Switch Lighting, a San Jose, California, company, was recently named as a 2012 Finalist for Best New Product for Energy and Sustainability by the Edison Awards for its Switch75 Light Emitting Diode (LED). 

The Switch75 is a liquid cooled LED designed to be used in any fixture, including those with dimmer switches, while providing warm white light.

The Switch75 is described in U.S. Patent Application Number 2012/0026723 entitled “Omni-Directional Channeling of Liquids for Passive Convection in LED Bulbs” (‘723 Application).

LEDs offer many advantages over incandescent and fluorescent bulbs, however, they also have some drawbacks.  One such drawback is that they cannot be allowed to get hotter than approximately 120 degrees Celsius.  LEDs are therefore limited to very low power, producing insufficient illumination for replacement of incandescent or fluorescent bulbs. 

The ‘723 Application describes a way to overcome this limitation by utilizing a thermally conductive fluid which passively circulates through the light bulb to transfer heat from the LEDs to the shell of the bulb, cooling the LED.

The ‘723 Application describes an LED bulb like the one depicted in Figure 1 of the application, reproduced below.   The bulb includes a base (112), a shell (101) encasing components of the bulb, and a plurality of LEDs (103) connected to LED mounts (107) made of any thermally conductive material. 

Figure 1

The bulb is filled with a thermally conductive liquid (111) for transferring heat generated by the LEDs (103) to the shell (101).  The liquid could be any thermally conductive material capable of flowing. 

Separating the LED mounts (107) are channels (109) which both increase the surface-to-area-to-volume ratio of the LED mounts, and facilitate efficient passive convective flow of the liquid (111).

Figure 2 of the ‘723 Application depicts the passive convective flow of the thermally conductive liquid (111) overlaid on a cross section view of the LED bulb shown in Figure 1.   Figure 2 depicts the bulb in an orientation where the base is located above the bulb.  This is but one of many orientations the bulb may assume. 

Figure 2

The arrows indicate the direction of flow of the liquid.  Once heated, the liquid rises and reaches the top portion of the shell (101) where heat is conductively transferred to the shell, cooling the liquid. 

As the liquid cools, its density increases, causing it to fall within the shell.  The heating/cooling process creates a convective cell.  This process is passive, meaning it requires no mechanical assistance.  The flow of the liquid is maintained merely by the heating and cooling of the liquid.

A cooled LED will allow the bulb to handle more power, illuminate brightly, and provide a lifespan much longer than an incandescent or fluorescent bulb. 

The Edison Awards winners will be announced at their Awards Gala in New York City on April 26, 2012.

David Gibbs is a contributor to Green Patent Blog.  David is currently in his third and final year at Thomas Jefferson School of Law in San Diego.  He received his undergraduate degree in Geology from the University of California, Berkeley.

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