Improvements in or relating to Electric Furnaces
Year: 1896

page_text: Date of Application, 23rd Dec., 1896
PROVISIONAL SPECIFICATION.
"Improvements in or relating to Electric Furnaces."
I, WILSON WALTER HUGHES, of 31 Queen Victoria Street, in the County of
Middlesex, Engineer, do hereby declare the nature of this invention to be as
follows:-
This invention relates to electric furnaces in which the electric are is employed
directly as the reducing agent. It has been found that in these furnaces as hitherto
usually constructed certain materials are not completely treated; it is the object of
the present invention to ensure that the whole of the material delivered into the
furnace shall come under the direct influence of the arc.
According to this invention the hearth of the furnace is used as one electrode, and
an annular arc or its equivalent is set up between the hearth and the other electrode
or electrodes, which are so disposed as to constitute or surround a supply tube through
which material for treatment is delivered on to the hearth. It will be understood
from the foregoing that all the material delivered down this tube and passing radially
therefrom across the hearth in the space between the latter and the annular electrode,
cannot avoid going through the field of the arc.
A single tubular electrode may be employed or a series of electrodes so disposed as
to constitute the equivalent of such a tube in giving an annular arc or a ring of arcs.
This construction of furnace although suitable for general purposes is particularly
applicable for the manufacture of carbide of calcium say from carbon and lime.
Dated this 23rd day of Decr, 1896.
BOULT & WADE,
Agents for the Applicant,
COMPLETE SPECIFICATION.
"Improvements in or relating to Electric Furnaces."
I, WILSON WALTER HUGHES, of 31 Queen Victoria Street, in the County of
Middlesex, 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:-
This invention relates to furnaces in which the electric arc is employed directly
as the reducing agent. It has been found that in these furnaces as hitherto usually
constructed some of the material introduced into the furnace escapes treatment; it
is the object of the present invention to ensure that the whole of the material
delivered into the furnace shall come under the direct influence of the arc.
According to this invention the hearth of the furnace is used as one electrode and
an annular arc or its equivalent is set up between the hearth and the other electrode

page_text: or electrodes, which are so disposed as to constitute or surround a supply tube through
which material for treatment is delivered on to the hearth. Since the material
delivered from this tube passes radially therefrom across the hearth in the space
between the latter and the annular electrode, all the material delivered to the furnace
must pass through the field of the arc.
To adjust the arc-length means are provided to raise and lower one of the
electrodes either the hearth which forms the cathode, or the carbon anode preferably
the former.
The invention will be best explained by reference to the accompanying drawings.
of which
Figures 1 to 4 show the invention as applied to a furnace for the production of
calcium carbide from peat charcoal and lime.
Figure 1 is a front view of the upper part of such a furnace.
Figure 2 is a horizontal section on the line 2-2 of Figure 1;
Figure 3 is a vertical section on the line 3-3 of Figure 3;
Figure 4 is a vertical section on the line 4-4 of Figure 1; and
Figures 4 and 5 show alternative forms of arrangement of the electrodes.
Like letters indicate like parts in all figures.
Referring to Figures 1 to 4, A A are two retorts, in which the material to be reduced,
in this case a mixture of peat carbon and lime, is placed. The retorts A are shown
exposed to the products of combustion of a furnace, which may be of any ordinary
construction, the object being to heat the material before subjecting it to the action
of the electric are for the purpose of economizing the expenditure of electric energy;
this portion of the apparatus however forms no part of the present invention.
A Y tube A¹ connects the bottom of each retort with a tube B, to which is attached
an insulating block C, carrying the carbon anode C.
The furnace is shown and described with two retorts; it is however evident that
only one may be employed A¹ being then a plain tube or more than two retorts may
be used A' comprising as many branches as there are retorts.
The anode C is preferably formed as a hollow rod, down the centre of which the
material to be reduced passes from the tube A' and is furnished with a suitable
fitting G for connecting the cable from the source of electric energy.
Instead of a single hollow rod the anode C may be formed of a number of solid rods
arranged in a circle the essential point being that a central passage be constituted
surrounded by the carbon of the anode, down which the material to be acted on can
pass.
Or the carbon anode might be formed of a single solid rod and surrounded by a
tube, the material to be treated passing down the annular space thus formed; but
this arrangement is not as efficient as those previously described.
A throttle valve A' or an adjustable slide is placed in the delivery tube from each
retort to regulate the supply of material to the furnace, so that no more may be
delivered than the are will fase. This may conveniently be manipulated by a cross-
bar As and chain as shown in Figure 1.
The hearth of the furnace comprises a plate D of iron or other suitable material,
which constitutes the cathode, and has a connection D leading to the source of electric
energy. The plate D is carried on an insulating base plate D' and may be provided
with suitable means for being gradually raised or lowered within the limits shown by
the dotted lines in Figure 4.
A convenient form is shown in Figures 3 and 4 in which the hearth D is placed
over a well E formed in the floor of the furnace, containing a frame E¹ which forms
a guide for a screw-rod D³ fixed to or engaging with the base plate D
The rod D³
works in the threaded hub of a toothed wheel E carried horizontally between
bosses E, E of the frame E¹. The toothed wheel E is geared with a worm Fl
carried on a horizontal shaft F and operated by a band wheel F through the bevel
gearing F³.
In the furnace described above the carbon anode C is fixed and the metal cathode D
movable to regulate the length of the arc. This arrangement may be reversed as

page_text: shown in Figures 4A in which the tube B is prolonged and fitted with a sleeve B¹
which carries the insulating block C¹ and anode C. The sleeve B¹ is furnished with
a stuffing box B2 so as to give sufficient frictional contact to hold the sleeve stationary
in whatever position it may be placed in relation to the tube B, but at the same time
allow it to be readily moved up and down on the same so as to regulate the distance
between the two electrodes C and D. The sleeve may be adjusted by hand or by any
convenient mechanism. In Figure 5 another arrangement of the movable anode is
shown. In this case the tube B leading from the retort is made flexible to allow for
the movements of the anode C, to which it is connected by an insulating mouth
piece C. The anode carbon C is suspended by a metallic stirrup G and the cable H
leading to the source of electric energy over an insulated pulley I so that it may be
raised or lowered at will.
The furnace may be lined internally with any suitable highly refractory material
but preferably is pasted with charcoal impregnated with lime water which latter on
drying leaves the walls and metal base protected by a film of lime from the corrosive
action of the heat of the arc. As the furnace is filled with carbon vapour the oxygen
of the atmosphere has not access to the material under treatment and therefore no
waste of material is caused by oxidation.
In operating the furnace the material to be operated on is placed in the retort or
retorts A and may for the sake of economy be heated as shown in Figures 1 to 4
before proceeding to the electric furnace, but this is not essential.
From the retort or retorts A the material descends by gravity through the tubes
A¹, B and the hollow anode C the amount being regulated by the valve A² and passes
in a radiating stream through the conical electric are J (figure 5) established by the
electric current between the anode carbon C and the cathode furnace hearth D, fusion
of its component parts being thereby induced by reason of the accompanying intense
heat. By the method of feeding the ingredients to the furnace and the arrangement
of the hearth described the subjection of every part of the material undergoing treat-
ment to the action of the arc is ensured.
Although specially applicable to the manufacture of calcium carbide from peat-
charcoal and lime the construction of furnace comprised by this invention is suitable
for the general purposes for which electric furnaces are employed.
I am aware that furnaces have been described in which hollow electrodes are used,
the material to be treated being delivered to the furnace through one electrode and
discharged therefrom through the other, but this arrangement is very inefficient, as
the material does not pass directly through the field of the arc.
Having now particularly described and ascertained the nature of the said inven-
tion and in what manner the same is to be performed I declare that what I
claim is;-
1. In an electric furnace the combination with a solid hearth forming one electrode
of a second electrode through or about which the material to be treated passes.
2. In an electric furnace the combination with an electrode through or about which
the material to be treated passes of a solid hearth forming the other electrode and
adjustable in relation to the first electrode.
3. The combination and arrangement of parts constituting the electric furnace
substantially as described and illustrated in the accompanying drawings.
Dated this 22nd day of September 1897
WILSON WALTER HUGHES.
Boult and Wade,
Agents for the Applicant.