Abstract:
A light fixture optimized for directional lighting, including LED lighting, includes a fixture housing, further including a lighting element shelf and a window opening; a reflector, which is configured with a special parabolic shape, a lighting element which is mounted on an inside surface of the lighting element shelf, such that light emitted from the lighting element will reflect at least one time on the reflector, before exiting the light fixture via the window opening as a wide and uniform field of asymmetric indirect illumination. The light fixture can be configured in versions suitable for wall illumination, conference room illumination, ceiling illumination, ground surface illumination, and related illumination applications for interior and exterior use.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    N/A 
       FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to the field of light fixtures, and more particularly to improvements related to use of light emitting diodes in compact indirect light fixtures of the offset hidden source type for illuminating selected flat surfaces in commercial and residential buildings. 
       BACKGROUND OF THE INVENTION 
       [0003]    Use of light emitting diodes, also known as LEDs, in light fixtures have become increasingly popular. LED lighting is more energy efficient and has a longer expected mean time before failure than both incandescent and fluorescent lamp systems. Additionally, LED lighting does not have the warm-up time characteristic of fluorescent lighting. 
         [0004]    On initial introduction to the market, prices of LED lamps and LED modules/assemblies were generally too high for most consumer and commercial use. In recent years, prices have been falling and consequently, due to the aforementioned advantages, LED lighting is gaining widespread acceptance in both the consumer and commercial markets. 
         [0005]    LEDs typically do not emit light in all directions, and require a plurality of LED elements to achieve sufficient luminosity. Therefore, light fixtures will in many cases have to be redesigned in order to perform optimally. Typically, such redesigns may incorporate the use of special lenses that compensate for the more directional light emitted from LEDs. Such light fixture redesigns may be more bulky and more costly to manufacture than traditional fixtures for fluorescent or incandescent light sources. 
         [0006]    U.S. Pat. No. 4,748,543, for a HIDDEN SOURCE FLUORESCENT LIGHT WASH FIXTURE issued May 31, 1988, contains background information relevant to the present invention. The abovementioned patent and the various embodiments of the present invention, address offset hidden source type light fixtures designed especially for the purpose of providing architecturally distinctive indirect lighting treatments wherein a fixture (or row of side-by-side fixtures), flush mounted into a flat surface such as wall or ceiling of a room, “washes” a nearby flat surface such as a wall, floor or ceiling, perpendicular to the mounting surface, with uniform illumination. 
         [0007]    In the abovementioned patent, a thin flexible offset reflective lining is adhesively attached to a rigid aluminum reflector mounting body extruded in a special compound curved shape having an offset lamp-surround portion blending into an extended “throw” portion so as to provide uniform “wash” illumination from the fluorescent lamp concealed within the lamp-surround portion. 
         [0008]    U.S. Pat. No. 5,142,459, for a HIDDEN SOURCE FLUORESCENT LIGHT WASH FIXTURE issued Aug. 25, 1992, discloses further development of this type of light fixture with an alternative reflector configuration and associated mounting system for an improved “wash” light fixture of the offset hidden source type, based on refinements of the optical principles of U.S. Pat. No. 4,748,543, but providing new benefits with regard to illumination coverage, manufacturability, and reflector replaceability. 
         [0009]    This product improvement allows configuration of a light fixture of the fluorescent offset-reflector hidden-light-source wall-wash type, such that it provides substantially uniform illumination along with improved shielding of direct light from the source and suppression of spurious highlights reflected from fixture surfaces. 
         [0010]    Additionally, it provides a reflector mounting configuration in which a specially shaped curved reflector is secured to the fixture in a manner that enables the reflector to be easily installed, removed and replaced, and which also provides the unique curved reflector surface shape required in this type of fixture, uniformly and reliably. 
         [0011]    However, despite the improvements obtained in the aforementioned patents, these types of light fixtures are designed for light sources that emit light in all directions, and are therefore not well suited for LED lights in general, and modern commercial LED assemblies in particular, which generally emit light from a side of a plane surface, only in the direction away from the side of the plane surface. 
         [0012]    Additionally, while light fixtures according to embodiments disclosed in U.S. Pat. No. 5,142,459 provide significantly improved shielding from direct light, these types of light fixtures still allow unshielded view of the lighting elements from some viewing positions. 
         [0013]    As such, considering the foregoing, it may be appreciated that there continues to be a need for novel and improved devices and methods for LED based light fixtures. 
       SUMMARY OF THE INVENTION 
       [0014]    The foregoing needs are met, to a great extent, by the present invention, wherein in aspects of this invention, enhancements are provided to the existing models for illumination with LED light fixtures. 
         [0015]    Various aspects of the present invention provide a light fixture that is optimized for directional LED lighting, achieving a wide and uniform field of asymmetric illumination with virtual elimination of any direct light. 
         [0016]    In an aspect, a light fixture, can include:
       a. A fixture housing, which is closed in a rear side, and comprises a window opening in a front side, bordered along one side by a side panel, to which is connected a lighting element shelf;   b. A reflector, in the form of a one piece snap-in that requires no tools for installation, which is configured with a special parabolic shape, such that the reflector extends from a starting edge, and projects initially substantially asymptotically perpendicular in the cross-sectional plane to the window opening, thereafter extending towards the rear side of the light fixture, reaching an apex, from which the reflector continues an elongated parabolic curve, from the apex to an ending point; and   c. At least one lighting element, which is mounted on an inside surface of the lighting element shelf, inside the fixture housing, such that the lighting element provides directional light, towards the rear side of the fixture housing;   Such that substantially all light emitted from the lighting element, will reflect at least one time on the reflector, before exiting the light fixture via the window opening.       
 
         [0021]    In various related aspects, the light fixture can be configured in version suitable for wall illumination, conference room illumination, ceiling illumination, ground surface illumination, and related illumination applications for interior and exterior illumination. 
         [0022]    In a related aspect, the lighting element shelf can further include an angled ledge, which protrudes inward at an angle, in order to eliminate direct visibility of the lighting element. 
         [0023]    In a related aspect, the lighting element can be a LED lighting assembly. 
         [0024]    There has thus been outlined, rather broadly, certain embodiments of the invention in order that the detailed description thereof herein may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional embodiments of the invention that will be described below and which will form the subject matter of the claims appended hereto. 
         [0025]    In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of embodiments in addition to those described and of being practiced and carried out in various ways. In addition, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, are for the purpose of description and should not be regarded as limiting. 
         [0026]    As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]      FIG. 1  is a perspective partially exploded view of a LED light fixture for indirect asymmetric illumination, according to an embodiment of the invention. 
           [0028]      FIG. 2  is a cross-sectional side view of a LED light fixture for indirect asymmetric illumination, according to an embodiment of the invention. 
           [0029]      FIG. 3  is a cross-sectional side view illustrating illumination of a wall by a LED light fixture, according to the embodiment of the invention shown in  FIG. 2 . 
           [0030]      FIG. 4  is a cross-sectional side view of a LED light fixture for indirect asymmetric illumination, according to an embodiment of the invention. 
           [0031]      FIG. 5  is a cross-sectional side view illustrating illumination of a person by a LED light fixture, according to the embodiment of the invention shown in  FIG. 4 . 
           [0032]      FIG. 6  is a cross-sectional side view of a LED light fixture for indirect asymmetric illumination, according to an embodiment of the invention. 
           [0033]      FIG. 7  is a cross-sectional side view illustrating illumination of a ceiling by a cove mounted LED light fixture, according to the embodiment of the invention shown in  FIG. 6 . 
           [0034]      FIG. 8  is a cross-sectional side view of a LED light fixture for indirect asymmetric illumination, according to an embodiment of the invention. 
           [0035]      FIG. 9  is a cross-sectional side view illustrating illumination of an exterior floor surface by a LED light fixture, according to the embodiment of the invention shown in  FIG. 8 . 
           [0036]      FIG. 10  illustrates a light intensity distribution for a LED light fixture for wall illumination, according to an embodiment of the invention. 
           [0037]      FIG. 11  illustrates a light intensity distribution for a LED light fixture for video conferencing, according to an embodiment of the invention. 
           [0038]      FIG. 12  illustrates a light intensity distribution for a LED light fixture for cove illumination, according to an embodiment of the invention. 
           [0039]      FIG. 13  illustrates a light intensity distribution for a LED light fixture for exterior ground surface illumination, according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0040]    Before describing the invention in detail, it should be observed that the present invention resides primarily in a novel and non-obvious combination of elements and process steps. So as not to obscure the disclosure with details that will readily be apparent to those skilled in the art, certain conventional elements and steps have been presented with lesser detail, while the drawings and specification describe in greater detail other elements and steps pertinent to understanding the invention. 
         [0041]    The following embodiments are not intended to define limits as to the structure or method of the invention, but only to provide exemplary constructions. The embodiments are permissive rather than mandatory and illustrative rather than exhaustive. 
         [0042]    In the following, we describe the structure of an embodiment of a light fixture for indirect asymmetric illumination  100  with reference to  FIG. 1 , in such manner that like reference numerals refer to like components throughout; a convention that we shall employ for the remainder of this specification. 
         [0043]    In an embodiment,  FIG. 1  shows a partially exploded perspective view of a light fixture  100 . The light fixture  100  is shown in a downward facing orientation, such as for installation in a ceiling. The fixture housing  110  is closed on top and provides a large light window opening at the bottom bordered along one side by a side panel  112  connected along its edge with a lighting element shelf  114 , which is in plane with the window opening  211  (illustrated in  FIG. 2 ), shown in dotted line. One or more lighting elements (not visible in  FIG. 1 ) can be mounted on the top surface of the lighting element shelf  114 , inside the fixture housing  110 . 
         [0044]    The fixture housing  110  can be attached to the framing of a building by a mounting bracket  116 . Once installed, the housing&#39;s leading bottom edge  117  can be set flush with the lower surface of the ceiling, or another surface of a building or structure. An electrical connection plate  118  further including a pair of knockout holes is located on the outside of fixture housing  110 . Mounted inside the fixture housing  110  can be a ballast/driver  120 , shown in dashed lines, for driving one or more lighting elements. 
         [0045]    The reflector  130 , shown removed from the fixture housing  110 , can be made from a sheet of an appropriate material, which can be a plastic or a fiber composite, or a metal such as high purity aluminum formed into a special parabolic curved cross-sectional shape as shown. The reflector&#39;s ending edge can be formed with two bends to provide a Z-shaped cross section with an offset mounting flange  132  extending outwardly as shown, and the reflector ending edge can be straight, and can include at least one clearance notch  134 , as shown. The reflector  130  can include other notches or cutouts, as required to provide clearance during installation or removal of the reflector  130 . The formed reflector  130  can be manufactured in one piece and be spring loaded. It can snap into the fixture housing  110  without the need of tools. 
         [0046]    A trim frame  140 , for hard surface installations, can include flanges extending outward on all four sides from a four-sided collar portion. The collar portion can be dimensioned to fit around the outside of housing  110 , and be held in place by fastening clips  122  attached onto the housing, such that the collar portion is configured with a shape such that it can snap on in place by the fastening clips  122 . Other variations can be configured for installation in T-bar ceilings and surface/pendant installations. 
         [0047]    In a related embodiment,  FIG. 2  shows a cross sectional view of a light fixture  100 , wherein the reflector  130  can be configured with a short parabolic shape, such that the reflector  130  extends from the starting edge  234 , such that the reflector  130  is initially substantially asymptotically perpendicular in the cross-sectional plane to a window opening  211 , such that an initial angle between the reflector  130  and the window opening  211  is in a range of −5 to +5 degrees from a 90 degree perpendicular angle, thereafter extending in a parabolic curve towards the rear panel  213  of the light fixture, reaching an apex  236 , after 20-30%  250  of the horizontal projection length or reflector width  244  in the plane of the window opening, from the starting edge  234  of the cross-sectional reflector  130  curve to the ending edge  232 , from where the curve continues an elongated parabolic curve, from the apex  236  to the ending point  232 . As shown on  FIG. 2 , a short parabolic shape of the reflector  130  can be configured with a reflector depth  242  to width  244  ratio of the reflector  130  of equal to or less than 1:3, wherein the reflector depth  242  is the length of the shortest straight line in the cross-sectional plane from the apex  236  to the straight line between the starting and ending points  234   232 , and the reflector width is the length of the straight line between the starting and ending points  234   232 . A short parabolic shape of the reflector  130  can have depth to width ratio of equal to or less than 1:3, such as for example, as shown in  FIG. 2 , approximately 1:2.5, 1:2, or even 1:1 or less. 
         [0048]    As shown on  FIG. 2 , lighting elements  228  can be positioned on the top surface of the lighting element shelf  114 , inside the fixture housing  110 , in the plane of the window opening, from the starting edge  234  of the cross-sectional reflector  130  curve to the ending edge  232 , whereby the lighting elements  228  are effectively shielded from direct visibility, such that all light is transmitted indirectly via the reflector  130 , as shown by light paths in dotted lines. 
         [0049]    In a related embodiment, the light fixture  100  can further include an angled ledge  204 , which is connected to an inner edge of the lighting element shelf  114 , and protrudes inwards at an angle, which can be fixed at an angle in a range of 0 to 90 degrees. In  FIG. 2 , the angled ledge  204  is shown protruding at approximately 45 degrees. The angled ledge  204  can serve to improve shielding of direct light from the edge of the lighting elements  228 . 
         [0050]    In a related embodiment, the angled ledge  204  can be reflective on the inner side, such that light from the lighting elements  228  is reflected back on to the reflector  130 , and is eventually emitted from the light fixture  100  as indirect light. 
         [0051]    In a related embodiment, the angled ledge  204  can be adjustable such that the angle can be adjusted between 0 and 90 degrees. 
         [0052]      FIG. 3  illustrates the embodiment of  FIG. 2  mounted into a ceiling  302  and directed to an adjacent wall  304  and a floor  306 , such that light emitted from the lighting elements  228  is “washed” on to the wall  304  and the floor  306 . 
         [0053]    All light paths, as shown on  FIG. 3 , represent indirect, reflected light. The design provides optimum uniformity of lighting on the surface being illuminated. The light paths  312  and  314  represent the boundaries of reflected light. The light fixture can be configured in a plurality of sizes and reflector shapes for positioning at varying distances from the wall  304 , thereby providing uniform lighting on the wall  304 . 
         [0054]      FIG. 10  illustrates the light intensity distribution from the light fixture  100  installed in a ceiling. Numeric values in  FIG. 10  indicate light intensity readings in foot-candles, in a position on a wall  1000 , specified by the center point of a numeric value, as distributed over a 20′ width  1002  by 8 foot height  1004  wall  1000 ; with the light fixture  100  installed 3′ from the wall. 
         [0055]    In a related embodiment,  FIG. 4  shows a cross sectional view of a light fixture  400  for illumination of a conference room, wherein the reflector  430  is shown configured with an elongated parabolic shape, such that the reflector  430  extends from the starting edge  434 , such that the reflector  430  is initially substantially asymptotically perpendicular in the cross-sectional plane to a window opening  411 , such that an initial angle between the reflector  430  and the window opening  411  is in a range of −5 to +5 degrees from a 90 degree perpendicular angle, thereafter extending in a parabolic curve towards the rear panel  413  of the light fixture  400 , reaching an apex  436 , after approximately 20-30%  450  of the horizontal projection length or reflector width  444  in the plane of the window opening, from the starting edge  434  of the cross-sectional reflector  430  curve to the ending edge  432 . As shown on  FIG. 4 , an elongated parabolic shape of the reflector  430  can be configured with a reflector depth  442  to width  444  ratio of the reflector  430  of more than 1:3, wherein the reflector depth  442  is the length of the shortest straight line in the cross-sectional plane from the apex  436  to the straight line between the starting and ending points  434   432 , and the reflector width is the length of the straight line between the starting and ending points  434   234 . An elongated parabolic shape of the reflector  430  can have depth to width ratio of more than 1:3, such as for example, as shown in  FIG. 4 , approximately 1:3.7, 1:4, or even 1:6 or more. 
         [0056]    As shown the upper surface of the lighting element shelf  114  can be elevated such that the lighting elements  228  are higher than the plane of the window opening. 
         [0057]      FIG. 5  illustrates the embodiment of  FIG. 4  mounted into a ceiling  502 , such that the light fixture  400  illuminates a person  560  in a room. 
         [0058]    In a related embodiment, a plurality of light fixtures  400  can be installed in the ceiling of a video conference meeting room, such that the light fixtures  400 , provides uniform illumination of the participants in a video conference. 
         [0059]      FIG. 11  illustrates the light intensity distribution on the face of a video conference participant, as emitted from the light fixture  400  installed in a ceiling. Numeric values in  FIG. 11  Indicate light intensity readings in foot-candles, as distributed over the face of the video conference participant, with the light fixture  400  installed 4′ in front of the face and pointed in the direction of the participant&#39;s face, positioned at a location optimum to the height of the ceiling, such that the primary light distribution is at eye level  4 ′ above the floor level  1102 . 
         [0060]      FIG. 6  illustrates a light fixture  600  for cove illumination, as an inverted configuration of the embodiment of  FIG. 1 . 
         [0061]      FIG. 7  illustrates the embodiment of  FIG. 6  mounted in a cove  702 , such that the light fixture  600  can illuminate a ceiling  704 . 
         [0062]    In a related embodiment, a plurality of light fixtures  600  can be installed in the cove in a room, such that the light fixtures  600 , provides uniform illumination of the ceiling. 
         [0063]      FIG. 12  illustrates the light intensity distribution on a ceiling, as emitted from the light fixture  600  for cove illumination. Numeric values in  FIG. 12  indicate light intensity readings in foot-candles, as distributed over the ceiling in units of one foot, with the light fixture  600  installed in a cove 3′ below ceiling and pointed in the direction of the ceiling. 
         [0064]    In a related embodiment,  FIG. 8  shows a cross sectional view of a light fixture  800  for exterior ground surface illumination, wherein the reflector  830  is shown configured with a short parabolic shape, such that the reflector  830  extends from the starting edge  834 , such that the reflector  830  is initially substantially asymptotically perpendicular in the cross-sectional plane to a window opening  811 , such that an initial angle between the reflector  830  and the window opening  811  is in a range of −5 to +5 degrees from a 90 degree perpendicular angle, thereafter extending in a parabolic curve towards the rear panel  813  of the light fixture  800 , reaching an apex  836 , after 20-30% of the vertical projection length in the plane of the window opening  811 , from the starting edge  834  of the cross-sectional reflector  830  curve to the ending edge  832 , from where the curve continues an elongated parabolic curve, from the apex  836  to the ending point  832 . The window opening of the light fixture can be covered by a regressed lens  802 , thereby providing a more vandal resistant product, while eliminating lamp imaging. 
         [0065]      FIG. 9  illustrates a light fixture  800 , as shown in  FIG. 8 , mounted in a wall  902 , such that the light fixture  800  can illuminate a ground surface  904 . 
         [0066]    In a related embodiment, as shown in  FIG. 8 , an inner surface  815  of the lighting element shelf  814  can be recessed, such that the inner surface is further inside the fixture housing, as compared to the window opening plane  811 , shown in dotted line from a cross-sectional view. In addition, the inner surface can be angled in the cross-sectional plane, such that the cross-sectional inner surface is not parallel with the cross-sectional window plane. In  FIG. 8 , the inner surface is shown with a slightly negative angle, approximately −5 degrees, directing light such that it is tilted towards the side of the lighting fixture. In various embodiments, the angle can configured in a range of −20 to +20 degrees. In various embodiments, the recess of the inner surface can be in a range of 0.5-10 cm. Depending on the size of the light fixture  800 , the recess in some cases can be larger than 10 cm. 
         [0067]    In a further related embodiment, the angle of the lighting element shelf  814  and/or the inner surface of the lighting element shelf  814  can be adjustable, for example via a pivotal axle. 
         [0068]      FIG. 13  illustrates the light intensity distribution on a ground surface, as emitted from the light fixture  800  for exterior ground surface illumination. Numeric values in  FIG. 13  indicate light intensity readings in foot-candles, as distributed over the ground surface in units of one foot, with the light fixture  800  installed in a wall by the ground surface, such that the lower part of the light fixture  800  is 2′ above the ground surface. 
         [0069]    In a related embodiment, two reflective end plates can be provided, one at each end of the fixture housing  110 , attached to the inside of the housing end walls with double-sided adhesive foam material so as to urge the end plates against the two ends of the reflector. 
         [0070]    In the various related embodiments, the lighting element  228  can be an LED lighting assembly or a group of LED lighting assemblies. For example, the lighting element can be a distributed array module of the brand PrevaLED™, manufactured by Osram™, such as for example modules of the type 73574PLPG2-BAR-1100-830-280X38-DC. 
         [0071]    In various alternative embodiments, other directional lighting element types, styles, and ratings can be used for the lighting element  228 . 
         [0072]    In various related embodiments, the basic reflector shape can be scaled in size, and fixtures can be supplied in various common nominal lengths such as 18″, 2′, 3′, 4′, etc. 
         [0073]    In various related embodiments, the reflector can be configured with a plurality of alternative mating tongue-and-groove type attachment approaches; for example, male members at the two reflector ends could be made to engage female members on the two opposite housing window edges, or female members at the two reflector ends could be made to engage male members on the two opposite housing window edges. 
         [0074]    In related embodiments, the fixture housing can be formed entirely from sheet metal such as steel or the major portion surrounding the reflector and defining its mountings can be extruded from aluminum. Alternatively, the fixture housing can be made of plastic or plastic and/or fiber composites. 
         [0075]    In related embodiments, the ballast/driver  120 , transformer, and associated wiring can be enclosed by a sheet metal baffle plate in compliance with electrical safety requirements. 
         [0076]    In related embodiments, LED drivers used to power LED assemblies should provide pure DC (direct current) output to the LED assemblies, such that there is no issue of flicker. Flicker can be caused by the design of the driver&#39;s power output having any derivative of 60-hertz cycle AC (alternating current) power delivered to the LED assemblies. 
         [0077]    In related embodiments, the reflective surface of the reflector can be highly polished or finely diffused, and can be color-tinted for special effect. 
         [0078]    The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention, which fall within the true spirit and scope of the invention. 
         [0079]    The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, and all variations, substitutions and changes, which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. 
         [0080]    Many such alternative configurations are readily apparent, and should be considered fully included in this specification and the claims appended hereto. Accordingly, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and thus, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.