World's First Double-coil Bulb

The invention of light bulbs filled with inert gases such as nitrogen or argon by Dr.Langmuir of General Electric (GE) lengthened the lifetime of a tungsten filament bulb.

He discovered there is always a sheath of stationary gas around the surface of tungsten wiring.
It was also found that a bigger wire gauge reduces the loss of the gas.
Those discoveries led to the idea of tightly coiling tungsten wiring which thickens its diameter.
In 1921, Junichi Miura, an engineer of Tokyo Electric Company, coiled a standard single-coiled filament and made the worlds first prototype double-coiled filament bulb.