US1939956A

US1939956A - Indoor lighting fixture

Info

Publication number: US1939956A
Application number: US559640A
Authority: US
Inventors: Samuel S Dauman
Original assignee: Individual
Current assignee: Individual
Priority date: 1931-08-27
Filing date: 1931-08-27
Publication date: 1933-12-19
Anticipated expiration: 1950-12-19

Description

Dec. 19, 1933. 5 DAUMAN 1,939,956

nmooa LIGHTING FIXTURE Filed Aug. 27, 1931 :1 a u I w 15 .71 01 .W emu OJJWTNVJ Q N d N E i 1x} w N1 a i j g m I Q a N a INVENTOR Jamaal fialzman g If? t m TTORNEYS Patented Dec. 19, 1933 f-gUNITED STA S PATENT oFFic V mnoon LIGHTING, FI XTURE Samuel S. Dauman, New York, N. Y.

Application August 27, 1931. SerialNo. 559,640

The present invention relates to the art of illumination and more especially to a lighting fixture unit adapted for indoor illumination with the major portion of the light thrown downwardly. The lightingunit comprising the present in vention is particularly adapted for store lighting where the illumination is preferably concentrated on goods on counters, and wherein the lighting fixtures should be located above and out of the Way while being constructed to direct the rays of light from the source in an efiicient downward direction. 7

The present invention comprises a lighting fixture constructed to deliver the major portion of the effective light within a forty five degree cone, the axis of which comprises a line extending through the source of illumination; the intensity of the light at the boundary of the forty five degree cone being substantially one half of the intensity of the light at the axis of the cone.

The preferred construction of the fixture in accordance with the present invention comprises a relatively large dome reflecting member preferably forming the support for a diffusion globe. The reflecting member is constructed on a curve approaching the curve of a parabola and an electric light, comprising the source of illumination, is mounted within the reflector in such manner that the filament is slightly above the lower edge of the reflector. The reflector carries a diffusion globe having an edge telescoping with the rim of the reflector, so that the entire unit is substantially dust proof and is constructed to direct the rays of light from the filament downwardly as a cone.

Preferably the reflecting surface of the dome is aluminum having a satin finish or sand blasted surface. Various types of diffusion globes may be utilized but the preferred globe comprises a clear glass member which is sand blasted on the inner surface to form a diffusion surface. Diffusion may also be accomplished by providing a plurality of pendant prisms, preferably arranged to'hang in circles beneath the reflector in such manner as to receive rays of light direct from the lamp and also from the reflector.

The reflector dome may or may not be covered with ornamentation such as ornamental stamp- ;ings, castings, andthe like.

Other and more specific features of the invention will be pointed out hereinafter, but it is to be understood that the specific constructions shown and described are illustrative and not to be considered in the limiting sense.

Figure 1 illustrates a cross section through a preferred'form of the invention.

Figure 2 illustrates a chart of the illuminosity of the device illustrated in Figure 1. 1

The preferred embodiment of the present inso vention comprises a large dome-like supporting member 1 which is treated on its inner surface 2 in such manner as to comprise a reflector. Preferably the inner surface comprises a surface of aluminum that has been satin finished or sand blasted, which produces a brilliant reflecting surface with a soft diffusion efiect. This dome reflector is provided at its upper portion with an electric socket recess 4 adapted to receive a socket for an electric light bulb.

This socket may be secured in place by a supporting ring 5 which may connect with various forms of supports, as, for example, a chain 6.

Suitable electric wires 7 and 8 may pass through the supporting ring 5 into the socket 9. Prefer ably the supporting dome is provided with a flange 10 which carries thumb screws 11 adapted to engage the inturned rim 12 of a diffusion globe 14. Various types of diffusion globes may be utilized, but the preferred diffusion globe comprises a globe of crystal glass sand blasted on the interior 15. A sand blasted surface is one having a large number of small recesses from which particles of the glass have been broken so that in effect these recesses act as small prisms which 85- break up the light and cause difiusion without undesirable dispersion or serious loss of light.

The curvature of the interior of the reflecting dome 1 approaches a parabola, but is not of a true parabola form in view of the fact that it is desired that the rays from the filament 16 of the lamp 1'7 shall be dispersed in the form of a downwardly spreading cone instead of a beam. The device may be constructed'of different sizes, but in order to clearly point out the preferred form, the following dimensions are given; for a 150 watt light, the reflector dome preferably is slightly more than 11 inches in diameter and the dome portion is substantially 6 inches deep. The light is so mounted that the filament thereof prefer- 100 ably is substantially 5 inches from the curvature of the reflector on its vertical axis. In the preferred form, as illustrated in Figure 1, the diffusion globe is slightly more than 14 inches in diameter and slightly more than 8 inches deep. Pref- 105 erably the major portion of this globe is substantially spherical.

Figure 2 is an actual chart showing the candle power distribution of a 150 watt lamp mounted in a fixture of the dimensions above given and of the form illustrated in Figure l. The dotted line A on the chart illustrates the candle power of the electric light alone, measured at ten feet away without being mounted in the fixture. The full line B illustrates the candle power of the light when in the fixture as measured ten feet from the fixture on the angles specified on the chart. The radial ordinates of the chart being in degrees while the polar ordinates of the chart are in candle power. From the chart illustrated in Figure 2 it will be observed that very little light is wasted in an upward direction and that the majority of the light is all within a forty five degree cone and that the intensity of the light at the edge of the forty five degree cone is sub,- stantially one half the intensity of the light on the axis of the cone. It will also be noted that the entire light within the axis of the forty five degree cone is substantially greater than the maximum direct light from the lamp without the fixture.

The fixture comprising the present invention combines great .efiiciency with economy of manum .uwtwmm W facture and simplicity of structure. The reflecting aluminum surface and the frosted crystal globe with an ordinary tungsten electric bulb give a light which closely approaches daylight.

Having described my invention, what I claim A lighting fixture comprising in combination a substantially semi-spherical dome having an inner reflecting surface and having a neck portion above said reflecting surface shaped to closely surround an electric light socket, a diffusing globe secured to said dome and having a portion comprising in effect a flare continuation of said substantially semi-spherical dome and having another portion substantially semi-spherically shaped, said interior reflecting surface being of such outward curvature that rays of light from asource located slightly above the center of the dome are reflected downwardly and outwardly in lines of single reflection through said semispherically shaped portion of the globe with the major portion thereof distributed cone fashion.

SAMUEL S. DAUMAN.