ACTUATOR FOR CUT-OFF VALVE

PROBLEM TO BE SOLVED: To provide an actuator for a cut-off valve in which power consumption can be reduced when the valve is held open through a simple structure. SOLUTION: The actuator for a cut-off valve comprises an operation shaft 18 imparted with a running torque in the direction for closing the channel of the cut-off valve, a DC motor 2 for driving the operation shaft 18 while resisting against the running torque, and a power transmitting means 3 coupling the operation shaft 18 and the DC motor 2. In the actuator for a cut-off valve, the power transmitting means 3 comprises a clutch 4 coupled with the output shaft 21 of the DC motor 2 and including a spur gear 42 having a plurality of pawls 42a in the circumferential direction, a pinion gear 43 having a plurality of pawls 43a engaging with the pawls 42a and an electromagnetic drive means 5 for driving the pinion gear 43 to advance/retract with respect to the spur gear 42, and a motor drive circuit 80 provided with a gear reduction mechanism 6 for transmitting rotation of the pinion gear 43 to the operation shaft 18 and having a self current control member 81 for reducing a holding current being consumed by the DC motor 2 when it is stopped through opening of the cut-off valve. COPYRIGHT: (C)2004,JPO&NCIPI