A swing-type landing gear equipped with a shimmy-dampening device, and an aircraft incorporating such a landing gear
The articulated landing gear system with elastic return modules addresses shimmy vibrations by allowing additional degrees of freedom and using preloaded springs to continuously dampen vibrations, enhancing stability and reducing wear.
Patent Information
- Authority / Receiving Office
- FR · FR
- Patent Type
- Patents
- Current Assignee / Owner
- SAFRAN LANDING SYSTEMS
- Filing Date
- 2024-04-26
- Publication Date
- 2026-05-08
AI Technical Summary
Existing aircraft landing gear systems experience shimmy, a combination of torsional and lateral bending vibrations, which current damping devices struggle to effectively mitigate.
An articulated landing gear system with an elastically deformable element at the pivot joint between the leg and pendulum, allowing additional degrees of freedom and incorporating elastic return modules to dampen vibrations, including preloaded springs and pistons to compensate for angular deflections.
The solution effectively limits shimmy vibrations by providing continuous damping across various movements, reducing wear and maintaining structural integrity through elastic compensation.
Smart Images
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Abstract
Description
Title of the invention: A shimmy-damping landing gear, equipped with a shimmy-reducing device, and an aircraft comprising such a landing gear
[0001] The present invention relates to the field of aeronautics and more particularly to aircraft landing gear equipped with a vibration damping device.
[0002] BACKGROUND OF THE INVENTION
[0003] In the aeronautical field, a "shimmy" is a vibrational phenomenon occurring on the landing gear of an aircraft during taxiing. More precisely, shimmy is a combination of torsional and lateral bending vibrations of an axle that takes into account the flexibility of the entire landing gear assembly.
[0004] Landers comprising a box, a rod sliding within the box, a compass having two arms, one articulated to the rod and the other to the box, and a shimmy-damping device located on a shaft connecting the compass arms are known. The damping device comprises an elastic element interposed between the outer lateral face of one of the compass arms and one end of the shaft articulating the compass arms to each other, in order to resist relative displacement of the arms and the shaft as long as the torsional moment to which the joint is subjected is below a predetermined threshold. When the torsional moment exceeds this determined threshold, the device allows the compass arms to move against the elastic force produced by the elastic element.
[0005] SUBJECT OF THE INVENTION
[0006] The invention is notably aimed at solving shimmy problems on swing landing gear. Summary of the invention
[0007] To this end, the invention provides an articulated aircraft landing gear comprising: - a leg having a first end arranged to be articulated with a structure of an aircraft and a second end; - a pendulum supporting wheels; - an articulated linkage of the balance wheel to the leg, comprising a U-shaped yoke, integral with one of the leg and the balance wheel, having two arms extending on either side of the other of the leg and the balance wheel, and a shaft carried by the arms to define a main axis of rotation of the balance wheel on the leg;
[0008] the articulated joint is arranged to allow movement along at least one additional degree of freedom and in that an elastically deformable element is positioned at the level of this articulated joint to compensate for this movement and dampen vibrations of the articulated joint according to this additional degree of freedom.
[0009] Thus, the attenuation device makes it possible at least to limit the vibrations in particular related to the shimmy phenomenon within said pendulum lander by introducing, at the level of the pivot joint between the leg and the pendulum of the lander, a link containing an elastic element allowing to dampen the movements and vibrations.
[0010] The lander may also include the following optional features, individually or in combination: - the elastically deformable element comprises at least two elastic return modules each comprising at least one preloaded spring, a piston, a cage holding the spring and piston in place, the elastic return modules being positioned symmetrically each between one of the two arms of the yoke and the outer surface of the second opposite end, the pistons being in contact with the outer surfaces; - the elastic return modules are housed at least partially each in one of the arms of the clevis; - each of the elastic return modules has a crown shape and is coaxial with the shaft; - the articulated joint is arranged to allow at least one angular movement around a secondary axis of rotation coinciding with a central axis of the leg; - at least one axial stop is included to oppose the translational displacement of the second end relative to the yoke parallel to the shaft; - The deformable elastic element is supported by the shaft and comprises: • an external socket; • an internal socket housed within the internal socket; • an elastically deformable sleeve interposed between the inner and outer bushings.
[0011] The invention also relates to an aircraft comprising a structure on which at least one such landing gear is mounted.
[0012] Other features and advantages of the invention will become apparent from the following description of particular, non-limiting embodiments of the invention. Brief description of the drawings
[0013] Reference will be made to the attached drawings, among which:
[0014] [Fig-1] is a representation of an aircraft comprising a landing gear according to the invention;
[0015] [Fig.2] is a general diagram of a lander according to the invention;
[0016] [Fig.3] is a diagram of the articulated link of a lander according to the invention;
[0017] [Fig.4] is a cross-sectional view, along line AA of [Fig.2], of the articulated joint of a lander, equipped with a vibration damping device according to a first embodiment;
[0018] [Fig.5] is a cross-sectional view, similar to [Fig.4], of the articulated link of a lander, equipped with a vibration damping device according to a second embodiment;
[0019] [Fig.6] is a cross-sectional view, similar to [Fig.4], of the articulated link of a lander, equipped with a vibration damping device according to a third embodiment;
[0020] [Fig.7] is a cross-sectional view, similar to [Fig.4], of the articulated link of a lander, equipped with a vibration damping device according to a fourth embodiment;
[0021] [Fig.8] is a cross-sectional view of the vibration damping device according to a fifth embodiment;
[0022] [Fig.9] is a diagram of a cross-sectional view, similar to [Fig.4], of the articulated link of a lander, equipped with the vibration damping device according to the fifth embodiment. DETAILED DESCRIPTION OF THE INVENTION
[0023] With reference to figures 1 to 4, the invention relates to a lander 101 comprising a leg 1 having a first end 1.1 articulated to the structure of an aircraft 100 and a second end 1.2 provided with a U-shaped clevis 3.1 comprising two arms 3.11 which are parallel to each other and which each have an inner face 3.12, these two faces 3.12 being opposite each other.
[0024] The lander 101 also includes a pendulum 2 having a first end 2.1 linked to a wheel 102 and opposite a second end 2.2. The second end 2.2 is received between the two arms 3.11 of the yoke 3.1. The second end 2.2 has two external lateral faces 2.21 opposite the internal faces 3.12.
[0025] A shaft 3.2 passes through the two arms 3.11 of the yoke 3.1 and the second end 2.2 of the balance wheel 2 to form a main axis of rotation of the balance wheel 2 on the leg 1. The yoke 3.1 and the shaft 3.2 thus form an articulated connection 3 of the leg 1 and the balance wheel 2.
[0026] The articulated joint 3 is arranged to allow movement along an additional degree of freedom different from rotation about the main axis of rotation, between the leg 1 and the rocker arm 2. A joint element 4 is then positioned between the shaft 3 and the rocker arm 2, here a radial ball joint for example, as shown in [Fig.1]. The presence of this element 4 makes the articulated joint 3 of the lander 101 more flexible, by freeing up at least one additional degree of freedom between the leg 1 and the rocker arm 2 (here rotating around a longitudinal direction of the leg 1).
[0027] In order to compensate for this travel and dampen vibrations of the articulated joint 3 according to this additional degree of freedom, elastically deformable elements are provided positioned at the level of the articulated joint 3.
[0028] These elastically deformable elements are elastic return modules 5 which include at least one spring 5.1, a piston 5.2, a cage 5.3 holding in place the spring 5.1 and the piston 5.2 and having an internal stop 5.4 to stop the movement of the piston 5.2 and prevent excessive compression of the spring 5.1. The spring 5.1 is preloaded and arranged in the cage 5.3 so as to apply a stress to the piston 5.2 in an axial direction of the shaft 3.2.
[0029] These elastic return modules 5 are in the shape of a crown, allowing their positioning around the shaft 3.2, the axis of translation of the piston 5.2 in the elastic return module 5 being coincident with the central axis of the crown.
[0030] These elastic return modules 5 are two in number, symmetrically positioned on either side of the rocker arm 2, facing each other, and coaxially with the shaft 3.2. Cavities 8 adapted to the dimensions of these elastic return modules 5 are provided in the arms 3.11 of the yoke 3.1. These cavities 8 open onto the inner faces 3.12 of the arms 3.11 of the yoke 3.1 and each receives one of the elastic return modules 5. The elastic return modules 5 positioned in these cavities 8 are then integrated into the arms 3.11 of the yoke 3.1. The pistons 5.2 of the elastic return modules 5 are in contact with the outer faces 2.11 of the balance wheel 2, and the preload of the springs 5.1 allows the pistons 5.2 to apply an axial stress to the balance wheel 2, and thus to dampen the axial movements or rotations of the balance wheel 2. Indeed, if the contact force of the balance wheel 2 exceeds the preload of the springs 5.2, the balance wheel 2 moves along the shaft 3.2 and compresses the spring 5.1 on the side in which it moves, while the other spring 5.1 relaxes. It should be noted that regardless of the amplitude of the movement of the balance wheel 2 and the direction of movement, none of the pistons 5.2 loses contact with the balance wheel 2, so that the pistons 5.2 constantly apply a force to the balance wheel 2. It is understood that the springs 5.1, thus positioned at the articulated joint 3, compensate for the angular deflection allowed by the articulation element 4 around the central axis of the leg 1, which makes it possible to quickly dampen vibrations of the articulated joint 3 that would occur due to this additional degree of freedom.
[0031] Translational stop elements are provided on the shaft 3.2, positioned between the arms 3.11 of the yoke 3.1 and the rocker arm 2. These elements are spacers 6 being in abutted against the rocker arm 2 on one side, and against the arms 3.11 of the yoke 3.1 on the other. These spacers 6 are placed on the shaft 3.2, contributing to the translational locking of the rocker arm 2 relative to the leg 1.
[0032] Contact surfaces 7 are provided on the lateral faces 2.2 of the balance wheel 2, capable of withstanding the friction and the forces of the piston heads 5.2 of the elastic return modules 5. These surfaces 7 have the function of protecting the balance wheel 2 from wear, or from heating for example.
[0033] The identical or analogous elements to those previously described shall bear the same numerical reference as the latter in the following description of the four other embodiments in connection with figures 5 to 9.
[0034] With reference to [Fig. 5], and according to the second embodiment, the elastic return modules 5 have a different shape than the crown shape presented in the first embodiment. Here they have a cylindrical shape.
[0035] Each arm 3.11 of the yoke 3.1 carries at least two elastic return modules 5, positioned symmetrically around said shaft 3.2 and regularly distributed around said shaft 3.2. The dimensions of the cavities 8 are then adapted to the geometry of the elastic return modules 5, so that they are fixedly positioned in the arms 3.11 of the yoke 3.1. This solution thus offers a simplified structure for the elastic return modules 5.
[0036] With reference to [Fig.6], and according to a third embodiment, the elastic return modules 5 can be positioned outside the arms 3.11 of the clevis 3.1, fixed on the inner faces 3.12 of said arms 3.11 of the clevis 3.1. This configuration allows a simplification of the geometry of the arms 3.11 of the clevis 3.1 and of the elastic return modules 5.
[0037] With reference to [Fig. 7], and according to a fourth embodiment, the connecting element 4 described in the first embodiment as a ball joint is not present in the articulated joint 3. The shaft 3.2 is pivotally received about its longitudinal axis in the rocker arm 2. Additional degrees of freedom are maintained by allowing functional clearance between the shaft 3.2 and the rocker arm 2. For example, the articulated joint 3 is arranged to allow an additional degree of freedom in translation along the shaft 3.2 between the rocker arm 2 and the leg 1. The additional degree of freedom in rotation about the central axis of the leg 1 is eliminated. The contact surfaces 7 are retained, and one or more bushings are provided between the shaft 3.2 and the rocker arm 2 to prevent premature wear of either of these parts due to friction. The contact surfaces 7 belong, for example, to collars extending around said rings.
[0038] With reference to Figures 8 and 9, and according to the fifth embodiment, the elastic element 5, which allows for the attenuation of the shimmy phenomenon, is supported by the shaft 3.2 and comprises: an outer bushing 10 made of a rigid material, an inner bushing 11 also made of a rigid material and housed within the outer bushing 11, and a deformable elastic sleeve 12 interposed between the inner bushing 10 and the outer bushing 11. This arrangement, designed to dampen vibrations directly around the shaft 3.2, simplifies the device, reduces its size within the lander 101, and decreases its mass. The elastic sleeve 12 is sufficiently rigid to withstand the design forces, yet also sufficiently flexible to dampen the rotational movements of the boom 2 relative to the leg 1 around a secondary axis of rotation other than the primary axis of rotation.
[0039] Of course, the invention is not limited to the embodiments described but encompasses any variant falling within the scope of the invention as defined by the claims.
[0040] In particular, the elastic return modules 5 may include any elastic element and in particular helical springs, Belleville type washers, elastic buffers, volute springs, leaf springs, or gas springs.
[0041] The rocker arm 2 can be fixed to the leg 1 by one of its ends or by an intermediate part between its two ends.
[0042] The rocker arm 2 can carry one or more wheels or pairs of wheels.
Claims
Demands
1. Aircraft landing gear (101), comprising: - a leg (1) having a first end (1.1) arranged to be articulated with a structure of an aircraft (100) and a second end (1.2); - a balance beam (2) carrying wheels (102); - an articulated linkage (3) of the balance beam (2) to the leg (1), comprising a U-shaped clevis (3.1), integral with one of the leg (1) and the balance beam (2), having two arms (3.11) extending on either side of the other of the leg (1) and the balance beam (2), and a shaft (3.2) carried by the arms (3.11) to define a principal axis of rotation of the balance beam (2) on the leg (1); characterized in that the articulated joint (3) is arranged to provide a deflection in at least one additional degree of freedom and in that an elastically deformable element is positioned at the level of this articulated joint (3) to catch this deflection and dampen vibrations of the articulated joint (3) in this additional degree of freedom.
2. Lander according to claim 1, wherein the elastically deformable element comprises at least two elastic return modules (5) each comprising at least one preloaded spring (5.1), a piston (5.2), a cage (5.3) holding in place the spring (5.1) and the piston (5.2), the elastic return modules (5) being positioned symmetrically each between one of the two arms (3.11) of the clevis (3.1) and the outer surface (3.12) of the second end (2.2) opposite, the pistons (5.2) being in contact with the outer surfaces (3.12).
3. Lander according to claim 2, wherein the elastic return modules (5) are housed at least partially each in one of the arms (3.11) of the clevis (3.1).
4. Lander according to any one of claims 2 and 3, wherein each of the elastic return modules (5) has a crown shape and is coaxial with the shaft (3.2).
5. Lander according to any one of the preceding claims, wherein the articulated linkage (3) is arranged to permit at least one angular deflection about a secondary axis of rotation coinciding with a central axis of the leg (1).
6. Land according to one of the preceding claims, comprising at least one axial stop (6) to oppose translational displacement of the second end (2.2) relative to the clevis parallel to the shaft (3).
7. Land according to claim 1, wherein the deformable elastic element is carried by the shaft (3.2) and comprises: - an outer bushing (10); - an inner bushing (11) housed in the inner bushing (10); - an elastically deformable sleeve (12) interposed between the inner (10) and outer (11) bushings.
8. Aircraft comprising a structure on which is mounted at least one landing gear (101) according to one of the preceding claims.