High intensity discharge lamp for use in explosive atmospheres such as mines

Claim 1

A high intensity discharge lamp permissible for use in explosive atmospheres such as mines comprising: a rectangular bulb housing and a cage-like outer guard assembly therefor; said bulb housing having four sidewalls extending between head and tail endwalls; one of said sidewalls being substantially imperforate to serve as a mounting base, and window means of transparent material in at least some of the other three of said sidewalls; said head endwall having electrical power conductor means extending therethrough, and gland means including flanged threaded bushing means on the outside of said head endwall, said bushing means having flange means with a plurality of wrench-engageable flats; screw-threaded head and tail cover members threadedly engageable with opposite, aligned, screw-threaded openings in the head and tail endwalls respectively; said head cover member having mounted on the inside surface thereof a bulb socket member in substantially coaxial relation therewith, and a grounding lug in eccentric relation therewith, said head cover member having a central boss on the outside thereof with a plurality of wrench-engageable flats; said head cover member having a first locking plate removably fastened to the outside surface thereof and simultaneously engageable with flats on said boss and on said bushing means to prevent rotation and loosening thereof; a screw-threaded inspection plug threadedly engageable with a threaded access opening in one of said sidewalls, said access opening positioned to provide access to said bulb socket member and grounding lug within the housing, and a second locking plate removably fastened to the outside of the housing abutting a flat on said inspection plug to prevent rotation and loosening thereof; said outer guard assembly including an elongated support plate, a pair of hoops fastened to the ends of said support plate, and a plurality of bars fastened to said hoops extending parallel to said support plate; and means for fastening said bulb housing within said outer guard assembly with said one sidewall of said bulb housing supported on said support plate of said outer guard assembly.