Single-filament headlamp unit capable of throwing both upper and lower beams

Claim 1

An electric lamp unit for particular use as a vehicular headlamp capable of selectively throwing upper and lower beams, comprising: (a) a reflector having an optical axis extending horizontally, a first focus, and a second focus disposed farther away from the reflector than is the first focus; (b) a light source disposed at the first focus of the reflector, the reflector being capable of reflecting rays of light from the source so as to converge at the second focus thereof; (c) a shade disposed adjacent the second focus of the reflector; (d) a converging lens disposed opposite the reflector and having a focus in the vicinity of the shade; (e) means for selectively and pivotally moving both the converging lens and the shade in fixed relation relative to the reflector between a "lower beam" position in which an optical axis of the converging lens is aligned with the optical axis of the reflector and in which the shade is placed adjacent the second focus thereby to permit the rays that have been reflected from approximately an upper half of the reflector to impinge on the converging lens, and an "upper beam" position which is disposed upwardly from the "lower beam" position and in which the shade is placed downward away from the adjacency of the second focus thereby to permit substantially all the rays that have been reflected from the reflector to impinge on the converging lens.