GB570791A - Improvements in or relating to lamp structures - Google Patents

Abstract

570,791. Lamps for illuminating instrument dials &c. STEVENS, A. H. (Electronic Laboratories, Inc.). Feb. 22, 1944, No. 3284. [Class 75 (iv)] [Also in Group XXXVII] A lamp suitable for use in aircraft for illuminating instrument dials, maps, &c., comprises a fluorescent type lamp 6, arranged in a two part cylindrical casing 1, 2 fitted at the end with a primary and secondary shutter, the primary shutter being movable from a fully open to a fully closed position in which only light rays of a predetermined wavelength can issue and the secondary shutters being then movable to cut off or reduce to a minimum the rays of predetermined wavelength. The predetermined wavelength may be that of ultra-violet, or nearultra-violet rays to illuminate indicators coated with fluorescent material or near-infra-red rays not visible from a great distance. The shutters may be mounted at the end of the casing in a ring 26 and consist of aperture discs 33, 44 of a material pervious only to light rays of the predetermined wavelength and iris diaphragm segments 53 impervious to all rays pivoted to a ring 50 and having pins 55 engaging radial slots 52 in flange 51 on the casing. Rotation of the ring 26 operates through a ring 31 first to turn the disc 33 relatively to the disc 44 till the openings 34, 35 in the disc 33 cease to register with the openings 45, 46 in the disc 44 and then to turn a ring 41 engaging the ring 50 to close the iris diaphragm. The lamp 6 is mounted in the casing 1, 2 by a cup 4 supporting on guide posts 10 a spring-pressed plate 7 carrying a lamp switch consisting of a base 12 and cap 18 of insulating material arranged on a central post 19. To start the lamp the cap 18 is turned to the "on" position and pressed inwards for a short time to cause a conical contact member 22 on the post 19 to complete at contacts 23, 24 the circuit for heating the lamp cathode 6b.