GB192001A - Improved apparatus for preventing dazzle in vehicle lamps - Google Patents

Abstract

192,001. Pougher, A. W. April 25, 1922. Lenses.-A double or two distinct lenses, formed of a plurality of prisms, are disposed in front of the source of light in a vehicle lamp so as to project two concentric divergent beams, the inner beam being stronger than the outer in order to prevent glare. Each of the lenses has a central boss the face of which has a different inclination to the central axis from that of the faces of the remaining prisms. The lenses are preferably of plano-concave type, the concave surface of the rear lens A being next to the source of light C, and that of the front lens B being directed forwardly. The lenses are built of concentric ring-shaped prisms, the centre part constituting a conical boss, that of the rear lens A being of greater cross-sectional area than the annular prisms E - - H. The angular faces of these prisms are of successively greater length from the centre outwards. The face of the central boss D of the rear lens A is inclined at an angle of from 60‹ to 63‹ and the faces of the prisms E - - H, are inclined at about 58‹ to the central axis, while the face of the central boss L of the front lens B is at an angle of about 75-76‹; the faces of the outermost prism M, which may be frosted, are at approximately 40‹, and those of the intermediate prisms N, N are at or about 48‹ to the axis. The outer faces of the lenses may be plane surfaces. The inner concentrated light beam produced is a cone with an angle of approximately 20‹. In order to obtain a flat beam, the prisms may be made D- shape or other suitable shape. Portions of the rings may be frosted or coated with opaque material, and the centre part of one or both lenses may be omitted. Glass having a specific gravity of 2.9 and a refractive index of 1.574 may be employed.