Functional units of combine harvester

This presentation will provide a complete understanding on functional units of combine harvester and their functions.

1. Functional units of Combine harvester Vijitha Vikneshwaran Lecturer(Temporary) Faculty of Technology University of Jaffna

2. Introduction Harvesting is the process of gathering the economically viable part from the ripe crop.   On smaller farms with minimal mechanization, harvesting is the most labor-intensive activity. On large mechanized farms, harvesting utilizes the most expensive and sophisticated farm machineries. There are different types of tools and machineries are available for harvesting. 2

3. Different harvesting tools 3 Sickle Scythe Flail Reeper

4. Combine harvester Combine harvester is a versatile machine designed to efficiently harvest a variety of grain crops. This name is derived from combining 3 separate harvesting operations . Reaping Threshing Winnowing It is used to harvest crops like paddy, wheat, oats, barley and soybean. 4

5. Classification 5 Combine harvester Source of power Based on movement Self propeller type Crawler type Wheel type PTO mount type

6. Classification, cont …. 6 Self propelled type PTO operated/mounted type Wheel type Crawler type

7. Factors effecting the performance 1. The combine: a. Power needed to run the combine at constant rpm b . Speed of forward travel c. Adjustment of the combine d. Skill of the operator e. Width of the combine . 2 . The natural conditions a. Land condition: Topography, Moisture, Amount of weed b. Condition of the crop: Stand, Variety, Moisture 7

8. Main functional units 1.Cutting and feeding unit The functions of this units are, Cut only as much of the crop as is necessary to get all the heads Lay the cut crop on the platform or auger F eed it uniformly into the threshing unit . 8

9. Components of cutting and feeding unit Cutter bar It works like a series of shears running through the field to cut the grain. This action is accomplished by knife sections reciprocating over ledger plates which are held in place by guards. Hold down clamps, wearing plates and shims are used to keep the knife flat on the ledger plates. The sickle bar is usually driven by a pitman drive assembly. Power will usually be supplied to the pitman crank by means of a series of belts and chains. 9

10. Components of cutting and feeding unit, cont …… Reel It momentarily holds the crop against the guards until the knife cuts the stems. Then it will sweep the cut material onto the platform. Platform It holds the cutter bar and feeding mechanisms. Cutting platform auger It moves the cut grain to the center of the platform. 10

11. Components of cutting and feeding unit, cont …. Retractable finger feeder beater It moves the grain into the feeder conveyor Feeder conveyor It feeds the grain in a steady even flow into the threshing unit . Proper feeding into the threshing unit will cause less clogging . Feeder beater It takes the grain from the feed conveyor and feeds it uniformly into the threshing unit. 11

12. Main functional units, cont … 2.Threshing Unit The function of this section to thresh the grain from the heads. This is done by passing the grain between a rapidly revolving cylinder and a stationary surface underneath(concave). The bars on the cylinder passing over the concave channel bars causes rubbing action on the grain . It causes the grain to be removed from the head . 12

13. Components of threshing unit Cylinder It will have either bars or spikes that will cause the rubbing of the grain against the concave . There are different types of cylinders, namely Rasp bar cylinder : Cylinder bars are rasp shaped Rub bar cylinder : Cylinder bars are angle shaped and faced with rubber Spiked tooth cylinder : The cylinder has spikes instead of bars . 13

14. Components of threshing unit, cont …. Concave It is the stationary part that the cylinder works against during threshing. It is a grate composed of rods and bars or wires. 90 % of the grain is separated from the husk at the concave grate and finger grate. The separated grain falls through the grate onto the shoe where it is delivered to the cleaning unit . The straw and the remaining grain pass on in to the separation unit . Raddle located behind the cylinder facilitate the separation of the grain from the straw . Clean grain falls through the suspended straw and is conveyed to the cleaning shoe. 14

15. Components of threshing unit, cont …. Cylinder beater It slows down the material coming from the cylinder Then it tears the straw apart and delivers the material to the straw rack. It helps to prevent cylinder wrapping and feed back by cleaning the straw from the cylinder. Feeding plate It is an adjustable plate. It is located where the cut grain is fed into the cylinder concave unit. Much of the threshing is taken place here. 15

16. Components of threshing unit, cont …. Cylinder stripper It is set parallel to and above the cylinder It prevents back feeding. 16

17. Main functional units, cont … 3 . Separating Unit This unit agitates the straw after it comes from the threshing unit. The loose grain remaining in the straw is shaken out by this unit and delivered in to the cleaning unit. Only about10 % of the grain remains to be separated in this unit as 90% of the grain separation occurs in the threshing unit . The rack carries the straw out of the combine. 17

18. Components of separating unit Concave grate and finger (Refer the threshing unit) One piece s traw rack It is a one piece unit with risers pointed toward the rear of the combine. It is mounted on cranks located at the front and rear which give it an oscillating motion. As the rack moves rear & upward the straw is tossed up and to the rear. As the rack returns forward and downward the straw stays in mid air for a short time. Then, it falls onto a section of the rack nearer the end of the combine . In this way the straw moves step by step out of the combine. This tossing action causes the grain to be separated from the straw. 18

19. Components of separating unit, cont … Walker type straw rack Some large combines may use a walker type straw rack. It operates on the same principle as the rack. It has 3 or more narrow sections placed side by side. Each section is mounted on multiple throw cranks located at the front and rear . The crank throws for each section are equally spaced around the circle of rotation. Grain return pan It is located under the straw rack. It catches the grain as it falls through the rack and moves forward to the grain pan. 19

20. Components of separating unit, cont … Grain return conveyor It catches the grain and moves it forward. It presents in some combine harvester instead of grain return pan. Grain pan It is located under the forward part of the straw rack behind and below the cylinder . It catches the grain from the concave, cylinder grates and grain return pan for delivery to the cleaning unit . 20

21. Components of separating unit, cont … Check flaps or curtains It deflects the straw and grain onto the rack as the full length of the rack is used for separation . They should not be in the way of the straw as the rack moves it to the rear . 21

22. Main functional units, cont … 4.Cleaning unit The functions of this units are, Separate the clean grain Send the clean grain to the grain tank Return the tailings to the cylinder for re-threshing Move the remaining material out of the combine . 22

23. Components of Cleaning unit Adjustable chaffer It acts as a sieve . It is made up of a series of cross pieces mounted on rods and fastened together. So they can be moved at the same time to adjust the size of the openings . Chaffer extension This is an extension of the chaffer . It has adjustable lips and swings up and down on the end of the chaffer . The un-threshed portions of grain heads fall through the chaffer extension into the tailings auger. The bulky material passes over the chaffer extension and out of the combine. 23

24. Components of clean ing unit, cont … Sieve It is like the chaffer except that the lips and openings are smaller. The final job of cleaning is done here . The material that is too large to pass through the sieve is carried over the tailings auger and returned to the cylinder for re-threshing . Cleaning fan It keeps the material alive on the chaffer and sieve. It furnishes a blast of air. The strength of the air blast is controlled by the speed of the fan and by shutters in the air intake. The direction of the air blast is controlled by wind boards . 24

25. Components of clean ing unit, cont … Clean grain auger It collects the cleaned grain and augers it to the clean grain elevator. Clean grain elevator It delivers the clean grain to the grain tank . Tailings auger It collects all of the material which comes off the lower sieve and other material which falls through the extension chaffer. 25

26. Components of clean ing unit, cont … Tailings elevator It delivers the un-threshed heads and other contents of tailing auger to the cylinder for re-threshing. Tail board : It keeps the un-threshed material from being blown out of the rear of the combine while allowing the chaff to be blown out. It can be raised or lowered as needed. 26

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