AU723764B3 - Light source - Google Patents

Description

TITLE: LIGHT SOURCE THIS INVENTION relates to lighting. In particular, it is directed to a light source for use in low voltage applications.

Outdoor lighting is becoming increasingly popular as a garden feature to delineate the boundaries of a footpath or driveway and as a decorative feature depicting nativity or other festive scenes. Similar lighting also finds use indoors where it may illuminate a feature such as a fish tank.

Such lighting utilizes the traditional incandescent and halogen filaments inside a glass bulb. The glass of the bulb can be pigmented or coated to enable various "coloured" lights to be manufactured.

These traditional filaments within a glass bulb suffer from a number of disadvantages including the glass bulb is susceptible to breakage, the filaments have a relatively short lifetime before breakdown occurs because of the thermal stress experienced by the filaments, the filaments require high wattage to be applied to produce the required brightness, thus necessitating relatively short cables between the power source and the light; consequent to this requirement of short cable length, the overall cabling requirements for any particular application of lighting are large leading to increased costs and the inconvenience of having to accommodate a number of separate cable runs, the filaments are weakened, and are thus more easily broken, by the power and voltage fluctuations inherent from a transformer as the mains voltage is reduced to the required voltage to operate the low voltage filaments, power supply to operate a traditional high wattage, low voltage filament is inefficient and consumes more power than is actually required to achieve the desired brightness; it is thus relatively costly to power such filaments, the high wattage required generates significant heat which is transferred to the outer June 2000] glass bulb and/or fitting which is thus hot to touch and thus potentially dangerous when placed in an environment commercial or domestic where inadvertent contact of the light by persons, particularly young children, is likely, and this type of light is difficult to mount permanently, for example, underwater, as it is difficult to create an effective seal to prevent ingress of water but still retain the ability to regularly replace the "bulb".

It is therefore a general object of the present invention to overcome, or at least ameliorate, one or more of the above problems.

According to a first aspect of the present invention, there is provided a light source, said light source including: a light emitting diode; means to supply power to said diode; and a cover for said diode having a convex outside surface at its apex, said cover further including at least one ridge positioned circumferentially around its inner surface; wherein said diode and said cover are adapted such that there is substantial refraction of that light emitted from said diode which impinges on each of said at least one ridge.

Preferably, said cover has a concave inside surface at its apex.

More preferably, there are three of said ridge.

Preferably, said means to supply power to said diode includes a holder to retain said diode thereon.

Optionally, said diode can be white or any appropriate colour.

Optionally, said cover can be clear, white or a colour of any hue.

The invention will now be described with reference to a preferred embodiment which is shown in the accompanying drawing which illustrates a partly exploded light source constructed in accordance with the present invention.

The light source comprises a light emitting diode retained in a suitable holder An electrical lead (3a) supplies power through the holder and thus the diode from any convenient electrical source (not illustrated) such as a transformer connected, in turn, to a mains supply. (A further electrical lead (3b) can extend from the holder to be connected in series to another light emitting diode and holder if required.) A cover is a snap or push fit over the diode and retained by the holder Alternatively, the cover can be permanently sealed to the holder The cover is manufactured from clear or coloured polycarbonate. Three internal spaced circumferential ridges (5a,b,c) are formed integrally with the cover. The inside surface of the top of the cover is concave and the outer surface is convex. The light emitting diode is positioned centrally within the cover with its tip substantially level with the lateral plane of the uppermost ridge In use, light emitted from the diode impinges primarily on the upper ridge the majority of the light being refracted to pass through the concavoconvex top of the cover whereby the light rays substantially converge.

The present inventor has established that a light source constructed as detailed above offers a number of advantages as follows: 1. It provides a light source which is essentially maintenance free with a life expectancy of about 100,000 hours.

2. The internal ridges and concavo-convex construction of the cover reduce the internal reflection of the light emission and increase the amount of refracted light passing through the cover over a conventional filament for a given power input, thus effectively reducing the power requirements for any given level of brilliance.

3. The reduction in power required for any given brilliance reduces the amount of associated cabling required.

4. The reduction in power required also means heat output is significantly reduced and thus the cover and/or base fitting of the light source is no longer hot to touch, even after 24 hours of continuous use.

Due to the long life capabilities of the light source, the diode can be permanently sealed within the cover and holder thus making the present invention suitable for permanent installations in places such as swimming pools whereby effective sealing against water ingress can be obtained as it would not be necessary to regularly "open" the light source to replace a conventional "bulb".

It will be appreciated that the above described embodiment is only an exemplification of the various aspects of the present invention and that modifications and alterations can be made thereto without departing from the inventive concept as defined in the following claims.

Claims (3)

1. A light source, said light source including: a light emitting diode; means to supply power to said diode; and a cover for said diode having a convex outside surface at its apex, said cover further including at least one ridge positioned circumferentially around its inner surface; wherein said diode and said cover are adapted such that there is substantial refraction of that light emitted from said diode which impinges on each of said at least one ridge.

2. A light source as defined in Claim 1, wherein said cover has a concave inner surface at its apex.

3. A light source as defined in Claim 1 or Claim 2, wherein said cover includes three of said ridge. DATED THIS 20th DAY OF June 2000 HAWKO AUSTRALIA PTY LTD by its Patent Attorney Dr Kevin M Pullen