GB2569376A

GB2569376A - 4-bar linkage

Info

Publication number: GB2569376A
Application number: GB1721057.6A
Authority: GB
Inventors: Holmes Vernon; Sakota Nebojsa; Mccormick Robert
Original assignee: Airbus Operations Ltd
Current assignee: Airbus Operations Ltd
Priority date: 2017-12-15
Filing date: 2017-12-15
Publication date: 2019-06-19
Also published as: GB201721057D0

Abstract

A 4-bar linkage has a first link 130 with arms 132,134 spaced apart and pivot about the same axis 125 at a second end; a second link 140, opposite the first link, pivots about a different axis 127 at a position in between the arms. Preferably, the first link has two arms joined at a first end and each extending to a respective spaced apart pivot point. Preferably, the linkage is suitable for use in an aircraft wing enabling the movement of a leading edge flap into an extended position relative to a machined bracket 120. The bracket may be rigidly connected to an aircraft wing structure between two ribs. A first component 110 may be integral with the flap. When extended, at least a portion of the second link may be positioned between the two arms of the first link.

Description

4-BAR LINKAGE

TECHNICAL FIELD [0001] The present invention relates to a 4-bar linkage for moving one component relative to another component. In particular, but not exclusively, the invention relates to a 4-bar linkage for moving one aircraft wing component relative to another aircraft wing component, to an aircraft wing deploying such a 4-bar linkage and to an aircraft deploying such a 4-bar linkage.

BACKGROUND [0002] Aircraft wings may comprise components such as spoilers and flaps, designed to change the shape of the aircraft wing and thus alter the performance characteristics of the aircraft wing. Flaps are typically movable between a retracted position and an extended position.

[0003] Aircraft typically comprise other components, such as aircraft doors, that are moveable relative to a main structure.

SUMMARY [0004] A first aspect of the present invention provides a 4-bar linkage for an aircraft, the linkage comprising: a first component and a second component movable relative to one another, and first and second links connecting the first component to the second component, wherein the first link is connected to the first component at a first pivot and connected to the second component at spaced-apart pivots on a first axis, and the second link is connected to the first component at a second pivot, having a different axis to the first pivot, and connected to the second component at a third pivot located between the spaced-apart pivots, and on a second axis different to the first axis.

[0005] Optionally, the first link comprises two arms, each arm extending from the first pivot to a respective one of the spaced-apart pivots.

[0006] Optionally, the 4-bar linkage is configured to move the first component and the second component relative to one another between a retracted position and an extended position, wherein, in the extended position, at least a portion of the second link is positioned between the two arms of the first link.

[0007] Optionally, the second component comprises a machined bracket that defines the spaced-apart pivots and the third pivot.

[0008] A second aspect of the present invention provides an aircraft wing comprising a 4-bar linkage according the first aspect of the present invention, wherein the first component is rigidly connected to a flap.

[0009] Optionally, the first component is integral with the flap.

[0010] Optionally, the flap is a leading edge flap.

[0011] Optionally, the second component is rigidly connected to a main fixed wing structure.

[0012] Optionally, the second component is integral with the main fixed wing structure.

[0013] Optionally, the second component is mounted between two leading edge ribs.

[0014] A third aspect of the present invention provides a 4-bar linkage, wherein a first link comprises two arms joined at a first end and spaced apart at a second end, wherein the two arms are pivotable about the same axis at the second end, and wherein a second link opposite the first link is pivotable about a different axis to the two arms and at a position between the two arms.

[0015] A fourth aspect of the present invention provides an aircraft comprising a 4-bar linkage according the first aspect or the third aspect of the present invention, or an aircraft wing according to the second aspect of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS [0016] Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0017] Figure 1 is a schematic plan view of a prior art 4-bar linkage for an aircraft wing according to an example;

[0018] Figure 2 is a schematic view of a 4-bar linkage according to an example;

[0019] Figure 3 is a schematic view of the 4-bar linkage of Figure 2;

[0020] Figure 4 is a schematic view of a component of the 4-bar linkage of Figure 2;

[0021] Figure 5 is a schematic view of the 4-bar linkage of Figure 2;

[0022] Figure 6 is a schematic view of the 4-bar linkage of Figure 2;

[0023] Figure 7 is a schematic view of the 4-bar linkage of Figure 2; and [0024] Figure 8 is a schematic view of an aircraft according to an example.

DETAILED DESCRIPTION [00251 In known systems, a leading edge flap for an aircraft wing is movable on a linkage mechanism between a retracted position and an extended position. Figure 1 shows an example of such a linkage mechanism 10. The linkage mechanism 10 comprises a first link 20, pivotally mounted between a first rib 1 and a second rib 2, and a second link 30, pivotally mounted between the second rib 2 and a third rib 3.

[0026] The linkage mechanism 10 is a passive mechanism that is movable in response to actuation of a flap actuator 6 mounted between the third rib 3 and a fourth rib 4. The flap actuator 6 is actuated in response to a signal from an aircraft control system to extend or retract a leading edge flap 8. The ribs, 1, 2, 3, 4 typically extend from a leading edge of the wing towards a trailing edge of the wing, and form part of a main fixed-wing structure.

[0027] The first link 20 is pivotally connected to the main fixed wing structure between the first and second ribs, 1, 2, at a first pivot 22 on a first axis, near to a leading edge of the main fixed-wing structure. The first link 20 is also pivotally connected to the leading edge flap 8 at spaced-apart pivots 24, 26. The spaced-apart pivots are on a second axis. The V-like shape of the first link 20 increases the strength of the first link 20 and reduces torsional loads and shear forces in the leading edge flap 8 as it is moved between the retracted position and the extended position by the linkage mechanism 10.

[0028] The second link 30 is pivotally connected to the main fixed-wing structure at a second pivot 32 on a third axis, the third axis being different to the first axis and also near to the leading edge of the main fixed-wing structure. The second link is also pivotally connected to the leading edge flap 8 at a fourth pivot point 34 on a fourth axis.

[0029] The first and second links 20, 30 are mounted to the main fixed wing structure and on the leading edge flap 8, on respective axes, to act as a 4-bar linkage. The arrangement causes the leading edge flap 8 (when actuated by the flap actuator 6) to be moved along a predefined path relative to the main fixed wing structure by the link mechanism 10. The predefined path comprises both a swinging and rotating motion relative to the main fixed wing structure, in a defined sweep motion. The sweep motion is a complex motion, i.e. the motion is not circular, determined by the relative positions, rotational axes and lengths of the links, acting as a 4-bar linkage. The sweep motion moves the leading edge flap 8 from a retracted position under the main fixed wing structure to an extended. In the extended position, the leading edge flap 8 provides high lift, for example during take-off, and shields a leading edge of the main fixed wing structure from debris and contamination.

[0030] There is a general desire to reduce the complexity and weight of aircraft components and systems, for instance, in order to improve the performance and fuel efficiency of the aircraft. Examples of the present invention are concerned with reducing the weight of an aircraft wing by providing an alternative to the linkage mechanism 10 shown in Figure 1.

[0031] Embodiments of the present invention comprise a 4-bar linkage in which first and second links generally overlie one another, as opposed to being spaced apart along a wing section, as will be described. A first link comprises two arms joined at a first end and spaced apart at a second end. The two arms are pivotable about the same axis at the second end. A second link, generally overlying the first link (or vice versa), is pivotable about a different axis to the two arms and at a position between the two arms.

[0032] Figure 2 shows a schematic view of a 4-bar linkage 100 according to embodiments of the present invention. The 4-bar linkage comprises a first component 110 and a second component 120, movable relative to one another, and first and second links 130, 140 connecting the first component 110 to the second component 120. The first link 130 is connected to the first component 110 at a first pivot 112 and to the second component 120 at spaced-apart pivots 122, 124 on a first axis 125. The second link 140 is connected to the first component 110 at a second pivot 116, spaced from the first pivot 112, and connected to the second component 120 at a third pivot 126, located between the spaced-apart pivots 122, 124, and on a second axis 127, which is different to the first axis 125.

[0033] In the embodiment shown in Figure 2, the first link 130 comprises two arms 132, 134. Each of the two arms 132, 134 extends from the first pivot 112 to a respective one of the spaced-apart pivots 122, 124. In some embodiments, the spaced-apart pivots 122, 124 are each positioned an equal distance from the first component 110 in the X-direction (e.g. in a spanwise direction along a wing). In other embodiments, the spaced-apart pivots

122, 124 may be asymmetrically spaced about the first component 110 in the X-direction. The Y-direction (e.g. in a fore-aft (or leading-trailing) direction across a wing chord) and Z-direction (e.g. in a vertical direction through a wing thickness) are shown for reference.

[0034] Figure 2 shows the 4-bar linkage 100 in a first position. In some embodiments, the first position is a retracted position. The 4-bar linkage 100 is movable between the first position and a second position. In some embodiments, the second position is an extended position. Figure 3 shows the 4-bar linkage 100 in the second position. Points a and b on the first component are illustrated in Figures 2 and 3, to indicate the sweep motion of the linkage and components between the first and second positions. As can be appreciated, locating the second link 140 between the two arms 132, 134 of the first link 130 avoids a collision between the two links as the 4-bar linkage 100 is moved between the first position and the second position.

[0035] In the context of a flap arrangement, movement of the 4-bar linkage 100 between the first position and the second position may be controlled by a flap actuator (not shown), in a similar fashion to the arrangement described with reference to Figure 1. In some embodiments, the second component 120 comprises stops (not shown) which help to prevent the 4-bar linkage 100 moving to a position beyond the first (e.g. retracted) position or the second (e.g. extended) position. In some embodiments, the flap actuator comprises stops which help to prevent the 4-bar linkage 100 moving to a position beyond the retracted position or the extended position. In other embodiments, movement of the 4-bar linkage 100 may be enabled by direct rotation of the first link 130 and/or the second link 140, for example comprising an axle, by an actuator, for example, a rotary actuator.

[0036] Figure 4 shows a schematic view of the second component 120. The second component 120 is a machined bracket that defines the spaced-apart pivots 122, 124 on the first axis 125 and the third pivot 126 on the second axis 127. In the embodiment shown in Figure 4, the third pivot 126 is positioned centrally on the second component 120 in the X-direction, and the spaced-apart pivots 122, 124 are equally spaced on either side of the third pivot 126. Such a configuration helps to balance the forces transferred through the 4-bar linkage 100, in use, thus helping to reduce torsional loads and shear forces in the 4-bar linkage 100. In other embodiments, one or more of the spaced-apart pivots 122, 124 and the third pivot 126 may be asymmetrically positioned on the second component 120.

[0037] In the embodiment shown in Figure 4, the second component 120 comprises mounting points 128 for mounting the second component to a main structure (not shown). The position of the second component 120 is fixed relative to the main structure.

[0038] In some embodiments, each of the spaced-apart pivots 122, 124, and third pivot 126, comprises a respective bearing 121 to facilitate smooth rotation of the first and second links 130, 140 relative to the second component 120. In the embodiment shown in Figure 4, the bearings 121 are mounted in flanges 129 on either side of each respective pivots 122, 124, 126. The flanges 129 provide stability on either side of each respective pivots 122, 124, 126, thus helping to reduce torsional loads and shear forces in the 4-bar linkage 100.

[0039] Providing the second component 120 as a machined bracket formed of a single part helps to improve the tolerances across the 4-bar linkage 100. The tolerance between the first axis 125 and the second axis 127 is the tolerance of the machined bracket, which may be smaller, for example, relative to tolerances when the links are spaced apart along a portion of an aircraft wing structure. More particularly, in a linkage mechanism 10 such as that shown in Figure 1, the tolerance between corresponding axes is the accumulative tolerance of at least the leading edge flap 8 and the ribs 1, 2, 3, which may be significantly larger than the tolerance of the machined bracket. An arrangement according to an example of the invention, may therefore help to simplify assembly operations and improve the reliability and lifespan of the 4-bar linkage 100 compared to known linkages.

[0040] Figure 5 shows a schematic view of a side elevation through a section of an aircraft wing 200, including a 4-bar linkage according to embodiments of the present invention. The aircraft wing 200 comprises the 4-bar linkage 100 shown in Figures 2 and 3. The first component 110 of the 4-bar linkage 100 comprises a bracket that is rigidly connected to a flap 210. That is, the position of the first component 110 is fixed relative to the flap

210. In some embodiments, the first component 110 is integral with the flap 210. For example, the flap 210 and the first component 110 may be comprised in a single composite component.

[0041] The aircraft wing has a leading edge 202 and a trailing edge (not shown). In the embodiment shown in Figure 5, the flap 210 is a leading edge flap, for example a Krueger flap, as is known in the art. The flap 210 is movable relative to a main fixed wing structure 220 via the 4-bar linkage 100. In some embodiments, the flap 210 may be movable relative to another component of the aircraft wing 200, for example another flap (not shown). When the 4-bar linkage 100 is in the retracted position, as shown in Figure 5, the flap 210 is positioned so that the aircraft wing 200 has a substantially sealed aerofoil shape. That is, the flap 210 forms an outer, lower surface of the aircraft wing 200 in the retracted position and conforms to the aerofoil shape of the overall aircraft wing 200.

[0042] The second component 120 of the 4-bar linkage 100 comprises a bracket that is rigidly connected to the main fixed wing structure 220. That is, the position of the second component 120 is fixed relative to the main fixed wing structure 220. In some embodiments, the second component 120 is integral with the main fixed wing structure 220. For example, the main fixed wing structure 220 and the second component 120 may be comprised in a single composite component. In the embodiment shown in Figure 6, the second component 120 is the second component 120 shown in Figure 4, and the second component 120 is fixed to the main fixed wing structure 220 at mounting points, for example the mounting points 128 shown in in Figure 5.

[0043] The aircraft wing 200 may comprise a plurality of 4-bar linkages 100 across its span. The plurality of 4-bar linkages 100 may be used to move a single flap 210 between a retracted position and an extended position, or to move a respective plurality of flaps 210 between a retracted position and an extended position.

[0044] Figure 6 shows a schematic side view of the side elevation through the section of the aircraft wing 200 shown in Figure 5. In Figure 6, the 4-bar linkage 100 is in the extended position. In the extended position, the flap 210 is positioned in front of the leading edge 202 of the aircraft wing 200, with a gap 204 between the leading edge 202 and the flap 210. The flap 210 may be moved to the extended position during a take-off procedure. In the extended position, the flap 210 helps to increase lift and protects the leading edge 202 from potential damage caused by impacts from debris and contamination. It is desirable to protect the leading edge 202 because defects in the surface of the leading edge 202 can adversely affect the performance of the aircraft wing 200 during flight. For example, defects can increase the drag generated by the aircraft wing 200.

[0045] As can be seen with regard to Figures 5 and 6, by virtue of the combined rotation of link 130 & 140 around their respective independent axes, the angle subtended by the flap 210, in moving from the retracted position to the extended position, exceeds the angle subtended by each of the first and second links 130, 140. The resultant sweep motion of the flap in the example shown is facilitated by the pivots mounted on the second component 120 being relatively closer to one another than the pivots mounted on the first component 110 in the plane shown in Figures 5 and 6. In some examples, the pivots 112, 116 mounted on the first component 110 and the pivots 122, 124, 126 mounted on the second component 120 may be positioned with respect to one another, in Y and Z directions (with reference to Figure 2), in generally the same locations as the respective link pivots 22, 24, 26, 30, 32 of Figure 1, whereby the same sweep motion is achieved.

[0046] Figure 7 shows a schematic view of a portion of the aircraft wing 200 shown in Figures 5 and 6. The main fixed wing structure 220 comprises a first leading edge rib 222 and a second leading edge rib 224. The second component 120 is mounted between the first and second leading edge ribs 222, 224 at a leading end of the first and second leading edge ribs 222, 224. The first and second leading edge ribs 222, 224 extend from the leading edge 202 of the aircraft wing 200 towards the trailing edge (not shown) of the aircraft wing 200, in direction Y. The 4-bar linkage mechanism 100 is oriented relative to the main fixed wing structure 220 such that the first component 110 is aft of the second component 120, and the second link 140 extends in the direction Y.

[0047] The 4-bar linkage arrangement according to embodiments herein has the benefit that the 4-bar linkage can be far more compact than known linkage mechanisms because the 4-bar linkage can reside between, or be mounted between, only two ribs. In contrast, the arrangement in Figure 1 has a first link 20 between two ribs and a second link 30 between two ribs (with a maximum of one common rib). It can be appreciated, therefore, that by deploying a 4-bar linkage according to the present invention, it is possible to reduce the number of ribs that are required for structurally supporting a flap, such as a Krueger flap. In this way, wing weight and thereby aircraft weight may be reduced.

[0048] Figure 8 shows an aircraft 300 according to embodiments of the present invention. In some embodiments, the aircraft 300 comprises one or more 4-bar linkages (not shown) according to the present invention, for example the 4-bar linkage 100 described with reference to Figures 2 and 3. In some embodiments, the aircraft comprises wings 310 according to the present invention, for example aircraft wings 200 as described with reference to Figures 6 and 7. The wings 310 have a leading edge 312 and a trailing edge 314.

[0049] Embodiments of the present invention provide a number of advantages over other linkage mechanisms used in aircraft, and in particular linkage mechanisms to move flaps on aircraft wings. 4-bar linkages according to the present invention are mounted between two ribs, as opposed to three ribs, as shown in Figure 1. This results in a weight reduction of a wing comprising a 4-bar linkage according to the present invention. This also helps to ease access to the 4-bar linkage during build, servicing and maintenance operations. Further, this reduces the complexity and cost of the wing due to the need for fewer parts and simpler assembly.

[0050] The use of common components for attachments to the first and second links increases the load capacity of 4-bar linkage compared to the linkage mechanism shown in Figure 1 and reduces torsional loads in the wing and flap because the number of point loads is reduced. Further, the use of these common components can help to improve the positional tolerance of the axes of rotation in the 4-bar linkage because the accumulation of tolerances in such an assembly is reduced compared to a linkage mechanism comprising more separate parts than a 4-bar linkage according to the present invention.

[0051] Although not shown in the drawings, the 4-bar linkage 100 may be used to move a trailing edge flap between a retracted position and an extended position. In other embodiments, the 4-bar linkage 100 may be used to move an aircraft door between a closed position and an open position. In other embodiments, the 4-bar linkage 100 may be used to move any part of an aircraft structure which is required to be moved along a predefined path relative to another part of the aircraft structure.

[0052] It is to noted that the term “or” as used herein is to be interpreted to mean “and/or”, unless expressly stated otherwise. The phrase “between a retracted position and an extended position” is intended to cover movement from the retracted position to the extended position, and from the extended position to the retracted position.

[0053] The above embodiments are to be understood as non-limiting illustrative examples of how the present invention, and aspects of the present invention, may be implemented. Further examples of the present invention are envisaged. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the present invention, which is defined in the accompanying claims.

Claims

1. A 4-bar linkage for an aircraft, the linkage comprising:

a first component and a second component movable relative to one another, and first and second links connecting the first component to the second component, wherein the first link is connected to the first component at a first pivot and connected to the second component at spaced-apart pivots on a first axis, and the second link is connected to the first component at a second pivot, having a different axis to the first pivot, and connected to the second component at a third pivot located between the spaced-apart pivots, and on a second axis different to the first axis.

2. The 4-bar linkage according to claim 1, wherein the first link comprises two arms, each arm extending from the first pivot to a respective one of the spaced-apart pivots.

3. The 4-bar linkage according to claim 2, configured to move the first component and the second component relative to one another between a retracted position and an extended position, wherein, in the extended position, at least a portion of the second link is positioned between the two arms of the first link.

4. The 4-bar linkage according to any one of the preceding claims, wherein the second component comprises a machined bracket that defines the spaced-apart pivots and the third pivot.

5. An aircraft wing comprising the 4-bar linkage according to any one of the preceding claims, wherein the first component is rigidly connected to a flap.

6. The aircraft wing according to claim 5, wherein the first component is integral with the flap.

7. The aircraft wing according to claim 5 or claim 6, wherein the flap is a leading edge flap.

8. The aircraft wing according to any one of claims 5 to 7, wherein the second component is rigidly connected to a main fixed wing structure.

9. The aircraft wing according to claim 8, wherein the second component is integral with the main fixed wing structure.

10. The aircraft wing according to claim 8 or claim 9, wherein the second component is mounted between two leading edge ribs.

11. A 4-bar linkage, wherein a first link comprises two arms joined at a first end and spaced apart at a second end, wherein the two arms are pivotable about the same axis at the second end, and wherein a second link opposite the first link is pivotable about a different axis to the two arms and at a position between the two arms.

12. An aircraft comprising a 4-bar linkage according to any one of claims 1-4 or 11, or an aircraft wing according to any one of claims 5-10.