Patent GB-111707-A (GB)
Title: Improvements in or relating to Light Projectors.
Inventor: AMES ADELBERT
IPC: F21V7/04
Filed: 1916-12-06
Abstract: 111,707. Ames, A. Dec. 6, 1916. Vehicular lanterns; searchlights. - A vehicular headlight or a searchlight is provided with a reflector having surfaces of different contours respectively above and below a horizontal plane through the light source, one reflecting- surface, such as a paraboloidal surface, being adapted to project a relatively concentrated beam of light for illuminating the distant parts of the roadway, and the other reflecting-surface, which may be an ellipsoidal surface, being adapted to project a relatively divergent beam of light for illuminating the nearer parts and sides of the roadway. The whole or part of the light source is vertically displaced from the axis of the apparatus, and the parts of the apparatus are so arranged and constructed so as to prevent the upward projection of light radiating approximately horizontally from the displaced parts of the light source. In one form, the reflector comprises an upper ellipsoidal surface F, Fig. 3, and a lower paraboloidal surface F" having a common focus f, f<1>, and the V-shaped light source L is arranged with its apex in the common focus. Upward glare resulting from parts of the light source being disposed below the horizontal plane con. taining the axis of the reflector may be prevented by forming a non-reflecting band N, for example by coating with black paint, adjacent the horizontal plane containing the axis, the band being preferably wider at the rear of the focus, or by forming a prism P, Fig. 6, or a band of frosted glass on the transparent lamp front, the band being preferably wider in the middle, or by making the lower part M, Fig. 6, of the upper reflecting-element tangential to the remainder of the element and by curving inwardly the upper part of the lower reflecting-element. Upward glare may also be prevented by positioning the focus of the upper half of the reflecting-element downwardly and rearwardly of the focus of the lower half of the reflecting-element, or by arranging the whole of the light source L, Fig. 3, above a horizontal plane through the axis of the reflector and behind a plane passing through the focus and the forward central point of the lower reflecting-surface. Another method of preventing upward glare consists in making the upper reflecting-element smaller than the lower reflecting-element, extending the tangentially arranged lower portion of the upper reflecting-element below the horizontal axial plane, and providing a lip piece on the upper reflecting-element at the rear of the light source. In a modification, the lower reflecting-element F<1>, Fig. 11, is smaller than the upper reflecting- element F<11>, and the inwardly curved upper portion 44 of the lower reflecting-element F<1> extends above the horizontal axial plane, the lip-piece 45 being provided on the lower reflecting-element. The slidably mounted lamp holder 107, Fig. 14, is adjustably held in an obliquely arranged socket 106 by a set-screw 113, and the socket 106 is held on an horizontal part 101 of the lamp by means of bolts and slotted ears on the socket, so that a V-shaped or conical filament 102 can be positioned with its apex in the focus of the lower reflector P, with its lower side along the axis, and with its upper side in a line 103 through the focus f and the lowermost point 40 of the reflector P, the focus e of the upper reflector E being axially behind the focus f. When the paraboloidal reflecting-element is arranged below the horizontal axial plane, the centre of the lamp bulb is arranged at or behind the focus of the reflector and behind the light source, so that light reflected from the surface of the bulb shall not be reflected upwardly by the reflector. When the paraboloidal reflecting-element is arranged above the horizontal axial plane, the light source is disposed behind the centre of the lamp bulb and' between it and the focus of the reflector. Specification 15885/15 is referred to.