GB777482A - Improvements relating to electric street lighting fittings - Google Patents

Abstract

777,482. Lantern reflectors. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 16, 1955 [Sept. 21, 1954], No. 27296/54. Class '75(2) A reflector system for a street lighting lantern comprises a first reflector 6 intercepting light from a source 3 over a vertical arc lying above a desired direction for a main beam 5 at one side of the lantern and directing the intercepted light on to a second reflector 7 in turn directing the light to augment the main beam 5 at the same side of the lantern and a third reflector 4 arranged back to back with the second reflector 7 for redirecting light, which would otherwise fall on the back of the latter, to augment the light emitted from the opposite side of the lantern. The system may be used with an elongated light source in which case a set of elongated reflectors is disposed symmetrically on opposite sides of the source to produce two main beams in opposed directions or it may be used with a point light source in which case each reflector may extend completely round the vertical axis through the source to produce a main beam of conical form. The first reflector 6 is elliptical with one focus at the centre F<SP>1</SP>of the light source and the other focus F<SP>2</SP> between the first and second reflectors 6, 7. The second reflector 7 is parabolic with its focus at the second focus F<SP>2</SP> of the first reflector and with its axis parallel to the main beam 5 at the same side of the lantern. The third reflector 4 is disposed inwardly of the first reflector 6 above the main beam 5 and is parabolic with its focus at the centre F<SP>1</SP> of the light source and with its axis parallel to the direction of the main beam at the opposite side of the lantern. In this embodiment the third reflector 4 also serves to intercept light which would otherwise pass below the edges of the hood 1 in a direction above the main beam. In a inodified construction the-second and third reflectors are disposed below the main beam and a fourth reflector forms a downward continuation of the first reflector and is parabolic with focus at the light source and axis parrallel to the main beam at the opposite side of the lantern. The third reflector in this case is planar with its plane preferably vertical and receives light from the source and from the fourth reflector on the opposite side. Specification 770,518 is referred to in the Provisional Specification.