| 摘要 |
PURPOSE:To detect a disconnection automatically and reliably, by detecting the difference in time taken until a sudden change occurs in the armature current of a tension motor between the case where a wire is caught by a tension rod and the case where the wire is not caught by the tension rod. CONSTITUTION:A voltage corresponding to the tension to be applied to a wire 2 is applied to a tension motor 14 of a tensioner D. When applying a tension to the wire 2, the tension rod 18 moves to a predetermined position; when the wire 2 is disconnected, the tension rod 18 moves to the highest position where the tension rod 18 is held from further moving by abutting on the end of a slot 12 formed in a guide plate 11. A disconnection of the wire 2 is declared when an operation stop current IS as the armature current of the tension motor 14 suddenly increases after a predetermined time t2 has elapsed which is longer than the time t1 taken from the time when the tension rod 18 is started to move in the direction for applying the tension by the tension motor 14 until the time when the tension rod 18 reaches the tension applying position. |
