From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Explanation of the operation and light path of a Bosch Headlight with a double-filament bulb, detailing the main light and anti-dazzle functions.
| Identifier | ExFiles\Box 61a\1\ scan0330 | |
| Date | 1st December 1926 guessed | |
| Page 4: half of the reflector and in this way the whole of the light from the headlamp is deflected downwards. A switch (foot or hand, Figs. 5 and 6) is provided for switching from main light to anti-dazzle light and vice versa. Fig. 3. Diagram Labels: reflector, light from main filament, anti-dazzle filament, screen, side view, main filament, top view, light from anti-dazzle filament is deflected diagonally downwards. Diagram Reference: 7216 c Light from anti-dazzle filament is screened from below and can therefore only strike the upper half of the reflector Path of the rays in a Bosch Headlight with Double-filament Bulb Top: Main Light. Bottom: Anti-dazzle Light. The operation of the Bosch Headlight with double-filament bulb is as follows: — When the main light filament which is in the focus of the reflector is switched on, the rays of the beam run parallel and — 4 — Page 5: are consequently projected a considerable distance (Fig. 4 top). Even at very high speeds the brilliant main light makes it possible to see an obstacle at a distance of about ¼-mile. When the anti-dazzle filament is switched on it produces diffused light directed downwards (Fig. 4 bottom). The screen of the anti-dazzle filament from below is an important feature in the Bosch Headlamp with double-filament bulb, as it makes it possible to use a filament of high power. Without the screen the light from a filament exceeding 10 watts would dazzle because the beam projected upwards would be too powerful. The use of a filament of 10 watts or less would, while avoiding dazzle, give insufficient light, and the transition from main light to anti-dazzle would be too pronounced, causing momentary darkness. The screen is closed at the front and the anti-dazzle filament can therefore not project any direct light in a forward direction. Fig. 4. Diagram Reference: 7333 Beam of the rays in a Bosch Headlight with Double-filament Bulb Top: Main Light. Bottom: Anti-dazzle Light. In the Bosch headlight “IL” with double filament bulb a clear non-frosted glass bulb and a diffusion lense with special ribbing are used. (Fig. 1). This diffusion lense spreads both the beam of the main light and that of the anti-dazzle light laterally and somewhat downwards without perceptibly reducing the penetrating power. The diffusion lense, therefore, in the case of both the main and anti-dazzle lights, illuminates the road over its whole width with a high even intensity giving a uniform distribution of lighting effect. Safety when negotiating — 5 — | ||