PURPOSE: To complete opening of a coil by a single stroke of a sliding plate, by providing a turnable wedge on the tip part of the slide-moving plate which is slided in parallel with the tangential direction of the terminal part of the coil, providing a guide roller on the wedge, and giving pressing force so that said roller is made to press-contact with the outside circumferential face of the coil.

CONSTITUTION: A sliding plate 37 which is capable of sliding in the direction being in parallel with the tangential direction of the terminal part of a coil 30 is provided, and to the tip part of its sliding plate 37, a wedge 40 which is pushed into the terminal part of the coil 30 is fitted so as to be turnable. Also, on the coil 30 press-contact side of the wedge 40, a guide roller 42 which rolls along the outside circumference of the coil 30 is provided, and on the other hand, an oil pressure cylinder 39 which slides the sliding plate 37 in the direction crossing its sliding direction and makes the guide roller 42 press-contact with the outside circumference of the coil 30 is provided. Accordingly, when the rod of an oil pressure cylinder 39 is projected, the guide roller 42 rolls along the outside circumference of the coil 30, the wedge 40 also moves in the same way, and opening of the coil 30 is completed by a single stroke.