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Publication numberUS3300562 A
Publication typeGrant
Publication dateJan 24, 1967
Filing dateJan 13, 1964
Priority dateJan 13, 1964
Publication numberUS 3300562 A, US 3300562A, US-A-3300562, US3300562 A, US3300562A
InventorsMoore James W
Original AssigneeMc Graw Edison Co
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Arc furnace electrode control apparatus
US 3300562 A
Abstract  available in
Images(3)
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Claims  available in
Description  (OCR text may contain errors)

J. W. MOORE ARC FURNACE ELECTRODE CONTROL APPARATUS Jan. 24, 1967 Filed Jan. 15, 1964 INVENTOR 77765 Z/ry/rt M70076 Jan. 24, 1967 w, MOQRE ARC FURNACE ELECTRODE CONTROL APPARATUS 5 Sheets-Sheet 2 Filed Jan. 13, 1964 A/E/I/Vl/E/V INVENTOR i 77785 Zfight Mame 5 M wfttormy iiii -uHIunu ill Jan. 24, 1967 J. w. MOORE ARC FURNACE ELECTRODE CONTROL APPARATUS 3 Sheets-Sheet '5 Filed Jan. 13, 1964 INVENTOR. ames Mfg/2t ukao/"e m wk FR m m & NM Q United States P ent O" I 3,300,562 ARC FURNACE ELECTRODE CONTROL APPARATUS James W. Moore, Pittsburgh, Pa., assiguor to McGraw- Edison Company, Milwaukee, Wis., a corporation of Delaware I Filed Jan. 13, 1964, S81. No. 337,289

' 13 Claims. (Cl.13-;13) I This invention relates toelectric arc furnaces and more particularly to apparatus for controlling the position of arc furnace electrodes.- 1 -It iscommon practice in the production of high-grade steel to utilize polyphase electric arc furnaces having a plurality of electrodes and electrode positioning means as-sociated with each electrode. Current flow in such furnacesis from the electrodes to the grounded furnace charge. That portion of the current path'between the electrodes and the. furnace charge is an are which provides the heat necessaryfor furnaceoperation.

Means are gene-rally provided toposition each of the electrodes relative to thefurnace charge in accordance with the length of its respective arc as indicated by the arc current and the arc voltage so that when the arc current rises, indicating that the arc is too short, the electrode is raised, and when the arcvoltage rises, indicating that the arc is ,too long,.the electrode is lowered.

One type of electrode positioning apparatus employs a: reversible hydraulic motor which is connected to the electrodes by means of an electrode clamp and a positioning arm. The hydraulic motor is connected to a source of hydraulic pressure through a hydraulic control mechanism which couples the ram to the source of hydraulic pressure in accordancewith the electrical conditions'in the furnace. Such hydraulic control systems generally include a servo valve which metersthe flow of hydraulic fluid between the hydraulic ram and the pressure source in accordance with electrode current, and 'voltage conditions. In order to achieve sufllcient amplification for the operation of the servo valve, it was often necessary to employ a'pilot valve and an intermediate control valve between the voltage and current sensing portions of the' device and the servo valve.' There is a tendency foreach valve in the amplification stages to slightly overshoot and this is multiplied by each succeeding stage so that such controlisystems have a tendency to hunt. Various schemes have been tried to compensate for such hunting but these tend to make control apparatus complicated and costly. This hunting is due to a phenomenon known as orificereaction, that is, thetendency for hydraulic fluid acting on a piston-type valve when the valve port is first opened to move the valve element beyond its desired position.

It is'an object of the invention to provide control apparatus for the hydraulic positioning assembly of an arc furnace electrodewherein metering of the hydraulic fluid is accomplished by pinch valves whichare free from orifice reaction'disturbances.

' Another object of theinvention'is'to provide a control means for the hydraulic positioning assembly of an arc furnace electrode wherein hydraulic metering is controlled by an electromagnetic variable transmission device to eliminate the necessity for hydraulic sensing and amplifying elements. v

A further object of the'invention is to-provide a control apparatusfo'r the hydraulic positioning assembly of an arc furnace electrode whereinelectromagnetic clutch means energized in'accordance with electrical conditions in the are for coupling continuously running'motor means to valve means so that the electrode is lowered when" its voltage exceeds a preselected value and raised when its current exceeds a preselected value. An object of one embodiment of the invention is to provide such apparatus with biasing means coupled to said clutch in a manner tending to operate said valve means in an electrode lowering direction and wherein an electrical signal is applied to said clutch means in an opposing sense relative to said biasing means. An object of another embodiment of the invention is to provide such apparatus with first and second electromagnetic clutches respectively energizable by signals proportional to voltageand current and each acting in opposition on reversible valve operating means.

These and other objects and advantages of the instant invention will become more apparent from the detailed description thereof taken with the accompanying draw ings in which:

l FIG. 1 schematically illustrates one embodiment of the electrode positioning assembly according to the instant invention;

FIGS. 2 and 3 illustrate in greater detail the pinch valve employed with the control mechanism of FIG. 1; and

FIG. 4 schematically illustrates an alternate embodiment of the instant invention. 7

Referring now to the drawing in greater detail, an electric arc furnace 10 is shown in FIG. 1 to include a furnace body 11 containing a quantity of molten furnace charge or melt 12 and three movable electrodes 13, 14 and 15'positioned above the melt 12. The electrodes 13, 14' and 15 are connected to three-phase supply conductors 16, 17 and 18 respectively, which are, in turn, connected to a suitable source of three-phase power (not shown). A hydraulic motor 20 is mechanically connected to each of the electrodes 13, 14 and 15 by an electrode positioning arm 21 so that said electrodes may be raised and lowered in accordance with furnace conditions. Since identical operating mechanisms are provided for controlling the positioning of each of the electrodes 13, 14 and 15, only one is illustrated for the sake of brevity.

The hydraulic motor 20 includes a cylinder 23 and a piston 24 coupled to the arm 21 and actuated by the control'mechanism according to the instant invention which is shown to' include a source of hydraulic pressure 25, a hydraulic control assembly 26 connected between the pressure source 25 and the fluid motor 20, and an electrode condition-sensing circuit 27 for initiating the operation of the control mechanism 26.

The source of hydraulic pressure 25 includes a hydraulic accumulator 30 which is connected by a pump 32 to a fluid reservior or sump 34. In a manner well-known in the art, a motor 36 drives the pump 32 so that substantially uniform high pressure is-maintained Within the accumulator 30.

The hydraulic control circuit 26 regulates the flow of hydraulic fluid between the fluid motor 20, the accumulator 30 and the sump 34. Control 26 includes a first pinch valve 40 which is disposed in a conduit 41 connecting the accumulator 30 to the pressure side of the piston 24 and a second pinch valve 42 which is connected in a conduit 44 between the sump 34 and the pressure side of cylinder 24.

FIGS. 2 and 3 show the pinch valve 42 in greater detail to include a generally tubular body portion 45 having a flange 46 suitably mounted at each end so that the valve 42 may be connected into the conduit 44. The tubular body portion 45 has a reduced central portion 48 provided with an opening 50 formed in one side thereof so that one edge of a pinch lever 52 may bear against a flexible lining 53 disposed within the tubular member 45. The lining 53 is suitably aflixed within tubular member 45 and is formed of any suitable material such as rubber. The pinch lever 52 is generally L-shaped and is pivotally mounted at one end about a fixed pin 55. A spring 56 urges clockwise rotation of lever 52, as viewed in FIG. 3, and toward a stop 58. This tends to move the edge of pinch lever 52 toward the right as viewed in FIG. 2 to force the opposite sides of the flexible lining 53 together and prevent the flow of fluid in conduit 44.

As seen in FIG. 1, valve 40 is identical with valve'42 except that its pinch lever 52a is urged toward counterclockwise rotation to close its flexible lining by the action of its spring 56a. .In addition, one end of anL- shaped lever 59 and 59a is respectively connected tothe upper end of pinch levers 52 and 52a and both extend in substantial alignment toward a valve operating member 71 whose purpose will be discussed in greater detail hereinbelow.

Valves61 and 64 are provided in the conduits 41-and 44 respectively in order to isolate the fluid motor 20 from the hydraulic accumulator 30 and the sump 34 if so desired. 1

The hydraulic control 26 includes 'adrive motor 70 which is mechanically coupled to a disc-shaped valve control member 71 through an electromagnetic clutch 72. The motor 70 rotates continuously in one direction to provide a counterclockwise torque'on the valve operating member 71 in opposition to a spring 75 and the magni-' tude' of this torque will depend upon the degree of coupling provided by the electromagnetic clutch 72.

More specifically, the clutch 72 includes an input member 76 which is rigidly afiixedto the motor'70 output shaft and is rotatable therewith. The clutchinput member 76 is ferro-magnetic and has a cup-shaped recess 77 in which a disc-shaped ferro magnetic clutch output member 78 is disposed. An annular coil 79 is disposed concentrically around the outer surface of the cup-shaped portion 77 of the clutch inputmember 76. As will be understood by those skilled in the art, the torque exerted by the clutch output member 78, and hence. that of the valve control member 71, will depend upon the degree of excitation in the coil 79.

-An output shaft 66 is' rigidly aflixed'to' the clutch out-. put member 78 and extends upwardly therefrom where its upper 'end rigidly engages the valve control member 71. A pair of lugs 67 and 67a extend upwardly in spaced relation from the upper surface of the valve control member 71 and each is disposed adjacent to and spaced from the-free ends of the links 59and159a, respectively} It can be seen that when the clutch 72 is in its neutral position shown in FIG. 1, that is, when the torque'on output member 78 just balances therestoring force of spring 75 the lugs 67 and 67a will be out of engagement with the ends of links 59 and 59a so that the valves 40 and 42-will remain closed. As will be pointed out in greater detail hereinbelow, a decrease in the torque on outputfmember 78 will allow spring 75 to rotate lug 67 into engagement with link 59 to move pinch lever 52 clockwise to open valve 42 whereby the fluid motor 20 is connected tothe sump 34 and the electrode 13 is lowered. Conversely, an

increase in the torque on output member 78 will rotate lug 67a into engagement with link 59a to open valve,52a so that the fluid motor 20 is'conn'ected to \the pressure source 30 and the electrode 13 is raised. 7 1

The control circuit 27Ifor the electromagnetic clutch 72 includes a first resistor 80 connected 'tothe electrode phase conductor 16 by means of a'current transformer 82, a potentiometer 83 connected across the secondary winding of the current transformer 82, and a full-wave rectifier 84 so that a voltage is derived across resistor80 which is proportional to the current flowing in electrode 13. Control circuit 27 also includes second resistor 86 connected to the phase conductor 16 through a potentiometer 8 8 and a full-wave rectifier 89 so that a voltage is derived across resistor 86 which is proportional to the voltage across the electrode 13. It can also be seen that the voltages derived across resistors 80 and 86 are subtractive- In addition, control circuit 27 includes an adjustable bias resistor 90 which is connected through a full-wave rectifier 92 to a source of alternating current 93 in such a man ner that the voltages across resistors 80 and 90 are additive.

It will be appreciated that the voltage derived across resistor 80. plus that derived across resistor 90 minus that derived across resistor 86 will be'the excitation voltage for coil-79 sothat the degree of coupling between clutch input member 76 and. clutch output member 77 will;- be a function'of the algebraic sum of these voltages; Potentiometers .83 and 88 and resistor 9t) are so adjusted that when the electrode current and voltage conditions are correct the excitation applied to coil 79 will provide sufficient coupling between the input member 76 andthe output member 78 to just hold the valve member 71 in a balanced condition relative to the spring 75 so that each of the valves 40 and 42 will be closed and the electrode 13 will'be held in position. I

Should the'gap between electrode 13' and melt 12 become too'large, causing an increase in arc'voltage and a decrease injarc current, the voltage across resistor 86 will increase and the voltage across resistor 80 will'dcrease. As a result, the excitation in the coil 79 will decrease below that required to'hold the valve member 71 in its neutral position and it will be rotated counterclockwise through a slight angle by the spring 75un'til the spring 75 torque is equal to that exerted by the clutch output member 78 and the spring 56, Such counterclockwiserotation of valvemember" 71'will movelug 67 into engagement with' link 59'to rotate pinch rod 52 clockwise to open the valve 42 thereby connecting the pressure side of piston'24 tothe sump 34 which'allows'the electrode 13 to begin lowering. the electrode 13 lowers the electrodevoltage will decrease and the electrode cur rent will increase so that the excitation of coil 79 will also raise until iteis again at the optimum of value, whereupon the output torque on valve member 71 will match that exerted by the spring 75, whereupon merm ber '71 will again assume its neutral position "wherein valve 42 isC1osedan d the electrode 13'isstationary. f Should the gap between electrode 13 and-the furnace charge 12 become too short, causing an increase in arc current and a decrease in arc. voltage,the voltage ,acros's' resistor 80 will increase'and that acrossresistor 86 will tatecountercldckwise against springs 75 and 56a. and

decrease. Upon this event the excitation. -on coil79 will increase from the optimum-value, thereby increasingthe output torque'v on the valve member 71"causing it torothereby .to open valve 40. This. connects the pressure side of pist0n24 to'the hydraulic accumulatorv30 whereupon hydraulic pressure will raise the electrode 13 As the electrode 13 rises,.the' arc'voltage will increase and the arc'currentwill decrease whereby the excitation of .coil 79 will also decrease toward the optimum value so that when electrode current, and voltage conditions are again in balance valve member 71 will have returned to its neutral position wherein the .valve 40 is closed and electrode 13 is stationary. 1

It will beappreciated that the rate offluid flow through the valves 40 and 42.will vary fromsome zero value when their respective pinch levers 52 and 52a. are in their fully closed positions to some maximum .values when these levers are in their fully rotated positions; Since the .de-

' g'ree that each pinch lever rotates from its closed position hydraulic motor 20, without the necessity of pilot valves and control valves to sense and amplify electrode voltage and current changes. v fl s In order to permit manual operation during the beginning or end of each operation, solenoid operated valves 1% and 101 may be provided in bypass conduits 102 and 103, respectively, which are in turn respective-1y connected in parallel with pinch valves 40 and 42.

FIG. 4'shows an alternate embodiment of the invention, wherein a second-electromagnetic clutch assembly 72 is provided for driving the valve member 71- in an electrode'lowering direction. This provides a balanced system and eliminates the necessity for a biasing Spring 75. The second electromagnetic clutch 72' is identical with the electromagnetic clutch 72 and, accordingly, corresponding parts have been given the same reference numeral. except that each is distinguished by a prime in the former.

' The electromagnetic clutch 72 of FIG. 4'is operative to impart a counterclockwise torque on the valve member 71 for opening the pinch valve 40 to initiate an electrode raising operation. Toward this end, the coil 79 of clutch 72 is connected to resistor 80, so that the coil 79- will receive an exciting voltage proportional to the current in electrode 13. On the other hand, the clutch 72' is operative to impart a clockwise torque on the valve member 71 to open pinch valve 42 and initiate an electrode lowering operation. For this reason the coil 79 of clutch 72' is connected to resistor 80' so that it will receive an excitation voltage proportional to the voltage in electrode -13. It is also desirable in the embodiment of'FIG. 4 to .provide a first biasing potentiometer 90 in series with resistor 80 and a second biasing potentiometer 90 in series with the resistor 80. The biasing potentiometers 90 and 90 are each connected to a source 93 through a rectifier 92 in such amanner that the voltage drop across each is in opposition to its respective series connected resistor 80 and 80, so that these voltages will be subtractive from .the voltages induced across said resistors.

When voltage and current conditions in electrode 13 are in balance, there will be zero torque on valve output member71 as the outputs of each of the clutches 72 and 72' will be equal and opposite acting; Should the arc gapbecome too short, causing an increase in arc current and a decrease in arc voltage, the output of clutch 72 will increase, and the output of clutch 72 will decrease, causing a net counterclockwise torque on output member 71 to open valve 40 and initiate an electrode raising operation. Should the arc gap become too long, on the other hand, causing an increase in arc voltage and a decrease in arc current, the output torque from clutch 72' will increase and the output of clutch 72 will decrease, to cause a net counterclockwise torque on valve member 71, so

that valve 42 will open to initiate an electrode lowering operation.

Because identical clutch and motor arrangements are employed for imparting both clockwise and counterclockwise torques to the valve member 71, a balanced system is obtained and equal torques are employed for opening each of the pinch. valves 40 and 42 in contrast to the embodiment of FIG. 1, on the other hand, where a spring 75 is employed to impart clockwise torque to the valve member 71.

While only two embodiments of the invention have ,been shown and described, and while they have been illustrated with respect to one type of hydraulic system, it is intended that the invention be limited only by the scope of the appended claims.

I claim:

1. In an electric arc furnace, the combination of a ,furnace body and an electrode, a hydraulic motor connected to said electrode, a hydraulic pressure system,

valve means operable in one manner to connect said hydraulic motor to said pressure system in an electrode raising relation and in another manner to connect said hydraulic motor to said pressure system in an electrode lowering relation, continuously operable electric motor means, electromagnetic clutch means coupled to said 'electric motor means and operatively associated with said -valve means, a first electrical signal source coupled to said electrode-for producing a first signal functionally related to the current in said electrode, said first signal source also being connected to said clutch means for opcrating said valve means in said one manner so that said electrode will be raised When the current therein rises above a desired value, and a second electrical signal 1 source coupled to said electrode for producing a second signal functionally related to the voltage in said electrode, said second signal means also being connected 'to said clutch means for operating said valve means in said another manner so that said electrode will be lowered when its voltage rises above a desired value.

2. In an electric arc furnace, the combination of a furnace body and an electrode, a hy raulic motor connected to said electrode, a hydraulic pressure system,

valve means operable in one direction to connect said hydraulic motor to said pressure system in' a manner tending to raise said electrode and in another direction -to connect said hydraulic motor to said pressure system in a manner tending to lower said elect-rode, continuously 'operable electric motor means, electromagnetic clutch means having magnetic input means coupled to said electric motor means and magnetic output means operatively associated with said valve means, said clutch means including exciting coil means for producing coupling between said input and output means to move said output means in accordance with the magnitude and sense of an applied electrical signal, a first electrical signal source coupled to said electrode for producing a first signal functionally related to the current in said electrode, said first signal source also being connected to said coil means in a sense tending to move said output means in said one direction so that said electrode will be raised when the current therein rises abovea desired value, and a second electrical signal source coupled to said electrode for producing a second signal functionally related to the voltage in said electrode, said second signal means also being connected to said coil means in a sense tending to move said output means in said another direction so that said electrode will be lowered when its a desired value.

3. In an electric arc furnace, the combination'of a voltage rises above -furnace body, an electrode, a hydraulic motor connected to said electrode, a hydraulic pressure system, first nor mally closed pinch valve means operable in one direction to connect said hydraulic motor to said pressure'system motor means for operating said valves in said another direction, a first electrical signal source coupled to said electrode for producing a first signal functionally related to the current in said electrode and connected to said electroresponsive means in a sense tending to increase the coupling between said motor and each of said valve means, and a second electrical signal source coupled to said electrode for producing a second electric sign-a1 functionally related to the voltage in said electrode and con- .nected to said electroresponsive means in a sense tending to decrease the coupling between said electric motor means and each of said valve means.

4. In an electric arc furnace, the combination of a furnace body and an electrode, a hydraulic motor connected to said electrode, a hydraulic pressure system, valve means operable in one direction to connect said hydraulic motor to said pressure system in a manner tending to raise said electrode and in another direction to .connect said hydraulic motor to said pressure system in a manner tending to lower sai-d electrode, continuously operable electric motor means, electromagnetic clutch means having magnetic input means coupled to said motor and magnetic output means operatively associated with said valve means, said electric motor means opersaid electrode will be raised when the current therein rises above a desired value, and a second electrical signal source coupled to said electrode for producing a second voltage signal functionally related to the voltage in said electrode,

, said second signal means also being connected to said coil means in a sense tending to decrease the coupling between said input and output means so that said electrode will be lowered when its voltage rises above a desired value.

5. In an electric arc furnace, the combination of a furnace body and an electrode, a hydraulic motor connected to said electrode, a hydraulic pressure system, first and second pinch valve means each having variable flow restricting means and control means, a first one of said control means being operable in a first direction to move a vfirst one of said flow restricting means between closed and controlled open positions to connect said hydraulic motor to said pressuresystem in a manner tending to raise said electrode, the second one of said control means being ,operable in another direction to move the second one of said flow restricting means between closed and controlled open positions to connect said hydraulic motor to said pressure system in a manner tending to lower said electrode, continuously operable electric motor means, electromagnetic' clutch means having an exciting coil, saidclutch means also having input means coupled to said electric motor means and output means operatively associated with said'control means for selectively operating the latter 1 in accordance with the magnitude of an applied electrical signal, said electric motor means tending to operate said output means in said one direction, means biasing said output means in said another direction, a first electrical signal source coupled to said electrode for producing a first voltage signal functionally related to the current in said electrode, said first signal source also being connected to said coil means in a sense tending to increase the coupling be tween said input and output means so that said electrode will be raised when the current therein rises above a desired value and a second electrical signal source coupled to said electrode for producing a second voltage, signal functionally related to the voltage in said electrode, said second signal means also being connected to said coil means in a sense tending to decrease the coupling beitween said input and output means so that said electrode will be lowered when its voltage rises above a desired value.

6. In an electric arc furnace, the combination of a "furnace body and an electrode, a hydraulic motor, a hytdraulic pressure system, valve means operable in one direction to connect said hydraulic motor to said pressure system 1n a manner tending to raise said electrode and in another direction to connect said hydraulic motor to said pressure system in a manner tending to lower said electrode, continuously operable electric motor means, elec- :tromagnetic clutch means having magnetic input means coupled to said electric motor means and magnetic output means operatively associated with said valve means,

said electric motor means operatingsaid input means in said one direction, means biasing said output means in said another direction, said clutch means including exciting coil means for producing coupling between said input and output means in accordance with the magnitude of an applied electrical signal, a first electrical signal source coupled to said coil in a sense tending to produce coupling between said input and output means in opposition to said biasing means, a second electrical signal source coupled to said electrode for producing a second signal functionally related to the current in said electrode, said second signal source also being connected to said coil means in an additive sense relative to said first signal source to move said output means in said first direction whereby said electrode will be raised when the current 'therein rises above a desired value, and third electrical signal source coupled to said electrode for producing a third signal functionally related to the voltage in said electrode, said third signal means also being connected to said coil means in a subtractive sense relative to said first signal source so that said biasing means can move said output means in said another direction whereby said electrode will be lowered when its voltage rises above a desired value. 7

7. The combination set forth in claim 6 wherein said valve means comprises first variable flow pinch valve means operable in one direction to connect said hydraulic motor to said pressure system in a manner tending, to

raise said electrode and second variable flow pinch valve means operable in another'direction to connect said hydraulic motor to said pressure system in a manner tending to lower said electrode. 7

8. In an electric arc furnace, the combination of a furnace body, an electrode, a hydraulic motor connected to said electrode, a hydraulic pressure system, first normally closed valve means operable in one direction to connect said hydraulic motor to said pressure system in a manner tending to raise said electrode, second normally closed valve means operable in another direction to connect said hydraulic motor to said pressure system in a manner tending to lower said electrode,-first and second continuously operable electric motor means, first electroresponsive variable transmission means operable to couple said first electric motor means to said valves for operation in said one direction in accordance with the magnitude of a first applied electrical signal and second electroresponsive variable transmission means operable to couple said second electric motor means to said valves foroperation in an opposite direction in accordance with the magnitude of a second applied electrical signal, a first electrical signal source cou led to said electrode-for producing a first signal functionally related to the current in said electrode and connected to said first electroresponsive means in a sense tending to increase coupling between said first motor means and each of said valve means for operation in said one direction, and a second electrical signal source coupled to said electrode for producing a second electric signal functionally related to the voltage in said electrode and connected to said electroresponsive means in a sense tendring to increase the coupling between said'second motor means and each of said valves for operation in said opposite direction.

9. The combination set forth in claim 8 wherein each of said normally closed valve means is a variable flow pinch valve.

10. In an electric arc furnace, the combination of a furnace body and an electrode, a hydraulic motor, a hydraulic pressure system, valve means operable in one direction to connect said hydraulic motor to said pressure system in a manner tending to raise said electrode and in an opposite direction to connect said hydraulic motor to said pressure system in a manner tending to lower said electrode, first and second continuously operable electric motor means, first and second electromagnetic clutch means each having magnetic input means coupled to one of said electric motor means and magnetic output means coupled to said valve means, said first electric motor means operating said first input means in said one direction, said second electric motor mean operating said second input means in an opposite direction, each of said clutch means including exciting coil means for producing coupling between its respective input and output means in accordance with the magnitude of an applied voltage signal, a first electrical signal source coupled to said electrode for producing a first signal functionally related to the current in said electrode, said first signal source also being connected to said first coil means in a sense tending to move said valve means in said first direction whereby said electrode will be raised when the current therein rises above a desired value, a second electrical signal source coupled to said electrode for producing a second signal functionally related to the voltage in said electrode, said second signal means being connected to said second coil means in a sense tending to move said valve means in said opposite direction whereby said electrode will be lowered when its voltage rises above a desired value.

11. The combination set forth in claim wherein said valve means comprises first variable flow pinch valve means operable in one direction to connect said hydraulic motor to said pressure system in a manner tending to raise said electrode and second variable flow pinch valve means operable in another direction to connect said hydraulic motor to said pressure system in a manner tending to lower said electrode.

12. In an electric arc furnace, the combination of a furnace body and an electrode, a hydraulic motor connected to aid electrode, a hydraulic pressure system, valve means operable in one manner to couple said hydraulic motor to said pressure system in an electrode raising relation and in another manner to couple said hydraulic motor to said pressure system in an electrode lowering relation, continuously operable electromotive means, electroresponsive variable transmission means for coupling said electromotive means to said valve means, a first electrical signal source coupled to said electrode for producing a first electrical signal functionally related to the current in said electrode, said first signal source also being connected to said electroresponsive variable transmission means for coupling said valve means to said electromotive means for operating said valve means in said one manner so that said electrode will be raised when the current therein deviates from a desired value, and a second electrical signal source coupled to said electrode for producing a second signal functionally related to the voltage in said electrode, said second signal means also being connected to said electroresponsive variable transmission means for coupling said valve means to said electromotive means for operating said valve means in said another manner so that said electrode will be lowered when its voltage deviates from a desired value.

13. In an electric arc furnace, the combination of a furnace body and an electrode, a hydraulic motor connected to said electrode, a hydraulic pressure system, valve means operable in one direction to couple said hydraulic motor to said pressure system in a manner tending to raise said electrode and in another direction to couple said hydraulic motor to said pressure system in a manner tending to lower said electrode, continuously operable electromotive means, electroresponsive variable transmission means having input means coupled to said motive means and output mean operatively associated with said valve means, said electroresponsive variable transmission means including electroresponsive means for producing coupling between said input and output means to move said output means in accordance with the magnitude and sense of an applied electrical signal, a first electrical signal source coupled to said electrode for producing a first signal functionally related to the current in said electrode, said first signal source also being connected to said electroresponsive means in the sense tending to move said output means in said one direction so that said electrode will be raised when the current therein rises above a desired value, and the second electrical signal source coupled to said electrode for producing a second signal functionally related to the voltage in said electrode, said second signal means also being connected to said electroresponsive means in a sense tending to move said output means in said another direction so that said electrode will be lowered when its voltage rises above a desired value.

References Cited by the Examiner UNITED STATES PATENTS 412,013 10/1889 Beebe 2519 2,450,427 10/1948 Hal-pert 91459 FOREIGN PATENTS 524,989 5/1956 Canada.

JOSEPH V. TRUHE, Primary Examiner.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US412013 *Apr 3, 1888Oct 1, 1889 Temperature-regulator
US2450427 *May 15, 1942Oct 5, 1948The Sperry CorporationServo units fob
CA524989A *May 15, 1956Asea AbRegulating device for electric arc furnaces
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3379919 *May 17, 1965Apr 23, 1968Lectromelt CorpHydraulic electrode positioning means for an electric arc furnace
US4142845 *Sep 27, 1977Mar 6, 1979Lepp William ADialysis pump system having over-center cam tracks to lock rollers against tubing
US4586187 *Nov 16, 1983Apr 29, 1986Mannesmann Rexroth GmbhControl apparatus for controlling movements of an electrode in an electric arc furnace
US5539768 *Mar 21, 1995Jul 23, 1996Ltv Steel Company, Inc.For heating a charge
WO1985003853A1 *Nov 2, 1984Sep 12, 1985New Regina CorpMachine for cleaning surfaces such as carpets, floors and the like
Classifications
U.S. Classification373/106, 314/61, 251/9
International ClassificationH05B7/109, H05B7/00
Cooperative ClassificationH05B7/109
European ClassificationH05B7/109