US2412000A - Electric arc furnace - Google Patents

Description

Dec. 3,v 1946. W E 'MOORE 2,412,000

ELECTRIC ARC FURNAGE Filed Jan. 5l, 1945 i l l INVENTOR Patented Dec. 3, 1946 UNITED STATES PATENT OFFICE ELECTRIC ARC FURNACE William E. Moore, Pittsburgh, Pa., assigner to Delaware Engineering Corporation, Pittsburgh, Pa., a corporation of Delaware Application January 31, 1945, Serial No. 575,406

(Cl. S14-61) 7 Claims. 1

This invention pertains to electric arc furnaces and is for an electrode operating apparatus and method for such furnaces. The application constitutes a continuation-in-part of my application Serial No. 498,317, nled August l2, 1943.

As disclosed in my said application it has been proposed to mount the carbon electrode of a furnace on any suitable form of guideway operated by a piston movable in a cylinder or by any desired form of fluid motor. The cylinder is connected through a reversing pump with a reservoir with means for confining air under pressure in the reservoir. The reversing pump is driven by a reversing electric motor, which in turn is controlled by the current being supplied to the electrode by well known means, so that if the arc lengthens the pump is driven to remove liquid from the cylinder and return it to the reservoir, whereas ii the arc shortens, the pump is driven in a direction to force liquid from the reservoir into the cylinder to lift the electrode and increase the length of the arc. The air over the reservoir is kept at a pressure slightly less than that necessary to counterbalance the electrode assembly, including the piston, so that the pump merely works against a slight differential in pressure.

According to the present invention, the pressure in the reservoir is maintained somewhat higher, instead of lower, than that necessary to counterbalance the electrode assembly. This has in some cases certain important values. If there is a current interruption or failure, the electrode is lifted clear of the charge in the furnace, avoiding carbonization of the charge which results when the electrode drops and remains in the charge. If the control mechanism fails, the electrode likewise is raised.

My invention further provides an improved arrangement for cooling the oil or other liquid used in the system.

The invention may be more fully understood by reference to the accompanying drawing in which the gure is a more or less schematic View of an electric furnace embodying my invention.

In the drawing, the furnace 2 is of conventional form. A single electrode is indicated at 3, but, there may be any desired number of such electrodes, three commonly being used, but for present purposes one is suicient. The electrode 3 is carried on a supporting arm 4 at the top of a piston 5 operating in a cylinder 6, the piston serving as a means for raising or lowering the electrode. Power from a line 1 is supplied through cable 8.

Connected with the bottom of the cylinder is a pipe 9 leading to one side of a reversible metering pump i8 which is of any usual or preferred construction. It may ce of the familiar gear or eccentric vane type, and in either case is incapable of completely blocking the flow or" iiuid therethrough, and may be capable of being operated by the fluid pressure in the line.

The opposite side of the pump l@ is connected with a pipe I i, and at l 2 is a huid pressure reservoir. Pipe Il has one branch Ha leading through check valve i3 to a spray nozzle or distributor lli inside the top of the reservoir. Another branch, l5, leads from pipe ll through a check valve iii to the bottom of the reservoir, Check valve Iii permits outflow from the reservoir but not inn flow, and check valve i3 permits iniiow, but not out-now.

A compressor Il maintains a pressure on the liquid I8 in the reservoir, which pressure is maintained at a substantially uniform value, this pressure being suiiicient, when transmitted through the pump, even though the pump is not being driven, to overloalance the electrode mounting` assembly and raise the electrode.

The reversible pump lil is driven by a re versble motor which is controlled by a control unit 2| electromagnetically or electronically o perated by the current and/or voltage supplied the electrode, as indicated, controls of this kind being well known in the art and being cormnercially available through Westinghouse Electric and Manufacturing Company, General Electric Company, Allis-Chalmers, and others.

In operation the motor 20 drives the pump one way or the other to eiiect the raising and lowering of the electrode according to variations in the current. Since the pressure in the reservoir is only slightly higher than the pressure created by the piston on the liquid in the cylinder, the pump has only to work at the most against a relatively slight differential to overcome resistance and raise or lower the electrode and the system responds readily to any need for adjustment.

As previously stated, metering pumps such as l0 are not fluid tight, or they may be rotated by a diierential pressure in the fluid system. This is a definite advantage, because when the pump is not operating the superior pressure in the reservoir is effective, but slowly however, against the piston to urge it very gradually upward. Hence, if current to the electrode is interrupted or the control unit fails to operate, the electrode will be gradually lifted to a point well clear of the charge in the furnace. At the same time, the effect of 56 this superior counter pressure is such, by reason of the pump, that movement of the electrode upwardly is very gradual when the pump is not working. When the pump is working, the movement of the electrode in either direction may take place more or less rapidly.

When the pump is operating to lower the electrode, the oil or other liquid withdrawn from the cylinder cannot enter the reservoir through check valve I8 and hence, must be discharged through spray nozzle it, which sprays it against the sides of the reservoir to cool it. The liquid becomes hot, not only by reason of the more or less frequent operation of the pump, but by reason oiV the cylinder being in proximity to the furnace, and this cooling of the liquid is a desirable feature of my invention. On the other hand, I3 prevents back flow of air into the system.

While I have shown as a preferred embodiment of my invention, a system in which a superior pressure is maintained in the reservoir by reason of air pressure maintained on a confined space above the liquid, other familiar means of securing the same result, as 'cy elevating the reservoir to secure a desired hydrostatic pressure head may be employed, and the invention may be otherwise embodied within the scope of the following claims.

I claim:

l. The method of operating an electrode mounting for an electric furnace in which there is a fluid pressure cylinder for raising and lowering the mounting, a source of fluid pressure connected with the cylinder to work in opposition to the weight of the electrode and its mounting with a reversible pump controlled by power ow to the electrode operatively disposed between the cylinder and fluid pressure source, which comprises continuously flowing the fluid from said source through said pump and continuously maintaining the pressure of the fluid from said source at a point sufiicient to raise the electrode when the pump is not operating.

2. In an electric arc furnace, an electrode, a mounting for the electrode, a servo-motor comprising a fluid-operated motor for raising and lowering the mounting, a source of duid under pressure connected with the servo-motor, a reversible pump operatively connected lbetween said source and the servo-motor, said pump when idle transmitting pressure between the source and the servo-motor, and means for maintaining a lconstant pressure on said source sufficient to operate the servo-motor to lift the electrode mounting when the pump is idle.

3. The method of operating an electric furnace electrode wherein the electrode is carried on a support which is raised and lowered by a fluidoperated motor, the fluid motor being connected with a source of iiuid pressure with a reversible pump in the connection between the cylinder and the source of fluid pressure, the pump being driven according to variations in currents applied to the electrode which comprises maintaining the source of fluid to operate the support under a pressure sufficient to lift the electrode when the reversible pump is not operating.

4. The method of operating an electric furnace electrode wherein the electrode is carried on a support which is raised and lowered by a fluid pressure cylinder, the cylinder being connected with a source of fluid pressure with a reversible pump in the connection between the cylinder and the source of fluid pressure, the pump being driven according to variations in currents applied to the electrode which comprises maintaining the source of fluid to operate the cylinder under a pressure suicient to lift the electrode when the reversible pump is not operating, while flowing the fluid through the pump as a metering means whereby such lifting of the electrode when the pump is not operating occurs slowly.

5. In the combination comprising an electric furnace electrode and its support, a fluid pressure cylinder for raising and lowering the support, a fluid reservoir, and a pipe connection between the reservoir and the cylinder including a reversible pump, the herein described invention which comprises providing two pipe connections in the line leading from the pump to the reservoir, one of said :connections opening into the reservoir below the liquid level therein, and the other opening into the'reservoir above the liquid level, there being an outwardly-opening inwardly-closing check valve in the first connection, and an inwardly-opening outwardly-closing check valve in the second connection, and a distributor in the reservoir to which the said second :connection delivers fluid.

6. In an electric fluid electrode operating mechanism wherein there is an electrode support, a fluid pressure cylinder for operating the support, a pipe for supplying liquid under pressure to the cylinder and withdrawing liquid from the cylinder, a reversible motor to which said pipe connects, and a fluid pressure reservoir, the reservoir having air under pressure confined in the upper part thereof and a body of liquid in the lower part, the herein dened invention comprising a pipe leading from the pump to the upper part of the reservoir and terminating in a distributor, there 'being a check valve in said pipe to prevent the flow of uid from the spray nozzle toward the pump, and a second pipe leading from the pump to the lower part of the reservoir, there being a check valve in said second pipe through which nuid may flow from the reservoir to the pump, but which prevents the flow of fluid in the reverse direction whereby upon operation of the pump to supply liquid to the cylinder such liquid is withdrawn from the bottom of the reservoir and when the pump is operated to return the liquid to the reservoir it is forced through said nozzle whereby the heated oil being returned may thereby be cooled while the oil which flows from the reservoir is cool.

7. In an electrode operating system including an electrode support, a iiuid pressure cylinder for raising and lowering the support, a pipe communicating with the cylinder, a reversible pump to which the pipe connects, a iluid pressure reservoir connected to the other side of said reversible pump, means for maintaining a body of air in the reservoir over the liquid for exerting a pressure upon the liquid greater than that required to elevate the electrode support, said reversible pump being of the non-blocking type, hence when it is idle forming a passageway for a back-flow of fluid from the reservoir to the cylinder at a relatively small rate such as to slowly raise the electrode support.

WILLIAM E. MOORE.

Images