FIELD OF THE INVENTION

This invention relates to luminaires, and in particular luminaires used for linear trunking lighting, namely lighting formed as elongate channels which may be recessed into a surface or may be suspended from, or mounted against, a ceiling.

BACKGROUND OF THE INVENTION

Trunking lighting is used widely in large area buildings, such as warehouses, sports arenas etc. The trunking is formed using modular sections, which will be termed "luminaire units" in this description. In order to provide a desired path of illumination, comer units are typically used between adjacent straight units. At present, most corner schemes of for luminaires for trunking lighting use welding, which limits the possible shape of the luminaires.

It would be desirable if the trunking could follow any desired free-form continuous path, instead of requiring welded angular joints in order to approximate to the desired path shapes.

US 2022120954A1 discloses an LED lighting system includes a light guide plate.

US 2022162856A1 discloses a configurable linear lighting module for use within a suspended ceiling grid assembly.

SUMMARY OF THE INVENTION

The invention is defined by the claims.

According to examples in accordance with an aspect of the invention, there is provided a luminaire unit comprising: at least one side wall having a height direction and a length; a light guide having a pair of opposing total internal reflection, TIR, surfaces and a light entry region extending between the pair of TIR surfaces, wherein one of the TIR surfaces is attached to the side wall; a flexible LED board coupled to the side wall for delivering light to the light entry region of the light guide, wherein the flexible LED board is parallel with the height direction, with LEDs of the LED board being arranged to emit light with an optical axis in a normal direction of the LED board; and a reflector surface for reflecting said emitted light into the light entry region of the light guide, wherein the reflector surface is slanted with respect to the optical axis, and wherein the side wall, the light guide and the flexible LED board are curved about at least one axis parallel to the height direction, so that the luminaire unit follows a curved path within a plane perpendicular to the height direction.

This luminaire unit is curved about at least one axis parallel to the height direction (e.g. a z-axis). This means the light guide can be formed into a desired shape within a plane perpendicular to the height direction (e.g. an xy axis plane). In use, the height direction is for example vertical so the luminaire can be shaped in the horizontal plane. Light enters the light guide at a top portion, and preferably exits from a bottom portion. In this way, a luminaire can be shaped into a free-form continuous shape by using one or more of these luminaire units to form desired curves. This avoids sharp corners of trunking luminaires. Connecting linear luminaire units with rounded connecting pieces as can be provided by the luminaire unit of the invention, e.g., making curved connections, is much appreciated for cosmetic reasons and safety reasons - avoiding harm to operators with sharp corners.

The side wall is for example initially manufactured in a straight shape and then it can be deformed into a desired curved shape. Thus, it is bendable from a straight initially- manufactured shape into a desired end shape. The curvature is thus produced as a final part of the manufacturing process.

By mounting the LED board with its general plane in the height direction, e.g. vertically, it is able to be curved about one or more axes parallel to the height direction e.g. in a horizontal plane. Thus, in-plane bending of the LED board is not needed in order to produce the desired curvature of the shape of the luminaire. The light is emitted laterally with respect to the shape of the luminaire and then is reflected into the light guide. The reflector enables the LED board to be mounted in this desired orientation parallel to the height direction (giving the advantage of easy bending) and the normally emitted light from the LED board is hence laterally emitted light.

The light guide for example comprises a slab having a top surface, a bottom surface and opposing lateral surfaces, wherein the top surface comprises the light entry region, the bottom surface comprises a light exit region and the lateral surfaces comprise the total internal reflection surfaces.

Note that "top", "bottom" and "lateral" are not intended to require any particular orientation of the luminaire. For example, "top" and "bottom" merely designate opposing surface which may in use be positioned one above the other.

The light guide slab is easy to manufacture and can be formed simply as a cuboid, and then curved into the desired end shape. The light guide is for example extruded and then cut to length. The end surfaces are then polished to the desired optical smoothness level.

One or both of the opposing TIR surfaces may be provided with light extraction features.

These allow some light to escape from the light guide from the sides before the remainder of the light reaches the bottom of the light guide (the light exit region). This can for example be used to provide lateral as well as downward lighting.

The LEDs of the LED board are for example arranged to emit light in an outward direction. This means the light is directed away from the LED board on which the LEDs are mounted, with an optical axis in (or close to) a normal direction relative to the plane of the LED board. The light is directed laterally away from a central axis of the luminaire. In a typical orientation of the luminaire, this means the light is emitted in a sideways direction, and the reflector surface then redirects the light to a downward direction. Thus, the reflector surface directs outwardly directed light into the light guide, in particular into the top surface of the light guide, which lies in a plane perpendicular to the height direction.

The luminaire unit may comprise: two opposing side walls; a respective light guide attached to each side wall; and two flexible LED boards, each for delivering light to a light entry region of a respective one of the light guides.

Thus, light is emitted as two lines from the bottom of two side walls, at light exit faces of the light guides.

The, or each, light guide is for example formed of PMMA. PMMA can for example be formed into a desired shape by hot bending.

The, or each, side wall for example comprises a support which supports a respective light guide and a respective flexible LED board. The side wall thus ensures the correct alignment between the LED board and the light guide. It also provides strength to the luminaire unit. The, or each, side wall is for example aluminum. The side wall or walls can thereby be formed into a desired shape by extruding a straight length and then bending.

The luminaire unit may comprise: two opposing side walls; and a strut extending between the side walls, such that the side walls and the strut together define a side wall assembly with an H-shaped cross section.

This provides a strong assembly which maintains the desired positional relationship between the side walls.

The luminaire unit for example further comprising a cover over the top of the, or each, side wall. The cover is for example also formed of aluminum. The cover closes a space which may be used for housing electronic components of the luminaire such as the LED driver, although an external LED driver is also possible..

The invention also provides a luminaire comprising a set of luminaire units arranged in a line, wherein at least one luminaire unit comprises a curved luminaire unit as defined above, so that the luminaire follows a curved path within a plane perpendicular to the height direction.

At least one luminaire unit may also comprise a straight luminaire unit.

There is also preferably an end cap at each end of the luminaire. The end cap is a rigid part, for example formed by die casting.

The luminaire preferably comprises a trunking luminaire.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment s) described hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, and to show more clearly how it may be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, in which:

Figure 1 shows in schematic form a trunking luminaire;

Figure 2 shows that the curved shape of Figure 1 may be formed by combining straight sections and curved sections;

Figure 3 shows the construction of one luminaire unit in more detail; Figure 4 shows an exploded view of the various components of the line of luminaire units;

Figure 5 shows more clearly the optical parts of one possible design; and Figure 6 shows an alternative optical design.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The invention will be described with reference to the Figures.

It should be understood that the detailed description and specific examples, while indicating exemplary embodiments of the apparatus, systems and methods, are intended for purposes of illustration only and are not intended to limit the scope of the invention. These and other features, aspects, and advantages of the apparatus, systems and methods of the present invention will become better understood from the following description, appended claims, and accompanying drawings. It should be understood that the Figures are merely schematic and are not drawn to scale. It should also be understood that the same reference numerals are used throughout the Figures to indicate the same or similar parts.

The invention provides a luminaire unit which comprises a side wall and a light guide having a pair of opposing total internal reflection, TIR, surfaces, with one of the TIR surfaces attached to the side wall. A flexible LED board is coupled to the side wall for delivering light to the light guide. The flexible LED board is parallel with a height direction of the side wall, with LEDs of the LED board being arranged to emit light with an optical axis in a normal direction of the LED board. A slanted reflector surface is used to reflecting said emitted light into the light guide. The side wall, the light guide and the flexible LED board are curved about at least one axis parallel to the height direction.

Figure 1 shows in schematic form a trunking luminaire 10. The luminaire comprises side walls 12 and a top cover 14. As shown, the luminaire has a curved shape. In particular, the luminaire generally lines in a plane, which in use is typically a horizontal plane, but the luminaire follows a non-linear path within that plane. The luminaire is formed of multiple units, and curved units may be used to provide a junction between straight units so that together a desire free-form path may be followed.

Figure 2 shows that the curved shape of Figure 1 may be formed by combining three straight sections 20 and two curved connecting sections 22. The multiple sections may be considered together to define a luminaire. For the purposes of this description, each individual section may be considered to be a "luminaire unit". A luminaire may even comprise only a single curved luminaire unit.

Figure 2 shows the luminaire partially exploded and shows only the top cover 14 and the side walls 12. The side walls are connected together as a single integrated support, with an H-shaped cross section. The H-shaped cross section has a cross strut 13 which connects the two side walls. The cross strut extends between the two side walls, perpendicular to the side walls, and extends along the length of the integrated support, so that the integrated support has a same cross sectional shape along its length. This integrated support may be considered to comprise a side wall assembly. The side wall assembly can be extruded straight and then bent to shape. It is for example formed of aluminum.

Figure 3 shows the construction of each luminaire unit in more detail.

The luminaire unit comprises two opposing side walls 12. The side walls (and each luminaire unit, and the luminaire as a whole) have a height direction H and a length direction L. Since the luminaire is not straight, at least for one of the curved luminaire units along the length of the luminaire, the length direction may be considered to be the tangential direction at any given point along the length of the luminaire.

In a preferred design, each side wall incorporates a light guide, but there may be only one light guide so that only one side wall is used for delivering the lighting.

The light guide 30 comprises a slab, again having a height in the height direction and a length in the length direction. A top surface 32 of the light guide is a light entry region. The light entry region extends between facing parallel total internal reflection, TIR, surfaces 34. These TIR surfaces define the lateral sides of the light guide slab.

One of the TIR surfaces is attached to the side wall 12 of the luminaire. In the example shown, the light guide 30 is attached to the outward facing surface of the side wall 12 so that the light guide itself defines the outermost lateral surface of the luminaire unit.

A flexible LED board 36 is coupled to the side wall 12 for delivering light to the light entry region 32 of the light guide. The flexible LED board 36 is parallel with the height direction, with LEDs of the LED board being arranged to emit light with an optical axis in a normal direction of the side wall. The LEDs are for example arranged as a single line of LED in the length direction, or there may be a two dimensional array of LEDs. In a typical orientation of the luminaire, the flexible LED board is vertical and light is emitted with a horizontal optical axis, directed outwardly with respect to the luminaire shape.

The outwardly directed light is redirected towards a generally downward direction, towards the light entry region 32 of the light guide 30, by a reflector surface 40. The reflector surface 40 is slanted with respect to the optical axis so that it performs a redirection of the emitted light. In a most simple example, the reflector surface 40 is slanted by 45 degrees relative to the optical axis so that it redirects light from the optical axis direction (e.g. horizontal and laterally outwardly directed) to an orthogonal direction (e.g. vertically downwardly) into the light guide 30.

For at least one of the luminaire units, the side wall 12 and the flexible LED board 36 are curved so that the luminaire can follow a desired path within a plane. For this purpose, the curvature is about at least one axis parallel to the height direction. By mounting the LED board in the height direction, e.g. vertically, it is able to be curved about one or more of these axes, avoiding the need for in-plane bending (i.e. bending about an axis perpendicular to the plane of the LED board). The bending is also about the length direction of the LED board rather than about the width direction. This is the bending axis of the LED board with the least bending resistance.

Light enters the light guide at the top and exits from the bottom, into a volume to be illuminated. In this way, the luminaire, in particular the sections 22 that are to form curved connecting pieces, can be shaped into a free-form continuous shape thereby avoiding sharp corners of trunking luminaires.

The side wall, top cover, and the light guide are for example initially manufactured in a straight shape and then they can all be deformed into a desired curved shape. Thus, the luminaire is deformable from a straight initially-manufactured shape into a desired end shape. The curvature is thus produced as a final part of the manufacturing process. For sections that are to be straight, the luminaire units may be used as originally manufactured without the need for any bending process.

The light guide slab is easy to manufacture and can be manufactured simply as a cuboid, and then if needed it can be curved into the desired end shape. The light guide is for example extruded from PMMA and then cut to length. PMMA can then for example be formed into a desired shape by hot bending. The end surfaces are then polished to the desired optical smoothness level so that the set of luminaire units function as a single trunking luminaire.

The side wall assembly functions as a support for supporting the light guide 30 (or light guides if there are two) and the respective flexible LED board 36 (or boards). The side wall assembly thereby ensures the correct alignment between the LED board and the light guide. It also provides strength to the luminaire. The side wall assembly is for example aluminum which can be formed into a desired shape by extruding a straight length and then bending.

The top cover 14 follows the shape of the side walls and light guides. It is for example also formed as extruded aluminum, which again can be bent into shape after initial manufacture. The cover closes a space which may be used for housing electronic components of the luminaire such as the LED driver, although an external LED driver is also possible. The cover 14 also engages with the light guide 30 and holds and clamps it against the side wall 12. Mounting accessories may also be provided in the space, for suspending the luminaire from a ceiling.

Figure 4 shows an exploded view of the various components of the line of luminaire units, namely the outer light guides 30, the side walls 12, the LED lines 50 (the LED boards are not shown), the top cover 14 and two end caps 52 at the ends of the luminaire. The end caps 52 may be rigid parts, for example formed by die casting.

Figure 5 shows more clearly the optical parts of the design, and for a design with light guides at both side walls 12. The light path from each LED board 36 is shown as generally outwardly directed. The light is reflected by the reflector surface 40 towards the light guide slab 30. The light is emitted from the LEDs of the LED over a range of angles (not shown). However, the design is such that the resulting range of angles of the light when entering the light guide, after reflection, is sufficient to maintain total internal reflection as the light propagates from the top, light entry region, of the light guide to the bottom from which light escapes.

In this example, the light guide 30 defines a part of the outer surface of the luminaire.

Figure 6 shows an alternative optical design, in which the cover 14 extends to the bottom of the luminaire and hence covers the light guide. The portion of the top cover which extends over the light guide is provided with light extraction features 31. These are features used to interrupt the total internal reflection. These may comprise a pattern of dots of higher refractive index than air so that the conditions for total internal reflection are not met at those locations. Thus, a portion of the light is able to escape in a lateral direction and the remainder of the light reaches the bottom region of the light guide.

The light extraction features may instead be defined by a property of the light guide itself, for example regions of surface roughness. The luminaire in this way can provide lateral as well as downward lighting. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

If the term "adapted to" is used in the claims or description, it is noted the term "adapted to" is intended to be equivalent to the term "configured to". If the term "arrangement" is used in the claims or description, it is noted the term "arrangement" is intended to be equivalent to the term "system", and vice versa.

Any reference signs in the claims should not be construed as limiting the scope.