Patent Publication Number: US-7589459-B2

Title: Infrared radiation automotive lamp filter

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     REFERENCE TO A SEQUENCE LISTING, A TABLE, OR A COMPUTER PROGRAM LISTING COMPACT DISC APPENDIX 
     Not Applicable 
     BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     This invention relates in general to incandescent vehicle lamps, and more specifically, to an efficient infrared radiation absorbing filter for an automotive lamp. 
     2. Background of Related Art 
     A lamp assembly for a vehicle typically includes a reflective housing enclosed by a transparent lens. A replaceable incandescent light source is coupled to a removable socket adjacent a rear reflective surface within the reflective housing. The illumination source extends into an interior space through an aperture formed in the rear of the reflective housing. The removable socket couples to the rear of the reflective housing for securing the removable socket and illumination light source to the lamp assembly. 
     The illumination light source emits radiation of all wavelengths. Short wave infrared radiation is the desirable radiation since short waves infrared radiation is within the visible range of light spectrum. Long wave infrared radiation is undesirable radiation since long wave infrared radiation is in the non-visible range of the light spectrum. For an illumination source such as a light bulb, only 5% to 10% of the total emitted radiation is visible light (i.e., short wave) and 90% to 95% is parasitic radiation (i.e., long wave) which only contributes to thermal heat and not light. 
     The heat generated by the long wave infrared radiation causes thermal management issues within the vehicle lamp assembly. Due to the heat generated by the long wave infrared radiation, lamp assemblies must be designed to thermally manage the heat. This typically includes added cost to the components of the lamp assembly for providing material that can withstand and manage the heat generated by the long wave radiation. Other issues involve design constraints which are the result of the heat generated. Heat reducing devices such as ventilators may be added to the lamp assembly but such devices require added cost. In addition, as the lamp cools and contracts, atmospheric air is drawn into the interior of lamp assembly as a vacuum thereby creating a passage for moisture and dust into the lamp assembly. Lamp assemblies are typically sealed components specifically to prevent any moisture or contaminants from entering the interior of the lamp assembly. Therefore, there is a need to reduce the heat generated by the illumination light fixture from reaching interior components within the lamp assembly without utilizing vents and the like. 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention includes at least one advantage of reducing a substantial portion of the long wave infrared radiation from reaching a substantial portion of the internal components of a lamp assembly which reduces the heat acting on these components. By reducing the heat exposure to the components of the lamp assembly, material cost may be reduced for those components not exposed to the heat. In addition, complex designs required to avoid extreme heat exposure to internal components may be since such components are not subjected to the extreme heat. 
     In one aspect of the present invention, a thermal filter is provided within a vehicle lamp assembly for reducing thermal radiation from reaching selected portions of the lamp assembly from an illumination light source disposed within the vehicle lamp. The thermal filter includes an inner envelope and an outer envelope in spaced relation to the inner envelope. The inner envelope and the outer envelope define a closed chamber therebetween. The closed chamber being disposed between the illumination light source and the selected portions of the lamp assembly. The inner envelope includes an interior portion. A thermal radiation absorbing agent disposed within the closed chamber. The thermal radiation absorbing agent receives radiation emitted from the illumination source. The thermal radiation absorbing agent is transparent to short wave visible radiation and is substantially opaque to long wave infrared radiation. A substantial portion of the long wave infrared radiation is absorbed by the absorbing agent is retained within the closed chamber. 
     In yet another aspect of the present invention, a lamp assembly is provided for a vehicle lamp. An illumination light source radiates short wave radiation and long wave infrared radiation. A lamp housing includes a reflective surface on an interior surface of the lamp housing. A socket retains an illumination light source at a predetermined position for illuminating the reflective surface. A thermal filter is disposed between the reflective surface and the illumination light source. The thermal filter comprises a glass chamber containing a thermal radiation absorbing agent disposed within the glass chamber. 
     In yet another aspect of the present invention, a lamp assembly is provided for a vehicle that includes a lamp housing with a transparent lens affixed to the housing. An illumination light source radiates infrared radiation. A socket provides an electrical connection to the illumination light source. A thermal filter assembly is disposed within the lamp housing enclosing the illumination light source. The filter assembly includes an open end coupled to the socket. The filter assembly includes an inner envelope having an interior portion. The interior portion substantially encloses the illumination light source. An outer envelope is positioned proximal to the inner envelope within the lamp housing. The outer envelope and the inner envelope form a closed chamber therebetween. A thermal radiation absorbing agent is disposed within the closed chamber. The thermal radiation absorbing agent is transparent to the short wave visible radiation and substantially opaque to long wave infrared radiation. A substantial portion of the long wave infrared radiation absorbed by the thermal radiation absorbing agent is retained in the closed chamber. 
     Various objects and advantages of this invention will become apparent to those skilled in the art from the following detailed description of the preferred embodiment, when read in light of the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a lamp assembly for a vehicle. 
         FIG. 2  is cross section view of a thermal filter assembly for a lamp assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the Drawings and particularly to  FIG. 1 , there is shown generally at  10  a light fixture for a motor vehicle. The light fixture  10  is a lamp assembly for a motor vehicle. The lamp assembly includes housing  12  and a transparent lens  14  sealingly affixed to the front of the housing  12 . The housing  12  includes a reflective surface  15  on at least one portion of an inner surface  16  of the housing  12 . 
     A removable socket  18  is coupled to a rear of the housing  12 . The removable socket  18  includes a first end  20  that is received at the rear of the housing  12 . An illumination light source  22 , such as a light bulb, includes a male terminal end  24  that is received and secured in the first end  20  of the removable socket  18 . A second end  26  of the removable socket  18  is coupled to a conduit  28  for providing power the illumination light source  22 . 
     An aperture  30  is formed in the rear of the housing  12  for receiving the illumination light source  22  therethrough. The illumination light source  22  extends through the aperture  30  to an interior of the lamp assembly as the removable socket  18  is secured to the rear of the housing  18 . The removable socket  18  secures the illumination light source  22  within the lamp assembly so that illumination light source  22  is stationary within the lamp assembly. The removable socket  18  also positions the illumination light source  22  within the lamp assembly at a predetermined position from the reflective surface  15  so that visible light generated by the illumination light source  22  is reflected by the reflective surface  15  for illuminating an area forward of a vehicle&#39;s path. 
     A thermal filter  32  is disposed around the illumination light source  22  for reducing long wave infrared radiation from reaching the internal components of the lamp assembly. The thermal filter  32  is disposed between the illumination light source  22  and the reflective surface  15  in addition to the transparent lens  14 . The thermal filter  32  is transparent to short wave radiation (i.e., visible light), but substantially opaque to long wave infrared radiation. 
       FIG. 2  illustrates the thermal filter  32  used to reduce long wave infrared radiation from reaching the lamp assembly components. The illumination light source  22  is disposed within the thermal filter  32 . The thermal filter  32  is disposed over the illumination light source  22  thereby encapsulating the illumination source within an interior portion  34 . The thermal filter  32  includes an inner envelope  36 , such as a shell structure, that is disposed around the illumination light source  22 . The inner envelope  36  is substantially tubular-shaped having an open end  37 . The open end  37  is received by the removable socket  18 . The inner envelope  36  is preferably made of glass and is transparent to short wave infrared radiation. Alternatively, the inner envelope may be produced from any transparent material having similar properties as glass. 
     The thermal filter  32  further includes an outer envelope  38  spaced a predetermined distance from the inner envelope  36  thereby forming a closed chamber  40  (e.g., glass chamber) therebetween. The outer envelope  38  is preferably made of glass or other similar material and is transparent to short wave radiation. The outer envelope  38  is substantially the same shape as the inner envelope  36 . Alternatively, the shape of the inner envelope  36  and outer envelope  38  may be other than tubular-shaped or each respective envelope may include different shapes within a respective lamp assembly. Furthermore, the spacing between the respective envelopes may be non-uniform. 
     A closed end  42  of the inner envelope  36  and the outer envelope  38  are formed integral to one another for forming the closed chamber  40 . The thermal filter  32  is coupled to the removable socket  18  and is positioned between the illumination light source  22  and selected portions of the housing  12 . The thermal filter substantially encapsulates the illumination light source  22  within the interior portion  34  of the thermal filter  32  so that substantially all infrared radiation penetrating the inner envelope  36  is received by the thermal filter  32 . 
     A thermal radiation absorbing agent  44  is disposed within the closed chamber  40  between the inner envelope  36  and the outer envelope  38 . Preferably, the thermal radiation absorbing agent  44  includes carbon dioxide. Alternatively, the thermal radiation absorbing agent may include any green house gas such as methane, nitrous oxide, or chlorofluorocarbons (CFC&#39;s). The thermal radiation absorbing agent  44  is transparent to short wave infrared radiation, and as a result, allows visible light to pass through the thermal filter  32  for illuminating the vehicle pathway. 
     The thermal radiation absorbing agent  44  is substantially opaque to the long wave infrared radiation emitted by the illumination light source  22 . The long wave infrared radiation is absorbed by the thermal radiation absorbing agent  44 . Heat is generated by a portion of the absorbed long wave infrared radiation and is retained within the closed chamber  40 . The portion of the long wave infrared radiation retained by the thermal radiation absorbing agent  44  within the closed chamber  40  is maintained therein until the illumination light source  22  is de-energized and the heat is dissipated thereafter. 
     The portion of the heat generated by long wave radiation and retained within the interior chamber  34  is exposed to the removable socket  18  and is thereafter dissipated through the removable socket  18 . 
     The thermal filter  32  isolates the substantial portion of the long wave infrared radiation retained within the interior chamber  34  and closed chamber  40  from the majority of components of the lamp assembly (shown in  FIG. 1 ). The components of the lamp assembly which are not subjected to the extreme heat generated by the long wave infrared radiation may utilize materials that do not require a high heat index since these components will be not exposed to elevated temperatures as a result of the thermal filter  32 . In addition, respective lamp assemblies that required complex designs to avoid extreme heat expose to the lamp assembly components may be avoided since such components are not subjected to the extreme heat generated by the long wave infrared radiation. As a result, the cost as well as the complexity of the lamp design is reduced. 
     In accordance with the provisions of the patent statutes, the principle and mode of operation of this invention have been explained and illustrated in its preferred embodiment. However, it must be understood that this invention may be practiced otherwise than as specifically explained and illustrated without departing from its spirit or scope.