Aircraft throttle control device including a cam coupling

An aeroengine control device including a mount and having pivotally mounted thereon a code wheel together with a main lever and a secondary lever, both for turning the code wheel. Each lever is movable between a rest position and a maximum actuation position. The secondary lever is mounted to pivot on the main lever. Cam paths are mounted on the code wheel and on the mount in such a manner that the main lever can move the code wheel when the main lever is moved while the secondary lever is in the rest position. The secondary lever can move the code wheel when the secondary lever is moved while the main lever is in the rest position, with movement of either lever being prevented when the other lever is clearly away from its rest position.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an aeroengine throttle control device.

Brief Discussion of the Related Art

Modern turbojets are fitted with a thrust reversal device that enables a fraction of the exhaust stream leaving the turbojet to be directed towards the front of the turbojet (generally in a direction that makes an angle of about 45° relative to the forward direction of the aircraft) in order to assist the slowing down action of brakes while the aircraft is landing. Various reversal devices are in existence, and in particular devices using doors and devices using grids.

There also exist propeller engines that incorporate a thrust reversal device arranged to reverse propeller pitch.

The cockpit of an aircraft having such an engine is fitted with a throttle control device that enables the pilot to control both the rate at which fuel is admitted into the combustion chamber of the engine, and also the thrust reversal device. For this purpose, the control device comprises a mount having pivotally mounted thereon both a code wheel and a main lever or throttle lever, together with a secondary lever or thrust reversal lever, which levers are arranged to turn the code wheel. The code wheel is associated with sensors connected to an engine control unit. Each lever is movable between a rest position and a maximum actuation position. The thrust reversal lever is hinged to the throttle lever. The assembly comprising both levers is connected to the code wheel via a complex coupling system including an intermediate wheel on the pivot axis of the throttle lever and which is connected to the code wheel. Drive of the intermediate wheel by the levers is under the control of a device that prevents either lever from moving if the other lever is away from its rest position. That device relies on cams, toggle-action parts, or parts having strokes that present cusps, i.e. points where movement is reversed.

In the more elaborate systems, the stroke of each lever includes a transition zone in the immediate vicinity of its rest position. When a lever is in the transition zone and the other lever is moved away from its rest position, the first lever is returned to its rest position.

The coupling system occupies a considerable amount of space and is heavy, in particular because of the intermediate wheel. In addition, the forces transmitted are high and require parts of the coupling system to be dimensioned accordingly, thereby adding to the weight and the volume of the coupling system, particularly since any element in the coupling system between either of the levers and the code wheel must be duplicated in order to ensure the redundancy that is essential for the safety of the device.

SUMMARY OF THE INVENTION

An object of the invention is to provide means making it possible to improve at least some of the above drawbacks.

To this end, the invention provides an aeroengine control device comprising a mount, having pivotally mounted thereon a code wheel together with a main lever, and a secondary lever, both for turning the code wheel, each lever being movable between a rest position and a maximum actuation position, the secondary lever being mounted to pivot on the main lever. A first cam path is formed on a part secured to the code wheel and a second cam path is formed on the mount, the two cam paths having respective facing portions in which there is received a finger that is mounted on the main lever to slide parallel to the code wheel, with a connecting rod permanently connecting the finger to the secondary lever. The cam paths are arranged in such a manner that the main lever can move the code wheel when the main lever is moved while the secondary lever is in its rest position, and the secondary lever can move the code wheel when the secondary lever is moved while the main lever is in its rest position, with movement of either lever being prevented when the other lever is away from its rest position.

Thus, action on the main lever causes the finger to move along a circular arc, thereby directly driving the code wheel, and action on the secondary lever causes the finger to move in a straight line, which movement is transformed by the first cam path into turning of the code wheel. The finger co-operates with the cam paths that are arranged in such a manner that the main lever can drive the code wheel when the main lever is moved while the secondary lever is in the rest position, and the secondary lever can drive the code wheel when the secondary lever is moved while the main lever is in the rest position, with movement of either lever being prevented when the other lever is away from its rest position.

According to a first characteristic, the main lever pivots about the axis of the code wheel and the second cam path includes a first segment that is circularly arcuate about the axis of the code wheel, being of a radius that is determined to allow the main lever to pivot while keeping the secondary lever in the rest position, and a rectilinear second segment extending in a direction that is adapted to allow the secondary lever to move while keeping the main lever in the rest position.

Preferably, the second cam path includes a ramp between the first segment and the second segment, which ramp defines a transition zone in the vicinity of the rest position by acting on the finger in such a manner that when a first one of the levers is in the transition zone, moving the other lever towards its maximum actuation position causes the first lever to return to its rest position.

It is thus possible to move one of the levers while the other lever is close to its rest position, with the other lever then being returned automatically to its rest position.

According to a second characteristic, the first cam path has a first segment arranged to cause the code wheel to pivot when the finger is driven by the secondary lever being moved between its two positions, the first segment having a shape selected from the following group:rectilinear, forming an angle relative to a radial direction of the code wheel; andcurved, with its concave side facing towards the pivot axis of the code wheel.

Advantageously, the first cam path has a second segment extending radially from a periphery of the code wheel to the first segment.

This makes it possible to limit transmission of force from the code wheel to the secondary lever while the code wheel is being moved by the main lever.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The throttle control device described herein is arranged to control both the fuel flow rate and a thrust reversal device of an aeroengine.

With reference toFIGS. 1 to 5, the control device comprises a mount1having a code wheel2pivotally mounted thereon. Sensors100for sensing the angular position of the code wheel2(only shown inFIG. 6) are mounted on the mount1in register with the outline of the code wheel2.

A main lever4is mounted on the mount1to pivot about the same axis as the code wheel2. The main lever4has a radially offset structure with a secondary lever5mounted thereon to pivot about an axis parallel to the axis of rotation of the code wheel2and of the main lever4. Each of the levers4and5pivots between a rest position (shown inFIG. 1for both levers) and a maximum actuation position. The main lever4is a throttle control lever for controlling fuel flow rate, and its maximum actuation position can be seen on the right ofFIG. 1: the pilot pushes the main lever4in order to increase the power delivered by the engine. The secondary lever5is a lever for controlling the thrust reversal device and its maximum actuation position is to the left ofFIG. 1: the pilot pulls on the secondary lever5to obtain maximum thrust reversal.

The secondary lever5pivots on the radially offset structure of the main lever4and is connected directly and permanently by a connecting rod6to a finger3mounted on the main lever4in an oblong slot8therein so as to slide along a radial direction of the code wheel2. In this example, the finger3extends on a side of the pivot axis of the code wheel2that is opposite from the side on which the secondary lever5is located.

A first cam path7is arranged in the code wheel2to receive the finger3slidably. The cam path7has a curved segment7.1with its concave side facing towards the pivot axis of the code wheel2and arranged to transform the sliding of the finger into turning movement of the code wheel2, and a rectilinear segment7.2extending in a radial direction of the code wheel2from the end of the curved segment7.1that is furthest from the center so as to terminate in the vicinity of the periphery of the code wheel2.

A second cam path9is arranged in the mount1to receive the finger3slidably. The cam path9comprises a circularly arcuate segment9.1extending in the vicinity of the periphery of the code wheel2but having a radius that is smaller than the radius of the code wheel2, and a rectilinear segment9.2that extends in a radial direction of the code wheel2and that is connected to the circularly arcuate segment9.1by a ramp9.3.

Whatever the position of the code wheel2relative to the mount1, the cam paths7and9have portions that face each other and that receive the finger3.

When the code wheel2is in its position common to the rest positions of both levers4and5(seeFIG. 1), the finger3is in the rectilinear segments7.2and9.2, facing the ramp9.3.

From this position of the code wheel2that is common to the rest positions of both levers, the main lever4may be moved towards its maximum actuation position (FIGS. 2 and 3). By doing this, the finger3is engaged in the circularly arcuate segment9.1while remaining engaged in the rectilinear segment7.2so that the finger3moves along a circular arc and turns the code wheel2. The circularly arcuate segment9.1prevents the finger3from moving towards the pivot axis of the code wheel2and thus prevents any movement of the secondary lever5away from its rest position.

From the position of the code wheel2that is common to the rest positions of both levers, the secondary lever5may be moved towards its maximum actuation position (FIG. 4). In so doing, the finger3is engaged in the curved segment7.1while remaining engaged in the rectilinear segment9.2, such that the finger3moves in a straight line with this being transformed into turning movement of the code wheel2by the curved segment7.1. The rectilinear segment9.2prevents any angular movement of the finger3and thus prevents any movement of the main lever4away from its rest position.

The ramp9.3serves to define a transition zone: when the finger3is level with the ramp9.3, then the main lever4and/or the secondary lever5is in the vicinity of its respective rest position. When either lever4or5is moved towards its maximum actuation position, the ramp9.3serves to bring the other lever5or4into its rest position while the movement of the first lever4or5continues (FIG. 5).

The angle of inclination and the size of the ramp9.3serve to determine the extent of the transition zone for each of the levers. Thus, for example:if the main lever4is offset through less than two degrees relative to its rest position, any movement of the secondary lever5away from its rest position causes the main lever4to return to its rest position; andif the secondary lever5is offset by less than fifteen degrees from its rest position, any movement of the main lever4away from its rest position causes the secondary lever5to be returned to its rest position.

The curvature of the curved segment7.1enables the pivoting of the code wheel2to be adapted to the stroke of the finger3.

Elements that are identical or analogous to those described above are given the same numerical references in the description below of the second embodiment.

With reference toFIGS. 6 to 8, the control device in the second embodiment comprises, as above, a mount1, a code wheel2, levers4and5, a connecting rod6connecting the secondary lever5to a finger3received in a slot8in the main lever4, and cam paths7and9formed respectively on the code wheel2and on the mount1.

In this embodiment, the slot8lies between the pivot axis of the main lever4and the secondary lever5, thereby leaving the bottom of the code wheel2free for engaging the sensors100(shown inFIG. 6).

The curved segment7.1lies in the vicinity of the periphery of the code wheel2. The curvature of this segment defines the pivoting performed by the code wheel2as a function of radial movement of the finger3. The rectilinear segment7.2receives the finger3when the main lever4is used for moving the code wheel2. The finger3is then in contact with one or the other of the substantially radial faces of the rectilinear segment7.1, thereby facilitating the transmission of force from the finger3to the code wheel2when the main lever4is actuated (FIG. 6, the maximum actuation position of the main lever4is to the left).

The cam path9has the same shape as above.

The movement of the code wheel2under drive from the main lever4can be seen inFIG. 6. The movement of the code wheel2under drive from the secondary lever5can be seen inFIG. 7(the beginning of the movement is shown inFIG. 8).

In the variant ofFIG. 9, the cam path7has a first rectilinear segment7.1at an angle relative to the second rectilinear segment7.2that extends in a radial direction relative to the code wheel2. The segment7.1, which is made rectilinear in contrast with the above-described variant so that it is easier to make, is oriented in such a manner as to transform the radial sliding of the finger3into pivoting of the code wheel2(FIG. 9c).

The rest positions of the levers and the actuation of the main lever4can be seen inFIGS. 9aand9b.

In the variant ofFIG. 10, the slot8forms an angle relative to the radial direction of the code wheel2, and the rectilinear slot9.2forms an identical angle relative to the radial direction of the code wheel2when the main lever4is in its rest position.

The angle serves to adjust the pivoting movement of the code wheel2as a function of the stroke of the secondary lever5.

Naturally, the invention is not limited to the embodiment described but covers any variant coming within the ambit of the invention as defined by the claims.

In particular, the invention may be obtained by combining characteristics from the above-described embodiments and variants.

The main lever may have two side plates between which the secondary lever and the connecting rod are mounted.