Electrodes for Arc-lamps.
Year: 1899

page_text: Date of Application, 30th Oct., 1899-Accepted, 6th Jan., 1900
Electrodes for Arc-lamps.
HUGO BREMER, of Neheim on the Ruhr, Wesphalia, Germany, 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 refers to electrodes for arc-lamps, consisting of a mixture of
pure carbon or carbon powder and metallic salts. The extra yield of light thus
obtained is not confined to the application of few materials, but on the contrary
a large number of metals, or salts of metals or metalloids, and more especially
the salts of earthy alkaline metals, will form vapors which are brought to a
state of brilliant incandescence by the heat generated by the combustion of the
carbon pencils.
The extra yield of light will increase with the percentage of the addition of
above mentioned substances, while the tendency to flickering of the luminous
arc will be reduced by the application of a somewhat high percentage. Dis-
turbing influences, standing in the way of the application of metallic salts, are
constituted, firstly, by the scorified secretions formed by the metallic salts and
secondly, by the circumstance that if the percentage of metallic salts is ex-
cessively increased, the percentage of pure carbon being reduced accordingly,
the heating effect produced by the combustion of the carbon is greatly reduced,
so that the metallic vapors are not completely brought to incandescence.
The scorified secretions, however, are chiefly formed at the margin of the
carbon pencils, in those parts where they are not vaporised by the heat of the
small intensely luminous points from which the luminous arc issues. They will,
sooner or later, form an incombustible coating which will eventually smother
the luminous arc.
Now the principle on which the present invention is based consists essentially
in causing the otherwise solid scoria which is formed by the luminous metallic
vapors under the influence of the electric arc, to be softened or liquefied by a
so-called "flux thus causing them to drip off periodically. Such fluxes are
formed, for instance, by boron and fluorine added in a pulverized or liquid
state. If a sufficient quantity of such substances is suitably added to the re-
spective salts of metals or metalloids, in a proportion of not less than 1% of the
total weight, or more according to the height of percentage of the addition of
luminous substances, it will be found that the secretions, instead of forming a
hard granular scoria will assume a soft liquid character, and can be still further
influenced, and caused to drip off with as little disadvantage as possible, by
anyone of the arrangements to be described hereinafter.
In preparing the electrodes care should be taken to prevent that the carbon
pencils (which under ordinary circumstances are generally calculated to generate
the highest possible degree of heat during their combustion), are not heated to

page_text: such a degree as to cause the fluxes, which in most instances will be vaporised
at a comparatively inferior temperature, to be expelled prematurely from the
carbon pencil.
Secondarily, an electrode thus impregnated with metallic salts etc., may be
treated so as to cause the light to assume any desired tint. Thus for instance
the inventor has found that a yellowish tint, is best imparted to the light of
the luminous are by adding to the composition some fluorine, bromine or iodine.
Fluorine in particular, unless admixed to the carbon compound in conjunction
with more than twice its quantity of calcium or calcic salts, will yield a light
of a pleasant yellowish tint which, if desired, may be made of a more whitish
tinge by adding some magnesia.
The means adopted in order to remove the drops of liquefied scoria formed on
such an electrode, without interfering with the light, will be seen from the figures
shown in the annexed drawing.
On the ordinary round carbon pencils, (Fig. 2), the scoria will collect in the
form of little clots at the lower extremity and, the latter being tapered, these
clots will frequently glide down towards the incandescent point, as shown in
Fig. 3, when they will interfere considerably with the light, both while, it is
burning and at the time of re-lighting.
This evil is remedied by providing the carbon pencil with ribs. In this case
the drops of scoria (s) will have a tendency to collect at the ribs, as shown in
Fig. 4, and will then drip off straight downwards, so that the luminous are will
continue to burn uninterruptedly in the centre of the pencil end.
If desired, notches or grooves a a¹ placed transversely to these ribs, may
also be made on the carbon pencils (see Figs. 4 & 5).
It will be seen that if the carbon pencil is further consumed, as shown in
Fig. 5, the rib, together with the drops of scoria adhering to it, must drop off
with absolute certainty. If only two such ribs are provided these will not in
any way impair the emission of light, because these ribs may be placed in the
same plane with the conducting rods of the lower pencil holders, and as on the
whole, the formation of the long arc is much impeded by a great area of emission.
Consequently, any carbon pencil shaped so as to have sharp edges, (Figs. 1-1),
if impregnated with a high percentage of salts of metals or metalloids will afford
these advantages, because even with an inferior strength of the electric current
an area free from any scoria will always remain in the centre, thus ensuring
steady burning, while the scoria will always accumulate at the sharp edges and
drip off from these at intervals.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is
1) An electrode for arc-lamps having an addition of 10-70% of such metallic
salts, metal powder or salts of metalloids the vapours of which are brought to
incandescense by the carbon, the addition of 1 or more percentage of a so called
flux for the purpose as described and set forth.
2) An electrode for arc-lamps having an addition of 10-70% of such metallic
salts, metal powder or salts of metalloids the vapours of which are brought to
incandescense by the carbon and having further on contained a so called flux
in such proportions that during the combustion said flux is not expelled prema-
turely from the electrode for the purpose as described and set forth.
3) An electrode for arc-lamps having an addition of 10-70% of such metallic
salts, metal powder or salts of metalloids the vapours of which are brought to
incandescense by the carbon the addition of 1 or more percentage of a so called
flux and a further addition of fluorine, bromine or iodine in a quantity of about
25% of the metallic salts for the purpose as described and set forth."
4) An electrode for arc-lamps having an addition of 10-70% of such metallic
salts, metal powder or salts of metalloids the vapours of which are brought to

page_text: incandescense by the carbon with addition of 1 or more percentage of a so called
flux being provided with ribs, notches or grooves so as to receive a sharply edged
section for the purpose as described and shown in the drawings.
HUGO
BREMER.
By A. Daumas,
Agent for Applicant.