Improvements in the Manufacture of Illuminating Conductors for Incandescent Electric Lamps.
Year: 1888

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Illuminating Conductors for
Incandescent Electric Lamps.
I, RUDOLF LANGHANS, of 12 Schillingstrasse Berlin O. Germany, Electrician, do
hereby declare the nature of this invention to be as follows:-
The present invention relates to electric incandescent lamps in which the electric
current is converted into light by the resistance of its conductor enclosed in a vacuum,
and it consits in composing this conductor, which constitutes the filament or lighting
element, of an inner mineral vein or core of great light-emitting power, which is
itself a conductor of electricity and in providing this mineral core externally with a
firmly adhering and thin coating of carbon, silicon or boron, which has to conduct
the current to the mineral vein or core as soon as the former has passed to the radiating
condition.
The new filament or lighting element differs materially from the filaments or
lighting elements heretofore devised for electric incandescent lamps, which for the
purpose of increasing the emission of light have been combined with a mineral con-
stituent, such as magnesia, lime, other earths, or their silicates in that its mineral
constituent is itself a conductor of electricity and is caused to light from its mass by
the current itself, whereas in the filaments or lighting elements above mentioned the
mineral constituent is a "non-conductor of electricity" and is put into the lighting
condition not by the current itself, but through the heat of the incandescent constituent
which conducts the electricity.
I produce this metallic vein conducting electricity of metallic salts or salt-like
compounds of metallic oxide, which contain, as the constituent forming the base, the
oxide or oxidized compounds of calcium, magnesium, barium, strontium, aluminium,
beryllium, cerium, lanthanium, didymium, erbium, terbium, yttrium and gallium
whilst they contain as the constituent acting as an acid, the oxide or oxidized com-
pounds of titanium, uranium, zircon, molybdenum and thorium.
The substances of the first oxide group behave at high temperatures towards the
substances of the second oxide group as bases towards acids, that is to say the oxides
of the two groups are capable of chemically combining with each other, and by their

page_text: combination produce metallic salts. The latter in conducting the electric current
offer so much resistance that they become incandescent; they possess in this condition
a high capacity for emitting light; they are infusible, refractory, and bear the action
of the electric current and the glowing heat without being decomposed;
are they decomposed by the contact with glowing carbon, silicon or boron.
nor
I produce from these salts thin bodies in the form of threads, wires or strips. For
this purpose I can proceed in various manners, starting either from solutions
which contain the selected oxides of those mentioned as salts in combination
with suitable volatile acid, or from the oxides as such, or from their metals
themselves.
In the former inode of preparation I preferably take a thread-shaped body of
vegetable fibre, impregnate the same with a solution of the oxides, for example in
hydrochloric acid or acetic acid or any other suitable volatile acid, and then heat this
impregnated thread. with admission of air or in a powder yielding oxygen, whereby
the organic substance is destroyed the volatile acid is driven off, and the oxides
liberated from the latter become chemically combined with each other. The product
is a thread-shaped body consisting of the metallic salt or salts formed. Or I form
of the selected oxides and a suitable organic adhesive medium, such as cellulose, heavy
liquid or molten hydrocarbons, a homogeneous paste, draw from it threads, or roll
it into a thin sheet which I then cut into narrow strips. These threads or strips I
glow in order to destroy the organic adhesive medium and to chemically combine
the oxides with each other. Or I form from the metals of the oxides selected, an
alloy, and from this wires which I then first heat slowly in order to oxidize them,
and then heat them more intensely in order to chemically combine the oxides with
each other.
In all cases the nineral body obtained in the form of a thread or strip and con-
sisting of metallic salt is finally glowed in an atmosphere which contains suitable
compounds of carbon, silicon or boron, in order to deposit thereon a firmly adhering
and thin coating of carbon, silicon or boron, and thus to produce at the same time a
thread which is everywhere of uniform thickness and strength and which possesses
everywhere the same sectional resistance.
In each of these lighting elements can of course be any number of the oxides of
the two groups.
The improved lighting element presents the following advantages viz. that almost
all the energy used is converted into light; that' currents of lower tension can be
used than with other lighting elements having mineral constituents, and in conse-
quence of which the combined action of electricity, heat and incandescent carbon
silicon or boron, has no effect upon the said element thus greatly increasing its
durability.
Dated this 17th day of Fahr 1888
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C.,
Agents for the Applicant.

page_text: COMPLETE SPECIFICATION.
Improvements in the Manufacture of Illuminating Conductors for
Incandescent Electric Lamps.
I, RUDOLF LANGHANS, of Berlin, Germany, 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 :-
My invention relates to electric incandescent lamps in which the electric current is
converted into light by the resistance of its conductor enclosed in a vacuum, and it
consists in composing the said conductor, which constitutes the filament or lighting
element, of a mineral vein or core of great light-emitting power, which is itself
electrically conductive, and in providing this vein or core with a firmly adhering thin
coating, which assists in conducting the current to the vein or core, and whereby the
radiating energy of the filament is increased.
The substances which I employ for producing the said vein or core, are certain
salts the basic component whereof consists in one or more of the oxides of the
metals calcium, magnesium, barium, strontium, aluminium, beryllium, cerium,
lanthanum, didymium, erbium, terbium, yttrium and gallium, while their acid
component is formed by one or more of the oxydes of the metals: titanium,
uranium, zirconium, molybdenum, and thorium; the latter class of oxides when
brought together with the former at high temperatures, assuming, as is well known,
the character of acids and combining therewith to form salts, which I shall call
metallates. The coating by which I cover the filaments produced from the said salts
consists in carbon, silicon or boron.
One mode of proceeding for carrying out the invention is as follows.
A thread or
filament of vegetable substance is treated with sulphuric acid in view of swelling the
same, it is thereupon freed from the acid by means of caustic ammonia or carbonate
of ammonia, and after having been carefully washed with water, it is dried. The
thread thus prepared is impregnated with one or more of the aforesaid oxides of the
first series (or basic oxides), and with one or more of those of the second series (or
acid-forming oxides). This may be done with advantage by dissolving the basic
oxide or oxides in hydrochloric, acetic or other suitable volatile acidlin excess, adding
to the solution one or more of the acid-forming oxides, and steeping the thread in the
said solution. The impregnation of the thread is very much promoted by carrying
out the operation in vacuo, and, in order to incorporate the greatest possible quantity
of the oxides into the thread, the impregnating operation is repeated several times, the
thread being dried after every operation. The thread is then cut into pieces of the
requisite length which are bent into the desired form, and these pieces are suspended
in an open crucible and glowed while being exposed to the air. In order to avoid
distortions, it is, however, preferable to perform the glowing while the threads are
imbedded in an oxydizing powder, such as magnesia or carbon containing an excess
of oxygen, these substances being powerful absorbents of the oxygen of the air, while

page_text: they give it off in heated state. By means of the said glowing-process the hydro-
chloric, acetic or other volatile acid employed for dissolving the oxides, is driven off,
the oxides liberated therefrom are caused to become chemically combined with each
other, and the organic substance of the thread is destroyed, so that, subsequent to the
glowing, filaments remain, which consist of the said metallates in the state of an
amorphous dense mass, and which completely retain the shape of the original
vegetable base.
A modification of the described glowing-process consists in first glowing the.
impregnated threads while being imbedded in an indifferent pulverulent substance,
such as graphite, in view of expelling the hydrochloric, acetic or other acid, and
destroying the vegetable base, and in then exposing them to the oxidizing glowing-
operation for producing the union of the oxides to metallates.
Another mode of carrying out the whole process, which has the advantage of
obviating the use of acid solvents, is as follows. The oxides selected from the two
groups are mixed together with liquid or molten heavy hydrocarbons to form a dough.
This dough is pressed into filaments, or it is rolled into thin sheets which are cut into
narrow strips. The filaments or strips thus obtained are first carefully glowed in a
manner to oxidize and destroy the hydrocarbon, and thereupon glowed at a higher
temperature for causing the metallic oxides to combine with each other.
In case the metals of the oxides to be combined are at hand, an alloy may be made
thereof and wires formed out of the said alloy by pressing or drawing. These wires
are then carefully oxidized, the oxidizing process being carried out slowly, as other-
wise portions of the material are apt to fly off. Subsequently, the filaments, which
at the time consist but of a mixture of the oxides, are exposed to a heat sufficient to
cause the said oxides to act chemically upon each other and to combine so as to form
the required salts.
For the purpose of covering the filaments produced by any one of the described
processes, with a coating of carbon, silicon or boron, they are glowed with exclusion
of air in an atmosphere of suitable compounds of the said substances. The filaments
may for instance be heated while being suspended in a closed crucible through which
a current of carburetted, siliciuretted or borated hydrogen, or any mixture thereof is
passed. Or they are packed into the crucible with alternate layers of graphite and
solid hydrocarbons, such as naphthalene, paraffine and anthracene, and heated to
incandescence. Or the coating is performed by passing an electric current through
the filaments while they are surrounded by vaporized or gaseous hydrocarbons or other
gaseous compounds of carbon having the property of giving off carbon in the heat.
The carbon, silicon or boron is thereby deposited on the filaments in a compact layer
firmly adhering. thereto.
In all filaments hitherto employed in electric incandescent lamps, and in which is
incorporated a mineral substance in view of increasing their light-emitting power,
the mineral constituent is a non-conductor of electricity, which is brought into
luminous state by the transferrence to the same of the heat resulting from the passage
of the current through the conductive constituent. This mode of producing light
has, however, the main defect that the electric energy consumed is but partly converted
into light, and in addition thereto it is accompanied by other inconveniences.
The
In the new filaments produced as described, the mineral vein is on the contrary itself
a conductor of electricity and is therefore directly acted upon by the current, while it
presents sufficient resistance as to become luminous by the passage of the same.
substances composing the veins have a great light-emitting power, which is even
superior to that of the individual oxides; they are infusible and refractory even at
the highest temperature to which they may be exposed in the lamps, they are in no
wise decomposed by the current, they remain unchanged by their contact in
incandescent state with carbon, silicon or boron and the veins possess considerable
strength.
If, however, the filaments were to consist of the mineral veins alone, they would
require currents of great tension, whereas for known reasons currents of low tension
have to be employed in practice. In order to allow such low-tension currents to be

page_text: used with the said veins, these are covered with the coatings of carbon, silicon or
boron, which assist in conducting the current to the veins especially in their state of
incandescence. Moreover, as the veins and the coatings present different resistance
to the current, a tensional difference accrues whereby the total sectional resistance is
increased, the result thereby obtained being that the radiating energy produced by
the current, consists almost entirely in light with very little heat, the electric energy
being thus utilized to the greatest possible extent. Besides, the said coating allows of
the production of a filament having throughout equal thickness and therefore in all
its sections uniform resistance. The coating being more ductile than the mineral
vein, protects the latter from deteriorations, such as its becoming fissured, or the
splitting off of particles, which would be inevitable if the vein were uncovered; it
insulates the vein against the action of gases, and finally, the unequal expansion of
the vein and the coating operates to further increase the sectional resistance of the
filament, inasmuch as both undergo an alteration of condition, which produces in the
substance of the coating, and probably also in the mineral vein, an increase of
conductive resistance.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is:
A filament for electric incandescent lamps consisting in a vein or core composed of
one or more of the oxides of calcium, magnesium, barium, strontium, aluminium,
beryllium, cerium, lanthanum, didymium, erbium, terbium, yttrium and gallium, and
one or more of the oxides of titanium, uranium, zirconium, molybdenum and thorium,
the said vein or core being coated with carbon, silicon or boron, substantially as
hereinbefore set forth.
Dated the Twentieth day of Santamber 1888
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London,
Agents for the Applicant.