Edison incandescent lamp filament patentIn 1899, Thomas A. Edison was issued a patent for his “Filament for Incandescent Lamps, and Process of Manufacturing Same” (U.S. No. 626,460). “I form a filament of highly-refractory non-conducting material which is preferably porous, and incorporate therein isolated particles of carbon, so as to produce spark gaps between the particles, whereby high-tension currents, either alternating, continuous, or intermittent, will be conducted from particle to particle of the carbon to raise the filament to incandescence. ... I prefer to use ... an oxid or oxids of the rare earths—such as the oxid of zirconium, thorium and others. ... I prefer to admix ... a carbonizable organic compound—such as a solution of sugar, asphalt or tartrate of the oxid itself” which will be carbonized.« |
