and inner shaft  26  removed. This embodiment incorporates an internal position sensor which is disposed within the inner shaft  26 . Thus, actuator assembly  14  need not include an external position sensor such as position sensor  16  ( FIGS. 1A and 1B ).  FIG. 3B  shows the outer shaft  22  with gearbox  28  removed.  FIGS. 3A and 3B  show a worm gear assembly  56  and a position sensor  58 .  FIG. 3B  shows worm gear assembly  56  with worm gear  60  and wheel  62 . 
         [0025]    As shown in  FIG. 3A , gearbox  28  can utilize a gimbal mount, blade/clevis or another mounting configuration known in the art in order to connect to nacelle  12  ( FIG. 1A ). As previously discussed, gearbox  28  is connected to and receives torque from one or more flex shafts (not shown). Gearbox  28  transfers torque from the flex shaft(s) to outer shaft  22  utilizing worm gear assembly  56 . In other embodiments, torque transfer to outer shaft  22  can be accomplished by a bevel gear set or any mechanical arrangement capable of transferring torque 90°. 
         [0026]    As shown in  FIG. 3B , worm gear assembly  56  comprises worm gear  60  which is positioned within gearbox  28  ( FIG. 3A ) and is driven by flex shaft (not shown) and wheel  62 . Wheel  62  is positioned around and splined to outer shaft  22 . Worm gear  60  is configured to drive wheel  62  in order to transfer torque to outer shaft  22  from flex shaft (not shown). 
         [0027]    As shown in  FIGS. 3A and 3B , position sensor  58  such as a linear variable differential transformer  58  can be disposed within inner shaft  26 . Electrical wires and position sensor  58  can be inserted through open distal portion of inner shaft  26  as illustrated in  FIG. 3B . Position sensor  58  determines the position of inner shaft  26  and ball screw mechanism  24  in order to determine the position of thrust reverser cowl  18  ( FIGS. 1A and 1B ) and VAFN cowl  20  ( FIGS. 1A and 1B ) for control purposes. 
         [0028]    The actuator assembly described allows for surface movements between different components with minimal parts by providing for passive movement of a second (inner shaft  26 ) shaft relative to a first shaft (outer shaft  22 ) when a surface (such as a thrust reverser cowl  18 ) is being moved by another actuation system. Because the second shaft is able to passively move and extend, portions of the actuation system such as the gearbox and first shaft can be fixed to a stationary surface, which provides stability. This also results in an efficient system allowing for passive movement instead of having to separately actuate (and coordinate) each surface. 
         [0029]    While the invention has been discussed in terms of actuating a VAFN cowl connected to a thrust reverser cowl assembly, it could be used on any system which requires differential surface movement in connection with an actuation system. For example, it may be used on flap or slat systems on an aircraft. 
         [0030]    While the invention has been described with reference to an exemplary embodiment(s), it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiment(s) disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.