EP3075208B1 - Device and method for adjusting an electrode for a metallurgical furnace - Google Patents

Description

The invention relates to a device for repositioning an electrode of a metallurgical furnace, and a corresponding method for such repositioning.

In the case of electric arc furnaces, the electrodes at their electrode tips are subject to constant consumption and must therefore be replenished during operation of the electric arc furnace. For this purpose, adjustment devices are known from the prior art, e.g. B. off DE 43 42 511 A1 or EP 1 969 902 B1 . These adjustment devices have at least one clamping ring which can be clamped around the electrode for holding. The clamping ring can be moved relative to the furnace cover by hydraulic cylinders. The electrode can be moved into the furnace if it is held by the clamping ring and this is moved in the direction of the furnace cover by means of the hydraulic cylinder.

Support arms are traditionally used in electric arc furnaces to hold, guide and move the electrodes. In this context, will be on EP 1 484 566 A1 referenced, which shows a device for repositioning an electrode of a metallurgical furnace according to the preamble of claim 1. A lower clamping ring is integrated into an electrode support arm, an upper clamping ring being connected to the lower clamping ring via hydraulic cylinders. By actuating the hydraulic cylinder, a distance between the clamping rings can be adjusted, in conjunction with repositioning the electrode. The power supply to the electrode is ensured via both the lower clamping ring and the upper clamping ring. Here, the power supply is switched alternately between the two clamping rings when the other clamping ring is used to move the device with respect to the electrode is temporarily not clamped or opened with the electrode. This switching back and forth of the power supply between the electrodes is complex in terms of control technology. In addition, there is the disadvantage that the clamping rings, which mostly also contain copper contact jaws for the transmission of current to the electrode, are prone to wear and tear in order to apply sufficient clamping forces.

US 2005/0259711 A1 shows a system for lowering and / or lifting an electrode of a metallurgical furnace, in which, according to one embodiment, clamping rings are provided, one of which is de-energized and a current transfer to the electrode is ensured by another clamping ring, these clamping rings not being provided by lifting cylinders or the like are connected to each other.

Accordingly, the invention is based on the object of creating a device and a method for repositioning an electrode of a metallurgical furnace, an improved power supply to the electrode being ensured with simplified and robust means while at the same time increasing operational reliability.

This object is achieved by a device with the features of claim 1 and by a method with the features of claim 12. Advantageous further developments of the invention are defined in the dependent claims.

The invention is based on the essential knowledge that the power supply to the electrode takes place permanently only via one of the two clamping rings, which for this purpose has a contact jaw designed for this purpose. The other of the two clamping rings, on the other hand, is permanently de-energized and is designed to apply sufficient holding or clamping forces to the electrode. Thus, the current transfer to the electrode takes place permanently only via the clamping ring, which, as explained, is equipped with at least one contact jaw for this purpose. Switching the current transmission between the two clamping rings back and forth does not take place in the present invention.

In an advantageous development of the invention, at least one of the two clamping rings is equipped with at least one pressure jaw, which is permanently biased in the direction of the electrode by at least one spring device, and is thus designed to be self-locking. The pressure jaw can be moved in the opposite direction by at least one clamping ring cylinder, i. be moved against the bias of the spring device. The clamping ring cylinder is expediently operated hydraulically. The self-locking mechanism just mentioned is to be understood in the sense of the present invention to the effect that the pressure jaw is pressed against the electrode by the bias of the spring device when the clamping ring cylinder is not actuated. As a result, the pressure jaw applies a sufficiently high holding force to the electrode, which is matched to the dead weight of the electrode and accordingly prevents the electrode from slipping or relative displacement of the electrode with respect to the clamping ring. In the event of failure of the clamping ring cylinder, e.g. B. in the event of a defect in the hydraulic system, it is ensured in the sense of a self-locking in any case that the pressure jaw clamps the electrode as explained as a result of the preload by the spring device. If the electrode is to be readjusted, the clamping ring cylinder is moved against the bias of the spring device, so that at least a relative displacement of the electrode with respect to the clamping ring and its pressure jaw is possible. Optionally, it is also possible here to move the clamping ring cylinder so far against the bias of the spring device that the pressure jaw is released from the electrode and lifts off, which also enables the electrode to be repositioned.

In the further development of the invention just mentioned, the sole purpose of the clamping ring with the pressure jaw is to apply sufficiently large holding forces in the radial direction to the electrode. However, this clamping ring does not fulfill the function of transmitting electricity and is therefore not made of copper or comparable metals. This has a beneficial effect on increased Operational reliability of the device 1 from, in conjunction with a reduced susceptibility to wear.

In an advantageous development of the invention it is provided that the permanently currentless clamping ring is designed to be self-locking, with the mode of operation just explained.

It can optionally be provided that both clamping rings are designed to be self-locking. This increases the safety of the device in the event of a possible failure of the hydraulic system.

The device according to the invention can be used for different types of furnaces, and in this case e.g. be connected with a support arm or with a traverse attached to a furnace platform. It is advantageous here if the clamping ring, which has the contact jaw and is used to transmit power to the electrode, is integrated in the support arm or in the cross member.

For the space above the furnace, it is advantageous if the upper first clamping ring is permanently de-energized, the lower, second clamping ring having the contact jaw for power transmission to the electrode and is expediently integrated in the support arm or in the cross member.

By integrating the adjustment device according to the invention, in which the two clamping rings are connected to one another by lifting cylinders and their spacing can be adjusted relative to one another, in a known electrode support arm, a compact and space-saving one thus becomes Electrode support arm solution found that offers the possibility of automated electrode replacement. Here, the adjustment device can be placed directly above the electrode holder or holder on the support arm. This means that the position at which the electrode is clamped and thus held can be changed without manual intervention. This has the advantage of retrofitting conventional electrode support arms with the adjustment device according to the invention with limited effort.

Electrodes used in electric arc furnaces can be composed of adjoining electrode parts. The connection point between the electrode parts represents a sensitive length of the electrode. In this regard, an advantageous development of the invention is that the control device for controlling the lifting cylinder and the two clamping rings is programmed or control-technically set up in such a way that the compensation stroke for the The lifting cylinder for moving the first clamping ring relative to the second clamping ring can be set variably and automatically so that the first or second clamping ring is clamped again around the electrode after the compensation stroke has been reached exclusively adjacent to the sensitive length of the electrode, but in no case within it Length section.

Exemplary embodiments of the invention are described in detail below with the aid of schematically simplified drawings.

Figur 1

eine vereinfachte Seitenansicht einer erfindungsgemäßen Vorrichtung,

Figur 2

eine Längsschnittansicht der Vorrichtung entlang der Linie A-A von Figur 1,

Figur 2a

eine Längsschnittansicht der Vorrichtung entlang der Linie A-A von Figur 1 nach einer alternativen Ausführungsform,

Figur 3

eine vereinfachte Seitenansicht einer erfindungsgemäßen Vorrichtung nach einer weiteren Ausführungsform,

Figur 4

eine vereinfachte Darstellung eines Teilbereichs einer Elektrode für einen Lichtbogenofen, in Wechselwirkung mit einem Klemmring der erfindungsgemäßen Nachsetzvorrichtung,

Figur 5

eine vereinfachte Seitenansicht eines Klemmrings der erfindungsgemäßen Vorrichtung,

Figur 6, 7

Seitenansichten eines Teilbereichs einer Elektrode zur Verwendung mit der Erfindung während bzw. nach einem Montagevorgang zum Verbinden von zwei Elektrodenteilen, und

Figur 8, 9

Seitenansichten eines Teilbereichs einer Elektrode zur Verwendung mit der Erfindung nach einer weiteren Ausführungsform während bzw. nach dem Montagevorgang zum Verbinden von zwei aneinander Elektrodenteilen.

Show it:

Figure 1

a simplified side view of a device according to the invention,

Figure 2

a longitudinal sectional view of the device along the line AA of Figure 1 ,

Figure 2a

a longitudinal sectional view of the device along the line AA of Figure 1 according to an alternative embodiment,

Figure 3

a simplified side view of a device according to the invention according to a further embodiment,

Figure 4

a simplified representation of a partial area of an electrode for an electric arc furnace, interacting with a clamping ring of the adjustment device according to the invention,

Figure 5

a simplified side view of a clamping ring of the device according to the invention,

Figure 6, 7

Side views of a portion of an electrode for use with the invention during or after an assembly process for connecting two electrode parts, and

Figure 8, 9

Side views of a partial area of an electrode for use with the invention according to a further embodiment during or after the assembly process for connecting two electrode parts to one another.

In Fig. 1 an adjustment device 1 according to the invention is shown in simplified form in a side view, with which an electrode 2 for an arc furnace (not shown) can be adjusted relative to the furnace or can be adjusted into the furnace. The device 1 comprises an upper, first clamping ring 4 and a lower, second clamping ring 6. The clamping rings 4, 6 are connected to one another by lifting cylinders 8 and can be activated by actuating these lifting cylinders 8 in their distance to one another are adjusted, namely by a compensation stroke a. The lifting cylinders 8 are designed as hydraulic cylinders and are correspondingly connected to a hydraulic system (not shown).

The compensation stroke a is in Fig. 1 shown with a maximum size. Correspondingly, the compensation stroke a or a distance between the two clamping rings 4, 6 can also be smaller than in FIG Fig. 1 shown. Details regarding a change in the distance between the two clamping rings 4, 6 are explained in detail below.

The lower, second clamping ring 6 is connected to a support arm 9 and is preferably integrated into the support arm 9. The support arm 9 can be positioned lower in the vertical direction according to the consumption of the electrode (in Fig. 1 down), usually hydraulic. The support arm 9 is a known component and is therefore not explained in further detail.

The lower, second clamping ring 6 is used to transmit current to the electrode 2. For this purpose, the second clamping ring 6 has at least one contact jaw 10 which is in contact with the electrode 2. The power supply to the second clamping ring 6 and thus to the electrode 2 takes place via a power supply line 12 which is connected to the second clamping ring 6.

The upper first clamping ring 4 is designed to be permanently currentless and serves to hold or clamp the electrode 2. For this purpose, the first clamping ring 4 is equipped with at least one pressure jaw 14, as evidenced by the sectional view according to Fig. 2 . The pressure jaw 14 is moved radially in the direction of the electrode 2 by a spring device 16, preferably in the form of a spring assembly preloaded so that a sufficient holding or clamping force is applied to the electrode 2. The holding force for the electrode 2 is thus generated by the spring assembly 16. In addition, the first clamping ring 4 has at least one clamping ring cylinder 18, which is preferably designed as a hydraulic cylinder. The clamping ring cylinder 18 has the function of moving or opening the pressure jaw 14 against the bias of the spring assembly 16 in order to reduce the clamping force applied to the electrode 2 for moving the electrode 2 relative to the first clamping ring 4 or cancel.

The clamping ring cylinder 18 can be actuated in such a way that either the electrode 2 can be displaced relative to the pressure jaw 14, or the pressure jaw 14 lifts completely from the electrode 2 and is no longer in contact with the electrode 2.

According to the representation of Fig. 2 the first clamping ring 4 has a total of three clamping ring cylinders 18. Alternatively, it is also possible that for the clamping ring z. B. four clamping ring cylinders 18 are provided, such as in Fig. 2a shown. Notwithstanding this, the number of clamping ring cylinders 18 can also be less than three or more than four.

It should be noted that the sectional views according to Figures 2 and 2a are greatly simplified and, in particular, are to be understood without a scale.

The lower, second clamping ring 6 can also be equipped with a pressure jaw for holding the electrode, in conjunction with at least one clamping ring cylinder which, as explained, interacts with the pressure jaw. For the purpose simplification are in the illustration of Fig. 1 the pressure jaw and the clamping ring cylinder for the lower second clamping ring 6 are not shown.

The device 1 comprises a control device 20 by means of which the two clamping rings 4, 6 and also the lifting cylinders 8 can be controlled.

Fig. 3 shows a further embodiment of the device 1. In comparison to FIG Fig. 1 the same features are provided with the same reference numerals. In the embodiment of Fig. 3 the lower, second clamping ring 6 is integrated in a cross member 22 which is attached to a furnace platform 26 in a suspended manner via hydraulically operated regulating cylinders 24. Correspondingly, the second clamping ring 6 and thus the entire device 1 can be moved in the vertical direction by actuating the regulating cylinder 24, in the direction of a furnace lid (not shown) or away from it.

The pressure jaws 14 of the first and second clamping rings 4, 6 are shown in FIG Fig. 3 indicated in greatly simplified form. The clamping ring cylinder 18 and the contact jaw 10, which is provided for the lower second clamping ring 6, are in the Fig. 3 not shown for the sake of simplicity.

Regarding the in Fig. 3 It goes without saying that, as an alternative, the electrode string can also be designed in an upright design, in which the regulating cylinders 24 are supported downward on a suitable frame or the like.

When an arc furnace is in operation, the electrode 2 is compensated for by adjusting it in the direction of the furnace cover. This can in the embodiment according to Fig. 1 by a vertical lowering of the support arm 9, and in the embodiment according to FIG Fig. 3 by extending the regulating cylinder 24, the electrode 2 being held at least by the upper first clamping ring 4, and optionally also by the second lower clamping ring 6, provided this is provided with pressure jaws 14. Such readjustment of the electrode 2 by a vertical movement of the support arm 9 or by actuating the regulating cylinder 24 is known per se and is therefore not explained further.

The invention functions with regard to a readjustment of the electrode 2 as follows:
At the beginning of a readjustment process, it is assumed that the two clamping rings 4, 6 are only at a small distance from one another, the compensation stroke a being essentially zero. The clamping ring cylinders 18 are each completely relieved, as a result of which the pressure jaws 14 are pressed against the electrode 2 with the full bias of the respective spring assemblies 16 in order to hold them. The clamping ring cylinders 18 of the upper first clamping ring 4 are now actuated so that the pressure jaws 14 of the upper first clamping ring 4 either press against the electrode 2 with only a reduced clamping force or lift off the electrode 2. The hydraulic cylinders 8 are then actuated and extended so that the upper, first clamping ring 4 is spaced apart from the lower, second clamping ring 6, namely until, for example, the maximum compensation stroke a (cf. Fig. 1 ) is reached. Thereafter, the clamping ring cylinders 18 of the first clamping ring 4 are relieved again, whereby the pressure jaws 14 of the first clamping ring 4 are closed and the electrode 2 clamped. The clamping ring cylinders 18 of the lower second clamping ring 6 are now actuated, so that a relative movement of the electrode 2 with respect to the lower second clamping ring 6 is possible. Then the lifting cylinders 8 are relieved again, whereby the upper first clamping ring 4 together with the Electrode 2 is moved downwards, in the direction of the lower second clamping ring 6 and thus in the direction of the furnace. As soon as the compensation stroke a is essentially balanced and the upper first clamping ring 4 is positioned again adjacent to the lower second clamping ring 6, the clamping ring cylinders 18 of the lower second clamping ring 6 are relieved and the pressure jaws 10 thereof are closed again. After this, both the upper first clamping ring 4 and the lower, second clamping ring 6 are closed and the repositioning process is thereby ended.

It should be pointed out that during the above-explained resetting process of the electrode 2, there is a permanent power supply to the electrode 2 via the contact jaw 10 of the second clamping ring 6.

The above-explained configuration of at least the upper first clamping ring 4 with pressure jaw 14 and clamping ring cylinders 18 is to be understood in the sense of a self-locking mechanism, which is also referred to below as a "fail-safe design". This means that in the event of a failure or defect in the hydraulic system, it is guaranteed that the electrode 2 is automatically held by the pressure jaw (s) 14 as a result of the pretensioning of the spring assembly 16 and does not slip. As already explained, the lower, second clamping ring 6 can also be designed according to this “fail-safe design”.

The electrode 2 can be composed of different electrode parts which are connected to one another at their respective end faces. When connecting such electrode parts, it can be problematic that an axial offset is formed at a connection point between adjacent electrode parts.

In Fig. 4 an electrode 2 with an axial offset at a connection point between adjacent electrode parts is shown schematically in a greatly simplified manner. If one of the clamping rings 4, 6 radially braces the electrode 2 for holding or clamping in the area of the connection point between the electrode parts with a force F, this connection point is subjected to disadvantageous shear loads. Particularly in the case of long or heavy electrodes, this can lead to immediate or time-delayed damage, or even cause the electrode to break. A possible electrode break leads to a malfunction and disadvantageous business interruption with corresponding costs.

To avoid the disadvantage just mentioned of an inadmissible shear stress on the electrode 2, the device 1 according to the invention can have at least one sensor device 28 on the first clamping ring 4 and / or on the second clamping ring 6. Such a sensor device 28 has the purpose of detecting a marking provided on the electrode 2 for a sensitive length section of the electrode 2 so that the clamping rings or their pressure jaws 14 do not clamp the electrode 2 in this sensitive length section. When carrying out a readjustment process, the lifting cylinders 8 are activated or regulated accordingly by the control device 20 as a function of signals from the sensor device 28. Details regarding the sensor device 28 and the markings on the electrode 2 are explained below as follows:
A sensor device 28 can be provided at least on the first upper clamping ring 4, which is shown in the side view of FIG Fig. 5 is shown in greatly simplified detail. Three sensor devices 28 can be attached to an upper edge of the first clamping ring 4 by means of suitable mountings. In the Fig. 5 it is a developed representation, with the three Sensor devices 28 are attached to the annular first clamping ring 4 at a uniform distance from one another. The sensor devices 28 are attached to the first clamping ring 4 in such a way that they lie together in a virtual horizontal plane E. In conjunction with the representation of Fig. 1 or. Fig. 3 it should be noted that this plane E is transverse or perpendicular to the longitudinal axis of the electrode 2. It is also possible for more or less than three sensor devices 28 to be attached to the first clamping ring 4, in the latter case preferably at an even distance from one another.

Alternatively to the representation according to Fig. 5 the sensor devices 28 can also be arranged in the region of an inner circumferential surface of the clamping ring 4.

In the Fig. 1 and 3 a sensor device 28 on the upper first clamping ring 4 is in each case greatly simplified and shown symbolically only in the form of a rectangle. The sensor device 28 is connected to the control device 20, with which the hydraulic components of the device 1 can also be controlled. The purpose of the sensor device 28 is to use it to detect markings that are provided on the electrode 2. In the representations of the Figures 6 to 9 these markings 30 are shown in simplified form and explained below.

The electrode 2 consists in its longitudinal direction of a plurality of electrode parts which are connected to one another at their respective end faces. In the Fig. 6 two such electrode parts 2a, 2b are shown before they are connected to one another by means of a screw connection 32. Adjacent to their end faces, the electrode parts 2a, 2b are each provided with a marking 30 which runs transversely to the longitudinal side of the electrode 2 and can, for example, consist of a luminescent colored ribbon or the like. In Fig. 7 are the Electrode parts 2a, 2b shown in their assembled state. The two markings 30 define or identify in the longitudinal direction of the electrode 2 a sensitive length section 2l, the axial length of which is defined by the screwed connection point between the two electrode parts 2a, 2b.

In the Figures 8 and 9 an alternative embodiment of the markings 30 on the electrode 2 is shown in simplified form. The FIGS. 8 and 9 show in the same way as that FIGS. 6 and 7 two adjacent electrode parts 2a, 2b before and after a connection at their opposite end faces. In the embodiment according to Figures 8 and 9 The markings 30 on the electrode parts 2a, 2b are each formed by an annular groove 30r which runs transversely to the longitudinal axis of the electrode 2. The position of such an annular groove 30r can, for example, be detected by a sensor device in the form of a light sensor which emits radiation in the direction of the electrode 2. In other words, at least one light sensor, which emits radiation in the direction of the electrode 2, is attached to the upper, first clamping ring 4. Here, the light sensor can direct the radiation to an edge region of the electrode 2, so that the radiation passes through the annular groove 30r when the annular groove 30r is at the level of the light sensor. In this case, it is then detected that the upper clamping ring 4 is located within the area of the sensitive length section 2l of the electrode 2. Otherwise, ie if the annular groove 30r is not positioned adjacent to the light sensor, the radiation is interrupted by the wall of the electrode 2, which means that the light sensor and thus also the first clamping ring 4 are located on a non-critical section of the electrode 2 . The design of the marking 30 in the form of the aforementioned annular groove 30r has the advantage that it can be manufactured inexpensively and is insensitive to contamination.

For the markings 30 on the electrode 2, it goes without saying that the design in the form of a luminescent colored ribbon (cf. Fig. 6, Fig. 7 ) also with the design in the form of the annular groove (cf. Fig. 8, Fig. 9 ) can be combined. In addition and / or as an alternative, the marking 30 can also have magnetic properties that can be detected by a correspondingly adapted sensor device 28.

In the event that the lower, second clamping ring 6 is also equipped with a pressure jaw 14, the second clamping ring 6 can also be provided with a sensor device 28 which is signal-connected to the control device 20 and with which a marking 30 on the electrode 2 and so that a sensitive length section 2l of the electrode 2 can be detected. In the Fig. 1 and 3 this is symbolized in a simplified manner by a rectangle with the reference symbol “28” above the second clamping ring 6. This ensures that the second clamping ring 6 according to this embodiment does not clamp the electrode 2 in a region of its sensitive longitudinal section 2l. At least one sensor device 28 can be attached to the second clamping ring 6 in the same way as to the first clamping ring 4, so that reference is made to the above explanation to avoid repetition.

The control device 20 is represented symbolically in the drawing by a rectangle and in this respect only in a greatly simplified manner. The individual data connections between the control device 20 and the respective sensor devices 28 or hydraulic units 8, 18, 24, which can be read out or controlled by the control device 20, are indicated in the drawing with dashed lines 21. These data connections 21 can be implemented, for example, by cable links or by radio links.

In order to prevent damage to the electrode 2, it goes without saying that clamping or holding of the electrode 2 at its connection points or in a respective sensitive length section 21 by the clamping rings 4, 6 is to be avoided. The following explains how this is implemented when the electrode 2 is repositioned.

After the first clamping ring 4 has been released from the electrode 2 or the clamping force of the pressure jaw 14 of the first clamping ring 4 has been reduced with respect to the electrode 2, the distance between the first clamping ring 4 and the second clamping ring 6 is increased by extending the lifting cylinder 8. Before the electrode 2 is clamped again by means of the pressure jaw 14 of the first clamping ring 4, an evaluation of the signals from the sensor devices 28 is used to check whether the first clamping ring 4 is possibly positioned in the area of a sensitive length section 2l of the electrode 2. A renewed clamping or holding of the electrode 2 by the first clamping ring 4 is initiated exclusively in the event that the first clamping ring 4 is not positioned in the area of a sensitive length section 2l of the electrode 2 after the lifting cylinder 8 has been extended.

If, after the lifting cylinder 8 has been extended, it is detected by evaluating the signals from the sensor devices 28 that the first clamping ring 4 should be located in the area of a sensitive longitudinal section 2l of the electrode 2, the lifting cylinders 8 - if possible - are either extended further, or, conversely, retracted a little. In any case, the lifting cylinders 8 are actuated or extended so far that the first clamping ring 4 is not located in the area of the sensitive length section 2l of the electrode 2. Only then is the electrode 2 clamped again by adjusting the pressure jaw 14.

The mode of operation explained above for actuating the first clamping ring 4 in order to clamp the electrode 2 in a sensitive length section 2l Avoid, applies in the same way to an actuation of the second clamping ring 6, provided that it is equipped with a pressure jaw for holding the electrode 2.

As explained above, the sensitive length section 2l of the electrode 2 is detected by the at least one sensor device 28 with the aid of the markings 30, 30r provided thereon, in order to prevent the electrode 2 from jamming in this area by a clamping ring. The sensitive length section 21 of the electrode or the end-face sections of the respective electrode parts are also referred to as the nipple area, which is thus effectively protected against jamming by a clamping ring and possible damage resulting therefrom.

The invention is suitable for various forms of electrodes that are used in electric arc furnaces or electric reduction furnaces. Exemplary electrode types are “pre-baked” electrodes (e.g. graphite or carbon electrodes) or self-baking (Söderberg) electrodes.

With the invention, a so-called "back lip" is also possible, in which the electrode is pulled out of the arc furnace 2 piece by piece. Here, too, the activation of the lifting cylinders 8 by means of the control device 20 as a function of the signals from the sensor devices 28 ensures that the electrode 2 is not clamped by the clamping rings 4, 6 in the area of its sensitive length sections 21.

List of reference symbols:

1

contraption

2

electrode

2l

sensitive length section

4th

upper first clamping ring

6th

lower second clamping ring

8th

Lifting cylinder

9

Beam

10

Contact jaw

12

Power supply device

14th

Pressure jaw

16

Spring device / spring package

18th

Clamping ring cylinder

20th

Control device

21st

Data connections

22nd

traverse

24

Regulating cylinder

26th

Furnace platform

28

Sensor device

30th

Marking (of the electrode)

30r

Ring groove

32

Screw connection

a

Compensation stroke

Claims (16)

1. Device (1) for adjusting an electrode (2) of a metallurgical furnace, comprising an upper, first clamping ring (4) and a lower, second clamping ring (6), wherein the clamping rings (4, 6) are connected together by stroke cylinders (8) and are adjustable in their mutual spacing through a compensating stroke (a) by actuation of the stroke cylinders (8), and wherein the clamping rings (4, 6) for holding the electrode (2) are tightenable around this and for a relative movement of the electrode (2) with respect to the clamping rings (4, 6) are releasable from this, and
   a control device (20) for activating the stroke cylinders (8) and the clamping rings (4, 6),
   characterised in that
   at least one of the two clamping rings (4, 6) is permanently without current, wherein the respective other one of the two clamping rings (6, 4) has at least one contact jaw (10) by means of which a constant current transfer to the electrode (2) is provided.
2. Device (1) according to claim 1, characterised in that at least one of the two clamping rings (4, 6) has a pressure jaw (14), which is permanently biased against the electrode (2) by at least one spring device (16) and is thus formed to be self-securing, wherein the pressure jaw (14) is movable by at least one clamping ring cylinder (18) against the bias of the spring device (16), preferably in that the pressure jaw (14) is releasable from the electrode (2) through actuation of the clamping ring cylinder (18).
3. Device (1) according to claim 2, characterised in that the spring device (16) is constructed as a spring packet.
4. Device (1) according to claim 2 or 3, characterised in that two clamping ring cylinders (18), preferably four clamping ring cylinders (18), by which the pressure jaw (14) is movable against the bias of the spring device (16) are provided.
5. Device (1) according to any one of claims 2 to 4, characterised in that the clamping ring (4, 6) permanently without current is constructed to be self-securing and thus has the pressure jaw (14) and the clamping ring cylinders (18).
6. Device (1) according to any one of claims 1 to 5, characterised in that the clamping ring (4, 6) having the contact jaw (10) is connected with a support arm (9) or with a cross member (22), wherein the support arm (9) or the cross member (22) is vertically movable with respect to the furnace, preferably in that this clamping ring (4, 6) is integrated in the support arm (9) or in the cross member (22).
7. Device (1) according to any one of claims 1 to 6, characterised in that the upper, first clamping ring (4) is permanently without current, wherein the lower, second clamping ring (6) has the contact jaw (10).
8. Device (1) according to any one of claims 1 to 7, characterised in that the control device (20) is programmed in such a way that the compensating stroke (a) for the stroke cylinders (8) for movement of the clamping rings (4, 6) relative to one another is settable in variable and automated manner so that repeated tightening of the first or second clamping ring (4, 6) around the electrode (2) after attainment of the compensating stroke (a) takes place exclusively adjacent to a sensitive length section (2l) of the electrode (2) and not within this length section (2l).
9. Device (1) according to claim 8, characterised in that at least the first clamping ring (4) or the second clamping ring (6) has at least one sensor device (28) by which markings (30), which are provided at the electrode (2), for a sensitive length section (2l) of the electrode (2) are detectable, wherein the stroke cylinders (8) can be regulated by the control device (20) for execution of the compensating stroke (a) in dependence on signals of the sensor device (20).
10. Device (1) according to claim 9, characterised in that the stroke cylinders (8) can, for movement of the first or second clamping ring (4, 6) by the compensating stroke (a), be actuated by the activation by means of the control device (20) only under the condition that the stroke cylinders (8) have a predetermined stroke reserve greater than an axial length of the sensitive length section (2l) of the electrode (2).
11. Device (1) according to claim 9 or 10, characterised in that the sensor device (28) is suitable for the purpose of detecting a marking (30), which is formed to be optical and/or magnetic and/or has the form of annular groove (30r), at the electrode (2).
12. Method of adjusting an electrode (2) of a metallurgical furnace with use of a device (1) according to any one of claims 1 to 11, characterised in that current is supplied to the electrode (2) only by way of one of the two clamping rings (4, 6) and the other one of the two clamping rings (6, 4) is permanently without current.
13. Method according to claim 12, characterised in that at least one of the two clamping rings (4, 6) has a pressure jaw (14) which is permanently biased by means of at least one spring device (16) against the electrode (2) for holding the electrode (2), wherein the pressure jaw (14) is moved by at least one clamping ring cylinder (18) against the bias of the spring device (16) so as to enable relative movement of the electrode (2) with respect to the clamping ring (4, 6), preferably in that the pressure jaw (14) lifts off the electrode as a consequence of the actuation of the clamping ring cylinder (18).
14. Method according to claim 12 or 13, characterised in that a sensitive length section (2l) of the electrode (2) is provided with markings (30) which are detected by a sensor device (28) mounted at least at the first or second clamping ring (4, 6), wherein the stroke cylinders (8) for movement of the clamping rings (4, 6) relative to one another are regulated in dependence on the signals of the sensor device (28).
15. Method according to claim 14, characterised in that the stroke cylinders (8) for movement of the first clamping ring (4) relative to the second clamping ring (6) are so regulated in dependence on the sensitive length section (2l) of the electrode (2) that repeated tightening of the first or second clamping ring (4, 6) around the electrode (2) after attainment of the compensating stroke (a) takes place exclusively adjacent to the sensitive length section (2l) of the electrode (2) and not within this length section (2l).
16. Method according to claim 15, characterised in that the stroke cylinders (8) for movement of the first clamping ring (4) relative to the second clamping ring (6) are actuated only under the condition that they have a predetermined stroke reserve (a) greater than an axial length of the sensitive length section (2l) of the electrode (2).

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