Many light fixtures in office buildings, retail stores and other indoor environments utilize so-called “T8” fluorescent tubes that are linear tubes one inch in diameter. These are often featured in “troffer” fixtures that are designed for standard suspended ceiling geometries such as 2×2 feet, 2×4 feet and other sizes. Fluorescent tubes are reasonably energy-efficient light emitters and are relatively comfortable for viewers to look at. However, fluorescent tubes are typically designed for long term degradation and/or failure, due to attack by the plasma that generates the fluorescent light, on components near the ends of the tubes. The ends of the tubes typically darken as the plasma sputters material from the components onto the nearby tube wall, diminishing efficiency and leading to a “dirty” tube look. The damaged components may eventually fail to ignite the plasma at all. Fluorescent tube based light fixtures accommodate this eventual failure by providing a replaceable part interface for the tubes. Certain fluorescent tubes also include trace amounts of mercury that can present a hazard if the tube is broken, and for which reason disposal of used tubes as hazardous material is recommended.
Light emitting diodes (LEDs) are increasingly used as light emitters at the present time due to their high light production efficiency, high reliability, light stability over time and other attributes. Cost of LEDs is currently decreasing as manufacturers increase chip yields. This encourages production of large LED chips as a cost-effective mode of generating the largest amount of usable light generation per LED wafer processed while minimizing downstream costs for testing, packaging and handling that are proportional to the number of chips produced.
In an embodiment, a tri-lobe optic for a linear light source is disclosed. The linear light source defines a light emitting region along an axis. The tri-lobe optic includes an optical material having a constant cross-sectional profile along a direction of the axis from a first axial end to a second axial end. The cross-sectional profile includes a first azimuthal side relative to the axis and concave and convex curves relative to the axis. The curves are a first concave curve coupled with the first azimuthal side, a first convex curve, a second concave curve, a second convex curve and a third concave curve. Each of the concave curves defines a lobe of the optical material along the direction of the axis. The cross-sectional profile also includes a second azimuthal side relative to the axis, coupled with the third concave curve.
In an embodiment, a light rail for a fluorescent light fixture is disclosed. The light rail includes a light engine that includes a plurality of light emitting diodes (LEDs) coupled with a printed circuit board (PCB), defining a light emitting region and an axis that is centered within the light emitting region and extends along an upper surface of the PCB. The light rail also includes a bracket that extends along a direction of the axis, the PCB coupling with the bracket, and a tri-lobe optic having a constant cross-sectional profile along the direction of the axis. The cross-sectional profile includes a first azimuthal side that forms a first slot for the bracket, and concave and convex curves relative to the axis. The curves are a first concave curve coupled with the first azimuthal side, a first convex curve, a second concave curve, a second convex curve and a third concave curve, such that each of the concave curves defines a lobe of the tri-lobe optic along the direction of the axis. The cross-sectional profile also includes a second azimuthal side coupled with the third concave curve and forming a second slot for the bracket. The light rail also includes two end caps, each of the end caps coupling with a respective first and second one of two axial ends of the tri-lobe optic, such that the end caps enclose the bracket axially and the slots enclose the bracket azimuthally.
In an embodiment, a retrofit kit for a fluorescent light fixture is disclosed. The retrofit kit includes a back plate configured to couple with a frame of the fluorescent light fixture, and two light rails coupled with a first side of the back plate. Each of the light rails includes a light engine that includes a plurality of light emitting diodes (LEDs) coupled with a printed circuit board (PCB) to define a light emitting region. The PCB extends along an axis. Each of the light rails also includes a bracket extending along a direction of the axis. The PCB couples with the bracket. Each of the light rails also includes a tri-lobe optic having a constant cross-sectional profile along a direction of the axis and disposed facing the light emitting region. The LEDs emit light through the tri-lobe optic. The cross-sectional profile includes concave and convex curves relative to the axis. The curves are a first concave curve, a first convex curve, a second concave curve, a second convex curve and a third concave curve. Each of the concave curves defines a lobe of the tri-lobe optic along the direction of the axis. The cross-sectional profile also includes coupling features disposed with azimuthal sides of the cross-sectional profile, for restraining the bracket in a lateral direction. Each of the light rails also includes two end caps that couple with respective first and second axial ends of the tri-lobe optic and about ends of the bracket, for restraining the bracket in an axial direction.
In an embodiment, a light fixture is disclosed. The light fixture includes a frame, a front panel that forms one or more windows for light to emit therethrough, and a back plate configured to couple with the frame. The light fixture also includes one or more light rails coupled with a first side of the back plate and oriented to emit the light through the one or more windows. Each of the light rails includes a plurality of light emitting diodes (LEDs) coupled with a printed circuit board (PCB) to define a light emitting region, the PCB extending along an axis, a bracket extending along a direction of the axis, the PCB coupling with the bracket, and a tri-lobe optic having a constant cross-sectional profile along the direction of the axis and disposed facing the LEDs, such that the LEDs emit the light through the tri-lobe optic. The cross-sectional profile includes concave and convex curves relative to the axis. The curves are, in sequence, a first concave curve, a first convex curve, a second concave curve, a second convex curve and a third concave curve. Each of the concave curves defines a lobe of the tri-lobe optic along the direction of the axis.
The present disclosure is described in conjunction with the appended figures:
The present disclosure may be understood by reference to the following detailed description taken in conjunction with the drawings described below, wherein like reference numerals are used throughout the several drawings to refer to similar components. It is noted that, for purposes of illustrative clarity, certain elements in the drawings may not be drawn to scale. Specific instances of an item may be referred to by use of a numeral in parentheses (e.g., curves 114(1), 114(2), etc.) while numerals without parentheses refer to any such item (e.g., curves 114). In instances where multiple instances of an item are shown, only some of the instances may be labeled, for clarity of illustration.
Large LED chips running at typical light output levels often emit so much light in such a small emitting area that they are uncomfortable to view directly. Embodiments herein recognize this, and provide new and useful functionality for lighting products that utilize LEDs, particularly large LED chips as are desirable for the purpose of providing a low cost, high lumen output, LED based fixture. Certain embodiments herein include optics that spread approximately as much light (generated by LEDs) as a (new) T8 fluorescent tube, over an area equivalent to the light emitting surface area of a T8 tube. By matching the light intensity per unit of emitting area with that of a T8 tube, viewing discomfort is minimized or eliminated. Embodiments herein include the optics, complete fixtures based on them, and retrofit kits for existing fixtures that include intermediate level assemblies.
Optic 110 is formed of an optical material and generally has a constant cross-sectional profile along its length, although features such as apertures or tabs may be fabricated into optic 110 to facilitate mounting and mechanical support. Optical materials utilized to form optic 110 may include acrylic, polycarbonate, silicone or glass, with or without coatings applied thereto. Optic 110 is typically formed by extrusion, but may also be formed by other techniques such as blow molding, vacuum forming, injection molding and continuous casting.
For purposes of accurately identifying features of light rail 100, an axis 90 is defined as extending along an upper surface of PCB 150 (e.g., the surface on which LEDs 140 are mounted), centered within a light emitting region provided by LEDs 140. Thus, PCB 150 and optic 110 extend along an axial direction relative to axis 90, while useful emitting angle α is generally in an azimuthal direction relative to axis 90 (although useful emitting angle α is measured with respect to edges of a light emitting region, rather than axis 90 itself; see
An overall height of optic 110, measuring perpendicularly with respect to axis 90 from a bottom to an apex of the optic, as shown, is denoted as h3. In embodiments, bracket 160 does not extend below optic 110, although this is not required (e.g., bracket 160 can be modified as appropriate when other features of a light fixture that includes light rail 100 are arranged so as to accommodate an extra height if bracket 160 extends beneath optic 110). In a particular embodiment, height h3=d+h1=d/2+h2, such that optic 110 can fit into a fixture originally designed for fluorescent tube 10 or light bar 30. Optic 110 also defines coupling features 170 for bracket 160, and coupling features 180 for end caps (discussed below) to enclose ends of light rail 100, within each azimuthal side of optic 110.
The number and shapes of lobes 118-1, 118-2 and 118-3, and total arc lengths of the curves defining the lobes, may vary within certain ranges and still spread the light flux density of an LED light engine over an area to make the associated light fixture acceptable to view directly. For example, in embodiments, arc lengths of the first and third concave curves may be within the range of 0.4 to 0.6 inches within the 140 degree azimuthal range from the light emitting region, arc lengths of the first and second convex curves may be within the range of 0.4 to 0.6 inches, and an arc length of the second concave curve may be within the range of 0.9 to 1.6 inches. A total arc length of the cross-sectional profile may be within the range of 2.5 to 4 inches within the 140 degree azimuthal range from the light emitting region.
The foregoing is provided for purposes of illustrating, explaining, and describing various embodiments. Having described these embodiments, it will be recognized by those of skill in the art that various modifications, alternative constructions, and equivalents may be used without departing from the spirit of what is disclosed. Different arrangements of the components depicted in the drawings or described above, as well as additional components and steps not shown or described, are possible. Certain features and subcombinations of features disclosed herein are useful and may be employed without reference to other features and subcombinations. Additionally, a number of well-known processes and elements have not been described in order to avoid unnecessarily obscuring the embodiments. Embodiments have been described for illustrative and not restrictive purposes, and alternative embodiments will become apparent to readers of this patent. Accordingly, embodiments are not limited to those described above or depicted in the drawings, and various modifications can be made without departing from the scope of the claims below. Embodiments covered by this patent are defined by the claims below, and not by the brief summary and the detailed description.
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