A driving-force transmission mechanism includes a driving-force transmission shaft that is provided so as to protrude from a side wall of a side frame while extending parallel to a driving shaft within a space of the side frame and connected to a driving motor, and a transmission mechanism that connects the driving-force transmission shaft and the driving shaft, the transmission mechanism connects the driving-force transmission shaft and the driving shaft at a position on a main shaft side in a width direction of the side frame from a connection position between the driving shaft and a swing mechanism.

A driving-force transmission mechanism includes a driving-force transmission shaft that is provided so as to protrude from a side wall of a side frame while extending parallel to a driving shaft within a space of the side frame and connected to a driving motor, and a transmission mechanism that connects the driving-force transmission shaft and the driving shaft, the transmission mechanism connects the driving-force transmission shaft and the driving shaft at a position on a main shaft side in a width direction of the side frame from a connection position between the driving shaft and a swing mechanism.