US2560281A

US2560281A - Luminaire with glare shielding means for producing an optimum distribution of light on a work surface

Info

Publication number: US2560281A
Application number: US631644A
Authority: US
Inventors: Leroy C Doane
Original assignee: SIGHT LIGHT CORP
Current assignee: SIGHT LIGHT Corp
Priority date: 1945-11-29
Filing date: 1945-11-29
Publication date: 1951-07-10
Anticipated expiration: 1968-07-10

Description

July 10, 1951 DOANE 2560,21

LUMINAIRE WITH GLARE SHIELDING MEANS FOR PRODUCING AN OPTIMUN DISTRIBUTION OF LIGHT ON A WORK SURFACE Filed Nov. 29, 1945 Z8 7 1 J2 2 5 a2 5 l 10 r I g a i 74 E IL-DJU E DISTANCE INVENTOR 7W1. W [Av/w: ATTORNEYS M? Patented July 1 0, 1 95i LUMINAIRE WITH GLARE SHIELDIN G MEANS FOR PRODUCING AN OPTIMUM DISTRIBUTION OF LIGHT ON A WORK SURFACE Leroy C. Doane, Essex, Conn., assignor to The Sight Light Corporation, a corporation of Connecticut Application November 29, 1945, Serial No. 631,644

This invention relates to luminaires, and par ticularly to luminaires for indirectly lighting desks, work-tables, or the like. It is particularly directed towards a luminaire which is designed to be located below the normal eye level but above the working space to be illuminated. The luminaire of the present invention is particularly 2 Claims. (o1. aim-51.11)

designed for use with one or more fluorescent tubes as the source of light, although any other elongated source of light may be employed. Means are provided for shielding the source of light so as to largely prevent direct illumination therefrom, particularly to prevent directobservation of the light source by the person working at the illuminated desk or table, so as to prevent glare and injury to the eyes; Reflectin means are provided which produce spread illumination of the working space with sufficientconcentration to give intense illumination where required.

The accompanying drawing shows, for purposes of illustrating'the present invention, a preferred embodiment thereof but it is to be understood" that the drawings are illustrative of the'inven- Fig. 2 is a bottom plan view of the luminaire.

Fig. 3 is a section similar to Fig. 1; showing the shields swung outwardly to permit removaland replacement'of the fluorescent tubes.

Fig. 4 is a transverse sectional View of the main reflector.

Fig.5 is a graph showing the approximate light distribution and showing the luminaire in end view. r Y

7 Referring naire comprises a casing I which-may be mounted in anysuitable manner, as on standard l2 (Fig. which supports it above a desk or other Working surface. The luminaire is preferably located at such height above the working surface that its top is substantially below the normal eye level of the person sitting at the desk or table. The eyes of the worker are thus protected from direct light from the luminaire. The casing comprises a top 20, preferably curved downwards at its front, as indicated at 22, and at the bottom ofthe curved portion 22 a flange 24 may be formed for holding the edge of the reflector to be described. The casing is provided with end walls 26, between which are supported the fluorescent tubes 28 or other sources of light. As shown, two tubes are provided mounted one above the to the drawing in detail, the lumi-- g z 7 other near the back of the reflector. The back part of the casing may be in the form of a box 30 to contain the ballast or other electrical equipmentiused in connection with the fluorescent tubes, although such equipment need not necessarily be located in the luminaire casing as it may be placed in the lamp base or in any other desired location.

The casing has a flange 32 extending at leastpart way under the fluorescent tubes so as to cut off most or all of the light which would otherwise be directed downwardly from said tubes. This prevents too intense illumination directly under the luminaire. If desired the upper surface of the flange 32 may be made as a reflecting surface so as to return as much as possible of the light from the tubes to the main reflector. By mounting the tubes when more than one is used one above the other, the source of light may be concentrated near the back of the casin and a relatively narrow. flange 32 is sufiicient to cut ofi direct downward rays.

In the casing is, the main reflector 40 which preferably includes an upright back portion 42 mounted back of the tubes, a fairly sharply curved.

portion 44 extending from the back of the reflector up over the tubes, and a'forwardly extending shallow or slightly curved portion. This shallow reflector portion, which is the principal reflecting surface of the main reflector, may be slightly curved throughout but preferably it comprises a curved portion of large radius of curvature 46 and a front portion 48 which may be a plane surface. The reflector is preferably so mounted that the back portion is fairly close to the tubes so that the source of light is concentrated near the back of the lamp and the curved portion 44 extends fairly closely over the top tube. extends a substantial distance forwardly of the tubes, such distance being preferably several times the diameter of the tubes. In the example shown the distance of the front edge of the reflector from the front of the tubes is about four times the diameter of a tube. Obviously this distance may be varied to suit conditions. The reflector may be mounted in the casing in any suitable manner, for instance the lower edge of the upright portion 42 may be held behind or secured to a narrow upright flange 59, while the front of the reflector is retained behind the flange 24 at the front of the casing. In a longitudinal direction the elements of the reflector surface are preferably straight and parallel to the axes of the fluorescent'tubes.

The front part of the reflector preferably The inner reflecting surface of the reflector is preferably a specular or semi-specular surface depending on the diffusion of the light source, and the reflector may be conveniently formed of a single sheet of aluminum finished in such a way as to produce a reflecting surface of the desired type. If a semi-specular surface is used, such a surface gives a partially diffused reflection which has a directional component so that by properly shaping the reflector the degree of illumination can be distributed as desired over the work to be illuminated. At the same time no images are cast and a soft diffusion of light is secured. If the source of light itself produces sufficient diffusion then the reflector may have a specular surface with similar results as to light distribution.

To further distribute the light and to shield the eyes of the user from direct observation of the light source in case he bends over so that his eyes are below the level of the top of the luminate, one or more shields are provided. Two shields 60 are shown but the number maybe increased or decreased as needed. Two or more shields usually produce a better distribution of light than a single shield, particularly if more than one light tube is used. These shields are relatively narrow and are preferably inclined somewhere in the neighborhood of 30 more or less to the horizontal. They are also preferably slightly curved transversely so as to present elongated concave surfaces 62 facing downward and toward the rear. These concave surfaces are preferably treated so as to be diffusing reflectors. (For instance they may conveniently be painted with flat white paint.) The outer surfaces of the shields may be painted black or a neutral color, or otherwise finished. They are not intended to act as reflecting surfaces. The shields may be mounted in any suitable manner, as for instance, by being provided with end flanges 64 which are riveted. to arms 66. The arms are pivoted at their front ends upon pivots 68, mounted in the end walls 26 of the casing. By swinging the arms 66 downwardly as shown in Fig. 3 the shields are moved out of the way so as to permit access to the inside of the casing for removing and replacing the fluorescent tubes. For holding the arms in their normal position suitable latch means are provided. For instance, the ends of the arms maybe made slightly elastic and provided with holes which will snap over pins 12 mounted in the ends of the casing. The ends of the arms are provided with ears 14, which may be grasped so as to bend in the ends of the arms and release them from engagement with the pins. 7

The main reflector is so shaped as to spread the light forwardly. A preferred curvature of the reflector is shown in Fig. 4, and as stated, comprises as its more important elements the more or less sharply curved part over the source of light flattening into a broad curve, which may, as shown, actually merge into a flat, slightly inclined part. In the particular form shown the inclined front part of the reflector is at an angle of 70 more or less to the vertical. Obviously the particular dimensions of the reflector, including particular curvatures and. inclinations may be varied in accordance with the particular distribution of light desired. With the form of main reflector and of the reflecting surfaces of the screens illustrated the distribution of light transversely to the luminaire will. be somewhat as indicated approximately by the light distribution. curve be a more or less intense distribution of light under the luminaire and forwardly thereof, and a substantial distribution of light for a considerable distance in front of the luminaire. Of course, there will also be, a spreading of the light longitudinally beyond the ends of the luminaire sufficient to take care of the needs of the worker standing or seated in front of the luminaire.

While I have illustrated and described in detail certain preferred forms of my invention, it is to be understood that changes may be made therein and the invention embodied in other structures. I do not, therefore, desire to limit myseu to the specific construction illustrated, but intend to' cover my invention broadly in whatever form its principles may be utilized.

I claim:

l. A luminaire for use with a horizontally disposed source of light consisting of a plurality of luminous tubes mounted one directly above the other, comprising means for holding the tubes, a shield mounted below the tubes for cutting off downward rays therefrom, and a shallow reflector having a back mounted closely behind the tubes and a portion curving upwardly and'over the tubes, and a wide forward portion extending for a considerable distance in front of the tubes in a somewhat fiat but downwardly sloping direc tion, said reflector having a continuous reflecting surface of a specular character, and a plurality of spaced inclined shields mounted in the region between the front edge of the reflector and-the tubes, the shield nearest the front edge of the reflector having its upper edge about on a level with, the front edge of the reflector but being spaced a substantial distance rearwardly thereof, the rearmost shield being lower than the shield nearest the front of the reflector and bein wholly infront of the lowermost tube, both of said shields having light diffusing reflecting surfaces facing the tube.

2. A luminaire for use with a horizontally dis= posed elongated source of light such as a fluores cent tube and intended for desk illumination or the like and designed to be used below the normal eye level comprising a casing provided with means for holding the tube, a light shield carried by the casing below the tube and cutting off downward rays therefrom, and a curved sheet metal reflector having a continuous specular surface and including an upright portion mounted closely behind the tube and a portion curved upwardly and over the tube and lying close thereto and'then extending forwardly in a downward curve Ofi-Ilcreasing radius of curvature and ending, finally in a substantially flat but downwardly sloping.

portion extending forwardly of the tube for a distance at least several times the diameter of the tube, the reflector surface being generated by elements parallel to the axis of the tube, and a pair of. shields carried by the casing, said shieldsbeing inclined in the same general directionas the front part of the reflector but at a steeper angle of inclination, said shields having concave diffusely reflecting surfaces positioned to intercept' and reflect light rays coming from said tube, the upper edge of the forward'shield being about on a level with the front edge, of the reflector, the upper edge of the rearward shield being about on a line with the lower edge of the forward shield, the lower edge of the rearward shield being'lower' than the tube, said shields being spaced in a horizontal direction so'thatj the forward shield shown in Fig. 5. As will be apparent, there will is substantially in'therear of the front edge of the reflector and the rear shield is spaced in front of the tube.

LEROY C. DOANE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Meneely Sept. 5, 1916 Weishan Dec. 1, 1925 Ferree et a1 Mar. 10, 1936 Wetzel Dec. 22, 1936 Glover Jan. 20, 1942 Livers Dec. 22, 1942 Carter Mar. 28, 1944