Electric incandescent lamp, especially for air raid precaution purposes

摘要

490,736. Electric incandescent lamps. EGYESULT IZZOLAMPA ES VILLAMOSSAGI R. T. Feb. 19, 1938, No. 5325. Convention date, Feb. 19, 1937. [Class 39 (ii)] A lamp adapted particularly for air raid precaution purposes is provided with two incandescent filaments 3, 4 of different luminosities which can be switched on alternatively, within a bulb 1 which is partly covered with an opaque or substantially opaque layer or layers 2, the filament 3 which is of higher luminosity for " reduced lighting " purposes being so arranged within the bulb that the angle of spread of the beam of light furnished thereby is greater than that of the beam furnished by the filament 4 of lower luminosity which is for " black-out " purposes. As shown, the filament 4 is located between the stem tube 13 and filament 3, the latter being nearer to the transparent end portion of the bulb. A light filter 5 consisting of a disc of blue glass is mounted on the rod carrying the filament supports, between the filaments 3, 4. Alternatively or additionally, the bulb 1 itself may be made of blue glass. The inside of the bulb is preferably frosted, and the coating 2, which may be black or dark blue, may be applied by spraying. Switching - mechanism of known type, e.g. a movable contact arm operated by chains 11, 12, may be located within the head 6 of the lamp. The bulb may be made of tubular shape, with or without a gas filling, and the colour of the coating may be modified to adapt the lamp for photographic or laboratory purposes.