The Sawyer-Man Incandescent Lamps.
Reading edition
As before stated Edison fixed upon carbonized filament of bamboo. The Sawyer-Man company however applied for a patent on carbonized filament for incandescent lamps on January 19th 1880, and after five years litigation with Thos. A. Edison they were granted a patent No. 317,676, on May first, 1885, covering their invention. The Sawyer-Man lamp Fig. 25, consists of a carbonized connected to platinum wires fused in a glass tube from which all the air possible had been extracted. The light is produced by the glow of the filament and heat of gases given from filament. The life of a lamp is from 1000 to 1500 hrs. and requires a current of 1¼ to 1.3 amperes and give 20 to 25 C.P. When the filament becomes brittle and breaks the tube is unscrewed from the key Fig. 26, and a new one screwed in. They are run on the arc light circuit by the use of an individual distributor Fig. 27 which consists of a brass case containing a magnet in the circuit of the lamps and a resistance coil automatically substituted in case the lamp should break or is turned off by key Fig. 26. The scheme of arranging lamps so as to get the right current is shown at Fig. 28. the number of lamps in a group depending on the current.
Prof. Thomson has gotten out a lamp Fig. 29 in two styles one for 6.8 amperes current and one for 10 amperes current. Three lamps of different candle power, due to different potential differences at binding post of lamp, are use on the same current. The method of connecting them is shown in Fig. 30. It will be perceived that the lamps carry the full current yet have a life of 1000 hrs. or more. This is a great invention indeed doing away with a great loss of power due to high resistance coils. It will be noticed however that a 125 C.P. incandescent lamp uses as much energy as a 2000 C.P. arc light, the 65 C.P. lamp one half as much and the 32 C.P. lamp one fourth as much.