US1389291A

US1389291A - Headlamp

Info

Publication number: US1389291A
Application number: US350073A
Authority: US
Inventors: Evan P Bone
Original assignee: Individual
Current assignee: Individual
Priority date: 1920-01-08
Filing date: 1920-01-08
Publication date: 1921-08-30
Anticipated expiration: 1938-08-30

Description

E. P. BONE.

HEADLAMP.

APPLICATION FILED 1AN.8. 1-920.

Patented Aug. 30, 1921.

lizv'entor EmnBBone Attorney tion at shorter UNITED STATES PATENT OFFICE.

EVAN P. BONE, 0F CINCINNATI, OHIO.

HEAJDIAMP.

To all whom it may concern."

Be it known that I, EVAN P. BONE, a citizen of the United States, and a resident of Cincinnati, in the county of Hamilton and State of Ohio, have invented new'and useful Improvements in Headlamps, of which the following is a full, clear, and eX- act description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to headlamps, and has particular reference to such headlamps as are designed for use with motor vehicles.

The principal object of the present invention is to provide in a headlamp means whereby the projected beam may be defined within limits whereby glare in the eyes of opposing drivers or pedestrians is prevented.

A further object of the present invention, and one incidental to the principal object above mentioned, is to obtain, in connection with the elimination of objectionable glare, improved road illumination.

In order that the roadway may be satisfactorily and economically illuminated, it is desirable that substantially even illumination be made at both long and short ranges. To effect this the rays intended for illumination at long ranges must have greater density than those intended for illuminaranges. In headlamps as at present designed and generally in use, the beam of light from the lamp fringes away so gradually from the area of greatest concentration of the rays, that if substantially adequate illumination at long ranges be ob tained, the rays projected into the eyes of opposing drivers or pedestrians are of suflicientdensity to produce undesirable and dangerous glare, even when the eyesare not 4 in the portion of the beam of greatest inand to .tensity. This condition results by reason of the fact that the angle between the light rays reaching the road at long ranges, which of course, should be the rays of greatest concentration, and those reaching the eyes of opposing drivers or pedestrians is comparatively small.

In attaining the objects of the present invention, I employ in a headlamp, an image forming lens having such dimensions that there is a conjugate focal point inside the lamp for each point in the field of illumination, viz: the roadway and objects upon the side thereof. These conjugate Specification of Letters Patent.

Patented Aug. 30, 1921.

Application filed January 8, 1920. Serial No. 350,073.

focal points within the lamp cover an imaginary surface which approximates and for all practical-purposes may be spoken of i as a plane. The

illumination, therefore, of any point along the roadway and in the general field of illumination, is dependent jquantity of light emitted from view,

along the roadway is effected as desired and,

as will be seen, the illumination of the roadway at long rangesmay be intensified while at the same time the beam is sharply cut off so that glare in the eyes of approaching persons is prevented.

With the foregoing and further objects in as will more fully hereinafter appear, the present invention consists of details of construction herein fully described.

In the particular embodiment of my invention selected for illustration- Figure l is a central longitudinal section of a headlamp'constructed in accordance with this invention.

Fig. 2 is a diagrammatic view, illustratthe principle of operation of said lamp. ig. 3 is a diagrammatic view illustrating the principles of satisfactory road illumination.

Fig. 4 is a detail of the screen from the rear.

Fig. 5 is a sectional view of a modified form of screen construction.

The numeral 1 indicates the maincasing or body of the lamp constructed in accordmice with this invention. Mounted in said body is an ellipsoidal reflector 2, having. its

foci at 3 and 3 the front portion of the re thereof is approximately in the cross sec- .generally devoid of spherical aberration.

The use of the aplanatic lens permits the employment of a lens of extraordinarily wide aperture, in comparison with its focal length,'such aperture being essential 1n order to accommodate the pencil of rays di verging from the focus at a wide angle, to obviate the necessity of extreme length in the body of the lamp. The lens as used 1s also an exceptionally wide angle lens but the absence of aberration is not soessential accordance with optical laws. reflected from the forward portion. of the except at points near the center of the field.

Mounted in the lamp, in the plane 9-10, is also a screen 6. The screen 6 as illustrated in Fig. 4:, is of generally rectangular form and has an upper projection-7 at one side of the middle thereof for the purpose hereinafter set forth. The support 8 of the screen 6 is bent so that the-vertical section will be removed some distance from the focal plane 9-10. As illustrated in Fig. 5, the screen 6 may be arranged for Vertical adjustment by means of an electro-magnet 11, operated from a convenient place in the vehicle. Theforward portion of the support of the screen 6 is secured to the body 41 of the lamp by means ofa spring 12, which drawsit downwardly against the threaded pin 13. The support of the screen. 6 is pivoted at 14, and as will be seen when the electro-magnet 11' is energized the screen will be raised against the tension of the spring 12.

The lamp is provided with a socket for an electric bulb 15, the filament of which is located at the focal point3" of the reflector 2. The reflector incloses the bulb so as to collect a major portion of the rays radiating therefrom.

The principle of operation 'of the device is illustrated in the several figures of the drawings by means of typical rays indicated by broken lines. Rays from the filament of the bulb 15 striking the ellipsoidal portion of the reflector 2 are concentrated in the plane 9-10, around the point 3, the crosssectional area of the concentration being proportional to the size of the filament, in Other rays reflector pass the. focal plane 9-10 at vari ous points, the density thereof decreasing gradually away from the area of concentration at 3. The forward portion, of the reflector extends well into the front half of the lamp, causing rays to enter the lens from exceptionally wide side angles to make "possible the illumination of a correspondingly wide field. The lens 5 is, as above stated, arranged relative to the plane 910, so that said lens throws an optical image .of whatever may be located in said plane into the field of illumination'and the mapping out of the light distribution over the plane forms a plan, in miniature, of the light tration 3, in the plane 910, being of maxi:

'mum density, the projected image thereof will be more brightly illuminated, and this portion of the optical image is indicated at 17. All of the rays passing the plane 9--10 at any other one pointas for instance 18, in Fig. 2, will be projected to its conjugate focal point in the optical image, for instance the point 19 on the plane 16. The rays at the point 18, however, being of less density,

as above set forth than the rays at the point 8 in the area of concentration, said portion of the image will be of correspondingly less brilliance, as indicated in the image on the plane 16; and as aforesaid, as the density 'graduallydecreases to the edges from the point 3, the brilliance of the image gradually decreases radially from the area of greatest brilliance 17. The screen ,is located in the focal plane 9--10 of the lens 5, and the image of, said screen will therefore be projected with sharp definition into the field of illumination. as indicated at 20 on the plane 16, the downwardly projecting portion 21 to the left of the centerof illumination 17 as viewed from the lamp,being the optical image of the upper projection 7 of the screen 6.

The screen is opaque and therefore blocks out rays from the portion of the focal plane covered by it; hence the portions 2021 of the field of illumination are in. comparative darkness. It is, of course, only'by placing the screen 6 in the focal plane of the-lens 5 that sharpness of definition of the area of area may be located at theproper angle of Since however, the

elevation above the roadway at practlcable operating ranges, this angle being very small. Thus the screen forms a partial border to the concentrated area around 3, so that,

the dark area 20-21 in the image appears to partly border the bright area 17 The dark area must, however, only partly border the bright area so as not to cut off the light below 17 which is needed for close, range illumination.

From the foregoing description of the optical principle of the lamp it may be noted that two distinct means,the reflector and the screen,are used for controlling the intensity of the light emitting from the various points in the plane 9-10 to the lens.

The reflector operates with economy while the screen operates with precision and each is used where its particular feature is most needed. The reflector is economical because it functions without loss of light by interception as the rays pass the plane; and having any fixed available quantity of light radiating from the filament source, the same is collected by the reflector which by the varying angles of its surface directs said light to the various points in the plane with a concentration and distribution best suited for illumination. However, by reason of the appreciable size of the source of light, infperfections in the reflector, and deviations of the source of light from accurate location in the focus of the reflector, the concentration of the rays at any particular point as intended is indefinite, causing a blurring effeet. This effect is not necessarily obj ectionable except at certain critical locations where bright light as emitting from certain points must be prevented from closely adjacent points. Atsuch locations the screen is used and, although losing light by interception, it serves to block out the rays alongsharply defined limits with the accuracy required to illuminate the roadway at long range without projecting glaring light into the eyes.

Changesmay be made from the precise formof headlamp herein shown and described, within the scope of accompanying claims, without departing from the principles of my invention and Without sacrificing its objects and advantages. a

In order to utilize some of the intercepted light the screen 6 may have a reflecting sursold reflector 2.

face, 6 In Fig. 5 of the drawings 1 have illustrated the intercepted ra '2!) being reflected as shown by the line 30 to the ellip- In Fig. 3' I have illustrated diagrammatically the application of the present lamp to road conditions. In said figure the arc 22'23 represents the angle of the projected beam of sufficient intensity for useful illumination, and while this beam is of greatest intensity near the center, except where darkened by the screen, it is at all points within this angle of such brillianey as to cause objectionable glare. In placing the lamp 24 on the vehicle, the same is so disposed with relation thereto that the bright central portion 17 of the optical image reaches the roadway at 25 and the area of darkness 20, the

central portion 25 of the beam, the density of the rays reaching the roadway decreases from the central portion toward the vehicle. As the shorter distances require less flux density than the greater ranges to obtain equivalent illumination, this decreasing of the density from the center serves to give the roadway a nearer uniform illumination. The distribution of-the lightalong the roadway in this manner accords with the stand ards of efliciency'and economy in headlighting for the reason that the illumination at close ranges does not have to be unduly bright inorder to obtain sufiicient brightness for long range. The angular width of the close range illumination is of necessity greater than that of long ranges. The distribution of light as illustrated on plane surface 16, shows how the concentrated area 17 .is only a small percentage of the total area light at .27, within the necessarily small angle.

The dark area 21, produced by the projection 7 of the screen 6, is on the left side of the roadway as viewed'from behind the lamp and comes inalinement with the position of an approaching vehicle when the two vehicles have turned aside to pass, thus providing an additional factor of safety against glare when the car having these headlamps receives upward tilts from uneven roads or abnormal loading. The screen forming the dark area 2021 may in various shapes and sizes as is consistent with the general object of preventing glare and providing longrange-illumination during the greatest number of circumstances on .varied road conditions. -Inasmuch asthe positions of theeyes of opposing drivers are, in general, above and to the left of the surface of the roadway, the darkened area is correspondingly disposed, in general, above and to the left of the central portion of the beam. Whether it isentirely above, entirely tothe side, or both, and of whatever size'andproportions is a matter of design or specified requirements. It will be understood that the geometrical-relations of the size and shape of the dark areal20-21 to" the illuminated areas 17," etc., are similar'to those of the however, be designed p screen 67 to the concentrated light in the plane 9-10 in accordance with well known laws of optics.

The means provided in this invention for projecting areal optical image do not necessarily have to be of a structure permitting the degree of refinement required in devices generally used for projecting images upona screen to form pictures.

By means of the; adjusting mechanism points inside the body of said lamp conju=, w gate with a field of desired illumination,

means for concentrating rays from said source of light at a point'in the focus of said lens inside the lamp, and means for distributing rays from said source .in gradually decreasing density radially from said point of concentration over 1 the focal plane of said lens inside the lamp.

2. In a headlamp in combination with they casing and a source of light, a. projecting lens mounted 1n sa1d casing, having focal points inside the body of said lamp conjugate with a field of desired illumination, an ellipsoid reflector for concentrating rays from said source of light at a point in the focus of said lens inside the lamp, and a reflector for distributing rays from said source in gradually decreasing density radially from said point of concentration over the. focal plane of said lens inside the lamp.

3. In a headlamp in combination with the casing and a source of light, a projectin lens mounted in said casing, havlng focal points inside the body of said lamp con ugate with a field of desired illumination,

means for concentrating rays from said source of light at a point in the focus of said lens inside-the amp, means for,d1s-

tributing rays from said source in gradu-' ally decreasing density radially from said point of concentration over the focal *plane of said lens inside the lamp, and means for intercepting a portion of said rays. 1 Y

- 4. In a headlamp in combination with the casing and a source of light, a projecting lens mounted in said casing, having focal points inside -the body 'of said lamp conjugate ,with a field of desired illumination, an ellipsoid reflector for concentrating rays from said source of light at a point in the focus of said lens inside the lamp, a reflector the focal plane of said lens for interceptmeans for concentrating raysfrom said for distributing rays from said source in gradually decreasing density radially from said point of concentration over the focal plane of said lens inside "the lamp, and means for interceptinga portion of said rays. i 5. Ina headlamp in combination withthe casing and a source oflight, a projecting lens mounted in said casing, having foca points inside the b0dy of said lamp conjugate with a field of desired illumination,

means for concentrating rays from. said source of light at a point in the focus of said lens inside the lamp, means located in ing a portion of said rays, and means for moving said intercepting means in said plane.

6 In a headlamp in combination with the casing and a source of light, a projecting lens mounted in said casing, having focal points inside the body of said lamp conjugate with a field of desired illumination,

source of light at a point in the focus of said lens inside the lamp, means for distributing rays from said source in: gradually decreasing density radially from said point of concentration over the focal plane of said lens insidethe lamp, means for intercepting a portion of said rays, and means for moving said intercepting means in said plane. r

7 In a headlamp in combination with the casing and a source of light, a projectin lens mounted in said casing, having foca points inside the body of said lamp conjugate with a field of desired illumination, an ellipsoid reflector for concentrating rays from said source of light at a point in the focus of ssaid lens inside the lamp, means for intercepting aportion of said rays, and means'for moving said intercepting means in said plane. 1

8.' In a headlamp in combination with the casing and'a, source of light, a project-' ing lens mounted in said casing, having focal points inside the body of said lamp conjugate witha field of desired illumination, an ellipsoid reflector for. concentrating rays from said source of light ata oint in the focusiof said lens inside "the amp, a reflector for distributing rays from said source in graduallydecreasing density radially from said ointof concentration over the focal planeof s'aidlens inside the lamp, means for intercepting a portion of said rays, and means for moving said intercepting means in. said plane.

9. In a headlamp in combination with the casing and a source of light,an aplanatic projecting lens mounted in said casing, havmg, focal points inside the 'body of said. lamp conjugate witha field of desired illumination, means fofponcentrating rays from said source of light at a-point in the focus of said lens inside the lamp, means located in the focal plane of said lens for inter cepting a portion of said rays, and means for moving said interceptingmeans in said plane.

10. A headlamp comprising an ellipsoidal reflector, a source of light at one focus of the reflector, an aplanatic lens in the'lamp having a principal focus at the other focus of the reflector, and light interceptingjmeans mounted within the lamp laterally adjacent said principal focus of the lens.

11. In a headlamp of the character, indi cated, the combination of an electric incandescent source oflight, a lens having its rearward focal'plane within-the headlamp; and a deeply cupped ellipsoidal reflector to direct a preponderanceof the light rays toward said lens, said reflector having one focus at said. source of light and the other substantially at said rearward'focal plane of the lens, and a screen substantially in said focal plane and encroachlng upon the of the lens, and having said adjacent re area of intense light concentration atone side thereof; i

12. In a headla of the character indicated, the combination of an electric incandescent source of light, a lens having its rearward focal plane within the headlamp,

and a reflector surrounding the source of light hemispherically and extended thence forwardly to direct a preponderance ofthe light ra 5 toward said lens; "said reflectorbeingformed with its closed end ellipsoidal and "having one focus at the source of llght and the other at the rearward focal plane fleeting surfaces of lesser curvature, whereby the distribution of light-rays .insaid rearward focal plane comprises a compare.

tively small-area of. intense concentration surrounded-by ,a large area of lessconcentration; and-a screen so placed as to partly encroach tration.

uponsaid area of intense concen .trated, said I13. In a light'concentrating and projecting device, the combination of a. source of llght; means for concentrating the rays of 1 said light within the device, means for proectmg the ra s of sand light when concenatter means having a' focal plane within the device, the concentrating focal plane within the'headlaiv p, a light' concentrating reflector adapted to produce its area of greatest light concentration in. the rearward focal plane of said lens and a screen substantially in said focal plane and partly encroaching upon said area of great est-light concentration but not surrounding same.

15. In a headlamp havinga source of light; a reflector having an ellipsoidal surface to produce the greatest light concentration within the lamp; adjacent portions of said reflector having a lesser curvature than said first mentioned ellipsoidal portion, a

lens in the front of said lamp whose rearward principal focus is substantially in the same cross-sectional plane as said greatest light concentration and a screen substantially in said plane of the focus and light concentration area so placed as to partly encroach upon said area of greatest light concentration but not surround the; same.

16. In combination with a headlamp having a sourceof'light,'a light concentrating reflector and a lens having its rearward principal focus within the headlamp; 'a screen stantiall y in the rearward focal plane of said .lens and contiguous to said focus and only partly surroundin said focus. A E P. BONE