Abstract:
The present invention relates to systems and methods for mechanically supporting and electrically coupling arc tubes in high intensity discharge (“HID”) lamps. The systems and methods provide mechanical support and electrical coupling of the arc tube in an HID lamp. The electrical coupling between the electrical leads of the arc tube and the lamp base includes one or more weldless electrical connections.

Description:
CLAIM OF PRIORITY  
       [0001]     This application claims the priority of U.S. Provisional Patent Application Ser. No. 60/125,999 filed Mar. 24, 1999. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to systems and methods for mechanically supporting and electrically coupling arc tubes in high intensity discharge (“HID”) lamps such as metal halide lamps. More particularly, the invention relates to such systems and methods which provide mechanical support and electrical coupling of the arc tube in an HID lamp with few or no welds.  
         [0003]     HID lamps such as metal halide lamps have found widespread acceptance in lighting large outdoor and indoor areas such as athletic stadiums, gymnasiums, warehouses, parking facilities, and the like, because of the relatively high efficiency, compact size, and low maintenance of HID lamps when compared to other lamp types. A typical HID lamp includes an arc tube which is mechanically supported within a light-transmissive outer lamp envelope. The arc tube includes two or more electrical leads which are each electrically coupled to a source of electrical power exterior of the outer lamp envelope.  
         [0004]     In such a lamp, the mounting structure which provides mechanical support and electrical coupling for the arc tube within the outer lamp envelope includes one or more metal components which are welded for mechanical and electrical integrity. In the fabrication of such lamps, the practice of welding such components, unless automated, is labor intensive which adds expense to the fabrication process. Further, the welding of various lamp components requires numerous weld schedules for the components which may comprise different materials and geometries. Still further, the welding electrodes require a significant amount of maintenance to achieve an optimum weld. Thus the elimination of welds in the mounting structure for the arc tube is desirable to reduce the time and expense required to fabricate such lamps.  
         [0005]     Another disadvantage of the typical HID lamp mounting structure having welds to maintain the mechanical and electrical integrity of the structure results from the susceptibility of the one or more welds in such lamps to mechanical failure during shipping of the lamps. The welds provide a relatively strong mechanical coupling of components when the weld is subjected to shear. However, the welds are relatively weak when subjected to a bending moment, which is the typical mode of mechanical failure in such lamps during shipping.  
         [0006]     In the fabrication of HID lamps, it is important to properly position the arc tube within the outer lamp envelope so that the light center of the lamp is optimized. In the known methods of fabricating HID lamps, the various components of the arc tube mounting structure must be aligned manually by the production operator before being mechanically joined or fixtured with specialized tooling. Such an alignment process is time consuming if done manually and expensive if done using fixtures. Thus the elimination of the alignment process in the fabrication of HID lamps is desirable to reduce the time and expense required to fabricate such lamps.  
         [0007]     Accordingly, it is an object of the present invention to provide a novel system and method for mechanically supporting and electrically coupling arc tubes in HID lamps which obviates the deficiencies of known systems and methods.  
         [0008]     It is another object of the present invention to provide a novel system and method for mechanically supporting and electrically coupling arc tubes in HID lamps with few or no components which are welded for mechanical integrity.  
         [0009]     It is yet another object of the present invention to provide a novel system and method for mechanically supporting and electrically coupling arc tubes in HID lamps with few or no components which are welded for electrical integrity.  
         [0010]     It is still another object of the present invention to provide a novel system and method for mechanically supporting and electrically coupling arc tubes in HID lamps which is amenable to automation.  
         [0011]     It is a further object of the present invention to provide a novel system and method for mechanically supporting and electrically coupling arc tubes in HID lamps which reduces mechanical failure during shipping of the lamp.  
         [0012]     It is yet a further object of the present invention to provide a novel system and method for aligning the light center of an HID lamp.  
         [0013]     These and many other objects and advantages of the present invention will be readily apparent to one skilled in the art to which the invention pertains from a perusal of the claims, the appended drawings, and the following detailed description of the preferred embodiments. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1   a  is a schematic illustrating a front view of a prior art pinched body arc tube.  
         [0015]      FIG. 1   b  is a schematic illustrating a front view of a prior art formed body arc tube.  
         [0016]      FIG. 2   a  is a schematic illustrating a front view of a prior art mounting structure for a 400 watt metal halide lamp.  
         [0017]      FIG. 2   b  is a bottom view of  FIG. 2   a.    
         [0018]      FIG. 3   a  is a schematic illustrating a front view of a 350 watt open fixture metal halide lamp according to one aspect of the present invention.  
         [0019]      FIG. 3   b  is a bottom view of  FIG. 3   a.    
         [0020]      FIG. 4   a  is a schematic illustrating a front view of the mounting structure of the lamp illustrated in  FIG. 3 .  
         [0021]      FIG. 4   b  is a bottom view of  FIG. 4   a.    
         [0022]      FIG. 5   a  is a schematic illustrating one embodiment of the frame suitable for the mounting structure illustrated in  FIG. 4 .  
         [0023]      FIG. 5   b  is a bottom view of  FIG. 5   a.    
         [0024]      FIG. 5   c  is a section of  FIG. 5   b.    
         [0025]      FIG. 6   a  is a schematic illustrating one embodiment of the stem clamp suitable for the mounting structure illustrated in  FIG. 4 .  
         [0026]      FIG. 6   b  is a bottom view of  FIG. 6   a.    
         [0027]      FIG. 7  is a schematic illustrating a top view of a shroud cap suitable for the mounting structure illustrated in  FIG. 4 .  
         [0028]      FIGS. 8   a  and  8   b  are schematics illustrating different embodiments of the arc tube retaining tabs suitable for the shroud cap illustrated in  FIG. 7 .  
         [0029]      FIG. 9   a  is a schematic illustrating a front view of the mounting structure illustrated in  FIG. 4 .  
         [0030]      FIG. 9   b  is a bottom view of  FIG. 9   a.    
         [0031]      FIG. 10  is a schematic illustrating one embodiment of a wire connector according to the present invention.  
         [0032]      FIG. 11  is a schematic illustrating another embodiment of a wire connector according to the present invention.  
         [0033]      FIG. 12  is a schematic illustrating one embodiment of the electrical coupling between the wire connectors and the stem leads according to the present invention.  
         [0034]      FIG. 13   a  is a schematic illustrating a front view of a 350 watt enclosed fixture metal halide lamp according to one aspect of the present invention.  
         [0035]      FIG. 13   b  is a bottom view of  FIG. 13   a.    
         [0036]      FIG. 14   a  is a schematic illustrating a front view of the mounting structure in the lamp illustrated in  FIG. 13 .  
         [0037]      FIG. 14   b  is a bottom view of  FIG. 14   a.    
         [0038]      FIG. 15   a  is a schematic illustrating a front view of one embodiment of the frame suitable for the mounting structure illustrated in  FIG. 14 .  
         [0039]      FIG. 15   b  is a bottom view of  FIG. 15   a.    
         [0040]      FIG. 15   c  is a section of  FIG. 15   b.    
         [0041]      FIG. 16   a  is a schematic illustrating a front view one embodiment of a stem clamp suitable for the mounting structure illustrated in  FIG. 14 .  
         [0042]      FIG. 16   b  is a top view of  FIG. 16   a.    
         [0043]      FIG. 17   a  is a schematic illustrating a front view of one embodiment of an arc tube clip suitable for the mounting structure illustrated in  FIG. 14 .  
         [0044]      FIG. 17   b  is a bottom view of  FIG. 17   a.    
         [0045]      FIG. 18  is a schematic illustrating a front view of one embodiment of a mounting structure suitable for a medium base lamp according to the present invention.  
         [0046]      FIG. 19   a  is a schematic illustrating a side view one embodiment of a heat shield suitable for the mounting structure illustrated in  FIG. 18 .  
         [0047]      FIG. 19   b  is a bottom view of  FIG. 19   a.    
         [0048]      FIG. 20  is a schematic illustrating a bottom view of one embodiment of the frame suitable for the mounting structure illustrated in  FIG. 18 .  
         [0049]      FIG. 21  is a schematic illustrating a front view of a portion of a mounting structure for a pinched body arc tube.  
         [0050]      FIG. 22   a  is a schematic illustrating a side view of one embodiment of the arc tube clip suitable for the mounting structure illustrated in  FIG. 21 .  
         [0051]      FIG. 22   b  is a bottom view of  FIG. 22   a.   
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0052]     While the present invention is suitable for mechanically supporting and electrically coupling arc tubes in any type of HID lamp, it may be easily understood in the embodiment suitable for metal halide lamps.  
         [0053]     Metal halide lamps include light emitting chemicals which are hermetically sealed within an arc tube formed from light transmitting material such as quartz glass or ceramics. The arc tube may comprise a pinched body or a formed body as illustrated in  FIGS. 1   a  and  1   b  respectively. The arc tube must be mechanically supported and electrically coupled within the outer lamp envelope and there are many known configurations for the arc tube mounting structure. However, there are only two basic types of arc tube mounting structures, i.e., enclosed (unshrouded) and open (shrouded). The open fixtures include a generally tubular shroud formed from light transmitting material positioned around the arc tube. The shroud provides protection in the unlikely event of a non-passive failure of the arc tube.  
         [0054]     There are many sizes of metal halide lamps which range between about 32 watts and 2000 watts and generally include either a medium type base for lower wattage lamps (150 W or below) or a mogul type base for higher wattage lamps (175 W or greater).  
         [0055]      FIGS. 2   a  and  2   b  illustrate a typical prior art mounting structure for providing mechanical support and electrical coupling for a shrouded formed body arc tube in a 400 watt metal halide lamp having a mogul type base. With reference to  FIGS. 2   a  and  2   b , the arc tube mounting structure  10  includes a metal frame  12  which is mechanically supported by a stem assembly  14 . The stem assembly  14  comprises a stem  16  which is typically formed from hard glass, a metallic spring clip  18 , and two stem leads  20  which provide an electrical coupling between the arc tube  22  supported within the outer lamp envelope (not shown) to a source of electrical power (not shown) for operating the lamp.  
         [0056]     The frame  12  is mechanically supported at one end by the stem assembly  14 . The integrity of the mechanical support of the frame  12  by the stem assembly  14  is maintained by one or more welds between the frame  12  and the spring clip  18 .  
         [0057]     The arc tube  22  is mechanically supported at one end by an arc tube retaining clip  28  and at the other end by a strap  30 . The retaining clip  28  and strap  30  are each mechanically supported from the frame  12 . The integrity of the mechanical support of the retaining clip  28  and strap  30  from the frame  12  is maintained by one or more welds.  
         [0058]     The generally tubular shroud  24  surrounds the central portion of the arc tube  22  and is mechanically supported at each end by a shroud cap  26 . Each of the shroud caps  26  is mechanically supported from the frame  12 . The integrity of the mechanical support of the shroud caps  26  from the frame  12  is maintained by one or more welds.  
         [0059]     The arc tube  22  includes an arc tube lead  32  at each end. Each arc tube lead  32  is electrically coupled to one of the stem leads  20 . The integrity of the electrical coupling between the arc tube leads  32  and the stem leads  20  is maintained by one or more welds.  
         [0060]     While of utility in HID lamps of any type and wattage, the present invention may be easily understood in the embodiments suitable for mechanically supporting and electrically coupling the arc tubes of metal halide lamps.  
         [0000]     Open Fixture Lamps:  
         [0061]      FIGS. 3   a  and  3   b  illustrate a 350 watt open fixture metal halide lamp. With reference to  FIGS. 3   a  and  3   b , the lamp  40  includes a formed body arc tube  42  which is mechanically supported and electrically coupled within the outer lamp envelope  44  by the mounting structure  50 .  
         [0062]      FIGS. 4   a  and  4   b  illustrate the arc tube mounting structure for the lamp illustrated in  FIGS. 3   a  and  3   b . With reference to  FIGS. 4   a  and  4   b , the mounting structure  50  comprises a frame  52  which is mechanically supported by the stem assembly  54 . The stem assembly  54  comprises a stem  56  which may be formed from hard glass, a metallic stem clamp  58 , and two stem leads  60  which provide an electrical coupling between the arc tube  42  supported within the outer lamp envelope (not shown) and a source of electrical power (not shown) for operating the lamp.  
         [0063]     The frame  52  is mechanically supported at one end by the stem assembly  54 . In one embodiment of the present invention, the integrity of the mechanical support of the frame  52  by the stem assembly  54  is maintained without a weld.  
         [0064]      FIGS. 5   a  and  5   b  illustrate one embodiment of the frame according to the present invention. With reference to  FIGS. 5   a  and  5   b , the frame  52  comprises a metallic wire formed into an end portion  62  and a pair of generally parallel legs  64  extending in substantially the same direction from the end portion  62 . Each leg  64  includes one or more swaged portions  66  at predetermined locations along the length thereof.  FIG. 5   c  illustrates an enlarged cross-section of the leg  64  at a swaged portion  66  thereof.  
         [0065]      FIGS. 6   a  and  6   b  illustrate one embodiment of the stem clamp according to the present invention. With reference to  FIGS. 6   a  and  6   b , the stem clamp  58  is a generally tubular metallic clamp which is adapted to fit over the stem  56  as illustrated in  FIGS. 4   a  and  4   b . The stem clamp  58  includes two pairs of frame retaining tabs  67 , each pair having an upper tab  68  and lower tab  69  and being positioned opposite the other pair about the curved surface of the stem clamp  58 . Each retaining tab  68 , 69  forms an aperture  70  and is adapted to receive therethrough a portion of one of the legs  64  adjacent the terminal end thereof. Each pair of frame retaining tabs  67  is aligned so that the leg  64  received therethrough is substantially parallel to the longitudinal axis  71  of the stem clamp  58 .  
         [0066]     The frame  52  may be mechanically supported by the stem assembly  54  by positioning each leg  64  through the apertures  70  formed by the upper tab  68  and the lower tab  69  of one of the pairs of retaining tabs  67 . Each pair of retaining tabs  67  laterally constrains the leg  64  received therethrough. With further reference to  FIG. 3   a , the rigid attachment between the outer lamp envelope  44  and the lamp base  41  axially constrains the mounting structure  50  supported therein. The integrity of the mechanical support of the frame  52  by the stem assembly  54  is maintained by axial constraint of the frame  52  after the terminal ends thereof are received through the pairs of retaining tabs  67 . Thus the integrity of the mechanical support of the frame  52  from the stem assembly  54  may include no welds.  
         [0067]     With further reference to  FIGS. 4   a ,  4   b ,  5   a  and  5   b , the arc tube  42  and the shroud  44  may be mechanically supported at each end by a shroud cap  76 . Each shroud cap  76  is mechanically supported by the frame  52 . In one embodiment of the present invention, the integrity of the mechanical support of one or both shroud caps  76  is maintained without a weld.  
         [0068]      FIG. 7  illustrates a shroud-cap of one embodiment of the present invention. With reference to  FIG. 7 , the shroud cap  76  is a generally planar member having a generally circular shape and comprises one or more shroud retaining tabs  78  positioned about the circumference thereof, two frame retaining tabs  80  each positioned opposite the other about the circumference thereof, and a central arc tube retaining tab  82  positioned at or about the center thereof.  
         [0069]     Each frame receiving tab  80  forms a slot  81  which is adapted to receive therein a swaged portion  66  of one of the legs  64  of the frame  52 . The swaged portions  66  on each leg  64  are positioned so that when received in the frame receiving tabs  80  of the shroud cap  76 , the shroud cap may be mechanically supported between the legs  64  at a substantially right angle thereto. The integrity of the mechanical support may be maintained by crimping the tabs  80  about the swaged portion  66  received therein. The integrity of the mechanical support is further maintained by the lateral constraint of the terminal ends of the legs  64  by the stem assembly  54 . Thus the integrity of the mechanical support of one or both of the shroud caps  76  from the frame  52  may be maintained without a weld.  
         [0070]     The shroud  44  is a generally tubular member formed from light transmitting material. The shroud may be mechanically supported at each end by positioning the shroud  44  between each shroud cap  76  so that the longitudinal axis of the shroud  44  is substantially parallel to each leg  64 . The integrity of the mechanical support of the shroud  44  between each shroud cap  76  may be maintained by bending the shroud retaining tabs  78  to be in contact with the outer surface of the shroud  44  as illustrated in  FIGS. 4   a  and  4   b.    
         [0071]     The arc tube  42  includes a bulbous light emitting chamber  43  between two end portions  45 . The arc tube  42  may be supported at each end portion  45  by the arc tube retaining tab  82  of one of the shroud caps  76 . Each tab  82  forms an aperture  83  adapted to receive a portion of one end portion  45  of the arc tube  42  therethrough. The arc tube  42  is positioned between the tabs  82  of each shroud cap  76  so that the longitudinal axis of the arc tube  42  is substantially parallel to the legs  64  of the frame  52 .  
         [0072]     Each end portion  45  of the arc tube  42  includes an axial positioning portion  47  which is of larger cross-sectional dimension than the end portion  45 . The cross-sectional dimension of the axial positioning portion  47  is large enough to prevent the passage of the axial positioning portion  47  through the aperture  83  of tab  82  of each shroud cap  76 . The shroud caps  76  may thus be spaced apart a distance to prevent axial movement of the arc tube  42  supported therebetween.  
         [0073]     The arc tube  42  forms the light emitting chamber of the lamp, and thus the axial positioning of the arc tube is critical in optimizing the light center of the lamp. Thus the light center of the lamp may be determined by positioning the swaged portions  66  of the legs  64  which thus determines the axial position of the shroud caps  76 , which thus determines the axial position of the arc tube  42 . This method of aligning the light center of the lamp eliminates the time consuming process of manually aligning the arc tube during fabrication of the lamp.  
         [0074]     In some lamps, the radial position of the arc tube is critical to the operation of the lamp. In such lamps having formed body arc tube as illustrated in  FIG. 1   b , the end portions of the arc tube may terminate at the pinched region which is flattened. the cross-section of the terminal portion of the end portions of the arc tube will not rotate relative to an aperture or slot having a similar geometry if inserted therethrough.  FIGS. 8   a  and  8   b  illustrate yet other embodiments of the arc tube retaining tabs according to the present invention. With reference to  FIGS. 8   a  and  8   b , the tab  84  forms an elongated aperture  85  adapted to receive the flattened end portion of an arc tube. The tab  86  forms an elongated slot  87  adapted to receive the flattened end portion of an arc tube. The dimension of the aperture  85  and slot  87  may be adapted to prevent rotation of the end portion of the arc tube received therethrough. Thus the arc tube may be radially aligned by positioning the elongated dimension of the aperture  85  or slot  87  and thus radially positioning the arc tube supported by the tabs  84 , 86 .  
         [0000]     Electrical Coupling:  
         [0075]     In addition to providing mechanical support for the arc tube in HID lamps, the mounting structure provides electrical coupling of the arc tube to a source of electrical power for operating the lamp. The aspect of the present invention directed to the electrical coupling of the arc tube to a power source is suitable for any type HID lamp and may be easily understood in the embodiment for open fixture metal halide lamps.  
         [0076]      FIGS. 9   a  and  9   b  illustrate the embodiment of the present invention illustrated in  FIGS. 4   a  and  4   b . With reference to  FIGS. 9   a  and  9   b , the mounting structure  50  includes the stem leads  60  which each provide electrical coupling between the arc tube  42  and a source of electrical power (not shown).  
         [0077]     The arc tube  42  includes the arc tube lead  90  at one end and the arc tube lead  92  at the other end thereof. The connector  94  provides electrical coupling between the arc tube lead  90  and one of the stem leads  60 . The connector  96  provides electrical coupling between the arc tube lead  92  and the other stem lead  60 . In one embodiment of the present invention, the integrity of the electrical coupling between the arc tube leads  90 , 92  and the stem leads  60  may be maintained without welds.  
         [0078]      FIGS. 10 and 11  each illustrate an embodiment of a connector for electrically coupling an arc tube lead to a stem lead according to the present invention. With reference to  FIG. 10 , the connector  94  comprises an elongated wire having a coil  100  formed at one end and a coil  102  formed at the other end thereof. The coil  100  is adapted to receive a portion adjacent the terminal end of one of the stem leads  60  therein so that the coil  100  extends axially around the portion of the stem lead  60  received therein. At least a portion of the coil  100  is crimped around the portion of the stem lead  60  received therein to establish and maintain the integrity of the electrical coupling between the connector  94  and one of the stem leads  60 .  
         [0079]     The coil  102  is adapted to receive a portion adjacent the terminal end of the arc tube lead  90  therein so that the coil  102  extends axially around the portion of the arc tube lead  90  received therein. At least a portion of the coil  102  is crimped around the portion of the arc tube lead  90  received therein to establish and maintain the integrity of the electrical coupling between the connector  94  and the arc tube lead  90 . Thus the integrity of the electrical coupling between the arc tube lead  90  and one of the stem leads  60  may be maintained without a weld.  
         [0080]     With reference to  FIG. 11 , the connector  96  comprises an elongated wire, commonly referred to as a flywire, having a coil  104  formed at one end and a coil  106  formed at the other end thereof. The coil  104  is adapted to receive a portion adjacent the terminal end of one of the stem leads  60  therein so that the coil  104  extends axially around the portion of the stem lead  60  received therein. At least a portion of the coil  104  is crimped around the portion of the stem lead  60  received therein to establish and maintain the integrity of the electrical coupling between the connector  96  and one of the stem leads  60 .  
         [0081]     The coil  106  is adapted to receive a portion adjacent the terminal end of the arc tube lead  92  therein so that the coil  106  extends axially around the portion of the arc tube lead  92  received therein. At least a portion of the coil  106  is crimped around the portion of the arc tube lead  92  received therein to establish and maintain the integrity of the electrical coupling between the connector  96  and the arc tube lead  92 . Thus the integrity of the electrical coupling between the arc tube lead  92  and one of the stem leads  60  may be maintained without a weld.  
         [0082]     In the fabrication of lamps, the stem is susceptible to breakage due to its relative fragility. In the event that the stem must be replaced after the connectors  94 , 96  and the stem leads  60  have been electrically coupled, such electrical coupling must be suitable for uncoupling and recoupling the connectors with a new stem and stem leads.  FIG. 12  illustrates an embodiment of the electrical coupling between the arc tube leads and the stem leads which is suitable for recoupling the leads. With reference to  FIG. 12 , the electrical coupling between the stem leads  60  and the connectors  94 , 96  is established and maintained by crimping only a portion  101  of the coil  100  and a portion  105  of the coil  104  sufficient to establish and maintain such electrical coupling. In the event that the crimped portions  101 , 105  must be removed from the connector  94 , 96  to uncouple the connectors  94 , 96  from the stem leads  60 , the uncrimped portion  103  of the coil  100  and portion  107  of the coil  104  are of sufficient length so that the electrical coupling between the connectors  94 , 96  may be reestablished and maintained by crimping portions  103 , 107 . Thus the arc tube  42  may be electrically uncoupled and recoupled to the stem leads  60 .  
         [0000]     Enclosed Fixture Lamps:  
         [0083]      FIGS. 13   a  and  13   b  illustrate a 350 watt enclosed fixture (i.e. unshrouded) metal halide lamp. With reference to  FIGS. 13   a  and  13   b , the lamp  110  includes a formed body arc tube  112  which is mechanically supported and electrically coupled within the outer lamp envelope  114  by the mounting structure  115 .  
         [0084]      FIGS. 14   a  and  14   b  illustrate the arc tube mounting structure for the lamp illustrated in  FIGS. 13   a  and  13   b . With reference to  FIGS. 14   a  and  14   b , the mounting structure  115  comprises a frame  116  which is mechanically supported by the stem assembly  118 . The stem assembly  118  comprises a stem  120  which may be formed from hard glass, a metallic stem clamp  122 , and two stem leads  124  which provide electrical coupling between the arc tube  112  supported within the outer lamp envelope (not shown) to a source of electrical power (not shown) for operating the lamp.  
         [0085]     The frame  116  is mechanically supported at one end by the stem assembly  118 . In one embodiment of the present invention, the integrity of the mechanical support of the frame  116  by the stem assembly  118  is maintained without a weld.  
         [0086]      FIGS. 15   a  and  15   b  illustrate one embodiment of the frame according to the present invention. With reference to  FIGS. 15   a  and  15   b , the frame  116  comprises a metallic wire formed into an end portion  126  and an leg  128  extending therefrom. The leg  128  includes one or more swaged portions  130  at predetermined locations along the length thereof.  FIG. 115   c  illustrates an enlarged cross-section of the leg  128  at a swaged portion  130  thereof.  
         [0087]      FIGS. 16   a  and  16   b  illustrate one embodiment of the present invention suitable for mechanically supporting the frame in an enclosed fixture lamp. With reference to  FIGS. 16   a  and  16   b , the stem clamp  122  includes two pairs of frame retaining tabs  132 , each pair having an upper tab  134  and a lower tab  136  and being positioned opposite the other pair about the curved surface of the stem clamp  122 . Each of the lower retaining tabs  136  forms an aperture (not shown) and is adapted to receive the terminal end of the leg  128  of the frame  116  therethrough. Each of the upper tabs  134  forms a slot  135  which is adapted to receive a swaged portion  130  of the leg  128  therein. Each pair of frame retaining tabs  132  is aligned so that the leg  128  received therethrough is substantially parallel to the longitudinal axis  138  of the stem clamp  122 . Because there is only one leg  128  of frame  116 , only one pair of retaining tabs  132  is needed to support the frame  116 . Also because there is only one leg  128 , the frame  116  is susceptible to radial movement about the axis of the leg  128 . Thus the slot  135  must also be adapted to constrain such radial movement of the frame  116  by preventing rotation of the swaged portion  130  received therein.  
         [0088]     The frame  116  may be mechanically supported by the stem assembly  118  by positioning the terminal end of the leg  128  through the aperture formed by the lower tab  136  and positioning the swaged portion  130  nearest the terminal end of the leg  128  into the slot  135  formed by the corresponding upper tab  134 . The tabs  134 , 136  laterally constrain the terminal end of the leg  128 . The integrity of the mechanical support may be maintained by crimping the upper tabs  134  about the portion of the leg  128  received therein.  
         [0089]     With further reference to  FIG. 13   a , the rigid connection between the outer lamp envelope  114  and the lamp base  111  axially constrains the mounting structure  115  and thus the frame  116  supported therein. Thus the integrity of the mechanical support is further maintained by the axial constraint of the frame  116  and may include no welds.  
         [0090]     With further reference to  FIGS. 14   a ,  14   b ,  15   a  and  15   b , the arc tube  112  may be mechanically supported at each end by an arc tube clip  140 . Each arc tube clip  140  is mechanically supported by the frame  116 . In one embodiment of the present invention, the integrity of the mechanical support of one or both arc tube clips  140  may be maintained without a weld.  
         [0091]      FIGS. 17   a  and  17   b  illustrate an arc tube clip of one embodiment of the present invention. With reference to  FIGS. 17   a  and  17   b , the arc tube clip  140  is a substantially rigid member comprising a pair of frame receiving tabs  142  at one end and an arc tube receiving tab  144  at the other end thereof.  
         [0092]     Each frame receiving tab  142  forms a slot  143  which is adapted to receive therein a swaged portion  130  of the leg  128  of the frame  116 . The integrity of the mechanical support of the arc tube clips  140  may be maintained by crimping the tabs  142  about the swaged portion  130  received therein. Thus the integrity of the mechanical support of one or both of the arc tube clips  140  from the frame  116  may be maintained without a weld.  
         [0093]     With further reference to  FIGS. 14   a  and  14   b , the arc tube  112  includes a bulbous light emitting chamber  113  between two end portions  117 . The arc tube  112  may be supported at each end portion  117  by the arc tube retaining tab  144  of one of the arc tube clips  140 . Each tab  144  forms a slot  145  adapted to receive a portion of one end portion  117  of the arc tube  112  therethrough. The arc tube  112  is positioned between the tabs  144  of each arc tube clip  140  so that the longitudinal axis of the arc tube  112  is substantially parallel to the leg  128  of the frame  116 .  
         [0094]     Each end portion  117  may include an axial positioning portion  119  which is of larger cross-sectional dimension than the end portion  117 . The cross-sectional dimension of portions  119  is large enough the prevent the passage of portions  119  through the slots  145 . Thus the arc tube clips  140  may be spaced apart a distance to prevent axial movement of the arc tube  112  supported therebetween.  
         [0095]     The light center of the lamp  110  may be determined by positioning the swaged portions  130  along the length of the leg  128 .  
         [0096]     Metal halide lamps of lower wattage (i.e. about 150 W and below) typically include a medium type base.  FIG. 18  illustrates a mounting structure for a metal halide lamp having a medium type base. With reference to  FIG. 18 , the mounting structure  150  includes a frame  152  and a stem assembly  154  comprising a heat shield  156 . The frame  152  is mechanically supported by the heat shield  156 .  
         [0097]      FIGS. 19   a  and  19   b  illustrate one embodiment of the heat shield according to the present invention. With reference to  FIGS. 19   a  and  19   b , the heat shield  156  comprises a generally planar shield portion  158  and a pair of frame retaining tabs  160  positioned on opposites sides of the shield portion  158 . Each of the retaining tabs  160  overlies a portion of the shield portion  158  forming a gap  161 . Each of the retaining tabs  160  also forms a slot  162 .  
         [0098]      FIG. 20  illustrates the frame  152 . With reference to  FIG. 20 , the frame  152  comprises a wire formed into and end portion  164  and a pair of substantially parallel legs  166  extending in the same direction from the end portion  164 . Each leg  166  terminates in a terminal portion  168  extending at a substantially right angle from the major portion  170  of the leg  166 .  
         [0099]     Each of the slots  162  is adapted to receive one of the legs  166  therein at the portion of the leg  166  adjacent the terminal portion  168 . Each of the gaps  161  is adapted to receive therein the terminal portion  168  of the leg  166  received in the adjacent slot  162 . The tabs  160  may be crimped to retain the terminal portions  168  received in the gaps  161 .  
         [0100]     With further reference to  FIG. 18 , the shroud cap  172  has a dimension normal to the legs  166  which is larger than the corresponding dimension of the heat shield  156 . Thus the terminal portions  168  of the legs  166  are compressed toward the each other when received within the gaps  161  formed in the heat shield  156 . The crimping of the tabs  160  about the terminal portions  168  received therein maintains the integrity of the mechanical support of the frame  152  by the stem assembly  154  without a weld. The mechanical support is further enhanced by the resistance of the legs  166  to the compression of the terminal portions, as well as the frictional engagement between the heat shield  156  and the legs  166  received therein. In some embodiments, crimping of the tabs  160  may not be necessary.  
         [0101]     The present invention is suitable for supporting pinched body arc tube as well as formed body arc tubes.  FIG. 21  illustrates one embodiment of the present invention suitable for supporting a pinched body arc tube. With reference to  FIG. 21 , the arc tube  180  is supported at each end from the frame  182  by an arc tube clip  184 .  FIGS. 22   a  and  22   b  illustrate one embodiment of the arc tube clip suitable for supporting a pinched body arc tube from the frame. With reference to  FIGS. 22   a  and  22   b , the arc tube clip  184  includes a pair of frame retaining tabs  186  at one end. Each frame retaining tab  186  forms a slot  187  adapted to receive a swaged portion of the frame  182  therein. The tabs  186  may be crimped to maintain the integrity of the mechanical support of the arc tube clip  184  from the frame  182 .  
         [0102]     The arc tube clip  184  further includes a pair of arc tube clamping portions  188  adapted to receive one pinched end of the arc tube  180  therebetween. The pinched end of the arc tube may be retained between the clamping portions  188  by compressing the clamping portions  188  around the pinched end of the arc tube and securing the tab  189  behind the frame received in the slots  187  formed by the frame retaining tabs  186 .  
         [0103]     In many HID lamps it is desirable to getter excess gasses such as hydrogen and oxygen from within the outer lamp envelope. Typically a getter material is mounted within the outer lamp envelope by welding a getter cap to the lamp mounting structure. In yet another aspect of the present invention, the getter cap may be supported within the outer lamp envelope with no welds between the getter cap and the mounting structure.  
         [0104]      FIG. 23  illustrates a typical getter cap. With reference to  FIG. 23 , the getter cap  190  comprises a getter containing portion  192  which contains the getter material  194 . A getter cap mounting wire  196  is typically attached at one end to the getter containing portion  192  by a weld. The getter cap  190  is typically supported by a lamp mounting structure by welding the other end to the mounting wire  196  to the structure. In one embodiment of the present invention, the getter cap  190  may be supported from the lamp mount by providing a getter mount tab such as tabs  197 , 198 , 199  illustrated in  FIGS. 9   a ,  14   a , and  22   a  respectively, feeding the distal end of the mounting wire  196  through one or more apertures formed by the tab  197  or tab  198  or tab  199 , and wrapping the end of the wire  196  around a portion of the tab. Thus the getter cap may be supported by the mounting structure without a weld between the getter cap and the structure.  
         [0105]     While preferred embodiments of the present invention have been described, it is to be understood that the embodiments described are illustrative only and the scope of the invention is to be defined solely by the appended claims when accorded a full range of equivalence, many variations and modifications naturally occurring to those of skill in the art from a perusal hereof.