New Head-lamp Mask of High Efficiency
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EWEN, distribution over a wide area of light at the maximum permitted intensity is the object of a new headlamp mask designed and produced by Joseph Lucas, Ltd., Great King Street, Birmingham. At present, the types available range in price from 9s. 6d. to 11s. 6d. They include models suitable for many commercial-vehicle head lamps, and it is anticipated that others will be forthcoming to complete the range.
A single slot is used, instead of the three in the familiar type, and this is placed well above the centre of the lamp. Outside and above this slot there is a cowl with its front edge approximately level with the slot, so th'at no ra:ys, direct from the filament, can emerge;: all the emitted •light being froin the lamp reflector. Provided the bulb is propefly foeusedl-this gives a sharp cut-off and there -is,in fact, a
well-defined edge to the main beam.
To ensure that this beam shall reach from kerb to kerb, even on a wide road, a prismatic spreading device is Incorporated on the same basic lines as the vertical flutes in some lamp glasses. This consists of a glass mouldino.° placed on the inner side of the mask behind the slot, and provided, incidentally, with a rubber gasket to prevent the entry of dirt or water.
For ease of cleaning, the forward surface of this glass ,is smooth and the prisms are formed on its inner face. The smooth surface can eaMly be wiped with a cloth without removing' any part of the . mask or lamp.
This new Lucas single-slot mask appears to combine the desired optical result with features of practical utility. To facilitate, fitting a rim is , incorporated, so that the mask cart replace
tile, existing glass and rim,