Control Apparatus

For a better understanding of the invention and to show how the same may be carried into effect, reference will be made, by way of example, to the accompanying drawings in which:

FIG. 1 is a sectional diagrammatic view of an aircraft throttle-box, and

FIGS. 2 to 5 are diagrammatic views of respective actuators for use in or in association with aircraft throttle-boxes.

FIG. 1 shows an aircraft throttle-box comprising a rectangular enclosure 1 with a slotted top from which protrudes a handle 2. Within the enclosure 1 there is a ball-screw and rotary stepper motor assembly including a fixed helically grooved shaft 3 on which there is mounted a co-acting recirculating ball-nut 4. As is known, the nut of a ball-screw comprises a cage holding a series of balls 11 which are engaged in the groove of the shaft 3 and which are guided by the cage along a continuous or recirculating path. A ball-screw acts in just the same way as an ordinary threaded lead-screw and nut--the balls together act like the thread of the ordinary nut to transmit motion between the nut and the screw-shaft but because the balls are able to roll within the shaft-groove, the ball-screw may have a very low coefficient of friction such that, for a much finer thread pitch than the case with an ordinary lead-screw assembly, the ball screw is reversible in the sense that, if the nut thereof is pushed along the shaft, it will move either by rotating itself around the shaft or by rotating the shaft. In the present case, the ball-nut 4 is fixed within, or is formed as an integral part of, the rotor 5 of an electrical stepper motor 10 which also comprises a stator 6. The stator is supported with respect to the rotor by thrust transmissive bearings 7. The inner end of the handle 2 is fixed to the stator 6. The motor windings are connected to an electronic motor drive and control output unit 8. The throttle-box also includes any suitable means for signalling to unit 8 the position along shaft 3 of the movable part of the ball-screw and motor assembly. This can be by use of any suitable ones of the encoding methods and devices described in our UK patent No. 2,O73,887B and UK patent No. 2,114,717A, or by any other suitable device. For example, a rotary or linear position encoder 9 could be provided as part of the ball-nut and motor assembly.

During manual throttle operation of the aircraft, the handle 2 is moved back and forth along the shaft 3 carrying with it the motor and ball-nut, the ball-nut and motor rotor rotating with respect to the motor stator to permit this rotary movement. The movement is translated to a control signal acting on the engine throttle(s) either electrically by way of the position encoder 9 and unit 8, or any suitable kind of mechanical output could be provided, for example a simple Bowden cable arrangement coupled to the motor. The motor can be energised during such manual operation to give a predetermined `feel` resistance to the movement and/or to generate marked detents at certain positions just as described in the aforementioned patent and patent application. In auto-throttle mode, the motor is powered to a level sufficient to produce rotation of the rotor and ball-nut and hence driven movement of the motor and handle 2 along the shaft 3. At any time during the auto-throttle mode, either when the motor is being electrically moved or when it is being electrically held in a position to which it has been moved, the motor force can be overcome by the pilot if he wishes without having to disconnect or de-clutch the motor.

The handle 2 could be replaced by a lever of which one end protrudes from enclosure 1, the other end is pivotably connected to the enclosure at a point below the shaft 3 and motor, and which is pivotably coupled at an intermediate point to the motor stator. This gives a quadrant movement of the protruding portion of the lever but the operation is otherwise the same as for the illustrated embodiment.

The apparatus shown could be used for other applications, as well as for aircraft throttle control, either on-board an aircraft to control say wing sweep or the like, or elsewhere, for example to control valves, and like equipment in the factory.

Instead of being constructed as a control box with an operator's handle, apparatus according to the invention could be in the form of an actuator unit which can be incorporated in or added to some existing manual control device to give that device a servo or automatic operating capability if it does not already have one or simply so as to provide for electrically generated `feel` resistance and/or detents to the manual movement. FIGS. 2, 3, 4 and 5 illustrate respective actuator units which could be incorporated into the design of aircraft auto-throttle-boxes or retro-fitted to an existing manual throttle-box.

In FIG. 2, an assembly of a rotary stepper motor 20 and rotary position encoder 27 is fitted in one end of a cylindrical housing 21, the motor shaft 22 being formed as the lead-screw of a recirculating ball-screw which also comprises a ball-nut 23. The nut 23 is fixed to one end of a hollow, elongate actuator output member 24 which is able to slide within, and the other end of which protrudes from, housing 21, this other end being adapted (for example by comprising an eyelet 26 as shown) for coupling to the handle of a throttle-box either locally or elsewhere in the mechanical transmission between the handle and engine throttle. The motor and encoder are coupled to an electronic motor drive and interface unit 25.

The FIG. 3 actuator comprises an output member 34 with an eyelet 36, a ball-screw shaft 31 and ball-nut 33 arranged in a housing 35 in a manner similar to that shown in FIG. 2 except that, in FIG. 3, the assembly of a motor 30 and encoder 37 is mounted below the ball-screw shaft 31 and is coupled thereto by gears 32.

In FIG. 4, the motor 40, position encoder 41 and ball-nut 42 form an integral assembly like that in FIG. 1. Here, however, the ball-screw shaft 43 is able to move linearly with respect to a housing 45, but not rotate, while the motor stator is fixed with respect to the housing 45. Rotation of the motor rotor and ball-nut thus move the shaft 43 and the attached actuator output member 44 with its eyelet 46 linearly.

In FIG. 5, the actuator output member 50 has an eyelet 59 at one end and its other end connected to a shaft 51 which also supports a gear wheel 52 in engagement with respective further gear wheels 53 and 54 on the shafts of a rotary stepper motor 55 and a position encoder 56, both of which are connected to an electronics unit 57 as before. In this case, the actuator output member 50 has a quadrant movement as shown by arrows 58.