US 3483366 A
Description (OCR text may contain errors)
V. S. WlNCE Dec. 9, 1969 LUMINAIRE LENS Z5 Sheets-Sheet 1 Filed Nov. 1. 1966 2 c S R W Y WWW E W Mm MM? f v. s. WINCE LUMINAIRE LENS Dec. 9, 1969 3 Sheets-Sheet 2 Filed Nov. 1, 1966 mvzm'on VIE/9%; ,Si M/WE ATTORNEYS Dec. 9, 1969 v. s. WXNCE 3,483,366
LUMINAIRE LENS 3 Sheets-Sheet 3 Filed Nov. 1, 1966 INVENTOR VEAWA ,5. M/VCZ BY 7WW ATTORNEYS United States Patent US. Cl. 240-106 8 Claims ABSTRACT OF THE DISCLDSURE A refractor lens for use with a linear light source is provided and which utilizes a unique combination of linear and point apexed cut-off prisms for control of both longitudinal and transverse components of light from the linear source. A row of point apexed light cutoff prisms are disposed substantially directly below the linear light source and rows of line apexed cut-01f prisms are disposed on either side of the row of point apexed prisms and extend in paths transversely of the axis of the linear light source. The results are such that a much wider transverse light distribution is effected as compared to similar luminaire units because of the use of the linear cut-off prisms. A variation in longitudinal light transmission from the incident surface to the linear cut-off prisms and a variation in reflection at the light emitting surfaces of the linear cut-off prisms causes a variation in light distribution in the longitudinal and transverse directions below the units. Because of the total reflection of light by the sides of the linear apexed cut-off prisms, small conical cut-off prisms with oval bases are disposed in the valleys between such prisms and are so oriented that the greatest projected area of light emission extends in the longitudinal direction. The ends of the refractor lens may be provided with point apexed cut-off prisms to brighten up the end portions of the luminaire where opaque socket and fixture elements normally create dark areas.
The present invention relates to luminaires, and more particularly to a refractor lens for use in a luminaire. Such luminaires can be recessed in a ceiling, or mounted exposed, on or below the ceiling. With either type, there is usually some kind of light controlling member below the lamps which shields these lamps from direct view and directs transmitted light into directions to provide the best utilization of the light on a working plane.
The most common type of light controlling member is a flat, or substantially flat, panel with cut-off prisms on its lower face. Since the lateral and vertical range of light from the lamps in such units is greater than can be handled by linear type cut-off prisms, these prisms are usually in the form of cones or pyramids.
Luminaires using conical cut-off prisms provide good direct glare control, but since practically no variation can be allowed in the angle of the cut-off prisms, the candlepower distribution of such luminaires cannot be varied. Because of the geometry of the lamps, the longitudinal distribution of the candlepower is rather narrow. For this reason it is common practice to mount the luminaires end to end or nearly so, in rows, so as to obtain even longitudinal illumination on a working plane.
Transversely, in areas where higher illumination is required, the rows of luminaires will be spaced relatively close together. Where lower levels of illumination are desired, the rows of luminaires are spaced further apart. As the spacing is increased, however, a point is reached where the illumination becomes too uneven to be acceptable. More specifically, there is a spacing range where Patented Dec. 9, 1969 the total downward output of light is sufficient to provide lower levels of illumination, but the normal candlepower distribution is too narrow. There will be too much light in areas below the luminaires and not enough light in areas between the rows of luminaires.
It is, therefore, an object of the present invention to provide a luminaire for linear light sources, as for instance, fluorescent lamps, for general interior illumination which will provide a wider transverse light distribution.
It is another object of the present invention to provide a luminaire as set forth in the preceding paragraph which will make it possible to obtain both a low and even level of illumination across a working plane or room.
These and other objects and advantages of the invention will appear more clearly from the following specification in combination with the accompanying drawings in which:
FIG. 1 is a perspective view of a luminaire with a refractor lens designed in conformity with the present invention;
FIG. 2 is a diagrammatic bottom view of the refractor lens according to FIG. 1;
FIG. 3 illustrates the candlepower distribution of prior art luminaires, and of the luminaire according to the present invention in transverse and longitudinal directions;
FIG. 4 is a section on the line 44 of FIG. 1;
FIG. 5 illustrates the distribution of light over a working plane as .provided by a luminaire according to the present invention;
FIG. 6 is a side view of a portion of the refractor lens according to FIG. 1;
FIG. 7 is a partial bottom view of the refractor lens according to FIG. 1;
FIG. 8 shows the dot-dash enclosed portion 8 of FIG. 1 on a larger scale than FIG. 1;
FIGS. 9 and 10 are sections respectively taken on lines 9-9 and 1010 of FIG. 8.
Referring now to the drawings in detail, FIG. 1 illustrates a luminaire v10 including a fixture 11 and a refractor 12. Refractor 12 has a bottom lens portion 13 and sidewalls 14 and 15 enclosing a pair of lamps 16, 17 (see FIG. 4). The ends of refractor 12 are closed by end plates 18 fastened to the refractor in any convenient manner well known in the art. End plates 18 may be made of opaque plastic or another dense material. Hinge and ledge pockets (not shown) are molded in the end plates so as to engage projections 19 carried by a fixture channel 20. Fixture channel 20 houses the electrical parts of the luminaire and is covered by a removable cover pan 21. Elements 16 through 21 are all well known in the art so that a detailed description thereof does not appear to be necessary.
The prismatic structure of the bottom portion 13 of refractor 12 With which the present invention is mainly concerned, carries three rows, 22, 23, 24 of transverse linear cut-off prisms on its lower or light emergent side and carries two rows 25, 26 of conical cut-off prisms in the areas immediately beneath the lamps 16 and 17.
Sidewalls 14 and 15 carry horizontal refracting prisms 27 on the inside of the refractor and vertical diffusing prisms 28 on the outer face of refractor 12. The upper faces of prisms 27 direct the light downwardly in a direction 50 and the lower faces of prisms 27 upwardly in a direction 51.
In order to illustrate the optical action of the bottom portion 13 of the luminaire lens 12 two longitudinal planes of light 30 and 31 emanating from lamp 16 are shown. The light in plane 31 strikes the cones 32 and is spread as indicated by the emitting rays 33 and 34. The light in the inclined plane 30 is emitted through the row 22 of transverse linear cut-off prisms. This light is directed into a rather complex pattern as will be explained in connection with FIG. 5. Considering a longitudinal fan of incident light on one small point 35 of a prism 36 of row 22, this light is emitted in directions such that it would form a trace on a working plane W as shown by a line L on FIG. 5. If more small points 35 were chosen along the length of the luminaire in plane 30, each would form a trace as shown in FIG. 5. Similarly, a reverse trace L would be projected from the adjacent surface of the cut-off prism 36. The light intensity of these traces varies from end to end. For example, light striking the top surface of the lens bottom 13 at approximately horizontal directions is largely reflected with only a small part of the light entering and passing through the bottom 13 of the lens. This reduces the amount of light emitted near the end of the traces L. Also, light transmitted through the linear cut-off prisms and directed towards the 50 degree ends of the L traces is refracted at approximately the critical angle so that only a small amount is transmitted while the remainder is being reflected. Between these two extremes there is an increase in the amount of light refracted through the lens bottom so that the greater portion, as indicated by the solid line part of traces L and L, is transmitted quite efficiently. In other words, while the light from plane 30 is emitted in a range of from zero to 50 vertically, the greater portion is concentrated in a zone between 35 and 50, as can be clearly seen from the solid lines in FIG. 5.
A similar pattern of light is also projected onto working plane W by light from lamp 17 through prisms 37 in section 23. Since refractor 12 is symmetric, the same action described above occurs in reverse order toward the right hand side of FIG. 4.
The luminaire of FIG. 1, with the combination of prisms shown, acting as described above, projects a transverse candlepower distribution as shown by curve C in FIG. 3. Curve B represents the transverse candlepower distribution of a luminaire similar to that of FIG. 1, but using conical cut-off prisms only for light control instead of a combination of conical and linear cut-off prisms. A comparison of curves B and C shows that with the luminaire according to the invention less light is emitted vertically from approximately nadir to 30 and more light between 30 and 55". This wider candl..- power distribution allows greater spacing between rows of luminaires with a more even illumination pattern on the work plane W.
If conical cut-off prisms were placed in the area of prisms 36, light would be spread vertically into a transverse zone of approximately to 50 from nadir. Since this would mean that the same amount of light confined to the much narrower 3550 zone of the linear prisms would be distributed over the wide range of from20 to 50 nadir it is obvious that the resulting transverse distribution curve would be narrower. Curves B and C have been verified by many tests made with refractor lenses.
There is a limit to the sections in which the linear cut-01f prisms can be used. For example, incident light in a plane 38 (FIG. 4), would be emitted higher than that in plane 30. Too much light at this high angle would make the luminaire too bright for commercial use. Therefore, the width of the linear prism areas 36, 38- and the placement of the linear light sources 16, 17 must be selected so that not too much light is emitted in angles of more than 55 from nadir. The luminaire of FIG. 4 is about optimum in its proportions and placement of linear and conical cut-off prisms.
Luminaires using conical cut-off prisms have a certain luminosity from most any normal lateral viewing angle. This is so since not only do the prisms emit directly a small amount of light at high angles, but they also emit some light that is scattered by the many facets and intersections that occur in a panel of such prisms.
This, however, is not the case with linear cut-otf prisms. In directions normal to their longitudinal extension they are quite dark, since they emit no light at high angles in such directions, and since they emit practically no scattered light because of their simple form.
Therefore, when viewing the luminaire of FIG. 1 in longitudinal directions, the three sections 22, 23 and 24 appear unpleasantly dark. To overcome this drawback. small conical cut-off prisms 40 are disposed in the valleys of linear prisms (see FIGS. 7 to 10). These small prisms scatter suflicient light to relieve the gloomy appearance of panels 22, 23 and 24. The small conical prisms 40 have a substantially elliptical base and are so oriented that their greatest projected area extends in longitudinal direction of said linear cut-off prisms since most light is needed in this direction.
Due to the decrease in the amount of light emitted near the ends of fluorescent lamps 16, 17 and the opaque lamp ends and lampholders, normally luminaires appear dark near their ends. By ending the panels or rows 22. 23, 24 as shown on FIG. 7 and covering the remainder of the refractor with conical cut-off prisms 41, a break in the optical pattern is made in the area where the transition from light to dark occurs. Since from most any normal viewing angle the panels or sections 25, 26 with conical prisms appear of different luminosity than the sections 22, 23, 24 with linear prisms 36, the change due to lamp darkness is disguised as being normal prism pattern change.
Similarly, this break in pattern is also employed at the ends of the sidewalls as shown by prisms 42 in FIG. 6.
It is, of course, to be understood that the present invention is, by no means, limited to the particular constructions shown in the drawing, but also comprises any modifications within the scope of the appended claims.
What is claimed is:
1. In the combination with a luminaire having a linear light source, a lens comprising an extended piece of transparent material having an upper and a lower surface and extending substantially in a plane below said light source. light cut-off prism means on the lower surface of said lens for redirecting portions of light from said light source. said light cut-off prism means including a row of point apexed cut-off prisms substantially vertically below said light source and extending in a direction parallel to the longitudinal axis of said linear light source; said light cut-off prism means further including a row of line-apexed cut-off prisms in the area of said lens laterally outwardly of and parallel to said row of point-apexed cut-off prisms, the apices of said line-apexed cut-off prisms extending in a horizontal plane parallel to the longitudinal axis of said linear light source and transversely to and substantially wholly laterally of the longitudinal axis of said linear light source, said upper surface comprising means for receiving a longitudinally oriented fan of direct light on any point laterally of the light source and above the active surfaces of said line-apexed cut-off prisms and for trans mitting the light from the fan of direct light received between horizontal and normal in increasingly varying amounts to said line-apexed cut-off prisms, said lineapexed cut-off prisms constituting means for receiving said varying portions of light and for internally reflecting varying portions thereof and for distributing the remainder of the light not reflected downwardly in increasingly varying portions from the inner and outer sides of areas below the luminaire.
2. The combination of claim 1, which includes pointapexed cut-off prisms between adjacent ones of said line apexed cut-off prisms for redirecting light downwardly which would otherwise be reflected by said line-apexed prisms.
3. The combination of claim 2, in which said cut-off prisms between adjacent line-apexed cut-off prisms have elliptical bases with the long axes thereof extending transversely to the axis of said linear light source.
4. The combination of claim 1, in which said row of line-apexed prisms ends short of the ends of said lens, and point-apexed cutofi prisms are disposed between the ends of said lens and the ends of said row of said lineapexed prisms.
5. The combination of claim 1, wherein said lens includes side sections extending upwardly from said upper surface, and there are provided horizontally extending refracting prisms on the surfaces of said side sections which face said light source, and vertically extending diffusing prisms on the surfaces of said side sections which face away from said light source.
6. The combination of claim 5, which includes vertically extending linear cut-01f prisms on the end portions of said side sections on those surfaces thereof which face away from said light source.
7. A lens for use in combination with a luminaire having at least one linear light source, said lens comprising a row of point-apexed cut-off prism means substantially vertically below said linear light source and extending in a direction parallel to the longitudinal axis of said linear light source for cutting off light from the linear light source at predetermined longitudinal and transverse vertical angles below a predetermined glare zone and a row of linear cut-off prisms in the area of said lens laterally laterally and longitudinally thereof in increasingly varying 35 intensity from the outer and inner ends toward the intermediate sections outwardly directed, substantially arcuate patterns below the lens and for internally reflecting decreasingly varying amounts of light from the outer and inner ends toward the intermediate sections of the same patterns.
8. In combination with a luminaire having a linear light source, of a lens comprising an extended piece of transparent material having an upper and a lower surface and extending substantially in a plane below said light source, light cut-off prism means on the lower surface of said lens for redirecting light from said light source, said light cut-off prism means including a row of point apexed cutoff prisms substantially vertically below said light source and also including a row of line-apexed cut-off prisms in the area of said lens and laterally outwardly of and parallel to said row of point-apexed cut-off prisms, the apices of said line-apexed cut-off prisms extending substantially transversely to the longitudinal axis of said linear light source, side sections extending upwardly from said upper surface, horizontally extending retracting prisms on the surfaces of said side sections which face said light source, vertically extending diffusing prisms on the surfaces of said side sections which face away from said light source, and vertically extending linear cut-off prisms on the end portions of said side sections on those surfaces thereof which face away from said light source.
References Cited UNITED STATES PATENTS 2,474,317 6/1949 McPhail 240l06 2,737,577 3/1956 McPhail 2405l.11 3,038,065 6/1962 Frank et al 240l06 3,258,590 6/1966 Goodbar 240l06 3,275,822 9/1966 Wince et al. 240l06 XR 3,340,393 9/1967 Frank et al 240l06 XR NORTON ANSHER, Primary Examiner RICHARD M. SHEER, Assistant Examiner U.S. Cl. X.R. 2405 1.11