Aircraft landing gear with a leaf spring locking device

Description

[0001] The present invention relates to the field of landing gear and more particularly to means of locking the landing gear in the deployed position. BACKGROUND OF THE INVENTION

[0002] We know, for example from document EP 3 069 993, of aircraft landing gear comprising a leg mounted movable on the structure of an aircraft between a deployed position (for takeoff and landing) and a retracted position (for flight) under the action of a maneuvering actuator.

[0003] The leg is held in the deployed position by a breakaway strut which is attached to the leg and the aircraft structure, and which has two connecting rods articulated together and held in an aligned position by a stabilizing device.

[0004] The stabilizing device comprises two connecting rods articulated together and held in a substantially aligned position by a passive locking device in order to prevent misalignment of the counter brace.

[0005] In general, the locking mechanism includes one or more helical springs having ends connected to the strut and the stabilizing element to exert a tensile force on said stabilizing element and thus prevent misalignment of the connecting rods.

[0006] It is common for the lander to be designed to move by gravity from the retracted to the deployed position in the event of a maneuvering actuator failure. Helical springs are typically used to assist the lander's movement to the deployed position and to lock it in that position.

[0007] That being said, helical springs oppose the action of the maneuvering actuator when raising the lander and their linear behavior implies significant additional forces to counteract when moving the lander to the retracted position for which the maneuvering actuator must be sized.

[0008] Moreover, helical springs are expensive and relatively heavy. SUBJECT OF THE INVENTION

[0009] The invention therefore aims to provide an aircraft landing gear that makes it possible to overcome, at least in part, the aforementioned disadvantages. SUMMARY OF THE INVENTION

[0010] To this end, the invention proposes an aircraft landing gear comprising: a leg arranged to be mounted movably on an aircraft structure between a deployed position and a retracted position; at least one bracing member to maintain the leg in the deployed position, comprising a first connecting rod articulated on the aircraft structure and a second connecting rod articulated on the first connecting rod and on the leg; a stabilizing member to maintain the first and second connecting rods in an aligned position, comprising a first connecting rod and a second connecting rod articulated with each other and at least one of which is articulated on the bracing member; and at least one spring to elastically return the articulations of the first and second connecting rods to a generally aligned position.

[0011] The spring is a leaf spring arranged to be elastically subjected to an axial compression force when the joints of the first and second connecting rods leave their generally aligned position.

[0012] According to the invention, the spring has a first end (7.1) pivotally mounted on the first or second connecting rod, and a second end (7.2) pivotally mounted on the stabilizing member

[0013] The axial compression of the blade causes it to buckle, so the force required to break the alignment of the connecting rods changes very little during the blade's buckling. This leaf spring behavior allows, during lander deployment, sufficient force to be obtained after a short stroke to lock the lander in the deployed position, and during lander retraction, to limit the forces that the maneuvering actuator must overcome.

[0014] Moreover, such a locking mechanism is inexpensive to produce and is relatively lightweight.

[0015] In particular, the leaf spring is pivotally mounted on the first connecting rod and on the stabilizing member.

[0016] In a further particular way, the leaf spring is pivotally mounted on the second connecting rod and on the stabilizing member.

[0017] According to one particular characteristic, the leaf spring is a metal plate of substantially constant thickness.

[0018] According to another special feature, the lander includes two leaf springs to provide redundancy in case one of the two leaf springs fails.

[0019] In particular, the two leaf springs are substantially identical and are pivotally mounted on the first connecting rod and on the stabilizing member.

[0020] In particular, the two leaf springs are substantially identical and are pivotally mounted on the second connecting rod and on the stabilizing member.

[0021] In particular, one of the leaf springs is pivotally mounted on the first connecting rod and on the stabilizing member, and the other of the leaf springs is pivotally mounted on the second connecting rod and on the stabilizing member.

[0022] In particular, the first connecting rod is articulated on the leg and the second connecting rod is articulated on the bracing element.

[0023] In particular, the first connecting rod is articulated on the second connecting rod and the second connecting rod is articulated on the first connecting rod.

[0024] The invention also relates to an aircraft comprising at least one such landing gear. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] The invention will be better understood in light of the following description, which is purely illustrative and not limiting, and should be read in conjunction with the accompanying drawings, among which: therefigure 1a is a schematic view of an aircraft landing gear according to a first embodiment of the invention, shown in the deployed position; the figure 1b is a view analogous to the figure 1a showing the lander in an unlocked position; the figure 1c is a view analogous to the figure 1a showing the lander in an intermediate position at the beginning of the lifting phase; the figure 2 is a graph illustrating the compressive force produced by the leaf spring as a function of its displacement; the figure 3 is a view analogous to the figure 1 representing an aircraft landing gear according to a second embodiment of the invention; the figure 4 is a view analogous to the figure 1 representing an aircraft landing gear according to a third embodiment of the invention; the figure 5 is a perspective view of a portion of a lander according to a fourth embodiment of the invention; the figure 6 is a schematic view of the landing gear locking mechanism illustrated in the figure 5 . DETAILED DESCRIPTION OF THE INVENTION

[0026] With reference to Figures 1a to 1d, an aircraft landing gear 1 comprises, in a manner known per se, a leg 2 having a first end articulated to an aircraft structure 3 along an articulation axis X1 so that the leg 2 is movable between a deployed position ( figure 1a ) and a retracted position under the action of a maneuvering actuator (not shown), for example a hydraulic cylinder. Leg 2 includes an opposite end (not visible in the figures) carrying an axle on which one or more wheels are mounted for pivoting.

[0027] A breakaway strut 4 is articulated, on one side, to the leg 2 and, on the other side, to the aircraft structure 3, and forms a bracing element to maintain the leg 2 in the deployed position. The strut 4 comprises two connecting rods 4a, 4b, articulated to each other at a knee 4c, along a pivot axis X2. Connecting rod 4a is also articulated to the aircraft structure 3 along a pivot axis X3, while connecting rod 4b is articulated to the leg 2 along a pivot axis X4.

[0028] The breakaway strut 4 is stabilized in a substantially aligned position by means of a stabilizing member 5 comprising two connecting rods 5a, 5b, also articulated to each other at a knee 5c along a pivot axis X5. Connecting rod 5a is articulated to the leg 2 along a pivot axis X6, and connecting rod 5b is articulated to the breakaway strut 4 along the axis X2. Connecting rods 5a, 5b are held in a substantially aligned position by a locking member 6 which returns connecting rods 5a, 5b to the locked position illustrated in the figure. figure 1a and defined by stops between the connecting rods 5a, 5b.

[0029] Thus stabilized in a substantially aligned position, the breaking strut 4 opposes any rotation of the leg 2 around its articulation axis X1, so that the deployed position illustrated in the figure 1a is a stable position. As is well known, connecting rods 4a, 4b and connecting rods 5a, 5b are designed so that to reach the locked position illustrated in the figure 1 The 4c ​​joint of connecting rods 4a, 4b and the 5c joint of connecting rods 5a, 5b pass slightly beyond the geometric alignment of connecting rods 4a, 4b and connecting rods 5a, 5b. In a manner known in itself, the joints are arranged to avoid hyperstaticity, for example by means of operating clearances or at least a ball joint.

[0030] The locking member 6 includes a spring for elastically holding the connecting rods 5a, 5b in a substantially aligned position. According to the invention, this spring comprises an elongated metal blade 7 extending along the connecting rod 4a. The blade 7 has a generally constant thickness and width, the width extending substantially along the articulation axes X1-X6 and being greater than the thickness. For example, the blade 7 has a length of 800 millimeters, a width of 50 millimeters, and a thickness of 3.5 millimeters.

[0031] The blade 7 comprises a first end 7.1 pivotally mounted on the connecting rod 4a along a pivot axis X7 located near the articulation axis X3 of the connecting rod 4a, and a second end 7.2 pivotally mounted on the stabilizing member 5 along a pivot axis X8 near the articulation axis X2 of the knee 4c. Thus, when the leg 2 is in its deployed position, the blade 7 is in a deformed state close to its resting state and the end 7.1 is a first distance away from the end 7.2; when the leg 2 is in its folded position, the blade 7 has buckled and is in a deformed state and the end 7.1 is a second distance away from the end 7.2 that is less than the first distance. It is the folding of the locking member 6 which causes the ends 7.1 and 7.2 to come closer together and therefore the buckling of the blade 7.The blade 7 thus works elastically in compression and tends to return to its resting state, the ends 7.1, 7.2 tending to move apart from each other up to the first distance.

[0032] For this purpose, the blade 7 is substantially straight when the connecting rods 5a, 5b are in the locked position ( figure 1a ), and takes on an arched shape when the connecting rod 5b pivots around the X2 axis ( figures 1b And 1c ).

[0033] The blade 7 thus forms a leaf spring applying a force P to the connecting rod 5b to bring the connecting rods 5a, 5b into a substantially aligned position.

[0034] With reference to figures 1b And 1cThe operating actuator is sized to break the alignment of the connecting rods 5a, 5b by counteracting the force P exerted by the blade 7 resisting its own buckling. The raising of the knee 5c causes the misalignment of the connecting rods 4a, 4b, which causes the knee 4c to rise and therefore the pivoting of leg 2 towards the retracted position ( figures 1b And 1c ).

[0035] As illustrated in the figure 2 The force P generated by the blade 7 after a small deformation U is sufficient to ensure that the connecting rods 5a and 5b remain in the locked position. Furthermore, the force P changes very little as the deformation U increases, especially compared to the linear behavior of helical springs. Thus, when the leg 2 moves from the deployed to the retracted position, the force P produced by the blade 7 is limited, which reduces the forces that the maneuvering actuator must overcome to raise the lander 1. Moreover, the leaf spring formed by the blade 7 is less expensive and relatively lighter.

[0036] It should be noted that the position of the blade 7 on the breaking strut 4 must be different from that of the helical springs, the blade 7 being arranged to work exclusively in compression and not frequently in tension.

[0037] The main parameters required for dimensioning blade 7 are: the effort required to maintain the connecting rods 5a, 5b in a substantially aligned position; the mechanical characteristics of the material in which the blade 7 is made (conventional elastic limit Rp0,2, Young's modulus E, fatigue curve...); the maximum deformation of the blade 7 during the deployment and retraction of the leg 2, in particular to guarantee the mechanical strength of said blade 7; and the maximum buckling of the blade during the deployment and retraction of the leg 2, in particular to limit the bulk of the blade 7 during the entire retraction / extension kinematics of the leg 2.

[0038] There figure 5 This illustrates another embodiment of the invention in which the landing gear 1 includes a stabilizing element 5' whose assembly is said to be "internal" for maintaining the first and second connecting rods 4a, 4b in an aligned position. The stabilizing element 5' comprises two connecting rods 5a', 5b', articulated to each other at a knee 5c' along an articulation axis X5'. Connecting rod 5a' is articulated to connecting rod 4b along an axis X2' and connecting rod 5b' is articulated to connecting rod 4a along an articulation axis X6'. The articulation axes X2', X5', X6' of connecting rods 5a', 5b' are maintained in a substantially aligned position by a locking element 6' which returns connecting rods 5a', 5b' to the locked position illustrated in the figure. figure 6 and defined by a stop 5d' between the connecting rods 5a', 5b'.

[0039] Thus stabilized in a substantially aligned position, the breaking strut 4 opposes any rotation of the leg 2 around its articulation axis X1. As is well known, the connecting rods 5a', 5b' are designed so that, in order to reach the locked position illustrated in the figure 6 The X2' axis of articulation of the connecting rod 5a' passes slightly beyond the geometric alignment of the X2', X5', X6' axes of articulation. In a manner known in itself, the articulations are arranged to avoid over-constraint, for example by means of operating clearances or at least a ball joint.

[0040] With reference to the figure 5 The locking member 6' includes a spring to elastically maintain the pivot axes X2', X5', X6' of the connecting rods 5a', 5b' in a substantially aligned position. This spring comprises two elongated metal blades 7' that extend parallel to each other along the connecting rod 4a. The blades 7' are identical and have a generally constant thickness and width, the width extending substantially along the pivot axes X1-X4 and being greater than the thickness.

[0041] The blades 7' comprise first ends 7.1' pivotally mounted on the connecting rod 4a along the same pivot axis X7' located near the articulation axis X3 of the connecting rod 4a, and second ends 7.2' pivotally mounted on the connecting rod 5b' along the same pivot axis X8' located near the articulation axis X2 of the knee 4c. Thus, when the leg 2 is in its deployed position, the blades 7' are in a deformed state close to their resting state and the ends 7.1' are separated from the ends 7.2' by a first distance; when the leg 2 is in its folded position, the blades 7' have buckled and are in a deformed state and the ends 7.1' are separated from the ends 7.2' by a second distance less than the first distance. It is the folding of the locking member 6' which causes the ends 7.1' and 7.2' to come closer together and therefore the buckling of the blades 7'.The blades 7' thus work elastically in compression and tend to return to their resting state, the ends 7.1', 7.2' tending to move apart from each other up to the first distance.

[0042] To this end, the first and second ends 7.1', 7.2' of each blade 7' are riveted to a fitting 8 arranged to be rotationally assembled to a clevis 9.1 fixed to the connecting rod 4a or to a clevis 9.2 formed from the material with the connecting rod 5a', so that the blades 7' are substantially straight when the connecting rods 5a', 5b' are in the locked position ( figures 5 And 6 ), and take on an arched shape when the connecting rod 5b' pivots around the X6' axis.

[0043] Each of the blades 7 thus forms a leaf spring, applying a force to the connecting rod 5b' to bring the articulation axes X2', X5', X6' into a substantially aligned position. The presence of two blades 7' provides redundancy in case one of the two blades 7' fails.

[0044] The operating actuator is sized to break the alignment of the X2', X5', X6' articulation axes by counteracting the force exerted by the blades 7 resisting their own buckling. The upward movement of knee 5c' causes misalignment of connecting rods 4a, 4b, which in turn causes knee 4c to rise and thus pivots leg 2 towards the retracted position.

[0045] The force exerted by the blades 7' after a slight deformation is sufficient to maintain the connecting rods 5a', 5b' in the locked position. This force changes very little as the deformation increases. Thus, when leg 2 moves from the deployed to the retracted position, the force produced by the blades 7' is limited, thereby reducing the forces that the maneuvering actuator must overcome to raise the lander 1.

[0046] Of course, the invention is not limited to the embodiment described but encompasses any variant falling within the scope of the invention as defined by the claims.

[0047] The number, shape and dimensions of blades 7, 7' may differ from those illustrated in figures 1a-1d, 5 .

[0048] Although here the blades 7, 7' extend along the connecting rod 4a (so-called "internal" mounting), they can also extend along the connecting rod 4b (so-called "external" mounting). The blades 7, 7' are then pivotally mounted on the stabilizing member 5, 5' and on the connecting rod 4b so as to work in compression ( figure 3 ).

[0049] The stabilization of leg 2 can also combine the action of one or more blades pivotally mounted along connecting rod 4a with that of one or more blades pivotally mounted along connecting rod 4b ( figure 4 ).

[0050] The 7, 7' blades can be made from any suitable material (metal, composite...).

[0051] The blades 7, 7' can be pivotally mounted on the connecting rods 4a, 4b and the stabilizing member 5, 5' by any suitable means.

[0052] Although the leg 2 is here held in the deployed position by a single breaking strut 4, the invention can also be applied to landers comprising a leg held in the deployed position by several breaking struts. At least one of the breaking struts is then equipped with a stabilizing element comprising at least one leaf spring.

Claims

1. An aircraft undercarriage (1) comprising: · a leg (2) arranged to be connected to an aircraft structure (3) to be movable between a deployed position and a retracted position; · at least one brace member (4) for holding the leg in its deployed position and comprising a first rod (4a) hinged to the aircraft structure and a second rod (4b) hinged to the first rod and to the leg; · a stabilizer member (5, 5') for holding the first and second rods (4a, 4b) in an aligned position and comprising a first link (5a, 5a') and a second link (5b, 5b') that are hinged to each other, with at least one of them being hinged to the brace member; and · at least one spring for elastically urging the hinges of the first and second links into a generally aligned position; wherein the spring is a spring blade (6, 6', 7, 7') arranged to be subjected elastically to an axial compression force (P) when the hinges of the first and second links leave their generally aligned position, the undercarriage being characterized in that the spring has a first end (7.1) pivotally mounted on the first or second rod, and a second end (7.2) pivotally mounted on the stabilizer member.

2. An undercarriage (1) according to claim 1, wherein the spring blade (6, 6', 7, 7') is pivotally connected to the first rod (4a) and to the stabilizer member (5).

3. An undercarriage (1) according to claim 1, wherein the spring blade (6, 6', 7, 7') is pivotally connected to the second rod (4b) and to the stabilizer member (5).

4. An undercarriage (1) according to any preceding claim, wherein the spring blade (6, 6', 7, 7') is a metal plate of substantially constant thickness.

5. An undercarriage (1) according to any preceding claim, including two spring blades (6, 6', 7, 7') in order to provide redundancy in the event of one of the two spring blades failing.

6. An undercarriage (1) according to claim 5, wherein the two spring blades (6', 7') are substantially identical and they are pivotally connected to the first rod (4a) and to the stabilizer member (5').

7. An undercarriage (1) according to claim 5, wherein the two spring blades (6', 7') are substantially identical and they are pivotally connected to the second rod (4b) and to the stabilizer member (5').

8. An undercarriage (1) according to claim 5, wherein one of the spring blades (6, 7) is pivotally connected to the first rod (4a) and to the stabilizer member, and the other spring blade (6, 7) is pivotally connected to the second rod (4b) and to the stabilizer member.

9. An undercarriage (1) according to claim 1, wherein the first link (5a) is hinged to the leg (2) and the second link (5b) is hinged to the brace member (5).

10. An undercarriage (1) according to claim 1, wherein the first link (5a') is hinged to the second rod (4b) and the second link (5b') is hinged to the first rod (4a).

11. An aircraft including at least one undercarriage (1) according to any preceding claim.