US2896003A - Apparatus for controlling slipping of continuous electrodes - Google Patents

Description

July 21, 1959 M.YEATON 2,896,003

APPARATUS FOR CONTROLLING SLIPPING OF CONTINUOUS ELECTRODES Filed June 7, 1957 3 Sheets-Sheet 1 Inoezztor Milton EA 7' 01V M. EATON July 21, l959\ APPARATUS FOR CONTROLLING SLIPPING OF CONTINUOUS ELECTRODES Filed June 7, 1957 3 Sheets-Sheet 2 Inventor iii/f0 EA TON {gent M. EATON July 21, 1959 APPARATUS FOR CONTROLLING SLIPPING OF CONTINUOUS ELECTRODES Filed June 7, 1957 3 Sheets-Sheet 3 0 f f. mm v fi w WWW Q 4 L m, m ,m Tnwj i m J x 5 m m m P F; w a F United States Patent APPARATUS'FOR CONTROLLING SLIPPING 0F CONTINUOUS ELECTRODES Milton Eaton,.Shawinigan Falls, Quebec, Canada, as-

signor to Shawinigan Chemicals Limited, Montreal, Quebec, Canada, a corporation of Canada Application June 7,1957, Serial .No..664,281

"11 Claims. (Cl. 13-14) This invention relates to improvements in electric furnaces and more particularly to those having continuous electrodes such as are commonly used in furnaces in which the electrodes penetrate the charge.

Continuouselectrodes are those to which electrode material is added at one end to compensate for electrode consumption through gradual burning off of the other end during normal operation ofelectric furnaces'eq uipped with such electrodes. Inorder to maintain a substantially constant length of electrodes below their supporting contact shoes, it is necessary, intermittently or continuously, to, slip the electrodes through the contact shoes.

The conventional method of; slipping the electrodes of'multi-electrode furnaces through the contact shoes manually and at infrequent intervals, e.g. six to twelve times daily, has the'inherent disadvantage that. it. disturbs the normal operation of the furnace- The'disturbance is caused by the substantial increasein the electrode penetration of the-charge, occasioned by; the slippingv operation, and thetemporary unbalance resulting from the electrodes [being slipped one at a time.

The principal-object of'the' invention is to provide means for slipping the electrodes ofvmulti-electrode furnaces through their holders simultaneously and at frequent intervals or continuously. A further object is to provide independent means for adjusting the rate of slippage for each electrode. The means for'slipping the electrodes through their-holders, as provided by this invention, improves furnace operating conditions. Since the. slipping of the electrodes may be conveniently effected at frequent intervals, the. amount slipped at one time is not suflicient to disturb the operation of the furnace. The various other objects and advantages of the invention disclosed will become apparent to those-skilled in the art from the following description thereof.

The invention consists primarily of an apparatus for controlling the slipping of a continuouselectrode through its holders comprising. (1) an electrode supporting yoke suspended from fixed supports by hoisting gear, .(2). contact shoes suspended from the said electrode supporting yoke, (3) means for adjusting the pressure of the contact shoes on the electrodeto-maintain said contact shoes capable of supporting a maximum proportion. of the electrode weight whichis less than the whole weight, (4) secondary supporting means for partially supporting the weight of the electrode fromuthe said elect-rode supporting yoke, said secondarymeans being adapted also to support a maximum. proportionof" the electrode weight which is less than the whole weight, said secondary means. and said contact shoes together being adaptedto support at least the whole weight. of the electrode, .and (.5) power actuated motive means for lowering the said secondary supporting means in relation to the supporting yoke- The invention further consists of electrical circuit means for energizing poweractuated motive means to control the simultaneous slipping of continuous electrodes of a mult'i-electrode furnace through their holders, said circuit comprising (1) a source of electric power, (2) timing meansfor periodically completing a timing circuit to energize it for a period of time adequate to complete the slipping of each electrode, (3') a magnetic switch for each electrode of the furnace, said switches being closed simultaneously on completion of said timing circuit, said switches each completing power circuits to energize themotive means associated with the electrodes pertaining to the respective switches, (4) timing means associated with. each switch for opening the associated switches after. individually adjustable time periods thereby interrupting the said power circuits and de-energizing themotive means of the associated electrodes, whereby the motive means motivating the slippage of the respective electrodesare simultaneously energized and individually de-energized after periods of time to provide the slippage individually requiredby each associated electrode.

The invention further, more particularly, consists of apparatus for controlling the simultaneous slipping of continuous electrodesof a multi-electrode furnace through their holders as aforesaid, inv which power actuated motive means, for loweringsecondary supporting means in relation to supporting yokes, is energized by electrical circuit means as aforesaid to control the simultaneous slipping of the continuous electrodes. More specifically, the invention consists of apparatus for controlling the slipping of continuouselectrodes of a multi-electrode furnace through. their holders, comprising (1) an electrode supporting yokefor each electrode, suspended from fixed supports by hoisting gear, (2) contact shoes suspended fromsaid electrode supporting yokes, (3) means for adjustingthe pressure of the contact shoes on the eleo-. trodes, (4) secondary supporting means for supporting the electrodes from said yokes (5) power actuated means for vertically moving said secondary supporting means in relation to the associatedsyokes, (6) timing means for periodically energizing said power actuated means to initiate vertical movement of said secondary supporting means simultaneously for all electrodes, and (7) timing means for independently tie-energizing each of said power actuatedmeans atv thetermination of adjustable time periods. The invention may be understood from the following detaileddescription of preferred'embodiments of it, reference rbeing made to the accompanying drawings in which Figure l shows-in elevation, an electrode of the continuous type suspended by a device according to the invention, shown partly in section.

Figure 2 shows (in part) an alternative form of the invention adapted for usewith Soderberg electrodes provided with Wisdom ribbon suspension.

Figure 3 is a horizontal sectional view of a clamping device taken on line A-A of Fig. 1.

Figure 4 shows a horizontal sectional view of an alternative clamping device.

Figure 5 is a schematic wiring diagram for electrical apparatus suitable for use with the embodiment of the inventionshown in Figure 1.

Referring to Figure 1, a continuous electrode 2 with associated. equipment is shown schematically in relation to an electric furnace- 1. This electrode may be either of .the prebaked or Soderberg type. Contact shoes 3 and4-aresuspended from the electrode supporting yoke 12 by element 11 which is usually a cylindrical casing acting as a dust shield. To simplify the drawing, only two contact shoes are shown, whereas the usual numberis six toten. Aclamping ring 5 serves as means for maintaining pressure between the contact shoes and the electrode, which pressure is required for effective electrical contact. This pressure can be adjusted by means of-clamping screw 6. This pressure also permits the contact shoes to support a substantial part of the weight of the electrode but not the entire weight. The electric current is carried to the contact shoes by busbars 9, located in a fan-cooled duct 10. Connections between the busbar terminals and contact shoes are made by means of flexible leads 8 which permit movement of the electrode. The flexible leads, contact shoes, and clamping rings are exposed to the heat of the furnace and for this reason they are usually water-cooled. For simplicity water-cooling connections are not shown.

Pressure between the contact shoes and the electrode can be applied mechanically, hydraulically, or pneumatically. Referring to Fig. 3, the pressure between contact shoe 4 and the electrode 2 is determined by the pressure applied by spring 7 in clamping ring 5, which pressure is adjusted by means of clamping screw 6. Liquid or air pressure can also be used to maintain the desired pressure. Figure 4 shows schematically how fluid pressure can be applied. The spring assembly shown in Fig. 3 is replaced with bellows 70, fluid connection 60, and pressure pin 80 in clamping ring 5. The pressure between clamp 4 and electrode 2 is determined by the fluid pressure which is adjustable.

Referring again to Figure 1, electrode hoisting gear of the hydraulic type is indicated by cylinder and piston assembly 13, at least two such assemblies being required, evenly spaced around the electrode. The hoisting gear suspends the electrode from fixed beams, such as beam 14, and provides means for vertical movement of the electrode to regulate the electric current taken by the furnace. The foregoing elements are all conventional and are used in association with the apparatus of the present invention. Apparatus of this embodiment of the invention includes auxiliary electrode supporting clamps 15 and 16 with clamping ring 17 and clamping screw 61. These can be similar to the contact shoes 3 and 4, clamping ring 5 and clamping screw 6 except that no provision for water-cooling and electrical connections is required. These auxiliary electrode supporting clamps are adjusted by the clamping ring so that they too can support a substantial proportion of the weight of the electrode without the electrode slipping through them, and so that the electrode slips through them when more than this proportion of the weight is applied on them. The electrode supporting clamps 15 and 16 are connected with a secondary yoke 18 which is carried by two screw jacks 25 mounted on opposite sides of the electrode supporting yoke 12. The screw jacks are operated by a geared reversible motor 62 through bevel gears 23 and 24. Motor 62 operates both jacks simultaneously through suitable interlinkages shown schematically by line 65. Although only two supporting clamps (15 and 16) are shown, their number and width are preferably such that there is little clearance between them. Limit switches 26 and 27 with operating cam 28 determine limits of travel of the secondary yoke. Each furnace elecrode is similarly equipped.

Figure 2 shows the apparatus required for adapting the invention to a continuous electrode of the Soderberg type which is provided with Wisdom ribbons as a secondary means for supporting part of the weight of the electrodes. Wisdom ribbon apparatus is described in U.S. Patent No. 1,972,849. A flexible metal band or ribbon, 29, preferably made of steel and spot-welded to the electrode casing, passes over a pedestal 30, on yoke 12, through clamps 31 and 32, and on to a take-up reel 33. Clamp 31 is normally loose and the steel ribbon is normally securely clamped in clamp 32. Clamp 32 is moved vertically by screw 21 driven by a geared reversible motor 62 limit switches 26 and 27 are operated by contact with cam 28 thus determining limits of travel of clamp 32. Similar apparatus is required for each side of the electrode except that motor 62 is geared to move both clamping devices simultaneously. Wisdom ribbuns, with associated apparatus, serve t e P11119086 0f the 4 secondary yoke, supporting clamps, and associated clamping ring, shown in Figure 1, and need have only sufficient tenacity to support that proportion of the total weight of the electrode which the contact shoes do not support. Conventional apparatus, not shown in Fig. 2, is the same as in Fig. 1, and includes supporting contact shoes, clamping ring and screws, busbars, flexible leads, etc. Each furnace electrode is similarly equipped.

Figure 5 shows schematically the electrical connections of control apparatus suitable for use with the apparatus of Figure 1. The control power is supplied through a fused switch 40. The operating motor 42 of a repeat cycle timer is connected with the control power supply through auxiliary switch contacts 41 of the furnace circuit breaker. Contacts 42-0 of repeat cycle timer 42 are connected to energize simultaneously three stop cycle timers 43, 44, and 45 (one for each electrode of a 3- phase, 3-electrode furnace). Contacts 43C of stop cycle timer 43 are connected in series with limit switch 27 to'energize solenoid coil 52L of the reversing magnetic switch 52. When 52L is energized, magnetic switch 52 closes contacts which energize motor 62, cansing it to rotate in the direction to lower yoke 18 (Fig. 1) supporting the electrode. The contacts 44-C and 45-C of stop cycle timers 44 and 45 are similarly connected with limit switches 37, 47 and solenoid coils 53-L and 54-L of magnetic reversing switches 53 and 54 to energize motors 63 and 64 to lower the clamp supporting yokes pertaining to the other furnace electrodes. When solenoid coil 52R of reversing magnetic switch 52 is energized, motor 62 rotates in the direction to raise yoke 18. This solenoid coil 52R is connected in series with limit switch 26 and parallel circuits including pushbutton 49, a normally open contact of limit switch 27 and normally open contacts 52R-C of reversing switch 52. Solenoid coil 53-R of reversing switch 53 is similarly connected in series with limit switch 36, and parallel circuits including pushbutton 50, limit switch 37 and contacts 53-R-C, of reversing switch 53. Solenoid coil 54 R of reversing switch 54 is similarly connected in series with limit switch 46 and parallel circuits including pushbutton 51, limit switch 47 and contacts 54-R-C of reversing switch 54.

Reversing magnetic switches 52, 53, and 54 are provided with interlocks 52a, 53a, and 54a, to prevent both operating solenoids of each switch being energized at the same time.

' Limit switches 26, 27, 36, 37, 46, and 47 are provided with springs which function to return them to their normal positions when their operating levers are disengaged.

Preliminary settings of the operating and controlling mechanism of this embodiment of the invention are made as follows:

(1) The pressures of supporting contact shoes 3, 4, etc. and on the supporting clamps 15, 16, etc. are made such that each group of clamped supports is capable of supporting a maximum load which is less than the full weight of the electrode, and the combination of the supports is capable of supporting at least the full weight of the electrode.

(2) The timing period of repeat cycle timer 42 is set so that contacts 42-C close for an effective operating period, for example 10-20 seconds, at regular intervals, forexample, about once every hour or as frequently as it is desired to lower the electrodes, i.e. slip them through their supporting contact shoes. These contacts 42C must remain closed during the timing period of stop cycle timers 43, 44, and 45, but they must reopen within a period of less duration than the cycle of the repeat cycle timer.

(3) The timing periods of the stop cycle timers are set so that their contacts 43-C, 44-C, and 45-C remain closed for the time necessary to slip their associated electrodes an amount equivalent to the electrode consumption during the time cycle of the repeat cycle timer. The speed at which the electrodes are lowered should preferablybe such that the electrodes are lowered the desired amount in not less than about 5-10 seconds.

The apparatus then operates as follows:

The slipping of the electrodes through their holders isgoverned by repeat -cycle timer 42 and stop cycle timers 43, 44, and 45. Referring to Figure 5, when switches 40 and 41 are closed the repeat cycle timer operates continuously, thus periodically closing its contacts 42-C. When contacts 42-C close, the stop cycle timers 43, 44, and 45 become energized and immediately close their contacts 43C, 44-C, and 4'5-C, thus energizing solenoid coils -52.L, 53L, and 54-L of reversing magnetic switches 52, 53, and 54. The stop cycle timer contacts remain closed for adjustable periods and during these intervals motors 62, 63, and 64 operate in the direction to lower the secondary yokes (eg. 18 in Fig. 1), thus placing a larger proportion ofthe weight of the electrodes on the contact shoes than they can support and causing electrodes to slip through their contact shoes until'the secondary yokes come to rest and the weights of the electrodes are again adequately distributed between and supported by both the contact shoes and the secondary yokes.

The apparatus just described preferably allows sufficient electrode slippage to accommodate the requirements of 24 hours of furnace operation. Periodically, for example, once a day, the secondary yokes are returned to their start positions. This is accomplished manually by the use of pushbuttons 49, 50, and 51. Return of the secondary yokes to their start positions can also be accomplished automatically by allowing the secondary yokes to reach their low limits as determined by limit switches 27, 37, and 47.

Limit switch 27, Figure 5, operates only while contacts 43-C are closed, and upon operation, the double-throw contact of the limit switch closes its normally open contacts to energize solenoid coil 52R. Reversing magnetic switch 52 then closes contacts to rotate motor 62 in the direction to raise yoke 13. At the same time auxiliary contacts 52-RC close to complete a holding circuit which maintains operation of motor 62 until the start position of the secondary yoke is reached at which limit switch 26 opens to stop the raising opera-tion. The holding circuit is required to keep solenoid 52R energized after limit-switch 27 is disengaged. This occurs at the start of the raising operation. The secondary yokes pertaining to the other two phases are automatically raised by similar operations. When yoke 18 is raised, the auxiliary supporting clamps tend to lift the electrode, and because they cannot support the full weight of the electrode, they slip up the electrode until the yoke is returned toits start position.-

If the secondary yokes are to be returned to their start positions manually, pushbuttons 49, 50 and 51 are closed, energizing solenoids 52-R, 53-R, and 54-R of reversing switches 52, 53 and 54 and causing motors 62, 63, and 64 to rotate in the desired direction. If the pushbuttons are held closed, the yokes will reach their limit of travel when limit switches 26, 36, and 46 open.

With the embodiment of the invention illustrated in Figure 2, it is possible to use control apparatus and electrical connections similar to those shown in Figure 5. The only modification of the electrical connections which is required is removal of the connections 72, 73, and 74 shown between limit switches 27, 37, and 47 and their corresponding limit switches 26, 36, and 46. The embodiment shown in Figure 2 operates in the following manner.

With clamp 32 tight on the Wisdom ribbon 29 and clamp 31 loose, the weight of the electrode is supported partly by the Wisdom ribbon and partly by contact shoes via element 11. Motor 62 operates periodically as pro- Yided for by electrical connections like those shown in 6 Figure 5, modified as indicated above. Normal operation of motor 62 raises clamp 32 on screw 21 and allows the Wisdom ribbon to slip over pedestal 30 through clamp 31 and places the full weight of the electrode on the contact shoes. Because these are adjusted to support only part of the total electrode weight, the electrode slips downwardly through the shoes until clamp 32 is stationary and the Wisdom ribbon taut and again supporting part of the electrode weight. When clamp 32 reaches the upper limit of its travel, limit switch 27 operates to stop motor 62 and to energize a warning device 34. Electrical connections for the warning device correspond to those shown for the corresponding warning device 34a associated with another electrode and operated by switch 37 (Fig. 5) which corresponds to switch 27 and functions correspondingly. Clamp 31 is then tightened to hold the V /isdom ribbon temporarily, clamp 32 is loosened and lowered to the lower limit of its travel by reverse rotation of motor 62 activated by operation of push button 49 (Fig. 5). When clamp 32 is in its lower limit positioned, it is tightened again to hold the Wisdom ribbon and clamp 31 is loosened. The apparatus is then ready to lower (slip) the electrode periodically on normal operation of motor 62 controlled by electrical connections shown. Each electrode of a multi-electrode furnace is likewise equipped with Wisdom ribbons, clamps, and motors controlled by appropriate electrical connections.

During the operation of the furnace the extension of each electrode below its contact shoes is periodically measured, for example by probing. If the length is more or less than normal, the timing period of the associated stop cycle timer is decreased or increased accordingly. Although the automatic slipping of the electrodes begins at the same time, the slipping time and consequently the slippage of each electrode is independently adjustable. This provides an opportunity to compensate for unequal electrode consumption.

Electrode furnaces are periodically shut down for inspection. When the furnace operation is interrupted for this or any other reason, auxiliary switch contacts 41 of the circuit breaker open to stop the automatic slipping of the electrodes.

Both the foregoing specific embodiments of the invention have been described as operating to slip the electrodes of a furnace through their holders frequently but intermittently. These embodiments both can be adapted to permit continuous slow slipping of the electrodes through the holders, merely by operating the controlling motors 62 etc., slowly and continuously at independently controlled speeds to lower the electrodes. Such operation would, of course, require infrequent interruption to adjust the secondary yokes or the wisdom ribbon clamps to their start positions. From the standpoint of practical operation of large furnaces, it is preferred to use the frequent intermittent slipping controls as described above.

Although the invention has been described as applied to a 3-phase, 3-electrode furnace, the number of phases or electrodes does not limit its application.

The motor-operated screw jacks of the slipping mechanism can be replaced with conventional hydraulicallyoperated hoisting gear such as represented by the cylinder and piston assembly 13.

It will also be understood that additional modifications to those already mentioned may be made in the specific embodiments disclosed without departing from the spirit of the invention or the scope of the claims.

What is claimed is:

1. An apparatus for controlling the slipping of a continuous electrode through its holders comprising (1) an electrode supporting yoke suspended from fixed supports by hoisting gear, (2) contact shoes suspended from the said electrode supporting yoke, (3) means for adjusting the pressure of the contact shoes on the electrode to maintain said contact shoes capable of supporting a maximum proportion of the electrode weight which is less than the whole weight, (4) secondary supporting means for partially supporting the weight of the electrode from the said electrode supporting yoke, said secondary means being adapted also to support a maximum proportion of the electrode weight which is less than the whole weight, said secondary means and said contact shoes together being adapted to support at least the whole weight of the electrode, and power actuated motive means for lowering the said secondary supporting means in relation to the supporting yoke, said secondary supporting means comprising (a) a secondary yoke mounted on the electrode supporting yoke through the power actuated motive means, (b) auxiliary electrode supporting clamps suspended from said secondary yoke, and (0) means for adjusting the pressure of said auxiliary supporting clamps on the electrode.

2. An apparatus as claimed in claim 1, in which the power actuated motive means is a set of motor driven screw jacks.

3. Electrical circuit means for energizing power actuated motive means to control the simultaneous slipping of continuous electrodes of a multi-electrode furnace through their holders, said circuit comprising (1) a source of electric power, (2) timing means for periodically completing a timing circuit to energize it for a period of time adequate to complete the slipping of each electrode, (3) a magnetic switch for each electrode of the furnace, said switches being closed simultaneously on completion of said timing circuit, said switches each completing power circuits to energize the motive means associated with the electrodes pertaining to the respective switches, (4) timing means associated with each switch for opening the associated switches after individually adjustable time periods thereby interrupting the said power circuits and de-energizing the motive means of the associated electrodes, whereby the motive means motivating the slippage of the respective electrodes are simultaneously energized and individually de-energized after periods of time to provide the slippage individually required by each associated electrode.

4. Electrical circuit means as claimed in claim 3 in which the magnetic switches are reversing switches, and further comprising reversing circuits for energizing the motive means to move in the opposite direction to that energized by the timing circuit and limit switches for regulating movement of the motive means between limits of travel in each direction.

5. Electrical circuit means as claimed in claim 3, in which the timing means completing the timing circuit is a motor operated repeat cycle timer, and the timing means associated with the magnetic switches are motor operated stop cycle timers.

6. An apparatus for controlling the slipping of continuous electrodes of a multi-electrode furnace through their holders, comprising (1) electrode supporting yokes for each electrode, suspended from fixed supports by hoisting gear, (2) contact shoes for each electrode, suspended from said electrode supporting yokes, (3) means for adjusting the pressure of the contact shoes on the electrodes, (4) secondary supporting means for supporting the electrodes from said yokes, (5) power actuated means for vertically moving said secondary supporting means in relation to the associated yokes, (6) timing means for periodically energizing said power actuated means to initiate vertical movement of said secondary supporting means simultaneously for all electrodes, and (7) timing means for independently de-energizing each of said power actuated means at the termination of adjustable time periods.

7. Apparatus as claimed in claim 6, in which the secondary supporting means comprises (1) a secondary yoke mounted on the electrode supporting yoke through the power actuated motive means, (2) auxiliary electrode supporting clamps suspended from said secondary yoke, and (3) means for adjusting the pressure of said auxiliary supporting clamps on the electrode.

8. An apparatus as claimed in claim 7, in which the pressure of the contact shoes on the electrodes is adjusted to make the contact shoes capable of supporting a maximum proportion of their associated electrode weight which is less than the whole weight, and the pressure of the auxiliary supporting clamps on the electrodes is adjusted to make the clamps capable of supporting a maximum proportion of their associated electrode weight which is less than the whole weight, said contact shoes and clamps together being adapted to support at least the whole weight of the electrode.

9. Apparatus as claimed in claim 8, in which the motive means is a set of motor driven screw jacks.

10. Apparatus as claimed in claim 9, including means for energizing said power actuated means to initiate vertical movement of said secondary supporting means in the direction opposite to that initiated by said timing means, and means for limiting movement of the motive means between limits of travel in each direction.

11. Apparatus as claimed in claim 6, in which the secondary supporting means comprises (1) continuous flexible metal bands each fastened in part to the sides of the electrode, and (2) clamping means to secure the metal bands to the power actuated motive means.

References Cited in the file of this patent UNITED STATES PATENTS 1,737,890 Noichl et a1. Dec. 3, 1929 1,836,880 Sem Dec. 13, 1931 1,892,109 Marshall Dec. 17, 1932 1,972,849 Wisdom Sept. 4, 1934 2,297,484 Lehrer et al Sept. 29, 1942 2,668,183 Foyn Feb. 2, 1954 2,797,251 Damgen et al. June 25, 1957 FOREIGN PATENTS 516,697 Germany Jan. 30, 1931

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