CN103975189A - Side-emitting guidepipe technology on led lamp to make filament effect - Google Patents

Abstract

A lamp (10) includes at least two light emitting diodes (12, 40) in heat communication with a heat sink. A translucent housing (14) receiving light emitted from the light emitting diodes (12, 40) is also provided. A light guide (16) is positioned to receive light emitted from at least one (12) of the light emitting diodes. The light guide (16) includes a first leg extending away from the heat sink towards the interior of the housing (14) and a light emitting second leg angled relative to the first leg. The second leg can be at least substantially perpendicular to the longitudinal axis of the lamp (10).

Description

Side-emitting tube technology for creating filament effect on LED lights

Background technique

Solid state lighting technology, including light emitting diodes (LEDs), has long been seen as a way to produce lamps with greater energy efficiency than conventional incandescent lamps and less adverse environmental impact than conventional compact fluorescent lamps. Accordingly, many so-called retrofit lamps using solid state lighting technology have been introduced.

However, a significant disadvantage of these solid state retrofit lamps from the customer's point of view is that they do not have the appearance of conventional incandescent lamps. Furthermore, LEDs primarily provide point source light distribution. To provide the general appearance of a traditional incandescent bulb, a coating can be provided on the lamp envelope to create a lambertian light distribution. However, the traditional incandescent look of filament-generated light is not created. This is especially the case for retrofits intended to replace conventional candelabra-style incandescent lamps.

Contents of the invention

According to a first embodiment, a lamp is provided. The lamp includes at least two light emitting diodes in heat communication with a heat sink. A translucent housing that receives light emitted from the light emitting diode is also provided. A light guide is positioned to receive light emitted from at least one of the light emitting diodes. The light guide includes a first leg extending away from the heat sink toward the interior of the housing and a light emitting second leg that is angled relative to the first leg. The second leg can be at least substantially perpendicular to the longitudinal axis of the lamp.

According to a second embodiment, there is provided a lamp comprising a transparent envelope at least substantially surrounding a light guide. The light guide includes a first leg with a first end in light receiving relationship with the light emitting diode. The light guide includes a second leg angled relative to the first leg and oriented at least substantially perpendicular to the longitudinal axis of the lamp. The second strut also includes an element for emitting light therethrough.

Description of drawings

Figure 1 is a partial side view in section of a typical lamp embodiment; and

FIG. 2 is a partial top view in section of the lamp of FIG. 1 .

Detailed ways

Referring now to FIGS. 1 and 2 , a light assembly 10 includes a first pair of light emitting diodes (LEDs) 12 disposed within a housing 14 . Housing 14 may be formed from a dielectric material such as polymer or glass. It is contemplated that housing 14 could be transparent or translucent. Optional clear form when traditional candelabra style light is expected. Select Translucent when including a light-diffusing coating on the housing to create a more Lambertian style of light distribution. LED f12 emits light into light guide 16 .

The light guide can be a columnar structure through which light is guided or transmitted by total internal reflection. Total internal reflection prevents light from passing from the inside of the light guide to the outside of the light guide. Total internal reflection occurs when light strikes the interface between the light guide and the atmosphere surrounding the light guide at an angle greater than the critical angle. The critical angle is a function of the refractive indices of the medium of the light guide and the medium of the surrounding atmosphere. Light guide 16 can be formed from a light transmissive material such as glass, polycarbonate, acrylic, or other suitable plastic.

In one embodiment, the light guide includes an attachment end 18 having an end wall defining a cavity 19 surrounding the LED 12 to capture substantially all of the light generated by the LED. Attachment end 18 is a snug fit with printed circuit board 20 on which LED 12 is mounted. The printed circuit board provides electrical connections to the LEDs and can be a metal core printed circuit board (MCPCB) to provide heat dissipation. In this regard, heat dissipation can include only the MCPCB or other typical heat dissipation devices, such as heat dissipating fins in heat transfer with the MCPCB.

Transparent epoxy 21 can fill cavity 19 and secure light attachment end 18 of light guide 16 to LED 12 and circuit board 20 and orient light guide 16 to receive light emitted by light emitting diode 12 . Light travels through the light guide 16 from the attachment end 18 to the remote end 24 via total internal reflection. The light guide 16 can be an integral injection molded part. In order to generate visible light from the light guide, it is possible to associate a phosphor or other wavelength converting material with the LED 12 . Alternatively, associating a wavelength converting material with light pipe 16 is optional. The light pipe emitting light is expected to have a color temperature CCT in the range of approximately 2700K to 10000K.

The distal end 24 of the light guide 16 can include internal or external reflective strips or other surface elements that reflect light impinging on the surface elements. At least a portion of the reflected light reaches the interface between the outer surface of the light guide and the surrounding atmosphere at an angle less than the critical angle of the light guide-atmosphere interface, thereby allowing light to escape from the light guide as emitted light.

A strip or pattern 26 of individual reflective surface elements 28 can be provided on the distal end 24 of the light guide 16 . The surface elements 28 can be separated from each other. Surface elements 28 may be printed or otherwise affixed to outer surface 30 of light guide 16 . Alternatively, the surface elements 28 may be formed on the inside of the light guide 16 .

In one embodiment, the surface elements 28 reflect light impinging on the surface elements 28 . For example, at least a portion of the light transmitted through light guide 16 reaches surface element 28 and is reflected or scattered by surface element 28 . At least a portion reflected by the surface elements may exit light guide 16 as emitted light 32 . Emitted light 32 may emerge from light guide 16 in a direction transverse to lamp longitudinal axis 34 . Of course, emitted light 32 may emerge from light guide 16 in a variety of directions.

The pattern 26 of surface elements 28 may be arranged along the length of the light guide distal end 24 in one or more of shape and distribution to provide a desired distribution of light 32 emitted from the light guide 16 . The emitted light 32 can have a distribution defined by the length and the angle of projection. Length represents the distance along the distal end of light guide 16 that light 32 emanates from light guide 16 in a direction parallel to transverse axis 38 and transverse to the longitudinal axis. The projection angle is the radial distance that light extends over the surface of the light guide 16 . In a typical embodiment, the distribution angle extends from about 30° to about 330° (with 0° facing the printed circuit board) to provide the light pattern typically associated with an incandescent filament.

Alternatively, surface elements 28 may comprise light transmissive elements having a different refractive index than that of light guide 16 , as opposed to shaped elements. The interface between surface element 28 and light guide 16 can change the critical angle required for total internal reflection. For example, surface element 28 may have an index of refraction that increases the critical angle at the interface between light guide 16 and surface element 28 . Increasing the critical angle reduces the amount of light reflected internally in the light guide 16 and increases the amount of light emitted from the light guide 16 . Light reflected by surface elements 28 may exit light guide 16 through surface elements 28 . For example, the emitted refracted light may exit the light guide 16 on the same side of the light guide 16 proximate to the light guide 16 on which the surface elements 28 are disposed.

By controlling the size and/or density of surface elements 28 or patterns 26 , the amount of emitted light 32 can be controlled along longitudinal axis 38 . For example, light 32 may be emitted from light guide 16 such that there is no perceivable gradient in the intensity of emitted light 32 , or it may be designed to act as an increase in intensity in transverse axis 38 as longitudinal axis 34 is approached.

The lamp assembly 10 also includes a pair of auxiliary LEDs 40 disposed on the printed circuit board 20 . LED 40 emits light, which radiates directly onto housing 14 . In one embodiment, LED 40 is capable of emitting a first radiation to excite phosphorescent material 42 (or other light conversion material) associated with housing 14 for conversion into a desired visible spectrum (eg, white light). Alternatively, the phosphorescent material can be directly associated with the LED 40, eg coated directly thereon. As another option, multiple colored LED devices should be utilized where the radiated light from each is mixed to obtain the desired spectral output (eg R-G-B mixing to produce white light). Of course, the lamp is not limited to any particular number of auxiliary LEDs or light guide illumination LEDs. An electronic package (not shown) can be disposed in the connector mount 44 .

Exemplary embodiments have been described with reference to preferred embodiments. Obviously, modifications and alterations will occur to those skilled in the art upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiments be understood to embrace all such modifications and alterations provided they come within the scope of the appended claims or their equivalents.

Claims (19)

CLAIMS 1. A lamp comprising at least two light emitting diodes in thermal communication with a heat sink, a translucent housing positioned to receive light emitted from said light emitting diodes, positioned to receive light emitted from said at least two light emitting diodes at least one light guide for emitted light, the light guide comprising a first leg extending from adjacent the heat sink toward the interior of the housing and a second leg angled relative to the first leg, the second leg At least substantially perpendicular to the longitudinal axis of the lamp, the second strut emits light from the light guide. 2. The lamp of claim 1, wherein said first leg is at least substantially above parallel to said longitudinal axis of said lamp. 3. The lamp of claim 1, wherein said light guide further comprises a third leg extending toward said interior of said housing from adjacent said heat sink, said third leg intersecting said second leg . 4. The lamp of claim 3, wherein the third leg intersects the second leg at an end opposite to the end intersecting the first leg. 5. The lamp of claim 1, further comprising a light emitting diode emitting light into the third leg. 6. The lamp of claim 3, wherein the first and third legs have at least substantially total internal reflection. 7. The lamp of claim 1, wherein at least one light emitting diode emits at least a substantial portion of its qualified light directly onto said envelope. 8. The lamp of claim 7, further comprising a wavelength converting material associated with said envelope that is energized by light emitted by said at least one light emitting diode and that emits light in a different spectrum. 9. The lamp of claim 7, further comprising a wavelength converting material associated with the at least one light emitting diode. 10. The lamp of claim 1, wherein the heat sink comprises MCPCB. 11. The lamp of claim 1, wherein a wavelength converting material is disposed between the light emitting diode and the light guide. 12. The lamp of claim 1, wherein the light guide comprises a wavelength converting material. 13. A lamp comprising a translucent housing at least substantially surrounding a light guide, said light guide comprising a first leg comprising a first end in light receiving relationship with at least one light emitting diode, said The light guide includes a second leg angled relative to the first leg and oriented at least generally perpendicular to the longitudinal axis of the lamp, the second leg including elements that cause light to exit the light guide. 14. The lamp of claim 13, wherein the envelope is transparent. 15. The lamp of claim 14, wherein the first leg of the light guide includes a cavity that receives the light emitting diode. 16. The lamp of claim 13, wherein the light guide includes a third leg intersecting the second leg, the third leg being in light receiving relationship with a further light emitting diode. 17. The lamp of claim 16, wherein the light guide is generally u-shaped. 18. The lamp of claim 13, wherein the element comprises a reflector. 19. The lamp of claim 13, wherein the second leg is at least generally cylindrical, and light exits between about 30° and 330° around the second leg, wherein the second leg A 0° orientation is favorable for the LED.