AU2014253507A1 - Luminaire and Light Emitting Assembly Therefor - Google Patents

Abstract

A light emitting assembly suitable for retrofitting to luminaires, the light emitting assembly comprising an LED module, and a heat sink device, wherein the heat sink device comprises a projecting central portion for mounting the LED module.

Description

P/00/011 Regulation 3.2(2) AUSTRALIA Patents Act 1990 ORIGINAL COMPLETE SPECIFICATION STANDARD PATENT Application No. Lodged: Invention Title: Luminaire and Light Emitting Assembly Therefor The following statement is a full description of this invention, including the best method of performing it known to: 2 LUMINAIRE AND LIGHT EMITTING ASSEMBLY THEREFOR FIELD OF INVENTION [0001] The present invention relates to the field of lighting, particularly decorative lighting assemblies and fixtures used for exterior lighting. [0002] In one particular aspect the present invention relates to a light assembly, that is, an electrical device used to create artificial illumination. [0003] In one particular aspect the present invention is suitable for use as outdoor lighting of the type found in private gardens or public areas such as parks and gardens, leisure areas, and thoroughfares such as paths and driveways in housing estates. [0004] It will be convenient to hereinafter describe the invention in relation to public street lighting however, it should be appreciated that the present invention is not limited to that use only as it may also be used for other purposes such as the illumination of a wide variety of both private and public areas. [0005] Where used herein the term 'light assembly' includes luminaires within its scope. A luminaire is a term of the art that includes a lighting assembly comprising a light source (lamp), a reflector for directing the light, an aperture covered by a lens/diffuser, an outer casing for lamp alignment and protection, an electrical ballast and connection to a power source. BACKGROUND ART [0006] It is to be appreciated that any discussion of documents, devices, acts or knowledge in this specification is included to explain the context of the present invention. Further, the discussion throughout this specification comes about due to the realisation of the inventor and/or the identification of certain related art problems by the inventor. Moreover, any discussion of material such as documents, devices, acts or knowledge in this specification is included to explain the context of the invention in terms of the inventor's knowledge and experience and, accordingly, any such discussion should not be taken as an admission that any of the material forms part of the prior art base or the 3 common general knowledge in the relevant art in Australia, or elsewhere, on or before the priority date of the disclosure and claims herein. [0007] The use of electric street lighting dates back to the late 19th century, when carbon arc lamps employing alternating current were used to ensure the electrodes burned down at the same rate. However due to their intense, harsh light and need for constant maintenance to replace burnt out carbon electrodes, by the start of the 20th century they had been replaced by incandescent light bulbs. Incandescent bulbs remained in use until replaced by high-intensity discharge lamps, often operated in high voltage series circuits. Before the invention of photoelectric controls, a single switch or clock would be used to regulate the turning on and off of all the light in an entire district. [0008] Street lighting today typically uses high intensity discharge lamps or high pressure sodium lamps or compact fluorescent lamps. [0009] Street lights are located in elevated positions, typically at the top of poles of 5 or more metres in height or on brackets attached to building walls in order to maximise the amount of light they cast to the area below. Often the poles are curved at the top or include a bracket to locate the luminaire closer to the centre of a thoroughfare. [0010] Luminaires for lighting freeways and other roadways are often located at the top of tall poles, up to 10 or more metres in height. Figures 1a and 1b depict typical luminaires of this type. Many of these types of street lights are produced including those sold under the registered Australian trade mark Greenstreet® by Pierlite Pty Ltd and the street light described in Pierlite's Australian patent application AU 2004 205200. They typically comprise an elongate casing and lens and their configuration and construction design is principally dictated by functional requirements. [0011] While these luminaires tend to have an elongated shape, other external luminaires such as 'bunker luminaires' or 'canopy luminaires' of the type described in US patent 6,843,580 tend to have a bulbous shape. [0012] Luminaires that are highly visible in urban setting often have a strong decorative component to their design. Luminaires that include a traditional bell or lantern 4 shaped reflector are often preferred for older urban areas and streetscapes and include GEC's ClearmainTM street lanterns and the 'bell shaped' versions sold by Rexel under the trade mark Boston TM TE. [0013] Figures 1c and 1d depict a typical decorative luminaires of this type. The lantern reflector design prevents light being lost vertically upward, providing better illumination at ground level. These decorative luminaires typically house lamps that operate between 40 and 125 Watts. For example, the lamp chosen is often compact fluorescent (42W), mercury vapour (80 or 125W) or High Pressure Sodium/Metal Halide (70W). [0014] A single suburb or housing estate may have many thousands of decorative luminaires lighting thoroughfares and public spaces, each luminaire drawing electricity. The total supply cost may be significant for the city council or other responsible authority. Accordingly, there is always a need for energy savings and concomitant cost savings. However, although replacing existing lamps with more energy efficient varieties, or lamps having reducing wattage may reduce the amount of energy drawn, supply cost savings are often substantially diminished by the cost of the new lamps. Furthermore, the illumination efficiency of the luminaire may be compromised. [0015] Due to their shape or size, some types of lamps cannot be retro-fitted to existing lamps. In this case the electricity cost savings must be balanced against the cost of replacing the entire luminaire. Prior art luminaires were not designed to be compatible with new energy saving lamps and retro fitting may also lead to technical problems. [0016] Light emitting diode (LED) modules are well known solid state light sources in which current flows in a forward direction through a junction of two different semiconductors. Electrons and cavities combine at the junction to generate light. They have become popular for lighting due to their robustness, resistance to shock and long lifetime under optimal conditions and offer a cost-effective alternative to incandescent and fluorescent lamps. For example, US patent 8,251,551 describes an LED module for domestic use.

5 [0017] For example, an incandescent lamp turns 90% of electricity used into heat and only 10% into light. By contrast, LED lights can use only 15% of the energy that lamp uses, yet provide up to 85% of the light output. LED lights also have a long life span of up to 80,000 hours - lasting up to 8-10 times longer than incandescent lamps. This would appear to make them a suitable replacement for existing non-LED modules. However although prior art wisdom is that LEDs do not generate much heat, this is not true in the confined space of a luminaire where heat builds up to a level where it can damage the LED and the associated electronics or even cause a fire. [0018] Furthermore, luminaires of the prior art are designed so that the centre of illumination emanating from the lamps is located at a predefined location relative to the visor/diffuser. The exterior surface of the visor typically includes regions comprising multiple small bevels at angles that reflect or refract the light from the lamp to the ground according to a desired photometric design. LED modules are smaller than prior art lamps, and sit in a different position within the visor, producing the possibility of a different photometric outcome. [0019] Accordingly there is a need to make greater use of LEDs in lighting applications to take advantage of their beneficial characteristics. SUMMARY OF INVENTION [0020] An object of the present invention is to provide a more energy efficient decorative luminaire. [0021] Another object of the present invention is to provide an LED system that can be retrofitted to decorative external luminaires. [0022] A further object of the present invention is to alleviate at least one disadvantage associated with the related art. [0023] It is an object of the embodiments described herein to overcome or alleviate at least one of the above noted drawbacks of related art systems or to at least provide a useful alternative to related art systems.

6 [0024] In a first aspect of embodiments described herein there is provided a light emitting assembly suitable for retrofitting to luminaires, the light emitting assembly comprising: - an LED module, and - a heat sink device, wherein the heat sink device comprises a projecting central portion for mounting the LED module. [0025] In a second aspect of embodiments described herein there is provided a luminaire, the luminaire comprising: - a reflector defining a recess configured to receive a light emitting assembly, and - a visor in engagement with the reflector, wherein the light emitting assembly has an LED module mounted on a heat sink device. [0026] Typically the luminaire is a decorative luminaire, such as those for external use in private or public areas. [0027] The heat sink device is typically manufactured of a metal having good heat conductivity such as aluminium, copper or an alloy thereof. Preferably the heat sink is of unitary construction. For example it may be cast or pressed in one piece, or consist of a number of metal pieces made integral by welding. The shape of the heat sink may be optimised to maximise surface area and obtain the greatest heat dissipation possible subject to the limitations imposed by the area in which it is enclosed, principally dictated by the shape and size of the reflector and the visor. The positioning of the LED module may also used to optimise heat dissipation.

7 [0028] The heat sink may also be shaped or positioned to take maximum advantage of air flow through, or in convection currents, within the reflector that may help to dissipate heat. [0029] Typically the heat sink device further comprises a peripheral flange. In one embodiment the heat sink is generally circular, having a projecting flange around the circumference and a projecting frusto-conical central section on which the LED module is mounted. The circular flange is shaped to fit flush with the inner surface of a bell-shaped reflector. [0030] In another aspect of embodiments described herein the heat sink device of the light emitting assembly is generally circular in cross section and includes: - a projecting central portion for mounting the LED module, - a peripheral flange, and - a flat region intermediate the projecting central portion and the peripheral flange. [0031] In another embodiment the heat sink is generally rectangular having a projecting flange around the periphery and a projecting rectangular central section on which the LED module is mounted. The circular flange is shaped to fit flush with the inner surface of a rectangular-shaped reflector. [0032] In one preferred embodiment the heat sink is a generally 'W' or 'M' shaped in vertical cross section and circular in horizontal cross section. [0033] The projecting central section may be of any convenient conformation. For example, it may be frusto-conical shaped, T- shaped or of square in cross section. The uppermost surface of the projecting central portion is typically flat, or may be contoured to receive the LED module. The LED module will typically include a printed circuit board to which one or more LEDs, typically a plurality of LEDs is attached. Through-holes in 8 the heat sink device can allow electrical wires to extend from a driving module or control gear to the LED module. [0034] The visor may be of any convenient cross sectional shape, such as circular, oval or square. Typically the visor is generally frusto-conical in shape. The visor may engage with the reflector by any means well known in the art such as screw fitting, interference fit, snap fit or by use of attachment means such as latches. Preferably a thermopaste, also known as heat sink paste, is applied at the interface between the LED module and the raised central portion of the heat sink. Thermopaste improves thermal conductivity between components, for example, by filling micro-air gaps at the interface that have formed due to imperfections at the surface of the LED module and the heat sink. [0035] Typically the outer surface includes areas that include multiple small bevels or contours that control the spread of illumination from the lamp. The altered surfaces reflect or refract light from the LED module to the ground according to a desired photometric design. Preferably, when mounted on the heat sink device the LED module is located in the optimal position for generating the desired photometric design. It is particularly preferred that when the light emitting assembly is retrofitted to an external luminaire, the projecting section of the heat sink device locates the LED module in the optimal position. [0036] In a particularly preferred embodiment the projecting section of the heat sink device locates the LED module in a generally central position, for example, in the vicinity of a focal point within the visor. For example, the LED module is preferably located in the mid 60%, more preferably the mid 30% of the typical height dimension of the visor. [0037] In yet a further aspect of embodiments described herein there is provided a method of retrofitting the light emitting assembly of the present invention to an external luminaire comprising the steps of; - disengaging a visor from a reflector of the luminaire, - removing a non-LED lamp from the luminaire, 9 - inserting the light assembly into the reflector and attaching the heat sink device to the inner surface of the reflector, - re-engaging the visor with the reflector of the luminaire. [0038] Other aspects and preferred forms are disclosed in the specification and/or defined in the appended claims, forming a part of the description of the invention. [0039] In essence, embodiments of the present invention stem from the realization that a heat sink of appropriate conformation could be provided to overcome problems associated with the different physical characteristics of LEDs as compared with prior art lamps. [0040] Advantages provided by the present invention comprise the following: * the desirable characteristics of LEDs can be utilised; e can be readily retrofitted into existing decorative luminaires to improve energy efficiency, cost efficiency, and life span; e increases safety by reducing the risk of overheating; and * relatively economical. [0041] Further scope of applicability of embodiments of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the disclosure herein will become apparent to those skilled in the art from this detailed description.

10 BRIEF DESCRIPTION OF THE DRAWINGS [0042] Further disclosure, objects, advantages and aspects of preferred and other embodiments of the present application may be better understood by those skilled in the relevant art by reference to the following description of embodiments taken in conjunction with the accompanying drawings, which are given by way of illustration only, and thus are not limitative of the disclosure herein, and in which: Figure 1 illustrates prior art luminaires including luminaires of the type used for lighting freeways and roadways (Figs 1 a &1b) and decorative luminaires (Figs 1c & 1d); Figure 2 illustrates external luminaires according to the present invention having two different reflector shapes (Fig. 2a and Fig. 2b); and Figure 3 illustrates an embodiment of the heat sink device according to the present invention in bottom perspective view (Fig. 3a), top perspective view (Fig. 3b) and in vertical cross-section (Fig. 3c). DETAILED DESCRIPTION [0043] Figures 1a and 1b depict typical luminaires of the type used for lighting freeways and other roadways. These luminaires have a metal or polymer casing comprising a main body (1) with a port (3) for receiving a hollow support/bracket (5) which would typically be located at the top of a pole (6) up to 10 metres or more in height. A mains cable (not shown) would ordinarily be located within the support (5). [0044] The visor (7) is of unitary construction and at least in the vicinity of the lamp it is conformed to act as a prismatic lens. The visor (7) is typically made of acrylic, polycarbonate or other hard wearing polymer that can be made clear or translucent, however, other suitable materials may used as would be understood by the person skilled in the art. The electrical components for controlling operation of the luminaire are located within a termination chamber (13). The lamp and components of a reflector assembly (not shown) are visible through the visor (7).

11 [0045] The main body (1) and visor (7) are held together by clips (9) and integral hinges (not shown) located in corresponding positions on the other side of the main body (1) and visor (7), thus permitting movement of the visor (7) from a first, closed position to a second, open position permitting full access to the reflector assembly, lamp and termination chamber (13). [0046] Figures 1c and 1d depict a typical decorative luminaire. These include a bell or lantern shaped reflector (11) to provide an attractive appearance because these luminaires are readily visible - attached to walls or poles (16) by a decorative support bracket (15) at an elevation of 3 metres or higher. The support bracket (15) includes the mains cable and enters a port (14) in a termination chamber (18) that houses the electrical fittings (not shown) to which the lamp (20) is attached. The bell shape of the reflector (11) prevents light being lost vertically upward, providing better illumination at ground level. [0047] A visor (17) is provided to protect the lamp and the exterior surface of the visor (17) typically includes regions comprising multiple small bevels at angles that reflect or refract the light from the lamp (20) to the ground according to a desired photometric design. The visor (17) is attached to the reflector (11) by any convenient means such as clips. [0048] Figure 2a depicts an external luminaire according to the present invention. The external luminaire includes an integral body and reflector (30) having an outer surface that is typically painted or powder coated, and an inner surface that is shiny metal or painted with a very light colour for maximum deflection of light from the LED module. The reflector body and reflector (30) defines a recess configured to receive a light emitting assembly (32) comprising an aluminium heat sink device (34) and an LED module (36) mounted thereon. A visor (38) is in engagement with the reflector (30). The heat sink device (34) is seated against a gasket (31) and is removably attached to the body of the reflector by three quarter-turn screws (39a, 39b and 39c(not shown)). [0049] The reflector body and reflector (30) is attached to a bracket (37) which encloses a main electricity cable (not shown). The cable wires connect to a driving 12 module or control gear which in turn connects to the LED module. A photoelectric cell may additionally be included for alternate control of the illumination. [0050] Figure 2b depicts an external luminaire that is substantially the same as Figure 2a, except that the shape of the reflector (31) differs. Arrows indicate a potential path for air to pass through the interior of the luminaire, taking heat away from the heat sink device (34). When the visor (38) is connected to the heat sink device (34), such as, by clips, the LED Module (36) is hermetically sealed to avoid ingress of moisture, dust and insects. As there is no free air flow past the LED module (36), heat is typically conducted away from the heat sink device (34) and dissipated by free air flow and convection currents within the reflector (30). [0051] Figure 3a illustrates an embodiment of the heat sink device according to the present invention in bottom perspective view. Figure 3b illustrates the same heat sink device in top perspective view. Figure 3c illustrates the heat sink device of Fig.3(a) viewed in vertical cross-section, better illustrating that this embodiment of the heat sink is generally 'W' shaped. In horizontal cross-section the heat sink is generally circular. [0052] Around the periphery is a projecting flange (40). The free end of the flange is adapted on one side (43) to engage a visor. The other side (42) may optionally be designed to engage the inner surface of a reflector. The other end of the flange is integral with a flat disc shaped section (46). [0053] Holes (60) may be provided in the disc shaped section (46) to receive fitting such as screws or bolts used to retain the heat sink device within the reflector. The disc shaped section is integral with a projecting central portion (48) of frusto-conical shape. The planar top (50) of the frusto-conical projecting central portion is adapted for mounting an LED module and includes through-holes (52) for electrical connections or mechanical connectors for the LED module. The control gear and wiring can thus be kept on the opposite side of the planar top (50), enclosed in the space between the heat sink and the reflector. [0054] While this invention has been described in connection with specific embodiments thereof, it will be understood that it is capable of further modification(s).

13 This application is intended to cover any variations uses or adaptations of the invention following in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice within the art to which the invention pertains and as may be applied to the essential features hereinbefore set forth. [0055] As the present invention may be embodied in several forms without departing from the spirit of the essential characteristics of the invention, it should be understood that the above described embodiments are not to limit the present invention unless otherwise specified, but rather should be construed broadly within the spirit and scope of the invention as defined in the appended claims. The described embodiments are to be considered in all respects as illustrative only and not restrictive. [0056] Various modifications and equivalent arrangements are intended to be included within the spirit and scope of the invention and appended claims. Therefore, the specific embodiments are to be understood to be illustrative of the many ways in which the principles of the present invention may be practiced. In the following claims, means-plus-function clauses are intended to cover structures as performing the defined function and not only structural equivalents, but also equivalent structures. [0057] "Comprises/comprising" and "includes/including" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof. Thus, unless the context clearly requires otherwise, throughout the description and the claims, the words 'comprise', 'comprising', 'includes', 'including' and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Claims (10)

1. A light emitting assembly suitable for retrofitting to luminaires, the light emitting assembly comprising: - an LED module, and - a heat sink device, wherein the heat sink device comprises a projecting central portion for mounting the LED module.

2. A luminaire comprising: - a reflector defining a recess configured to receive a light emitting assembly according to claim 1, and - a visor in engagement with the reflector.

3. A luminaire according to claim 2 wherein the mounted LED is located in a generally central position within the visor.

4. A luminaire according to claim 1 wherein the heat sink device is generally circular in cross section and further includes: - a peripheral flange, and - a flat region intermediate the projecting central portion and the peripheral flange.

5. A heat sink device suitable for use in the light emitting assembly of claim 1, the heat sink device being generally circular in cross section and includes; - a projecting central portion for mounting the LED module, 15 - a peripheral flange, and - a flat region intermediate the projecting central portion and the peripheral flange.

6. A heat sink device according to claim 5 wherein the device is of unitary construction and manufactured of metal.

7. A heat sink device according to claim 5 being generally 'W' or 'M' shaped in vertical cross section, and circular in horizontal cross section.

8. A method of retrofitting the light emitting assembly of claim 1 to a luminaire comprising the steps of: - disengaging a visor from a reflector of the luminaire, - removing a non-LED module from the luminaire, - inserting the light assembly into the reflector and attaching the heat sink device to the inner surface of the reflector, - re-engaging the visor with the reflector of the luminaire.

9. A method according to claim 8 wherein the LED module of the inserted light assembly is located in the optimal position for generating a desired photometric design.

10. A method according to claim 8 wherein the LED module of the inserted light assembly is located in the mid 60% of the height dimension of the visor.