US2545058A

US2545058A - Lighting fixture for use with elogated tubular lamps

Info

Publication number: US2545058A
Application number: US40707A
Authority: US
Inventors: John S Walsh
Original assignee: Individual
Current assignee: Individual
Priority date: 1948-07-26
Filing date: 1948-07-26
Publication date: 1951-03-13
Anticipated expiration: 1968-03-13

Description

March 13, 1951 2,545,058

J. S. WALSH LIGHTING FIXT FOR USE WITH ELONGATED ULAR LAMPS Filed July 26, 1948 4 Sheets-Sheet 1 INVENTOR. JOHN S. WALSH ATTORNEY March 13, 1951 J. s. WALSH LIGHTING FIXTURE FOR USE WITH ELONGATED TUBULAR LAMPS 4 Sheets-Sheet 2 Filed July 26, 1948 INVENTOR. JOHN S. WALSH Wm a ATTORNEY March 13, 1951 Y J. s. WALSH 2,545,058

LIGHTING FIXTURE FOR USE WITH ELONGATED TUBULAR LAMPS Filed July 26, 1948 4 Sheets-Sheet 3 INVENTOR. 25 JOHN s. WALSH A TTOR/VEY March 13, 1951 J. s. WALSH LIGHTING FIXTURE FOR USE WITH ELONGATED TUBULAR LAMPS Filed July 26, 1948 4 Sheets-SheetA 3/ A52 83 a; 33 9/ 9 23 k 87 i 79 I E Q 57 W 8/ J9 6/ 63 INVENTOR. JOHN S. WALSH ATTORNEY Patented Mar. 13, 1951 LIGHTING FIXTURE FOR;- USE ELONGATED" TUBULAR LAMBS.-

Johns. Walsh, San Francisco, Calif.

Application-July 26, 1948, SeriaI NO. 40,107

16 Claims.

This invention relatesto an improved: lighting fixture. More particularly it relates to a. lighting fixture for use. with tubular or linear types of light sources, such as fluorescent lamps.

This invention solves several previously unsolved problems in connection. with luminous indirect fixtures for fluorescent. and other lineartype tubular lamps. Although the modern fluorescent lamps have agreater lumen output per watt than any other: commercially available light source, their efficiency has been impaired by the lighting fixtures in which they are placed. A typical luminousindirect fixture is a rectangular box of diffusing glass open. at the top, and suspended from the ceiling by two or three tubular fixture stems of small cross-section. Inside the box are four LO-watt 48-inch fluorescent lamps mounted horizontally parallel to. one another just above the bottom panel of diffusing. glass, and the necessary ballasts, in a wiring channel of square or rectangular cross-section. some fixtures modify the shape by employing semir-cyline drical plastic difiusing panels beneathv the tubes instead. of the fiat glass panels. However, in.- all of. these luminous indirect fixtures, the maximum light intensity is directed upward against that portion of the ceiling immediately over the fixture, and secondarily through the panels tothe work area immediately below the fixture. When parallel rows of such fixtures are used the unevenness of the light. is seen by the alternation of very bright and very' darlc areas on the ceiling caused by a lack of proper light control: The indirect light thus produced gives very poor results in general illumination of a room, both because of the low overall eificiency of the fixtures, and because of the objectionable contrasts in ceiling brightness which precludecomfortable V1S101'l.

Another problem heretofore encountered is the great weight of fixturesemployed. filtypical fixture such as has been described weighs 50 pounds, and constitutes a heavy load to suspend from the ceiling on slender fixture stems, especially in areas subject to earthquakes. They'are dangerous and are difficult to install andrepair;

Still another problem is that present-day fluorescent luminous indirect fixtures are difiicult to clean. If the glass of plastic panels can beremoved at all, the process is made difficult by latches, hinges, or other locking devices conventionally employed. If the glass or plastic difiusing panels are fixed, the fixturesmust be cleaned in place. Often this must be done bya. maintenance man on a ladder with water and. soap 2 immediately over a. desk' or over a heavily-trafficked work. area.

One object of this invention is to solve the aboveiproblems.

Another object. is to provide a luminous indirectfiuorescent. lamp fixture which utilizes maximum light output. from the lamps.

Another object; of. this invention: is to provide a lighting fixture. for. fluorescent lamps. which will. give an even illumination on: the: working plane.

Another object is:to. provide'a. suspended lighting fixture for fluorescent lamps-which; willLg-ive more. even. illumination: on. the ceiling, resulting in a minimum of brightness contrast. between the areas. directly above and the areas between fixtures.

Another object of the; invention to prouide a highly efiicient luminous indirect fixture, that is, one in which to of thefix-ture light output is. emitted. above a horizontal plane through. the I fixture center;

Another. object of the invention is; toprovide: a luminous indirect fixture having; a light shield; or baiile for alinear light so.urce,,which.operates to reduce glare below the fixture and operates: at

the-sametime to provide wide-spread upward refiection oflight fromthe-lamp;

Another object of the invention; is; to. provide a luminous indirect lighting. fixture adaptedfor use as a. single tubular lamp. fixtureior. a multilamp fixture by simple assembly of standardized parts.

Another object of the: invention is to provide a luminous indirect lighting fixture unit which can be used forsingleonmulti-lamp illumination and in lamp fixtures to be suspended from; the ceiling aswell as fixtures mounted on the wall.

Another object of the invention is to. provide asuspended lighting fixture for fluorescent lamps which is light in weight.

Another object is to provide a luminous. indirect lighting fixture for fluorescent-lampsv with ballasts or transformers, attached. directly: to the ceiling, rather than suspended on: light weight tubular stems.

A further object: is to provide arr attractive linear. type fixture which is easy to? clean.

A further object is to providea fixture with easily removable plastic or glass panels which merely lie inplace-due to the force of gravity;

Other objects and advantages of. the; invention will appear from the following description ofa preferred embodiment- In accordancewith United States Revised Statutes, section 4888, this embodiment is described in detail but it is not intended to thereby limit the claims.

In the drawings:

Fig. l is a view in perspective from below of a fixture embodying the invention; the fixture here shown is a four-lamp ceiling unit;

Fig. 2 is a view in perspective from below of the ceiling detail of the same fixture, with the canopy slid down the stems to show the ballast mounting;

Fig. 3 is a view in vertical cross-section of the fixture shown in Fig. 1

Fig. 4 is a diagram showing the reflection pattern of the upper lamp on one side of the fixture shown in Fig. 3;

Fig. 5 is a diagram similar to Fig. 4 showing the reflection pattern of the lower lamp;

Fig. 6 is a candle-power distribution curve showing the light distribution of the right hand half of the fixture shown in Fig. 3; the curve represents the intensity of the light emanating from one side of the fixture of Fig. 3, plotted against angle of emanation;

Fig. 7 is a view in vertical cross-section of a modified form of lighting fixture similar to that shown in Fig. l the fixture here shown is a twolamp unit adapted for wall installation;

Fig. 8 is a view in vertical cross-section of another modified type of lighting fixture-a twolamp unit adapted for suspension from the ceil- 111g;

Fig. 9 is a view in vertical cross-section of another modified type of lighting fixture similar to that shown in Fig. 8-a one-lamp unit adapted for wall installation; and

Fig. 10 is a diagram showing the relation of the reflecting surfaces in Fig. 9 or the lower-left hand portion of the other lamps, to a more complete parabola.

In general the invention comprises a lighting fixture for use with tubular light sources. It includes a frame member, reflecting surfaces supported by the frame member and having an approximately parabolic cross-section with the axis of the parabola inclined upwardly, and a linear lamp supported by the frame member at the focus of the parabola. The fixture also includes a shield or baflle which substantiallyreduces the direct lighting through the bottom of the fixture and has a reflecting surface which adds further ceiling illumination to that from the main reflectors.

The fixture ||l shown in Figs. 1 and 3 is designed primarily for suspension mounting from a ceiling II. A flat strap l2 of wrought iron is bolted against the ceiling by toggle bolts l3, and lamp ballasts or transformers M are fastened to the strap l2. The ballasts of transformers l4 and the strap |2 are then covered by a canopy l5, which slides up stems Hi and H. The canopy I5 is secured in place by cylindrical metal collars l8 and |9 whose set screws tighten into the fixture stems It and H. Because the heavy transformers or ballasts l4, etc. are held directly on the ceiling H, the weight of the fixture i0 itself is correspondingly reduced. When constructed from aluminum and acrylic plastics it weighs only about pounds, and gives over 0% more illumination than a 50 pound prior-art unit.

The fixture I0 as shown generally in Fig. 1 and more specifically in Fig. 3 comprises two identical frame members 26 and 2|, on which are mounted four

linear fluorescent lamps

22, 23, 24, and 25, and four

shields

26, 21, 28, and 29, one for each lamp.

Each of the frame members 20, 2| is preferably extruded, formed or rolled of aluminum, with the outer surface given a specular or mirror-like finish of high reflectance for light control. At the top of the right frame member 20 (Fig. 3), a vertical flange 30 is designed to be joined to a corresponding vertical flange 3| on the left frame member 2| by riveting, bolting, welding, or other means.

Horizontal shoulders, 32, 33 join the flanges 30, 3| to upper

parabolic reflecting surfaces

34, 35, respectively. Each

parabolic reflector

34, 35 is part of an optical system with the center of its linear

light sources

22, 23 at its focal point, and its

axis

36, 31 preferably inclined at an angle of approximately above nadir.

Below the

upper reflectors

34, 35 there are inclined flat surfaces 40, 4|, having openings 42, 43 at intervals corresponding to the lamp length. Into these openings 42, 43, the

lampholders

44, 45 of

lamps

22, 23 are inserted and fastened to the inner surface of the frame 26, 2| before the bases are joined together. Wires 46 run from the center of the hollow stems Hi and into a channel 41 inside the frames 26, 2| and thence to the

lamps

22, 23, 24 and 25.

Below the inclined flat surfaces 40, 4| are the lower reflector surfaces 50, 5|, which are also approximately parabolic and are each part of an optical system with the center of the linear

light sources

24, 25 at its focal point. The

axis

52, 53 of each of these parabolas preferably lies at an angle of approximately above nadir, so that the lower parabolas are somewhat more vertically inclined than the upper parabolas.

Below the lower reflector surfaces 59, 5|, the surfaces of the frames 20, 2| are plane and approximately vertical at 54, 55. Into openings 56, 51 at intervals corresponding to the lamp length,

lampholders

58, 59 are inserted and fastened in a manner similar to that used with

lampholders

44, 45 above.

Underneath the

surfaces

54, 55, the frame members 20, 2| are inturned at 68, 6| to

channels

62, 63. The frames are joined together at these

channels

62, 33 by riveting, bolting, welding or other means.

Outturned flanges

64, 65 run along the lower edge as a support for the bottom shields 28, 29.

The bottom shields 28, 29 may be opaque refleeting members, but preferably they are translucent panels of glass or plastic. Translucent acrylic resin panels are ideal because of their light weight, their strength, and their lightdiffusing and shatterproof qualities. Each

panel

28, 29 comprises an incurved central portion Ill, H of parabolic cross section, an outcurved, inner, almost horizontal supporting portion 72, i3, and an outcurved, upstanding outer portion 1'4, 75. The inner edges of the reverse-curve portions Ill, rest onffi'ie

lowermost frame flanges

34, 65, and their arching provides support to the panel and helps prevent deformation by cold flow.

The ends of the

bottom reflector panels

28, 29 rest on curved supporting strips or flanges 80 of T-section extruded or die cast supporting members 8|, or on flanges 82 on the inside surface of end plates 83 which follow the form of the reflector panel, and are joined to the central frame members 26, 2|. Fig. 1 shows two pairs of

bottom panels

28, 29 supported along their inner edges by the

flanges

64, 65, supported at their outside ends on flanges 82 of the plates 83 and at their inside ends by the strips 8|. Preferably the

panels

28, 29 are held in place solely by gravity and may 5. be removed for cleaning simply by lifting them off the supporting

flanges

80 and 82.

The parabolic portions 120: and 1.1 are continuations of the same parabolas as the reflectors 50, i. Their

axes

52, 53 are identical, and the lamps 2.4, 25 are atthe focus. Fig. illustrates this fact diagrammatically. The parabola P is interrupted near the vertex V, Where the light would mostlybe reflected back through the focus F and be absorbed by the lamp 25, but. the important side arcs 50, BI and 1.0, II are there. to send the light rays in inclined, parallel paths toward the ceiling. Due to the; angle at Which the light. strikes. the surfaces III, II, a comparatively small amount is. refracted through the

panels

28, 29. Most of the light. is reflected-off with high efficiency; What light does shine through enhances the attractiveness of the fixture and the evenness of the diffused lighting below.

At their outer extremities the surfaces 1 0;, II break sharply, arcs '16, ll" ofsmall radius leading into the gentle reverse curve surfaces'l'fi, 'IEwhich serve as shields or baflles to protect the eye from the glare of: bare lamps. At their outer edge,.the baflie portion terminates in short stiffening beads or flanges I8, 79;.

The upper translucent or

opaque reflector panels

20, 21, shown in Fig. 3, are cylindrical arcs, i. e., their cross sections are circular arcs. The outer side edges 84 of the

panels

26, 27 rest on upper flanges 85, of the end plates 33. The inner side edges 36 rest on curved supporting strips or flanges 81: of T-section extruded or die cast supporting members 08, joined to the central frame members 20, 2|. The strips 81 and flanges 85 follow the form. of the

panels

20, 21. Like the

panels

28, 29, the panels are held solely by gravity and are merely lifted off the

flanges

85 and 81 when it is desired to remove them.

The lengthwise edges 90, 9I of the

panels

20, 21" are bent over and beaded or flanged to give added strength. The inner edges 90 also help prevent slipping by abutting against stop members 32 on the flanges 8-5 and 31.

The upper reflector panels are generally parallel to the

respective axes

52, 53 of the optical system formed by the reflector surfaces 50-, 70 and 5|, II. Preferably the

axes

52, 53 coincide with the chords of the

arcs

26, 27. In this position, the upper reflectors 26, 2! provide the least interference with the light directly radiated from the

lamps

24, 25 or reflected from the surfaces 50, I0 and 5|, II.

The main purpose of the

upper reflector panels

25, 21 isto shield the eye of the observer from the glare of the upper linear

light sources

22, 23. By presenting convex specular surfaces to the

lamps

22, 23, the upper reflector panels tend to spread the light reflected by its upper surfaces 94, 05 rather than to concentratethe reflected light onthe ceiling II over the fixture I0 as it would if its surface Were fiat or concave. In addition, the arc shape adds appreciably to the strength of the

upper reflector panels

28, 29, which are supported only at their ends.

When the electrical circuit is energized the ballasts or transformers I4 produce an inductive kick to establish the are within the

lamps

22, 23, 20, and 25. The lamps then radiate visible energy or light, which travels in straight lines except where reflected by surfaces or refracted through translucent material.

Fig. 4 is a right half section of the lighting fixture I 0, showing only the paths of light from the right upper lamp 22-. If the tubular; lamps are assumed to be linear light sources, then light is radiated equally in all directions in a plane normal to the lamp from 0 at nadir (directly down) through 180 at zenith and around to nadir at 360. Fig. 4 shows the light radiationfrom. the upper lamp 22 at approximate 30 intervals. That light radiating directly downward from 0 through about 8, as shown by the 0 beam I00, strikes the lower lamp 24 and is partially reflected, but largely absorbed. From. about 8 through about 42 the light is reflected from the lower reflecting surface I0 to light the under surface of the upper reflector panel 28' or to pass between the panels to the ceiling, as does beam, I0! at 30.

Frornabout 43 through about 100 light rays I02 (60) and I03 from the lamp 22 are scattered at wide angles by the convex upper surface 94' of the upper reflecting panel 26. From about through about 188 light rays I04 (120), I05 (150 ),and I00 (180 from the upper lamp are radiated directly to the ceiling with no loss due to reflections within the fixture. Between about 188 and about 255, light is re flected by the parabolic surface 34 in a line parallel to the axis 36 of the optical system at Typical beams are I01 (210) and I03 (240). Light from about 255 to about 352, striking the plane surface 40, is either scattered at wide angles I09 (270) and III (330), or reflected back into the lamp to be largely absorbed, as at I I0 (300). From about 352 back to- 0 the light from the upper lamp strikes the lower lamp and is partially reflected but largely absorbed.

Fig. 5 is similar to Fig. 4 and shows the light radiation from the lowerlamp- 24- at 30 intervals. That light which radiates directly downward from 0 through about 20 as shown by the 0 beam I20 is reflected by the surface "It into. the area immediately above the upper bafile 25- or on its surface. From about 20 to about 66 thelight radiated from the lower lamp 24 is reflected by the near parabolic curve 70 generally along the axes 520i the optical system at 125; beam i2I- at 30 is typical. Between about 66 and about 95, light from the lowerlamp 25 isreflected to the reverse curve I4 and thence is reflected to.light the under surface of the upper reflector panel 26, as is the case with beam I-22 at 60, or it-directly-strikes the curve- "50- and then is reflected as before; as is the case with beam I23 at 90. Between about 94 and about 100 the light which strikes the reverse curve I4 is reflected at wide angles to the ceiling.

From about 100 to about 125 the light'reaches the ceilingdirectly at near horizontal angles to build up the widespread distribution of the fiX-' ture at high efliciency, (e. g. beam I20 at Bet-ween about and about 132 radiation from the lower lamp is redirected to the. ceiling bythe reflector surface 94, much of it at wide angles. Between about 132 and. about 172 radiation, the beam such as beam- I 25. again reaches the ceiling directly to. buildv up fixture efllciency. From about 172 to about 134C light, such as the beam I20 from the lower lamp 2% strikes: the upper lamp 22 where it is partially redirected, but largely absorbed.

The near parabolic reflector surface 5!] reflects light from the lower lamp between about 184 and about 235 largely parallel to. thev optical system axis 52. at 125. Beam I217 at210 isillustrative. Behind the lower lamp from about 235 to about 315 the plane surface- 54: scatters the light at wide. angles (e; g beam I20 at 240and beam I30 at 300") or reflects it back into the lamp (e. g. beam I29 at 270) where it is largely absorbed between about 315 and some of the radiation is subjected to multiple reflections and absorption (e. g. beam ISI at 330).

Fig. 6 is a candlepower distribution curve, showing the intensity in candlepower for light emanating from the fixture I0, when the

lamps

22, 23, 24, and are Gil-watt, 3950-lumen, fluorescent tubes and when all four lamps are lighted. The left half of the complete curve is the mirror image of the right half and is therefore omitted. It will be noted from this curve that the candlepower between and 90 in the direct glare zone is a minimum, while the candlepower between 0 and 45, in the reflected glare zone is also very low. From 0 to about 90 (a 180 arc spread constituting everything below the level of the fixture II!) the candlepower varies from about 250 to about 550. The candlepower between about 90 and about 105 rises sharply to about 1500, and then continues to increase at a slower rate, reaching a peak of 1960 candlepower at 118. As the curve shows, the maximum candlepower is emitted at a wide angle, so that the ceiling brightness will be relatively even. The candlepower then decreases gradually to approximately 1500 at 160, and then sharply to 1000 at 180 immediately upward from the fixture. This as Figure 6 shows, the fixture shrows out most of the light along upwardly inclined paths. This may be contrasted with prior art indirect fixtures, whose maximum candlepower is directly upward to the ceiling over the unit.

When a series of fixtures I0 are suspended about 2'7" below the ceiling along parallel lines spaced about eight feet apart the brightness midway between each line of fixtures is about half as great as that directly over the flxturea difference in brightness very difficult to tell with the eye. Prior art fixtures similarly suspended produce typical ceiling brightness directly over the light source as compared to the aforesaid mid-point of from 4 to 1 up to 10 to 1 or more. This malconcentration of light has been one of the big problems in handling fluorescent light.

Fig. 7 shows a modified fixture I adapted to be mounted against a vertical surface, such as the wall ISI. This fixture I50 actually comprises one half (in this case the left half) of the fixture I0 already described, and for this reason the same numbers are used for the same parts. Screws I52 and I53 through the flange 3| and channel 63 respectively comprise the fastening means to secure the fixture I50 to the wall I5I. Ballasts or transformers may be installed within a recess behind the fixture, or remotely. The parts and their operation having already been described in connection with Figs. 1 to 6, this part of the description will not be repeated.

Similarly, the fixture I shown by Fig. 8 is identical to the lower half of the fixture I0. The fixture I60 is a two lamp unit for ceiling suspension. The frames I52 and I63 are very similar to the bases 20 and 2|, except that there is no upper lamp mount or reflector, and the

shoulders

32, 33 join the reflecting surface 50, 5I to the flanges 30, 3|. In all other respects the fixture I60 corresponds to the lower half of the fixture I0 and operates according to the description of Fig. 5.

Fig. 9 shows a fixture I10, which is one half of the device of Fig. 8. It is adapted for wall mounting, where the screws I12 and I13 secure it to the wall I! I. The ballast or transformer is in- 8 stalled within a recess behind the fixture or nearby.

Fig. 10 isa diagram of the parabola in Fig. 9, showing that the surface 'II is a continuation of the same parabola as 5|. This diagram also shows that the missing vertex of the parabola is unimportant, because the light reflected from that portion would merely go back to the lamp and would be absorbed there. The side arcs are represented by the reflecting surfaces 5I, II, and these do reflect the light toward the ceiling at a wide angle.

As noted already, all of the shields and baffles are held in solely by gravity-in all of the fixtures described. The feature of ease of cleaning is important in fixtures used in commercialbuildings and offices. With the present device the

baffles

26, 21, 28, and 29 lift out easily and can be removed and replaced without the use of any tools. This allows the device to be kept clean and at maximum efficiency. Also when the baflles are removed the frame members 20, 2| and the

lamps

22, 23, 24 and 25 are easily reached for dusting and replacement.

Iclaim:

l. A luminous indirect lighting fixture including in combination a frame member, one or more portions of which comprise reflectors having a parabolic cross section, the axis of said parabola being inclined upwardly; one or more linear light sources supported by said frame member along the foci of said reflectors; and a translucent light shielding means supported by said frame member below said light sources, said means having a substantial portion of its surface parabolic in cross section and having the same foci and axes as the adjacent reflector, so that all but a fraction of the'light striking said means is reflected upwardly from said means parallel to the light reflected by its adjacent reflector, the said fraction being refracted through said means to illuminate it.

2. The fixture claimed in claim 1 in which the outer edges of said shielding means are outcurved away from the light sources and are upturned so as to reduce the direct glare from said light sources.

3. A luminous indirect lighting fixture comprising a frame member adapted for support by a wall, a portion of said frame member being formed as a long, rectilinear reflecting surface of parabolic cross section, the axis of the parabola inclining upwardly; a linear light source supported by said frame member below said parabolic reflecting surface and at the focus thereof; and a light shield supported below said light source by said frame member, part of the upper surface of said shield havin a parabolic reflecting surface which comprises an arc of the same parabola as the reflecting surface of said frame member, so that the light is reflected up therefrom parallel to the light reflected from said frame member.

4. The fixture claimed in claim 3 in which the outer portion of said light shield is upturned to reduce the direct glare from said light source, and is cylindrically outcurved.

5. A luminou indirect lighting fixture comprising a frame member having two portions, one positioned over the other, each formed as a longitudinal reflecting surface of parabolic cross section with its parabolic axis inclined upwardly the axis of the lower parabolic reflector being inclined more upwardly than the axis of the one being held below and at the focus of its adjacent parabolic reflector; and means to substantially reduce the amount of light which emanates from said fixture below the level of said light sources.

6. The fixture in claim in which the lightreducin means comprises a light shield below the lower light source, supported by said base member, a portion of the upper surface of said light shield being parabolic in cross section and a continuation of the parabola of the lower reflecting means.

7. The fixture claimed in claim 6 in which said light shield is translucent, so as to transmit a relatively small amount of refracted light therethrough, most of the light being reflected up by its upper surface.

8. The fixture claimed in claim 6 in which the outer portion of said shield is upturned to extend above the lower light source and i cylindrically outturned.

9. The fixture claimed in claim 6 in which there is an outturned cylindrical-arc baffle supported by said frame, the chord of said are lying substantially along the axis of the parabola of said lower reflecting surface.

10. A luminous indirect lighting fixture for suspension from a ceiling, comprising a longitudinal central frame member, on each side of which are upper and lower reflecting surfaces of parabolic cross section, with their axes upwardly inclined, the axis of the lower parabolic reflector bein inclined more nearly vertically than the axis of the upper reflector; and a plurality of linear light sources held by said frame member at the foci of said reflecting surfaces.

11. A luminous indirect lighting fixture for suspension from a ceiling, comprising a longitudinal central frame member, on each side of which are upper and lower reflecting surfaces of parabolic cross section, with the axes of the parabolas being inclined upwardly; and a plurality of linear light sources held by said base member at the foci of said reflecting surfaces; and baffies supported by said frame beneath the lower light sources for reducing the intensity of light emanating below said fixture, said baifles having a substantial portion of their upper surface parabolic in cross section with the same focus and axis as the lower reflecting surfaces.

12. The fixture claimed in claim 11 in which said baiiles are translucent, so as to transmit a 10 small proportion of the light, most of the light being reflected off the upper surface of said bafiles.

13. The fixture claimed in claim 11 in which there is the additional element of an outturned convex baflle supported by said base, the chord connecting the ends of said baflle lying substantially parallel to the axis of said lower reflector.

14. The fixtures claimed in claim 12 in which the outer portion of said baflles are upturned and extend above the horizontal plane of said lower light sources and are cylindrically outcurved.

15. A luminous indirect lighting fixture for suspension from a ceiling comprising suspension rods dependin from said ceiling; a central frame member comprising a longitudinal strip on each side of which are an upper reflector and a lower reflector, each having a parabolic cross section whose axis is upwardly inclined; four linear light sources, each held by said frame member below a reflector and at the focus thereof; a lower translucent baffle positioned below said lower light sources and having parts of its surface parabolic with the same focus and axis as said lower reflectors, and being upturned and outcurved at each long edge and terminating above the plane of said lower light sources; and upper translucent bafiies each comprising an outcurved cylindrical arc whose chord is positioned along the axis of one of said lower reflectors.

16. The fixture claimed in claim 15 in which the axes of the upper reflectors lie approximately above nadir, and in which the axes of the lower reflectors lie approximately above nadir.

JOHN s, WALSH.

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

UNITED STATES PATENTS Number Name Date 2,032,622 Le Guillou Mar. 3, 1936 2,147,959 Arbuckle Feb. 21, 1939 2,306,700 Kantack' Dec. 29, 1942 2,331,774 Guth Oct. 12, 1943 2,341,895 Beck Feb. 15, 1944 FOREIGN PATENTS Number Country Date 185,517 Switzerland Oct. 1, 1936 650,365 Germany Sept. 21, 1937