Explosion proof lighting fixture

Claim 1

In an electric light fixture for use in a potentially combustible atmosphere wherein the fixture comprises a base, a glass globe below the base, an attachment device connected to the base and supporting the globe with respect thereto whereby the base and globe define a light receiving enclosure, said device including means for venting said enclosure while preventing the propagation of flame from the enclosure to the exterior of the fixture in the event of combustion within the enclosure, the improvement wherein said device comprises: a first annular generally horizontal flange integral with the bottom of the base, said flange having a bottom face with a plurality of annular ridges extending downwardly therefrom and defining grooves between the ridges; a second annular generally horizontal flange concentric with and below said first flange, said second flange having an upper face with a plurality of annular ridges extending upwardly therefrom and defining grooves between the ridges thereof; at least one annular horizontal disc concentric with and between said flanges, said disc having a top face with annular ridges extending upwardly therefrom and defining grooves therebetween, and a bottom face with annular ridges extending downwardly therefrom and defining grooves therebetween, said ridges and grooves on the upper and lower faces of the disc interdigitating with the ridges and grooves of said first and second flanges to define circuitous passageways radiating in all directions about said fixture and increasing in volume from the interior end to the exterior end of the passageways; said flanges and disc having vertically aligned bosses at spaced intervals adjacent the interior ends of the passageways, said bosses being in vertical contact with each other to define the thickness of said passageways, and fastening means at each of said bosses, connecting the flanges and holding said bosses in contact.