GB2458683A

GB2458683A - Aircraft slat deployment mechanism

Info

Publication number: GB2458683A
Application number: GB0805595A
Authority: GB
Inventors: Alan Mann
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2008-03-28
Filing date: 2008-03-28
Publication date: 2009-09-30
Also published as: GB0805595D0

Abstract

An aircraft slat deployment mechanism comprises a first curved track 4 coupled to the slat 2 at a first pivot point 5, a main bearing system arranged to guide the first curved track along a curved path, a second track 6 coupled to the slat at a second pivot point 7 which is offset from the first, an internal bearing 22 between the first and second tracks, and a drive system arranged to drive the first curved track along the curved path guided by the main bearings, and the second track along the curved first track guided by the internal bearings. Ideally the second track is partially nested within a channel in the first curved track. Ideally the second track 6 is also curved. Preferably both tracks comprise toothed racks, which are preferably driven from the same driveshaft 10, having pinions 11, 12 of different radius. The differential movement of the telescopic tracks results in rotation of the slat.

Description

SLAT DEPLOYMENT MECHANISM

FIELD OF THE INVENTION

The present invention relates to a mechanism for deploying an aircraft slat, and a method of deploying an aircraft slat using such a mechanism.

BACKGROUND OF THE INVENTION

Leading edge slats are commonly used and well understood. They are commonly driven on a circular track mechanism.

The simple circular track restricts design freedom when optimising both take-off and landing slat settings. Non-circular tracks are not generally used due to loads and kinematic complications. Applying an additional rotation to the slat beyond that provided by the track deployment enables greater design freedom. For example this allows a sealed setting at take-off where drag performance is important and a slotted setting at landing where CLmax is the design driver.

The track is commonly long and, when stowed, extends aft through the wing front 1 5 structural spar. This requires a slat track "can" to be installed at each slat track to seal the fuel tank, reducing the fuel volume, and adding time and cost to the manufacture of the wing. Adding holes is especially inefficient for composite wing spars. Thus there is a strong driver to avoid front spar penetration in wing spars by the high lift mechanism.

Once again applying an additional rotation to the slat enables a shorter track to be used whilst achieving a similar maximum slat deployment angle.

Double action slat mechanisms achieving an additional rotation about the slat heel exist.

The most common form generates the additional rotation through the addition of a follower arm that is guided through a contoured rail as the slat is deployed by the track. An example is described in US3272458. A track is mounted within guide rollers, and driven by a rack and pinion mechanism. Rotation of the slat is effected by a push-pull rod driven by a bell crank which is carried by the track. One arm of the bell crank carries a cam follower which is entrapped within a camming track.

SUMMARY OF THE INVENTION

A first aspect of the invention provides an aircraft slat deployment mechanism comprising: a curved track coupled to the slat at a first pivot point; a main bearing arranged to guide the curved track along a curved path; a drive member coupled to the slat at a second pivot point which is offset from the first pivot point; an internal bearing between the drive member and the curved track; and a drive system arranged to drive the curved track along the curved path guided by the main bearing, and arranged to drive the drive member along the curved track guided by the internal bearing.

The first aspect of the invention provides a more compact arrangement than US3272458.

The bearings may comprise rolling-element bearings (which may use cylindrical, spherical or any other suitably shaped rolling elements) or plane bearings without rolling elements.

The curved track may comprise a toothed rack and the drive system may comprise a pinion which is coupled with the toothed rack. However other drive arrangements, such as a hinged crank, are possible for driving the curved track. The drive member may also be driven by a rack and pinion mechanism, although again other drive arrangements are possible for driving the drive member along the curved track. The drive system may drive the drive iiiember independently and in parallel with the curved track, or may drive the drive member by a dependent motion for instance using a cam follower as in US3272458.

The drive member may comprise a second curved track. In this case the first and second curved tracks are preferably shaped as substantially concentric arcs of a circle.

The drive member may be fully or partially nested within a closed or open channel defined by the curved track. Alternatively, this arrangement may be reversed (that is, the curved track may be fully or partially nested within a channel defined by the drive member). In a further alternative, the two parts may not be nested.

A second aspect of the invention provides a method of deploying an aircraft slat with a deployment mechanism according to the first aspect, the method comprising: driving the curved track along the curved path defined by the main bearing; and driving the drive member along the curved track guided by the internal bearing so as to rotate the slat about the first pivot point.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a first slat deployment mechanism showing the slat in its fully retracted position; Figure 2 is a view of the slat deployment mechanism in an intermediate position; Figure 3 is a view of the mechanism in a fully deployed position; Figure 4 is a cross-sectional view through the tracks and pinions; Figure 5 is a schematic side view of a second slat deployment mechanism with the slat in its fully retracted position; Figure 6 is a view of the mechanism with the slat in an intermediate position; Figure 7 is a view of the mechanism with the slat fully deployed; Figure 8 is a schematic side view of a third slat deployment mechanism; Figure 9 shows the slat in an intermediate position; and Figure 10 shows the slat in a fully deployed position.

DETAILED DESCRIPTION OF EMBODIMENT(S)

Figure 1 is a schematic side view of a slat deployment mechanism I according to a first embodiment of the invention, acting between a slat 2 and a main wing element 3. The mechanism 1 comprises a curved main track 4 which is coupled to the heel of the slat 2 at a first pivot point 5, and a curved secondary track 6 which is coupled to the slat at a second pivot point 7 by a pivoting drive link 8. The drive link 8 is pivotally coupled to the distal end of the secondary track 6 at a third pivot point 9.

A drive shaft 10 running in a span-wise direction along the wing carries a first pinion 11 and a second pinion 12. Although not apparent from the side view of Figure 1, the pinions 11, 12 are spaced apart axially along the drive shaft 10 as shown more clearly in Figure 4.

The first pinion 11 has a smaller radius than the second pinion 12. The first pinion 11 is coupled with a toothed rack on the main track 4 and the second pinion 12 is coupled with a second toothed rack on the secondary track 6.

The main track 4 is guided along a curved path 15 by a main bearing defined by a set of rollers 13. The rollers 13 are carried by a slat track support rib (not shown) which forms part of the main wing element 3. As the pinion 11 rotates, the main track 4 is driven along the curved path 15. The tracks 4, 6 and the path 15 are shaped as substantially concentric arcs of a circle, centred on a point indicated approximately at 16 in Figure 3.

Referring to Figum 4, the secondary track 6 is nested within a channel in the main track 4, which is open on its lower side to accommodate the pinion 12. Specifically, the main track 4 is U-shaped in cross-section with a pair of spaced apart walls 20, 21 which define the channel receiving the secondary track 6. A set of rollers 22 act as an internal bearing between the tracks 4, 6. Three of such rollers 22 are shown in the sectional view of Figure 4, and further rollers (not shown) are distributed along the length of tracks. The rollers 22 may be carried by the secondary track 6 or by the main track 4, or may be free to move within the space between the tracks 4,6.

The secondary track 6 has a rack comprising a series of teeth extending from its lower side, one of the teeth 23 being shown in Figure 4 with the mid point between the base and top of the tooth being indicated by a dashed line 24. The pinion 12 has a set of teeth which engage with the rack on the secondary track 6, so as to drive the secondary track 6 along its respective curved path. Similarly, the smaller pinion 11 has a set of teeth which engage with a rack on the lower side of the main track 4, one of the rack teeth being indicated at 25 in Figure 4.

The larger radius of the pinion 12 causes a differential speed between the tracks 4, 6 giving a resultant motion illustrated in Figures 2 and 3. In the intermediate position shown in Figure 2, the higher speed of the secondary track 6 causes a small anti-clockwise rotation of the slat 2 about the pivot point 5. The position of the slat with this rotation is shown in solid line in Figure 2, and the position that the slat would adopt in the absence of such differential motion is illustrated by a dashed line 30.

The fully deployed position of the slat is shown in Figure 3. Again, the natural position of the slat (incorporating the differential motion between the tracks) is shown in solid line, and a dashed line 31 illustrates the position that the slat would adopt in the absence of this differential rotation.

Figures 5-7 illustrate how the slat deployment mechanism of Figure 1 can be adjusted to give a different motion during deployment. Only the distal ends of thc tracks 4, 6 are shown, for purposes of clarity. Also, the tracks 4, 6 are illustrated schematically as being straight in Figures 5-7 for purposes of clarity, but in practice they will be curved as shown in Figures 1-3.

In the retracted position of Figure 5 the link 8 is aligned with the secondary track 6, and as the slat rotates to the deployed position of Figure 7, the link 8 rotates relative to the secondary track 6 as shown.

In the alternative arrangement of Figures 8-10, in the retracted position of Figure 8 the link 8 is at an angle to the secondary track 6 with the pivot 9 positioned aft of the pivot 7. Thus in the intermediate setting of Figure 9, the slat 2 has moved away from the main wing element and rotated slightly clockwise about the pivot point 5, as indicated by arrow 32.

As the slat moves to the deployed position of Figure 10 the pivot 9 moves forward of the pivot 7 and the slat rotates anticlockwise as indicated by arrow 33 The track 6 functions as a secondary drive member which is driven along the main track 4 by the pinion 12 guided by the internal bearing 22, as the main track 4 is driven along the curved path 15 guided by the rollers 13. The tracks 4,6 are at the same span-wise position and mounted to the main wing element by a single set of rollers 13.

In the examples described in Figures 1-10, the secondary track 6 requires an additional link 8 due to the changing distance between the pivot 7 and the pivot 9. This change will be small, so instead of using a pivoting link 8, the pivot 9 may instead be accommodated by fitting it into a short vertical slot in the slat structure. Alternatively the track 6 may be designed, in terms of the deployment locus, to avoid the need for such refinements.

In summary, the embodiments illustrated in Figures 1-10 achieve a non-circular slat deployment through the differential deployment of two circular tracks of different radii.

Pinions of two different radii drive the two tracks. Thus the tracks are driven to slightly different extents, creating a rotation at the extreme end where they are connected by hinges to the slat heel. Only a small amount of differential motion is required to provide a useful amount of additional slat rotation. The mechanism enables additional slat rotation with a shorter track thus eliminating front spar penetration by the mechanism.

The two pinions 11,12 are driven off thc same drive shaft and gearbox, and thus transmit mechanical power from the drive shaft to the two tracks 4,6 via parallel transmission paths.

The larger radius of the pinion 12 ensures that the track 6 moves at a higher speed than the track 4.

Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.

Claims

CLAIMS1. An aircraft slat deployment mechanism comprising: a curved track coupled to the slat at a first pivot point; a main bearing arranged to guide the curved track along a curved path; a drive member coupled to the slat at a second pivot point which is offset from the first pivot point; an internal bearing between the drive member and the curved track; and a drive system arranged to drive the curved track along the curved path guided by the main bearing, and arranged to drive the drive member along the curved track guided by the internal bearing.
2. The mechanism of claim 1 wherein the curved track comprises a toothed rack and the drive system comprises a pinion which is coupled with the toothed rack.
3. The mechanism of any preceding claim wherein the drive member comprises a second curved track.
4. The mechanism of claim 3 wherein the first and second curved tracks are shaped as substantially concentric arcs of a circle.
5. The mechanism of any preceding claim wherein the drive member comprises a toothed rack which is driven by a pinion.
6. The mechanism of any preceding claim wherein the drive member is at least partially nested within a channel defined by the curved track.
7. The mechanism of claim 6 wherein the channel defined by the curved track is open on at least one side.
8. The mechanism of any preceding claim wherein the main and/or internal bearing comprises a rolling-element bearing.
9. The mechanism of any preceding claim wherein the drive member is coupled to the slat by a pivoting link.
10. A method of deploying an aircraft slat with a deployment mechanism according to any preceding claim, the method comprising: driving the curved track along the curved path defined by the main bearing; and driving the drive member along the curved track guided by the internal bearing so as to rotate the slat about the first pivot point.