Working principle of combine harvester

• Header is used to cut and gather the grain and deliver it to the threshing cylinder. The straw is pushed back on the platform by the reel.
• Harvesting is done by a cutting unit, which uses a cutter bar similar to that of a mower.
• The knife has got serrated edge to prevent the straw from slipping while in operation. There is a suitable cutting platform which is provided with a reel and a canvas.
• The reel is made of wooden slats which help in feeding the crops to the cutting platform. The reel gets power through suitable gears and shafts. The reel revolves in front of the cutter bar, while working in the field. The reel pushes the standing crops towards the cutting unit. The reels are adjustable up and down as in or out.
• The cutter bar of the combine operates like a cutter bar of a mower. Its cuts the standing crops and pushes them towards the conveyor.
• The conveyor feeds the crop to the cylinder and concave unit. Canvas table conveyors are mostly used with scoop type headers which have narrow cut.
• In most of the machines, a beater in front of the cylinder, rotating in the same direction is used with under shot conveyors. This aids in stripping the crop from the conveyor and feeding it to the cylinder.
• The threshing takes place between the cylinder and concave unit of the combine. The basic components of the threshing unit of the combine is similar to a power thresher.
• As soon as the crops are threshed, the threshed materials move to straw rake. These rakes keep on oscillating and separating the grains.
• The cleaning unit consists of a number of sieves and a fan. The cleaning takes place on these sieves with the help of fan. The unthreshed grains pass through tailing auger and go for rethreshing. The clean grains pass through grain elevator and finally go to packing unit.
• Grains are collected in a hopper provided at the suitable place. The fan is adjusted such that the chaff etc. are blown off to the rear side of the machine.
• The size of the combine in indicated by the width of cut, it covers in the field.