This invention relates to a lighting device, a lighting system, a method of cooling a luminaire and a method of illuminating a temperature-controlled environment. In particular, it relates to a lighting device for use in a temperature-controlled environment.

Background

In many industries, it is necessary to store goods under controlled temperature conditions. In many cases, typical storage conditions would be between 278K and 233K. The temperature-controlled storage environment would typically be comprised of a warehouse constructed in a conventional manner, with a separate structure fabricated from insulated panels within. Air conditioning equipment is used to reduce the temperature within the insulated area and to maintain it at the desired temperature.

The size of these storage areas varies from relatively small rooms to full size warehouse units. The operating cost of these facilities is greatly affected by the efficiency of the insulation and the air conditioning plant. Great effort is put into ensuring that as little heat energy as possible enters the chilled area, as any heat entering will need to be removed by the air conditioning plant, thereby increasing the energy consumption of the facility.

Although the storage area is held at low temperature, it will operate in all other respects in the same way as a conventional warehouse. Items will need to be put away, picked, packed and shipped as usual. This means that appropriate lighting levels are required, so that staff can carry out their work.

Light sources used for such applications have always involved a high level of compromise. Incandescent light sources will work at low temperatures, but have a very low ratio of light produced to heat, making them inefficient. Gas discharge light sources have a better light to heat ratio, but they become less efficient at lower temperatures and will not re-strike. This means that they cannot be controlled by sensors in such a way that they are only lit at appropriate times, i.e. they need to be permanently on. Known lighting devices for temperature-controlled environments also include standard high and low bay LED fittings. Although these have a good ratio of light produced to heat, they still release heat into the cold area. This heat must then be removed by air conditioning, which leads to an increase in the energy cost of the temperature-controlled facility.

Description of the Invention

It is an aim of the present invention to overcome the drawbacks associated with prior art lighting devices. This aim is achieved by providing a lighting device including heat transference means, to reduce the amount of heat energy released into the cold area by the lighting device.

Summary of the invention In accordance with a first aspect of the present invention there is provided a lighting device comprising:

a luminaire portion comprising a light-emitting means;

a heat sink; and

a heat transference means which connects the light-emitting means to the heat sink.

The light-emitting means may comprise at least one LED.

The heat transference means may comprise a heat pipe. Said heat pipe could be housed in a conduit. Such a conduit could comprise a plastics tube. A 'heat pipe' is a well known term in the art, and heat pipes are commonly used to cool computer systems.

The luminaire portion may comprise a thermally-insulated and watertight housing. The luminaire portion may incorporate a lens structure.

At least one such lighting device could be used in lighting system for a temperature- controlled environment, wherein

the luminaire portion of the or each lighting device is located in the temperature-controlled environment, and

the heat sink of the or each lighting device is located externally to the temperature-controlled environment.

The temperature-controlled environment may be delimited by an insulated wall.

The heat transference means of the or each lighting device may pass through the insulated wall.

Such a lighting system could further comprise control circuitry for the or each lighting device, the control circuitry being external to the temperature-controlled environment. Said control circuitry could be connected to the or each light emitting means via the heat transference means.

In accordance with a second aspect of the present invention there is provided a method of cooling a luminaire, the luminaire comprising a light-emitting means;

the method comprising the steps of:

providing a heat sink; and

providing a heat transference means connecting the light-emitting means to the heat sink.

The heat transference means may comprises a heat pipe. Said heat pipe could be housed in a conduit. Said conduit could comprise a plastics tube.

The luminaire portion may comprise a thermally-insulated and watertight housing. The luminaire portion may comprise a lens structure.

The luminaire portion may be located in a first area, and the step of providing a heat sink could further comprise locating the heat sink in a second area of a higher temperature than the first area.

The first area may be separated from the second area by an insulated wall. The step of providing a heat transference means may further comprises passing the heat transference means through the insulated wall.

Control circuitry for the lighting-emitting means may be provided in the second area. Said control circuitry may be connected to the light-emitting means via the heat transference means. In accordance with a third aspect of the present invention there is provided a method of illuminating a temperature-controlled environment comprising the steps of:

providing a luminaire portion comprising a light-emitting means inside the temperature-controlled environment;

providing a heat sink outside the temperature-controlled environment; and connecting the light emitting means to the heat sink via a heat transference means which passes through an insulated wall of the temperature-controlled environment.

The temperature-controlled environment may comprise a cold store.

Detailed description

The invention will now be described with reference to the accompanying drawings, in which:

Fig. 1 schematically shows an exemplary lighting device in accordance with the present invention;

Fig. 2 schematically shows a cross-sectional view of the lighting device of Fig. 1 ; and Figs. 3-5 schematically show perspective views of the lighting device of Fig. 1. Fig. 1 schematically shows a lighting device 1 . The lighting device 1 comprises three major components:

i) A luminaire portion 2;

ii) A heat transference means 3; and

Hi) A heat sink 4.

These three components are shown in more detail in the cross-sectional view of Fig. 2.

As can be seen in Fig. 2, in this example the luminaire portion 2 comprises a pair of LEDs 5a, 5b mounted onto respective heat pipes 6a, 6b, the heat pipes 6a, 6b in turn being mounted within a thermally insulated and watertight housing 7. A lens structure 8 is incorporated into the luminaire portion 2 by attachment to an open end of the housing 7, in the path of light produced in use from the LEDs 5a, 5b. Lens structure 8 acts to control light distribution.

The heat transference means 3 comprises a plastics tube 9, which is designed to, in use, pass through a dedicated channel in an insulated wall (for example, a ceiling of a cold store or other temperature-controlted environment) and which contains the heat pipes 6a, 6b, and an electrical wiring loom (not shown) for the LEDs 5a, 5b.

The heat sink 4 is designed to interface with the heat pipes 6a, 6b and to provide a mounting point for a power supply driver (not shown). A retaining collar 10, which surrounds an end section of the heat transference means 3, holds the lighting device 1 in position. The position of the retaining collar 10 may be varied to allow different thicknesses of insulated wall to be accommodated. In this embodiment, the heat sink 4 also has a centra! aperture 12, through which electrical cables for the LEDs 5a, 5b may be passed.

In use, the luminaire portion 2 is mounted inside a cold store or other temperature- controlled environment, the plastics tube 9 passes through an insulated wall (not shown) of the cold store, and the heat sink 4 is mounted on the opposite side of the insulated wall. In this embodiment, each LED 5a, 5b, has its own respective heat pipe 6a, 6b, however multiple LEDs may share the same heat pipe. Where there are multiple heat pipes, it is preferable to have all the heat pipes enclosed by a single plastics tube 9, and for all the heat pipes to pass through a single channel in the insulated wall to minimize disruption to the thermal wall and its insulating properties. However, providing respective channels for each heat pipe is not precluded by the present invention.

The luminaire portion 2 in this embodiment comprises a pair of LEDs 5a, 5b contained within a housing 7. The housing 7 is typically constructed of a circular rim formed of a plastics material, and a lens portion 8 formed of a plastics material, e.g. polycarbonate. The lens 8 can be double-glazed to minimize heat transfer from the LEDs through the lens 8. When the light-emitting portion is connected to an insulated wall, a gasket (not shown) may be disposed between the housing and the insulated wall to minimize heat leakage at the interface. Such a gasket may be formed of, for example, neoprene.

The heat sink 4 is located on the opposite side of the insulating wall to the luminaire portion 2. In this embodiment, the heat sink 4 comprises a metal heat sink having a plurality of cooling fins 11 (see Fig. 1). The heat sink 4 transfers heat from the heat pipes 6a, 6b to the ambient air. This allows heat from the LEDs to be transferred from one side of the insulated wall and released into the ambient air on the opposite side of the insulated wall. A gasket (not shown) may be disposed between the heat sink 4 and the insulated wall to prevent ambient air from entering the channel. Such a gasket may be formed of, for example, neoprene.

Advantages of the invention

There are numerous advantages associated with the present invention. For example, conventional lighting devices normally mount the electronic drivers and controls within the housing of the lighting device, or attach them to the outside of the housing. If such a conventional lighting device is used in a cold store, this means that these components are within the cold environment. Consequently, the components are difficult to access, due to restrictions on working within a cold environment, and the components themselves disadvantageous^ produce heat, further adding to the air-conditioning operating cost. With the device of the present invention, these components are situated at the distal end of the heat transference means, i.e. outside the cold store, in an ambient temperature area, where they are easily accessible and also able to lose their heat into ambient temperature air.

The invention is not limited to the specific embodiments disclosed above, and other possibilities will be apparent to those skilled in the art. For example, For example, the luminaire could be evacuated to further prevent heat conduction from the light- emitting means to the temperature-controlled environment (in use). Where the heat transference means is electrically conductive, such as when the heat transference means comprises one or more copper heat pipes for example, the heat transference means can be used to supply electricity to the light-emitting means. This allows dedicated electrical cables to be removed from the lighting device. Although the embodiment disclosed above uses heat pipes as the heat transference means, there are alternative methods of achieving a similar effect, e.g. via a pumped air circulation system or by using a solid conductor (e.g. a metal bar) to transmit the heat. However, heat pipes are particularly useful due to their efficiency, thermal capacity and lack of moving parts. A combination of such techniques could be used if appropriate and if available space allows.

In an alternative embodiment, air could be pumped through the lighting device and an air source heat pump is used to recover the heat for use elsewhere, e.g. to heat another location in the building in which the lighting device is situated.