Omaha daily bee., 1902-10-04
-ncandescent Lamps.

The manufacture Of an incandescent
electric lamp, says the Electrical World, is
of special interest because many of the
operations have hitherto bean regarded as
trade secrets and carefully kept from the
public.
The delicate hlaments which produce the
light, are formed by squirting a paste
made from cellulose wood pulp) through
dies, from which 1t energies in the form Of
fine threads, which when dried, are tough
and flexible. These threads before they
are dry are formed into the 7desired shape.
They are then packed in carbon dust and
subjected to intense heat for many hours.
The cellulose is completely cAarred, and
the flament now practically consists OF
charcoal. 1t is then suspended In an at
mosphere Of hydro-carbon vapor, in a ves-
sci in which a partial vacuum has been
made and a current Of electricity sufficient
to bring it to incandescence is sent through
It. This ~decomposes the hydro-carbon, and
q carbon SCOT somewhat resembling graph
lite is deposited on a hlament. This is
technically known as flashing" After this
treatment the flament has a metallic luster
resembling polished steel.
The glass bulbs are blown in molds to
secure absolute uniformity, and as they
SOAhS thO bidob nOuoc lHtg are per-
fectly smooth at the rounded end, and
have a long open neck. To the rounded
end is fused a short length Of glass tubing
opening into the interior of the bulb. This
is subsequently used for connecting the
bulb to the exhaust pump. '' ~
For making the connection through the
glass between the carbon hlament and the
wire-bringlng current the most satisfac-
tory material is platinum, because It ad-
heres very firmly to the fused glass and be-
cause II expands and contracts at the same
rate. n-this were not the case when II
got hot through the passage OF the cur
rent 1t would either expand more or less
than the surrounding glass, and either
break 1t or make a space through which air
would leak. So through the little glass stop-
per which will eventually project down into
the neck Of the bulb are fused two platinum
wires. This stopper. which has a hange at
one end, is now called the mount or stem.
Next the hlament is fastened to the ends
OF the platinum wire which projects from
the stem. This is accomplished by means
OF a special cement which will stand a red
heat. Over this paste is deposited a layer
OF carbon. The paste is then dried in an
oven, and the stem, with its attached hla-
ment, is fastened into the bulb by fusinR
the hange on its upper end about the neck
OF the bulb.
After this Joint is carefully tested to be
sure there are no leaks, the exhaustion of
the air is accomplished by means Of a me-
chanical air pump, the last traces Of gas or
air being removed from the bulb by chem
ical means. When the vacuum Is sum
GENTLY high the tube through which the
air has been exhausted is sealed of by
means Of a small lamp. leaving the small
round tip seen on the spherical end of the
finished lamp.
The lamp is now practically completed
and is sent to the testing department. Here
1t is subjected to a series OF severe tests
before 1t is considered ready for the mar
ket. II 1t passes these successfully the base
1.-THE portion by means Of which IL is
screwed into the bracket) is cemented on
and the completed lamp goes to the ship
ping department.