Patent ID: 7647855

Claim:
An electrically-operated chuck opening-closing device, comprising: a chuck provided at a tip of a main spindle of a machine tool to grasp a workpiece by a gripper; a conversion device having on an outer circumference thereof a control gear, being provided on the axis of the main spindle to convert rotary motion into linear motion in the direction of the axis of the main spindle; a drawbar provided between the conversion device and the chuck to perform linear motion by means of the conversion device so that the gripper of the chuck is operated to hold and release the workpiece; a transmission gear provided on an outer circumference of the main spindle; a first gear rotatably provided on a second rotary shaft parallel to the main spindle and meshes with the control gear; a second gear rotatably provided on the second rotary shaft and meshes with the transmission gear; an auxiliary motor that rotates the first gear; a first clutch that couples and decouples the auxiliary motor and the first gear; and a second clutch that couples and decouples the first gear and the second gear.