Improvements in Electrodes for Arc Lamps.
Year: 1894

page_text: Date of Application, 27th Feb., 1894-Accepted, 7th Apr., 1894
COMPLETE SPECIFICATION.
Improvements in Electrodes for Arc Lamps.
I, EDGAR OLCOTT CLARK, a citizen of the United States of America, residing
at 537 West 152nd Street New York City, in the County and State of New York,
Manufacturer, 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 relates to electrodes for are lamps provided with protective
coverings, and has for its objects to prolong the life of the electrodes and prevent
useless dissipation of the electrodes or their coatings.
In the embodiment of this invention, hereinafter described and illustrated in the
drawing accompanying this Specification, the carbon electrodes are coated as
usual with a film or covering of copper, and after the electrode has thus been
covered, another coating of a metal, differing in nature from copper, is applied
mechanically or by chemical or electrical deposition upon the copper_coating, so
as to cover the same. Zinc and nickel have in practice produced excellent results
when used for this outer coating, and either one may be used as desired, as well as
other metals differing in nature from copper. An electrode covered with this
plurality of metallic coatings has a much longer life, and is in every way more
satisfactory than the copper coated electrode or the plain and uncoated electrode,
while it is very much cheaper to manufacture and more satisfactory than the other
forms of coated electrodes that have been heretofore used. The carbon of the
electrode is protected by this plurality of metal coatings so that it does not waste
or flake away, or dissipate, or come to a sharp point in burning, but it is gradually
and uniformly consumed, and the consumption of its material takes place only at
and immediately about the extremities of the electrodes. The electrodes when in
use maintain about the same degree of bluntness throughout their consumption, as
when the operation is commenced. The metal coatings are gradually dissipated
in close proximity to the arc and do not melt or run off, or leave the carbon
exposed, or form a shell extending over the consumed ends of the electrodes.
In the accompanying drawings,
Figure 1 is an elevation showing portions of the two electrodes of an arc lamp
with parts of the coatings broken away, and illustrates an embodiment of this
invention; and
Figure 2 is a transverse section on an enlarged scale cut through one of the
electrodes.
The carbon portion of the electrode a is shown immediately covered and
protected by a coating of copper, and this coating of copper imparts to the
electrode the high conductivity desired. The copper coated electrode is then
covered with a coating of a metal differing in nature from copper, such as nickel
or zinc, and this latter coating covers the copper coating and extends from end to
end of the electrode, or to such point near the arc-forming end of the electrode as
may be desired. The electrodes are preferably slightly tapered at their arc-
forming points as shown, and in practical use, when covered with the coatings, as
described in this Specification, maintain practically the same degree of taper at
the ends throughout the entire consumption of the electrodes as that shown in the
drawings as the original shape of the arc-forming ends.

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 for arc lamps provided with two coatings of different metals,
substantially as set forth.
2. An electrode for arc lamps provided with an inner coating of copper and an
external coating of a metal differing in nature from copper, substantially as
.Bet forth.
3. An electrode for arc lamps provided with a plurality of metal coatings of
different natures, substantially as set forth.
4. An electrode for arc lamps provided with a coating of copper and an external
coating of nickel or zinc, substantially as set forth.
5. An electrode for arc lamps comprising a carbon portion or stick, a coating
or covering of copper applied directly to or upon the surface of the carbon
substantially throughout its length and a coating of metal of a nature different
than copper applied directly to or upon the copper coating substantially throughout
the length of the electrode, as and for the purpose set forth.
Dated the Sixteenth day of February A.D. 1894.