Louvres are used to control the light output of lamps. Generally, they are designed to direct the light from the lamp so that as much as possible falls within a chosen range of output angles and with precise control of the maximum that falls outside those angles. This produces efficient lighting with minimal glare.

For example, in the case of an overhead light fitting mounted in a suspended ceiling, the light fitting may be designed to direct the light downwards, within an angle of about 60 of the vertical. This produces efficient lighting for horizontal work surfaces but minimizes glare.

An example of a louvre is described in International patent application W096/25623 (Philips Electronics N. V.). The louvre consists of two curved side reflectors and a plurality of blades (lamellae) that extend perpendicular to the side reflectors. The blades have concave lower edges and concave or straight upper edges. The concave upper edges interfere with the light beam and reduce optical efficiency, while straight edges can cause highlights (ladder effect) on the side reflectors.

It is an object of the present invention to provide a light controller that mitigates at least some of the disadvantages of existing light controllers, and an improved method of manufacturing a light controller.

According to the present invention there is provided a light controller for a light fitting, the light controller including a pair of side reflector elements and a plurality of blade elements that extend between the side reflector elements.

The upper edge of each blade portion may be substantially convex. This produces a more uniform cut-off angle, thereby increasing the efficiency and reducing glare from the light fitting.

Each blade portion may consist of two face elements that are connected to one another at their upper edges by a bridging portion. The bridging portion may be located

substantially centrally between the ends of the face elements. Such a blade element is relatively simple and inexpensive to manufacture and is suitable for automated manufacturing processes.

The bridging element may also serve to reflect light that would otherwise be lost into the gap between the two face elements, thereby reducing light loss and increasing the efficiency of the louvre element. The bridging element may be provided with reflective wing members, to reduce losses and increase the efficiency still further.

The blade element may include at each end a mounting member for attaching the blade element to the side reflector elements. The mounting member may include a first part that serves as pivot point and a second part that engages a detent on the side reflector element to secure the blade element to the side reflector element. The resulting louvre element can be assembled relatively quickly and easily.

According to a further aspect of the invention there is provided a method of assembling a light controller in which mounting members on both ends of each of a plurality of blades are partially engaged in corresponding mounting apertures in each of two side reflector elements, and the side reflector elements are rotated about the points of engagement of said mounting members with said side reflector elements to bring said mounting members into full engagement with said side reflector elements.

The assembly method is very quick and simple, and is capable of automation.

The blade elements may be manufactured from blanks that are connected to one another by the bridging element. This helps to simplify automation of the manufacturing process.

Embodiments of the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view from below of a louvre element; Figure 2 is cross-section on line II-II of figure 1; Figure 3 is a cross-section on line 111-111 of figure 2, at a reduced scale;

Figure 4 is a side view of a blade element; Figure 5 is a cross-section on line V-V of figure 4; Figure 6 is a top view of a blank for constructing a blade element, prior to folding; Figure 7 is a perspective view, at an enlarged scale, of part of the inner surface of a side reflector and parts of two blade elements; Figure 8 is a perspective view, at an enlarged scale, of part of the outer surface of a side reflector; Figure 9 is a side view, at an enlarged scale, of part of the inner surface of a side reflector and one blade element; Figure 10 is a schematic diagram illustrating the main steps of a process for manufacturing the blade elements; Figure 11 is a top view of a strip of blade blanks, prior to separation and folding; Figures 12 to 14 illustrate individual steps of the process for manufacturing blade elements, on an enlarged scale; Figure 15 is an end view of a louvre element during assembly thereof; Figure 16 is an end view of a louvre element after partial assembly; Figure 17 is a perspective view from below of a light fitting, and Figure 18 is a view from directly below of the light fitting.

A light controller in the form of a louvre element 6 is shown in Figs. 1 to 3. In use, the louvre element 6 is mounted below a tubular lamp, for example a fluorescent tube, the longitudinal axis of which is indicated by the broken line 10.

The louvre element consists of two side reflectors 12 that curve inwards towards one another at their upper edges and a plurality of blade elements 14 that are positioned substantially perpendicularly to the longitudinal axis 10 of the tubular lamp and extend

between and interconnect the two side reflectors 12. End reflector plates 15 are attached to the two ends of the side reflector elements 12.

Each side reflector 12 has a side wall 16 that is highly polished or light coloured on its inner surface to serve as an efficient reflector. At the lower edge of the side wall 16 there is provided an outwards-extending flange 18 that is used when mounting the louvre element 6 in a light fitting. The lower part of the side wall 16 is pierced by a number of identical apertures 20 that are used as mounting locations for the blade elements 14.

The mounting apertures 20, which are shown in more detail in Figs. 7 to 9, each consist of an upper portion 22 having inclined side edges 24 and a lower portion 26 having two side edges 28 that are slightly less steeply inclined towards one another.

The lower portion 26 is slightly wider at its upper end than the lower end of the upper portion 22 and there is thus a small step 30 on each side of the aperture where the upper and lower portions meet. These steps 30 serve as detents for retaining the blades 14 in the mounting apertures 20, as will be described below. The upper edge 32 of the upper portion is V-shaped and the lower edge 34 of the lower portion is straight.

The blade element 14, which is shown in more detail in Figs. 4 and 5, is constructed by folding a blank 35 of highly polished reflective metal, which is shown in Fig. 6.

The blade element 14 consists of two face elements 36, each of which has a concave hyperbolic lower edge 38 and an upper edge 40 that has convex hyperbolic central portion 42 and two substantially straight outer portions 44 that protrude slightly above the edge of the central portion 42. The two face elements 36 are connected to one another at their upper edges 40 by a bridging element 46.

The blade element 14 is formed by first pressing the face elements 36 so that the reflective face of each has a concave parabolic surface and folding the blank along two primary fold lines 48 that connect the face elements 36 to the bridging element 46, so that the cross-sectional shape of the blade resembles approximately an inverted isosceles triangle (as shown in Fig. 5), the two similar sides of the"triangle"formed by the face elements 36 being curved slightly inwards.

The primary fold lines 48 connecting the bridging element to the two face elements 36 are only approximately one third the length of the bridging element 46 and the portions of the bridging element that extend beyond the fold lines comprise two flap- like wings 50 that extend outwards into the gap between the upper edges 40 of the face elements 36. These wings 50 are bent upwards along secondary fold lines 52 to subtend an angle 8 of approximately 118.75 (as shown in Fig. 4).

Each face element 36 has at each of its two ends a mounting tag 54 for engaging the mounting apertures 20 provided in the side reflector elements 12. The mounting tag 54 extends outwards beyond the curved line of intersection between the blade 14 and the side reflector element 12, which is represented in the drawings by the broken line 56, and includes an upper edge 58, an outer edge 60 and a lower edge 62. The outer edge 60 is substantially vertical and the upper edge 58 extends upwards towards the outer edge so that the two edges subtend an angle of approximately 45. At the point where the upper edge 58 joins the main part of the blade face element 36, a notch 64 is formed that serves as a pivot point during assembly of the louvre element. The lower edge 62 is substantially horizontal, the corner where the lower edge joins the outer edge being curved or bevelled.

A slot 66 is provided at each end of each face portion 36. The slot 66 extends approximately along the curved line of intersection 56 and includes a central portion 68 and two narrower end portions 70. In the assembled louvre, these slots 66 are engaged by the detents 30, thereby securing the blade elements 14 to the side reflector elements 12.

A process for manufacturing the louvre element is illustrated schematically in Fig. 10.

First, a length of polished aluminium 72 for manufacturing the blades is fed from a coil (not shown) into a blanking machine 74, which produces a continuous strip 76 of joined blade blanks (shown in more detail in Fig. 11). The strip 76 is fed into a forming machine 78 that forms the parabolic curves in the face elements 36, then separates the blade blanks 35 from one another and folds each blank to form a finished blade element 14 as shown in Figs. 4 and 5.

The finished blade elements 14 are removed from the forming machine 78 by a first

pick and place device (not shown) and placed on a track 80. The track 80 twists through 180', inverting the blade elements 14, which are removed one by one from the track 80 by a second pick and place device (not shown) and placed in position in a pair of side reflectors 12 at an assembly station 82. After each blade element 14 has been located in position, the side reflectors 12 are indexed forward one place, so y. that they are ready to receive the next blade element. This process is repeated until all the blade elements 14 have been located in position, and the side elements 12 are then locked to the blade elements 14 by pressing downwards on the edges of the blade elements, as described in more detail below with reference to Figs. 15 and 16.

The louvre element 6 is completed by attaching the end reflector plates 15 to the ends of the side reflector elements 12, for example by means of small bendable tags 84 provided on the ends of the side reflector elements (shown in Figs. 1 and 3).

The strip 76 of joined blade blanks produced by the blanking machine 74 is shown in more detail in Fig. 11. The blade blanks are connected to one another end-to-end by the bridging element 46 that connects the two face elements 36 of each blade element to one another. The forming machine 78 receives the strip 76 from the blanking machine 74 and forms the parabolic curves in the face elements 36. A practically perfect parabolic form is achievable owing to the fact that, apart from the short length that is connected to the bridging element 46, the upper edge 40 of each face element is unsupported. The bridging element 46 is then cut, separating the blade blanks from one another but leaving the wing elements 50 attached. The wing elements 50 are folded upwards along the secondary fold lines 52 and the face elements 36 are then folded downwards along the primary fold lines 48, forming the finished blade element 14 shown in Figs. 4 and 5.

The track 80 for carrying the blade elements 14 from the forming machine 78 to the louvre assembly station 82 is shown in more detail in Figs. 12 and 13. The track has a concave surface 86 that engages the convex central portion 42 of the upper edge 40 of the blade elements 14. A groove 88, which extends along the length of the track 80, is formed in this surface 86, the groove having a cross-sectional shape resembling an inverted truncated triangle. The two inclined surfaces 90 of the groove 88 engage

the unpolished lower surfaces of the wing elements 50, thereby retaining the blade elements 14 on the track 80. The blade elements 14 are therefore retained on the track 80 without any contact between the track and the reflective surfaces of the blade elements, thereby avoiding any possibility of the surfaces being scratched.

The procedure for assembling the louvre element 6 at the assembly station 82 is shown in detail in Figs. 14,15 and 16. First, as shown in Figs. 14 and 15, the two side reflector elements 12 are inverted and mounted on an assembly jig 92. The jig 92, which is shown in cross-section, consists of a rectangular base member 94 and two inwardly inclined side members 94, the upper edges of which engage the flanges 18 of the inverted side reflector elements 12.

The blade elements 14 are inverted and located in position on the side reflector elements 12 with the upper corners of the mounting tags 54 engaged in the upper portions 22 of the mounting apertures 20, between the side edges 24 and the V-shaped upper edge thereof 32.

Next, a downward force is applied to the lower edges 38 of the inverted blade elements 14 as shown by the arrow B in Fig. 16. As the louvre element 6 is forced downwards, the side members 96 of the assembly jig move inwards, driving the lower comers of the mounting tags 54 into the lower portions of the mounting apertures 20.

The face elements 36 of the blade elements 14 are simultaneously pressed towards one another by the inclined edges of the mounting apertures 20, the face elements 36 subsequently springing apart again slightly as the detents 30 engage the slots 66. This locks the blade elements 14 and the side reflector elements 12 together.

An example of a light fitting 100 that includes the louvre element 6 is shown in Figs.

17 and 18. The light fitting 100 consists of a square frame 104 containing three louvre elements 6 and two infill panels 108, each comprising a grid-like array of square lattice control elements. In use, the light fitting is mounted in a luminaire (not shown) containing three tubular fluorescent lamps that are located above and extend parallel to the longitudinal axes of the three louvre elements 6.

In use, light from the lamp is output in various different ways, as follows:

direct light output results from light that passes downwards from the lamp between the side reflector elements 12 and the blade elements 14. Direct light output is controlled by the lower edges of the side reflector elements 12 and the lower and upper edges 38,40 of the blade elements 14. The convex shape of the upper blade edges 40 and the concave shape of the lower blade edge 38 represent lines of intersection between the blades and cones of light emitted by the lamp, thus ensuring that the cut-off angle for direct light output is substantially uniform (i. e. independent of the viewing angle); -reflected light output results from light that is reflected from the highly polished surfaces of the side reflector elements 12 and the blade elements 14.

The parabolic surfaces of these elements ensure that the light is reflected downwards to minimise glare; -internally reflected light output results from light that travels upwards from the lamp 10, into the luminaire, and light that is reflected upwards by the bridging element 46 and the two wing elements 50. Because this light is not lost into the gaps between the blade face elements 36, the overall efficiency of the light fitting is improved. This light is reflected by polished or light-coloured internal surfaces within the luminaire and then leaves either through the louvre elements 6 or through the infill panels 108, where these are provided. This internally reflected light is highly diffused, which helps to soften the lighting effect produced by the fitting.

The wing elements 50 serve three purposes: they connect the blade blanks together in the strip 76, thereby simplifying the forming process; they attach the formed blade elements 14 to the track 80 without scratching of the reflective surfaces, and they increase the optical efficiency of the louvre by preventing light loss into the gaps between the face elements 36.

Various modifications of the invention are possible. For example, the lower edges 38 of the blade elements 14 may for aesthetic reasons be straight or convex instead of concave. The louvre element may also be mounted in many other types of light fitting.