Improvements in Methods and Apparatus for the Manufacture of Calcium Carbide.
Year: 1898

page_text: Date of Application, 5th Dec., 1898-Accepted, 6th May, 1899
COMPLETE SPECIFICATION.
Improvements in Methods and Apparatus for the Manufacture of
Calcium Carbide.
I, HUDSON MAXIM, Chemist and Mechanical Engineer, of 219, West 34th
Street, New York City, United States of America, do hereby declare the nature of
this invention and in what manner the same is to be performed, to be particu-
larly described and ascertained in and by the following statement:―
The present invention relates to improvements in processes and apparatus for
electro-thermally treating materials, and has particular reference to electric
furnaces for the manufacture of calcium carbide.
The object of the invention is mainly to utilise with the greatest economy the
electric current, reduce to a minimum the wear and tear of the apparatus, pro-
duce a uniform product, and to save labor.
In carrying out the invention, I preferably employ a polyphase current, and
preferably three or more electrodes, which are disposed horizontally, and adapted
to be moved in longitudinal direction, back and forth, and preferably by a motor
controlled by the variations in the resistance to the electric current passing
through an incandescent carbide conductor between the electrodes, the character
and purposes of which conductor are hereinafter more fully explained. The
electrodes are positioned above an endless belt, which forms the bottom of the
furnace or receptacle for the carbide-forming material, the material being fed
into the receptacle or furnace at or near the rearward portion of the same.
Means are provided for the escape through the top of the furnace, of gases set
free by the reaction.
In starting the operation, a small rod or filament of carbon is preferably
employed to make electrical contact between the forward ends of the electrodes.
By the passage of the electric current through it, it becomes highly incandescent,
the heat of which serves to rapidly convert the surrounding material into carbide,
and which is rapidly replaced by a conductor of molten carbide. When the
electric current through the molten carbide conductor shall encounter too low
resistance, in other words, when the electrical carrying capacity of the carbide
conductor shall become too great to offer sufficient resistance for the main-
taining of an adequate degree of heat for the purposes of the invention and the
continual reduction of the adjacent material into carbide, then the motor above
referred to will be caused automatically to act and withdraw the electrodes suffi-
ciently to so attenuate the conductor, or to alter the position of the current or
of the field of the greatest heat produced by the current through the conductor,
and in a direction, of course, through or upon fresh material, whereby new
portions of the carbide conductor are formed continuously, together with the
continuous advance of the electric current, or field of greatest electrical resistance
and heat in a direction towards the rearward of the furnace, until the electrodes
shall be withdrawn to their furthest rearward position, then the aforesaid motor
is caused automatically to act and to rapidly thrust the electrodes forward and
to advance simultaneously the floor of the furnace or the upper portion of the

page_text: endless belt at the same rate of speed, so that the heating field or carbide con-
ductor between the forward ends of the electrodes is not broken or distorted, or
its position relative to the electrodes altered by the forward movement of the
electrodes. By the forward movement of the bottom of the furnace, simul-
taneously with the electrodes, the body of contained carbide-forming material
is likewise advanced at the same time, and fresh material takes its place through
a feeding shaft at the rear of the furnace afore-mentioned.
As the electrodes are advanced, the body of carbide formed and that which
has become sufficiently cool for the purpose, is, by the forward movement, or
by a movement actuated from an independent source, made to pass between
scrubbers, or roller brushes, whereby the body of carbide is cleaned, and the
carbide-forming material carried outward upon it simultaneously brushed back
into the furnace, or other receptacle.
The carbide-forming material carried forward upon the body of carbide is
removed and retained in the furnace, preferably by a plough, which may be
fixed to the furnace structure.
Independent and metal supports are employed for supporting the electrodes,
and the electrodes are adapted, as they become worn or eroded away, to be
advanced with respect to the support or supports, so that the carbon electrodes may
be used up until but comparatively short pieces of them are left.
With this general statement of some of the leading features and advantages
of the invention, I have, in order to make the same more clearly understood,
shown in the accompanying drawings means of carrying it into practical effect,
without thereby limiting the improvements in their useful applications to the
particular construction taken for illustration herein.
In the said drawings:-
Fig. 1 is a vertical longitudinal section through the furnace.
Fig. 2 is a horizontal section on the line 2, 2 of Fig. 1.
Fig. 3 is a vertical cross-section on the line 3, 3 of Fig. 1.
Fig. 4 is a vertical section through one of the electrode casings showing the
electrode in elevation.
Fig. 5 is an end view of the casing, the rod attached to the electrode being
in section.
Fig. 6 is a plan view partly diagrammatical, of the furnace, and means for
operating the same with the electrical connections and devices, to be herein-
after described.
Fig. 7 is a section taken on the line 7, 7 of Fig. 6, showing a detail of the
apparatus used to operate the furnace.
Referring to the drawings, the furnace structure 1 is preferably made of fire-
brick or other suitable material, and is provided through its end wall
with a
plurality of electrodes 3, 3, in this case preferably three in number, which extend
substantially paralleled with each other in a horizontal plane into the end of
the furnace.
The hearth of the furnace consists preferably of an endless linked belt 4, of
metal, which is supported upon two pulleys, 5, 6, one of which, 5, is idle, while
the other, 6, is driven by a worm gear 44, hereinafter described, and is provided
with a number of teeth 7, to engage the transverse bolts 8, of the belt in order
to operate the latter when required.
At
Each section of the belt is provided with side laps, through which passes a
long bolt or rod 8, securing the adjacent sections together. The rod carries
three or more rollers 9, supporting the belt on each side and in the center.
the upper part of the belt the side rollers pass on a track 10 in the walls of the
furnace, and the center rollers are supported by a track 11, resting on transverse
beams, 12.
The lower part of the belt beneath the pulleys 5 and 6 rests upon a number of
cylinders 18, secured in the walls of the furnace.
The top of the furnace structure preferably arched, and is provided at the

page_text: end wall with an opening 14, extending transversely across the furnace for the
purpose of supplying carbide-forming material thereto, from any suitable bin
or hopper, 15. It is obvious that although the material may not descend directly
on that part of the hearth directly above which the carbide is forming, the
material is carried forward as required, into such position, by the intermittent
forward motion of the belt.
The top of the furnace is also provided with a manhole 16, which is used in
beginning the operation of the furnace for placing the initial incandescence
conductor or filament between the electrodes. Finally, another opening or flue 17,
nearer the exit end of the furnace, serves to carry off the vapors and gases
liberated during the operation of the furnace.
As the strip of carbide a, is formed and is intermittently passed towards and
through the exit end of the furnace, the greater part of the carbide-forming
material upon the carbide is removed by a stationary plough 18, which throws
the material on either side of the strip into the pit 19, at the end of the belt,
where it may be received by any suitable receptacle 20, the material underneath
the layer or strip of carbide also falling off the end of the belt to the said
receptacle or pit.
At the exit end of the furnace, there is provided two transversely mounted
scrubbing cylinders, 21, 22, which consist preferably of metal cylinders covered
with strong wire brushes, it being understood, however, that any other con-
struction may be employed, if found suitable for the work required. The strip
of carbide passes between the cylinders, and is aided in its movement by the
motion of the lower cylinder 21, revolving in the direction of the movement of
the strip, and at a greater speed than the upper cylinder 22, which revolves in the
opposite direction. The upper cylinder is supported by the strip which in turn
rests on the lower cylinder. It will be seen, therefore, that this device provides
for an exceedingly efficient means for cleaning the strip of carbide before it is
passed from the furnace, and prevents so great a production of dust offensive to
the workmen cleaning the carbide as heretofore. Suitable gears 63 are provided
for running the scrubbing cylinders in the directions, and at the speeds described.
The electrodes 3, 3 are supported in iron casings 23, and insulated therefrom
by asbestos or other suitable material 24. Each electrode is preferably attached
to a copper or brass band or is sweated in a copper or brass cup 25 to which
in turn is attached a rod 26, of brass or other suitable metal for conveying the
electric current to the electrode. The rod is insulated by means of a layer of
asphaltum or asbestos 27, in an iron tube 28, supported in part by a clamp 29,
attached at the end of the iron casing. The hold of the clamp upon the tube 28,
may be tightened or loosened so as to allow the latter to be fixed or moved for-
ward or revolved together with the electrode as the latter wears. One or two
wires or cables 30, supplying the electric current from the generator 47, may be
attached to the outer end of the rod 26.
The electrode casings are rigidly supported in an iron frame 31, which is
moved backward and forward longitudinally with the electrodes by means of
the screw 32, to which it is meshed. The screw is supported in bearings 33, and
is revolved by any suitable power applied to the pulley 34, or to the hand
wheel 85.
To
In order to secure the entire automatic operation of the furnace, the invention
also consists in means for reversing and regulating the movement of the electrode,
and for intermittently operating the belt and cleaning cylinders 21, 22.
this end I have provided preferably an induction electric motor 36, which is
geared by the pinion 37, to two gear wheels, one of which, 38, operates by
means of the pawl 40, and ratchet 41, the shaft 42 carrying a worm 43 operating
the worm gear 44, on the belt pulley shaft 45. The other gear wheel 39, is
attached to the screw 32 heretofore described. The motor is supplied with a
polyphase current and is preferably included in a shunt 46, off the main circuit

page_text: to the electrodes, but it is obvious that the electric current may be supplied
thereto from any other suitable source.
The speed of the motor is regulated by a device 60, consisting of a number
of resistances 48, on each branch 49, of the polyphase circuit attached to rheostat
contact pins 50 and lever 51. The lever is operated on the one hand by a
spring 52, which tends to keep it in the position shown, and is operated on the
other hand by an electro-magnet 53, attracting an armature 54, on the said
lever 51, and excited preferably directly by one of the branches 30, of the
polyphase current supplied to the furnace. It will be seen that during the
withdrawal of the electrodes over the hearth of the furnace, should the incan-
descent conductor a, grow or enlarge to such dimensions as to allow too great a
current to pass, the electro-magnet is strongly excited and strongly attracts the
armature 54, against the pull of the spring 52, and thereby moves the rheostat
lever to decrease the resistance in the motor circuit and accelerate the speed of
the motor. The electrodes are then withdrawn more rapidly, and the conductive
incandescent body of carbide attenuated to a degree sufficient to increase its
resistance, so that the armature is allowed to return to its normal position. It
will be seen that by the foregoing apparatus, the strength or intensity of the
current supplied to the furnace may be nicely regulated.
as to
In order to provide for reversing the motion of the electrodes and the simul-
taneous forward movement of the belts, an electrical reversing switch 55, is
supplied in the motor circuit 46, and is operated by the frame 31, carrying the
electrodes as it reaches each end of its stroke. Means for carrying this operation
into effect are provided by an arm 56, attached to the said frame sliding over
a rod 57, having two collars 58, 59, attached to it on each side of the arm,
but at each end of the travel of the frame. The rod is extended so
enter the switch box 55, and operate the switch. As the frame near's
the end of the stroke the arm engages the collar 58, on the rod, and moves the
latter a sufficient distance to operate the switch, and on its return movement,
the reversing switch is placed in its former position by a similar engagement of
the arm against the opposite collar, 59. It will be seen that the belt and
electrodes move in one direction simultaneously, and preferably at the same speed,
the strip of carbide conductor being not attenuated during the return stroke,
decreases in resistance, and causes the regulator 60 to allow the motor to revolve
at its greatest speed, and to return the electrodes to their former position as
rapidly as possible.
During the action or during the forward movement of the belt and electrodes,
that portion of the strip of carbide which has been formed, and which is com-
paratively cool, passes beneath the plough 18, between the scrubbing
cylinders 21, 22, and out of the furnace.
The shaft 42, also operates the scrubbing cylinders by pulleys 61 and 62, and
it is revolved only when the movement of the belt and said cylinders are
required, by means of the ratchet 41, which is attached to the shaft 42, and
which is engaged by the pawl 40, carried on the gear wheel 38, only when the
latter is revolving in one direction, its movement in the other direction having
no effect on the ratchet.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is;
1. The herein described process of making calcium carbide, which consists
in converting progressively by incandescence of a carbide conductor, carbide-
forming material into carbide, in a direction at right angles to the passage of an
electric current through said conductor, advancing both material and the formed
carbide in a direction opposite to that in which the carbide was formed and
then again progressively forming a body of carbide in the original direction.
2. The herein described process of making calcium carbide, which consists

page_text: .
in alternately forming carbide in one direction in a body of material and removing
the formed carbide and surrounding material in an opposite direction, the
carbide being produced in the form of a continuous strip.
3. The herein described process of producing calcium carbide, which consists
in forming a continuous strip of carbide intermittently by distinctly separate
periods of production.
4. The herein described process of making calcium carbide, which consists
in advancing an electrical heating field through a body of carbide-forming
material, and regulating the rapidity of the said advancement by the variations
in resistance of the electric current through the heating field.
5. The herein described process of making calcium carbide in the form of a
continuous strip, by an incandescent carbide conductor advanced through carbide-
forming material, removing the excess of carbide simultaneously with a forward
movement of the surrounding material, and simultaneously scrubbing or clean-
ing the ejected body of carbide.
6. The herein described process of making calcium carbide in the form of a
continuous strip and scrubbing or cleaning the body of carbide as it is produced.
7. The herein described process of making calcium carbide in the form of a
continuous strip beneath a body of carbide-forming material and removing the
superimposed carbide-forming material as the carbide is produced.
8. In an electric furnace, the combination of substantially parallel-horizontal
electrodes, a furnace hearth and means for moving the said hearth and electrodes
longitudinally in unison, as described.
9. In an electric furnace, the combination of a plurality of substantially
parallel and horizontal electrodes, a horizontally movable hearth and means for
moving the electrodes longitudinally independent of the hearth, as described.
10. In an electric furnace, the combination of a plurality of substantially
parallel and horizontal electrodes, a horizontally movable hearth, and means for
moving the electrodes longitudinally backward and forward and means for
moving the hearth in unison with the electrodes in one direction, as described.
11. In an electric furnace, the combination of a plurality of substantially
parallel and horizontal electrodes, means for maintaining an incandescent heat-
ing conductor between the said electrodes, means for longitudinally moving the
electrodes and means for regulating the speed of movement of the electrodes
according to the resistance of the said conductor, as described.
12. In an electric furnace, the combination of a plurality of substantially
parallel and horizontal electrodes, means for maintaining an incandescent heat-
ing conductor between the said electrodes, means for moving the electrodes
longitudinally and means for automatically reversing the motion of the said
electrodes, as described.
13. In an electric furnace, the combination of longitudinally reciprocating
electrodes, an intermittently moving furnace hearth consisting of an endless
belt and means for moving the said belt and electrodes in one direction in unison,
as described.
auto-
14. In an electric furnace, the combination of longitudinally reciprocating
electrodes an electric motor for operating the said electrodes and an
matically operating electric switch for reversing the motion of the electrodes, as
described.
15. In an electric furnace the combination of substantially parallel electrodes,
an electric motor for moving the electrodes, means for maintaining an incan-
descent conductor between the electrodes and means for regulating the speed
of the said motor, as described.
16. In an electric furnace, the combination of longitudinally movable electrodes,
an electric motor, an electric resistance for the motor, and means for connect-
ing the regulator within the circuit of the electrodes, as described.
17. In an electric furnace the combination of means for producing a continuous

page_text: strip of carbide and a plough for removing unconverted material from the
surface of the strip of carbide, as described.
18. In an electric furnace, the combination of means for producing a continuous
strip of carbide and cleaning brushes, for cleaning carbide as it is produced,
as described.
19. In an electric furnace the combination of means for producing a continuous
strip of carbide and a plurality of cleaning brush rollers for cleaning the said
strip as it is produced, as described.
20. In an electric furnace, the combination of means for producing a continuous
strip of carbide and two brush rollers reyoluble at different speeds and in different
directions, as described.