GB2076602A

GB2076602A - Control Unit

Info

Publication number: GB2076602A
Application number: GB8114284A
Authority: GB
Original assignee: Smiths Group PLC
Current assignee: Smiths Group PLC
Priority date: 1980-05-08
Filing date: 1981-05-11
Publication date: 1981-12-02
Also published as: GB2076602B

Abstract

A manually-actuable control unit has a linearly-movable handle 1a connected to a flexible loop 2 that extends around drums 30, 31 and is optionally encoded with alternate transparent and opaque regions that are illuminated by LED's, transmitted light being sensed by photoelectric cells to give an output indicative of the position of the handle. <IMAGE>

Description

SPECIFICATION Control Units This invention relates to control units. The invention is more particularly concerned with control units having a manually-actuable handle that is moved to a location along a linear path in accordance with a demanded value.

Control units are known in which the position of a moveable member is determined by means of an optically-encoded rigid element in the form of a strip having transparent and opaque regions.

The element is arranged to be moved with respect to a sensing head having an array of radiation sources on one side of the strip and an array of radiation sensors on the other side, so that the opaque regions prevent radiation falling on some of the sensors. By determining which of the sensors are obscured by the encoded element, the position of the element, and hence the moveable member, can be determined. One disadvantage of such an arrangement is that the encoded element must be at least as long as the path of travel of the moveable member, since every location along its path must have an associated encoding. With conventional encoded elements, the control unit must therefore have a casing that is at least twice the length of the path of travel of the moveable member so as to accommodate full displacement of the encoded element.This can of course be a disadvantage where the unit is for mounting in a confined space.

In order to overcome the need to make the control unit large enough to accommodate displacement of a linear element it has been proposed to use a disc having optically-encoded sectors on its surface. The disc is coupled to the moveable member through suitable gearing so that linear displacement of the moveable member causes corresponding rotation of the disc. Such an arrangement has the advantage of avoiding the need to accommodate such large linear displacement but it does have the disadvantage of the additional complexity, cost and weight of the gears, and leads to an additional loading on the moveable member which may not be desirable.

It is an object of the present invention to provide a control unit that substantially avoids the above-mentioned disadvantages.

According to one aspect of the present invention there is provided a control unit of the kind having an operator-actuable member that is arranged for displacement by the operator along a linear path, wherein said member is connected to a flexible strip such that said strip is displaced along its length in accordance with displacement of said operator-actuable member, said strip being guided away from the path towards the ends of the path, wherein said strip has an encoded area extending along a part at least of its length, and wherein said control unit includes sensing means arranged to co-operate with said encoded area such as to enable the position of said strip, and hence of said operator-actuable member to be determined.

By using a flexible strip that is guided away from the path of the operator-actuable member at an end of the path, the member can be displaced to either end of the path without any hindrance to movement from the encoded strip and the control unit need therefore only be substantially as long as the path of travel of the moveable member.

The encoded strip may be in the form of a continuous loop, the guide means being provided by two rollers located at opposite ends of said path. In such an arrangement, the operator actuabie member may be connected to said strip on one side of the loop, and the sensing means may be mounted to co-operate with the strip on the other side of the loop.

An aircraft throttle control, in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a cross-sectional side elevation showing the control unit; Figure 2 is a sectional view across the width of the control unit on the line Il-Il: Figures 3 and 4 show parts of the control unit in greater detail and to a larger scale; and Figures 5, 6 and 7 show schematically alternative forms of control unit.

With reference to Figures 1 and 2, there is shown a control unit having a moveable coupling member 1 the upper part of which has a handle 1 a, the lower part being secured to a flexible strip 2. The strip 2 is optically-encoded and extends through a sensing head 3.

The control unit has an elongate outer casing 10 of rectangular shape that is provided in its upper surface with a groove 11. The upper part of the coupling member 1 projects through and is supported by the groove 11 so that it is free to slide along the linear path defined by the groove.

Secured to the lower part of the coupling member 1 there is a clamping plate 12 that clamps the strip 2 to the coupling member. In the present embodiment, the strip 2 is formed into a continuous loop by having both ends secured between the coupling member 1 and the clamping plate 12. Alternatively, the strip 2 itself might be a continuous loop formed by any wellknown method.

With reference particularly to Figure 4, the strip 2 is of transparent polyster and is formed along approximately half its length with an opticallyencoded area 20. The area 20 is formed on the outer surface of the loop by photographic means and comprises eight parallel tracks 21A to 21 H, Each track is divided into alternate transparent and opaque regions 22 representing an eight-bit gray code, with a ninth track 211 representing a parity check. The strip 2 extends along the length of the control unit and around two horizontal drums 30 and 31 mounted for free rotation at opposite ends of the casing 10.

The sensing head 3 has an array 4 (Figure 3) of light-emitting elements and an array 5 of lightresponsive elements. The sensing head 3 is mounted at the lower part of the casing 10 so that the lower part of the loop formed from the strip 2 extends through it. The array 4 of lightemitting elements has nine light-emitting diodes 40 arranged at spaced intervals in a row along its length and across the width of the strip 2. The array 4 directs light downwardly through the strip 2 to the array 5 of light-responsive elements.

Power is supplied to the diodes 40 from a supply unit 6. The array 5 of light-responsive elements has nine photoelectric cells 41 located opposite respective diodes 40 so as to receive light transmitted through the strip 2. The output from the cells 41 are supplied via respective cables 42 to an amplifying and output unit 43 where the signals are amplified and processed to a suitable form of analogue or digital output as required.

When the coupling member 1 is moved along its path to the left of the control unit, the upper part of the strip 2 is guided around the drums 30 and 31 away from the path of travel of the coupling member. The lower part of the loop will be moved, in the opposite direction, by the same distance as the coupling member 1, thereby causing different regions 22 of the encoded area 20 to be brought through the sensing head 3 and thereby altering the output from the unit 43 so as to give a representation of position.

It will be appreciated that the strip need not be of polyster but could be of any transparent material or even of an opaque material through which apertures could be cut to form transparent regions.

The array 5 of light-responsive elements 41 could be arranged to be responsive to radiation reflected from the strip 2 rather than radiation transmitted through it. In this arrangement, the strip would be opaque and provided with an area of reflective and non-reflective regions of the same configuration as shown in Figure 4; the arrays 4 and 5 of light-emitting and lightresponsive elements 40 and 41 would both be mounted on the same side of the strip.

Two optical sensing heads could be used to provide redundancy in the event of failure of one head. The sensing heads could be mounted at different locations along the same encoded area 20, or two separate encoded areas could be provided for use with the respective heads. The light-emitting and receiving elements could be provided by the ends of optical fibres connected to light sources and detectors mounted remote from the transducer itself.

To accommodate for stretching of the strip 2, and differential thermal expansion, the strip may be held in tension. This could be done by having one or other of the drums 30 or 31 resiliently urged away from the other roller. Alternatively, the coupling member 1 could include some form of tensioning device applying resilient force to the strip.

The sensing head 3 could operate in the ultraviolet, visible or infra-red regions or could include detectors and emitters of sub-atomic particles or other radiation.

Instead of using the absolute form of optical encoding described above and shown in Figure 4, where every location along the length of the encoded area has its own uniquely identifiable code, an incremental form of coding could be used. In such an incremental coding, the code might take the form of a single track of alternate opaque and transparent regions in the same manner as any one of the tracks 21 A to 21 H shown in Figure 4. The position of the strip would be determined by means of a counter, the count of which is incremented or decremented as the strip is moved past the sensing head. In order to determine the direction of movement, the sensor head would preferably have two sensing units spaced from one another along the length of the encoded strip such that the direction of travel could be determined by observing the relationship of the outputs from the two units.

It is not essential that the flexible strip carrying the optical encoding has its ends joined to form a loop in the manner shown in Figure 1. In, for example, Figure 5, there is shown a strip 50 that extends around two rollers 51 and 52 but which has its ends 53 and 54 connected to one end of respective springs 55 and 56, the other ends 57 and 58 of which are secured to the control unit casing. Such an arrangement could provide a return force on the coupling member 1 urging it to a predetermined position. Alternatively, only one roller and one spring need be used.

In Figure 6 there is shown a flexible encoded strip 60 that has its ends wound about respective rollers 61 and 62. Spiral springs 63 and 64 respectively are coupled with the rollers 61 and 62 to urge them in an anti-clockwise and a clockwise direction respectively.

In Figure 7, the flexible strip 70 is of a spring steel or like material that is relatively stiff axially but can be bent about its length. To increase the axial stiffness of the strip 70 it may be made to take up a curved shape across its width. The strip 70 extends between suitably shaped guide plates 71 that may be provided where necessary with windows 72 to enable observation of the strip by the sensor head 3. Displacement of the coupling member 1 causes the strip 70 to slide between the guide plates 71.

It will be appreciated that various alternative configurations could be used employing an encoded flexible strip in the manner of the present invention so as to provide a control unit of compact form.

Claims

1. A control unit of the kind having an operator-actuable member that is arranged for displacement by the operator along a linear path, wherein said member is connected to a flexible strip such that said strip is displaced along its length in accordance with displacement of said operator-actuable member, said strip being guided away from the path towards the ends of the path, wherein said strip has an encoded area extending along a part at least of its length, and wherein said control unit includes sensing means arranged to co-operate with said encoded area such as to enable the position of said strip, and hence of said operator-actuable member to be determined.

2. A control unit according to Claim 1, wherein said unit includes rotatable drum means mounted at the ends of the path, said encoded strip being guided around said drum means.

3. A control unit according to Claim 2, wherein said drum means are urged resiliently away from one another so as to apply tension to said strip.

4. A control unit according to any one of Claims 1 to 3, wherein said encoded strip is in the form of a continuous loop.

5. A control unit according to Claim 4, wherein said operator-actuable member is connected to said strip on one side of said loop, and wherein said sensing means is mounted to co-operate with the strip on the other side of the loop.

6. A control unit according to any one of the preceding claims, wherein said strip is optically encoded and said sensing means includes optical sensing means.

7. A control unit according to Claim 6, wherein said strip is encoded with alternate opticallytransparent and optically-opaque regions, said sensing means being arranged to respond to radiation transmitted through said transparent regions.

8. A control unit according to any one of the preceding claims, wherein said path is substantially straight.

9. A control unit according to any one of the preceding claims, wherein said operator-actuable member is a manually-actuable member.

10. An aircraft throttle control unit according to Claim 9, wherein said manually-actuable member is a throttle lever that is positioned in accordance with the desired throttle setting.

11. A control unit substantially as hereinbefore described with reference to Figures 1 to 4 of the accompanying drawings.

12. A control unit substantially as hereinbefore described with reference to Figures 2 to 3, and any one of Figures 5 to 7 of the accompanying drawings.