Patent Description:
Increasing the wing span of a fixed wing, commercial aircraft may limit the number of airports at which it can land (for example, airport stands may have a maximum wing span capacity). In military applications, an increased wing span could mean that more storage space is required (for example on an aircraft carrier or in a storage facility). Folding wing tip assemblies are known and used to reduce the span of the wings when the aircraft is on ground. In such assemblies, a distal portion of the wing rotates relative to the rest of the wing to vary the total wing span. Such assemblies have actuations means (typically a rotary actuator) that rotate the distal portion of the wing, and are contained within the body of the wing. Such actuators must be powerful enough to apply the required moment to rotate the distal portion, and as a result these actuators can be quite heavy, which decreases the efficiency of the aircraft.

Accordingly, there is a need to provide a lighter folding wing tip assembly which still provides the necessary moment to rotate the distal wing portion.

<CIT> discloses a wing according to the preamble of claim <NUM>. <CIT> discloses a wing fold actuator system for an aircraft.

According to a first aspect, there is provided a wing as set forth in claim <NUM>.

This provides an improved actuation mechanism for moving the wing tip between an unfolded and folded position. In particular, the use of a pivotal attachment on each of the fixed portion and movable portion, as well as a linear actuator extending between the two, provides various technical effects as discussed herein. For example, this means that the actuator can more easily move the wing tip, as compared to, e.g., a rotary actuator.

A lever arm of the linear actuator increases upon the linear actuator moving the tip of the wing from the unfolded position to the folded position. The lever arm is defined as the perpendicular distance from the axis of rotation (e.g., of the tip of the wing) to the line of action of applied force of the linear actuator, which is its linear/longitudinal axis. Increasing the lever arm in this manner means that it can easily move the wing tip throughout its range of movement.

The lever arm of the linear actuator may increase from a minimum value when the tip of the wing is in the unfolded position to a maximum value when the tip of the wing is in the folded position. The lever arm may increase progressively and/or continuously.

The linear actuator defines a line of action of applied force, wherein the line of action extends between the first pivotal attachment and the second pivotal attachment throughout the range of movement of the actuator, to repeatedly move the tip of the wing from the unfolded position to the folded position. The line of action coincides with the longitudinal axis of the linear actuator.

An angle between the line of action of applied force of the linear actuator and a longitudinal axis of the fixed body of the wing may increase upon the linear actuator moving the tip of the wing from the unfolded position to the folded position.

An angle between the line of action of applied force of the linear actuator and a longitudinal axis of the tip of the wing may increase upon the linear actuator moving the tip of the wing from the unfolded position to the folded position. This means the linear actuator may start at an internal position within the body/frame/etc. of the wing (e.g., both the fixed body and the tip) and move to an external position outside the body/frame/etc. of the wing (e.g., of both the fixed body and the tip). In other words, the linear actuator is exposed upon moving the tip of the wing from the unfolded position to the folded position. This allows the lever arm of the actuator to increase considerably as compared to an arrangement that involves, for example, one or more linkages between multiple actuators that remain within the body/frame/etc. of the wing. The assembly may comprise no linkages or other connecting parts, such that the linear actuator can always act along a single line of action throughout its entire range of movement.

The linear actuator may comprise a shaft (e.g., a piston or screw shaft) movable along a longitudinal axis of the linear actuator and extending between the first and second pivotal attachments.

The linear actuator may be configured to rotate the tip through at least about <NUM>, <NUM> or <NUM> degrees.

The assembly may further comprise locking means configured to selectively prevent movement of the linear actuator.

The assembly may further comprise one or more doors configured to selectively enclose the linear actuator, e.g., within the wing body.

The locking means may be the one or more doors, wherein the doors are configured in a closed position to prevent movement of the linear actuator. The doors may be locked in their closed position by a door locking mechanism. The doors may be configured to prevent pivoting movement of the linear actuator when they are in the closed/locked position (enclosing the linear actuator), which in turn prevents actuation of the linear actuator. This is a particularly useful way of locking the mechanism described herein, which has a synergy with the features provided above (in particular the use of a pivotal attachment on each of the fixed portion and movable portion, as well as a linear actuator extending (and pivoting) between the two attachment locations).

The doors may be configured to open/release (e.g., using a separate actuation mechanism or release of the door locking mechanism) to allow the linear actuator to pivot about both the first and second pivotal attachments as aforesaid.

The wing tip and main body of the wing may be shaped to allow the wing tip to rotate relative to the main body without obstruction. The wing and main body may have shapes which complement each other when in the extended position, and each comprise tabs and recesses, wherein a tab of the main body is shaped to fit into a recess of the wing tip and vice versa.

According to a further aspect, there is provided a method of moving the wing tip of the wing of any of the above.

The method may comprise using the linear actuator to move (e.g., repeatedly) the tip of the wing from an unfolded position to a folded position. In operation, the wing tip may be moved to an unfolded position when the aircraft is being prepared for a flight mode, and/or moved to a folded position when the aircraft is on ground.

A longitudinal axis of the linear actuator may not coincide with the axis of rotation of the tip throughout the full range of movement of the linear actuator.

The first and second pivotal attachments of the linear actuator may be both above or both below (e.g., in a vertical direction) the axis of rotation of tip when the tip is in an unfolded position.

<FIG> illustrates a commercial aircraft <NUM> with folding wing tips <NUM>. The aircraft <NUM> comprises a fuselage <NUM>, two main wings <NUM>, and an engine assembly <NUM> located under each wing <NUM>. Each wing <NUM> extends from the fuselage <NUM> in a generally radial direction (relative to a fuselage central axis).

Each wing <NUM> of the aircraft <NUM> comprises a main body <NUM> and a tip assembly <NUM> that forms a movable wing tip <NUM>. For the purposes of this disclosure, 'main body' <NUM> is the fixed portion of the wing <NUM> (i.e., rigidly attached to the fuselage), and 'tip assembly' <NUM> is the movable portion of the wing <NUM> at its distal end.

As discussed above the tip assembly <NUM> allows the tip <NUM> of the wing <NUM> to rotate relative to the main body <NUM>. Although illustrated as a commercial aircraft <NUM>, it would be understood that the present disclosure is not limited to a specific type of aircraft, and the technology described herein could be applied to other types of fixed wing aircraft, for example military aircraft. The technology could also be applied to other types of airfoil that utilise movable tips, for example rudders or helicopter blades, and is not limited to aircraft wings.

<FIG> illustrates a cross-section A-A (<FIG>) of the tip assembly <NUM>. The tip assembly <NUM> includes a movable wing tip <NUM> and an actuator <NUM> configured to rotate the wing tip <NUM> relative to the main body <NUM> of the wing <NUM>. An axis of rotation X is shown, which defines the axis X about which the wing tip <NUM> rotates (e.g. via hinges or any suitable means).

The wing tip <NUM> is shown in the extended position in <FIG>, which is the position of the wing tip <NUM> during flight. In the extended position, the top surface <NUM> of the main body <NUM> is flush with the top surface <NUM> of the wing tip <NUM>, and the bottom surface <NUM> of the main body <NUM> is flush with the bottom surface <NUM> of the wing tip <NUM>. This results in a smooth transition between the main body <NUM> and wing tip <NUM>, which results in an aerodynamic wing shape that reduces drag during flight. The movable wing tip <NUM> of the present disclosure is shown as less than <NUM>% of the total wing span. The technology disclosed herein is applicable to any dimension of movable wing tip <NUM>, for example a wing tip <NUM> of about <NUM>% of the total wing span, or even about <NUM>% of the total wing span.

The actuator <NUM> comprises a linear actuator <NUM>. The linear actuator <NUM> may be pneumatic, hydraulic, electromechanical, or any other type. For example, the actuator <NUM> may comprise a piston or other shaft (e.g. screw shaft) movable along an axis, between a retracted position and an extended position. The extended position corresponds to the extended position of the wing tip <NUM> as shown in <FIG>.

The actuator <NUM> has a first end <NUM> and a second end <NUM> (opposite to the first end). The actuator <NUM> is pivotally attached to the main body <NUM> of the wing <NUM> at the first end <NUM>, and also pivotally attached to the wing tip <NUM> at the second, opposite end <NUM>. Thus, the actuator <NUM> defines two axes of rotation <NUM>, <NUM>. A first axis of rotation <NUM> is provided by the pivotal attachment at the first end <NUM>, and a second axis of rotation <NUM> is provided by the pivotal attachment at the second end <NUM>. Thus, the linear actuator <NUM> extends between the two axes of rotation <NUM>, <NUM> and is configured to rotate about each of these axes <NUM>, <NUM> in use.

In the extended/unfolded position of the wing tip <NUM>, as shown in <FIG>, the linear actuator <NUM> is also in its extended position. Upon retraction of the linear actuator <NUM> from its extended/unfolded position, the wing tip <NUM> rotates to its retracted/folded position, and this is shown in <FIG>. As will be explained in more detail below, the linear actuator <NUM> rotates about both axes of rotation <NUM>, <NUM> during this movement, and brings the axes of rotation <NUM>, <NUM> of the linear actuator <NUM> closer together. The linear actuator <NUM> moves from a first, internal position within the wing body (below the surfaces <NUM>, <NUM> of the wing) to a second, exposed position outside of the wing body (above the surfaces <NUM>, <NUM> of the wing <NUM>).

The linear actuator <NUM> defines a line of action of applied force, wherein the line of action extends in a straight line between the first pivotal attachment <NUM> and the second pivotal attachment <NUM> throughout the range of movement of the linear actuator <NUM> (i.e., when moving the tip <NUM> of the wing <NUM> between the extended/unfolded position and the retracted/folded position).

As shown in <FIG>, when the wing tip is in the extended/unfolded position the axes of rotation <NUM>, <NUM> of the linear actuator <NUM> are both displaced (in the same direction) from the axis of rotation X of the wing tip <NUM>. That is, the first and second axes of rotation <NUM>, <NUM> of the actuator <NUM> lie above the axis of rotation X of the wing. This is exemplary, however, and the linear actuator <NUM> and axes of rotation <NUM>, <NUM> thereof may be placed in any suitable location to effectuate folding of the wing tip.

Displacing the linear actuator <NUM> from the axis of rotation X of the wing tip <NUM> allows the linear actuator <NUM> to easily and efficiently rotate the wing tip <NUM> (anti-clockwise as shown in <FIG>). This means that a longitudinal axis of the actuator <NUM> (corresponding in the illustrated embodiment to its line of action of applied force) does not coincide with the axis of rotation X of the wing tip <NUM> throughout movement of the linear actuator <NUM> between its extended and retracted positions.

The technology of the present disclosure increases the lever arm of the linear actuator (<NUM>) upon the linear actuator (<NUM>) moving the tip (<NUM>) of the airfoil from the unfolded position to the folded position. The lever arm is the distance between the axis of rotation X of the wing tip <NUM> and the longitudinal axis of the linear actuator <NUM>. Accordingly, a low force is required from the linear actuator <NUM> to achieve the moment necessary to overcome the weight of the wing tip <NUM> and rotate it upwards. In such an arrangement, a small, low power linear actuator <NUM> may be used to apply the necessary moment, as opposed to, for example, a larger, higher power rotary actuator. The present disclosure therefore has weight saving and power saving advantages over conventional arrangements.

<FIG> show one linear actuator <NUM> in the tip assembly <NUM>, and in some embodiments only one may be provided. However, it will be appreciated that there may be more than one linear actuator <NUM> in each tip assembly <NUM>, for example two, three or more linear actuators <NUM> could be provided in each tip assembly <NUM>. Where multiple actuators are provided, they may have substantially the same features as described above.

<FIG> illustrates the same cross section as <FIG>, but with the wing tip <NUM> in a retracted position.

As noted above, the wing <NUM> can be rotated into its retracted position when on ground, for example if a decreased wing span is desired. In the illustrated embodiment the wing tip <NUM> has been rotated up by the linear actuator <NUM>, and forms an approximate <NUM> degree angle relative to the main body <NUM>. This could be the fully retracted position of the wing tip <NUM>, or in some cases the wing tip <NUM> may be rotated through more than <NUM> degrees.

As the linear actuator <NUM> retracts from the fully extended position (shown in <FIG>) to the retracted position (shown in <FIG>), it moves outside of the wing body and above the surface <NUM>, <NUM> thereof. Allowing the linear actuator <NUM> to rotate outside of the wing surface <NUM>, <NUM> further increases the lever arm between the linear actuator <NUM> and the wing tip <NUM>. Thus, the more the linear actuator <NUM> retracts, the larger the moment that can be applied by the linear actuator <NUM> to the wing tip <NUM> about the axis of rotation X of the wing tip <NUM>. This is advantageous because the wing tip <NUM> can experience larger external forces when in the retracted position due to the wing tip <NUM> being less aerodynamic in that position and thus more susceptible to forces such as wind. This decrease in the force required from the linear actuator <NUM> means that a less powerful and smaller linear actuator <NUM> can be used.

<FIG> is a top view of the tip assembly <NUM> when in the extended position. As shown, the tip assembly <NUM> further comprises doors <NUM> that enclose the linear actuator <NUM>. In the illustrated embodiment, there are four doors <NUM>; two on the main body <NUM> and two on the wing tip <NUM>. Each door <NUM> is pivotally attached to the respective wing portion <NUM>, <NUM> by hinges or any suitable means. In the closed position illustrated in <FIG>, the doors <NUM> are flush with the top surface <NUM>, <NUM> of the wing <NUM> to form a continuous top surface. The doors <NUM> can be opened by actuating means (not shown) which rotate the doors <NUM> up and away from each other to expose the linear actuator <NUM>, which is located below the doors <NUM>. This exposure of the linear actuator <NUM> allows the linear actuator <NUM> to rotate outside of the wing surface <NUM>, <NUM>, thus allowing the linear actuator <NUM> to retract the wing tip <NUM>. When the doors <NUM> are closed, the linear actuator <NUM> is enclosed and locked in place (at least partly by the doors <NUM>, since the actuator is not able to retract because the doors <NUM> obstruct rotation thereof). The doors <NUM> are closed during flight and act as a line of defence in preventing the wing tips <NUM> from retracting. As another line of defence, power can be removed from the linear actuator <NUM> by a control system during flight. It would be appreciated that other types of doors could be used, for example sliding doors, and that fewer than or more than four doors could be used. Furthermore, locking pins could be used instead of or as well as the doors <NUM>, or any other suitable locking means. It should be noted that the locking means (e.g., doors <NUM>) are not essential to the broadest aspects of the present disclosure.

As also shown in <FIG>, the wing tip <NUM> and main body <NUM> are shaped to complement each other when in the extended position, and each have tabs <NUM> and recesses <NUM>, where a tab <NUM> of the main body <NUM> is shaped to fit into a recess <NUM> of the wing tip <NUM> and visa versa. The recesses <NUM> and tabs <NUM> are shaped to allow the wing tip <NUM> to rotate relative to the main body <NUM> without obstruction from the main body <NUM>, as the tabs <NUM> of the wing tip <NUM> are free to rotate into the recesses <NUM> of the main body <NUM>, and vice versa. The embodiment in <FIG> shows three tabs <NUM> and three recesses <NUM> on each of the main body <NUM> and wing tip <NUM>, but there may be more than or fewer than three recesses <NUM> and tabs <NUM> on the main body <NUM> and wing tip <NUM>. Furthermore, alternative recess and tab shapes may be used or the wing tip <NUM> and main body <NUM> may not have tabs and recesses.

<FIG> is a side view of the tip assembly <NUM> in a retracted position. The locking doors <NUM> are shown in the open position.

The tip assembly described above and herein provides various advantages. Using a linear actuator leads to a reduction in manufacturing and maintenance costs. In addition, it is easier to remove, replace and maintain than other types of actuators (for example rotary actuators). Furthermore, allowing the linear actuator to rotate outside of the wing surface means that the actuator is able to provide a higher moment when the wing tip is retracted than when extended, so that the maximum force requirement of the linear actuator can be reduced.

Claim 1:
A wing for an aircraft comprising a fixed body (<NUM>), a movable tip (<NUM>), and an assembly (<NUM>) for moving the movable tip (<NUM>) relative to the fixed body (<NUM>), the assembly (<NUM>) comprising:
a linear actuator (<NUM>) configured to pivotally attach to both the fixed body of the wing and the movable tip of the wing, such that the linear actuator is configured to extend between a first pivotal attachment on the fixed body and a second pivotal attachment on the movable tip,
wherein the linear actuator (<NUM>) is configured to repeatedly move the movable tip (<NUM>) of the wing from an unfolded position to a folded position, wherein throughout such movement the linear actuator (<NUM>) is configured to pivot about both the first and second pivotal attachments,
characterised in that:
a lever arm of the linear actuator (<NUM>) increases upon the linear actuator (<NUM>) moving the movable tip (<NUM>) of the wing from the unfolded position to the folded position, the lever arm being defined as a perpendicular distance from an axis of rotation of the movable tip (<NUM>) of the wing to a longitudinal axis of the linear actuator (<NUM>).