US1502453A - Headlight - Google Patents

Description

www@ W. H. WOOD HEADLIGHT may 22 11924.,

Filed May. ll. 192) Patented july 22, 1924..

Umso As'iuafnszs WILLIAM m. woon or som'mrcmn, omo.

HEADLIGHT.

Application nledfllay 11,

To aZZ wLomz't may concern' Be 1t known-that I, WILLIAM H. Woon,

acitizen of the United States, residing at,

South Euclid, in Athe county of Cuyahoga and State of Ohio, have invented "a certain new and useful Improvement in Headlights,`

of which the .following is a full, clear, and' exact description, reference being had to the accompanying drawings.

This invention relates Ato headlights for automobiles and vlike vehicles and has for its generalobject the' provision of a re- Hector of' simple form by which the'light ,rays can be controlled in such-wise as to use the largest possible proportion of them beneficially withoutv causmg such an upwardly projected glare as todazzle or'con,

fuse meeting-travellers. From a commercial standpoint Iit is imperative 'that the device be one that canbe drawn in dies and polished by machinery in the same way' that plain parabolic reflectors are polished; that the dies be of simple and rugged construction so` as to be kept in order easily;

that the rays emitted by a V-shaped filament be controlled as effectively as those produced by the ol'dertypes of ilament'g'and that the use of special lenses or glasses be dispensed lwith. All these requirements ,are met by my invention. p

The essence of my invention resides in inclining downwardly the axis of a greater or smaller proportion of the 'reiecting sur-4 .facewhich lies forward of the light source, while retaining horizontal the axis, of a lgreater orsmaller proportion ofsuch vsurace/which lies at the rear of such light source. The basic optical theory .is as follows: y

Assuming al paraboloid reector and a light source consisting l"of ay eometrical.

oint, if that light fsource coinci e with the ocal point all rays falli-ng onthereector will be reflected forwardly parallel with the parabolic axis; yif the source be .moved to a position on lthe axis forward of such focal point, all-rays fallingy on the reflector will be converged ;an d if the source be moved t a positionon the reflector-axis at the rear .of the focal -point all'rays kfalling on the reflector will'be diverged; 'However'no practical `light source isknown which even approximates. the dimensions of a geometri- .cal point, but all sources exhibit a Idecided l extension laterally of the axis aswell as longitudinallyI thereof.v The commonest paraboloid reflector 1921. Serial N0. 468,638.

present-day source is anv incandescent le ment having a V shape, mounted in a horizontal position symmetrically of the reilec# tor-axis and -having its apex located sub-v stantially at the focal point with the legsA thereo extending `toward the vertex of the lreiector and also diverging laterally; and

it is this divergence which has entailed more difficulty in light-control thin any other single element. v

This diiculty arises largely fromthe fact that if a' 4light'souroebe shifted laterally of the axis of a plain paraboloid reflector, all rays which fall thereon'inside a given point are thrown to the opposite side of the neflector axis while all rays which fall lon this reiectorl outside the point are thrown to the .same side on which the source is located, this point being determined by the intersection 'with the reflecting surface ofa straight line which passes through the focal point and through this particular vlight source. Assuming that the light rays are emitted equally in alll directions, which owing to the constructional details of the lamp is not 'strictly truev although approximately so, one half of all the light emitted by the source isv reflected inside the parameter and this constitutes about five-sixths of all the rays which are reflected, owing to the large open front of the reiector; but the ra s .reflected by the part of the reflector nition I have `defined this point as being a 'proximately yat the parameter, and whl e this is not strictlyl accurate scienticall it isl sufficient practically since no objectionable glare everfarises inside the true parameter. By'I the expression approximately at the parameter I mean an where melde that region, although the brea between the different portions may fall anywhere within a considerable area thus generally defined.

Experiments "readily showI that a plain produces Aits worst glare when used with a' shaped lament and that the most objectionable part of this glare comes from the portion of the reflector which lies forward of the parameter. It has been `suggested to leave this part ofl'` completely, indeed this is exactly what was done in the gas and oil lamps which preceded these incandescent bulbs, but such a construction at the presen day is considered neither artistic, economical, nor mechanically practical. Certain manufacturers in order to lapproximate this condition' have made their reflectors very large and shallow, bringing the bulb so far forward as to necessitate convex lenses; and these rdo indeed help, although the lenses are expensive and exposed to breakage, and less of the light is used.

In the drawings accompanying and forming part of this application 'I have shown a few physical structures, embodying the idea nf my invention, together with certaindiagrammatic views illustrating the principles involved in my method of light control. In these drawings Fig. l is a horizontal section illustrating diagrammatically the course of rays arising at different parts of a V shaped filament kand reflected by dierent parts of a araboloid reflector, the portion of the re ector forward of the parameter being shown in dotted lines; Fig. 2 is a'diagrammatic View illustrating one mode of curing the objections indicated in Fig. l; Fig. 3

Villustrates a practical reflector embodying this principle; Fig. 4 is a diagrammatic view illustrating the principle of my invention as applied to a composite reflector; Fig. 5 is a face view of the reflector shown in Fig. 4; Fig. 6 is a diagrammatic view showing another modification of my invention; and Fig. 7 is a face view of the reflector shown in Fi 6.

In F ig. 1, A represents a plain paraboloid reflector having an axis -a a parameter p-p, and a focal point f, while S represents a V-shaped light source symmetrically located relatively to such axis with its apex coinciding with the focal point. All rays arising at f arereflected parallel to the axis as shown at b, b, no matter which'side of the parameter they fall; all rays arising at vthe extremities ofthe source are diverged or converged depending upon whether they fall upon the reflector outside or inside the straight line whichintersects both the focus and the point of origin. However the defiection is comparatively slight as to the rays which fall inside the parameter as shown at vc and very pronounced as to those rays which fall `outside the parameter as shown at d. Indeed the action is really even more marked than can be shown on any drawing, since a drawing is confined to two dimen sions while the action really occurs in' three dimensions, thps giving rise to a cross-'lire of rays producing a very objectionable' glare,

though this is confined almost entirely to the forward art of the reflector as any one can verify y taking two reflectors and blaclrening the portion of one outside the parameter and the portion of the other inside the parameter and comparing their operation.

The simplest way to remedy this is to cut ofi' the portion forward of the parameter and to substitute therefor a portion E whose axis e, e, is inclined downwardly a sufficient amount so that substantially all the stray beams are confined at or beneath a horizontal plane as shown in Fig. 3. This portion E can be either a portion of the same original paraboloid o r can be a different paraboloid. An excellent light can be produced in this way, the rays reflected by the heel-portion A constituting a concentrated distance beam and the rays reflected by the forward portion E constituting a diffused beam for near lighting and for curb illumination. The inclination can well be made somewhat lateral toward the curb side as well as downward. The only care requisiteis to avoid such an extreme inclina tion as to separate the two beams and produce a dark region between them, or to produce such a lop-sided condition as might be difficult to draw or'polish.

The simplest way to produce such a reflector is to sever a plain paraboloid ieflector upon a transverse plane G, G passing through or near the focal point and making an angle with the parametral plane equal to one half the desired angle between the axes of the front and rear portion. The severed portions are then rotated 180 relatively to each other and fastened together again, and the forward portion cut off at rightangles to the axis of the heel portion, thus producing the reflector shown in Fig. 3. A better way isto apply this process to the dies, thus enabling the reflectors to be drawn in one piece in the same way as the common paraboloid reflector, the mouth being provided with an integral youtturned rim H. Suche reflector can be polished in automatic machinery and costs no more than the cheapest.

In this embodiment the two reflector portions have. a common focal point which is located upon the lamp axis, though such an arrangement is not necessary since by suitably choosing the size of the forward portion'and the point and angle of severing .the same its axis can be caused to intersect vthe axis of the heel portioirat other point. and its focal point to lie either ahead of`or behind the focal point of the heel portion, thus enabling 'the direction and character of the light beam to be varied independently of the inclination of the axis' and a smaller amount of inclination employed. y Some inclination is always ,essential according to this invention, and such inclination always llO results in an elliptical section at the point of junction. It is necessary that the ellipses of the forward and rearward portions be substantially equal but this can easily be accomplished by a suitable choice of sizes and angles.

It is not necessary to my invention that either lportion of the reector constitute a complete surface of revolution, but either can be made of a plurality of segments so long as certain segments of each portion possess the relation herein defined, and I will now describe the application of my inventive idea to such a condition. In the embodiment shown in Figs. 4 and 5, A represents a segment of a paraboloid and a-a its axis which coincides with the lamp axis. No part of this segment extends materially forward of the parameter P nor below the hori zontal plane whichcontains the axis a.-a, but its vertex merges with the vertex of a semi-paraboloid J of larger size whose axis is substantially parallel and coincident with the axis ar-a. However its greater size causes its focal point y' to fall sufficiently far forward of the focal point f of the segment A so that this fact alone creates a sufficient downward divergence of the rays which fall thereon to overcome any glaring tendency they might otherwise possess.

The portion K of the reflector which lies above the lamp axis and forward of the seg ment A is made of a paraboloid segment having its axis c-c inclined downwardly relatively to the axis a-a an amount sufficient to overcome the glaring tendency. The dotted lines indicate the amount of the displacement, and 7c indicates its focal point which is here located above the axis a-a and rearwardly of the parameter p-L thus for numerous reasons producing a downward deiection ofthe rays reiiected thereby, all of which are assumed to be derived from a V shaped filament located on the axis -a with its apex at the point f. The small size and inclination of the portion K produce gaps at both sides of the reflector which are bridged by slanting wings L, L, as described and claimed in my Patents Nos. 1,235,274 and 1,235,275 issued July 31, 1917. It will be understood that I have exaggerated the displacement of the focal points in this view and that it is seldom that the focal point K will loe-both elevated above and brought behind the point f, but Ihave indicated this to show the scope of the adjustments possible under my invention.

In Figs. 6 and 7 I have illustrated the mode of applying the present invention to j a refiectorof the specific construction shown in said Patent No. 1,235,27 5. In these views A, as before, represents a paraboloid segment whose axis a-*ais horizontal and coincident with the lamp axis. This segment is terminated forwardly at the parameter P,

and at a point slightly above the axis mer with a section M vconsisting of the zone 0 a paraboloid whose axis m-m is inclined for wardly and having a focal point m. The lower margin of thiszone mergesy with a semi paraboloid segment N having an axis n-fa also inclined downwardly' but not so much as m-m, and having a focal point n. The portion yO of the reflector which lies above the lamp axis and forward of the segment A is made of a paraboloid segment whose axis is inclined downwardly as shown at 0 0 and whose margins merge with the margins of adjacent sections. This inclination is so chosen as to divert downwardly any glare-producing rays produced by the extremities of the light source. While I- do not restrict myself thereto the arrangement I prefer and advocate is that wherein all the focal points f, m', a', o are located in a single vertical line as shown.

It will be understood that my invention can be employed without employing segments that are, in all res ects and at all places true paraboloids. n exact paraboloid is at best not easy'to make, and the joining of two paraboloid segments together is sometimes attended with various minor irregularities caused by the workmans attempt to justify the joints,or even to dress the dies, which in time become slightly misshapen. Nearly all the paraboloids here described can be fitted together lwith theoretical accuracy` and all can be joined within practical limits; but if by choice, chance, or poor workmanship the segments vary more or less from the true geometrical terms herein employed to define them, I still assert that the same fall within the purview of my inventive idea.

ln all the devices here shown it will be noted that all the paraboloid portions forward of the parameter of the portion A are inclined so as to fall beneath the imaginary surface of revolution produced by extending such portion A. In Figs. 2 and 3 this is effected by inclining the single axis e-e; in Figs. 4 and 5 this is effected by inclining the axis of the portion K while increasing the size of the portion J in Figs. 6 and 7 this is effected by inclining the axes of the portions M. N and O. I do not, therefore,

limit myself to any one mode of securing the relative inclination herein described, no1' do I restrict myself in any wise except as specifically recited in those claims, since many changes can be made in these minor details within the scope of my invention.

Having described my invention what I claim,is:-l

1. A one piece, sheet metal refiector for headlights, comprising, in combination a semi-paraboloid heel portion terminating substantially at its parameter, the portion of ythe reiector on the opposite side of the axis being located outside the imaginary surface denedby said first portion and the remaining portion of the reiiector which lies upon the'same side of the axis being located in- 5 side such imaginary surface. i

. 2. Av one p1ece,.sheet metal, reflector for rheadlights, comprising, in combination, a semi-,paraboloid heel lportion lWhich-terminates substantially at its own parameter, 10 and a plurality of additional paraboloid porL tions merging with vthe margins thereof, and all having their axes deflected to one side of the axis of saidfrst portion.

l 3. A one piece, sheet metal refiector for signature.

headlights, -comprising, in combination, a l5 semi-paraboloi-d heel portion which terminates substantially at i'tsown parameter andy a' plurality .ofadditional paraboloi portionsmerg'ing with the margins thereof, said additional portions having 4their axes l20 deected to one side ofthe axis ofsaid first portion, andthe focal pointsof all of said portions being 'arranged in a straight line which is transverse to the general axis of the reflector. y

In testimony whereof,I hereunto aiiix my WILLIAM H. Woon'.

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