Improvements in Electrodes for Arc Lamps.
Year: 1893

page_text: Date of Application, 23rd May, 1893-Accepted, 8th July, 1893
COMPLETE SPECIFICATION.
Improvements in Electrodes for Arc Lamps.
I, ALBERT COOPER SEIBOLD, of 36 Fifteenth Avenue, Mount Vernon, in the
County of Westchester, and State of New York, in the United States of America,
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 :-
My invention has reference to means for prolonging the life of the carbon
electrodes employed in arc lamps, and also for effecting a saving of labour involved
in the trimming of the same, it relating especially to the electrodes provided with
protective coverings consisting of a combination of metallic coatings successively
electro deposited upon the carbons to prevent useless dissipation of the same.
I have found by experiement that the life of such carbons may be materially
prolonged by combining with the metallic coatings, a coating of refractory material
located intermediate of the two metallic coatings.
My invention therefore consists essentially in an electrode or carbon provided
with an inner metallic coating, an outer metallic coating and an intermediate non-
metallic coating of refractory material, such as graphite (plumbago).
I will now proceed to describe the said invention with reference to the annexed
drawing in which :
Figure 1 represents an elevation of the two electrodes or carbons of an arc lamp
embodying my invention, parts of the carbons and coatings being broken away.
Figure 2 is a transverse section in the plane X X Figure 1.
In carrying my invention into effect a thin coating of copper is first formed about
the carbon either by dipping or otherwise mechanically applying the metal, or by
electro deposition in the well known manner. The copper coating is made about
the same thickness as that found on the carbons of commerce. The second coating
consists of a non-metallic refractory material, by preference commercial graphite.
It is applied preferably by dipping the electrode or carbon in a wash or bath of
graphite. In place of graphite ordinary gas carbon may be used, but graphite
being the more refractory is more suitable for the purpose. The third coating,
preferably consisting of a metal differing in nature from the copper, such for
instance as nickel, is applied either mechanically or by electro deposition, and is
made about the same in thickness as the copper coating. The coating of graphite
is somewhat heavier than the metallic coating, but of course the thickness of either
of the coatings may be varied without departure from my invention.
As before stated I have determined by practical experiment that the intermediate
coating of refractory material is an important factor in prolonging the life of the
carbons when combined with the metal coatings described. The good results
obtained by this combination I attribute to the protection afforded to the copper
coating from the air, so that oxidation and consequent volatilization of the metal
is greatly retarded and can take place only directly at the extreme ends or points
of the electrodes, and consequently dissipation of the carbon is retarded by its
exclusion from the air. Again the refractory material being protected from the air
by the outer nickel coating remains intact and is disintegrated or consumed only in
close proximity to the arc.
I have also found by experiment that there is no tendency for the protective
coating to form a shell about or envelop the arc and then run off in balls, but that
it is gradually dissipated in close proximity to the arc ;-nor is it liable to melt and
run off and leave the carbon exposed.

page_text: 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. An electrode or carbon provided with two metallic coatings and an inter-
mediate coating of a non-metallic refractory material, substantially as described.
2. An electrode or carbon provided with two coatings of different metals and an
intermediate coating of graphite, substantially as described.
3. An electrode or carbon provided with an inner coating of copper, a graphite
coating upon said copper and an external coating of nickel, substantially as
described.
4. An electrode or carbon provided with a plurality of metal castings and a
non-metallic refractory coating separating the metallic coatings, substantially as
described.
5. An electrode or carbon provided with a coating of copper, a graphite
coating upon said copper, and an external coating of a different metal, substantially
as described.
Dated May 23rd 1893.
A. C. SEIBOLD,
By Harris & Mills,
23, Southampton Buildings, London, W.C., Agents.