Elijah McCoy, Lewis Latimer and Granville Woods: African-American Inventors of the 19th Century – Part 2 – The Inventions – Lewis Latimer
Latimer’s excellent artistic flair and drafting abilities at Crosby, Halstead and Gould – a patent law firm – advanced him quickly and he found himself eventually working for Alexander Graham Bell. At Bell’s patent law firm, he was in charge of drafting the necessary drawings required to receive a patent for Bell’s telephone. After a time with Bell, he found employment at the U.S. Electric Lighting Company, where he patented in 1881 the “Process of Manufacturing Carbons”, an improved method for the production of carbon filaments for light bulbs. Latimer’s patent improved on the original designs of Thomas Edison, who’s light bulbs, because of the way the carbon fibers that emitted light were constructed, would often break after only a couple of days.
In discussing the improvements, Latimer stated in his patent application for the process –
“My invention relates more particularly to carbonizing the conductors for incandescent lamps, though it is equally applicable to the manufacture of delicate sheets or strips of dense and tough carbon designed for any purpose whatsoever….
“When heated the confining-plates expanded, while the blanks between them contract very considerably under the intense heat of the furnace, so that many of them are broken and distorted in consequence of their extremely-delicate structure and their tendency to shift their position between the plates. This I avoided by the method I propose…”
His method was to coat the carbon in graphite (to keep it from sticking) and then place it inside of a cardboard sleeve which would prevent the super-heated carbon from breaking during the carbonizing process. His method reduced the amount of broken carbons to almost zero, allowing for more useable carbons instead of the few that were being produced per batch at the time. His mass production process could be applied to many different uses, and because of this the Latimer carbons had a much longer life and made them less expensive.10
Next time, The Educational System in 19th Century America