| 摘要 |
The invention provides a new apparatus for controlling the sag in a moving metal strip as it passes, for example through a pickle bath to ensure that it does not sag so much as to drag on the floor of the bath, or tighten so much that it lifts out of the bath. Such control is achieved using a proximity detector disposed at the entry end of the bath between the bath wall and an idler roll over which the strip feeds into the bath. The signal from the detector is fed to a controller that controls the drive motor for the entry feed rolls. Preferably at least two, usually three, transversely spaced detectors are used connected to an auction circuit which determines which detector is operative to give the controlling signal, thereby avoiding signal errors due to a narrow strip, transverse movements of the strip and the presence of non-flat sections, particularly at the edges. The detector or detectors are shielded by a casing of thin non-magnetic, acid resistant material, such as a polypropylene, and may be mounted for movement out from under the strip to a service position at one side. The top edge of the bath entry wall may be provided with a smooth inclined edge of an acid resistant material such as granite, or a second idler roll, to prevent the strip from contacting the device. The system replaces a prior art system in which a detector is located in the bath on the bath floor where it is in constant contact with the bath liquid, which usually is an acid, and is in constant danger of being impacted by the moving strip. |
