US2517528A - Furnace electrode regulator - Google Patents

Description

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W. E. MOORE FURNACE ELECTRODE REGULATOR Flled July l0, 1947 Aug. l, 1950 Patented Aug. 1, 1950 FURNACE ELECTRODE REGULATOR William E Moore, Pittsburgh, Pa., assigner to Delaware Engineering Corporation, Pittsburgh, Pa., a corporation of Delaware Application July 10, 1947, Serial No. 760,031

Claims.

This invention relates to a furnace electrode regulator for electric arc furnaces of the type in which the position of the movable electrodes is automatically adjusted by means of a fluid operated regulator. The regulator is controlled by apparatus which responds to variations in the electric current supply to the furnace.

This application is a continuation of my copending application entitled Furnace Electrode Regulator, Serial No. 498,317, led August 12, 1943.

The variations of the electric current are employed through the medium of suitable apparatus to control the power supplied to a fluid operated motor, the operation of which will cause the electrode to which it is connected to move toward or awayfrom the metal charge in the furnace.

In many installations the weight of the electrode and electrode gear is quite considerable and various counterbalancing means have been used to cushion this weight so as to. avoid shocks or application of undue weight on the electrode when it meets the furnace charge, and permit prompt movement of the electrode proportional to the change in the current and/or voltage of the electric power supplied to. the electrode.

Most of these arrangements have been either complicated, expensive, and dimcult to maintain, or they have `rendered unsatisfactory service, whereas the system I have 'invented requires relatively little equipment, affords very satisfactory electrode control, is inexpensive and substantially trouble free.

One object of my invention is to provide an automatic regulator for the electrodes of an electric arc furnace which will ensure that a substantially constant supply of current or power is taken from the furnace electric supply system, and that the electrode is moved gently.

Another object is to provide apparatus which is operated by fluid power, and which is susceptible to close control.

A further object is to provide an electrode control system which is simple in construction, durable, inexpensive to construct and operate, and which affords a high load factor operation.

According to my invention, the electrode is moved by a fluid operated cylinder piston which is automatically controlled in response to variations in the power flowing through the electrode and the weight of the electrode and connected parts is balanced so that no great weight will be transferred to the electrode.

Broadly speaking, my invention comprises a fluid motor operatively connected with a furnace electrode and adapted to move it to adjust the length of the arc, means controlled by the electric condition of the electrode current for controlling the operation of the motor, and balancing means for the electrode.

In the accompanying drawings in which I have shown for purposes of illustration only the presently preferred embodiment of my invention,

Figure 1 is a diagrammatic view of one embodiment of my invention;

Figure 2 is a schematic view of a type of control valve suitable for use in my invention; and

Figure 3 is a schematic view of still another type of control valve suitable for use in my lnvention.

The drawing, Figure 1, shows an electric furnace Y I0 containing a usual charge II ofmetal, and an electrode I2 connected to an electrode arm I3. The arm is insulated from and supported by a plunger or ram I4 which is slidably received in a fluid operated power cylinder I5. The piston and cylinder arrangement is commonly referred to as a hydraulic servo-motor.

The cylinder I5 is connected at its lower end by a pipe I6 to a control valve I'I. The control valve is connected -by means of a pipe I8 to the lower end of an air cushion hydraulic tank I9, sometimes referred to as the pressure tank, and by means of the pipe 20 to the lower end of another air cushion fluid tank 2l sometimes referred to as the equalizing or balancing tank. The lower end of tank 2| is connected to the tank I9 by a pipe or conduit 22 which is providedwith a pump 23 driven by an electric motor 2li. A check valve 25 is locatedv in the pipe 22 between the pump 23 and the tank i9. v

The control valve I1 includes a slide valve or piston 26 which is slidably movable to regulate the supply of liquid medium from tank I9 and pipe I8 to pipe I6 and cylinder I5 or the liquid exhaust from cylinder lI5 and pipe I6 to pipe 20 and I prefer to so arrange the openings from the regulator to the pipes I6 and I8 so that the valve 26 may close both openings at the same time.

A suitable source of air under pressure, for example, an air compressor 2l, supplies air at a convenient predetermined pressure above the liquid in pressure tank I9, so that the tank is only partially filled with liquid, such as a hydrocarbon oil, over which is an air cushion. The compressor 2l keeps the air pressure at a desired level so that the liquid is ,under a pressure sufficient to overcome the weight, friction and inertia of the plungff. Q1? ll. and the supported equipment. The

tank I9 has a sight gauge 2l, and a valve controlled liquid supply pipe 23 connected toit.

A suitable source of air under pressure, for example, an air compressor 30, supplies air at a convenient pressure above the liquid, such as a hydrocarbon oil, in tank 2|. A sight gauge 3| and a valve controlled liquid supply pipe 32 is connected to the tank as shown. v The pressure in tank 2| is suilicient to substantially counterbalance the weight of the plunger I4 and the weight of the equipment supported thereby so that when the piston 25 is positioned to allow the flow of liquid from pipe I through the valve and pipe 20 to be established, the liquid will ilow from cylinder I to tank 2| and the plunger I4 and its connected electrode I2 will move slowly and gently downwardly.

The position oi the piston 28 is controlled by an automatic regulator 3l which is actuated in accordance with the' electric powersupply to the electrode I2 in a manner well-known in the art. Typical ofsuch regulators'are CR4913 Amplidyne-type Electrode Regulator for Arc Furnace Control (General Electric Co.), and the Automatic Current Regulator for Electric Arc Furnaces (Westinghouse Electric and Manufacturing Company). The construction and operation of such devices are well-known. Suiiice it to say that if the electrode I2 approaches too closely to the charge II, the power supply to the furnace will be unduly high, and the regulator will cause the piston 2B of valve I1 to be moved downwardly I so as to permit liquid to pass from the pressure tank I9, pipe I8, valve I1 and pipe I6 to the cylinder I5 and cause'the electrode to be raised, thus lengthening the arc, until the power input is that desired, whereupon the piston 26 will be moved upwardly to shut of! the now from pipe i8. When the electrode is too far away from the metal charge, the current will drop and the regulator 33 will lift the piston 26 so as to allow fluid to pass from the cylinder I5 through the pipe I6, valve I1 and pipe 20 to the equalizing tank 2| until the power input reaches the desired valve, whereupon the piston 26 is lowered so as to cut off the fluid discharge through pipe I6.

When the liquid is being discharged into tank 2|, the level of the fluid in the tank will rise and operate the oat valve switch or control device 34 and thus start the ow of electric energy to the motor 2d which will operate pump 23 to force the liquid through pipe 22 and check valve 25 to the high pressure tank I9. The ow to tank i9 will continue so long as liquid is moved from the cylinder i5 to the tank 2|.

Instead of using air compressors 27 and 30, any other source of air supply may be employed, for example, the ordinary shop air supply. with suitable reducing valves. Suitable air pressures, for example, may be about 200 p. s. i. on tank I9 and about 100 p.` s. i. on tank 2| when the pressure in cylinder I5 caused by the pressure of supported parts is about 125 p. s. i. v

It is also possible to elevate the tanks I 9 and 2| so as not to require air pressure on top of the liquid, but even in this case, the pump 23 will be -required to force the liquid from-the tank 2| at a lower level to tank I9 at a higher level.

The balancing tank or reservoir 2| is normally maintained at a pressure insuiiicient to eifect positive operation of the servo-motor I5. The pump 23 is used to draw fluid out of the reservoir 2| and return it through tank I8 and valve I'| to the line at a higher pressure.

In Figure 2 I have shown schematically 8.' 291?- trol valve 4U which may be used in place of the control valve .|'I shown in Figure l. The control valve 40 includes a slide valve or piston 4I which is slidably movable in a cylinder 42 to regulate the now of liquid from pipe I3 to pipe I3, or the now of liquid from pipe I5 to pipe 20. The valve 4| is connected to and controlled by the regulator 33. The control valve includes an equalizingpipe 43 for substantially equalizing the pressure between the bottom of the cylinder 42 and the top thereof. The openings of the pipes I6, Il and 20 to the cylinder 42 are so arranged that the three openings cannot be-opened at the same time, nor can openings to pipes I8 and 2li ever be opened together. Thus, fluid may ilow from pipe I3 to pipe I8 at one time. or from pipe I3 to pipe 20. or vice versa.

In Figure 3 I have shown schematically still another form of a control valve 50 which may be used in my invention. The valve 50 consists of a cylinder 5I having a centrally disposed piston rod 52 4which is connected to and controlled by `regulator 33. Rod 52 has two fluid-tight piston heads 53 and 54 spaced apart on the rod 52 and slidable in the cylinder 5|. A slide valve 55 is mounted on the rod '52 betweenthe heads 53 and 54 and is likewise duid-tight with respect to the cylinder walls. The pipes I6 and I8 are received in openings in the cylinder walls and are covered or uncovered by the valve 55, depending upon its position. The pipe 20 is received in an opening in the lower part of the cylinder wall as shown between the lower head 54'and the valve 55. The valve 55 and the openings of the pipes I5, I8 and 20 are so arranged that uid may flow from pipe I8 to pipe IB, or from pipe I6 to pipe 2|), but not from pipe I8 to pipe 20 or vice versa. It will be observed that this valve arrangement is balanced so that it is responsive to comparatively small force exerted on the piston rod 52.

In the accompanying drawings I have illustrated diagrammatically an electrode regulating apparatus as applied to one of the electrodes of a well-known electric arc furnace, it being understood that a similar regulating device may be associated with each of the other furnace electrodes.

While I have described an exemplary embodiment of my invention, it is to be understood that various changes may be made within the scope of the claims.

I claim: l. In an electrode regulator which includes a liquid pressure operated servo-motor having a piston for raising and lowering the electrode, a

pressure tank for supplying liquid under pressure to the servo-motor as will move the piston to raise the electrode and an equalizing tank containing liquid under pressure suiicient to substantially counterbalance the weight on the piston to allow the electrode to lower the piston and cause flow of the liquid from the servo-motor to the equalizing tank; a pump having an inlet and an outlet, a pipe connecting the inlet directly to the liquid in the equalizing tank, a pipe connecting the outlet directly to the pressure tank, and a control device in the equalizing tank responsive to the liquid level in the equalizing tank for rendering said pump operable to pump liquid under the operating pressure existing in the equalizing tank directly from the equalizing tank and into the pressure tank.

2. In an electrode regulator which includes a liquid pressure operated servo-motor having a piston for raising and lowering the electrode, a

`pressure tank for supplying liquid under pressure to the servo-motor as will move the piston to raise the electrode and an equalizing tank containing liquid under pressure suillcient to substantially counterbalance the weight on the piston to allow the electrode to lower the piston and cause flow oi' the liquid from the servo-motor to the equalizing tank; a pipe connecting the tanks, a power operated pump connected in the pipe for withdrawing liquid from the equalizing tank and f forcing it at a, higher pressure into the pressure tank, and a switch controlled by the level of liquid in the equalizing tank for controlling the supply of power to the pump.

' 3. For use in combination with an electrode regulator for the electrodes of an electric arc furnace, including a liquid operated servo-motor with a movable piston, for adjusting the length of the furnace arc, a pressure tank containing liquid under a pressure sufficient to move the piston so as to raise the electrodes, an equalizer tank containing liquid under pressure less than the pressure in the pressure tank but sumcient w slightly less than balance the weight on the piston; a pump having an inlet and an outlet, a pipe under the pressure vin the equalizing tank connecting the lower part of the equalizing tank to the pump inlet, a pipe connecting the pump outlet to the pressure tank. a motor for driving the pump. and a control switch responsive to a 1 change in the level of the liquid in the equalizing tank for controlling the flow of power to the motor.

4. For use in combination with an electrode regulator for the electrodes of an electric arc furnace, including a liquid operated servo-motor with t. movable piston, for adjusting the length ot the furnace arc, a pressure tank containing liquid under a pressure suiliclent to move the piston so as to raise the electrodes, an equalizer tank containing liquid under pressure less than the pressure in the pressure tank but suiiicient 6 to slightly less than balance the weight on the piston; a motor driven pump having an inlet and an outlet, a pipe connecting the equalizing tank to the pump inlet, a pipe connecting the pump outlet to the pressure tank, a check valve in one of said pipes to prevent flow of liquid from the pressure tank to the equalizing tank, and a switch operable by a change of level in the equallzing tank to control the flow of power to the pump.

5. The combination with a uid pressure m0- tor for regulating the position of an electric furnace electrode, an elevating tank having fluid therein under a higher pressure sumcient when connected with said motor to elevate the electrode, and an equalizing tank having iiuid therein under a lower pressure suflcientwhen connected with said motor to counterbalance the electrode against movement; of a pump having WILLIAM E. MOORE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,528,510 Ritz Mar. 3, 1925 1,766,648 Keller June 24, 1930 1,774,213 Tagliaferri Aug. 26, 1930 1,895,699 Ziska Jan. 31, 1933 2,201,483 Eklund May 21, 1940

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