NEW LAMP FILAMENTS

Hawke's Bay Herald-Tribune, Issue 201, 10 September 1937, Page 7

NEW LAMP FILAMENTS

IjQcreasing Light Output Increasing the light output by 10 per cent, without additional electricity, new high-efficiency tungsten lamp filaments soon will be saviug the public millions of dollars each year, states Popular Mcehanics." First drawn into a straight wire 19/10000 of an inch iu diainetcr, so fine it is almost invisible, the tungsten then is wound, 335 tijrns to the iueh, around a thin molybdenura wire or mandrel, leaving the coils 1/1000 of an inch apart. The coils must be kept close to-geth-er to reduce . heat loss, but must not touch because a short circuit would cause. immediato lamp failure. Then the coiled wire is coiled on another mandrel, seventy turns to the inch, with a spacing of 7/1000 of an inch between the secondary coils. This process reducee the twenty-inch wire to a length of fiw«ights of an inch. Following the second •eiling the mandrel is dissolved out by means of chemicali. Use of certain gases within the bulb introduces prcssiire which rcduces fila« mcnt evaporation, with its accompanyiug evil of bulb blackening, and allows the lamp to operate at a higher tempe ra ture for the same life. Presence of gas, however, is conducive to cooJing of the filament, xedueing the temperature and also the light output. This problem has been solved by reducin§ the length of the filament, thus low*v« ing the heat lass aud permitting the lamp to give 10 per cent more light for the same amount of current. Gas employed in the new lamps is a ifiaxture of nitrogen and argon.