GB840344A - Improvements in or relating to electric incandescent lamps for projection purposes - Google Patents

Abstract

840,344. Electric incandescent lamps. PHILIPS ELECTRICAL INDUSTRIES Ltd. July 1, 1957 [July 2, 1956], No. 20690/57. Class 39(2). In an incandescent electric lamp for projection purposes having a concentrated filament lying on the axis of a mirror part 6 of the lamp bulb formed as a body of revolution, e.g. an ellipsoid, the filament 11 is supported only at its ends by supporting wires 9, 10 arranged symmetrically to the axis X-X of the lamp in a plane at right angles to the axis of the revolution Y-Y of the mirror part, the distance between the filament and the end of the pinch 8 holding the supporting wires being at least 0À6 times the distance between the centre of the filament and the position where the pinch is sealed into the bulb. The filament may be displaced into the correct position by a strong impact on the bulb in the direction of the axis Y-Y. Means are provided on the bulb to indicate the plane at right angles to the axis of revolution in which the filament must lie. The line of transition between two glass surfaces of the bulb, e.g. the mirror part and the clear part may be used for this purpose. The bulb may be provided with a domed portion 5 to ensure that deposits formed by evaporation of the material of the filament do not interfere with the mirror surface or with the clear front surface of the bulb. The operating voltage is preferably not more than 24 volts, the energy consumed at the filament being not more than 200 watts.