GB2485164A

GB2485164A - Retrofit LED light source for luminaire.

Info

Publication number: GB2485164A
Application number: GB1018489.3A
Authority: GB
Inventors: Ian Mulhall
Original assignee: FW Thorpe PLC
Current assignee: FW Thorpe PLC
Priority date: 2010-11-03
Filing date: 2010-11-03
Publication date: 2012-05-09
Anticipated expiration: 2030-11-03
Also published as: GB2485164B; GB201018489D0

Abstract

A retrofit LED light source 22 for a luminaire 10â has a base 24 and LEDs (28, fig 3) mounted on the base 24 by mounting arrangements 26. The base 24 has a reservoir body 30 which provides a thermal reservoir for heat from the LEDs (28, fig 3). The source 22 has a second mount 32 for mounting the base structure 24 in a luminaire housing 12â . The second mount 32 mounts the base structure 24 in the luminaire housing 12â in place of a conventional lamp (18, fig 1) and lamp holder (16, fig 1). The second mount 32 provides thermal contact between the reservoir body 30 and the luminaire housing 12â , to cause the luminaire 10â to serve, in use, as a heatsink for heat received in the reservoir body 30 from the LEDs (28, fig 3).

Description

lmjovernents in or Relating to Luminaire The present invention relates to improvements in or relating to luminaires.

Modern luminaires incorporate lamps constructed with various technologies, such as discharge lamps, amalgam lamps and fluorescent tubes. These operate most effectively at temperatures above typical ambient room temperatures. For example, modern discharge lamps may operate at temperatures from around 80°C up to 300°C, or higher. Luminaires therefore incorporate lamp holders which provide a thermal break between the lamp and the body of the luminaire, to reduce the heating effect of the lamp on the luminaire body.

The running temperature results in inefficiency arising from energy being lost to heating effects, rather than in providing light output from the luminaire. It has been proposed to substitute conventional lamps with LEDs for increased overall efficiency. However, the thermal operating requirements of LEDs are significantly different to those of conventional lamps. The light output efficiency of LEDs generally increases as the operating temperature is reduced.

Conventional luminaires, being designed for thermal operating conditions well above ambient room temperature, are therefore not optimal for use with LEDs.

Examples of the present invention provide a luminaire component comprising: a base structure; a first mounting arrangement operable to mount at least one LED on the base structure; the base structure comprising a reservoir body which provides a thermal reservoir for heat from the LED; and a second mounting arrangement operable to mount the base structure in the luminaire; wherein the second mounting arrangement is operable to mount the base structure in a luminaire in place of the lamp and lamp holder and, in use, provides thermal contact between the reservoir body and the luminaire to cause the luminaire to serve, in use, as a heat sink for heat received in the reservoir body from the LED.

The first mounting arrangement may provide a plurality of alternative mounting positions of LEDs on the base structure. The first mounting arrangement may be operable to clamp the or each LED to the base structure. The first mounting arrangement may comprise a carrier to which the LED is attached, and fixing means operable to fix the carrier to the base structure.

The reservoir body may be metal. The reservoir body may be aluminium. The reservoir body may have a mass of at least 0.1kg. The reservoir body may have heatsink fins.

The base structure may be elongate to extend from the second mounting arrangement and mount the LEDs at a position corresponding with a centre of light output of the replaced lamp.

Examples of the present invention will now be described in more detail, by way of example only, and with reference to the accompanying drawings, in which: Fig. 1 is a simplified schematic view of a conventional lamp luminaire; Fig. 2 is a simplified schematic view of a lamp luminaire incorporating a luminaire component in accordance with the present invention; Fig. 3 is a perspective view of the luminaire component incorporated in the luminaire of Fig. 2; Figs 4 to 8 are respectively side, front, rear, mount end, and remote end views of the luminaire component of Figs 3.

Background

Fig. I illustrates a luminaire 10 which incorporates a housing 12 containing a reflector 14, lamp holder 16 and lamp 18. The lamp 18 may be a discharge lamp, amalgam lamp or fluorescent tube, for example. The lamp 18 is mounted in the housing 12 by the lamp holder 16, in conventional manner. The housing 12 is wholly or largely metal, for robustness, and may be closed by a diffuser (not shown).

The lamp holder 16 and reflector 14 are arranged to provide the desired light distribution from the luminaire 10, by appropriate positioning of the lamp 18 relative to the reflector 14, appropriate shaping of the reflector 14, and other conventional approaches. These approaches take into account the distribution of the locations from which the lamp 18 provides light. This will differ according to the type of lamp. For the purpose of the following explanation, it will be assumed that the lamp 18 has at least one position 20 of particularly intense light output, here termed the "optical centre" of light output.

During use, the lamp 18 will run at elevated temperature, as noted above.

Accordingly, the lamp holder 16 provides thermal isolation of the housing 12 from the lamp 18. This reduces the heating of the housing 12, helping to protect other components (not shown) such as electronic control circuits.

Overview of first example Fig. 2 illustrates a luminaire having some features which correspond closely with those described above. Accordingly, those features are given the same reference numeral, with an apostrophe suffix. Thus, the luminaire in Fig. 2 is indicated as 10'.

The luminaire 10' incorporates a housing 12' containing a reflector 14'. The housing 12' is wholly or largely metal, for robustness, and may be closed by a diffuser (not shown). The lamp 18 and lamp holder 16 of the luminaire 10 (Fig. 1) are replaced in this example by a luminaire component 22. As can be seen from comparison of Fig. 1 and Fig. 2, the luminaire component 22 generally occupies the same position in the luminaire 10' as the lamp 18 occupies in the luminaire 10 of Fig. 1. The significance of this will be described below. It is first appropriate to describe the luminaire component 22 in more detail, with reference to the remaining drawings.

Luminaire component The luminaire component 22 comprises a base structure 24. A first mounting arrangement is indicated at 26 and is operable to mount at least one LED 28 on the base structure 24.

The base structure 24 comprises a reservoir body 30 which provides a thermal reservoir for heat from the LED 28. A second mounting arrangement 32 is operable to mount the base structure 24 in the luminaire housing 12'. The second mounting arrangement 32 mounts the base structure 24 in the luminaire housing 12' in place of the lamp 18 and lamp holder 16 of the luminaire 10. In use, the second mounting arrangement 32 provides thermal contact between the reservoir body 30 and the luminaire housing 12' to cause the luminaire 10' to serve, in use, as a heat sink for heat received in the reservoir body 30 from the LED 28.

in more detail, the reservoir body 30 is an elongate bar of a material which has a high specific heat capacity and a high thermal conductivity. "High specific heat capacity" is intended to refer to a value greater than 0.8J/g/°C, such as at least 0.9J/g/°C. "High thermal conductivity" is intended to refer to a value greater than W/mk, such as at least 200 W/mk. in this example, the reservoir body 30 is a metal, such as aluminium. The mass of the aluminium body 30 may be at least 0.1 kg. The body 30 is provided with heat sink fins 34, visible from the end profile (Fig. 3 and Fig. 8).

The drawings illustrate various LED components 28, each of which is a length of ladder LEDs. That is, each LED component 28 includes a line of LEDs wired in parallel within a common package. Each LED package 28 is mounted on a carrier 36 at fixing positions 38. Electrical wiring for supplying power to the LED packages 28 will be required, but is not illustrated in the drawings, in the interests of clarity.

Two carriers 36 are illustrated in the drawings. Each carrier 36 is fixed to the reservoir body 30 by fixing screws 40. The fixing screws 40 mate with corresponding threaded sockets in the reservoir body 30. In this example, there are more threaded sockets in the reservoir body 30 than are required to support the two carriers 36. This allows the carriers 36 to be fixed at various alternative mounting positions on the reservoir body 30, to match the LED position with the optical centre of the lamp which is being replaced. Some unused threaded sockets 42 are illustrated in the drawings.

The carriers 36 hold the LED packages 28 in intimate contact with the reservoir body 30 to provide good thermal contact between the packages 28 and the body 30. Thermal contact may be further improved by providing a thermal transfer medium between the LED packages 28 and the carriers 36, and/or between the carriers 36 and the body 30. Examples include graphite pads, thermal pastes and other media which are known in themselves.

In an alternative example, the LED packages 28 may be held against the reservoir body 30 by a clamping action performed by the carrier 36, rather than being attached to the carriers 36. Again, a thermal transfer medium may be used.

The reservoir body 30 is mounted in the housing 12' by means of the second mounting arrangement 32, which includes a bracket 44. The bracket 44 has a base plate 46 (see Fig. 7 in particular) having a surface area which is significantly larger than the cross-section of the reservoir body 30. Holes 48 are provided for fixing screws, fixing bolts or other fixings used to secure the base plate 46 to the housing 12' in place of the lamp holder 16 in the luminaire 10. In particular, the holes 48 are provided at a spacing corresponding with the spacing of fixing holes in the lamp holder 16, so that the bracket 44 can directly replace the lamp holder 16 without other modification being required in the housing 12. Thus, the housing 12' can be identical with the housing 12, allowing the Iuminaire component 22 to be fitted retrospectively to an existing luminaire 10 and housing 12.

The bracket 44 also has a support arm 50 which extends away from the base plate 46 and provides two screw fixings at 52, allowing the reservoir body 30 to be securely but removably attached to the bracket 44 and thus supported within the housing 12'. The support arm 50 has a large surface area and is held in intimate contact with the body 30 by the screw fixings 52, to provide good thermal contact between the body 30 and the support arm 50, and thus between the body 30 and the bracket 44.

Use of the luminaire component 22 When the luminaire component 22 has been mounted in the luminaire 10' in the manner described above, the luminaire 10' can be illuminated by providing power to the LED packages 28. The packages 28 will then produce light. The distribution of the light output of the luminaire 10' will therefore depend on the position of the packages 28 within the housing 12' and in particular, the relative positions of the packages 28 and the reflector 14'. In this example, the packages 28 are positioned around the reservoir body 30 at a spacing from the bracket 44 which generally corresponds with the spacing of the optical centre of light output 20, from the lamp holder 16 in the luminaire 10 of Fig. 1. The provision of alternative mounting positions for the carriers 36 on the body 30 allows the position of the LEDs to match the optical centre of a variety of different conventional lamps. Consequently, the light output of the packages 28 interacts with the reflector 14' in substantially the same manner as the lamp 18 interacts with the reflector 14. Consequently, the light output of the luminaires 10, 10' will be closely similar. In particular, if the luminaire component 22 is retrospectively fitted to an existing luminaire 10, as indicated above, we expect little or no change will be perceived in the overall distribution of the light output of the luminaire.

However, the thermal regime within the Iuminaire 10' will be significantly different to the thermal regime within the luminaire 10. As noted above, the lamp holder 16 will provide a thermal break between the lamp 18 and the housing 12, allowing the lamp 18 to run at an appropriate temperature, such as 80°C, without overheating the housing 12. However, in the luminaire 10', the packages 28 should be maintained at a lower running temperature, such as ambient room temperature, for improved efficiency. This is achieved in the following manner.

When the packages 28 are running, they create heat, which will tend to elevate their temperature. However, the packages 28 are in good thermal contact with the reservoir body 30, as noted above. Furthermore, the thermal mass of the body 30 is very large in comparison with the thermal mass of the packages 28, because of the size of the body 30 and because of the high specific heat capacity. Consequently, heat created within the packages 28 will flow into the reservoir body 30, thus allowing the temperature of the packages 28 to be maintained at, or close to their optimal working temperature of ambient room temperature. This heat flow is encouraged by the high thermal conductivity of the body 30.

Heat absorbed into the reservoir body 30 from the packages 28 can then flow along the body 30 and from the body 30 into the bracket 44. As noted above, close thermal contact is provided between the bracket 44 and the reservoir body 30, particularly between the support arm 50 and the body 30.

Heat absorbed into the bracket 44 from the reservoir body 30 can then flow from the bracket 44 into the housing 12'. As noted above, close thermal contact is provided between the bracket 44 and the housing 12', particularly by the large surface area of the base plate 46.

Accordingly, heat generated within the packages 28 is efficiently drawn first into the reservoir body 30, and then through the bracket 44 to the housing 12', allowing the whole of the housing 12' to serve as a heat sink for the packages 28.

Although that is undesirable in the case of a conventional lamp 18, in view of the relatively high operating temperature of a conventional lamp 18, the low operating temperature of LED packages 28 is expected to allow the housing 12' to be used as a heat sink in this manner, without resulting in unacceptable temperature rises within the housing 12'. Therefore, by using the housing 12' as a heat sink, rather than by thermally separating the light source from the housing, as in the luminaire 10, LED packages 28 can be maintained at or close to ambient temperature without adverse thermal effects arising elsewhere within the luminaire 10'.

Concluding comments The provision of multiple mounting locations for the LED packages 28 allows the same luminaire component 22 to mimic the light output of a range of conventional lamps 18. This1 in combination with the thermal management described above, is expected to allow the luminaire component 22 to be retrospectively fitted to a range of existing luminaires 18 designed for conventional lamps 18, providing the same or virtually the same light distribution from the luminaire, with the efficiency achieved from operating LED packages at or near to ambient temperature, and without other adverse thermal effects arising. This allows existing luminaires to be upgraded for the efficiency available from LED lighting, without redesign, retooling etc. Many variations and modifications can be made to the apparatus described above. In particular, many different materials, shapes, sizes and relative shapes and sizes could be chosen for the various components. In particular, these will be selected in accordance with the lamp holder being replaced, the light distribution of the lamp being replaced, and the thermal requirements of the LED structures being used.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or shown in the drawings whether or not particular emphasis has been placed thereon.

Claims

CLAIMS1. A luminaire component comprising: abase structure; a first mounting arrangement operable to mount at least one LED on the base structure; the base structure comprising a reservoir body which provides a thermal reservoir for heat from the LED; and a second mounting arrangement operable to mount the base structure in the luminaire; wherein the second mounting arrangement is operable to mount the base structure in a luminaire in place of the lamp and lamp holder and, in use, provides thermal contact between the reservoir body and the luminaire to cause the luminaire to serve, in use, as a heat sink for heat received in the reservoir body from the LED.
2. A component according to claim 1, wherein the first mounting arrangement provides a plurality of alternative mounting positions of LEDs on the base structure.
3. A component according to claim 1 or 2, wherein the first mounting arrangement is operable to clamp the or each LED to the base structure.
4. A component according to any preceding claim, wherein the first mounting arrangement comprises a carrier to which the LED is attached, and fixing means operable to fix the carrier to the base structure.
5. A component according to any preceding claim, wherein the reservoir body has a specific heat capacity of at least O.8J/g/°C.
6. A component according to any preceding claim, wherein the reservoir body has a thermal conductivity of at least 180 W/mk.
7. A component according to any preceding claim, wherein the reservoir body is metal.
6. A component according to claim 7, wherein the reservoir body is aluminium.
9. A component according to any preceding claim, wherein the reservoir body has a mass of at least 0.1 kg.
10. A component according to any preceding claim, wherein the reservoir body has heatsink fins.
11. A component according to any preceding claim, wherein the base structure is elongate to extend from the second mounting arrangement and mount the LEDs at a position corresponding with a centre of light output of the replaced lamp.
12. A luminaire component substantially as described above, with reference to the accompanying drawings.
13. Any novel subject matter or combination including novel subject matter disclosed herein, whether or not within the scope of or relating to the same invention as any of the preceding claims.