GB614305A - Improvements in and relating to photo-flash flares - Google Patents

Abstract

614,305. Photo-flash flares; flash-light projectiles; fuzes. FINCH, G. I. March 25, 1944, No. 5585. [Classes 9 (i) and 9 (ii)] In a photo-flash flare of the kind in which a light-metal powder is ignited and dispersed by an explosive, the explosive is a high explosive and the powder comprises a proportion of between 15 and 100 per cent of particles passing a 120 British Standard screen. The weight of explosive is not less than one-tenth the weight of metal powder. Fig. 2 shows a flare for dropping from aircraft and comprising a lightmetal casing 2 with tail fins 1 filled with lightmetal powder 10 surrounding a core 8 of high explosive in a light casing 9 of paper or metal. The arrangement shown gives a horizontal sheet of light-emitting particles. The explosive is preferably of the aluminized type, e.g. Al: TNT 30: 70. The light-metal powder may be aluminium, magnesium, or mixtures or alloys of these, and is preferably in flake form, having a high specific surface. As shown, a charge 11 of carbonaceous or organic powder such as pitch or flour may be disposed above the metal powder and surrounding an extension of the explosive core. Ignition is initiated by a barometric fuze 3, detonator 5 and C.E. gaine 6. The explosion ignites all the metal powder substantially simultaneously by the rise in temperature due to the adiabatic compression of the air trapped between the particles which thus .all burn rapidly, whereas the powder 11 burns comparatively slowly and with a low intensity flame, thus screening the main light from the aircraft camera. In a modification, Fig. 3, a small pilot charge 18 with explosive core 23 may be located above the main charge 10 of metal powder, a metal plate 19 and steel washer 20 being interposed to protect the main charge from the explosion of the core 23. The pilot charge is ignited a short time before the main charge by a length of fuze 15 from the barometric fuze 3, the fuze 15 being shorter than that leading to the detonator 6 of the main charge. The pilot flash is utilised to open the camera shutter of the aircraft in known manner. A simple flare with a " safety " fuze instead of a barometric fuze for ground photography, similar to the aerial flares, is .described and an arrangement of string-like fuzes by means of which a number of such flares may be successively ignited at short intervals after an underwater explosion to photograph the results of this explosion. Specific examples of flares are described.