GB2277305A

GB2277305A - Mechanism for moving flap

Info

Publication number: GB2277305A
Application number: GB9408028A
Authority: GB
Inventors: Graham James Walden
Original assignee: Individual
Current assignee: Individual
Priority date: 1993-04-22
Filing date: 1994-04-22
Publication date: 1994-10-26
Anticipated expiration: 2014-04-22
Also published as: GB2277305B; GB9408028D0; GB9308336D0

Abstract

A mechanism for moving a portion 11 of an aircraft wing 10 such as a high lift flap or slat incorporates a hollow section carrier member 14 (or 39, 37 figs 2 and 4) secured to the flap and mounted for generally linear movement in guide rollers 15 in the wing, the carrier member having a flexible tooth-engaging drive member such as a toothed strap 17 secured at two spaced positions therewithin so that the teeth 21 of the strap face inwardly towards the base of the carrier member. The mechanism further includes a toothed drive wheel 20 which meshes with the toothed strap and tensioning rollers 32. Rotation of the drive wheel 20, which may be mounted on a shaft with other drive wheels, feeds the strap to cause corresponding movement of the carrier member and hence the flap 11. A plurality of drive wheels mounted on a shaft may be driven from a fixed primary toothed drive wheel (26 fig 3) having a toothed strap (27 fig 3) which is moved by a primary actuator such as an hydraulic jack (31 fig 3). Detent means 35, 36 are provided for the limit positions of the flap. <IMAGE>

Description

MECHANISM FOR MOVING FLAP This invention relates to a mechanism for moving a portion of an aircraft wing, hereinafter generically referred to as "a flap" in a direction generally aligned with the wing chord, for example for the forward movement of a high lift flap, otherwise known as a slat, at the leading edge of a wing.

It has been proposed to mount a flap on a wing using linear carrier members extending through apertures in a portion of the wing adjacent the flap, and to move it either using a ball screw or a linear actuator which also extends through the adjacent wing surface. It is essential to minimise the number and size of apertures for aerodynamic reasons.

In another proposal, the carrier member has comprised a channel within which teeth are provided to mesh with a stationarily mounted rotatable drive wheel within the wing.

This arrangement needs only an opening for the carrier channel and drive in the surface of the wing adjacent the flap.

However, the teeth being housed within the channel are difficult to inspect for any damage or fatigue cracking, irrespective of whether the teeth are formed integrally with the carrier channel or are formed separately and attached thereto.

It is an object of the invention to provide a new or improved mechanism for moving a flap.

According to the invention there is provided a mechanism for moving a flap portion of an aircraft wing in a direction generally aligned with the wing chord, the mechanism comprising a carrier member secured to the flap and mounted for generally linear movement in guide means, the carrier member being driven by drive means comprising a flexible drive member having tooth-engaging portions defined thereon, secured to the carrier member at two spaced positions, the mechanism further comprising a stationarily mounted rotatable toothed drive wheel which meshes with the flexible drive member whereby, on rotation of the drive wheel, the flexible drive member is fed past the position at which the drive wheel is mounted, causing corresponding movement of the carrier member relative to the guide means.

The carrier member may comprise a hollow section.

The hollow section carrier member may comprise a channel section or a slotted tube which may be circular in crosssection.

The carrier member may be non-rectilinear.

The drive means may comprise a flexible toothed strap.

The tooth-engaging portions of the flexible drive member may face inwardly towards the base of the hollow section carrier member.

There may be one or more tensioning means for the flexible drive member.

Said tensioning means may include a movable mounting for at least one end of the flexible drive member.

The tensioning means may comprise a stationary resiliently biased tensioner disposed at a side of the drive wheel. It may additionally comprise a further tensioner disposed at the other side of the drive wheel which may be a fixed tensioner.

At least one limit position of the carrier member may be defined by a detent. The detent may comprise a resiliently biased latch engageable with the carrier member.

Alternatively at least one limit position may be determined by limit means incorporated in the drive means.

The toothed drive wheel may itself be driven from a drive shaft having a fixed primary toothed drive wheel rotated by movement of a primary toothed drive member connected to an actuator such as an hydraulic jack.

A plurality of toothed drive wheels of varying diameters may be connected to the drive shaft at different positions along a wing in order to control a plurality of flaps requiring to be moved simultaneously but by different distances.

Alternatively or additionally, a high speed shaft extending span-wise of the wing may transmit drive to each mechanism by a series of reduction gearboxes.

An embodiment of the invention will now be described in more detail by way of example only with reference to the accompanying drawings in which Figure 1 diagrammatically illustrates a high lift device at the leading edge of an aircraft wing, Figure 2 is a sectional view on the line A-A of Figure 1, Figure 3 diagrammatically illustrates a drive mechanism, Figure 4 diagrammatically illustrates an alternative section on the line A-A.

Referring to the drawings, a portion of a leading edge of an aircraft wing is indicated at 10 and has a high lift flap (or slat) 11 which can be extended to the position shown but can be retracted so that its trailing edge 12 conforms to the forward edge 13 of the main wing airfoil.

The high lift flap is mounted for movement on a carrier member 14 which, in Figure 2, is of generally channel section, having the conformation of an I-beam 39 with a central slot 16 forming the channel.

Figure 4 shows an alternative cross-section of carrier member.

The carrier member shown at 37 is in the form of a circular cross-section tube having a slot 38. The tube 37 may be preferred to the channel 39 shown in Figure 2 for reasons of reduction of cost and/or improved resistance to deformation.

In the following description it should be understood that references to the channel section carrier member 39 will in general also be relevant to the tube section 37 and corresponding reference numerals will be given in brackets.

The carrier member 14, as shown in Figure 1, is arranged to run between pairs of rollers 15 mounted within the wing.

These guide the movement of the carrier member 14 but are not powered.

The carrier member 14 may be rectilinear or arcuate.

As will be seen from Figure 1, a flexible drive member having tooth engaging portions defined thereon is provided in the form of a toothed strap 17, which is mounted at two spaced positions 18 and 19 to the carrier 14. The strap 17 is looped around a toothed drive wheel 20 which can also be seen in the sectional views of Figure 2 and 4.

The strap 17 is tensioned by a pair of tensioning rollers 32, one of which has a fixed mounting 33 and is resiliently biased, for example by a coil spring 34, into engagement with the strap 17. One tensioner is provided on each of the opposite sides of the toothed drive wheel 20. In addition to the resilient biasing spring 34, the mounts 33 may be adjustably positioned. In normal use, the strap 17 will therefore be held in engagement over a large portion, preferably more than half, of the periphery of the drive wheel 20. Stretching of the toothed strap 17 in use will be accommodated by the resilient bias of the tensioner means.

The tensioners can be removed or disengaged to replace or service the strap, which is then relatively loose between its spaced mounting positions 18 and 19.

An alternative form of tensioner may include a movable mounting for at least one end of the strap.

Although desirable, tensioning means are optional. As an alternative, the toothed strap 17 can pass beneath the drive wheel 20 and over the two lower guide rollers 15, thereby ensuring adequate engagement between the toothed drive wheel 20 and the teeth of the strap 17.

However it is preferred to use tensioning means to compensate for extension and contraction of the strap due to temperature changes or stretching in use.

The teeth 21 of the strap 17 are shown to face upwardly and hence towards the slot 16 (38) in the carrier 14. This reduces the danger of the teeth becoming clogged with dirt or debris. As an alternative, the teeth may face downwardly, with suitable modification of the drive arrangements.

Consideration of Figure 1 will show that the strap is arranged to conform closely to a large part of the circumference of the toothed drive wheel 20 with several teeth of the strap being engaged with the drive wheel simultaneously. This is achieved by passing the strap over the lower guide rollers 15 and optionally the tensioners 32, to define a rolling loop.

In use, the drive wheel 20 is rotated by a drive shaft 22. In the fully extended condition of the high lift flap 11, the drive wheel 20 is at the position shown in Figure 1 indicated by the arrow 23. When the drive shaft is rotated, the drive wheel 20 retains its position relative to the wing airfoil 10 but draws the strap 17 rearwardly until the faces 12 and 13 come into abutment, closing up the arrows 24 and bringing the drive wheel 20 into a position of the carrier corresponding to the arrow 25.

It will be appreciated that a number of flaps 11 may be provided along the wing and that the geometry of the wing make it necessary for these to move by different distances. To this end, the drive shaft 22 is extended through the wing and a plurality of drive wheels 20 of different diameters may be provided along it. The tooth pitch of the drive wheels may differ. The drive strap corresponds to its respective drive wheel to provide the full travel of the flap.

Detents are provided to define the limit positions of travel of the carrier channel. Each detent comprises a notch or similar formation 35 in the outer surface of the carrier channel 14 which is engageable by a resiliently biased latch 36. The latch may operate automatically. It may be disengaged by the powered movement of the carrier 14 compressing the latch mechanism against the spring bias, forcing it to swing over into position ready to engage the latch at the other end of the carrier travel.

It will be noted that the strap 17, being housed largely within the slot 16 (38) of the carrier channel 39 (37), does not need a separate opening through the forward edge of the airfoil. Furthermore, since the teeth are facing into the slot 16 (38), they are concealed for the most part but can be revealed for inspection purposes throughout the length of the strap. This is important so that any damage to the strap can be monitored.

All of the drive wheels 20 are driven from a common shaft 22 as previously referred to and this can be rotated by a primary drive wheel 26 which is driven by a toothed strap 27 again housed within a channel 28. The channel is mounted for movement in pairs of rollers 29 and is secured to the rod 30 of an hydraulic piston and cylinder assembly 31.

Thus operation of the hydraulic piston and cylinder assembly causes the movement of the channel 28 and hence causes the strap 27 to pass around the fixed primary drive wheel 26 to rotate it, the shaft 22 and the individual drive wheels 20.

The channel form 14 and the tubular form 37 can be used either at the individual flap mechanism shown in Figure 1 or for the common drive arrangement shown in Figure 3.

Alternatively a high-speed shaft may extend span-wise of the wing to transmit drive to each individual flap mechanism by a series of reduction gearboxes.

Heating elements can be built into the flexible straps to facilitate low temperature operation. A firm and positive drive is obtained because of the fact that each strap contacts several teeth of the associated toothed wheel simultaneously perhaps over more than half its periphery, and hence isolated damage to a tooth of the wheel or the strap is less likely to cause catastrophic failure than for example in the case of a rack and pinion in which only a single tooth is fully engaged at any time.

Alternative forms of flexible tooth-engaging drive members may be provided, for example in the form of a chain.

Although described in relation to operating a high-lift flap or slat at the leading edge of a wing, the mechanism could be used for operating other control surfaces of an airfoil in which there is a movement generally aligned with the airfoil.

It will be seen that the expression 'generally aligned" is intended to cover movements of an arcuate nature for example that of the high-lift flap illustrated in Figure 1.

Claims

1. A mechanism for moving a flap portion of an aircraft wing in a direction generally aligned with the wing chord, the mechanism comprising a carrier member secured to the flap and mounted for generally linear movement in guide means, the carrier member being driven by drive means comprising a flexible drive member having tooth-engaging portions defined thereon, secured to the carrier member at two spaced positions, the mechanism further comprising a stationarily mounted rotatable toothed drive wheel which meshes with the flexible drive member whereby, on rotation of the drive wheel, the flexible drive member is fed past the position at which the drive wheel is mounted, causing corresponding movement of the carrier member relative to the guide means.

2. A mechanism according to claim 1 wherein the carrier member comprises a hollow section.

3. A mechanism according to claim 2 wherein the hollow section carrier member comprises a channel section.

4. A mechanism according to claim 2 wherein the hollow section carrier member comprises a slotted tube.

5. A mechanism according to claim 4 wherein the slotted tube is of circular cross-section.

6. A mechanism according to any preceding claim wherein the carrier member is non-rectilinear.

7. A mechanism according to any preceding claim wherein the flexible drive means comprise a flexible toothed strap.

8. A mechanism according to any preceding claim wherein the tooth-engaging portions of the flexible drive member face inwardly towards the base of the hollow section carrier member.

9. A mechanism according to any preceding claim wherein one or more tensioning means are provided for the flexible drive member.

10. A mechanism according to claim 9 wherein the tensioning means include a movable mounting for at least one end of the flexible drive member.

11. A mechanism according to claim 9 wherein the tensioning means comprise a stationary resiliently biased tensioner disposed at a side of the stationary drive wheel.

12. A mechanism according to claim 11 wherein the tensioning means additionally comprise a further tensioner disposed at the other side of the drive wheel.

13. A mechanism according to any preceding claim wherein at least one limit position of the carrier member is defined by a detent.

14. A mechanism according to claim 13 wherein the detent comprises a resiliently biased latch engageable with the carrier member.

15. A mechanism according to any one of claims 1 to 12 wherein at least one limit position of the carrier member is determined by limit means incorporated in the drive means.

16. A mechanism according to any preceding claim wherein the toothed drive wheel is itself driven from a drive shaft having a fixed primary toothed drive wheel rotated by movement of a primary flexible toothed drive member connected to an actuator.

17. A mechanism according to claim 16 wherein the actuator comprises an hydraulic jack.

18. A mechanism according to claim 16 or claim 17 wherein a plurality of toothed drive wheels are connected to the drive shaft at different positions along its length in order to control a plurality of flaps requiring to be moved simultaneously.

19. A mechanism according to claim 18 wherein the plurality of toothed drive wheels have different diameters so that said plurality of flaps may be moved simultaneously but by different distances.

20 A mechanism according to any one of claims 1 to 15 wherein a high speed shaft extends span-wise of the wing to transmit drive to each of a plurality of flaps by a series of reduction gearboxes.

21. A mechanism for moving a flap portion of an aircraft wing substantially as hereinbefore described with reference to and as illustrated in Figures 1 and 2 of the accompanying drawings.

22. A mechanism for moving a flap portion of an aircraft wing substantially as hereinbefore described with reference to and as illustrated in Figure 3 of the accompanying drawings.

23. A mechanism for moving a flap portion of an aircraft wing substantially as hereinbefore described with reference to and as illustrated in Figures 1, 3 and 4 of the accompanying drawings.