Patent Description:
Movable wing tips and foldable wing tip mechanisms on wing structures for aircraft are commonly known. Existing actuation systems for wing tips are typically used on the ground to fold wing tips for a more efficient storage of the aircraft, e.g. on an aircraft carrier. A few aircraft, e.g. North American-Rockwell B70 Valkyrie, have been equipped with foldable wing tips that could also be moved during flight to optimize the load distribution and drag of the wing.

Also, wing structures are known, in which wing tips are movable for load alleviation. For example, <CIT> shows an aircraft comprising a wing having a fixed wing with a wing tip device moveably mounted about a hinge at the tip thereof. The wing tip device is operable between a flight configuration, and a load alleviating configuration for load alleviation during flight. The aircraft comprises a restraining assembly operable between a restraining mode in which the wing tip device is held in the flight configuration using a restraining force such as by a brake, and a releasing mode in which the restraining force on the wing tip device is released, such that the wing tip device may adopt the load alleviating configuration.

<CIT> describes a flight control surface control unit for controlling the swinging angle of a flight control surface by swinging the flight control surface of an aircraft. A swinging force is provided to the flight control surface and the flight control surface is swung about a pivot. The unit includes an actuator mounted on an airframe of the aircraft with a final output shaft of the actuator positioned coaxially with the pivot of the flight control surface. Further, the final output shaft of the actuator and the flight control surface are connected. The actuator is preferably an oscillating rotary actuator.

<CIT> describes the provision of an actuator assembly for moving an aircraft wing tip device. The wing tip device is rotatable about a hinge axis relative to a fixed wing of the aircraft. The hinge axis is orientated non-parallel to a line-of-flight direction of the aircraft. The actuator assembly comprises a primary shaft having an axis of rotation orientated substantially parallel to the line-of-flight direction, a motor to cause rotation of the primary shaft, and a secondary shaft orientated substantially parallel to the hinge axis. The secondary shaft is couplable to the primary shaft and is arranged to rotate the wing tip device in response to the rotation of the primary shaft.

<CIT> describes a multiple-stage geared rotary actuator having a plurality of balanced compound differentials providing a multiple-stage output and for converting a high-speed, low-torque input to a low-speed, high torque output for moving a member, such as an aircraft flight control surface.

It is an object of the invention to provide an alternative solution for a movable wing tip operable for load alleviation with an improved reaction time and a minimum installation space.

This object is met by an actuator assembly according to claim <NUM>. Advantageous embodiments and further improvement are given in the subclaims and the following description.

According to the invention, an actuator assembly for moving a movable aerodynamic surface of an aircraft is proposed, comprising an input section for introducing an externally provided rotary motion into the actuator assembly, and a geared rotary actuator having at least one actuator slice comprising a planetary gear with a sun gear couplable to the input section, a fixed gear attachable to a fixed component of the aircraft and an output gear couplable with the movable aerodynamic surface. According to the invention, at least one clutch is connected to the geared rotary actuator and is designed to couple the movable surface with the input section and to selectively decouple the movable surface from the input section, such that it is freely movable.

The actuator assembly thus comprises a geared rotary actuator for moving the movable aerodynamic surface couplable with a respective output gear through introducing a rotary motion at the input section. For providing the desired motion it comprises at least one actuator slice, which comprises a planetary gear in a cage or housing. It is preferred, that the geared rotary actuator comprises a plurality of actuator slices attached to one another in a row and to operate all of them simultaneously, such that all output gears are driven simultaneously.

Each planetary gear, or epicyclic gear, comprises a sun gear, which is arranged on a central axis of the geared rotary actuator. It is surrounded by several planet gears, which mesh with the sun gear and are coupled with an outer ring gear. It may be possible to use another setup with additional elements. In the setup of the geared rotary actuator, the one component of the planetary gear is intended to be fixed to a structurally fixed component. This component will be referred to as fixed gear in the following. Another component of the planetary gear will be driven to rotate according to the gear ratio. This component will be referred to as output gear in the following and will be coupled with the movable aerodynamic surface. Depending on the detailed design, the fixed gear and at the output gear may vary through different embodiments. However, it may be advantageous but not limiting to use the ring gear as the output gear and to use a support cage of the planet gears as the fixed gear.

The input section may simply comprise an input shaft, which is couplable to a drive unit, such as an electric or a hydraulic motor. However, the input section may also comprise a separate input gear stage having a first gear ratio, wherein a shaft or another torque transferring element extends from the input gear stage to the respective actuator slice. In case several actuator slices are used, they are all driven by the input section.

Each output gear may comprise a lug that protrudes in a radial direction to mechanically couple the respective movable surface with the output gear.

The purpose of this actuator assembly is to selectively allow a free movement of the movable aerodynamic surface in conditions that would lead to excessive structural loads on the structure, to which the movable component is attached. For example, the movable aerodynamic surface may be a wing tip, which is movably attached to a fixed wing structure through a hinge. In the majority of all flight conditions the wing tip is rigidly attached to the wing structure and cannot move. Hence, loads that act on the wing tip may be transferred into the fixed wing structure. However, the actuator assembly is a key enabler for the semi aeroelastic hinge technology. It is designed such that the wing tip or another movable component can selectively be disengaged during flight under full bending load to allow a free flapping mode of the respective component. According to the invention, drag torques and associated bending moments on the hinge line of the free moving wing tip or other component are excluded or minimized through the various embodiments. By including a clutch directly into the geared rotary actuator assembly it allows a very fast reaction time to release the component, while at the same time, it occupies a minimized space envelope.

In an advantageous embodiment, that the input section comprises an input shaft, which comprises or is coupled with the sun gear. The input shaft is provided for coupling a drive unit with the at least one actuator slice. It may comprise a bevel gearbox that provides a transition of the input shaft direction. This allows to place a drive unit in a direction lateral to the central axis of the geared rotary actuator to reduce the installation space along the central axis. For minimizing the weight the shaft may be hollow. As the sun gear is the central element of each actuator slice it is couplable with the input shaft. If desired, a first gear ratio may be provided through an input gear section as explained above.

In an advantageous embodiment the input shaft completely extends through the at least one actuator slice, wherein a first end of the input shaft is couplable with a drive unit and wherein a second end of the input shaft is couplable with a brake. Providing a brake at the second end is a safety function. The brake may be selectively engageable to arrest the input shaft. Also, additional elements may be coupled with the second end, such as a position sensor couplable with a control unit to provide information about the rotational position of the respective actuator slice and/or the input shaft.

According to an example the at least one clutch is arranged upstream of the at least one actuator slice. The term "upstream" relates to an installation position of the at least one clutch between the at least one actuator slice and the input section. Thus, a connection between the input section and the at least one actuator slice may selectively be canceled or restored. A drag torque acting onto the output gear is only generated by the respective actuator slice and does not include any drag torque from the input section.

In an example, two clutches may be provided, wherein a first clutch is arranged upstream of the at least one actuator slice in the region of the first end, and wherein a second clutch is arranged downstream, of the at least one actuator slice in the region of the second end, such that the movable surface is decouplable from a brake that is couplable with the second end. Thus, the two clutches isolate the at least one actuator slice from the input section and a part of the input shaft that comprises the second end, where other drag torque inducing elements are provided.

According to the invention, the at least one clutch is arranged in or at the at least one actuator slice, such that the respective output gear is decouplable from the remaining part of the respective planetary gear. This approach differs from the arrangement upstream of the at least one actuator slice. Here, the at least one clutch is installed in a way that the output gear and the movable component couplable therewith, from the remaining part of the actuator slice. This further decreases the drag torque to a minimum. The respective clutch is however exposed to a higher load level, which requires a sturdier design. Further advantageously, a clutch is arranged at each output gear of each of the at least one actuator slice to selectively decouple the respective output gear from the movable surface. Thus, in case a plurality of actuator slices is used, each one of them comprises a clutch to selectively decouple the output gear from the remaining part of the planetary gear. the load of the movable component is distributed to the individual actuator slices, such that the load is also distributed to the plurality of clutches.

In a further advantageous embodiment, at least a part of the output gear of each of the at least one actuator slice is movable along a central axis of the geared rotary actuator in a first direction to decouple the respective output gear from the remaining part of the respective planetary gear, and in a second direction to couple the respective output gear to the remaining part of the respective planetary gear. The at least one clutch is actuated by a mechanism, which moves the whole movable component along the central axis. For example, if the component is a wing tip, it may be pushed forward in the direction of the leading edge to be disengaged. Clutch elements may be installed between the output gear of the respective actuator slice and attachments to the movable component. The output gear may be changed such that a rotational movement of the component is achieved by a simple sleeve bearing which also allows the component to move forward by a short distance, e.g. by approximately <NUM> in case of a wing tip.

In this embodiment it is preferred that a spring unit is provided, which is designed to urge the respective output gear to the second direction. Thus, a clutch actuator may be provided at one end of the geared rotary actuator, wherein a counter force is provided at the other end through the spring unit. This reduces the required installation space, weight and number of active elements.

In another advantageous embodiment, the at least one clutch comprises a first element and a second element, wherein the first element comprises a first toothing, wherein the second element comprise a second toothing, and wherein the first toothing and the second toothing are designed to engage each other upon flush contact of the elements to transfer a torque. The toothings are designed to mesh with each other to allow a torque transfer. To avoid the creation of axial forces the toothings may preferably comprise a rectangular cross-sectional surface.

In an alternative embodiment the at least one clutch is a friction clutch, which comprises at least two friction disks that are designed to be brought into a surface contact to engage the clutch.

It is preferred that at least one clutch actuator is provided to selectively open or close the at least one clutch. The clutch actuator may be a hydraulic actuator or an electric actuator, which directly or indirectly acts upon the at least one clutch. In a preferred embodiment, the clutch actuator is a linear actuator that is provided to push or pull a component to engage or disengage the at least one clutch. It may be advantageous to provide a lever arrangement between the respective component and the at least one clutch actuator to reduce the required actuator force. A similar arrangement may be installed in a jack head of a ball screw actuator.

Preferably, the at least one clutch comprises a bearing having rolling elements to reduce a required clutch actuation force. For example, roller bearings or other rolling elements at all movable contact surfaces may be provided.

In a further advantageous embodiment one of the first toothing and the second toothing comprises rollers rotatably supported in one of the first clutch disc and the second clutch disc, wherein the other one of the first toothing and the second toothing is designed to receive the rollers. The friction between the toothings can thus be minimized, which leads to a clear reduction in the required clutch force, as well as the reaction time.

Also, the actuator assembly may comprise at least one lug, wherein a first lug is couplable with the fixed component and wherein a second lug is couplable with the movable surface, wherein the at least one clutch is designed to selectively decouple the output gear from the second lug. Thus, the output gear may remain coupled with the remaining parts of the planetary gear and the at least one clutch may act to decouple a second lug from the output gear. The second lug may exemplarily be attached to an element that surrounds the output gear.

The invention further relates to a wing structure comprising a fixed wing portion, a hinge, a movable wing tip portion coupled to the fixed wing portion through the hinge, and at least one actuator assembly which comprises the actuator assembly of the preceding description, wherein the at least one actuator assembly is coupled with the fixed wing portion and the wing tip portion to selectively move the wing tip portion about the hinge. According to the invention, the actuator assembly comprises a clutch to selectively decouple the wing tip portion from the actuator assembly, such that it freely rotates about the hinge. The wing structure thus comprises a wing tip portion that is movable about a hinge. It provides the ability to reduce the footprint of the wing on ground by swiveling the wing tip portion from a use state into a stowed state. In the use state the wing tip portion extends in a spanwise direction. The hinge axis may be arranged parallel to a symmetry axis of the wing, which is parallel to a longitudinal axis of an aircraft to which the wing structure is attached. The wing tip portion may be swiveled about the hinge axis to reduce the spanwise extension of the wing structure. The wing tip portion may then preferably extend into an upward direction and may be folded onto the fixed wing portion.

Still further, the invention relates to an aircraft comprising at least one wing structure as explained above and/or a movable aerodynamic surface and an actuator assembly according to the above description. The movable component may preferably be an exterior component for an aircraft, which can be swiveled around at least one swiveling axis to be brough into a use position and into a stowed state. For example, the movable component may be a flow body that is swivably supported on a fuselage or a wing of the aircraft. The use state corresponds to an operating state of the movable component during a smooth cruise flight. Besides flaps and doors, also wing tips can be considered.

Other characteristics, advantages and potential applications of the present invention result from the following description of the exemplary embodiments illustrated in the figures.

Furthermore, identical or similar objects are identified by the same reference symbols in the figures.

<FIG> shows an actuator assembly <NUM> in a schematic view. Here, the actuator assembly <NUM> comprises a geared rotary actuator <NUM> having a plurality of actuator slices <NUM>, which comprise a planetary gear. All actuator slices <NUM> are attached to one another along a central axis <NUM>. An input section <NUM> is provided for introducing an externally provided rotary motion into the actuator assembly <NUM>. As an example, then input section <NUM> is coupled to a drive unit <NUM>, which may comprise a redundant arrangement of two motors, a differential gear, and an output shaft. The drive unit <NUM> is connected to a first shaft <NUM>, which is connected to a first bevel gear <NUM>. In doing so, the drive unit <NUM> may be placed in a region lateral to the central axis <NUM>. The input section <NUM> comprises an input shaft <NUM> that extends along the central axis <NUM> from a first end <NUM> to a second end <NUM>. At the second end <NUM> a second bevel gear <NUM> is provided, which is connected to a second shaft <NUM>. Here, the brake <NUM> as well as a system position sensor <NUM> are arranged.

The actuator slices <NUM> are coupled with first lugs <NUM> couplable with a fixed component <NUM>, such as a wing box, which may comprise stiffening elements such as stringers, spars and skin portions. In this example, the actuator assembly <NUM> is arranged in a wing structure of an aircraft, which is described further below. Also, output gears (not shown) of the actuator slices <NUM> are coupled with second lugs <NUM>, which are coupled with a movable surface <NUM>. The surface <NUM> may be a wing tip portion, which is swivably arranged on the central axis <NUM>, which is thus also a swivel axis. By driving the geared rotary actuator <NUM>, the second lugs <NUM> swivel the surface <NUM> about the central axis <NUM>.

For reducing structural loads in certain conditions it is desirable to decouple the surface <NUM> from the fixed component <NUM>. For achieving this, it is decouplable from the input section <NUM>, such that it is freely swivable. In the exemplary embodiment shown in <FIG> a first clutch <NUM> and a second clutch <NUM> are provided. The first clutch <NUM> is arranged in the region of the first end <NUM>. The second clutch <NUM> is arranged in the region of the second end <NUM>. Both clutches <NUM> and <NUM> are adapted to selectively disengage the input shaft <NUM> from the actuator slices <NUM>. In this exemplary embodiment, the clutches <NUM> and <NUM> are arranged upstream of the geared rotary actuator <NUM>, i.e. between the input shaft <NUM> and the geared rotary actuator <NUM>.

The arrangement of elements shown in <FIG>, i.e. gears, gearboxes, brake, drive unit and shaft elements depends on the installation constraints and is not limiting the subject-matter of the invention. It may also be possible to use an arrangement without shafts and gearboxes, e.g. having drive units directly mounted on the geared rotary actuator.

<FIG> shows a detail of on actuator slice <NUM>, the input section <NUM> and the first clutch <NUM>. The input section <NUM> exemplarily comprises an input gear stage <NUM>, which is coupled to the input shaft <NUM>. The detailed setup of this input gear stage <NUM> is not crucial for the invention and it may be selected by a skilled person appropriately.

For transferring torque from the input shaft <NUM> to the first actuator slice <NUM>, the first clutch <NUM> comprises a first element in the form of a first clutch disc <NUM> and a second element in the form of a second clutch disc <NUM>. The second clutch disc <NUM> is coupled with a sun gear <NUM> through a hollow shaft <NUM>. A lever <NUM> is movable by a clutch actuator (not shown herein), which is designed to let the clutch discs <NUM> and <NUM> contact or to separate them from each other. The first clutch disc <NUM> comprises a first toothing <NUM>, while the second clutch disc <NUM> comprises a second toothing <NUM>. The toothings <NUM> and <NUM> are designed to complement each other, such that they mesh with in a torque-transferring manner when the clutch discs <NUM> and <NUM> contact each other. Hence, the first clutch <NUM> can selectively couple the actuator slice <NUM> with the input shaft <NUM> or decouple it therefrom.

For the sake of completeness, the actuator slice <NUM> comprises a ring gear <NUM>, which meshes with planet gears <NUM>. The planet gears <NUM> may be supported by a cage <NUM>, which is coupled to the fixed component <NUM> through the first lug <NUM>. The ring gear <NUM> constitutes the output gear and comprises the second lug <NUM> for driving the movable component <NUM>.

<FIG> shows simplified illustrations of the first clutch <NUM> and the second clutch <NUM>. Here, the first clutch <NUM> and the second clutch <NUM> comprise a first clutch disc <NUM> and a second clutch disc <NUM>. Both clutches <NUM> and <NUM> are shown in the disengaged state, where the toothings <NUM> and <NUM> are separated from each other. In each of the clutches <NUM> and <NUM>, a clutch actuator <NUM> is connected to the clutch lever <NUM>, which exemplarily moved the first clutch disc <NUM> along the central axis <NUM>. The clutch actuator <NUM> may be provided in the form of a hydraulic actuators, or an electrical or electromechanical actuators, e.g. in the form of a ball spindle drive with a low gear ratio.

<FIG> shows another actuator assembly <NUM>, which differs from the assembly <NUM> of <FIG>. Here, clutches <NUM> are provided, which may be designed similarly to the first clutch <NUM> and the second clutch <NUM>. However, in this exemplary embodiment the clutches <NUM> are fully integrated into a geared rotary actuator <NUM>, i.e. directly in actuator slices <NUM> to selectively decouple the respective output gears <NUM> from the surface <NUM>. This is further explained in conjunction with <FIG>.

Here, the output gear <NUM> is arranged inside an output member <NUM>, which is coupled with two first clutch discs <NUM> at both axial sides. Two second clutch discs <NUM> can be brought into engagement or disengagement with the first clutch discs <NUM> for selectively coupling the output gear <NUM> with the output member <NUM>. For this, the second clutch discs <NUM> are movable through clutch actuators <NUM>, which are provided as hydraulic actuators and are selectively supplied with hydraulics fluid through a solenoid valve <NUM>. For providing a reversing force, springs <NUM> are provided. The valve <NUM> may comprise a very low reaction time in the region of <NUM> to <NUM>. Thus, upon request, both second clutch discs <NUM> can rapidly be disengaged from the first clutch discs <NUM> to disengage the associated output gear <NUM>. All actuators <NUM> may be attached to the output member <NUM> and coupled with a flexible hose <NUM> for receiving hydraulics fluid. Thus, if the output member <NUM> moves about the central axis <NUM>, the flexible hose <NUM> compensates a positional offset.

<FIG> shows a still further exemplary embodiment in the form of an actuator assembly <NUM>. Here, a geared rotary actuator <NUM> has several actuator slices <NUM> with integrated clutches <NUM>. Here, each output gear <NUM> comprises a first clutch disc <NUM>, which is engageable or disengageable from a second clutch disc <NUM>. However, different than in <FIG>, only one axial side of the output gear <NUM> comprises such an arrangement. This is further explained in conjunction with <FIG>.

It becomes apparent that by moving all output gears <NUM> along the central axis <NUM> towards the first end <NUM>, the first clutch discs <NUM> are disengaged from the second clutch discs <NUM>. To reverse this motion, a spring unit <NUM> is provided in the region of the first end <NUM>, which is compressed during said motion and which expands if an actuation force is removed. A clutch actuator <NUM> is arranged in the region of the second end <NUM>. As shown in <FIG>, sleeve bearings <NUM> are provided on the side of the output gear <NUM> facing away from the associated first clutch disc <NUM>.

A component position sensor <NUM> is directly coupled with the component <NUM> in addition to the system position sensor <NUM>. Thus, a control unit may gather the exact position of the movable component <NUM> after it has been decoupled from the input shaft <NUM>.

<FIG> shows an upper part of a sectional view of a further actuator assembly <NUM>, which is a modification of the assembly <NUM> shown in <FIG> and <FIG>. Here, the ring gear <NUM> is separated from the second lugs <NUM>, which are indicated by an arrow onto a first clutch disc <NUM> of a clutch <NUM>. The first clutch disc <NUM> as well as the ring gear <NUM> comprise circumferential grooves <NUM> and <NUM> at the same axial position, which enclose a first set of rollers <NUM> for rotatably supporting the first clutch disc <NUM> on the ring gear <NUM>. The first toothing <NUM> is provided for receiving rollers <NUM>, which are rotatably supported on a second clutch disc <NUM>. Exemplarily, this is conducted by a needle bearing <NUM> held by a bolt <NUM> pressed or screwed into the second clutch disc <NUM>. The second clutch disc <NUM> is axially and concentrically supported by a second set of rollers <NUM> running in axial grooves <NUM> and <NUM> provided in the second clutch disc <NUM> and the ring gear <NUM>. A spring <NUM> is placed between a flange <NUM> of the ring gear <NUM> and the second clutch disc <NUM> and provides a reversing force to clutch actuators <NUM>. As shown in <FIG>, a hose <NUM> is coupled with the clutch actuators <NUM> to supply hydraulics fluid. In this exemplary embodiment, very short reaction times for engaging or disengaging the clutch <NUM> can be realized.

Lastly, <FIG> shows an aircraft <NUM> having a wing structure <NUM> comprising a fixed wing portion <NUM>, a hinge <NUM> and a movable wing tip portion <NUM>. For moving the wing tip portion <NUM>, and actuator assembly <NUM> is provided, wherein the central axis <NUM> of the actuator assembly <NUM> is parallel to a longitudinal axis x of the aircraft <NUM> as an example. However, it may also enclose an angle of up to <NUM> or <NUM>° with the longitudinal axis. The other actuator assemblies <NUM>, <NUM> and <NUM> are also applicable to be integrated into the aircraft <NUM>.

Claim 1:
An actuator assembly (<NUM>, <NUM>, <NUM>, <NUM>) for moving a movable aerodynamic surface (<NUM>, <NUM>) of an aircraft (<NUM>), comprising:
- an input section (<NUM>) for introducing an externally provided rotary motion into the actuator assembly (<NUM>, <NUM>, <NUM>, <NUM>), and
- a geared rotary actuator (<NUM>, <NUM>, <NUM>) having at least one actuator slice (<NUM>, <NUM>, <NUM>) comprising a planetary gear with a sun gear (<NUM>) couplable to the input section (<NUM>), a fixed gear (<NUM>) attachable to a fixed component (<NUM>) of the aircraft (<NUM>) and an output gear (<NUM>) couplable with the movable aerodynamic surface (<NUM>, <NUM>),
- at least one clutch (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) which is connected to the geared rotary actuator (<NUM>, <NUM>, <NUM>) and which is designed to couple the movable surface (<NUM>, <NUM>) with the input section (<NUM>) and to selectively decouple the movable surface (<NUM>, <NUM>) from the input section (<NUM>), such that it is freely movable,
characterized in that the at least one clutch (<NUM>, <NUM>, <NUM>, <NUM>, <NUM>) is arranged in or at the at least one actuator slice (<NUM>, <NUM>, <NUM>), such that the respective output gear (<NUM>) is decouplable from the remaining part of the respective planetary gear.