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

6. Classification,cont….
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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
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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
• Feed it uniformly into the threshing unit.
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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.
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10. Componentsofcuttingandfeedingunit,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.
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11. Componentsofcuttingandfeedingunit,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.
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12. Mainfunctionalunits,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.
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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.
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14. Componentsofthreshingunit,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.
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15. Componentsofthreshingunit,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.
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16. Componentsofthreshingunit,cont….
Cylinder stripper
• It is set parallel to and above the cylinder
• It prevents back feeding.
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17. Mainfunctionalunits,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.
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18. Components of separating unit
Concave grate and finger (Refer the threshing unit)
One piece straw 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.
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19. Componentsofseparatingunit,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. Componentsofseparatingunit,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.
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21. Componentsofseparatingunit,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.
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22. Mainfunctionalunits,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.
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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.
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24. Componentsofcleaningunit,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.
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25. Componentsofcleaningunit,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.
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26. Componentsofcleaningunit,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.
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27. THANK YOU