Linear Light Passing Media Having Certain Striped Characteristics

The present invention relates to luminaires generally; it particularly relates to ceiling mounted, wall mounted, furniture mounted, suspended, or free standing luminaires having light passing media, such as light directing lenses or non-directional diffusers, wherein the media is normally seen by persons in the vicinity of the fixture.

Fluorescent luminaires of the type frequently used in office and commercial environments are characterized by a linear geometry, that is, they are elongated fixtures with a uniform cross-sectional shape. Such fixtures are commonly fabricated of steel or extruded aluminum parts, and commonly use elongated, linear plastic lenses or diffusers to mask or control light emitted from the bare fluorescent lamps. Prismatic lenses, which act to converge, diverge, or redirect light, and diffusers, which are translucent, non-directional media that pass light in a cosine distribution, have been used in direct lighting fixtures for many years. More recently lenses, and particularly linear prismatic lenses, have been adapted for use in indirect lighting fixtures where the light source is normally masked by the fixture housing itself. In the case of indirect fixtures, lenses, such as disclosed in co-pending application Ser. No. 046,970, achieve desirable indirect light distributions and are used to eliminate bright spots on wall and ceiling surfaces. They also permit the lamps to be raised within the housing for increased luminaire efficiency.

In the case of both the direct, indirect, and direct-indirect fixtures, all or a portion of the lens or diffuser surface will be seen by persons standing in view of the fixtures. The diffuser will appear as a plain white surface. The prismatic lens will, up close, display a lens pattern characterized by alternating areas of relative brightness and darkness, but further away the prismatic lens pattern will become less perceptible. The prismatic lens presents special problems in terms of visual comfort in that overly bright areas often appear at individual prism surfaces and/or along the base of the lens. Apart from these possible bright spots, the surface of a conventional prismatic lens, like that of a diffuser, appears as a substantially flat, illuminated surface with no distinguishing characteristics.

In the present invention the fixture's light passing media, be it a prismatic lens or a diffuser, is provided with unique visual characteristics at the light emitting surface of the media. The invention is intended to improve visual comfort of a fixture and permit a lighting designer to create different psychological environments through the design of the light passing media. The invention also provides, in a prismatic lens, a lens media wherein surface bright spots can be masked out.

The invention is a light passing media, such as a prismatic lens or diffuser, for a linear luminaire wherein special visual characteristics are given to the media by one or more linear coloration areas which change the transmission characteristics of the lens along this linear area. In one aspect of the invention, a plurality of linear areas of lens coloration are separated by linear areas of lens with no coloration or different coloration such that the lens has an actual striped appearance. For visual stripes, colors can be chosen to create particular psychological or visual effects, for example, blue color striping to provide a visually cool environment as compared to a red color striping for a warm environment.

In a further aspect of the invention, one or more stripes can be employed on a prismatic lens to mask normally occurring bright spots. For example, in an indirect fixture having a linear prismatic side lens, it is commonly a problem that a distracting strip of brightness appears along the transparent base of the lens adjacent the housing rim. In accorance with the invention, the bottom-most lens portion of the lens would be provided with a stripe which would act to mask out this bright area. Such a stripe could be either semi-transparent, translucent or opaque. It could also be of a neutral color and could be gradually shaded at its top edge so as to make the stripe itself practically unnoticeable to the observer; rather what the observer would see would be a prismatic lens without brightness due to the stripe.

In a still further aspect of the invention, lens coloration, preferably a neutral coloration, is provided at the mounting edge of the lens of a direct lighting fixture to prevent, in certain fixtures, undesirable housing rim reflections.

In yet another aspect of the invention, a unique comb-like lens construction is provided wherein the striping is provided by linear baffle walls separated by flat lens separators.

It is therefore seen that the primary object of the invention is to provide a light passing media having a surface which, when illuminated, is pleasing to look at and creates a desired psychological effect not produced by a conventional uniformly clear lens. A further object of the invention is to provide a linear prismatic lens having striped characteristics that reduce lens bright spots. Further objects of the invention will become apparent from the following description and claims.

FIG. 1 is a cross-sectional view of a direct luminaire having a linear prismatic lens with color stripes in accordance with the invention.

FIG. 2 is a bottom plan view of the luminaire shown in FIG. 1 showing the lens in plan view.

FIG. 3 is a cross-sectional view of an indirect luminaire having linear prismatic side lenses with color stripes in accordance with the invention.

FIG. 4 is an end elevational view of the side lens of the indirect luminaire chown in FIG. 1.

FIG. 5 is a front elevational view of the side lens shown in FIG. 4.

FIG. 6 is an end elevational view of a side lens such as used in the indirect luminaire shown in in FIG. 4, except with a blended linear coloration area on the lens.

FIG. 7 is a front elevational view of the side lens shown in FIG. 6.

FIG. 8 is a perspective view of a comb-shaped lens in accordance with the invention.

FIG. 9 is an end elevational view of the comb-shaped lens shown in FIG. 8 positioned in a luminaire housing having a rectangular cross-sectional shape.

Reference is now made to the drawings, and particularly to the direct luminaire illustrated in FIGS. 1 and 2. The direct luminaire 11, has an elongated linear cylindrical extruded housing 13, fluorescent lamps 15 mounted within the housing, and a lens opening, shown to be a 120.degree. lens opening, for receiving an elongated lens 17. The luminaire's light passing media is in the form of linear prismatic lens 17 which has an exterior linear prismatic surface 18 and is attached to the housing by means of its depressable mounting edges 19, 21 formed to snap over correspondingly retainer ribs 23, 25 formed along the two bottom rims of the luminaire's cylindrical housing 13. It is seen that light emitted by the lamps 15 will, with the aid of reflector 26, be directed generally downwardly into the room and that the light will be redirected or disbursed by the lens' prismatic surface 18. When viewed by persons standing in the room the lens will present a luminous surface and the lamps themselves will normally not be seen.

It shall here be noted that the luminaire's light passing media is, in reference to FIGS. 1-5, herein described as a prismatic lens wherein lens stripes can be used to mask lens bright spots. It shall be understood, however, that the stripes as hereinafter described could, in accordance with the invention, also be applied to a linear diffuser to provide a diffuser with a pleasing appearance and to produce the described psychological effects. It will further be understood that the linear geometry of the fixture and lenses specified herein can be satisfied by any fixture or lens having a substantially uniform cross-sectional shape throughout its length. For example, a doughnut shape fixture would have a "linear" geometry within the mean of this description.

Lenses of conventional linear light fixtures are fabricated o have subbstantially uniform transparency throughout. Uniformly transparent lenses have been fabricated, for example, from clear acrylic extrusions or by injection molding. In accordance with the present invention, and referring to the direct lighting fixture in FIGS. 1 and 2, the lens 17, rather than being clear throughout, has at least one linear coloration area, such as linear coloration areas 29 which, as shown, are separated by linear areas 31 with no lens coloration. The linear areas of coloration on lens 17 are seen to present a series of stripes spaced over the lens surface, stripes that if transparent or translucent will appear as luminous stripes to an obbserver when the lamps 15 are on. As shown, each stripe spans a selected number or group of prismatic surfaces with successive stripes being separated by an equal number or group of prisms; thus, as shown, the transition between adjacent stripes occur at the linear prism's riser surfaces 16. It is possible, however, to in accordance with the invention have the stripes span unequal prism groupings. It is also possible to provide imbalanced separations between stripes, such that the stripe boundaries fall between prism riser surfaces. The color stripes can be made an integral part of the lens, such as by a known co-extrusion process wherein the lens is formed by extruding a clear and colored, or different colored, plastic material together. Alternatively the color stripes could be applied to the lens such as by taping or by a color surface coating. A surface coating might be applied by a silkscreening process using a transparent acrylic paint. The color selected for the stripes will depend on the particular visual and psychological effect desired by the lighting designer. For example, the following colors can be used for the following indicated effects:

It should be understood that the lens stripes described herein can be transparent, semi-transparent, translucent or opaque stripes or a combination thereof. Opaque stripes would necessarily have to be interspersed with transparent stripes of colored or clear lens.

With further reference to the direct luminaire shown in FIGS. 1 and 2, the first lens surface areas 33, 35 immediately adjacent the extensions 37, 39 of the lens' mounting edge 19, 21 are preferably transparent, that is, without coloration. This, it is found, will prevent the total lens from appearing too dark. The lens' mounting edges 19, 21 are also preferably provided with a suitable opaque neutral coloration to prevent objectionable light reflections from the housing rims 23, 25 from being transmitted through the mounting edges.

FIGS. 3-5 illustrate the use of the color striped lens of the present invention in connection with an indirect luminaire where normally only the side portions of the fixture lens can be seen. Referring to FIG. 3, the fixture housing 41 supports fluorescent lamps 43, and two arcuate linear prismatic side lenses 45, 47 having interior prismatic surfaces 46, 48. The side lenses are linear prismatic lenses wnhich extend the length of the fixture and, like the direct lighting fixture, can be fabricated of a plastic extrusion or by other fabrication methods such as injection molding. With reference to side lens 45 shown in FIGS. 4 and 5, the linear prismatic lens has linear coloration areas 49 which an observer sees from the side as a series of stripes which will be luminous if the stripes are transparent or translucent. As illustrated, the stripe boundaries appear at the riser surfaces 50 of the lens' interior prismating surface 46, but could appear elsewhere as well. It is seen in the case of the indirect fixture that the first color stripe 51 is preferably provided at the lens mounting edge which is in the form of lens base 54 immediately adjacent the housing support rim 56, 58. This positioning permits the first color stripe to be used to mask the bright strip of light that frequently appears along the base 54 of the lens. The color stripes, therefore, can be used to mask objectionable bright areas on the lens as well as provide the above stated psychological impressions to the observer.

As with the lens for the direct lighting fixture, the color striping in the lens for the indirect fixture can be provided by a plastic co-extrusion process or by an applied method. Also, some or all of the color stripes can be of a neutral color, particularly where masking is desired, and can be transparent, semi-transparent translucent or opaque.

It is noted that to accentuate the color striped linear lens, the stripes might be presented in relief by providing either elevated or recessed striped lens surfaces, such as the elevated striped surface 55 of the FIG. 4 lens. Such relief in a linear extruded lens can be provided for in the lens extrusion die.

With reference to FIGS. 6 and 7, a linear prismatic lens 61 for an indirect fixture, similar to the indirect fixture lens 45 shown in FIGS. 4 and 5, is provided, instead of with a series of stripes, with a single linear area of lens coloration 63 which extends along the base 65 of the lens and which, moving upwardly on the lens, gradually shades into a clear lens area 65 to produce a non-distinct edge to the stripe. This lens base stripe (shown in FIGS. 6 and 7 by strippling) can be of a neutral coloration and translucent such that the stripe itself will be practically unnoticeable to an observer of the lens; what the observer will see is a lens without apparent coloration but which has the prism brightness at the base of the lens removed. Again the lens base strips of FIGS. 6 and 7 can be applied by any of the above described fabrication processes. It is noted that a coating could suitably be coextruded on the lens to achieve the blended stripe edge.

It is further noted that the lens base stripe 63 shown in FIGS. 6 and 7 could be provided instead with a distinct edge, however, such a stripe would generally be more noticeable, which may be intended for psychological effect. The stripe could also be very narrow compared to that shown in FIGS. 6 and 7 to simply mask out the bright strip occurring right at the lens base 67; as mentioned above this strip of light is usually the most troublesome area in terms of excessive lens brightness in an indirect luminaire.

FIGS. 8 and 9 show a unique flat comb-shaped lens 71 for a direct luminaire. The comb lens 71 is formed by a series of elongated projecting linear baffle walls 73 in parallel alignment separated by relatively thin clear media strips 75. The linear baffle walls 73, which are preferably formed of a translucent material with coloration, will baffle direct light from the fixture's light source. With the baffle walls pointed downwardly in the direct luminaire as shown in FIG. 9, the baffling would normally prevent the source light from being seen directly at medium to high viewing angles (high viewing angles being angles near horizontal which are high relative to the zero degree vertical axis below the fixture.) The color baffle provided by the colored linear baffle walls 73 allow light to pass through the lens in designated directions and would give the lens a distinct striped lens appearance. It is noted that the clear media strips 75 between the baffle walls are shown as prismatic lens strips. The prismatic strips are provided for prismatic control of the baffled light, and preferably would have prismatic surfaces 76 which act to concentrate the light passing through the strips. However, the prismatic surfaces 76 of the clear media strips might also act to bend or disburse the light.

As shown in FIG. 9, the comb lens 71 can set in an elongated rectangular housing 74 of a direct luminaire with the baffle walls 73 oriented longitudinally of the housing whereby the lens baffles medium to high angle light directed laterally of the fixture. Alternatively, lens sections with the comb-like structure of FIGS. 8 and 9 can be placed crosswise in the housing 74 (so that the comb baffle walls are transversely oriented) whereby baffling of medium to high angle light occurs in a longitudinal direction.

It is contemplated that a suitable dimensioning for the comb lens 71 to achieve the object of suitably baffling high angle light would be to provide comb baffle walls of approximately 1/8 inch thickness and approximately 3/8 inches high with an approximately 3/8 inch separation. Thus, the comb-like lens 74 of FIGS. 8 and 9 would have approximately 3/8 inch square channels 77 between baffle walls 73 running the length of the lens sections. It is noted that baffling with essentially square channels 65 will shield direct light passing through a substantially horizontally disposed lens in viewing angles above approximately 45.degree..

It shall be understood that the above-stated dimensions of the comb lens 71 is exemplary and not intended to limit the lens to the dimensions stated. It shall also be understood that while the comb lens 71 is illustrated as a flat lens, a curved lens with radially projecting baffle walls would be an example of an alternative construction. In either case the comb baffle walls 73 would give a striped appearance to the lens as well as providing a baffle for direct light.

Therefore, it is seen that the present invention provides an improved linear lens or diffuser for a luminaire wherein striping is added to the lens surfaces to give the lens surface a desired pleasing appearance, and to give the lighting designer additional control over the visual effects produced by an overhead luminaire. The striping additionally provides, by proper location, a means for masking undesired bright spots on a prismatic lens surface or baffling direct light. It is understood that the stripes can be used selectively for the purpose of masking only or for psychological purposes only.

While the invention has been described in considerable detail in the foregoing specification, it is not intended that it be limited to such detail, except as necessitated by the appended claims.