High intensity discharge lamp for use in explosive atmospheres such as

Abstract

Lamp having a rectangular bulb housing and a cage-like outer guard assembly therefor. The bulb housing is generally in the shape of a modified cube elongated in one direction. The housing has four substantially same size rectangular sidewalls extending between substantially square head and tail endwalls. One of the sidewalls is imperforate and serves as a mounting base. The other three sidewalls have windows of heavy, heat-resistant, transparent glass-like or ceramic material. The head endwall has a pair of glands including flanged, threaded bushings to seal electrical power conductors extending through it. The flanges of the bushing have wrench-engageable flats. The endwalls have a pair of axially aligned, screw-threaded openings of identical thread diameter and pitch. Screw-threaded head and tail cover members are threadedly engageable within these openings. A bulb socket member and a grounding lug are mounted on the inside surface of the head cover member, all being removable as a unit by unscrewing the head cover member. There is a central boss with wrench-engageable flats on the outside surface of the head cover member. A locking plate simultaneously engages flats on the gland bushings, and on the boss, to prevent loosening. A screw-threaded inspection plug in one of the sidewalls provides access to the grounding lug. The entire bulb housing is protected within a cage-like outer guard assembly. Different shaped reflector means between the bulb and housing direct the light through one or more selected side windows, in addition to an end window in the tail cover member.