Thomas Edison of the Edison patent to charge a more reasonable rate for the use of the Edison patent rights and lowering the price of the electric lamp. On October 8, 1883, the US patent office ruled that Edison's patent was based on the work of William E. Sawyer and was, therefore, invalid. Litigation continued for nearly six years, until October 6, 1889, when a judge ruled that Edison's electric light improvement claim for "a filament of carbon of high resistance" was valid. To avoid a possible court battle with Joseph Swan, whose British patent had been awarded a year before Edison's,
William Greener William Greener William Greener (1806–1869) was an English inventor and gunmaker. He developed a self-expanding bullet in 1835, an electric lamp in 1846 (patent specification 11076 of that year) some 33 years before Thomas Edison's patent in 1879. William Greener also invented the percussion system for firing cannon, made improvements to the miner's safety lamp and won a prize for designing a mechanical device by which four gates at railway/road level crossings could be opened or closed simultaneously. He also invented a self-righting lifeboat, which was exhibited with a rocket gun and several of his famous percussion muzzle-loading shotguns and