A combine harvester is a versatile machine that performs three key functions in the crop harvesting process: reaping, threshing, and winnowing. Here’s how it works, step by step:
1. Reaping (Cutting the Crop)
- The combine harvester has a header at the front, which cuts and gathers the standing crops. The size and type of header can vary depending on the crop being harvested (e.g., wheat, corn, soybeans).
- As the combine moves through the field, the header cuts the crops and feeds them into the machine.
2. Threshing (Separating Grain from the Stalks)
- After the crop is cut, it is fed into the threshing drum or cylinder, where the grain is separated from the straw and chaff. The threshing drum rotates, beating the crop to loosen the grains from the heads or ears.
- The loosened grain falls through small openings in the concave below the threshing drum, while the larger straw and other materials move to the next stage.
3. Winnowing (Cleaning the Grain)
- The separated grain is passed to the cleaning system, which typically consists of sieves and a fan. The grain is shaken through the sieves to remove any remaining chaff or debris.
- The fan blows away lighter material like chaff and straw, while the heavier, cleaned grain is collected in a grain tank or hopper.
4. Straw Management
- The remaining straw and other crop residues are either discharged out the back of the combine as a swath (to be baled later) or chopped and spread across the field, depending on the combine’s setup.
5. Grain Collection and Unloading
- The harvested grain accumulates in a grain tank or hopper within the combine. Once full, the grain is unloaded into a truck or trailer using an unloading auger.
Summary of Key Components:
- Header: Cuts and gathers crops.
- Threshing Drum: Separates grain from stalks.
- Sieves and Fan: Clean the grain by removing lighter materials.
- Grain Tank: Stores the collected grain.
- Unloading Auger: Moves grain from the tank to an external storage system.
This efficient process allows a single machine to complete all the major tasks required for harvesting in one pass through the field, saving both time and labor.