Here is a list of machines used for harvesting of crops: 1. Chaff Cutter 2. Feed Grinders 3. Sugarcane Crusher (Bullock Driven) 4. Seed Processing Plant.
Machine # 1. Chaff Cutter:
It is a machine used for cutting fodder.
On the basis of cutting mechanism chaff cutter may be of two types:
1. Cylinder type
2. Flywheel type
1. Cylinder Type:
It has got knives which are spirally arranged on a revolving cylinder. The cutting head of a lawn mower is somewhat similar to this arrangement. Usually four knives are spirally fixed. It is mostly used on power chaff cutters. Blades are easily sharpened with a grinder.
2. Flywheel Type:
Flywheel type cutting unit has got a number of knives. These knives are arranged radially on the side of a big flywheel which is usually made of cast iron. Straight knives are used on power chaff cutters and curved knives are used on hand chaff cutters. There are usually two knives on hand chaff cutters, whereas two to six knives on power chaff cutters.
On the basis of dropping position of cut chaff, this machine may be of three types:
1. Let-Fall type
2. Throw-Away type
3. Blow-up type
On the basis of source of power it may be of following types:
i. Manually operated
ii. Animal operated and
iii. Power operated
1. Let-Fall Type:
In this type, the cut fodder is dropped down to the bottom of the chaff cutter.
2. Throw-Away Type:
In this type, the cut fodder is thrown away to the front ward of the chaff cutter.
3. Blow-Up Type:
In this type, the cut fodder is blown up through the blow up pipe.
Working of a Power Chaff Cutter:
A power chaff cutter usually consists of:
i. Cutting mechanism
ii. Blower and
iii. Conveyor
The fodder is fed to a conveyor which runs along the bottom of a feed trough. At the throat of the conveyor, the fodder is gripped between two toothed rollers, which allow and pass it forward to a shear plate, where it is chopped into short lengths by rotating knives, mounted on a heavy fly wheel. The back portion of the knives are bolted to the fly wheel about 1.5 cm away from the shear plate.
The cutting edges are adjusted such that they nearly touch the edge of the shear plate. The drive for the feed rolls and conveyor is taken through bevel gears with two dog clutches, arranged to provide forward, neutral and reverse gears to a countershaft running at right angles to the main shaft.
The length of the chopped fodder can be adjusted in the following ways:
(a) By changing the speed of the feed rolls.
(b) By reducing the number of knives.
(c) By increasing the speed of the cutter head.
Chaff Cutter (Manually Operated):
It is a machine operated by hand for cutting chaff for animal feeding.
The following are the components of manually operated chaff cutter:
1. Flywheel
2. Main shaft
3. Shear plate
4. Feed rolls
5. Feeding trough
6. Back plate
7. Worm gear
8. Springs
9. Cover plate
10. Handle
11. Stand and
12. Worm
The flywheel, cover plate, shear plate and feed rolls are usually made of cast iron. Feeding trough, blade cover and leg are made of mild steel.
Blade:
Blade is the most important component of a chaff cutter. Blades for hand driven chaff cutter are usually manufactured by blanking rolled sheets. The minimum thickness of the blade is about 2.4 mm. The cutting edge of the blade is bevelled to a distance of at least 10 mm. The blades are heat treated to obtain requisite hardness. The back side of the blade is ground flat. The corners of the square holes are slightly rounded. The blades may be made of plain carbon steel having carbon % varying from 0.60 to 0.75% or alloy steel having 0.35 to 0.45% carbon.
Capacity of Chaff Cutter:
Capacity [C] = Volume [V] per unit time x Density (d)
C = Vd
V = throat width × throat height x length of cut × rev/min × no. of knives
V = W × H × L × N × n
Where,
W = throat width
H = throat height
L = length of cut
N = rev/min
n = no. of knives
d = density of chaff
C = W× H× L× N× n× d
Theoretical Length of Chaff:
The length of chaff can be obtained by the formula:
Where,
x = length of cut, mm
N’ = rev/min of feed roll
N = rev/min of fly wheel
D = diameter of feed roll, and
n = number of knives
Machine # 2. Feed Grinders:
Farm products are usually reduced in sizes by cutting or crushing operations. Cutting is done generally by some blades. Crushing operation breaks the products to small size, which are suitable both for human and animal consumption.
For grinding of materials, mainly two types of grinder are used:
1. Hammer mill and
2. Burr grinder
1. Hammer Mill:
Hammer mill is used to break the product by means of revolving beaters. The beaters may be either rigid type or swinging type. As the material is fed from the feed hopper into the mill, the beaters strike the materials with great force and break them into pieces. After the materials are reduced in sizes, they pass through screen, fitted near the periphery of the beaters. The fineness of grinding is regulated by use of screen of different mesh. It is simple in construction but initial cost is a bit high.
Hammer mills are operated at high speeds, usually from 1500 to 4000 rev/min. The hammer tip speed generally ranges from 4000 to 5000 m/min. Hammers are made of tough steel with wear resistant tips.
This mill is simple in construction, available in different sizes and easily repairable.
In most of the hammer mills, the lower half of the cylinder is enclosed by screens. They are made of high carbon steel and can often be reversed to distribute wear. Openings ranging from 3 mm to 30 mm in diameter are usually used. Capacity of the hammer mill depends upon many factors such as rate of feeding, speed of hammer, power available, kind of materials, size of sieve and fineness of grinding.
2. Burr Grinder:
Grinders using burrs are called Burr grinder. Plates may be made of chilled iron. The plates are cast with corrugations which force the materials outward. Grinding is done by shearing and crushing action between two plates. Grinding surfaces are held either in horizontal position or in vertical position. One of the plates or rollers is fixed to the drive shaft of the power unit and the other is fixed in stationary position.
The fineness of the product depends upon roughness of the grinding surface and clearance between two plates mounted on the spindle. There is a hand screw provided to adjust the gap.
The grain is fed from the hopper over a small oscillating screen which removes any foreign material present in the grain. A spiral spring between the plates prevents them from touching when no grain is passing through it. Conical grinding burrs are also used at suitable places. A popular size of burr mill has 30 cm diameter plates, operating between 650 to 750 rev/min.
Machine # 3. Sugarcane Crusher (Bullock Driven):
Sugarcane crusher is used for extracting juice from sugarcane. It has got a minimum crushing capacity of 150 kg of sugarcane per hour when worked by a pair of bullocks at a radius of 3 metres at an average speed of 2.5 revolutions per minute. It usually extracts a minimum of 60% of the juice present in the sugarcane on the basis of 12.5 percent fibre.
A bullock driven sugarcane crusher has the following main parts:
1. Frame
2. Roller
3. Axles
4. Bearings, and
5. Gears
1. Frame:
The frame is usually made of cast iron. It holds the rollers in position and keeps the crusher in stable condition.
2. Rollers:
Rollers are made of cast iron.
There are three types of rollers:
(a) King roller
(b) Extracting roller
(c) Crushing roller
The king roller is fixed in position while the crushing and extracting rollers are movable and capable of being moved for adjusting the gap for ensuring good crushing action on sugarcane. The usual length and diameter of the king and extracting rollers are between 180 and 230 mm. The surfaces of the rollers are properly grooved to have a good grip on sugarcane.
3. Axles:
The axles of the roller are made of carbon steel having about 0.4 percent carbon content. The axles are securely fixed to the rollers.
4. Bearings:
Gun metal or leaded tin bronze bearings are used. They are so assembled that it is easy to lubricate and replace them when desired. Sometimes well-seasoned wood, impregnated with oil is also used as material for bearing.
5. Gears:
The gears may be made as separate pieces or may be cast integrally with the roller shells.
Machine # 4. Seed Processing Plant:
Modern seed processing plant consists of a number of equipments, such as:
1. Prime mover
2. Seed moving equipment
3. Scalper
4. Debearder
5. Scarifier-Huller
6. Air-screen cleaner
7. Aspirators and pneumatic separators
8. Seed treater and
9. Bagger weigher
1. Prime Mover:
Prime mover may be I.C. engine or electric motors, depending upon the design of the equipment. Power is supplied from the prime mover to the different components of the seed processing plant.
2. Seed Moving Equipment:
There are different types of equipments for seed movement such as bucket, elevator, trough, belt conveyor, flat belt conveyor, mass flow conveyors, vibrating conveyors, and augers. These equipments are used for receiving, conveying and elevating the seeds. Bucket elevators are commonly used in processing plant. They are designed to be operated at a specific speed. Belt speed, slower or faster than the recommended speed causes spillage and seed damage.
3. Scalper:
A scalper is used to remove the bulk of trash from seed to facilitate elevating and processing operations. The scalper consists of vibrating or rotating screens. The perforations are large enough to allow the rough seeds to pass through the screen easily while large inert material is scalped off and removed from the seed lot.
4. Debearder:
Oats, barley, some vegetables and flower seeds have awns or appendages that make them difficult to process the seed. Awns, hairs and other appendages can be removed from seed by a vigorous rubbing or abrading action. The seeds are rubbed by mechanical device known as debearder.
Debearder consists essentially of a steel cylinder with rows of stationary steel bars on the inside. Rotating beater arms are fixed on a shaft, extending through the cylinder of the machine. The rotating beater arms turn between the stationary bars and route the seeds.
5. Scarifier-Huller:
Seeds like lucerne, berseem, sweet clover etc. contain hard seed and they cannot absorb moisture for germination. Hence it is necessary to scratch the hard seed coat so that moisture can penetrate into the seed. This process is known as Scarification. This object is achieved by equipment called Scarifier.
6. Air-Screen Cleaner:
Air-screen cleaner is the basic machine for all seed processing plants.
The air-screen cleaner uses three cleaning principles:
i. Aspiration
ii. Scalping screen
iii. Grading screen
The typical air-screen cleaner for processing seed uses two air blasts and four screens. The first screen allows the good seed to drop into the second screen. The second screen is a grading screen. The good seeds drop into third screen.
The third screen acts as a close scalper. It allows the good seed to drop into the fourth screen for final grading. The seeds then drop off the fourth screen and fall through the lower air blast. The shaking motion of the screens may be imparted in several ways but usually by eccentrics.
7. Aspirators and Pneumatic Separators:
Aspirator has a fan at the air discharge point which creates a vacuum or negative pressure within the machine. Air rushing to fill the vacuum, creates a stream of air which is used to separate seed. Conversely, in the pneumatic separator, the fan is on the intake end and a pressure within the machine, greater than normal atmospheric pressure is built up, and this air blast helps in seed separation.
8. Seed Treater:
It is an equipment which permits application of small amounts of chemicals to seed and spread it uniformly over the surface of each seed.
A seed treater has the following components:
i. Metering device for seed
ii. Metering device for chemicals
iii. Means of applying treatment to the seed
iv. Mixing chamber
v. Means of discharging treated seed
There are many types of seed treaters, available for treatment of seeds.
Packaging and Handling:
After processing and treating are completed, seeds are packaged into container of specified net weight. Packaging or bagging is the last operation in the series. Bagging requires filling the bag to an exact weight, closing and labelling the bag. These operations are often done by hand in several steps.
9. Bagger Weigher:
Bagger weighers are small machines, which when properly mounted beneath a bin, will fill and weigh a bag in a single operation.