A device and a method for stabilising a web or a filament of ferromagnetic material moving in one direction

(54) (56) (57)

AGENT

NAME

ABB AB, 721 83 Västerås SE

Per Lennart Eriksson, Västerås SE, Bengt Rydholm, Västerås SE, Sven Karlsson, Västerås SE, Magnus Hallbäck, Bromma SE Gothenburg Tallbäck, Västerås SE

Bjerkéns Patentbyrå KB

Device and method of stabilization ng of an elongated metallic object

CALLED PUBLICATIONS:

WO Al 0 071 977 (G01D 05/20), DE Al 4 118 975 (H01F 07/18)

SUMMARY:

The invention relates to an apparatus and method for stabilizing metallic objects (1) of magnetic material. The metallic object is intended to be transported along a transport path (2, 3) which includes a plane (x). The plane comprises a direction of transport (x) and is substantially parallel to the longitudinal direction of the object (1) in said plane. A sensor (5, 6) is arranged to sense the value of a parameter which depends on the position of the object (1) with respect to the plane (1). A substantially stationary electromagnetic actuator (7, 8) is arranged to apply a magnetic force to the object in response to the sensed position. The magnetic force comprises at least one force component

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The numbers in brackets indicate international identification code, INID code. Letter within noon letters indicate international document code.

519 928

Summary

The invention relates to an apparatus and method for stabilizing metallic objects (1) of magnetic material.

The metallic object is intended to be transported along a transport path (2, 3) which includes a plane (x). The plane comprises a direction of transport (x) and is substantially parallel to the longitudinal direction of the object (1) in said plane. A sensor (5, 6) is arranged to sense the value of a parameter which depends on the position of the object (1) with respect to the plane (1). A substantially stationary electromagnetic actuator (7, 8) is arranged to apply a magnetic force to the object in response to the sensed position. The magnetic force comprises at least one force component directed across the direction of transport (4) and across the plane (x) ·

519 928

BACKGROUND OF THE INVENTION AND PRIOR ART

The present invention relates to a device for stabilizing an elongated metallic object of magnetic material, the metallic object being intended to be transported along a conveying path comprising a plane, which includes a direction of transport and is substantially parallel to the longitudinal direction of the object in said plane. Furthermore, the invention relates to a method for stabilizing an elongated metallic object of magnetic material, the metallic object being conveyed along a conveying path comprising a plane, which comprises a conveying direction and substantially parallel to the longitudinal direction of the object in said plane.

In various industries, there is a need to continuously transport elongated metallic objects, such as metal bands or wires in rolling mills, in various metal coating applications, such as continuous galvanizing of steel bands or steel wires, continuous casting, extrusion, etc. During such continuous transport, a section of the object is extended. a plane and is carried in a longitudinal direction by the object in said plane. For efficiency reasons, it is important to achieve a high transport speed. However, a high transport speed can result in problems in keeping the object stable in the plane, i.e., maintaining

519 928 the position of the object with respect to the plane and prevent transverse deviations of the object.

US-A-4 655 166 discloses a device for preventing oscillations of a running belt in connection with galvanizing the belt. The device comprises permanent magnet units arranged in the vicinity of two opposite side edges of the conveyor belt. Detectors are provided to detect the gap between the side edges and the respective magnetic unit. In order to maintain the size of the gap at a certain level, control motors are provided to adjust the position of the magnetic units in response to the detected gap.

US-A-3,661,116 discloses a similar device for stabilizing a meta llband. An electromagnet extends along a path such that the poles are arranged outside and near each side edge of the band.

SUMMARY OF THE INVENTION

The object of the invention is to improve the stabilization of a metallic object during transport, especially during transport with a high transport speed.

This object is achieved with the device initially indicated, characterized in that it comprises a sensor adapted to sense the value of a parameter which depends on the position of the object with respect to the plane, and a substantially stationary electromagnetic actuator adapted to apply a magnetic force on the object in response to the sensed position, the magnetic force comprising at least one force component directed transversely to the transport direction and across the plane.

With such a device it is possible to achieve a correct positioning of the object with respect to on the plane so that

519 The 928 object runs along the plane in a stable manner. Furthermore, since the actuator enables correction of the transverse position of the object with respect to the plane with a magnetic force, it is not necessary that it be in contact with the object.

According to an embodiment of the invention, the actuator comprises at least one first actuator arranged on a first side of the plane and at a certain distance from the plane. Furthermore, the actuator may also comprise a second actuator arranged on a second side of the plane and at a certain distance from the plane. Thus, the actuator defines said plane between the first actuator and the second actuator. Preferably, the first actuator may be arranged at the same distance from the plane as the second actuator but on the opposite side thereof.

According to a further embodiment of the invention, the first a the actuator is positioned substantially exactly opposite to the second actuator. Preferably, the first actuator may be substantially identical to the second actuator. By such a symmetrical arrangement of the actuators connected with respect to the plane, both the sensing function and the control function can be achieved in a simple manner.

According to a further embodiment of the invention, the actuator is arranged to increase the magnetic force of one of the actuators when the position of the object deviates from said plane.

According to a further embodiment of the invention, said actuating means comprises a magnetic flow carrier which forms a magnetic flow circuit with a part of the object. Said magnetic flow carrier may have a first end arranged to be

519 928 located near the article and a second end to be located near the article, said portion of the article extending substantially between the first end and second end. Such a magnetic flow carrier may be made of any suitable magnetic material, such as iron plates, magnetic powder, etc., and may be formed as a loop extending between the first end and the second end, the ends forming magnetic poles of said actuator.

According to a further embodiment of the invention, the device comprises a control unit which is arranged to apply voltage pulses to the actuator in response to said sensed value and thereby generate said magnetic force. Said actuating means may comprise a winding connected to said control unit, the control unit being arranged to apply said voltage pulses to the winding to induce a magnetic flux in the magnetic flux carrier. Preferably, the control unit is arranged to apply said voltage pulses which have a substantially constant amplitude and thus vary the magnetic force by varying the length of the voltage pulses. .

According to a further embodiment of the invention, the sensor is arranged to sense the level of the electric current through the winding. Such a sensor is not in contact with the object and the sensing function will not affect the position of the object. Furthermore, the winding with such a sensor can comprise both the activation function and the sensing function.

According to a further embodiment of the invention, the control unit is arranged to increase the magnetic force applied to said actuating means as the level of the electric current through the corresponding winding increases. Thereby, the sensor may comprise a first sensor means which is arranged by the sensor

519 928 the level of current through the first actuator and a second sensor means arranged to sense the level of current through the second actuator, the controller being arranged to compare the current level through the first actuator with the current level through the second actuator. means, and to increase the length of the voltage pulses through the winding of the actuator having the highest current level.

According to a further embodiment of the invention, the control unit comprises a so-called DC chopper.

The object is also achieved by the procedure initially indicated, which is characterized by the steps:

sensing the value of a parameter which depends on the position of the object with respect to the plane and applying a magnetic force to the object in response to the sensed value, the magnetic force comprising at least one force component acting on the object and being directed transverse to the transverse direction and transversely planet.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will now be explained in more detail with reference to various embodiments shown by way of example only and with reference to the accompanying figures.

Fig. 1 shows schematically a device for stabilizing a metallic object according to u ppfinningen.

Fig. 2 is a diagram showing the current through a winding of a respective actuator in response to voltage pulses.

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DETAILED DESCRIPTION OF DIFFERENT EMBODIMENTS OF

INVENTION

Fig. 1 shows a device for stabilizing an elongated metallic object 1 of magnetic material. In the embodiment shown, the object is a metal band 1. However, it should be noted that the invention is also applicable to other elongated objects, such as various bands, wires, tubes, etc. In the embodiment shown, the metal band 1 is transported from a first roll 2 to a second roll 3 along a conveying path comprising a plane x. In Fig. 1, the plane x is substantially vertical. However, the plane x and the conveying path may extend in directions other than a vertical one, for example in a horizontal direction.

It should be noted that rollers 2, 3 are schematically indicated to indicate the conveying path. Such a tra sports track can form part of many different industrial processes, such as galvanizing steel strips, rolling mill processes, extrusion etc.

The device according to the invention comprises a sensor arranged to sense the value 'of' a parameter which depends on the position of the metal band 1 with respect to the plane x. The sensor comprises a first sensor means 5 and a second sensor means 6. Each sensor means 5, 6 is arranged to sense a current level. The sensor means 5, 6 will be described in more detail below.

Further, the device comprises a substantially stationary electromagnetic actuator adapted to apply a magnetic force to the metal band 1 in response to said sensed value. The electromagnetic actuator comprises a first substantially stationary actuator 7 arranged on a first side of the plane x and at a definite distance from the plane x and thus from the running surface.

519 928 The Metal Band 1. The actuator comprises and a second substantially stationary actuator 8 arranged on a second side of the plane x and at a certain distance from the plane x, and thus from the metal band 1. Each actuator 7, 8 comprises a magnetic flow carrier in the form of a core 9 ', 9. '' of iron or any other suitable magnetic material, such as iron plates, magnetic iron powder, etc. Each core 9 ', 9' 'is formed as a loop extending between a first end and a second end, said ends forming two magnetic poles of respective actuators 7, 8. Furthermore, each actuator in the suspension means 7, 8 comprises an electric winding 11 ', 11' ', which is wound around the respective core 9', 9 ''. Accordingly, a voltage applied to the winding 11 ', 11' 'will induce a magnetic flux in the core 9', 9 '' and a substantially closed magnetic flux circuit is achieved with the core 9 ', 9' 'and a portion of the metal band 1, which portion extends between the two magnetic poles of the respective core 9 ', 9' '.

In it In the illustrated embodiment, the first actuator 7 is positioned substantially exactly opposite to the second actuator 8. Furthermore, the first actuator 7 is substantially identical to the second actuator 8, and the two actuators 7, 8 are positioned at the same distance from the plane x and thus from the metal band 1. when the metal strip 1 is located in the intended conveying path. The plane x thus forms a center plane x between the actuators 7, 8.

The device according to the invention also comprises a control unit 13 adapted to apply voltage pulses to the windings 11 ', 11' 'of the first actuator 7 and of the second actuator 8, respectively, in response to the values ​​sensed by the first sensor means 5 and the second sensor means 6, respectively. .

519 928

The controller forms a so-called DC chopper and includes a rectifier 14 to be supplied with a three-phase AC voltage. In parallel with rectifier 14, a capacitor 15 is provided d. The windings 11 ', 11' 'are also connected in parallel to the rectifier 14 via respective sensor means 5, 6 and a switching device represented by an antiparallel diode 16', 16 '' and a one-way current switch 17 ', 17' '(the filled arrows indicates current direction). Further, the control unit 13 comprises a processor 18 connected to the first sensor means 5, the second sensor means 6, the switch 17 'and the switch 17' '.

The first sensor means 5 and the second sensor means 6 are arranged to sense the current level through the respective winding 11 'and 11' '. The processor 18 is connected to the sensor means 5 and 6 and arranged to receive the sensed level from the sensor means 5, 6. Furthermore, the processor 18 is connected to the switches 17 'and 17' 'and arranged to initiate switching of the switches 17', 17 '' between a open state, see switch 17 ', and closed state, see switch 17' '. By closing switch 17 ', 17' ', a voltage will be applied to it respective winding 11 ', 11' '. Accordingly, the processor 18 will apply voltage pulses V to the actuators 7, 8 of 'one definite length T, see Fig. 2. The voltage pulses induce a current in the respective winding 11', 11 '' and with the aid of the sensor means 5, 6 the current level is measured by windings 11 ', 11' '. Current level through windings 11 ', 11'¹ depends on the magnetic inductance of the respective magnetic flow carrier. If the distance between the metal band 1 and the ends of the core 9 ', 9' 'increases, the magnetic inductance of the magnetic flux circuit will decrease, which means that the current through the winding 11', 11 '' will increase since the magnetic inductance of the magnetic flux circuit is inversely proportional to the current. through the winding 11 ', 11' '.

519 928

Fig. 2 indicates voltage pulses V and current I with respect to the windings 11 'and 11' '. In the winding 11 ', the current I is at a higher level for the voltage pulse V_1Z meaning the metal band 1 is positioned closer to the second actuator 8 than the first actuator 7. To compensate for this, the second voltage pulse V is extended₂ so that the first actuator 7 will apply an attractive magnetic force to the metal band 1 for a longer period of time than the second actuator 8, and consequently the metal band 1 will be forced to the x-plane of the center plane.

The present invention is not limited to the embodiments shown but can be varied and modified within the scope of the following claims.

519 92δ; Ί