To transmit a torque of a single auger to an output coupling to obtain a reverse torque against the output coupling from a reversal output coupling by connecting the input coupling of an output changeover device to the output coupling of the single auger.

A fitting bracket 4 is fitted to be vertically movable and also hold a guide pipe therein. A rotary main shaft 1 having an external spur gear and an output coupling is provided with a reversing output coupling 5. A reversing cylinder shaft 2 having an internal spur gear 15 is provided at the periphery to be coaxially rotatable. The fitting bracket 4 is provided to mesh with the external spur gear and the internal spur gear 15 between the reversing cylinder shaft 2 and the rotary main shaft 1. A pinion 14 is disposed in a state fitted to a reactive shaft cylinder 3 whose rotation is fixed. The output coupling 7 is concurrently rotated by the rotation of the single auger. The pinion 14 is moved with the external spur gear in an interlocking motion does not revolve around the rotary main shaft 1, but transmits the power to reversing cylinder shaft 2 to rotate the reversing output coupling 5 countercurrently against the rotation of the output coupling 7.