IMPROVEMENTS IN THE MANUFACTURE OF INCANDESCENT ELECTRIC LAMPS AND IN VACUUM PUMPS SUITABLE FOR BEING USED IN THEIR MANUFACTURE
Year: 1883

page_text: PROVISIONAL SPECIFICATION left by Sebastian Ziani de Ferranti at the
Office of the Commissioners of Patents on the 29th December 1883.
SEBASTIAN ZIANI DE FERRANTI of No 5 Stanwick Road, West Kensington in
the County of Middlesex Electrician "IMPROVEMENTS IN THE MANUFACTURE OF
INCANDESCENT ELECTRIC LAMPS AND IN VACUUM PUMPS SUITABLE FOR BEING USED
IN THEIR MANUFACTURE
"
This invention has for its object improvements in the manufacture of incandescent
electric lamps and in vacuum pumps suitable for being used in their manufacture.
For carrying the carbon filament of an incandescent electric lamp I employ a
glass stem it may be a small tube into each end of which a wire terminal is sealed.
Each wire passes up a distance into the end of the tube and is then led out sidewise
from it. The carbon filament is formed as an open spiral it is placed around the
glass stem and its ends are coupled to the two wires which stand out sidewise from
the stem. To couple the filament to the wires I form the end of each wire into a
coil of a diameter just large enough for the end of the filament to be passed into
it. I then heat the wire by passing through it au electric current and at the same
time I keep the wire surrounded by hydro-carbon vapour or liquid containing
carbon.
In this way carbon is deposited on to the wire and a very efficient connection is
formed between the wire and the filament. The glass stem carrying the filament
I subsequently introduce into a glass globe and seal the globe leaving the two ends
of the glass stem projecting out from its upper and lower ends—afterwards I form
a vacuum in the interior of the globe by a pump of the following construction.
The pump is composed of a plunger worked in and out of a pump barrel containing
mercury. From the pump barrel a pipe is carried upwards to a closed chamber.
At the top of the upper chamber is an outlet closed by a valve. Above the valve
is a small column of mercury with an overflow by which whenever a quantity of
mercury is made to rise up past the valve an equal quantity may flow away from
the top of the column.
Just below the upper chamber a branch pipe is led off from the pipe which
passes from this chamber to the pump barrel. The lamps to be exhausted are put
into communication with this branch pipe.

page_text: As the plunger of the pump is moved to and fro mercury is alternately forced
upwards from the pump barrel into the upper chamber and drawn back from this
chamber into the pump barrel. When mercury rises up into the chamber it
compresses the air therein and the air so compressed is allowed to escape by the
valve. In other pumps this valve is usually opened and closed by hand I cause it
to open by introducing into the chamber at each upward movement of the
mercury more mercury than the chamber will hold The excess rises up past the
valve.
On the downward movement of the plunger the mercury falls back from the
upper chamber leaving a vacuum in it and when the mercury has descended below
the branch pipe which carries the lamps to be exhausted there is free communication
between the interior of the lamps to be exhausted and the vacuum chamber. This
operation is repeated at each stroke of the plunger. To cause an excess of mercury
to rise up into the chamber at each stroke I employ a second smaller plunger
working in another pump barrel and moving to and fro with the other plunger.
At each upward stroke of the plungers mercury is drawn into the smaller pump
barrel from a tank and at each downward stroke of the plunger the mercury so
drawn in to this pump barrel is discharged past a valve into the larger pump
barrel.
The corresponding quantity of mercury which at each descent of the plungers
passes off from the top of the upper chamber may be allowed to flow back direct
into the tank from which the pump is supplied or may be allowed to pass to
another tank where it may be boiled to free it from air and then cooled by being
passed through a condenser before again using it to supply the pump.
When the requisite vacuum has been obtained in the lamp globes they are sealed
in the ordinary way and are then ready for use.
The upper and lower terminals of the lamps I connect to the positive and
negative conductors in the following manner:-One of the conductors is made
tubular the other is contained within and insulated from it. The glass stem
carrying the lower terminal of the lamp I drop into a deep cup of insulating
material at the bottom of which is a metallic surface coupled to the end of the
inner conductor so that the end of the lower terminal may rest on this metallic
surface.
To the extremity of the outer tubular conductor the ends of a wire loop are
jointed.
When the stem of the lamp has been dropped into the cup or socket above
mentioned the wire loop is turned upwards so that a small cup carried at its centre
may be sprung over the top of the upper terminal of the lamp and thereby put
this terminal into metallic connection with the outer tubular conductor at the same
time that it holds the lamp in place. To prevent the lamp from swaying about the
side arms of the wire loop may be caught by spring catches attached to any suitable
ornamental fitting carried by the end of the tubular conductor.