To extend the operating cycle life of an electromagnetic repulsing device by providing a protecting plate between the clamp arid the short circuit plate of the electromagnetic repulsing device provided on a link mechanism.

An electromagnetic repulsing device 81 is arranged with a protecting plate 62 on the lower face of a clamp 43 via compression springs 60, and a short circuit plate 61 is provided between the protecting plate 62 and an electromagnetic coil 49. The coil 49 is fixed to a fixed frame 45 via a fixed section 54. The short circuit plate 61 is made of a copper material having large electric conductivity, and the protecting plate 82 is made of a light material strong against mechanical shocks such as reinforced aluminum, for example. When the device 81 is operated, the protecting plate 62 collides with the clamp 43, the damage of the short circuit plate 61 is prevented, and the operating cycle life of the device 81 can be extended. Since the protecting plate 62 is made lightweight, the electromagnetic repulsion can be strengthened.