Improved Method of Coating Metal Conductors with Glass.
Year: 1899

page_text: Date of Application, 10th Apr., 1899-Accepted, 8th July, 1899
[Communicated from abroad by ALLGEMEINE ELEKTRICITÄTS-GESELLSCHAFT, .of
Schiffbauerdamm 22, Berlin, Germany.]
11"
1
:
Improved Method of Coating Metal Conductors with Glass.
I, VICTOR ISIDORE FEENY, of 60, Queen Victoria Street, in the City and
County of London, Consulting Engineer and Chartered Patent Agent, do hereby
declare the nature of this invention and in what manner the same is to be per-
formed, to be. particularly described and ascertained in and by the following
statement:-
This invention relates to a process for the production of an impermeable and
adherent glass covering for iron wires, nickel wires and other similar metal
conductors, whereby the same are isolated and protected from external gases.
Hitherto expensive platinum wire has been used for conducting the electric
current through the bulbs employed in incandescent lighting, notwithstanding
that, for about five years, the Jenaer Glaswerk Schott & Gen. (Schott and Co's
glass works at Jena) have been supplying a kind of glass which in consequence
of its high co-efficient of expansion can be combined with iron and with nickel,
so as to form a durable substance. The employment of wires made of these
inexpensive metals must still, however, remain in abeyance, since, when melted
in glass, they are strongly oxidised, in consequence of the heat, and the resulting
combination remains permeable by gases along the oxide layer, whilst, at the
same time, the gases arising in consequence of the high temperature, upon the
oxidation of the iron containing carbon and other admixtures or impurities,
enter and are embedded in the surrounding layer of glass in the form of bubbles
and may materially affect the impermeability and insulation of the material.
As it does not seem possible to prevent the iron wires from being
oxidised when directly melted in the glass bulb, the idea readily suggests itself
to furnish these wires with a covering which excludes the air, but which will
readily melt with the glass of the bulb. For a covering of the kind, glass again
appears to be suitable material, and it has been suggested as a covering for a
non-oxidising metal, viz. platinum wire which, likewise, is intended for passing
through the side of the bulb. In such case it was thought (incorrectly) that
by heating in a vacuum the wire placed in a glass tube and suddenly admitting
atmospheric air, a combination is formed between the platinum wire and the
surrounding glass tube, which is impermeable to gases. This is not so.
" evacuating "of the glass tube surrounding the wire, and subsequent heating,
also, will not attain the object, because the extra-pressure of the atmosphere
lays the side of the glass tube with one or more longitudinal folds against the
wire, before the complete softening requisite for uniform contraction of the
tube, takes place.
The
The difficulties mentioned are overcome by the invention here set forth in
a novel and simple way, and a glass covering or coating produced which adheres
to the iron or nickel wire, and is completely impermeable by gas.
For this

page_text: purpose, the iron wire is inserted in a thin tube made of glass having the neces
sary high co-efficient of expansion and air expelled from the tube by the intro-
duction of a gas of some kind (illuminating gas, hydrogen gas, carbonic acid,
etc.) Thereupon the glass tube is smelted on to the wire core by means of the
ordinary blow-pipe flame.
Iron wires treated with glass by this process show no trace of bubbles in the
glass covering, are permanently impermeable by gases and can be heated as
long as may be desired without the iron core being oxidised.
Having now particularly described and ascertained the nature of my said in-
vention and in what manner the same is to be performed, I declare that what I
claim is:-
A process for the production of an impermeable and adherent glass covering
or coating for iron wire, nickel wire and the like, the distinguishing feature of
which is that, before the smelting on operation is effected, the air is expelled from
the glass tube into which the wire has been inserted by the introduction into the
tube of a gas of a suitable nature, substantially, as described.
Dated this Tenth day of April 1899.
For the Applicant,
GEDGE & FEENY,
Chartered Patent Agents, 60, Queen Victoria Street, London, E.C.