GB2201237A

GB2201237A - Luminaires

Info

Publication number: GB2201237A
Application number: GB08701355A
Authority: GB
Inventors: Walter Whittaker; Stewart Chapman
Original assignee: AC DC HOLDINGS Ltd
Current assignee: AC DC HOLDINGS Ltd
Priority date: 1987-01-22
Filing date: 1987-01-22
Publication date: 1988-08-24
Also published as: GB8701355D0

Abstract

A luminaire comprises a main body 2 and a lens 4 which are fixed together to provide a sealed unit. Within the body 2 there is provided a discharge tube 7 which may be substantially triangular mounted within a channel 6 defined by the main body 2 and the sides of a secondary body portion 3. Light from the discharge tube is directed through the lens 4. An electronic converter 9 is mounted on the secondary body portion 3 which converter receives a very low AC voltage which is converted to a high voltage, low current output at high frequency. A socket 11, sealed at one end, is provided for mounting the luminaire on an appropriate bracket. The luminaire may be especially suitable for illuminating road signs. <IMAGE>

Description

LUMINAIRES This invention relates to luminaires, and is concerned particularly although not exclusively with luminaires for use in illuminating road signs.

Road signs are commonly illuminated by overhead luminaires. For example, such a luminaire may be mounted upon a support at the top of a road sign, being angled downwardly to shed light on to the face of the road sign.

From time to time, such luminaires require to be opened, in order to replace the light element, and for periodic cleaning. The light elements that are commonly used in such luminaires generally require a significant voltage e.g. 240 volts - for operation. Such a voltage can be dangerous, in the event that the road sign is damaged, and the electric conductors become exposed.

Preferred embodiments of the present invention aim to provide generally improved luminaires for use with road signs.

More generally, according to a first aspect of the present invention, there is provided a luminaire which comprises: a body which defines therein a cavity having-an opening; a cold-cathode discharge tube mounted in the cavity; reflecting means so arranged in the cavity as to reflect light from the discharge tube towards said opening; and a lens which covers said opening and is permanently secured to said body, so as to afford a seal around said opening.

Preferably, said body and lens are of plastics material, andare welded together.

The discharge tube is advantageously shaped as a polygon. In a particularly preferred embodiment, the discharge tube is shaped as a triangle.

In such an arrangement, said body may comprise a central portion which is disposed within the polygon, and a channel which extends around said central portion, in the form of said polygon, to receive the discharge tube.

The luminaire preferably includes a converter adapted to receive a very low voltage input, and to output a high voltage at high frequency and very low current to the discharge tube. Such a converter may be mounted at or adjacent said central portion of said body.

The reflecting means may be provided as a reflective surface on said body, or as a separate member.

The reflecting means may advantageously be of parabolic cross-section.

The luminaire may be used with advantage in a road sign. In such an arrangement, there may be provided a transformer adapted to receive an input voltage which is high relative to the output voltage (but may nevertheless itself be an officially classified "low" voltage - e.g. 240v.), and provide an extra low voltage output to the discharge. tube, the transformer being mounted at or adjacent ground level.

For a better understanding of the invention and to show how the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawing, in which: Figure 1 is a side view of a luminaire for use with a traffic sign; Figure 2 is a bottom plan view of the luminaire; and Figure 3 is a sectional view on the line A-A of Figure 2, showing a lens of the luminaire removed.

The illustrated luminaire 1 comprises a main bodyportion 2 of plastics material, a secondary body portion 3, also of plastics material, and a plastic lens 4.

The main body portion 2 is triangular in plan, and the secondary body portion 3 has a central portion 5, around which there is defined a channel 6, partly defined by the wall of the main body portion 2, and partly defined by the sides of the secondary body portion 3.

Mounted within the channel 6 is a cold-cathode discharge tube 7, which is also substantially triangular in shape. The surfaces of the body portions 2 and 3 which are adjacent the tube 7 are silvered, polished, painted, ink-screened, or otherwise treated, to provide reflectors to direct light from the tube 7, towards the opening 8 in which the lens 4 is mounted. The walls of the body portions 2 and 3 are so shaped as to provide a substantially parabolic reflecting surface, adjacent the tube 7.

An electronic converter 9 is mounted on the secondary body portion 3, in a space defined between the central portion 5 and an outer wall 14 of the main body portion 2. The converter receives a very low voltage of, for example, 24 volts AC, and converts this to a relatively high voltage of 500 to 800 volts at 30 to 100 kHz (e.g. 65 kHz), at very low current (e.g. around 10 mA), which is supplied to the tube 7.

The lens 4 is welded to the main body portion 2, to close the opening 8 in a fluid-tight manner. The lens 4 has a dished central portion 10 which makes contact with, and is preferably welded to, the central portion 5 of the secondary body portion 3.

The main body portion 2 defines a socket 11 to receive a suitable bracket, by means of which the luminaire 1 may be mounted on a road sign. Electrical connections to the converter 9 are made by conductors (not shown) which extend through the socket 11. The inner end of the socket is sealed by a resin 12, through which the conductors to the converter 9 pass, to render the luminaire 1 a completely sealed unit.

In use, therefore, the luminaire 1 is mounted by means of an appropriate bracket at the top of a road sign, and a suitable very low supply voltage below 100 volts and preferably in the range 12 to 50 volts AC at 50 Hz is supplied to the conductors to the converter 9.

Such a very low voltage may be obtained from a transformer at or adjacent ground level (for example, at the base of a pole of the road sign), which is connected to receive a relatively high input voltage (e.g. 240 volts at 50 Hz - which is actually classified officially in the U.K. as "low" voltage).

Since the luminaire 1 is a completely sealed unit, no internal maintenance is required, and the life of the unit may be relatively long, since the ingress of moisture, dirt, etc., -is substantially prevented. Thus, the luminaire 1 may maintain optimum operation, throughout its life. The triangular shape of the tube 7 gives good light distribution - generally better than an arrangement of parallel tubes, and it is relatively easy to manufacture tubes such as 7 in the shape of a polygon.

The parabolic reflecting surface adjacent each part of the tube 7 optimises the light output through the lens 4, and also provides a convenient location for the converter 9 with associated ballast. Since the tube 7 operates at high frequency and very low current, very little energy is consumed, and no lethal energy is available, in the region of the luminaire 1. The low energy operation of the cold-cathode tube 7 enhances long life of the tube. When, eventually, the tube 7 reaches the end of its life, the entire luminaire 1 is discarded and replaced by another, similar sealed unit. It will be appreciated that the luminaire 1 may be produced of plastics materials at a relatively low cost and, given the relatively long service life of the sealed unit, we have found that its cost can be significantly less than that of conventional units, which require regular maintenance and replacement of light elements.

The dished configuration of both the secondary body portion 3 and the lens 4 can lend appreciable strength to the unit as a whole. The plastics materials can be selected to make the luminaire 1 generally tough and vandal resistant. The triangular shape of the luminaire body does not provide an easy area for a person to grip, so that they may hang from the luminaire (an activity which has some popularity amongst younger people).

As a modification of the illustrated arrangement, the secondary body portion 3 may be formed integrally with the main body portion 2 and/or the outer wall 14 may be a separate detachable part.

The invention is not restricted to the details of the foregoing embodiment(s). The invention extends to any novel one, or any novel combination, of the features disclosed in this specification and/or drawings, or to any novel one, or any novel combination, of the steps of any method or process disclosed herein.

Claims

1. A luminaire-comprising: a body which defines therein a cavity having an opening; a cold-cathode discharge tube mounted in the cavity; reflecting means so arranged in the cavity as to reflect light from the discharge tube towards said opening; and a lens which covers said opening and is permanently secured to said body, so as to afford a seal around said opening.

2. A luminaire according to Claim 1, wherein said body and lens are of plastics material, and are welded together.

3. A luminaire according to Claim 1 or 2, wherein the discharge tube is shaped as a polygon.

4. A luminaire according to Claim 3, wherein the discharge tube is shaped as a triangle.

5. A luminaire according to Claim 3 or 4, wherein said body comprises a central portion which is disposed within the polygon, and a channel which extends around said central portion, in the form of said polygon, to receive the discharge tube.

6. A luminaire according to any of the preceding claims, wherein the luminaire includes a converter adapted to receive a very low voltage input, and to output a high voltage at high frequency and very low current to the discharge tube.

7. A luminaire according to Claim 6, wherein said converter is mounted at or adjacent said central portion of said body.

8. A luminaire according to any of the preceding claims, wherein the reflecting means is provided as a reflective surface on said body.

9. A luminaire according to any of Claims 1 to 7, wherein the reflective means is provided as a separate member to said body.

10. A luminaire according to any of the preceding claims, wherein the reflecting means is of parabolic cross-section.

11. A luminaire according to any of the preceding claims, including a transformer adapted to receive an input voltage which is high relative to its output voltage and provide an extra low voltage output to the discharge tube.

12. A luminaire substantially as hereinbefore described with reference to the accompanying drawings.

13. A road sign provided with a luminaire according to any of the preceding claims, adapted to illuminate the road sign.

14. A road sign according to Claim 13, wherein the luminaire is in accordance with Claim 11, and the transformer is mounted at or adjacent ground level.