GB669180A - Improvements in or relating to lighting fixtures - Google Patents

Abstract

669,180. Lighting fittings. SOC. ANON. POUR LES APPLICATIONS DE L'ELECTRICITE ET DES GAZ RARES ETABLISSEMENTS CLAUDE-PAZ ET SILVA. Jan. 17, 1950 [Feb. 11, 1949], No. 1227/50. Classes 75(ii) and 75(iv) In a lighting fitting having at least one reflector, for use in conjunction with at least one light source, the shape of the reflecting surface being generated geometrically by the displacement of a co-planar continuous line which includes at least one parabolic arc and at least one elliptical arc having a common focus which coincides substantially with a point on said light source or on one of said light sources, the concave sides of these curves facing the light source or sources, the distance between the foci of the elliptical arc is longer than the width of said light source or sources measured in a direction parallel to the major axis of the ellipse and said common focus is farther from the vertex of the parabola than the other focus of said ellipse. The light source may be a tubular fluorescent lamp 1, Fig. 1, the length of which is parallel to the generatrices of the curved reflecting surface having a section shown by the continuous co-planar line 2, 3, 4, 5. The latter comprises a first elliptical arc 2 to 3, a second elliptical arc 3 to 4, and a parabolic arc 4 to 5, the parabola having its apex at the point 4 and a horizontal axis I-I coinciding with the major axes of the ellipses. The end 2 of the first elliptical arc is located on the axis I-I; and the focus 6 of the parabola substantially coincides with the centre of the section of the light source 1 as well as with one of the foci of each of the ellipses, the other foci 7, 8 of the latter being located between the focus 6 and the apex 4 of the parabola. The distance between the foci 6, 7 is slightly greater than the width of the envelope of the source 1 measured along the axis I-I in order to minimize the amount of rays reflected by the portion 2 to 3 impinging on this envelope. Light rays such as 9 are reflected directly by the parabolic portion 4, 5 as horizontal rays 10, whilst rays 11, 15 emitted towards and reflected by the elliptical portions 2, 3 and 3, 4, respectively, are subsequently reflected by the parabolic portion 4, 5 as rays 13, 14. The light source 1 may be a tubular lamp of toroidal shape. Two reflectors of the cross-section shown in Fig. 1 may be associated with a single straight tubular lamp for providing light beams in opposite horizontal directions.