Patent Publication Number: US-6670768-B1

Title: Blue incandescent general purpose lamp

Description:
TECHNICAL FIELD 
     This invention relates to incandescent lamps and more particularly to general purpose lamps having a particular emission spectra. Still more particularly, it relates to lamps useful for household lighting and has still greater applicability where enhanced skin tones are desired. 
     BACKGROUND ART 
     Common household incandescent lamps emit light that is high in the yellow/green portion of the spectrum. While suitable for most illumination it has been objected to as being deficient when it come to illuminating normal skin tones. A recent development in the art has provided a general purpose household lamp with strong emission in the blue/white portion of the spectrum which has been deemed to provide a more aesthetically pleasing appearance, especially when the important skin tone appearance is considered. However, this particular blue/white spectrum has been achieved by developing a new glass for the lamp envelope, which glass uses an additive of neodymium in the form of Nd 2 O 3 , a material which adds approximately 15-20 cents to the cost of the lamp envelope. It would be an advance in the art to provide a lamp that has a similar color output at a more conventional cost. 
     DISCLOSURE OF INVENTION 
     It is, therefore, an object of the invention to obviate the disadvantages of the prior art. 
     It is another object of the invention to enhance general purpose household lamps. 
     It is yet another object of the invention to provide a general purpose household lamp lamp that is environmentally safe, allowing the spent lamp to be landfilled. 
     These objects are accomplished, in one aspect of the invention, by the provision of an electric lamp which emits a blue color when energized and which comprises a light transmissive envelope formed from a typical soda/lime glass and enclosing an electric light source within. The envelope has an internal surface on which is a coating comprising precipitated silica, aluminum silicate pigment, manganese ammonium pyro phosphate and cobalt aluminate spinel. 
     The soft blue color provides a higher color temperature and enhances the lighting appearance, particularly of skin tones. The internal powder coating uses an environmentally safe formula that enables the spent lamp to be landfilled. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The single figure is a diagrammatic view, partially in section, illustrating an embodiment of the invention. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in conjunction with the above-described drawing. 
     Referring now to the drawing with greater particularity, there is shown in the figure an A-line incandescent type lamp  10  having on an interior surface  11  of its light transmissive glass envelope  12  a coating  14  in accordance with an aspect of the invention. A filament  16  of, for example, tungsten, is electrically connected to and supported by lead-ins  18  which extend through the seal of the lamp and are attached, as is known, to a screw base  20 . Other forms of bases can be employed, such as the type known in the art as bayonet bases. Additionally, other support for the filament  16  can be provided by support wires  17 . 
     The interior surface  11  of envelope  12  is coated with a powder coating  14 . Coating  14  is applied electrostatically by means well know to those skilled in the art, see, for example U.S. Pat. Nos. 2,995,463; 3,125,457; 3,320,460 and 4,633,127. 
     The coating  14  of the present invention comprises precipitated silica, aluminum silicate pigment, manganese ammonium pyro phosphate and cobalt aluminate spinel. The lamp, when energized, has color coordinates of X=0.4373 to 0.4382 and Y=0.3973 to 0.3983 on a standard ICI diagram and a color temperature of between 2931 and 2941. The ICI diagram (International Commission on Illumination) is also known, especially in England and the European continent as the CIE (Commission Internationale d&#39;Eclairage) system or diagram. The CRI of tested 60 watt lamps averages 91 and the light output averaged 575 lumens. 
     The applied powder was formulated by combining, in wt. %, 48 to 50% PPG Hi-Sil T-700 Precipitated Silica; 38 to 40% Burgess 50 Aluminum Silicate Pigment, 6.5 to 7.5% Shepard Violet #11 Manganese Ammonium Pyro Phosphate, and from 3.0 to 4.0 Shepard Blue #3 Cobalt Aluminate Spinel. 
     This coating costs less than 1 cent per lamp envelope and would be applicable to many bulb sizes, including A 15 , A 19  A 21  three ways, G 25  and B 10  shapes. 
     While there have been shown and described what are at present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modification can be made herein without departing from the scope of the invention as defined by the appended claims.