Process for Producing Filaments for Incandescent Lamps.
Year: 1891

page_text: Date of Application, 3rd Nov., 1891
Complete Specification Left, 2nd Aug., 1892-Accepted, 3rd Nov., 1892
PROVISIONAL SPECIFICATION.
Process for Producing Filaments for Incandescent Lamps.
I, RUDOLF LANGHANS, of 61, Fore Street, London, E.C., County of Middlesex,
Electrical Engineer, do hereby declare the nature of this invention to be, as
follows:-
The present invention relates to the production of filanients of gelatinous cellulose
to form luminous bridges for incandescent lamps.
The process for producing the filaments in general consists in treating purified
cellulose in successive operations with sulphuric acid of varying concentration for
the purpose of producing a gelatinous and plastic substance which I call sulphur-
cellulose.
In order to produce my sulphur-cellulose I take for instance cotton or other
suitable substance and treat it with a weak alkaline solution, and afterwards with
dilute hydrochloric acid sufficiently diluted so as not to affect the structure of the
cellulose, for instance, at the temperature of 15 degrees centigrade a solution of
40 or 50 per cent. is suitable. Whilst stirring and kneading the cellulose I then add
acid of 70 to 80 per cent. H₂SO, until a stiff gelatine is formed.
I then extract the
air from this stiff gelatine either by means of a vacuum pump, or other suitable
means. I then place this gelatine into a vessel out of which it is ejected into water
through an aperture, thus forming hydro-cellulose, and in the shape of a filament of
continuous length and equal area, and which has the necessary strength to be at
once wound on a drum and dried. I then carbonize this filament in a crucible in.
the ordinary manuer.
Dated this Third day of November 1891
COMPLETE SPECIFICATION (AMENDED).
Process for Producing Filaments for Incandescent Lamps.
I, RUDOLF LANGHANS, of 61, Fore Street, London E.C. County of Middlesex,
Electrical Engineer 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 present invention relates to the production of filaments or luminous bridges
for incandescent lamps.
The process for producing the filaments in general consists in treating purified
cellulose in successive operations with sulphuric acid of varying concentration until a
gelatinous substance is obtained. The latter is then coagulated & hardened by
immersion in water whereby it is transformed into hydro-cellulose after having been
shaped into continuous threads or filaments by suitable means. The filaments are
then dried and subjected to gradually increasing heat until white heat.

page_text: In order to more fully explain my process I will now describe it in detail.
I take natural cellulose for instance cotton or other suitable substance & purify
the same by first treating it with a weak alkaline solution and afterwards with dilute
hydrochloric or other suitable acid. I then wash and dry it. The purified cellulose
is then subjected to the action of sulphuric acid in successive operations and of
varying concentration. By this treatment a very perfect gelatination is obtained
and a too rapid alteration of the structure of the cellulose is prevented whereby it
would be rendered useless for my purposes. I may take for instance a very weak
solution of acid to commence with, then add a very concentrated solution and at
last one of medium strength, for instance acid of 42 to 48° Beaumé to commence
with, after that acid of 58 to 63° B. and finally acid of 50 to 54° B. (measured at a
temperature of 15° centigrade). The diluted acid must be added slowly &
gradually in portions & well kneaded into the cellulose in such a manner as to effect
a very thorough saturation of the cellulose with the acid. As the result of this
successive and gradual treatment I obtain a homogeneous, gelatinous and semi-liquid
substance. The whole operation should be performed at a low temperature of not
more than 7 to 8° centigrade. I then de-aërate this gelatinous substance either by
means of a vacuum-pump or in a centrifugal machine, and it then becomes an
absolutely homogeneous substance which immediately coagulates in water; thin
layers become hard in a few minutes even in a moist atmosphere. This gelatinous
substance is then shaped into a continuous thread or filament by pressing it through
a fine aperture, the size of which may be varied to suit requirements, & the filament
so formed may be wound on a drum or reel. I then immerse these filaments in
water or watery solution. I may for this purpose place the entire drum or recl
with the filament wound on it in water or I may cause the filament to drop into
water as it is pressed out through the aperture. The substance contains sulphuric
acid and in order to prevent heating when it touches the water I provide a layer of
ethyl-alcohol on the surface of the water. The filaments are immersed and rinsed
in water until they are quite hard & then dried. The continuous filament is then cut
in pieces of the requisite length, bent horse-shoe or other shape and subjected to a
slow dissociating process which consists in gradually heating it up to a white heat
keeping it protected from oxydation. I thus produce a filament for use as a
luminous bridge for incandescent lamps having a perfectly smooth & shiny surface,
which consists substantially of chemically pure carbon, which is more durable and
of a more uniform electrical resistance than filaments made hitherto of animal or
vegetable or artificial carbon.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, 1 declare that what I
claim is:
1. A luminous bridge for incandescent lamps made of a material consisting mainly
of chemically pure carbon and resulting from the treatment of cellulose in successive
operations with sulphuric acid of varying concentration until a gelatinous semi-liquid
substance is obtained, substantially as herein described.
2. The process for producing filaments for incandescent lamps consisting in treating
cellulose in successive operations with sulphuric acid of varying concentration until
a gelatinous semi-liquid substance is obtained; shaping such substance into
continuous threads; immersing such threads in water; drying them and subjecting
the filaments so obtained to a gradually increasing heat up to white heat, keeping
them protected from oxydation for the purpose and substantially as herein before
described.
Dated this Second day of August 1892