Improvements in the Manufacture of Wires for Incandescent Lamps.
Year: 1891

page_text: The decision of the Comptroller-General, of the 6th day of August 1895, allowed,
under Section 18 of the Patents, &c. Act, 1883, an Amendment of this
Specification.
PROVISIONAL DILUIFICATION
Improvements in the Manufacture of Wires for Incandescent Lamps.
I, RUDOLF LANGHANS of 12-14 Schillingstrasse Berlin in the Kingdom of
Prussia and Empire of Germany Electrician do hereby declare the nature of this
invention to be as follows:-
The object of the present invention is to reduce the cost of the conducting wire
which are sealed into the glass bulbs of incandescent lamps and at the same time
to facilitate the attaching the said wires to the filaments. These wires must on
heating and cooling expand and contract equally with the glass surrounding them
and they must be capable of making an air tight joint with the glass.
"
Of all the metals hitherto employed for these wires platinum is the only one
which completely fulfils the above conditions since its coefficient of (thermal)
expansion up to 100 degrees Centigrade is 000008842, at 300° C. 000009183
for 1° C. whereas the coefficient of expansion of the glass employed for the lamps
is 000008710 and 00001070 at the above temperatures. In addition the glass is
capable of adhering closely to the platinum.
According to my invention the baser metals such as iron or nickel or alloys of
iron and nickel with antimony or other metals or alloys capable of being welded to
platinum are utilised in the manufacture of wires possessing a coefficient of
expansion approximately equal to that of the glass employed for the lamps these
baser metals or alloys being covered with platinum or other equivalent metal as
hereinafter described.
Iron having a coefficient of expansion of 00001182 and antimony having a
coefficient of expansion of 00001083 or nickel with a coefficient of expansion
of 00001286 may be employed. Antimony could not be employed alone
owing to its low melting point and its tendency to break. Owing however
to the fact that the coefficient of expansion of an alloy is the mean of the
coefficients of the elementary metals composing it, the antimony becomes of value
for lowering the coefficients of expansion of iron and nickel and approximating
them to that of glass and platinum; in such alloys however the amount of nickel
or. iron must considerably exceed that of the antimony in order to produce a
sufficiently strong material. Other metals may be employed for lowering the
coefficient of expansion but are too expensive in practice. Nickel and iron and
their alloys with comparatively little antimony have, however, shewn themselves to
be suitable for the object in view.
These metals are provided with a covering of platinum by proceeding as follows.
A strong carefully cleaned wire of iron or nickel or of an alloy thereof with
antimony or a wire of any other metal or alloy capable of being welded to
platinum is firmly pressed into a platinum tube having thin sides and the compound

page_text: wire thus obtained is put through a draw bench and drawn down to the required
thickness.
Before or after or in the intervals between the drawing the wire is introduced
into a vessel deprived of air or filled with nitrogen, or a reducing medium such as
hydrogen or a light hydrocarbon and highly heated to about white heat by an
electric current. The core of the wire expanding in this heating process somewhat
more than the platinum tube, is pressed against and welded to the latter.
thus prepared may be sealed into the glass employed for lamps, in a thoroughly
airtight and durable manner and effect a saving of 70 per cent. and upwards of
platinum.
Wires
For the purpose of attaching the filament to these wires the end of the wire
being cut to the required length is immersed in an acid (for instance sulphuric acid
mixed with a small percentage of nitric acid) which does not attack platinum, but
dissolves the underlying metal or core. By this means the immersed ends of the
wire are hollowed out, the platinum skin remaining in the form of a tube, into
which the ends of the filament may be inserted. A subsequent compression of the
tube and cementing of the filament completes the joint. The removal of the end
of the wire core may also be performed by means of a galvanic process.
Doted this 4th day of November 1801
J. H. JOHNSON & Co.,
47. Lincoln's Inn Fields, London, W.C., Agents.
Improvements in the Manufacture of Wires for Incandescent Lamps.
I, RUDOLF LANGHANS of 12-14 Schillingstrasse Berlin in the Kingdom of
Prussia and Empire of 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 :-
The object of the present invention is to reduce the cost of the conducting wires
which are sealed into the glass bulbs of incandescent electric lamps. These
wires must on heating and cooling expand and contract equally or practically
equally with the glass surrounding them and they must be capable of making an
air-tight joint with the glass.
Of all the metals hitherto employed for these wires platinum is the only one
which completely fulfils the above conditions, since its co-efficient of thermal
expansion up to 100 degrees Centigrade is 000008842 at 300 degrees C. 000009183
for 1 degree C., whereas the coefficient of expansion of the glass employed for the
lamps is 000008710 and 000010700 at the above temperatures.
In addition the
glass is capable of adhering closely to the platinum.
•
According to my invention iron or nickel or alloys of iron and nickel or of both
or either of them with antimony are utilized in the manufacture of wires possessing
a coefficient of expansion approximately equal to that of the glass employed for
the lamps these baser metals or alloys being covered with platinum.
•
Iron having a coefficient of expansion of 00001182 and antimony having a
coefficient of expansion of 00001083, or nickel with a coefficient of expansion
of 00001286 may be employed. Antimony can not be employed alone
owing to its low melting point and its tendency to break. Owing, however,
to the fact that the coefficient of expansion of an alloy is the mean of
the coefficients of the metals composing it, the antimony becomes of value for
lowering the coefficients of expansion of iron and nickel and approximating them
to that of glass and platinum. In such alloys, however, the amount of nickel or
iron must considerably exceed that of the antimony in order to produce a sufficiently
strong material say from 1 to 5 per cent. of the alloy may be antimony.

page_text: A
These metals are, to produce the wire according to my invention, provided with
a covering of platinum which may be effected by proceeding as follows.
carefully cleaned rod or wire of iron or nickel or of an alloy of both or of an alloy
of either or both with antimony is firmly pressed into a platinum tube and the
compound wire thus obtained is put through a draw bench and drawn down to
the required thickness.
Wires thus prepared may be sealed into the glass employed for lamps in a
thoroughly air-tight and durable manner and by this means I can effect a very
considerable saving of platinum.
The filament can be attached to these wires in any well known or convenient
manner.
The hereinbefore given coefficients of expansion are taken from Matthieson's
tables.
In the expression iron herein and in the claims I include steel but as iron can
much more readily be manipulated in the manufacture I of course use iron in
preference to steel and under the expression platinum herein and in the claims I
include the platinum metals such as iridium palladium and the like but platinum
being more generally available I have specified that particularly in describing
my invention.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed I declare that what I
claim is
1. For use in incandescent electric lamps, in-which-the leading-in wires or con-
ductors consist having a coefficient of expansion approximately equal to that of glass
and consisting of a core of iron or nickel, or of alloy of iron and nickel, or of iron-or
nickel or both alloyed with antimony and coated or covered with platinum.
2. For use in incandescent electric lamps, in which the leading-in wires or con-
ductors consist consisting of a core of iron or nickel, or of alloy of iron and nickel,
or of iron or nickel or both alloyed with antimony and coated or covered with
platinum by inserting the core into the in a platinum tube and drawing down the
tube and core together.
Dated this 01.
1000