EP1670601A1

EP1670601A1 - System for contactless application of tension in electrically conductive metal strips

Info

Publication number: EP1670601A1
Application number: EP04765897A
Authority: EP
Inventors: Norbert Umlauf; Frank Jurisch; Jürgen BEHRINGER
Original assignee: Individual
Current assignee: Individual
Priority date: 2003-10-08
Filing date: 2004-10-08
Publication date: 2006-06-21
Anticipated expiration: 2024-10-08
Also published as: WO2005035158A1; EP1670601B1

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

"System for the contactless application of the tape tension with electrically conductive metal tapes"

1 State of the art

In all discontinuous and continuous cold strip aluminum plants and process lines, the metal strips must be transported from the decoiler in the input section through the process section to the decoiler in the exit section. In the course of this tape transport, changeable tape speeds and tape pulls, tape running controls, tape storage, tape pull decoupling loops etc. are required. The processing of the strips is carried out in the process parts, e.g. metallurgical processes in pickling processes, rolling plants, continuous annealing and dressing plants.

The circulating eddy current linear drive was designed as a brake and / or train frame, optionally connected with a belt run control for metal belt production lines, which enables fundamental design changes. It is used wherever, for example, the tension rollers, drivers, flat brakes, the mechanical linear drive and vacuum brakes are used. In these systems, the strip tension is applied to the strip surface by pressing forces on the strip surface.

BESTATIGUNGSKOPIE The system is suitable for all electrically conductive metals and their alloys, especially for aluminum and copper, but also for example for electrically conductive powder metallurgical materials, sintered materials and their alloys.

In the case of a circulating eddy current linear drive, the entrainment effect is achieved by a magnetic field moving with respect to the belt. 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 metal strip product have increased significantly in recent years. The circulating eddy current linear drive meets these requirements; in addition, quality improvements can be achieved. The mode of operation of the circulating eddy current linear drive is particularly valuable for the highest demands on the surface quality, to avoid multiple bending of the strips with longitudinal tension, for special strip flatness with minimization of the winding curvatures and for discontinuous process lines due to the problem-free handling. For the first time, it will be possible to transport the strips through the process lines after the finishing process without touching the two sides of the strip.

To wind up tapes during rewinding or in the finishing line after splitting from wide to narrow tape, a restraint is required in order to obtain coils that are wound in a mechanically stable manner. This is essential for the transport, handling and further processing of these coils. The required belt tension is usually applied by mechanical brakes, the friction surface being the belt surface. These are jaws covered with textiles (so-called carpet brakes), or the contact pressure is generated by inflating a (fire) hose. With this system you can only build retreat and no preference. It can only be used on undemanding surfaces, since the retraction is generated with 100% relative movement. This system is very common because it is inexpensive to build.

With the S-roll system, the belt tension is built up by wrapping a roll. The train structure can only be changed for each reel depending on the preference, the wrap angle and the coefficient of friction between the belt and the reel coating.

If the belt tension is set up in a driver unit, considerable specific loads are created on the belt surface. The forces to be transmitted are very limited.

This disadvantage could be eliminated by the mechanical linear drive. The transport area is adapted to the need using a car chain. With the highest demands on the surface, limits are also reached with this system.

In order to avoid scratches and streaks on sensitive surfaces (eg polished surfaces), in some solutions the belt tension is applied by deflection rollers with an integrated brake. Here, however, exists there is still the danger of imprints and the introduction of tension into the material (especially in the case of larger strip thicknesses) due to the flexing work that occurs when these brake rollers are wrapped around to avoid slippage, which would otherwise result in scratches. When strips are split, however, the outer strips are generally longer than the central strips due to the rolling process. This means that a deflection roller brake cannot be used because either the belt tension is missing or scratches are caused by the slippage.

All of these mechanical friction brakes and recirculating brake rollers cannot be used with very high surface requirements (e.g. materials for decorative purposes or for mirrors and other reflectors) or with thin metal foils. This technology is also interesting for the automotive industry, especially for the aluminum outer skin of modern passenger cars.

Non-contact retraction devices are known using the eddy current forces when moving a tape in a magnetic field. A permanent magnet arrangement, usually multi-pole in the direction of tape travel, arranged above and below the tape, ensures the field build-up and the tape speed depending on the tape thickness and the electrical conductivity of the tape material for the retraction force (braking force F _B ) against the tape travel 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 retraction force cannot be set independently of one another. As a result, either scratch-free hovering cannot be secured or the tape tension becomes too great.

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

An eddy current brake is described in German Patent DE 195 24 289 C2. The main difference is that the permanent magnets are moved on a circular path. Only one magnetic track is available for the retention effect. In addition, the parallelism of the permanent magnets only occurs for a fraction of the period, as a result of which the retention effect is built up unevenly and significantly reduced. In order to be able to set up specific, specific belt pulls, the speeds of the brake rollers would have to be reduced to orders of magnitude that could no longer be controlled. In addition, great drive power is achieved with a very unfavorable efficiency.

In the PCT Patentan avoidance 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 variety of permanent magnets be moved parallel to the belt. The belt tension can be determined via the difference in speed between the belt and the permanent magnets, the number of chain carriages acting, the material and shape of the permanent magnets and the distance between the opposing permanent magnets. This embodiment has the defect that the center position of the belt cannot be influenced.

In the German Offenlegungsschrift DE 23 01 434 a device is described in which the strip tension is generated by a traveling magnetic field by means of stationary inductors. This system has not proven itself in practice, as too little belt tension is generated with a very unfavorable efficiency.

In the patent specification DD 96 206 of the German Democratic Republic, a system is described in which magnet systems (inductors) constructed according to the principle of linear motors are used to brake the electrically conductive slit band and are powered by three-phase current. A magnetic field is built up between the inductors in the air gap, which moves against the direction of movement of the belts, the speed depending on the feed frequency and the pole pitch, which makes adaptation to different operating conditions - if at all - difficult.

With the present invention, the aforementioned shortcomings are remedied. 2 Solution according to the invention

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

The band 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 band and the magnetic field, which creates a traveling wave field 3a. The traveling wave field can move with the speed V _F in or against the tape running direction or can also stand still, depending on the relative speed v = V _A - V _F required to apply the desired tape tension. The braking or retraction force results from the geometry (thickness d and width b _B ), the electrical conductivity K of the strip, the active length l _{M of} the magnetic field (overlap) and the air gap induction peak value Bδ, which is dependent on the gap width δ.

The vertical force F _v for compensating the belt's own weight is derived from the braking force F _B by a shift Δ of the upper to the lower field wave. The vertical force F _v = F _B sin (Δφ) results from the displacement angle Δφ = arctan (Δ / δ). The lifting force F _H described above then only serves to center the band in the gap and to dampen vertically acting band vibrations. Fig. 1

A belt tension measuring device 5 regulates the relative speed by influencing the traveling wave speed and possibly its direction. Distance sensors for detecting the band position in the gap control the phase angle between the upper and lower traveling waves.

The traveling wave can be generated in different ways:

Movement of bars 7 arranged with alternating poles and equipped with permanent magnets 6 in a length that corresponds to the maximum working width, which are attached to a chain 8, 9 running around the top and bottom (FIGS. 1 to 4). Speed and phase shift are regulated by two separately controlled converter-fed drives 10, 11 (FIG. 1). The two chains can also be driven by a regulated motor via reversing gear 12 and chains 13. The phase shift is set by a displaceable chain tensioner 14 (see FIG. 5). Another constructive measure for the phase shift takes place via a differential comb roller gear 15 or a normal comb roller gear 17, in which a controllable advance or a Caster is provided (see Figure 6). It is driven by a motor 16.

If a rigid connection between the chain wheel of the upper and the lower carriage chain drive is ensured by means of a worm gear, the offset of the permanent magnets can be achieved by mechanically displacing the upper chain case 18 against the lower one (see FIGS. 7, 7a and 7b).

If a mechanical shift is carried out on a stationary eddy current brake 19, 20, for example at a chain speed V _F = 0, the center position of the belt can also take place in this system by shifting the magnets. 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 mounting electromagnets, preferably three-phase stators 22, 23 (analogous to the armatures of linear motors) on top and bottom of the strips instead of the permanent magnets and feeding them from one or two (for electrical phase shift) converters be (see Figs. 10 and 11).

However, it is also possible to generate the traveling field using three-phase stators (analogous to the armatures of linear motors), as already suggested in the documents cited. The phase shift then takes place via two synchronized converters or a mechanical shift of the stators to one another. The advantage of this solution would be that there are no more mechanically moving parts one depends on the phase shift and the gap height adjustment. This would reduce the noise and maintenance work. The traveling field speed and its phase shift are regulated by two synchronized inverters analogous to the control in FIG. 1. It would thus be possible to drive higher frequencies and thus higher field speeds than with mechanically driven circulation chains.

Claims

claims:

1.System for contactless application of the tape tension, in which the levitation force generated by moving magnetic fields arises from the retraction force, characterized in that a phase shift is introduced between the two synchronously running upper and lower magnetic traveling wave fields (3a) and is controlled so that a central one Floating of the tape, or a desired tape position is achieved.

2. System according to claim 1, characterized in that the traveling field waves are generated by systems (1, 2) with magnetic strips (6, 7) positioned alternately with respect to the strip running direction.

3. Plant according to claim 2, characterized by two mechanically driven rotating systems (1, 2) arranged above and below.

4. Installation according to one of claims 1 to 3, characterized in that the magnetic strips (7) are equipped with permanent magnets (6).

5. Installation according to one of claims 1 to 3, characterized in that electrically excited coil systems (22, 23) are arranged on the strips.

6. Installation according to one of claims 1 to 5, characterized in that the phase shift of the traveling waves by mechanically opposing changes in the lengths of the two not in Engaged portions of a drive chain or other slip-free transmission links is generated (Fig. 5).

7. System according to one of claims 1 to 5, characterized in that the drive takes place via two motors (10, 11), which are fed via two synchronized converters, and the phase shift of the traveling waves takes place electrically by phase shift of the control signals (Fig . 1).

8. Plant according to one of claims 1 to 5, characterized in that the phase shift is carried out mechanically by geometric displacement (18) of one of the two chain systems carrying the magnetic strips (8, 9) (Fig. 6 and 7).

9. Plant according to claim 8, characterized by a worm gear (17) or a differential worm gear (15) for generating the geometric displacement.

10. System according to one of claims 1 to 5, characterized in that, in the case of opposing stationary three-phase stators (19, 20), the phase shift is carried out mechanically by geometrically displacing the two multiphase electrically excited stators (19, 20) relative to one another (FIG. 8 and 9).