IMPROVEMENTS IN THE MANUFACTURE OF CARBON FILAMENTS FOR INCANDESCENT LAMPS
Year: 1885

page_text: Incandescent Lamps.
WILLIAM MAXWELL Engineer 34 Claybrook Road Fulham S.W do hereby
declare the nature of my invention for IMPROVEMENTS IN THE MANUFACTURE OF
CARBON FILAMENTS FOR INCANDESCENT LAMPS, to be as follows:-
In preparing Carbon Filaments for Incandescent Lamps it is usual to subject the
raw material, after chemical or other treatment, to the action of a gas or other
furnace, in order to carboniso it. This process has many disadvantages, and my
process is designed to overcome these disadvantages, and to produce a purer denser
and more durable carbon.
My invention is an improved process or system of carbonising fibre thread or
any other suitable substance or form of matter by means of Electricity.
In carrying out my invention, I make use of a box casing or chamber, into which
the substance or matter to be carbonised is introduced. The said box, casing, or
chamber, can be rendered air tight, and may be placed in communication-by means
of suitable connections furnished with valves or taps--with an exhaust pump or
chamber, or with the atmosphere, or with any gases vapours or liquids, which may
be required during the process.
The said casing, box, or chamber, may be surrounded or enclosed by an outer
casing, or jacket, around or through which air gases vapours or liquids at any
required temperature may circulate or travel.
To the said box, casing, or chamber, electrical connections are also attached,
and may be furnished with any suitable forms of resistances switches or other
instruments required to make break regulate or indicate the current, or currents of
electricity in use.
The substances to be carbonised may be placed in a mould of any required form,
or they may be carbonised without the use of a mould.
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The air gases vapours or liquids may be introduced into the box, casing, or
chamber, or into the mould, at any required or suitable temperature.
The fibre, thread, or any other substance, or form of matter, to be carbonised,
may be subjected to the direct, or indirect, action of the electrical current, or
currents, and the electrical currents may be used in vacua or in conjunction with
gases vapours or liquids at any temperature.

page_text: Incandescent Lamps.
I, WILLIAM MAXWELL, Engineer of 34 Claybrook Road, Fulham, S.W 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:-
My invention relates to a method of carbonising the fibres, threads or filaments
that are to form the illuminating conductors of incandescent electric lamps.
I effect this by subjecting them in or on a suitable case or mould to a high
temperature produced by electrically heating the case or mould while the whole is
'enclosed in a chamber containing or having passed through it a gas which does
not enter injuriously into combination with the heated carbon. Or instead of
charging the chamber with gas, it may be exhausted to a high degree but this is
troublesome.
The case or mould is made of highly refractory material such as carbon which
is a conductor of electricity but has considerable electrical resistance, so that it can
be highly heated by the passage of an electrical current through it. When applied
for carbonising filaments of the ordinary horseshoe type, the mould is conveniently
made of saddle form, either open or covered by a corresponding form so that the
filaments may rest on it astraddle. A mould or case may also be made as a block
or slab on which the filaments are laid, or preferably the block or slab may have
sunk in it a groove or hollow in which the filaments are laid either open or covered
by a lid. The two ends or sides of the mould or case are connected to conductors
preferably of very low resistance which pass insulated through asbestos or other
suitable stuffing boxes in the wall of the enclosing chamber. The gas such as
nitrogen which does not practically act on the filaments, or a hydrocarbon such as
Marsh gas which has very slight action on them at low pressures should be dry and
at a reduced pressure so as the better to eliminate from the material of the filaments
operated on the gases or vapours liberated by the heating. Coal gas free from
vapour and oxygen may be conveniently used at a reduced pressure about or under
the tenth of an atmosphere.
In carrying out the process, I place in the chamber the mould or case with the
filaments and connect it to the two conductors, I then close the chamber by a cover
making tight the joint and, having withdrawn the air, and charged it with the
desired atmosphere such as nitrogen or hydrocarbon gas at a pressure below that
of the atmosphere, I past first a moderate current and then an increasing current
of electricity through the conductors and mould so as gradually to heat the mould
und the filaments, while I maintain a constant change of the atmosphere within
the chamber, and I continue this until the filaments attain a very high temperature,
The chamber may be supplied with a heated atmosphere as thus the electricity
required for heating can to a certain extent be economised and the gases and
vapours are more readily evolved and abstracted during the early stage of the
process.

page_text: Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is
In the manufacture of carbon filaments for incandescent lamps, effecting their
carbonisation by placing them in or on a mould or case which is electrically heated
within a closed chamber containing a suitable atmosphere, substantially as herein
described.
ABEL & IMRAY,
Agents for the Applicant.