Light fittings, particularly long fluorescent tube fittings, are often provided with an anti-dazzle screen and/or a re- flector with bent long sides and transverse ribs, which ex- tend between these sides. The anti-dazzle screen and the re- flector respectively usually are made of metal, which has been provided with a reflecting surface layer.

One problem with the known ribs, which in cross-section are wedge-shaped, the point being turned away from the source of light, is that it is difficult to shape the tip or the wedge point in an appropriate way, since it must be as thin as possible in cross-section, so that is will not take up too much space in the light opening of the fitting.

Up to now the wedge point has been obtained through bending around a tool, which includes a sharp tooth having a linear edge. In this connection a certain, not insignificant ben- ding radius always arises, because said tooth close to the bending edge actually, i. a. for strength reasons, must be designed with a certain, not insignificant minimum thick- ness in cross-section. Consequently, the distance between the rib walls in the edge point will be roughly four times as large as the material thickness, which is unsatisfactory from i. a. a lighting efficiency point of view. Also, it is not possible, without certain inconveniences, afterwards to flatten the rib point, since the reflection properties might become inferior and increased tool and production costs and an extended production time might result respectively.

EP-B-0 435 394 relates to a light fitting with transverse ribs, the point of which has been obtained by bending a me- tal sheet around two central lines at a mutual distance, until the free edge areas of the sheet in cross-section bear on each other and in this way form a point (Fig. 4). It is true, that in this way the above described inconveniences, which are connected to a bend within the area of the rib point, have been avoided, but new problems, inconveni- ences and risks have arisen. First of all a sheet blank, bent in this way, has an inherent elasticity, which tends to remove the free ends of the rib legs from each other.

Consequently, means are required, which constantly press said free ends against each other. It is true, that such means are available, designed as recesses in laterally po- sitioned reflectors, in which recesses the rib ends are int- roduced and fastened, but if any play in such recesses and/ or manufacturing variations and deformations in the ribs arise, an opening between the free ends of the rib legs results and the advantages of this production method are wiped out, completely or partially, which affects the ref- lection properties and the efficiency of the fitting, and at the same time the appearance is negatively changed.

Another inconvenience is that such rib points easily can be subjected to permanent damages, e. g. deformations due to blows and shocks. The bending of the base of the ribs, which so far has been a relatively uncritical and uncomplicated operation, now is more critical and decisive. Even if the rib legs are mutually displaced to a very small extent, e. g. in a plane-parallel direction, a rib point cannot be obtained with rib legs ending within the same area but with mutually displaced leg ends, that end which protrudes more being particularly sensitive to e. g. cross-directed strains.

There is also a risk that an oval space between the rib leg ends is obtained, particularly in the middle of a rib de- spite the fact, that said ends bear on each other at the rib ends, which fully or partially can be caused by said inherent elasticity.

The object of the present invention is to counteract and eliminate as far as possible the above-mentioned inconven- iences and risks. Another object of the invention is to de- velop the state of the art in this field in various respects, primarily to develop a product of superior quality with small use of machines and at favorable prices.

Additional characterizing features and advantages of the in- vention are set forth in the following description, refe- rence being made to the enclosed drawings, which show a few non-limiting embodiments of the invention. The drawings show in detail : Fig. 1 a perspective view from below of an electric fluore- scent tube fitting with i. a. lateral reflectors and ribs, which connect the reflectors to each other ; Fig. 2 a planar view of a completely punched blank for a rib according to the invention; Fig. 3 an end view of the blank according to Fig. 2; Fig. 4 the rib blank according to Figs. 2 and 3 in a planar view after the bending of lateral tongues and a material weakening; Fig. 5 the blank according to Fig. 4 in an end view; Figs. 6 and 7 views corresponding to Figs. 4 and 5 of the blank in an intermediate production phase subsequent to an additional joining of the blank parts to a finished rib; Figs. 8 and 9 views corresponding to Figs. 6 and 7 of the finished rib; Fig. 10 a perspective view from above and from one end of the rib according to Figs. 8 and 9 ; and Figs. 11 and 12 views corresponding to Fig. 10 of two diffe- rently designed ribs according to the invention.

In Fig. 1 an electric light fitting 1 is shown, particular- ly a fluorescent tube fitting, in its entirety. A combina- tion 3 of an anti-dazzle screen and a reflector is inserted in its light opening 2. In the now shown embodiment there are reflectors 4 located at the top, reflectors 5 lateral- ly located and transverse ribs 6, which connect said re- flectors to each other and ends 7 of which are inserted and fastened in openings 8 in reflectors 5.

In Figs. 2-10 the production of a transverse rib 6 according to the invention is shown, the rib being made of metal and/ or a plastic material. The rib is provided, in a way known per se, with fastening means 9,10 and 11 in both ends 7, designed to fasten the rib in the laterally located reflec- tors 5. Said ends suitably are inclined in order to connect to the shape and position of reflectors 5.

In Fig. 2 a plane, completely punched blank for a transverse rib 6 according to the invention is shown. The blank is sym- metrically designed with a longitudinal central line 12, a flank line 13 located at a distance from the central line 12 on each side of the same as well as e. g. mainly triangu- lar end fields 14, which are defined by flank lines 13, and tongues 15 for reflection and/or fastening purposes.

In one production phase according to Figs. 4 and 5 tongues 15 have been bent at an e. g. right angle in one direction away from the plane of the blank and flanks 16, positioned between lines 12 and 13 have been slightly bent in the same direction. At the same time or before then, possibly alrea- dy in connection with the punching according to Figs. 2 and 3 or efter said punching central line 12 has been formed or reinforced in order to obtain a material weakening 17, which in a preferred embodiment is wedge-shaped with an acute angle of 15°-90°, preferably roughly 30° between flanks 21 of the material weakening. The material weakening is ob- tained by stamping, cutting or the like and is located on that side of the rib, which will constitute outer side 18 of rib point 19. The depth of the material weakening will suitably be 1/4-3/4, preferably 2/3 of the thickness of the blank.

Flank lines 13 can also be designed as material weakenings or only be imaginary in Fig. 2 to only emerge in connection with the above-described central bending according to Figs.

4 and 5, namely as the lateral border line of the bending.

In case central line 12 has not yet been designed as a ma- terial weakening according to Fig. 2, line 12 in Fig. 2 must be seen only as an imaginary line for a subsequent material weakening.

In one production phase according to Figs. 6 and 7 the blank sides have been swung roughly half-way on their way to the end position, and this shows the design of a bridge 20 bet- ween flanks 16 within the area of rib point 19, which bridge at least partially or mainly is preserved also during or in connection with the continued swinging towards the end po- sition according to Figs. 8-10. As is shown, the angle bet- ween flanks 21 of the material weaking successively increases to be about 180° in the position shown in Figs. 8-10. In this way a straight and relatively insensitive point end is ob- tained.

In Figs. 11 and 12 two alternative rib designs are shown, in which however the rib point is obtained and the production phases for the rib ensue according to the above-described and in the drawings shown manufacturing steps.

The present invention is not limited to the embodiments described above and shown in the drawings, but it can be modified and supplemented in arbitrary ways within the scope of the inventive idea and the following claims.