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U.S. Patent 2,883,571
Elmer Fridrich and Emmett Wiley's
Tungsten Halogen Lamp

Image of Elmer Fridrich and Emmitt Wiley's tungsten halogen lamps patent, 1958

This patent, granted on 21 April 1959, is for the tungsten halogen lamp. The lamp in figure 1 (at top) shows what has become the typical configuration for these lamps. Figure 2, however, shows a low-voltage configuration that is less familiar. The low-voltage design played a role in a little known project in the early 1970s. 

Around that time, lamp engineers at General Electric's Nela Park operation were looking for ways to more efficiently manufacture tungsten halogen lamps. Fridrich, one of the participating engineers in the project, became inspired to invent a new lamp he called "Gemini." His goal was to create a replacement for regular incandescent lamps.

Tungsten halogen lamps operate at higher pressures than regular lamps, and this creates a slight chance of an explosion. For this reason lamp makers have been very careful about tungsten halogen replacement lamps. (Today, these lamps often use thick, heavy glass envelopes that will not shatter in case of a problem.) 

Fridrich's Gemini lamp avoided the problem by mounting two of the low-voltage capsules in electrical series inside a regular bulb. Since the lamps operated at low voltage, their internal pressures were reduced, lessening the chance of an explosive failure. The Gemini lamp was, however, not produced. 

In 1996, Fridrich donated the original patent document to the National Museum of American History, along with other historical materials including a large collection of experimental lamps. A Gemini lamp mock-up, several experimental pieces, and some documents were part of the donation.

The image above has been enhanced electronically.


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