Abstract:
The lamp includes a cap engaged to a bulb composed of a glass lens and a glass reflector, the lens and reflector each having an inner surface which is parabolically shaped and coated with an IR reflective material layer. The interior configuration of elements of the lamp is mathematically molded to cause infrared rays emitted by the filament to evenly reflect back to the filament heating same and thereby increasing lighting efficiency up to 50%, with the lamp emitting cool light and without compromising longevity of the lamp. The lamp may be any of a plurality of diversified types, such as high pressure sodium, metal halide, incandescent, halogen, etc.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a lamp which has improved efficiency. More specifically, a bulb of the lamp is configured to incorporate parabolic inner surfaces which are coated with an IR reflecting material to reflect emitted infrared rays back to a filament of the lamp, thereby increasing the lighting coefficient of the lamp, and, inherently, its efficiency. 
     2. Prior Art 
     Generally, the efficiency of incandescent lamps is less than 15%, with infrared (IR) radiation comprising over 85% of the radiant energy thereof. Even more efficient high-pressure sodium, metal halide and xenon lamps still emit 20%-30% of their total radiant energy as IR. Further, the filaments of lamps and the rods of, and an arc produced by, an arc lamp are usually linear, with such linearity creating a key problem in manufacturing lamps with a proper geometric shape for IR reflection. The substantial degree of IR radiation emitted by the above mentioned lamps not only increases costs for lighting due to inefficiency, but also pollutes our environment. 
     In the early 1980&#39;s, it was determined that IR reflecting material layers coated on an interior bulb surface are able to reflect IR radiation emitted from a filament, back to the filament, heating same and greatly increasing the lighting coefficient of the lamp. The reflecting material layers used in early units, however, could only accommodate temperatures up to 500° C., leading to the development of crystalline substances for use in creating a high temperature filament, typically having the form of a dot. 
     Next, it was proposed to curve a filament to a plane and to position the filament at the center of a spherical bulb, with a dot to dot symmetry about a center point, making it possible to coat an IR reflecting material layer onto the inner surface of the bulb. However, much of the emitted IR radiation is still not reflected to the filament, inasmuch as a spherical lamp bulb produces non-symmetric reflection, when viewed in light of optical geometry. 
     To further improve lighting efficiency, a type of halogen tungsten filament incandescent lamp incorporating an IR reflecting material layer has been developed in some countries. In a lamp of this type, a filament is positioned along a major axis of an elliptical bulb, the outer surface of which is coated with an IR reflecting material layer. However, lamps of this type have a decreased useful life because two reflective foci around which IR rays are concentrated are inherently produced, forming two hot spots on the filament. Simultaneously, the many IR rays generated near each of the two ends of the filament cannot be reflected back to the filament. Even spherical or cylindrical bulb embodiments of such lamps still do not afford higher efficiency. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is a primary object of the invention to provide a lamp providing a high degree of energy savings and incorporating a bulb of a double parabolic configuration, a parabolic lens thereof being coated with an IR reflecting material layer on an inner surface thereof and a reflector thereof being coated with aluminum on an inner surface thereof to reflect, with a high degree of coincidence, substantially all IR rays emitted by a linear filament thereof back to the filament to heat same, thereby improving lighting efficiency of lamps of the incandescent, halogen and arc type and significantly increasing the useful life of the bulb. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a lamp made in accordance with the teachings of the present invention, with portions of a bulb thereof broken away to show internal elements of the bulb. 
     FIG. 2 is a perspective view of a lamp made in accordance with the teachings of the present invention, with portions of a bulb thereof broken away to show internal elements of the bulb, and wherein the filament comprises an arc tube. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawing in greater detail, there is illustrated therein a lamp made in accordance with the teachings of the present invention and generally identified by the reference numeral  10 . The lamp  10  includes a cap  11  suitably engaged to bulb  12  incorporating a glass reflector  14  and glass lens  16 . An inner surface  18  of the glass reflector  14  and an inner surface  20  of the glass lens  16  are both parabolic in shape, the lens  16  and reflector  14  being specially processed via known molding, fusion, pinching, and sealing technologies under high pressure to create the bulb  12 . The inner surface  20  of the lens  16  is coated with a layer of IR reflecting material such as TiO—SiO 2 , Ta 2 O 5 —SiO 2 , while the inner surface  18  of the reflector  14  is coated with a layer of aluminum, silver, or an IR reflecting material, as defined above. 
     Inasmuch as the teachings herein are considered equally applicable for use in lamps  10  incorporating a linear filament  22 , as well as in arc lamps (FIG.  2 ), the term filament  22  will be used herein as symbolizing all embodiments for the sake of brevity. During design of the lamp  10 , through mathematical modeling, a focal distance f 2  for the lens  16  and a focal distance f 1  for the reflector  14  must be calculated, relative to a length of the linear filament  22 , to provide coincidence between the lens  16  focus f 2  and the reflector  14  focus f 1  after the reflector  14  and lens  16  have been joined together about a peripheral area  21 . The lines of IR reflection  26  and  28  were obtained by theoretical calculation and experimental tracing of such rays while all visible light rays as indicated at  24  are transmitted outwardly of the lamp  10 , through the lens  16 . The area of the inner parabolic surface  18  of the reflector  14  can be calculated from the following equation: 
     
       
         y 1   2 =(r 2 /b 1 )X, 
       
     
     where: 
     Y 1 =Y coordinate axis of reflector parabolic plane 
     r=radius of parabolic reflector 
     b 1 =height of reflector parabolic plane 
     X=X coordinate axis of reflector parabolic plane 
     The area of the inner parabolic surface  20  of the lens  16  is also calculated from 
     
       
         y 2   2 (r 2 /b 2 )X, 
       
     
     where: 
     Y 2 =Y coordinate axis of lens parabolic plane 
     r=radius of parabolic lens 
     b 2 =height of lens parabolic plane 
     X=X coordinate axis of lens parabolic plane 
     It will be understood that the filament  22  is maintained vertical by engagement thereof across a support  30 , along which a metal weld plate  32  is provided across which the filament  22  is electrically coupled to a conductor  34 . 
     The conductor  34  is further engaged by a joint support  36  which is welded to the cap  11 . 
     It will be understood that the filament  22  lies along a center axis X of the bulb  12 , extending from the lens  16  to the reflector  14 , with a free end  40  of the conductor  34  engaging within a positioning dimple  42  created in the inner surface  20  of the lens  16 , at a centered position, along the axis X, assuring linear alignment of the conductor  34  and filament  22  along the center axis X of the bulb  12 . 
     A double ended high pressure sodium (HPS) lamp  10  made in accordance with the teachings of the present invention was comparison tested against an identical lamp without IR reflectivity, by the Electric Light Sources Institute of Fundan University, Peoples Republic of China, with the following result: 
     
       
         
               
               
               
             
               
               
               
               
               
               
               
             
           
               
                   
               
               
                 HPS Lamp 
                 HPS Lamp 
                   
               
               
                 with IR reflector 
                 without IR Reflector 
               
             
          
           
               
                   
                   
                 Signal 
                   
                   
                 Signal 
                   
               
               
                   
                   
                 tested 
                   
                   
                 tested 
               
               
                 Voltage 
                 Wattage 
                 (value 
                 Voltage 
                 Wattage 
                 (value 
                 Efficiency 
               
               
                 (V.) 
                 (W.) 
                 gained) 
                 (V.) 
                 (W.) 
                 gained) 
                 Improved (%) 
               
               
                   
               
               
                 220 
                 70 
                 263 
                 220 
                 70 
                 230 
                 14.35% 
               
               
                   
               
             
          
         
       
     
     From the result of such testing, it will be seen that efficiency has been improved approximately 15% through use of the teachings herein. 
     Also, theoretical calculations have illustrated that lighting efficiency of double ended incandescent lamps and halogen lamps could be increased by as much as 50% if the teachings herein were to be applied thereto. Further, in newly developed HPS and LPS lamps, metal halide lamps, xenon lamps, etc., a bulb  12  coated with an IR reflecting material layer on an inner surface thereof promises bright prospects due to advantages such as a sufficient distance between the filament  22  and the reflector  14  surface  18 , controlled temperature of under 500° C., and impossibility of peeling of the IR material layers. 
     The invention has wide usage applications, such as in home lighting, commercial lighting, highway lighting, etc. Also, due to coolness of the lighting produced by the lamp  10 , it could be substituted for existing hot burning light sources, providing capability for creating cool burning lamps of different power, voltage and dimensions. 
     Considering a halogen lamp as an example for realizing this capability, the following are taken into account. 
     1) Design and calculation of reflector&#39;s parabolic plane: 
     The halogen lamp  10  is molded of hard glass and the inner surface  18  of the reflector  14  is parabolic in shape and coated with an aluminum material layer. A halogen lamp requiring a 120V source and having a 100W tungsten filament with a length of 14 mm will be used for the example. It is known that the focal length f 1  of the reflector  14  should be slightly longer than the length of the filament  22 , obtained by adding 2 mm+14 mm=16 mm. For example, if the diameter of the reflector&#39;s  14  parabolic plane is taken as 100 mm, by using the equation: 
     
       
         f 1 =r 2 /4b 1   
       
     
     where 
     f 1 =focal length 
     r=radius of the reflector parabolic plane 
     b 1 =height of the reflector parabolic plane 
     we can manipulate the equation to determine b 1 : 
     
       
         b 1 =r 2 /4f 1 =(50) 2 /(4×16)=39.0625 mm. 
       
     
     Thus we obtain by using the parabolic plane equation: 
     
       
         Y 1   2 =((r 2 )X)/b 1 =((50) 2 X)/39.0625=64X, i.e., Y 1   2 =64X. 
       
     
     We know that the filament of a halogen lamp  10  has two ends, one of which is mounted at focal point  15  and the other end of which is mounted near the bottom of the reflector&#39;s parabolic plane, on the axis X. 
     2) Design and calculation of lens&#39;s parabolic plane: 
     Being made from hard glass, the inner surface  20  of the lens  16  takes a parabolic shape with the inner surface  20  being coated with an IR reflecting material layer of TiO 2 —Sio 2 . It is known that a diameter of the lens  16  is equal to a diameter of the reflector  14 ; here 100 mm. Suppose that the height of the lens&#39;s parabolic plane, b 2 =16 mm (focal length f 1  of the parabolic plane of the reflector  14 ), thus we obtain by using the equation: 
     
       
         f 2 =r 2 /4b 2 , where: 
       
     
     f 2 =lens  14  focal length f 2    
     b 2 =height of the lens&#39;s parabolic plane so: 
     f 2 =(50) 2 /(4 mm×16 mm)=39.0625 mm and we obtain by using the equation of the lens&#39;s parabolic plane: Y 2   2 =(r 2 X)/b 2 =((50) 2 X)/16=156.25X. Total height of inner surface of the bulb B=eight of the lens b 2  plus height of parabolic plane of the reflector b 1 =16+39.0625=55.0625 mm. Thus: f 2 =total height of the bulb B−f 1 =55.0625 minus 16=39.0625 mm (focal distance of the lens). 
     The above result indicates that the focus of lens  16  will be coincident with the focus of reflector  14  when they are suitably engaged about the periphery  21 . The positioning dimple  42  is centered (positioned at a vertex  50  of lens  16 ) during molding to center the conductor  34  and thus the filament  22  continuing therefrom along the center axis X of the bulb  12 , extending between the lens  16  and the reflector  14 . 
     Spatial configuration parameters for an incandescent or arc lamp would be similarly calculated, as defined above. 
     In FIG. 2, an arc tube  60  replaces the filament  22 , with the remainder of the structures being identical to those of FIG.  1 . 
     As described above, the lamp  10  provides a number of advantages, some of which have been described above and others of which are inherent in the invention. Also, modifications can be proposed to the lamp  10  without departing from the teachings herein. Accordingly, the scope of the invention is only to be limited as necessitated by the accompanying claims.