US1621752A - Headlight reflector - Google Patents

Description

March 1927' J. F. RAYNOLDS HEADLIGHT REFLECTOR 4 Sheets-Sheet 1 Filed April 27. 192.5

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irron lvk Y's 17v YEN Ton Patented Mar. 22, 1927.

, UNITED sra'ras PATENT OFFICE.

JOHN F. RAYNOLDS, or MINNEAPOLIS, MINNESOTA, ASSIGTNOR TO THE rARAFL-Eo'r'on COMPANY, OF MINNEAPOLIS, MINNESOTA, A CORPORATION OF DELAWARE.

HEADLIGHT REFLECTOR.

Application filed April 27, 1925.

This invention has for its main obj ect the projection of a beam of light for use 1n motor vehicle head lamps and the like, having a. more desirable shape, and with better distribution of candle-power or light intensities than is aiiiorded' by the various devices now in use.

The invention consists generally in the construction and arrangement of parts forming a reflector as hereinafter described and particularly pointed out in the claims.

In the accompany'ng drawings forming part of this specification,

Figure 1 illustrates a front elevation of a reflector having its surface divided into strips by means of circular arcs; lines I-1 etc. indicating the planes in which the light is spread. from various points on a single strip; pp

Figure 2, is a horizontal. sectional view on the line 2,-'-2 of Figure 1 showing a reflector of preferred form, comprising a plurality of flat strips arranged to produce the desired spread of the reflected light rays;

Figure 3 is av diagrammatic view illustrating a cross section of a light beam from two headlamps arranged as on a motor vehicle', to show the particular form of beam structure which, it is desired to produce tor illuminating the roadway ahead oi" said vehicle;

Figure t illustrates a front elevation of a single strip formec'tfrom a circular parabolic reflecting surface as shown in Figure 2, b h being a transverse element lying in plane Pat its intersection with strip S;

Figure 5 illustrates a side elevation of't he strip shown in Figure 4, showing its curvature in a vertical plane parallel to the principal axis of the reflector.

Figure 6 illustrates an enlarged cross sectional view in plane P (Figure 4;), showing various curvatures into which the transverse element of the strip may be formed to give a, desired amountof spread or divergenes to the reflected'rays Figures 7 and8 are modiflcationsshowing reflectors having differently designed curvatures of reflecting strips to produce varying amounts of divergence to the rays striking said strips;

Figure 9illustrates a front elevation'o'f a modified form of reflector showin'gthestrips arranged in non-circular continuous curves,

the whole axes Serial No. 26,105.

identical in curvature and symmetrically arranged with respect to the vertical meridian V-V; and

Figure 10 illustrates a method of laying out the surface of a reflector (or die) into strips, using circular arcs.

It is well recognized by illuminating engineers that the light'beamprojected from the headlamps of motor vehicles should have a pattern in cross section similar to that shown in Figure 3' and that the distribution of light intensities within such a beam should be substantially as shown by the lines of equal intensity in Figure 3.

The figures merely indicate the comparative candle powers in a suitable beam projected from two lamps, when correctly adjusted as on a motor vehicle and "readings made at 100 feet. This beam resembles onehalf of an ellipse, divided on its major axis, preferably having a ratio of about 1.8 to 1. I I

The commonest form of reflector used in motor vehicle headlamps is a circular paralbolic reflector of about 1 7 focal length (paraboloid of revolution)- There are also a number of patented reflectors having an unbroken reflecting surface but which are non-circular in sections transverse to the principal axis, being so designed according to a certain plan or theory, which causes the light rays to be projected in lines which de viate from parallelism by an. amount measurably greater than in the case ofthe abovementioned circular parabolic reflector-the source of light being considered the same and adjusted for least divergence of the rays.

The improvement disclosedherewith' is distinctly applicable to both classes or rex I rays m-one plane or in several'planes. They must be spread in continuously changing planes depending upon the point on the reflectin surface which is under consideration.

By constructing the reflector with a plurality of strips 11, (as shown in Figures 1 and 2) whose edges are continuous curved lines if projected on the plane of the reflectors mouth perpendicular to the principal axis; and by the use of suitably curved cross sections or transverse elements, for symmetrically located strips, the most desirable and etlicient distribution of light may be secured in a beam of correct cross-section or pattern. Instead of spreading the rays horizontally (in one plane), thus producing a band of light with highest intensity near its horizontal center line; the distance and direction of travel of the various rays are considered, and the reflecting surface made to direct the proper amount of light to each portion of the lighted field which is assumed to be a level, slightly crowned highway.

My invention consists of a broken, divided or configurated reflecting surface, originally either paraboloidal in shape or modified as above mentioned, said surface being divided into two series of strips, which are symmetrically arranged about the vertical meridian VV of the reflector. The bounding edges of these strips are continuously curved lines or circular arcs when projected on a plane perpendicular to the main axis of the reflector (plane of reflector mouth opening) having their convex sides toward the vertical meridian of the reflector. Broken lines 11, 2-2, etc, in Figure 1, show the planes in which light is spread from points on various transverse elements of a single strip. The surface of the strips at such transverse elements is made to assume a curvature less marked than that of the original smooth surface or it may be made flat or plane, or may have a curvature opposite to that of the original reflector surface, i. e. convex with relation to the main reflector axis (Figure 8). Furthermore the radius of curvature of a strip at any such transverse element may be greater near one edge than the other so as to produce greater deviation of the rays in one direction in the spreading plane than in the other. With this method or combination of methods practically any desired alteration may be effected in a beam from a reflector as described above, and the distribution of light within the projected beam may be arranged to best meet the requirements of State laws and actual conditions of service. No diffusing or refracting lens is necessary, only a piece of clear sheet glass as a cover in the lamp door is required. Loss of light by absorption and diffusion is diminished.

The light is concentrated to a proper ex tent, in the upper central portion of the beam (Figure 3), thus illuminating more distant points on the roadway and producing less apparent change in illumination to the operators eye as it is directed along the lighted path.

Referringto Figure 4, the transverse element bb originally had a smaller radius of curvature as a part of the unbroken circular parabolic surface before this surface was divided into strips and reformed, as shown at a-a, Figure 6. Line TT' is tangent to the curved edge of the strip at Z). Now in Figure 5, the inclination of plane P to the horizontal is fixed by its construction )erpendicular to the tangent TT. Plane it contains the transverse element 72-1), also its radius of curvature which is centered at in Figure 6. This figure shows an enlarged view in plane P of the transverse element b-b and also shows the original curvature of this element at a-a, with radius centered at 0, together with c--c a straight line or flat transverse element with radius of curvature infinite, andd-d' having its center of curvature on the opposite side of the strip.

The preferred embodiment consists of a reflecting surface divided into strips whose edges are concentric circular arcs when projected on the plane of the reflector mouth opening. Figure 10 illustrates how these arcs may be constructed. In this case a single base line perpendicular to the vertical meridian plane of the reflector is used. The centers of the two series of ares are located on this line equidistant from the meridian plane, The radius arm 12 is adapted to slide vertically on the upright post or rod 13, so as to preserve the same radius throughout a given are.

Where arcs of'equal radius are used as illustrated in Figure 9, the scribing point on arm 12 retains the same radius or distance from post 13, while post 13 is moved away from or toward the vertical meridian plane of the reflector die, in order to describe circular arcs of equal radii on the surface of the die.

I claim as my invention:

1. A concave reflector having its surface divided into two series of strips or zones; each strip being formed so that its mean radius of curvature, in the plane containing a transverse element of said strip, is greater than the means radius of curvature of the same section of the original surface; said strips or zones arranged symmetrically with respect to the vertical meridian of said reflector and having their edges in curved lines on the reflector surface, the projections of said lines on a plane perpendicular to the main axis of said reflector forming two series of concentric circular arcs having their centers on opposite sides of the projected vertical meridian, equidistant from it and below the horizontal axial plane, said arcs lying between the projected vertical meridian and their respective centers.

2. A concave reflector having its surface divided into two series of strips or zones; each strip being formed so that its mean radius of curvature, in the plane containing a transverse element of said strip, is greater than the mean radius of curvature of the same section of the original surface; said strips or zones arranged symmetrically with respect to the vertical meridian of said reflector and having their edges in curved lines on the reflector surface the projections of said lines on a plane perpendicular to the main axis of said reflector forming two series of circular arcs of equal radii and having their centers on opposite sides of the projected vertical merdian and below the horizontal axial plane of said reflector, said arcs lying between the projected vertical meridian and their respective centers.

In witness whereof, I have hereunto set,

my hand this 14th day of April, 1925.

JOHN F. RAYNOLDS.

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