Device for stretching thin metal strips by traction

Metal deforming – By use of roller or roller-like tool-element – Including tautening of work during deformation

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B21B 3908

Patent

active

061090840

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The inventions relates to an apparatus for stretch leveling thin metal strips, in particular aluminum strips having a thickness between 0.1 and 0.5 mm.


BACKGROUND OF THE INVENTION

To continuously level thin metal strips two processes are known: With stretch leveling a free length of the metal strip is tensioned between two roller pairs with a force exceeding its yield limit so as to be plastically lengthened. With stretch bending a strip pretensioned below its yield limit is deflected about rollers of small diameter so that the bending subjects the outer surface to an additional tension. The bending tension combined with the prestress creates a plastic lengthening of the strip that takes place on the upper and lower faces as the strip is looped back and forth.
Stretch bending is likely to mar the surface from the many contacts with the small rollers that are normally made of steel. This method is thus disadvantageous when strips with a high surface quality are needed, e.g. for lithographic purposes.
German patent 3,525,343 describes the advantages and disadvantages of the two leveling methods and advises for thin metal strips, e.g. aluminum strips 0.1 to 0.33 mm thick, a combination of the two methods.
German patent 3,912,676 describes an apparatus of this type that works according to the principles of pure stretch leveling. Between a set of torque-controlled braking rollers and a set of torque-controlled driven rollers is a rotation-controlled pair of leveling rollers by means of which the strip is subjected to the necessary stretching to plastically deform it.
It is recognized--as described in German patent 3,912,676--that with each lengthening, whether elastic or plastic, there is a transverse contraction. With metal strips the ratio of longitudinal stretch to transverse contraction, the Poisson number, is about 0.3; that is the width change is about one-third of the length change. It has been proven that the planarity during leveling is damaged when the transverse shrinkage is impeded by the strip sticking to the retaining rollers. Only in the free stretches between two succeeding rollers can the strip draw together unhindered transversely.


OBJECT OF THE INVENTION

It is an object of the invention to provide a stretch-leveling apparatus that can produces strips of extremely high quality.


SUMMARY OF THE INVENTION

An apparatus for stretch leveling thin metal strips, in particular aluminum strips between 0.1 and 0.5 mm thick, has a group of braking rollers that are interconnected via differential transmissions and controlled jointly with respect to speed to form a first leveling path with a downstream central speed-controlled leveling roller and that downstream a group of pulling rollers connected together by means of differential transmissions and controlled jointly with respect to speed form a second leveling path with the central leveling roller.
The apparatus according to the invention does stretch leveling in two stages. The strip thus has several opportunities to draw together transversely during the leveling in free strip stretches.


BRIEF DESCRIPTION OF THE DRAWING

The drawing serves to show the invention with reference to a simplified illustrated embodiment wherein:
FIG. 1 is a side view of the main elements, and
FIG. 2 is a schematic top view of the drive system.


EMBODIMENTS OF THE INVENTION

The apparatus serves for stretch leveling thin metal strips, preferably aluminum strips between 0.1 and 0.5 mm thick. It is comprised of a group--here five--of braked rollers 1-5 that are all connected together via differential transmissions 12-16 and controlled jointly with respect to speed. The distribution of the braking torque in the individual rollers 1-5 takes place in the known manner corresponding to the desired force increase between the strip 1 and the individual rollers 1-5 as for example shown in FIG. 2 of German patent 2,529,899. Subsequently there is a central leveling roller 6 that is connected with a drive motor 18. The drive motor 18 is controlled with re

REFERENCES:
patent: 4408474 (1983-10-01), Hutzenlaub et al.
patent: 4765169 (1988-08-01), Bradlee
patent: 4819470 (1989-04-01), Noe' et al.
Abstract-Pub-No: DE 25 29 899 C1 to Armin Hutzenlaub, Jan. 13, 1977.

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