US1374654A - Lighting-fixture - Google Patents

Description

W. HARRISON.

LIGHTING FIXTURE.

APPLICATION FIL ED JUNE 25. 1917.

' JZYY NTUR Iii 332:1: Hannrsazxr Hrs Arraa IVE-Z Patented Apr.'12, 1921.

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WARD HARRISON, OF CLEVELAND, OHIO, ASSIGNOR TO GENERAL ELECTRIC COM- PANY, A CORPORATION OF NEW YORK. v

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special application in commercial or industrial lighting, although it is applicable to any form of lighting in which concentrated light sources are availed of.

Fixtures which have heretofore been used in connection with concentrated light sources are objectionable'in several ways. Part1cularly, direct glare arises from insuflicient.

screening of the intense light source from the field of vision, and reflected glare from the reflection into the eye of brilliant images of the light source from metal and other polished surfaces of the reflector. Unshlelded concentrated light sources also glve rise to disagreeable sharp shadows which render vision diflicult. An object of my invention is to difl'usethe light from the lamp over a large area so that the light may be comfortable to look at, reflections Wlll not be glaring and shadows will be soft. A further ob- 'ect is to provide a fixture practicable for installation in an industrial plant or other location where more or less dirt is normally present and where rough usage 1s to be ex-.

I In carrying out my invention I place beneath the light source a small .cap or reflector, which is preferably opaque and has a highly polished inner surface, and,above;v

the light source, I place a large distributing" reflector so designed as to redirect the light downwardly and outwardly. I provide the distributing reflector with a, mar'glnal portion so disposed as to'intercept the specular or skin reflection from the main or body portion and, if need be, to recover t hc direct rays issuing from the source within the angle between the outer edge of the mam ortion and the upper edge of the lower reector.

Another novel feature embodied in my invention is that of so shaping the contour of the small cap or reflector and so modlfymg I Specification of Letters Patent. Patented Apr. 12', 1921,

Application filed Tune 25,

1917. Serial No. 176,698.

tion reference may be had to the drawings accompanyin thisapplication, Figure 1 of which is an e evation of an asssembled unit embodying my invention; Fig. 2 is a part sectlonal and elevational view thereof; Fig.

3 is an elevation showing the cap or small opaque reflector and one form of support therefor; Fig. 4 is a similar View showing another form of support; Fig. 5 is a partial side elevation of the construction shown in' Fig. land Fig. 6 is a diagrammatic. view illustratlng a method of laying out the contour of the distributer or upper reflector.

Referring to the drawings, a suitable arti- I ficial light source of high intensity and candle power, as for instance,incandescent lamp 1, is suitably mounted in a standard fixture holder 2. This-incandescent lamp 1 has located beneath the filament thereof a cap or reflector 3 and in its preferred form this consists of a detachable metal cap having its interior surface silvered or otherwise I polished Preferably this metal cap-is in substantlally the form of a hemisphere,

whose center is the center of the filament or light source, and is inclose proximity to the lamp bulb whereby the light issuing from the light source below the horizontal is reflected back substantially in the direction of issuance from the light source, the intensity of the lightsource being thereby enhanced 'tributing element of the unit in much the same manner as if coming from the light source.

One form of support for the cap 3 is shown in Fig. 3 and comprises the coiled wire band 4 which closely engages the neck and the reflected rays passing up to the dis-;

'of the lamp 1 and the depending wires 4 having hooked ends engaging apertures in the cap '3 and comprising means such asthe spring portions 4" rendering them resilient and extensible. This affords an eflicient means for holding the cap 3 closely to the bowl of the lamp 1.

The unit comprises a distributing reflector 5 which embodies a main body portion 6 and a mar 'nal downwardly extending portion 7. he reflector .5 has incorporated therein the customary glazed orgloss fin- 6, thereby uniforml ished reflecting surface, a porcelain finish being preferably used as it is easy to clean. The rays of light 8 upon encountering the glazed finish of the reflector experience both skin and diffuse reflection. The skin reflected portion. ordinarily causes glare and irregularities in the distribution of the light and this skin reflected light which is designated by the numeral 9 encounters the marginal portion 7 of the reflector and there experiences both diffuse and specular reflec- 3 and the outer edge of the main body p0r-" A tion 6 of the distributer, which light rays would otherwise be lost. It is to be noted that the outer edge of the main body portion 6 is at a higher level than the inner'edge next to the lamp, but that the reflector is concaved downwardly. This particular contour gives a uniform illumination on both the main body portion 6 and the marginal portion 7. For instance, the skin-reflected li ht 9 is distributed over the entire surface 0 the marginal portion 7 by reason of the particular contour of the mam body portion illuminating the reflecting surface. T is particular contour also serves to equalize the illumination on the main body 6, the light within equal solid angles being distributed to larger areas on the reflector 6 as the reflecting elements approa'ch the light source where the illumination is greater or, expressed in a different way, the reflecting elements which are farthest away from the light source receive the light rays .at angles more nearly af proaching the normal to the surface. 11 prior units thecentral part of the dome reflector is usually brighter and more intensely illuminated than the outer portion, dueto the fact that the elements nearer thesource receive more light'per unit area.

.In Figs. 4 and 5 is illustrated another xmeans for supporting the cap or opaque' refleetor The thin metal" cap is slotted at 1ts upper edge to form two spaced outwardly extending ears 11v which are apertured to receive a bolt 10. By tightening the bolt, the

cap is'caused to closely engage the bulb and pon loosening *the bolt, the cap may be I readil removed.

In ig. 6 is illustrated one method of lay- "ing out the contour of the main portion 6 of the upper reflector or distributer. The diameter of the reflector is fixed for ap earance and also'to'secure the desired brightness. The angle, which the margin 7 makes with the horizontal, is usually fixed at about 60, although this may be varied so as to direct the specular reflections to the outside of the cap 3, in order to light it up somewhat. of such value as to allow all specular reflections-to clear the margin on the opposite side of the reflector and still cause these light raysto approach the horizontal as nearly as possible. A point A is taken slightly below the lower right hand corner of the filament and a point B is taken on the margin a short distance, say about one inch, above the bottom so as to allow a factor ofsafety, it being intended that all light reflected from the mainportion 6 shall strike the margin 7. The depth of the upper reflector is chosen for appearance and also to correspond with the size of the lamp, point C is found on the horizontal line fixed b the depth of the reflector, such that an le GB is bisected by the vertical line D at this point. Any number of points on the curve may be found by starting with the point C and working to the right and left. 1? or instance, taln'ng EC as the unit distance, a bisector EF to the angle AEB is. drawn and then a line HK is drawn from a point H midway between E and C, perpendicular to this bisector. The intersection of this line with the bisector gives another point on the curve. This procedure is then repeated the unit distance being laid ofl ton the line HK, a bisector being drawn to the new angle and a perpendicular to this being drawn from the midway point, as before. It will be obvious that the curve thus pro ducd will be substantially an'ellipse one focus of which will be approximately at the source of light and the other substantially on the marglnal portion, since it is a property of the ellipse that the normal at any.

point thereof, bisects the focal radii. It will be obvious that there will be a variety'of curves for the main portion 6, de-' pending upon the depth of the reflector and the position thereof relative to the light source.

What I claim as new and desire to secure The angle in any event should be by Letters Patent of the United- States, is p 1. A lighting fixture comprising a concentrated artificial light source inclosed in a bulb and a reflector disposed below said light source, conforming to and closely engaging the lower portion of said bulb and adapted to project upwardly the light rays below the horizontal, and a larger reflector located above the said source having a main body portion ooncaved downwardly, and a downwardly extending marrginal portion adapted to intercept substantially all of the specular or skin reflection from the main portion and to recover the direct rays issuing from the source within the angle between the outer edge of the said main portion and the upper edge of the lower reflector.

2. The combination of an incandescent lamp comprising a bulb, a cap inclosing the lower portion of said bulb and means for holding said cap to said bulb comprising a spring member surrounding and closely engaging an upper portion of said lamp and means comprising springs connecting said cap with said spring member.

3. The combination of a cap adapted to engage a lamp bulb and means for attaching the said cap to said bulb comprising a spring band adapted to engage the upper "portion of the said bulb and spring means connecting said band to said cap.

4. A lighting fixture comprising an, electric incandescent lamp mounted base up, a reflecting means disposed below said lamp comprising a hi hly reflecting surface substantially coinci ent with the surface of the bottom of the said bulb and a comparatively large reflector mounted over the said lamp.

5. A lighting unithaving a lamp socket and a reflector shade held in definite relation to it, the shade having a crown-conforming substantially to an ellipse with one focus at the point from which the light emanates, there being an annular flange depending from the rim of the crown, and passing approximately through the other focus of said ellipse whereby all the light rays which strike the crown are deflected to the flan e.

6. A ighting unit having a lamp socket and a reflector shade held in definite relation to it, the shade having a crown conforming substantially to an ellipse with a focus approximately at the point from which the light emanates, there being an annular flange depending from the rim of the crown,"

and passing approximately through the other focus of said ellipse.

In witness whereof, I have hereunto set my hand this-22nd day of June, 1917.

WARD Harrison;

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