GB641386A - Street lighting luminaires and refractors therefor - Google Patents

Abstract

641,386. Street lighting luminaires. HOLOPHANE, Ltd. (Holophane Co., Inc.) Feb. 16, 1948, No. 4482. [Classes 75(ii) and 75(iv)] A refracting bowl of semi-circular crosssection with respect to a horizontal axis, has transverse semi-circular refracting crossing the vertical longitudinal plane, and laterally refracting and transmitting them in beams oblique to the vertical longitudinal plane. As shown a street lighting luminaire for side of street mounting comprises a light source 12, a specular reflector 10 of parabolic contour in two planes at right angles to one another intersecting through the light source and arranged to reflect light in a rectangular cross-section beam of parallel light rays parallel with the street direction, and a refractor 11 intercepting the reflected rays, having refracting prisms 47 parallel with the street direction and all of the same sign, arranged to deviate the beam laterally towards the street area without vertical deviation. The reflector 10 is symmetrical about a vertical longitudinal plane and has a profile in a vertical plane lengthwise of the street as illustrated in Fig. 3, the parabolic zone in this plane extending from the mouth 20 of the reflector to the lines 37. Fig. 6 shows the reflector profile in a vertical plane across the street (the light source 12<SP>1</SP> being shown here as a mercury vapour discharge lamp) to be quasielliptical, the parabolic zone of which extends between the lines 23, 24. The refractor 11, shown in top plan in Fig. 4, is in the form of a quasi-ellipsoid of prisms all of the same sign (refracting in the same direction) for intercepting light rays normal to the horizontal axis and revolution about a horizontal axis through the light source, its mouth being flanged as at 13 and conforming with the shape of the mouth 20 of the reflector 10. A shield 43 is carried internally of the refractor to intercept the direct light which would otherwise fall on the " house " end of the refractor. The inner surface of the refractor is formed with the laterally refracting prisms 47 except at the steep end walls 44 which are provided with. deep diffusing flutes 441. To produce an even light distribution the prisms 47 are arranged in tiers 50, 51, 52, Fig. 3, the top tiers 50 refracting mainly high angled reflected light, the intermediate tiers 51 refracting less reflected light and more direct light and the bottom tier 52 dealing mainly with direct light rays. Also, in order that the luminaire will provide an evenly illuminated appearance from all directions, the prism surfaces have varying contours over the length of the refractor and in the various tiers so that each prism provides a slight diffusion of the light it receives. A pattern 70 of vertically refracting convex flutes 71, Fig. 14, is formed on the outer surface of the refractor transverse to the street direction, the flutes being of uniform width and separated by concave flutes 72 which taper towards each end.