GB1574387A

GB1574387A - Light signalling devices

Info

Publication number: GB1574387A
Application number: GB2266/77A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1976-01-28
Filing date: 1977-01-20
Publication date: 1980-09-03
Also published as: DE2702823A1; NL7700912A; FR2339922A1; CH601880A5; FR2339922B1; LU76643A1; BE850456A

Description

(54) IMPROVEMENTS IN AND RELATING TO LIGHT SIGNALLING DEVICES (71) 1, HENRI BOURBLON of 3 bix rue du Transvaal 92, Boulogne, S. Seine; France. A French citizen, do hereby declare the invention, for which I pray that a patent may be granted to me, and the method by which it is to performed, to be particularly described in and by the following statement:- The present invention relates to lightsignalling devices.

According to the invention there is provided a signalling device comprising as array of electroluminescent diodes, control means for energising the diodes and a cover covering the array, the cover having a plurality of lens elements, each lens element being associated with a corresponding diode to modify the divergence and/or the direction of the light beam produced by the diode.

According to the invention there is further provided a signalling device comprising an array of electroluminescent diodes arranged in a plurality of separate groups, control means for energising each group of diodes in succession so that each diode draws a peak current substantially higher than the rated current for the diodes under continuous energisation, and a cover covering the array, the cover defining a plurality of lens elements, each lens element being positioned to control the width and direction of the beam of light emitted by a corresponding diode.

A light-signalling device embodying the invention will now be described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front elevation of the device with the cover removed; Figure 2 is a section taken on the line AA of Fig. 1; Figure 3 is a block diagram of the control circuit of the device; and Figure 4 is a time chart illustrating the energisation of successive groups of diodes.

The light-signalling device 10 shown in Figure 1 Is arranged to transmit an optical warning signal indicating the presence of an obstacle, or the presence of a dangerous passage. The device can also be used in traffic lights. As one of a group of three traffic lights the device is of circular configuration. In a modification the device can be of triangular or rectangular configuration.

The device includes a circular printed circuit board 100 having a central area 11 carrying an array of light-emitting diodes 120. The array includes one hundred and twenty-eight electro-luminscent diodes 120, divided into sixteen groups 101 to 116 each of eight diodes.

The printed circuit 100 carries a cover 13 of transparent or translucent plastics material and which encloses array of diodes. The cover is profiled to form an array of lens elements 130 each associated with a corresponding diode.

Each lens element 130 is formed by a small spherical cap moulded into the outer surface of the cover. The centre of each lens element is aligned with the luminous junction of its corresponding diode 130.

Each lens element is arranged to deflect the light rays from its corresponding diode to form a beam. The beam can have a smaller or greater divergence as required.

Advantageously, the printed circuit is planar, the light junctions of the diodes all lie in a common plane extending parallel to the printed circuit board, and all the lens elements lie in another common plane parallel to the other two planes.

The interconnection of the diodes 120 into sixteen groups of eight is made on the printed circuit board itself. Preferably, each group of diodes comprises two sets of four diodes in which the diodes of each set are connected in series, and the two sets are connected in parallel. The groups of diodes are connected to a diode control circuit 40 located under the printed circuit board.

Finally, a bottom 15 encloses the underside of the printed circuit board 100; both the cover 13, and the bottom 15 forming a tight seal with the printed circuit 100.

As shown in Figure 3, a supply unit is fed with an AC supply voltage of 48 volts, a voltage which is lower than the traditional 110 or 220V used for traffic lights.

The supply unit 140, rectifies and filters the 48V AC voltage and provides at first output 141 a 12V fixed voltage. The fixed output voltage feeds a clock pulse generator 142, a counter 143, and a decoder 144. A second output 145 of the supply unit 140 supplies a DC voltage which varies between 0 and 28 volts. The variable output voltage is fed to one input terminal of each group of diodes.

The clock pulse generator 142 supplies clock pulses at a frequency of 800 Hz to the 4-bit binary counter 143. This counter 143 therefore will count repetitively from zero to 15, that is through sixteen different states.

The four stages of the counter 143 are connected in parallel to four inputs of the decoder 144. The decoder 144 has sixteen outputs 1 to 16 of which one, and only one, will be energised at any one time according to the instantaneous count of the counter 143.

The sixteen outputs of the decoder 144 are connected to respective ones of sixteen switching stages 146. Each switching stage (only one shown) has two transistors 1460 and 1461, which are connected in Darlington configuration. The base of the transistor 1460 is connected to a corresponding output of the decoder 144, and the collector of the transistor 1461 is connected to the other terminal of a corresponding group of diodes.

On the first line of the time chart of Figure 4 will be seen that the clock pulse generator 142 produces a cycle of sixteen clock pulses over a period of 20 milliseconds; the first three pulses 17, 18 and 19 of the second cycle are also shown.

The second line of Figure 4 indicates the period over which the first group of eight diodes No. 101 is excited from the start of the first clock pulse until the start of the second.

The third and subsequent lines of Figure 4 indicate the excitation period of corresponding groups of diodes ending with the sixteenth, diode group No. 116 which is excited from the start of clock pulse No. 16 until the start of the clock pulse No. 17. The cycle is then repeated.

For each diode group, illumination lasts about 1.25 milliseconds and is repeated once every 20 milliseconds. Under these conditions an observer viewing through the human eye will perceive a constant illumination, because of retinal persistance.

Moreover, while ordinary diodes are rated to tolerate an average current of 15 miffiamperes during continuous energisation without significantly effecting the life of the diodes, it is possible the diodes can sustain a peak current of 250 milliamperes during their brief period of ignition, without significantly affecting their life. Thus, the observer will perceive a higher luminous intensity from each diode corresponding to that produced by the peak current of 250 milliamperes.

Thus by operating the diodes at a high peak current a signalling device is provided having the reliability associated with electroluminescent diodes, having a high light output and having a low consumption of electricity.

There is added to that the fact that it is possible to provide a low voltage alternating current supply which has numerous advantages for traffic lights. Finally, by varying the voltage available at the output of the supply unit 140 between 0 and 28 volts the brilliance of the diode output can be readily adjusted according to whether it is day or night.

Each of the electroluminescent diodes thus provides a source of illumination of about 0.6 to 1 mcd in a beam having a beam angle of about 30 , the beam angle being modified by the lens elements 32 of the cover 13.

Currently available electroluminescent diodes are guaranteed for a working life of about 100,000 hours without an appreciable loss of light flux. Moreover, diodes in the majority of cases are self-short-circuiting, that is to say when they break down they do not normally suffer a break of the contact between their electrodes. Thus the expiry of a diode will not prevent the others in its group from operating. Even if a diode upon breakdown were to open circuit then only one chain of four diodes in the group would remain extinguished, and all the others would be free of operate. It will then be appreciated that apart from the facet of long life the signalling device has a structure which exhibits a good impact resistance, which is advantageous during storage, fitting, and in use (vehicle colliding into same). Finally the power consumed by the diodes is relatively low (of the order of a few watts in the above example).

The long service life of the signalling device described makes it especially suitable for sealing or permanently fixing the device in a building construction (for traffic indication purposes, for example).

The device can be partly buried or fixed permanently at a particular spot on the highway to signal a sharp bend or a particularly dangerous crossing.

The colour of the light output is dependent upon the type of diode chosen.

Also it will be appreciated that the lens elements can be appropriately chosen to give the beam output from each diode a particular directivity or to establish a uniform dispersion of light.

WHAT I CLAIM IS: 1. A signalling device comprising an array of electroluminescent diodes, control means for energising the diodes and a cover covering the array, the cover having a plurality of lens elements, each lens element being associated with a corresponding diode to modify the divergence and/or the direction of the light beam produced by the diode.

2. A device according to claim 1, wherein each lens element comprises a spherical lens.

3. A device according to claim 1 or to claim 2, including a printed circuit board supporting the diodes so that they all lie in substantially the same plane.

4. A device according to claim 3, wherein the cover is sealed to the printed circuit board.

5. A device according to any preceding claim, including a housing, the housing and cover providing a sealed enclosure for the array of diodes.

6. A device according to any preceding claim, wherein the array of diodes are arranged in groups in which the diodes in each group are electrically interconnected and wherein the control means is arranged to energise each group in succession.

7. A device according to claim 6, wherein the control means comprises an AC to DC converter, a sequential control circuit having a plurality of outputs at least equal in number to the number of said plurality of groups and a plurality of switching circuits one for each group of diodes to control the energisation of that group of diodes, each switching circuit being connected to a corresponding output of the sequential control circuit.

8. A device according to claim 7, wherein the sequential control circuit comprises a clock pulse generator, a counter for counting the generated clock pulses and a decoder for decoding the count of the counter, the decoder providing said outputs of the sequential control circuits.

9. A device according to claim 7 or to claim 8, wherein the converter provides a first variable DC output for energising the groups of diodes and a second fixed DC output for energising the remaining circuits of the control means.

10. A signalling device comprising an array of electroluminescent diodes arranged in a plurality of separate groups, control means for energising each group of diodes in succession so that each diode draws a peak current substantially higher than the rated current for the diodes under continuous energisation, and a cover covering the array, the cover defining a plurality of lens elements, each lens element being positioned to control the width and direction of the beam of light emitted by a corresponding diode.

11. A device according to claim 10 wherein the diodes of each group are of even number, and interconnected to form two series of chains each containing an equal number of diodes, the two chains being electrically connected in parallel.

12. A light signalling device substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. particular directivity or to establish a uniform dispersion of light. WHAT I CLAIM IS:

1. A signalling device comprising an array of electroluminescent diodes, control means for energising the diodes and a cover covering the array, the cover having a plurality of lens elements, each lens element being associated with a corresponding diode to modify the divergence and/or the direction of the light beam produced by the diode.