Patent GB-799929-A (GB)
Title: Improvements relating to flameproof electrical lighting fittings
Inventor: HOLLOWAY JOHN ASTLEY
IPC: F21V25/12
Filed: 1954-12-02
Abstract: 799,929. Lighting fittings. SIMPLEX ELECTRIC CO., Ltd. Dec. 2, 1955 [Dec. 2, 1954], No. 34901/54. Classes 75(3) and 75(4) [Also in Group XXXVI] In a flameproof electrical lighting fitting for electric discharge lamps having terminals or connectors at separated localities connected by electrical conductor means, extending between said localities, a sheath or covering surrounds the conductor means to render the latter flameproof independently of the intervening structure which mechanically connects and maintains the said terminals &c. in the required separated positions. As shown, the transparent tubular housing 10 for the lamp 11 is cemented at its ends to sleeve members 37, 38, the sleeve 38 being secured as by bolts 9 to a flameproof connector housing 13 provided with a flameproof fitted cap 28 and with an internal flameproof barrier 16 mounting, in flameproof fashion in an aperture therein, a lamp holder 17 and terminals 21 on insulating blocks 22 let into the barrier wall 16. The terminals 21 connect up to the feed cable 23, 24, Fig. 3, and to the lamp holder terminals 18 as by conductors 25. 26. The incoming feed cable enters, in flameproof manner through one of a pair of laterally projecting bosses 27, Fig. 1, integral with the housing 13 or alternatively through a flameproof entry in the end cap 28. The sleeve 37 is secured as by bolts 9 to a connector housing 12 with flameproof fitted end cap 33 and containing a lamp holder 32 supported without being fitted in a barrier wall such as the barrier wall 16, as, e.g. in a piston-like construction, Fig. 6 (not shown), to avoid vortex ring formation as would happen in the construction shown, should excess pressure be generated in the chamber 10 as the result of an internal explosion. The lamp 11 is supported at each end within the chamber 10 by three resilient convex metal tongues 41 equally spaced around the tube and secured by screws 42 to the sleeve fittings 37, 38. The housings 12, 13 are held together by a channel-section member 44 of sheet steel secured preferably adjustably as by the provision of axially disposed apertures or of slots through which bolts 47, 48 pass to threaded holes in bosses 45, 46 on the housings. Electrical connection to the lamp holder 32 is effected by an external conductor 49 extending between the housing 12, 13 and rendered flameproof by passing through a bendable adjustable sheath 50, e.g. of copper, brass, aluminium or lead, which enters the housings by flameproof glands 52, Fig. 3, and contains a non-inflamable insulating material preferably of a mineral character in which the conductors are embedded. The gland 52 is formed as part of one of the bosses 27, the bore of the gland entering the housing tangentially. The part of the sheath 50 between the two glands 52 may be accommodated within the channelsection member 44. Alternatively the conductors may have a cover of non-inflamable non-metallic insulating material such as polyvinyl chloride or polythene. The whole assembly may be supported from a ceiling or wall, &c. by a U-shaped stirrup 54 the limbs of which have slots 55 to receive the bosses 27 and at the other end of the assembly a releasable support co-operates with that end of the member 44.