| 摘要 |
513,912. Ceiling lamps; reflectors. RAMBUSH, N. E . (Rambusch, E., and Anderson, V. G.). March 24, 1938, No. 9048. [Classes 75 (ii) and 75 (iv)] A reflector for a ceiling lamp comprises a frusto-spherical part 16, and a frusto-ellipsoidal part 14, the latter extending above and below the common centre and focus 15 of these reflectors, where the light source is positioned, to such an extent that the angular dip of its lower rim beneath the focus 15 exceeds the angular elevation of its top rim above the focus by the angle which the spherical zone 16 in section subtends at the focus, i.e., the horizontal focal plane bisects the angle between the lines 35 and 34. Preferably this plane also trisects the angle between the lines 35 and 33. The outer edge of the reflector beam is thus intensified and uniform illumination obtained. The reflector may also have a parabolic upper part 17 confocal with the reflector 14 and a conical part 14a. It may be mounted in a tiltable casing 3 having annular baffle plates 10-13 projecting beneath the reflector to darken the side walls thereof and ventilation apertures 23b at the top, the lamp being mounted above a plate 1 fixed to a ceiling 1a in an aperture in which plate the lower focus 2a of the reflector 14 falls. The ellipsoidal reflector 14 may also have a depending extension in the form of a segment of the same ellipsoid to illuminate a wall at one side beneath the lamp. The lower tubular part and baffles of the casing may be replaced by an outwardly flaring part containing a frusto-conical reflector having a diffusing matt surface and the light obstructing part of the ceiling plate replaced by a dished diffusing globe apertured at the centre. |
