Improvements in Pencils or Electrodes for Electric Aro Lamps.
Year: 1891

page_text: Date of Application, 29th Sept., 1891-Accepted, 31st Oct., 1891
COMPLETE SPECIFICATION.
[Communicated from abroad by EDMUND TWEEDY, of Danbury, Connecticut,
United States of America, Manufacturer.]
Improvements in Pencils or Electrodes for Electric Aro Lamps.
I, HENRY HARRIS LAKE, of the firm of Haseltine, Lake and Co., Patent
Agents, 45 Southampton Buildings, in the County of Middlesex, 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 pencils or electrodes for arc lamps, and is an improve-
ment on the carbon and other pencils now in general use, the said improvements
being hereinafter described.
Pencils for arc lamps have been heretofore made of metal rods, tubes or holders
and various refractory non-conducting substances, but the main difficulty with such
pencils has been due to the fact that the slag or vitreous compound formed by their
fusion is non-conducting when cold, so that should the are become extinguished for
any reason for a sufficient time for the points to cool the lamp will not relight.
According to the present invention, this difficulty is avoided by associating with
a suitable form of metallic rod, tube or holder, any substance into the composition
of which chromium enters, either chemically or mechanically. Such a substance
when fused together with certain metals, such for example as copper or iron, yield
a slag or compound which, while a conductor of electricity even when cold is at the
same time very highly infusible.
As the refractory non-conducting substance many compounds of or containing
chromium may be used, such as common chrome iron ore, or ferrous chromate or
chromite of iron, but these substances should be very free from earthy matters, as
the presence of these in the pencils gives rise to volatile fumes and smoke.
The pencils may be made up in many ways. A tube of iron may be packed with
ferrous chromate, or the latter may be moulded around an iron wire. In some
instances the refractory substance is packed into a tube or cylinder of wire gauze.
To increase the illuminating power of the pencils other substances may be
combined with the chromate, for example, about five per cent. of hydrate of sodium
or any of the sodium or potassium salts.
In lieu of using as the refractory material one made up entirely of a non-
conductor, improved results will be obtained by the use of a compound of conducting
carbon and a substance containing chromium, as by this means a superior light is
obtained, the pencil rendered more durable and which, particularly after extin-
guishment of the arc offers a lower resistance and relights more readily. The best
results are obtained by the use with a suitable holder, of a mixture of ten per cent.
of plumbago and 90 per cent. of pulverized chrome iron ore or similar substance.
Pencils made in the manner described consume very slowly and are of great
commercial value, but their resistance being somewhat higher than ordinary
carbons they may not be successfully used in the lamps which are adapted for the
ordinary carbons without some change in the construction of such lamps. To avoid
this a composite and a carbon pencil may be used together. The positive pencil
may be one of the composite pencils herein described, and the negative an
ordinary carbon pencil, or conversely, but in either case the rate of combustion is
rendered much slower than when two pencils of carbon are used, as exceptionally
good light obtained and a saving of expense effected.

page_text: Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed as communicated to me by
my foreign correspondent I declare that what I claim is :-
First. A pencil for arc lamps, composed of a metal associated with a refractory
substance containing chromium.
Second. A pencil for arc lamps, composed of a metal rod, tube or holder filled
or carrying a substance containing chromium with or without an illuminant such as
hydrate of sodium.
Third. A pencil for arc lamps, composed of a tube or cylinder of woven wire or
ganze filled with a refractory substance containing chromium and carbon.
Fourth. The employment in an arc lamp in combination with a composite pencil
such as herein described of a pencil of carbon, as set forth.
Dated this 20th day of September 1891.
TOOK TO TO CO
TAAR CO muna
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, Agents for the Applicant.