DESCRIPTION "LAMP HOLDER AND METHOD FOR MANUFACTURING THE SAME" The present invention relates to a lamp holder and to a method for manufacturing said lamp holder, designed in particular for discharge metal halide lamps used especially for technical interior lighting devices or for spotlights used for lighting display locations such as shops, showrooms or the like. These types of light source have an extremely high light efficiency and their chromatic effect is very similar to natural light. This advantage has made this light source the most widely used, searched for and appreciated by peo- ple working in the field of technical lighting for shops or display locations, both device manufacturers and field operators and installers. Moreover, since the aforesaid requirements should be combined with aesthetic needs due to the more and more modern design of lighting devices, lamp holders had to become smaller and be safely installed within the structures of lighting devices. Furthermore, the use of discharge halide lamps ensures beyond a high. lighting power low energy consumptions, so that these lamps are preferred with respect to traditional incandescent or fluores- cent lamps for many applications. Concerning this, ac- cording to known techniques, lamp holders for dis- charge halide lamps are generally made of a ceramic material, i. e. porcelain, or of a plastic material normally resisting temperatures of at least 200°C. As a matter of fact, ceramic proves to be a particularly suitable material thanks to its very low coefficient

of electric and thermal conductivity. In particular, some commercially available lamp holders for discharge halide lamps consist of two half-portions engaged one with the other, incorporating the electrical contacts and having a cavity designed to house the light bulb.

It is known about lamp holders in which the two half- portions are. connected one to the other by means of steel clips or rivets, placed so as to comply with minimum distances from portions under voltage as re- quired by lamp holder manufacturing rules, i. e."air" distances and"surface"distances, which are generally referred to in the aforesaid rules for manufacturing electrical appliances. Moreover, said lamp holders usually contain an element engaging with the end por- tion of the bulb, as a rule a base made of ceramic ma- terial, so as to hold said bulb onto the lamp holder.

Said engaging element is usually made up of one ore more elastic metal plates. Eventually, lamp holders according to the prior art are connected to a support- ing frame through connecting means such as screws, or rivets, or bolts, which engage into holes made di- rectly onto the lamp holder body. The Applicant has found that lamp holders according to the prior art can be improved under several points of view. In particu- lar, one of the main drawbacks of lamp holders manu- factured with the aforesaid fastening system, when these are mounted by an unskilled person or care- lessly, consists in a possible break of the holes made in the lamp holder; indeed, these breaks damage the lamp holder structure, causing the loss of the suit-

able and necessary electrical insulation of the inner portions under voltage. As a matter of fact, both ce- ramic and plastic materials these lamp holders are made of are very brittle, and since they are always coupled to the fastening structures of the lighting devices, which are far stiffer and more resistant, they are then easily subject to breaks when undergoing too strong a tightening Moreover, another drawback of lamp holders according to the prior art consists in their complex manufacturing and assembly due to the presence of means for fastening the lamp holder onto the supporting frame, means for holding the bulb onto the lamp holder and means for joining the two half- portions constituting the lamp holder, which are inde- pendent from one another.

An aim of the present invention is to solve the prob- lems found in the prior art by means of a lamp holder and a method for manufacturing said lamp holder that can obviate the aforesaid drawbacks. In particular, an aim of the present invention is to propose a lamp holder in which means for fastening the latter to a supporting frame operate without damaging the lamp holder structure. A further aim of the present inven- tion is to propose a method for manufacturing a lamp holder enabling an easy assembly and construction.

These and other aims, which shall be more evident from the following description, are basically achieved by a lamp holder and by a method for manufacturing said lamp holder, comprising the characteristics listed in the characterizing portions of claims 1 and 14, re-

spectively. Further characteristics and aims shall be more evident from the detailed description of a pre- ferred but not exclusive embodiment of a lamp holder and of a method for manufacturing said lamp holder ac- cording to the present invention. Said description will be disclosed in the following with reference to the accompanying figures, provided to a merely indica- tive and therefore non-limiting purpose, in which: Figure 1 shows an exploded view of the lamp holder according to the invention; Figure 2 shows a perspective view of the lamp holder of Figure 1; Figure 3 shows a construction detail of the lamp holder of Figure 2; Figures 4 and 5 show schematically two manufac- turing steps of a detail of the lamp holder according to the present invention; Figures 6 and 7 show schematically two further manufacturing steps of a first embodiment of the de- tail of the lamp holder of Figures 4 and 5; Figures 8 and 9 show schematically two further manufacturing steps of a first embodiment of the de- tail of the lamp holder of Figures 4 and 5; Figures 10 and 11 show a comparison between the two embodiments of the detail of the lamp holder of Figures 6-7 and 8-9, respectively; Figures 12 to 15 show an execution variant of an elastic element of the lamp holder in lateral view, perspective view, view from above and lateral view ac- cording to a plane perpendicular to the one of Figure

. 12, respectively; Figures 16 to 19 show a further execution variant of an elastic element of the lamp holder according to views corresponding to those of Figures 12 to 15.

With reference to the accompanying figures, number 1 globally refers to a lamp holder according to the pre- sent invention. The lamp holder 1 comprises a base 2, electrical connection elements 3 and a supporting body 4 mounted onto the base 2. The base 2, basically prism-shaped, houses inside two separate channels 2a symmetrical to one another, designed to contain the electrical connection elements 3 and to electrically insulate them one from the other. The electrical con- nection elements 3 are made up for instance of two electrical cables and two contacts. The supporting body 4 has at least two through holes 5'for contacting the ends of a light bulb, not shown because of conven- tional type, with the electrical connection elements 3. Moreover, the supporting body 4, basically prism- shaped too, has a surface matching the channels 2a, which is designed to engage with the base 2. The sur- face of the supporting body 4 comprising the two holes 5 has a cavity 4a matching the lamp socket so as to enable the bulb to rest onto the lamp holder. The lamp holder 1 further comprises means 6 for positioning or fastening the lamp holder onto a supporting frame 7 and means for holding the light bulb onto the lamp holder. Advantageously, the fastening means 6 and the holding means 8 are defined by one elastic element 9.

Advantageously, the elastic element 9 further com-

prises means 10 for joining the base 2 to the support- ing body 4. Preferably, the elastic element 9 is made up of a metal or plastic plate or a plate made of any material with elastic properties resembling those of the aforesaid materials. As can be seen in Figure 1, the elastic element 9 is basically shaped as a fork and comprises a base plate 11 and two prongs 12, which are plate-like, too, and develop starting from oppo- site ends and transversally to the base plate 11. Ad- vantageously, the base plate 11 comprises at least an extension 13, and preferably two extensions 13 placed in opposite positions with respect to the lamp holder, beyond each of the prongs 12. Said extension 13 has at least one through hole 14. The extension 13 and the hole 14 define the means 6 for fastening the lamp holder onto the supporting frame 7. Said fastening means 6 enable to connect the lamp holder 1 to the supporting frame 7 for instance by means of screws 15 (as shown in Figure 2). In an execution variant, shown in Figures 12 to 15, said extension 13 can be made of one plate only. Preferably, so as to be stronger and reliable, said extension 13 is made up of a double plate layer, as shown in Figures 1 to 9. In order to obtain the arrangement described above, the elastic element 9, i. e. the plate, is deformed according to a bend lla made on a free end of said plate until two adjacent portions 13a and 13b of the plate overlap at least partially (as shown schematically in Figure 4).

Then, a bend llb pointing away from the underlying portion is made on the overlapping plate portion 13a

until an approximately square angle is defined, thus forming one of the prongs 12.

Advantageously, in order to obtain the extension 13 at least one section in which two plate portions 13a and 13b overlap is kept with said arrangement (as shown in Figure 5) and pierced so as to enable the introduction of a screw 15 or of any other fastening element. All these manufacturing steps are repeated in a basically analogous manner on the opposite end of the plate, not engaged during the steps described above. The base 2 of the lamp holder is inserted into the fork in con- tact with the base plate 11 of said fork. Preferably, a groove 16 matching the base plate 11 is made on the base 2, on which groove said base 2 rests. Advanta- geously, each of the prongs 12 has an inner appendage 17 comprising a projection 18 pointing inside the fork; the assembly including inner appendage 17 and projection 18 defines the means 10 for joining the base 2 to the supporting body 4. The appendage 17 is obtained by cutting the plate making up the elastic body 9 on the position occupied by at least one of the prongs 12. The appendage 17 can be cut in the inner portion of the prongs 12, as shown in Figures 1 to 3, or it can be cut in the outer side portion 12 of said prongs 12, as shown in Figures 16 to 19, thus obtain- ing two outer appendages 17. Preferably, the support- ing body 4 comprises at least one groove 19 shaped so as to engage with the projection 18. The supporting body 4 is placed on the base 2 and between the prongs 12 of the fork, so that the groove 19 faces the pro-

jection 18..

Advantageously, at least one of the prongs 12 of the fork comprises an element 20 shaped so as to engage with the bulb socket, said shaped element 20 defining the means for holding the bulb onto the lamp holder 1.

Preferably, the shaped element 20 is made up of a first bend 20a of the free end of a corresponding prong 12 pointing inside the fork and away from the base plate 11 of said fork. The bend 20a defines a tongue 21 on which a second bend 20b is made, pointing towards the corresponding prong and approaching the base plate 11 of the fork (as shown in Figures 6 and 7). The prong 12 is thus granted a higher elasticity, since the bending shape as described above defines three bending areas or angles acting upon the lamp holder, instead of the two traditional bending angles of known embodiments (see Figures 10 and 11).

Alternatively, the shaped element 20 is made up of a first bend 20c of the free end of a corresponding prong 12 pointing inside the fork and away from the base plate 11 of said fork. The bend 20c defines a tongue 21a on which a second bend 20d is made, point- ing outside and away from the base plate 11 of the fork (as shown in Figures 8 and 9). The lamp holder according to the present invention is assembled by in- serting the base 2 between the prongs 12 and in con- tact with the base plate 11, and by inserting the sup- porting body 4 onto the base 2 so that the projections 18 of the inner appendages 17 can hold the supporting body 4 through the grooves 19. As a matter of fact,

the elasticity of element 9 ensures that the body 4 is suitably held in its seat. The lamp holder 1 can thus be connected to the supporting frame through the screws 15 engaged into the holes 14 of the extensions 13. Eventually, by pressing the bulb socket towards the surface 4a of the supporting body 4, the elastic- ity of element 9 allows the bulb socket to move the prongs 12 away from one another and to rest onto the surface 4a. The shaped elements 20 then engage with the bulb socket and thanks to the elasticity of the prongs 12 they hold the light bulb onto the lamp holder 1. The present invention solves the problems found in the prior art and achieves the fixed aims.

Thanks to the fastening means of the lamp holder in- cluded in the elastic element, the lamp holder accord- ing to the present invention can be connected to any supporting frame also by an unskilled user. As a mat- ter of fact, the screws act directly upon the elastic element without coming into contact with the ceramic material of the lamp holder, thus eliminating possible breaks due to an excessive tightness of said screws or of similar fastening means or means performing the same function. Moreover, the two overlapping sections of the extension ensure solidity and strength to the means for fastening the lamp holder onto the support- ing frame. More to the point, the particular arrange- ment, shown in Figures 6 and 7, of the shaped element designed to hold the light bulb onto the lamp holder ensures such a stiffness of the prongs as to eliminate any clearance between prongs and bulb socket. Eventu-

ally, the fact that the means for fastening the lamp holder onto the supporting body, the means for holding the light bulb onto the lamp holder and the means for joining the base to the supporting body are positioned on one element ensures a simpler and faster assembly and manufacturing of the lamp holder.