| 摘要 |
PURPOSE:To prevent the damage of back-up roll by releasing the pressure of an unjamming cylinder when a straightening reaction force of the plate material is exceeded the allowable straightening reaction force of the back-up roll obtained previously according to a plate width. CONSTITUTION:The allowable straightening reaction force of the back-up roll 3 is calculated correspondingly to the plate width, when the specification information of the plate 1 to be straightened is given. On the other side, when the actual value of the straightening reaction force becomes larger than the allowable value, a relief pressure is set to operate a relief valve 14 of the unjamming cylinder 10. Then, when the straightening is started, the actual internal pressure of the unjamming cylinder 10 is measured to compare with this setting value of the relief pressure. If the actual internal pressure becomes higher than the set value, the relief valve 14 is to be operated. In this way, an excessive pressure portion in the unjamming cylinder is released to the outside, so the prevention of the overload on the back-up roll is performed.
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