Improvements in and connected with Electrical Furnaces.
Year: 1897

page_text: Date of Application, 20th July, 1897-Accepted, 18th Dec., 1897
COMPLETE SPECIFICATION.
Improvements in and connected with Electrical Furnaces.
I, FRANCIS JARVIS PATTEN, of 41 Park Row, in the city, county 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 consists in a system of electrical furnace construction involving
the application of a principle not hitherto adopted in such construction.
The said Invention and the system of construction will be hereinafter explained
with reference to the accompanying drawings in which:-
Figures 1 to 3 inclusive-and Figure 7 illustrate the principle applied, and
Figures 4, 5, 6, 8 and 9, different applications of the principle.
The majority of electrical furnaces depend upon the use of a local arc playing
between two carbon electrodes, thereby rapidly producing the heat of fusion at,
or in the immediate vicinity of the arc. The extent of heat dispersion is neces
sarily small and only that portion of the mixture which is to be fused which comes
into the arc itself or very near to it, is attacked by the desired temperature.
It is my purpose to largely extend the function of the arc in such furnaces
by making it move about and attack parts of the material which could not be
reached if the are remained stationary.
The idea is to give motion to the are so that it will pass from point to point
in the mass to be fused and so attack a far greater quantity of it than could. 'be
attacked if the are remained at rest.
The arc could of course be moved by giving motion to the electrodes, but this
method would involve mechanical difficulties of a difficult nature.
It is possible however to cause the arc or arcs to move about and attack a relat-
ively large quantity of material without moving any material thing or mechanical
part whatever and my present invention rests upon this fact.
My new system will be understood from a consideration of Figures 1 to 3
inclusive which have been drawn to illustrate the principle applied.
In Figure 1, R represents a magnetic ring having a closed Gramme ring-
winding with four connecting leads L L L L₂, connected in pairs to separate
alternate currents in quadrature relation. Supplied with such currents, the
interior of the ring R will be the seat of a rotary magnetic field, or one in which
the polar line NS, revolves about an axis perpendicular to the plane of the ring
and at a rate of rotation expressed by the current frequency in periods per second.
Now, it is a well known property of the electric arc that it tends to get out of
or to avoid a magnetic field. This peculiar action of the arc, combined with the
rotating magnetic field, gives the means for moving the arc in space without
moving any material thing whatever except the arc."
Thus, referring to Figure 1, let C represent in cross section, the upper of two
carbons or pencils, and A the arc. Assuming the current producing the latter
to flow downward from the upper to the lower carbon (the magnetic field of the
ring having the polarity and direction N-S indicated), then, the electric arc A

page_text: will take the position shewn and remain there so long as the magnetic field of
the ring remained unchanged in position and intensity.
If biphase alternating currents be introduced into the circuits L, L, and L, L
the magnetic field will revolve rapidly in the plane of the ring and the arc, in its
endeavour to keep out of it will likewise describe a circuit around the carbons
instead of passing direct from one to the other as it would do if the magnetic field
were not present.
In this way and by this means I am enabled to obtain a far greater amplitude
than is usually formed between carbon points. I will only briefly refer to the
remaining illustrations of the theory of my new system of construction.
Figures 2 and 3 represent in sectional elevation and plan respectively, a tubular
carbon C, forming the upper electrode, a disc of carbon C₂ forming the lower
electrode, and a magnetic ring R.
If a series of independent tubular electrodes be inserted, one within the other,
each insulated from its neighbours, and a single large slab be made to extend
over all at the bottom, then each tube will have its separate independent arc and
all these ares will revolve each in its own circle under the influence of the rotating
magnetic field, thus producing practically a sheet of fire between the upper and
the lower carbons or electrodes.
Figures 4, 5 and 6, represent in sectional elevation, different forms of electrical
furnaces in which the herein before described principles are embodied. In Figure 4,
Bindicates a suitable enclosing fire-brick structure arranged to surround the
working elements which are:-C₁, the upper or positive electrode consisting of
a carbon rod flared at its lower end to produce a circumference suited to the action
of the rotating arc, and C₂, a dish shaped lower carbon having a trough in its
central position and an outlet or draught tube T. The space surrounding the
vertical carbon is filled with the mixture to be fused and the carbons normally
in contact are slightly separated so that an arc is formed between their nearest
points. The magnetic ring N-S, shewn in cross section, is excited in the way
herein before described, by biphase alternating currents which produce the re-
volving field causing the are A to rotate around the periphery of the flared upper
carbon C, thus attacking the material as it passes down through the annular
space between the upper and lower electrodes. F, indicates an iron slab on which
the lower carbon rests and to which the negative lead is connected. The ring N, S
and its coils may be protected from the heat of the furnace by a flange on the
lower carbon C2. A hand wheel W, having a screwed spindle R, working in a
stationary nut can be rotated for the adjustment of the upper electrode which is
attached to the lower end of the spindle R₁.
This furnace obviously differs from the ordinary electrical furnace mainly by
the embodiment therein of my new system of control and production of motion
of the arc whereby it is enabled to attack the material in a definite and improved
manner.
In Figure 5, a modification of the same general form is similarly illustrated.
The upper carbon C, is tubalar, its central hollow serving as a feed pipe or tube
through which the material to be acted on can be passed into the are heated space.
The lower carbon electrode C₂ has such a form that the molten products resulting
from the action of the arcs can flow downward and outward to the outlet T. In
this form of furnace, as in that illustrated by Figure 4, a magnetic ring N-S,
produces a rotary field which controls the movement of the arc and causes it to
travel rapidly in a circle about the edge of the upper carbon, so that it attacks
the material all around the annular opening between the two electrodes.
happer H, may be fixed above the upper carbon through which the mixture to
be fused is supplied, and a yoke Y, connecting the carbon C, with the spindle R,
serves for the adjustment of the upper carbon by the motion of the hand wheel W.
F is a ring of firebrick, asbestos, mica or other suitable refractory material to
protect the ring N, S.
A
In the modification represented by Figure 6, the construction is practically

page_text: identical with that shewn by Figure 5 except that two concentric tubular upper
electrodes are employed, C, and C. It will be obvious that more than two upper
electrodes can be used in a similar manner.
"
A further application of the same principle may be made according to this
Invention to that class of electrical furnaces in which a carbon pencil is embedded
in a mass of the material to be fused. The pencil being first brought to incan-
descence and finally to the fusing temperature by means of an electric current
of sufficient density, this type of electrical furnace may be called the "in-
candescence furnace to distinguish it from the arc type. This further applica-
tion will be described with reference to Figure 7 which represents it diagram-
matically, and to Figures 8 and 9 which shew respectively, a sectional elevation
and plan of an incandescence electrical furnace in which my Improvements are
embodied. As indicated in Figure 7, C, and C, are carbon rods connected to a
source or direct current T T. The carbon ends are separated by a considerable
distance, so that under the pressure or voltage used the current cannot possibly
produce an arc between the carbons, and, were not some provision made to bridge
the gap, no current could pass between C, and C₂-
It is well known that in furnaces of this type, in which for example a mixture
of lime and coke G, is fused for the production of calcium carbide, a carbon
pencil P is arranged as indicated between the ends C₁ C₂. When a working
current is sent into the system, the carbon pencil acts as a nucleus of fusion and
produces also fusion of the mixture in its immediate neighbourhood along its
entire length, thus creating in the mass of the mixture, a central core of fused
material having an approximately ellipsoidal form. The lime and coke mixture
is normally a very poor conductor of electricity, but when fused as hereinbefore
described, the fused part is a comparatively good conductor and takes the place
of the carbon pencil which has melted away and united with the surrounding
fused mass.
In this way, a central nugget or core of calcium carbide is formed
which gradually increases in size as more and more material becomes fused.
Finally, the nugget is withdrawn and the process is repeated. Evidently, as the
nugget of molten material becomes larger and larger in diameter, its cross section
between the carbon terminals (of conducting material), becomes large enough
to convey many times the fusing current and an artificial resistance has to be
introduced to prevent short-circuiting the source of current. Now, it is my
purpose, by the application of the principles herein before elucidated, to confine
the current between the electrodes, to a certain definite portion of the molten or
conducting nugget and to give it motion around the central core or nugget so
that it will get at new material which has not been attacked by the fusing current.
Figure 7 illustrates how this may be accomplished in dependance upon the
principle that an electric current having a choice of several paths of equal resist-
ance, some of which pass through a magnetic field and some of which do not,
will invariably select the path farthest removed from the magnetic field. Thus
as represented by Figure 7, a mass of molten material of ellipsoidal form K is
supposed to fill the space between the carbon electrodes C, C₁. The molten core K
is highly conductive and if it be of greater cross section than the current requires
for its transit, a small linear element of the core would convey all the current and
under ordinary circumstances, the current would be confined to a central pencil
of the core extending from one carbon to the other. If however, the core is in
a magnetic field as shewn, the lines of force N-S being transverse to the current
direction, the current between the electrodes will no longer take the direct path
through the central axis of the molten material from one carbon to the other, but
will be pushed off to one side, taking the course R R, as shewn. In other words,
the current will take the longer curved path in order to avoid traversing the
magnetic field. This of course, only providing that there is no very great differ-
ence of resistance between the longer and the shorter path. In this way, by the
use of a strong magnetic field the fusing current can be driven from the central

page_text: portion already fused, to the surface of the nugget or unfused portions of the
mixture, thus attacking new material.
One other step is necessary for the perfect application of the principle. Evi-
dently, if the magnet in Figure 7 be revolved about the axis of the carbons as a
centre, the field will turn with the magnet, and the current path R R will revolve
around the surface of the magnet in its endeavour to avoid traversing the magnetic
field, and attack fresh or unused material on all sides. Thus the current can,
in this way, be forced to adopt a revolving electrical path which continually spins
around the surface of the molten mass, describing an ellipsoid of revolution in
space. In applying this principle in practice however, I create a revolving
magnetic field electrically, by energising an iron ring through the medium of
biphase alternating currents in the manner previously described.
Figures 8 and 9 illustrate the practical application of the principle. Figure 8
shew's a sectional elevation and Figure 9, a horizontal section along the line D-D,
Figure 8. Here, B B is an enclosing wall of brick-work; C, C₂ the upper and
lower carbon electrodes; P, the carbon pencil which is fused early in the opera-
tion; S-N a section of the magnetic ring R which surrounds the mass to be
fused and the shifting magnetism of which causes the current to assume a
curved path which revolves around the surface of the molten nug-
get E. By this means there is in effect produced a revolving electric current
which gets at the surface of the molten mass at every point and so attacks new
unmolten material in a much more effective manner.
As indicated by Figure 8, the upper carbon C, can be suspended from a derrick
by a chain and be raised and lowered by the winch h.
.
my said
declare that what I
Having now particularly described and ascertained the nature of
Invention and in what manner the same is to be performed,
claim is:-
1. In an electrical furnace, a furnace wall, a pair of carbon electrodes within
said wall one of the electrodes being circular in cross section, means for rotating
the arc between and relatively to the electrodes, and passages to convey material
through the annular arcing space, substantially as hereinbefore described with
reference to the accompanying drawings.
2. In an electrical furnace, the combination with the electrodes of passages
for conveying material through the arcing space between the electrodes, a ring
of magnetisable material surrounding the arcing space, means for creating a
rotating magnetic field in the ring, and means for protecting the ring and its
winding from the arc, substantially as herein before described and as illustrated
by the accompanying drawings.
3. In an electrical furnace, the combination with two enclosed electrodes consist-
ing of a lower carbon slab and a round upper carbon rod, of means for rotating the are
about the axis of the upper carbon, means for adjusting the upper carbon, and
passages arranged to convey the material through the annular arcing space, sub-
stentially as hereinbefore described and as illustrated by the accompanying
diawings.
4. In an electrical furnace, the combination with a carbon slab constituting the
lower electrode, of an upper tubular electrode separated from the slab by an
arcing space, passages for feeding the material through the arcing space, a sur-
rounding ring of magnetisable material, and means for rotating the magnetic
field in the ring so as to produce rotation of the arc, substantially as herein before
described and as illustrated by the accompanying drawings.
5. In an electrical furnace, the combination with two or more terminal elec-
trodes primarily connected by a carbon pencil of relatively small cross section,
of a transverse rotating magnetic field surrounding the pencil, substantially as
and for the purpose hereinbefore described with reference to the accompanying
drawings.
6. In an electrical furnace in which the electrodes are primarily connected by

page_text: a relatively small pencil or pencils, enclosing the pencil or pencils in a rotating
magnetic field the lines of force in which are approximately transverse to the
pencil or pencils, substantially as and for the purpose herein before described and
as illustrated by the accompanying drawings.
7. The herein before described process for electrically heating a homogeneous mass
of material of low and approximately uniform conductivity, which consists in
passing an electric current through the mass, establishing around it a magnetic
field having its lines of force transverse to the line of current flow, and causing
the magnetic field to rotate about the line of current flow, substantially as and
for the purpose hereinbefore described with reference to the accompanying
rawings.