US2647203A - Light reflector - Google Patents

Description

July 28, 1953 H. E. SMITH 2. 4 303 LIGHT REFLECTOR Filed Aug. 2, 1950 5 Sheets-Sheet J.

INVENTORY i a {Mzow E. JM/I'H July 28, 1953 H. E. SMITH L IGHT REFLECTOR 5 Shets-Sheet 2 Filed Aug. 2, 1950 #42040 E. SMITH BY 7/r @M% A TTOR/VEY y 1953 H. E. SMITH 3,647,203

LIGHT REFLECTOR Filed Aug. 2, 1950 3-Shaets-Sheet 3 INVENTOR'. I HAEQLD E. SM/TH A 7702MB Patented July 28, 1953 LIGHT REFLECTOR Harold Smith,x1aykens, Ea.

Application August 2, 1950., IS erialNo; 17?,173

trixplaneanda series of generating ellipses. The

generating ellipses are normal to the directrix pi nennd diminish insize as thcymove away f One verth maior axis ofthe directrix ellipse.

tex offithe generating ellipse. is leaned in the di- .rectrixellipse andtheremote focus of the generatrix .isglocusedlon acurvedline =(Patent. Number.1.9 13,5l8) or va straightline (application Serial Number'169,869)

IptheiQImerinstance the reflected lightrays allpass'thrcugh, the curved. line locus. Conseguently the ultimate reflector and baffle plate .tl'imn1ing..,e.d e.used with .the reflector must: also "be curred tocorrespondtherewith or alossof andlultimate reflector. requires more critical ad- 'iustmentt prevent light from leaving the ultinmate reflector. and headlamp in upward}. direc- 'tiona. .Inthe. la ter nstance allofthe light rays from he r flector focalpoint are notreflected through the--v straight line locus but some pass sliahtlytoonehside or theother thereof. When .thisrefleotor iscombined with an ultimate cylindrical lparabolic reflector as described, the rays not passing.- through the remote focal line are reilected downwardly: by the ultimate reflector or trimmed :by thehaifle and represent a reduction in intensity. of the. horizontally projected portion of the projector. beam-- ltiisaageneral object of, this invention to provideianimproyed,ovoidal reflector which overcomes the disadvantages of known reflectorsas .ontlinedabovet A more, particular; object of the invention ,lies n memo-Vision ofan ovoidal reflector. having elliptical ,directricesand capable. of reflecting. all "light fron aufocal pointin converging directions :through alstraightline remote focus.

Another objectlies in the provision, of an ovoidal reflector having an. e1lipti caldirectrix and "an'elliptical generating ellipse of varying size such "the-tall 'light'from a focal point will'ihe converged "through afocal llne'thereby enabling more efficient concentratlon ofilight into a beam of parr ars=iahen theef ect rs combined Withan Y 18 Claims. (01. 24041.1)

ultimate parabolic reflector "having a focal i'line, and reducing the loss of light When-combined with a'bafile having a straight line light trimming e'dge.

Still another object of the invention lles in the v provision of an ovoidal reflector capable of reflecting all .light from a point sourcethrough a straight line. remote focus in converging directions, Whose angle oftconvergencemaybewarled by selection-of proper elliptical-directrices "so that the lateral divergencejof the reflected light lieam may be controlled.

A further object of 'the; invention lies" in the provision of a reflector capable of reflecting light from a source at itsfocal point through a remote focal straightlinewhich' is obliquely angled with respect to the. primary; axis of therefl-ector-sothat the lateral or horizontal direction-ofalight-beam reflected therefrom"may, be "controlledby selection of an appropriate oblique angle-forsaidremote focal line.

A still furtherpbj ectofrtheinventio-n lies inthe provision of a. reflector having 'ajproxiniate focal point and a remotefocalstraightlinetand'adapted to reflect all focal raysj'fro-m' saidipoint through said focal straight .line, the "directionfofthe reflected .beambeing controllable by. selection'of" an appropriate angle for the focallline with respect to the primary axis o-fthe reflector; and the spread ofthe reflected beam rbeing. controllable .by the selection. of an appropriately sized conic section curve as a directrix in the plane which. includes thejfocaljline.

Iachieve these. objects andsuch other additional objects,;features and advantages asnnay hereinafter appear or be pointed out, in the'manner illustrated by several embodiments shown in the appended drawings, wherein:

Figure l isa frontelevationof a reflector in acoorclance with the invention.-

Figure 2 is a cross-section taken along lined-2 of Fig. 1.

Figure 3. is aperspectiveview of'the reflector.

figures. is a diagrammatic front elevation illustrating the paths of. rays reflected, irrtheplaneof the rear boundary *edgesmf thereflector;

Figured is a diagrammatic-viewshowing-the paths of rays'reflectcd in the plane corresponding to that-of-Fig. 2 and'normal to the plane depicted in Fig. 4.

Figure 6 is a diagrammatic central section of a headlamp; including the reflector of'the invention disposed substantially horizontally andillustratlng one typical application thereof.

Figure '7 is a diagrammatic top plan'view-of the headlamp of Fig; 6.

' Figure-Elisaview similarto' l igurefi of andistance I-3I6.

ellipses II, I5 and 20 is generated by an infinite other headlamp in which the reflector is vertically disposed and illustrating another and preferred mode of use.

Figure 9 is a diagrammatic top plan view of the headlamp of Fig. 8.

Figure 10 is a diagram illustrating a mode of generating the reflector surface and represents the directrix ellipse in the central bisecting plane of the reflector-corresponding to Fig. 2 with portions of the directrix ellipses which fall in a plane normal to the first named plane rotated into said plane for illustrative purpose.

Figures 11 and 12 are views of the reflector respectively similar to those of Figs. 1 and 3 and showing certain of the surface generating ellipses.

Figure 13 is a front elevation similar to Fig. 11 of a modified reflector utilizing surface generating parabolas.

Figure 14 is a diagram illustrating preliminary steps in another method of generating the reflector surface.

Figure 15 is a diagram illustrating additional preliminary steps in generating the reflector surface.

ovoidal in shape and having a central bisecting section which is an ellipse II whose foci are located at I2 and I3. The rear boundary edges of the reflector as viewed in Fig. 1 are also ellipses identified as I5 and 28 which fall in a plane including the points I2 and I3 and normal to the bisecting plane of ellipse I I.

Referring to Figs. 10 to 12, where is shown the method of generating the reflector warped surface connecting ellipses II, I5 and 20, it will be noted in Fig. 10 that the curves I 5 and have been rotated into the plane of ellipse II for purpose of clarifying the mode of fabrication. In forming the surface, a directrix ellipse I I with foci I2 and I3 is selected. Directrix ellipse I5 is then chosen in a plane including points I2 and I3 but at right angle to the plane of ellipse I I. A common point I2 is used as a focus for both ellipses II and I5, the second focus I6 of ellipse I5 being selected in such manner as to produce the desiredlateral convergence of the reflected light. An ordinate for ellipse I5 is then drawn through I3 at right .angle to line I 2--I3.

This ordinate intersects ellipse I5 at points I! and I8, one half of this ordinate being shown in Fig. 10 at line I3-I8.

Av second directrix ellipse 20 is then drawn in the plane of ellipse I5, passing through end points II,

I8 of the ordinate and having its vertex coincident with the vertex of ellipse Il. The points I2 and 2i are the foci of ellipse 2|] and point 2| will generally fall on the same side of ordinate II, I8 as point I2 at a distance from point I3 equal to Now the surface connecting series of ellipses of varying size, certain of which are indicated by the numerals 3| through 41. Each of these ellipses lie in planes making successively larger angles with the plane of ellipse I5, which in Fig. 10 is represented by line, ZI, I2,

to the primary axis of the directrix ellipse.

I3 and I6. Each ellipse has its vertex lying on ellipse II and passes through points I! and I8. In effect, therefore, the reflector surface is generated by rotation of an ellipse of varying size about axis I'II8, the vertex of the generating ellipse being locused on directrix I I, the generating ellipse retaining a common ordinate on the axis and defined by end points ll and I 8, and the foci of the generating ellipse drawing closer together as the ellipse is rotated being locused on curves 50 and BI and moving in the direction of the arrows in Fig. 10. For example, the foci of ellipse 32 would fall at points 52 and 53 While the foci of ellipse 43 would fall at points 5 3 and '55.

When formed in the described manner, reflector l0 will reflect all light rays from focal point I2 through ordinate line III8 by reason of the directrix ellipse II warping the surface in one dimension. This action is diagrammatically illustrated in Fig. 5 for the light rays in the plane of ellipse II. Rays striking portions of surface Ill displaced laterally from ellipse I I are reflected along the planes of the generating ellipses which pass through the points of impingement and include the ordinate I'I--I8. Hence these raysalso pass through ordinate I l-I8. Laterally, all rays from focal point I2 are converged toward circular arc 5I of Fig. 10 and such rays in the plane of the directrix ellipses are illustrated in Fig. 4 as being converged toward foci I 6 and 2I. Rays striking the surface I0 outside of this plane are reflected toward the arc 5| which includes the traveling foci such as I6, 53, 55 and El except in that a slight reduction in convergence of light rays is obtained due to the displacement of the second foci along path 50. It is therefore apparent that the reflector though formed with elliptical directrices in two dimensions nevertheless provides a straight line as a remotefocal line.

It will be apparent from the above that the reflector surface may be considered as generated by the revolution about a, fixed axis defined by end points I! and I8 of a conic section curve, varying in size as it revolves and having a directrix ellipse in a bisecting plane normal to the axis as the locus of the vertex of the generating curve, the generatrix curve retaining the axis with its end points as a common ordinate. Conic section curves other than ellipses may be utilized as the varying generatrix. One example is illustrated in Fig. 13 wherein the reflector surface I0 is formed by the revolution of a varying parabola 'IIl'II which at intermediate stages of revolution is shown as parabolas in different planes and of differing size referenced 32, 34, 36, etc., corresponding to the generating ellipses of similar number shown in Figures 10-12. Reflector surfaces 50 formed by rotation of conic section curves other than ellipses will modify the obtained lateral spread of the reflected beam but still reflect all focal rays through the commo ordinate II'-I8'.

Referring now to Figures 14-16, there is shown another method of forming the improved reflector, the illustration being directed to a reflector having a remote focal line which is oblique A directrix ellipse I5 is selected having foci I2 and I6. A remote focal line II'I8 is then drawn in the directrix plane at any desired angle to the primary axis I2I6' and intersecting the latter at I3. For each focal ray 1', fromio'cal point I2, an ellipsoid is drawn having fociat I? and 15 (Fig. 14) and which is tangent to the plane "with the ellipsoid) illreetrir *l5 at =as -interseetioa it With-line lfi' -"i The ellipsoid thus reamed is shovva in I}! scan e11ips'e s! representing the intersectiei-i bf the "ellipsoid with; the agreemeplane"; A plurality-ersegmeatser these ellipsoios'are iii-"Fig; "l5 *rererenced 80 through 90, and these "degiliefitseirt'eiid fronl the point at *tangeney of the ellipsoid with t'liedirectrix ellipse to the tefsetion T1 with line I6 l5, lfi'ior each ellipsdid. Ease ellipsoid is intersected by a plane vertical totlle directrix plane and ineludingthe dlieetrii tems It and-the intersection 15 oitlie ellipsoid airi's with the selectediocal line |1---I8'. 'l he "intersections or these vertical; converging planes with their corresponding ellipsoids are eal'll avertically positionedellipse. one of these designated 91in Fig. 14 hasbeen'rota-tedmtethe directrlx plane for clarity. These intersections or-generates ellipses when formed for an infinite series" of-ellipsoids 'comprise the reflector surface 100; which is shown 'in'perspective' in Fig..-l6 With certam oi'the' generatrix ellipses '9 I through 'Qfindidated in dottedline's. It will be observed iromthe example in Fig. 14, that the generatrix ellipses'each have a vertex 76 (the point of-ellipsoid tangency) on the directr'ix ellipseand the other vertex at IT (the intersection of the vertioal One focal point is located-at wane intersection of the ray with the 'seleeted -focal line and theother focal point "'isspaced inwardly from the directrix ellipse "a distance equal to the distance from focus 15*130 "vertexll. The lower boundary 29 oi reflector flfl lying in tlie'dlrectrix plane includes all of the vertices =11.

It is apparent that eachof the ellipsoids 80=90 would direct all reflected rays from focal point iii toits respective axis intersection with line l'l'l8' as shown at 15 in Fig. 14. The vertical sectionsof the ellipsoids --9l- 99 must therefor alsddirect all reflected rays to this line; Since the reflector 18-0 is formed of an infinite number dfi such'sectionsit will necessarilyreflect allrays received; from focus l2 through remote focal 'linedl lfi in directions converging toward 46'.

It "will be observed. irom the above that-reflector surface Hi will-be identical with reflector surface l0 oi'Figs. 1, zand l2 if -l5'- is-seleete'd equal in size to and remote'focal line I1'--l8' is selected at right angles to the primary-axis r intersecting the letter at point it even-though generatedin a diiierent manner.

To illustrate the application at my improved reflector, reference will be made to Figs. 6-to- 9 wherein such reflectors are shown diagrammatically as combined with a cylindrical parabolic reflector and a baiiie plate having a light trim- 1 1mg. edge. In Figs. 6 and 7 the reflectorl0 issubs'tantially horizontally disposed, making only a-small angle-therewith, and its focal line ti -l8 coincides with the'straight focalli ne of cylindrical parabolic reflector 66-. It isalso desirable to utilize a baflle plate GI having a light trimming edge substantially coincident with line l'l -l sso to prevent any rays from striking v the ultimate --refleetor from a position in: front of its focal line and thereby eliminate upwardly directed-reflections therefrom.- This application of--the reflector is similar to that-describedin datent Number 1313,5133; referred to above; but provides the advantages of concentrating more attire-light from the source; in thebeai-ri of parallel rays emerging from the headlampbecause otthe straight fecal: nee obtain-ed wi tll' refflcctor Mb The reflector also redizutes the light llifiSS- 'dfl to trimming i-byrthebafile plate edges, and runner is advantageous in simplifying the "structure "of the ultimate reflector andheadlamp thereby reducingcost of fabrication Figsxa and 9 'il-lustrate a mode'of utiliz'ingthe improved reflector disposed verticallyand paired similar .to the use disclosed inmy 'cepending'. ap-

plication Ser. No. 169,869, referred to above; In sueh'application one of the tworefleetors is plieferably-cu t oil in the horizontal "level of its remote iocal line which coincides 'with'generating ellipse '39 of Fig: 10 and it is at this level that itmeets the parabolic, cylindrical reflector 62. -The=other reflect-tor 1-0 is '"cut oil at-a higher level where it disconnected to or merged with baffle plate63 whieh has a' straigl'l't-iline light trimming edge substantially coineident with the 'focal lines of bdth' ovoidal reflectors and-the ultimat'e reflector "6-2; in this application reflectors it provide better control of the lateral divergence-of the filial light beam bythe use-of elliptical directricesand at-the same time increase the beam-intensity and headlamp efficiency by concentrating the reflect'ed'light fr'omtheovoids into a straight line.

Fig. 17 illustrates a mode of utilizing aplurality of reflectors disposed vertically and paired i'n amannersimilar to that disclosed in my copending application Ser. No. 169,869. Here a pair-of reflectors le'lone notshown') back to back; are

located centrally of acomposite projector having It will be re--'eflected' bythe= ultimate reflector and projected in a'forward direction. Thebea-ins reflected by the outside reflectors l M are angled toward the center and "will be r'e reflected by the ultimate reflector laterally. so as to cross the center reflector beam.

in actual head-light :practice the angle selected for the remote focal line will be in th'e'order of 2-3 degrees from normal to the primary axis rather than the larger angle illustrated for clarity; Asmallangle will cross the beams at approximately 30D-400-feet in fronto'f thehe'adlamp:

It will be'observecl that 'theseleetion of suitable elliptical directrices in my improved reflector provides control of horizontalbr lateralab'eam divergence, while selection of a'remotefocal line suitably'an-gled with respeetto the primary axis oi thereflectorprovidescontrol of the direction of-beam emission.- The existence of bothtypes of control in one reflector: provides great'fiexibi-lit-y-of design and use i n will be apparent iiiipr ovedreflector maybe used difieren angular dispositions thantliose illustrated andin ccm'unctionwith etlisrreflectcrs tna-n 'tlieseshcwn. it is in "fact useful whenever-leis seared to eo-llect'lightfrom assume and converge it through a straight focal line. various'amdirlcations in form and detail Will siiggst tllemselvs to those skilled in the are without necessarily'departing' from the spirit andine seeped? the appendedclaims;

Having thus described my'inveiitior'i, that I new and desire te-securety Letters face having a" proximate focus-which is a point and a remote focus which is a straight line, said -surface being composed of an infinite series of common ordinate coinciding with said focal line, -a third directrix ellipse having one focus on said focal line and the other focus coinciding with the point focus of the surface, said third ellipse lying in a plane at right angles to said directrix plane, said ovoidal surface being formed to include the three directrix ellipses by a series of ellipses of varying size each lying in planes swung about said focal line so as to make successively larger angles with said directrix plane and each ellipse having a vertex lying in said third directrix ellipse and a common ordinate coinciding with the common ordinate of said pair of elliptical directrices.

3. A light reflector comprising, an ovoidal surface, having a directrix ellipse lying'in a directrix plane, said directrix ellipse having a proximate focus coincident with that of the reflector and a primary axis, said surface being formed by a series of generating ellipses which are intersections of planes, vertical to said directrix plane and converging to the remote focus of said directrix ellipse, with a series of ellipsoids all havin a common focus coincident with the proximate focus of the directrix ellipse and remote foci lying on a straight line in the directrix plane oblique to the directrix primary axis, said ellipsoids being each tangent to the directrix ellipse at the intersection of the vertical plane which includes its remote focus with the directrix ellipse, whereby the ovoidal surface is characterized by a proximate focal point coincident with that of the directrix ellipse and a remote focal line coincident With the said straight line oblique to the primary axis of the directrix ellipse.

4. A light reflector comprising an ovoidal surface curved in two dimensions so as to provide a proximate focal point and a remote focal straight line, said surface being characterized by an elliptical directrix in a directrix plane and having a proximate focus coincident with the focal point of the reflector surface, a remote focus and a primary axis connecting the directrix -,foci, a directrix straight line intersecting said primary axis, a series of ellipsoids all having proximate foci coincident with the proximate focus of the directrix ellipse and remote foci lying in said directrix straight line, said ellipsoids being tangent to said directrix ellipse, said sur- -face being generated by a series of varying ellipses said surface generating ellipses being intersections with said ellipsoids of a series of 1 planes vertical to said directrix plane, all including the remote focus of the directrix ellipse, and each intersecting the directrix ellipse at the point of tangency of its correspondin ellipsoid.

5. A light reflector as set forth in claim 4 wherein said straight line directrix is inclined at an oblique angle to said primary axis of the elliptical directrix.

6. A light reflector comprising an ovoidal surface having a proximate focal point and a remote focal straight line spaced apart in a directrix,

plane, an elliptical directrix in said plane having a focus coincident with said proximate focal point and a remote focal point lying on a primary axis, said ovoidal surface being formed to include a series of generatin ellipses of varyingsize, each lying in a plane vertical to the directrix plane and converging toward the remote focus of the directrix ellipse, said generating ellipse each having a vertex lying in the directrix ellipse and a remote focus lying in the said remote focal straight line, the proximate focus of each generating ellipse falling within the directrix ellipse and in the directrix plane a distance equal to the distance between its remote focus and its remote apex.

7. A light reflector as set forth in claim 6 wherein said remote focal straight line lies in said directrix plane inclined at an oblique angle to said primary axis of the elliptical directrix.

8. A light reflector comprising an ovoidal surface having a proximate focal point, a selectively angled remote straight line focus, and a selected directrix, all in the directrix plane, said ovoidal surface being generated by a series of ellipses in planes perpendicular to said directrix plane and said'perpendicular planes extending along the paths of focal rays of the directrix.

9. A light reflector comprising an ovoidal surface having a proximate focal point, a selectively angled remote straight line focus, and a selected directrix, all in the directrix plane, said ovoidal surface being generated by a series of ellipses in planes perpendicular to said directrix plane and said perpendicular plane extending along the paths of focal rays of the directrix, said generating ellipses each having its proximate apex located in the directrix and its remote focus located in said selectively angled remote straight focal line.

10. A light reflector comprising an ovoidal surface having a proximate focal point, a selectively angled remote straight line focus, and a selected directrix, all in the directrix plane, said ovoidal surface being generated by a series of ellipses in planes perpendicular to said directrix plane and said perpendicular planes extending along the paths of focal rays of the directrix, said generating ellipses each having its proximate apex located in the directrix and its remote focus located in said selectively angled remote straight focal line, the proximate focus of each generating ellipse being located Within the directrix by a distance equal to that by which its remote apex extends beyond said selectively angled straight remote focal line in the plane of the directrix and on the major axis of the generating ellipse.

11. In combination, a parabolic cylindrical reflector having a straight focal line, and an ovoidal reflector having a proximate focal point, a selectively angled remote straight line focus which coincides with the focal line of the parabolic reflector, and a selected directrix, all in the directrix plane, said ovoidal reflector being generated by a series of ellipses in planes perpendicular to said directrix plane, and said perpendicular planes extending along the paths of focal rays of the directrix. I

12. The structure of claim 11, said generatin ellipses each having its proximate apex located in the directrix and its remote focus located in said selectively angled remote straight line focus. 13. The structure of claim 12, the proximate focus of each generating ellipse being located within the directrix by a distance equal to that by which its remote apex extends beyond" said selectively angled remote straight line focus in the plane of the directrix and on the major axis of the generating ellipse.

14. A light reflector comprising a warped surface having a proximate focal point and a remote focal straight line spaced apart in a directrix plane, a conic section curve as a directrix in said plane having a focus coincident with said proximate focal point, said warped surface being formed to include a series of generating ellipses of varying size, each lying in a plane perpendicular to the directrix plane and extending along the path of a focal ray of the directrix, said generating ellipses each being a vertical section of an ellipsoid by its associated perpendicular plane through its remote focus, said ellipsoid having a point in its surface which is coincident with the directrix at the point of intersection of the directrix with said associated perpendicular plane, said ellipsoid having its proximate focus coinciding with said focal point and its remote focus coinciding with the point of intersection of said remote straight focal line with said associated perpendicular plane.

15. The structure of claim 14, and wherein the remote apex of each generating ellipse is located beyond the said remote straight focal line and in the directrix plane at the point of intersection of said ellipsoid and the major axis of said generating ellipse.

16. The structure of claim 14, and wherein the remote apices of the series of generating ellipses form the rear boundary edge, in the plane of the directrix, of said reflector.

17. A light reflector comprising a warped surface having a proximate focal point and a remote focal straight line spaced apart in a directrix plane, a conic section curve as a directrix in said plane having a focus coincident with said proximate focal point and a principal axis, said warped surface being formed to include a series of generating ellipses of varying size, each lying in a plane vertical to the directrix plane, said generatin ellipse each having a vertex lying in the directrix curve and a remote focus lying in said remote focal line, the proximate focus of each generating ellipse falling within the directrix curve and in the directrix plane a distance equal to the distance between its remote focus and its remote apex, and wherein said remote focal straight line lies in said directrix plane inclined at an oblique angle to said principal axis of the directrix curve.

18. A light reflector comprising a warped surface having a proximate focal point and a remote focal straight line spaced apart in a directrix plane, a conic curve section as a directrix in said plane having a focus coincident with said proximate focal point and a principal axis, said warped surface being formed to include a series of gen erating ellipses of varying size, each lying in a plane vertical to the directrix plane, said generating ellipses each having a vertex lying in the directrix curve and a remote focus lying in said remote focal line, the proximate focus of each generating ellipse falling within the directrix curve and in the directrix plane a distance equal to the distance between its remote focus and its remote apex, and wherein said generating ellipses all converge to include a common point in said directrix plane.

HAROLD E. SMITH.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,819,725 Wood Aug. 18,1931 1,913,519 Smith et al. June 13, 1933 2,516,377 Fink July 25, 1950 2,592,075 Smith Apr. 8, 1952

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