| 摘要 |
PROBLEM TO BE SOLVED: To improve load detecting and obstacle detecting accuracy by forming an electric motor main body or a motor motive power transmission member as a displacing member displaced according to a load change, holding this displacing member in a neutral position by a neutral holding spring, and detecting a displacement quantity of the displacing member against this spring by sensors. SOLUTION: A winding drum 2 balances a load of a shutter curtain increasing as it lowers by energizing force of a balance spring 9, and opens/closes the shutter curtain on the basis of reciprocal driving of an electric motor 11 to share its difference. Here, an almost U-shaped neutral holding spring 30 interposed between a rear side motor holder and a rear side motor bracket 22, elastically holds the electric motor 11 supported so as to be freely rotatable/ displaceable in an almost intermediate position of its rotational range, and the electric motor 11 is displaced in rotation against the neutral holding spring 30 by a quantity according to a load. A control panel 34 arranged in a lower part of a winding shaft 6 detects this rotational displacement angle by a pair of limit switches (displacement sensors). |
