GB2311874A - Scrollers - Google Patents

Abstract

A scroller selects for display a particular frame or area 12 of a flexible strip 11 wound onto a pair of drivable rollers 10. The scroller may be used, for example, for stage lighting purposes for positioning different coloured gels in front of a light source. Each roller 10 is associated with an independent indexable motor, control means, preferably in the form of a circuit board providing power and control electronics to control the motor, and position sensing means, such as a hall effect device, in order to control the positioning of the roller 10.

Description

IMPROVEMENTS IN SCROLLERS The invention relates to improvements in scrolling arrangements used, say, for scrolling coloured gels into position.

It is frequently required in many lighting applications, particularly in entertainment lighting used in the theatre, concerts, for displays and their architectural applications, to control the colour of light. The most common way to do this is by placing a flexible coloured plastic gel in front of the light source. In older equipment, the gels had to be changed manually to change the colour of the light, but a number of techniques have been used in recent years to change the gel, and therefore the colour, by remote control. One of the most popular in most recent years is a colour scroller in which a number of, usually, rectangular panels of gel of different colours are spliced together to form a long strip.

The strip is held between two rollers on which its ends are wound. These two rollers are mounted to the front of a light fitting, in the path of the light, and are rotated by a motor arrangement. By rotating the rollers to wind the gel strip from one to another, it is possible to position any desired section of the gel strip in front of the light source and to select thereby the appropriate colour. Conventional scrollers are driven by one motor which drives both rollers through a sprung belt arrangement to maintain tension in the gel strip.

This general arrangement is popular as it allows a large number of different shades of gel to be held in a compact space and selected from, as the user requires. There are a large number of scroller types available which differ not only in the size and type of light source there designed to fit onto, but also in the control techniques and the arranagement of the motor drive.

The invention relates to an improved technique for control of the roller position in such an arrangement and preferably also the tension in the strip.

According to the invention there is therefore provided a scroller for selecting for display a particular frame or area of a flexible strip wound onto a pair of driveable rollers, each roller being associated with an independent indexable motor, further comprising control means, position sensing means associated with each motor and connected to the control means to provide a signal relating to the operation and/or position of each motor.

The invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a pictorial view of the innards of a typical colour scroller; Fig. 2 is a pictorial view of a typical colour scroller mounted to the front of a light fitting, with parts omitted for clarity; Fig. 3 is a schematic of a motor drive used in the scroller of the present invention; Figs. 4 and 5 are schematic representations showing the tape markers used in the scroller of the present invention.

Referring to Figs. 1 and 2, a typical colour scroller 14 is illustrated having a pair of rollers 10 onto which a strip or string of gel 11 is wound. The gel string 11 is made up of a plurality of frames 12 of different translucent coloured gels.

The arrangement shown in Fig. 1 is mounted in a housing 13 as shown in Fig. 2 to form the scroller 14.

The housing 13 has an aperture 15 in both sides through which a light source 16 is directed through gel string 11. The scroller 14 has appropriate fittings to allow it to be attached to the front of the light source 16.

According to the present invention each of the rollers 10 is driven directly by a separate indexable motor, preferably a brushless DC servo motor which are advantageous in that they are usually very quiet in operation, which is mounted on the same axis as the roller and coupled directly thereto. Control means 17 are provided, preferably in the form of a circuit board providing power and control electronics, to control the motors. The motors are provided with position sensors 22, such as Hall Effect or other devices which may be inbuilt, and these are connected to the control means. The combination of the indexable motor with sensing feedback may be used:a) to commutate the motor coils thereby allowing the motor to run continuously (this is the normal mode of operation of a brushless DC motor; b) to index the motor positively to a predetermined position in the manner of a stepper motor but with the additional benefit of confirmation feedback and c) to indicate the number of revolutions or partial revolutions that the motor turns from an initial starting point.t the motor turns from an initial starting point.

The general combination of three motor coils 19 (see Fig. 3) and a pair of poles N-S on each rotor give a combination of six possible electrically determined index positions for each rotor in which it is in static equalibrium. Thus nine possible operating conditions are provided:1. Rotor stationary in position 1 2. Rotor stationary in position 2 3. Rotor stationary in position 3 4. Rotor stationary in position 4 5. Rotor stationary in position 5 6. Rotor stationary in position 6 7. Rotor running clockwise (electronically commutated) 8. Rotor running anti-clockwise (electronically comutated) 9. Electromagnetic braking by connecting the ends of the coil together.

Motors may be used which have more than one pair of poles in which case the final number of rotor positions that can be achieved increases. However, the principle of operation is the same as if the motor has one pair of poles.

The scroller 14 is preferably calibrated before operation to establish the reference point for the motors. The gel string 11 is driven to one of its ends. In the example illustrated, as shown in Fig. 4, each colour frame 12 is marked by a marker, such as a piece of tape 20. The marker may be adjacent the frame edge 12a or in another appropriate position.

The tape 20 causes an optical sensor 21, mounted on the scroller 14, to send a signal to the control means 17. Various alternative sensors/marker combinations may be used in the present invention, e.g. reflective optical or magnetic systems and so on. The end of the gel string 12b is marked by a further marker, such as two tapes 20 in close succession or an extra wide tape. This provides the reference point for the motors. The gel string 11 is then driven to the opposition end, also indicated by two tapes 20, the logic circuit of the control means 17 notes the rotor position via the feedback signal from the motor position sensors 22. The position of each frame 12 is calculated in terms of the number of motor revolutions or partial revolutions from the reference position and the number of colours in the gel string 11 is also calculated as a part of this process.

In use, when instructed to move to a particular colour by control software, the logic circuit of the control means 17 calculates the number of revolutions or partial revolutions that each motor is required to be moved from the current position and drives the motors to the required positions. As the gel string 11 passes the optical sensor 21 the signals from the optical sensor 21 are fed back to the control means 17 and used as a check on the position stored by the logic circuitry. When the desired motor positions are reached, each rotor is held stationary.

During operation both when static and in motion, the tension of the gel string 11 is maintained by driving the motors in opposition to each other, or at different speeds, by driving the trailing roller at a lower rate than the leading one.

Thus the use of brush less motors allows a combination of servo drive and stepping drive techniques with positional feedback to control the position and speed of movement of the gel. This positive indexing can be provided with smooth tension control and fast movements, features of stepper and servo motors respectively with the additional benefit of incremental position feedback. A combination of digital and analogue electronics is used to process the position of sensing information and provide the appropriate drive to the motor coils. Algorithims are used to control the two motors in so far as the position and tension of the rollers 10 is required.

The use of two independent small motors which can be directly coupled to the rollers, allows a large part of the motor to be placed within the roller.

This provides considerable space saving and a reduction in mechanical complexity over the previously used system of springs and linked drives to allow both rollers to be driven by one motor. However, the invention may also be used in certain applications with the motor linked to the rollers by other methods, e.g. a belt drive whilst still retaining the advantage of the invention.

Alternatively stepper motors may be used with a well matched position encoder "bolted on". This would effectively provide a brushless DC motor.

Although the invention has been described mainly with reference to use as a colour scroller for scrolling gel strings, it may be used in other applications involved in the display of a particular frame or area of a flexible strip, e.g. film etc.

Claims (14)

CLAIMS:

1. A scroller for selecting for display a particular frame or area of a flexible strip wound onto a pair of driveable rollers, each roller being associated with an independent indexable motor, further comprising control means, position sensing means associated with each motor and connected to the control means to provide a signal relating to the operation and/or position of each motor.

2. A scroller as claimed in claim 1 in which each roller is mounted on an axis and the motors are also mounted on said axes and coupled directly to the rollers.

3. A scroller as claimed in claim 1 in which the motors are coupled indirectly to said rollers.

4. A scroller as claimed in any one of the preceding claims in which the signal from each position sensing means is used by the control means to control the electronic commutation of the coils of the motors, and/or to provide a plurality of discrete positions of the rotors of each of the motors.

5. A scroller as claimed in any one of the preceding claims in which the frames or areas of the strip are marked by at least one marker, the scroller further comprising marker sensing means connected to the control means to provide a signal relating to the presence of a marker.

6. A scroller as claimed in any one of the preceding claims in which differential drive of the two rollers is used to maintain tension in the strip.

7. A scroller as claimed in any one of the preceding claims in which the motors are brush less DC servo motors.

8. A scroller as claimed in any one of the preceding claims in which the control means provide power to and control electronics for the motors.

9. A scroller as claimed in any one of the preceding claims in which the motor position sensing means of each motor provide a signal relating to the number of revolutions turned by the motor from a reference point.

10. A scroller as claimed in any one of the preceding claims in which calibration of the scroller enables the position of a particular area or frame of the strip to be calculated by the control means in terms of a number of motor revolutions to be turned from a reference point.

11. A method of selecting for display a particular frame or area of a flexible strip wound onto a pair of driveable rollers, each driven by an independent indexable motor with associated position sensing means, comprising the steps of sensing the starting position of each of the motors, electronically calculating from this information and stored information relating to the position of various frames or areas on the strip the number of revolutions for each motor to turn to move the strip to the required position, driving the motors to turn them either continuously or to index them to a predetermined position or by turning the calculated number of revolutions, and checking the actual position of the strip by detecting markers on the strip having the frames or areas thereof.

12. A method as claimed in claim 11 in which the motors are driven in opposition to each other to maintain tension of the flexible strip.

13. A method as claimed in claim 11 in which the motors are driven at different speeds, to maintain tension of the flexible strip.

14. A scroller substantially as hereinbefore described with reference to and as shown in the accompanying drawings.