O Level Notes : Agriculture - Appropriate technology used in agriculture

In this topic, we are concerned with maize and ground nuts Sheller as the simple machines mostly required to process the crop before selling or consumption.

Sheller

This is a machines used to remove the unwanted material from the grains. The unwanted material include maize husks, maize cobs, shells of ground nuts and pods of beans.

Maize Sheller

The Sheller is designed to separate the grain from husks and cobs of maize. They can be manually operated or electrically motor driven.

Parts and their functions

• Feeding tray- that is where unshelled maize cobs are fed into the machine. Its size varies with the size of machine and rate of processing. With faster machines, the feeding tray should be relatively bigger.
• Threshing cylinder- it consist of revolving threshing pedal and beating bars. It squeezes the cobs to remove all the grain.
• Base plate- it has some small holes on it to allow the grains to pass through and not the cobs.
• Maize drum- is a large hollow structure in which the threshing cylinder is mounted. It holds the maize cobs before separation of grain and cobs.
• Fan blower- responsible for blowing air into the grain to separate the chaff from
• Rollers- keep on revolving to avoid the clogging of grain outlet.
• Sieve- to let the separation of grain and other impurities like soil and small insects.
• Grain chute- is the outlet where the grain can be collected into empty bags during packaging.
• Cob outlet- is the point through which shelled cobs move out from the machine.
• Dust exhaust- it let the dust out from the machine during shelling.

Operating principles of a maize Sheller

The maize cobs are poured into the feeding tray. Some machines can remove the husks inside the machine but other machines require the husks to be removed as they can only separate grains from cobs. The maize cobs will be moved by the conveyor belt into the maize drum. Inside this, the maize cobs are turned around by the revolving threshing cylinder. As they are turned, they are squeezed by the beating bars and this action will remove the grains from the cobs. The grains will then drop into the grain chute where they are blown by fan generated air to remove the chaff. The grains will then continue to move down the chute and collecting bags are put at the chute opening for collection and packing. The shelled cobs are pushed out of the Sheller through the cob outlet and chaff dust is blown out through the dust exhaust.

Ground nuts Sheller

The Sheller is designed to remove the shells from the ground nuts. The machine can be manually or electrically driven.

Parts and their functions

• Feeding box- that is where the unshelled ground nuts are poured in bulk. They will move slowly onto the half cylinder wire mash screen during shelling.
• Beating bars- they move to and fro due to the force exerted on the handle thereby threshing the ground nuts against the half cylinder wire mash screen. This action will break the shells.
• Handle- it is moved forward and back ward to allow movement of beating bars in order to break the shells.
• Half cylinder wire mash- it is netted with small holes to allow the nuts and shells to pass through after threshing them.
• Fan blower- is fitted below the half cylinder wire mash and it generate air pressure that blows the light crushed shells towards the shell outlet. Some small machines does not have this part and both nuts and shells will fall into the same chute and are decanted by the vibration effect of the machine.
• Grid- it provide the surface area for the beating bars to crush the ground nuts shells.
• Frame- is where all other parts are mounted and its weight will make the machine to remain stable during vibration when the machine is operating.
• Chute- that is where collecting container or bag is place to collect shelled ground nuts.

Operating principles of a groundnuts Sheller

The ground nuts are dried and all the soil clogging are removed. They are then fed into the feeding box. From there, the groundnuts drops little by little onto the half cylinder wire mash where there are rubbed together by the forward and backward movement of the beater bars. This will cause the breaking of shells thereby separating the shells from the nuts. They will both drop into the collecting chute where the chaff is blown by air being generated by the fan blowers. The nuts will finally pass out of the chute into the container.

Here is what we have discussed on this topic

• Sheller are machines used to remove the unwanted materials from the grains.
• They can remove husks and cobs from maize grains, shells on ground nuts and pods from beans.
• Amaize Sheller is designed to separate the maize grain from the husks and cobs.
• Feeding tray- this is where the unshelled maize cobs are fed into the machine.
• Threshing cylinder- it consist of a revolving threshing pedal and beating bars to squeeze the cobs and remove the grain.
• Base plate- is for the passage of grain leaving the cobs behind.
• Maize drum- to hold the maize cobs during shelling.
• Fan blower- it blows the air into the grains to remove the chaff.
• Rollers- revolves continuously to prevent clogging of grain outlet.
• The sieve separates the grain from impurities such as stones, soil and insects.
• Grain chute is the outlet of shelled grain.
• Cob outlet- is an opening through which cobs are removed from the machine.
• Dust exhaust- is for breathing the dust out.
• The maize cobs are poured into the tray and are moved by the conveyor belt into the maize drum.
• Inside the drum, there are beating bars on the threshing cylinder which thresh the maize by squeezing.
• The grains will drop into the grain chute where there are blown by the fane to remove chaff. Grains will be collected using empty containers and empty bags.
• The ground nuts Sheller is designed to remove the shells from the nuts without causing damage to them.
• Groundnuts are dried and soil clogging will be removed before being fed into the machine.
• After being fed into the feeding box, the ground nuts are squeezed by the beater bars against the half cylinder wire mash.
• The shelled nuts will drop into the collecting container and the shells will come out using another outlet.
• The frame provide weight to prevent shaking of the machine during operation.

Definition of terms used in this topic

• Threshing- to crush into smaller pieces.
• Grain chute- an outlet through which the grain flows out of the machine.
• Clogging- means sticking to the surface of something.