4UD series of sweet potato harvester is mounted with the tractor of 12-60HP with back power(side power)output shaft.The working principle is that the digging shovel digs up the soil and crops through the impetus of the tractor.And the digging shovel make crop and soil separate through vibration sieve,the soil first drip down from the clearance of vibration sieve,finally the crop crashed down on to the road from the back..