US1515221A - Electric lamp - Google Patents

Description

, hlg W. w. ROBERTS ET All,

ELECTRIC LAMP Filed March lO. 1924 (CJ num/Lto@ Wllmmw Rbwh.

p atented Nw., n, aan.

'WILLIAM WODDR'UFF ROBERTS AND LYNN T. RBEBTS, 0F SBY'VTLLE, KENTUCKY.

MECTRIC Ll?.

applicati@ mea March 1o, 1924.. serial No. 698,138.

To all 'whom t may concern.

Be it known that we, .WILLIAM W. Ron- Entrs and LYNN T. ROBERTS, citizens of the United States, residing at Shelbyville, in the county of Shelby and State of Kentucky, have invented certain new and useful Improvements in Electric Lamps, of which the following is a specification.

- This invention relates to electricA lamps of the type employing a bulb and filament such as are commonly known as incandesj cent lamps. l

The invention also relates to light-projectors Where such lamps are employed.

In the employment cf light projectors such as the head lights on' automobiles. Tt is the direct intense rays from the filament which tend to cause such intense illumination as to produce glare with its accompanying dangers. Attempts fhave been made to over come this by providing a screen between the filament and the eye of a person observing the lamp. Such attempts have revolved themselves into two classes; in one of which the outer or front end of the lamp is frosted, made from opalescent glass or in some other manner made translucid instead of transparent. In the other methods, an opaque screen has been employed. By the use of the first method much light is wasted,

being absorbed by the construction of the lamp employed and in the second method not only' is light wasted 'but a shadow is thrown by the opaque screen.

One important object of the present invention is to provide,v an improved construction of lamp of this type especially adapted for use in connection with automobile headlights and the like and which is of such nature as to eliminate direct observation of the filament while at the same time utilizing as much of the light 'as could be utilized with an ordinary clear glass lamp and without a screen.

A second important object ofthe invention is to provide an yimproved lamp of this character wherein the injurious' effects of shadow will be eliminated. y

A third important object of the invention is to provide an improved combination of parabolic reliector with the improved lamp in such manner that certain of the rays from the filament will, after double reflection, be p iojected in a straight parallel beam or penci be projected to intersect each other and then Other rays, after single reflection, will' spread in a cone, while still other ra s, without reflection, will spread out to iluminate the sides of the road.

With the above and other objects in view as will be hereinafter apparent, the invention consists in general of certain novel details of vconstruction and combinations of parts hereinafter fully described, illustrated in the accompanying drawings and specically claimed.

In the accompanying `drawings like characters of reference indicate like parts in the several views, and:

Figure 1 is a transverse section through 70 a headlight showing the improved lamp in position and indicating by dotted lines the course of the light rays.

Figure 2 is a greatly enlarged side elevation, partly in section, through the improved lamp showing itsV construction.

In the present disclosure the lamp is shown as having an ordinary oval bulb l0 provided with the usual metallic neck 11. This bulb also has the usual filament 12 disposed cen- 80 trally of the greatest transverse diameter of the lamp. The bulb is made of the usual clear glass but on the exterior of its outer or forward end it is provided with a coating the filament and bulb at the greatest diam\ 90 eter of the latter. lt is preferred that the silver coating cover about one-sixth of the surface of the bulb, though it may cover somewhat more than this.

lfVith this construction the silver coating acts as a reflector and constitutes a concave mirror confronting the filament 12. When such a lamp as this Ais placed in the usual manner in a headlight 15' provided with a parabolic reflector 16 and is soarranged that 100 the mirror 13 is in alinement with and in Ifront of the focus of the reflector 16, and the filament l2 also in front of the reflector focus, then, under these circumstances, cer

tain light rays as 17 emanating from the 105 filament 12 will strike the mirror 13, be reected through the reflector focus to the re- Hector 16 and there be ra second time reflected to pass forwardly in substantially parallel relation. Others of these rays, as the 1104 rays 18, will pass directly from the filament to the reflector 16 and be reflected in converging relation to a `iooint lttand thence inl diverging relation as shown. None of the rays Jfrom the ilament will nass directly forwards but the opaque kmirror coating will e not appear to cast a shadow because the rays 18 meeting at the point 19 will greatly reduce and practically destroy all shadow effeet. Finally, by proper proportioning the mirror, certain rays 20 will nass from the '10 lament l2 without striking the reflector ofv the lamp in dii/erging relation and thus illuminate the sides of the roads. lt is, of course., to be understood that the :filament and mirror are in proper relation to each 15 other to accomplish this result. l

By the use of this arrangement it is found that a headlight gives more light -with the same voltage than with any other lam of correspondingn candle power, the 2U nel of blindness is reduced to a greater degree than with any other bulb of smooth clear glass lens and it can be used in the headlight without producing any blinding ehects, and no dark spot or shadow is cast. 25 yllhere has thus been provided a simple and ecient device of the kind described and for the purpose sioecied.

intranet I ,if

Having thus described the invention, what is claimed as newe is:

The combination with a headlight having a housing and a main parabolic reflector mounted therein and facing the forward end of the housing and terminating forwardly closely adjacent said end; of a lamp soclret projecting through the rear end of the relec- 3 tor in the axis thereof. of an incandescent lamp bulb mounted in said socket and han ing its filament close to but in front of the focus of the reflector, said bulb being coated on its forward end with a reecting surface and a protecting coating' on said sur face, whereby rays of light from the lame? lament directed on the parabolic retlectoh issue in a converging beam, While rays old light directed against the reflecting surface 4 on the bulb are redected to the parabolic reflector and redirected by the latter in a parallel beam of light forward of the headlight housing.

lin testimony whereof we afiix our signatures.

WILLIAM WUDRUFF RBERES. LYNN T. EGBERTS.

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