Patent Publication Number: US-11644089-B2

Title: Telescopic ballscrew actuator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. application Ser. No. 16/016,778 filed Jun. 25, 2018, which claims priority to European Patent Application No. 17178314.5 filed Jun. 28, 2017, the disclosures of which are incorporated herein by reference in their entirety. 
    
    
     FIELD 
     The present disclosure relates generally to actuators for use in aerospace applications (e.g., an aircraft), such as a thrust reverser actuation systems (“TRAS”) and/or a variable area fan nozzle (“VAFN”), and specifically a new type of telescopic ballscrew actuator for use in such systems. 
     BACKGROUND 
     Thrust reversers are provided on jet engines typically to increase the amount of braking on an aircraft upon landing. When deployed, a thrust reverser will change the direction of thrust of the jet engine such that some or all of the thrust is directed forwards, which acts to slow the aircraft so that it can then taxi off the runway. 
     There are a number of types of thrust reverser, all of which must be stowed during normal aircraft operation, for example so that the thrust reverser cannot be deployed during take-off or at a cruise altitude and can only be deployed during landing. In order to ensure this, one or more lock members are provided to prevent unwanted deployment of the thrust reverser, and in particular the actuators that move the various parts of the thrust reverser assembly. 
     New aerospace engine nacelle systems are being developed to increase engine efficiency (e.g., increased fuel burn with reduced drag) and reduce engine emissions (noise). To support these new types of nacelle, new nacelle architectures (e.g., reduced length) and system configurations (e.g., alternative thrust reverser kinematics) are being designed and developed. These new nacelle architectures and systems require the thrust reverser actuation system to be fitted into a significantly smaller installation envelope on the nacelle, whilst providing increased stow and deploy strokes, all the while maintaining the performance characteristics of previous systems. 
     It is desired to improve the actuator in a thrust reverser actuation system, and this is the aim of the present disclosure. 
     SUMMARY 
     In accordance with the invention, there is provided an apparatus for use in an aircraft (e.g., an aircraft thrust reverser), the apparatus comprising: an input shaft; a first component located concentrically around the input shaft; a second component located concentrically around the first component; a first ballscrew mechanism between the input shaft and the first component, and configured such that rotational movement of the input shaft causes a translational movement of the first component via the first ballscrew mechanism; and a second ballscrew mechanism between the first component and the second component, and configured such that rotational movement of the first component causes a translational movement of the second component via the second ballscrew mechanism. 
     The first ballscrew mechanism may comprise a screw thread located on an outer surface of the input shaft and a cooperating screw thread located on an inner surface of the first component. 
     The outer surface of the input shaft and the inner surface of the first component may be circumferential surfaces of the input shaft and the first component, respectively. 
     The second ballscrew mechanism may comprise a screw thread located on an outer surface of the first component and a cooperating screw thread located on an inner surface of the second component. 
     The outer surface of the first component and the inner surface of the second component may be circumferential surfaces of the first component and the second component, respectively. 
     The input shaft may be fixed against axial movement. 
     In a first mode the first component may be configured to translate along an axis upon rotational movement of the input shaft, and in a second mode the first component may be configured to rotate about the axis. 
     In the first mode the second component may be configured to translate with the first component along the axis. 
     In the second mode the second component may be configured to translate along the axis due to the operation of the second ballscrew mechanism. 
     A stop may be located on the first component that is configured, in the first mode, to abut the second component so as to cause the second component to translate with it along the axis as aforesaid. 
     The apparatus may be configured such that the first mode and the second mode occur sequentially, so as to provide two separate and distinct translational movements of the second component. 
     The first mode may occur prior to the second mode, and a transition between the first mode and the second mode may be caused by a stop attached to the first component abutting a stop attached to the input shaft, which abutment prevents further translation of the first component such that further rotational movement of the input shaft causes the first component to start rotating and the second component to translate along the axis due to the operation of the second ballscrew mechanism. 
     The second mode may occur prior to the first mode, and the transition between the second mode and the first mode may be caused by a stop attached to the second component abutting a stop attached to the first component, which abutment prevents further translation of the second component such that further rotational movement of the input shaft causes the first component to start translating and the second component to translate with it along the axis. 
     References to “translating” and “rotating” as used herein and above may be with reference to the longitudinal axis of any one of the input shaft, first component, second component, first ballscrew mechanism or second ballscrew mechanism. The input shaft, first component, second component, first ballscrew mechanism and second ballscrew mechanism may all comprise the same longitudinal axis. 
     In accordance with the invention, there is provided an actuator for an aircraft and comprising an apparatus as described above and herein. 
     In accordance with the invention, there is provided a thrust reverser actuation system (“TRAS”) or variable area fan nozzle (“VAFN”) comprising an apparatus as described above and herein. 
     In accordance with the invention, there is provided a method of operating an actuator of an aircraft, comprising: rotating an input shaft of the actuator about an axis to cause a first component to translate along the axis due to operation of a first ballscrew mechanism; and rotating the first component about the axis to cause a second component to translate along the axis due to operation of a second ballscrew mechanism. 
     The actuator may be part of an apparatus as described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various embodiments will now be described, by way of example only, and with reference to the accompanying drawings in which: 
         FIG.  1    shows schematically an embodiment of the present disclosure; 
         FIG.  2    shows an embodiment of the present disclosure in further detail; 
         FIG.  3    shows a conventional arrangement; and 
         FIG.  4    shows the embodiment of  FIG.  2    as it fits into a thrust reverser actuator. 
     
    
    
     DETAILED DESCRIPTION 
     The broad concept of the present disclosure is a thrust reverser actuator that utilises two ballscrew components that are arranged concentrically and achieve a defined actuator stroke, with a reduced installation length compared to existing technologies. 
     Conventional technologies may use only a single ballscrew component to achieve a given actuator stroke, and the presently described technology allows the thrust reverser actuator to be fitted in a shorter installation envelope offering size benefits to the engine nacelle whilst maintaining its performance characteristics. 
       FIG.  1    shows an embodiment of the present disclosure, in which an apparatus  1  comprises an input shaft  10  that is rotatable about an axis A in a rotational direction  2 . The input shaft  10  may be a rotating driveshaft of an actuator, and the axis A may be the longitudinal axis and/or rotational axis of the actuator. The input shaft  10  may be fixed in an axial direction, and may comprise a screw thread  12  that extends around an outer surface  14  of the input shaft  10 . 
     A first component  20  is located concentrically around the input shaft  10 , and a first ballscrew mechanism  22  is provided such that rotation of the input shaft  10  applies a force to the first component  20  in a direction of actuation  3 , via the first ballscrew mechanism  22 , to actuate a component (e.g., deploy a thrust reverser cowl). As will be discussed in more detail below, this will cause the first component  20  to move, either axially along the axis A, or rotationally around the axis A to drive the component. 
     The first component  20  comprises a first screw thread  24  that extends around an inner surface  25  of the first component  20 . Thus, the first ballscrew mechanism  22  comprises the screw thread  12  of the input shaft  10 , as well as the first screw thread  24  of the first component  20 . Upon rotation of the input shaft  10 , the first ballscrew mechanism  22  will operate by forcing balls of the first ballscrew mechanism  22  around a track formed by the screw thread  12  of the input shaft  10  and the first screw thread  24  of the first component  20 . As is known, the balls may be captured and recycled (e.g., through recycling tubes), as the first component  20  translates along the axis A. 
     The first component  20  further comprises a second screw thread  26  that extends around an outer surface  27  of the first component  20 , and forms part of a second ballscrew mechanism  32  (described below). 
     A second component  30  is located concentrically around the input shaft  10  and the first component  20 . A second ballscrew mechanism  32  is provided, which is formed by the second screw thread  26  of the first component  20  and a screw thread  34  that extends around an inner surface  36  of the second component  30 . 
     The second component  30  is fixed against rotational movement, and as such will be caused to move in the direction of actuation  3  upon axial or rotational movement of the first component  20 . That is, upon axial or rotational movement of the first component  20 , the first component  20  will apply an axial force to the second component  30  via the second ballscrew mechanism  32 . 
     If the first component  20  is translating (as opposed to rotating) along the axis A, then the second component  30  will also move axially with the first component  20 . 
     If the first component  20  is rotating, then the second ballscrew mechanism  32  will operate by forcing the balls of the ballscrew mechanism around a track formed by the second screw thread  26  of the first component and the screw thread  34  of the second component  30 . The balls may be captured and recycled (e.g., through recycling tubes) as is known generally in the art. 
     As briefly discussed above, due to the configuration of the apparatus  1  described above, different operational sequences may occur upon rotation of the input shaft  10  depending mainly on the frictional forces between the various components. 
     In a first operational sequence, input rotation may be provided (e.g., by an electric or hydraulic motor) to the input shaft  10 . Rotation of the input shaft  10 , which is axially fixed, may result in translation of the first component  20  via the first ballscrew mechanism  22 . Translation of first component  20  results in translation of the second component  30  (which is rotationally fixed) via the second ballscrew mechanism  32 . The second ballscrew mechanism  32  may be restrained in rotation, for example, by a clevis attachment to a fixed structure (e.g., a fixed nacelle). Translation of the second component  30  results in translation of the component to which the actuator is attached. 
     In the second operational sequence, rotation of the input shaft  10  may result in rotation of the first component  20  (rather than translation as discussed above), which means that the second component  30  is initially driven to translate along the axis A by the translation of the first component  20 . Subsequently, and once the first component  20  reaches the end of its travel (e.g., reaches a stopper as described below), the first component  20  will begin to rotate, resulting in further translation of the second component  30  due to the rotation of the first component  20 . 
     It will be appreciated that the operational sequences of the apparatus  1  are not limited to the first and second operational sequences discussed above, and it is possible that operational sequences of the apparatus  1  involve other sequences. 
     In any of the operational sequences, the first component  20  and the second component  30  each have a certain amount of travel. However, translations of the first component  20  and the second component  30  do not have to occur sequentially, as described above. Rather, the apparatus  1  may be configured such that the translations of the first component  20  and the second component  30  alternate a plurality of times during rotation of the input shaft  10  to actuate the component. 
       FIG.  2    shows an embodiment of the present disclosure in further detail, and within an actuator assembly  50 , which houses the apparatus  1 . Reference numerals in  FIG.  2    correspond to the same components as those described with the same reference numerals in respect of  FIG.  1   . 
     As can be seen from  FIG.  2   , the apparatus  1  fits inside the actuator assembly  50 , with the second component  30  being slidably received within an extended portion  52  of the actuator assembly  50 . The first component  20  is also contained within the extended portion  52 , and the input shaft  10  is partially received within the extended portion  52 . 
     In use, the first component  20  and the second component  30  protrude and extend from an open end  54  of the actuator assembly  50 . As discussed above, the input shaft  10  is fixed against axial movement and does not change its axial position with respect to the extended portion  52 . 
     In order to control the translation of the first component  20  and the second component  30 , and plurality of stops are provided. Each stop is fixed to one of the input shaft  10 , first component  20  and second component  30 , and cooperates with another stop to limit the stroke of each of the first component  20  and the second component  30 . 
     The discussion/example below assumes that the apparatus  1  operates in line with the first operational sequence described above. 
     A first stop  39  is connected to the first component  20  and may be located around the outer surface  27  of the first component  20  and/or axially between the first ballscrew mechanism  22  and the second screw shaft  26  of the first component  20 . The first stop  39  is configured to abut the second component  30  such that translation of the first component  20  along the axis A (i.e., upon rotation of the input shaft  10 ) causes the second component  30  to translate along the axis A. 
     A second stop  40  is connected to the input shaft  10 , for example at a distal end  16  thereof, and cooperates with a third stop  42  that is connected to the first component  20  (e.g., at an inner surface thereof and adjacent to the first ballscrew mechanism  22 ). 
     As the first component  20  moves in the direction of actuation  3 , the third stop  42  moves progressively closer to the second stop  40  and will eventually abut the second stop  40 . At this point, further movement of the first component  20  in the direction of actuation  3  is prevented, since the second stop  40  is connected to the input shaft  10 , which is fixed against axial movement (i.e., along axis A). As such, the first component  20  will begin to rotate due to the engagement of the second stop  40  and the third stop  42 , resulting in axial movement of the second component  30  (which, as discussed above, is fixed against rotational movement). 
     A fourth stop  44  is connected to the first component  20  (e.g., at an outer surface thereof), for example at the end of the second screw thread  26  of the first component  20 , and cooperates with a fifth stop  46  that is connected to the second component  30  (e.g., as an inner surface thereof and adjacent to the second ballscrew mechanism  32 ). 
     Continued rotation of the input shaft  10 , and first component  20  causes the second component  30  continue to translate in the direction of actuation  3 , such that the fifth stop  46  moves progressively closer to the fourth stop  44  and eventually abuts the fourth stop  44  once the second component  30  has reached its maximum stroke. 
     It will be appreciated that the same arrangement can operate in the second operational sequence described above. This would depend on the frictional forces between the various components. 
     For example, if input shaft  10  rotates and passes a load to the first component  20  via the first ballscrew mechanism  22 , it may be that the load is not enough to overcome the frictional forces (which may depend on the design of the particular ballscrew mechanism used) between the screw thread  12  of the input shaft  10  and the first screw thread  24  of the first component  20 , and other parts of the first ballscrew mechanism, e.g., the balls. In this case, the load may be passed to the second ballscrew mechanism  32 . If the frictional forces between the components of the second ballscrew mechanism  32  are sufficiently small, then the first component  20  will initially rotate with the input shaft  10 , causing the second component  30  to translate along the axis A. 
     The second component  30  may translate until the fifth stop  46  reaches the fourth stop  44 , at which point the load passed to the second ballscrew mechanism  32  cannot translate the second component  30 , and the rotation of the input shaft  10  will begin to translate, rather than rotate the first component  10 . The first component  20  will then translate along the axis A until the third stop  42  reaches the second stop  40 . At this point the actuator will have reached its maximum stroke (which is the same for either operational sequence). 
     As will be appreciated, the translation of the second component  30  may be effectuated in two modes of operation. In a first mode, the first component  20  may translate upon rotation of the input shaft  10 , causing the second component to translate, either using a stop (e.g., first stop  39 ) as in the first operational sequence, or using relative frictional forces between the ballscrew mechanisms as in the second operational sequence. In a second mode, the first component  20  may rotate upon rotation of the input shaft  10 , causing the second component  30  to translate via the ballscrew arrangement of the first ballscrew mechanism  22 . 
     Regardless of the sequence of the above modes of operation, the overall stroke of the actuator, and the stroke of the actuator during either mode of operation will be the same. 
     This telescopic arrangement means that the extended portion  52  of the actuator assembly  50  can be fitted in a shorter installation envelope than conventional arrangements that do not utilise multiple ballscrew mechanisms, offering size benefits to the engine nacelle whilst maintaining its performance characteristics. 
     It will be appreciated that the present disclosure is not limited to the use of two ballscrew mechanisms, and it is possible that any number of ballscrew components may be provided, with suitable ballscrew mechanisms between adjacent ballscrew components (in the same manner as described above in respect of  FIGS.  1  and  2   ), to achieve a defined actuator stroke depending on the installation envelope and specific requirements of particular systems. 
       FIG.  3    shows an example of a conventional actuator  100  that uses a single ballscrew component, which may have an installation length 1 of about 39 inches, and a stroke s of about 28 inches. 
       FIG.  4    shows an example of an actuator assembly  50  in accordance with the present disclosure (e.g., corresponding to the actuator assembly  50  described above in respect of  FIG.  2   ) that has an installation length L of about 27 inches, and a stroke S equal to that of the conventional actuator  100  of about 28 inches. 
     Although the present invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes in form and detail may be made without departing from the scope of the invention as set forth in the accompanying claims. For example, and as discussed above, any number of ballscrew components and ballscrew mechanisms may be used to provide a telescopic actuator that reduces the installation length of a previously employed conventional actuator. 
     Furthermore, the technology disclosed herein may be used in other aircraft or aerospace applications, for example a variable area fan nozzle (“VAFN”) or other nacelle actuation systems.