US2368014A - Luminaire - Google Patents

Description

jam, B945. K. FR

ANCK

LUMINAIRE Filed Feb. 10 1943 3 Sheets-Sheet 2' TiETEa.

www? ART floyd, y

ASVMMET/P/C FLTES Z6 INVENTOR //BT FRANCK www 2' ATTORNEY K. FRANCK Jan. 23, 945.

LUMINAIRE 3 Sheets-Sheet 5 Filed Feb. l0, 1943 Patented Jan. 23, 1945 LUMINAIRE Kurt Franck, Newark, Ohio, assignor to Holophane Company, Inc. poration of Delaware New York, N. Y., a cor- Application February 10, 1943, Serial No..475,'3627 3 Claims.'

The present invention relates to luminaires and more particularly to luminaires of the type eniploying uorescent light sourcesand designed to produce extensive light distribution.

The candlepower distribution designated usually as extensive allows spacing of the units atv twice thev mounting height to produce uniformity of horizontal illumination on the. working plane. With theextended length of the` fluorescent lamp itis, of course, only possibleto produce a distribution of extensive character in the vertical plane at right angles to theaxis `of the lamp.

're Obtain extensive. distribution of iight from fluorescent lamps by lens actiondirectf light is caused to fall on a light spreading.- plate sym-- metrical about a median plane, and wherein the 'prism surfaces to oneside of this plane spread alll the light possible away from the nadir to build up intensities .at higher angles, generally in the neighborhood of 45. This divides the light so that except for the diiiusion in the plate and for the scattered reected light falling'V on the plate, there is nothing to contribute brightness' on the portions of the surface of the plate remote from an observer stationed the dominant rays are directed. As a consequence the plate doesnot light'up with complete uniformity over its entire surface. the plate nearer the observer lights up Very uniiormly, but the remote half is not so well lighted and consequently comparatively dull.

To improve the appearance of the plate it has been provided with shallow symmetrical flutes which lspread the rays each side ofthe direction into which the general prismatic action sends them. As this general directiony is in the neighborhood of 45 of the nadir there-is a tendency for these symmetric flutes to elevate some of the light too high, i. e., into regions 60 above the nadir causing it to get into the glare zone.-

The present invention,l contemplates extensive lighting luminaires and light4 transmitting' plates forfuse in the' same,v wherein the light is controlled in such a increase in the lmninousfarea of the plates and a diminution of the high Vangle diffused light so that the light is kept outo-f the. glare zone.

The present invention also contemplatesA che taining either of theseresults singly.A

Other `and further objects will hereinafter appear as the .description proceeds.

The accompanying .drawings show, for purposes of illustratingr the: presentinvention an embodiment in which the' invention in'av region toward which` The half f' way as to obtain a material may take torni, it-55 l 'plate is lighted' up- (Cl. 24U-106.1)

being understood that Athe;y drawings are illustrativer of the invention ratherr than; limiting: the

same.

In these'drawings:

Figure 1 dagrammatically illustratessa typical f extensive lighting installation: with; spacing of the luminaires twice the -mounting height;

Figure 2 is a.diagrammatic'.view illustratingV a. typical extensive lighting distribution and'. the;

brightness aspects' ofthe-plate of usual construcf tion;

ing the: approach tothe ideal as' herein;

Figure. 3 isal crossr'seotionalview through the:

sources and lens plate showing. light control;

Figure 3a.Y shows ata greatlyyenlargedxscale:the; light controlof certain'of the prismatic ribsand contrasts their contour with the prim'fartvcon-` tour;

Figure 4 is a View at. anenlarged: scale illustrating diffusion obtained byfi'lutes;

Figure 5 Ais adiagram illustratingtheA directional control at various pointsfacross:thewidtlrof a' iiute; and

Figure 6 shows comparative curves of yrelative illumination results in a horizontal plane.

A typical installation. o-f extensive lighting'A equipment is illustrated in Figure" 1 where themounting height' H ofthe luminairesI iswtwice the spacing D, i. eg, D=2Ha;ndthe angle'between" nadir. 'and thel rays fallin'gfmidway" between th'e-` luminaires is A's thisisthe' region hardest: to light by' reason of the. greater' distance'- f (1,41 H) and the'angleofincidenceiitfis im;

portant to get'as f much light as possible inv the region approximately 45above nadir.`

tures and contributes to glare.

Where the light output is divided in-thetypi'- cal manner illustratedby the extensive 'distribue y tion photometric curve I0 'of Figure-2,' by-a simple I priorart prismatic plate' I'I whose' prism outline half of the plate so the right/half only appears tion of the arrow I4'.

The present invention makes itI possible to have,` ,j' tts-illustrated in Figure 2a, a; fairly `wide middle Figure 2a is a viewsimilarrto Figure 2 illustrate! provided; for.

Higher angled light tends' to be wasted under'reniote xportion II6 of l the plate I1 appear bright, whether viewed from the right or left of the centerline I8, I8, this being diagrammatically illustrated by the arrowed lines in small rectangles I9, I9, which overlap in the region I5-IS. The distribution curve is shown at I9'. To facilitate comparison of values the curves I4' and I9' are at the same scale. In IS' there is an increase in candlepower in both beams. The reason for this increase in efficiency will be pointed out below.

In Figure 3 the plate I1 is assumed to be receiving the direct light from two fluorescent lamps 20, whose centers yare in planes 2'20" as indicated. The overall width of the combined sources is approximately equal to the width of the middle portion I5-I6. Outside of points I5 and I6 the upper surface of the lens plate has regressed prisms 2| with active surfaces 22 which concentrate rays such as 23, 24, 25, and render them substantially parallel in the refracting rnedlum at such angles that the emergent rays would be transmitted at an angle of approximately 45 from the nadir, provided the lower surface of the plate were smooth. Such dominant ray directions are indicated by the lines 23', 24' and 25'. The lower surface of the plate I1, opposed to prisms ZI, is, however, provided with small flutes 26 which are preferably asymmetric `as explained below.

The middle portion I5I6 of the plate is again divided into a central portion I5'-I6 of a width substantially equal to the spacings 2Il'20 of the light source centers and portions I5-I5 and I6'I6 under the outer halves of the lamps and intermediate the central portion and the' outer or marginal portions which are beyond I5 and I6, respectively. As shown in Figures 3 and 3a the plate has eight ridges or ribs 21a-21h, inclusive, in the left half of the central portion (IB-45') and four ridges or ribs 2li- 211, inclusive, in the left intermediate portion I5--I 5'.

The surfaces of the ridges 21a- 2171, inclusive, on the sides toward the plane Ill- I8 are active and have such slopes as to receive light, e. g., rays 29, 3D, 3I and 32, originating in portions of lamps 20--20 between the planes 20'-26", and refract these rays away from the axis I8-IB in such directions that the dominant transmitted rays 29', 3l and 32' are in directions generally parallel with the rays 23', 24', 25. The left faces of ridges 21a-21h, inclusive, are also active in diverting light rays such as 35, 36 and 31 to-ward the right for transmission into the right hand beam. Similar action takes place in the corresponding ridges to the right of center line I8-I 8.

The ridges 21i-21l, inclusive (between I5' and I5) have active surfaces on the side toward center line I8-I8 which act on rays such as 28 from the nearer source and bend them away from the nadir for transmission as shown at 28', and also active surfaces acting on rays such as 34 and bending them to the right as shown at 34'.

Each ridge surface receives a bundle of subincidence i lof ray to the normal to such a horistantially parallel rays from the source of a width equal to the apparent width of the ridge. For example, ridge 21e may be assumed to receive (as indicated in Figure 3a) a bundle of rays 3l of a width 3I`a and another bundle of rays 31 of a width 31a. Each bundle will be divided into definite proportions depending upon the location of the apex of the ridge. Portions such as 3Ia' and 31a' strike the respective left and right active surfaces and are refracted with the directions indicated by the arrows 3Ib and 31h, while portions 3Ia" and 31a" strike the left and right surfaces, respectively, which for such rays are substantially inactive. The ridge 211 receiving ray 28 divides the bundle of rays 28 of a width 28a as indicated at 28a' and 28a.

The ridge outline (21a,-21l') of prior art plate I I is shown in Figure 3a by dotted lines superposed on the outline of the new plate. In the prior art plate a considerably greater portion of the bundle 3 Ia to the right of line 3 Iaa impinges on the surface near the center line and is sent to the left, while a much 'smaller portion -of the bundle 31a. to the left of line 31aa is intercepted by the left surface of the ridge and transmitted through the plate. This left surface is in fact merely a riser to provide a connection from one active ridge surface to the next with proper mechanical strength. In the ridge outline in full lines the left surface instead of being a mere riser handles a considerable portion of the light and transmits it in a direction to build up the brightness of the plate. The action of the dotted prior art ridge (corresponding in position to 211) in dividing a ray bundle such as 28a is also indicated. There the contribution of the riser surface was negligible.

It will thus be seen that at each side of the axis I8, I8 there is a substantial area of the plate wherein the ribs have supplemental action which contributes light in a direction so as to cross the axis, therefore this area of the plate will appear bright when viewed from a position on either side of the fixture. The lens plate therefore has a much larger projected areal of uniform brightness. As more of the lens surface is lighted up to increase the projected area of high brightness,

more luminous output is emitted in the directions under discussion. The resultant increase in efflciency is obtained because in the region I5-I6 the two beams (in both directions) can be generated as efliciently as one beam in one direction.

In practice the distance between the center lines of the lamps may be varied within a considerable range, from that of the requirements of mechanical clearance to the width separations within the limitations imposed by considerations of efficiency of the entire light control system which decreases when the lamps are spaced too far apart. For practical ranges of distance, the principle discussed in Figure 3 is applicable.

Figure 4 illustrates asymmetric flutes 26 for altering the general contour which gives shape to a light transmitter. To analyze the operation of the flute, its width is divided into four equal parts and lines 38, 39, 4D, 4I and 42 (to represent parallel rays originating on the right hand side of the flute) are drawn at angles to the general (horizontal) contour such that if the bottom of the plate were smooth, as indicated by the dotted line 43, the light would be refracted so as to be emitted at an angle of 45 with the nadir. The angle of incidence i of ray 40 to the normal to such a. horizontal plane is such that the angle of refraction r of ray 40' would be 45 as indicated. Such refracted rays are indicated at 38', 39', 40', 4I' and 42', respectively, and it is obw'ous that throughout the width of the plate surface being considered there would be no diffusion and all the light (except losses) would be emitted at 45 to the nadir.

Each flute 26 in Figure 4 is composed of a cylindrical portion at the left, or remote side, as indicated by the arc 44 struck about a center at 45 to the left of the middle of the flute, and a plane portion at the right, or near side, as indicated by the tangent line 46. In the drawings the rays '48 at point 52.

38--4.2, inclusive, are continued to the 'flute surface where it will be seen that the angle of incidence for 'the rays striking the -oonvex surL face diminishes from the value i near the point G to afsmaller Iangle i at -point Vvandthe angle of incidence for the `rays striking the yplane surface is uniformly increased to i over theentire plane surface. The refracted rays are indicated by the lines. 38a, 39a, 40a, Maand 42a, 'respectively. 'Ilhe flutes 2li therefore introduce a diffusion as represented `by -the langle a -between rays 42a and 38a', rthe light from 'the -plane portion being at higher angles and the light from 'the convex portion being at lower angles than l'it would have come from the plane surface l43.

Figure 4 also shows 'by a dotted varc 4'41 the con-- tour of the symmetric Viute used inthe central part of the plate of Figure 3J thereby indicating the departure in contour -of the asymmetric -flute from a symmetric flute.

Figure 5 shows graphically at the various reference points E, F, G, H, I, on the fiat surface 43, the asymmetric flute 26 and the symmetric flute 41 the angle in degrees from the nadir at which the light is, or would be, emitted. The horizontal line 48 at 45 from the nadir indicates the absence of diffusion for the rays from the smooth plate. The curved line 49 shows that at point E the ray 38a is at an angle of about 33 to the nadir, and that the angle continuously changes along the convex portion of the flute 26 up to the point of tangency with the line 46, where the maximum departure from the nadir of about 52 is achieved. This angle is retained over the plane area of the asymmetric flute as indicated by the horizontal line 50. This provides a denite upper limit to the angle into which the light can be diffused. The dotted line 5I shows the diffusion from the comparison symmetric ute in which spread of light is between about 38 and 60 from the nadir. The more highly elevated light of the near edge of the symmetric flute is avoided by the asymmetric flute, and hence adequate diffusion may be had without building up plate brightness in the region adjacent 60 from nadir.

Further analysis of Figure 5 shows that the solid curve representing the emission of light from the asymmetric flute intersects the horizontal line Reference point G divides the width of the flute in half. Thus the horizontal distance from E to 52 is less than half and the horizontal distance from 52 to I more than half. Accordingly, less light is diffused downward below 45 than upward above 45. By scaling olf Figure 5 the actual location of point 52, itcan be shown that about 45% of the incident light is diffused downward and upward; expressed differently this means that 20% more light is diffused upward than downward.

The ordinary symmetric flute does exactly the opposite. This is shown by point 53 at which the dashed curve, representing the emission from the symmetric flute, intersects the 45 line a little to the right of reference point G. This means that more light is diffused downward than upward.

The asymmetric flute as shown on Figure 4 might well be considered as a combination of a flute and a prism.

The curved part generated by a radius around center 45, constitutes the ute part and produces diffusion of the incident light. The straight line portion extending on Figures 4 from `2t to 31 acts as a prism, elevating the beam without diffusing it.

'The result :of -thislelevation'is graphically shown on Figure 5 lby the horizontal straight Iline ipertion vvof .the emission curve of the asymmetric figuration 'as 'shown between points 54 and 55. The fact that line -54-55 is lhorizontal indicates that no diffusion is produced; the fact that it 'lies at about 253 :against nadir shows 'that `the beam is elevated Iby Aabout 8 above the 45 emission which would be obtained 4if no lprismatic formationwere 1provided on the outside surface fof the lens.

Figure 6 illustrates the lcomparative output yof the luminaires of Figures '2 and `r2a when spaced twice the mounting height. The relative horizontal illuminations are given in percentage.-

With the earlier construction the illumination midway between the luminaireslwas about '64% of that immediately under them, as vshown in the dotted line curve 160, while with the changed construction above described-the corresponding cur-ve 64I jindicates .approximately '80% of the maximum illumination over a wide area between the fixtures. A difference such as 35% in illumination appears spotty to the eye, while a 20% difference is not noticed.

Since it is obvious that the invention may be embodied in other forms and constructions within the scope of the claims, I wish it to be understood that the particular form shown is but one of these forms, and various modications and changes ibeing possible, I do not otherwise limit myself in any way with respect thereto.

What is claimed is:

1. A direct lighting luminaire for producing an extensive light distribution with high output in regions approximately 45 above the nadir each side of a central median plane and having two adjacent horizontal fluorescent light sources of substantial Width side by side, one on each side of said median plane, and a flat horizontal light transmitting plate substantially wider than the overall width of the two sources and disposed below the sources, the upper surface of the plate having a central portion of a width substantially equal to the spacing of the light source centers,

and composed of longitudinally extending V shaped ridges wherein both surfaces of each ridge are active and receive light from both light sources and are of such slopes as to refract it away from the nadir for transmission from the lower surface of the plate at substantially 45 angles above the nadir, the upper surface of the plate also having intermediate portions extending laterally of the central portion and composed of longitudinally extending V-shaped ridges wherein both surfaces of each ridge are active and receive light from the nearer source and are of such slopes as to refract it for transmission at substantially 45 angles above the nadir, the upper surface of the plate also having marginal portions provided with longitudinally extending regressed prisms of variant refracting power with active surfaces sloped in variant amounts for spreading away from the nadir light incident thereon from the adjacent source for transmission from the lower surface of the plate at a substantially 45 angle above the nadir and inactive riser surfaces receiving substantially no direct light from either source, whereby the area of brightness of the plate when Viewed in either direction of the dominant light outputextends over the corresponding marginal portion, the central portion, and both intermediate portions.

2. A luminaire such as claimed in claim 1, wherein the lower surface of the plate has sym metric light spreading flutes opposite the central and intermediate portions for symmetrically diffusing light and has asymmetric light spreading iiutes opposite the marginal portions for strengthening the upward diffusion and limiting its angle from the nadir.

3. A direct lighting luminaire for producing an extensive light distribution with high output in regions approximately 45 above the nadir each side of a central median plane with controlled diffusion above and below said 45 angle and having two adjacent horizontal fluorescent light sources of substantial width side by side, one on each side of said median plane, and a at horizontal light transmitting plate substantially wider than the overall width of the two sources and disposed below the sources, the upper surface of the plate having marginal portions provided with longitudinally extending regressed prisms of variant refracting power with active surfaces sloped in variant amounts for spreading away from nadir light incident thereon from the adjacent source and rendering it parallel in the plate and at an angle to the normal to the horizontal plane corresponding with an angle of refraction of substan tially 45 from said normal, the lower surface of the plate opposite said regressed prisms being composed of longitudinally extending flutes, each ute having a downwardly convex portion disposed in the more remote portion of the iiute andr KURT FRANCK.

Images