Improvements in the Manufacture of Carbon for Electric Lighting and other Electrical Purposes.
Year: 1893

page_text: Date of Application, 14th Dec., 1893
Complete Specification Left, 14th Sept., 1894-Accepted, 20th Oct., 1894
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Carbon for Electric Lighting
and other Electrical Purposes.
°
I, REGINA NIEWERTH, of Spener Strasse, Berlin, Prussia, no occupation, do
hereby declare the nature of this invention to be as follows:-
This invention relates to a manufacture of carbon particularly suitable for
arc lighting in which resistance to the passage of the current is greatly reduced.
Such carbons have heretofore been manufactured as follows:-
Carbon in a state of fine division (soot, ground coke, or graphite, or other
material) is mixed with a suitable adhesive, such as tar, to form a plastic mass,
which is then condensed and moulded by pressure to form carbon articles of the
desired shape. The products so obtained are subsequently baked in special
furnaces (generally generator furnaces) by tedious processes, the object being to
transform the tar into carbon. The moulded rods are, for the purpose of being
baked, made up into bundles placed in a crucible, the interstices between the rods
and the crucible filled with coal-dust and the crucible is then placed in the furnace
in order to be made red-hot.
In this process, it is obvious, the outside of the carbons becomes heated first,
the tar on the surface is charred and an almost impermeable layer of dense, hard
carbon is formed, which does not allow that rapid and ready escape of the gases
forming within the rod that is desirable if a dense material of good conductivity is
to be obtained. A portion of the gases unable to escape will remain suspended
within the carbon presenting an appreciable resistance to the passage of the
current. Moreover a considerable portion of the carbons become warped, and so
useless.
I employ the following process to obtain a carbon that is very dense in structure,
practically free from resistance occluding no gases that are non-conductors or bad
conductors, the rods being moreover perfectly straight.
According to this invention the carbon is first moulded in a mould of a non-
conducting material. Then one end of the carbon is connected with the positive
pole of a suitable source of electricity, the other end being connected with the
negative pole of the same. A current of gradually increasing strength is now
passed through. This will gradually raise the temperature of the carbon; and
when the strength of the current has risen to a sufficient height to bring the whole
carbon to glow heat the temperature will in this process rise from within, and
gradually. If the carbon is readily combustible the process may be carried on in
a space filled with some gas that will prevent combustion of the carbon.
In order further to increase the capacity of the carbons I add to the mixture
from which they are moulded a certain quantity of aluminous earth intimately
mixing the same with the tar and carbon powder.
Thus an
The
By subsequently raising the whole to red-heat the metallic compound is reduced
and the entire carbon is interspersed with particles of the metals.
amount of conductivity is attained that practically gives no loss of current.
dimensions of the carbon may even be reduced in comparison with ordinary ones.
In lieu of aluminous earth, magnesia, or other metalliferous compounds may be
employed. Not only is the conductivity of the carbon much increased by these
means but a great increase in the illuminating power is also effected when such

page_text: carbons are used in arc lamps as the metal burning simultaneously with the carbon
gives a very great illuminating effect as will be readily understood.
Dated this 14th day of December 1893.
FREDERIC PRINCE,
Agent for Applicant.
COMPLETE SPECIFICATION.
Improvements in the Manufacture of Carbon for Electric Lighting
and other Electrical Purposes.
-
I, REGINA NIEWERTH, of Spener Strasse, Berlin, Prussia, no occupation, do
hereby declare the nature of this invention and in what manner the same is to be
performed to be particularly described and ascertained in and by the following
statement:-
This invention relates to the manufacture of carbon particularly suitable for arc
lighting in which resistance to the passage of the current is greatly reduced.
Carbon rods have heretofore been manufactured as follows:-
Carbon in a state of fine powder (soot, ground coke, or graphite) is mixed with
a suitable adhesive such as tar for instance to form a plastic mass, which is then
condensed and moulded by pressure to form carbon articles of the desired shape.
The products so obtained are subsequently baked in special furnaces (generally
generator furnaces) by tedions and cumbersome processes, the object being to
transform the tar into carbon. The moulded rods are, for the purpose of being
baked, made up in bundles, placed in a crucible, the interstices between the rods
and the crucible filled with coal dust and the crucible is then placed in the furnace
in order to be made red-hot. In this process it is obvious, the outside of the
carbons become heated first, the tar on the surface is charred and an almost
impermeable layer of dense hard carbon is formed which does not allow that
rapid and ready escape of the gases forming within the rod that is desirable if a
dense material of good conductivity is to be obtained. A portion of the gases,
unable to escape will remain suspended within the carbon presenting an appreciable
resistance to the passage of the current. Moreover a considerable portion of the
carbons become warped and so useless.
In order to obviate these difficulties, that is to say for the purpose of obtaining
--a carbon that is very dense in structure, free from resistance, occluding no gases
that are nou-conductors or bad conductors, and obtaining straight rods, I proceed
as follows:-
I place the carbons when moulded into proper shape into a sleeve, mould, or the
like, made of non-conducting material. One end of the carbon is next connected
with the positive pole of some suitable source of electricity, the other end being
connected with the negative pole of the same. A current of gradually increasing
strength is now passed through. This will gradually raise the temperature of the
carbon, and when the strength of the current has risen to a sufficient height, the
whole carbon will glow, the temperature will in this way rise from within, and
gradually. If the carbon is readily combustible, the process may be carried on in
a space filled with some gas that will prevent combustion of the carbon. As will
be readily understood from the foregoing description the product so obtained must
be of much greater value than any carbon heretofore produced, as all non-
conducting bodies are eliminated from the carbon, the carbon itself is also
.necessarily more dense and therefore a better conductor than others.
In order to further increase the capacity of the carbons I add to the mixture
from which they are moulded a certain quantity of aluminous earth intimately
mixing the same with tar, and carbon powder. By subsequently raising the whole
to red-beat, the metallic compound is reduced and the entire carbon interspersed
with particles of the metals. Thus an amount of conductivity is attained that no

page_text: longer allows of any loss of current. The dimensions of the carbon may De
In lieu of aluminous earth, magnesia
reduced in comparison with ordinary ones.
or other metalliferous compounds may be employed. Not only is the conductivity
of the carbon much increased by these means but a great increase in illuminating
power is also effected when such carbons are used in arc lamps, as the metal
burning simultaneously with the carbon gives a very great illuminating effect, as
will be readily understood.
It is obvious that the machine for carrying this method into practice may be
constructed in a variety of ways. I have constructed a machine in which the
current is admitted by rotary cylinders, and is led away by similar cylinders
placed at suitable distances from the admission cylinders. The carbons to be
treated are fed through as in a roller-mill so that the production is very rapid.
Having now particularly described and ascertained the nature of this inven
tion and in what manner the same is to be performed I declare that what I
claim is :-
1. In the manufacture of carbon for eliminating resistance; heating the carbons
after moulding, by means of an electric current in place of baking, as and for the
purposes set forth.
2. During the heating of the carbon by electricity, supporting the carbon in a
holding sleeve of non-conducting material to prevent warping.
3. Adding a metallic compound to the material from which such carbons are
produced for the purpose of eliminating resistances, and raising the conducting
capacity of the same; said metallic compound being reduced when the carbon is
subsequently raised to red-heat, as described.
Deted this 14th day of September 1894.
FREDERIC PRINCE,
37, Cursitor Street, Chancery Lane, London, Agent for Applicant.