Osram 105v, 20w lamp, c1920
A wonderful 'squirrel-cage' Osram 105v, 20w lamp dating from c1920. This lamp was manufactured in the days before the invention of the coiled filament.
The long, fine, straight-drawn filament, no thicker than a human hair had to be incorporated into these small lamps. The so called 'squirrel-cage' arrangement was the way manufacturers got around the problem. However, once the coiled tungsten filament was invented, this type of filament arrangement became obsolete.
The pip-top on the crest of the lamp, is the remnant of the vacuum tube, where air was drawn out of the lamp by a vacuum pump during manufacture, prior to sealing off the tube, leaving the sharp pip. Pip-top laps had largely been phased out by the early 1930s in preference to more advanced manufacturing processes and advancements in gas-filled lamps.
Due to their delicate nature it's hard to find a working squirrel cage lamp of this vintage. Using a Variac (auto-transformer), I've only dared put a limited current through it, just enough to illuminate the delicate filament. The lamp is a recent find, and is still dust covered from years of storage.
Osram 105v, 20w lamp, c1920
A wonderful 'squirrel-cage' Osram 105v, 20w lamp dating from c1920. This lamp was manufactured in the days before the invention of the coiled filament.
The long, fine, straight-drawn filament, no thicker than a human hair had to be incorporated into these small lamps. The so called 'squirrel-cage' arrangement was the way manufacturers got around the problem. However, once the coiled tungsten filament was invented, this type of filament arrangement became obsolete.
The pip-top on the crest of the lamp, is the remnant of the vacuum tube, where air was drawn out of the lamp by a vacuum pump during manufacture, prior to sealing off the tube, leaving the sharp pip. Pip-top laps had largely been phased out by the early 1930s in preference to more advanced manufacturing processes and advancements in gas-filled lamps.
Due to their delicate nature it's hard to find a working squirrel cage lamp of this vintage. Using a Variac (auto-transformer), I've only dared put a limited current through it, just enough to illuminate the delicate filament. The lamp is a recent find, and is still dust covered from years of storage.