Method of driving an aircraft undercarriage between a deployed position and a retracted position

The invention relates to a method of driving an aircraft undercarriage between a deployed position and a retracted position, the undercarriage comprising a leg (2) that is hinged to a structure of the aircraft in order to be movable between those two positions and being stabilized in the deployed position by means of a brace member (10) comprising two limbs (11, 12) that are hinged to each other, one of which is coupled to the leg and the other of which is coupled to the structure of the aircraft, the limbs being brought into an aligned position when the leg is in the deployed position. According to the invention, a rotary actuator (20) is arranged on the aircraft, which actuator comprises first and second cranks (22, 24) that are mounted to turn freely about a common axis of rotation but that have a relative angular position that can be controlled, and that are arranged to stabilize the limbs of the brace member in the substantially aligned position.

The invention relates to a method of driving an aircraft undercarriage between a deployed position and a retracted position.

BACKGROUND OF THE INVENTION

Aircraft undercarriages are known that comprise a leg hinged to a structure of the aircraft so as to be movable between a deployed position and a retracted position. The leg is stabilized in the deployed position by means of a brace member that often comprises two limbs that are hinged together, one of the limbs being coupled to the leg and the other being coupled to the structure of the aircraft, the two limbs being held in a substantially aligned position by a stabilizer member that forms a lock that can be unlocked in order to enable the leg to be raised from the deployed position to the retracted position. For this purpose, such undercarriages generally include an unlocking actuator for unlocking the stabilizer member and for breaking the alignment of the brace member, and a drive actuator for raising the leg towards the retracted position.

Nevertheless, it is possible to use a single actuator that performs both functions. By way of example, Document FR 2 946 319 proposes using a drive actuator of rotary electromechanical type coupled to one of the arms of the member for stabilizing the brace in the aligned position, for the purposes both of driving the undercarriage and of unlocking the stabilizer member.

Keeping the leg in the retracted position generally requires the use of an uplock box secured to the structure of the aircraft and including a hook that engages a roller secured to the leg when the leg reaches the retracted position. Nevertheless, realignment solutions are known in which the two limbs of the brace member or the two limbs of the stabilizer member are in the aligned position when the undercarriage is in the retracted position, which makes it possible to omit the uplock box.

OBJECT OF THE INVENTION

The invention seeks to propose a method of driving an aircraft undercarriage between a deployed position and a retracted position that makes use of only a single actuator.

SUMMARY OF THE INVENTION

In order to achieve this object, there is provided a method of driving an aircraft undercarriage between a deployed position and a retracted position, the undercarriage having a leg hinged to a structure of the aircraft to be movable between the deployed position and the retracted position, being stabilized in the deployed position by means of a brace member comprising two limbs that are hinged to each other, one of the limbs being coupled to the leg and the other to the structure of the aircraft. According to the invention, a rotary actuator is arranged on the aircraft, the actuator having first and second cranks mounted to turn freely about a common axis of rotation but presenting a relative angular position that can be controlled, the first crank being connected to the brace member by a first connecting rod, while the second crank is connected to the leg by a second connecting rod, such that the cranks present:a first relative angular position in which the first crank and the first connecting rod are brought into a first alignment when the leg is in the deployed position, thereby stabilizing the limbs of the brace member in a substantially aligned position; anda second relative angular position in which the second crank and the second connecting rod are brought into a second alignment while the leg is in the retracted position, thereby stabilizing the leg in the retracted position.

Such a provision associates the angular position of the leg relative to the structure of the aircraft in one-to-one correspondence with the relative angular position of the two cranks. In the invention, it is ensured that the deployed position of the leg corresponds to a first alignment of the first crank and of the first connecting rod, while the retracted position corresponds to a second alignment of the second crank and of the second connecting rod. The first alignment serves to stabilize the brace member in the aligned position, and thus to stabilize the leg in the deployed position, while the second alignment stabilizes the leg in the retracted position, thereby eliminating any need to have recourse to an uplock box.

A crank and the associated connecting rod are said herein to be “in alignment” when the two elements are in a position such that their mutual hinge axis, the hinge axis between the connecting rod and the undercarriage, and the axis of rotation of the crank are contained substantially in a single plane. Nevertheless, and as is well known, an alignment can be stabilized by going a little beyond the perfectly aligned position so as to take the two elements into a position that is very slightly out of alignment (i.e. an “over-centered” position) that is defined by abutments between said elements. These positions in abutment are held by the residual torque of the actuator when it is not powered (electromagnetic torque due to the permanent magnet for an electromagnetic actuator, or torque due to fluid held captive in the chambers of the actuator for a hydraulic actuator). This provision thus makes it possible to avoid any need for having recourse to an auxiliary locking member, since its function is replaced by each of the crank and connecting rod pairs being in alignment.

DETAILED DESCRIPTION OF THE INVENTION

With reference toFIGS. 1 and 2, the invention in this example applies to an undercarriage1comprising a leg2carrying wheels3at its bottom end and hinged to a structure of an aircraft about a hinge axis X1that is substantially horizontal in service. The leg is movable between a deployed position shown inFIG. 1and a retracted position that can be seen inFIG. 2. The leg2is stabilized in the deployed position by means of a brace member10comprising two limbs that are hinged together, specifically a panel11hinged to the structure of the aircraft about a hinge axis X2and an arm12hinged to the leg2and to the panel11about respective hinge axes X3and X4. In the deployed position, the arm12and the panel11are in a substantially aligned position.

According to the invention, a rotary actuator20is provided that is free to rotate on the structure of the aircraft about an axis of rotation X5that is parallel to the hinge axes X1to X4. The rotary actuator comprises a casing21having an appendix that forms a first crank22, and it includes a shaft23mounted to rotate about the axis of rotation X5and carrying a second crank24. The relative angular position between the two cranks22and24can be modified by powering the actuator so as to cause the shaft23to turn relative to the casing21, and it can be fixed and held by means of the residual torque of the actuator20when it is not powered. In this example, the first crank22is coupled to the panel11of the brace member10by means of a first connecting rod25(in this example two connecting rods extending on either side of the end of the panel11) hinged to the first crank22about a hinge axis X6and hinged to the panel11about a hinge axis X7, while the second crank24is coupled to the leg2, and more particularly to a horn26on the leg, by means of a second connecting rod27hinged to the second crank24about a hinge axis X8and hinged to the horn26about a hinge axis X9. In this example, all of the axes X1to X9are mutually parallel.

Such a configuration associates the relative angular position of the cranks22and24and the angular position of the leg2relative to the structure of the aircraft in one-to-one correspondence. In the position shown inFIG. 3, in which the leg2is in the deployed position, the relative angular position of the crank is such that the first crank22and the first connecting rod25are in a substantially aligned position, referred to as the first alignment. More precisely, the first alignment is a position obtained by causing the first crank22and the first connecting rod25to pass a little beyond their geometrically aligned position (as defined by the axes X5, X6, and X7being in perfect alignment in a single plane) so as to cause them to reach respective abutments. As can be seen inFIG. 7, the abutment is in the form of fingers28extending from the end of the first crank so as to come to bear against obstacles29secured to the first connecting rod25, which obstacles extend facing the fingers28and form a stop defining the first alignment. Likewise, the second connecting rod27has a finger36that comes to bear against an obstacle37secured to the second crank24(specifically a pin36). InFIG. 7, the second crank25and the second connecting rod27are in the second alignment position, in which the finger36bears against the obstacle37.

Returning toFIG. 3, it can be seen that the first crank22cannot turn since the actuator20is not powered, so its residual torque prevents the casing21and the shaft23from turning relative to each other, thereby constraining them together in rotation. However, the shaft23is blocked by the second crank24, itself blocked against rotating by its coupling with the leg2via the second connecting rod27, which is not in alignment with the second crank24.

In order to raise the leg2towards the retracted position, the actuator20is powered so as to cause the shaft23to turn, thereby modifying the relative angular position between the cranks22and24. As shown inFIG. 4, a first effect of this turning is to break the alignment between the first crank22and the first connecting rod24, thereby breaking the alignment between the panel11and the arm12of the brace member10. The undercarriage2is then no longer stabilized in its deployed position and the leg can be raised towards the retracted position. With the actuator20continuing to be powered, the leg2continues to rise, and it reaches an intermediate position as shown inFIG. 5in which the first connecting rod25pulls on the panel11, while the second connecting rod27pushes against the leg2, thereby having the effect of raising the leg towards the retracted position as shown inFIG. 6, in which position the cranks are in a relative angular position such that the second crank24and the second connecting rod27reach a position in which they are substantially in alignment, referred to as the second alignment. In the same manner as for the first alignment, the second alignment is specifically a position that is obtained by causing the second crank24and the second connecting rod27to pass a little beyond the geometrical alignment (as defined by the axes X5, X8, and X9being in perfect alignment in the same plane) so as to cause them to engage against respective abutments. This alignment blocks the leg2in the retracted position, such that this position is stable and does not require the use of an uplock box.

According to a particular aspect of the invention, the undercarriage has doors30coupled thereto, which doors30are hinged to the structure of the aircraft about axes X10and that serve to close the well in which the undercarriage is housed when in the retracted position, with this being done by links31that are coupled directly to horns32projecting from the panel11of the brace member10. In order to facilitate understanding of the invention, the figures do not show the fairing that is coupled to the leg and that co-operates with the two doors30to close the well when the undercarriage is in the retracted position, and that remains open when the undercarriage is in the deployed position. In both of the positions of the undercarriage that are shown inFIGS. 1, 2, 3, and 6, it can be seen that the doors30are in the closed position, even though they open while the undercarriage is being driven, as can be seen inFIGS. 4 and 5. Holding the doors in the closed position requires prestress to be installed on the doors30so as to be certain that they do not gape open in flight under the effect of aerodynamic forces. For this purpose, the links31are of a length that is determined so that both in the retracted position and also in the deployed position of the undercarriage, the doors30come to bear against an abutment35(visible inFIG. 1) that is secured to the structure of the aircraft a little before the connecting rod and crank assembly comes into alignment, and in particular a little before its preceding passage through the geometrically aligned position. The doors30coming up against the abutment35then make it necessary to pull on the links in order to prestress the doors30, which then act as return springs confirming the crank-and-connecting rod assembly in its internal abutment position, and thus confirming that it is in alignment.

In order to add to the prestress induced by closing the doors, or in order to replace it if the doors are not coupled to the undercarriage, it is possible to use another external source of prestress, such as for example a resilient abutment50, as shown inFIG. 8. The resilient abutment has a base51for fastening to the ceiling of the well. The base51carries a hollow cylinder or body52provided with a terminal opening carrying a guide53. A piston54is slidably mounted in the guide53to project from the body52. As shown inFIG. 8, the piston54is pushed towards a projecting position by Belleville spring washers55that are positioned inside the hollow body52and that exert prestress on the piston54. In order to cause the piston54to retract, it is necessary to apply a force thereon that is not less than the prestress imparted by the Belleville washers55.

As can be seen inFIG. 9, the resilient abutment50is positioned on the ceiling of the undercarriage well in such a manner that a portion of the brace member, specifically the brace panel11, comes into abutment against the piston54when the undercarriage reaches the retracted position, before the second crank24and the second connecting rod27come into the geometrical alignment that precedes the “second alignment” position. Thus, in order to pass through the geometrical alignment and go beyond it so as to reach the second alignment, the brace panel11needs to push the piston54back against the prestress imparted by the Belleville washers55. In this manner, the prestress from the Belleville washers is transmitted to the brace panel11, in the same manner as the prestress from the doors is transmitted to the brace panel via the horns32.

Naturally, the prestress from the doors and/or from the resilient abutment may be transmitted to a location on the undercarriage other than the brace panel, e.g. directly to the strut leg of the undercarriage. The prestress may also be exerted by one or more internal springs that confirm the second crank24and the second connecting rod27in their second alignment.

The invention is not limited to the above description, but on the contrary covers any variant coming within the ambit defined by the claims.

In particular, although the hinge axes in this example are all mutually parallel, the invention naturally applies to linkages with axes that are not parallel, providing each crank and connecting rod assembly of the actuator comes into alignment when the leg is in one or the other of its deployed and retracted positions.