Patent Application
20120120651
A luminaire is a light unit used to artificially illuminate surfaces and objects with white light so that the reflected light may be reasonably seen by humans. A luminaire provides sufficient illuminance levels on walls, objects, and working surfaces adequate for human navigation and interaction. Previous luminaires were made using thermally conductive metals, such as aluminum, in their enclosure in order to dissipate heat. The metal enclosures efficiently conducted heat away from the light source; however, the metal adds significant weight and cost to the luminaire.
In addition, some applications require luminaires that have restrictions on the type of materials that may be used for the enclosure. For example, the presence of metal enclosures may be prohibited in some applications.
In one embodiment, the present disclosure teaches a light emitting diode (LED) luminaire. In one embodiment, the LED luminaire comprises an enclosure having an interior volume and a flat side along a length of the enclosure, wherein the flat side comprises an inside surface and an outside surface, wherein the enclosure comprises an extruded optically clear plastic and one or more LEDs coupled to one or more circuit boards, wherein the one or more circuit boards are mounted on the inside surface of the flat side of the enclosure.
In another embodiment, the present disclosure teaches an LED luminaire for producing at least 1000 lumens of visible light. The LED luminaire comprises an enclosure having an interior volume and a flat side along a length of the enclosure, wherein the flat side comprises an inside surface and an outside surface, wherein the enclosure does not contain any metal and one or more LEDs coupled to one or more circuit boards, wherein the one or more circuit boards are mounted on the inside surface of the flat side of the enclosure.
In another embodiment, the present disclosure teaches a method for producing an LED luminaire. In one embodiment, the method comprises extruding an optically clear non-metallic material to form an enclosure, wherein a cross-section of the enclosure does not change during the extruding, wherein the enclosure has an interior volume and a flat side along a length of the enclosure, wherein the flat side comprises an inside surface and an outside surface, cutting the enclosure after the extruding to a length of at least twelve inches to form a first open end and a second open end, coupling one or more LEDs coupled to one or more circuit boards on the inside surface of the flat side of the enclosure and sealing the first open end with a first end cap and the second open end with a second end cap.
So that the manner in which the above recited features of the present invention can be understood in detail, a more particular description of the invention may be had by reference to embodiments, some of which are illustrated in the appended drawings. It is to be noted, however, that the appended drawings illustrate only typical embodiments of this invention and are therefore not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments.
To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures.
Embodiments of the present disclosure are directed towards a light emitting diode (LED) based luminaire utilizing a non-metallic enclosure. Herein, a luminaire is a light unit that emits at least 1000 lumens of visible light. Luminaires may be used for various types of applications. However, for some applications, at least 1000 lumens of visible light are needed. For example, humans need at least 0.1 foot-candles to navigate in outdoor areas and at least 10 foot-candles function effectively in office areas. It should be noted that toys, computers, calculators, electronics, entertainment units, handheld flashlights, gadgets, or other small electronic units that use LED based indicator lights do not emit at least 1000 lumens of visible light and are not considered luminaires.
Currently, luminaires are made using metal enclosures. Aluminum enclosure may provide good thermal conductivity; however, this makes the luminaire very heavy and expensive. The metal enclosure is typically sand cast or die cast. However, some applications prohibit the use of metal for the enclosure for luminaires.
A plastic enclosure can provide a lighter and lower cost option for the enclosure; however the geometry of the enclosure needs to be significantly different than traditional LED-based enclosure geometries in order to effectively dissipate heat away from the LEDs and keep the LEDs at low operating temperatures. Non-metallic enclosures may also be required in such applications as nuclear reactors or for corrosion resistance applications. In addition to the unique geometry, various materials may be used within the enclosure in order to transfer heat efficiently away from the individual LEDs. As a result, a lighter and lower cost LED-based light luminaire can be made.
In addition, previous luminaires were designed to include a set of components including a light source, a circuit board, a metal enclosure, and a lens cover. In contrast, the new LED-based light luminaire may be designed to include a set of components including one or more LEDs, an LED circuit board, a heat transfer material, a light-transmitting plastic extrusion, and two or more sealing caps.
In one embodiment, the one or more LEDs 105 may be alternating current (AC) LEDs so that a power supply is not needed. The one or more LEDs 105 may be arranged in a series-parallel fashion and powered directly from a high voltage AC input power. As an example, the one or more LEDs 105 may be configured in two long strings. In one embodiment, there is a first string of LEDs 105 and a second string of LEDs 105. The LEDs 105 are arranged in one electrical direction for the first string and in the opposite electrical direction for the second string. When the AC input voltage is positive, the current flows through the first string. When the AC input voltage is negative, the current flows through the second string. Other electrical components may be used in addition to the first string and second string. This arrangement will be referred to as an AC LED configuration herein. In one embodiment, the LED-based luminaire 100 utilizes an AC LED configuration. This simplifies the LED-based luminaire 100 by eliminating the need for a power supply.
In another embodiment, a power supply 120 may be used to power the one or more LEDs 105, as illustrated by
In another embodiment, the power supply 120 may be located towards the one or more ends 108 of the one or more LED circuit boards 106 as shown in
The electrical connection to the LED-based luminaire 100 may be made through a hole in one or more of the one or more end caps 103 or through a hole in the enclosure 101.
In another embodiment, the electrical connection 111 is made through a curved portion 132 of the enclosure 101. In other words, the electrical connection 111 is made on the same side of the enclosure 101 as the direction of light emitted by the one or more LEDs 105 as shown in
Referring back to
In one embodiment, some parts of the enclosure 101 may be textured. Providing texture helps to diffuse light emitted by the individual LEDs 105 to give the luminaire 100 a less “pixilated” look. The texture may also help to hide other internal components. The texture may be applied with any process such as sand blasting, chemical etch and the like. Although the surface of the enclosure 101 may have texture, the enclosure 101 may still maintain a substantially constant cross section along the length of the extrusion.
In one embodiment, the enclosure 101 may also be extruded to have features such as ribs to help diffuse light.
Referring back to
In one embodiment, graphite is used as a filler for the plastic extrusion material. The graphite may have an adhesive backing on one or more sides so that it could be used to secure the one or more LED circuit boards 106 to the flat side 109 of the main enclosure 101.
In another embodiment, the one or more LED circuit boards may be coupled to the flat side 109 using one or more mechanical fasteners 112 as illustrated in
In a further embodiment, the mechanical fasteners 112 may be separate parts from the extrusion. In a further embodiment, the mechanical fasteners 112 may be metal. This may improve the spring retention strength of the mechanical fasteners 112 over time. The metal mechanical fasteners 112 may be completely enclosed inside the enclosure 101.
In one embodiment, a combination of the mechanical fasteners 112 and the interface material 107 may be used. For example, a graphite sheet may be placed between the one or more LED circuit boards 106 and the flat side 109 of the enclosure 101 and the mechanical fasteners 112 may be used.
Referring back to
The extruded enclosure 101 provides a very extended enclosure (i.e., along a length of the enclosure 101). In other words, the enclosure 101 is extended linearly and has a generally constant cross section along a length of the enclosure 101. Extrusion is a process used to create objects of a fixed cross-sectional profile. A material is pushed or drawn through a die of the desired cross-section. For example,
The main advantages of this process over other manufacturing processes are its ability to create very complex cross-sections and work materials that are brittle, because the material only encounters compressive and shear stresses. It also forms finished parts with nice surface finishes. In addition, depending on the size of the object, extrusion can provide a cheaper process due to the high cost of creating a unique mold for large objects.
The extruded enclosure 101 is one important feature of the present disclosure. The extruded enclosure 101 provides many advantages of previous luminaires that used metallic housings. For example, when using metal enclosures for luminaires, heatsink fins are commonly used as an integral part of the enclosure. Metal fins efficiently conduct heat away from the light source.
Long integral plastic fins, as part of a plastic enclosure, are not highly effective at dissipating heat due to the lower thermal conductivity of plastics compared to metals. Heat is not transferred efficiently along a long fin length when using plastic. For example, polycarbonate has a thermal conductivity of 0.2 w/(m*K) compared to aluminum of about 200 w/(m*K). As a result, compact enclosure designs typical for luminaires, such as round or square geometries, would not be effective for an LED luminaire utilizing a non-metallic enclosure. An enclosure made using an extrusion makes for a very extended enclosure and helps spread the LEDs 105 away from each other and therefore reduce the heat density. This allows the LEDs 105 to run cooler and therefore last longer and maintain higher light levels, while avoiding the use of metallic enclosures. Short integral plastic fins, as part of a plastic enclosure may provide some minor improvement to the heat dissipation and would not add cost to an extrusion.
In order to operate typical high power LEDs at acceptable temperature limits, each watt of LED power typically requires at least 1 square inch of surface area as a general rule. Heatsink fins are not very effective with a plastic enclosure and, therefore, the plastic enclosure may be extended to ensure that there is at least 1 inch between each watt of LED power. In one embodiment, the extruded enclosure 101 should be extended at least 12 inches (in) in length in order to provide sufficient heat transfer and, therefore, adequate LED density and light, while sufficiently dissipating the heat generated by the LEDs 105 to avoid the heat from having an adverse effect on the LEDs 105 or the enclosure 101. In one embodiment, the enclosure 101 is about 24, 48 or 96 inches in length.
Another advantage of using an extruded enclosure 101 is that it is a 1-piece enclosure and, therefore, provides a better seal than a 2-piece enclosure. For example, the one or more open ends 108 are formed by a continuous surface when the enclosure is created via an extrusion process. In one embodiment, continuous is defined as being absent of any breaks along a perimeter or outer edge. For example, the continuous surface is formed such that the enclosure cannot be opened along a length of the enclosure.
Notably, the corners 130 of the enclosure 101 do not have any gaps or openings created by mating two pieces together. That is, in previous luminaire designs that use a metallic enclosure, a lens would typically be coupled to the metallic enclosure. As a result, when sealing the ends an imperfect seal would be created due to the fact that it would be difficult to seal the corners where three different surfaces (e.g., a metallic enclosure, lens and end cap) would meet.
However, the design of the present enclosure only requires the seal to be formed between two surfaces, i.e., one or more end caps 103 and the one or more ends 108 of the enclosure 101. For example, the one or more end caps 103 have a continuous surface along the perimeter or outer edge 142. Notably, there are no breaks along the perimeter 142. The one or more ends 108 of the enclosure 101 also have a continuous surface along the perimeter or outer edge 140. Notably, there are no breaks along the perimeter 140. As a result, only two surfaces need to be sealed.
The end caps 103 may be machined or they may be molded. The end caps 103 may be sealed to the one or more ends 108 of the enclosure 101 with a gasket, an o-ring, or with glue. The end caps 103 may also be attached to the enclosure 101 by ultrasonic welding or by press-fitting. Notably, no gaps or openings are present in the corners 130 of the enclosure 101, thereby creating a better seal.
Referring back to
The one or more flange sections 102 serve a key purpose in that it provides material for features such as the one or more holes 104. The one or more holes 104 may be used for mounting without creating a leak path into the enclosure 101. The one or more holes 104 may be drilled, stamped or punched after the extrusion process. The fixture may also be hung using the holes.
The flat side 109 allows for mounting to a flat surface such as a wall or ceiling in order to have consistent physical contact with the surface to help conduct heat away. In one embodiment, the one or more flange sections 102 are on a same plane as the flat side 109. In other words, the flat side 109 and the one or more flange sections 102 are in alignment as illustrated by
In summary, the LED-based luminaire 100 provides a lower cost and more efficient luminaire that can be used in a wider variety of applications than currently used luminaires. The extended geometry of the extruded enclosure 101 made from an optically clear material, such as an optically clear plastic for example, leads to many advantages. The novel design of the present LED-based luminaire 100 provides sufficient lighting (e.g., at least 1000 lumens of visible light) and heat management of heat generated by the LEDs using a non-metallic enclosure. This allows the LED-based luminaire 100 to be used in applications such as a nuclear power plant, which typically prohibits the use of metal enclosures due to corrosion concerns.
At step 904, the method 900 extrudes an optically clear non-metallic material to form an enclosure, wherein a cross-section of the enclosure does not change during the extruding, wherein the enclosure has an interior volume and a flat side along a length of the enclosure, wherein the flat side comprises an inside surface and an outside surface. As discussed above, the material may be any optically clear non-metallic material suitable for the extrusion process such as, for example, a polymer, a plastic, a glass, a ceramic and the like.
A cross section of the enclosure, may be considered to be along the axis 201 as illustrated in
In one embodiment, the extrusion step 904 may also create various features of the enclosure as discussed above. For example, the extrusion step 904 may be used to create the one or more flanges 102 illustrated in
At step 906, the method 900 cuts the enclosure after the extruding to a length of at least twelve inches to form a first open end and a second open end. As discussed above, the enclosure must be long enough to reduce the heat density generated by a number of LEDs required to provide at least 1000 lumens of visible light. Since the enclosure is non-metallic, rather than transferring all of the heat generated by the LEDs away via a metallic enclosure or metallic heat sink fins, the enclosure of the present disclosure is designed to reduce heat density by elongating a length, thereby, resulting in an enclosure. As a result, in one embodiment the enclosure should be at least 12 inches. In another embodiment, the enclosure may be 24 in, 48 in or 96 in.
Moreover, using the extrusion process helps to manufacture the LED-based luminaire 100 more efficiently. For example, the extrusion step 904 may occur continually and as the extrusion is coming out, an enclosure of the desired length may be cut as described by step 906. This is in contrast to using a mold that would be a batch process, which requires starting and stopping the process between batches. Furthermore, building a mold for a large extended enclosure would likely be prohibitively expensive and molding the large extended enclosures would likely create significant manufacturing challenges.
At step 908, the method 900 couples one or more LEDs coupled to one or more circuit boards on the inside surface of the flat side of the enclosure. As discussed above, the one or more circuit boards may be coupled via an interface and/or one or more mechanical fasteners.
At step 910, the method 900 seals the first open end with a first end cap and the second open end with a second end cap. As discussed above, a consistent and reliable seal can be formed between the enclosure and the end caps because only two surfaces need to be sealed, i.e., the continuous surface of one end of the extruded enclosure and the continuous surface edge of the end cap. Referring to
While various embodiments have been described above, it should be understood that they have been presented by way of example only, and not limitation. Thus, the breadth and scope of a preferred embodiment should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
