WO1993009379A1

WO1993009379A1 - Lighting

Info

Publication number: WO1993009379A1
Application number: PCT/GB1992/002039
Authority: WO
Inventors: Julian Ding; Philip Leslie Martin
Original assignee: MARTIN, Phyllis, Barbara
Priority date: 1991-11-04
Filing date: 1992-11-04
Publication date: 1993-05-13
Also published as: GB9223107D0; GB2261061A; GB2261061B; AU2876792A

Abstract

A building includes downlights (D) supplied with light from a light source (L) via optical fibre cables (C). Each light (D) includes a lens (10) at the forward end of a terminal (T) which receives the end of the fibre in its rearward end.

Description

LIGHTING

The invention relates to lighting, especially to background lighting of the type provided by so-called downlightε, downlighter luminaires and the like. Such lights are typically used in large installations such as attria, shopping centres, restaurants, hotels, conference centres, theatres, concert auditoria, and the like. It is known to transmit light from electric bulbs within the downlights, but there is a need to replace the bulbs from time to time. Some installations are subjected to vibration and this, together with other factors, can mean that the bulbs need to be replaced every six weeks or so. The lighting is not easily accessible, as a result of which there is a high maintenance charge just for this job. It is one object of this invention to provide an improved downlighting system in which no such maintenance is required.

According to the invention in one aspect there is provided a downlight system comprising a source of light, at least one cable comprising optical fibre means extending from the light source to a fitting at the area to be illuminated.

Preferably there is a plurality of cables, each having a fitting, the cables drawing light from one or more sources of light. Most advantageously the fittings of the downlight system are located in a high rise ceiling or other inaccessible place. So far as we are aware, we are the first to realise that optical fibre cables can be used commercially for illumination in buildings etc, as opposed to just decoration or ornamentation.

Preferably a lens component is present at the fitting, the lens being in line with the free end of the cable. The shape of the lens will be determined by its physical location with respect to the end of the cable or the optical fibre means. The distance between the front end of the optical fibre means and the front end of the lens is one factor controlling the degree of illumination and the external shape of the lens is another. The lens is preferably conical in shape, having side walls which at their apex are inclined at about 60 degrees to the horizontal base. It is a much preferred feature of the invention that the diameter of the lens base corresponds to the diameter of the optical fibre means; preferably the diameter is about 10 mm.

Preferably the lens is made of a clear plastic such as polycarbonate or acrylic and is associated with a connection piece which comprises an elongate socket to receive an end length of the optical fibre body of the cable. The cable comprises a sheath, which may be formed of one or more layers, and a body or core of optical fibre, which may be a single element or a number of smaller diameter strands. It is a preferred feature of the invention that the core is formed of a solid single element which is flexible. Preferably the light conductive material is polymethylmethacrylate .

Preferably the fitting includes a reflector, preferably a parabolic reflector, having at or adjacent its centre a passageway through which extends a terminal having the lens component at a forward end, the rearward end comprising a connection piece to connect with the cable. Advantageously, the connection piece comprises an elongate socket to receive an end length of cable.

The lighting system is typically located in a high ceiling or other place to which access cannot be had readily.

In another aspect the invention provides a terminal comprising an elongate body having a lens component at one end and connection piece towards the other, the connection piece being arranged to receive the optical fibre body of a cable, the terminal being formed of light transmittive material.

Preferably the lens component is generally conical. Preferably the apex of the conical lens defines an angle of about 60 degrees with respect to an axis parallel to the base. Preferably, the terminal connection piece is arranged to receive an optical fibre having a fibre diameter of from 3mm to 12mm.

In order that the invention may be well understood it will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 is a diagram showing an overall downlighting system of the invention;

Figure 2 is a side elevation showing the detail of one downlight; and

Figure 3 is an enlarged sectional view of the terminal in the downlight of Figure 2.

Downlights D are spaced where required to provide illumination in a public place, e.g. a shopping centre, not shown. The downlights are located in a high rise ceiling or otherwise inaccessible place. As shown in Figures 2 and 3, each downlight comprises a terminal T having a lens 10 set in a hole 11 in the ceiling 12. Cables C comprising a plastics light insulation sheath Cl comprising an inner layer of Teflon and an outer layer of polyethylene surrounding a body C2 comprising a single solid flexible core of optical fibre extend between a light source L (e.g. a light box) at a central location to each of the downlights D. The cables may be of any appropriate length.

Preferably the cables have an outer black polyethylene sheath 10 mm in diameter and an inner Teflon sheath, 8 mm in diameter about a core 8 mm in diameter.

Each terminal T comprises a tubular element 13 having a rearward connection piece defining a passageway 14 dimensioned to receive an end length of the cable, i.e. the fibre and sheath of the cable and a forward extension defining the lens 10. The passageway 14 is of the same internal diameter as the body C2. The terminal T extends forward to the lens 10 which is of a conical shape to a point (rather like a bullet lens), the sides of the cone forming an angle of 60 degrees, as shown with respect to a plane parallel to the base of the cone. The terminal is formed of optically clear plastics, such as acrylic or a polycarbonate so that there is little, ideally no, loss of light in transmission. The exterior wall of the terminal passageway portion is threaded at 15, and two lock nuts 16a, 16b are present. A bracket 17 is mounted over each hole 11 in the ceiling 12, the roof 18 of the bracket having a hole 19 through which the terminal T passes. By adjustment of the two locknuts 16a, 16b, the position of the terminal T may be moved until the lens 10 is located appropriately in the hole of the ceiling or depending therefrom. In use, the downlight D is installed in the roof or ceiling, the forward end of the cable C is urged into the passageway 9 to reach the base of the lens 10. The terminal T is passed through the hole in the roof 18 of the bracket 17 and the nuts 16 fitted. The light is cold, and there are no parts which in use are consumed so little or no maintenance is required. A plurality of the downlights spaced closely together in an array provides the necessary illumination, even when a reflector is absent.

The invention is not limited to the embodiment shown. The terminal may be located in the hole using means other than the bracket. A parabolic reflector may be present. The lens component may be omitted. The wall need not be a roof or ceiling.

The invention can be applied to a wide range of available optical fibre cables. Typically fibre diameters will range from 3 mm to 12 mm. The lenses will be dimensioned according to the fibre diameter and may range from about 15 mm to about 100 mm in length; the outside diameter may range from about 5 mm to about 15 mm, and the inside diameter from about 3 mm to about 12 mm.

Claims

1. A downlight system comprising a source of light, at least one cable comprising optical fibre means extending from the light source to a fitting at the area to be illuminated.

2. A system according to Claim 1, wherein there is a plurality of cables, each having a fitting, the cables drawing light from one or more sources of light.

3. A system according to Claim 1 or 2, wherein the fittings are located in a high rise ceiling or other inaccessible place.

4. A system according to Claims 1, 2 or 3, wherein a lens component is present at the fitting, the lens being in line with the free end of the cable.

5. A system according to Claim 4, wherein the lens component is generally conical.

6. A system according to Claim 4 or 5, wherein the apex of the conical lens defines an angle of about 60 degrees with respect to an axis parallel to the base thereof.

7. A system according to any of Claims 4, 5 or 6, wherein the lens has substantially the same diameter as the cable or the optical fibre component thereof.

8. A system according to Claim 7, wherein the diameter is 10mm.

9. A system according to any of Claims 4 to 8, wherein the fitting includes a reflector, preferably a parabolic reflector, having at or adjacent its centre a passageway through which extends a terminal having the lens component at a forward end, the rearward end comprising a connection piece to connect with the cable.

10. A system according to Claim 9, wherein the connection piece comprises an elongate socket to receive an end length of cable.

11. A system according to any preceding Claim, wherein the cable comprises a sheath surrounding a single solid flexible light conductive element.

12. A terminal comprising an elongate body having a lens component at one end and connection piece towards the other, the connection piece being arranged to receive the optical fibre body of a cable, the terminal being formed of light transmittive material.

13. A terminal according to Claim 12, wherein the lens component is generally conical.

14. A terminal according to Claim 12 or 13, wherein the apex of the conical lens defines an angle of about 60o with respect to an axis parallel to the base.

15. A terminal according to any of Claims 12 to 14, wherein the terminal connection piece is arranged to receive an optical fibre having a fibre diameter of from 3mm to 12mm.