US1718256A - Headlight reflector - Google Patents

Description

)1411925 1929- J. F. RAYNoLDs 1.718.256

' HLADLIGH;1 maFLEc'ro11-V Filed pril 2'5, 1927 2 sheets-sheet 1 Patented June l25, `11929.

UNITED STATES;

.ToIIN FQRAYNOLDS, or MINNEAPOLIS, MINNESOTA.

lnnlwLIeII'r minnen-ron.

Application' mea yapril 25, 1927. serial No. 186,406.

This invention relates to improvements ill concave reflectors adapted for projecting a beam of light ofr relatively high concentration or intensity, and more particularly rej lates to reiiectors adapted for use in headlights of motor vehicles.

The present forms/of light projecting apparatus are more or les's unsatisfactory in practical use because they require that the 310 incandescent bulb be' accurately focused, i. e., it must be locatedy so that the center of the lighted filament is at the focal point of the reiiector. l

Since the present allowable commercial I5 variation in the light-center length of headlight bulbs is plus or minus 3/64, it is cleary that if the reflecting surface is designed, as

is common practice, for one geometric focal point having. location but no dimensions, it

-aolwill be necessary to adjust or focus each v bulb that is' used` in a 'ven reiector.`

This invention is designed to eliminate the.

necessity of axial adjustment of the bulb, by providing in conjunction with a suitable rismatic lens or cover glass, a desirable, egal, practically constant beam of light with any,bulb,the dimensions of which conform to commercial variation allowances as above mentioned. In practice the bulb may be inserted in a suitable fixed socket which fits an aperture in the vertex ofthe reector and holds the bulb with its filament in the axis of the reiector,y the center of mass of the filament-lying within the compensatlng limits .of the reflector as shown below. Thus,

the vusual axial focusing mechanism 1s eliminated, and it becomes simpler to retain a satisfactory light beam whlch., of course, may be modified in shape and direction by a suit-able prismatic lens or cover glass.

.Ther particular object of the present in-A vention, therefore, is to provide an .improved reflector for headlights, deslgned 1n such a manner that it will not be necessary to axrally adjust the light bulb wlth respect to the reflector to focus the lamp.

Other objects ofthe invention will appear from .the following description and accompanying drawingsand will be pointed out in the annexed claims. j

' In the accompanying drawings there has `beendisclosed a structure desi ed to carry out the various objects of themvention, but

it is to be understood that'the` invention is not confined to the ,exact features shown;v as various changesmay be made within the scope of the claims which follow.

In the accompanying drawings forming part of this speciiicationy Figure 1 is a vertical'sectional view of the `upper half of Inyimproved reflector, 'show- Ing the various zones and th'e direction of the rays of `reiiected, light from the respective zones;

Figure 2 is a frontl elevation ofa whole reflector as constructed from, Figure l;

e Figure 3 is a perspective View' of a 4reflettor havingl the various zones indicated; 3,11 i

Figure 4 is a diagrammatic .view showing` on an enlarged' scale, a portion of' the reiector surface. d

The novel reflector featured in this invention has its reflecting surface divided into'a' plurality of concentric circular zones, which I have marked on t xe drawings vasZl, Z2-Z3, Z4, Z",'Z, and Z1. The center or innermost zone Z1 includes the vertex of the reflector, and has its outenedge terminating in an imaginary plane perpendicular to the axis A--A of the reflector, as indicated'by T-.T.l

in Figure I1. F represents theA focal point of the center zone Z1. All lof Ithe zones illustrated in Figure are sections of paraboloids of revolution, each section being bounded by planes perpendicular Ito the 'common axis .Af-A of all the paraboloids, as for instance U-U', V.V, W-W, X-X, and Y-Y.

The'center zone Z1, in Figure 1, has been arbitrarily chosen-with 'its focus at point F andA a focal length of approximately 11/4 inches.l The second zone Zzhas its focus at point S, and the focal length is determinedI so that the curve contains point T and oins the curve of the center zone Z1 to lma e a continuous, practically smooth surface. The third zone Z? similarly has its focal length located so that the curve contains U., but 'the focal point forthis zone is-iocated at point L. Points S and L lie substantially in the axis A-f-A at suitable distances respectivel inside and outside point F.y Similarly,'t e 4th zone has its focus at Sgthe 5th lzone at L, and so on in alternation, each focal length being located so as to make `the ends lof adjacent 'hopes-coincide, thus avoiding.

VVilh relation to zone Z, the center of the filament will be slightly in front of the focal point S, hence the various rays reflected from this zone will converge relative to correspondlng rays from the center' zone, and

will cross each other a short distance ahead of the reflector, producing a circular beam or spot of light, larger and of less intensity at any considerable distance, than the beam from the center Zone. The rays projected from any point of zone ZZ are shown by SN5 and LNG. In this case, it will be noted that ixnel5 is substantially parallel to the axis With relation to zone Z3, however, the center of the filament is back of the focal point L, hence reflected rays from this zone will diverge more than those from any other zone, the focal point of which lies between point L and the vertex, and will therefore again produce a beam of greater diameter than that from the center Zone Z1. Zones Z4l and Z6 will reflect similarly to zone Z2, and zones Z55l and Z7 similarly to zone Z3. The rays projected from any point of zone Z8 are shown by SM'I and LMS, and those projected from Zone Z4 are shown by SQ9 and LQl". (See Figure l.) In this figure, it will be noted that the rays MS and Q9 are also substantially parallel to the axis A-A of the reflector. The rays M'I and Q10, however, converge, and will therefore cross each other a shortvdistance ahead of the headlights. It 1s to be understood. ofcourse, that the particular relation of the zones with respect to one another need not necessarily bev followed as Illustrated in the drawings,"y as their order may be reversed and practically the same results obtained. Also the number of zones lemployed may be varied, as desired, without departing from they invention. The important feature of the invention, however, is to provide a reiector having its surface divided into annular concentric zones which are arranged in such a manner that a desired light beam will be projected therefrom without the necessity of having to focus the light bulb therein. 4

Now it is clear that movement of the lightcenter along the axis, within the limits between S and L will cause the beams `fromone set of zones to increase in diameter wh11e those from the other set of zones will decrease in diameter. The center zone, as

owing to the small change in the angle of incidence of the projected rays to this zone, when the source of light varies axially, the change in diameter of the reflected beam will be less than for any other zone outside the center' zone. This is shown in Fi ure 1 by the angles SPL'and SQL, the ormer being the smaller angle. It is to be understood, however, that if desired, the center zone Z1 ma be designed with its focal point at either or L instead of at the intermediate point F, provided an alternating relationship between the focal points for adjacent zones is preserved as hereinbefore described.

If the sum of the areas of zones with focus S is made approximately equal to the sum of those with focus L, we shall have roughly equal areas tending to produce a more concentrated beam, and a more divergent beam respectively, when the light center is axially removed from point F. Hence, the refiector is less sensitive to variations in the light-center length of incandescent bulbs, and may be used without means for axial adjustment of the bulb. It may be desirable to provide in a headlight with the reflector, means for adjusting the bulb perpendicular to the axis A-A, in order to secure the most desir? able distribution of rays from the various portions, or if a bulb is used which contains two filaments of equal light center length arranged one above the other in parallel planes.

I claim as my invention:

l. A concave reflector, adapted for a centrally located concentrated source of light,

the reflecting surface of said reflector being continuous and unbroken and composed of a plurality of zones defined by planes cutting said surface and perpendicular'to the main axis thereof, each zone having a focal point lying substantially in said axis, and the`focal points of adjacent zones being displaced alternately closer to' and further away from the vertex of the inner zone.

2. A concave reflector, adaptedrfor a concentrated source of light located substantially in the main axis thereof, the reflecting surface being continuous and unbroken and composed of a -plurality of zones defined by planes cutting the refiecting surface perpendicular to the main axis thereof, the inner zone containing the vertex and having a single focal pointin said axis, and the outer zones having their lrespective focal points in said axis and alternately closer to and further away from the vertex than the focal point of said inner zone.

, 3. A reflector having a continuous surface4 com osed of a plrality of sections of parabrespective focal points lie alternatel nearer oloi s of revolution, all sections having a p to and further from the vertex of t e inner common axis and being bounded by planes section than the focal Apoint of said inner 10 erpendicular to said axis, the radii of adsection. Y p y v 5 ]acent sections in their common bounding In witness whereof, I have hereunto set plane being equal, and the various parabmy hand this 22d daf of April, 1927.

oloids being of'such focal lengths that their l JOlN F. RAYNOLDS.

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