Retractable landing gear with a towed steering axle and an electric motor, and an aircraft with at least one such landing gear

Description

[0001] The present invention relates to the field of aircraft landing gear.

[0002] The present invention relates to a motorized retractable landing gear intended to equip an aircraft and an aircraft provided with at least one such landing gear.

[0003] Typically, an aircraft has a landing gear. The landing gear is sometimes equipped with a plurality of landing gears. An aircraft landing gear may include at least one wheel and one shock absorber.

[0004] In one example, the landing gear may include two main landing gears and one auxiliary landing gear, each of which may be swing-type.

[0005] For example, a balancer landing gear may include an oscillating landing gear leg, more simply called a "balancer". The landing gear leg is articulated to a supporting structure of the aircraft and carries at least one wheel. The landing gear leg, or even the wheel, may be retracted in flight into a landing gear well. Therefore, a balancer landing gear includes a retraction device for moving the wheel from a deployed or extended position to a retracted or retracted position in order to retract all or part of the landing gear into the landing gear well in flight. For example, a strut equipped with a shock absorber and a hydraulic cylinder may act as a retraction device.

[0006] For example, retractable landing gear, as described in EP 3248869 and WO 2008 / 060338, comprises a retraction system integrated with a shock absorber and using the compression of the landing gear shock absorber to move the landing gear from the deployed position to the retracted position. However, the compression of such a shock absorber requires a significant force, generally requiring a hydraulic retraction system. In addition, during a hard and / or violent landing, significant forces are exerted on the shock absorber and can in this case damage the retraction system, or even the shock absorber and the airframe of the aircraft.

[0007] According to another example, document EP 3492375 describes a retractable landing gear for an aircraft comprising a shock absorber connecting the structure to a balance assembly provided with a balance carrying a wheel and a breaker strut formed by two connecting rods. The landing gear also comprises two linear actuators, one actuator connected to the breaker strut and one actuator connected to the structure of the aircraft and to the balance assembly. The two actuators allow two rotations around separate axes of the balance assembly, below the shock absorber, in order to retract the balance assembly. In this case, the shock absorber remains in a fixed position during retraction of the landing gear. Such a retraction system is complex due to the use of two actuators, the multiplicity of connections and the movements necessary for the retraction and deployment of the landing gear.

[0008] Document FR 3001708 describes a retractable landing gear equipped with a balance beam carrying a wheel and a shock absorber. The shock absorber is provided with a body and a rod movable relative to the body. The landing gear is provided with a knee joint comprising two joints connected respectively to the balance beam and to the shock absorber. The knee joint has an area bearing on a stop of the balance beam when the landing gear is in a deployed position.

[0009] Document FR 2946319 describes a pendulum landing gear comprising a shock absorber, a wheel connected to a movable rod of the shock absorber, a breaker strut formed of two connecting rods articulated together and a stabilizing member connected to one of the connecting rods of the breaker strut. The stabilizing member is provided with two connecting rods articulated together and kept aligned by a locking spring. The two connecting rods of the strut are kept aligned by the stabilizing member when the landing gear is in the deployed position. An actuator, such as a motor, is connected to one of the connecting rods of the stabilizing member in order to move the entire landing gear between the deployed and retracted positions.

[0010] Document FR 3011816 describes a rocker landing gear for a rotorcraft equipped with a rocker connected to a wheel, a shock absorber and an operating cylinder, as well as a guide rail fixed relative to the rotorcraft and a slider sliding along the guide rail using the operating cylinder. The shock absorber is articulated to the slider and the rocker. The operating cylinder thus allows, via the movement of the slider along the rail, to move the landing gear between a deployed position and a retracted position.

[0011] The prior art also includes document FR 2884801 which describes a retractable landing gear equipped with a linear actuator while document WO 2017 / 182955 describes a straight landing gear retractable by rotation.

[0012] The present invention then aims to propose an alternative landing gear aimed, for example, at limiting the retraction and deployment efforts of the landing gear, its size and / or the effects on the landing gear of a hard or violent landing.

[0013] An object according to the present invention is a retractable landing gear for an aircraft, the landing gear comprising: a balancer intended to be articulated to a structure of the aircraft and carrying at least one wheel, said at least one wheel being movable between a deployed position and a retracted position, a shock absorber provided with a rod sliding in a body, the shock absorber being intended to be articulated to the structure, a strut provided with a first connecting rod and a second connecting rod articulated together by a first mechanical connection, the first connecting rod being articulated to the shock absorber, and an actuator.

[0014] This landing gear is remarkable in that the actuator is on the one hand intended to be connected to the structure of the aircraft and on the other hand connected to the second connecting rod in order to drive the second connecting rod in rotation relative to the structure, the landing gear comprising: a connecting rod articulated on the one hand to the shock absorber by a second mechanical connection with a single degree of freedom in rotation and on the other hand to the rocker arm, the connecting rod being misaligned from the shock absorber when a force less than a predetermined force is exerted on the shock absorber, and a locking device comprising an elastic return member and a stop device, the elastic return member being fixed by two ends respectively to the strut and to an articulated assembly comprising the rocker arm, the connecting rod and a third mechanical connection connecting the rocker arm and the connecting rod, the elastic return member exerting a tensile force between the strut and the articulated assembly, the stop device being configured to stop a relative movement between the first and second connecting rods around an axis of rotation of the first mechanical connection,under the action generated by the tensile force of the elastic return member when the wheel is in the deployed position.

[0015] An aircraft may have one or more retractable landing gears forming a landing gear of the aircraft. The aircraft then has at least one housing capable of accommodating at least one landing gear. A housing thus makes it possible to accommodate at least partially, or even completely, a landing gear in flight in the retracted position of the wheel.

[0016] The actuator allows the wheel to be moved from the deployed position to the retracted position, and vice versa from the retracted position to the deployed position. The actuator is in fact linked to the second link and generates the movement of the second link relative to the structure of the aircraft, which consequently causes the simultaneous movements of the first link, the shock absorber, the link, the balancer and the wheel.

[0017] The wheel is positioned in the deployed position before landing and while the aircraft is on the ground. The wheel may be arranged in flight in the retracted position, the landing gear then being partially or completely retracted into a housing of the aircraft.

[0018] The term "articulated" means that the two parts articulated together are connected by a mechanical connection comprising at least one degree of freedom in rotation. Two parts articulated together may, for example, be connected by a mechanical connection with a single degree of freedom in rotation, of the pivot type, such a pivot-type mechanical connection allowing rotation around a single axis of rotation. Two parts articulated together may alternatively be connected by a mechanical connection with three degrees of freedom in rotation of the ball joint type allowing rotations around three axes of rotation intersecting at a point, or by a connection with two degrees of freedom in rotation of the cardan type allowing rotations around two intersecting axes of rotation.When the lander has several mechanical links with a single degree of freedom in rotation, the axes of rotation of these mechanical links, including the first mechanical link, are parallel to each other.

[0019] The first mechanical connection connecting the first link and the second link is for example formed by a ball joint type connection allowing relative rotational movements of the first link and the second link around three intersecting axes of rotation. Alternatively, the first mechanical connection may be of the pivot type or of the cardan type. In the case of a pivot type connection, the single axis of rotation is for example oriented substantially horizontally, when the aircraft is resting on horizontal ground.

[0020] The second mechanical connection between the connecting rod and the shock absorber is formed by a pivot-type connection allowing relative rotational movements of the connecting rod and the shock absorber around a single axis of rotation.

[0021] The third mechanical connection connecting the balance and the connecting rod may be formed by a ball-and-socket type connection allowing relative rotational movements of the balance and the connecting rod around three intersecting axes of rotation. Alternatively, the third mechanical connection may be of the pivot type or of the cardan type.

[0022] The shock absorber and the connecting rod thus constitute a main bracing of the balance beam when the wheel is in the deployed position. The strut, and therefore the first and second connecting rods, constitute a secondary bracing ensuring in particular the maintenance and locking in position of the main bracing and, consequently, of the balance beam and the wheel when the wheel is in the deployed position.

[0023] The landing gear according to the invention thus benefits from double bracing to ensure effective maintenance of the wheel in the deployed position.

[0024] Furthermore, the connecting rod is misaligned from the shock absorber, while forming an obtuse angle with the shock absorber, in the deployed position when a force less than a predetermined force is exerted on the shock absorber. A force less than the predetermined force is for example exerted on the shock absorber when no force is applied to the wheel, namely when no force other than those due to the acceleration of the Earth's gravity is applied to the wheel. Thus, the connecting rod is misaligned from the shock absorber in the deployed position when the aircraft equipped with the landing gear is in flight. The connecting rod is also misaligned from the shock absorber in the deployed position when the aircraft equipped with the landing gear is statically placed on the ground, namely motionless, the force exerted on the shock absorber then being less than the predetermined force.

[0025] When the aircraft equipped with the landing gear is in flight or static on the ground, the shock absorber rod is in a position described as "median" relative to the shock absorber body, i.e. the rod is not in abutment in the body, and can then move both to enter the body and to leave the body depending on the forces that can be applied to the wheel. When a force less than a predetermined force is exerted on the shock absorber, the shock absorber can thus be extended and compressed.

[0026] The connecting rod and the shock absorber thus form an angle greater than 0 degrees (0°), and more precisely between 0 degrees (0°) and 180 degrees (180°), when a force less than a predetermined effort is exerted on the shock absorber.

[0027] This misalignment of the connecting rod relative to the shock absorber advantageously makes it possible to ensure traction of the brace guaranteeing effective locking of the main bracing formed by the shock absorber and the connecting rod over the entire compression range of the shock absorber and, consequently, effective locking of the deployed position of the wheel of the landing gear according to the invention.

[0028] The kinematics of the landing gear, and in particular the kinematics of the balancer and the connecting rod, also make it possible to progressively reduce this misalignment of the connecting rod relative to the shock absorber when the shock absorber is compressed, the force exerted on the shock absorber increasing, for example during contact of the wheel with the ground during a landing and when the airframe of the aircraft approaches the ground during this landing. This reduction in misalignment is characterized by an increase in the aforementioned angle between the connecting rod and the shock absorber and makes it possible to limit the shear forces in the shock absorber. The limitation of these shear forces in the shock absorber induces, for example, the reduction of friction between the rod and the body of the shock absorber during compression of the shock absorber, which thus improves the operation, efficiency and effectiveness of the shock absorber.

[0029] In addition, locking the strut, connecting the structure to the shock absorber, using the locking device, in the deployed position of the wheel, makes it possible to prevent any angular movement of the shock absorber during its compression. This feature advantageously makes it possible to maintain a constant lever arm between the shock absorber and an axis of rotation of the balance beam relative to the structure of the aircraft, thus ensuring a mechanical advantage, substantially constant over the entire compression stroke of the shock absorber, in particular during a landing of the aircraft.

[0030] The locking of the strut, in the deployed position of the wheel, is ensured by the tensile force generated by the elastic return member on this strut and by the presence of the stop device. Indeed, the stop device makes it possible to limit the angular movement of the first link and the second link around the axis of rotation of the first mechanical connection under the action of the tensile force of the elastic return member and to stop a relative angular movement of the first link and the second link in a direction around the axis of rotation of the first mechanical connection when the maximum angular movement is reached.

[0031] This locking of the strut advantageously prevents unwanted retraction, for example when the landing gear is subjected to vibrations, shocks, accelerations and ground forces, within predefined limits. The actuator makes it possible to unlock the strut by opposing the tensile force generated by the return member and by moving the second link, in order to move the wheel from the deployed position to the retracted position.

[0032] The elastic return member is thus dimensioned so that this locking resists these vibrations, these shocks, these accelerations and these ground forces, within the predefined limits. The elastic return member may comprise, for example, a helical spring subjected to traction.

[0033] The presence of this lock also makes it possible not to introduce torque or force into the actuator when the wheel is in the deployed position. The actuator is therefore not permanently stressed, significantly increasing its lifespan thanks to the invention.

[0034] In addition, this locking of the strut, combined with the double bracing, advantageously allows the actuator to no longer be stressed once the wheel is in the deployed position and the strut is locked. The actuator then exerts no force or torque on the second link, and its electrical energy consumption is limited, or even zero.

[0035] Furthermore, the wheel can be held in the retracted position, for example, by means of the actuator. The actuator can apply sufficient force or torque to the strut for this holding, in particular to counteract the weight of the wheel and the balance beam. The kinematics of the landing gear and the arrangement of the elastic return member are advantageously defined so as to reduce the force or torque required at the actuator to hold the wheel in the retracted position. Alternatively or in addition, a locking member can lock the actuator when the wheel is in said retracted position.

[0036] Likewise, this kinematics of the landing gear and the arrangement of the elastic return member are advantageously defined so as to reduce the force or torque required to move the wheel between the retracted and deployed positions.

[0037] In addition, the innovative kinematics of the landing gear according to the invention advantageously allows for emergency deployment of the wheel by gravity from the retracted position to the deployed position, for example in the event of a breakdown or malfunction of the actuator.

[0038] The landing gear according to the invention may comprise one or more of the following characteristics, taken alone or in combination.

[0039] According to one example, the stop device may comprise a first stop arranged on the first connecting rod and a second stop arranged on the second connecting rod. The first stop and the second stop are in contact with each other when the wheel is in the deployed position and under the tensile force generated by the elastic return member. The first stop and the second stop thus jointly make it possible to limit the angular movement of the first connecting rod and the second connecting rod around the axis of rotation of the first mechanical connection under the action of the elastic return member.

[0040] Alternatively, the stop device may comprise a stop arranged on the first connecting rod and coming into contact with the second connecting rod under the action of the elastic return member so as to limit the angular movement of the first connecting rod and the second connecting rod around the axis of rotation of the first mechanical connection.

[0041] Alternatively or additionally, the stop device may comprise a stop arranged on the second connecting rod and coming into contact with the first connecting rod under the action of the elastic return member so as to limit the angular movement of the first connecting rod and the second connecting rod around the axis of rotation of the first mechanical connection.

[0042] Alternatively, the stop device may comprise a first stop arranged on the first connecting rod and coming into contact with the shock absorber under the action of the elastic return member so as to limit the angular movement of the first connecting rod relative to the shock absorber, and a second stop arranged on the second connecting rod and coming into contact with the structure or the actuator under the action of the elastic return member so as to limit the angular movement of the second connecting rod relative to the structure. Alternatively, the first stop may be arranged on the shock absorber and come into contact with the first connecting rod. Alternatively, the second stop may be arranged on the structure or the actuator and come into contact with the second connecting rod.

[0043] According to another example compatible with the preceding ones, the actuator can be a rotary electric motor. The second link is then connected to a rotating output shaft of the electric motor, a fixed part of the electric motor being connected to the structure of the aircraft. For example, a first end of the second link is integral with such a rotating output shaft of the electric motor, the second end of the second link being connected to the first link via the first mechanical connection. Thus, the electric motor causes a rotation of the second link about its first end, and consequently a movement of the first link, and of the wheel, to move the wheel from the retracted position to the deployed position, and vice versa.

[0044] The use of such a rotary electric motor as an actuator simplifies the installation of the landing gear according to the invention compared to a landing gear of the prior art using, for example, a hydraulic cylinder. In addition, the energy consumption of such a rotary electric motor is reduced and its use is possible thanks to the particular kinematics of the landing gear according to the invention which requires reduced operating torques to move the wheel between the retracted and deployed positions as well as a reduced torque to maintain the wheel in the retracted position. The use of such a rotary electric motor as an actuator also allows a significant angular displacement of the second link, for example greater than 90°, or even close to 180°, which, combined with the kinematics of the landing gear, makes it possible to obtain a small footprint of the landing gear when the wheel is in the retracted position.

[0045] Advantageously, the use of such an electric motor as an actuator can allow, during emergency deployment of the wheel by gravity, the control of the speed of deployment of the wheel by short-circuiting the electric motor which then acts as a brake.

[0046] Alternatively, the actuator may be an electric, pneumatic, or even hydraulic linear actuator, articulated to the structure of the aircraft and to the second link, a first end of the second link being articulated to the structure and the second end of the second link being connected to the first link via the first mechanical connection. In this way, this actuator causes a rotation of the second link around its first end, and consequently a movement of the first link, the shock absorber, the link and the balancer, to move the wheel from the retracted position to the deployed position, and vice versa.

[0047] According to another example compatible with the previous ones, the connecting rod can be articulated to the rod and the first connecting rod can be articulated to the body, the body being articulated to the structure.

[0048] Alternatively, the connecting rod may be hinged to the body and the first connecting rod may be hinged to the rod, the rod being hinged to the structure.

[0049] According to another example compatible with the previous ones, an axis of rotation of the first connecting rod relative to the shock absorber and an axis of rotation of the second connecting rod relative to the structure can form a substantially horizontal plane, the wheel being in the deployed position, such a horizontal plane being perpendicular to a direction of Earth's gravity. The axis of rotation of the second connecting rod relative to the structure is for example the axis of rotation of the actuator when the actuator is a rotary electric motor.

[0050] This location of the rotation axes of the first link relative to the shock absorber and of the second link relative to the structure makes it possible to minimize the maneuvering efforts of the landing gear, in particular to move the wheel from the deployed position to the retracted position, and vice versa, the lever arm between the secondary strut and the mechanical connection between the shock absorber and the structure being maximized.

[0051] According to another example compatible with the preceding ones, an axis of rotation of the first link relative to the shock absorber, an axis of rotation of the second link relative to the structure and the axis of rotation of the first link relative to the second link may be parallel to each other and coplanar when the wheel is in the deployed position. The stop device may be configured to allow such alignment in the deployed position.

[0052] This parallelism and coplanarity of the three aforementioned rotation axes contribute to minimizing the maneuvering efforts of the landing gear actuator, in particular to move the wheel from the deployed position to the retracted position, and vice versa.

[0053] In this way, when the first link and the second link are straight, the first link and the second link are aligned in the deployed position. The angle between the first link and the second link about the axis of rotation of the first mechanical connection is in this case substantially equal to 180°.

[0054] According to another example compatible with the preceding ones, the elastic return member can be fixed by one of its ends to the first connecting rod, to the second connecting rod or to the first mechanical connection. The elastic return member is preferably fixed directly to the first mechanical connection. The elastic return member can also be fixed to the first connecting rod or to the second connecting rod, this fixing point being located close to the first mechanical connection. The other end of the elastic return member can be fixed to the third mechanical connection between the rocker and the connecting rod, to the rocker or to the connecting rod. This location of the elastic return member makes it possible to minimize the operating forces of the actuator to move the wheel from the deployed position to the retracted position, and vice versa.

[0055] According to another example compatible with the preceding ones, a first length of the first connecting rod can be greater than a second length of the second connecting rod.

[0056] These dimensions of the first link and the second link also make it possible to minimize the maneuvering forces of the landing gear. The first length of the first link can be defined between two ends of the first link, in a direction passing through the axes of rotation of the first link relative to the shock absorber and the second link respectively. The second length of the second link can be defined between two ends of the second link, in a direction passing through the axes of rotation of the second link relative to the structure and the first link respectively.

[0057] For example, the second length of the second link may be between one-quarter (1 / 4) and one-fifth (1 / 5) of the first length of the first link.

[0058] In another example consistent with the preceding, the connecting rod may be straight and aligned with the shock absorber when the shock absorber is compressed under a force equal to the predetermined force, with the wheel in the extended position. When such a force equal to the predetermined force is exerted on the shock absorber, the shock absorber compresses so that the rod is almost completely retracted into the body.

[0059] A significant force can sometimes be applied to the wheel and transmitted at least partially, via the connecting rod, to the shock absorber. Such a significant force is for example exerted on the wheel by the ground during a landing. Under the action of this significant force, the shock absorber compresses, possibly almost completely, namely that the rod can come to bear against an end-of-stroke stop arranged in the body when the force exerted on the shock absorber is substantially equal to, or even greater than, the predetermined force.

[0060] The kinematics of the landing gear according to the invention is defined so that the connecting rod, which may be straight, is aligned with the shock absorber when the shock absorber is compressed under the effect of a force substantially equal to this predetermined force. In this way, the connecting rod can transmit to the shock absorber the majority of this significant force due to the reaction of the ground on the wheel so that the shock absorber absorbs and dissipates this significant force as much as possible to protect the connecting rod and / or the structure of the aircraft.

[0061] Alternatively, the connecting rod may remain misaligned with the shock absorber when the shock absorber is compressed under a force equal to the predetermined force, with the wheel in the deployed position. The previously mentioned angle between the connecting rod and the shock absorber is then very close to 180° while remaining strictly less than 180° and is for example between 175° and 180°.

[0062] According to another example compatible with the preceding ones, the shock absorber may comprise a deformable end-of-travel stop arranged in the body, the end-of-travel stop being configured to deform when the shock absorber compresses under the effect of a force greater than the predetermined force, the wheel being in the deployed position.

[0063] The end stop can thus deform under the effect of a force greater than the predetermined force.

[0064] The deformable end stop thus acts as a fuse to dissipate part of the energy transmitted to the wheel, and consequently to the shock absorber, for example during a landing usually called a "hard landing".

[0065] For example, the deformable end stop comprises a tube forming a hollow body and configured to buckle from a force exerted on the shock absorber, greater than or equal to the predetermined force.

[0066] According to another example compatible with the previous ones, the landing gear may comprise a lever, the lever being configured to be in contact with the first link when the shock absorber is compressed under the effect of a force substantially equal to the predetermined force, the wheel being in the deployed position. The lever is then in contact with the first link without causing any movement of the first link. The lever is thus arranged so as to cause a movement of the first link when the shock absorber is compressed under the effect of a force greater than the predetermined force.

[0067] The lever may alternatively be very close to the first link, without being in contact against the first link, when the shock absorber is subjected to a force substantially equal to the predetermined force. The lever makes contact, then moves the first link as soon as the shock absorber compresses under the effect of a force greater than the predetermined force.

[0068] When the shock absorber compresses under the effect of a force greater than the predetermined effort, the lever thus causes a displacement of the first link relative to the shock absorber, which causes a displacement of the second link around the axis of rotation of the first mechanical connection. The strut is then unlocked. The wheel can then move away.

[0069] The predetermined force and the shock absorber are for example defined so that the landing gear is unlocked and the wheel is no longer in the deployed position before the maximum energy absorption capabilities of the shock absorber are reached. The predetermined force is therefore less than or equal to a maximum force that the shock absorber is capable of absorbing.

[0070] This unlocking of the strut, which can be referred to as "erasure", makes it possible to limit the forces that the shock absorber must absorb. This erasure of the strut, and the subsequent unlocking of the deployed position of the wheel, advantageously prevents too large a portion of the force applied to the wheel from being transmitted to the structure of the aircraft, limiting, or even avoiding, the occurrence of damage to this structure or to the landing gear itself.

[0071] Furthermore, the lever can be arranged on the connecting rod or on the rod when the connecting rod is articulated to the rod or on the body when the connecting rod is articulated to the body.

[0072] In addition, when the shock absorber comprises a deformable end-of-travel stop arranged in the body, as previously described, the lever can be configured to be very close to, or even in contact with, the first link when the rod is pressing against the end-of-travel stop.

[0073] In addition, the shock absorber may comprise a valve configured to connect an interior space located in the body and an external environment located outside the body, the valve opening when a pressure prevailing in the body is greater than a predetermined pressure. The valve thus prevents an excessive increase in the pressure in the body of the shock absorber, when a force greater than or equal to the predetermined force is exerted on the shock absorber. An excessive increase in the pressure in the body may, for example, prevent the rod from bearing against a deformable end-of-travel stop. According to another example, the shock absorber may comprise a valve configured to connect the chambers on either side of a throttling diaphragm of the shock absorber, making it possible to limit the throttling forces beyond a predefined value.

[0074] The present invention also relates to an aircraft comprising one or more landing gears as described previously.

[0075] This aircraft may comprise, for example, three landing gears as well as three housings in which these landing gears are respectively retracted and stored at least partially.

[0076] The invention and its advantages will appear in more detail in the context of the description which follows with examples given for illustrative purposes with reference to the appended figures which represent: there Figure 1 , a landing gear according to the invention in the deployed position of the wheel, the Figure 2 , the lander of the Figure 1 in the retracted position of the wheel, the Figure 3 , the lander of the Figure 1 in the deployed position of the wheel with the shock absorber compressed, the Figure 4 , an end stop for the shock absorber of the landing gear of the Figure 1in the retracted position, and the figures 5 to 8 , the lander of the Figure 1 in the deployed position.

[0077] Elements present in several distinct figures are assigned a single reference.

[0078] A retractable landing gear 10 according to the invention is shown in the figures 1 to 8 , the landing gear 10 being connected to a structure 41 of an aircraft 40.

[0079] An orthogonal coordinate system (X,Y,Z) is shown in the figures. An elevation direction Z extends from bottom to top, parallel to the direction of Earth's gravity. An X direction and a Y direction extend perpendicular to the elevation direction Z and perpendicular to each other. The (X,Y) plane thus forms a horizontal plane, namely perpendicular to the direction of Earth's gravity, and the X and Y directions form horizontal directions.

[0080] An aircraft 40 may comprise landing gear comprising one or more landing gears 10. A landing gear of an aircraft 40 may for example comprise three landing gears 10.

[0081] A retractable landing gear 10 according to the invention comprises at least one wheel 4, and a balance 1 extending from a first end zone 11 articulated to the structure 41 by a connection called the “fourth mechanical connection 54”, towards a second end zone 12 carrying the wheel(s) 4. To move the balance 1, the retractable landing gear 10 further comprises an actuator 5 connected to the structure 41.

[0082] The retractable landing gear 10 comprises a shock absorber 2 provided with a rod 21 sliding in a body 22. The shock absorber 2 is connected to the rocker arm 1 by a connecting rod 6. One end of the rod 21 can be articulated to the connecting rod 6 by a connection called the “second mechanical connection 52”, one end of the body 22 being articulated to the structure 41 by a connection called the “fifth mechanical connection 55” as shown in the figures. Alternatively, the rod 21 can be articulated to the structure 41, the body 22 being articulated to the connecting rod 6.

[0083] The connecting rod 6 is also articulated to the balance 1 by a connection called the “third mechanical connection 53”.

[0084] The connecting rod 6 is arranged so as to be misaligned from the shock absorber 2 when a force less than a predetermined force is exerted on the shock absorber 2, the wheel 4 being in the deployed position POSD.

[0085] The connecting rod 6 and the shock absorber 2 then form an angle strictly greater than 0° and strictly less than 180°. The wheel 4 of the landing gear 10 is in this case not subjected to any other force other than those due to the acceleration of Earth's gravity, the aircraft 40 being in flight or on the ground.

[0086] The retractable landing gear 10 comprises a strut 3 provided with a first mechanical connection 51 having at least one degree of freedom in rotation, a first connecting rod 31 and a second connecting rod 32 articulated together by the first mechanical connection 51. For example, the first mechanical connection 51 may be a ball joint type connection having three degrees of freedom in rotation. Alternatively, the first mechanical connection 51 may be a pivot type connection and comprise a rod passing through orifices arranged in the first connecting rod 31 and in the second connecting rod 32. Alternatively, the first mechanical connection 51 may be a cardan type connection.

[0087] The first connecting rod 31 is also articulated to the shock absorber 2 by a connection called the “sixth mechanical connection 56” while the second connecting rod 32 is connected to the actuator 5. According to the example shown in the figures, the first connecting rod 31 is articulated to the body 22 of the shock absorber 2.

[0088] The third, fourth, fifth and sixth mechanical connections 53-56 comprise at least one degree of freedom in rotation, or even three degrees of freedom in rotation. For example, the third, fourth, fifth and sixth mechanical connections may each comprise a single pivot-type connection. In this case, the first, second, third, fourth, fifth and sixth mechanical connections each allow rotation around axes of rotation parallel to each other, and parallel to the X direction according to the example shown in the figures.

[0089] Alternatively, the first, third, fourth, fifth and sixth mechanical links may each comprise a ball joint or cardan joint type link.

[0090] The second mechanical connection 52 has a single degree of freedom in rotation and is for example of the pivot type. This single degree of freedom allows rotation around a single axis parallel to the X direction according to the example shown in the figures.

[0091] Furthermore, the retractable landing gear 10 comprises a locking device 7 comprising an elastic return member 71 and a stop device 72. The elastic return member 71 comprises two ends fixed respectively to the strut 3 and to an articulated assembly comprising the rocker 1, the connecting rod 6, and the third mechanical connection 53. The elastic return member 71 can thus generate a tensile force between the strut 3 and the articulated assembly. The elastic return member 71 can be, for example, a helical spring subjected to traction.

[0092] The elastic return member 71 can for example be fixed by one of its ends to the first connecting rod 31, to the second connecting rod 32 or to the first mechanical connection 51. The elastic return member 71 is preferably fixed directly to the first mechanical connection 51 or to the first connecting rod 31 near the first mechanical connection 51 or to the second connecting rod 32 near the first mechanical connection 51.

[0093] The other end of the elastic return member 71 can be fixed to the articulated assembly, and more precisely to the third mechanical connection 53, to the balance 1 or to the connecting rod 6. When the elastic return member 71 is fixed to the balance 1 or to the connecting rod 6, the fixing point of the elastic return member 7 can be located close to the third mechanical connection 53.

[0094] The stop device 72 may comprise one or more stops 35, 36 in order to stop a relative rotational movement between the first and second connecting rods 31, 32 around an axis of rotation AX51 of the first mechanical connection 51 caused by the tensile force generated by the elastic return member 71.

[0095] The stop device 72 may, according to the example shown, comprise a first stop 35 on the first connecting rod 31 and a second stop 36 on the second connecting rod 32. The first stop 35 and the second stop 36 may thus be in contact with each other by the application of this tensile force generated by the elastic return member 71 in the deployed position POSD and thus limit the amplitude of the relative rotational movement of the first connecting rod 31 and the second connecting rod 32 around the axis AX51 of rotation of the first mechanical connection 51.

[0096] Alternatively, the stop device 72 may comprise, for example, a stop which may be arranged on the first connecting rod 31 and come into contact with the second connecting rod 32 under the action of the elastic return member 71 or conversely which may be arranged on the second connecting rod 32 and come into contact with the first connecting rod 31 under the action of the elastic return member 71.

[0097] Alternatively, the stop device 72 may also comprise a first stop limiting the movement of the first connecting rod 31 relative to the shock absorber 2 and a second stop limiting the movement of the second connecting rod 32 relative to the structure 41 or to the actuator 5 under the action of the elastic return member 71.

[0098] Furthermore, the actuator 5 is thus connected on the one hand to the structure 41 and on the other hand to the second connecting rod 32 in order to drive the second connecting rod 32 in rotation relative to the structure 41. The actuator 5 then makes it possible to move the wheel 4 between a deployed position POSD and a retracted position POSR.

[0099] According to the example shown in the figures, the actuator 5 is an electric motor. Alternatively, the actuator 5 may be a cylinder.

[0100] In the retracted position POSR of the wheel 4, the landing gear 10 is positioned partially or totally in a housing 42 of the aircraft 40. On the Figure 2 , the landing gear 10 is shown in an embodiment where it is partially retracted into the housing 42. The wheel 4 is in the retracted position POSR during a flight of the aircraft 40 in order in particular to reduce the aerodynamic drag generated by the landing gear 10 during the advancement of the aircraft 40 in flight.

[0101] In the deployed POSD position, the wheel 4 of the landing gear 10 can be positioned completely outside the housing 42 as shown in the Figure 1 , the wheel 4 being in contact with the ground 100. The wheel 4 is in the deployed position POSD, when the aircraft 40 is on the ground as well as before a landing phase and after a takeoff. On the Figure 1 as well as on the figures 3 And 5 à 8 , the lander 10 rests on a horizontal ground 100.

[0102] The landing gear 10 thus allows on the one hand the rolling of the aircraft 40 on the ground 100 and on the other hand the cushioning of a landing of the aircraft 40 on the ground 100, in particular thanks to the shock absorber 2 and the particular kinematics of the landing gear 10 according to the invention.

[0103] The landing gear 10 thus comprises a particular architecture comprising two complementary bracings which together contribute to effectively maintaining the wheel 4 in the deployed position POSD when the landing gear 10 is subjected to various stresses such as vibrations, shocks, accelerations and ground forces, while remaining within predefined limits. The landing gear 10 in fact comprises, in the deployed position POSD, a main bracing of the balance 1 formed by the shock absorber 2, the connecting rod 6 and the third mechanical connection 53 and a secondary bracing of the shock absorber 2 formed by the brace 3, and therefore the first connecting rod 31, the second connecting rod 32 and the first mechanical connection 51.

[0104] The installation of the elastic return member 71 associated with the architecture of the landing gear 10 also makes it possible to ensure locking of the strut 3, and therefore of the secondary bracing to resist these different stresses. In addition, the misalignment of the connecting rod 6 relative to the shock absorber 2 ensures traction of the strut 3, thus guaranteeing effective locking of the deployed position POSD of the wheel 4.

[0105] This implementation of the elastic return member 71 associated with the architecture of the landing gear 10 also makes it possible to minimize the maneuvering forces that the actuator 5 must apply to move the wheel 4 between the deployed POSD and retracted POSR positions. This thus allows the use of an electric motor as actuator 5, or even a small cylinder, for example electric or pneumatic.

[0106] Furthermore, once the wheel 4 is in the deployed position POSD and the strut 3 is locked, the actuator 5 can be deactivated, i.e. can be controlled so as not to provide any force or torque on the second link 32. Indeed, the locking of the strut 3 advantageously makes it possible, thanks to the use of the main and secondary bracing, to effectively maintain the wheel 4 in the deployed position, without the actuator 5 providing any force or torque.

[0107] In addition, the first link 31 and the second link 32 may have different lengths. In particular, a first length of the first link 31 may be greater than a second length of the second link 32 in accordance with the example shown in the figures. These differences in length of the first and second links 31, 32 contribute to minimizing the maneuvering forces of the actuator 5 to move the wheel 4 between the deployed position POSD and the retracted position POSR.

[0108] Furthermore, for the example shown, the axis of rotation AX32 of the second connecting rod 32 relative to the structure 41 is coincident with the axis of rotation AX5 of the electric motor constituting the actuator 5 and these axes of rotation AX31, AX56 form a plane perpendicular to the direction Z.

[0109] Alternatively, the rotation axis AX56 of the sixth mechanical connection 56 and the rotation axis AX32 of the second connecting rod 32 relative to the structure 41 can form a plane perpendicular to a movement axis AX2 of the shock absorber 2 in the deployed position POSD.

[0110] In addition, these axes of rotation AX56, AX32 of the first connecting rod 31 relative to the shock absorber 2 and of the second connecting rod 32 relative to the structure 41 may also be substantially coplanar with the axis of rotation AX51 of the first mechanical connection 51 in the deployed position POSD. In this way, when the first connecting rod 31 and the second connecting rod 32 are straight, they are aligned.

[0111] The architecture of the landing gear 10 can be defined so that the axis of rotation of the connecting rod 6 relative to the balance 1, namely the axis of rotation AX53 of the third mechanical connection 53, is aligned with the axis of travel AX2 of the shock absorber 2 when the shock absorber 2 is compressed under the effect of a force substantially equal to a predetermined effort and the wheel 4 is in the deployed position POSD. The axis of movement AX2 of the shock absorber 2 may be a translation axis of the rod 21 relative to the body 22. In this configuration, when the connecting rod 6 is straight, the connecting rod 6 is aligned with this axis of movement of the shock absorber 2. The shock absorber 2 is thus compressed when a significant force, directed partly vertically and upwards, is applied to the wheel 4. Such a significant force may be applied to the wheel 4 during a hard landing of the aircraft 40 in particular.

[0112] The shock absorber 2 may also comprise a deformable end-of-travel stop 23 arranged in the body 22. This end-of-travel stop 23 is positioned in the body 22 and configured to deform when the shock absorber 2 compresses under the effect of a force greater than the predetermined force. The end-of-travel stop 23 may for example comprise a tube 25 as shown in the Figure 4 , the tube 25 being defined and dimensioned to deform, for example by buckling, from a force greater than the predetermined force exerted on the shock absorber 2.

[0113] The end-of-travel stop 23 can deform directly under a force applied by the rod 21 to the end-of-travel stop 23, the rod 21 then bearing against the end-of-travel stop 23 as shown in the Figure 7 .

[0114] The end-of-travel stop 23 can alternatively deform under a force applied by a fluid present in the body 22 and compressed by the rod 21, the rod 21 then not being in contact with the end-of-travel stop 23.

[0115] The lander 10 may also include a lever 61, as shown in the figures 5 to 8 . The lever 61 is for example integral with the connecting rod 6 and configured to be very close, or even in contact with the first connecting rod 31 when the shock absorber 2 is compressed under the effect of a force substantially equal to the predetermined force. Other layouts of the lever 61 are possible depending on the kinematics of the landing gear 10. The lever 61 can for example be integral with the rod 21, the rod 21 protruding sufficiently from the body 22 when the shock absorber 2 is completely compressed.

[0116] THE figures 5 to 8represent the different positions of the landing gear 10 when the wheel 4 undergoes a force which gradually increases up to a significant force.

[0117] On the Figure 5 , the wheel 4 is in contact with the ground 100. A reaction of the ground is applied to the wheel 4 so that a force less than the predetermined force is exerted on the shock absorber 2. The shock absorber 2 is in an intermediate position in which the rod 21 is not bearing against the end-of-travel stop 23. The strut 3 is locked thanks to the tensile force of the elastic return member 71 and the stop device 72. The wheel 4 is held in the deployed position POSD.

[0118] On the Figure 6, the shock absorber 2 is compressed under the effect of the movement of the structure 41 of the aircraft 40 towards the ground 100. The rod 21 is in abutment against the end-of-travel stop 23 when the force exerted on the shock absorber 2 becomes substantially equal to the predetermined force. The connecting rod 6 is then aligned with the shock absorber 2 and in particular with the rod 21. In this way, the risk of deformation of the connecting rod 6, in particular by buckling, is limited. In addition, the lever 61 is very close to the first connecting rod 31, or even in contact against this first connecting rod 31. The strut 3 is always locked thanks to the tensile force of the elastic return member 71 and the stop device 72. The wheel 4 is maintained in the deployed position POSD.

[0119] According to the Figure 7, the force exerted on the shock absorber 2 may become greater than the predetermined force. The end-of-travel stop 23 deforms, for example by buckling of the tube 25. The rod 21 can then move in the body 22 of the shock absorber 2. The lever 61 moves with the rod 21, causing the first connecting rod 31 to move around the axis of rotation AX56 of the sixth mechanical connection 56, and consequently the second connecting rod 32 to move around the axis of rotation AX51 of the first mechanical connection 51. The connecting rod 6 is no longer aligned with the rod 21 of the shock absorber 2. Following the movements of the first and second connecting rods 31, 32, the strut 3 is no longer locked despite the tensile force of the elastic return member 71 and the stop device 72. The wheel 4 is then no longer held in the deployed position POSD.

[0120] In reference to the figure 8, following the unlocking of the strut 3, the first connecting rod 31 and the second connecting rod 32 continue to move relative to each other, causing the landing gear 10 to move out of position. In this way, the significant force experienced by the wheel 4 is not completely transmitted to the shock absorber 2 and to the structure 41 of the aircraft 40, thus avoiding damage to the shock absorber 2 and the structure 41.

[0121] Finally, the shock absorber 2 may include a valve 24 shown in the Figure 4. The valve 24 is configured to connect an interior space INT located inside the body 22 and an external environment EXT located outside the body 22 when the valve 24 opens. The valve 24 is defined and dimensioned to open when a pressure of a fluid prevailing in the body 22 is greater than a predetermined pressure, for example to prevent the fluid from preventing a movement of the rod 21 in the body 22. Alternatively, this valve 24 can also be configured to connect two chambers on either side of a throttling diaphragm of the shock absorber 2 beyond a predetermined pressure in order to reduce the throttling forces and therefore the internal pressure in the shock absorber 2.

[0122] Naturally, the present invention is subject to numerous variations in its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible embodiments.

Claims

1. Retractable landing gear (10) for an aircraft (40), said landing gear (10) comprising: - a trailing arm (1) intended to be articulated to a structure (41) of said aircraft (40) and having at least one wheel (4), said at least one wheel (4) being movable between a deployed position (POSD) and a retracted position (POSR), - a damper (2) provided with a rod (21) sliding in a body (22), said damper (2) being intended to be articulated to said structure (41), - an actuator (5), and - a connecting rod (6) articulated on the one hand to said damper (2) by a second mechanical link (52) with a single degree of freedom in rotation and on the other hand to the trailing arm (1), said connecting rod (6) being out of alignment with said damper (2) when a force less than a predetermined effort is applied to said damper (2), characterised in that said landing gear (10) comprises: - a strut (3) provided with a first tie-rod (31) and a second tie-rod (32) articulated between one another by a first mechanical link (51), said first tie-rod (31) being articulated to said damper (2), said actuator (5) being on the one hand intended to be connected to said structure (41) and on the other hand connected to said second tie-rod (32) in order to cause said second tie-rod (32) to rotate relative to said structure (41), and - a locking device (7) comprising an elastic return member (71) and a stop device (72), said elastic return member (71) being fixed by two extremities respectively to said strut (3) and to an articulated assembly comprising said trailing arm (1), said connecting rod (6) and a third mechanical link (53) between said trailing arm (1) and said connecting rod (6), said elastic return member (71) exerting a traction force between said strut (3) and said articulated assembly, said stop device (72) being configured to stop any relative displacement between said first and second tie-rods (31, 32) about an axis of rotation (AX51) of said first mechanical link (51) caused by said traction force when said wheel (4) is in said deployed position (POSD).

2. Landing gear (10) according to claim 1, wherein said actuator (5) is a rotational electric motor.

3. Landing gear (10) according to any one of claims 1 to 2, wherein said connecting rod (6) is articulated to said rod (21) and said first tie-rod (31) is articulated to said body (22), said body (22) being articulated to said structure (41).

4. Landing gear (10) according to any one of claims 1 to 2, wherein said first connecting rod (6) is articulated to said body (22) and said first tie-rod (31) is articulated to said rod (21), said rod (21) being articulated to said structure (41).

5. Landing gear (10) according to any one of claims 1 to 4, wherein an axis of rotation of said first tie-rod (31) relative to said damper (2) and an axis of rotation of said second tie-rod (32) relative to said structure (41) form a plane perpendicular to an axis of stroke (AX2) of said damper (2), said wheel (4) being in said deployed position (POSD).

6. Landing gear (10) according to any one of claims 1 to 5, wherein an axis of rotation of said first tie-rod (31) relative to said damper (2) and an axis of rotation of said second tie-rod (32) relative to said structure (41) and an axis of rotation of said first tie-rod (31) relative to said second tie-rod (32) can be parallel to one another and coplanar when said wheel (4) is in said deployed position (POSD).

7. Landing gear (10) according to any one of claims 1 to 6, wherein said elastic return member (71) is fixed by one of its two extremities to said first tie-rod (31), to said second tie-rod (32) or to said first mechanical link (51), and by its other extremity to said trailing arm (1), to said connecting rod (6) or to said articulation between said trailing arm (1) and said connecting rod (6).

8. Landing gear (10) according to any one of claims 1 to 7, wherein said connecting rod (6) is straight and aligned with said damper (2) when said damper (2) is compressed under a force equal to said predetermined effort, said wheel (4) being in said deployed position (POSD).

9. Landing gear (10) according to any one of claims 1 to 8, wherein said damper (2) comprises a deformable end-of-travel stop (23) arranged in said body (22), said end-of-travel stop (23) being configured to deform when said landing gear (10) is compressed under a force greater than said predetermined effort, said wheel (4) being in said deployed position (POSD).

10. Landing gear (10) according to any one of claims 1 to 9, wherein said landing gear (10) comprises a lever (61), said lever (61) being configured to be in contact with said first tie-rod (31) when said damper (2) is compressed under a force equal to said predetermined effort, said wheel (4) being in said deployed position (POSD), said lever (61) being arranged so as to cause a displacement of said first tie-rod (31) when said damper (2) is compressed under a force greater than said predetermined effort.

11. Landing gear (10) according to claims 9 and 10, wherein said lever (61) is configured to be in contact with said first tie-rod (31) when said rod (22) is resting against said end-of-travel stop (23).

12. Landing gear (10) according to any one of claims 10 to 11, wherein said lever (61) is arranged on said connecting rod (6), or on said rod (21) when said connecting rod (6) is articulated to said rod (21), or on said body (22) when said connecting rod (6) is articulated to said body (22).

13. Landing gear (10) according to any one of claims 9 to 12, wherein said damper (2) comprises a valve (24) configured to create communication between an internal space (INT) located inside said body (22) and an external environment (EXT) located outside said body (22), said valve (24) opening when the pressure prevailing inside said body (22) exceeds a predetermined pressure.

14. Landing gear (10) according to any one of claims 1 to 13, wherein a first length of said first tie-rod (31) is greater than a second length of said second tie-rod (32).

15. Landing gear (10) according to claim 14, wherein said second length is between one quarter and one fifth of said first length.

16. Aircraft (40) comprising at least one landing gear (10) according to any one of claims 1 to 15.