Brakes – Operators – Electric
Patent
1998-05-29
2000-02-01
Oberleitner, Robert J.
Brakes
Operators
Electric
2424193, B60L 700, B65H 2324
Patent
active
060192003
DESCRIPTION:
BRIEF SUMMARY
The present invention relates too a device for the braking of electrically conducting strips provided with a device for the production of a magnetic field, which is located before a processing station in which the strip being subjected to traction is further processed, whereby the magnetic field producing device produces an alternating magnetic field which induces eddy currents into the strip, these currents exerting a force upon the strip that is contrary to the direction of its movement
Devices of the type mentioned above are used to hold strips under a constant tension while they are conveyed to a station for further processing. Such a station for further processing could be a winding device in which the strips of a band previously divided lengthwise are wound up into individual coils of smaller width. In such devices tight winding with precise edges of the individual metal strip bands without danger that the strip runs off center is only possible if the strips are held under constant tension.
In conventional braking devices known in practice, the traction on the strips is produced by means of braked rollers lying on the surface of the strip and running with the strip. The disadvantage of such devices is that the contact between the strip and the rollers exposes the strip surface to the danger of becoming damaged. This applies even when the rollers are provided with a soft lining, as a certain frictional force must always be produced between strip and roller in order to achieve the necessary braking effect. It has therefore been attempted to use presses covered with felt for the purpose of braking. However, due to the considerable pressing forces, these have the same disadvantages as the rollers described earlier.
In devices for the braking of electrically conductive strips known in practice and which the applicant is unable to document in further detail through printed documents the above-mentioned disadvantages are found only to a lesser degree. In the known devices a static magnetic field is produced by means of the magnetic field generating device, said magnetic field inducing eddy currents in the strip which is moving relative to the magnetic field. The strip is braked by these eddy currents. The advantage of such devices consists in the fact that braking and the build-up of tensile stress occur without contact. It is however a disadvantage that the braking effect depends directly on the speed of the strip. For this reason it is required also with this known device to brake the strip mechanically when it is stopped, e.g. before starting up the downstream processing station.
Devices of the type mentioned initially no longer have the above-mentioned disadvantages. Such devices are known e.g. from U.S. Pat. No. 2,731,212 or from the German application DE-AS 22 46 558. The known devices produce a magnetic field of alternating polarity, so that an eddy current subjected essentially to no influence from the movement of the strip is induced in the strip captured by this magnetic field. Whatever the width of the strip may be, this eddy current exerts a force on the strip that is opposed to the direction of movement of said strip. Based on the fact that in the known devices the apparatus for the production of a magnetic field itself produces an alternating magnetic field, the eddy current is effective even when the strip is stopped. The known braking device has the disadvantage that considerable expenditures for equipment and controls are necessary in order to adapt braking force exerted by the device for the production of a magnetic field on the strip to the requirements of a given operating situation. The complexity of controls and the costs involved to implement it make this more expensive in manufacture and maintenance than known braking devices.
It is the object of the present inventing to create an efficient and at the same time easily made device of the type mentioned initially based on the above mentioned devices, by means of which it is possible to brake a strip without contact and independently of
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patent: 3433398 (1969-03-01), Fadden et al.
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patent: 5337608 (1994-08-01), Egan et al.
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Cassing Wilhelm
Janzen Klaus
Oberleitner Robert J.
Tridelta Magnetsysteme GmbH
Woller Jeffrey
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