Abstract:
A reflector lamp which is structurally compact in its axial direction has a light capsule surrounded by a tubular shield with electric leads which are anchored or fixed in a base at one end of the lamp with the leads structurally arranged to support opposite ends of the light capsule and urge the shield against a wall through which the leads extend adjacent said base.

Description:
FIELD OF INVENTION 
   This invention relates to a reflector lamp, particularly to a metal halide reflector lamp. 
   BACKGROUND OF THE INVENTION 
   In European Patent EP 0 902 458 A2 a metal halide reflector lamp is shown comprising an outer envelope formed as a reflector with a neck portion and a base. A light transmitting cover in the form of a lens is connected along its circumference to an outer edge of the reflector, whereby reflector, base and cover are shaped generally rotationally symmetrical around a longitudinal axis. A light capsule or an arc tube, resp., having pinch seals at its ends and being surrounded by a shield formed as a tubular envelope and being arranged in the reflector within the shield by means of a first and a second electric lead. The first lead is at a first end of the capsule adjacent the base, and the second lead is installed on the outside of the shield and is introduced into the other end of the shield opposite the cover adjacent the second end of the capsule with both leads being sealed in the pinch seal adjacent the base. The reflector lamp shown in EP 0 902 458 A2 has a melting-in of the tubular envelope of the shield in the base area such that the two leads emerging from the base area are sealed into this pinch seal-like melting-in from which they exit in order to enter into pinch seals at opposite ends of the capsule. The shield thereby provides a so-called burst protection which protects the environment as against shards of a capsule which could explode possibly sometimes. 
   This known shield closed all around can be filled with a protective gas like nitrogen in order to protect from oxidation, at temperatures above 400 degrees Celsius, the welding between the respective lead-in and the respective sealed-in foil made from molybdenum which is necessary when quartz is used fox the capsule. It is known that sealings of lead-ins within quartz glass are not gas-tight because the thermal expansion coefficients are too different. The known shield as such, however, does not need any foils melted in because aluminum silicate glass is used for the shield, the thermal expansion coefficient of which corresponds essentially to that of the material of the lead-ins. 
   Even if this known structure is relatively compact already, the presence of a melt-in of the leads into the pinch seal-like end of the shield opposite the base and the use of protective gas constitutes a remarkable manufactural-technical expenditure on the one hand, on the other hand such melt-in makes the shield longer and by this enlarges the reflector lamp in the direction of its longitudinal axis. 
   With the reflector lamp known from WO 96/27205 A1 the first as well as the second lead-in are installed within the shield and exit from the shield at the side of the base, whereby a sealing consisting of curable cement is present between the shield and the lead-ins which is to be regarded as an additional expenditure the same way as melt-in which is for granting a hermetic sealing of the shield. 
   Finally the EP 0 560 936 B1 teaches a reflector lamp with a cylindrical shield which is retained by special clips which at least partially grip around the circumference of the shield at its two ends. The clips form part of a separate maintenance structure for the shield which comprises a holding web between the two clips and a special holding ring for the holding web in the base area of the lamp. This complicated maintenance structure for the shield forms a special expenditure. 
   SUMMARY OF INVENTION 
   In view of this the object underling the invention is seen in the provision of a reflector lamp of this kind which can be manufactured with remarkably lesser expenditure and which, beyond that, is structurally more compact, i.e., is shorter in the direction of its longitudinal or rotational, resp., axis. 
   This object is solved in accordance with the invention in that, eliminating melt-ins of the electric leads within the shield which seal the capsule as against the environment, the leads are fixed in the base only, and in that the second lead is biased such that, by this second lead which abuts from the outside against the end of the shield adjacent the cover or lens, the shield is pressed against a bottom of the neck portion of the reflector, the leads being guided through openings in this bottom towards the base, which is secured to the bottom, and are fixed there. 
   To dispose of melt-ins or sealings, reasp., of the lead-ins in the shield which seal the capsule as against the environment, whereby the lead-ins are fixed in the base of the reflector lamp only, makes the reflector lamp in accordance with the invention shorter between base and cover or lens, reasp., and by this renders same more compact; in addition thereto it provides savings in manufacture expenditure. The fixation of the shield at the reflector being necessary anyway is accomplished by the inventive development of the second lead-in in that the second lead-in draws the shield to the bottom of the reflector and keeps it fixed to the bottom, the ring shaped abutment surface of the end of the shield present at the side of the base providing stability. 
   It is understood that this ring shaped abutment surface means no hermetic seal and that, therefore, the ambient air and by this oxygen have access to the interior of the shield and, hence, to the light capsule or arc tube, reap., and temperatures above 400 degrees Celsius may lead to oxidation of the welding between lead-in and sealed-in foil. This has negative effects and should be avoided, therefore. But in further development of the invention the temperature should be kept low in this area or the access of air and by this oxygen to this area should be prevented. 
   To avoid this several possibilities are offered according to the invention: 
   1. 
   A first heat protection which surrounds the end of the arc tube in the region of its pinch seal on the side of the base above the welded joint of lead-in and melted-in foil and which lies opposite the bottom of the reflector neck is provided with an opening for the passage of the second lead-in, this opening being aligned with the first passage opening in the bottom. 
   The heat protection prevents the temperature in the region of the welding between lead-in and melted-in foil from becoming so high that oxidation occurs. 
   Suitably the first heat protection on the side of the base is fixed by support in the neck region and on the side of the cover is fixed by the shield being drawn to such support by the second lead-in. Further, the second lead-in and the first heat protection are insulated from each other in the region of the opening. 
   Advantageously a second heat protection can also be provided which surrounds the end of the capsule on the side of the cover in the region of its pinch seal below the welding between second lead-in and melted-in foil and lies opposite the upper end of the shield on the inner side in order to achieve the same effects with regard to the end of the capsule on the side of the cover. 
   2. 
   Between the end of the arc tube on the side of the base and the shield on the one hand as well as between the shield and the neck of the reflector on the other hand cement can be inserted such that the lower region of the pinch seal end is covered by cement. By this a cooling effect is achieved which prevents the oxidation mentioned under 1, and in addition thereto the whole structure becomes more stabile thereby.
 
3.
 
The location at which the first lead-in enters the appertaining pinch seal of the first end of the capsule can be closed by glass solder. Advantageously also the location at which the second lead-in enters the appertaining pinch seal of the second end of the capsule can be closed with glass solder. Instead of glass solder sodium silicate glass can be used as well. By this any access of air and, therefore, oxygen is reliably prevented and an oxidation of the welding between lead-in and melted-in foil blocked.
 
   Two further advantageous possibilities consist in either to platinize the lead-ins or to cover same with quartz glass, which in both cases prevents its oxidation. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention and its advantageous developments are explained in more detail by the assistance of embodiments depicted in the drawings. 
       FIG. 1  is a cross section through a first embodiment of the invention; 
       FIG. 2  is a cross section through a second embodiment; 
       FIG. 3  is a cross section through a third embodiment; 
       FIG. 4  is a cross section through a fourth embodiment; 
       FIG. 5  is a cross section through a fifth embodiment: 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates a first embodiment of a reflector lamp  1 , particularly a meal halogen vapor reflector lamp, having an outer envelope formed as a reflector  2  with a neck region  3  having a base  4  fixed thereon and a light transmitting cover  5  comprising a lens which along its circumference  6  is connected to an outer edge  7  of the reflector  2 . 
   Reflector  2 , base  4  and lens or cover  5  are formed essentially rotationally symmetrically around a longitudinal axis  8 . 
   Between base  4  and lens  5  a light capsule or arc tube  9  having pinch seals  10  and  11  at its ends is arranged in the reflector  2  and is surrounded by a shield  14  in the shape of a tubular envelope. The shield can serve not only as a burst protection but can also consist of UV absorbent glass or can be coated with a UV absorbent layer in order to avoid an undesirable sodium loss. The arc tube  9  is held within the shield  14  by a first and by a second lead  12  and  13 , the first lead  12  being sealed-in at the first arc tube end  15  near the base  4  and the second lead  13  being sealed-in at the second arc tube end  16  near the lens  5 , each within pinch seals  10 ,  11 . The arrangement of the arc tube  9  is done preferredly concentrically along the rotational or longitudinal, resp., axis  8 . 
   The second lead  13  is installed on the outside of the shield  14  and is inserted in the end  17  of same adjacent the lens  5 . 
   In accordance with the invention, eliminating melt-ins of the leads  12 ,  13  within the shield  14  which seal the light capsule or arc tube  9  against the environment, the leads  12 ,  13  are fixed the base  4  only. Further, the second lead  13  is biased such that, by this second lead  13  which abuts from the outside at  17 ′ against the end  17  of the shield  14  adjacent the lens  5 , the shield  14  is pressed against the bottom  18  of the neck portion  3  of the reflector  2 , the lead  12 ,  13  being guided through openings  19 ,  20  in this bottom  18  towards the base  4 , which is secured to the bottom  18 , and are secured there or mechanically fixed, resp. The ends of the leads  12  and  13  are electrically connected with terminals  21  and  22  fixed within base  4 . 
   In the further embodiments according to  FIGS. 2 to 5  similar parts are designated by the same reference numerals. 
   The second embodiment of the reflector lamp  1   a  illustrated in  FIG. 2  corresponds essentially to the first embodiment according to  FIG. 1  with the exception of the fact that the shield  14  is open adjacent the lens  5  the same way it is adjacent the base, in other words, the shield is a cylinder open at both ends. Thereby the second lead-in  13  lies in the region  17 ′ at the bottom edge of the shield  14  and presses same against bottom  18 . 
   With the third embodiment of the reflector lamp  1   b  illustrated in  FIG. 3  a first heat protection  23  with a passage  24  for the second lead-in  13  is provided which surrounds the end  10  of the arc tube  9  at the side of the base in the region of its pinch seal above the welding between lead-in  12  and melted-in foil  12 ′ and lies opposite bottom  18 . This passage  24  is aligned with the respective passage  20  in bottom  18 . 
   As to be taken from  FIG. 3 , this first heat protection  23  at the side of the base  4  is fixed by support  23 ′ in the neck region  3  and at the side of the cover  5  by the shield  14  drawn to the bottom by the second lead-in  13 . 
   Suitably the second lead-in  13  and the first heat protection  23  are insulated from each other in the area of the passage  24 . 
   The heat protection  23  protects the area of the pinch seal in which the welding between lead-in and melted-in foil  12 ′ is to be found, as against the heat which is emitted from the arc tube  9 . 
   Besides, in  FIG. 3  a suitable extension on both sides  26  of the pinch seal end  10  is shown which effects a positioning of the arc tube  9  at the heat protection  23 . 
   Suitably a second heat protection  23 A can be provided which surrounds the end  16  of the arc tube  9  at the side of the cover  5  in the region of its pinch seal  11  above the welding between lead-in and melted-in foil and lies opposite to the lower end  17  of shield  14  interiorly. 
   With the fourth embodiment of the reflector lamp  1   c  illustrated in  FIG. 4 , between the first end  15  of the arc tube  9  at the side of the base and the shield  14  on the one hand as well as also between the shield  14  and the reflector neck  3  on the other hand, cement  28  is inserted such that firstly a cooling effect is achieved which prevents an oxidation of the welding between lead  12  and melted-in foil, and secondly the whole structure becomes more stable. 
   With the fifth embodiment of the reflector lamp  1   d  illustrated in  FIG. 5  the location  25  at which the first lead-in  12  enters into the appertaining pinch seal  10  of the first end  15  of the arc tube  9  is closed by glass solder  29 . 
   Suitably also the location  27  at which the second lead-in  13  enters into the appertaining pinch seal  11  of the second end  16  of the arc tube  9  is closed by glass solder  29 ′. Instead of glass solder  29  and  29 ′ sodium silicate glass can be used as well. 
   In a manner not shown the lead-ins  12 ,  13  can optionally be platinized or covered with quartz glass, which is not demonstrated in detail. Also in a manner not shown the lead-in  13  can be electrically insulated in the region of the pinch seals  10  and  11 , e.g. by a ceramic sleeve.