US1347268A - Parabolic sectional reflector - Google Patents

Description

C. E. GODLEY.

PARABOLIC SECTIONAL REFLECTOR.

APPLICATION man SEPT. 17. I917.

Patented J uly' 20, 1920.

I z a K 8mm Q/Vi/bneoo Q 1; Char/e95. Gad/e19 'f'] Noun 5 f UNITED STATES PATENT, OFFICE.

was 1 GODLEY, or :onrnorr, moment, ASSIGNOB minimum JONES CORPORATION,

OF DETBOTT, 'MICHIGAN, A CORPORATION OF NEW YORK.

PARABOLIC SECTIONAL REFLECTOR.

Application-filed September 17, 1917. Serial no. 191,684.

To alljahom it may concern: q

Be it known that I, CHARLES E. GonLnY,.a-

, citizen of the United States, and residing at ever, the'construction has been such as pre Detroit, in the county of Wayne and State of :Michi an, have invented a new and Improved arabolic Sectional Reflector, of which the following is a specification.

Various eifortshave been made heretofore to prevent glarein automobile headlights by forming the upper half of the reflectors of a shape different from the lower half,

.thethought being generally to project the vented manufacture by commercial processes, particularly in that the finishing and buffing had to be done by hand.

The primary object of the present invention is to produce a headlight reflector, which i can be made at substantially'the samecost as the ordinary well known parabolic type, whereby all objectionable glare is prevented and whereby the light is efliciently directed over the roadway without the formation of bands or shadows. To this end, it consists in a reflector, the lower half of which is substantially a standard parabolic surface, whereas the upper half is formedof a series of parabolic sectors the transverse cross sections of which are -surfaces of .revolution about the axisof the reflector and the foci of which are located rearwardly from the focus of the lower half. In use the source of light is positioned in the last mentioned focus. It also consists in a reflector-the main portion of the surface'of the lower half of which is parabolic, said lower half being provided, near its rear end, with one or more parabolic sectors having a focus forward of the focus of the main portion.

The invention further consists in a method for forming the reflector wherein the blank is first stamped and finished substantially into the shape of 'a' paraboloidal surface, afterward stamped a second time to offset the parabolic sectors therefrom, and finally: subjected to bufing while turning around its axis about a rotating tool.

In the drawingspFigui-e 1 is a vertical transverse section through a preferred embodiment of the invention, and Fig. 2 is a front view corresponding thereto, but somewhat reduced.

The reflector is formed of a continuous sheet metal stamping 1 the lower half of.

which is preferably substantially the same as the lower half of an ordinary parabolic reflector having the longitudinal axis 2 and the focal point 3, thus forming the parabolic reflecting surface ifrom which the reflected rays of a filament 5 are directed forwardly 1n substantiallyparallel relation to one another, as indicated at 6. The upper half. of the reflector is made up of a series of parabolic sectors 8, 9, 10, 1]., etc. (nine being shown, although the number may vary), having a common focus 20 located on the axis 2 rearwardly'from the focus 3. Preferably, the central transverse section of each of the sectors is located on an extension of the parabolic surface 4:; in other words, planes perpendicular to the axis 2 and passing through the middle of the corresponding parabolic sector intersect the reflector in complete circles. Because of the relative locations of the foci 3 and 20, all rays emanating from the filament located in the former and reflected by the sectors are directed downwardly and diffused over the roadway as indicated at 21.

it will be observed that the rear edges of the sectors 8, 9, 10, etc, are offset slightly outwardly and the front edges are offset slightly inwardly from the imaginary parabolic surface of revolution corresponding to the lower half of the reflector. It is important that the front edge of each sector project sufliciently to prevent light from the filament from striking the surfaces whereby the particular sector is joined to the next forward sector, as glare would otherwise tend to result.

it is found that the rays reflected from that portion of the standard parabolic reflector just below and rearwardly from the bulb also tend to cause glare. To prevent this action, this surface may be offset from the main paraboloid to forni one or more parabolic sectors 25, 26, the foci of which are located at a point 28'somewhat forward of the focus '3. Putting it another way, the rear edge .portionsof the sectors 25, 26 are offset inwardly and the forward edge por- Speeification of Letters Patent. Patented J ul'y 20, 1920.

tions are offset outwardly from the extended surface of the main paraboloid. Rays striking the surfaces 25,: 26 are therefore diffused downwardly over the road surface as indicated at 29.

The purpose of arranging the, foci of the sectors 8, 9, 10, etc., at. a single'point, and the. foci of the sectors 25, '26 at a single point, is to prevent the formation of-alternating belts .of light and shadows in the roadwayin other words, to spread the light uniformly.

In the manufacture of the reflector, the metal is first stamped by dies to form a full parabolic sheet or cup of the same curvature as the main portion of the lower half. This blank is then held in a slritable finishing machine (not shown) whereby it is rotated about the axis 2, and while so rotating is-subjected to the action of a hard finishing or cutting tool 30 which turns counterclockwiseat high speed about an axis per endicular to the plane of the paper (Fig; 15. Relative movement is simultaneously given the tooland blank along a parabola 31 (parallel to the parabola whereby the surface 4: is

generated), thus cutting the inner-surface of the latter to true paraboloidal shape, as is common practice in the manufacture of ordinary parabolic reflectors. "Thereafter the blank is again placed in suitable dies and pressed to offset the metal sufliciently to forin'the parabolic sectors 8, 9, 10, etc,

and the sectors 25, 26 (if the-la tter are used) ina single operation. Because the bending incident thereto is very slight it is unnecessary to further out the inner surfaces of the sectors 8, 9, 10-25, 26, the final bufling operation taking place by substituting a w eel having a soft exteriorfor the cutting tool 30 and again'subjecting the blank to the action of the finishing or bufi'ing machine as before. The buffing tool, being soft, conforms to the inner surface of the sectors substantially as well as to the surface 4. In

. this manner the reflector can be made wholly by machinery, no hand finishing or buffing being required, the whole operationbeing the same as ordinary practice except the added step of ofisetting the parabolic sectors.

between the steps of cutting and buffing.

1. A reflector having upper and lower halves, the reflecting surfaceof the main portion ofthe lower half of the reflector conforming to a true paraboloid, the upper half of the reflector including a plurality of sectors ofparabol'oidal surfaces, each sector" boloidal surfaces, said strips being slightly offset from one another and having foci spaced from the focus of the first menflector.

tioned surface longitudinally of the re- 4;. A cup shaped reflector formed of thin sheet metal, the upper portion of the reflector including a plurality of transversely extend-ing strips of paraboloidal surfaces oflset slightly from each other and having different focal lengths, the foci of said surfaces substantially other.

5. In combination, a sheet metal reflector having an upper portion, a lower porcoinciding with each tion, and a longitudinal axis,the lower portion constituting substantially the lower half of said reflector and having its inner face conforming to the surface of'a paraboloid the focus of which lies substantially on the longitudinal axis, the upper portion constituting substantiallythe upper half of the reflector and having its inner face formed of a plurality of substantially parallel .narrow transversely extending strips conforming to the surfaces of different paraboloids, the portion of each of the-surfaces which has the greatest diameter be ing forward and the foci of said last named paraboloidal' surfaces being rearward of the first mentioned focus.

6. A parabolic reflector having a longitudinal axis, the reflector being so constructedthat the'trace of the vertical plane which includes the axis with the inner surface includes in its upper half a series of short sections of forwardly diverging parabolas, said trace including in its lower half alonger section of a parabola, planes perpendicular' to the axis and passing through substantially the mid-point of said first mentioned sections, intersecting the last named section at the same distance from the axis as they do the corresponding one of said first named sections; i

7, A cup-shaped reflector vhaving a. central portion comprising a plurality o'f'conccntrit ipurabo'ltn'dal rm theouter-ring being 0 setrearwardly m the inner, the

remainder. of the reflector consisting-pf an upper and a lower portion central horizontal plane, the inner face of the lower portion being a paraboloidal surface, the mner face of the upper portion 5 consisting of a plurality of narrow transversely extending strips, of even widths throu hout their lengths, of different paraholoid hl surfaces, the foci of the last mentloned surfaces being rearward of the focus 10 of the lowerforward portion of the reflector.

divided by a 8. A reflector comprising an upper portion and a lower 'ortion meeting in a horizontal plane whicli of the reflector, the portion bein a paraboloidal surface, inner face 0 the upper portion including a pluralityof narrowtransversely extending strips of different vparabololdal surfaces, said strips being of even widths throughout their len hs, the foci of said strips being rearwar of the focus of the first mentioned surface.

CHARLES E. GODLEY.

inner face 'of the lower passes through the axes

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