Patent ID: 8183480

Claim:
A withdrawable device of a main circuit for a vacuum circuit breaker, comprising: a cradle; a carrier having a main circuit loaded thereon and movably disposed in the cradle, the main circuit electrically connected to or separated from the cradle; a lead screw for moving the carrier in back and forth directions with respect to the cradle; a transfer nut coupled to the carrier so as to be screw-coupled to the lead screw, for selectively transmitting a rotation force of the lead screw to the carrier according to a rotation direction of the lead screw; and a plurality of rotation prevention pins coupled to the transfer nut, for allowing the transfer nut to transmit a rotation force of the lead screw to the carrier while the carrier is being moved, and for allowing the transfer nut to perform an idle operation when the carrier has been completely moved, wherein a guide recess having a ring shape is formed on an outer circumferential surface of the transfer nut in a circumferential direction such that the rotation prevention pins are inserted thereinto in a radius direction to slide in a circumferential direction, and wherein a plurality of supporting surfaces are symmetrically formed on both sidewalls of the guide recess such that the rotation prevention pins are supported in opposite directions to each other.