Information
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Patent Grant
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6573536
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Patent Number
6,573,536
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Date Filed
Wednesday, May 29, 200222 years ago
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Date Issued
Tuesday, June 3, 200321 years ago
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Inventors
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Original Assignees
-
Examiners
Agents
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CPC
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US Classifications
Field of Search
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International Classifications
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Abstract
A light source that utilizes light emitting diodes that emit white light is disclosed. The diodes are mounted on an elongate member having at least two surfaces upon which the light emitting diodes are mounted. The elongate member is thermally conductive and is utilized to cool the light emitting diodes. In the illustrative embodiment, the elongate member is a tubular member through which a heat transfer medium flows.
Description
FIELD OF THE INVENTION
This invention pertains to lighting sources, in general, and to a lighting source that utilizes Light Emitting Diodes (LED's), in particular.
BACKGROUND OF THE INVENTION
LED's have many advantages as light sources. However, in the past LED's have found application only as specialized light sources such as for vehicle brake lights, and other vehicle related lighting, and recently as flashlights. In these prior applications, the LED's are typically mounted in a planar fashion in a single plane that is disposed so as to be perpendicular to the viewing area. Typically the LED planar array is not used to provide illumination, but to provide signaling.
Recent attempts to provide LED light sources as sources of illumination have been few, and generally unsatisfactory from a general lighting standpoint.
It is highly desirable to provide a light source utilizing LED's that provides sufficient light output so as to be used as a general lighting source rather than as a signaling source.
One problem that has limited the use of LED's to specialty signaling and limited general illumination sources is that LED's typically generate significant amounts of heat. The heat is such that unless the heat is dissipated, the LED internal temperature will rise causing degradation or destruction of the LED.
It is therefore further desirable to provide an LED light source that efficiently conducts heat away from the LED's.
SUMMARY OF THE INVENTION
In accordance with the principles of the invention, an improved light source is provided. The light source includes an elongate thermally conductive member having an outer surface. A plurality of light emitting diodes is carried on the elongate member outer surface. At least some of the light emitting diodes are disposed in a first plane and others of said light emitting diodes are disposed in a second plane not coextensive with the first plane. Electrical conductors are carried by the elongate thermally conductive member and are connected to the plurality of light emitting diodes to supply electrical power thereto. The elongate thermally conductive member conducts heat away from the light emitting diodes.
In accordance with one aspect of the invention, an illustrative embodiment of the invention utilizes light emitting diodes that emit white light. However, other embodiments of the invention may utilize light emitting diodes that are of different colors to produce monochromatic light or the colors may be chosen to produce white light or other colors.
In accordance with another aspect of the invention the elongate thermally conductive member transfers heat from the light emitting diodes to a medium within said elongate thermally conductive member. In the illustrative embodiment of the invention, the medium is air.
In accordance with another aspect of the invention, the elongate thermally conductive member has one or more fins to enhance heat transfer to the medium.
In accordance with another aspect of the invention the elongate thermally conductive member comprises a tube. In one embodiment of the invention, the tube has a cross-section in the shape of a polygon. In another embodiment of the invention, the tube has a cross-section having flat portions.
In accordance with another embodiment of the invention, the elongate thermally conductive member comprises a channel.
In accordance with the principles of the invention, the elongate thermally conductive member may comprise an extrusion, and the extrusion can be highly thermally conductive material such as aluminum.
In one preferred embodiment of the invention the elongate thermally conductive member is a tubular member. The tubular member has a polygon cross-section. However, other embodiments my have a tubular member of triangular cross-section.
In one embodiment of the invention, a flexible circuit is carried on a surface of said elongate thermally conductive member; the flexible circuit includes the electrical conductors.
In another aspect of the invention, the flexible circuit comprises a plurality of apertures for receiving said plurality of light emitting diodes. Each of the light emitting diodes is disposed in a corresponding one of the apertures and affixed in thermally conductive contact with said elongate thermally conductive member.
The elongate thermally conductive member includes a thermal transfer media disposed therein in a flow channel.
At least one clip for mounting the elongate thermally conductive member in a fixture may be included.
BRIEF DESCRIPTION OF THE DRAWING
The invention will be better understood from a reading of the following detailed description of a preferred embodiment of the invention taken in conjunction with the drawing figures, in which like reference indications identify like elements, and in which:
FIG. 1
is a planar side view of a light source in accordance with the principles of the invention;
FIG. 2
is a top planar view of the light source of
FIG. 1
;
FIG. 3
is a perspective view of the light source of
FIG. 1
with mounting clips;
FIG. 4
is a planar side view of the light source of
FIG. 3
showing mounting clips separated from the light source;
FIG. 5
is a top view of the light source and mounting clips of
FIG. 4
; and
FIG. 6
is a partial cross-section of the light source of FIG.
1
.
DETAILED DESCRIPTION
A light source in accordance with the principles of the invention may be used as a decorative lighting element or may be utilized as a general illumination device. As shown in
FIG. 1
, a light source
100
in accordance with the invention includes an elongate thermally conductive member or heat sink
101
. Elongate heat sink
101
is formed of a material that provides excellent thermal conductivity. Elongate heat sink
101
in the illustrative embodiment of the invention is a tubular aluminum extrusion. To improve the heat dissipative properties of light source
100
, elongate heat sink
101
is configured to provide convective heat dissipation and cooling. As more clearly seen in
FIG. 2
, tubular heat sink
101
is hollow and has an interior cavity
103
that includes one or more heat dissipating fins
105
. Fins
105
are shown as being triangular in shape, but may take on other shapes. Fins
105
are integrally formed on the interior of elongate heat sink
101
. In the illustrative embodiment convective cooling is provided by movement of a medium
102
through elongate heat sink
101
. The medium utilized in the illustrative embodiment is air, but may in some applications be a fluid other than air to provide for greater heat dissipation and cooling.
The exterior surface
107
of elongate heat sink
101
has a plurality of Light Emitting Diodes
109
disposed thereon. Each LED
109
in the illustrative embodiment comprises a white light emitting LED of a type that provides a high light output. Each LED
109
also generates significant amount of heat that must be dissipated to avoid thermal destruction of the LED. By combining a plurality of LEDs
109
on elongate heat sink
101
, a high light output light source that may be used for general lighting is provided.
Conductive paths
129
are provided to connect LEDs
109
to an electrical connector
111
. The conductive paths may be disposed on an electrically insulating layer
131
or layers disposed on exterior surface
107
. In the illustrative embodiment shown in the drawing figures, the conductive paths and insulating layer are provided by means of one or more flexible printed circuits
113
that are permanently disposed on surface
107
. As more easily seen in
FIG. 6
, printed circuit
113
includes an electrically insulating layer
131
that carries conductive paths
129
. As will be appreciated by those skilled in the art, other means of providing the electrically conductive paths on the
Flexible printed circuit
113
has LED's
109
mounted to it in a variety of orientations ranging from 360 degrees to 180 degrees and possibly others depending on the application. Electrical connector
111
is disposed at one end of printed circuit
113
. Connector
113
is coupleable to a separate power supply to receive electrical current. Flexible printed circuit
113
, in the illustrative embodiment is coated with a non-electrically conductive epoxy that may be infused with optically reflective materials. Flexible printed circuit
113
is adhered to the tube
101
with a heat conducting epoxy to aid in the transmission of the heat from LEDs
109
to tube
101
. Flexible printed circuit
113
has mounting holes
134
for receiving LEDs
109
such that the backs of LEDs
109
are in thermal contact with the tube surface
107
.
Tubular heat sink
101
in the illustrative embodiment is formed in the shape of a polygon and may have any number of sides. Although tubular heat sink
101
in the illustrative embodiment is extruded aluminum, tubular heat sink
101
may comprise other thermal conductive material. Fins
105
may vary in number and location depending on particular LED layouts and wattage. In some instances, fins may be added to the exterior surface of tubular heat sink
101
. In addition, apertures may be added to the tubular heat sink to enhance heat flow.
Light source
100
is mounted into a fixture and retained in position by mounting clips
121
,
123
as most clearly seen in
FIGS. 3
,
4
, and
5
. Each of the clips is shaped so as to engage and retain light source
100
. Each clip is affixed on one surface
122
,
124
to a light fixture.
Although light source
100
is shown as comprising an elongate tubular heat sink, other extruded elongate members may be used such as channels.
In the illustrative embodiment shown, convection cooling by flow of air through tubular heat sink
101
is utilized such that cool or unheated air enters tubular heat sink
101
at its lower end and exits from the upper end as heated air. In higher wattage light sources, rather than utilizing air as the cooling medium, other fluids may be utilized. In particular, convective heat pumping may be used to remove heat from the interior of the heat sink.
In one particularly advantageous embodiment of the invention, the light source of the invention is configured to replace compact fluorescent lighting in decorative applications.
As will be appreciated by those skilled in the art, the principles of the invention are not limited to the use of light emitting diodes that emit white light. Different colored light emitting diodes may be used to produce monochromatic light or to produce light that is the combination of different colors.
Although the invention has been described in terms of illustrative embodiments, it is not intended that the invention be limited to the illustrative embodiments shown and described. It will be apparent to those skilled in the art that various changes and modifications may be made to the embodiments shown and described without departing from the spirit or scope of the invention. It is intended that the invention be limited only by the claims appended hereto.
Claims
- 1. A light source comprising:an elongate thermally conductive member having an outer surface; at least one light emitting diodes carried on said elongate member outer surface; one or more electrical conductors carried by said elongate thermally conductive member and connected to said at least one light emitting diodes to supply electrical power thereto; and said elongate thermally conductive member being configured to conduct heat away from said at least one light emitting diode to fluid contained by said elongate thermally conductive member.
- 2. A light source comprising:an elongate thermally conductive member having an outer surface; a plurality of light emitting diodes carried on said elongate member outer surface at least some of said light emitting diodes being disposed in a first plane and others of said light emitting diodes being disposed in a second plane not coextensive with said first plane; electrical conductors carried by said elongate thermally conductive member and connected to said plurality of light emitting diodes to supply electrical power thereto; and said elongate thermally conductive member being configured to conduct heat away from said light emitting diodes to fluid contained by said elongate thermally conductive member.
- 3. A light source in accordance with claim 2, wherein:each of said light emitting diodes emits white light.
- 4. A light source in accordance with claim 2, wherein:said fluid comprises air.
- 5. A light source in accordance with claim 4, wherein:said elongate thermally conductive member comprises one or more heat dissipation protrusions.
- 6. A light source in accordance with claim 2, wherein:said elongate thermally conductive member comprises a tube.
- 7. A light source in accordance with claim 6, wherein:said tube has a cross-section in the shape of a polygon.
- 8. A light source in accordance with claim 6, wherein:said tube has a cross-section having flat portions.
- 9. A light source in accordance with claim 2, wherein:said elongate thermally conductive member comprises a channel.
- 10. A light source in accordance with claim 2, wherein:said elongate thermally conductive member comprises an extrusion.
- 11. A light source in accordance with claim 10, wherein:said extrusion is an aluminum extrusion.
- 12. A light source in accordance with claim 11, wherein:said elongate thermally conductive member is a tubular member.
- 13. A light source in accordance with claim 12, wherein:said tubular member has a polygon cross-section.
- 14. A light source in accordance with claim 12, wherein:said tubular member has a triangular cross-section.
- 15. A light source in accordance with claim 2, comprising:a flexible circuit carried on a surface of said elongate thermally conductive member, said flexible circuit comprising said electrical conductors.
- 16. A light source in accordance with claim 15, wherein:said flexible circuit comprises a plurality of apertures for receiving said plurality of light emitting diodes.
- 17. A light source in accordance with claim 16, wherein:each of said light emitting diodes is disposed in a corresponding one of said apertures and affixed in thermally conductive contact with said elongate thermally conductive member.
- 18. A light source in accordance with claim 2, wherein:a thermal transfer media disposed therein.
- 19. A light source in accordance with claim 18, wherein:said elongate thermally conductive member comprises a flow channel for said thermal transfer media.
- 20. A light source in accordance with claim 2, comprising:at least one clip for mounting said elongate thermally conductive member in a fixture.
- 21. A light source in accordance with claim 2, comprising:an electrically insulating layer disposed on said elongate thermally conductive member outer surface and carrying said electrical conductors thereon.
- 22. A light source in accordance with claim 21, wherein:said electrically insulating layer comprises a plurality of apertures, each aperture receiving one of said light emitting diodes; and each light emitting diode of said plurality of light emitting diodes being mounted in a corresponding one of said apertures and in thermally conductive contact with said elongate thermally conductive member.
- 23. A light source in accordance with claim 22, wherein:each of said light emitting diodes emits white light.
US Referenced Citations (6)