US 1998967 A
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April 23, 1935. .1, F; RAYNOLDS HEADLIGHT Filed March 5, 1928 3 Sheets-Sheet 1 familiar .b/wfifiqrumos ATT ENEYJ' April '1935- J. F. RAYNOLDS 1,998,967
HEADLIGHT Filed March 5, 1928 3 Sheets-Sheet 2 April 1935- .1. F. RAYNOLDS I 1,998,967
HEADLIGHT Filed March 5. 1928 5 Sheets-Sheet 3 Patented Apr. 23, 1935 UNITED STATES PATENT OFFICE HEADLIGHT John F. Raynolds, Minneapolis, Minn, assignor, by mesne assignments, to The Corcoran-Brown Lamp Company, Cincinnati, Ohio, a corporation of Ohio Application March 5, 1928, Serial No. 259,141
5 ment, suitable for use with reflectors such as are commonly employed in the headlamps of motor vehicles and the like, to project a light beam therefrom.
In the illumination of a highway by means of headlamps, such as are commonly used.on motor vehicles, it is desirable that all of the light flux emanating from the electrically heated filament in every direction, be so controlled as to reach, in correctly proportional amounts, the various parts of the area which is to be illuminated.
The incandescent lamps in commonest use, are generally rated at 21 spherical candle power and, under ordinary conditions all of the light flux emanating from a pair of such lamps in conjunction with suitable reflectors, prismatic lenses, or other apparatus, is necessary to produce sufficient illumination. The light beams projected from the headlamps must also be so arranged as to comply with the various State laws relating to headlights on motor vehicles.
In various headlamps in common use, an incandescent lamp with a bulb of clear glass is employed, and usually has its filament located at the focus of a reflector of parabolic or modified parabolic form; and a prismatic lens which bends or spreads the reflected beam in a horizontal plane, and sometimes bends portions of the beam downward to avoid annoyance to persons in front of the vehicle. In such a combination, a substantial part of the total light emitted by the heated filament escapes forward of the reflector. That part of this unrefiected light which is directed toward the sides of the reflector along planes which contain the main axis of the reflector, and which make comparatively small angles with the horizontal plane through such axis, serves a useful purpose, since it illuminates the road and the road side, curb, or ditch alongside and immediately forward of the front wheels. It
' is also of value in reading highway signs at the shoulder of the graded portion of the highway. On the other hand, all the unreflected light rays which are emitted upwardly or downwardly, or in directions close to the main axis of the refiector, are of no value to the driver; the downwardly emitted rays touching the road surface directly in front of the vehicle where it is invisible from the drivers seat, while the upwardly directed rays cause an annoying halo or back glare when driving in fog, smoke or dust. Also,
the forwardly emitted unreflected light rays make the headlight appear unnecessarily bright to persons approaching in other vehicles or on foot. This last effect becomes worse as the distance from the light decreases, while a properly 5 directed beam of unreflected light becomes easier to look at, as the angle between the observers line of vision and the main axis of the beam is increased, as occurs when two vehicles meet and pass each other on a highway.
Therefore, if an incandescent lamp is constructed, and positioned in a suitable reflector as disclosed in the following full and clear explanation, a new and improved result will be obtained, which will utilize all of the light to the best advantage and will be simple to manufacture, assemble and retain in correct adjustment.
The particular object of the invention, therefore, is to provide an improved incandescent electric lamp adapted for use in connection with headlamps and other light-projecting apparatus.
Other objects of the invention will appear from the following description and accompanying drawings and will be pointed out in the annexed claim.
In the accompanying drawings, there has been disclosed a structure designed to carry out the various objects of the invention, but it is to be understood that the invention is not confined to the exact features shown as various changes may be made within the scope of the claim which follows.
In the accompanying drawings forming part of this specification;
Figure 1 is a side elevation of an incandescent lamp showing the invention applied thereto;
Figure 2 is a front elevation of the bulb shown in Figure 1;
Figure 3 is a horizontal axial diagrammatic section of a parabolic reflector such as used in motor vehicle headlamps, showing the improved incandescent lamp and the paths of various raysof light projected from the filament;
Figure 4 is a diagrammatic plan view showing a motor vehicle on a highway, and illustrating the areas illuminated by the headlights when the invention is applied to the lamp bulbs thereof;
Figure 5 is a diagrammatic side elevation of Figure 4, illustrating the vertical spread of the 50 non-reflected or directly emitted rays of light, projected from a lamp embodying the invention,- and also illustrating the path of the reflected beam;
Figure 6 is a view similar to Figure 5 illustrat- 55 ing the vertical spread of the non-reflected light rays of an ordinary lamp bulb;
Figures 7, 8, 9, and 10 are views showing modified forms of the coating shown in Figure 2; and
Figure 11 is a vertical axial diagrammatic section of a modified reflector, showing the position of the filament of the lamp with relation to the foci of the reflector.
The improved incandescent lamp, as disclosed in Figure 1, consists of the ordinary form of glass bulb I, affixed in a metallic cylindrical base member 2, through which one or more wires are led to the filament 4. The filament is of the usual concentrated V-shaped type, and when the lamp is mounted in its socket by means of the usual pins 3, engaging in two bayonet slots, as shown in Figure 3, the filament lies substantially in a horizontal plane through the reflectors axis. Also, the filament is located with its center" of mass at the center of the forward spherical portion of the glass bulb I.
An important feature of this invention resides in the provision of means at the forward portion of the lamp bulb I to prevent the emission of unreflected or direct light rays from the headlamp in a vertical plane, and to permit the projection of a portion of such rays horizontally to illuminate predetermined areas at each side of the lamp or vehicle. To thus restrict the emission of direct light rays from the lamp, a coating of suitable material as, for example, metal, paint and the like is applied to the forward spherical surface of the bulb I, as shown in Figures l, 2, and 3, The inner side or surface of this coating adjacent to the surface of the bulb I, is formed of a suitable reflecting, material such as mercury or silver, which is covered by an opaque outer coating which protects the inner reflecting material and cooperates therewith to form a concaved spherical mirror. In the preferred embodiment, this mirror is in the shape of a segment of a hollow sphere, with two rectangular or slightly trapezoidal areas removed, as shown in Figures 1 and 2, thus providing in the coating 5, marginal indentations 6. These indentations and the entire mirrored coating are bisected by the horizontal plane through the filament.
Referring to Figure 3, it is seen that when the filament 4 is located at the focus of the parabolic reflector 1, the only rays (1 which are emitted forwardly of the reflector are those which pass through the clear areas or indentations 6, provided in the mirrored coating. Except at these areas, the mirrored coating extends rearwardly from the forward end of the bulb to a point where the coating will be intercepted by the broken lines -fD, as shown in Figure 3. These lines, it will be noted, are drawn from the center of mass of the filament to the-outer forward edge of the reflector 1. Thus, the rays d are permitted to illuminate the road or surface on each side of the front of the vehicle; but all such rays emitted at a sufficient angle below or above the horizontal to avoid the uncoated areas or indentations 6, are intercepted by the mirrored coating 5 and are reflected back through thefocus point of the parabolic reflector and projected from its surface in substantially parallel lines with the reflector axis A-A'. Starting at the filament 4, m-m mm denotes the path of a ray of light which is emitted from a point. on the filament at one side of the center of the spherical portion 1 of the bulb; is returned by the mirrored coating 5 through the opposite side of the filament, and thence, goes to the reflector, from which it is avoiding dark spots or shadows within the refleeting beam.
Referring to Figure 4, d denotes certain of the unreflected rays which are emitted through the clear glass areas or indentations 6, above mentioned, and which incline downwardly to illumihate the two portions of the ground surface G as indicated. The main beam of reflected light, after being modified, will illuminate a thirty foot wide highway up to and beyond a point two hundred feet from the headlamps, as indicated by the broken line H in Figure 4, and customarily does not extend closer than twenty-five feet from the front of the vehicle. Figure 4 also illustrates the side spread of the unreflected or direct light rays emitted from the lamp, which pass through the clear areas or indentations 6, oppositely pro vided in the coating 5. The upper and lower portions, and also the central portion 8 of the coating 5, prevents any direct or unreflected rays from being projected onto the ground surface in the triangular area indicated by the letter J, in Figure 4. This non-illuminated area J, it will be noted, lies directly in front of the vehicle. Figure 5 illustrates substantially the vertical spread of the direct rays d, shown in Figure 4.
Figure 6 illustrates the objectional vertical spread of the unreflected light rays emitted from a lamp bulb not having any intercepting substance around the bulb. These rays are indicated by the dotted lines 11., while the reflected main light beam is shown by the lines 1. 8-3 indicates the ground line. It will therefore be understood by referring to Figures 4 and 6, that the unreflected light rays or flux emitted from an ordinary lamp bulb will spread in all directions, substantially as indicated by the broken lines d and u.
It will also be seen that if any rays like those lettered u are permitted to escape, the undesirable eifects hereinbefore referred to are obtained; while, ifall rays emitted forward of the reflector are intercepted, whether by an opaque coating or an opposed reflecting surface, there will be practically no illumination of the road surface within twenty-five feet from the front of the vehicle, as indicated by the area J in Figure 4. Thence, the principle shown in the several types of mirrored coatings in Figures 2, 7, 8, 9, and 10 will produce an improved and more desirable illumination.
If the filament 4 be placed wholly in front of or behind the focus ,1 of a reflector having a single common focus for all its elements, the rays which are intercepted and returned by the spherical mirror to the reflector, will be projected at sufficient angles to the main axis to cause an indefinite and illegal beam with any lens designed for use with substantially parabolic reflectors.
However, in a reflector of the type shown in Figure 11, 'in which the focus fu of the upper portion thereof, is located rearwardly of the focus I of the lower portion, both foci lying in the common axis A-A', the filament should be placed at d between the two foci. The rays which are intercepted by the mirror and returned to the reflector through the filament, will be projected from either the upper or lower portion in directions inclined downwardly to the axis A--A. This is similar to the action of the reflector on all rays arriving at its surface directly from the filament, hence no objectionable effect takes place with regard to the final reflected beam of light.
I claim as my invention:
The combination with an incandescent electric lamp comprising a. compact filament affixed to a cylindrical base and lying within a glass bulb amxed at one end to said base and having the portion which is opposite said base spherically formed, of an integral segment of spherical outline mounted at the forward end of said spherical bulb portion and coated on one side with a refiecting material, the opposite side of said segment being covered with an opaque protective material, both coatings covering the same area which has its segmental shape indented symmetrically on each side of a horizontal plane only through the center of said spherical portion, said filament lying substantially at said center.
JOHN F. RAYNOLDS.