An Improvement in Filaments for Incandescent Electric Lamps.
Year: 1890

page_text: Date of Application, 26th Feb., 1890
Complete Specification Left, 23rd Sept., 1890-Accepted, 25th Oct., 1890
PROVISIONAL SPECIFICATION.
An Improvement in Filaments for Incandescent Electric Lamps.
I, RUDOLF LANGHANS, of No. 12/14, Schillingstrasse, Berlin, Kingdom of Prussia,
Electrician, do hereby declare the nature of this invention to be as follows:-
My invention relates to conductors for incandescent electric lamps consisting in
filaments of carbon or metal, and its object is to render the same more resistant against
oxidation. Eor this purpose I provide the said filaments with a coating of silicon or
boron, which is electrically conductive, and which in addition thereto has the property
of being but little or not at all attacked by oxygen and oxidizing gases.
The substances from which I produce these coatings, consists in compounds of
silicon or boron which are gaseous or liquid, or which may be liquefied, dissolved or
converted into gas, vapor or smoke, and which are at the same time capable of being
decomposed by heat, or electricity, or both, with or without the aid of chemical agency,
in such manner that silicon or boron separates out in the graphitoidal or crystalline
form, either in pure state or together with carbon.
For carrying out the process, the filaments are brought with the compound into a
vessel evacuated of air, or filled with a chemically indifferent gas, and subjected
therein to the action of heat, or electricity, or both, and of any chemical agent, if
desired.
n 1 111
1000
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.
COMPLETE SPECIFICATION.
An Improvement in Filaments for Incandescent Electric Lamps.
I, RUDOLF LANGHANS, of No. 12/14, Schillingstrasse, Berliu, Kingdom of Prussia
do hereby declare the nature of this invention and in what manner the same isto
be performed, to be particularly described and ascertained in and by the following
statement:-
My invention relates to conductors for incandescent electric lamps consisting in
filaments of carbon or metal, and its object is to render the same more resistant against
oxidation. For this purpose I provide the filaments with a coating of silicon or
boron; the said coating Laving, in addition to its possessing electric conductivity, the
property of being but little or not at all attacked by oxygen and oxidizing gases.
Heretofore, filaments for electric incandescent lamps have been covered with an
electrically-conductive coating of carbon, for the purpose of leading the current to the
filaments (which are in themselves but little conductive) upon their whole surface, and
thereby to reduce the total resistance of the filaments against the passage of the
current and to enhance the illuminating power of the same. These coatings, however,
furnish but little or no protection against oxidizing influences.
Moreover, to the filaments composed of metallates, for which I have obtained British
Letters Patent A.D. 1888, No. 2438,coatings of silicon or boron are applied, which are
produced, respectively, by means of silicinretted and borated hydrogen. These
coatings were originally designed for the same purpose as the coatings of carbon, but
the specific conductive power which they possess, is greater than that of the latter, 80
that by their use a reduction in the consumption of electric energy is rendered possible.
Now, it has been proved by experiments that the coatings of silicon and boron have
the property, particularly valuable for filaments of carbon and metals, of protecting
the filaments in considerable measure against oxidizing influences, so as to increase

page_text: their duration or to allow of a lower degree of evacuation of the lamps. Moreover, I
have found that the said coatings may be obtained from various other compounds of
silicon and boron besides silicinretted and borated hydrogen.
Serviceable for the production of the coatings are all compounds of silicon or boron
which are gaseous or liquid at the normal temperature of the air and at atmospheric
or lower pressure, or which may be liquefied, dissolved, or converted into gas, vapor or
smoke, and which are at the same time capable of being decomposed by heat, or
electricity, or both, with or without the aid of chemical agency (double decomposition)in
Buch manner that silicon or boron separates out in graphitoidal or crystalline form.
Compounds which, amongst others, have proved advantageous for the purpose of my
invention are silicon-tetramethyl, silicon-tetraethyl, silicon-propyl, silicon-phenyl,
rhodanide of silicon, silicinretted nitrogen, silicon-pyridine, and the analogous boric
compounds.
In respect to such compounds of silicon or boron as consist in gases, vapors or
liquids, or which can be liquefied or volatilized by heat, the process of producing the
coatings is alike to the known process of making coatings of carbon with application
of hydrogen compounds of carbon. If the silicon or boron compounds are solid, they
may be dissolved in a suitable liquid, for instance rhodanide of silicon in a solution of
sulphocyanic acid in benzol, the filaments being dipped into the silicic or boric solution
and dried, and the adhering substance being decomposed by glowing through the
medium of electricity, while the filaments are contained in a vessel evacuated of air or
filled with a chemically indifferent gas. Or the walls of the decomposing vessel are
covered with the substance, the filaments are brought into the same and glowed
subsequent to the evacuation of the vessel. In this case the substance evaporates or
is converted into smoke by the heat radiating from the filament and is decomposed as
it comes in contact with the latter. As an example of substances which furnish the
coating during incandescence by double decomposition, tetrachloride of silicon and
benzol may be mentioned.
The coatings may, however, also consist in a mixture or compound of silicon and
boron, and whether composed of one or of both substances, carbon may be contained
therein. Moreover, compounds of silicon or boron with metals may originate in case
metallic filaments are covered with the coating of silicon or boron, as for instance in
the treatment of iron filaments with tetrachloride of silicon. The different means for
producing decomposition of the silicic or boric compounds, viz. glowing by heat or
electricity, electrolysis and chemical energy, may be employed either singly or in
combination with each other, as may be found most advantageous in any special case.
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 :
"
The process of covering carbon and metallic filaments for electric incandescent
lamps with an electrically-conductive coating which is but little or not at all attacked
by oxygen and oxydizing gases, this process consisting in bringing the filaments,
within a vessel evacuated of air or filled with chemically indifferent gases, in contact
with a compound of silicon or boron capable of being decomposed so that silicon or
boron separates out in graphitoidal or crystalline form, and exposing the filaments to
the action of heat, or of an electric current, or both, with or without the aid of a
chemical decomposing medium.
Dated this Twenty-third day of September 1890.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.