Improvements in Electric Furnaces.
Year: 1897

page_text: Date of Application, 26th Nov., 1897--Accepted, 19th Feb., 1898
Improvements in Electric Furnaces.
I, CHARLES SCHENCK BRADLEY, of Avon, in the County of Livingston, and State
of New York, United States of America, Electrical Engineer, 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 relates to electric furnaces for the reduction or formation of re-
fractory materials. The object of the invention is to permit a continuous and
uninterrupted operation of the furnace and withdrawal of the product, and to
protect said product from the action of the air when at a high temperature. The
furnace is especially designed for employment in the manufacture of metallic
carbides. It comprises a receptacle for the charge to be operated upon in which is
inserted an electrode, means being provided for continuously moving the receptacle
with relation to the electrode so as to bring fresh portions of material under the
action of the electric current. The construction which I prefer to employ com-
prises a rotary wheel or annulus into which projects at one side an electrode or
pair of electrodes, and provided with means for preventing the material from
spilling and means for supplying fresh material to be acted upon by the current
and facilities for removing the product, the whole being so arranged that the
operation may be carried on in an uninterrupted manner, the furnace constantly
forming fresh additions to the product and permitting the latter to be removed
as frequently as may be necessary. The wheel is preferably turned by power
driven machinery and is provided with a hollow periphery to which is attached
over an arc covering the lower part of the wheel, a sectional receptacle forming
throughout said are a closed receptacle for the material to be operated upon; the
sections are arranged to be withdrawn or opened when they reach the discharge
end of the wheel arc. The material in the form of powder or granules is supplied
to the side of the wheel which contains the electrode or electrodes. The electric
arc or the limits of the space within which the electric action on the material takes
place are wholly within the mass of pulverized material, so that a wall of unchanged
or unconverted material will surround the product of the furnace, and the motion
of the wheel is in such direction as to surround the converted material by a body
of unconverted material and thus exclude air until the converted mass has become
sufficiently cool to permit its removal and further treatment for packing for
shipment or storage. In the formation of a carbide of calcium, for ex-
ample, an intimate mixture of ground lime and ground carbon is supplied to
that side of the wheel arc into which the current is introduced and is
fused, permitting the carbon and calcium to combine and forming a pool of liquid
carbide of calcium within the wheel rim, which pool is surrounded by a mass of
uncombined mixed carbon and lime which acts as an efficient heat insulator keep-
ing the walls of the receptacle comparatively cool; as the wheel turns, the pool is
withdrawn from the neighborhood of the electric are or region of electrical activity
and the liquid carbide cools and solidifies under a superincumbent and surrounding
mass of material which prevents access of air and thus prevents wasteful consump-
tion of carbon by combustion; thus a core of solid carbide of calcium is formed

page_text: within a granular or pulverized mass of material said core growing in length as
the receptacle recedes from the electrode until it emerges from the other end of the
wheel are, when the removable sections of the wheel rim may be taken off one at a
time permitting the pulverized material to fall away from the solid core of carbide
which may be broken off or otherwise removed periodically. Thus the formation
of carbide goes on continuously without necessary interruption for recharging or
removal of the product. I am aware that an electric furnace has been proposed
by M. Patin of Puleaux, France and also by Vincent of Philadelphia, Pa., in
which the pulverized material is fed into a stationary tube in which the electric
are is maintained, a removable platform being placed below the are to form a core of
carbide, but in this type of furnace the carbide is formed in short lengths which
are periodically discharged into a receptacle for cooling, after which the platform
is returned to permit another core of carbide to be formed. My apparatus differs
from this in the essential feature of permitting the formation of carbide to go on
without interruption, the finished cooled product being removed with convenience
as often as desired without a moment's interruption of the process of formation.
The invention will be more perfectly understood in connection with the accompany-
ing drawings forming part of this specification, in which :-
-
Figure 1 is a sectional view on a plane at right angles to the wheel axis; and
Figure 2 is a sectional view on a plane parallel to the wheel axis.
1 represents a wheel formed in sections and bolted together and having a
horizontal axis 2 mounted in boxes at or near the floor level. The rim of the
wheel is dish-shaped in cross-section and is provided at intervals with pivoted
latches 3, 3 to engage studs 4, 4 on semicylindrical sections of plate iron 5 to
support them on the wheel. Auxiliary plates of thin sheet iron may be bent
around the joint between the sections on the inside of the wheel rim to prevent
the pulverized material from sifting through the cracks at the joints. The wheel
may with advantage be made about 15 feet in diameter and the rim and plate
iron sections of such proportions as to form a circular receptacle of 36 inches in
diameter. The inner wall of the wheel rim is provided with holes at intervals to
receive copper plugs 6 connecting with the several plates of a commutator 7 by
conductors G on which bears a brush S connecting with one pole of an electric
generator 9. The other pole of the generator connects with a carbon electrode 10
about 4 inches in diameter mounted in a sleeve 11 provided with a screw-thread on
the outside which engages an internally threaded sleeve 12 secured to a bevel
gear 13 meshing with a gear 14 on the axis of which is a crank 15 for adjusting
the electrode. The electrode and its regulating mechanism are mounted on a frame-
work adjacent to the wheel pit so that the electrode may be fed into the receptacle
formed by the wheel rim and the rim sections when partly consumed. 16 is a feed
hopner provided with a spout 17 projecting into the wheel rim and a gate 18 for
regulating the supply of mixed material to be acted upon. The wheel pit is prefer-
ably provided with sloping sides so that any powdered material which drops from
the wheel at its discharging end or elsewhere may slide by gravity to a conveyor 19
the buckets of which return it to the feed hopper to again pass through the furnace.
The wheel is preferably connected with an electric motor by speed reducing gear-
ing; said motor is shown diagrammatically at 20. The motor shaft carries a worm 21
acting on a spur gear 22 on the shaft of which is secured a worm 23 meshing
with another gear 24, on the shaft of which is a third worm 25 meshing with a
gear on the wheel-shaft. By this mechanism a very slow speed of the wheel may
be maintained, a complete revolution being made once in 5 days. In using the
apparatus the rim sections are latched over the wheel-rim over an are covering the
lower part of the wheel, and the gate of the feed hopper is opened. A charge of in-
timately mixed pulverized carbon and lime in proper proportions to form carbide of
calcium falls into the receptacle around the wheel-rim, and accumulates until the
top of the electrode is immersed therein. The circuit of the dynamo-electric
machine may then be closed and the electric motor thrown into operation; as the

page_text: charge is moved away from the electrode intense heat is created and the refractory
material fuses forming a pool of liquid carbide of calcium or other compound
depending upon the nature of the furnace charge. As the wheel turns the pool
gradually recedes from the electrode and slowly cools while enclosed within walls
of refractory uncombined material on all sides, the cooled product forming a
bottom for the liquid compound. Thus a continuous core of the product is
formed, new rim-sections being added by a workman at intervals of a few hours.
the electrode at starting should project well into the receptacle, and as the wheel
turns the electrode rises relatively to the charge, and when it reaches a point near
the top of the rim-section a new rim-section is hung on the wheel by means of the
next set of supports and a strip of sheet iron is bent around the joint between
the rim-sections: the gate of the hopper is then opened and the rim filled or
partially filled with material; as this material in its powdered state is a very poor
conductor of electricity as well as of heat the immersion of the electrode does
not interfere with the heating action. When a new rim-section is added on the
electrode side of the wheel one is removed at the other side. Thus the process
continues until the solid core of the furnace product appears at the discharge end
of the wheel when a rim-section is taken off and the powdered material falls into
the pit, leaving a pillar of solid product projecting vertically which may be broken
off or otherwise removed. Solid carbide of calcium is a conductor of electricity
and the copper plugs make a good contact with the same, thereby constituting
the carbide itself one of the electrodes. The action of the commutator leads the
current to a point of the carbide core close to the electrode and thereby prevents
unnecessary resistance which would intervene if the plugs were more widely spaced.
The conducting plugs which are remote from the are help to carry the current
and thus heating of any one contact with the carbide core is reduced. It is evident
that two electrodes or carbon pencils might be employed with similar results; such
an arrangement would be desirable in cases where the core or product of the
furnace is a very poor electric conductor. The two carbon pencils in such a case
should be placed in a plane lying across the receptacle and dipping into the same,
the two pencils being at an angle to one another. The rationale of the process
would, however, be precisely the same. I prefer the arrangement herein described
at length in all cases in which it is capable of employment, as resulting in a more
uniforin shape of the core product.
In starting the furnace into operation the receptacle should be primed with
carbon between one of the plugs and the electrode before starting the motor:
motion of the wheel then draws the electric arc and fuses part of the material
of the charge after which the process goes on as hereinbefore described.
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 electric furnace comprising a receptacle to contain a charge of material
to be operated upon, electric connections for leading a current through the charge
from an external circuit, including a current-leading electrode extending into
the receptacle, and means for effecting a continuous downward movement of the
charge relatively to the electrode.
2. An electric furnace comprising a sectional receptacle for the charge of material
to be operated upon, electric connections for leading a current through the charge
from an external circuit including a current-leading electrode extending in to the
receptacle, and means for effecting a continuous recession of the receptacle and
charge relatively to the electrode, the several sections of the receptacle being
capable of removal.
3. An electric furnace comprising a rotary annulus turning on a horizontal axis,
means for forming a closed receptacle for a charge of material to be operated upon
over an are at the lower part of the annulus and a current leading electrode at
one end of the arc-shaped receptacle.

page_text: 4. An electric furnace comprising a rotary annulus turning on a horizontal axis,
means for forming a receptacle for material to be operated upon over an arc at the
bottom of the annulus, an electrode at one end of the arc-shaped receptacle, and a
source of supply for fresh material around the electrode.
5. An electric furnace comprising a rotary annulus turning on a horizontal axis,
removable rim-sections for forming a closed receptacle for material to be treated
by the furnace over an are of the annulus, a current leading electrode in operative
relation to the receptacle when the sections are in place, and means for sealing
the joints to prevent leakage of the material to be treated.
6. An electric furnace provided with a sectional receptacle for the charge movable
with relation to an electrode, electric connections with the inside of the receptacle,
the sections being capable of removal, a feed hopper for supplying material, and an
elevator for returning the unconsumed material to the hopper.
7. An electric furnace comprising a rotary wheel turning on a horizontal axis,
removable rim-sections forming a receptacle for a charge over an are of the wheel,
a current leading electrode connecting with one pole of an electric generator, con-
dueting plugs in the wall of the wheel-rim projecting into the receptacle space, and
a commutator for cutting the plugs successively into circuit.
Dated this 26th day of November 1897.
BOULT & WADE,
Agents for the Applicant.