Provided is a hollow swivel actuator including: a lower housing in which a driving motor is arranged; and an upper housing in which three gear trains and three pinion gear units for reduction are arranged at intervals of 120 degrees. A rotor worm gear for transferring an output of the driving motor is coupled through gear engagement to a ring gear integrally formed on a rotational table to transfer reduced rotational power therebetween. The hollow swivel actuator obtains a great reduction ratio by: primary reduction between the rotor worm gear of the driving motor and first to third worm wheels of the first to third gear trains; secondary reduction between first to third worm gears and fourth to sixth worm wheels of the first to third pinion gear units; and tertiary reduction between the ring gear and the first to third pinion gears, thereby achieving a large torque increase.

Provided is a hollow swivel actuator including: a lower housing in which a driving motor is arranged; and an upper housing in which three gear trains and three pinion gear units for reduction are arranged at intervals of 120 degrees. A rotor worm gear for transferring an output of the driving motor is coupled through gear engagement to a ring gear integrally formed on a rotational table to transfer reduced rotational power therebetween. The hollow swivel actuator obtains a great reduction ratio by: primary reduction between the rotor worm gear of the driving motor and first to third worm wheels of the first to third gear trains; secondary reduction between first to third worm gears and fourth to sixth worm wheels of the first to third pinion gear units; and tertiary reduction between the ring gear and the first to third pinion gears, thereby achieving a large torque increase.

Provided is a hollow swivel actuator including: a lower housing in which a driving motor is arranged; and an upper housing in which three gear trains and three pinion gear units for reduction are arranged at intervals of 120 degrees. A rotor worm gear for transferring an output of the driving motor is coupled through gear engagement to a ring gear integrally formed on a rotational table to transfer reduced rotational power therebetween. The hollow swivel actuator obtains a great reduction ratio by: primary reduction between the rotor worm gear of the driving motor and first to third worm wheels of the first to third gear trains; secondary reduction between first to third worm gears and fourth to sixth worm wheels of the first to third pinion gear units; and tertiary reduction between the ring gear and the first to third pinion gears, thereby achieving a large torque increase.