Heat sinking and flexible circuit board, for solid state light fixture utilizing an optical cavity

• US 8,172,424 B2
• Filed: 10/30/2009
• Issued: 05/08/2012
• Est. Priority Date: 05/01/2009
• Status: Active Grant

• Current Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Original Assignee: ABL IP Holding LLC (Acuity Brands, Inc.)
• Inventors: Hanley, Roger T., Lyons, Steven S., Ramer, David P., Sanders, Chad N., Phipps, Michael, Becker, Robert M.
• Primary Examiner(s): BRUCE, DAVID VERNON
• Application Number:
  US12/609,523
• Publication Number:
  US 20100277907A1
• Time in Patent Office: 921 Days
• Field of Search: 362/235, 362/244, 362/245, 362/249.02, 362/294, 362/296.01, 362/311.02
• US Class Current: 362/245
• CPC Class Codes: F21K 9/62 using mixing chambers, e.g. housings with reflective walls
• CPC Class Codes: F21K 9/64 using wavelength conversion means distinct or spaced from the light-generating element, e.g. a remote phosphor layer
• CPC Class Codes: F21S 41/323 the reflector having two perpendicular cross sections having regular geometrical curves of a distinct nature
• CPC Class Codes: F21S 45/47 Passive cooling, e.g. using fins, thermal conductive elements or openings
• CPC Class Codes: F21V 11/16 using sheets without apertures, e.g. fixed
• CPC Class Codes: F21V 13/04 the elements being reflectors and refractors for vehicle rear lights F21S43/40
• CPC Class Codes: F21V 29/74 with fins or blades
• CPC Class Codes: F21Y 2113/13 comprising an assembly of point-like light sources
• CPC Class Codes: F21Y 2115/10 Light-emitting diodes [LED]
• CPC Class Codes: H05K 1/0206 by printed thermal vias
• CPC Class Codes: H05K 1/189 characterised by the use of a flexible or folded printed circuit H05K3/326 takes precedence
• CPC Class Codes: H05K 2201/09081 Tongue or tail integrated in planar structure, e.g. obtained by cutting from the planar structure
• CPC Class Codes: H05K 2201/10106 Light emitting diode [LED]
• CPC Class Codes: H05K 2201/2009 Reinforced areas, e.g. for a specific part of a flexible printed circuit
• CPC Class Codes: H05K 3/0061 onto a metallic substrate, e.g. a heat sink heat sinks for electric apparatus H05K7/20

Abstract

Disclosed exemplary solid state light fixtures use optical cavities to combine or integrate light from LEDs or the like. In such a fixture, the cavity is formed by a light transmissive structure having a volume, and a diffuse reflector that covers a contoured portion of the structure. A circuit board has flexible tabs mounting the light emitters. A heat sink member supports the circuit board and is contoured relative to the shape of the light transmissive structure so that the tabs bend and the emitters press against a sufficiently rigid periphery of the light transmissive structure. TIM may be compressed between the heat sink member and the opposite surface of each tab. Various contours/angles of the periphery of the light transmissive structure and the mating portion of the heat sink member may be used.

Claims

1. A light fixture for providing general lighting in a region or area intended to be occupied by a person, the fixture comprising:

a light transmissive structure forming a volume, the structure having a contoured outer surface, an optical aperture surface and a peripheral optical coupling surface between the contoured outer surface and the optical aperture surface, the peripheral optical coupling surface forming an obtuse angle with respect to the optical aperture surface;

a reflector having a diffusely reflective interior surface extending over at least a substantial portion of the contoured outer surface of the light transmissive structure to form an optical cavity including the volume of the light transmissive structure, a portion of the aperture surface of the light transmissive structure forming an optical aperture of the cavity;

a heat sink member having an inner peripheral portion of a size somewhat larger than the outer peripheral portion of the light transmissive structure and having an inner surface at an angle at least substantially corresponding to the angle formed by the peripheral optical coupling surface of the light transmissive structure;

a flexible circuit board, the flexible circuit board comprising;

(a) a mounting section mounted on the heat sink member, and

(b) at least one flexible tab attached to and extending from the mounting section of the flexible circuit board, each flexible tab being bent around the heat sink member and positioned between the angled inner surface of the inner peripheral portion of the heat sink member and the angled peripheral optical coupling surface of the light transmissive structure; and

one or more solid state light emitters, for producing light intensity sufficient for a general lighting application of the fixture, at least one solid state light emitter being mounted on a respective tab of the flexible circuit board and positioned by the respective tab between the respective tab and the angled peripheral optical coupling surface of the outer peripheral portion of the light transmissive structure,

wherein the respective tab holds said at least one solid state light emitter against the peripheral optical coupling surface of the light transmissive structure for emission of light through the peripheral optical coupling surface into the volume formed by the light transmissive structure.

2. The light fixture of claim 1, wherein at least a substantial portion of the contoured outer surface of the light transmissive structure has a roughened or etched texture.

3. The light fixture of claim 2, wherein at least any portion of the angled peripheral optical coupling surface of the light transmissive structure receiving light from the one or more solid state light emitters is highly transparent.

4. The light fixture of claim 1, wherein at least a substantial portion of the optical aperture surface of the light transmissive structure has a roughened or etched texture.

5. The light fixture of claim 4, wherein at least any portion of the angled peripheral optical coupling surface of the light transmissive structure receiving light from the one or more solid state light emitters is highly transparent.

6. The light fixture of claim 5, wherein at least a substantial portion of the contoured outer surface of the light transmissive structure has a roughened or etched texture.

7. The light fixture of claim 1, further comprising:

thermal interface material (TIM) positioned between the respective tab and the angled inner surface of the inner peripheral portion of the heat sink member, for providing electrical insulation between the respective tab and the heat sink member and for providing thermal conductivity to the heat sink member;

wherein pressure created by contact of the at least one solid state light emitter with the outer peripheral optical coupling surface of the light transmissive structure compresses the TIM against the heat sink member.

8. The light fixture of claim 7, further comprising:

one or more vias formed through the respective tab, from a first surface of the respective tab supporting the at least one solid state light emitter to an opposite second surface of the respective tab; and

heat conductive material extending through each via, to conduct heat from each solid state light emitter on the respective tab.

9. The light fixture of claim 8, further comprising:

heat conductive material forming a first pad on the first surface of the respective tab, in contact with each light emitter on the respective tab; and

heat conductive material forming a second pad on the second surface of the respective tab and in contact with the angled inner surface of the inner peripheral portion of the heat sink member,

wherein the heat conductive material extending through each via through the respective tab conducts heat from each solid state light emitter on the respective tab from the first pad on the respective tab to the second pad on the respective tab for transfer to the heat sink member.

10. The light fixture of claim 1, wherein each solid state light emitter comprises a light emitting diode (LED).

11. The light fixture of claim 10, wherein each LED is a white LED.

12. The light fixture of claim 1, wherein the light transmissive structure comprises a light transmissive solid, at least substantially filling the volume of the light transmissive structure.

13. The light fixture of claim 12, wherein:

the light transmissive solid comprises two light transmissive sections joined together with a gap therebetween; and

the light fixture further comprises a phosphor contained in the gap between the two sections of the light transmissive solid.

14. The light fixture of claim 13, wherein at least one of the light transmissive sections is located at the optical aperture surface of the light transmissive structure.

15. The light fixture of claim 1, wherein the light transmissive structure comprises a container filled with a liquid.

16. The light fixture of claim 15, wherein the liquid contains a phosphor.

17. The light fixture of claim 1, wherein diffuse reflections of light within the volume of the light transmissive structure optically integrate light from the one or more solid state light emitters, for emission of optically integrated light through an optical aperture of the fixture at the aperture surface of the light transmissive structure.

18. The light fixture of claim 17, wherein the respective tab holds said at least one solid state light emitter against the peripheral optical coupling surface of the light transmissive structure for emission of light through the peripheral optical coupling surface in such an orientation that the aperture surface of the light transmissive structure reflects a portion of direct emissions from each of the solid state light emitters back into the optical cavity by total internal reflection, for subsequent diffuse reflection off of the reflector for optical integration within the cavity before emission through the optical aperture.

19. The light fixture of claim 18, further comprising:

a mask having a reflective surface facing inward with respect to the volume, covering a portion of the aperture surface of the light transmissive structure in proximity to the solid state light emitters,

wherein the optical aperture is formed by a portion of the aperture surface not covered by the mask.

20. The light fixture of claim 18, wherein the respective tab holds said at least one solid state light emitter against the peripheral optical coupling surface of the light transmissive structure for emission of light through the peripheral optical coupling surface in such an orientation that the central axis of emission of each light emitter is substantially at an acute angle relative to the axis of the aperture surface of the light transmissive structure and inclined somewhat away from the aperture surface of the light transmissive structure.

21. The light fixture of claim 20, wherein:

the obtuse angle of the peripheral optical coupling surface with respect to the optical aperture surface of light transmissive structure is approximately 120°

; and

the acute angle of the central axis of emission of each light emitter relative to the axis of the aperture surface of the light transmissive structure approximately 60°

.

22. The light fixture of claim 21, wherein:

the volume of the light transmissive structure has a shape corresponding to a substantial section of a sphere;

the outer peripheral portion of the structure along the contoured surface of the light transmissive structure is circular about said axis;

an inner peripheral portion of the mounting section of the flexible circuit board is circular; and

the inner peripheral portion of the heat sink member is circular.

23. The light fixture of claim 1, further comprising an optical grease, glue or gel between the peripheral optical coupling surface of the light transmissive structure and at least one solid state light emitter for providing refractive index matching relative to a material of the light transmissive structure forming at least the angled peripheral optical coupling surface.

24. The light fixture of claim 1 in combination with circuitry for driving the solid state light emitters to generate light.

25. The light fixture of claim 24, wherein the flexible circuit board includes a strip extending away from the mounting section of the flexible circuit board providing electrical connections to the circuitry.

26. A solid state lighting system for providing general lighting in a region or area intended to be occupied by a person, comprising a light fixture and drive circuitry,

the fixture comprising:

a light transmissive structure forming a volume, the structure having a contoured outer surface and an optical aperture surface;

a reflector having a diffusely reflective interior surface extending over at least a substantial portion of the contoured outer surface of the light transmissive structure to form an optical cavity including the volume of the light transmissive structure, a portion of the aperture surface of the light transmissive structure forming an optical aperture of the cavity;

a heat sink member having an inner peripheral portion of a size somewhat larger than an outer peripheral portion of the light transmissive structure and having an inner surface at least substantially conforming in shape to the outer peripheral portion of the light transmissive structure;

a flexible circuit board, the flexible circuit board comprising;

(a) a mounting section mounted on the heat sink member,

(b) a strip extending from the mounting section of the flexible circuit board providing electrical connections to the drive circuitry, and

(c) at least one flexible tab attached to and extending from the mounting section of the flexible circuit board, each flexible tab being bent around the heat sink member and positioned between the inner surface of the inner peripheral portion of the heat sink member and the outer peripheral portion of the light transmissive structure; and

one or more solid state light emitters, for producing light intensity sufficient for a general lighting application of the fixture, at least one solid state light emitter being mounted on a respective tab of the flexible circuit board and positioned by the respective tab between respective tab and the outer peripheral portion of the light transmissive structure,

wherein the respective tab holds said at least one solid state light emitter against the outer peripheral portion of the light transmissive structure for emission of light into the volume formed by the light transmissive structure.