Apparatus or Furnaces therefor.
Year: 1886

page_text: Apparatus or Furnaces therefor.
I, WILLIAM PHILLIPS THOMPSON, Fel. Inst. P.A. of the Agency for Foreign
Patent Solicitors, 6 Lord Street, Liverpool, in the County of Lancaster, and
323 High Holborn, in the County of Middlesex, Civil Engineer, do hereby declare
the nature of this invention (a communication from abroad by Alfred H. Cowles
of Cleveland, in the County of Cuyhoga, State of Ohio, United States of America
Inventor) 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 electrical smelting furnaces operating on the incan-
descent principle, in which metallurgical operations requiring an intense heat are
carried on, with electricity as the heat producing agent.
This invention consists in the improved method of operating incandescent
electric furnaces herein described, and in the combination with a furnace con-
taining a charge of electrical resistance material, of two movable electrodes
situated at opposite ends of the furnace, and projecting into the body of the
charge contained within it, so that the said electrodes may when the resistance
runs down be drawn apart thereby increasing the amount of the charge between
the electrodes and consequently increasing the resistance, and thus preserving a
uniform resistance within the furnace.
The invention also consists in the arrangement of suitable mechanism actuated
by the current or a portion of the same for automatically moving the electrodes so
as to govern the amount of energy utilized in the furnace.
Figure 1 in the drawings represents a longitudinal section of the furnace.
Figure 2 shows substantially the same view of the furnace, and shows also the
arrangement of mechanism for automatically drawing apart the electrodes by
means of a magnet vibrating armature and shunt circuit. Also is shown the
construction of the contact boxes employed.
A are the furnace walls, which may be constructed of firebrick or other similar
material; they are preferably constructed so that the furnace has its largest
dimensions in a horizontal direction, and is comparatively shallow in depth, as
,

page_text: this form of construction is found to be best adapted for the free escape of the
gases evolved from the charge during the process of reduction. B, is a lining for
protecting the walls of the furnace; this lining is formed of finely pulverized
charcoal or other similar material of inferior electrical conductivity to the charge
to be operated on, and which is also a bad conductor of heat.
C is the positive and C¹ the negative electrode; connected to these are the
wires c and c¹ for conducting the electricity to the furnace.
These electrodes are preferably formed of rods of carbon which project into the
Lody of the charge, through the furnace walls and lining.
D is the charge, this consists ordinarily of electrical resistance material, such as
electric light carbon, and the ore to be reduced; both of these are previously
pulverized, and intimately mixed together before being placed in the furnace.
But in some cases pulverized ore alone is used, when it is a sufficient conductor of
electricity. The charge fills the whole length, with the exception of the protecting
packing B, at the ends of the furnace, and it presses against the sides and ends of
each of the electrodes which project into it.
The current of electricity flows from the sides and ends of the said electrodes
through the charge and causes the electrical resistance material in the charge to
become incandescent; and the intense heat of the said incandescent material
reduces the ore.
When the furnace is employed for the reduction of ore, the metal is found, at the
close of the operation, filling the interstices between the particles of carbon, mixed
with it, and at the bottom of the furnace where it collects upon the charcoal floor,
after having worked down through the charge. When the furnace is started the
electrodes are near together in the positions indicated by dotted lines, the
resistance at the start being very great. After the furnace has been running for
awhile and this portion of the charge between the electrodes has become heated
the resistance falls and the electrodes are then drawn out a little increasing
the length of the charge between them and bringing into the active part of the
electrical field additional parts of the charge. In this manner by successive
withdrawings of the electrodes, a uniform resistance is preserved until the entire
charge is brought into action. The electrodes are employed not alone to maintain
a given resistance, but also to throw fresh ore into the zone of reduction.
The movement of the electrodes may be effected by clockwork mechanism, by
hand, or automatically by the current of electricity in the circuit, so that the
greatest possible amount of electrical energy in the circuit may be utilized from
the beginning to the end of the operation, in the furnace.
In Fig. 2 is shown a convenient manner of operating the electrodes automatically
by means of a shunt circuit magnet and vibrating armature.
G, represents magnets connected in the main circuit, and wound in the opposite
direction with the wire of the shunt circuit that from the positive pole leads to
the positive electrode C, and that of the negative pole leading to the contact
point g.
H, is a vibrating armature with a contact point h, connected by a wire leading
to the negative electrode C¹, or to the main wire leading thereto. To the armature
is attached the spring I, the tension of which is regulated by the key i¹.
J, is the rod by which the armature is suspended, and at the upper end is
provided with a friction clutch j, embracing the hub of the ratchet wheel k, the
teeth of which are engaged by the retaining pawl kl.
A train of gears connect the ratchet wheel with the gear L, that engages the
rack M, that is attached to the electrode C¹¹.
This rack also engages the pinion N, that is connected by a cross-belt, or other
suitable means, with the duplicate pinion N1, engaging the rack M¹ connected with
the electrode C, by which arrangement the electrodes are simultaneously moved
equal distances in opposite directions.
In operating the furnace, as the heat increases and the electrical resistance
consequently decreases, causing too great a current, the armature H is drawn

page_text: toward the magnet causing a contact of the points gand h, connecting the shunt
circuit, by means of which a portion of the current is passed around instead of
through the furnace, thus lessening the power of the magnet, so that the armature.
is again drawn to its normal position by the tension of the spring. With the
movement of the armature toward the magnet, the friction clutch slides on the hub
of the ratchet wheel, but with the reverse movement of the armature caused by
the spring, the ratchet wheel is advanced a notch, thereby withdrawing the
electrodes a trifle from the furnace, and such increase in the distance between
the electrodes of course increases the electrical resistance and consequently decreases
the volume of electric current through the furnace.
As the electrodes are drawn apart by successive increments, additional portions
of the charge drop into the spaces in front of the electrodes and a continuous body
of material is preserved between them and in contact always with both. The
extent of this mass of material within the zone of action gradually increases until
the whole of the charge is involved.
Of course various modifications of the governing mechanism may be made
without departing from the spirit of my invention. In charging the furnace the
pawl may be thrown back and the ratchet wheel turned by hand to adjust the
electrodes.
If the electrodes in the heated condition in which they usually emerge from the
furnace, were exposed to the air, they would oxidize and be reduced in size, to
avoid which I have provided the copper contact boxes P, that are secured to the
walls A, and have lateral holes through which the electrodes pass.
The boxes are filled, with, preferably copper shot R, of small size, surrounding
the electrodes.
Copper on account of its well known properties of conducting heat and elec-
tricity is preferable in most cases for this purpose, and the wires are attached to
the boxes P.
As the heated portions of the electrodes emerge slowly from the furnace, they
first encounter the shot, by means of which the heat is rapidly transmitted from
the electrodes, so that the heated portions as they pass out of the respective boxes
are so much reduced in temperature that they are not injured by exposure to
the air.
•
The shot or globular form for the packing, or filling, in the box P, is not
essential, but is preferable.
The movement may be confined to but one of the electrodes or both may be
made movable. It will be seen that the feed mechanism of an are light may be
readily adapted to move the electrodes outward as the resistance falls. But in
the present case such a feed mechanism instead of being adjusted so as to maintain
the extremities of the electrodes at a uniform distance apart and to feed them in
towards each other as they are consumed, is so arranged that it feeds the electrodes
outward farther and farther apart as the operation progresses, the space between
them always being kept filled with the charge.
If it were desired to lessen the resistance during the smelting operation by
lessening the amount of the charge between the electrodes they may be pushed in
and in order to allow this they should be made with pointed ends.
E, is a layer of granular charcoal covering the top of the charge.
F is a slab of fire clay or other suitable material, provided with vent holes f;
this slab covers the whole of the top of the furnace, and is luted around the edges
before the operation commences.
A small space is left between the top of the layer of charcoal E, and the bottom
of the slab F.
The gases given off by the charge during the process of reduction pass off through
the layer of granular charcoal and out of the vent holes f.
I am aware that it is not new to make the electrodes of an electric furnace
automatically adjustable so that as the resistance diminishes they are drawn apart,
and I do not claim the same broadly, but all such attempts and experiments have

page_text: relation to furnaces in which, the electric arc is employed, and the electrodes being
subject to rapid wear the loss must be compensated for.
The conditions there existing are similar to those found in the case of an electric
arc light, a constant distance must be preserved between the electrodes and the
wear thereof must be compensated for, but in the present instance, there is no
material wear to the electrodes a continuous body of material is preserved between
the electrodes and the distance between the electrodes and the distance between
them varies, gradually widening from the beginning of the operation until the whole
of the charge is brought into action.
Having now particularly described and ascertained the nature of the said
invention, 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 :-
1. The method of smelting ores and other substances by the incandescence of an
electrical resistance material contained in said substances or mixed therewith,
which consists in first bringing a limited quantity of the material to be treated
between a pair of electrodes and then gradually increasing the quantity of such
material by causing the electrodes to recede from each other, substantially as herein
set forth.
2. In the art of smelting ores and other substances by the direct heating action
of the electric current, the method of obtaining a uniform action of said electric
current upon the mass or charge to be treated herein described, which consists in
introducing into the charge electrodes which are normally in proximity to each
other, and then gradually causing said electrodes to recede from each other, the
contact with the charge still being preserved until the mass of the charge is
contained between the said electrodes, substantially as set forth.
3. In an incandescent electrical smelting apparatus, the combination of a furnace
chamber having electrodes fitted into its opposite sides, with suitable mechanism
for bringing said electrodes normally in proximity to each other within the furnace
chamber and gradually separating the same during the smelting process to the full
extent of said furnace chamber, substantially as herein set forth.
4. In an incandescent electrical smelting apparatus, the combination of a furnace
chamber having electrodes fitted into its opposite sides, mechanism for normally
bringing said electrodes in proximity to each other and gradually separating the
same during the smelting process to the full extent of the furnace chamber and a
charge of electrical resistance material in contact with both electrodes during the
entire process, substantially as herein set forth.
5. The combination with an adjustable electrode, of an electric furnace of a mass
of heat conducting particles, preferably globular, encompassing the electrode outside
of the furnace chamber, substantially as and for the purpose set forth.
6. The combination with adjustable electrodes of contact boxes, preferably of
copper, located one at either end of an electric furnace and through which the
electrodes pass, and filling for the boxes preferably of copper, and preferably of a
globular formation, arranged around the respective electrodes and in contact
therewith, substantially as set forth.