US3721818A

US3721818A - Ceiling mounted luminaire and light-transmitting enclosure therefor

Info

Publication number: US3721818A
Application number: US00038238A
Authority: US
Inventors: L Stahlhut
Original assignee: KSH Inc
Current assignee: K S H INC US; KSH Inc
Priority date: 1970-05-18
Filing date: 1970-05-18
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20
Also published as: CA935799A; BE767113A; LU63178A1; DE2124021A1; SE7106307L; BR7102942D0; NL7106512A; GB1365507A; FR2091760A5; DE7118967U; ZA712854B

Abstract

A light transmitting enclosure for a ceiling mounted lighting fixture provides novel lighting patterns heretofore obtainable, if at all, only with reflectors and baffles. In the preferred embodiments, the light distribution pattern is a batwing pattern which reduces both direct and reflected glare. In a preferred embodiment, a lenticular pattern on the lower face of a horizontal reach of the enclosure enlarges a pattern of upwardly convergent protrusions having light reducing upper surfaces which form a light reducing pattern on the upper surface of the reach directly above the lenticules, to reduce luminance at viewing angles near the nadir; the lenticular pattern also cuts off high angle luminance to complete the batwing pattern. In other embodiments the light reducing pattern is provided directly on a flat upper face of the reach. In other embodiments the pattern is positioned relative to the lenticules to provide different lighting patterns. In still other embodiments the upwardly convergent protrusions provide the principal or sole means for reducing luminance at low viewing angles.

Description

LIGHT-TRANSMITTING ENCLOSURE United States Patent 11 1 [111 3,721,818

Stahlhut l lMarch 20, 1973 [541 CEILING MOUNTED LUMINAIRE AND OTHER FU BLICATICNS i Catalog pages K-ll Lighting of Distinction, K-S-H THEREFOR Plastics, Inc., 1963, 4 pp. [75] Inventor: Leo G. Stahlhut, Kirkwood, Mo. Illuminating Engineering Society Handbook, Forth Edition, 1966, pp. 2-21 to 2-26 and p. 11-5. [73] Assrgnee: K-S-H, Inc., St. Louis, Mo. 22 Filed; May 1 1970 Primary Examiner-Richard C. Queisser Assistant Examiner-C. E. Snee, IH [21] Appl- 38,238 AttorneyPolster and Polster 52 u.s.c1.....24o/1o6 R, 240/78 LD, 240/51.11 R, [571 ABSTRACT 350/16 A light transmitting enclosure for a ceiling mounted Cl lv 5/0 FZlV F218 /0 lighting fixture provides novel lighting patterns heretol Field of Search 73 P, fore obtainable, if at all, only with reflectors and baf- 240/41.4, 51.11 R, 93; 313/ 1 10, 116; fies. In the preferred embodiments, the light distribu- 350/259-261, 103, 104, 106, 109, 167-169 tion pattern is a batwing pattern which reduces both direct and reflected glare. In a preferred embodiment, [56] References Cited 21 lenticular pattern on the lower face of a horizontal reach of the enclosure enlarges a pattern of upwardly UNITED STATES PATENTS convergent protrusions having light reducing upper 755,196 3 1904 Wadsworth ..350/260 Surfaces which a light reducing Patem the 2,057,395 10/1936 Sharp ..350/l06 x upper Surface of the reach directly 2,434,049 1/1948 Nordquist 240 93 x ticules, to reduce luminanCe at viewing angles near the 3,085,473 4/1963 Bourgeaux ..350/l67 nadir; th nticular pattern also cuts off high angle lu- 3,265,804 8/1966 Berger 240/51.11 X minance to complete the batwing pattern. In other 3,288,990 11/1966 Stahlhut ..240/106 embodiments the light reducing pattern is provided 3,351,753 11 1967 Berger ..240/106 directly on a flat upper face of the reach. in other em- 3,398,273 8/1968 Rex bodiments the pattern is positioned relative to the len- 3,40s,491 10/1968 George ..240 41.4 ticules to provide different lighting patterns. In still FOREIGN PATENTS OR APPLICATIONS 9 upwardly mergem s1ons provide the prmclpal or sole means for reducmg Q4330] 4/1937 Germany ..350/ 106 luminance at low viewing angles. 858,736 12/1952 Germany 240/106 215,086 5/1924 Great Britain 350/101 9 Claims, 17" 'gii 55 55 l9 l7 '1 /7o 50 51, 50 i 51 57 l 2W A37 an 7% '1 PATENTEnnAazolsra SHEET 2 BF 3 CEILING MOUNTED LUMINAIRE AND LIGHT- TRANSMIT'IING ENCLOSURE THEREFOR BACKGROUND OF THE INVENTION This invention relates to a luminaire and light transmitting enclosure for providing special lighting patterns. It has particular, but not exclusive, usefulness in providing what is known in the art as a batwing lighting pattern.

Lighting engineers have long recognized two types of glare which are detrimental to visual tasks. The first of these is direct glare. This term refers to the effects of luminance at large angles from the nadir (i.e. near the horizontal), which produce glare directly from the light source into the field of vision of the worker. The other type of glare is known as reflected glare or veiling reflections. These terms refer to the effect of reflection of a light source from a visual task. Extensive study has been made of reflected glare as it relates to the visual task, the worker and the lighting system. These studies have shown that 85 percent of seeing occurs within a range of viewing angles from to 40, with the maximum at about 25". Further analysis of the range of positions at which the visual task may be oriented indicates that the offending zone for most reflected glare lies within a cone having its apex at the surface of the visual task and the side spread about 25 from the nadir. A discussion of these problems and possible solutions to them is found in Illumination Engineering Society Handbook, 4th Edition, 1966, particularly at 2- 21 through 2-26 and at 1 1-5.

Direct glare has been effectively reduced by the use of prismatic lighting enclosures or by louvers, which cut off large angle luminance from ceiling mounted lighting fixtures. There has been far less success in reducing reflected glare and veiling reflections. Diffusing (translucent) panels reduce reflected glare but do not by any means eliminate it. Furthermore, diffusing panels restore the direct glare problem. Panels made in accordance with my U.S. Pat. No. 3,288,990 overcome the direct glare problems associated with diffusing panels, but like diffusing panels merely reduce reflected glare.

Therefore, heretofore the only truly effective methods of controlling unwanted glare have involved a combination of effective lighting panel for controlling direct glare and careful placing of light sources, workers and their visual tasks.

It has been suggested that luminaires could be produced which distribute light in a batwing pattern in which virtually all of the light is directed in a band between the high angle direct glare zone and the low angle reflected glare zone. The use of luminaires having a batwing light distribution pattern in even one transverse plane would reduce or eliminate most glare problems, without requiring careful placement of the luminaires or excessively high lighting levels. Unfortunately, satisfactory luminaires have never been developed which produce a batwing pattern with properly shaped and spread wings or which are simple enough to be commercially acceptable.

One of the object of this invention is to provide a ceiling mounted luminaire which provides a highly desirable batwing pattern.

Another object is to provide such a luminaire which can be adapted to provide other desirable lighting patterns.

Another object is to provide a light transmitting panel which will provide such patterns when used in a conventional fixture and when used with either a lineal or point light source.

Other objects will become apparent to those skilled in the art in view of the following description and accompanying drawings.

SUMMARY OF THE INVENTION In accordance with this invention, generally stated, a ceiling-mounted luminaire is provided having the usual mounting means, lamp or bulb supporting means, light transmitting enclosure and support for the enclosure. The enclosure includes a horizontal reach including light control means for producing the desired lighting pattern. In the preferred embodiments the light control means include a lenticular pattern on the lower surface of the horizontal reach and a cooperating pattern of upwardly convergent protrusions on the upper surface of the reach. The protrusions have light transmitting side walls and light reducing upper surfaces. The protrusions are arranged with their light reducing upper surfaces directly over the centers of the individual lenticules of the lenticular pattern to form a light reducing pattern which is magnified by the lenticules at small viewing angles from the nadir. Also at small angles, the side walls increase the effective size of the light reducing areas to essentially the size of the protrusions. The lenticules, protrusions and flat upper face also cut off most luminance at high angles. The lighting pattern of this embodiment is a batwing pattern with the wings spread at about 40 and with sharp cut-offs at around 20-25 and 55-60 from the nadir.

In the presently preferred embodiment the lenticules are cylindrical and straight and the protrusions are straight ribs. ln another embodiment the lenticules are cylindrical and bent and the protrusions are bent ribs. In another embodiment the lenticules are spherical and the protrusions are frustums, either conical or pyramidal.

In other embodiments, the configuration of the upper surface or the lower surface of the horizontal reach is altered. Thus, in one alternative embodiment the upper surface is flat and light reducing areas are provided on the flat surface. In another embodiment, the lower surface is flat. In still another embodiment, the light reducing pattern is positioned over the junctions of the lenticules to provide a l ouvered effect.

The protrusions, in those embodiments in which they are used, cover a substantial portion of the upper face of the horizontal reach, on the order of 30 percent or more. The light reducing areas are preferably positioned considerably closer to the lower surface than the focal point of the lenticules.

The light reducing areas are areas which are more light reducing than the surrounding surface. That is, the light reducing areas may be opaque and the surrounding surface translucent or clear, or the light reducing area may be translucent and the surrounding surface clear. The light reducing areas are preferably reflective to increase efficiency, but may be absorptive. They may be any color that is aesthetically suitable for the intended use of the enclosure or fixture.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings,

FIG. 1 is a sectional view of a ceiling-mounted luminaire of the present invention;

FIG. 2 is a lighting pattern diagram showing a desirable batwing lighting pattern which may be obtained with a luminaire of the invention;

FIG. 3 is an enlarged sectional view of a part of the preferred embodiment of light transmitting enclosure of the luminaire shown in FIG. 1;

FIG. 4 is a transverse sectional view of the light transmitting enclosure of FIG. 3, taken along the line 44 of FIG. 3;

FIG. 5 is a view in bottom plan of the light transmitting enclosure shown in FIGS. 3 and 4;

FIG. 6 is a view in top plan of the light transmitting enclosure shown in FIGS. 3-5;

FIG. 7 is a fragmentary sectional view, corresponding to FIG. 3, of another illustrative embodiment of light transmitting enclosure;

FIG. 8 is an enlarged sectional view, corresponding to. FIG. 3, of another illustrative embodiment of light transmitting enclosure;

FIG. 9 is a transverse sectional view, corresponding to FIG. 4, of the light transmitting enclosure of FIG. 8, taken along the line 9-9;

FIG. 10 is a view in bottom plan, corresponding to FIG. 5, of the light transmitting enclosure of FIGS. 8 and 9;

FIG. 11 is a view in top plan, corresponding to FIG. 6, of the light transmitting enclosure of FIGS. 8-10;

FIG. 12 is a fragmentary sectional view corresponding to FIG. 3 of another embodiment of light transmitting enclosure;

FIG. 13 is a fragmentary sectional view corresponding to FIG. 3 of another embodiment of light transmitting enclosure for reducing luminance at high viewing angles;

FIG. 14 is a fragmentary sectional view corresponding to FIG. 3 of another embodiment of light transmitting enclosure for reducing luminance at small viewing angles;

FIG. 15 is a fragmentary sectional view corresponding to FIG. 3 of another embodiment of light transmitting enclosure;

FIG. 16 is a view in bottom plan, corresponding to FIG. 5, of the light transmitting enclosure of FIG. 15; and

FIG. 17 is a view in top plan, corresponding to FIG.

6, of the light transmitting enclosure of FIGS. 15 and 16.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, and in particular to FIGS. 1 and 2, reference numeral 1 indicates one illustrative embodiment of luminaire embodying the present invention. The luminaire 1 includes a grid 2 of T-rails 3 having mounting holes 4 on their vertical legs 5 for mounting the grid 2 on a ceiling structure 7, as with wires 9. The ceiling structure 7 may be a traditional finished ceiling or may be simply a framework under an upper floor or a roof. The luminaire 1 also includes ballasts 10 held to the ceiling structure 7 by screws 11. Brackets 12 are provided on ballasts 10 for supporting fluorescent lamps 13 which act as a fixed light source. The horizontal arms 15 on the grid 2 support light transmitting enclosures in the form of horizontal, flat lighting panels 17 having an upper surface 19 and a lower surface 21. As thus far described, the luminaire l is, of course, simply a typical luminous ceiling. As will be described, however, the lighting panel 17 permits the production of special lighting patterns including among others a batwing lighting pattern. A particularly desirable batwing pattern is shown in FIG. 2. As also indicated in FIG. 2 the luminaire of the invention may be a lighting fixture 23 in which the lighting panel 17 and fluorescent lamps 13 are supported and which is itself mounted on the grid 2. The luminaire may also be of other types such as surface mounted, flush, recessed or regressed.

Details of a particularly desirable lighting panel 17 are shown in FIGS. 3-6. This illustrative embodiment of panel 17 is made of a transparent material such as clear acrylic or polystyrene plastic or clear glass.

The upper surface 19 of the panel is provided with a pattern of upwardly convergent protrusions in the form of linear ribs 30. The ribs 30 have side walls 31 which slope about 20 from the normal to the plane of the panel. Flat upper surfaces 33 on the protrusions 30 are coated with an opaque paint 35. The painted surfaces of the ribs form a light reducing pattern on the upper surface 19 of the panel 17. Flat surfaces 37 are left between the ribs 30. The side walls 31 and surfaces 37 are optically clear.

The lower surface 21 of this illustrative embodiment of panel 17 includes a lenticular pattern consisting of clear cylindrical lenticules 40, each of which is positioned directly beneath one of the ribs 30 on the upper surface of the panel. Downwardly convergent transverse ridges 50 are provided on the lower surface.

This embodiment of panel 17 may be formed as a single piece by conventional methods, and the upper faces 33 of the ribs 30 may be roller painted with the opaque paint 35.

The use of the panel of FIGS. 3-6 in the fixture of FIG. 1 produces a batwing lighting pattern almost identical with that shown in FIG. 2, except that with some luminaires above about some high angle brightness may occur. This may be eliminated by shallow louvers below or incorporated into the panel or by a prismatic panel over the panel 17.

The proportions of this embodiment of panel may be varied considerably to provide a desired combination of strength, economy, over-all lighting efficiency and light distribution characteristics. Two examples of desirable proportions are shown in the following table:

Total thickness 0.235 0.26 Total thickness less 30 0.127 0.18 Total thickness less 0.220 0.24 Radius of curvature, 40 0.]35 0.127 Width of ribs 30 at root 0.108 0.13 Width of surfaces 37 between ribs 0.059 0.055 Width of ribs 30 at their upper surface 0.032 0.065 Spacing between transverse ridges 50 0.375 0.38

The proportions A are preferred because they provide a painted surface covering about 20 percent of the upper face of the panel in top plan elevation and therefore provide a relatively high lighting efficiency. The wings of the batwing pattern produced by these proportions are somewhat wider than those shown in FIG. 2, but the pattern is still a highly desirable one. The proportions B provide lower lighting efficiency, with about.

35 percent of the upper surface paint covered, but given even narrower wings, spread farther apart, than those shown in FIG. 2. The precise efficiencies and lighting patterns will depend on the design of the rest of the luminaire, the clarity of the material of which the panel is made, and the extent if any to which the paint 35 covers the upper sides 31 adjacent the surfaces 33.

The method by which a batwing pattern is produced by the illustrative panel of FIGS. 3-6 is shown diagramatically in FIG. 3. The arrows 60 indicate the limits of theoretically permissible light paths through the ribs and lenticules of the panel 17. The permissible light paths are shown for a single representative viewing angle through each lenticule, and therefore the relative brightness for each viewing angle may be approximated by noting the relative amount of shading at each angle.

As shown by the arrow in broken lines at 60a, at viewing angle the lenticular part of the panel is completely dark. This is because the rib 30 is magnified by the lenticule 40 and because at this angle the side walls 31 completely reflect the painted upper surface 33 of the rib by internal reflection.

As shown at 60b, at 25 most of the light paths through the panel are cut off, directly or by internal reflection from the rib wall 31, by the opaque face 33. Some light, however, emerges through the surface 37 between ribs.

At 30, almost all light paths are open, as shown at 60c, including a band which falls within the critical angle of the side wall 31 of the rib and thus represents a light path directly through the side wall. A small band of paths is blocked by internal reflection of the opaque surface 35 from a side wall 31.

At 45 the entire side wall 31 becomes transparent. Because the surface 37 between the ribs 30 is also transparent at this angle, virtually the entire lenticular portion of the lens is lighted, as shown at 60d. Only a small band of possible light paths is cut off by the opaque upper surface of the adjacent rib.

At 55, as shown at 60c, most of the possible light paths are cut off because they lie outside the critical angle of the surface 37 between the ribs, because they are cut off by the opaque upper surface 33 of the adjacent rib, or because they are bent downwardly through successive ribs.

At 60, only a very thin band of permissible light paths exists through the side wall 31, as shown at 60f.

It will be seen that the side walls 31 of the ribs 30 cffectively increase the size of the opaque upper surfaces 33 by about I00 percent at small viewing angles. At angles near 45, the side walls become completely transparent and increase brightness by shifting the angle of incidence for permitted light paths toward the normal to the plane.

It should also be noted that the opaque upper surfaces 33 are positioned at a distance from the lenticular faces considerably less than the one-and-a-half diameters which is taken as the nominal focal point of a semicircular lens. This is done intentionally, because unlike most lenticular lens arrangements used heretofore, the purpose of the panel and luminaire of this invention is not to provide a sharp image to be observed by a viewer, but to provide carefully modulated lighting intensities through nearly a complete 180 of viewing angles.

The ridge 50 on the lower surface does not enlarge the opaque areas on the upper face of the lighting panel. Therefore, at 0 its luminance is approximately one half of its luminance at 45. This brightness of the ribs is important in alleviating the psychological effect of having the lighting panel become completely dark as one walks under it or views it at high angles in line with the ribs.

Because the lengthwise strength of the panel depends on the distance between the top of the ribs 30 and the lower edge of the lenticules 40, and the crosswise strength depends on the distance between the surface 37 of the upper face and the lower edge of the ridges 50, this embodiment of panel is extremely rigid, and has a very favorable strength to weight ratio, as compared with other panels.

The embodiment of light transmitting enclosure 17 shown in FIGS. 3-6 is the presently preferred embodiment, for all of the reasons described. However, numerous modifications are possible which share many of the advantages of the embodiment of FIGS. 3-6 and which provide advantages of their own.

In FIG. 7, an embodiment is shown which differs from the first embodiment in lacking ridges 50 and in having roughened rib side walls 131 and surfaces 137 between the ribs, corresponding to the clear walls 31 and surfaces 37 of the first embodiment. The roughening of the walls and surfaces performs the dual function of permitting some light leakage at 0 viewing angle and of diffusing the light source image, particularly at viewing angles of maximum luminance. If merely diffusing the light source image is desired, a thin sheet of light diffusing material may be bonded to the upper surfaces of the ribs of the first embodiment, as shown at at the right-hand side of FIG. 3. This alternative approach does not affect the optical performance of the embodiment of FIGS. 3-6.

Another modified embodiment is shown in FIGS. 8-11. In this embodiment, the protrusions 230 corresponding to the ribs 30 of the first embodiment are in the form of pyramidal frustums, the sides 231 of which are upwardly convergent at an angle of about 20 from the normal and the upper surfaces 233 of which are coated with an opaque paint 235. The lenticular pattern on its lower surface consists of overlapping spherical lenticules 240 having the same'relative centers of curvature and the same radii of curvature as the lenticules 40 of the first illustrative embodiment. The dimensions of this embodiment may be precisely the same as those shown for the corresponding parts of the first illustrative embodiment. It will be seen that this embodiment provides a batwing pattern in all planes 360 around the panel. The pyramidal frustums may also provide more light along the diagonal, a light distribution characteristic which is frequently desirable. It will also be seen that the proportion of the upper surface covered with light reducing areas is far less (hence the efficiency far greater) than in the first illustrative embodiment. Thus, the protrusions cover only about 50 percent of the upper surface 19 and the coated surfaces cover only about 4-12 percent of the upper surface 19, as compared with about 70 percent and 20-35 percent respectively for the first embodiment.

The effective thickness of this embodiment is only the distance between the junctions of the lenticules 240 and the surface 237 between the protrusions 230, and therefore the strength to weight ratio of this embodiment is considerably less than for the first embodiment. Reinforcing ribs on the upper or lower surface, or a different proportioning of the elements could be used to strengthen this embodiment.

The embodiment of panel shown in FIG. 12 lacks any protrusions on its upper face, and a light reducing pattern is painted directly onto its upper face, such as by silk screening. The pattern consists of opaque painted strips or dots 335, depending on whether the lenticules 340 on its lower face are cylindrical or spherical. The light reducing areas 335 are again placed much closer to the lenticules 340 than the nominal focal points of the lenticules in order to provide a substantial reduction of luminance at viewing angles up to 25. Nonetheless, luminance below 25 is still considerably greater than ideal. To reduce this luminance, a thin translucent sheet 370 is bonded to the upper surface at the opaque areas 335 and is spaced away from the upper surface of the panel 17 by the opaque areas, to reduce the luminance at small viewing angles without affecting the cut-off at high viewing angles. At viewing angles between about 55 and 75 the cut-off is not as great as is provided by the first embodiment, but at extremely high angles the cut-off is virtually complete. Therefore, for certain purposes this panel may be more desirable than the panel of the first embodiment, although as noted it lacks certain light distribution qualities and also is optically less efficient, has less strength as compared with its weight, and is harder to manufacture accurately.

As shown in FIGS. 13 and 14, the light transmitting enclosure of this invention may be modified in other ways to produce other lighting patterns. These patterns are frequently desirable for special lighting purposes.

In the embodiment shown in FIG. 13, the body of the light transmitting enclosure is identical with the embodiment of FIG. 12. The light reducing areas 435 however, are provided over the junctions 441, rather than the centers, of the lenticules 440. Light reducing areas 480 are also provided on the centers of the lenticules 440 to reduce high angle luminance to a very small value. This embodiment acts as a louver which focuses most of the light directly downward. The cutoff angle of this embodiment may be made as small and as complete as desired, by varying the width of the

opaque areas

435 and 480 and the thickness of the panel.

The embodiment shown in FIG. 14 has precisely the opposite effect. In this embodiment, protrusions 530, which may be identical with those of any of FIGS. 3-11, cut off light at very small viewing angles. They also reduce luminance at high viewing angles. The spacing between the protrusions determines luminance at small angles. The wings of this embodiment are far too broad for most lighting purposes in which a batwing pattern is desired. It may be used in situations in which direct glare is not a problem and most work is done looking almost straight down at the visual tasks. Furthermore, supplementary means may be used to improve the lighting pattern for other purposes. This panel may also be turned over and used as an effective louver.

Although the illustrative embodiments of luminaires described heretofore have had fluorescent tubes as their fixed light source, any other fixed light sources such as incandescent bulbs or mercury vapor lamps may be used in luminaires incorporating the panels already described or other light transmitting enclosures particularly designed for use with these sources. The enclosure of FIGS. 15-17 is particularly suitable for use in an incandescent bulb fixture, although its use is not limited thereto. In this embodiment, the lower face of the panel includes a pattern of linear lenticules 640 bent to form concentric squares, with diagonal ridges 650. Cooperating rib protrusions 230 are provided on the upper face of the panel. The cross-sectional dimensions of this embodiment may be the same as for corresponding elements of the embodiment of FIGS. 3-6. This embodiment is conveniently cast in glass.

Numerous other variations may be made in the light transmitting enclosure of this invention, within the scope of the following claims, to produce desirable lighting patterns with ceiling-mounted luminaires. Merely by way of example, the light reducing areas may be placed asymmetrically with respect to the lenticules to provide asymmetric lighting patterns, for example for providing indirect lighting from a wall. The side walls of the protrusions may be concave of otherwise contoured rather than straight. The lenticules may be spaced apart rather than intersecting, although this arrangement would tend to degrade the lighting pattern. Some lenticules or some light reducing areas may be omitted. The lenticules may be concentric rings or other figures. The features of some embodiments may be combined with other embodiments. The enclosure may have side walls with or without light controlling means like those on the horizontal reach of the enclosure. These variations are merely illustrative.

Having thus described the invention, what is claimed and desired to be secured by Letters Patent is:

1. In a luminaire having means for mounting said luminaire on a ceiling structure, means for supporting a fixed light source in said luminaire, a light transmitting enclosure having a broad horizontal reach, said reach having an upper surface and a lower surface, and means for supporting said light transmitting enclosure with said horizontal reach in a generally horizontal position beneath the light source, the improvement comprising means for reducing luminance at small viewing angles from the nadir, said means comprising a pattern of upwardly convergent protrusions on the upper surface of said reach of said enclosure, said protrusions being isosceles trapezoids in cross section, said protrusions having light transmitting side walls and light reducing upper surfaces, the side walls of said protrusions sloping about l0-30 from the normal to the plane of the reach.

2. The improvement of claim 1 including a light controlling pattern on the lower surface of said reach of said enclosure.

3. The improvement of claim 2 wherein the light con trolling pattern comprises means for reducing luminance at high viewing angles from the nadir.

4. The improvement of claim 3 wherein said means for reducing luminance at high viewing angles from the nadir comprises a pattern of lenticules, the centers of said lenticules being positioned directly below said light reducing upper surfaces of said protrusions, the pattern of lenticules further enhancing said reduction of luminance at said small viewing angles from the nadir.

5. In a light transmitting enclosure having a broad reach with an upper surface and a lower surface, the

'improvement comprising means for reducing luminance at small viewing angles from the normal below the enclosure, said means comprising a pattern of upwardly convergent protrusions on the upper surface of said reach of said enclosure, said protrusions being isosceles trapezoids in cross section, said protrusions having light transmitting side walls and light reducing upper surfaces, the side walls of said protrusions sloping about 30 from the normal to the plane of the reach, said light reducing upper surfaces forming a light reducing pattern, said protrusions covering at least thirty percent of said reach when viewed in top plan.

6. The improvement of claim 5 wherein said light reducing pattern comprises an opaque paint on said upper surfaces of said protrusions.

7. The improvement of claim 5 including a diffusing sheet overlying said upper surface of said reach, spaced therefrom intermediate said light reducing pattern by said light reducing pattern.

8. The improvement of claim 5 including a pattern of lenticules on the lower surface of said reach, the centers of said lenticules being positioned directly below said light reducing upper surfaces of said protrusions.

9. The improvement of claim 8 wherein said protrusions are linear ribs and the lenticules of said lenticular pattern are cylindrical.

10. The improvement of claim 9 wherein the upper surfaces of said protrusions are coated with an opaque paint, said paint covering at least about percent of said upper surface of said reach when viewed in top plan.

11. A light transmitting enclosure for use in a luminaire having a light source, said enclosure including a broad reach positionable below said light source, said reach having an upper surface and a lower surface, a lenticular pattern on the lower surface and a cooperating light reducing pattern on the upper surface, and a diffusing sheet overlying said upper surface, spaced therefrom intermediate said light reducing pattern by said light reducing pattern.

12. In a luminaire having means for mounting said luminaire on a ceiling structure, means for supporting a fixed light source in said luminaire, a light transmitting enclosure having a broad horizontal reach, said reach having an upper surface and a lower surface, and means for supporting said light transmitting enclosure with said horizontal reach in a generally horizontal position beneath the light source, the improvement comprising means for producing a batwing lighting pattern below said fixture, said means comprising a lenticular pattern on the lower face of said reach of said enclosure and a cooperating light reducing pattern on the upper face of said reach of said enclosure, said light reducing pattern being arranged over the centers of the individual lenticules of said lenticular pattern, said light reducing pattern being positioned substantially closer to the lenticular pattern than the nominal focal length of the lenticules of said lenticular pattern.

13. The improvement of claim 12 wherein said reach is proportioned to permit most light to pass through said reach at viewing angles between about 25 and 55 from the nadir.

14. The improvement of claim 12 wherein the lenticules of said lenticular pattern are circular in crosssection.

15. The improvement of claim 14 wherein the light reducing pattern is positioned closer to the lenticular pattern than twice the radius of curvature of said lenticules.

16. The improvement of claim 12 including light diffusing means on said upper surface of said reach, said light diffusing means and said light reducing pattern covering substantially all of the upper surface of the reach when viewed in top plan.

17. The improvement of claim 16 wherein the light diffusing means comprises a diffusing sheet overlying said upper surface of said reach, spaced therefrom intermediate said light reducing pattern by said light reducing pattern.

18. The improvement of claim 12 including a pattern of upwardly convergent protrusions on said upper surface of said reach, said light reducing pattern being provided on an upper surface of said protrusions.

19. The improvement of claim 18 including a diffusing sheet overlying said upper surface of said reach, spaced therefrom intermediate said light reducing pattern by said protrusions.

20. The improvement of claim 18 wherein the protrusions have side walls which slope about l030 from the vertical.

21. The improvement of claim 20 wherein 'said protrusions cover at least about 30 percent of said upper surface of said reach.

22. The improvement of claim 18 wherein the protrusions are ribs and the light reducing pattern is painted on the upper surfaces of the ribs.

23. In a light transmitting enclosure having a broad reach with an upper surface and a lower surface, the improvement comprising light control means on the reach for producing a batwing lighting pattern, said light control means comprising a lenticular pattern on the lower surface of the reach and a cooperating pattern of upwardly convergent protrusions on the upper surface of the reach, said protrusions having light transmitting side walls and light reducing upper surfaces,

said light reducing upper surfaces forming a light reducing pattern directly above the centers of individual lenticules of said lenticular pattern, said light reducing pattern being positioned substantially closer to the lenticular pattern than the nominal focal length of the lenticules of said lenticular pattern.

24. The improvement of claim 23 wherein said light reducing pattern comprises an opaque paint on said upper surfaces of said protrusions.

25. The improvement of claim 24 including light diffusing means on said upper surface of said reach, said light diffusing means and said light reducing pattern covering substantially all of the upper surface of the reach when viewed in top plan.

26. The improvement of claim 23 wherein the side walls of said protrusions slope about l-30 from the normal to the plane of the reach.

27. The improvement of claim 26 wherein said reach is proportioned to permit most light to pass through said reach at viewing angles between about 25 and 55 from the nadir.

28. The improvement of claim 26 wherein the lenticules of said lenticular pattern are cylindrical, the protrusions are ribs and the light reducing surfaces are stripes, said stripes covering at least about percent of the upper surface when viewed in top plan.

29. The improvement of claim 28 wherein the ribs cover at least about 50 percent of the upper surface when viewed in top plan and said stripes cover between about 20 and 35 percent of the upper surface when viewed in top plan.

30. The improvement of claim 23 wherein the lenticules of said lenticular pattern are cylindrical, the protrusions are ribs and the light reducing surfaces are stripes.

31. The improvement of claim 30 wherein said stripes cover at least about 20 percent of the upper surface when viewed in top plan.

32. The improvement of claim 31 wherein the ribs cover at least about 50 percent of the upper surface when viewed in top plan and said stripes cover between about 20 and 35 percent of the upper surface when viewed in top plan.

33. The improvement of claim 30 including transverse ridges on the lower surface of the reach.

34. The improvement of claim 23 wherein the lenticules of said lenticular pattern are spherical, the protrusions are frustums and the light reducing surfaces are dots.

35. The improvement of claim 34 wherein the frustums cover at least about 25 percent of the upper surface when viewed in top plan and said dots cover between about 4 and 12 percent of the upper surface when viewed in top plan.

36. The improvement of claim 23 wherein said protrusions cover at least 30 percent of said reach when viewed in top plan.

37. The improvement of claim 23 including a diffusing sheet overlying said upper surface of said reach, spaced therefrom intermediate said light reducing pattern by said light reducing pattern.

38. The improvement of claim 23 wherein the lenticules of said lenticular pattern are circular in crosssection.

39. The improvement of claim 38 wherein the light reducing pattern is positioned closer to the lenticular pattern than twice the radius of curvature of said lenticules.

* =l III

Claims

1. In a luminaire having means for mounting said luminaire on a ceiling stRucture, means for supporting a fixed light source in said luminaire, a light transmitting enclosure having a broad horizontal reach, said reach having an upper surface and a lower surface, and means for supporting said light transmitting enclosure with said horizontal reach in a generally horizontal position beneath the light source, the improvement comprising means for reducing luminance at small viewing angles from the nadir, said means comprising a pattern of upwardly convergent protrusions on the upper surface of said reach of said enclosure, said protrusions being isosceles trapezoids in cross section, said protrusions having light transmitting side walls and light reducing upper surfaces, the side walls of said protrusions sloping about 10*-30* from the normal to the plane of the reach.

3. The improvement of claim 2 wherein the light controlling pattern comprises means for reducing luminance at high viewing angles from the nadir.

5. In a light transmitting enclosure having a broad reach with an upper surface and a lower surface, the improvement comprising means for reducing luminance at small viewing angles from the normal below the enclosure, said means comprising a pattern of upwardly convergent protrusions on the upper surface of said reach of said enclosure, said protrusions being isosceles trapezoids in cross section, said protrusions having light transmitting side walls and light reducing upper surfaces, the side walls of said protrusions sloping about 10*-30* from the normal to the plane of the reach, said light reducing upper surfaces forming a light reducing pattern, said protrusions covering at least thirty percent of said reach when viewed in top plan.

10. The improvement of claim 9 wherein the upper surfaces of said protrusions are coated with an opaque paint, said paint covering at least about 20 percent of said upper surface of said reach when viewed in top plan.

13. The improvement of claim 12 wherein said reach is proportioned to permit most light to pass through said reach at viewing angles between about 25* and 55* from the nadir.

14. The improvement of claim 12 wherein the lenticules of said lenticular pattern are circular in cross-section.

20. The improvement of claim 18 wherein the protrusions have side walls which slope about 1030* from the vertical.

21. The improvement of claim 20 wherein said protrusions cover at least about 30 percent of said upper surface of said reach.

23. In a light transmitting enclosure having a broad reach with an upper surface and a lower surface, the improvement comprising light control means on the reach for producing a batwing lighting pattern, said light control means comprising a lenticular pattern on the lower surface of the reach and a cooperating pattern of upwardly convergent protrusions on the upper surface of the reach, said protrusions having light transmitting side walls and light reducing upper surfaces, said light reducing upper surfaces forming a light reducing pattern directly above the centers of individual lenticules of said lenticular pattern, said light reducing pattern being positioned substantially closer to the lenticular pattern than the nominal focal length of the lenticules of said lenticular pattern.

26. The improvement of claim 23 wherein the side walls of said protrusions slope about 10*-30* from the normal to the plane of the reach.

27. The improvement of claim 26 wherein said reach is proportioned to permit most light to pass through said reach at viewing angles between about 25* and 55* from the nadir.

28. The improvement of claim 26 wherein the lenticules of said lenticular pattern are cylindrical, the protrusions are ribs and the ligHt reducing surfaces are stripes, said stripes covering at least about 20 percent of the upper surface when viewed in top plan.

38. The improvement of claim 23 wherein the lenticules of said lenticular pattern are circular in cross-section.