An aircraft undercarriage carrying at least two wheels (4) and for mounting on an aircraft structure to be movable between a deployed position and a retracted position, the undercarriage being characterized in that the wheels are rotatably mounted on axles (3) carried by arms (2) hinged to a bottom portion of a strut-leg (1) of the undercarriage, each arm being associated with a shock absorber (5) coupled firstly to the arm and secondly to a collar (6) that extends around the strut-leg and that is mounted to slide on the strut-leg between a high position in which the collar bears against an abutment (7) of the strut-leg when the undercarriage is in the deployed position and a low position into which the collar is taken when the undercarriage is moved from the deployed position to the retracted position, so as to bring the wheels closer together.

The invention relates to an aircraft undercarriage of spread that can be reduced in the retracted position in order to facilitate storing it in a wheel well.

BACKGROUND OF THE INVENTION

Undercarriages are known that are mounted to move on an aircraft between a deployed position and a retracted position and that include a plurality of wheels, in particular undercarriages having a bogey for carrying four or more wheels. In particular when they include braked wheels, such undercarriages are wide and occupy a large volume in a wheel well when retracted.

OBJECT OF THE INVENTION

The invention seeks to propose an aircraft undercarriage of spread that can be reduced on being retracted in order to facilitate storing it in a wheel well.

SUMMARY OF THE INVENTION

In order to achieve this object, there is provided an aircraft undercarriage carrying at least two wheels and for mounting on an aircraft structure to be movable between a deployed position and a retracted position. According to the invention, the wheels are rotatably mounted on axles carried by arms hinged to a bottom portion of a strut-leg of the undercarriage, each arm being associated with a shock absorber coupled firstly to the arm and secondly to a collar that extends around the strut-leg and that is mounted to slide on the strut-leg between a high position in which the collar bears against an abutment of the strut-leg when the undercarriage is in the deployed position and a low position into which the collar is taken when the undercarriage is moved from the deployed position to the retracted position, so as to bring the wheels closer together.

When the undercarriage is in the deployed position and the aircraft is on the ground, the forces coming from the wheels are transmitted to the collar, while being filtered by the shock absorbers, with the collar transmitting these forces to the strut-leg via the abutment. Bringing the collar into the low position while moving the undercarriage towards the retracted position moves the wheels closer to the central axis of the strut-leg, thereby reducing the spread of the undercarriage, and thus making it easier to store it in flight in a wheel well of the aircraft.

According to a particular aspect of the invention, the collar is connected by a link to a brace member comprising two hinged-together elements for stabilizing the undercarriage in the deployed position.

In the deployed position, the two elements of the brace member are held in an aligned position, thereby stabilizing the strut-leg. The link holds the collar in the high position, in the immediate proximity of or bearing against the abutment of the strut-leg. While moving the undercarriage towards the retracted position, the two elements of the brace member are taken out of alignment, and use is made of the movement of one of these two elements relative to the strut-leg to cause the link to push the collar towards the low position, thereby moving the wheels closer together and reducing the spread of the undercarriage. Thus, there is no need for any specific actuator nor for any locking of the collar. During the deployment movement, the link pulls on the collar in order to return it to the high position, thereby splaying apart the wheels and returning them to their landing position.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with a first particular embodiment of the invention, as shown inFIGS. 1 to 4, the undercarriage shown comprises a strut-leg1hinged to the structure of an aircraft about an axis X1so that the undercarriage can move between a deployed position as shown inFIGS. 1 and 2, and a retracted position as shown inFIGS. 3 and 4. The drive actuator is not shown for greater clarity. The bottom portion of the strut-leg1has two arms2hinged thereto about axes X2that are substantially horizontal when the undercarriage is in the deployed position. In this example, the arms2extend forwards and rearwards relative to a direction of advance of the aircraft. In this example, each of the arms2carries an axle3for rotatably receiving two wheels4(the wheels of one of the axles being omitted inFIGS. 1 and 4for greater clarity). Shock absorbers5are coupled respectively between each of the arms2and a collar6extending around the strut-leg1in order to absorb the vertical kinetic energy of the aircraft on landing and in order to filter out ground irregularities while taxiing.

In the invention, the collar6is mounted to slide on the strut-leg1between a high position as shown inFIGS. 1 and 2, in which the collar6bears against a high abutment7of the strut-leg1, and a low position as shown inFIGS. 3 and 4. Sliding of the collar6during the retraction movement has the effect of causing the spread E of the undercarriage when in the deployed position to pass to a spread E′ that is smaller when in the retracted position by moving the wheels closer together, thereby making the undercarriage in the retracted position easier to store in the wheel well.

The collar6may be moved by any actuator means, in particular by a dedicated actuator, which would require an actuation sequence. In a particular provision of the invention, shown in this example, use is made of the relative movement between one of the elements of a brace member10of the strut-leg1for the purpose of moving the collar6. More precisely, in this example the brace member is a folding brace comprising two hinged-together elements11and12, the first element11being hinged to the structure of the aircraft about axis X3and the second element12being hinged to the strut-leg. These two elements11,12come into alignment when the undercarriage is in the deployed position and they are held in alignment by a stabilizer member (not shown). The collar6is coupled to a horn13of the second brace element12by means of a link14in such a manner that in the deployed position, the link14constrains the collar6to be in the immediate proximity of or against the abutment7of the strut-leg1. A resilient member or a slot mechanism may be provided between the link14and the collar6so that forces coming from the wheels bearing against the ground urge the collar6against the abutment7without giving rise to forces in the brace member10that subject it to stress pointlessly.

When moving the undercarriage towards the retracted position, as shown inFIGS. 3 and 4, the elements11and12of the brace member10are taken out of alignment, causing the second element12to turn relative to the strut-leg1. This movement causes the collar6to slide under thrust from the link14towards its low position on the strut-leg1. This sliding has the effect of moving the wheels4closer together, thereby reducing the spread of the undercarriage. The collar6being moved and held by the brace member10makes it possible to omit any dedicated actuator member, or indeed any member for locking the collar.

In a second particular embodiment of the invention, as shown inFIGS. 5 to 7, where references to elements that are common with the above-described embodiment are increased by one hundred, the strut-leg101is still hinged to the structure of the aircraft about an axis X1. In this example it carries two arms102that are hinged to the bottom portion of the strut-leg101, but that extend laterally relative to the direction of advance of the aircraft. In this example, each of the arms102carries an axle103rotatably carrying a single wheel104. In the deployed position in flight, as shown inFIG. 5, the planes of the wheels are oblique; however, as shown inFIG. 6, they straighten up on the ground once the shock absorbers are compressed under the effect of the weight of the aircraft. Shock absorbers105are coupled to the arms102and to a collar106that is mounted to slide on the strut-leg101. As above, the collar106is held in its high position when the undercarriage is in the deployed position, and it is returned to its low position when the undercarriage is in the retracted position, thereby having the effect of reducing the spread of the undercarriage. The position of the collar106is also controlled by the element112of the brace member110, which is hinged to the strut-leg101by means of a link114coupled to the element112and to the collar106for actuation in the same manner.

The invention is applicable to any type of wheel arrangement on the undercarriage.FIGS. 8 and 9show the invention applied to undercarriages having four wheels204,304, each of which is carried by a respective arm. InFIG. 9, two of the arms302extend longitudinally and two of the arms302extend laterally relative to a direction of advance of the aircraft so as to place the wheels304in a cross-configuration. The hinge axes of the arms303on the bottom of the strut-leg301are still substantially horizontal when the undercarriage is in the deployed position, and they extend longitudinally and laterally relative to the direction of advance of the aircraft. InFIG. 8, the arms302extend in directions that are oblique relative to the direction of advance of the aircraft in order to provide arms in a cross-configuration that leads to the wheels204being in a configuration that is more conventional, i.e. like that of a four-wheel bogey. The hinge axes of the arms302on the bottom of the strut-leg201are still substantially horizontal when the undercarriage is in the deployed position, and they extend obliquely relative to a direction of advance of the aircraft. Naturally, the invention may be applied to an undercarriage having six wheels.

In a practical provision, the collar is made out of two parts that are assembled together around a cylindrical portion of the strut-leg. Advantageously, the collar is connected in such a manner as to be capable of sliding without any possibility of turning, e.g. by using a non-circular profile for the cylindrical portion of the strut-leg on which the collar slides.

The invention is not limited to the description above, but on the contrary covers any variant coming within the ambit defined by the claims. In particular, the invention may be applied to an undercarriage leg that is braced by two braces. Furthermore, the collar may be controlled independently of the brace(s). The collar may be held in its high or low position and it may be moved between those positions by any means. In particular, it is possible to use a dedicated actuator and locking means, or indeed to make use of the relative movement between the structure of the aircraft and the strut-leg while the undercarriage is being moved from the deployed position to the retracted position, e.g. by using a connecting rod hinged firstly to the structure of the aircraft and secondly to the collar. In general manner, any other relative movement enabling the collar to move from the high position to the low position could be used. The connection between the collar and the element having the relative movement that is used for moving the collar may be provided by any mechanical means, such as a link or a rack.