*2.2. Working Principle*

When the Chinese milk vetch seed combine harvester works in the field, the pods and stems of Chinese milk vetch enter the longitudinal rod-teeth-type threshing device under the combined action of the reel, the flexible anti pod-dropping seedling-lifting header and the conveying device. At this time, the pods of Chinese milk vetch are threshed under the rotating strike of the rod teeth and extruded by the concave sieve. Then, the threshed mixture falls into the sieve surface of the layered impurity-controlled cleaning device and the air cleaning of threshed materials under the action of a centrifugal fan is completed. The Chinese milk vetch seeds fall along the gaps between the sieving slices of the scale sieve, and fall into the horizontal seed auger through the round-hole screen. The seed auger directly transports them to the seed bin, and a small part of the unthreshed materials are not blown out of the machine; instead, seeds fall into the horizontal residual auger, and the residual auger transports this part of materials back to the threshing device for secondary threshing and cleaning so as to reduce the loss rate and impurity rate of seeds and complete the harvest operation of Chinese milk vetch seeds.
