A Metal Halide Lamp that Provides Unique Lightiig System Brightness and Uniformity Opportunities

Typically, metal halide lamps exhibit a substantial loss in efricacy and reduction in life when operated horizontally. A novel lamp design is described that permits transverse mounting of the optimal arc tube design within an outer bulb. Combined with a prefocusing type mogul base, this lamp operates the arc tube vertically while the outer bulb is horizontal. Thus the high lamp efficacy, long life, and better lumen output maintenance throughout life previously only available in the vertical burning lamp is available in the horizontal burning type. From an application viewpoint, a lighting fixture designed to utilize a horizontal burning lamp intrudes less into the plenum area. Particularly in a new multifloor construction, a reduction in plenum height can reduce initial cost. In addition to possible reduced cost, this horizontal burning lamp controls the direction in which light is emitted from the lamp that can result in lighting distributions from typical luminaires that provide better lighting uniformity and a reduction in luminaire luminance when compared with typical lamps having the arc tube parallel to the lamp axis. This improved system performance has applications in both indoor and outdoor lighting systems in existing and new lighting luminaires.