| 摘要 |
PROBLEM TO BE SOLVED: To balance winding-up torque to a winding drum of a shutter member with an extremely simple structure.SOLUTION: A balancing device 21 delivers a balance wire 23 from a balance drum 22 when winding a grille screen 17 on the winding drum 14, and allows weight members 27A-27C of a balance weight 24 to reach a weight storage pit 25 sequentially from the lower end side. Balance torque BT is reduced corresponding to winding drum torque DT reduced by the grille screen 17 wound on the winding drum 14. The winding drum torque DT and balance torque BT are thereby balanced almost uniformly in all winding positions of the winding drum 14. |
