Improvements in the Manufacture of Carbon for Electrical and other Purposes.
Year: 1894

page_text: Date of Application, 18th Aug., 1894
Complete Specification Left, 17th June, 1895-Accepted, 18th Nov., 1895
PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Carbon for Electrical and
other Purposes.
We, CHARLES PERCY SHREWSBURY, Engineer, FRANK LAURENCE
MARSHALL, Gentleman, and JOHN COOPER, Gentleman, all of No. 8, Furnival's
Inn, in the City of London, and JOHN LASKEY DOBELL, of Traine, Modbury,
in the County of Devon, Electrician, do hereby declare the nature of this invention
to be as follows:-
This invention relates to improvements in the manufacture from carbonaceous
matter of plates, slabs, pencils and other articles for electrical and other purposes.
Now, the object of the present invention is to produce carbon articles from a
novel compound which, when treated in a particular way, is equal or superior to
graphite as an electrical conductor, and, at the same time, the cost thereof is
considerably less.
For this purpose, the compound employed in the above manufacture consists of
anthracite coal, bituminous coal and tar or pitch or a mixture of tar and pitch, and
the articles which are formed from such mixture are submitted to pressure and to a
gradual baking and cooling process.
During the baking process above referred to, certain ingredients, for instance,
hydro-carbons, of the coal are driven off, and, in the absence of tar or pitch or a
mixture thereof, the density of the finished material which is of paramount
importance would be too small, but the addition of the tar or pitch or tar and pitch
to the coal binds or assists in binding the same into a cohesive mass, if added in
proper proportion, and compensates for the hydro-carbons driven off.
The bituminous coal best suited for the purposes of this invention is that kind
which will readily cake, that is to say, such as will in the presence of heat swell,
and then become as it were fused into a mass, the less freely the coal becomes
caked when submitted to heat the less suitable is it for the purposes of this
invention.
The anthracite coal and bituminous coal are first reduced to a fine state of
division and then placed in a suitable mixing machine in or in about the following
proportions:
Anthracite coal
10 parts by weight
Bituminous coal
4
وو
دو
59
and after having been thoroughly mixed a suitable quantity of tar or pitch or tar
and pitch is added thereto but such quantity may be varied according to the caking
quality of the bituminous coal employed.

page_text: material through a die, the degree of pressure being varied according to the nature
of the materials and the form of the article required.
When the material is moulded under a light pressure, for instance, a pressure
not exceeding twenty pounds per square inch it is not sufficiently condensed to
retain its form during the baking process if removed from the moulds previous to
being placed in the oven but in order to avoid this difficulty the articles are baked
in the moulds and for this purpose the moulds with their contents are placed in an
oven and submitted to the baking operation in a covering of ashes, as hereinafter
described. After which the articles may be removed from the moulds, and, if
they are required to have a high electrical resistance, they are ready for use, but
if, on the contrary, they are required to be of low electrical resistance, they are
submitted to another baking at a high temperature, as hereinafter described.
When the material is lightly pressed within the moulds as lastly described, the
moulds with the containing material are placed in an oven and covered or embedded in
ashes; the oven is then closed and the temperature thereof is raised, the maximum
temperature varying with the purposes for which the manufactured articles are
required, for instance, if the article to be produced is required to possess a high
electrical resistance the temperature must be above 1450° F. but must not exceed
about 1600° F., if the material is required for Le Clanché or Bünsen batteries and
similar purposes the temperature must be above 1600° F.; the oven is allowed to
remain at the maximum temperature for a period of about four hours. If the
articles produced are required to be of a low electrical resistance, such as the
carbon plates required for electrolysis or are to be subjected to a high temperature,
the temperature should be raised to from about 1600° to 1800° F., and having been
allowed to remain at this temperature for a period of about four hours the oven is
allowed to cool gradually and when cold the moulds are taken therefrom and the
contained articles are removed from the moulds or receivers and placed in tiers in
an oven with ashes between and surrounding them the oven is then closed and the
temperature thereof is gradually raised to 2500° F. or upwards the maximum
temperature being maintained for a period of about four hours, the oven is then
allowed gradually to cool down and the baked articles are removed in a finished
state.
If, however, the material in the moulds be submitted to a pressure of say three
hundred pounds or upwards per square inch, the moulded articles may before being
placed in the oven be removed from the moulds and placed in a drying chamber
where the moisture is gradually driven off therefrom by the application of heat, or
they might be dried by exposure to a dry atmosphere, or they might be sun-dried,
after which, even if the article is to be of a low electrical resistance, the baking
may be effected at one operation.
The important feature of the material herein before described is that, when
'exposed to heat, during the baking process above referred to, it shrinks or
contracts very considerably and equally all over thereby gradually increasing the
density thereof.
This contraction of the material is very important, and, in order that it may
take place evenly without causing cracks, breakage or loss or shape, care should be
taken not to apply the heat to the middle of the article, when baking, but so to
apply the heat that it operates especially on the ends.
For the same reason, it is of paramount importance that the temperature of the
ovens should be raised and lowered very gradually, as in the operation of baking
the contraction of the material is so great that any sudden change of temperature
would cause to article to crack or break.
Dated this 18th day of August 1894.
VAUGHAN & SON,
Agents for the Applicants.
1.

page_text: Improvements in the Manufacture of Carbon for Electrical and
other Purposes.
We, CHARLES PERCY SHREWSBURY, Engineer, FRANK LAURENCE
MARSHALL, Gentleman, and JOHN COOPER, Gentleman, all of No. 8, Furnival's
Inn, in the City of London, and JOHN LASKEY DOBELL, of Traine, Modbury,
in the County of Devon, Electrician, do hereby declare the nature of this inven-
tion and in what manner the same is to be performed to be particularly described
and ascertained in and by the following stateinent :-
This invention relates to improvements in the manufacture from carbonaceous
matter of plates, slabs, pencils and other articles for electrical, and other purposes,
such for example as crucibles and the linings of furnaces for metallurgical
purposes.
In carrying the invention into effect, a compound is employed consisting of
anthracite coal, bituminous coal and tar or pitch or a mixture of tar and pitch all
in special proportions, and the articles which are formed from such mixture are
submitted to pressure and to a gradual baking and cooling process.
During the baking process, certain ingredients, for instance, hydrocarbons, of the
coal, are driven off, and but for the presence of tar or pitch or a mixture thereof
the deusity of the finished material which is of paramount importance would
be too small but the addition of the tar or pitch or tar and pitch, if added. in
proper proportions to the coal, biuds or assists in binding the same into a
cohesive mass.
The bituminous coal best suited for the purposes of this invention is that kind
which will readily cake, that is to say, such as will in the presence of heat swell
and become as it were, fused into a mass, the less freely the coal cakes when
submitted to heat the less suitable is it for the purposes of this invention.
The anthracite coal and bituminous coal are first reduced to a fine state of
division and then placed in a suitable mixing machine in or in about the following
proportions :-
Anthracite coal
Bituminous coal
-
10 parts by weight
4
"
"
and after having been thoroughly mixed, a suitable quantity of tar or pitch or tar
and pitch is added thereto and mixed therewith but such quantity may be varied
according to the caking quality of the bituminous coal to he employed.
If the bituminous coal be of good quality, for this purpose, that is to say, good
caking quality, about seven parts by weight of tar or pitch or tar and pitch may be
added to the mixture of coal above given.
The poorer the caking property of the coal, the greater must be the proportion
of tar or pitch or tar and pitch employed in combination therewith, as will be
readily understood.
The material consisting of the coal and tar or pitch or tar and pitch having been
thoroughly mixed is submitted to a suitable degree of pressure which may be
exercised upon the material when placed in moulds or by expressing the material
through a die, the degree of pressure being varied according to the form and nature
of the articles required; the articles so formed are then allowed to dry and afterwards
baked at a high temperature.
If the material is pressed in the moulds by a light pressure for instance not
exceeding about 20 lbs. per square inch, the moulded articles should be submitted to
a preliminary baking in the moulds at a comparatively low temperature. but if the
articles are formed at a higher pressure for example 200 to 300 lbs. per square inch

page_text: or upwards either in moulds or by expressing through a die they may be removed
from the moulds or expressing machine dried or permitted to dry and baked without
a mould at one operation, that is to say, without any preliminary baking but the
temperature for the final baking in either case should be from 2,000 to 4,000 degrees
Fahrenheit more or less as may be required according to the purpose for which the
finished article is intended.
The important feature of the material hereinbefore described is that, treated and
baked as herein specified, it shrinks or contracts very considerably and equally all
over thereby greatly increasing the density thereof.
It is of paramount importance that the temperature of the ovens should be raised
and lowered very gradually, as, in the operation of baking, the contraction of the
material is so great that any sudden change of temperature would cause the article
under treatment to crack or break.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is :-
1. In the manufacture of carbon for electrical and other purposes, mixing
anthracite coal, bituminous coal and tar or pitch or tar and pitch in such proportions
as to constitute a material which contracts when exposed to heat, submitting the
same to pressure and drying and baking the articles formed therefrom at a high
temperature, substantially as herein described.
2. In the manufacture of carbon for electrical and other purposes, mixing
anthracite coal and bituminous coal in or in about the proportions given with tar or
pitch or tar and pitch, in order to obtain a material which contracts when exposed
to heat and submitting the same to pressure and drying and baking the articles
formed therefrom at a high temperature, substantially as herein described.
3. In the manufacture of carbon for electrical and other purposes mixing
anthracite coal, bituminous coal and tar or pitch or tar and pitch all in or in about
the proportions stated, so as to constitute a material which contracts when exposed to
beat and submitting the same to pressure and drying and baking the articles formed
therefrom at a high temperature, substantially as herein described and for the
purposes stated.
Dated this 17th day of June 1895.
VAUGHAN & SON,
Agents for the Applicants.