Year: 1885

page_text: We THEOPHILUS VAUGHAN HUGHES of Greenfield Copper Works Holywell,
North Wales, Associate of the Royal School of Mines and CHARLES ROLAND
CHAMBERS of 2 Knaresborough Place, South Kensington in the County of
Middlesex Electrician do hereby declare the nature of this invention to be as
follows:-
--
Our invention relates to an improved method of and apparatus for manufacturing
carbon filaments suitable for use in electric glow lamps, and it has for its object to
produce filaments of greater density and homogeneity and consequently of greater
durability than carbons manufactured by the ordinary methods.
The invention consists in a process of destructive distillation of a carbon
compound in the gaseous or liquid form during its ejection under pressure through
a suitable nozzle or orifice into a chamber containing an atmosphere incapable of
combining with the carbon of the compound, which is condensed in the form of a
filament, the temperature of this atmosphere being sufficient to produce the
decomposition of the carbon gas or liquid.
In practice the nozzle or orifice would be preferably situated at the top of the
chamber containing the inert atmosphere in order that the filament may be
produced in a pendent position, the chamber being made of sufficient height to
enable a long straight filament to be produced and to permit of its being cooled
sufficiently before leaving the hot chamber.
Any number of nozzles or orifices may be provided in the same chamber for the
production of any desired number of filaments.
In order to render the filament of uniform electrical conductivity we cause a
current of sufficient strength to pass through the filament at its point of formation.
DL: CAL
-- 100
S

page_text: Electric Lighting.
We THEOPHILUS VAUGHAN HUGHES of Greenfield Copper Works Holywell
North Wales Associate of the Royal School of Mines, and CHARLES ROLAND
CHAMBERS of 2 Knaresborough Place South Kensington in the County of
Middlesex Electrician, 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:-
Our Invention relates to an improved method of manufacturing Carbon filaments,
suitable for use in electric glow-lamps; and it has for its object to produce
filaments of greater density and homogeneity, and consequently greater durability
than those manufactured by the ordinary methods. Hitherto, it has been usual to
manufacture such carbon filaments by carbonizing a filamentous material by baking
it when bent into the intended shape. This process, however, destroys the homo-
geneity of the filaments by rendering them porous, and this defect is only partially
remedied by the subsequent process known as "flashing."
Our Invention consists in a method of manufacturing carbon filaments by the
destructive distillation of a gaseous carbon compound capable of yielding carbon
when decomposed by heat whereby we obtain flue-hair like filaments which
undergo no appreciable change in their homogeneity during the subsequent processes
of lamp making, almost all the hydrogen having been eliminated during their
formation. Since from the time of their formation the filaments are of dense hard
carbon of great purity and having a low specific resistance, the operation of baking
is avoided. The great density of the filaments produced by the method of our
Invention is due to their formation (more or less molecular) directly from a
gaseous carbon compound capable of yielding carbon when decomposed by a high
temperature the carbon being deposited and the hydrogen escaping. These hair
like carbon filaments combine with density, great strength and flexibility, so that
they may be bent and twisted into various shapes, and will spring back to their
original form on being released.
The process of this Invention is carried on in a nearly closed retort placed in a
furnace the gas being conveyed into the retort at, or just above, atmospheric
pressure through a distributing inlet or nozzle from the orifices of which the gas
issues in fine streams directed against the sides of the retort. The gas on striking
the heated sides of the retort becomes decomposed and carbon is at first deposited
upon the sides and bottom of the retort and over the nozzle in the form of a loose
fibrous or cobweb-like mass. This deposit having been formed, and the gas con-
tinuing to be supplied the deposit now takes the form of hair-like filaments,
growing as it were out of the lining as a base towards the central and upper part
of the retort which ultimately becomes nearly filled with a loose, and but slightly
entangled, mass of said filaments growing more or less in the same general direction,
and of a length of 4 or 5 inches, more or less, according to the size of the retort
employed. When the operation is completed, and the retort has become cool, it

page_text: may be opened and the long filaments can then be easily removed. The filaments
are now ready for mounting and "< flashing."
The conditions which we have found to be essential to the proper formation of
the filaments are as follows; -The temperature should be that at which the
thorough decomposition of the gas used takes place, and should be maintained as
constant as possible during the operation. We prefer to use a gas containing
about 40% hydrogen, and not less than 45% marsh gas, together with other
usual hydro carbons equivalent to about 7°%. Ethylene. Such a gas may be
obtained from North Staffordshire coal. Where the gas of the required com-
position is not at hand ordinary lighting gas may be treated by passing it over
hydro carbons to enrich it, or if too rich, by depriving it of its carbon by passing
it over heated brick or charcoal. The gas must be as free from moisture as possible,
the presence of moisture in any appreciable quantity being fatal to the formation
of the filaments. The gas should, therefore, be passed through refrigerating
worms, and over quicklime.
The flow of gas, and time of firing, vary with the size of the apparatus, but if
the flow be too rapid, or the gas itself be too rich, no filaments will be formed.
Having explained the process in its general outlines, we will now proceed to
describe the means we have adopted for carrying it out in practice, but we would
have it understood that our Invention is not limited to the particular apparatus
herein described, which may be modified according to circumstances nor to the
particular composition of the gas herein before specified.
Reference is to be had to the accompanying drawing illustrating the apparatus
by means whereof our improved process of manufacture of carbon filaments may
be carried into effect. The drawing represents a section through a furnace and
retort in position therein.
It is
The retort we prefer to use is a crucible a of plumbago or iron of a size known
as Morgan's 130 lbs. It is placed in a furnace of any suitable construction. b is a
distributing inlet or nozz'e leading through the bottom of the crucible.
provided with a number of radial orifices 6* at the upper end, through which the
gas issues into the crucible. These orifices may be 6 in number and for a crucible
of the size above mentioned should be about a quarter of an inch in diameter.
The nozzle is made of fire clay and passes through a hole in the bottom of the
crucible which is seated upon a flange b¹ formed upon the nozzle. The pipe c for
conveying the gas to the nozzle passes in under the furnace and up through the
bars, and is attached to the nozzle 6 preferably by a flange d screwed on the pipe
bolted to a split collar e embracing the base of the nozzle b, a gas-tight joint being
made between the flange b' on the inlet b and the flange d on the pipe with red
lead paint and hemp. The flange b' of the inlet should be about two inches below
the level at which the furnace bars will be placed, and in the centre of the furnace.
The crucible is bedded on the flange b¹ with fire clay suitably tempered which is
forced up around the nozzle b to make a thoroughly gas-tight joint, dry powdered
clay being sprinkled around the nozzle nearly up to the level of the inlet holes, and
then well tamped down. The mouth of the crucible is now closed by a disc of fire-
clay placed within it an inch or two below the lid g, the intervening space h
being filled up with wet luting clay with which may be mixed pieces of broken
pot. The shrinkage of this clay plug in drying leaves a minute annular space
around the mouth of the crucible for the escape of the hydrogen resulting from the
decomposition of the hydro carbon. The lid g is luted on, and a heavy weight
placed on it. To prevent the crucible shifting in the furnace it may be packed
with clay wedges at the sides. The furnace bars are now put in and the fire
lighted. To permit the escape of steam from the luting clay when drying, and
prevent it blowing back and condensing in the pipes, a stop-cock i is placed on the
pipe c and immediately next to it a blow-off cock k, the foriner being closed and
the latter being opened whilst the crucible is being heated.
When all the steam has been expelled k is closed and i opened, to allow the flow
of gas to commence. The crucible should be kept as constantly as possible at a

page_text: bright red heat for 5 to 7 hours, after which it is allowed to cool, the gas con-
tinuing to be admitted until the crucible is cool enough to permit of its removal.
The crucible must on no account be jarred or disturbed when adding fresh fuel.
Having now particularly described and ascertained the nature of the said
Invention; and in what manner the same is to be performed; we declare that what
we claim is;—
The manufacture of Carbon filaments for glow-lamps by the destructive dis-
tillation of a gaseous carbon compound capable of yielding carbon when decomposed
by heat, substantially in the manner specified.
Dated this 4th day of August 1886.
.T. V. HUGHES.
C. R. CHAMBERS.
By A, M. & W™ Clark, Agents.
H