[No Photo Available]
This single coiled tungsten filament tipped light bulb was manufactured from 1911 to 1919 as a tipped bulb. By coiling a very long tungsten filament, the coiling method gives the filament the advantage of increased length (in order to increase the wattage) but not taking up more space. Its development was the next step resulting from Dr. William D. Coolidge’s [see A50]
hard work in creating a bright, glowing ductile tungsten filament. It looks more modern and was one of the last phases in the evolution of today’s modern, economical and popular incandescent household light bulb.
A few years after Dr. William D. Coolidge’s work on the ductile-tungsten filament, in 1913, another famous Schenectady General Electric scientist by the name of Dr. Irving Langmuir
(1881 – 1957) [see A51]
took the ductile-tungsten filament lamp one step further and developed the nitrogen and argon gas-filled tungsten filament lamp in order to reduce blackening of the bulb due to the evaporation of the tungsten filament. Previously light bulbs with carbon or tungsten filaments lamps were made with a vacuum (gas-free) bulb. But the presence of a pure or near pure vacuum in a glowing light bulb allowed a carbon or tungsten filament to give off or evaporate bits of the filament (otherwise called “soot”). These particles of the filament would settle onto the interior surface of the bulb thereby darkening the bulb and reducing its light output as well as its useful life span. The introduction of an argon/nitrogen gas at a pressure of slightly less than 1 atmosphere greatly inhibited this evaporation, thereby prolonging the useful life of the bulb. (See A13
for an example of a light bulb whose interior surface had been darkened by the deposition of soot from the filament.) The ductile tungsten filament lamps shown above were manufactured from 1911 to about 1919 (as tipped bulbs).
NEXT PAGE in the Evolution of Incandescent Light Bulbs