Abstract: In a wrinkling prevention device, a work roll having a diameter smaller than that of a press-roll is pressed against the press-roll, and the work roll is supported by a bearing frame through a backup. With this configuration, an uncoated part can be elongated with a uniform pressing force. Further, an edge roller is disposed at an end part of the bearing frame which supports the work roll, and the edge roller is brought into contact with the other press-rolls not in contact with the work roll so that the axis parallelism of the work roll with the press-roll can be ensured.

Abstract: In a small-size rolling mill or a roll press machine, to provide a hydraulic screw-down device compatible with the plate thickness accuracy without using a hydraulic control servo valve. A hydraulic screw-down device that is comprised of a screw to move a piston arranged in a booster cylinder back and forth, and a motor that gives rotational force to the screw controlling freely the rotational angle of the screw so as to move the piston to the purpose position. A screw-down cylinder connected with the booster cylinder through piping makes a ram in the screw-down cylinder move vertically by the move of oil caused by the movement of the piston in the booster cylinder and thereby enables push-up and push-down of the mill roll.