Improvements in and connected with Carbons for Electric Arc Lamps.
Year: 1892

page_text: Complete Specification Left, 5th Sept., 1893-Accepted, 11th Nov., 1893
PROVISIONAL SPECIFICATION.
Improvements in and connected with Carbons for Electric Arc Lamps.
I, CHARLES WALTER HAZELTINE, of University Club, City of St. Louis,
State of Missouri, United States of America, Electrician, do hereby declare the
nature of this invention to be as follows:-
My invention relates to improvements in and connected with carbons for electric
arc lamps by which a substantial saving is effected.
The primary object of my invention is to effect a substantial saving of carbon in
the electrodes of arc lamps.
Various devices independent of the electrodes have been recently proposed for
prolonging the life of carbons, or electrodes, in arc lamps, to such an extent as to
double or materially prolong the life of the carbons and enable a single arc lamp,
if necessary or desirable, to burn all night, or to perform the functions of a double
arc lamp, and to effect a material saving in carbon and in labour of trimming.
My present invention or discovery and the means I have devised for carrying it
into effect, dispenses with the use of a device or means which attains the result
and is independent of the carbons, and accomplishes the same result, namely: a
saving in labour in trimming and a substantial saving of carbon, or the doubling or
materially prolonging of the life of the carbons in electric arc lamps so as to
enable a single arc lamp, if necessary or desirable, to burn all night, and thus
accomplish if necessary or desirable, the results attained by a double arc lamp.
By a series of experiments I have ascertained that by suitably coating the
electrodes or carbons of an electric arc lamp, a great saving of labor can be
effected and the carbons may be made to burn substantially twice as long as or
much longer than when uncoated, or coated in the ways already known in the art.
To best carry out the objects of my invention, the carbons are first given a
coating of copper which should be very thin and about the same as the ordinary
copper-coating with which the carbons are now often provided. After coating the
carbons with copper, a coating of zinc, preferably somewhat heavier, is put over
the copper.
The electrodes may be coated in any suitable manner, either by mechanically
coating them or by electro-plating them but it is preferable to electro-plate the
coatings upon the carbons. I have found a protective covering for carbons to
answer well the purpose of doubling the life of the carbons when made as follows:
A ten ampere current of a plating dynamo is used for fifteen minutes for the
copper coating, and twenty minutes for the zinc coating, sulphate of copper and
sulphate of zinc being used respectively as the electrolytes. The copper coating
is of about the same thickness as the ordinary copper coating now used on carbons.
The zinc coating as would be indicated by the time given is somewhat thicker.
The same thickness of coatings may be plated upon the carbons by varying the
solution the current or the time. I do not wish to limit my invention to any of
these details. The thickness of the coating or coatings may be varied without
departing from the invention.

page_text: I am unable to state definitely the reason or theory on which my present
invention depends but from experiments made, I am of the opinion that the beat
developed by the arc turns the zinc into oxide of zinc (zinc white) which seeins to
permeate the copper coating closing up the pores thereof and preventing access of
cold air to the heated part of the carbon thus preventing oxidation and wasting at
the points. If an ordinary copper-coated carbon be examined under a magnifying
glass, it will be found to be very thinly coated with copper and to cover the carbon
here and there only leaving large pores or interstices in the copper covering. In
other words the carbon is not completely covered with copper but is only partially
protected. If the coating of copper be made thicker so as to completely cover and
protect the carbon then the functions of the carbon will be interfered with in the
manner to be hereinafter set forth.
Another theory on which my invention may depend and perhaps the correct one
is that the zinc oxide referred to covers the copper plating and protects the copper
plating rather than the carbon itself from the air and thus prevents the oxidation
of such plating and in this way prevents the copper from burning off above the arc.
That is to say the zinc coating holds the copper on the carbon to a point
substantially even with the arc. The oxide of zinc although infusible is light and
fluffy and is readily dissipated either forming a slight deposit in the globe or being
carried off in the atmosphere; zinc being more fusible than copper is well adapted
for a coating for the purpose set forth.
If a heavy coating of copper or zinc aloue should be applied to a carbon such
coating will not eat away from the arc but will in time envelope the arc and will
then run off in balls and be liable to break the globe of the lamp. The heated carbon
near the end seems to disintegrate a single coating of zinc or copper, no matter
how heavy and the air penetrates and oxidizes the carbons inside of the shell
formed by the coating at the ends of the carbons. There seems to be a limit to
which an arc lamp carbon can be successfully coated with any single metal this
limit being that the covering shall not be so thick as to envelope or interfere with
the arc or run off in balls or flame and give rise to dense fumes and smoke and
injuriously affect the light. When a single coating of copper is applied to a carbon
so as to keep out of the way of the arc but about one hour is added to the
life of the carbons. While with the copper-zinc coating an ordinary copper-coated
eight-hour carbon will burn about fourteen and one-half hours giving an all night
run, and making a single arc lamp equivalent to the double arc lamp as now used.
I have experimented with various coatings, but have got the best results with the
zinc-copper coatings.
I have found the following coatings for carbons to give fairly good results,
namely: iron and zine; zinc and iron; iron and copper; iron, copper and zinc ;
zinc iron and copper; brass and zinc; copper and metallic paint; copper, zinc
and mercury; copper and fire clay; copper and adamant plaster. The substance
first mentioned in each case is the one which is placed directly upon the carbon
and the others are used in the order mentioned. A coating of brass electro-
deposited upon the carbons covered by a coating of zinc electro-plated thereon gives
the next best result to copper and zinc. The objection to a brass-zinc coating is
that it is difficult to electro-plate with brass. The composition of the brass coating
cannot be accurately determined beforehand owing to the varying behaviour in
electro-plating brass under apparently unvarying conditions.
The zinc oxide, which forms by the heat of the arc when a zinc coating is
employed over a copper coating, as referred to above, is highly infusible, and when
the pores of the copper coating are covered with it the coatings remain on the
carbons substantially even with the incandescent ends of the same so that the
carbons burn with blunt points and a large crater. This coating does not hang
down into the arc but wastes away at the incandescent ends of the carbons so that
the burning of the same is unobstructed. A covering composed of copper electro-
deposited upon the carbon and protected by a coating of cadmium electro-deposited
upon the copper gives, good results, and is the next best to the zinc-brass coating,

page_text: it giving a twelve-hour run and keeping out of the way of the arc and not
interfering with the lamp and the light. Cadmium, however, being more volatile
than zinc, does not remain upon the electrodes as effectually as zinc.
While I have described my invention as applied to carbon I do not wish to limit
it to the coating of carbons as other substances may be used for electrodes.
Neither do 1 wish to limit my invention to coating the electrodes or carbons with
zinc and copper specificially, except where such substances shall hereafter be
specified in my claims, for other protective coverings, and combination of coatings,
may be made to carry out the purposes of my invention whether such consist of a
single coating or substance or of several coatings or substances. I am not aware
that carbons or electrodes have ever previously been coated in such a way as to
effect a material saving in carbon or to make an ordinary single arc lamp
provided with carbons of the usual size, that is twelve inches long and half inch in
diameter, perform the duty of a double arc lamp or, in other words, to double or
materially increase the life of the ordinary carbons in an electric are lamp without
interfering with the lamp or the light thereof.
Dated this 5th day of December 1892
CHARLES W. HAZELTINE,
Per J. G. L.
COMPLETE SPECIFICATION.
Improvements in and connected with Carbons for Electric Arc Lamps.
I, CHARLES WALTER HAZELTINE, of University Club, City of Saint Louis,
State of Missouri, 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 :-
The primary object of my invention is to effect a substantial saving in the carbons
of arc lamps.
The invention has also for its object the saving of labour in the trimming of arc
lamps.
Various devices have been recently proposed for prolonging the life of carbons
in arc lamps to such an extent as to double or materially prolong the life of the
carbons, and enable a single arc-lamp, if necessary or desirable, to burn all night,
or to perform the functions of a double arc-lamp and to effect a material saving in
carbon and in labour in trimming. In my Patent, No. 2,297 of 9th July 1891 I
have described a device for such purpose which accommodates itself to the shifting of
the arc, that being the first instance of such a device.
My present invention or discovery and the means I have devised for carrying it
into effect dispenses with the use of a device or means which is independent of the
carbons and accomplishes the same result-namely, a saving in labour in trimming,
and a substantial saving of carbon or the doubling of, or materially prolonging the
life of the carbons in electric arc lamps, so as to enable a single arc lamp, if
necessary or desirable, to burn all night, and thus accomplish, if necessary or
desirable, the results attained by a double arc lamp.
By a series of experiments, I have ascertained that by suitably coating the
carbons of an electric arc lamp a great saving of carbon can be effected and the
carbons may be made to burn substantially, twice as long as, or much longer than
when uncoated or coated in the ways already known in the art.
To best carry out the objects of my invention the carbons are first given a coating
of copper, which should be very thin and about the same as the ordinary copper
coating with which carbons are now usually provided. After coating the carbons
with copper a coating of zinc, preferably somewhat heavier, is put over the
copper.
In the accompanying drawings I have illustrated two carbons provided with the
best kind of protective covering so far devised by me.

page_text: In the drawings
Figure 1 is an elevation of two carbons provided with suitable coatings and
illustrating the zinc coating Z broken away on each carbon at some distance from
the are so as to show the copper coating C beneath the same.
Fig. 2 is a transverse section on an enlarged scale, taken on the plane of the
line 2, 2, of Fig. 1.
The carbons may be coated in any suitable manner either by mechanically
coating them or by electroplating them; but it is preferable to electroplate the
coatings upon the carbons. I have found a protective covering for carbons to
answer well the purpose of doubling the life of the carbons when made as follows:
A ten ampère current of a plating-dynamo is used for fifteen minutes for the copper
coating and for twenty minutes for the zinc coating, sulphate of copper and sulphate
of zinc being used as the electrolytes respectively. The copper coating is of about
the same thickness as the ordinary copper coating now used on carbons. The zinc
coating, as would be indicated by the time given, is somewhat thicker. The same
thickness of coatings may be plated upon the carbons by varying the solution, the
current, or the time.
I do not wish to limit my invention to these details. The
thickness of the coating or coatings may be varied without departing from my
invention.
I am unable to state definitely the reason or theory on which my present inven-
tion depends; but from the experiments made I am of the opinion that the heat
developed by the are turns the zine into oxide of zinc (zinc white,) which seems to
permeate the copper coating, closing up the pores thereof and preventing access of
air to the heated part of the carbon thus preventing oxidation and wasting at the
points. If an ordinary copper-coated carbon be examined under a magnifying glass
it will be found to be very thinly coated with copper and to cover the carbon here
and there only, leaving large pores or interstices in the copper covering. In other
words, the carbon is not completely covered with copper, but is only partially
protected. If the coating of copper be made thicker, so as to completely cover and
protect the carbon, then the functions of the carbon will be interfered with in the
imanner to be hereinafter set forth.
arc.
Another theory on which my invention may depend, and perhaps the correct
one, is that the zinc oxide referred to covers the copper plating and protects
the copper plating rather than the carbon itself from the air, and thus
prevents the oxidation of such plating, and in this way prevents the copper
from burning off above the arc-that is to say, the zinc coating holds the
copper on the carbon clear down to a point in immediate proximity to the
The oxide of zinc, although infusible, is light and fluffy and readily
dissipated, either forming a slight deposit in the globe or being carried off in the
atmosphere. Zine being more fusible than copper is well adapted for a coating for
the purpose set forth. If a heavy coating of copper or zinc alone should be applied
to a carbon, such coating will not eat away from the arc, but will in time envelop
the are and will then run off in balls and be liable to break the globe of the lamp.
The heated carbon near the end seems to disintegrate a single coating of zinc, or
copper, no matter how heavy, and the air penetrates and oxidizes the carbon inside
of the shell formed by the coating at the ends of the carbons. There seems to be a
limit to which an are lamp carbon can be successfully coated with any single metal,
this limit being that the covering shall not be so thick as to envelope or interfere
with the arc or run off in balls or give rise to dense fumes and smoke and injuriously
affect the light. When a single coating of copper is applied to a carbon, so as to
keep out of the way of the arc, but about one hour added to the life of the carbon,
while with the copper zinc coating an ordinary copper-coated eight hour carbon
will burn about fourteen and one half hours, giving an all night run and making a
single arc lamp practically equivalent to the double arc-lamp as now used. I have
experimented with various coatings, but have obtained the best results with the
zine copper coatings.
I have found the following coatings for carbons to give fairly good results,

page_text: ;
namely: iron and zinc; zine and iron; iron and copper; iron, copper, and zinc
zinc, iron, and copper; brass and zinc; copper and metallic paint; copper, zinc,
and mercury; copper and fireclay; copper and adamant plaster. The substance
first mentioned in each case is the one which is placed directly upon the carbon, and
the others are used in the order mentioned. A coating of brass electro-deposited
upon the carbons covered by a coating of zinc electro-plated thereon gives the next
best result to the copper and zinc. The objection to a brass-zinc coating is that it
is difficult to electroplate with brass. The composition of the brass-coating cannot
be accurately determined beforehand, owing to the varying behaviour in electro-
plating brass under apparently unvarying conditions. The zinc oxide which forms
by the heat of the arc when a zinc coating is employed over a copper coating, as
referred to above, is highly infusible, and when the pores of the copper coating are
covered with it the coatings remain on the carbons clear down to the incandescent
ends of the same, so that the carbons burn with blunt points and a large crater, the
same as is now the case when burned with the electrode shield applied thereto as
set forth in my Patent previously referred to. This coating does not hang down
into the arc, but wastes away at the incandescent ends of the carbons, so that the
burning of the same is unobstructed.
A covering composed of copper electro-deposited upon the carbon and protected
by a covering of cadmium electro deposited upon the copper gives good results and
is the next best to the zinc-brass coating, it giving a twelve hour run and keeping
out of the way of the arc and not interfering with the lamp and the light.
Cadmium, however, being more volatile than zinc, does not remain upon the carbon
as effectually as zinc.
While I have described my invention as applied to carbon, I do not wish to limit
it to the coating of carbons, as other substances may be used for the rods or pencils
of are lamps. Neither do I wish to limit my invention to coating the rods or
carbons with zinc and copper specifically, except where such substances are
specified in my claims, for other protective covering and combinations of coatings
may be made to carry out the purposes of my invention. I am not aware that
carbons or rods have ever previously been coated in such a way as to effect a
substantial saving or to make an ordinary single-arc lamp perform the duty of a
double arc lamp, or, in other words, to double or materially increase the life of the
ordinary carbons or rods in an electric arc lamp without interfering with the lamp
or the light thereof. By a single-arc lamp performing the duty of a double-arc
lamp I do not necessarily mean that a single-arc lamp must burn twice as long as
before or to the full length of time that a double-arc lamp will necessarily burn.
If, for instance, a ten or eleven hour run with carbons of ordinary size and now in
commercial use is required, this can only be obtained by employing a double-arc
lamp, wherein after one set of carbons is consumed another set is automatically put
in circuit to give the additional amount of time required. I include in the statement
above any material additional run that a double-arc lamp is usually required to
answer.
I am aware that Letters Patent of the United States No. 196,425 were granted
on October 23, 1877, to Charles F. Brush for covering carbons with various
substances which increase the conductivity of the carbons and incidentally only
prolong the life of the same; but this Patent points ont no such result as is
contemplated herein, nor could any such result be accomplished by said patented
invention as is herein set forth.
I am aware, also, of reissued Letters Patent No. 10,544, granted December 23,
1884, to Charles F. Brush, as a reissue of the last-mentioned Patent, and the same
statements just made apply with full force to what is disclosed in this reissue
Patent.
I am aware, also, of British Letters Patent No. 471, of 1878, granted to Gray,
wherein nickel or iron is electro-deposited on carbons to prevent useless burning
away of the carbons. The state of the art as to nickel and iron being used for
such a purpose is duly acknowledged in the reissued Letters Patent of Brush

page_text: alluded to above and in referring to Reynier's French Patent, hereinafter mentioned,
and describing nickel and iron, as well as platinum, palladium, iridium, gold, silver,
copper, cobalt, chromium, and manganese for such purpose. The substances
referred to will not, however, accomplish the purpose of my invention and will not
give as good results as the ordinary copper coating of the Brush Patent
referred to.
I have also become, aware since making my experiments and devising means for
carrying out the discovery herein set forth, of Carré's original French Patent,
No. 80,793, of 1867, and Patent of addition to the same, and also French Patent,
No. 109,895, of 1875 to Reynier, and two additions to the same granted in 1876
and 1877, all of which French Patents are referred to in the reissued Patent of
Brush specified above. In these French Patents the result accomplished by me
could not be attained, the main purpose of said French Patents being merely to
form a sheath, mold, or tube for the carbon in order to give it sufficient rigidity and
hold the particles thereof together. In none of these French Patents is suggested
the idea of effecting a material saving of carbon or the doubling or materially
increasing the life of the carbons without increasing their size or varying their
length, so as to make a single-arc lamp perform the duty of a double-arc lamp or
enable a double-arc lamp to run two nights and require trimming every other day
instead of every day, as is at present required in double-arc lamps without protectors,
and at the same time not interfere with the lamp and the light thereof.
I am aware, also, of United States Letters Patent issued to Atwood, No. 272,017,
of February 13, 1883, and British Patents No. 3,402 of 1881 to Mignon and
Ronart, No. 4805 of 876 to Wederman, No. 4,432 of 1877 to Rapieff, No. 783 of
1879 to Harding, and No. 277 of 1879 to Cohne. These Patents do not and cannot
accomplish any such result as is contemplated and actually attained by my invention.
In all of said Patents, except Rapieff and Cohne, the carbons are covered with
material of an insulating character; and Rapieff' coats his carbons, which are of
an angular shape, on one or several sides with metal for the purpose of increasing
the conductivity of the carbons. Cohne places his carbons in a zinc tub before
baking, and the zinc is caused to be disseminated through the carbon in the process
of manufacturing the same. Nearly all of said Patents have for their object to
produce a more intense and steadier light by causing the coating or material about
the electrodes to become incandescent. In my invention, on the other hand, the
carbons are preferably coated with a thin film of conducting material, and the
coating is of such a nature as to cause the carbons to burn with blunt points and
prevent their pencilling. My coating does not run off in balls and give rise to
dense fumes and smoke or injuriously affect the light and does not protrude beyond
the end of the electrode, but is dissipated by the heat of the arc, so as not to
interfere with the light thereof. I hereby disclaim all the aforementioned patented
devices and do not wish to be understood as claiming anything set forth in any of
said Patents, my invention securing results which none of the aforesaid inventions
can accomplish.
Having now particularly described and ascertained the nature of my inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :
1. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon provided with a composite metallic coating increasing its
conductivity and protecting it, substantially as and for the purpose described.
2. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon provided with a protective coating composed of a plurality
of metals, substantially as and for the purpose described.
3. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon provided with a metallic coating protected by a suitable
outer covering of different character carried by the carbon, substantially as and for
the purpose above described.

page_text: 4. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon having a protective covering composed of a plurality of
metallic coatings of different material, substantially as and for the purpose
described.
5. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon having an inner metallic coating protected by an outer
coating of different material, which outer coating is capable of being oxidised by
the heat of the arc, the oxide formed being dissipated by the heat of the arc at a
point substantially even with the arc, substantially as and for the purpose described.
6. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon provided with a plurality of metallic coatings of different
materials electro-deposited thereupon, substantially as and for the purpose
described.
7. The improvements in and connected with carbons for electric arc lamps,
consisting in an ordinary copper-coated carbon provided with a suitable additional
coating of different character, substantially as and for the purpose described.
8. The improvements in and connected with carbons for electric arc lamps,
consisting in a carbon provided with a coating of copper protected by a metallic
covering of different material, substantially as and for the purpose described.
9. The improvements in and connected with carbons for electric arc lamps,
consisting in a protective covering for the carbons made up of a coating of copper
and zinc, substantially as and for the purpose described.
10. The improvements in and connected with carbons for electric arc lamps, by
which the protective covering for the carbons consists of an inner coating of copper
and an outer coating of zinc, substantially as and for the purpose described.
11. The improvements in and connected with carbons for electric arc lamps, by
which the protective covering for the carbons consists of a coating of copper
electro-deposited upon the carbons and a second coating of zinc electro-deposited
upon such copper coating, substantially as and for the purpose described.
Dated this 5th day of Santambor IX4K
Dated this 5th d
Santambor LXYX
J. G. LORRAIN, Mem. Inst. E.E., Mem. Inst. M.E.,
Norfolk House, Norfolk Street, London, W.C.,
Chartered Patent Agent,
Per A. P. W.