AU2005100101A4

AU2005100101A4 - A lighting unit

Info

Publication number: AU2005100101A4
Application number: AU2005100101A
Authority: AU
Inventors: Ian James Maitland
Original assignee: Individual
Current assignee: Individual
Priority date: 2005-02-03
Filing date: 2005-02-03
Publication date: 2005-03-03
Anticipated expiration: 2013-02-03

Description

Regulation 3.2

AUSTRALIA

Patents Act 1990 (Cth) IAN JAMES MAITLAND COMPLETE SPECIFICATION FOR AN INNOVATION PATENT (ORIGINAL) Invention Title: A LIGHTING UNIT The following statement is a full description of this invention, including the best method of performing it known to me/us: 112612733 2 A LIGHTING UNIT FIELD OF THE INVENTION The invention relates to a lighting unit suitable for providing outdoor lighting. Preferred embodiments of the invention find particular application as garden lights and for lighting swimming pools or water features such as fountains or ponds.

BACKGROUND OF THE INVENTION Various outdoor low wattage lights with halogen or non-halogen tungsten filament light bulbs for providing outdoor lighting are known in the art. The life span of each of these types of light bulbs is typically in the order of about 5000 hours and 500 hours of operation, respectively. Accordingly, these light bulbs typically fail one or more times during the working life of the lights requiring replacement with the associated inconvenience involved in doing this.

Swimming pool lighting mounted in the wall of swimming pools below the water line is also known in the art. Such lights are normally mounted behind a waterproof cover fixed to the wall of the pool. Accordingly, in order to change a light bulb which has failed or to carry out maintenance on the light unit itself, it is necessary for water to be drained from the swimming pool until the level of the water is below the waterproof cover. This, of course, is time consuming, inconvenient and additional cost is incurred by the need to refill the pool to the normal water level. Due to the cost and disruption to pool use, the maintenance of such lights may be significantly delayed, meaning that the light may be non-functional for extended periods.

It is desirable that lights for outdoor applications having a light source with a longer working life compared to conventional halogen light bulbs or non-halogen tungsten filament bulbs be provided, or that at least an alternative lighting unit be provided to offer the consumer greater choice.

SUMMARY OF THE INVENTION In an aspect of the present invention there is provided a lighting unit suitable for outdoor installation, the lighting unit comprising: at least one light source for providing light; a heat sink to which the light source is mounted for transfer of heat from the light source to the heat sink and which is adapted to dissipate the heat from the light source, the light source being disposed in the heat sink and the heat sink forming an outer casing 112612733 3 of the lighting unit; and a transparent cover covering the light source and carried by the heat sink, the light passing through the cover from the heat sink.

Typically, the lighting unit will further comprise power supply circuitry for providing power to the light source and which is housed in the heat sink.

Preferably, the lighting unit will be essentially waterproof and most preferably, be adapted for being submerged in water such as when used for lighting a swimming pool or a water feature such as a fountain or pond.

Preferably, the heat sink will be adapted for being inserted into a housing for mounting the heat sink in a position that is normally submerged in water during operation of the light source, such that one or more spaces are provided between the heat sink and the housing for passage of water into the housing into contact with the heat sink. As the water contacts the heat sink, heat generated by the LED is drawn off by the water thereby cooling the heat sink.

Thus, in another aspect of the present invention there is provided a lighting system for providing underwater lighting, the system comprising: a light source for providing light; a heat sink to which the light source is mounted for transfer of heat from the LED to the heat sink and which is adapted to dissipate the heat from the light source, the light source being disposed in the heat sink and the heat sink forming an outer casing of the lighting unit; and a transparent cover covering the light source and carried by the heat sink, the light passing through the cover from the heat sink; and a housing adapted for mounting the heat sink in a position that is normally submerged in water during operation of the light source, the housing receiving the heat sink such that one or more spaces are provided between the heat sink and the housing for passage of the water into the housing into contact with the heat sink.

Any conventionally available light source may be used in the lighting unit. For instance, the light source may comprise a halogen or non-halogen light bulb. Preferably, however, the light source will be a light emitting diode (LED) and most preferably, a super bright LED. LED's typically have substantially longer working lives and accordingly, the risk of failure of an LED during the working life of the lighting unit may be reduced compared to lights with halogen or non-halogen tungsten filament light bulbs.

112612733 4 All publications mentioned in this specification are herein incorporated by reference.

Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed anywhere before the priority date of each claim of this application.

Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

The features and advantages of the present invention will become further apparent from the following detailed description of preferred embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a lighting unit embodied by the present invention; Figure 2 is a schematic longitudinal cross-section of the lighting unit of Fig 1; Figure 3 is a schematic longitudinal cross-section of a further lighting unit embodied by the present invention; Figure 4 is a schematic cut-away side view illustrating the lighting unit of Fig 3 inserted in a housing adapted for being fitted in a side wall of a swimming pool in a normally submerged position; Figure 5 is a rear view of the lighting unit of Fig 3; and Figure 6 is a circuit diagram of power supply circuitry of the lighting unit of Fig 1 and the lighting unit of Fig 3.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE PRESENT INVENTION The lighting unit 2 shown in Fig 1 comprises a heat sink 4 made of an aluminium alloy that houses a super bright light emitting diode (LED) 6 centrally disposed in an associated lens assembly 8. A 3mm transparent acrylic front cover 10 is secured to the heat sink by peripherally located screws 13. A seal in the form of an O-ring 12 located in a groove 14 of the heat sink 4 seals the lighting unit against entry of water from the environment under the front cover 10 into the heat sink. The lens assembly 8 comprises a 112612733 reflector 16 and transparent reflector cover (indicated by the numeral 17) mounted on the reflector over the LED. A plastic holder 18 receives the lens assembly, and holds the lens assembly in position centrally within the front cavity 20 defined in the heat sink 4 (see Fig 2).

The heat sink is provided with a plurality of radially projecting spaced apart ribs 22 for maximising surface contact with ambient air for dissipation of heat generated by the LED in use. The heat sink is mounted on a mounting bracket 24. The base of the mounting bracket is provided with an aperture 26 for receipt of a fastener such as a screw or coach bolt for facilitating outdoor installation of the lighting unit. As will be appreciated, the heat sink is pivotable about oppositely located screws 28, which secure the mounting bracket to the heat sink to enabling the light from the LED to be orientated as desired.

As shown in Fig 2, a rear cavity 30 is also formed in the heat sink by dividing wall 32 of heat sink 4. A mounting strip 36 on which the LED 6 is seated for heat transfer from the LED to the heat sink is held in position against the dividing wall 32 by screws 38. The mounting strip 36 comprises a printed circuit board and an aluminium backing plate to which the printed circuit board is fixed by a thin layer of glue. The aluminium backing plate in turn is in heat transfer contact with the dividing wall 32 of the heat sink and the LED is glued to the printed circuit board to facilitate the transfer of heat from the LED to the printed circuit board. An epoxy glue will normally be used to secure the printed circuit board to the aluminium backing plate and for gluing the LED to the printed circuit board but any glue(s) deemed suitable may be used. As also indicated, the holder 18 is provided with a plurality of stakes 40 spaced equidistantly around a frustoconical region 42 of the holder 18. The stakes 40 are received in apertures 44 defined in the dividing wall 32 of the heat sink in a friction fit such that the lens assembly 8 is held fixedly in position within the front cavity of the heat sink. As shown more clearly in Fig 1, the LED 6 extends through a hole 46 defined in the base region of the reflector so as to be housed within the lens assembly.

Returning now to Fig 2, the light unit 2 further has power supply circuitry on a printed circuit board 50 located in the rear cavity 30 of the heat sink 4 for providing power to the LED. The LED is connected to the power supply circuitry by insulated conductors soldered to conductive tracks on the printed circuit board of the mounting strip 36, and which pass through a further aperture (not shown) defined in the dividing wall 32 of the heat sink 4.

A waterproof cable gland 52 provided with a resilient washer 53 receiving power supply cable 54 is fitted to the rear cover 56 of the lighting unit, and prevents entry of water from the environment into the rear cavity 30 of the heat sink. Cable glands of this type and 112612733 6 their use are well known and so are not further described here. A rear seal in the form of a further O-ring 58 is located in circumferential groove 60 of the heat sink 4 preventing entry of water between the rear cover 56 and the heat sink to the power supply circuitry.

Accordingly, the lighting unit 2 is essentially waterproof and is suitable for being mounted in outdoor locations unprotected from the weather.

A further embodiment of a lighting unit of the invention is shown in Fig 3. This lighting unit 62 is adapted for being located in a housing 66 (see Fig 4) for being fitted in a wall of a swimming pool in a submerged position. Lighting unit 62 differs from that shown in Fig 1 in that a retaining ring in the form of an O-ring 64 is seated on the reflector cover 17 of the lens assembly 8 and presses against the underside of the transparent front cover of the lighting unit to assist retaining the lens assembly in position within the heat sink.

In addition, the heat sink 4 is provided with three lugs 48 located at 1200 intervals around its periphery for centering the heat sink when inserted into the housing 66 as illustrated in Fig 4. The rear cover 56 of this embodiment is also provided with a plurality of outwardly projecting arms 68 for centering the rear region of the heat sink within the housing 66. As shown in Fig 4, the arms are inclined forwardly from the central region of the rear cover to facilitate sliding of the lighting unit into the internal cavity 72 of the housing 66. As the outwardly extending arms 68 bear against the housing, the arms of the rear cover also act to hold the lighting unit in position within the housing. The spacing of the arms 68 of the rear cover is shown more clearly in Fig As also shown in Fig 4, the power supply cable 54 passes through a further waterproof cable gland 74 fitted at the rear of the housing 66 preventing the leakage of water from the swimming pool which enters the internal cavity 72 of the housing from the pool in use via spaces 76 provided between the heat sink 4 and the housing. The contact of the water with the heat sink 4 draws the heat generated by the LED away from the heat sink maintaining the LED at a suitable operating temperature.

Sufficient power supply cable 54 is provided within the housing 66 rearwardly of the lighting unit 62 to enable the lighting unit to be withdrawn from the housing to above the surface of the water in the pool. This enables maintenance to be carried out on the lighting unit without the need to lower the water level in the pool to below the housing 66. Removal of the lighting unit is achieved by simply grasping the lighting unit and sliding the lighting unit outwardly from the housing. The housing may be integrally formed with the wall of the swimming pool or be secured in the wall of the pool by fasteners (eg stainless steel for nylon screws) passing through circumferentially located apertures defined in the outer rim 67 of the housing.

112612733 7 A circuit diagram of the power supply circuitry of the lighting units illustrated in Fig 1 and Fig 3 is shown in Fig 6. Briefly, an AC or DC power supply is fed to full wave bridge rectifier BR1. The direct current (DC) output from BR1 is coupled to single chip switch mode power supply controller and output device U1. Voltage from the output of U1 is applied to LED W3 and resistor R1 which functions as a current measuring shunt. The voltage at the negative lead of R1 is applied to amplifier U2. The output from U2 is connected to the input of the comparator of U1 via pin 5, which controls the voltage applied to the LED W3 and resistor R1. Resistors R1, R2 and R3 are selected so that the output current from U1 to LED W3 is limited to a predetermined amperage typically in the range of from about 100 mA to about 1A. As will also be understood, capacitor C1 determines the switching speed of the power supply to the LED and capacitors C2 and C3 are output filters for the power supply. Capacitor C4 filters the input power supply from BR1.

Lighting units embodied by the invention may be provided for any outdoor low voltage application. Preferred lighting units of the invention will typically be rated for use with voltages of about 50V or less and normally in a range of from about 6V to about 32V and more usually, 6V or 12V power supplies.

The LED used may be any LED deemed suitable for the intended purpose. Preferably, the LED will have an output rating of from about 2500 mcd, more preferably at least about 4500 mcd and most preferably, about 6000 mcd or greater. Indeed, super bright diodes with an output rating over 10,000 mcd are now commercially available.

It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

1. A lighting unit suitable for outdoor installation, the lighting unit comprising: at least one light source for providing light; a heat sink to which the light source is mounted for transfer of heat from the LED to the heat sink and which is adapted to dissipate the heat from the light source, the light source being disposed in the heat sink and the heat sink forming an outer casing of the lighting unit; and a transparent cover covering the light source and carried by the heat sink, the light passing through the cover from the heat sink.

2. A lighting unit according to claim 1 further comprising power supply circuitry for providing power to the light source and which is housed in the heat sink.

3. A lighting unit according to claim 1 or 2 wherein the lighting unit is essentially waterproof.

4. A lighting unit according to any one of claims 1 to 3 wherein the heat sink is adapted to be inserted into a housing for mounting the lighting unit in a position that is normally submerged in water during operation of the light source, such that one or more spaces are provided between the heat sink and the housing for passage of water into the housing into contact with the heat sink. A lighting unit according to any one of claims 1 to 4 wherein the light source is a light emitting diode. Dated: 3 February 2005 Ian James Maitland Patent Attorneys for the Applicant: BLAKE DAWSON WALDRON PATENT SERVICES