1907

Shortly after the turn of the 20th Century, pressed or multiple tungsten filaments were first developed independently by a number of inventors (most notable those from Germany and Austria-Hungary).  These metallic looking filaments were also referred to as non-ductile tungsten filaments. General Electric in 1906 paid the inventors of this non-ductile tungsten lamp a sum total of $1.5 million dollars in order to secure the patent rights to this new filament and introduced them in this country the following year.  The preferred method of production was by mixing powdered tungsten with a sugar and gum solution, squirting the resulting paste through a diamond die, and then baking the resulting strands so that they became pure tungsten filaments.  But since tungsten is by nature a very brittle metal a room temperature, the filaments could only be produced in short, fragile segments that broke easily.  Hence the use of several shorter strands of filaments rather than a single long strand inside the lamp.  Lamps with these filaments would have several separate strands (i.e. several separate hairpin loops, hence the term “multiple”) connected in series and held up by a number of supports with hooks at both the top and bottom of the button rod.  Each single filament was welded to the lower supports with dark beads in order to connect to the next filament.  Only in this way could a lamp with these filaments give off a great deal of light.  This new lamp was thus called a “Multiple Tungsten Lamp” or even a “Tungsten Multiple Lamp.”  With their longer life (about 800 hours) and the increased brightness over the pure carbon lamps, they proved to be very popular with the public.  However, they were not without their faults.  The delicate filaments could not withstand rough handling and the lamps could only be mounted in an upright position.  Thus General Electric scientists were still searching for even a better filament for the electric lamp – one that was once deemed unattainable – a tough ductile tungsten filament that could be manufactured in longer segments and still remain unbroken.  The manufacturing of these non-ductile tungsten lamps was discontinued in 1919 (the same year tip-less bulbs came out).

NEXT PAGE in the Evolution of Filaments



 
close window