GB2367883A

GB2367883A - A light source comprising light devices mounted on a twisted substrate

Info

Publication number: GB2367883A
Application number: GB0122382A
Authority: GB
Inventors: Robert Ernest Myson
Original assignee: Luminaire Developments Ltd
Current assignee: Luminaire Developments Ltd
Priority date: 2000-09-16
Filing date: 2001-09-17
Publication date: 2002-04-17
Also published as: GB0022853D0; GB0122382D0

Abstract

A light source comprises electrical circuit means (6) electrically connected to electrical contact means (4), and a plurality of non-incandescent light-emitting devices (7) mounted on the electrical circuit means (6) and powered thereby, the electrical circuit means including a substrate twisted about its longitudinal axis. The invention also provides a pressure-sealed light unit including such a light source, and festoon lighting comprising a plurality of the light units.

Description

A LIGHT SOURCE, A LIGHT UNIT INCLUDING SUCH A LIGHT SOURCE, AND FESTOON LIGHTING INCLUDING SUCH LIGHT UNITS Field of the Invention This invention relates to a light unit, a light source for use in such a light unit, and to festoon lighting comprising a plurality of such light units attached along an electric cable.

Background to the Invention Festoon lighting comprises a plurality of light units attached at intervals along an electric cable which serves to provide electrical power to the lamps as well as providing a support for the light units. Such lighting requires a high level of maintenance, because of corrosion due to the ingress of moisture, and also because of tampering and vandalism. EP-B-0 422 117 and GB-B-2 281 820 disclose light units which are highly resistant to tampering and vandalism, and which provide pressure-tight enclosures for the lamps and the associated electrical connections with the conductors in the cable, thereby substantially increasing the service life of the lighting.

Conventionally, festoon lighting utilises incandescent lamps, which have a rela tively limited life and therefore need regular replacement. The use of tungsten-halogen lamps and xenon gas-filled lamps may significantly extend intervals between replacement, while increasing efficiency of light-emission, thereby reducing running costs, but as energy and labour costs increase, there is a continuing need to improve service life and energy efficiency.

Summary of the Invention According to the invention, a light source comprises electrical circuit means elec- trically connected to electrical contact means, and a plurality of non-incandescent lightemitting devices mounted on the electrical circuit means and powered thereby, the elec trical circuit means including a substrate twisted about its longitudinal axis.

Preferably, each device is mounted so that the principal direction of the light emitted therefrom is different from that of each other device.

Preferably, the light-emitting devices are light-emitting diodes (LEDs) or other electroluminescent devices. Sufficient of the devices are mounted together on the sup

port to give an impression of a continuous light surface, for example a spherical surface. The effect may be enhanced by the use of a frosted or translucent globe surrounding the light source.

The electrical circuit means may comprise rectifying means for rectifying an alternating current supply, and current-and/or voltage-regulating means, for example.

LEDs are typically configured to emit light in a relatively limited solid angle, for example 60 degrees in section, and so each of the LEDs may be mounted so as to emit light in a different direction to each other LED, so that the overall effect is of a larger light-source emitting light over a very wide solid angle. The circuit means may be a circuit board

having the LEDs or other such devices mounted on opposed surfaces thereof.

The support may be provided with mounting and electrical connection means permitting it to be used in place of an incandescent lamp, for example. The support may also carry electrical components for regulating the electrical power supplied to the individual devices thereon. For example, a rectifying bridge may be formed from diodes, while resistors and associated components may regulate the current flowing in the devices or the voltage applied thereto. It may also be possible to include control elements switching the individual devices on and off in accordance with a pre-determined sequence, for example, to provide special visual effects, such as twinkling, or candle flame effects. Although it will generally be desirable to use white light emitting devices to provide maximum illumination, it would be possible to use coloured devices, and to include combinations of different-coloured devices to provide different colour effects, especially when used in combination with selective switching of the devices.

The invention also provides a light unit comprising a pressure-tight body salable on to an electric cable and having contact means for making electrical contact with the conductors in the cable, electrical circuit means electrically connected to the electrical contact means, and a plurality of non-incandescent light-emitting devices mounted on the electrical circuit means and powered thereby, the electrical circuit means including a substrate twisted about its longitudinal axis.

The invention further provides a festoon lighting system comprising a plurality of light units attached to an electrical cable in spaced-apart relationship therealong, each

light unit comprising a pressure-tight body sealed on to the cable and having contact means in electrical contact with the conductors in the cable, electrical circuit means elec trically connected to the electrical contact means, and a plurality of non-incandescent light-emitting devices mounted on the electrical circuit means and powered thereby, the electrical circuit means including a substrate twisted about its longitudinal axis.

The light source, light unit and festoon lighting of the invention may use lightemitting devices having high efficiency, reducing energy consumption of festoon lighting significantly, for example up to about 90% saving in energy consumption compared with incandescent lamps for the equivalent appearance (although the measurable lumen output may be lower, the use of multiple devices for the one light source gives the same visual effect). A substantially longer working life is achievable in comparison with conventional incandescent devices, substantially reducing the need for maintenance. For example, a typical life expectancy for the light sources of the invention may be in the order of 100,000 hours. Other advantages of the light units of the invention are vibration resistance, making them suitable for use on vehicles and on other vibrating structures, and low UV and heat output, reducing degradation of plastics materials used in the light unit or the cable, and the low heat output rendering the light units especially suitable for temperature-controlled environments.

In each case, the twisted substrate improves the spread of light from the individual light-emitting devices and enhances the illusion that the light source consists of a single source.

Brief Description of the Drawings In the drawings, which illustrate exemplary embodiments of the invention: Figure 1 is a side elevation of a light unit containing a light source; Figure 2 is a top plan view of the light unit of Figure 1; Figure 3 is a circuit diagram for a light source according to the invention; Figure 4 is a side elevation of a light source in accordance with the invention but before twisting; Figure 5 is a side elevation of a light source in accordance with the invention; and

Figure 6 is a top plan view of the light source of Figure 5.

Detailed Description of the Illustrated Embodiments Referring first to Figures 1 and 2, the light unit 1 is essentially of the form described and claimed in our European Patent No 422 117, and will therefore not be described in detail here. A number of the light units will be attached to an electrical cable at pre-determined intervals along it to form festoon lighting. Within the transparent or translucent globe 2, which sealingly engages with the base 3 of the light unit 1, a pair of tubular connectors extend from the base which, in the prior art system as disclosed in the European Patent, receive the conductor pins extending from an incandescent lamp.

Figure 1 schematically represents the basic construction of the light source but, for the sake of clarity. does not illustrate the detail of the light source 5 within the unit 1. The light source 5 is illustrated as consisting of a miniature printed circuit board 6 with a spaced pair of connector tubes or ferrules 4 projecting therefrom arranged to fit on to the tubular connectors extending from the base. The tubes 4 are spaced apart from each other by a distance which is just shorter than the distance between the tubular connectors in the base, so that the light source may be held on the tubular connectors by the springiness of the connectors. Alternatively, crimped pins may replace the tubes 4, as in EP-B-422 117. Another alternative to this arrangement would be to solder the connectors directly to the miniature circuit board connectors.

A number of light-emitting diodes (LEDs) 7 are mounted on and project from each face of the board 6, which also carries electrical circuit components connected between the tubes 4 and the LEDs 7 to rectify the alternating current in the cable to the direct current required by the LEDs and to regulate the current and voltage in the LEDs to ensure that the LEDs are operating at peak efficiency. A typical circuit is described in more detail with reference to Figure 3.

Referring now to Figures 4 to 6, the circuit board 6 is shown in Figure 4 prior to twisting. The tubes or ferrules 4 are located at the lower end of an elongate board 6 on both sides of which are mounted the LEDs and other circuit components as will be described later with reference to Figure 3. A column of LEDs 7 is soldered 12 to each face of the board. The LEDs may thus be substantially flat against the board, rather

than necessarily projecting outwardly therefrom as depicted schematically in Figures 1 and 2. Preferably, the LEDs on one face are directed oppositely from those on the other face. This construction provides an even spread of light and enables the light source 5 to be more compact than when the LEDs face outwardly from the board 7.

The board 7 is preferably a double-sided flexiboard, having copper or other conductor tracks on both sides of a flexible substrate. A wire link 11 runs along the length of the board and is fastened, for example by soldering, to the ends of the board.

After assembly of the source 5, a twist is imposed along the length of the board. The wire link 11 provides a degree of stability to the twisted shape. The total angle may be of any size, depending on intended use, but a 900 total twist is regarded as providing a good spread of light for minimal twisting. However, if a long light source is required,

the board may be twisted through 360'or even more, depending on the flexibility of the board.

The LEDs 7 may be of the discrete packaged type, which typically have a generally directional light output, and are therefore oriented on the surfaces of the board 6 so as to radiate light in different directions such that, when viewed from normal distances, the appearance simulates that of an incandescent lamp with an approximately spherical surface. This effect can be enhanced by the use of a frosted or translucent globe 2. It is, of course, possible to use less narrowly directional light-emitting devices, where these are available, to reduce the numbers needed.

Figure 3 shows a typical electrical circuit diagram for a light source according to the invention. Six LEDs 7 are shown for convenience of illustration, connected in series in two groups of three, but it will be appreciated that a larger number may need to be employed to give the appearance of a larger spherical lamp. The tubes 4 connect to the alternating current supply in the connecting cable, which is suitably a 12V supply. A diode bridge rectifier 8 provides a full wave rectified supply to the two sets of LEDs 7 through respective current-regulating resistors 9.

Claims

1. A light source, comprising electrical circuit means electrically connected to electrical contact means, and a plurality of non-incandescent light-emitting devices mounted on the electrical circuit means and powered thereby, the electrical circuit means including a substrate twisted about its longitudinal axis.

2. A light source according to Claim 1. wherein each light-emitting device is mounted so that the principal direction of the light emitted therefrom is different from that of each other device.

3. A light source according to Claim 1 or 2, wherein the light-emitting devices are light-emitting diodes (LEDs) or other electroluminescent devices.

4. A light source according to any preceding claim, comprising sufficient of the light-emitting devices mounted together to give an impression of a continuous light surface, for example a spherical surface.

5. A light source according to any preceding claim, wherein the electrical circuit means comprises rectifying means for rectifying an alternating current supply, and current-and/or voltage-regulating means.

6. A light source according to any preceding claim, wherein the electrical circuit means comprises means for selectively switching individual LEDs or groups of LEDs on and off.

7. A light source, substantially as described with reference to, or as shown in, the drawings.

8. A light unit comprising a pressure-tight body salable on to an electric cable and having contact means for making electrical contact with the conductors in the cable, and a light source according to any preceding claim mounted within said body and electrically connected to the contact means.

9. A light unit, substantially as described with reference to, or as shown in, the drawings.

10. A festoon lighting system comprising a plurality of light units in accordance with Claim 8 or Claim 9 in sealing engagement with an electrical cable and in spaced-apart relationship therealong, the contact means in each of the light units being in electrical contact with the conductors in the cable.