Headlight permissible for use in explosive atmospheres

Claim 1

An explosion-proof closure for an electric light bulb having a base adapted to be connected to a source of electrical power for energizing the bulb, and a lens at the opposite end of the bulb, the closure being usable in potentially explosive atmospheres such as underground coal mines, the closure comprising: a housing having an opening therein at one end thereof, constituting the forward end of the housing, an end wall at the opposite end of the housing, constituting the rearward end of the housing, and side walls intermediate the ends of the housing, the interior surface of the side walls at the forward end of the housing tapering inwardly from the exterior to the interior of the housing a relatively long distance so as to define a relatively deep inwardly converging mouth surface at the opening in the housing; a bulb retaining member adapted to receive the lens of the bulb in generally surrounding relation, the retaining member being engageable generally at one end thereof, constituting its rearward end, with the bulb and having a lens cover at its opposite end, constituting its forward end, for protecting the lens, the retaining member further having a relatively wide peripheral surface tapering inwardly from the forward to rearward end thereof to define a relatively wide inwardly coverging retainer surface, said retainer surface being so sized and shaped relative to said mouth surface of the housing as to enable the retaining member to be fitted in the opening in the housing a significant depth, with the retainer surface and the mouth surface being in surface-to-surface sealing engagement along the entire peripheries thereof; means for detachably mounting the retaining member on the bulb to form a bulb sub-assembly, separate from the housing, adapted to be positioned in the housing and close the opening therein; and means for detachably securing the sub-assembly to the housing, whereby with the sub-assembly secured to the housing said explosion-proof closure presents a relatively long flame path at the opening to the housing for quenching any ignited gases tending to flow outwardly from the closure between the housing and the retaining member on an internal explosion in the closure, and with the sub-assembly removed from the housing, a defective light bulb readily can be replaced in the sub-assembly.