Improvements in the Manufacture of Filaments for Incandescence Electric Lamps.
Year: 1898

page_text: Date of Application, 13th Jan., 1898
Complete Specification Left, 10th Oct., 1898-Accepted, 26th Nov., 1898
Improvements in the Manufacture of Filaments for Incandescence
Electric Lamps.
I, CHARLES HENRY STEARN, of 47, Victoria Street, in the City of Westminster,
Electrician, do hereby declare the nature of this invention to be as follows:-
The object of my invention is to manufacture filaments for incandescence
electric lamps in a more economical manner and with more uniform results than
hitherto.
According to my invention I employ for this purpose a solution of cellulose
made by treating cellulose with strong alkali and then with carbon bi-sulphide
and dissolving the product in water. A process for the production of such a pre-
paration is described in the Specification of Letters Patent No. 8700 of 1892. I
precipitate the cellulose in the filamentary form by projecting the solution thereof
into a precipitating solution such as for instance, alcohol, brine, chloride or sul-
phate of ammonium or other suitable precipitant. In order to obtain satisfactory
results the solution should be as perfect as possible and be filtered to remove
impurities or undissolved cellulose. After precipitation the filament may be
purified by treatment with any of the usual reagents such as, for instance, sul-
phites or sulphurous acid and if desired with a bleaching solution such as sodium
hypochlorite. The filaments are then carbonised.
The 19th low of Tonuar 1898
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture of Filaments for Incandescence
Electric Lamps.
I, CHARLES HENRY STEARN, of 47, Victoria Street, in the City of Westminster,
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:-
The object of my invention is to manufacture filaments for incandescence
electric lamps in a more economical manner, and with more uniform results, than
hitherto.
According to my invention I employ, for this purpose, a solution of cellulose

page_text: made by treating cellulose with strong alkali and then with carbon bi-sulphide
and dissolving the product in water. A process for the production of such a pre-
paration (which is commonly known as viscose) is described in the Specification of
Letters Patent No. 8700 of 1892. I precipitate the cellulose in filamentary form
by projecting the solution thereof into a precipitating, or setting, solution, or
liquid. Alcohol, brine, and sulphate of ammonium solution, for example, are pre-
cipitating, or setting, liquids, or solutions; but I have found that a solution of
chloride of ammonium gives the best results as, at the proper strength, it is of a
specific gravity which will allow the cellulose solution to pass, downwards therein,
and which has the effect of immediately setting the said cellulose solution. A
suitable strength of the ammonium chloride solution is one of a specific gravity of
1.050 to 1.060 but I do not limit myself to this particular strength.
In the preparation of the viscose solution the greatest care must be taken to
render the solution perfectly homogeneous and free from all undissolved particles
of cellulose.
The ordinary viscose of commerce generally consists of a mixture of a true
solution of cellulose with a jelly-like substance, and contains many undissolved
fibres, or parts of fibres. This character remains in the viscose even after the
most careful filtering, and, if filaments be made of such a material, the outlines
when viewed under the microscope will be seen to be, more, or less, wavy, or
sinuous, presenting sections of unequal diameter and of unequal strength in
various parts of the filament.
The non-homogeneous nature of such a solution is clearly apparent, when viewed
in a thin film, or layer, under polarised light, by the variations in colour dis-
played.
'
A perfectly homogeneous solution can be obtained as follows, I first obtain. the
purest bleached cellulose and subject it to the action of alkali, as in the well
known process of mercerisation, and I continue the process until the solution of
alkali has thoroughly penetrated through the mass. The cellulose used should be
as loose in structure as possible so as to admit readily of the penetration of the
alkali solution. When the mercerisation is thoroughly accomplished the excess of
alkali is squeezed out and the alkali-cellulose is treated with carbon bisulphide.
When the reaction is complete sufficient water is added to make a solution contain-
ing say from 9 to 10 per cent. of cellulose, and the mixture is thoroughly stirred
for a considerable time by means of a mixer revolving at high speed, the vessel
containing the viscose being kept cool during the process of mixing.
The mixture must now be filtered very thoroughly and freed from air by the
air pump.
The solution, if carefully prepared and treated as aforesaid, will be perfectly
clear and structureless or homogeneous and of high viscosity, and fit for preci-
pitation, or setting, as aforesaid, and filaments of great tensile strength, and of
even section throughout their whole length, are obtained.
The cellulose solution can be squirted through the jet under any suitable pres-
sure (air, or hydraulic, or mechanical) into the precipitating, or setting, solution,
or liquid, the orifice in the jet being of the requisite diameter to give the size of
filament required. The filament as produced can be allowed to coil upon itself,
or be drawn off by a revolving pulley, as may be desired.
The filament produced can be purified and treated as follows;-
The filament should be placed, and remain from 6 to 12 hours, in fresh cold
chloride of ammonium solution, or other setting. liquid so as to remove, as
thoroughly as possible, all products soluble in that medium.
After digestion in the cold the filament is removed from the liquid and intro-
duced, for a few minutes, into a boiling solution of the same liquid, to regenerate
the cellulose, after which it is washed in boiling water to remove all traces of the
chloride. The resulting cellulose may then be purified in any suitable way, the
following being suitable:-
The filament is immersed in a hot solution of sodium carbonate (washing soda)

page_text: and is left for some time in the solution. From this it is well washed and
immersed in a solution of sodium hypochlorite, or other bleaching solution, till
colourless. It is then thoroughly washed and may then be treated with dilute
acids and washed. It is then dried in the air under tension, or passed, under
tension, through a heated chamber.
The filaments produced may be reduced, polished, or otherwise acted upon, by
passing them between rollers, and they are cut and shaped as required, and car-
bonized, which may be done in the usual way.
Having now particularly described and ascertained the nature of this
invention. and in what manner the same is to be performed, I declare that what
I claim is ;—
1. A filament for incandescence electric lamps made of carbon prepared from the
aforesaid solution of cellulose (viscose).
2. The manufacture of filaments for incandescence electric lamps by precipi-
tating, in a filamentary form, the aforesaid solution of cellulose (viscose) forming
the same into the required lamp filaments, and then carbonizing them.
3. The manufacture of filaments for incandescence electric lamps by precipi-
tating the aforesaid solution of cellulose, (viscose), by projecting it through a small
orifice into a solution of chloride of ammonium, forming the lamp filaments from
the material so precipitated, and then carbonizing them.
4. The manufacture of filaments for incandescence electric lamps by projecting
the aforesaid solution of cellulose, (viscose), through a small orifice, into a preci-
pitating, or setting, solution, or liquid, and drawing the same there-through.
5. The preparation of filaments for incandescence electric lamps by first sub-
jecting the aforesaid solution of cellulose, (viscose), to stirring and filtering, and
then projecting it from a small orifice into a solution of chloride of ammonium,
and drawing the same therethrough.
1001
1000
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.