US1390747A - Reflector for use in light-projectors - Google Patents

Description

J. G. BALSILLIE.

REFLECTOR FOR USE IN LIGHT PROJECTORS.

APPLICATION FILED NOV. 16. 1920.

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1,390,747. PatentedSept. v13, 1921..

UNITED STATES PATENT OFFICE.

FLATLITE LIMITED, OF SYDNEY, NEW SOUTH TION OF NEW SOUTH WALES.

WALES, A STRALIA, A CORPORA- REFLECTOR FOR USE IN LIGHT PRO-TECTORS.

Specification of Letters Patent. Patented Sept, 13, 1921,

Application filed November 16, 1920. Serial No. 424,530.

To all whom it may concern.

.Be it known that JOHN GRAEME BALSIL- LIE, subject of the King of GreatBritain. residing at Collins House, 360-366 Collins street, Melbourne, Victoria, Australia, has invented certain new and useful Improvements in Reflectors-for use in Lightlrojectors, of which the following is a specification. This invention relates to improvements in reflectors for use in light projectors more particularly adapted forthe headlamps of vehicles such as motor cars and' the like.

Though this invention is herein described as being adapted for the headlamps of motor cars, it will be understood that it is applicable for the head lights of locomotives, tramcars and the like, and is also adaptable for the projection of light for other purposes such as street lighting.

It is known'that when aroadway in front of a road vehicle is brilliantly illuminated by non-diffused light, the driver or an observer has great difficultyin seeing objects immediatelybeyond the area of bright illumination. The reason for this is that the brilliantly illuminated path of roadway in tereferes with the resolving power of the It has long been known that more satisfactory road illumination can be achieved by diffused lighting but hitherto this type of illumination has been-usually Chat acterized by glare which interferes with the vision of of light.

The object of the present invention is to provide means whereby light may be diffusely reflected and projected preferably in a beam of elliptical crosssection substantially. v

I accomplish thisobject by providing the reflecting surface of a reflector with configurations which function to reflect. light diffusely "in one plane and substantially regularly in the planeat i-ight angles there to i persons looking toward the source This is effected by providingthe reflecting surface of the reflector with parallel corrugations. grooves, or furrows.

' of the chief meridians and a. source of light is placed at or about the focal point of that chief meridian with which the configurations are parallel diffused light is projected in relatively parallel rays in one plane and divergent or convergent divergent rays in the plane at right angles thereto.

Vi hen such configurations are applied to the reflecting surface of an astigmatic reflector, preferably t right angles to its principal meridian and a source of light is placed at or about the focal point of the shortest principal meridian light is pro-' jected in relatively parallel rays in the plane of one meridian and divergent or convergent divergent rays in the plane of the other meridian.

The plane inwhich the light is projected in substantially parallel rays coincides with the plane of that meridian of the reflector witlll which the said configurations are paralle The type of configuration that I find most satisfactory is regularly parallel corrugations, furrows, or grooves, which may be of varying frequency and radius, but preferably of about 35 to an inch, each corrugation having a radius of curvature of seven thirty seconds of an inch. In this specification, the term corrugations will be understood to include furrows or grooves. These corrugations made on the reflecting surface function to give a regularly astigmatic effect to a stigmaticreflector. When the invention is adapted to a regular astigmatic reflector the corrugations are made parallel with one or other of the principal better understood, I will now proceed to describe same by reference to the accompanying sheet of drawings, in which,

Figure 1 is an elevation, and

Fig. 2a cross section of a regularly astigmatic reflector which has been configurated in accordance with this invention,

such configurations being in the form of corrugations parallel to the smallest principal meridian.

Fig. 3 is a vertical sectional elevation of a motor head lamp fitted with a reflector as shown'in Figs. 1 and 2.

Fig. 4 is a front elevation of a stigmatic parabolic reflector as ordinarily in use which has been conflgurated in accordance with this present invention such configurations being in the form of parallel corrugations.

. Figs. 5, 6, and 7, are sections of a portion of a reflector to which corrugations of different configurations have been applied for the purpose of this invention.

In these drawings A represents the reflector within which is fitted the source of light B (such as an electric lamp) adapted to fit within the socket C.

In Figs. 1, 2, and 3, a regular astigmatic reflector is shown, and this may bemounted .cause the corrugations only operate to diverge the light projected in a plane at right angles to the plane of the corrugations. The

source of light should be located at or about the focal point of that meridian of the reflector which is parallel with the plane of the corrugations.-

-The corrugations are made parallel with one of the chief meridians of the reflector and may be made to function to accentuatethe astigmatism- By varying the radius of these corrugations and their frequency, the amount of divergence can be altered to suit different conditions. For example, satisfactory results have been obtained with corru-.

gations in which the radius of. curvature and frequency have been of the following dimensions Curvature radius in Frequency per inches. inch. Seven thirtyseconds. Thirtyfive. Twelve thirtyseconds. Fifteen. Ten thirtyseconds. Twentyfive. Six thirtyseconds. Fortyfive.

The invention is applied in a similar mannor to reflectors of all types wherein all meridians are curves by configuring the reflecting surface as shown in Fig. 4- with a series of parallel corrugations.

In astigmatic reflectors the corrugations are preferably at right angles to the principal meridian. The corrugations may be con caval as shown in Fig. 5 or convexo-concaval as shown in Fig. 6, or in the form of V shaped depressions as shown in Fig. 7.

I claim 1. A reflector having its reflecting surface provided with parallel corrugations arranged to project light in relatively parallel rays in one plane and divergent rays in the plane at right angles thereto.

\ 2. A reflector for use in light projectors having its reflecting surface provided with corrugations parallel with one meridian.

3. A reflector for use in light projectors in which all the meridians are curves of graduating focal lengths having its reflecting surface provided with corrugations at right angles to the principal meridian.

4. A reflector for use in light projectors in which all the meridians are curves of graduating focal lengths and in which the chief meridians are mutually at right angles and the values of the intermediate semicurves in each quadrant decreases uniformly from the largest to the smallest having its reflecting surface provided with corrugations parallel with one of the said chief meridians.

5. In light projectors a reflector having the reflecting surface provided with corrugations parallel with one meridian and a source, of light placed at or about the focal point of that meridian.

6. In head lamps for vehicles, a reflector having its reflecting surface provided with corrugations arranged with the planes of the corrugations substantially perpendicular to the surface of the roadway and parallel with one meridian.

In testimony whereof he has affixed his signaturev in the presence of two witnesses.

JOHN GRAEME BALSILLIE.

lVitnesses:

CLEM A. HACK, G. I). ALLEN.

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