GB421663A - Improvements in directional lighting fittings - Google Patents

Abstract

421,663. Street &c. lamps. GENERAL ELECTRIC CO., Ltd., Magnet House, Kingsway, London, WEIR, W., and WILSON, G. H., c/o General Electric Co., Wembley, Middlesex. Aug. 11, 1933, No. 22493. [Class 75 (iv)] A fitting for street - lighting and the like by means of a linear source 1 having its axis horizontal and perpendicular to the length of the street or the like comprises refractory prisms 12 at the side or sides of the source with edges not substantially longer than the source and parallel to said axis, so constructed and arranged relatively to the source and so associated with any reflecting means included in the fitting that the polar distribution curve of the source and fitting in a vertical plane containing the length of the street is " disc-like." The polar distribution curve, Fig. 1, is termed " disc-like " when the maximum radius vector occurs at a value of # not less than 60‹ ; the radius vector decreases rapidly as # increases beyond the maximum value ; the curvature at all points distant from the maximum is much less than in the neighbourhood of the maximum and there is no region of great curvature at small values of #. One form of fitting, Fig. 3, comprises a linear source 1, lower side members 5, 5<1> with prisms 12 on their outer surfaces, an upper reflector comprising two paraboloidal sheets 7, 71 meeting above the source in the form of a V. The prisms and reflectors direct most of the light in planes at about 75‹ to the vertical. Regions immediately below the source are lit by direct light only. To avoid patchy distribution in directions nearer the horizontal, the upper parts of the sides of the fitting are provided with panels 6 of lined glass. The fitting has opal end members. In a modified form, Fig. 7, the source is positioned within a trough 3 having prisms at the lower parts of the sides. In a further modification, the reflectors are omitted and the prisms 12 extend to the top of the trough. If the light is required to be distributed to one side only of the source, the light on the other side can be suppressed by an opaque screen. Specification 298,839, [Class 75 (iv)], is referred to.