 In 1917, Burnie Lee Benbow was granted a patent for the "coiled coil filament", in which a coiled filament is then itself wrapped into a coil by use of a mandrel.In 1921, Junichi Miura created the first double-coil bulb using a coiled coil tungsten filament while working for Hakunetsusha (a predecessor of Toshiba).At the time, machinery to mass-produce coiled coil filaments did not exist.