GB2275141A

GB2275141A - Flashing warning beacon having a low-voltage lamp

Info

Publication number: GB2275141A
Application number: GB9401554A
Authority: GB
Inventors: Robert Ernest Myson
Original assignee: LUMISPHERE PRODUCTS Ltd
Current assignee: LUMISPHERE PRODUCTS Ltd
Priority date: 1993-02-12
Filing date: 1994-01-27
Publication date: 1994-08-17
Anticipated expiration: 2014-01-27
Also published as: GB2275141B; GB9401554D0

Abstract

A mains-powered flashing warning beacon has an adaptor unit 1 in place of the conventional lamp holder for the mains voltage lamp. The adaptor unit comprises an electronic transformer unit (9) providing a low-voltage high frequency intermittent output to a low-voltage tungsten-halogen incandescent lamp 6. The adaptor unit is in the form of an integral unit with the electronic components mounted within a casing having a bracket 2 replacing the conventional lampholder, and a lamp support 8 to position the low-voltage lamp 6 at substantially the same height as the filament of the conventional lamp which the unit replaces in a fixture at a pedestrian road crossing. The electronic circuit may give a soft-start so that the lamp voltage is increased from zero to maximum over a fraction of a second. <IMAGE>

Description

WARNiNG BEACON Field of the Invention This invention relates to a warning beacon of the type which flashes on and off, and to an adaptor unit for such a beacon.

BackWround to the Invention In the United Kingdom, some pedestrian road crossings, known as "Zebra Crossings" are marked by flashing beacons comprising an orange translucent globe set on a pole, with a conventional incandescent lamp inside, switched on and off by a flasher switch. Sucll beacons are commonly referred to as "Belisha Beacons", and were first introduced in 1934. Each year tllere is a significant number of accidents on or near Zebra crossings, and some of these appear to arise from drivers not noticing the crossing or its warning Belisha Beacons.

In 1934, traffic conditions were considerably different from those prevailing today. There are now many more street signs of different sorts and brightly-lit shop facias, the traffic density is much higher, and night-time street illumination has be Jn significantly increased, with the result that Belisha Beacons now stand out much less clearly from their surroundings during daylight or at night than when they were first introduced.

The life of the incandescent lamps generally used is relatively short, on average only a few hundred hours, which in practice normally means a life of less than one month, even for a "rough service" lamp, because of the repeated switching on and off of the lamps, and because of traffic vibration. This can lead to a significant failure rate, requiring constant monitoring and high maintenance costs, because of the road safety aspect. In addition, over the life of the lamps, their luminous output gradually decreases because of the deposit on the inside of the glass envelope of metallic tungsten evaporated from the filament, and rough service lamps have a lower light output than normal lamps, as a result of the heavier filament used.In general it is not now considered that the brightness of the beacons using normal mains voltage incandescent lamps is sufficient to alert approaching motorists.

Summary of the Invention One aspect of the present invention provides a mains-powered flashing warning beacon, comprising an electronic transformer unit providing a low-voltage high frequency intermittent output to a low-voltage lamp.

The invention also provides an adaptor unit for a mains-powered flashing traffic warning beacon, comprising an integral unit containing an electronic transformer and flashing control circuit controlling the output from the transformer, and mounting a low-voltage lamp connected to the transformer output.

The lamp is preferably a tungsten-halogen lamp, since these are noted for their high luminous efficiency, universal burning position and resistance to vibration.

The electronic transformer is a device which transforms the mains input voltage (for example 240V) to the lamp voltage, for example about 12V, without the need for a bulky and heavy iron-cored transformer. It achieves this by increasing the frequency from the 50 Hz supply frequency to a high frequency (for example 32kHz). Such devices are known for use with low voltage display lighting. The electronic control circuit providing the output to the toroidal windings may be arranged to give a "soft start" such that the lamp supply voltage is increased from o to its maximum gradually over a fraction of a second, reducing thermal stress on the filament in the lamp. This characteristic may be utilised in the present invention to extend the life of the lamp significantly.The lamp life is further enhanced by the fact that the filament remains at a relatively high temperature between the on cycles.

It is estimated that a lamp life of 8-10000 hours, or about one year of continuous service, can be achieved with the unit of the present invention. The light output for this type of lamp is considerably higher than for the conventional 60W rough service in incandescent mains voltage lamps, and is constant throughout the life of the lamp, while the electricity consumption is smaller. Since the colour temperature of the light is higher than for conventional lamps, the visibility of the beacons is further enhanced.

The adaptor unit of the present invention is readily fitted in place of the lamp holder in existing Belisha Beacons, and can be made sufficiently compact that the lamp is positioned at the approximate centre of the globe, giving uniform illumination.

Brief Description of the Drawings In the drawings, which illustrate an exemplary embodiment of the invention: Figure 1 is a diagrammatic perspective view of an adaptor unit; and Figure 2 is a block circuit diagram of the unit shown in Figure 1.

Detailed Description of the Illustrated Embodiments The unit comprises a case I in which are mounted an electronic transformer and flashing control circuit. The case I has a mounting bracket 2 attached to its lower end, the bracket having a hole 3 therethrough to enable it to be fixed on to the cable entry tube in the traffic warning beacon. A terminal block 4 is mounted on the side of the case 1 for connection of the mains power supply, wires 5 leading therefrom into the case to supply the components within. At the upper end of the case 1, a 12V 50W tungsten-halogen traffic signal lamp 6 is plugged into a socket 7 mounted on a support 8 which elevates the lamp to the correct position within the globe of the beacon, and which serves also as a heat sink for the lamp.

The lamp socket 7 is electrically connected to the transformer within the case by wires (not shown).

Figure 2 is a diagram representing the components in the case 1 of Figure 1 together with the lamp. The wires 5 lead to a flashing control circuit 9 which is arranged to switd the supply to a converter circuit 10, which is in turn connected to the primary winding 11 of a toroidal transformer 12. The secondary winding 13 supplies the lamp 6. The converter circuit 10 serves to increase the frequency of the supply voltage from 50Hz to 32Khz, thereby permitting the toroidal transformer 12 to be of small and light construction, not requiring a substantial iron core as would be required in a conventional mains frequency voltage transformer. The primary winding has 240 turns, while the secondary has 12, giving an approximately 12V (in practice electronically regulated not to exceed 11.8V) output for the lamp.

The converter circuit 10 includes electronic overload and short-circuit protection elements. All the circuits can be made small enough to fit into a case 1 which occupies a smaller height than the conventional lampholder and lamp. A reflector may be optionally mounted to one side of the lamp to further enhance visibility to the traffic flow.

it will be appreciated that, while the flashing control circuit in the embodiment illustrated operates to switch the power to the converter circuit on and off with the desired period, other arrangements will be apparent to those skilled in the art to control the electronic transformer components to supply low-voltage power to the lamp intermittently with the desired timing, and the circuits may be integrated.

Claims

I. A mains-powered flashing wanling beacon, comprising an electronic transformer unit providing a low-voltage high frequenty intermittent output to a low-voltage lamp.
2. A warning beacon according to Claim 1, wherein the low-voltage lamp is a tungsten-halogen lamp.
3. An adaptor unit for a mainspowered flashing traffic warning beacon, comprising an integral unit containing an electronic transformer and a flashing control circuit controlling the output from the transformer, and mounting a low-voltage lamp connected to the transformer output.
4. An adaptor unit according to Claim 3, wherein the low-voltage lamp is a tungsten-halogen lamp.
5. An adaptor unit according to Claim 3 or 4, wherein the control circuit is arranged to increase the lamps supply voltage from zero to its maximum gradually over a fraction of a second, whereby a thermal stress on the lamp filament is reducted.
6. An adaptor unit for a mains-powered flashing traffic warning beacon, substantially as described with reference to, or as shown in, the drawings.
7. A mains-powered flashing traffic warning beacon, substantially as described with reference to the drawings.

7. A mains-powered flashing traffic warning beacon, substantially as described with reference to the drawings.

Amendments to the claims have been filed as follows

1. A mains-powered flashing warning beacon, comprising an electronic transformer unit providing a low-voltage high frequency intermittent output to a low-voltage lamp.

2. A warning beacon according to Claim 1, wherein the low-voltage lamp is a tungsten-halogen lamp.

3. An adaptor unit for a mains-powered flashing traffic warning beacon, comprising an integral unit containing an electronic transformer and a flashing control circuit controlling the output from the transformer, and mounting a low-voltage lamp connected to the transformer output.

4. An adaptor unit according to Claim 3, wherein the low-voltage lamp is a tungsten-halogen lamp.

5. An adaptor unit according to Claim 3 or 4, wherein the control circuit is arranged to increase the lamps supply voltage from zero to its maximum gradually over a fraction of a second, whereby a thermal stress on the lamp filament is reduced.

6. An adaptor unit for a mains-powered flashing traffic warning beacon, substantially as described with reference to, or as shown in, the drawings.