Patent Application
20080273341
The invention relates generally to the field of lighting systems and, more particularly, to apparatus for mounting LED light sources in a lighting apparatus.
Light emitting diodes (LEDs) offer exciting benefits in the field of lighting apparatus. There is a strong trend in the industry to replace conventional incandescent light sources with LED units. Among the advantages offered by LED modules is increased flexibility of use. LED modules generally comprise an array of LED units each unit including a reflector (and optionally a refractor) and an LED. The assembly is durable and long-lasting. This arrangement further allows much smaller packages of such light sources which translate into much lower material usage within fixtures containing such sources. Another significant advantage of LEDs is that they yield reliable light with low-power consumption. Further, a solid package of LEDs may be positioned to focus light as might be required.
One of the main hurdles to using LEDs in certain applications is the management of the heat generated by the LED modules. Generally, LEDs themselves create little heat because of their high efficiency as measured by light output per unit power input. There are, however, LEDs that, due to their higher operating currents, may generate considerable more heat than traditional LED modules. Other power-related components within the lighting fixture may also create significant heat. LED performance, and the performance of other power-related components, is directly related to the amount of ambient heat within the housing of a lighting fixture. High levels of heat in a lighting fixture compromise the functionality and life of certain components that are highly susceptible to heat, including LED modules, ballasts, capacitors and other power-related components. The concern of heat is even more pronounced where LEDs are mounted in a confined space or more than one LED package is used. In such circumstances, it is especially crucial to manage the heat created by the LED module for optimal performance and to protect the overall life of the fixture.
It is known in the art to use a heat-dissipating structure, such as an aluminum plate, for mounting an LED module. This approach has a significant disadvantage in that the plate is generally welded to the housing. Welding of a heat-dissipating structure to the interior of a housing typically causes undesirable distortion of the housing. Alternatively, the heat-dissipating structure may be forced into the housing. This is undesirable because assembling a heat-dissipating structure in this manner typically requires the application of over two tons of force; consequently, the interior of the housing may be significantly damaged during assembly. Further, the application of such tremendous force makes it nearly impossible in the future to remove the heat-dissipating structure for access to the housing.
The relative permanency of traditional heat-dissipating structures within a lighting apparatus housing makes it much more difficult, costly and time-consuming to perform routine maintenance. These problems are only exacerbated in certain lighting fixtures that utilize more than one LED module. For example, in a bollard lighting fixture, it may be desirable in some circumstances to provide two LED modules, one being mounted in the upper portion of a tubular housing and the other in the lower portion of the housing. Where two heat-dissipating plates are welded to the housing, this would significantly impair one's ability to enter the housing for routine maintenance. There is, therefore, a need for lighting apparatus including an LED module where the LED is mounted on a heat-dissipating structure that is easily removable, thereby allowing access to the interior regions of the lighting fixture.
It is an object, in the field of lighting systems, to provide LED lighting apparatus which has improved dissipation of heat and which overcomes some of the problems and shortcomings of the prior art.
Another object is to provide an improved LED module mounting unit that is easily removable from the housing of a lighting fixture.
Another object is to provide a bollard luminaire having improved efficiency and product life.
Yet another object is to provide a bollard luminaire having improved lower temperature of operation.
Another object is to provide a bollard luminaire having a simplified construction and assembly.
Still another object is to provide a bollard luminaire that is easier and less expensive to manufacture, assemble and maintain.
These and other objects of the invention will be apparent from the following descriptions and the drawings.
The invention is an LED lighting apparatus having a heat sink assembly and, more broadly considered, a heat sink assembly for mounting an LED module to a surrounding heat sink member. Further disclosed is a method for mounting the inventive removable heat-sink assembly.
The LED lighting apparatus includes a tubular housing and a heat sink assembly for mounting an LED module to the inside of the housing. The heat sink assembly includes a first plate, a second plate movable with respect to the first plate, an expandable ring sandwiched between the first and second plates. The sandwiching device adjustably interconnects the first and second plates. The first plate includes inner and outer faces and a peripheral edge. The second plate includes inner and outer faces and an inwardly-tapered peripheral camming surface. The expandable ring includes an inward peripheral edge engaging the camming surface and an outward heat-transfer surface and is expandable to beyond the peripheries of the first and second plates.
Sandwiching of the ring occurs upon tightening of the sandwiching device which draws the second plate toward the first plate thereby causing expansion of the ring into heat-transfer contact with the interior of the housing. The sandwiching interaction facilitates transfer of heat generated by the LED module from the heat sink assembly to the interior of the housing. The ring is expandable to beyond the peripheries of the first and second plates for optimal heat transfer.
In certain embodiments the tubular housing is made of a heat-conductive material such that it forms a main heat sink member.
In most preferred embodiments, the second plate defines an aperture through which the sandwiching device extends and the inner surface of the first plate includes a receptor port configured for drawing engagement with the sandwiching device. In such embodiments, the receptor port can be threaded and the sandwiching device can be a screw, the rotation of which draws the second plate toward the first plate.
In other highly preferred embodiments, the expandable ring includes a gap and the gap facilitates radial expansion of the ring.
In some embodiments, the inward peripheral edge of the expandable ring and the inwardly-tapered peripheral camming surface are substantially parallel.
In yet other embodiments, the first and second plates have substantially equivalent footprints. In such embodiments, the first and second plates and the ring are substantially circular. The first and second plates and the ring may be concentrically mounted with respect to each other.
In most preferred embodiments, the heat sink assembly is made of heat-conductive material.
The invention further includes a method for mounting a removable heat-transfer facilitating assembly in a lighting apparatus having a tubular housing. The method includes the steps of providing a heat sink assembly having first and second plates, an expandable ring and a sandwiching device, each as described above. The second plate is drawn toward the first plate, thereby sandwiching the expandable ring such that the heat-transfer surface is biased against the interior of the tubular housing. The method facilitates easy access to the interior of the housing for routine maintenance and repair.
One embodiment of the heat sink assembly for mounting an LED module to a surrounding main heat sink member is shown in the figures as assembly 10. Heat sink assembly 10 is made of a heat-conductive material. Any suitable metal may be used for this purpose. Aluminum is a preferred material because of its cost-effectiveness. Those skilled in the art will recognize that any thermally-conductive metal could be used. Though metal is a preferred material, other materials may be used, such as thermally-conductive plastics. However, to facilitate optimal heat-transfer between the heat sink assembly and the tubular housing, metal is most preferred.
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When it is desirable to remove heat sink assembly 10 from tubular housing 52, for example because of required maintenance or repair, one may loosen sandwiching device 40, thereby permitting second plate 28 to move away from first plate 20 and facilitating retraction of expandable ring 42 from the sides of tubular housing 52. Then, heat sink assembly 10 may be easily removed from tubular housing 52 in any suitable manner. For example, one may pull heat sink assembly 10 up and out of tubular housing 52 by grabbing ahold of sandwiching device 40 and withdrawing assembly 10. Alternatively, heat sink assembly 10 could include, for example, finger holes, handle-like structure(s) or other suitable removal-facilitating device.
While the principles of this invention have been described in connection with specific embodiments, it should be understood clearly that these descriptions are made only by way of example and are not intended to limit the scope of the invention.
