Field of the Invention

The present invention relates to lighting units, and to replaceable light components and/or light fittings comprising the lighting unit.

Background of the Invention

Co-pending PCT application number PCT/GB2016/050338 (unpublished at the date of filing of the present application; a copy is attached hereto for reference) discloses a lighting panel (especially a lighting panel adapted and configured for use in a backlight unit for a display panel), the lighting panel comprising a substrate with a reflective surface, the substrate being formed of, or comprising, a plurality of channel sections, each channel section comprising a major light source and a minor light source, the light sources being disposed in a corresponding respective major and minor groove formed in the channel sections, the major and minor groove formed in the channel sections, the major and minor light sources within the same channel section being at least partially separated by an opaque projection therebetween, such that light output from one of the light sources is substantially prevented from being incident on the other light source in the same channel.

The preferred light sources disclosed in PCT/GB2016/050338 are electroluminescent tubes. These are deployed in channel sections which are linear, or preferably substantially linear. The electroluminescent tubes are themselves typically substantially linear, but the prior art document discloses that the tubes "preferably comprise curves or bends through 180° at the end of the linear channel sections, so as to follow a continuous serpentine path through the channel sections", and that the channel sections themselves "may similarly comprise 180° bends at the end of the linear section, so that the channel equally follows a single, continuous serpentine path". The present invention is based on the realisation that a preferred arrangement has both electroluminescent light tubes, and corresponding channel sections, of a shape not disclosed in PCT/GB2016/050338.

Summary of the Invention

In a first aspect the invention provides a lighting unit, the lighting unit comprising a substrate with a reflective surface, the substrate being formed of, or comprising, one or more channel sections, the or each channel section comprising a major light source and a minor light source, the light sources being electroluminescent tubes disposed in a corresponding respective major and minor groove formed in the channel section, the major and minor light sources within the same channel section being at least partially separated by an opaque projection therebetween, such that light output from one of the light sources is substantially prevented from being incident on the other light source in the same channel, characterised in that the channel sections and electroluminescent tubes are wholly or substantially non-linear along their length.

Particularly preferred embodiments of the channel sections and their associated electroluminescent tubes are circular or annular, elliptical, planar spiral (i.e. in which the channel section has a substantially constant vertical height) or a vertically ascending/descending helix. It will be apparent that the electroluminescent tubes are essentially parallel to, and follow the course of, the respective grooves in the channel sections.

The phenomenon of electroluminescence is well-known to those skilled in the art. Electroluminescent tubes typically comprise a tubular inner electrode, overlaid with one or more insulation layers, a light-emitting luminescent layer, a transparent, electrically-conductive layer, an outer filament electrode, and a transparent outer insulation layer. Electroluminescent inks suitable for use in EL tubes for the lighting unit of the invention are commercially available from e.g. EL International (Charlotte Street, London). Preferably the EL tubes comprise a rigid, hollow tubular inner electrode, typically comprising aluminium. The emission spectra of the electroluminescent tubes primarily depend on the composition of the luminescent material. The major light source and the minor light source may be different e.g. have different peak emission wavelengths. More preferably however the two light sources will both be of substantially the same type and/or have essentially identical emission spectra.

The preferred choice and characteristics (such as size, shape, colour etc.) of the light sources will depend on the intended application of the lighting panel.

A particular aim of the present invention is to provide a lighting unit providing visible light with a low electrical power consumption. Another advantage of the lighting unit of the present invention is the uniformity of light output. The lighting unit of the invention is suitable for use in general lighting applications, such as commercial or domestic lighting, especially where low power consumption and uniformity of light distribution are important factors.

To achieve these aims, the present invention maximises the light output by having at least two electroluminescent light tube sources in each channel section of the lighting unit. Moreover, in order to reduce the problem of the light emitted by one of the light sources being absorbed by the other light source in the same channel section, the two light sources are separated by an opaque projection, the geometry of which is preferably devised so as to allow the light to exit from the channel section in the desired direction (e.g. outwards from the channel section). In the present context, the projection between the major and minor light sources in question. The lighting unit of the invention may comprise a plurality of channel sections, each of which comprises a major and minor light source disposed within a respective major and minor groove, as described above.

The electroluminescent (EL) tubes preferably comprise inorganic zinc sulfide phosphor compounds. Preferred EL tubes for use in the lighting panel of the invention comprise a transparent, electrically-conductive indium tin oxide (ITO) layer, more especially a thin nanoparticular (65-75nm mean particle diameter) array ITO layer. Preferred EL tubes comprise a thin outer insulator layer comprising or substantially formed of silicone (which absorbs very little light). Preferably the EL tubes comprise a layer comprising nanoparticular ITO and an outer layer of silicone. Whilst thin films of ITO have the great advantage of being relatively transparent to visible light, they have lower conductivity than conventional conductors such as aluminium or copper. It is desirable for the EL tube to include an outer wire filament electrode in electrical contact with the electrically-conductive ITO layer, in order to distribute the current and potential difference effectively along the length of the EL tube. For example, the applicant has found that the use of an aluminium or copper wire filament, about 0.1-0.3mm in diameter, helically wound or otherwise arranged around the outside of the ITO layer, can be beneficial.

Conveniently the EL tubes, and the outer wire filament around the ITO electrically- conductive layer, communicate at each end (of the tubes and the wire filament electrode respectively) with positive and negative connectors, which provides electrical connection with a power source.

Preferably the EL tubes used in the lighting unit of the invention are formed by a process comprising electrophoretic deposition ("EPD"). The complex tube geometry means that it is difficult (but not impossible) to build the layers by more conventional deposition techniques such as sputtering or physical vapour deposition (PVD) etc. In addition, the Applicant considers that electrophoretic deposition can achieve greater uniformity of layer thickness giving greater performance and/or efficiency (also thereby avoiding formation of blackspots or pinholes, which can lead to premature degradation of the product) and facilitate automation. In one embodiment, a cathodic electrophoretic ("cataphoresis") process is used in which negatively-charged aluminium core tubes are coated with uniform layers of positively-charged particles of e.g. BaTi0 ₃ , ZnS:Cu phosphor and ITO. The electrophoretic system conveniently comprises an organic liquid solvent, such as an alcohol, and a salt of a metal such as aluminium, magnesium, thorium, zinc, nickel, yttrium or cerium. Methods of electrophoretic deposition of luminescent materials are known to those skilled in the art and, inter alia, are disclosed in US 2,851,408 and US 6,004,686. The preferred choice and characteristics (such as size, shape, colour etc.) of the light sources will depend on the intended application of the lighting unit.

For visible light, luminous intensity is a measure of the power emitted by a light source in a particular direction (per unit angle). The SI unit of luminous intensity is the candela (cd).

The preferred design of lighting unit of the present invention provides tubular light sources which have a light-emitting area that is greater than the area of the width of the channel through which light is emitted. In a preferred embodiment, the electroluminescent light sources emit light in a 360° plane along at least part of their length and are substantially tubular along most or substantially all of their length. This emitted light is gathered and reflected by the reflective substrate towards the top or aperture of the channel section, such that there is an increase in the nominal luminous intensity of the light sources in the desired direction (e.g. out of the channel section and towards an intended target).

Where a plurality of channel sections is present they may be preferably substantially identical in profile. A plurality of channel sections may conveniently be in a parallel array, but this is not essential and may depend on the intended purpose of the lighting unit. Desirably, in order to maximise the light intensity (in terms of candela per m ² ) output from the unit, adjacent channel sections should preferably be arranged with no spacing or gap between them, or as small a gap as is feasible, and preferably the channel sections form a regular array. For economy of material, the side wall of one channel section is preferably shared with, or common to, an adjacent channel section. It will be apparent that the maximum external dimensions of the array may be selected according to the size of the lighting unit required for the intended purpose.

In a preferred embodiment, the lighting unit of the invention comprises at least one annular, helical or elliptical channel section, with a correspondingly-shaped annular, helical or elliptical tubular light source within the respective major and minor grooves of the channel section. In a particular embodiment the lighting unit takes the form of a replaceable component with a conventional screw-fit, bayonet-fit, or other attachment means for attachment to a conventional electric lamp fitting, and can be used to retro-fit to existing conventional lamp fittings in place of, for example, incandescent light bulbs; LED light fittings, or compact fluorescent lamps.

Preferably, a highly reflective surface (such as a mirrored finish) is provided on the substrate to reflect light emitted from the light sources towards the aperture. The coating has a high reflectance (R), typically over 90%, and preferably a very high reflectance (over 95%). In preferred embodiments, the substrate is coated with a highly reflective coating comprising aluminium. A preferred coating comprises a specular, bright-dipped, anodised aluminium 6000 series alloy, such as aluminium 6063. (By way of explanation, 6000 series aluminium alloys comprise aluminium alloyed with magnesium and silicon). Alloy 6063 is widely used as it has high malleability, but other 6000 series alloys are also suitable.

An electrophoretic process may conveniently be used to apply the reflective coating to the substrate. If the substrate is conducting (e.g. aluminium or aluminium alloy), then the process is straight forward. If however, a plastic substrate is used this is not electrically conductive to a sufficient extent, and as an initial step therefore the plastics substrate must first be coated with a conductive layer. This is conveniently achieved by a "plating on plastics" (POP) process, which is known to those skilled in the art. Thereafter, the substrate (e.g. the synthetic plastics substrate chassis) is made the cathode and positively charged aluminium ions are reduced to aluminium metal on the substrate. Once coated with specular aluminium the coated chassis is then preferably subjected to a "bright dipping" process, which increases the brightness or reflectance of the aluminium by reducing, at a microscopic level, the roughness of the surface by reducing the "peaks" thereof. Most commercially available bright dipping procedures involve the use of dip baths comprising a mixture of phosphoric and nitric acids. Various additives may be included to reduce the amount of nitrogen oxide fumes produced and to enhance the brightening ability of the bath.

Preferably the reflective surface is profiled so as to reflect towards the aperture at least some, (preferably most) of the light initially emitted from the electroluminescent lights in directions other than towards the aperture. This further increases the proportion of the emitted light which reaches the aperture. The reflective surface may include curved portions for reflecting light emitted from the tubes towards the display panel. For example, the curved portions may define a parabolic surface profile in transverse cross-section.

Returning to the preferred features of the geometry of the channel sections and the disposition of the major and minor light sources within the channels, the substrate (typically formed of a synthetic plastics material, such as acrylonitrile butadiene styrene ["ABS"], or ABS polycarbonate blends, or the like) may conveniently be formed by extrusion moulding, or may be formed from extruded aluminium or an aluminium alloy. In a preferred embodiment, in cross-section, the channel section has a major groove, accommodating a major light source, and a parallel minor groove, accommodating a minor light source. The minor groove is shallower and thinner than the major groove. In addition, the minor groove is positioned higher than the major groove, and offset to one side. Conveniently part of one side wall of the major groove also forms part of one side wall of the minor groove, this being the projecting portion which at least partially separates the major and minor grooves. The major groove, in cross-section, may preferably be substantially goblet or tulip-shaped. The minor groove in cross-section may be substantially cup-shaped or semi-circular with one side wall of the groove being extended relative to the other side wall.

This arrangement is found to increase the amount of effective light-emitting surface area of the light source within the channel section (relative to the target plane aperture), whilst substantially minimising the amount of light which, emitted by one light source, is incident upon the other light source (and which might therefore be absorbed thereby).

Desirably, the channel section has a target plane aperture width (i.e. the width of the opening in the channel section through which light from the light sources exits the channel section) in the range 9-50mm, preferably 9-35mm but this may vary greatly depending on the intended purpose of the lighting unit (larger or smaller). The geometry and the reflective coating of the substrate acts as a light "concentrator" and director, by reflecting light emitted from the light sources within the channel section and directing it into a reduced cross-sectional area, thereby increasing the effective light intensity.

Conveniently both light sources are substantially tubular in cross-section along most or all of their length. Preferably the ratio of the diameter of the major light source to the diameter of the minor light source is in the range 1.3 : 1 to 1.7: 1, more preferably in the range 1.4: 1 to 1.6: 1. In one embodiment, the major light source has a diameter in the range 4.0- 15mm and the minor light source has a diameter in the range 2.5- 10mm. More especially the major light source preferably has a diameter of about 4.0-11.0mm and the minor light source has a diameter of about 2.5-7.0mm. Other embodiments may have larger or smaller diameter light sources, but the ratio of the diameters noted above is conveniently preserved. Conveniently, the diameter of the major and minor grooves in the channel section will be in substantially the same ratio as the diameters of the major and minor light sources, and the grooves may thus advantageously be scaled up or down in accordance with the diameter of the light sources.

In a second aspect, the invention provides a replaceable light component for emitting visible light, the component comprising a lighting unit in accordance with the first aspect of the invention (wherein the light sources are visible light-emitting electroluminescent tubes), and conventional attachment means for attachment to a conventional light fitting. The attachment means may be, for example, a bayonet attachment, or a screw-fitting attachment. Further, the replaceable component will conveniently comprise conventional means for making electrical contact with an electrical power supply provided to the light fitting. The power supply will typically be a mains power supply. Accordingly, in preferred embodiments, the replaceable light component may be simply attached and connected to a conventional light fitting and be illuminated in essentially the same way as a conventional bulb or the like. The entire replaceable component can be replaced, upon failure, by a new replaceable component. In particular embodiments the light component may be adapted and configured for connection to an otherwise conventional uplighter or downlighter light fitting.

In one embodiment, a common voltage may be provided to both the major and the minor light sources in the channel section of the lighting unit. In other embodiments, a different voltage is applied to the two light sources. The person skilled in the art can arrive at a suitable arrangement appropriate voltages and currents, with the benefit of the present disclosure, without requiring inventive effort.

In a third aspect, the invention may provide a light or lamp, comprising the lighting unit of the first aspect of the invention, which optionally may be powered (solely or in part) and/or recharged (solely or in part) by human effort. The light or lamp may be provided with an integral crank (especially a hand crank) or the like for converting work done by a human into kinetic energy. Alternatively, the light or lamp may be provided with means for accepting, in operable relationship, an external hand crank or other crank. The amount of cranking required to store a suitable amount of electrical energy to give a reasonable period of usage will depend on the power of consumption of the lighting unit when in operation and the presence/absence and capacity of any batteries. The person skilled in the art can calculate the amount of energy (in Joules) required to give, say, a 15 minute or 30 minute period of usage and design the crank (and indicate the necessary number of rotations of the crank, or period of cranking at a constant speed) accordingly. In other embodiments the light or lamp of the third aspect is conventionally powered by connection to a mains electrical power supply, or by batteries.

In some embodiments the light or lamp is a hand-held portable device. In some embodiments the light or lamp is configured to operate using one or more batteries as the primary power source, especially if the device is hand-held and portable. Desirably the batteries are rechargeable. In non-hand-held contexts, where weight considerations are less important, preferred rechargeable batteries comprise lithium iron phosphate (LiFeP0 ₄ ) batteries, such as those commercially available from pbq batteries. In some embodiments the batteries may be recharged by connection to a mains power supply. As an alternative, or in addition, to recharging by connection to a mains power supply, the batteries may be recharged by connection to a renewable power supply, (e.g. locally-generated electrical power deriving from wind or sunlight) and/or recharging by human effort.

In a fourth aspect the invention provides a method of making a lighting unit in accordance with the first aspect of the invention, the method comprising the step of: assembling, in operable relationship: a substrate with a reflective surface, the substrate being formed of, or comprising, at least one channel section; and a major light source and a minor light source, said light sources being electroluminescent tubes disposed in a corresponding respective major and minor groove formed in the channel section, the major and minor light sources within the same channel section being at least partially separated by an opaque projection therebetween, such that light output from one of the light sources is substantially prevented from being incident on the other light source in the same channel, and characterized in that the channel sections and the electroluminescent tubes are substantially non-linear along their length.

The preferred features of the lighting unit are as described above, and performance of the method of the fourth aspect of the invention preferably results in the production of a lighting unit having one or more of the aforesaid preferred features.

The invention will now be further described by way of illustrative example and with reference to the accompanying drawings, in which:

Figure 1A is a side view of one embodiment of a substrate for a lighting unit in accordance with the invention;

Figure IB is a detail of an enlargement of part of the substrate shown in Figure 1 A; Figure 1C is an enlargement of the part shown in Figure 1A;

Figures 2a, b and c are illustrations of a light fitting comprising a lighting unit in accordance with the first aspect of the invention: Figure 2a is a perspective view from above, Figure 2c is a perspective view from below, and Figure 2b is a median transverse sectional view;

Figures 3a-c are illustrations of a further embodiment of a light fitting comprising a lighting unit in accordance with the first aspect of the invention: Figure 3a is a perspective view from above, Figure 3c is a perspective view from below, and Figure 3b is a median transverse sectional view;

Figures 4a-d are illustrations of yet a further embodiment of a light fitting comprising a lighting unit in accordance with the invention: Figure 4a is a plan view from below, Figure 4b is a section along the line A-A in Figure 4a, Figure 4c is a plan view from above and Figure 4d is a perspective view from above;

Figures 5a-c and 6 are illustrations of an embodiment of a replaceable light component comprising a lighting unit in accordance with the first aspect of the invention: Figure 5a is a perspective view from above, Figure 5b is a median sectional view, Figure 5c is a perspective view from below, and Figure 6 is a view of the embodiment with a protective cover or diffuser in position.

Examples

Example 1 - substrate for use in a lighting unit in accordance with the invention.

Referring to Figure 1, a preferred substrate (2) is formed from extruded plastics material, such as ABS or ABS polycarbonate mix. (In other embodiments the substrate may be formed from extruded aluminium or an aluminium alloy). The substrate comprises a plurality of channel sections (4) arranged in a parallel array, the channel sections being substantially non-linear along their length (e.g. circular or annular). The entire upper surface of the substrate is coated with a highly reflective specular coating of bright-dipped, anodised aluminium 6063 alloy. The channel sections are arranged in the array with little or no gap between adjacent channel sections, in order to maximise the intensity of light output from the unit. The external dimensions of the array are determined according to the size of lighting unit required. Each channel section (4) comprises a major longitudinal groove (6), which is tulip or goblet-shaped in transverse section, and a parallel minor longitudinal groove (8), which is generally semi-circular in transverse section, which grooves are partially separated by a projecting portion (10), which forms part of one side wall of the major groove (6) and most or all of one side wall of the minor groove (8). The major groove (6) and the minor groove (8) accommodate, in the completed lighting unit, a respective major light source and minor light source (not shown in Figures 1A, IB). The light sources electroluminescent light tubes emitting light predominantly in the visible wavelengths (400-750nm).

Each channel section 4 comprises a pair of side walls (12), which side walls are shared with the adjacent channel section on each side. The side walls (12) are vertical when the substrate is laid horizontally, as shown in Figure 1.

In the embodiment shown, the major groove (6), at its widest point, is 22.5mm. The minor groove (8), is 12.0mm wide at its widest. The target plane aperture ("w" in Figure IB) of each channel section is 28.5mm wide. The major groove (6) accommodates a circular cross-section light source which is l l-12mm in diameter. The minor groove (8) accommodates a circular cross-section light source which is 7- 8mm in diameter. However, it will be apparent that the width of the grooves, the width of the target plane aperture etc. can be varied considerably according to the intended purpose or application of the lighting unit.

The minor light source is centred above and to one side of the major light source, with the opaque projecting portion (10) therebetween. This arrangement entirely, or almost entirely, prevents light emitted from one light source being incident upon the other light source in the same channel section, thereby minimising light lost due to absorption by the light sources.

The light sources preferably have a surface area considerably greater than the area of the channel section through which they emit. Thus, if one considers a very thin 1mm transverse "slice" through the display panel, the area of the aperture of the channel is 28.5mm ² .

The light-emitting surface area of the major tubular light source is given by the formula for the circumference of a circle (c= d). Assuming the diameter of the tube to be 11.5mm, the area of the 'slice' of tube is 36.1mm ² . The light emitting area of the minor tubular light source (assuming a diameter of 7.5mm ² ) is 23.6mm ² , so the combined light emitting area of the light sources is 59.7mm ² . Even allowing for absorption of some light by the reflective substrate and by the tubes themselves, it is clear that the apparent luminous intensity of the light sources, in the direction of the channel section aperture, is significantly increased.

The detailed geometry of an embodiment of the reflective substrate is apparent in Figure 1C, which is an enlargement of the embodiment shown in Figure 1, showing the dimensions of various features (in mm), from 0-4 lmm in height (scale on the left hand of the drawing) and from 0-29mm in width (scale at the top of the drawing), together with the measurements of selected angles and radii of curvature. The positions of the minor and major tubular light sources within their respective grooves are indicated by broken lines.

Radiometry is the science of measurement of radiant energy forms (such as light), in terms of absolute power. However, the human eye is not equally sensitive to all wavelengths of radiation, even within the visible part of the spectrum. Accordingly, photometry (the measurement of light in terms of its brightness as perceived by the human eye) accounts for this by weighing the measured absolute power with a factor that represents the sensitivity of the eye at that wavelength.

There are many different units in photometry, which measure many different characteristics, because the perceived "brightness" of a light source can be affected by many factors. For example, a light source may be bright if it has a high luminous flux or luminous power (measured in lumens, abbreviated as lm). Conversely a laser pointer, for example, may have a low luminous flux, but concentrates its output into a very narrow beam: it has (over a narrow angle), a high luminous intensity (measured in candelas, abbreviated as cd; candela = 1 lumen per steradian), which is the luminous power per unit solid angle.

The luminance of a source is measured in candela per square metre (cd/m ² ), and is the luminous power per unit solid angle per unit of the projected source area.

In the illustrated embodiment, the luminous intensity per unit area of each channel in the reflective substrate is determined according to the equation (1), where

(1) System luminous flux or output (in lumens or candela/m ² ) = (zrdjLi + d?L?) x R w w where

di = diameter (mm) of major light tube

d ₂ = diameter (mm) in minor light tube

Li = light output (as luminous flux at 2π cd) of major light tube

L ₂ = light output (as luminous flux at 2π cd) of minor light tube

w = target plane aperture width (mm) [indicated by "w" in Figure 2B) and R = the output coefficient of the total system (estimated as being approx. 75%, leading to a 1.4-1.5x gain on the initial luminous flux)

The Applicant has found that the illustrated embodiment provides a lighting unit with a luminous intensity comparable to that of a conventional lighting unit, but with a significantly reduced power consumption.

Example 2

Figures 2a-c shows various views of one embodiment of a light fitting in accordance with the invention. The light fitting comprises a housing 100 accommodating a substrate e.g. of extruded aluminium. The entire upper surface or the substrate is coated with a highly reflective specular coating of bright-dipped, anodized aluminium 6063 alloy. The substrate comprises a single channel section 4, which comprises a major longitudinal groove 6 and a parallel minor longitudinal groove 8, separated by a projecting portion 10, which forms part of one side wall of the major groove 6 and most or all of one side wall of the minor groove 8. The major groove 6 and the minor groove 8 accommodate a respective major (7) and minor (9) light source

The channel section 4 is annular, with the major and minor grooves and the major and minor electroluminescent light tubes being correspondingly shaped. Equally the housing 100 is essentially circular or annular to accommodate the channel section. In this embodiment, the electrical contacts and components may be provided in the centre of the housing.

In the illustrated embodiment, the light fitting comprises a single channel section, but in other embodiments the light fitting may comprise a plurality of channel sections. Where a plurality of such sections is provided, they may be formed in a regular array or multiplex with little or no gap between adjacent channel sections, in order to maximize the intensity of light output from the fitting. The external dimensions of the array are determined according to the size of light fitting required.

In one embodiment the channel sections may all be facing the same way in the array. In other embodiments, the channel sections may be "back-to-back".

Yet another embodiment of a light fitting is illustrated in Figures 3a-c. This embodiment is, in essence, a multiplexing of the embodiment shown in Figures 2a-c. In this multiplexed embodiment, there are four substantially identical circular channel sections positioned vertically in a stack, one on top of another, each channel section comprising respective grooves and circular or annular electroluminescent light tubes.

Example 3

This example relates to a light fitting comprising a lighting unit in accordance with the invention, which light fitting is especially useful for, and adapted and configured for use as, a downlighter, especially a ceiling-mounted downlighter. The embodiment is illustrated in Figures 4a-d.

Figure 4a shows a plan elevation of the embodiment from the underside. Figure 4b shows a sectional view through the fitting along the section indicated A-A in Figure 4a. Figure 4c shows a plan elevation of the embodiment from above, and Figure 4d shows a perspective view of the embodiment from above.

Referring to the Figures, the light fitting comprises a lighting unit in accordance with the first aspect of the invention. Topologically, the light fitting comprises only one channel section, but this follows a tightly wound planar spiral or helical pattern so as to form, in effect, an array of a plurality of channel sections adjacent one another, as best seen in Figure 4b (with seven channel sections each side of the spiral). As previously, the channel section comprises a major groove and a smaller, offset, minor groove, each of the grooves accommodating a respective major and minor fluorescent light tube.

The opposed ends 200, 202 of the light tubes are visible in Figure 4a at the outside (200) of the spiral and at the inside (202) of the spiral. As best seen in Figure 4d, the ends 200 and 202 are curved upwards above the plane of the spiral and terminate with a transverse support 204 which spans, on one side, from the centre of the spiral to its outer arm. The transverse support includes electrical terminals and connections to accept power from a mains electrical power supply and to transfer the electrical power to the electroluminescent light tubes. The support 204 is also provided with a ballast/starter to operate the tubes, along with any other electrical components necessary for the light fitting to operate.

The whole fitting is, in operation, covered with a protective transparent or translucent cover, comprised of glass or synthetic plastics material (e.g. polycarbonate) which may also act to diffuse the light emitted by the fluorescent light tubes.

Example 4 This example relates to an embodiment of a replaceable light component in accordance with the invention. The embodiment is illustrated in Figures 5a-c and Figure 6.

Referring to Figures 5a-c, the embodiment takes the form of an electroluminescent replacement for conventional incandescent electric light bulb, LED lighting fitting, or a conventional compact fluorescent lamp (CFL).

Figure 5a is a perspective view of the embodiment from above, Figure 5b is a median sectional view, and Figure 5c is a perspective view from below. As best seen in Figure 5b, the component comprises a lighting unit in accordance with the first aspect of the invention. The lighting unit comprises a single channel section arranged in a vertically ascending/descending helical pattern about a central core 206.

The helix has six complete turns so that the channel section forms, in effect, a multiplex array with six iterations of the channel section either side of the central core 206.

The channel section comprises a major groove and a minor groove, each accommodating a respective, appropriately-sized and shaped electroluminescent light tube. In this embodiment, the major light tube has a diameter of 3.8-4.7mm and the minor light tube has a diameter of 2.6-3.0mm, hence conforming to the preferred ratio range of 1.4-1.6: 1 for the tube diameters. The diameter of the major and minor grooves in the channel section are sized accordingly. The channel section has a target plane aperture width in the range 9.0-13.0mm, desirably in the range 9.7-12.5mm. The central core 206 accommodates a wire and electrical contact to established electrical connection with the bottom end of the tubes as indicated generally by numeral 208. A similar arrangement of wiring and contacts is provided (as indicated generally by numeral 210) at the upper end of the central core 206.

The top of the component is provided with a conventional screw fitting 212 for attachment to and electrical connection with a conventional screw-fitting light fixture, which provides mains electrical power to the replaceable light component. Finally, as shown in Figure 6, the component may preferably be provided with a transparent or translucent cover or diffuser 214, so as to protect the component and give it an aesthetically pleasing appearance.