GB513249A - Improvements in electric incandescent lamps - Google Patents

Abstract

513,249. Electric incandescent lamps. NAAMLOOZE VENNOOTSCHAP PHILIP'S' GLOEILAMPENFABRIEKEN. Dec. 16, 1937, No. 34907. Convention date, Dec. 18, 1936. [Class 39 (ii)] An electric incandescent lamp for surface lighting, e.g., for arranging in a cornice to illuminate a ceiling, is provided with an ellipsoidal bulb body which is partly formed as a mirror, the filament 11 being located in a meridian plane of the bulb. The axis D, D of the neck 13 of the bulb in one form makes an angle of more than 75‹, preferably of 90‹, with the major axis of the bulb body. The bulb body is a solid of revolution with a section according to a meridian plane including, as generating lines, two parabolic portions EF,. FG, Fig. 10, whose focal points coincide at the point. L. One half of the bulb is formed as a mirror, the edge of which forms substantially a meridian plane of the bulb. The axes of the parabolic portions EF, FG, are represented by the lines KL, ML, respectively, which make an angle of the order of 80 degrees with the axis CC, which is the axis of revolution of the !bulb body. The poles or top ,ends of the ellipsoid are spherically rounded, being formed by the rotation of circular portions HE, GJ at the ends of the parabolas EF, FG. The filament is so located that the centre of the circle of Which it forms a part lies substantially at the common focal point L of the parabolas, the locus of which is a circle about the axis of revolution. In order to obtain a maximum reflecting area the lamp bulb has a depression 12 in the neck..