US2321701A - Lighting fixture - Google Patents

Description

June 15, 1943. w, PQTTER LIGHTING FIXTURE Filed Nov. 9, 1940 lnventor z Wencvvofith M. Pohte13 y His Airlrorneg.

Patented June 15, 1943 LIGHTING FIXTURE Wentworth M. Potter, Lyndhurst, hio,assignor to General Electric Company, a corporation of New York Application November 9, 1940, Serial No. 364,989

2 Claims.

My invention relates in general to lighting equipment of the type employing an elongated light source such as the fluorescent lamp in commercial use at present. More particularly, my

invention relates to a lighting unit of the above type'for, use principally in the controlled lighting of specific areas, such as in the dome lighting or supplementary lighting of merchandising or display areas in stores as, for instance, display tables and counters.

Due to the recent growth in popularity of both fluorescent lighting and controlled lighting for store merchandising and other areas, the need arose for a practical and eflicient fluorescent lighting unit giving controlled illumination. Furthermore, with the rapidly expanding use of fluorescent showcase lighting, a demand was created for a practical means of lighting merchandise examination areas, e. g.,' the counter or showcase top, and adjacent spaces, with light of the same'color quality and intensity as that used in the case under which the merchandise is first viewed.

One object of my invention is to provide a lighting unit for elongated light sources which will produce controlled direct lighting or downlighting of favorable distribution and efiiciency, and which is characterized by adequate shielding of lamps and other bright areas both laterally and longitudinally of the unit.

Another object of my invention is to provide a suspended type of lighting unit for elongated light sources which will produce a certain amount of upward illumination to contribute to diffused general illumination and favorable ceiling and wall brightness, as well as controlled direct light- 7 ing or downlighting.

Still another object of my invention is to pro-- vide a lighting unit for elongated light sources which unit has a shallow cross-section and softly luminous exterior portions combining to give the unit an appearance of inappreciable weight and to render the same unobtrusive, the softly luminous exterior of the unit blending in with the diffused illumination of the surrounding areas.

A feature of the invention is the use of a pair of downwardly facing elongated light reflecting surfaces consisting of two segments, each approximately half of a parabolic or other shaped trough, placed back to back with their outermost or lower extremities juxtapositioned, together with a pair of elongated light sources, one for each of said reflecting surfaces, each light source being disposed with its longitudinal axis coincident with the focal axis of the cooperating reflector. Another feature of the invention is the use of softly luminous side members to give the unit an aspect of inappreciable weight, the said side members being positioned in parallel relation-to the lamps and reflectors so as to act as shields or louvers therefor at usual angles of view transversely of the longitudinal axis of the unit.

Further objects and advantages of my invention will appear from the following description of a species thereof and from the accompanying drawing in'which:

Fig. 1 is a perspective view of a lighting unit comprising my invention, and Fig. 2 is a transverse sectional view on the line 22 of Fig. 1.

Referring to the drawing, the lighting unit according to the invention comprises a frame consisting of front and rear elongated side plates or members l0, l0 respectively, supported at their opposite ends, in transversely spaced downwardly converging relation, by a pair of end plates ll. The side members l0, iii are secured to the end plates in any suitable manner. For example, the end plates may be formed with grooves or slots l2 within which the ends of the side members fit to thereby hold the said members and plates in assembled relation. To prevent the side members IB, ill from sliding down out of the grooves l2 in the end plates, a strip l3 of metal or other suitable material is secured to the lower edge ll of each plate ll so as to underlie the grooves l2 therein. This same result, however, may be accomplished, if desired, by terminating the grooves 52 short of the lower edge II of the end plates. Advantages of such construction lie in the ready assembly and disassembly of said parts for shipment, and for cleaning or other maintenance.

The downwardly converging side plates or members l0, ID are preferably made of suitable translucent material of reasonable rigidity such as laminated translucent plastic, or retracting, configurated surface, depolished, opal, opalescent, or enameled glass, having a degree of diffusion or refraction suflicient to reduce the brightness of the lamps within the unit from usual viewing directions. In addition, the side plates are preferably curved in vertical transverse cross-section so as to present an inner convex surface. Such an arcuate or curved section provides'the best arrangement for shielding the lamps and other bright-portions in the unit and for producing an increase in the upward component of light output therefrom, the reflection of light from the wireways, etc.

I or integral end-to-end relation.

upper areas of members l0, l contributing to this end. However, if desired, the side members 10, Hi may be planar, or outwardly curved to present an inner concave surface, such shaped members preserving the desirable shielding angles hereinafter described and the outwardly curved shape being the condition for most nearly uniform brightness appearance of said members l0, l0. Also, the said members may be formed of reflecting metal or plastic, with provision for directing a small amount of light to their outer surfaces by means of supplementary reflecting strips or small channels disposed along, and spaced a slight distance from the upper or lower edges, or both,

of the side members ill, Ill.

The end plates ll may be made of any suitable material, and may be either opaque or translucent. While I have shown the end plates H in the drawing as made of wood, they could be readily molded of translucent plastic including mounting facilities for the lamp sockets, small Such translucent end plates it would be especially desirable where lighting units according to the invention are suspended singly, as distinguished from the case in which a number of such units are mounted in contiguous In end-to-end mounting, one or both end plates H would be designed to act in the manner hereinbefore described for related parts (e. g., side members Hi, l0) of adjacent units in such end-to-end arrangement. The opposite ends of the end plates l l are preferably shaped to conform to and substantially coincide with the outer contour of the curved side members l0, In so as to present the most compact, generally symmetrical and favorable outward appearance.

The vertical extent of the side members l0, Ill and end plates II is preferably limited so as to provide a unit of shallow cross-section. Such a feature, together with the use of softly luminous side members Ill, ill, gives the unit an appearance of light weight very desirable for a unit of its size, particularly where used in numbers in a given room. I have found, in an embodiment of this invention, a vertical extent or depth of about 4 inches or thereabouts for the said members and plates to be particularly satisfactory for this purpose although the spacial requirements of light sources of various diameters and their corresponding reflectors and the sizes of auxiliary electrical apparatus, such as reactors, capacitors, resistors, switches and the like, may largely determine the desirable depth of the unit.

Mounted between the side members ill, l9. and extending longitudinally of the unit between the end plates H thereof, is a downwardly facing elongated asymmetric reflector iii in the form of a compound reflector having two separate refleeting sections or segments ll, l8, consisting of two approximately half-sections of aparabolic trough placed back to back with their outermost extremities preferably iuxtapositioned, as shown at 26 in Fig. 2. However, if the spacial requirements of the auxiliary electrical equipment necessary to the proper-operation of the light sources is greater than that shown between the backs of reflectors ii, it, then the cross-sectional area between reflector segments i1 and It may be enlarged by inserting at the intersection 26 a flat or otherwise conflgurated horizontal plate or strip of minimum width. The reflector is positioned with the apices of the two reflecting segments l1, l8 at the top of the unit with their concave reflecting surfaces facing downwardly. A pair of elongated light sources I9, 20, such as fluorescent lamps of the type and sizes in general commercial use at present, are disposed one along the focal axis of each of the reflector segments H and II, the two lamps being mounted in suitable sockets 2| at opposite ends of the unit. The said sockets are preferably of the type described and claimed in Reissue Patent No. 21,545, issued August 27, 1940, to A. J. Marshaus and assigned to the assignee of the present invention. The reflector I is supported within the unit by support blocks 23 of suitable material, such as wood, which is secured to the end plates II by screws 14 and to which the reflector I6 is secured by screws 25.

To provide the desired control of the downward light from'the unit, the two parabolic reflector segments l1, l8 and their axial planes, in the embodiment of invention illustrated, are tilted a slight amount toward one side of the unit, 1. e.. the rear side, the front reflector segment H and its axiai plane being tilted rearwardly preferably about 8", and the rear reflector and its axial plane preferably about 16, with respect to the vertical. By thus tilting the reflector segments l1, it, it is possible to obtain, with a unit located above the front edge of a counter or table, maximum illumination on the merchandising area while still eliminating all specularly reflected light (in a. glass counter top, for instance) which might be directed toward the eyes of customers standing before the counter or table and nearly under the unit, said specularly reflected light being directed upward at a low angle of reflection away from the customer, thus avoiding glaring or veiling images. The angles of tilt may, of course, be varied in relation to the vertical and to each other to compensate properly for variations in mounting height of the unit, width of surface or area to be illuminated, preferred distribution of illumination on horizontal and vertical planes and. other such considerations. If desired, no tilt whatever may be given to the reflector segments l1, l8, such as where the unit is to be used for general lighting purposes only.

Specular reflecting surfaces are preferably employed on the reflector IE, not only for the purpose of obtaining accurate control of the light reflected thereby, but also to avoid brightness effects in unshielded portions of the reflector as seen at usual angles, However, where wider distribution of illumination is desired, semi-matte or partially diffusing surfaces may be employed. The elimination of such brightness effects in the reflectors results in a relatively dark appearance thereof and an interesting pattern. or contrast on view of the unit from angles below horizontal but not approaching the vertical.

The focal length of the reflector segments I1. I8 depends, among other things, upon the diameter of the lamps i9, 20 to be used and the degree of concentration of light beam required. For lamps having a diameter of approximately 1" or thereabouts, the parabolic reflector segments l1. l8 used in the embodiment illustrated are preferably formed with a focal length of approximately Reflecting surfaces of shape other than parabolic, such as elliptical or circular, or of compound or combination cross-sections, and of different focal lengths may be desirable for the reflector segments l'l,l8 where other distributions of light are desired or lamps of different size are employed. While the reflector segments i1, 48 are preferably made integral so as to form single compound reflector member, they may be formed separately, if desired, and then mounted in proper relation to one another wlthinthe unit.

The intersection of the opaque reflector segments l1, 18, indicated at 26 in Fig. 2, provides .transverse louvering or shielding from view, at

or 20, since additional reflector length, at this the first described means. The number of louvers 28, their dimensions, and their spacing may, of

ing from the end plates II and from each other.

Such an arrangement shields the lamps. I9, 20 completely from view at angles above approximately 16 from the horizontal on endw'ise view of the unit from below the horizontal. Partial shielding is, of course, provided by such louver point, would contribute little to the downward component of light output. Instead, the light rad ations which would be intercepted by such additional reflector portions at the top of the unit are better utilized by permitting the same to rad ate upward to produce an adequate upward light component for illuminating the ceiling and upper walls of the room.

The luminous side plates or members III, III are preferably positioned a sufficient distance from the adjacent lamps I9, to avoid excessive brightness (either maximum or average) of said members and to produce acceptable gradation of brightness. A distance not less than 1%" from the outside arc of the lamp tube is recommended n the embodiment employing a tubular lamp 36" long and i" in diameter. In addition, the said side members III, II) are so positioned in relation tgrthe lamps I9, 20 and the reflector I6 as to act as shields or louvers at usual angles of view transversel'y of the longitudinal axis of the unit. AS

shown in Fig. 2, the front side member I ll provides complete shielding of the front lamp l9 at and above 23 or thereabouts from the vertical, while the rear side member ID provides complete shielding of the rear lamp 20 at and above 35 01 thereabouts from the vertical. The side members Ill, III also shield certain upper areas of the reflector l8. At the top of the unit, the side members l0, 10' preferably shield the lamps, and even the entire structure, from view at 90 from the vertical, as is especially desirable in large rooms. In certain cases, revisions in the above mentioned angles of cut-off may be desirable and permissible, as for example, where possible glare conditions may require greater or lesser shielding angles.

To provide longitudinal shielding of the lamps, one or more transversely extending louvers or shields 28, of metal, plastic or other suitable material, are mounted within the unit adjacent the bottom thereof. The said louvers 28 extend from one side member Hi to the other, and flt into suitable vert cal transverselyaligned slots in the reflector segments l1, l8. The louvers 28 may be retained in place within the units bysuitable brackets or other fastenings within the space between reflector segments ll, ill, or they may be completely or partially supported by, or help support in true position, the downwardly converging side members l0, ill, the opposite ends of the louvers being shaped to conform to and engage the curved inner'surface of the side members. For desirable outward appearance, it is desirable to have the louvers 28 spaced from the inner surface of the side members l0, l0 in which case the louvers 28 should be rigid and supported by arrangement at lower angles.

The longitudinal shielding provided by the louvers 28 is considered secured thereto is a metal brace member 29,'

preferably of inverted U shape, as shown, or of tubular shape. Besides serving as a brace and supporting member for the unit, the metal member 29 also serves as a housing or support by means of-which the various auxiliaries and connection wires for the fluorescent lamps I9, 28 may be contained and supported. The unit may be suspended from the ceiling of a room by means of a support rod 30 secured to the channel member 29 in any suitable manner, such as by a nut 31. The unit is suspended with its longitudinal axis parallel to the length of the counter or other specific surface or area with which it is related for illuminating purposes.

L ghting units, such as that described hereinabove. produce controlled downwardly-directed fan-shaped beams of light, the beams emerging non-symmetrically (in the illustrated embodiment) with respect to the longitudinal axis of the unit but symmetrically with respect to the transverse center line thereof. The light sources and other bright areas in such units are adeuuately shielded from the eyes of both the customer and sales person at all usual angles of view, while the luminous sides and shallow crosssc'tion of the unit give the latter an appearance of inappreciable weight. indirect illumination is provided by such units for better appearance of the room and lowered brightness contrasts.

The principles of the type of lighting unit according to the invention may be adaptable to services other than downlighting as such, for

example, with changes in reflector form, finish further adapted to other than suspended fixtures.

such as for ceiling mounting, shelf and wall case edges, etc., and for the primary purpose of lighting of vertical or sloping surfaces. The unit might be constructed in continuous form rather than in units of approximately lamp length, and might include additional lamps for indirect and/or direct lighting with variations in arrangement or additions to reflecting surfaces. A typical variation of this type would be the insertion, in a proportionately wider unit, of an additional reflector and lamp, etc., in space provided at the intersection 26 of segments l1, l8.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A lighting unit comprising a pair of elongated side plate members, a pair of elongated reflecting segments arranged longitudinally between said side plate members and each shaped In addition, adequate light sources and being spaced from the upper and lower longitudinal edges of said segments to provide opposed openings for the passage of light upward and downward from said unit.

2. A lighting vunit comprising a pair of translucent, downwardly converging, elongated side plate members curved in transverse section, a pair of elongated reflecting segments arranged longitudinally between said side plate members and each shaped as a light-concentrating surface of reflection in transverse section, said reflecting segments being arranged back to back with their concave reflecting surfaces facing downwardly, with their reflector axes tilted in the same direction at different angles to the vertical and with their lower longitudinal edges juxtapositioned, and elongated light sources disposed with their longitudinal axes coincident 10 with the focal axes of said reflecting segments,

the upper edge of each reflecting segment being vertically above'the focal axis of said segment. said side plate members being arranged laterally opposite said light sources with their convex 15 surfaces presented to said sources, and being spaced from the upper and lower longitudinal edges of said segments to provide opposed openings for the passage of light upward and downward from said unit. I

WENTWOR'I'H M. POTTER.

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