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Патент USA US2112161

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March 22, 1938.
Filed April 16, 1955
v 6AM
Patented Mar. 22, 1938
Thomas Daniel Kelly, Walllngton, England
Application April 16, 1935, Serial No. 16,717
In Great Britain August 15, 1934
(Cl. 13-9)
This invention relates to improvements in elec
tric furnaces using direct, alternating or in
duced currents, and has for its object to simplify
the manufacture, greatly reduce the weight and
increase the efficiency of such furnaces in both
small and large sizes.
The furnace, according to this'invention is so
constructed that alternating, direct or induced
currents can be used therein at different stages
10 of operation from the same supply. In order that
direct current can be used for refining, in which
case all impurities will go to the anode and the
pure metals to the cathode, such furnaces are
lined with a refractory, material which is a
16 conductor of electricity, and the furnace is pro—
vided with a spout or L attachment at the side
which is also lined and leads to the bottom of the
furnace, and down this spout is placed an elec
trode which constitutes a cathode and contacts
with the materials at the bottom of the furnace;
, so that the container for the metals or other
materials is thereby made negative. The spout
through which the molten material can be poured
from the furnace into moulds, is also of service
when it is required to add other metals, mate
rials, air or gases to the bottom of molten metals,
such an arrangement being simpler and less
dangerous to operate than the ordinary type of
converter now in use. The positive connection
for supplying ‘electric current to the furnace is
made by means of a swinging gallows arm or
other apparatus carrying a movable electrode
which constitutes the anode. The are is not
struck on the metals or materials but on a re
: l fractory '7 electrical conducting material which
protects the metals from burning or oxidizing
when an arc is used and has a similar effect when
used as a resistance material.
Instead of the usual very heavy refractory ?re»
40 bricks and surroundings of great thickness so
necessary in the ordinary electric furnace to pre
vent radiation of heat and to insulate the cur
rent when the furnace is hot, thin layers of ma,‘
terials may be used which are combined refrac
45 tories and absolute non-conductors of electricity
at all temperatures, as distinguished from the
magnesia, kaolin, lime, ?reclay, alundum, silica,
, carborundum, graphite and similar materials
heretofore used and which, although considered
electrically alive and melts or loses its strength.
An electric furnace according to the present in
vention therefore need not weigh any more than
the usual foundry ladies. In fact ordinary ladies,
and receivers, converters, or crucibles can be ,
quickly converted by this invention into light
weight electric furnaces.
Two materials which answer admirably for
heat and electrical insulation are, mica and
asbestos, and either of these materials or both 10
combined may be used in very thin layers be
tween the outer casing or reinforcement and the
metal container which is in direct contact with
the molten metal or other materials, thus pre
venting radiation of heat or electrical leakage 15
to the outside.
To prevent the metal being oxidized or burnt
by coming into contact with the arc, it is always
covered with a powdered material consisting of
alkaline earth chlorides and iodides, which may
be cheaply obtained from sea salt, mixed with
kaolin and carbon or similar materials which
will make an electrically conducting layer to
produce the same results. This material is al
ways between the metal and the arc and is at
the anode pole, so that all oxides and gases
which rise from the molten metal, are absorbed
by such material.
In order to prevent short circuiting caused by
liquid metal touching theelectrodes when work
ing with direct current, such current is usually
supplied by a differentially wound generator in
which the volts and amperes automatically inter
change according to the load, but for this in
vention I find it preferable to use rectifying 35
valves of the mercury vapour, thermionic or
other type, between the alternating current sup
ply and the furnace, and thus prevent the violent
?uctuations of current which are so troublesome
with are furnaces. In this way the same current
supply can be used all the time for supplying
alternating current for melting with arc, or for
heating by resistance or high or low frequency
induction, and the alternating current may be
changed to direct current by means of rectifying
The invention thus provides an electric fur
nace capable of using alternating and direct
current from the same supply for the same fur
refractory and insulators, or as having great re
nace at different stages of operation on the same
sistance, become conductors of electricity at the
high temperatures of electric furnaces and radi
mica or asbestos or a mixture of these materials
ate most of the heat so that very often the iron
casing of the furnace, which may be 18 inches
I ‘1 to 2 it. away from the molten metal, becomes
charge, and having an intermediate lining of
for electrical insulation and prevention of heat
radiation, combined with an electrically conduct
ing layer between the are (when used) and the
metal or other materials being treated or melted,
with a spout for the insertion or introduction of
electrodes, metals or other materials to the bot
tom of the furnace, in most cases without dis
turbing the protective conducting layer on top of
the metal or other material, as conditions may
require. When used as a converter, the top of
the metal is not covered in order that gases may
escape, but when the arc is in use the metal is
always covered.
The annexed drawing shows an example, more
or less diagrammatic, of a furnace constructed
Figure l is a sectional elevation of a furnace
15 having a spout and showing metal in the furnace
and a protective conducting layer applied there
to and showing the electrodes; and
Figure 2 is a diagram of the electrical connec
tions to the furnace.
l is the metal casing forming the body of the
furnace and carrying a spout 2 positioned at an
angle and leading from near the bottom of the
casing I.
Inside the casing I and spout 2 is positioned
25 a layer 3 or layers of asbestos or mica or both
as an electric insulating and heat resisting ma
terial, and inside this layer 3 is positioned an
other layer 4 composed of ordinary refractory
electrically conducting material.
5 is the metal contained within the furnace
and spout, the upper part of the metal being
covered with a material 6 forming an electrically
conducting layer of the character hereinbefore
‘I is the positive or anode electrode swung
from a gallows arm 8, and 9 is the negative or
cathode electrode positioned in the spout, with
its lower end contacting with the metal 5 in the
a double pole change over switch ll, either al
ternating or direct current can be used in melting
the metals.
What I do claim as my invention and desire to 10
according to my invention.
According to the diagramFlgure 2, the furnace
can be connected direct to the alternating elec
tric current supply A. C. or connected to said
current supply through a vapour or like recti
tying valve II which converts the alternating
current to direct current so that, by means of
secure by Letters Patent is:-—
In a metallurgical apparatus, a generally up
right chamber having an open top and a closed
bottom, said chamber being adapted to contain
a layer of metal having an overlying layer of 15
electrically conductive material, a spout oper
atively associated with a side of said chamber
and extending downwardly toward the bottom
of the latter and communicating therewith be
low the level of said electrically conductive layer, 20
an anode electrode extending downwardly
through the open top of said chamber into prox
imity to said conductive layer, and a cathode
electrode extending downwardly in said spout
and immersed in said metal layer and isolated 25
from the layer of electrically conductive ma
terial in said chamber, said spout extending up
wardly outside of said chamber and terminating
in a pipe-like conduit having coupling means
provided thereon for connecting it to a source of 30
air or other gas under pressure, whereby an air
current may be blown down said spout and up
wardly through said metal layer for assisting
in conveying impurities contained in the latter
to said conductive layer.
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