Patent Publication Number: US-2022228647-A1

Title: Thin wing multi slice rga on leading edge

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to European Patent Application No. 21275003.8 filed Jan. 15, 2021, the entire contents of which is incorporated herein by reference. 
     BACKGROUND 
     Exemplary embodiments of the present disclosure pertain to the art of rotary geared actuators. 
     The wings of an aircraft can contain geared actuators. There is a requirement to fit geared actuators such as a multi-slice rotary geared actuator (RGA) within a thin wing section. Unfortunately, due to the fact that the wing root at the leading edge of the wing is so thin, it is not possible to fit such multi-slice RGAs at the leading edge of the wing. 
     The examples described herein therefore aim to RGAs that have a smaller envelope than conventional RGAs so that they can be fitted into the leading edge of an aircraft wing. The RGAs described herein could also be used in other mechanical equipment and are not limited to use in aircraft wings. 
     SUMMARY 
     In one embodiment, A rotary geared actuator RGA includes an actuator body comprising a gear or gears and means configured to rotate said gear or gears about a first central longitudinal axis X′. The RGA further comprises a drive transmission shaft extending along a second central longitudinal axis X″, and means for rotating said drive transmission shaft about said central longitudinal axis X″. The RGA further comprises means for translating said rotation of said drive transmission shaft to said gears so as to cause rotation of said gears about said first central longitudinal axis X′, and wherein said second central longitudinal axis X″ of said drive transmission shaft is laterally offset from said first central longitudinal axis X′. 
     In some examples described herein, the means configured to rotate said gear or gears about said first longitudinal axis X′ comprises a shaft connected to said gear or gears. 
     In some examples described herein, said gear or gears may be positioned around a sun gear connecting shaft which extends along said first central longitudinal axis X′. The gears may comprise sun gears that are connected to said sun gear connecting shaft such that the sun gears operate as one. 
     In some examples described herein, the gears may further comprise pinion gears and ring gears and said pinion gears and ring gears may be positioned around the sun gear connecting shaft. 
     In some examples described herein, the first and second central longitudinal axes X′, X″ may extend parallel to each other. 
     In some examples described herein, the means for translating the rotation of the drive transmission shaft to the gear or gears may comprise an offset gearbox arrangement. 
     The offset gearbox arrangement may comprise an epicyclic, combined ring gear and housing that is connected to the laterally offset drive transmission shaft as well as connected to the sun gear connecting shaft. 
     A method for manufacturing a rotary geared actuator RGA is also described herein comprising: providing an actuator body comprising: a gear or gears and providing means configured to rotate said gear or gears about a first central longitudinal axis X′; and providing a drive transmission shaft extending along a second central longitudinal axis X″, and providing means for rotating said drive transmission shaft about said central longitudinal axis X″, and providing means for translating said rotation of said drive transmission shaft to said gears so as to cause rotation of said gears about said first central longitudinal axis X′, and wherein said second central longitudinal axis X″ of said drive transmission shaft is laterally offset from said first central longitudinal axis X′. 
     In some examples described herein, said means configured to rotate said gear or gears about said first longitudinal axis X′ may comprise a shaft connected to said gear or gears. 
     In some examples described herein, the method may further comprise positioning said gear or gears around a sun gear connecting shaft which extends along said first central longitudinal axis X′ and wherein said gears comprise sun gears and further comprising connecting said sun gears to said sun gear connecting shaft such that the sun gears operate as one. 
     In some examples described herein, the gears may further comprise pinion gears and ring gears and the method further comprises positioning said pinion gears and ring gears around the sun gear connecting shaft. 
     In some examples described herein, said first and second central longitudinal axes X′, X″ extend parallel to each other. 
     In some examples described herein, the means for translating the rotation of the drive transmission shaft to the gear or gears comprises an offset gearbox arrangement. In some examples this may comprise an epicyclic, combined ring gear and housing and the method further comprises connecting said epicyclic ring gear and housing to the laterally offset drive transmission shaft as well as to the sun gear connecting shaft. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The following descriptions should not be considered limiting in any way. With reference to the accompanying drawings, like elements are numbered alike: 
         FIG. 1  shows a known RGA: 
         FIG. 2  shows a new type of RGA as described herein; and 
         FIG. 3  shows a cross-section of the RGA of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION 
     A known geared rotary actuator (RGA)  10  is shown in  FIG. 1 . Geared rotary actuators are often used in aircraft to move, and control the position of the flight control surfaces, such as the wings, of the aircraft. In  FIG. 1 , a known RGA  10  has a through drive transmission shaft  11  which is connected at one end to a drive means (not shown) at an input end  20  and which extends centrally through the main body of the actuator  10  to an output end  21  and drives the sun gears  14 , pinion gears  15  and output ring gears  16   a  of the actuator  10 . Earth ring gears  16   b  are also provided on the actuator  10 , which are fixed in position and react to the torque of the output ring gears  16   a . That is, the drive transmission shaft  11  extends along a central longitudinal axis X. As can be seen in  FIG. 1 , the sun gears  14 , pinion gears  15  and ring gears  16   a ,  16   b  are arranged so as to be positioned around the circumference of the drive transmission shaft  11  so that when the drive transmission shaft  11  is rotated, the sun gears  14 , pinion gears  15  and output ring gears  16   a , also rotate about the central axis X of the drive transmission shaft  11 . An offset gearbox  23  is also provided. 
     The through drive transmission shaft  11  therefore carries a certain amount of torque and so has to be sized accordingly. Due to this, the size of this shaft directly affects the overall size of the RGA outside diameter, meaning that it is not possible to be used in some thin wing applications. 
     The examples described herein are therefore aimed towards providing an improved RGA that has a smaller diameter than known RGAs so that they can be used in a thin wing of an aircraft (or other component). 
     An example of a new type of RGA  100  is shown in  FIG. 2 , which depicts a cross-section of the RGA  100 . As can be seen in this figure, the RGA  100  comprises a gear, or gears, such as sun gears  140 , pinion gears  150  and ring gears  160   a ,  160   b . In this example, however, instead of these gears being positioned around a through drive transmission shaft, as in the known example of  FIG. 1 , the sun gears  140  are positioned around the circumference of a sun gear connecting shaft  200 . The sun gear connecting shaft  200  extends along a longitudinal axis X′ and joins up all the sun gears  140  so that they operate as one. The gears  140 ,  150 ,  160   a ,  160   b  are also positioned around the sun gear connecting shaft  200  as shown in  FIG. 2 . In use, the sun gears  140  drive the pinion gears  150 . There are multiple pinion gears  150  positioned around the sun gear  140 . The pinion gears  150  drive the output ring gears  160   a  and the torque is then reacted by the output ring gears  160   b.    
     The sun gear connecting shaft  200  of the actuator  100  in this example, however, is not a drive transmission shaft. Instead, in the new example shown in  FIG. 2 , the RGA comprises a separate drive transmission shaft  210  which has a longitudinal axis X″ that is laterally offset from the longitudinal axis X′ of the sun gear connecting shaft  200 , so that it extends substantially parallel to the longitudinal axis X′ of the sun gear connecting shaft  200  as shown in  FIG. 2 . 
     The drive transmission shaft  210  is, in turn, connected to means (not shown) for driving the sun gear connecting shaft  200  in a rotational direction about its central longitudinal axis X′, and means, such as an offset gearbox arrangement  230  may be connected to the laterally offset drive transmission shaft  210 , and further connected to the sun gear connecting shaft  200 . When the drive transmission shaft  210  of the example of  FIG. 2  is rotated, this rotation is therefore translated, via the offset gearbox arrangement  230  (or other suitable means) to the sun gear connecting shaft  200 , so that the sun gear connecting shaft  200  is also rotated about its central, longitudinal axis X′. In some examples the offset gearbox may comprise an epicyclic, combined ring gear and housing and the epicyclic ring gear and housing may be connected to the laterally offset drive transmission shaft as well as to the sun gear connecting shaft. 
     Due to the fact that the drive transmission shaft  210  is no longer positioned so as to extend centrally within the sun gears  140 , pinion gears  150  and ring gears  160 , but is instead laterally offset from those gears, the diameter D 1  of the RGA can be greatly reduced, whilst the gearbox depth GDI is increased. Due to this the RGA  100  can be fitted into thinner wing sections 
     Another view of the RGA shown in  FIG. 2  is also shown in  FIG. 3 . In this figure, the connection of the drive transmission shaft  210  to an offset gearbox arrangement is more clearly shown. 
     Due to the fact that the drive shaft of these new examples shown in  FIGS. 2 and 3  is located so as to be laterally offset from the axis of rotation X′ of the gears, the examples described herein provide advantages over known actuators in that they provide an RGA with a reduced diameter. Due to this, the aircraft wing section can in turn be reduced in size, leading to huge benefits for both the system and aircraft performance. Since the drive shaft  210  is not contained in the main body of the actuator, as in known devices, the diameter of the actuator overall is reduced. This reduction in aircraft weight allows also for the wing section to be made thinner and more aerodynamic. The examples could also be used in any thin wing application, thereby providing key weight, efficiency and performance benefits. The examples described herein are discussed in relation to their use in an aircraft wing, however, they are not limited to this use, and could be used in any device or mechanism that requires the use of a RGA.