Control device for a metallurgical vessel stopper-rod

Abstract

Control device (10) for a metallurgical vessel stopper-rod (3), said stopper-rod controlling a molten metal flow, said device comprising: an electric driving element (20); a hand lever (120) movable in rotation about an axis (X) of rotation and holdable by an operator; a load sensor and / or a motion sensor (40) configured to generate a motion measurement representative of the rotation of the hand lever (120); a control unit configured to issue a command to an electric driving element (20) for controlling an assistance drive load, wherein the assistance drive load is a function of at least one of: a load measurement generated by the load sensor and / or a motion measurement of the hand lever (120) generated by the motion sensor (40); wherein the control device (10) is configured to be operated in a manual assist-mode for a manual-assist control of the molten metal flow, in which the stopper-rod (3) is manually actuated by the operator with assistance of the electric driving element (20).

Description

CONTROL DEVICE FOR A METALLURGICAL VESSEL STOPPER-RODField of the Invention

[0001] The invention relates to a control device for a metallurgical vessel stopper-rod, a kit for mounting a metallurgical vessel stopper-rod assembly comprising said control device, a process for controlling a molten metal flow discharged from a metallurgical vessel comprising said control device as well as the use of said control device.Background and Prior Art

[0002] Traditionally, metallurgical vessels are drained using a stopper-rod to control the molten material flowing through a pouring orifice. The vertical displacement of the stopper rod is either automatically or manually controlled. A hand lever for the manual control is provided. The manual handling is complex, especially when the stopper-rod is heavy. It has been proposed to use detachable counterweights mounted on the hand lever to ease the actuation. However, such an approach presents limitations. The presence of these counterweights not only increases the inertia but also may prevent the stopper to be mechanically biased in the closed position (e.g. when too may counterweights are present). However, such a bias of the stopper in the closed position is however desirable for safety reasons. Additionally, such counterweights also bias the reaction time of the stopper rod, especially upon its closure, both in the automatic and manual modes.Aims of the Invention

[0003] The invention aims to solve at least one drawback of the teaching provided by the prior art.

[0004] More specifically, the invention aims to provide a solution to improve the control of the stopper-rod, in particular, to ensure more precise control of the stopperrod when handled by an operator while reducing the actuation load endured by the operator.Summary of the Invention

[0005] For the above purpose, the invention is directed a control device for a metallurgical vessel stopper-rod, said stopper-rod controlling a molten metal flow, said device comprising:an electric driving element;a first motion transformation mechanism, in particular a first rotation translation mechanism configured so that a displacement of said stopper-rod, in particular a vertical displacement of said stopper-rod is a first function of a motion, in particular a rotation, of a moving element, in particular a rotor, of the electric driving element, wherein a primary assistance drive load supplied by the moving element of the electric driving element is transformed into a secondary assistance drive load acting on said stopper-rod, via the first motion transformation mechanism, said secondary assistance drive load being oriented along a reference displacement direction, in particular an upward vertical displacement direction, either in the same direction as or the opposite direction to said reference displacement direction;a hand lever movable in rotation about an axis of rotation and holdable by an operator;a second motion transformation mechanism, in particular a second rotation translation mechanism configured so that the displacement of said stopperrod is a second function of a rotation of the hand lever, wherein a primary manual drive load applied by the operator on the hand lever is transformed into a secondary manual drive load acting on said stopper-rod via the second motion transformation mechanism, said secondary manual drive load being oriented along the reference displacement direction, either in the same direction as or the opposite direction to the reference displacement direction;at least one of:o a load sensor configured to generate a load measurement representative of the primary manual drive load applied by the operator on the hand lever; and / oro a motion sensor configured to generate a motion measurement representative of the rotation of the hand lever;anda control unit configured to issue a command to the electric driving element for controlling the primary assistance drive load, wherein the primary assistance drive load is a function of at least one of:o the load measurement generated by the load sensor; and / oro the motion measurement of the hand lever generated by the motion sensor;wherein the control device is configured to be operated in a manual assist-mode for a manual-assist control of the molten metal flow, in which the stopper-rod is manually actuated by the operator, via the secondary manual drive load, with an assistance of the electric driving element via the primary assistance drive load, and in which the hand lever and the electric driving element are mechanically connected so that the motion, in particular the rotation, of the moving element is kinematically linked to the rotation of the hand lever.

[0006] According to specific embodiments of the invention, the control device for a metallurgical vessel stopper-rod comprises one of more of the following technical features, taken in isolation or any combination thereof:• the control device is configured so that the secondary assistance drive load acting on said stopper-rod, as aligned with the reference displacement direction hereafter abbreviated - secondary assistance drive load - does not exceed a security load threshold or from 50% to 90% of said security load threshold, wherein the security load threshold being defined as either:- the maximal secondary assistance drive load ensuring that if the operator voluntarily or accidentally releases the hand lever and the maximal secondary assistance drive load is unduly maintained, the stopper-rod will still fall by gravity to close the opening the pouring orifice through which the molten metal flow, whatever a vertical position of the stopper-rod between a closed position and a maximal upper position of the stopper-rod in operation, preferably the opening the pouring orifice being closed in less than 5 seconds, in particular less than 2 seconds once the operator voluntarily or accidentally releases the hand lever,or- the maximal secondary assistance drive load to lift the stopper-rod form a closed position, in absence of molten metal surrounding said stopper-rod;• the control device is configured so that the secondary assistance drive load acting on said stopper-rod, said load being aligned with the reference displacement direction, is supplied by the electric driving element via the second motion transformation mechanism, when at least one of the following conditions are fulfilled:the secondary manual drive load, as derived from the load measurement generated by the load sensor or a vertical speed of the stopper-rod as derived from the motion measurement generated by the motion sensor, is aligned with the reference displacement direction, and / ora value associated with the motion measurement of the hand lever generated by the motion sensor is above a first threshold corresponding to a hold or stabilized state of the hand lever or a value associated with the load measurement of the hand lever generated by the load sensor is above a second threshold corresponding to a hold or stabilized state of the hand lever;• the control device is configured so that the secondary assistance drive load acting on said stopper-rod is aligned with the reference displacement direction and the primary assistance drive load supplied by the electric driving element is set to a predefined first value when at least one of the following conditions are fulfilled:the secondary manual drive load, as derived from the load measurement generated by the load sensor or a vertical speed of stopper-rod as generated by the motion measurement generated by the motion sensor, is aligned with the reference displacement direction, and / ora value associated with the motion measurement of the hand lever generated by the motion sensor is above a first threshold corresponding to a hold or stabilized state of the hand lever or the value associated with the load measurement of the hand lever generated by the load sensor is above a second threshold corresponding to a hold or stabilized state of the hand lever;• the control device is configured so that the primary assistance drive load supplied by the electric driving element is set to a predefined second value, lower than the first value, when at least one of the following conditions are fulfilled:the secondary manual drive load, as derived from the load measurement generated by the load sensor or the vertical speed of stopper-rod as generated by the motion measurement generated by the motion sensor, is oriented opposite to the reference displacement direction, and / orthe value associated with the motion measurement of the hand lever generated by the motion sensor is below first threshold corresponding to a hold or stabilized state of the hand lever or the value associated with the load measurement of the hand lever generated by the load sensor is below the second threshold corresponding to a hold or stabilized state of the hand lever;• the first threshold is defined such as a rotational speed of the hand lever as derived from the motion measurement is comprised in a rotational speed range from a negative rotational speed value to 0.0 revolution per minute, wherein the rotational speed of the hand lever being positive when the hand lever rotates in direction corresponding to the reference displacement direction;• the second threshold is defined such as a torque exerted on the hand lever as derived from the load measurement is comprised in a torque range from a negative torque value to 0.0 Nm, wherein the torque exerted on the hand lever being positive when the torque causes a rotation of the hand lever in direction corresponding to the reference displacement direction;• the rotational speed range corresponds to a vertical speed range of the stopperrod from -1.0 mm per second to 0.0 mm per second, wherein the vertical speed of the stopper-rod is positive when the vertical speed of the stopper-rod is aligned with the reference displacement direction;• the upward vertical displacement direction allows opening a pouring orifice through which the molten metal flow;• the motion measurement generated by the motion sensor is a rotation speed generated by a rotation sensor;• the rotation sensor is an encoder or resolver;• the rotation sensor is mounted in or on an electric motor of the electric driving element;• the rotation sensor is adapted to detect a rotation of at least one of the hand lever and / or a rotating member mechanically connected to and adapted to be synchronized in rotation to the hand lever and the electric driving element;• the load measurement generated by the load sensor is a force, a torque, a deformation parameter or a stress tensor parameter;• the load sensor is a torque sensor, a piezo or gauge sensor and is adapted to detect a load of the moving element, in particular a rotor, of the electric driving element, the hand lever, or to a rotating member mechanically connected to and adapted to be synchronized in rotation to the hand lever and the electric driving element;• the hand lever comprises a weight loading section adapted to be loaded with at least one weight;• at least one weight is attached to the weight loading section;• the control device is configured so that the secondary assistance drive load acting on said stopper-rod, as aligned with the reference displacement direction - hereafter abbreviated - secondary assistance drive load - is less than 90%, preferably less than 80%, more preferably less than 70% than the sum of the secondary assistance drive load and the secondary manual drive load acting on said stopper-rod, as aligned with the reference displacement direction when the secondary assistance drive load is greater than zero;• an assistance ratio is less than 90%, preferably less than 80%, more preferably less than 70%;• Control device is configured to be operable to switch between the manual-assist mode and a manual mode or an automatic mode, whereinin the manual mode said stopper-rod being exclusively manually actuated by the operator for a manual control of a molten metal flow,and optionally in the automatic mode, said stopper-rod is exclusively electrically actuated by said electric driving element for an automatic control of the molten metal flow.

[0007] The invention also relates to a kit for mounting a metallurgical vessel stopper-rod assembly, wherein said kit comprises a pouring orifice, a stopper-rod and the control device for a metallurgical stopper-rod, said assembly being adapted to be arranged in or at a bottom of a metallurgical vessel, in particular a tundish or ladle.

[0008] The invention also relates to a process for controlling a molten metal flow discharged from a metallurgical vessel, in particular a tundish or ladle, comprising the use of the control device for a metallurgical vessel stopper-rod.

[0009] The invention also relates to using the control device for a metallurgical vessel stopper-rod.

[0010] The present invention is also advantageous because the assistance can be performed through updating the software of an existing control system as the electric motor used for the automatic control and optionally its dedicated rotation sensor can serve as a cadence sensor for the electric assistance. This requires minimal adaptations.

[0011] In general, the preferred embodiments of each subject-matter of the invention also apply to the other subject-matters. As far as possible, each subject matter of the invention is combinable with other subject matter. The features of the invention are also combinable with the embodiments of the description, which, in addition, are combinable with each other.Brief description of the figures

[0012] Preferred aspects of the invention will now be described in more detail concerning the appended drawings, wherein the same reference numerals illustrate the same features and wherein:

[0013] Fig. 1 represents a side view of a control device according to a first embodiment of the invention.

[0014] Fig. 2 shows a control method to operate the control device according to the first embodiment.

[0015] Fig. 3 represents a side view of a control device according to a second embodiment of the invention.

[0016] Fig. 4 represents a side view of a control device according to a third embodiment of the invention.

[0017] Fig. 5 represents a side view of a control device according to a fourth embodiment of the invention.

[0018] Fig. 6 represents a side view of a control device according to a fifth embodiment of the invention.

[0019] List of reference symbols3 Stopper-rod7 metallurgical vessel9 Pouring orifice10 Control device20 Diving element30 Load (torque) sensor40 Motion (rotation) sensor70 Counterweight(s)101 Connecting rod102 Crank element103 Stopper-rod arm connection means104 Vertical sliding element105 Guiding body120 Hand lever126 Handle sectionX Rotation axisZ reference displacement direction (e.g. upward vertical displacement direction)Description of Preferred Embodiments of the Invention

[0020] In the first embodiment, according to Fig. 1 , a side view of a control device 10 for a metallurgical vessel stopper-rod 3 is presented. A cross-section of the metallurgical vessel 7 is illustrated in Fig. 1. The lower tip of stopper-rod 3 controls a molten metal flow discharged from metallurgical vessel 7 through a pouring orifice 9. The control device 10 can switch between a manual mode, a manual-assist mode, and an automatic mode.

[0021] In the automatic mode, the control device 10 is actuated by an electric driving element 20 to control a molten metal flow automatically. The driving element 20 cooperates mechanically with an internal vertically sliding member provided inside a guiding body 105 of the control device 10. The electric driving element 20comprises an electric motor and cooperates with the internal vertically sliding member through a first rotation translation mechanism, in which a rotation of the electric motor is transformed into a linear motion of the internal vertically sliding member. Preferably, the first rotation translation mechanism is a ball screw, roller screw or an inverted roller screw mechanism. Such mechanisms are known for their efficiency and minimal axial resistance. So, a translation of the internal vertically sliding member would cause a rotation of the motor without undue friction.

[0022] In the first embodiment according to Fig. 1, the electric motor 20 is positioned at the lower end of the control device 10. The axis of the electrical motor is oriented vertically so as to directly engage with the screw shaft of the ball screw or the roller screw mechanism. An electrical motor 20 with a vertically arranged rotor is preferred for its simplicity, although other configurations (e.g., horizontal shaft or linear electric motor) can be envisaged.

[0023] In the first embodiment according to Fig.1 , a stopper-rod arm 103 is attached to both the stopper-rod 3 and a vertical sliding element 104, and is interposed between them. The vertical sliding element 104 is arranged in an upper portion of the guiding body 105. The vertical sliding element 104 is also attached to the internal vertically sliding member. An inner contour of the sliding member 104 is preferably adapted to be guided in translation by an outer contour of the guiding body 105 for stiffness purposes. So, the stopper-rod arm 103 can be actuated by the internal vertically sliding member and undergoes vertical displacement in use.

[0024] In the first embodiment according to Fig.1 , the stopper arm 103 can also be actuated via the hand lever 120 in a manual or manual-assist control mode. For this purpose, a connecting rod 101 is provided with one end connected in rotation to the vertical sliding element 104, and the other to a crank element 102 (formed by the proximal end hand lever 120).

[0025] In the first embodiment according to Fig.1 , the crank element 102, the connecting rod 101 and the vertical sliding element 104 form a second rotation translation mechanism for transforming a rotation of the hand lever 120 about rotation axis X, into a vertical displacement of the stopper-arm 103. The second rotation translation mechanism shown in Fig. 1 is a crank mechanism. Alternatively, other rotation translation mechanisms, such as a gear rack or cam follower mechanism, can be foreseen. It can also be envisaged that the first and second rotation translation mechanisms are merged into a single translation mechanism. In this scenario, the rotor of the electric motor drives directly the hand lever 120.

[0026] In the first embodiment according to Fig. 1, the hand lever 120 comprises a handle section 126 holdable by an operator. By moving the hand lever 120 upward or downward, the operator can control the vertical position of the stopper-rod 3.

[0027] In the first embodiment, according to Fig.1, a motion sensor, in particular, a rotation sensor 40, is positioned in the electric driving element 20 to detect the rotation of the electrical motor 20. The rotation sensor is preferably an encoder or resolver mounted in the electric motor 20 or nearby. The motion detected (a rotation) by this sensor 40 is used as un input to control the manual assistance.

[0028] Indeed, in the first embodiment according to Fig. 1, the vertical sliding element 104 is mechanically coupled to the hand lever 120 and the electric driving element 20. So, a rotation of the hand lever 120 results in a rotation of the electric motor of the electric driving element 20. So, a rotation of the hand lever 120 can be indirectly detected in the electric motor's encoder or resolver 40. Generally, an electrical motor 40 used for a stopper rod is already equipped with an encoder or resolver. So, no extra sensor is needed to carry out a manual-assist control.

[0029] In the first embodiment according to Fig. 1 , the electric motor of the electric driving element 20 is controlled by the rotation of the hand lever 120, when the manual assist mode is selected.

[0030] In particular, Fig. 2 shows an advantageous control method to ensure the assistance of the stopper rod 3 when the manual-assist mode is selected. The control method of Fig. 2 is specifically adapted to control the control device 10 of the first embodiment according to Fig. 1.

[0031] In S01, the control starts. In step S02, it is detected whether the manual mode or manual-assist mode is required. In the negative, another control mode, such as the automatic mode is enabled in step S15. In the positive, the control scheme moves to step S03, where it is detected whether the manual-assist mode is selected. In the negative, the electric motor is de-energized. In the positive, the control moves to step S04, in which the electric motor 20 is energized, and then the electric motor is turned in step S05 in a predefined direction and ensures a drive load acting on said stopper-rod being aligned with a reference vertical displacement direction. Preferably, in the first iteration / loop / cycle after the detection that the manual-assist mode is detected, no torque or an initial torque is developed by the electric motor as the assistance current, by default. For the second and subsequent iterations / loops / cycles a target assistance is defined (e.g. in S08) and is used to control the electrical motor. In the first embodiment of Fig. 1, the assistance is performed in at least one direction, namely the reference verticaldisplacement direction corresponding to the upward direction. In step S06, it is detected whether the rotation speed of the electrical motor is above a predefined threshold. The electric motor's rotation speed is used to measure the hand lever's rotation speed, as their kinematics are mechanically linked. If the operator applies a movement to the hand lever, this motion is indirectly detected through the rotation sensor mounted on the electric motor. When the speed of the hand lever, as detected by the sensor, is above a certain threshold, it indicates that the operator moves the hand lever in the mechanism in the assistance direction. Advantageously, this threshold is a negative speed to ensure that an assistance load is present even if the operator does not hold the hand lever 120. So, when the operator grasps the hand lever 120 and then starts to move the hand lever 120 in a direction causing a lifting of the stopper-rod 3, the operator’s efforts are reduced ab initio. The assistance load and / or initial load is(are) selected so that there is not risk of accidental opening of the stopper-rod. Typically, the assistance load is not enough to lift the stopper-rod even in absence of the Archimedes' forces in a conservative approach (the vessel is dry). If so, the assistance current is set to a predetermined value in step S07. This value would not exceed a predefined threshold in step S08. In step S09, it is tested whether a request to repeat an iteration is present. In the negative, the control routine is ended in step S10. In the positive, the program returns to step S02 to resume the control cycle. In another cycle, if in step S06, it is detected that the rotation speed of the electrical motor is below a predefined threshold (typically when the stopper-rod is descending motion), the control routine moves to step S11, where it is detected whether the assistance current is still greater or substantially greater than zero. In the positive, the routine moves to step S12, where the assistance current is decreased by a certain amount, otherwise the assistance is set to zero in step S13. Advantageously, this stepwise decrease in the assistance current, permit to smooth the descent of the stopper rod 3, thereby avoiding a sudden disappearance of the assistance. Typically, this control routine is processed in a control unit (a.k.a. computing unit). In particular, the computing unit controlling of the electric motor can carry out the above-mentioned steps of Fig. 2 that are stored in a memory unit, in particular, the memory unit of the computing unit or an external one. The control data (speed threshold, assistance current..,) can be inputted via an interface.

[0032] The second embodiment, according to Fig. 3, differs from the first embodiment, according to Fig. 1, in that a load sensor 30 is used instead of a motion sensor 40. In particular, the assistance is controlled via a bending beam force sensor 30 or a gauge sensor mounted on the shaft of the hand lever 120. The load detected by the sensor 30 can be processed in the same way as the motion detected, in particular thespeed measured. For instance, when the torque is above a certain threshold, the assistance starts. The threshold is preferably set to a value close or equal to an absence of torque or force. More preferably, in a torque / force-based control, the level of the electric assistance is proportional to the torque / force measured. The presence of a torque / force sensor - or better yet, a combination of torque / force and rotation sensors -will generally ensure more responsive electric assistance compared to a solution with a rotation sensor (e.g., cadence sensor). The torque / force sensor provides a natural control.

[0033] The third embodiment, according to Fig. 4, differs from the first embodiment, according to Fig. 1, in that a load sensor 30 is used besides the motion sensor 40. In particular, the assistance is provided by a load sensor 30 in the form of a bending beam force sensor or gauge sensor mounted on the shaft of the hand lever 120 and an encoder or resolver mounted in the electric motor 20 or nearby. With this arrangement, better control can be achieved because acceleration (via load) and speed are used for the control. For instance, an arbitrage can be foreseen when the assistance with the load / torque / force or the speed sensor is to be selected. For example, the speed sensor can initiate assistance as soon as the handler's movement is detected. The assistant uses the load / torque / force sensor to adjust how hard the operator pushes on the hand lever. Moreover, this combination brings a safer configuration if one of the sensors is defaulted.

[0034] The fourth embodiment, according to the embodiment of Fig. 5, differs from the second embodiment, according to Fig. 3, in that the driving element 20 is an add-on electrical cylinder (first rotation translation mechanism) and in that a manual mechanism (second rotation translation mechanism) ensuring the transformation of the rotation of the hand lever 120 into a vertical translation of the stopper rod 7 is a rack gear mechanism. Alternatively, a cam, lever, or crank mechanism can also be foreseen.

[0035] The fifth embodiment, according to the embodiment of Fig. 6 differs from the fourth embodiment, according to the embodiment of Fig. 5, in that a linear displacement sensor (not represented) follows the vertical displacement of the screw of the electric cylinder instead of a torque sensor 30 mounted on the shaft of the hand lever 120.

[0036] A sixth embodiment (not illustrated) differs from the first embodiment of Fig. 1 in that a rotation sensor 40 is adapted to measure the rotation (e.g., rotation speed) of a rotating member (e.g. connecting rod or a bearing journal of the handlever) connected to and adapted to be synchronized in rotation to the hand lever 120 and the electric driving element 20.

[0037] A seventh embodiment (not illustrated) differs from the first embodiment depicted in Fig. 1 in that a clutch mechanism is interposed between the hand lever 120 and the electric driving element 20. The clutch can be disengaged, allowing desynchronization between the hand lever 120 and the electric driving element 20, such that the stopper rod can be automatically actuated by the electric driving element 20 while the hand lever remains static. When the clutch is engaged, the hand lever 120 is synchronized with the electric driving element 20.

[0038] By “assistance ratio” is meant a ratio between the electric power absorbed by electric driving element (20) and the sum of said power absorbed by electric driving element (20) and the mechanical power produced by the hand lever (120), when actuated by the operator in the manual assist-mode. The power absorbed by electric driving element (20) can be measured using electrical measurements. The electrical power allows a precise estimation of the mechanical power delivered by the electric driving element (20). The mechanical power produced by the hand lever (120), can be measured, if necessary, by combining the data provided by load and motion measurements. The level of assistance can be controlled by the level of the assistance current.

[0039] Alternatively or complementary to an “assistance ratio”, the control device 10 can be configured so that the secondary assistance drive load acting on said stopper-rod 3, as aligned with the upward vertical displacement direction hereafter abbreviated - secondary assistance drive load - does not exceed a security load threshold or from 50% to 90% of said security load threshold. The security load threshold is defined as the maximal secondary assistance drive load ensuring that if the operator voluntarily or accidentally releases the hand lever 120 and the maximal secondary assistance drive load is unduly maintained, the stopper-rod 3 will still fall by gravity to close the opening the pouring orifice 9 through which the molten metal flow, preferably in less than 5 seconds, preferably less than 3 seconds. This threshold can be determined with the weight of the stopper 3, stopper-rod arm connection means, and the Vertical sliding element 104. Additionally, the Archimedes’ force exerted on stopper 3, can also be considered to determine this security load threshold.

[0040] Alternatively or complementary to an “assistance ratio” and / or “security load threshold”, the control device 10 can be configured so that the secondary assistance drive load acting on said stopper-rod, as aligned with the reference upwarddisplacement direction - hereafter abbreviated secondary assistance drive load - is less than 90%, preferably less than 80%, more preferably less than 70% than the sum of the secondary assistance drive load and the secondary manual drive load acting on said stopper-rod, as aligned with the reference upward displacement direction when the secondary assistance drive load is greater than zero.

[0041] Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the scope of the present invention being limited only by the terms of the appended claims.

Claims

CLAIMS1. Control device (10) for a metallurgical vessel stopper-rod (3), said stopper-rod controlling a molten metal flow, said device comprising:an electric driving element (20);a first motion transformation mechanism, in particular a first rotation translation mechanism configured so that a displacement of said stopper-rod (3), in particular a vertical displacement of said stopper-rod (3) is a first function of a motion, in particular a rotation, of a moving element, in particular a rotor, of the electric driving element (20), wherein a primary assistance drive load supplied by the moving element of the electric driving element (20) is transformed into a secondary assistance drive load acting on said stopperrod, via the first motion transformation mechanism, said secondary assistance drive load being oriented along a reference displacement direction (Z), in particular an upward vertical displacement direction, either in the same direction as or the opposite direction to said reference displacement direction;a hand lever (120) movable in rotation about an axis (X) of rotation and holdable by an operator;a second motion transformation mechanism, in particular a second rotation translation mechanism configured so that the displacement of said stopperrod (3) is a second function of a rotation of the hand lever (120), wherein a primary manual drive load applied by the operator on the hand lever (120) is transformed into a secondary manual drive load acting on said stopper-rod via the second motion transformation mechanism, said secondary manual drive load being oriented along the reference displacement direction (Z), either in the same direction as or the opposite direction to the reference displacement direction;at least one of:o a load sensor (30) configured to generate a load measurement representative of the primary manual drive load applied by the operator on the hand lever (120); and / oro a motion sensor (40) configured to generate a motion measurement representative of the rotation of the hand lever (120);anda control unit configured to issue a command to the electric driving element (20) for controlling the primary assistance drive load, wherein the primary assistance drive load is a function of at least one of:o the load measurement generated by the load sensor; and / oro the motion measurement of the hand lever (120) generated by the motion sensor;- wherein the control device (10) is configured to be operated in a manual assist-mode for a manual-assist control of the molten metal flow, in which the stopper-rod (3) is manually actuated by the operator, via the secondary manual drive load, with an assistance of the electric driving element (20) via the primary assistance drive load, and in which the hand lever (120) and the electric driving element (20) are mechanically connected so that the motion, in particular the rotation, of the moving element is kinematically linked to the rotation of the hand lever (120).

2. Control device (10) according to claim 1, wherein the control device (10) is configured so that the secondary assistance drive load acting on said stopperrod (3), as aligned with the reference displacement direction hereafter abbreviated - secondary assistance drive load - does not exceed a security load threshold or from 50% to 90% of said security load threshold, wherein the security load threshold being defined as either:- the maximal secondary assistance drive load ensuring that if the operator voluntarily or accidentally releases the hand lever (120) and the maximal secondary assistance drive load is unduly maintained, the stopper-rod (3) will still fall by gravity to close the opening the pouring orifice (9) through which the molten metal flow, whatever a vertical position of the stopper-rod (3) between a closed position and a maximal upper position of the stopper-rod (3) in operation, preferably the opening the pouring orifice (9) being closed in less than175 seconds, in particular less than 2 seconds once the operator voluntarily or accidentally releases the hand lever (120),or- the maximal secondary assistance drive load to lift the stopper-rod (3) form a closed position, in absence of molten metal surrounding said stopper-rod (3).

3. Control device (10) according to claim 1 or 2, configured so that the secondary assistance drive load acting on said stopper-rod (3), said load being aligned with the reference displacement direction, is supplied by the electric driving element (20) via the second motion transformation mechanism, when at least one of the following conditions are fulfilled:the secondary manual drive load, as derived from the load measurement generated by the load sensor or a vertical speed of the stopper-rod (3) as derived from the motion measurement generated by the motion sensor (40), is aligned with the reference displacement direction, and / ora value associated with the motion measurement of the hand lever (120) generated by the motion sensor is above a first threshold corresponding to a hold or stabilized state of the hand lever (120) or a value associated with the load measurement of the hand lever generated by the load sensor is above a second threshold corresponding to a hold or stabilized state of the hand lever (120).

4. Control device (10) according to the preceding claim 1 or 2, configured so that the secondary assistance drive load acting on said stopper-rod (3) is aligned with the reference displacement direction and the primary assistance drive load supplied by the electric driving element (20) is set to a predefined first value when at least one of the following conditions are fulfilled:the secondary manual drive load, as derived from the load measurement generated by the load sensor or a vertical speed of stopper-rod (3) as generated by the motion measurement generated by the motion sensor (40), is aligned with the reference displacement direction, and / or18a value associated with the motion measurement of the hand lever (120) generated by the motion sensor is above a first threshold corresponding to a hold or stabilized state of the hand lever (120) or the value associated with the load measurement of the hand lever generated by the load sensor is above a second threshold corresponding to a hold or stabilized state of the hand lever (120).

5. Control device (10) according to the preceding claim, wherein the control device (10) is configured so that the primary assistance drive load supplied by the electric driving element (20) is set to a predefined second value, lower than the first value, when at least one of the following conditions are fulfilled:the secondary manual drive load, as derived from the load measurement generated by the load sensor or the vertical speed of stopper-rod (3) as generated by the motion measurement generated by the motion sensor, is oriented opposite to the reference displacement direction, and / orthe value associated with the motion measurement of the hand lever (120) generated by the motion sensor is below first threshold corresponding to a hold or stabilized state of the hand lever (120) or the value associated with the load measurement of the hand lever generated by the load sensor is below the second threshold corresponding to a hold or stabilized state of the hand lever (120).

6. Control device (10) according to any of the preceding claims 3 to 5 optionally in combination with claim 2, wherein the first threshold is defined such as a rotational speed of the hand lever (120) as derived from the motion measurement is comprised in a rotational speed range from a negative rotational speed value to 0.0 revolution per minute, wherein the rotational speed of the hand lever (120) being positive when the hand lever (120) rotates in direction corresponding to the reference displacement direction and / or wherein the second threshold is defined such as a torque exerted on the hand lever (120) as derived from the load measurement is comprised in a torque range from a negative torque value to 0.0 Nm, wherein the torque exerted on the hand lever (120) being positive when the torque causes a rotation of the hand lever (120) in direction corresponding to the reference displacement direction, preferably the rotational speed range corresponding to a vertical speed range of the stopper-rod (3) from -1.0 mm per second to 0.0 mm per second, wherein the vertical speed of the stopper-rod (3)19is positive when the vertical speed of the stopper-rod (3) is aligned with the reference displacement direction.

7. Control device (10) according to any of the preceding claims, wherein the upward vertical displacement direction allows opening a pouring orifice (9) through which the molten metal flow.

8. Control device (10) according to any of the preceding claims, wherein the motion measurement generated by the motion sensor is a rotation speed generated by a rotation sensor.

9. Control device according to the preceding claim, wherein the rotation sensor is an encoder or resolver.

10. Control device (10) according to any of the preceding claims, wherein the load measurement generated by the load sensor is a force, a torque, a deformation parameter or a stress tensor parameter.

11. Control device (10) according to any of the preceding claims, wherein the control device (10) is configured so that the secondary assistance drive load acting on said stopper-rod (3), as aligned with the reference displacement direction - hereafter abbreviated - secondary assistance drive load - is less than 90%, preferably less than 80%, more preferably less than 70% than the sum of the secondary assistance drive load and the secondary manual drive load acting on said stopper-rod, as aligned with the reference displacement direction when the secondary assistance drive load is greater than zero.

12. Control device (10) according to any of the preceding claims, wherein an assistance ratio is less than 90%, preferably less than 80%, more preferably less than 70%.

13. Control device according to any of the preceding claims, being configured to be operable to switch between the manual-assist mode and a manual mode or an automatic mode, whereinin the manual mode said stopper-rod (3) being exclusively manually actuated by the operator for a manual control of a molten metal flow,and optionally in the automatic mode, said stopper-rod is exclusively electrically actuated by said electric driving element (20) for an automatic control of the molten metal flow.

14. A kit for mounting a metallurgical vessel stopper-rod assembly, wherein said kit comprises a pouring orifice (9), a stopper-rod (3) and a control device for a metallurgical vessel stopper-rod, said assembly being adapted to be arranged in or at a bottom of a metallurgical vessel (7), in particular a tundish or ladle, wherein said control device is a control device (10) for a metallurgical vessel stopper-rod according to any of claims 1 to 13.

15. Process for controlling a molten metal flow discharged from a metallurgical vessel (7), in particular a tundish or ladle, comprising the use of a control device (10) for a metallurgical vessel stopper-rod (3) according to any of claims 1 to 13.

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