Oct 242013

LEDs provide consumers with many benefits and advantages, but there are still some drawbacks that need to be worked out. Inventors David Horn and Chris Vogdes have released a patent (no. 8558436) for one problem in particular that they hope to counter, which is the contamination that can occur in the thermally-conducive liquid in some LEDs.

Patent US8558436 detail

A liquid-cooled light emitting diode (LED) bulb which includes a base, a shell connected to the base forming an enclosed volume, and a plurality of LEDs attached to the base and disposed within the shell. The LED bulb also includes a volume of thermally-conductive liquid held within the enclosed volume. A scavenger element comprising a scavenger material is attached to the base and is exposed to the thermally-conductive liquid. The scavenger material is configured to capture contaminants in the thermally-conductive liquid.



By a News Reporter-Staff News Editor at Electronics Newsweekly — A patent by the inventors Horn, David (Saratoga, CA); Vogdes, Chris (Sunnyvale, CA), filed on September 13, 2011, was published online on October 15, 2013, according to news reporting originating from Alexandria, Virginia, by VerticalNews correspondents.

Patent number 8558436 is assigned to Switch Bulb Company, Inc. (San Jose, CA).

The following quote was obtained by the news editors from the background information supplied by the inventors: “The present disclosure relates generally to reducing contaminants in an optically translucent liquid, and more specifically to using a scavenger material to reduce contaminants in a liquid-filled light-emitting diode (LED) bulb.

“Traditionally, lighting has been generated using fluorescent and incandescent light bulbs. While both types of light bulbs have been reliably used, each suffers from certain drawbacks. For instance, incandescent bulbs tend to be inefficient, using only 2-3% of their power to produce light, while the remaining 97-98% of their power is lost as heat. Fluorescent bulbs, while more efficient than incandescent bulbs, do not produce the same warm light as that generated by incandescent bulbs. Additionally, there are health and environmental concerns regarding the mercury contained in fluorescent bulbs.

“Thus, an alternative light source is desired. One such alternative is a bulb utilizing an LED. An LED comprises a semiconductor junction that emits light due to an electrical current flowing through the junction. Compared to a traditional incandescent bulb, an LED bulb is capable of producing more light using the same amount of power. Additionally, the operational life of an LED bulb is orders of magnitude longer than that of an incandescent bulb, for example, 10,000-100,000 hours as opposed to 1,000-2,000 hours.

“While there are many advantages to using an LED bulb rather than an incandescent or fluorescent bulb, LEDs have a number of drawbacks that have prevented them from being as widely adopted as incandescent and fluorescent replacements. One drawback is that an LED, being a semiconductor, generally cannot be allowed to get hotter than approximately 120.degree. C. As an example, A-type LED bulbs have been limited to very low power (i.e., less than approximately 8 W), producing insufficient illumination for incandescent or fluorescent replacements.

“One approach to alleviating the heat problem of LED bulbs is to fill an LED bulb with a thermally-conductive liquid, to transfer heat from the LEDs to the bulb’s shell. The heat may then be transferred from the shell out into the air surrounding the bulb.

“However, in some circumstances, the thermally-conductive liquid may become contaminated with organics and/or other material. Contaminating organics may be the result of volatile organic compounds (VOCs) that have been emitted from bulb components and became trapped in the thermally-conductive liquid. Other contaminating materials may be soluble or insoluble depending on the temperature and concentration. For example, soluble contaminants may form due to prolonged exposure to certain elastomers, such as Viton. Insoluble or particulate contaminants may form when soluble contaminants cool and solidify in the thermally-conductive liquid. Particulate contaminants due to the presence of elastomers are also referred to herein as elastomer precipitate.

“Over time, organic and other contaminants may discolor optical materials in the LED bulb and degrade the quality of light produced by the LED bulb. The contaminants may also interfere with the operation of the LEDs and cause premature failure of the LED bulb. Thus, a method and system for reducing contaminants in a liquid-filled LED bulb is desired.”

In addition to the background information obtained for this patent, VerticalNews journalists also obtained the inventors’ summary information for this patent: “In one exemplary embodiment, a liquid-cooled LED bulb includes a base, a shell connected to the base forming an enclosed volume, and a plurality of LEDs attached to the base and disposed within the shell. The LED bulb also includes a thermally-conductive liquid held within the enclosed volume. A scavenger element is attached to the base and comprises a scavenger material that is configured to capture contaminants in the thermally-conductive liquid. The scavenger element is attached to the base in a location that exposes the scavenger material to the thermally-conductive. In some embodiments, the scavenger element is attached in a location that allows the thermally-conductive fluid to circulate through the scavenger material via passive convective flow.”

URL and more information on this patent, see: Horn, David; Vogdes, Chris. Scavengers for Reducing Contaminants in Liquid-Filled LED Bulbs. U.S. Patent Number 8558436, filed September 13, 2011, and published online on October 15, 2013. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=65&u=%2Fnetahtml%2FPTO%2Fsearch-bool.html&r=3211&f=G&l=50&co1=AND&d=PTXT&s1=20131015.PD.&OS=ISD/20131015&RS=ISD/20131015

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