SWIVELLING CHASSIS WITH A LOCKING SYSTEM

Description

[0001] The present invention relates to a pivotable landing gear provided with an immobilization system.

[0002] A landing gear of an aircraft, and for example of a rotorcraft or even a helicopter, may comprise at least one pivotable landing gear. Such a pivotable landing gear may comprise an assembly carrying at least one ground contact member, and capable of pivoting 360 degrees around a pivot axis in order to facilitate the movement of the aircraft on the ground. The term "ground" subsequently designates any surface on which an aircraft can land, such as a land surface, the roof of a building, the deck of a ship, etc.

[0003] For example, a tricycle rotorcraft may comprise two main landing gears and one auxiliary landing gear, each comprising at least one wheel. The two main landing gears are not pivotable. However, the auxiliary landing gear is pivotable to ensure the aircraft's maneuverability on the ground. The wheel(s) of the auxiliary landing gear are, on the ground, free to pivot about a pivot axis which is distinct from the rotation axis(es) of the wheels. On a helicopter equipped with a yaw angle control system, for example of the type comprising a tail rotor, a turn may be undertaken on the ground by controlling the thrust exerted by this yaw angle control system. The yaw angle control system generates a moment on an airframe of the aircraft carried by the landing gears, this moment automatically pivoting the auxiliary landing gear to steer the aircraft in the required direction.

[0004] Such a pivotable landing gear is nevertheless usually equipped with an immobilization system. The immobilization system locks, on command, the pivotable landing gear in a position generating a straight-line movement of the aircraft. Indeed, it is required to lock the pivoting of the auxiliary landing gear during a rolling landing with engine failure, or when landing the aircraft on a slope or on a ship deck or equivalent.

[0005] A known immobilization system comprises a pin capable of penetrating into a bore of a base secured to the pivoting assembly of a pivoting landing gear. In addition, the immobilization system comprises an elastic connecting rod connected to the pin and to a control. The control may comprise a handle connected by a non-elastic link to the elastic connecting rod.

[0006] To place the immobilizer system in an unlocked mode, the control is operated by an operator to position the elastic connecting rod in a first position. The locking pin is then outside the bore. The pivoting assembly is then free to pivot about a pivot axis.

[0007] To lock the pivoting landing gear, the control is operated by an operator to position the elastic connecting rod in a second position by bringing it closer to the bore.

[0008] If the pin is flush with the bore, the pin enters the bore. The immobilizer is then in a locked phase of a locked mode. The pivoting assembly is then no longer free to pivot 360 degrees around the pivot axis.

[0009] If the pin is not aligned with the bore, the pin comes into contact with the base. The elastic connecting rod compresses and tends to push the pin towards the base. The immobilization system is then in an armed phase of the locked mode. The pivoting assembly is temporarily free to pivot around the pivot axis. As soon as the pin reaches the bore, the elastic connecting rod relaxes and pushes the pin into this bore. The immobilization system thus automatically switches to the locked phase of the locked mode.

[0010] Another known immobilization system involves a pin, not mobile in translation, but in rotation.

[0011] Such locking systems are advantageous. However, when the pivoting assembly is in the locked phase and tends to pivot, the base exerts a shear force on the locking pin. Depending on the intensity of this force and the coefficient of friction between the pin and the base, unlocking may not be possible. In particular, in the presence of significant transverse thrust generated by the yaw angle control system, the shear force can be significant. If a pilot forces and nevertheless manages to move the control to place the immobilization system in the unlocked mode, the aircraft may be suddenly destabilized.

[0012] Document US3375999 A describes a releasable locking mechanism for a swivel wheel. This mechanism comprises a protrusion that can be received in a notch between two locking arms. The wheel is locked at rest, and unlocked when a force exceeds a threshold. This system is therefore not suitable for the present problem.

[0013] Document WO2010115893 A1 discloses a system comprising a friction member for exerting a friction force between two elements. The system comprises means for controlling the variation of the prestress exerted by the pressure member on the friction member.

[0014] Document EP 662906 B1 describes a means for rotationally locking a landing gear provided with a locking pin assembly.

[0015] Document CN104210654 A describes a wheel lock indicator comprising a pin which can move in translation relative to a housing and is automatically held in position by means of a return spring.

[0016] Document US2502522 A describes a landing gear provided with a base and a pivoting assembly carrying a contact member. The landing gear has an immobilization system which comprises a pin and a passage provided in the base. Furthermore, an elastic system comprises two springs. A first spring is disposed between an upper plate secured to the pivoting assembly and a collar secured to the pin, while a second spring is disposed between a lower plate secured to the pivoting assembly and the collar.

[0017] Document US 2384054 A describes a retractable landing gear equipped with a system comprising a cable passing around a pulley to reach a centering pin.

[0018] GB 970425 A describes a landing gear having a latch engageable in openings in a fork carrying a wheel.

[0019] The present invention therefore aims to propose a landing gear equipped with an innovative immobilization system to limit the risks of sudden destabilization occurring.

[0020] The invention thus relates to a landing gear provided with a base and a pivoting assembly carrying a contact member which is configured to be in contact with the ground, said pivoting assembly being rotatable about a pivot axis relative to the base, said landing gear having an immobilization system comprising a movable pin and a control configured to require application of a locked mode or an unlocked mode, the immobilization system comprising a passage provided in a base secured to the pivoting assembly, the pin being outside said passage in an unlocked phase of the unlocked mode, the pin being movable in said passage in azimuth relative to the pivot axis in a locked phase of the locked mode, the immobilization system having an elastic locking system tending to push / push the pin into the passage in the locked mode,the pawn being pushed into the locked mode by the elastic locking system, either against the base during an armed phase of the locked mode as long as the pawn does not enter the passage, or into the passage as soon as the pawn is in front of the passage in the locked phase.,

[0021] The immobilization system comprises an elastic unlocking system configured to cause said pin to exit the passage when the unlocked mode is commanded by the control, the elastic unlocking system being calibrated to allow extraction of the pin from the passage only in the presence of a shear force between the base and the pin lower than a threshold.

[0022] The immobilization system is thus configured to immobilize in a predetermined range of positions said pivoting assembly relative to the base during a locked phase of a locked mode and to allow without limitation a pivoting of the pivoting assembly relative to the base during an unlocked phase of an unlocked mode.

[0023] The expression "immobilization system configured to immobilize in a predetermined range of positions said pivoting assembly relative to the base during a locked phase of a locked mode" means that the pivoting assembly can pivot within the limit of the space present in azimuth, with respect to the pivot axis, between the base and the pin when the pin is in the passage. Indeed, the passage has, along an arc of a circle, with respect to the pivot axis, a dimension greater than a dimension of the pin. Therefore, the pin can easily enter the passage, but the base has a restricted freedom of movement in azimuth. Depending on the position of the pin in the passage, the base exerts or does not exert a shear force on the pin.

[0024] The expression "the pin being movable in said passage in azimuth relative to the pivot axis" means that a clearance always separates the pin from the base according to an arc of a circle centered on the pivot axis. This clearance gives freedom of movement to the base relative to the pin, when the pin is in the passage, restricted to the predetermined range of positions, for example of the order of 0.5 degrees. On an aircraft, this angle may depend on the longitudinal distance between fixed landing gears of the aircraft and the landing gear having the pivoting assembly of the invention.

[0025] In addition to the state-of-the-art armed, locked and unlocked phases, the elastic unlocking system allows for a disarmed phase to be created when switching from locked to unlocked mode.

[0026] If the base exerts a shear force below the threshold on the pin, the pin exits the passage directly, the immobilization system passing directly into the unlocked phase. The pivoting assembly is free to pivot around the pivot axis, at least 180 degrees for example, or even 360 degrees.

[0027] If the base exerts a shear force greater than or equal to the threshold on the pin, for example in the presence of a tail rotor generating a significant yaw moment on an aircraft cell, the transition from locked mode to unlocked mode induces compression of the elastic unlocking system. The immobilization system passes into a disarmed phase of the unlocked mode. This elastic unlocking system is calibrated so that it cannot relax under these conditions. In other words, the stiffness along the compression / relaxation axis of the elastic unlocking system is chosen to obtain the transition into the unlocked phase under the desired conditions. As soon as the shear force becomes lower than the threshold, following a slight pivoting of the pivoting assembly, the elastic unlocking system relaxes and automatically expels the pin from the passage to reach the unlocked phase.

[0028] Thus, the elastic unlocking system prevents unlocking in the presence of a significant shear force, synonymous on a helicopter with a significant moment exerted on the airframe. This elastic unlocking system makes it possible to avoid sudden movement when the unlocked mode is commanded by a pilot. Unlocking of the landing gear can thus only occur in specific operational cases. In the event of a high shear force, unlocking is prohibited, even if it is commanded by the pilot. Thus, the pilot can command unlocking regardless of the shear stress of the pin. Unlocking will be effective only when the force applied to this pin is less than a predetermined force threshold. The pivoting landing gear according to the invention thus makes it possible to optimize safety.

[0029] The landing gear according to the invention may have one or more of the following characteristics, taken alone or in combination.

[0030] According to a first alternative, the pawn can be movable in translation relative to the base along a translation axis, for example parallel to the pivot axis.

[0031] The first alternative is thus applicable to a system comprising a moving pawn in translation.

[0032] For example, the immobilization system may comprise a hollow support which extends towards the base along the translation axis of a bottom up to an open end, the open end being arranged between the bottom and the base, the pin comprising a head secured to a locking rod, the head being present in the hollow support and the locking rod exiting the hollow support via the open end at least in the locked phase, the elastic locking system being arranged between the bottom and the head.

[0033] The support guides the translation of the head, and consequently of the pawn. The base can also guide the translation of the pawn.

[0034] The elastic locking system can thus be compressed when switching from unlocked mode to locked mode while the pin is not facing the passage. The immobilization system is then in an armed phase, the elastic locking system being ready to relax to push the pin into the passage.

[0035] Optionally, the elastic locking system may include a locking spring having a coil fixed to the bottom.

[0036] According to a first variant of the first alternative, the support can be movable in translation relative to the base, said control being connected to the support.

[0037] When switching from unlocked mode to locked mode, the support moves from a first position to a second position. If the pin is not facing the passage, the support compresses the elastic locking system during a possible armed phase. The pin is then pressed against the support. As soon as the pin is facing the passage, the elastic locking system relaxes to obtain an automatic transition to the locked phase as soon as possible.

[0038] When switching from locked mode to unlocked mode, the support moves from the second position to the first position. If the base exerts a shear force on the pin greater than or equal to the threshold, the pin remains in place and the support compresses the elastic unlocking system during a possible disarmed phase. As soon as the shear force on the pin falls below the threshold, the elastic unlocking system relaxes to obtain an automatic transition to the unlocked phase.

[0039] The first variant of the first alternative can thus be relatively simple and easy to implement.

[0040] Optionally, the elastic unlocking system may be arranged between the head and an internal shoulder of the support, the locking rod passing through the internal shoulder, the internal shoulder being located between the head and the base.

[0041] Optionally, the elastic unlocking system may include an unlocking spring having a coil attached to the internal shoulder.

[0042] According to a second variant of the first alternative, the support can be stationary relative to the base, the pin comprising an entry rod secured to the head and passing through the bottom of the support.

[0043] For example, the input rod extends from the head to a top secured to a hollow tube, said control comprising a cable which extends to a plate movable in translation in the hollow tube by crossing a wall of the tube, the elastic unlocking system being arranged between said wall and said plate.

[0044] In addition, the elastic unlocking system may have a stiffness along the translation axis greater than a stiffness along the translation axis of the elastic locking system. Thus the elastic unlocking system relaxes when the pin is released by the base.

[0045] The second variant of the first alternative can also be relatively simple and easy to implement.

[0046] Furthermore, the elastic unlocking system may have a stiffness along the translation axis greater than a stiffness along the translation axis of the elastic locking system, in particular but not only according to the second variant of the first alternative. Thus the elastic unlocking system relaxes when the pin is released by the base.

[0047] According to a second alternative, the pawn presents, relative to the base, not a degree of freedom in translation but a degree of freedom in rotation.

[0048] For example, the pawn may be carried by a lever pivotally connected to the base, the elastic locking system being arranged between the base and the lever, the control comprising a cable connected to a plate movable in translation in a guide, the guide being connected to the lever, the elastic unlocking system being arranged between the plate and a partition of the guide crossed by the cable.

[0049] Regardless of the alternative, the contact member may comprise a wheel that is movable in rotation about a wheel axis relative to the pivoting assembly, said wheel axis being distinct from the pivot axis. The wheel axis and the pivot axis are furthermore not parallel.

[0050] According to another object, a rotorcraft may comprise at least one pivotable landing gear according to the invention.

[0051] The invention also relates to the method implemented, namely a method for locking and unlocking a landing gear provided with a base and a pivoting assembly carrying a contact member which is configured to be in contact with the ground, said pivoting assembly being movable in rotation about a pivot axis relative to the base, said landing gear having an immobilization system configured to immobilize in a predetermined range of positions said pivoting assembly relative to the base during a locked phase of a locked mode and to authorize without limitation a pivoting of the pivoting assembly relative to the base during an unlocked phase of an unlocked mode, the immobilization system comprising a movable pin and a control configured to require an application of the locked mode or the unlocked mode, the immobilization system comprising a passage formed in a base secured to said pivoting assembly,the pin being outside said passage in the unlocked phase, the pin being movable in said passage in azimuth relative to the pivot axis in the locked phase.,

[0052] This process includes: when the immobilization system is in the unlocked mode, activation of said command to switch to the locked mode, then: i) if the pin is opposite the passage, movement of the pin in the passage, ii) if the pin is not opposite the passage, pressing the pin against the base with an elastic locking system and movement of the pin in the passage as soon as the pin comes opposite the passage, when the immobilization system is in the locked mode, activation of said command to switch to the unlocked mode, then if the pin is in the passage and in contact with the base then compression of an elastic unlocking system, and: i) holding the pin in the passage as long as the pin undergoes a shear force greater than or equal to a threshold, the immobilization system being in a disarmed phase, ii) as soon as the pin undergoes a shear force less than the threshold,relaxation of the elastic unlocking system and expulsion of the pin outside the passage under the effect of said relaxation to move into an unlocked phase.

[0053] 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 diagram illustrating a rotorcraft according to the invention, the figure 2 , a diagram illustrating the rotorcraft of the figure 1 in top view, the figure 3 , a diagram illustrating a pivoting landing gear according to the invention having an immobilization system in a locked phase of the locked mode, the figure 4 , a diagram illustrating the swivel landing gear immobilization system of the figure 3 in a disarmed phase of unlocked mode, the figure 5 , a diagram illustrating the swivel landing gear immobilization system of the figure 3 in an unlocked phase of unlocked mode, the figure 6 , a diagram illustrating the swivel landing gear immobilization system of the figure 3 in an armed phase of the locked mode, the figure 7 , a diagram illustrating an immobilizer system in a locked phase of the locked mode, the figure 8 , a diagram illustrating the immobilization system of the figure 7 in a disarmed phase of unlocked mode, the figure 9 , a diagram illustrating the immobilization system of the figure 7 in an unlocked phase of unlocked mode, the figure 10 , a diagram illustrating the immobilization system of the figure 7 in an armed phase of the locked mode, the figure 11 , a diagram illustrating an immobilizer system in a locked phase of the locked mode, the figure 12 , a diagram illustrating the base of the immobilization system of the figure 11 , there figure 13 , a diagram illustrating the immobilization system of the figure 11 in a disarmed phase of unlocked mode, the figure 14 , a diagram illustrating the immobilization system of the figure 11 in an unlocked phase of unlocked mode, and the figure 15 , a diagram illustrating the immobilization system of the figure 11 in an armed phase of locked mode.

[0054] Elements present in several distinct figures are assigned a single reference.

[0055] There figure 1 presents a rotorcraft 1 according to the invention. This rotorcraft 1 comprises an airframe 2 possibly carrying at least one rotor and a yaw control system. In this case, the rotorcraft 1 illustrated comprises a main rotor 4 and a tail rotor 5 acting as a yaw control system.

[0056] Furthermore, the cell 2 is based on a landing system 6 comprising for example at least one landing gear, namely two main landing gears 7 and one auxiliary landing gear 8 according to the example.

[0057] This rotorcraft 1 comprises in particular at least one pivoting landing gear 10, namely the auxiliary landing gear 8 according to the example.

[0058] In reference to the figure 2 , when the yaw control system exerts a lateral thrust F1, then the pivoting landing gear 10 performs a rotation on the ground around a pivot axis AXP to modify the orientation of the rotorcraft 1.

[0059] The landing gear 10 therefore comprises an immobilization system to keep, under certain conditions, the pivoting landing gear 10 substantially aligned along the forward movement axis of the rotorcraft 1.

[0060] There figure 3 illustrates an exemplary embodiment of a pivoting landing gear 10 according to the invention. Whatever the embodiment, the landing gear 10 is provided with a base 11, connected to the cell 2, and a pivoting assembly 12 capable of pivoting about a pivot axis AXP relative to the base 11. The pivoting assembly 12 carries at least one contact member 15 which is configured to be in contact with the ground 100. For example, a contact member 15 comprises a pad, and / or a wheel 150 movable in rotation relative to the pivoting assembly 12 about a wheel axis AXROT.

[0061] There figure 3 gives by way of illustration an example of base 11 and pivoting assembly 12, but other embodiments of the pivoting assembly 12 are conceivable. In particular, the base 11 can be fixed or retractable without departing from the scope of the invention. According to the example illustrated, the pivoting assembly 12 can comprise a cylinder 13 movable in rotation around the pivot axis relative to the base 11. In addition, the pivoting assembly 12 comprises a damper 14 carried by the cylinder 13 and housed at least partially in this cylinder 13, this damper 14 possibly being provided with a device called “anti-shimmy” in English. In addition, a compass 16 is articulated to the cylinder 13 and to the damper 14. At least one contact member 15 can be carried by the compass 16 or the damper 14 for example.

[0062] Regardless of the manner of producing the pivoting assembly 12 and the base 11, the landing gear 10 comprises an immobilization system 20 configured to: i) immobilize, in a predetermined range of restricted positions, the pivoting assembly 12 relative to the base 11 during a locked phase of a locked mode and to ii) allow without limitation a pivoting of the pivoting assembly 12 relative to the base 11 during an unlocked phase of an unlocked mode.

[0063] There figure 3 illustrates a first version of a first alternative explained in the figures 4 à 6 , but other achievements are visible on the figures 7 à 15 .

[0064] Whatever the embodiment, the immobilization system 20 comprises a pin 25 movable relative to the pivoting assembly 12 and a control 30 configured to require application of the locked mode or the unlocked mode. Each mode may comprise two phases explained below. For example, this control 30 may comprise at least one cable 33 movable in translation, at least one return... The term “cable” designates an elongated link, for example non-elastic and / or advantageously housed in a protective sheath.

[0065] The immobilization system 20 further comprises a passage 22 formed in a base 21 which is integral with the pivoting assembly 12. For example, the base 21 forms a single piece with the cylinder 13 according to the figure 3 .

[0066] Therefore, the pin 25 is outside the passage 22 during an unlocked phase of the unlocked mode, to give total freedom of rotational movement to the pivoting assembly 12 around the pivot axis AXP.

[0067] Conversely, pin 25 is placed in passage 22 during the locked phase of the locked mode illustrated in the figure 3 , to provide the pivoting assembly 12 with a locking mechanism for rotational movement around the pivot axis AXP. The pivoting assembly then has freedom of rotational movement around the pivot axis AXP restricted to an operating clearance. The pin 25 is then slightly movable in the passage 22 in azimuth relative to the pivot axis AXP.

[0068] Furthermore, the immobilization system 20 has an elastic locking system 40, activated indirectly by the control 30 during the locked mode, to tend to push the pin 25 into the passage 22 in this locked mode. The method of the invention thus comprises, from the unlocked mode, an activation of the control 30 to move into the locked mode then, if the pin 25 is opposite the passage 22, a movement of the pin 25 in the passage 22 to reach the locked phase. If the pin 25 is not opposite the passage 22, the elastic locking system 40 presses the pin 25 against the base 21 during an armed phase, then moves the pin 25 into the passage 22 as soon as the pin 25 comes opposite the passage 22.

[0069] In addition, the immobilization system 20 comprises an elastic unlocking system 50 which is activated indirectly by the control 30 during the unlocked mode, to cause the pin 25 to exit the passage 22 and thus release the pivoting assembly 12. The elastic unlocking system 50 is configured to allow extraction of the pin 25 outside the passage 22 only in the presence of a shear force between the base 21 and the pin 25 less than a threshold. The method of the invention thus comprises, from the locked mode, an activation of the control 30 to switch to the unlocked mode, then if the pin 25 is in the passage 22 and in contact with the base 21, a compression of an elastic unlocking system 50 during a disarmed phase. The pin 25 is held in the passage 22 as long as this pin 25 undergoes a shear force greater than or equal to a threshold.On the other hand, as soon as the pin 25 undergoes a shear force lower than the threshold, the elastic unlocking system 50 relaxes and expels the pin 25 out of the passage 22 to enter an unlocked phase.

[0070] According to the first alternative of the figures 3 à 10 , the pin 25 is movable in translation relative to the base 21 along a translation axis AXT, for example parallel to the pivot axis AXP. The passage 22 can then be a bore in the base 21.

[0071] Therefore, the immobilization system 20 comprises a hollow support 60. This support 60 comprises a tubular guide which extends towards the base 21, along the translation axis AXT, from a bottom 61 of this support 60 to an open end 62 of this support 60. Consequently, the open end 62 is located, along the translation axis AXT, between the bottom 61 and the base 21.

[0072] The pin 25 then extends partially into the support 60, at least during the locked phase. Whatever the variant of the first alternative, the pin 25 comprises a head 26 sliding in the support 60 while being guided by the tubular guide. In addition, the pin 25 comprises a locking rod 27 secured to the head, and therefore connected to the head. This locking rod 27 exits the support 60 through the open end 62, at least during the locked phase, in order to be able to penetrate into the passage 22 of the base 21. For safety, the locking rod 27 may comprise a fusible zone 270. The locking rod 27 may also be guided by a guide secured to the base.

[0073] Under these conditions, the elastic locking system 40 is arranged between the bottom 61 and the head 26. Optionally, the elastic locking system 40 can be fixed to the bottom 61. For example, the elastic locking system 40 can comprise an elastic block or a locking spring 41 having a coil 42 fixed to the bottom 61 in the usual manner.

[0074] According to the first variant of the first alternative of the figure 3 , the support 60 is movable in translation relative to the base 21, along the translation axis AXT. For example, the support 60 slides in a guide secured to the base 11.

[0075] The control 30 is connected to the support 60 in order to move this support from a first position POS1 requiring the application of the unlocked mode to a second position POS2 requiring the application of the locked mode. For example, the control 30 comprises a handle 31, or an equivalent or even a linear actuator or other, connected by a cable 33 to the support 60 and for example to the bottom 61. The cable 33 can slide in a rigid sheath 32.

[0076] Furthermore, the elastic unlocking system 50 is arranged between the head 26 and an internal shoulder 63 of the support 60. The internal shoulder 63 is located between the head 26 and the base 21. The locking rod 27 passes through this internal shoulder 63 and the elastic unlocking system 50. For example, the elastic unlocking system 50 is fixed to the internal shoulder 63, or even comprises an elastic block or an unlocking spring 51 having a coil 52 fixed to the internal shoulder 63.

[0077] THE figures 3 à 6 explain how the first variant of the first alternative works.

[0078] In the locked phase of the figure 3 , the support 60 is pushed by the control 30 into the second position POS2. The pin 25 is arranged partly in the passage 22. The elastic locking system 40 and the elastic unlocking system 50 are slightly compressed to hold the pin 25 in position, namely to avoid a translation of the pin 25 relative to the support 60 under the effect of vibrations for example.

[0079] In reference to the figure 4 , a pilot can manipulate the control 30 to switch to the unlocked mode. The support 60 is moved into the first position POS1 while being moved away from the base 21 according to the arrow F2. A distance DIS between the bottom 61 and the base 21 increases. From then on, the elastic locking system 40 is at rest, being neither compressed nor extended. Optionally, the elastic locking system 40 no longer touches the pin 25, this elastic locking system 40 being carried by the bottom 61.

[0080] If the pivoting assembly 12 is slightly off-center, the base 21 rests against the pin 25 as illustrated in the figure 4 . The base 21 exerts a shearing force on the pin 25. In the presence of a shearing force between the base 21 and the pin 25 greater than or equal to a threshold, the pin 25 does not move. The translation of the support 60 then compresses the elastic unlocking system 50. This elastic unlocking system 50 is calibrated so as not to induce a translation of the pin 25 under these conditions. Indeed, the elastic unlocking system 50 is calibrated to allow extraction of the pin 25 from the passage 22 only in the presence of a shearing force between the base 21 and the pin 25 less than this threshold. The immobilization system 20 is then in an innovative disarmed phase.For example, the elastic unlocking system 50 is defined to prevent unlocking when the lateral thrust F1 exceeds by 20% the threshold thrust allowing the pivoting assembly to pivot around the pivot axis AXP when this pivoting assembly is not locked in pivoting.

[0081] In reference to the figure 5 , as soon as the shear force between the base 21 and the pin 25 becomes lower than the threshold, the elastic unlocking system 50 relaxes. The support 60 being made immobile by the control 30, the elastic unlocking system 50 exerts a force on the pin 25 to make it exit the passage 22. The immobilization system 20 is then in an unlocked phase.

[0082] Depending on the relative position of the pin 25 and the base 21 when activating the unlocked mode, the immobilization system 20 can switch directly from the locked phase to the unlocked phase.

[0083] From there, a pilot can manipulate the control 30 to enter the locked mode. The support 60 is moved into the second position POS2 by being brought closer to the base 21 according to the arrow F3 on the figure 6 . The distance DIS between the bottom and the base 21 decreases.

[0084] If the pin 25 is aligned with the passage 22, the immobilization system 20 can move into the locked phase of the figure 3 . In the negative and with reference to the figure 6 , the pin 25 comes into contact with the base 21. The translation of the support 60 then compresses the elastic locking system 40. On the other hand, the elastic unlocking system 50 is at rest, being neither compressed nor extended. Optionally, the elastic unlocking system 50 no longer touches the pin 25, this elastic unlocking system 50 being retained by the internal shoulder 63. The immobilization system 20 is then in an armed phase making it possible to automatically reach the locked phase when the pin 25 is at the right of the passage 22.

[0085] THE figures 7 à 10 present a second variant of the first alternative. With reference to the figure 7 , the support 60 is now immobile relative to the base 11, for example being integral with the base 11.

[0086] In addition to the aforementioned head 26 and locking rod 27, the pin 25 comprises an input rod 28 which is also integral with the head 26, namely connected to the head. The locking rod 27 and the input rod 28 are located on either side of the head 26 along the translation axis AXT. The input rod 28 also passes through the bottom 61 to extend partly outside the support 60.

[0087] Therefore, the input rod 28 cooperates with the control 30 and the elastic unlocking system 50. Indeed, this input rod 28 can comprise a top 29 carrying a tube 70. The control 30 can comprise a cable 33 which passes through a wall of the tube to reach a plate 71 guided in translation in the tube 70. The cable 33 can be connected to a handle, or to an output shaft 35 of an actuator 34 controlled by a human-machine interface for example.

[0088] The elastic unlocking system 50 may be arranged between said wall 72 and the plate 71. The elastic unlocking system 50 may comprise a spring or an equivalent, such as for example an elastic block and for example made of elastomer. The elastic unlocking system 50 may have a stiffness along the translation axis AXT greater than a stiffness along the translation axis of the elastic locking system 40.

[0089] In the locked phase of the figure 7 , the cable 33 is moved towards the base 21 or released. From then on, the plate 71 is arranged as close as possible to the base 21 in a locking position POS3. The elastic locking system 40 and the elastic unlocking system 50 are possibly slightly compressed to hold the pin 25, namely to avoid undue movement of the pin 25 under the effect of vibrations for example.

[0090] In reference to the figure 8 , a pilot can manipulate the control 30 to switch to the unlocked mode. The plate 71 rises by being moved into the unlocked position POS4. If the pivoting assembly 12 is slightly off-center, the base 21 bears against the pin 25. The base 21 exerts a shearing force on the pin 25. In the presence of a shearing force between the base 21 and the pin 25 greater than or equal to a threshold, the pin 25 does not move. The translation of the plate 71 then compresses the elastic unlocking system 50. The immobilization system 20 is then in an innovative disarmed phase.

[0091] In reference to the figure 9 , as soon as the shear force between the base 21 and the pin 25 becomes lower than the threshold, the elastic unlocking system 50 relaxes and exerts a force on the pin 25 to make it exit the passage 22. The immobilization system 20 is then in an unlocked phase.

[0092] Depending on the relative position of the pin 25 and the base 21 when activating the unlocked mode, the immobilization system 20 can switch directly from the locked phase to the unlocked phase.

[0093] From there, a pilot can manipulate the control 30 to enter the locked mode. The plate 71 is moved into the locked position POS3 by being brought closer to the base 21.

[0094] If the pin 25 is aligned with the passage 22, the immobilization system 20 can move into the locked phase of the figure 7 . In the negative and with reference to the figure 10 , the pin 25 comes into contact with the base 21. The translation of the pin 25 relative to the support 60 then compresses the elastic locking system 40. On the other hand, the elastic unlocking system 50 is at rest, being neither compressed nor extended, the cable 33 possibly being braced. The immobilization system 20 is then in the armed phase.

[0095] THE figures 11 à 15 illustrate a second alternative comprising a pin 25 mobile in rotation relative to the base in particular. With reference to the figure 12 , the pin 25 can penetrate into the passage 22 formed by a radial notch in the base 21.

[0096] According to the figure 11 , the pin 25 is carried by a lever 75 in pivot connection with the base 11. The elastic locking system 40 is then arranged between the base 11 and the lever 75.

[0097] Furthermore, the control 30 comprises a cable 33 connected to a plate 76 movable in translation in a guide 77. The elastic unlocking system 50 is then arranged between the plate 76 and a partition 78 of the guide 77 crossed by the cable 33. The cable 33 can be connected to a handle according to the example illustrated, or even to an actuator for example, possibly via one or more references.

[0098] The guide 77 is then secured to the lever 75.

[0099] In the locked phase of the figure 11 , the cable 33 is pulled by the lever 75 or released. From then on, the plate 76 is arranged as close as possible to the lever 75 in a locking position POS5. The elastic locking system 40 and the elastic unlocking system 50 are possibly slightly compressed. The lever 75 pivots to position the pin 25 in the passage 22.

[0100] In reference to the figure 13 , a pilot can manipulate the control 30 to switch to the unlocked mode. The plate 76 is moved into the unlocked position POS6. If the pivoting assembly 12 is slightly off-center, the base 21 is supported against the pin 25. The translation of the plate 76 then compresses the elastic unlocking system 50. The immobilization system 20 is then in an innovative disarmed phase.

[0101] In reference to the figure 14 , as soon as the shear force between the base 21 and the pin 25 becomes lower than the threshold, the elastic unlocking system 50 relaxes and exerts a force on the guide 77 which tilts the lever 75 to remove the pin 25 from the passage 22. The immobilization system 20 is then in an unlocked phase. From there, a pilot can manipulate the control 30 to switch to the locked mode. The plate 76 is piloted to be moved again into the locked position POS5. If the pin 25 is aligned with the passage 22, the immobilization system 20 can switch to the locked phase of the figure 11 . If not, the pin 25 comes into contact with the base 21. The lever 75 then compresses the elastic locking system 40. The immobilization system 20 is then in the armed phase illustrated in the figure 15. Naturally, the present invention is subject to numerous variations as to its implementation. Although several embodiments have been described, it is understood that it is not conceivable to exhaustively identify all possible modes. It is of course possible to replace a described means provided that it does not depart from the scope of the present invention as defined by the claims.

Claims

1. Landing gear (10) provided with a stand (11) and a pivoting assembly (12) carrying a contact member (15) that is configured to be in contact with the ground (100), said pivoting assembly (12) being able to rotate about a pivot axis (AXP) in relation to the stand (11), said landing gear (10) having an immobilization system (20) comprising a movable pin (25) and a control (30) configured to request the application of a locked mode or an unlocked mode, the immobilization system (20) comprising a passage (22), the pin (25) being outside said passage (22) in an unlocked phase of the unlocked mode, the pin (25) being able to move in the passage in azimuth relative to the pivot axis (AXP) in a locked phase of the locked mode, the immobilization system (20) having an elastic locking system (40) pushing the pin (25), when in the locked mode, either against the base (21) during an armed phase of the locked mode as long as the pin (25) does not enter the passage (22), or into the passage (22) as soon as the pin (25) is in line with the passage (22) in the locked phase, the immobilization system (20) comprising an elastic unlocking system (50) configured to move said pin (25) out of the passage (22) when activation of the unlocked mode is commanded by the control (30), characterized in that the passage (22) is provided in a base (21) secured to the pivoting assembly, the elastic unlocking system (50) being calibrated to allow the pin (25) to be extracted from the passage (22) only when there is a shearing force between the base (21) and the pin (25) below a threshold.

2. Landing gear according to Claim 1, characterized in that said pin (25) is able to move in translation in relation to the base (21) along a translation axis (AXT).

3. Landing gear according to claim 2, characterized in that said immobilization system (20) comprises a hollow support (60) that extends towards the base (21) along the translation axis (AXT) from an end wall (61) to an open end (62), the open end (62) being arranged between the end wall (61) and the base (21), the pin (25) comprising a head (26) integral with a locking rod (27), the head (26) being located in the hollow support (60) and the locking rod (27) emerging through the open end (62) of the hollow support (60) at least in the locked phase, the elastic locking system (40) being arranged between the end wall (61) and the head (26).

4. Landing gear according to Claim 3, characterized in that the elastic locking system comprises a locking spring (41) with a coil (42) fastened to the end wall (61).

5. Landing gear according to any one of Claims 3 to 4, characterized in that the support (60) is able to move in translation in relation to the stand (11), said control (30) being connected to the support (60).

6. Landing gear according to Claim 5, characterized in that the elastic unlocking system (50) is arranged between the head (26) and an inner shoulder (63) of said support (60), the locking rod (27) passing through said inner shoulder (63), the inner shoulder (63) being situated between said head (26) and said base (21).

7. Landing gear according to Claim 6, characterized in that the elastic unlocking system (50) comprises an unlocking spring (51) with a coil (52) fastened to the inner shoulder (63).

8. Landing gear according to any one of Claims 2 to 4, characterized in that the support (60) is stationary in relation to the stand (11), the pin (25) comprising an entry rod (28) integral with the head (26) and passing through the end wall (61) of the support (60).

9. Landing gear according to Claim 8, characterized in that the entry rod (28) extends from the head (26) to a top (29) integral with a hollow tube (70), said control comprising a cable (33) that extends up to a plate (71) that is able to move in translation in the tube (70), passing through a wall (72) of the tube (70), the elastic unlocking system (50) being arranged between said wall (72) and said plate (71).

10. Landing gear according to any one of Claims 2 to 9, characterized in that a stiffness of the elastic unlocking system (50) along the translation axis (AXT) is greater than a stiffness of the elastic locking system (40) along the translation axis.

11. Landing gear according to Claim 1, characterized in that the pin (25) is carried by a lever (75) pivotally connected to the stand (11), the elastic locking system (40) being arranged between the stand (11) and the lever (75), the control (30) comprising a cable (33) connected to a panel (76) that is able to move in translation in a guide (77), the guide (77) being connected to the lever (75), the elastic unlocking system (50) being arranged between the panel (76) and a partition (78) of the guide (77) through which the cable (33) passes.

12. Landing gear according to any one of Claims 1 to 11, characterized in that said contact member (15) comprises a wheel (150) that is able to rotate about a wheel axis (AXROT) in relation to the pivoting assembly (12), said wheel axis (AXROT) being distinct from the pivot axis (AXP).

13. Rotorcraft (1), characterized in that said rotorcraft (1) comprises at least one pivoting landing gear (10) according any one of Claims 1 to 12.

14. Method for locking and unlocking a landing gear (10) provided with a stand (11) and a pivoting assembly (12) carrying a contact member (15) that is configured to be in contact with the ground (100), said pivoting assembly (12) being able to rotate about a pivot axis (AXP) in relation to the stand (11), said landing gear (10) having an immobilization system (20) configured to immobilize said pivoting assembly (12) within a predetermined range of positions in relation to the stand (11) during a locked phase of a locked mode and to authorize unlimited pivoting of the pivoting assembly (12) in relation to the stand (11) during an unlocked phase of an unlocked mode, the immobilization system (20) comprising a movable pin (25) and a control (30) configured to request the application of the locked mode or the unlocked mode, the immobilization system (20) comprising a passage (22) provided in a base (21) integral with the pivoting assembly, the pin (25) being outside said passage (22) in the unlocked phase, the pin (25) being able to move in said passage in azimuth relative to the pivot axis (AXP) in the locked phase, the method comprising: - when the immobilization system (20) is in the unlocked mode, activating said control (30) in order to switch to the locked mode, then: i) if the pin (25) is in line with the passage (22), moving the pin (25) into the passage (22); ii) if the pin (25) is not in line with the passage (22), pressing the pin (25) against the base (21) with an elastic locking system (40) and moving the pin (25) into the passage (22) as soon as the pin (25) comes into line with the passage (22); - when the immobilization system (20) is in the locked mode, activating said control (30) in order to switch to the unlocked mode, then if the pin (25) is in the passage (22) and in contact with the base (21), compressing an elastic unlocking system (50), and: i) keeping the pin (25) in the passage (22) as long as the pin (25) is subject to a shearing force greater than or equal to a threshold, the immobilization system (20) being in a disarmed phase; ii) as soon as the pin (25) is subject to a shearing force below the threshold, expanding the elastic unlocking system (50) and ejecting the pin out of the passage (22) under the effect of said expansion to switch to the unlocked phase.