JPS54120268A - Controlling method for looper - Google Patents

Abstract

PURPOSE:To minimize the non-constant-tension part of the tail end of the strip, to minimize the fluctuation of sheet gauge and breadth, and to improve the yield, by installing the controller constituted of a special system, at the looper control in the continuous hot rolling mill. CONSTITUTION:The correction arithmetic circuit 61, for producing the correcting signal for the aim looper height, is installed in the looper height comparator 51 of the well-known looper controller. Above circuit 61 has the function to obtain the correction gradient (or taper) DELTAh/DELTAt produced from the time DELTAt through which the tail end E of the strip S travels from the first stand 1 to the third stand 3, and the difference DELTAh between the position of aim looper height and the lowest position; this correcting signal is inputted to the looper height comparator 51 through the gate circuit 63 actuating only when the tail end E passes over the stand 1; thereafter, the height of the looper 23 is gradually reduced down to the lower limit according to the conventional system, and the tension of the strip S between the stands 2, 3, is held constant. According to this method, the fluctuation of the sheet gauge and breadth is minimized and the yield is improved.