Patent ID: 12227287

DETAILED DESCRIPTION

Elements that are present in more than one of the figures are given the same references in each of them.

A retractable landing gear10according to the disclosure is shown inFIGS.1to8, the landing gear10being connected to a structure41of an aircraft40.

An orthogonal reference frame (X,Y,Z) is shown in the figures. An elevation direction Z extends upwards, parallel to the direction of Earth's gravity. A direction X and a direction Y extend perpendicular to the elevation direction Z and perpendicular to each other. The plane (X,Y) thus forms a horizontal plane, i.e., a plane perpendicular to the direction of Earth's gravity, and the directions X and Y form horizontal directions.

An aircraft40may comprise an undercarriage comprising one or more landing gears10. An undercarriage of an aircraft40may, for example, comprise three landing gears10.

A retractable landing gear10according to the disclosure comprises at least one wheel4and a rocker arm1extending from a first end region11hinged to the structure41by a link referred to as the “fourth mechanical link54” to a second end region12carrying the wheel or wheels4. In order to move the rocker arm1, the retractable landing gear10also comprises an actuator5connected to the structure41.

The retractable landing gear10comprises a shock-absorber2provided with a stem21that slides in a body22. The shock-absorber2is connected to the rocker arm1by a connecting rod6. One end of the stem21may be hinged to the connecting rod6by a connection referred to as the “second mechanical link52”, one end of the body22being hinged to the structure41by a connection referred to as the “fifth mechanical link55” as shown in the figures. Alternatively, the stem21may be hinged to the structure41, the body22being hinged to the connecting rod6.

The connecting rod6is also hinged to the rocker arm1by a connection referred to as the “third mechanical link53”.

The connecting rod6is arranged in such a way as to be out of alignment with the shock-absorber2when a force less than a predetermined force is applied to the shock-absorber2, the wheel4being in the deployed position POSD. The connecting rod6and the shock-absorber2then form an angle strictly greater than 0° and strictly less than 180°. The wheel4of the landing gear10is in this case not subjected to any force apart from that resulting from the acceleration of the Earth's gravity, the aircraft40being in flight or on the ground.

The retractable landing gear10comprises a strut3provided with a first mechanical link51having at least one degree of rotational freedom, a first connecting link31and a second connecting link32that are hinged to each other by the first mechanical link51. For example, the first mechanical link51may be a ball-joint link having three degrees of rotational freedom. Alternatively, the first mechanical link51may be a pivot link and comprise a pin passing through holes arranged in the first connecting link31and the second connecting link32. Alternatively, the first mechanical link51may be a universal joint link.

The first connecting link31is also hinged to the shock-absorber2by a connection referred to as the “sixth mechanical link56” while the second connecting link32is connected to the actuator5. According to the example shown in the figures, the first connecting link31is hinged to the body22of the shock-absorber2.

The third, fourth, fifth and sixth mechanical links53-56comprise at least one degree of rotational freedom, and possibly three degrees of rotational freedom. For example, the third, fourth, fifth and sixth mechanical links may each comprise a single pivot link. In this case, the first, second, third, fourth, fifth and sixth mechanical links each allow rotation about axes of rotation that are parallel with each other and parallel to the direction X, according to the example shown in the figures.

Alternatively, the first, third, fourth, fifth and sixth mechanical links may each comprise a ball-joint link or a universal joint link.

The second mechanical link52comprises a single degree of rotational freedom and is, for example, a pivot link. This single degree of freedom permits rotation about a single axis parallel to the direction X according to the example shown in the figures.

Moreover, the retractable landing gear10comprises a locking device7comprising an elastic return member71and a stop device72. The elastic return member71comprises two ends fastened respectively to the strut3and to a hinged assembly comprising the rocker arm1, the connecting rod6, and the third mechanical link53. The elastic return member71can thus generate a pulling force between the strut3and the hinged assembly. The elastic return member71may for example be a coil spring loaded in tension.

The elastic return member71may for example be fastened by one of its ends to the first connecting link31, the second connecting link32or the first mechanical link51. The elastic return member71is preferably fastened directly to the first mechanical link51or to the first connecting link31close to the first mechanical link51or to the second connecting link32close to the first mechanical link51.

The other end of the elastic return member71may be fastened to the hinged assembly, and more specifically to the third mechanical link53, the rocker arm1or the connecting rod6. When the elastic return member71is fastened to the rocker arm1or the connecting rod6, the fastening point of the elastic return member7may be situated close to the third mechanical link53.

The stop device72may comprise one or more stops35,36in order to prevent the first and second connecting links31,32from rotating in relation to each other about an axis of rotation AX51of the first mechanical link51as a result of the pulling force generated by the elastic return member71.

The stop device72may, according to the example shown, comprise a first stop35on the first connecting link31and a second stop36on the second connecting link32. The first stop35and the second stop36may thus be in contact with each other as a result of the application of this pulling force generated by the elastic return member71in the deployed position POSD and thus limit the amplitude of the relative rotational movement of the first connecting link31and the second connecting link32about the axis AX51of rotation of the first mechanical link51.

Alternatively, the stop device72may for example comprise a stop that may be arranged on the first connecting link31and come into contact with the second connecting link32under the action of the elastic return member71or conversely may be arranged on the second connecting link32and come into contact with the first connecting link31under the action of the elastic return member71.

Alternatively, the stop device72may also comprise a first stop limiting the movement of the first connecting link31in relation to the shock-absorber2and a second stop limiting the movement of the second connecting link32in relation to the structure41or the actuator5under the action of the elastic return member71.

Moreover, the actuator5is thus connected to the structure41and to the second connecting link32in order to rotate the second connecting link32in relation to the structure41. The actuator5therefore allows the wheel4to be moved between a deployed position POSD and a retracted position POSR.

According to the example shown in the figures, the actuator5is an electric motor. Alternatively, the actuator5may be a jack.

When the wheel4is in the retracted position POSR, the landing gear10is positioned partially or totally inside a housing42of the aircraft40. InFIG.2, the landing gear10is shown in an embodiment wherein it is partially stowed in the housing42. The wheel4is in the retracted position POSR when the aircraft40is in flight, in particular in order to reduce the aerodynamic drag generated by the landing gear10as the aircraft40moves forward during flight.

In the deployed position POSD, the wheel4of the landing gear10may be positioned totally outside the housing42, as shown inFIG.1, the wheel4being in contact with the ground100. The wheel4is in the deployed position POSD when the aircraft40is on the ground, before a landing phase and after take-off. InFIGS.1,3and5to8, the landing gear10is resting on horizontal ground100.

The landing gear10therefore allows the aircraft40to taxi on the ground100and absorbs the impact of the aircraft40landing on the ground100, in particular as a result of the shock-absorber2and the particular kinematics of the landing gear10according to the disclosure.

The landing gear10thus comprises a particular architecture comprising two complementary braces that together help effectively keep the wheel4in the deployed position POSD when the landing gear10is subjected to various stresses such as vibrations, impacts, accelerations and forces on the ground, while remaining within predefined limits. The landing gear10comprises, in the deployed position POSD, a main brace of the rocker arm1formed by the shock-absorber2, the connecting rod6and the third mechanical link53, and a secondary brace of the shock-absorber2formed by the strut3, and therefore the first connecting link31, the second connecting link32and the first mechanical link51.

The arrangement of the elastic return member71combined with the architecture of the landing gear10also makes it possible to ensure the locking of the strut3, and therefore the secondary brace, in order to withstand these different stresses. Furthermore, the disalignment of the connecting rod6in relation to the shock-absorber2ensures that the strut3is tensioned, thus guaranteeing effective locking of the wheel4in the deployed position POSD.

This arrangement of the elastic return member71combined with the architecture of the landing gear10also helps minimize the maneuvering forces that the actuator5needs to apply in order to move the wheel4between the deployed POSD and retracted POSR positions. This means that an electric motor, or indeed a small jack, for example an electric or pneumatic jack, can be used as an actuator5.

In addition, once the wheel4is in the deployed position POSD and the strut3has been locked, the actuator5may be deactivated, i.e., it may be controlled in order not to provide any force or torque on the second connecting link32. Indeed, locking the strut3advantageously makes it possible, owing to the use of the main and secondary braces, to effectively keep the wheel4in the deployed position without the actuator5providing force or torque.

Moreover, the first connecting link31and the second connecting link32may be of different lengths. In particular, a first length of the first connecting link31may be greater than a second length of the second connecting link32, in accordance with the example shown in the figures. These differences in length of the first and second connecting links31,32help minimize the forces required for the actuator5to maneuver in order to move the wheel4between the deployed position POSD and the retracted position POSR.

Furthermore, for the example shown, the axis of rotation AX32of the second connecting link32in relation to the structure41coincides with the axis of rotation AX5of the electric motor constituting the actuator5, and these axes of rotation AX31,AX56form a plane perpendicular to the direction Z.

Alternatively, the axis of rotation AX56of the sixth mechanical link56and the axis of rotation AX32of the second connecting link32in relation to the structure41may form a plane perpendicular to an axis of displacement AX2of the shock-absorber2in the deployed position POSD.

Moreover, these axes of rotation AX56,AX32of the first connecting link31in relation to the shock-absorber2and of the second connecting link32in relation to the structure41may also be substantially coplanar with the axis of rotation AX51of the first mechanical link51in the deployed position POSD. As a result, when the first connecting link31and the second connecting link32are straight, they are aligned.

The architecture of the landing gear10may be defined such that the axis of rotation of the connecting rod6in relation to the rocker arm1, i.e., the axis of rotation AX53of the third mechanical link53, is aligned with the axis of displacement AX2of the shock-absorber2when the shock-absorber2is compressed under the effect of a force substantially equal to a predetermined force and the wheel4is in the deployed position POSD. The axis of displacement AX2of the shock-absorber2may be an axis of translation of the stem21in relation to the body22. In this configuration, when the connecting rod6is straight, the connecting rod6is aligned with this axis of displacement AX2of the shock-absorber2. The shock-absorber2is thus compressed when a considerable force, part of which is directed vertically upwards, is applied to the wheel4. Such a considerable force may be applied to the wheel4, in particular when the aircraft40makes a hard landing.

The shock-absorber2may also comprise a deformable end-of-travel stop23arranged in the body22. This end-of-travel stop23is positioned in the body22and configured to be deformed when the shock-absorber2is compressed under the effect of a force greater than the predetermined force. The end-of-travel stop23may for example comprise a tube25as shown inFIG.4, the tube25being defined and dimensioned to be deformed, for example by buckling, when a force greater than the predetermined force is applied to the shock-absorber2.

The end-of-travel stop23may be deformed directly under a force applied by the stem21to the end-of-travel stop23, the stem21then resting against the end-of-travel stop23, as shown inFIG.7.

The end-of-travel stop23may alternatively be deformed under a force applied by a fluid present in the body22and compressed by the stem21, the stem21not then being in contact with the end-of-travel stop23.

The landing gear10may also comprise a lever61, as shown inFIGS.5to8. The lever61is, for example, secured to the connecting rod6and configured to be very close to, or indeed in contact with, the first connecting link31when the shock-absorber2is compressed under the effect of a force substantially equal to the predetermined force. Other arrangements of the lever61are possible depending on the kinematics of the landing gear10. The lever61may for example be secured to the stem21, the stem21protruding sufficiently far out of body22when the shock-absorber2is completely compressed.

FIGS.5to8show the different positions of the landing gear10when the wheel4is subjected to a force that gradually increases to a considerable force.

InFIG.5, the wheel4is in contact with the ground100. A reaction of the ground is applied to the wheel4so that a force less than the predetermined force is applied to the shock-absorber2. The shock-absorber2is in an intermediate position wherein the stem21is not resting against the end-of-travel stop23. The strut3is locked as a result of the pulling force of the elastic return member71and the stop device72. The wheel4is kept in the deployed position POSD.

InFIG.6, the shock-absorber2is compressed under the effect of the movement of the structure41of the aircraft40towards the ground100. The stem21rests against the end-of-travel stop23when the force applied to the shock-absorber2becomes substantially equal to the predetermined force. The connecting rod6is then aligned with the shock-absorber2and in particular with the stem21. This limits the risk of deformation of the connecting rod6, in particular by buckling. Furthermore, the lever61is very close to the first connecting link31, or indeed in contact with this first connecting link31. The strut3is still locked as a result of the pulling force of the elastic return member71and the stop device72. The wheel4is kept in the deployed position POSD.

According toFIG.7, the force applied to the shock-absorber2may become greater than the predetermined force. The end-of-travel stop23is deformed, for example the tube25buckles. The stem21can then move into the body22of the shock-absorber2. The lever61moves with the stem21, causing the first connecting link31to move about the axis of rotation AX56of the sixth mechanical link56, and consequently causing the second connecting link32to move about the axis of rotation AX51of the first mechanical link51. The connecting rod6is no longer aligned with the stem21of the shock-absorber2. Following the movements of the first and second connecting links31,32, the strut3is no longer locked, despite the pulling force of the elastic return member71and the stop device72. The wheel4is then no longer kept in the deployed position POSD.

In reference toFIG.8, following the unlocking of the strut3, the first connecting link31and the second connecting link32continue to move in relation to each other, causing the landing gear10to retract. Therefore, the considerable force applied to the wheel4is not transmitted in its entirety to the shock-absorber2and the structure41of the aircraft40, thus preventing damage to the shock-absorber2and the structure41.

Finally, the shock-absorber2may comprise a valve24shown inFIG.4. The valve24is configured to connect an internal space INT situated inside the body22and an external environment EXT situated outside the body22when the valve24opens. The valve24is defined and dimensioned to open when a pressure of a fluid in the body22is greater than a predetermined pressure, for example so that the fluid does not prevent the stem21from moving in the body22. Alternatively, this valve24may also be configured to connect two chambers to either side of a throttling diaphragm of the shock-absorber2when a predetermined pressure is exceeded, in order to reduce the throttling forces and therefore the internal pressure inside the shock-absorber2.

Naturally, the present disclosure is subject to numerous variations as regards its implementation. Although several embodiments are described above, it should readily be understood that it is not conceivable to identify exhaustively all the possible embodiments. It is naturally possible to replace any of the means described with equivalent means without going beyond the ambit of the present disclosure and the claims.