Pittsburg dispatch. [volume] (Pittsburg [Pa.]) 1880-1923, 1890-12-07
THE ELECTRIC LIGHT.
Details of the Construction of the
Incandescent Globes.
WHY TIE AIR MUST BE TAKEN OUT.
Interesting Process Of Attaching the Fila
ment to the Wires.
CARBoyIzISG THE SILK THREADS
WRITTEN FOR THE pIsPArca.1

WRITTEN FOR THE pIsPArcH1
There are two kinds of electric lamps, the
incandescent and the arc. The incandescent
are commonly used on the parallel system
of electric distribution and the arc on the
series system. These two systems of cleo
trio distribution have already been de-
scribed.
An incandescent lamp consists of a glass
globe, in size and shape very much like a
pear; and an electric conductor inside this
globe, of such construction and material
that when proper current OF electricity is
sent through the conductor, it will instantly
be brought to white heat and this pro-
duces light. This conductor is usually made
OF carbonIzed bamboo or carbonized silk.
The principal details in the manufacture
of this lamp are as follows: First the glass
globe is blown, leaving hole at the bottom
or smaller end of the globe large enough to
admit the illuminating conductor above
mentioned. This conductor is called the
filament. A small hole is also lett in the
top OF the globe and provided with glass
tube through which the air in the bulb is
eventually pumped out
PREPARING THE FILAMENT.
The bulb in this condition is ready to re-
ceive the filament. which, however, must
first be prepared in the following manner,
the preparation being very much the same,
whatever its material may be: A great
many short, silk threads are so wound or
adj usted on a block of carbon, that each
thread will have the shape or curve of
horse shoe-in fact, the very same shape
that can be seen in any incandescent lamp
in use. This carbon block with the silk
threads is then placed in a very hot furnace
and left there until the silk threads have
been burned into carbon.
When removed from the furnace they are
hard and brittle. In this condition they are
immersed in gasoline oil and while under
the oil they are brought to q red heat by
passing current OF electricity through
them. This operation causes a deposit of
carbon to be made from the oil into the fla
ments. When removed they are found to
be much less brittle than when they came
from the furnace. The next operation is to
attack short strip of platinum wire, about
an inch long, to each end of the horse
shoe shaped carbon filament.
ATTACHING THE PLATINUM.
The method of making this joint is very
interesting and is as follows: First the plat
| mum wire is twisted or clamped around the
end of the filament, then one pole OF an
| electric circuit is connected to one side of
| the joint and the other pole to the other side
of the joint. In this condition the joint is
| immersed in gasoline oil and sufficient cur
rent then turned on to bring the Joint up to
a red heat. This heat in the joint causes
carbon (soo) to be deposited there, thus
securing good electrical contact between the
carbon flament and platinum.
The ilament Is now ready to be inserted
/ 10 81 t1ha II
goes in first, and after it is in the bottom OF
the globe is heated and melted around the
two platinum ends and thus hermetically
sealed at that point. The two ends of the
platinum wires are lett protrudfng through
the glass bottom and to these are attached
two copper wires, which are eventually t.
be attached to the two poles OF an electric
circuit. SO that the current may flow
through the filament and bring it to white
heat for lighting purposes.
| EXHAUSTING THE GLOBE.
The only thing left to be done now is tc
pump the air out of the bulb and then the
lamp will be ready for use. To do this the
small glass tube on the top of the bulb il
connected to a mercury pump and the ali
thus exhausted as far as possible. Atte
this the glass tube is melted off and the built
sealed, leaving little point of glass on tn,
top. A suitable socket Is then provided ani
a switch attached for turning the current of
and on, and now the lamp is ready for use
The reason for using platinum wire tc
conduct the current through the glass bot
tom to the carbon flament is this: The
glass will OF course expand and contract &C.
cording to the temperature to which it is ex.
posed and the wire leading through the
glass will do the same, but ii the glass and