US1792848A - Reflector - Google Patents

Description

Feb. 17, 193

2 Shee'cs--Sheet l Filed sept. :5, 1927 fluor/swap Feb. 1K7, 1931,

J. H. LITTLE ET AL REFLEcToR ,Filed sept. s, 1927 2 Sheets-Sheet 2 Patented Feb. 17, 1931 UNITED'STATES PATENT OFFICEv JoHN H. LITTLE, or HIGHLAND rAItH, AND JOHN H. H'NT, or DETROIT, M'IoHIGAN, j i AssIGNons To GENERAL MoTons RDSHAHCH coRPonATIoN, or, DETROIT, MICHL' GAN, A conr'oRATIoN or DELAWARE REFLECTOR i .Application inea september 3,V 1927. `serial-1ro. 217,388,

This invention relates to reflectors 4and moreparticularly thosefor use in al headlight of thetype ordinarily used on an automotive vehicle. Y

The broad problem involved in construct-y ing a satisfactory headlight is that of providing a light which will adequatelyilluminate the roadway nearby and for a considerable distance ahead, but will not-appear glaring to the driver of an approaching car, and will illuminate the immediate foreground to a desirable extent. To conform to these requirements, the uppermost rays of the beam should. be substantially parallel with the surface of the road and the beam spread sufficient to illuminate the road at the desired distance aheadof the car. Owing to the factthat the car is moving over a more or less rough road and that cars :rnayhavel the loadvon the front and rear springs apportioned differently, it has up to the present proved impossible to design a reflector which, when used with a single filament bulb, will produce a VbeamV which adequately illuminates the roadway and does not at any time appear glaring to the driver of an approaching car..

It was as a partial solution to this problem that the two filament headlight bulb vwas evolved. This type of bulb hastwo independ-V ently energizable spaced filaments'. The Vsurface of the reflector is so shaped and the two filaments are so arranged and spaced that when one filament is energized, the beam -will be high enough so that the roadway/will be illuminated a considerable distance ahead for rapid travel whilea shifttothe other fila-V Y The twofilament. bulb has lbeen'used with ltwo kinds of reflectors, the plain and-theV flutedreflector. The plain reflector used is usually of a-substantially paraboloidal; el! lipsoidal or hyperboloidal .configuration orA a modificationof onel of these surfaces of rev'-V olution. In order to secure the desired-lateral dispersionof the beamfrom aplainreflector, Ait is necessary to use a lens with vertical corrugations. The fluted reflector renders'a vertically corrugated lens unnecessary,` a plain lens being sufficient.` The flutedtype of re- Y flector comprises segmentsof surfaces ofirevolution placed side by side.

In any of the two filament-headlights, the f upper and lower ,portions ofthe reflectorad Y jacent andahead of the parameterproduoe a beam which is very little affectedby a change from one filament to another.V As therupper line ofthe light pattern must be moved by a change from one filament to another, these portions of therefiector are bent downward about two degrees so that they always reflect into the lower partof the light pattern.

In the normaloperation of either the plain or the fiuted reflector` with the .double lilafnient bulb, the filament which gives the high light pattern is used for fast driving. When another car is approaching, the operator shifts to the. other filament and lowers the beam until the other car is past, then shifts back to the first filament. y V l In order to make thefmost effectiveuseof the lightavailable, that portion of the vbeam extending aconsiderable distance ahead of the car should be concentrated on the road, and the'pattern should be slightly higher in the center than on the sides while suflicient light should always be directed to thesides and intervening foreground to Vavoid any eX- treme differences in intensityover theentire fieldof illuminationfWith such a distribution' of light the eyeof the driver does not need to dilate and contract the pupilto have proper Vision for different'places or distances within the illuminated area.

for use with a two-,filament bulb which will vary the normal figure of the usual light pattern'byreflecting a small portion of the light to one side of the pattern or above the usual cutoff. vIt is a'furtherobject'- of the invention'to provide a reflector for use witha two filament :bulb which provides ajlight pattern of lthe desired shape, intensity and position,

which will not appear glaring to the-driver of an approaching car, and inwhich a change from the raised beamte the lowered Vbeam is instantly obvious tothe oncoming driver.

,. Other objects.ofthe invention will appear With this situation in mind, it islan object of thepresent invention to provide a reflector fill in the course of the following description, taken in connection with the accompanying drawings and appended claims.

In the drawings:

Figure lis a front View of a plain parabolic reflector embodying our invention, the lower portion being cut away.

Figures 2 and 4 are vertical longitudinal sections of the reflector, illustrating diagrammatically the direction of the'ligiht rays when the lower and upper filaments respectively are energized.

Figures 3 and illustrate the shape and location of the main light pattern secured by use of the lower and upper filaments respectively.

Figures 6 and 7 are vertical longitudinal sections of a modified form of reflector.

Figure 8 is a front view of a Huted reflector embodying our invention.

Figures 9 land 10 are vertical 'longitudinal sections of a fluted reflector embodying our invention.

Referring to Figures 1, 2 and 4 of the drawings, the numeral 10 indicates a plain substantially parabolic reflector having mounted in the center thereof :the light bulb 12 carrying upper and lower separately energizable filaments. In order to secure the desired lateral dispersion of the light rays we provide a. suitably designed lens 14. At points adjacent the light bulb we provide the modified reflecting areas 16. These small areas are modifications or variations in the normal contour of the reflector. @ne embodiment of our invention consists in giving the reflector the appearance of having been bumped in with a itool from the rear side. Owing to the fact that the distance from the filament to the inner surface of the reflector is very short compared to the distance from the reflector to the object illuminated, and that the angle of incidence equals the angle of reflection, it 'is apparent that a slight modification of the normal contour of the reflector' has a marked effect on the direction in which the light is reflected from that point. For illustrative purposes we have magnified the modified parts of the reflector.

Referring to Figures 2 and 4, the plain lines indicate the direction of the light rays from the regular sections of the reflector. The dotted lines indicate thedirection of the light rays from the modified portions. The upper portions of the modified'areas reflect the light slightly upward so that they strike the portion 18 inthe light pattern, it being understood that the upper limit of the light pattern has heretofore been a substantially straight line. When the upper filament is energized, the light rays change to a very slightly downward inclination. It must, of course, be obvious that while the filament is theoretically a point, it actually has dimensions. In view of this and the fact that the modified areas must necessarily have a somewhat curved surface, it is impossible to indiate with any accuracy the direction in which light is reflected from each minute unit of area on the reflector. that with the lower filament energized as in Figure 2, the greater part of the light striking the upper half of the modified area will be reflected slightly upward above the main body of the pattern and that when the upper filament is energized, the greaterpart of this Vupwardly reflected light is reflected downward. The numeral 20 indicates that part of the npper ,and lower portions (the latter not shown) of the reflector ahead of the parameter which are inclined slightly downward.

he modified areas may be in any'part of the reflector except these. As there may be any reasonable number of these modified areas from one upand as `they may be at any angle and at Vany place on the reflector except the portions 20, it is obvious that part of the light may be reflected to increase the intensity in any part of the pattern or to one side of or above or below the pattern.

rl'he rays striking the lower portion of the modified areas from either filament are reflected downward and merge with the less intense lower portion of the pattern.

In Figures 6 and 7 we have illustrated a modified form of' our invention in which the reflector is bent outward instead of inward. The effect is the saine as in the preceding views except that now it is the lower half oithe modified area 16 that reflects the rays upward above the main body of the pattern and it is the upper half which reflects the rays into the less intense lower portion of the pattern.

In Figures S, 9 and 10, we have illustrated our invention applied to a fluted reflector which is used with a plain lens. Since the surface is fluted, the shape of the modified area may be slightlydifferent from the shape of the modification in a plain parabolic reflector but its operation will be exactly the same.

The effect of a small portion of the light thus reflected is greater than will be at first realized. A beam of considerable intensity is required to light the roadway a considerable distance ahead of the car as the light rays strike the surface of the road at a very acute angle. An object above the surface of the road, however, such as a pedestrian or an obstaclev in or to one side of the road, is illuminated by rays striking it directly, and a beam of comparatively small intensity is sufficient to render it readily visible.

Vif e have thus provided a reflector which may be used to deflect a desired portion of the light to any desired part of or to any side of the usual light pattern. One or more modified areas may be used to reflect light upward or to one side only .of the car.

The effect of our reflector on the approach- It is sufficient to state ing motorist is striking. When the beam from the lower lament is used, the topportion of the beam is ordinarily a short distance below the eyes of the approaching'driver. The modified areas reflect a small portion of the light directly into the eyes'of the ap-l proaching driver. This reflected portion is quite noticeable butso little of the light is thus reflected that no noticeable glare is produced. In factA ones .vision remains unimpaired while gazing at such alight from such a position. f Vhen the upper filament is energized the light pattern is reiected downward as described and the light from the modified areas no longer strikes the eyes of the approaching driver. The change from the lower to the upper filament is quite marked and is instantly obvious to the driver of the approaching ear. By the usevof our invention, the advantages of `the best reflectors are retained while the light patternV may be varied at will to suit the anticipated uses and requirements ofsuch a headlight.

We claim:

l. A reflector having a central zone lying rearward of its focal plane and an outer zone lying forward ofthe focal plane, said central Zone being formed to project a main beam of light from its focus substantially straight ahead and said central Zone: being pro-vided with a plurality of light diusing means of relatively small area for projecting light of low intensity above the Vtop of the main beam, the outer Zone being free from said diffusing means.

2. A reflector having a Zone lying rearward of its focal plane and constructed to project light emanating from the focus of Vthe reector in the form of a forwardly directed main beam, said zone being provided with light reflecting means of relatively small area for projecting light emanating from said Vfocus above said main beam; and said means being conlgurated so that light projected therefrom, when emanating from a source slightly above the focus of the reiiector, will be directed below the top position of Vsaid main beam emanating from the focus of the reiector.

In testimony whereof I aix my signature. i

JOI-IN VH. LITTLE.

In testimony whereof I aiix my signature. 'i

JOI-IN I-I. HUNT.

Images