COIL DIAMETER DETECTING DEVICE AND COIL PRESSER DEVICE

PURPOSE: To provide a coil diameter detecting device and a coil presser device which can accurately detect variation of a coil diameter during winding or during rewinding of band material and surely press the band material with a snubber roll so as to improve safety. CONSTITUTION: An inner casing 16 mounted with a laser sensor 17 detecting the distance to the outer circumferential face of a coil C is movably supported with a drive motor 18, and a rotational angle detector 23 detecting the moved distance is provided. A snubber roll 24 pressing the outer circumferential face of the coil C is provided capably of being approached and separated by a hydraulic cylinder 26, and a coil diameter computing means 29 computes the coil diameter D based on a distance LD to the outer circumferential face of the coil C detected by the laser sensor 17 and a moved distance LM of the laser sensor 17 detected by the rotational angle detector 23, and controls variation of tension of band material S. Meanwhile, a snubber roll movement control means 30 controls movement of the snubber roll 24 by the hydraulic cylinder 26, based on the coil diameter D.