Rotary actuator for an aircraft

Abstract

A rotary actuator for an aircraft wing 38, 42 comprises a plurality of hinge elements arranged along a hinge axis 36, and a rotatable drive shaft arranged along the axis and configured to be driven in

Description

FIELD OF THE INVENTION This invention relates to a rotary actuator for an aircraft, and in particular to a geared rotary actuator for providing a powered hinge for a folding wing tip of an aircraft wing. Such a rotary actuator may also be used for any movable surface or structure of an aircraft, such as flight control surfaces, which can be moved relative to a fixed part of the aircraft. BACKGROUND TO THE INVENTION Aircraft wings may be provided with a folding wing tip section, for example such that the wing tip may be retracted to reduce the span of the aircraft wings on the ground, or for movement in flight for example to change the aerodynamic characteristics of the wing. Such folding wing tips are generally required to be lockable or latchable in place either whilst in flight or whilst on the ground. Many different aircraft, including military and commercial aircraft, having a folding wing section or tip make use of a geared rotary actuator (GRA) or 'power hinge' as part of the joint mechanism positioned between a fixed section of the wing and a movable or folding section. These take the form of a hinge mechanism having multiple sections or slices along the length of a hinge axis. A plurality of fixed hinge elements are attachable to the fixed part of the wing, and a plurality of movable hinge elements are attachable to the movable part of the wing. The elements may each be provided with a mounting member such as flange extending from the element for mounting to the respective wing structure, for example using bolts. The fixed and movable hinge elements may be arranged alternately along the length of the hinge axis. Rotary movement of the movable elements relative to the fixed elements about the hinge axis provides relative movement between the movable and fixed wing sections. The GRA is commonly accommodated within the wing profile and arranged along a hinge line between the fixed wing part and the movable wing part. The GRA may require associated equipment including a motor or power drive unit and latching and / or locking mechanisms for retaining the hinge in a required position. This means that a GRA of suitable size and associated equipment may extend beyond the wing profile, necessitating the use of a fairing on the outside of the wing to cover any protruding parts. A fairing will involve additional cost and will also likely increase drag. This is inefficient aerodynamically and in terms of material use and cost. SUMMARY OF THE INVENTION According to the present invention there is provided a rotary actuator for an aircraft, in particular for an aircraft wing, comprising a plurality of hinge elements arranged along a hinge axis, a rotatable drive shaft arranged along the axis and configured to be driven in rotation, the arrangement being such that rotation of the drive shaft causes relative rotation of at least one hinge element with respect to at least one other hinge element, and a latching mechanism having an unlocked configuration in which the drive shaft can be driven in rotation and a locked configuration in which the drive shaft is held against rotation, such that the hinge elements are secured against relative rotation. This arrangement serves to transfer loads to the elements of the hinged joint rather than being concentrated within the latching and locking mechanism. With this arrangement, when used in an aircraft wing, flight loads are carried directly by the rotary actuator, which is effectively secured in relative position. By using the rotary actuator both as a structural load path and as an actuator for causing movement of the hinge, a space saving may be achieved as compared with the use of separate structures and system elements, which need to be sized to carry the same or similar loads at different stages in the flight cycle. This allows for tighter packaging of the GRA equipment which can have drag (and therefore fuel-burn) benefits, since the requirement for a fairing is reduced or eliminated, thus also reducing cost. Preferably, the drive shaft is mechanically engaged with the hinge elements via a transmission mechanism. This provides a robust connection between the drive shaft and the hinge elements. The latching mechanism may be arranged to couple the drive shaft to a fixed latching member in the locked configuration. For example, the fixed latching member may be a first clutch member secured against rotation, a second clutch member being mounted to the drive shaft for rotation therewith, at least one of the first and second clutch members being axially movable between the locked and unlocked configurations, for engaging and disengaging the clutch respectively. The rotary actuator may comprise a powered input shaft for driving the drive shaft in rotation, the input shaft having a braking mechanism for braking the input shaft when it is not receiving power. Preferably, the latching mechanism is provided at or adjacent an end of the joint, and is aligned with the drive shaft. This provides a compact arrangement. At least one latching mechanism may be provided at or adjacent each end of the joint, for redundancy purposes. Preferably, the hinge elements comprise a plurality of fixed hinge elements for attachment to a fixed part of the aircraft wing, and a plurality of movable hinge elements for attachment to a movable part of the aircraft wing. The movable elements and the fixed elements may be arranged alternately along the length of the actuator. For example, each of the movable elements may conveniently be positioned between two fixed elements. The drive shaft may comprise a sun gear shaft, and the actuator may comprise a plurality of planetary gear shafts arranged between the sun gear shaft and the hinge elements in engagement with the hinge elements so as to cause rotation of the movable elements relative to the fixed elements. For example, the hinge elements may each comprise a circumferential body portion and a connector extending radially from the body portion for connection to the respective aircraft wing part. The hinge elements may each comprise a ring gear arranged to engage the planetary gears provided on an inner surface of the circumferential portion of each element. The invention also provides an aircraft wing comprising a fixed part and a movable part, and a rotary actuator as defined above, the actuator being arranged between the fixed part and the movable part and being arranged to cause relative movement of the movable part with respect to the fixed part. For example, the fixed part may be a main body of the wing, and the moveable part may be a folding wing tip. The actuator may be arranged to cause movement of the wing tip between an aligned position in which the wing tip is aligned with the main body, and a folded position in which the wing tip extends at an angle to the main body, for example at an upward angle. The invention also extends to an aircraft comprising a rotary actuator as defined above, or comprising an aircraft wing as defined above. BRIEF DESCRIPTION OF THE DRAWINGS Reference will now be made, by way of example, to the accompanying drawings, in which: Figure 1 is a perspective view of a conventional GRA; Figure 2 is a schematic plan view of a GRA according to an embodiment; Figures 3A and 3B are schematic side views of a latching and locking unit; Figure 4 is a schematic perspective view of a wing showing a GRA within a wing profile; and Figures 5A and 5B are front views of an aircraft having folding wingtips. DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS Referring to Figure 1, a conventional geared rotary actuator 2 comprises a plurality of hinge elements comprising a plurality of relatively fixed elements 4 and a plurality of relatively movable elements 6. These are arranged alternately along a hinge axis 8. The elements 4, 6 each have a generally circular inner body portion 10, 12. Flanges 16, 14 extend radially outwardly from one edge of each body portion 10,12, with the flanges 16 extending from the fixed elements 4 radially in one direction and the flanges 14 extending from the movable elements 6 radially in an opposing direction. In this example, each element 4, 6 has a pair of attachment flanges 16, 14 for securing to a structure within the aircraft wing. Referring to the fixed element 4, each of the pair of flanges 16 is substantially planar and includes a pair of lobes 22 each provided with an aperture 24 for receiving a bolt. In this way, the fixed elements 4 can each be secured to a structure within a fixed part of the wing. In a similar manner, each movable element 6 has a pair of flanges 14 which are also planar having a pair of lobes 18 having apertures 20 for receiving a bolt. In this way, the movable elements 6 can each be secured to a structure within a movable part of the wing, such as a folding wing tip. The elements 4, 6 each have a flattened profile 26, 28 along opposing sides corresponding to the upper and lower edges of the actuator. In association with the upper and lower edge surfaces of the flanges 14, 16, these provide a surface which sits within or adjacent the upper and lower profile of the wing, and can be shaped to correspond with the wing surfaces. A drive shaft comprises a sun gear 30 extends along the inside of the actuator, and operates planetary gears 32. The body portions 10, 12 of each element are provided with gear teeth on their inner surface, effectively serving as ring gears. Thus gear teeth provided on the planetary gears are arranged to mesh with gear teeth of the ring gears so as to provide relative movement between the fixed and movable elements 6. The sun gear 30 is connected to a power drive unit for turning the sun gear to actuate the hinge, and latching or locking features may also be provided to retain the hinge in a required position; for example folded or in-line. Such latching or locking features commonly comprise a movable element for mechanically connecting the fixed and movable elements together in a locked configuration, to prevent relative rotation, and a latch actuator for providing movement of the movable element into and out of an operative position. Various arrangements exist for the layout of the GRA, power drive units and latching and locking features and equipment. In use, the actuator is mounted spanwise within the wing profile, along a hinge line between a fixed part of the wing and a movable part such as a wing tip. The associated equipment including a power unit for driving the sun gear shaft, and a latching and locking arrangement for locking the hinge elements in place when the movable part of the wing structure is not being moved, is also required to be housed preferably within the wing profile. Referring now to Figure 2, a GRA 34 is mounted along a hinge axis 36 between a main wing structure 38 and a moving wing structure 40. The GRA has a plurality of fixed hinge elements 42, in this example numbering six, which are attached to the main wing 38 by means of connectors in the form of flanges 44 extending sideways from a circumferential body portion of the hinge element, and fixed for example using bolts in a known manner. The GRA also has a plurality of movable elements 46, in this example numbering five, which are attached to the movable wing structure 40 by means of flanges 48 which extend outwardly in an opposite directions from the body portion of each hinge element, when the wing structures are aligned. The actuator in this example has five actuator 'slices' 50, 52, 54, 56, 58, although it may have any number of slices. Each slice comprises a movable element 44 with a fixed element 42 arranged on each side of the movable element 44. Taking the fourth and fifth slices 56, 58 as an example, the movable element 561 of the fourth slice 56 is arranged between a first and second fixed element 562, 563. Adjacent the second fixed element 563 of the fourth slice 56 is a first fixed element 582 of the fifth slice. The first fixed element 582 of the fifth slice, together with a second fixed element 583 of the fifth slice 58 surround a movable element 581 of the fifth slice. The adjacent fixed elements 563, 582 can optionally be attached together, thus effectively forming a fixed element of twice the width of the movable elements 46. Referring also to Figures 3A and 3B, the GRA has a drive shaft in the form of a sun gear shaft 60 which extends along the length of the actuator, and is rotatable to cause relative movement between the fixed and movable elements in a known manner and as described above in relation to Figure 1. For example, the sun gear shaft 60 operates a plurality of planetary gear shafts (not shown) which engage with ring gears (not shown) provided on an inner surface of each hinge element 42,44. At one end of the actuator, a latching unit 62 is provided aligned with the hinge axis 36 and the hinge elements, for example having a slightly smaller diameter than the elements. Referring also to Figures 3A and 3B, the latching unit 62 comprises a toothed clutch for engaging and disengaging the sun gear shaft 60 so as to optionally lock the shaft 60 against rotation. The latching unit 62 comprises a first clutch member 64, which may be a toothed clutch member, having an aperture through which the sun gear shaft 60 passes. The first clutch member 64 is mounted in the latching unit 62 in a fixed position so that it is secured against rotation. The sun gear shaft is provided with a second toothed clutch member 66 which may be of a similar size and shape to the first clutch member 64, and is fixedly mounted on the sun gear shaft 60 for rotation therewith. The second clutch member 66 may be mounted towards first end 68 of the sun gear shaft 60. The first end 68 of the shaft 60 is drivably connected to an input gearbox 70 which in turn is operated by a motor shaft 72, which may be a braked shaft. The motor shaft 72 is connected to a power drive unit 76 for driving the motor shaft 72 in rotation. The power drive unit 76 may include a power-off brake. As can be seen in Figure 3A, in use of the actuator to cause rotation of the rotary actuator, the latching unit is in an unlocked configuration, with the first and second clutch members 64, 66 spaced apart axially in the latching unit 62. In this configuration, the sun gear shaft 60 may be caused to rotate by the motor shaft via the gearbox, thereby causing relative movement of the hinge elements, and thus hinged movement of the joint. When it is required to lock the hinged elements in place, the sun gear shaft 60 may be retracted axially relative to the latching unit 62, as indicated by an arrow 74. This causes the second clutch member 66 to move towards and engage with the first clutch member 64, in the latched configuration. Since the first clutch member 64 is rotationally stationary, this engagement effectively prevents rotation of the second clutch member 66, and thus the sun gear shaft 60 is prevented from rotating. The mechanical engagement of the sun gear shaft 60 with the hinge members then effectively locks the hinge members against rotation. Optionally, a second latching unit 63 may be provided at the opposite end of the actuator 34. This is operable in the same way, by providing a fixed clutch member which engages a corresponding clutch member provided on the sun gear shaft 60. Other means of latching and locking the sun gear shaft in place could be provided instead of or in addition to a clutch mechanism as described above, such as a spline coupling. In use, when it is required that the movable part 40 of the wing is to be fixed in place, either in line with the fixed part 38 or at an angle thereto, the latching units 62, 63 are moved to a locked configuration, and the drive shaft 72 of the power drive unit 76 is braked by the power-off brake. If the aircraft is in flight, flight loads are thus transferred to the actuator 34 and are carried directly by the actuator slices, with the latching units 62, 63 securing them in place. When it is required to fold or unfold the movable part 40 of the wing, for example on the ground, the latching units 62, 63 are moved to the unlocked configuration and the power unit is operated such that the power-off brake are disengaged. The power drive unit 76 can then drive the input gearbox 70 and hence the sun gear shaft 60 to cause relative rotation between the fixed elements 44 and the movable elements 46. The power drive unit 76 is shown in Figure 2 mounted in alignment with the rotational axis 36 of the actuator 34. However, as shown in Figure 4, the power drive unit 76 may be mounted in any convenient location, preferably within the profile of the wing 78. For example, the power drive unit 76a, 76b may be mounted perpendicular to the actuator 34, at or adjacent either end thereof. Alternatively, the power drive unit 76c, 76d may be mounted parallel to the actuator 34, but axially offset. More than one power drive unit may be provided, for redundancy reasons. Referring to Figures 5A and 5B, the actuator may be used for actuating a folding wingtip of an aircraft 80. The wings 82 of the aircraft 80 may comprise a fixed part 84 forming a main body of the wing 82, and a movable part 86 forming a wingtip. A rotary actuator 88 may be positioned along a hinge line, which extends substantially chord-wise, between the fixed part 84 of the wing 82 and the wingtip 86. As can be seen from Figure 5A, the wingtip 86 may have a folded position in which it extends an angle to the main body 84 of the wing, commonly extending upwardly. As shown in Figure 5B, the wingtip 86 also has an extended position in which it extends substantially in line with the main body 84 of the wing 82. The rotary actuator 88 may be operated to move the wingtip 86 between these two positions, for example so as to reduce the wingspan of the aircraft 80 when on the ground and / or to change the aerodynamic characteristics of the wings 82 in flight. 5

Claims

1. A rotary actuator for an aircraft wing comprising a plurality of hinge elements arranged along a hinge axis, a rotatable drive shaft arranged along the axis and configured to be driven in rotation, the arrangement being such that rotation of the drive shaft causes relative rotation of at least one hinge element with respect to at least one other hinge element, and a latching mechanism having an unlocked configuration in which the drive shaft can be driven in rotation and a locked configuration in which the drive shaft is held against rotation, such that the hinge elements are secured against relative rotation.

2. A rotary actuator as claimed in claim 1, wherein the drive shaft is mechanically engaged with the hinge elements via a transmission mechanism.

3. A rotary actuator as claimed in claim 1 or 2, wherein the latching mechanism is arranged to couple the drive shaft to a fixed latching member in the locked configuration.

4. A rotary actuator as claimed in claim 3, wherein the fixed latching member is a first clutch member secured against rotation, a second clutch member being mounted to the drive shaft for rotation therewith, at least one of the first and second clutch members being axially movable between the locked and unlocked configurations, for engaging and disengaging the clutch respectively.

5. A rotary actuator as claimed in any preceding claim, comprising a powered input shaft for driving the drive shaft in rotation, the input shaft having a braking mechanism for braking the input shaft when it is not receiving power.

6. A rotary actuator as claimed in any preceding claim, wherein the latching mechanism is provided at or adjacent an end of the actuator, and is aligned with the drive shaft.

7. A rotary actuator as claimed in claim 6, comprising a plurality of latching mechanisms, at least one being provided at or adjacent each end of the actuator.

8. A rotary actuator as claimed in any preceding claim, wherein the hinge elements comprise a plurality of fixed hinge elements for attachment to a fixed part of the aircraft wing, and a plurality of movable hinge elements for attachment to a movable part of the aircraft wing, rotation of the drive shaft causing relative rotation between the fixed hinge elements and the movable hinge elements.

9. A rotary actuator as claimed in claim 8, wherein the movable elements and the fixed elements are arranged alternately along the length of the actuator.

10. A rotary actuator as claimed in any preceding claim, wherein the hinge elements each comprise a circumferential body portion and a connector extending radially from the body portion for connection to the respective aircraft wing part.

11. A rotary actuator as claimed in any preceding claim, wherein the drive shaft comprises a sun gear shaft, and further comprising a plurality of planetary gear shafts arranged between the sun gear shaft and the hinge elements, and arranged to engage the hinge elements.

12. A rotary actuator as claimed in claim 11, wherein the hinge elements each comprise a ring gear provided on an inner surface of the circumferential portion and arranged to engage with the planetary gears.

13. An aircraft wing comprising a fixed part and a movable part, and a rotary actuator as claimed in any preceding claim, the actuator being arranged between the fixed part and the movable part and being arranged to cause relative movement of the movable part with respect to the fixed part.

14. An aircraft wing as claimed in claim 13, wherein the fixed part is a main body of the wing, and the movable part is a wing tip, wherein the actuator is arranged to causemovement of the wing tip between an aligned position in which the wing tip is aligned with the main body, and a folded position in which the wing tip extends at an angle to the main body.5 15. An aircraft comprising a rotary actuator as claimed in any one of claims 1 to 12, or anaircraft wing as claimed in claim 13 or 14.

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