Retractable chassis with a folding strut and integrated actuator

Description

BACKGROUND OF THE INVENTION

[0001] On high-speed aircraft, the landing gear is designed to be retractable in flight. Each landing gear is thus mounted movably (most often pivoting) between a deployed position and a retracted position in which the landing gear is stored in a cargo bay of the aircraft.

[0002] To stabilize the landing gear in the deployed position, a bracing element, called a strut, is used, which is attached between the aircraft structure and the landing gear leg, and which can be stiffened when the landing gear is in the deployed position to create a rigid assembly triangulated by the strut and thus immobilize the landing gear in the deployed position.

[0003] Among the known types of struts, the breakaway strut stands out. It consists of two articulated elements, one attached to the aircraft structure and the other to the landing gear leg. When the landing gear reaches the deployed position, the two strut elements align and are automatically locked in this position, thus stabilizing the landing gear in the deployed position. The strut's hinge (or knee) allows this alignment to break when the landing gear is retracted, permitting free movement between the deployed and retracted positions.

[0004] The locking of the breakaway strut in a substantially aligned position is ensured by an internal locking mechanism (for example, on the auxiliary landing gear of the ATR42 aircraft), or by an external locking mechanism in the form of a secondary strut coupled to the main strut (for example, on the auxiliary landing gear of the Airbus A320 aircraft). Locking can also be achieved simply by springs returning the strut elements to the substantially aligned position defined by stops.

[0005] To ensure the landing gear is raised to the retracted position, it must be equipped with a release actuator to move the strut from the approximately aligned position to a broken position, and a control actuator to raise the landing gear to the retracted position. The activation sequence of these two actuators must therefore be managed.

[0006] The state of the art is illustrated by document BE 414 427 A. This document proposes the use of a single linear actuator to both unlock and raise the landing gear to its retracted position. The two arms of the breakaway strut are articulated separately on the body of this actuator, resulting in a complex and bulky device. SUBJECT OF THE INVENTION

[0007] The invention aims to provide a landing gear equipped with a simple-to-implement breaker strut. PRESENTATION OF THE INVENTION

[0008] To achieve this goal, an aircraft landing gear is proposed comprising a leg intended to be movably mounted on an aircraft structure between a deployed position and a retracted position, the landing gear being equipped with a breakaway strut comprising two elements articulated together at a knee, with a first element intended to be attached to the aircraft structure and a second element intended to be attached to the landing gear, a return device being disposed between the two elements returning them to a substantially aligned position defined by respective stops.According to the invention, one of the elements of the strut incorporates a linear actuator comprising a sliding rod which is attached to the other element of the strut by means of a connecting rod, the whole being arranged so that the movement of the sliding rod of the actuator in one and the same direction successively causes the misalignment of the elements of the strut and the movement of the landing gear from the deployed position to the retracted position.

[0009] By integrated, we mean that the linear actuator is fully integral with the associated strut element, either by being attached by screws or any other means of fastening, or whose body directly forms the strut element. In the latter case, the actuator body directly articulates with the other strut element, and with the articulation with the landing gear or structure to which it is attached, making the actuator body a structural element of the strut.

[0010] The landing gear has a single actuator to unlock the strut and raise it to the retracted position. The actuator is integrated into one of the strut elements, so no additional joints are required.

[0011] According to a first particular embodiment, the rod slides along a sliding axis which is contained in a plane defined by articulation axes of the strut element into which it is integrated.

[0012] According to another particular aspect of the invention, the linear actuator is integrated into that of the strut elements which is attached to the leg of the lander.

[0013] According to yet another particular aspect of the invention, the strut elements that do not carry the linear actuator have a general panel shape.

[0014] According to a second particular embodiment of the invention, the rod slides along a sliding axis which is distinct from a plane defined by articulation axes of the strut element into which it is integrated.

[0015] According to yet another particular aspect of the invention, the stops comprise, on the one hand, an end of a protruding foot of the strut element carrying the linear actuator and, on the other hand, an end of the connecting rod which is articulated on the other strut element. DESCRIPTION OF THE FIGURES

[0016] The invention will be better understood in light of the following description of particular embodiments of the invention, with reference to the figures in the accompanying drawings, among which: there figure 1 is a schematic side view of an aircraft landing gear comprising a strut according to a first particular embodiment of the invention; the figure 2 is a perspective view of the strut equipping the landing gear of the figure 1 The connecting rod is shown with a dotted line for clarity; figure 3 is a cross-sectional view of the strut of the figure 1 in the locked position; the figure 4 is a view analogous to that of the figure 3 showing the strut in the unlocked position, the strut alignment having been broken; the figure 5 is a schematic view of the lander's skeleton and the associated strut during its raising, shown here in the deployed position while the strut is in a roughly aligned position; the figure 6 is a schematic view of the lander's skeleton and the associated strut during its raising, shown here in the position during raising while the strut is broken; the figure 7 is a schematic view of the lander's skeleton and the associated strut during its retraction, shown here in the retracted position; the figure 8 is a view analogous to that of the figure 3 of a variant embodiment of the invention; the figure 9 is a view analogous to that of the figure 3 of another variant embodiment of the invention. DETAILED DESCRIPTION OF THE INVENTION

[0017] With reference to the figure 1 The invention relates to an aircraft landing gear 100 comprising a leg 1 carrying one or more wheels at its lower end and mounted hinged to an aircraft structure (not visible here) along a hinge axis X1 (seen here at the end). The leg 1 is stabilized in the deployed position by a breakaway strut 2 comprising a lower element 2A hinged to the leg along a hinge axis X2, and an upper element 2B hinged to the aircraft structure along a hinge axis X3, the two elements 2A and 2B being hinged to each other at a knee along a hinge axis X4. The hinge axes are all parallel to each other. As can be seen in the figure 2 The upper strut element 2B has the general shape of a panel, while the lower strut element 2A is essentially formed by the body 3 of a hydraulic cylinder 4, which has at its end a yoke 5 for articulation with the leg 1 along the articulation axis X2, and trunnions 6 for articulation with the upper strut element 2B along the articulation axis X4. Thus, the body 3 of the cylinder 4 forms the structure of the lower strut element 2A and carries the components for its connection to the leg 1 and the upper strut element 2B. A sliding rod 7 is mounted within the body 3, associated with a piston 8 mounted for sealed sliding within the body 3 to define two hydraulic chambers. Here, the Y-axis of the sliding rod 7 is included in the plane defined by the articulation axes X2, X4 of the lower element 2A, but this is not mandatory, as will be seen later in relation to the figures 8 , 9 .

[0018] The end of the sliding rod 7 is attached to the end of a connecting rod 9, the other end of which is articulated on brackets 10 fixed to the upper strut element 2B. Here, the connecting rod 9 has a curved shape to avoid any interference with the other components of the strut, but if the configuration allows, the connecting rod 9 can be straight. Thus, the sliding rod 7 is attached to the upper strut element 2B via the connecting rod 9.

[0019] Stops are arranged to define a substantially aligned position of the strut elements 2A, 2B, as visible to figures 1 , 2 , 3This substantially aligned position corresponds here to a position in which the articulation axis X4 passes slightly beyond a plane P defined by the articulation axes X2, X3 (the so-called "overcentered" position). Here, the stops comprise the end 11A of a foot 11 extending from the body 3 of the hydraulic cylinder 4 and bearing against the upper strut element 2B, here indirectly by coming into contact with the end 11B of the connecting rod 9, itself articulated on the upper strut element 2B. Equivalently, the stops 11A, 11B could be arranged directly between the two strut elements 2A, 2B or between the connecting rod 9 and the upper strut element 2B, as long as they define the substantially aligned position of these two strut elements.Return springs 12 are positioned between the two strut elements 2A and 2B to return the two elements to their abutment position and thus maintain them in a substantially aligned position. Therefore, any movement of leg 1 extending the strut 2 results, at best, in a geometric realignment whereby the pivot axis X4 approaches plane P, but never exceeds it. The two strut elements 2A and 2B return to their abutment position immediately after this movement is complete, under the action of the return springs 12. Conversely, any movement of leg 1 compressing the strut 2 confirms the two strut elements 2A and 2B in their abutment position. The substantially aligned position is therefore a stable position.

[0020] The operation of the counter-brace of the invention is now explained in relation to the figures 5 à 7 Lander 1 is initially in the deployed position illustrated in the figure 5 (which corresponds to the position illustrated in the figure 1 In this position, the strut 2 is held in a substantially aligned position by the springs 12, which return the two strut elements 2A and 2B to their restraint position. The strut 2 then forms a rigid assembly that triangulates the leg 1 to hold it in the deployed position. If necessary, this position can be confirmed by supplying the hydraulic cylinder 4 to retract the sliding rod 7.

[0021] To break the alignment of the strut 2, and thus unlock the deployed position of the lander, the hydraulic cylinder 4 is powered to extend the sliding rod 7. This then pulls on the connecting rod 9, which results in the two strut elements 2A, 2B moving against the return springs 12 towards the broken position illustrated in the figure 6 but also to the figure 4 , on which we observe that the X4 axis of the knee of the brace has moved to the other side of plane P defined by the articulation axes X2, X3. The brace 2 is thus unlocked, so that leg 1 is no longer immobilized in the deployed position. Then, continuing to extend the sliding rod 7, it continues to pull on the connecting rod 9, and therefore forces the two brace elements 2A, 2B to fold, thus causing the leg 1 to move towards the retracted position as illustrated in the figure 7 . Thus, the same cylinder 4 ensures both the unlocking and the raising of the lander to its retracted position.

[0022] For the reverse movement, it is enough to let gravity and aerodynamic forces do their work, pulling the lander downwards, regulating if necessary the descent speed of the lander towards the deployed position by rolling the fluid expelled from the full chamber of the cylinder 4. The strut 2 will realign itself automatically under the effect of the springs 12.

[0023] According to the illustrated embodiment variants in figures 8 And 9 It is possible to position the cylinder 4 so that the sliding axis Y of the rod is not contained in the plane P' defined by the articulation axes X2, X4 (in other words, the sliding axis Y of the rod is distinct from the plane P'). In the arrangement illustrated in the figure 8 , the Y-axis of the sliding rod 7 remains concurrent with the articulation axis X2, whereas in the arrangement illustrated in the figure 9The Y-axis does not intersect with either of the X2 or X4 articulation axes. This freedom of placement allows for optimization of the sliding rod's axis position relative to the X2 and X4 articulation axes. Freeing the X4 articulation axis from the Y-axis also allows for more possibilities in designing the X4 articulation connection.

[0024] The invention is not limited to what has just been described, but on the contrary encompasses any variant falling within the scope defined by the claims.

[0025] In particular, although here we have illustrated the linear strut actuator as a hydraulic cylinder, we can also use an electric or electromechanical linear actuator.

[0026] Although it has been indicated that the strut element incorporating the linear actuator was the lower strut element attached to the lander leg, the linear actuator can of course be integrated into the other strut element.

[0027] Although it has been indicated here that the body of the linear actuator carried a clevis and trunnions so as to form the structure of one of the strut elements, the body of the linear actuator may alternatively be attached to the relevant strut element, for example by screwing or any other means of assembly.

[0028] Finally, although it has been indicated here that the sliding rod must be extended to unlock and fold the brace, it is of course possible to provide for a kinematics in which the unlocking and folding of the brace is achieved by retracting the sliding rod.

Claims

1. An aircraft undercarriage (100) including a leg (1) for mounting on a structure of the aircraft so as to be movable between a deployed position and a retracted position, the undercarriage being fitted with a breaker strut (2) comprising two hinged elements (2A, 2B) that are hinged together at a knee, with a first element (2B) for coupling to the structure of the aircraft and a second element (2A) for coupling to the undercarriage, a return member (12) being arranged between the two elements to urge them towards a substantially aligned position that is defined by respective abutments (11A, 11B), one of the strut elements incorporating a linear actuator (4) having a slidable rod (7) that is coupled to the other strut element by means of a link (9), the assembly being arranged in such a manner that moving the slidable rod of the actuator in a single direction causes, in succession, the elements of the strut to move out of alignment and the undercarriage to move from the deployed position to the retracted position.

2. An undercarriage according to claim 1, wherein the linear actuator has a body (3) in which the slidable rod (7) slides and that forms the associated strut element by carrying coupling members (5, 6) for coupling that element both to the other element and also to that one of the leg and the structure of the aircraft to which that element is coupled.

3. An undercarriage according to claim 2, wherein the rod (7) slides along a sliding axis (Y) that is contained in a plane (P') defined by hinge axes (X2, X4) of the strut element in which it is incorporated.

4. An undercarriage according to claim 1, wherein the linear actuator (4) is incorporated in that one (2A) of the strut elements that is coupled to the leg of the undercarriage.

5. An undercarriage according to claim 4, wherein that one (2B) of the strut elements that does not carry the linear actuator has the general shape of a panel.

6. An undercarriage according to claim 2, wherein the rod (7) slides along a sliding axis (Y) that does not lie in a plane (P') defined by hinge axes (X2, X4) of the strut element in which it is incorporated.

7. An undercarriage according to claim 1, wherein the abutments comprise firstly the end (11A) of a tab (11) projecting from the strut element (2A) carrying the linear actuator, and secondly the end (11B) of the link (9) that is hinged to the other strut element (2B).