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

page_text: PROVISIONAL SPECIFICATION.
Improvements in the Manufacture of Filaments for Incandescent
Electric Lamps.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings,
Chancery Lane, in the County of London, Chartered Patent Agent, do hereby
declare the nature of this invention (as communicated to me from abroad by Dr.
Carl Auer von Welsbach, of IV., Schleifmühlgasse, 4, Vienna, Austria)
to be as follows:-
In his researches for the purpose of making filaments for incandescent electric
lamps wholly or partially out of osmium my foreign correspondent has discovered
that the metal can be rendered more suitable for the purpose and superior fila-
ments can be made out of it if in the course of manufacture a suitable quantity
of certain substances be added which appear to have the power of removing the
impurities contained in ordinary osmium on the filament being raised to a state
of high incandescence. It would appear that they unite with these impurities
and in some cases, on being volatilized they take the impurities with them.
For the above purpose my correspondent prefers to use titanic acid and pro-
ceeds as follows. With the osmium paste made out of finely divided osmium or
osmium salt, with the necessary binding material, is thoroughly mixed a portion
of titanic acid and then the filament is shaped either by squeezing it through a
small hole or in any other convenient way. The binding material is next driven
out as described in the previous application for Letters Patent Nos. 1535 of 1898
and 13116 of 1898 by raising the wire to incandescence in a protective atmosphere
as there described, prior to its being raised to a still higher incandescence in a
vacuum. The titanic acid passes away and takes with it impurities from the
osmium or otherwise produces such an effect on the osmium that the wire remains
in a highly elastic condition eminently suitable for acting as the illuminating con-
ductor of an electric lamp.
Although my correspondent prefers to use titanic acid, other oxides of a more
basic character which will volatilize when brought to incandescence may be used.
Good results are obtained by alumina and magnesia and also with thoria and
zirconia. The latter however appear to purify the metal without being themselves
volatilized so that it is probable that the impurities pass into the thoria and
zirconia and remain there. The filaments manufactured as above are coherent and
elastic and of great durability.
ABEL & IMRAY,
Agents for the Applicant.

page_text: COMPLEIE SIMIFICATION.
Improvements in the Manufacture of Filaments for Incandescent
Electric Lamps.
I, OLIVER IMRAY, of Birkbeck Bank Chambers, Southampton Buildings,
Chancery Lane, in the County of London, Chartered Patent Agent, do hereby
declare the nature of this invention (as communicated to me from abroad by Dr.
Carl Auer von Welsbach, of IV., Schleifmühlgasse 4 Vienna, Austria)
and in what manner the same is to be performed to be particularly described and
ascertained in and by the following statement: -
This invention relates to the manufacture of osmium filaments for electric
lamps such as are referred to in the Specifications No. 1535 of 1898 and No. 13116
of 1898.
It has been found that the use of certain oxides which are volatile at a white
heat is of advantage for the manufacture of osmium incandescense filaments.
It appears that in ordinary osmium certain oxides exist which cannot be com-
pletely volatilised even at an intense white heat, and which interfere with the
uniform consolidation of the osmium filament and reduce its durability and illu-
minating power..
It has been discovered that those oxides which are not themselves volatilised
at an intense white heat can be volatilised out of the osmium filaments if there
are present in the same, other more readily volatilisable oxides.
The use of such more readily volatilisable oxides has therefore the effect that the
osmium particles are brought nearer and welded together under intense white
heat, so that the osmium filament becomes perfectly dense and elastic.
For the manufacture of osmium incandescence filaments with use of such more
readily volatile oxides, a paste is prepared consisting of an intimate and uniform
mixture of exceedingly finely divided titanium oxide, an organic binding sub-
stance and very finely divided osmium.
The proportions of the osmium and oxide to be employed in the paste should
correspond to their equivalent weights thus for example with 10 parts by weight
of osmium 4 parts by weight of titanium oxide should be used.
For the titanium oxide can be substituted in the paste other oxides which are
volatile in a white heat and are of a more basic character, such as aluminium
oxide, or magnesia or lime; silicic acid is not suitable for the purpose.
From the paste thus formed the filaments are prepared in the manner pre-
viously described such as by pressing through a die: these filaments must be
smooth and almost polished on the surface. Should this not be the case the
filaments should be rolled between glass plates covered with smooth paper or
similar material maintained at a certain distance apart.
While still in a flexible condition the filaments are brought to the required
form and are then subjected to dry distillation in order to produce a body of
osmium titanium and carbon compound in filament form.
as
The filament is then secured in a temporary holder with some magma
described in the Specification No. 1535 of 1898 and is secured in the manner there
described and it is then slowly heated by an electric current in an atmosphere of
reducing gas mixture until the carbon is burnt away. After this has been effected
the temperature is gradually raised by the electric current until a white heat is
obtained, during which time the titanium oxide melts and the filament becomes
compact. The temperature is then still further raised so as to volatilise the
titanium oxide, while the osmium particles are brought nearer and welded together
forming a perfectly dense and elastic filament.

page_text: The osmium incandescence filament is then ready; it is pure, dense, and elastic;
all parts thereof possess equal resistance if accurately prepared.
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
1. The process of purifying osmium filaments for electric lamps by means of
titanic oxide (or other oxide as above set forth) which said oxide is subsequently
volatilised and driven off substantially as described.
2. The herein described process for the purification of osmium by means of
titanic oxide or other oxide as above set forth.
3. Filaments for electric lamps consisting of osmium prepared as above set
forth.
Dated this 13th day of May 1800
ABEL & IMRAY,
Agents for the Applicant.