US 3275825 A
Description (OCR text may contain errors)
D. E. WELTY REFRACTOR Sept. 27, 1966 Filed Feb. 20, 1964 T1 CIA- 2 Sheets-Sheet 1 INVENTOR. I .DALE Wary ATTORNEYS D. E. WELTY Sept. 27, 1966 BEFRACTOR Filed Feb. 20, 1964 2 Sheets-Sheet 2 INVENTOR. 13445 5. W54 7 Y Patented Sept. 27, 1966 REFRACTOR Dale E. Welty, Newark, Ohio, assignor to Holophane Company, Inc., New York, N.Y., a corporation of Delaware Filed Feb.20, 1964, Ser. No. 346,218 Claims. (Cl. 240-106) The present invention relates in general to luminaires and in particular to a new and useful prismatic side panel lens for use with linear light sources enclosed within the luminaire.
When employing luminaires with fluorescent or other linear light sources in which side panel lenses are utilized, the side panels may present annoying glare-zones to a viewer. In such cases, it may be desired to position the light sources within a generally rectangular luminaire in a number of positions relative to the side panels. Thus, another problem arises in providing side panel refractors which will accommodate light sources in any position within the confines of the luminaire, and still provide glare free illumination regardless of'the position of the light source.
Accordingly, improved light it is an object of this invention to provide transmitting side panels in lurninaires having linear light sources, which panels will distribute light in an eflicient and uniform glare free manner regardless of how the light source or sources are positioned.
The present invention is particularly applicable to luminaires which require side panel lenses, separate from a bottom lens, and provide a series of identical horizontal prisms which control the vertical distribution of light emanating from one or more linear light sources located Within the luminaire. The prism design produces a glare free zone within predetermined critical angles. The novel design of the prisms also takes into account the possibility of varying the position of the light source or sources within the luminaire so that such positioning will not alter the desired distribution of the light refracted through the side panel.
Furthermore, the present invention enables substantial savings in cost because the side panels permit a universatility of lamp placement within the practical limits of ceiling luminaire construction. Additionally, the side panels of the invention may be employed in any luminaire regardless of size while still retaining the desired glare free zone. In fact, the lens panel may be cut to a desired height less than its original dimensions and still provide the same distribution of light.
For a better understanding of the invention, its advantages and specific objects obtained by its use, reference is made to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.
In the drawings:
FIG. 1 is a diagrammatic view of a luminaire of the present invention shown in relation to a viewer from the floor below.
FIG. 2 is a cross section of the luminaire of FIG. 1;
FIG. 3 is a sectional view of a portion of the luminaire of the invention but showing a variation of light source positioning;
FIG. 4 is a magnified sectional view of the encircled portion of the side panel lens of FIG. 3; and
FIG. 5 is a magnified sectional view of the encircled portion of the side panel lens indicated in FIG. 3. v
the drawings, wherein similar reference numerals identify corresponding parts throughout the several views, represents a generally rectangular luminaire. As illustrated in FIG. 1, anobserver 12 in the fifty to ninety-five degree glare zone will not be subjected to the effects 9f usualside wall brightness because the. particular design of the prismatic side panel of this lens at angles beneath less than fifty degrees).
invention serves to substantially eliminate glare in that zone, as described more fully below. Also, the present design provides a substantial, well distributed ceiling component to reduce the contrast between luminaire and ceilmg.
According to the invention, the luminaire includes a horizontal bottom lens 16, vertical side panel lenses 18, and a reflector plate 19 Side panel lenses 18 are sepa rated from the bottom lens 16 by right angle supports 20 supported in the housing by conventional means, not shown. Right angle supports 20 include stops 22 and ledges 24 on which bottom lens 16 rests. Bottom lens 16 may be secured to right angle supports 20 by fitting the lens snugly between opposing stops 22, or by any other suitable means. The upright leg 26 of right angle support 20 includes right angle side panel lens support 28 projecting inwardly of the leg and integrally formed therewith. Support 28 serves to hold the side panel lenses securely in place. The side panel lens may be secured to support 28 by fitting the lens snugly therein, or by afiixing the lens to the support by any other suitable means. A plurality of fluorescent lamps 30 are secured within the luminaire by any suitable means (not shown).
Each lens 18 includes a plurailty of identical horizontal light splitting prisms 40, which are asymmetric relative to a horizontal plane through the apices of the prisms, with the upper active surfaces 42 having a steeper slope than the lower active surfaces 44. Prisms 40 are positioned over the entire inner surface of side panel lens 18 in a contingent relationship, and provide substantially reduced glare from the side panel lens in a predetermined zone, which, for example, may extend from fifty to ninetyfive degrees. The zone of reduced glare may be adjusted by utilizing prisms of difl erent refractive power. Vertical cut-01f prisms 41, suitably positioned. on the outer surface of lens 18, provide for horizontal diffusion of the light.
To make a thorough analysis of the effect of the 'side panels on different lamp positions, it is only necessary to consider the extreme rays emanating from such positions upon the extreme portions of the side panel lens, that is, the upper and lowermost sections of the lens.
Turning now to FIG. 3, there are shown possible positions A and B of lamp 30, relative to side panel 18. The two positions are merely illustrative and any lamp position may be employed, or any practical member of lamps utilized within the scope of the invention. In lamp positions illustrated, extreme rays 32, 34, 36 and 38 are shown emanating from the lamps and impinging upon the upper and lower portions of side panel lens 18.
FIGS. 4 and 5 illustrate in detail the eflect of the top and bottom side panel prism-s, respectively, on rays emanating from the lamps within the luminaire. For purposes of explanation, parallellight rays will be identified by the same numeral, but with respective identifying letters A and B.
In FIG. 4, ray 32A impinges upon the upper surface 42 of prism 40 in the upper portion of the panel and wardly from the lens near the vertical as ray 32A2. As the light incident upon upper surface 42 impinges on the panel at higher vertical tangles relative to nadir it will be refracted downwardly but at higher angles than ray 32A2. The highest ray which can strike the top surface 42 is grazing light, illustrated as ray 33. Ray 33 is refracted downwardly through the lens as 33(1) and emerges as ray 33(2), the angle of which can be set by the slope of upper surface 42 at a desired maximum. Thus, the angle of the upper surfaces of the prisms is designed so that all of the raysimpinging thereon emerge from the the desired glare free zone (e.g.'
. When ray 32B enters the lower surfaces 44 of prisms 40. at the upper portion of the panel, it is refracted upwardly as ray 32B1, and emerges from the lens :as ray 32B2. As the rays on lower surfaces 44 impinge at higher vertical angles, ray 32131 asillustrated by ray 36-36(1)-36(2): conversely, any light entering the bottom surface at angles lower than ray 32B will emerge at angles lower than ray 32B (2) with the est angle accepted by the surface 44, being refracted up wardly as ray 35(1) and emerging from the lens as ray 35(2). The lower surface 44 is set at an angle to prevent limiting ray 35(2) from emerging from lens 18 at lower than the desired angle, in this case, not less than ninetyfive degrees .with respect to the vertical.
Any ray higher than ray 35 .will be refracted above the glare free zone limit. For example, extreme rays from lamp position B, such as my 36, enter the lower surface 44 and are refracted as ray 36(1), ultimately emerging as ray 36(2) 'at an angle above ninety-five degrees. 1
The section of side panel lens 18 depicted in FIG; is from the bottom portion of the lens. The extreme rays fromthe two possible lamp positions A and B incident upon this portion of, the lens can be analyzed in a manner similar to the above. Rays 34 and 38, as shown in FIG. 3, may be incident angles relative to the upper and lower surfaces of prisms 40 in this lower portion of lens 18.
Ray 38A enters the lower prism surface 44 and is refracted through the lens as ray38A1 emerging as ray 38A2 outside of the desired glare-free zone (i.e. above ninety-five degrees). As the light incidentonlower surface 44 impinges at lower vertical angles than ray 38A it is refracted and emerges at lower angles than ray 38A2 until the rays arrive at the greatest angle of incidence upon surface 44, as illustrated by grazing my 37;
Ray 37 isrefracted upwardly as ray 37(1) and emerges in an upward direction as ray 37(2) at :an angle corresponding to the upper limit of the desired glare-free zone. Rays incident upon the lower surface of the prism at a higher angle than ray 38A will be-refracted through the lens to emerge. at an angle above ray 38A2,1well above the glare-free zone limit.
Ray 38B, which enters the upper surfaces 42 of the lower prisms, is refracted lens, and again refracted downwardly as it emerges from the lens as ray 3832. As in the case of the upper prisms, light impinging on the upper surfaces of the lower prisms at higher angles than that of ray 38B cannot emerge from the lens at an angle greater than fifty degrees, although this limit is not normally approached in the case of the lower prisms, since they are not usually subjected to upwardly directed or high angled light.
Ray 46 represents the lowest ray which can enterthe upper surface of any prism 40 and be refracted through the lens. Ray 46 is refracted as ray 46A in the lens the rays are refracted higher than considered in a plurality of downwardly as ray 38B1 in the limiting or grazing ray 35,the low,- 1
and emerges at zero degrees vertical as ray 46B. All
rays which are lower than ray 46 and impinge upon an upper surface will be internally reflected. Thus, extreme.
ray 34, .lower than ray 46, passes. through the lens as my 34(1) but does not emerge from the lens, and instead, is internally reflected as ray 34(2). Hence, the highest ray incident upon the upper surface of the prisms emerges from the lower portionof the lens considerably below fifty degrees vertical,.and the lowest ray incident gponthe lower surface of the prisms emerge atninetyve between fifty and ninety-five degrees.
Thus, a prismatic side. panel lens has been provided for luminaires with an inside surface covered by a plurality of identical horizontal prisms. The, highest ray incident upon the upper surface of the prisms, and subsequeutly emergent from the lens, is set atan arbitrary maximum value (in this case fifty-degreesvertical).
degrees vertical, thereby producing a glare free. zone Other rays which enter the upper surface of the prisms are either refracted and emerge at angles lower than fifty degrees, or are reflected internally. The lowest ray incident on the lower surf-ace of the. prisms. and subsequently emergent fromthe. lens is set at an arbitrary minimum angle (in this caseninety-five degrees:vertical)..
.lower surface ofthe' from the lens at angles It will be understood 40 maybe varied to to accommodate any by practical considerations in the manufacture of naires.
Furthermore, since the prisms are identical, the lens may. be cut'to any desiredwidth less than-its original widthand still function satisfactorily. Thus the prismatic design allows considerable variation in lamp placement, making'the lamps suitable for use in a wide range of fixtures.
While a preferred been shown and described in detail to illustrate the appli cation of'the inventive principles, it should be understood,
otherwise without that the invention maybe embodied departing fromsuch principles. 1
I have described ments of my invention. confined to the embodiments cover by Letters Patent is set forth in the following claims.
What is claimed is:
1. Forusein a luminaire including at least one linear light source, a stantially vertical side panel, said side panel having a series of substantially identical horizontal. prisms lying parallel to saidlight source at the surfaceof; said side panel nearest said prising an upper and a lower light receiving surface asym metrically disposed on either side of a.horizont-al plane through the apex of'said prism, said upper surface con-' stituting means for re-directing incident light thereon at angles lower than a predetermined range of angles from nadir, and said lower. surface, constituting means for redirecting incident light thereon at angles greater than saidrange of angles,the area defined within said range of angles defining a glare free zone of light.
2. The refractor of claim 1 wherein all light incident on said .upper surface emerges at an angle less than 50. fromnadir and alllight emerging from said lowersurface emergesat an angle greater than from nadir;
3. The refractor of claim 1 wherein said series of identical prisms coverthe entire length and height of said side panel, said prisms being disposed in contiguous relationship. I p a a 4. The luminaire-of'claim 1 wherein :said light source is. placed in any substantially'horizontal plane along 'a substantially vertical plane substantiallyparallel. to said side panel.
5. The refractor of claim 1 wherein-said surfaces constitute said means regardless of the height of the linear light; source relative to said vertical panel.
' References Cited by theExaminer UNITED STATES PATENTS 6/1965 Franck eta1 240-106 NORTON ANSHER, Primary Examiner. C. R. VRHODES, Assistant Examiner.
identical, the lamps may -be embodiment of .the invention has.
what I believe to be the best embodi I do not wish; however, to be shownybut what I desire to refractor comprising at least one sub-- light source, said prisms each com-