GB709746A - Electric battery hand lamp for use in explosive atmospheres - Google Patents

Abstract

709,746. Electric battery lamps. ANGLOIRANIAN OIL CO., Ltd., and MACLEAN, T. T. July 30, 1952 [July 31, 1951], No. 18156/51. Class 39 (2) A safety hand lamp adapted for use in explosive atmospheres comprises a casing 10 with one end open for the insertion of a battery 29, and a laterally projecting compartment or cylindrical extension 11 at one side containing a reflector 16 and bulb (not shown), the casing being provided with an end cap 24 formed with a sleeve portion 25 which makes close sliding contact with the wall of the casing, and an internal switch 27, 31 operable by movement of the cap, access to the interior of the casing and compartment 11 being gained only by removing the cap and thereby breaking the electric circuit, and the dimensions of the passage between the cap and casing, and any similar passage, being such that a flame within the casing cannot pass to the external atmosphere. The cylindrical projection 11 on the casing receives with close sliding fit an internally screw-threaded sleeve 14 on a carrier ring 12 which has a thick lens 13 cemented within it adjacent to a pair of threaded rings 18, 19 holding the reflector 16 in position, while the other end of the sleeve 14 is engaged by a screw-threaded retaining-ring 21 with an end flange 22 which bears against a shoulder 23 on the casing wall. A pin 20 projecting from the part 11 engages within a socket in the ring 12 and prevents rotation of the latter. The flange 22 supports a terminal for one end of a contact strip 34 for the centre contact of the lamp bulb, connected by a lead 33 to a contact 31 of a switch mounted in a position to engage an arm 27 on the underside of the cap 24 when the latter is rotated. The extent of rotation is limited by providing an arcuate notch in the edge 48 of the cap to receive part of an upstanding handle bracket 39, the "on" and "off" positions being denoted by spaced detents for a ball-catch 49. Breaking of the lamp circuit before the cap is removed is ensured by providing the two handle brackets 39, 40 with inwardly projecting portions 45, 46 which overlie the edge of the cap, and hinging their lower ends to the casing, so that they can be held in the locking position by an interposed wooden handle 41 secured by a bolt 43 and a nut in a recess 44. In a modification, Fig. 3 (not shown), a switch mounted on the inner wall of the casing comprises a resilient strip with one end fixed and the free end normally spaced from a contact arm against which it is forced when the rotation of the cap causes an insulated stud thereon to depress the contact strip. Specification 665,115 is referred to.