Patent Application
20150167901
1. Field of the Invention
The invention relates to lighting fixtures and, more particularly, to linear lighting fixtures that are well-suited for use with solid state lighting sources, such as light emitting diodes (LEDs).
2. Description of the Related Art
Troffer-style fixtures (troffers) are ubiquitous in commercial office and industrial spaces throughout the world. In many instances these troffers house elongated fluorescent light bulbs that span the length of the troffer. Troffers may be mounted to or suspended from ceilings or walls. Often the troffer may be recessed into the ceiling, with the back side of the troffer protruding into the plenum area above the ceiling. Typically, elements of the troffer on the back side dissipate heat generated by the light source into the plenum where air can be circulated to facilitate the cooling mechanism. U.S. Pat. No. 5,823,663 to Bell, et al. and U.S. Pat. No. 6,210,025 to Schmidt, et al. are examples of typical troffer-style fixtures.
More recently, with the advent of the efficient solid state lighting sources, these troffers have been used with LEDs, for example. LEDs are solid state devices that convert electric energy to light and generally comprise one or more active regions of semiconductor material interposed between oppositely doped semiconductor layers. When a bias is applied across the doped layers, holes and electrons are injected into the active region where they recombine to generate light. Light is produced in the active region and emitted from surfaces of the LED.
LEDs have certain characteristics that make them desirable for many lighting applications that were previously the realm of incandescent or fluorescent lights. Incandescent lights are very energy-inefficient light sources with approximately ninety percent of the electricity they consume being released as heat rather than light. Fluorescent light bulbs are more energy efficient than incandescent light bulbs by a factor of about 10, but are still relatively inefficient. LEDs by contrast, can emit the same luminous flux as incandescent and fluorescent lights using a fraction of the energy.
In addition, LEDs can have a significantly longer operational lifetime. Incandescent light bulbs have relatively short lifetimes, with some having a lifetime in the range of about 750-1000 hours. Fluorescent bulbs can also have lifetimes longer than incandescent bulbs such as in the range of approximately 10,000-20,000 hours, but provide less desirable color reproduction. In comparison, LEDs can have lifetimes between 50,000 and 70,000 hours. The increased efficiency and extended lifetime of LEDs is attractive to many lighting suppliers and has resulted in their LED lights being used in place of conventional lighting in many different applications. It is predicted that further improvements will result in their general acceptance in more and more lighting applications. An increase in the adoption of LEDs in place of incandescent or fluorescent lighting would result in increased lighting efficiency and significant energy saving.
Other LED components or lamps have been developed that comprise an array of multiple LED packages mounted to a (PCB), substrate or submount. The array of LED packages can comprise groups of LED packages emitting different colors, and specular reflector systems to reflect light emitted by the LED chips. Some of these LED components are arranged to produce a white light combination of the light emitted by the different LED chips.
In order to generate a desired output color, it is sometimes necessary to mix colors of light which are more easily produced using common semiconductor systems. Of particular interest is the generation of white light for use in everyday lighting applications. Conventional LEDs cannot generate white light from their active layers; it must be produced from a combination of other colors. For example, blue emitting LEDs have been used to generate white light by surrounding the blue LED with a yellow phosphor, polymer or dye, with a typical phosphor being cerium-doped yttrium aluminum garnet (Ce:YAG). The surrounding phosphor material “downconverts” some of the blue light, changing it to yellow light. Some of the blue light passes through the phosphor without being changed while a substantial portion of the light is downconverted to yellow. The LED emits both blue and yellow light, which combine to yield white light.
In another known approach, light from a violet or ultraviolet emitting LED has been converted to white light by surrounding the LED with multicolor phosphors or dyes. Indeed, many other color combinations have been used to generate white light.
Some recent designs have incorporated an indirect lighting scheme in which the LEDs or other sources are aimed in a direction other than the intended emission direction. This may be done to encourage the light to interact with internal elements, such as diffusers, for example. One example of an indirect fixture can be found in U.S. Pat. No. 7,722,220 to Van de Ven which is commonly assigned with the present application.
Modern lighting applications often demand high power LEDs for increased brightness. High power LEDs can draw large currents, generating significant amounts of heat that must be managed. Many systems utilize heat sinks which must be in good thermal contact with the heat-generating light sources. Troffer-style fixtures generally dissipate heat from the back side of the fixture that which often extends into the plenum. This can present challenges as plenum space decreases in modern structures. Furthermore, the temperature in the plenum area is often several degrees warmer than the room environment below the ceiling, making it more difficult for the heat to escape into the plenum ambient.
One embodiment of a linear light fixture comprises the following elements. An elongated base comprises end panels at both ends. A light engine is removably fastened to the base. The light engine comprises a mount plate, at least one light source on the mount plate, and an elongated lens on the mount plate. A gap filler element is between the light engine and the end panels at an end of the fixture.
Another embodiment of a light fixture comprises the following elements. An elongated base has end panels at both ends. A light engine is removably fastened to the base. A gap filler element is between the light engine and one of the end panels.
An embodiment of a gap filler element comprises the following elements. A spacer portion is shaped to cover an end of a light engine. An internal ridge protrudes from the spacer portion having a minimum width to accommodate light engines of varying length. The gap filler element comprises a light-transmissive material.
a-d are various elevation views of a linear light fixture according to an embodiment of the present invention (3a: bottom elevation; 3b: right side elevation; 3c: top elevation; and 3d: right end elevation).
a and 5b are perspective views of a gap filler element according to an embodiment of the present invention.
c-f are various elevation views of a gap filler element according to an embodiment of the present invention (5c: right end elevation; 5d: bottom elevation; 5e: right side elevation; and 5f: top elevation).
a and 7b are polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees) of light fixtures.
a is a bottom perspective view of a linear light fixture according to an embodiment of the present invention.
a and 10b are polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees) of a simulated light fixture according to an embodiment of the present invention compared with existing fixtures.
a and 12b are polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees) of simulated light fixtures.
a and 14b are polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees) of a simulated light fixture according to an embodiment of the present invention compared with other simulated fixtures.
a and 16b are polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees) of a simulated light fixture according to an embodiment of the present invention compared with other simulated fixtures.
a and 18b are polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees) of a simulated light fixture according to an embodiment of the present invention compared with other simulated fixtures.
Embodiments of the present invention provide linear light fixture that is particularly well-suited for use with solid state light sources, such as LEDs, to provide a surface ambient light (SAL). The fixture comprises two primary structural components: a base and a light engine. These two subassemblies may be removably attached to operate as a singular fixture. The base comprises a body with end panels at both ends and is mountable to an external structure. The light engine comprises the light sources, an elongated lens, and any other optical elements that tailor the outgoing light to a particular profile. A gap filler element is disposed between the light engine and the end panels at one or both ends of the base to fill the space between those elements, giving the appearance that the light engine extends continuously to the end panel and eliminating direct imaging of the light sources outside the fixture. Electronics necessary to power and control the light sources may be disposed in either the base or the light engine. External reflectors may also be included to further shape the output beam.
It is understood that when an element is referred to as being “on” another element, it can be directly on the other element or intervening elements may also be present. Furthermore, relative terms such as “inner”, “outer”, “upper”, “above”, “lower”, “beneath”, and “below”, and similar terms, may be used herein to describe a relationship of one element to another. It is understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures.
Although the ordinal terms first, second, etc., may be used herein to describe various elements, components, regions and/or sections, these elements, components, regions, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, or section from another. Thus, unless expressly stated otherwise, a first element, component, region, or section discussed below could be termed a second element, component, region, or section without departing from the teachings of the present invention.
As used herein, the term “emitter” can be used to indicate a single light source or more than one light source functioning as a single emitter. For example, the term may be used to describe a single blue LED, or it may be used to describe a red LED and a green LED in proximity emitting as a single source. Additionally, the term “emitter” may indicate a single LED chip or multiple LED chips arranged in an array, for example. Thus, the terms “source” and “emitter” should not be construed as a limitation indicating either a single-element or a multi-element configuration unless clearly stated otherwise. Indeed, in many instances the terms “source” and “emitter” may be used interchangeably. It is also understood that an emitter may be any device that emits light, including but not limited to LEDs, vertical-cavity surface-emitting lasers (VCSELs), and the like.
The term “color” as used herein with reference to light is meant to describe light having a characteristic average wavelength; it is not meant to limit the light to a single wavelength. Thus, light of a particular color (e.g., green, red, blue, yellow, etc.) includes a range of wavelengths that are grouped around a particular average wavelength.
Embodiments of the invention are described herein with reference to cross-sectional and/or cutaway views that are schematic illustrations. As such, the actual thickness of elements can be different, and variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances are expected. Thus, the elements illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the precise shape of a region of a device and are not intended to limit the scope of the invention.
With reference to
This particular embodiment features mount brackets 218 that may be used to mount the fixture 100 to a ceiling or a T-grid, for example. The fixture 100 can be mounted in many different ways. For example, it can be surface mounted to a wall, a ceiling, or another surface, or it can be suspended from the ceiling with aircraft cable or in a pendant configuration.
As shown in
One challenge associated with the fabrication of linear fixtures is the availability of lenses that are uniformly cut to a specific length. It is often desirable to use an extrusion process to produce the lenses; however, such a process does not provide precise tolerances in the length of the lenses, especially for longer models. If a lens that is shorter than the specified length, there will be a gap between the lens and the base at one or both ends of the fixture. This can lead to imaging of the light sources external to the fixture. Embodiments of the present invention comprise the gap filler elements 216 to account for these gaps. The gap fillers 216 fill the space with a translucent material that gives the appearance that the light engine 104 extends all the way to the end panel 204 of the base 102. Because the light sources 208 are no long visible through the gaps, source imaging is eliminated. The gap fillers 216 compensate for inconsistency in lens manufacturing, allowing for a much more relaxed tolerance for lens length.
a-f show several views of a gap filler element 216 according to an embodiment of the present invention.
The gap filler 216 is removably attachable to the light engine 104 such that, when assembled, the gap filler 216 is interposed between the end panel 204 of the base 102 and the end of light engine 104. The gap filler 216 comprises tabs 502 that snap-fit into corresponding slots on the mount plate 206, fastening the gap filler 216 to the light engine 104. The snap-fit fastening mechanism allows for easier and faster assembly without the need for screws or adhesives.
The gap filler 216 also comprises a spacer portion 504 and a ridge 506. The spacer portion 504 is shaped to mimic the external contour of the lens 214 such that the lens 214 appears to extend continuously to the end panel 204. The ridge 506 protrudes from said spacer portion 504 and is shaped to conform to an interior surface of the lens 214. During assembly the ridge slides under the lens with the tabs 502 engaging slots in the mount plate 206 for a snap fit. The width of the ridge 506 is designed to compensate for a maximum deviation from length specification, with a wider ridge allowing for a more relaxed tolerance.
The gap fillers 216 comprise a light-transmissive (e.g., translucent) material. The material should diffuse the light sufficiently to prevent source imaging with the optimal diffusion providing an output that is similar in appearance to that emitted from the lens 214. In some embodiments, the gap filler 216 does not need to be as diffusive as the lens 214 because most of the light that exits the gap filler 216 will exit from its edge. Some suitable materials include polycarbonates or acrylics.
In one embodiment the driver electronics 202 comprise a step-down converter, a driver circuit, and a battery backup. At the most basic level a driver circuit may comprise an AC/DC converter, a DC/DC converter, or both. In one embodiment, the driver circuit comprises an AC/DC converter and a DC/DC converter both of which are located in the base 102. In another embodiment, the AC/DC conversion is done in the base 102, and the DC/DC conversion is done in the light engine 104. Another embodiment uses the opposite configuration where the DC/DC conversion is done in the base 102, and the AC/DC conversion is done in the light engine 104. In yet another embodiment, both the AC/DC converter and the DC/DC converter are located in the light engine 104. It is understood that the various electronic components may distributed in different ways in one or both of the base 102 and the light engine 104.
In one embodiment, the lens 214 comprises a diffusive element. A diffusive exit lens 214 functions in several ways. For example, it can prevent direct visibility of the sources and provide additional mixing of the outgoing light to achieve a visually pleasing uniform source. However, a diffusive exit lens can introduce additional optical loss into the system. Thus, in embodiments where the light is sufficiently mixed internally by other elements, a diffusive exit lens may be unnecessary. In such embodiments, a transparent exit lens may be used, or the exit lens may be removed entirely. In still other embodiments, scattering particles may be included in the exit lens 214.
Diffusive elements in the lens 214 can be achieved with several different structures. A diffusive film inlay can be applied to the top- or bottom-side surface of the lens 214. It is also possible to manufacture the lens 214 to include an integral diffusive layer, such as by coextruding the two materials or by insert molding the diffuser onto the exterior or interior surface. A clear lens may include a diffractive or repeated geometric pattern rolled into an extrusion or molded into the surface at the time of manufacture. In another embodiment, the exit lens material itself may comprise a volumetric diffuser, such as an added colorant or particles having a different index of refraction, for example.
In other embodiments, the lens 214 may be used to optically shape the outgoing beam with the use of microlens structures, for example. Microlens structures are discussed in detail in U.S. patent application Ser. No. 13/442,311 to Lu, et al., which is commonly assigned with the present application to CREE, INC. and incorporated by reference herein.
Several measurements were taken of various light engines and lenses according to various embodiments of the present invention. In addition, several simulations were performed to model the performance of the light engines and lenses and to compare with the measurements that were taken. All simulations referred to herein were created using the LightTools program from Optical Research Associates. LightTools is a software suite well-known in the lighting industry for producing reliable simulations that provide accurate predictions of performance in the real world. Measurements and simulations of the various embodiments discussed below include polar graphs showing radiant intensity (W/sr) versus viewing angle (degrees). The light sources used in actual fixtures are XH-G LEDs that are commercially available from Cree, Inc. Likewise, all simulations use sources that mimic the performance of XH-G LEDs. Those of skill in the art will understand that many different kinds of LEDs would work with the fixtures disclosed herein.
a and 7b are polar graphs of measured radiant intensity (W/sr) over the entire range of viewing angles of the light fixture 100 compared with a standard 2-lamp fluorescent strip. Two data sets are represented on both graphs: the fixture 100 data sets 702, 706 and the data sets 704, 708 for the standard fluorescent strip, with both all data sets scaled to 4500 lumens. In
In some embodiments, an elongated reflector can be included on one or both sides of the fixture to redirect light that is initially emitted at a high angle.
b shows a top side perspective view of the fixture 800.
The following exemplary embodiments feature fixtures similar to the fixture 100, each comprising a different reflector shaped and sized to provide a particular output profile.
a and 10b are polar graphs of modeled radiant intensity (W/sr) over the entire range of viewing angles of a simulated fixture 900 compared with two other kinds of fixtures. Three data sets are represented on both graphs: the fixture 900 data sets 1002, 1008, the data sets 1004, 1010 for an industrial fluorescent strip, and the data sets 1006, 1012 for a CS18 LED Linear Luminaire (commercially available from Cree, Inc.; http://www.cree.com/Lighting/Products/Indoor/High-Low-Bay/CS18) with all data sets scaled to 4500 lumens. In
a and 12b are polar graphs of modeled radiant intensity (W/sr) over the entire range of viewing angles of a simulated fixture 1100 compared with the simulated fixture 100. Two data sets are represented on both graphs: the fixture 1100 data sets 1202, 1206, the data sets 1204, 1208 for the fixture 100 without reflectors, with both data sets scaled to 4500 lumens. In
a and 14b are polar graphs of modeled radiant intensity (W/sr) over the entire range of viewing angles of a simulated fixture 1300 compared with the simulated fixture 100 and the fixture 1100. Three data sets are represented on both graphs: the fixture 1300 data sets 1402, 1408, the data sets 1404, 1410 for the fixture 100 without reflectors, and the data sets for the fixture 1100, with all data sets scaled to 4500 lumens. In
a and 16b are polar graphs of modeled radiant intensity (W/sr) over the entire range of viewing angles of a simulated fixture 1500 compared with the simulated fixture 100 and the fixture 1100. Three data sets are represented on both graphs: the fixture 1500 data sets 1602, 1608, the data sets 1604, 1610 for the fixture 100 without reflectors, and the data sets 1606, 1612 for the fixture 1100, with all data sets scaled to 4500 lumens. In
a and 18b are polar graphs of modeled radiant intensity (W/sr) over the entire range of viewing angles of a simulated fixture 1700 compared with the simulated fixture 100 and the fixture 1100. Three data sets are represented on both graphs: the fixture 1700 data sets 1802, 1808, the data sets 1804, 1810 for the fixture 100 without reflectors, and the data sets 1806, 1812 for the fixture 1100, with all data sets scaled to 4500 lumens. In
It is understood that embodiments presented herein are meant to be exemplary. Embodiments of the present invention can comprise any combination of compatible features shown in the various figures, and these embodiments should not be limited to those expressly illustrated and discussed. Many other versions of the configurations disclosed herein are possible. Thus, the spirit and scope of the invention should not be limited to the versions described above.
