Improvements in Electric Resistances, and in the Manufacture thereof.
Year: 1895

page_text: Date of Application, 24th June, 1895-Accepted, 27th July, 1895
COMPLETE SPECIFICATION.
Improvements in Electric Resistances, and in the Manufacture
thereof.
We, HEINRICH JULIUS FERDINAND VOIGT and JACOB ADOLF HAEFFNER
both of the Electrical Works, Bockenheim near Frankfort-on-the-Main in the
Empire of Germany, Electrical Engineers, 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 :-
This invention has for its object the manufacture of electric resistances formed of
a metallic coating applied to porcelain, glass, talc, earthenware, enamel or other
suitable insulating material. This metallic coating contains metal in a very finely.
divided condition like painters' gold or solid gold or in a thin coherent layer burnt
on the insulating substance as is done with metallic lustres or enamel colours in
porcelain manufacture.
The metallic coating may be produced in several different ways, namely,
a. The metallic coating may be directly conveyed as metal on to the insulating
material, as is the case in painters' gold or solid gold.
b. The metallic coating may be applied in the form of a solution, for instance by
painting it on the insulating bodies in the same way as ordinary liquid gold or
metalliferous colours or as the usual metallic lustres or enamel colours in porcelain
manufacture and then separating the metallic substance by firing, when it is
obtained as a continuous band, strip or the like.
By liquid gold, metalliferous colours metallic lustres and enamel colours in this
sense are understood the homogeneous solution of organic metals or compounds of
precious metals, such for instance as sulphide of gold combined with balsam of
sulphur or mixtures of the same inorganic solvents such as nitrobenzole with or
without the assistance of essential oils (oil of lavender, anise, cloves and rosemary).
The solutions may contain, compounds of bismuth, boric or phosphoric acid as
solvents and lavender oil as medium. In this sense also in addition to gold, silver
and platinum the following must be regarded as precious metals, namely, the
elements of the platinum group, palladium, rhodium, ruthenium, osmium and
iridium. Aluminium may also be employed.
c. The thin metallic coating may be precipitated from solutions as a coherent
metallic mass in a similar manner to the manufacture of silvered mirrors, the
metallic covering being fixed on the insulating body by means of firing.
d. Finally the thin metallic covering may be made by decomposition from nickel
tetra carbon oxide Ni (CO) or from like metallic carbon oxides.
By the process hereinbefore described, the resisting layer which is heated by the
passage of the current is applied in so thin a form to the insulating substance that
it can easily follow all the variations of expansion of the same without causing by
its own expansion the insulating layer to become cracked or burst.
For the purpose of conducting the electric current to or from the resistances,
either larger accumulations of the resisting substance are formed, or special metal
parts are arranged at the points in question.
In order to obtain an even section of the metallic layers produced in the
methods described in paragraphs a to d, the metallic layers may be strengthened
by electrolytic or galvanic deposits, and then these supplementary deposits be
burnt on

page_text: The metallic coatings formed in the manner hereinbefore described may, in
addition to their properties as ordinary electric resistances, be also utilized as
means for conveying heat for cooking, warming and igniting purposes and also as
switch resistances for lamps, meters, electromoters and also as safety devices
(melting fuses) for weak current installations for protection against strong
currents.
Having now particularly described and ascertained the nature of our said inven-
tion and in what manner the same is to be performed, we declare that what we
claim is-
1. Electric resistances consisting of a coating produced on glass, porcelain, talc,
enamel, earthenware or other suitable insulating material by a firing process either
as a coherent metallic sulphide, metallic oxide or metallic coating in the manner of
liquid gold, metalliferous colours, enamel colours, metallic lustres or painters'
gold or as a coherent metallic coating by separation or precipitation from solutions
in the manner of gilt or silvered mirror manufacture, substantially as hereinbefore
described.
2. In the manufacture of resistances such as described in Claim 1, the production
of the coherent metallic coating from nickel tetra carbon oxide (Ni (CO)) or other
like metallic carbon oxides substantially as herein before set forth.
3. In the manufacture of resistances such as described in Claims 1 and 2 the
production of an even cross section in the metallic coating by strengthening the
metallic layers obtained as described in Claims 1 and 2, by electrolytic or
galvanic deposits which may also be subsequently burnt on, substantially as
herein before set forth.
Dated this 22nd day of June 1895.
WM. P. THOMPSON & Co.,
Of 6, Lord Street, Liverpool, Agents for the Applicants.