The Sprengel pump was the key tool which made it possible in 1879 to sufficiently exhaust the air from a light bulb so a carbon filament incandescent electric light bulb lasted long enough to be commercially practical.
2.
In addition he invented a very robust and continuously operable device called the Sprengel Pump which could reduce the amount of air in a chamber to one-millionth of its volume paving the way for the filament light bulb.
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