Patent Application
20080285286
This invention relates to PAR lamps and more particularly to PAR lamps having an improved quality of light.
PAR (parabolic aluminized reflector) lamps are well known in the industry. They are made in flood and spot versions and usually have an incandescent filament as a light source. Such lamps provide adequate amounts of light but have suffered from quality since the beam is fuzzy and shadowed. Some of these problems have been addressed by providing the reflector portion of the lamp with a plurality of facets (for example, U.S. Pat. No. 5,272,408) and others wherein in addition to the faceted reflector the lens of the lamp is also provided with spiral, facets (U.S. Pat. No. 6,086,227). Such lamps yield a smooth circular beam pattern with a perceived sharp beam edge; however, this is accompanied by a subsequent loss of light output, as measured by the maximum beam candle power (MBCP) in candela and an increase in beam angle the full angle measured from the MBCP to 50%.
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 operation of PAR lamps.
Yet another object of the invention is the provision of a PAR lamp having a smooth beam pattern with a sharp beam edge having an increased light output and reduced beam angle.
These objects are accomplished, in one aspect of the invention, by a PAR lamp comprising: a body having an internal reflector surface disposed about a longitudinal axis; a cavity at one end of the body; an arc discharge tube that provides a substantially spherical light source positioned in the cavity and disposed on the longitudinal axis; a cover receiving opening at a second end of the body; a cover closing the cover receiving opening; and a plurality of elongated spiral facets formed on the internal reflector surface, the plurality of facets being sufficient to increase the maximum beam candle power and decrease the beam angle when compared to faceted lamps having a lesser number of facets.
Lamps so constructed have a beam angle reduced by 25% while MBCP is increased 30-50% depending on discharge and arc tube sizes.
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 arc discharge tube 22 has a substantially spherical center 22a positioned substantially at the focal point and extending regions 22b containing the electrode lead-ins 22c, one end of which, 22d, project beyond the body for attachment to an electrical power source, as is known. In a preferred embodiment the arc discharge tube is constructed of a ceramic material such as, for example, polycrystalline alumina and is surrounded by glass shroud 22e.
The spherical center 22a allows for the emission of a substantially spherical light that contributes to the overall effect of the lamp.
A cover receiving opening 24 is formed at a second end 26 of said body and a cover 27, of a suitable configuration, closes the cover receiving opening 24.
A plurality of spiral facets 28 is formed on said internal reflector surface 14, sufficient in number to increase the maximum beam candle power and decrease the beam angle when compared to faceted lamps having a lesser number of facets. The number of facets is greater than 75 and preferably equal to 100.
Each facet of the plurality of facets sweeps an area of 45 degrees from the cavity 18 at the one end 20 to the cover receiving opening 24 at the second end 26.
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 modifications can be made herein without departing from the scope of the invention as defined by the appended claims.
