Patent Application
20060043890
This invention relates to lamps and more particularly to reflector lamps. Still more particularly it relates to tungsten halogen PAR lamps having an enhanced light output in the red and blue regions of the spectrum.
Various doping agents have been employed for many years to correct or control the color output of electric lamps. One agent that has been used with some success is neodymium oxide. For example, U.S. Pat. No. 4,315,186 ('186) describes a sealed beam incandescent reflector lamp that a neodymium-doped glass lens flame sealed to a glass reflector. The lens of the '186 lamp is coated with an infrared refective film to reduce the lens temperature and prevent excessive outgassing. U.S. Pat. No. 5,548,491 describes an automotive headlamp, which uses a neodymium containing front lens to enhance contrast and reduce glare. U.S. Pat. No. 6,358,873 describes an aluminosilicate glass tubing that contains neodymium oxide and that can be used to manufacture tungsten halogen capsules that operate with increased correlated color temperature.
The appearance of neodymium oxide doped glass and the effect on the transmitted light spectrum is highly dependent on the spectral power distribution of the illumination source. Typical incandescent lamps have a coil or filament temperature of about 2700K with very little emission in the blue region of the spectrum. It has been found that the correlated color temperature of such light will not be increased by the use of a glass envelope or lens containing neodymium oxide. However, while it is known that light sources with ample blue content can experience a significant color temperature increase when neodymium oxide is present in the glass envelope or lens, such results have previously been achieved with high cost or difficult manufacturing techniques.
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 the light output of tungsten halogen lamps.
It is yet another object of the invention to provide this enhanced light output at a reasonable cost.
These object are accomplished, in one aspect of the invention, by the provision of an electric lamp comprising an envelope defining a cavity, the cavity having a base and an opening defined by an edge opposite the base. A tungsten halogen capsule is positioned in the base, the capsule having a filament designed for operation at greater than 2700K; and a light transmissive lens closing the opening and bonded thereto by an adhesive, the lens comprising a suitable glass containing, by weight, 0.3 to 5% neodymium oxide.
By using a tungsten halogen capsule with a high coil temperature in combination with a lens and envelope sealed together by an adhesive, thus avoiding the inherent cost disadvantage of flame sealing the lens and body together, an effective, cost efficient lamp is produced. Also avoided is the high cost of the neodymium containing aluminosilicate tungsten halogen capsule.
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 taken in conjunction with the above-described drawings.
Referring now to the drawings with greater particularity, there is shown in
The capsule lead-ins 28, 30 project through the base 20 and are connected to the screw shell 32 by connectors 34, 36, as is known.
To provide the appropriate color correction, the lens 16 is preferably a borosilicate glass and contains between 0.3 and 5 weight percent neodymium.
In a preferred embodiment of the invention, the capsule 12 contains, in addition to the conventional halogen, about 85 weight percent xenon at a cold fill pressure of bar. The lens 16 contains from 1 to 1.5 weight percent neodymium and the filament 26 is designed for operation at 3000K. The results of lamps so constructed and operated are shown in
Thus, there is provided a general service lamp with improved color output that operates at high efficacy and for a relatively lower cost than was heretofore achievable.
While there have been shown and described what are present considered to be the preferred embodiments of the invention, it will be apparent to those skilled in the art that various changes and modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
