| 摘要 |
<P>PROBLEM TO BE SOLVED: To appropriately detect the abnormality when the lowering of a gate is obstructed by clamping of foreign matter or the like. <P>SOLUTION: At normal time, a retaining stopper 30 is abutted to a position-fixed bracket 32 and positioned, and prescribed tension T imparted to a balance chain 20 is maintained. At the time, a magnet 30b of the retaining stopper 30 is not detected by a proximity switch 28 which is a detector. However, at abnormal time when the elevating/lowering operation of a gate 14 is obstructed by clamping of foreign matter or the like and the gate 14 is inclined or the like, the tension at a part extending downwards from one side end part of the gate 14 of the balance chain 20 is lost. Then, the retaining stopper 30 is moved in the direction of separating from the bracket, and the magnet 30b of the retaining stopper 30 is detected by the proximity switch 28. <P>COPYRIGHT: (C)2012,JPO&INPIT |
