| 摘要 |
826,919. Refractors for electric lamps. GENERAL ELECTRIC CO. Ltd. Sept. 13, 1957 [Sept. 14, 1956], No. 28215/56. Class 75(2) In a bowl or trough refractor, especially for street lighting fittings, of the kind. which has a set of light directing elements extending in parallel planes at right. angles to the vertical axis of the bowl or trough, and designed to concentrate light mainly about a preferred direction at 60 to 85 degrees to the vertical axis of the: refractor, the general contour of the bowl. or trough in the regions included between the zone angles P‹ and 2/3 P‹ where P‹ is the zone angle of the preferred direction of light emission, is such that the zone angle Z‹ for any point in the region is related to the angle N‹ between the vertical axis and the normal to the surface at the same point by the formulae Z‹-N‹=90‹-P‹, the light directing elements in the region consisting of flutes having angles of spread S‹ such that S‹2=P‹-Z‹ where Z‹ is the F F zone angle at the position of the flute. The flutes may be separated by narrow flats. The zone angle at a given point is defined as the angle between the vertical axis and the line joining the point to the light source. Outside the specified limits, the surface is shaped so as to form a smooth continuation of the surface within the limits. In this part of the refractor, crossed prismatic elements or doublesided flutes may be used. Specification 819,993 is referred to. |
