US2318715A - Luminaire - Google Patents

Description

y 1 'r. W.-ROLPH 2,318,715

LUMINAIRE Filed Oct. 5, 1940 ig mma'zw ATTORNEY Patented May 11, 1943 Thomas W. Rolph, Newark, Ohio, assignor to Holophane Company, Inc., New York, N. Y., a corporationof Delaware 7 Application October 5, 1940, Serial No. 359,868

7 Claims. (01. zit-93) The present invention relates to luminaires and is more particularly directed toward luminous indirect lighting luminaires employing incandescent lamp bulbs and spherical reflectors, such as the bowl silvered lamp.

The clear incandescent lamp delivers approximately one-half the light output below the horizontal while the bowl silvered lamp, or lamp with separate spherical reflector, delivers only a small portion (about 4 to 5%) of the light downwardly and, except for losses, substantially the entire output is delivered above the horizontal.

As the lumen output of the bare lamp is greatest in the regions just above and just below the horizontal and one effect of the reflector is to redirect the very high output just below the horizontal into the same region as the high output of the bare lamp just above the horizontal, there results a distribution in which a very large portion (upwards of 50% in typical cases) of the entire output of the lamp is concentrated in a region extending from the horizontal up to the 1301ine above the nadir. Approximatelyonehalf of this output is in the lower half of this region above the horizontal. I

It has heretofore been customary to provide some form of translucent or opaque element about the bowl silvered lamp to hide the lamp and for decorative purposes, and the light distribution of the resulting luminaire is but a slight modification of that of the bare bowl silvered lamp. In some cases the units have provision for increasing the downward component of light slightly and in other cases opaque reflectors are used so that the units become totally indirect, presenting a dull, lifeless appearance. All these fixtures send a very large proportion of their output outwardly at low angles above the horizontal and it therefore reaches the ceiling at points too remote from the fixture support to be readily utilized, or may cause sharp shadows and an.

objectionable cutoff line on vertical surfaces, such as walls.

The present invention contemplates the provision of luminaires employing the bowl silvered lamp, or the similar lamp reflector arrangement,

and having a luminous light refracting bowl,

adapted to intercept the low angle light immediately above the horizontal and elevate it so that it reaches less remote areas of the ceiling. The depth of the bowl is such as toextendfrOm practically the level of the bottom of the socket cover to below the top of the reflector, so that all luminous parts of the bulb are screened by it against observation in regions near the horizon tal, and the luminous bowl is further provided with a bottom light difiusing portion which extends outwardly from the bulb and prevents looking up toward the lamp from below the fixture. The invention also contemplates providing the bowl of the luminaire with large shallow decorative'fiutes to create an appearance of warmth and life when lighted or unlighted.

Other and further objects'will appear as the Figure 2 is a side elevational view with parts in section;

Figure 2a is a fragmentary inverted plan view of the luminaire;

Figure -2b is a fragmentary section taken-on the line 2b-2b of Figure 2a;

Figure-.3 is a photometric curve; and

Figure 4 illustrates a modification.

A suitable'suspension IIlis provided with'a socket H to receive a lamp bulb I2, here shown as being of the bowl silvered type; having the usual substantially hemispherical reflector I3, which comes up to the level of the light source. The usual socket cover is shown at I4.

An annular prismatic bowl I5 usually made of pressed glass is supported from the socket cover M by headed rods I6, which pass through rubber sleeves II received in holes Ila in the bowl. The bowl I5 has a lower inner portion I8 below the level of the upper edge of the reflector I3 and an outer upwardly and outwardly extending portion' I9 integral therewith. As the bottom of the hemispherical reflector I3 is at the level of the source it prevents direct light from the filament striking the bowl I5 below the horizontal and the bottom portion I8 is completely screened.

against such direct light, hence there is an absence of high brightness at and below the horizontal. The vertical depth of the bowl is preferably such that the upper edge is substantially.

level with the lower edge of the socket cover, so that the entire lamp bulb is suitably screened. The outer surface 20 of the portion I9 has a smooth profile in radial, or vertical, planes with a center of curvature a slight distanceabove the top of the bowl, but is provided with radial flutes 2|, which are comparatively wide and shallow, as indicated. The inner surface 22 of the outer portion IQ of the bowl has risers 22a to h, which, together with the sloping outer surface, form a band refractor having light transmitting prisms 23 whereby light rays 24 coming from the source are refracted and emitted at higher angles, as indicated at 25. Some of the light entering the glass sufiers internal reflection and scatters upwardly insid the glass, as indicated in dotted lines 26. Some of this scattered internally reflected light is returned downwardly by horizontal (or substantially horizontal) surfaces 27a to g intermediate the risers.

The bottom 18 of the bowl is intermediate the light elevating prisms on the outside of the bowl and the bowl of the lamp and its principal function is that of a light shield to prevent looking into the luminaire from below. It is also orna- Q mental to contribute to the appearance of the luminaire'and here shown as be integral with the outer prismatic wall and having small, closely spaced, radial flutes 28, which may be in the form of totally reflecting prisms for rays coming from the upper frosted part of the lamp bulb, as illustrated at 29. Various other forms of shield may be employed. A heat bafile 30 may be used where a large lamp bulb is required.

The candle power distribution curve of a bowl silvered lamp alone is shown at in Figure 3,

and the curve for the complete luminaire at M. The lumen outputs of the 500 watt bowl silvered lamp giving 9550 lumens, and of the luminaire with refracting bowl are tabulated below:

Change Zone above nadir ggg g Lnminaire naire Per cent -ll5 3870 2276 ll5l40 q +33 From the foregoing it will be apparent that a large part of the light emitted in the region immediately above the horizontal, within angles 90 to approximately above nadir, has been elevated so that it will fall on the ceiling nearer the support, yet with good intensity out as far as to give a pleasing and effective distribution of light on the ceiling.

From the above discussion and Figure 2 of the drawing it will be noted that the refracting band occupies a region between 90 and 115 ab th nadir, i. e., 25 above the horizontal, that the upper riser or prism 22h is very wide occupyig close to one third of the angular width above the horizontal, and that the prism widths decrease in angular extent toward the bottom of the band. In the example shown the prisms above the horizontal occupying zones from approximately 3 wide for 22c to 8 wide for 22h with an average width of substantially 4; there are also two narrower prisms below the horizontal.

The luminaire described above has a very pleasing appearance. The flutes 2| efiect a slight horizontal scattering of the rays 25 without sensibly affecting their vertical angle. As they cross horizontal prisms they produce a pleasing variation of surface brightness at ordinary angles of view. The rays reflected down by the flat areas between the risers provide scalloped areas of mirror-like appearance when the fixture is viewed from below. The bottom of the bowl receives light from the upper part of the lamp bulb and this gives a '75 small component or downward light and provides a luminous appearance. At the same time the bulb above the refractor is completely hidden from view.

In the form shown in Figure 4, the internal prisms of Figure 2 are replaced by external prisms 42 which have substantially the same light control. Vertical flutes 43 may be provided on the inner surface.

Since it is obvious that the invention may be embodied in other forms and constructions within the scope of the claims, I wish it to be understood. that the particular forms shown are but a few of these forms, and various modifications and changes being possible, I do not otherwise limit myself in any way with respect thereto.

What is claimed is:

l. A semi-indirect luminaire adapted to be suspended below the ceiling and comprising a concentrated light source, a substantially concentric hemispherical, opaque, specular reflector be low the source with its upper edge at the level of the source so that no direct light from the source escapes downwardly below the horizontal, andan upwardly flaring band refractcr extending upwardly from substantially the horizontal plane throughthe source to a substantial distance above the source to occupy an angle of substantially 25 above the horizontal and intercepting the corresponding direct light, said band refractor also intercepting the light reflected upwardly by the corresponding upper zone of the reflector and being open at the top to permit higher angle direct and reflected light to escape and having annular prisms of progressively changing width and refracting power for refracting said light rays and elevating them into substantial parallelism with the lowest angle direct light emitted over the top of the band refractor whereby the refracted light is directed onto the ceiling closer to the suspension.

2. A luminaire comprising a lamp bulb having a concentrated light source, a substantially concentric hemispherical specular reflector about the bottom part of the bulb with its upper edge at the level of the source so that no direct light from the source escapes downwardly below the horizontal, and a combined light directing refractor and bulb screening member having an open top, side walls forming a ring portion extending upwardly from immediately below the horizontal through the light source and provided with a series of light elevating prisms intercepting direct and reflected light between the horizontal and the cut oil angle of the upper edge of the said side walls, each prism raising the light intercepted by it to substantially the cut ofi angle. and a substantially flat, light diffusing bottom portion immediately below the horizontal through the source and screened by the reflector, said bottom having a central aperture through which the reflector and bottom of the bulb project, the said bottom portion screening the bulb above the reflector from observation from underneath the luminaire.

3. A luminaire such as claimed in claim 2, wherein said diffusing bottom portion has radially extending reflecting prisms which elevate ganglom light rays emitted from the top of the 4. A luminaire such as claimed in claim 2. wherein the ring portion intercepts a zone of light up to 25 above the horizontal.

5. A lighting fixture comprising a lamp bulb having a filamentary light source, a substantially concentric hemispherical reflector below the source with its upper edge at the level of the source so that no direct light from the source escapes downwardly below the horizontal, a refractor having an outer surface substantially that of the zone of a sphere below the equator and an inner surface which includes annular upward-' ly facing substantially horizontal areas and intermediate upwardly diverging conical areas steeper than the opposed portion of the outer surface, the bottom of said zone being slightly below the light source and upper edge of the reflector, the refractor having a lower substantially flat portion below the top of the reflector so that adapted for overhead mounting so as to be above the normal eye level and in theline of sight, and having a substantially point light source, and an annular, substantially transparent, prismatic refractor for effecting the elevation of light falling thereon, the refractor having an upwardly divergent outer surface extending upwardly from the level of the source through an angle of substantially 25 and an inner surface provided with alternate steep surfaces occupying zones of from 3 wide to 8 wide with an average width of substantially 4, and interconnected by substantially horizontal surfaces, said steep and horizontal surfaces bringing about horizontal bands of comparatively low and comparatively high brightness respectively when the source is lighted, said steep and horizontal surfaces being of such size and individually subtending such vertical angles with the eye when the fixture is viewed from normal eye level in substantially remote regions substantially below the horizontal, that each surface froms a band-like, individually demarked illuminated field not fused with the adjacent field, the outer surface having over the entire extent thereof shallow vertical flutes of substantial width which break up the bands of surface brightness to produce sparkle of the bowl in all normal directions of observation.

'7. A lighting fixture such as claimed in claim 6, wherein the refractor also extends slightly below the horizontal and has similar, but narrow, alternate steep and substantially horizontal surfaces, producing similarly demarked illuminated fields.

THOMAS W. ROLPH.

Images