US1513715A - Headlamp for automobiles - Google Patents

Description

Oct. 28 1924.

W. E. MARSHALL ET AL HEADLAMP FOR AUTOMOBILES Filed March 2O 1924 atented Oct. 428, 1924.

WILLIAM EDWARD HLL AND PHILIP GEORGE P-AGE MCCULLOCH, OFLONDO-N, ENGLAND, ASSIGNOBS T0 NON-DAZLITE, LIMITED, OF LONDON, ENGLAND.

HEADLAMP FOB AUTOMOBILES.

Application led Marcho 20, 1924. Serial No. 700,541.

l To all whom t may concern.

Be it known that we, WILLIAM EDWARD MARSHALL and PHILIP GEORGE PAGE MGCUL- LocII, both subjects of the King of Great Britain, residing at 32 Mortimer Street. London, England, have invented new and useful Improvements in Headlamps for Automobiles, of which the following is a specification. l

This invention relates to improvements in head lamps suitable for automobiles.

The object of this invention is to provide a head lam in which the beam therefrom whilst sufficlently illuminating the road will not dazzle persons facing the lam We have found that with head lamps having a paraboloidal reflector, the focal length of which is an inch and a quarter or less (this being the focal length of reflectors at present commonly used), the rays reflected from the central portion of the reflector-have a divergence at least four or five times greater than that of those proceeding from the outer portions thereof, this divergence being due to the great dierence between the maximum and minimum distances of the filament from the refiector.

We have also found that a reflector having a focal length of two inches reduces the maximum divergence of the rays from thel central portion of the reflector to less than twice that of the rays reflected from the outer portions.

In a head lamp constructed according to our invention the reflector has a focal length of at least two inches and preferably three inches or more, and in order toobtain a beam of light, the vertical section of which is considerably smaller than the horizontal section, so as to illuminate the sides of the road whilst at the same time keeping the top of the beam below the level of the eyes of an approaching pedestrian, we employ an incandescent electric lamp the filament of which is arranged horizontally in a plane at right angles to the axis of the reector, the bulb of the electric lamp being preferably spherical and the filament consisting referposition on the head lamp) this distance preferably being less than two millimetres and in no case greatly exceeding it, the ob- ]ect being to ensure that the whole of the filament is'slightly in front of the centre of curvature of the bulb.

The coil may be of considerable length, for example, three quarters of an inch or more.

With an electric lamp so constructed, the comparatively large 4percentage of rays reflected back from the glass of the bulb itself on to the refiector are divergent to a slight extent only, and only those proceeding from the upper portion of the reflector therefore rise upwards from the horizontal.

The electric lamp may be supported in an externally screw threaded holder, screwing into a threaded hole in the body of the lamp and held in position by an external lock nut, the holder being of such length that the centre of the filament can be placed in the focus of the reflector,'that is, outside the plane of the ed e of the reflector.

In t e accompanying drawings which illustrate the invention, Figure 1 is a vertical section with parts in elevation of a head lamp embodying the invention; Figure 2 is a plan view of the bulb and filament; and Figure 3 is a side elevation of the bulb and filament of Figure 2.

1 is the lamp body, 2 a paraboloidal reflector having a focal length of three inches.

3 is a spring ring for keeping the reflector in I position; 4 is an electric lam holder having an externally screw threade portion 5, and 6 is a tapped socket in which the screw threaded portion 5 of the lamp holder engages; 7 is a lock nut retaining the holder 4 in position after correct adjustment. 8 is an electric lamp having a spherical bulb '(except for the pip). A--A is a line passing through the geometrical centre of the bulb. 9 is the filament coil situated in front thereof at a distance of 2 mm. therefrom, so that the whole of the filament is slightly in front of the line A-LA,

The arrangement shown provides means which allow existing lamp casing bodies to be readily fitted with a reflector of greater focal length. l

The use of a two inch reflector will reduce the maximum divergence of the rays vfrom the central portion of the reector to less than twice thatof the rays reflected from the outer portions, and with the use oit a redector of still greater local length, this reduction is markedly larger.

Moreover, when employing an electric lamp as shown in Figures 2 and 3, a beam of* light is produced having a lateral spread as large as is required, but in which the upward divergence is almost or entirely eliminated, such upward divergence beingone of the main causes of the dazzling edect in lamps as heretofore used.

What we claim is A vehicle headlight comprising a casing, a substantially paraboloidal redectr within 7 the casing, the focal length of which is greater than two inches, a socket supported axially of the reflector, and a light source in the socket lying at the locus of the reflector, outside the plane oit the edge thereof and within the boundary of the casing, said light source comprising a substantially spherical incandescent lamp bulb having a long horizontal .lilament lying` in front of the geometrical as our invention we have signed our names 30 this 10th day of March, 1924.

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