GB272394A - Improvements in or relating to flash-light devices suitable for photographic purposes - Google Patents

Abstract

272,394. Vierk÷tter, P. Dec. 14, 1926. Magnesium powder lamps.-Magnesium flash powder containing an oxygen yielding agent is burnt in a transparent or translucent body from which the air has been wholly or partially exhausted or containing rarified gases. Fig. 1 shows a container 11 for a flashlight charge 12 supported by a glass cylinder 10 on an asbestos disc 8 which is secured to the stem 3 of the cap 1 of a glass flask or bulb 2. The bulb 2 is wholly or partially exhausted through a tube 7 embedded in the cap 1. An ignition wire 15 passing through the flashlight powder 12 has its ends connected by lead-in wires 4 to the cap 1 and an insulated disc 6, the connection between one end of the ignition wire and one lead-in wire being made when the bulb is exhausted by the expansion of a small volume of air in a capillary tube 16 moving a mercury drop 17 downwards. The ignition wire may be of iron, tungsten, tantalum or molybdenum. The increase of current on the flash powder becoming ignited causes the ignition wire to fuse and break the electric circuit. The container 11 consists of a glass or asbestos ring with end portions 13, 14 of the same material secured thereto by an inorganic cement so as offer no appreciable resistance to the gas pressure produced on ignition of the powder. The cup 1 may be either of the threaded or bayonet cap type and ignition may be effected by heat, spark, or chemical means. A shield 31 carried by a ring 32 engaging the cap 1 screens the light from and directs the light to any desired direction. In a modification two or more charges separted by a mica screen are enclosed in single bulb and arranged to be ignited successively.