EP1670601B1 - System for contactless application of tension in electrically conductive metal strips - Google Patents

Abstract

Phase displacement is applied and controlled between two synchronously running upper and lower magnetic fields of travelling waves in a system for the contactless application of strip tension, wherein the levitation force produced by means of a displaced magnetic field (3) arises from the return force in order to reliably prevent damage to the surface of the strip (4) and to maintain optimum power efficiency, thereby achieving central levitation of the strip (4) and/or the desired position of the strip.

Description

1 state of the art

The technical field of the invention relates to a system for the contactless application of a strip tension in electrically conductive metal strips according to the preamble of claim 1.

Such a plant is from the WO / 27544A known.

In all discontinuous and continuous cold strip rolling mills and processing lines, the metal strips must be transported from the decoiler in the entrance section via the process section to the take-up reel in the exit section. In the course of this tape transport variable tape speeds and tape runs, tape running controls, tape storage, tape tension decoupling loops, etc. are required. In the process parts, the processing of the bands, e.g. metallurgical processes in pickling processes, rolling mills, continuous annealing and dressing plants.

The rotary eddy-current linear drive was designed as a brake and / or scaffold, optionally combined with a strip conveyor control for metal strip production lines, which allows fundamental conceptual changes. It is used wherever previously the tension rollers, drivers, flat brakes, the mechanical linear drive and vacuum brakes are used. In these systems, the bands are each introduced by means of contact forces on the strip surface in the band.

The system is suitable for all electrically conductive metals and their alloys, in particular for aluminum and copper, but also, for example, for electrically conductive powder metallurgy materials, sintered materials and their alloys.

In the circulating eddy current linear drive, the entrainment effect is achieved by a magnetic field traveling relative to the strip. This magnetic field causes the strip tension via the eddy current excitation, at the same time the metal strip is repelled by this magnetic field.

The quality requirements for the product metal strip have increased significantly in recent years. The rotary eddy current linear drive meets these requirements; In addition, quality improvements can be achieved. The operation of the circulating eddy current linear drive is particularly valuable for the highest demands on surface quality, to avoid multiple bends of the bands with longitudinal tension, for special strip flatness with minimization of Wickelbogigkeiten and discontinuous process lines due to the easy handling. It becomes possible for the first time to transport the belts through the process lines without touching the two sides of the belt after the finishing process.

For winding tapes during rewinding or in the finishing after splitting from wide to narrow strip, a return pull is required to obtain mechanically stably wound coils (coils). This is essential for the transport, handling and further processing of these coils.

Usually, the required strip tension is applied by mechanical brakes, the friction surface representing the belt surface. These are cheeks coated with textiles (so-called carpet brake), or the contact pressure is generated by inflating a (fire hose) hose. With this system you can only build retreat and no preference. It can only be used on undemanding surfaces because the retraction is generated at 100% relative movement. This system is very common because it is inexpensive to build.

In the S-roll system, the strip tension is built up by looping a roll. The tensile structure can only be changed per roll depending on the preference, the wrap angle and the coefficient of friction between the belt and roller coating.

If the strip tension is built up in a driver unit, considerable specific loads for the strip surface arise. The forces to be transmitted are very limited.

This disadvantage could be eliminated by the mechanical linear drive. In this case, the driving range is adapted to the case of need by means of a wagon chain. With the highest demands on the surface, limits are also achieved with this system.

In order to avoid scratches and marks on sensitive surfaces (eg polished surfaces), in some solutions the belt tension is applied by pulleys with integrated brake. Here, however, exists still the risk of footprints and the introduction of stresses in the material (especially at larger tape thicknesses) by the resulting flexing work in the required wrap of these brake rollers to prevent slippage, which would otherwise cause scratches. When splitting strip but are due to rolling process the outer strips usually longer than the median strip. Thus, a pulley brake can not be used, either because the tape tension is missing or scratches caused by the slip.

All of these mechanical friction brakes and recirculating brake rollers are not applicable to very high surface requirements (e.g., decorative materials or mirrors and other reflectors) or thin metal foils. Also for the automotive industry, especially for the aluminum outer skin in modern passenger cars, this technique is interesting.

Non-contact retraction devices are known using eddy current forces when moving a tape in a magnetic field. A mostly in the strip running direction multi-pole permanent magnet arrangement, arranged above and below the belt, ensures the field structure and the belt speed in dependence on the strip thickness and the electrical conductivity of the strip material for the retraction force (braking force F _B ) against the strip running direction. The hovering of the belt is made possible by the lifting force F _H acting in the direction of the surface normal of the belt.

These arrangements have the disadvantage that the levitation and the withdrawal force can not be adjusted independently of each other. This has the consequence that either the scratch-free floating can not be secured or the tape tension is too large.

These forces are also directly dependent on the conductivity, the strip thickness and the belt differential speed. There are no forces when the band is at a standstill. When starting the belt, the forces are insufficient and the damage to the surface are avoided only at rated speed. The processing speeds no longer depend on the possible productivity of the system but on the required strip tension.

In the German patent DE 195 24 289 C2 an eddy current brake is described. The main difference is that the permanent magnets are moved in a circular path. For the retention effect, only one magnetic track is available. In addition, only for the fraction of the period, the parallelism of the permanent magnets, whereby the retention effect is built unevenly and substantially reduced. In order to be able to build practice-specific specific belt tension, the rotational speeds of the brake rollers would have to be brought into unmanageable orders of magnitude. In addition, large drive power sets in at a very unfavorable efficiency.

In the PCT patent application PCT / EP99 / 08606 . WO 00/27554 and in the European patent application 99 971 746.3-2302 an eddy current brake is described in which a plurality of permanent magnets be moved parallel to the tape. The belt tension can be determined by the belt speed difference to the permanent magnets, the number of chain wheels acting, the material and the shape of the permanent magnets and the distance between the opposing permanent magnets. This embodiment has the defect that the center position of the band can not be influenced.

In the German Offenlegungschrift DE 23 01 434 a device is described in which the strip tension is generated by a magnetic traveling field by means of stationary inductors. This system has not been proven in practice, since too small bands are produced at a very unfavorable efficiency.

In the patent DD 96 206 In the German Democratic Republic, a system is described in which used for braking the electrically conductive slit strip based on the principle of linear motors magnetic systems (Indu ktoren) are used, the supply is carried out by three-phase current. Between the inductors, a magnetic field is built up in the air gap, which moves counter to the direction of movement of the bands, the speed of the feed frequency and the pole pitch depends, making an adaptation to different operating conditions - if at all - difficult.

With the present invention, the aforementioned deficiencies are eliminated.

2 solution according to the invention

The band brake device consists of two opposing devices 1 and 2, in whose gap a magnetic alternating pole magnetic field 3 is generated. In this gap, the strip material 4 moves at the working speed v _A.

The strip tension σ _B = F _B / A _B (where A _{B is} the band cross-sectional area d * b _B ) is set by the differential velocity v between the belt and the magnetic field, thereby forming a traveling wave field 3a. The traveling wave field can move with the speed V _F in or against the direction of tape travel or even stand still, depending on the relative speed required for application of the desired tape tension v = V _A - V _F. The braking or retraction force results from the geometry (thickness d and width b _B ), the electrical conductivity κ of the band, the active length I _{M of} the magnetic field (coverage) and the air gap induction peak value Bs, which is dependent on the gap width δ.

The vertical force F _v for compensating the dead weight of the belt is derived from the braking force F _B by a displacement Δ of the upper to the lower field shaft. The shift angle Δφ = arctan (Δ / δ) results in the vertical force F _v = F _B sin (Δδ).

The lifting force F _H described above then serves only to center the belt in the gap and to dampen vertically acting belt vibrations. Fig. 1

A Bandzugmesseinrichtung 5 controls the relative speed on the influence of the traveling wave velocity and possibly their direction. Distance sensors for detecting the band position in the gap control the phase angle between the upper and lower traveling wave.

• Bewegung von wechselpolig angeordneten mit Permanentmagneten 6 bestückten Leisten 7 in einer Länge, die der maximalen Arbeitsbreite entspricht, welche an einer oben und unten umlaufenden Kette 8, 9 befestigt sind (Fig. 1 bis 4). Geschwindigkeit und Phasenverschiebung werden über zwei separat gesteuerte umrichtergespeiste Antriebe 10, 11 geregelt (Fig. 1).
• Die beiden Ketten können auch von einem geregelten Motor über Umlenkgetriebe 12 und Ketten 13 angetrieben werden. Die Phasenverschiebung wird durch einen verschiebbaren Kettenspanner 14 eingestellt (siehe Fig. 5).
• Eine weitere konstruktive Maßnahme für die Phasenverschiebung erfolgt über ein Differential-Kammwalzgetriebe 15 oder ein normales Kammwalzgetriebe 17, in dem eine regelbare Voreilung oder ein Nachlauf vorgesehen wird (siehe Figur 6). Der Antrieb erfolgt über einen Motor 16.
• Wird mittels Kammwalzgetriebe eine starre Verbindung zwischen dem Kettenrad des oberen und des unteren Wagenkettenantriebs sichergestellt, kann der Versatz der Permanentmagnete dadurch erreicht werden, dass der obere Kettenkasten 18 gegen den unteren mechanisch verschoben wird (siehe Figuren 7, 7a und 7b).
• Wird bei einer stationären Wirbelstrombremse 19, 20, zum Beispiel bei einer Kettengeschwindigkeit V_F = 0 eine mechanische Verschiebung vorgenommen, kann auch in diesem System die Mittenlage des Bandes durch die Verschiebung der Magnete erfolgen. Dies ist für die Praxis als Vorzuggerüst eine bedeutende Verbesserung (siehe Figur 8 und 9).
• Das Wanderfeld kann auch elektrisch erzeugt werden, indem oben und unten statt der Permanentmagnete auf den Leisten Elektromagnete, vorzugsweise Drehstromstatoren 22, 23 (analog den Ankern von Linearmotoren) angebracht sind und diese von einem oder auch zwei (für elektrische Phasenverschiebung) Stromrichtern gespeist werden (siehe Fig. 10 und 11).
• Es ist aber auch möglich, das Wanderfeld durch Drehstromstatoren (analog den Ankern von Linearmotoren) zu erzeugen, wie schon in den zitierten Schriften vorgeschlagen. Die Phasenverschiebung erfolgt dann über zwei synchronisierte Stromrichter oder eine mechanische Verschiebung der Statoren zueinander. Vorteil dieser Lösung wäre, dass keine mechanisch bewegten Teile mehr vorhanden sind, sieht man von der Phasenverschiebung und der Spalthöhenverstellung ab. Dadurch würden sich die Geräusche und Wartungsarbeiten vermindern. Die Wanderfeldgeschwindigkeit und deren Phasenverschiebung werden über zwei synchronisierte Umrichter analog der Steuerung zu Fig. 1 geregelt. Es wäre damit möglich, höhere Frequenzen und somit höhere Feldgeschwindigkeiten als mit mechanisch angetriebenen Umlaufketten zu fahren.

The traveling wave can be generated in different ways:

• Movement of alternating poles arranged with permanent magnets 6 fitted strips 7 in a length corresponding to the maximum working width, which are fixed to a top and bottom rotating chain 8, 9 ( Fig. 1 to 4 ). Velocity and phase shift are controlled via two separately controlled converter-fed drives 10, 11 ( Fig. 1 ).
• The two chains can also be driven by a regulated motor via deflection gear 12 and chains 13. The phase shift is adjusted by a displaceable chain tensioner 14 (see Fig. 5 ).
• Another constructive measure for the phase shift via a differential-comb gearbox 15 or a normal combed gear 17, in which a controllable lead or a Caster is provided (see FIG. 6 ). The drive takes place via a motor 16.
• If a rigid connection between the sprocket of the upper and the lower Wagenkettenantriebs ensured by comb-rolling gear, the offset of the permanent magnets can be achieved in that the upper chain case 18 is moved against the lower mechanically (see Figures 7, 7a and 7b ).
• If, in the case of a stationary eddy-current brake 19, 20, for example at a chain speed V _F = 0, a mechanical shift is made, the center position of the belt can also be achieved by the displacement of the magnets in this system. This is a significant improvement in practice as a preferred framework (see FIGS. 8 and 9 ).
• The traveling field can also be generated electrically by electromagnets, preferably three-phase stators 22, 23 (similar to the armatures of linear motors) are mounted on top and bottom instead of the permanent magnets and these are fed by one or two (for electrical phase shift) converters ( please refer 10 and 11 ).
• But it is also possible to generate the traveling field by three-phase stators (analogous to the anchors of linear motors), as already proposed in the cited documents. The phase shift then takes place via two synchronized power converters or a mechanical displacement of the stators relative to one another. Advantage of this solution would be that no mechanical moving parts are available, sees one from the phase shift and the gap height adjustment. This would reduce noise and maintenance. The traveling field velocity and its phase shift are via two synchronized converters analog to the controller Fig. 1 regulated. It would thus be possible to drive higher frequencies and thus higher field speeds than with mechanically driven circulation chains.

Claims (10)

1. System for contactless application of strip tension, in which the levitation generated by means of moved magnetic fields arises from the retraction force, characterised in that a phase displacement is applied and controlled between two synchronously running upper and lower magnetic travelling wave fields (3a) such that a central levitation of the strip or a desired strip position is achieved.
2. System according to Claim 1, characterised in that the travelling wave fields are generated by systems (1, 2) with magnetic strips (6, 7) positioned with alternating polarity transverse to the strip direction.
3. System according to Claim 2, characterised by two mechanically driven circulating systems (1, 2) arranged above and below.
4. System according to any one of Claims 1 to 3, characterised in that the magnetic strips (7) are fitted with permanent magnets (6).
5. System according to any one of Claims 1 to 3, characterised in that coil systems (22, 23) to be subjected to electrical excitation are arranged on the strips.
6. System according to any one of Claims 1 to 5, characterised in that the phase shift of the travelling waves is generated by mechanically opposing changes in lengths of the two part sections not in engagement of a drive chain or other slip-free transmission elements (Fig. 5).
7. System according to any one of Claims 1 to 5, characterised in that the drive takes place via two motors (10, 11) supplied via two synchronised converters and the phase displacement of the travelling waves takes place electrically by phase displacement of the trigger signals (Fig. 1).
8. System according to any one of Claims 1 to 5, characterised in that the phase displacement is achieved mechanically by geometric displacement (18) of one of the two chain systems (8, 9) carrying the magnetic strips (Figs. 6 and 7).
9. System according to Claim 8, characterised by a pinion gear (17) or a differential pinion gear (15) to generate the geometric displacement.
10. System according to any one of Claims 1 to 5, characterised in that with opposing stationary rotary current stators (19, 20), the phase displacement is achieved mechanically by geometric displacement of the two multiphase electrically excited stators (19, 20) in relation to each other (Figs. 8 and 9).

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