The following are the main parts that make up the combine harvester threshing mechanism:
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Threshing cylinder: The threshing cylinder is a rotating drum that has a series of teeth or rasp bars. It rotates at high speed and makes contact with the crop, separating the grain from the straw or chaff.
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Concave: The concave is a curved plate that is placed below the threshing cylinder. It serves to hold the crop in place as the threshing cylinder rotates, allowing the teeth or rasp bars to separate the grain from the straw or chaff.
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Grates: Grates are positioned on the concave and allow the separated grain to pass through while retaining the straw and chaff.
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Straw walkers: The straw walkers are a series of grated steps that are positioned behind the threshing cylinder. They move back and forth, shaking the straw and chaff, allowing any remaining grain to fall through and onto the sieves.
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Sieves: Sieves are screens that are positioned below the straw walkers. They allow the grain to fall through while retaining any remaining straw or chaff.
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Grain pan: The grain pan is located beneath the sieves and collects the separated grain, which is then conveyed to the grain tank for storage.
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Cleaning fan: The cleaning fan is located above the sieves and creates an airflow that blows away any remaining straw or chaff, leaving only clean grain on the sieves.
These parts work together to separate the grain from the crop residue during the threshing process. The threshing cylinder and concave separate the grain from the straw or chaff, while the straw walkers and sieves separate any remaining grain from the crop residue. The cleaning fan removes any remaining debris, leaving behind clean grain for storage in the grain tank.
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