Farm Power And Machinery (1+1)

Mechanism of seed drillers

The mechanism of a seed drill or fertilizer distributor which deliver seeds or fertilizers from the hopper at selected rates is called seed metering mechanism. There are a number of seed metering mechanism such as : Fluted roller feed type, internal double run type, cup feed type, cell feed mechanism, brush feed mechanism, auger feed mechanism, picker wheel mechanism and star wheel mechanism.
a) Fluted roller feed type

• It is a seed metering device with adjustable fluted roller to collect and deliver the seeds into the seed tube.
  
• Fluted roller feed type mechanism (Fig.16.1) consists of a fluted wheel, feed roller, feed cut-off and adjustable gate for different sizes of grains.


Fig. Fluted roller type

• The feed roller and the feed cut-off device are mounted on a shaft, running through the feed cups.
  
• The roller carries grooves throughout its periphery. It rotates with the axle over which it is mounted throws the grains out on the adjustable gate from where it falls into the seed tube.
  
• The fluted rollers which are mounted at the bottom of the seed box, receive seeds into longitudinal grooves and pass on to the seed tube through the holes provided for this purpose.
  
• By shifting the fluted wheel side ways, the length of the grooves exposed to the seed can be increased or decreased and hence the amount of seed is controlled.
  
• Thus a number of selection is available between closed position and full exposure of fluted wheel.
  
• The fluted feed mechanism is more positive in its metering action than the internal double run method.
b) Internal double run type

• It is a seed metering device in which the feed wheel is provided with fine and coarse ribbed flanges as shown in Figure.
• It consists of discs, mounted on a spindle and housed in a casing fitted below the seed box.
• It has double faced wheel. Internal double-run type roller one face has a larger opening for larger seeds and the other face has smaller opening for smaller seeds.
• A gate is provided in the bottom-of the box to cover the opening not in use.
• The rate of seeding is varied by adjusting the speed of the spindle which carries the discs.


Fig. 16.2 Internal double run type

c) Cup feed mechanism

It is a mechanism consisting of cups or spoons on the periphery of a vertical rotating disc which picks up the seeds from the hopper and delivers them into the seed tubes as shown in Fig.16.3. It consists of a seed hopper which has two parts. The upper one is called grain box and the lower one is called feed box. The seed delivery mechanism consists of a spindle, carrying a number of discs with a ring of cups attached to the periphery of each disc. The spindle with its frame and attachment is called seed barrel. When the spindle rotates, one disc with its set of cups rotates and picks up few seeds and drops them into small hoppers. The cups have two faces, one for larger seeds and the rate at which the seed barrel revolves. This type of mechanism is common on British seed drills.



Fig. 16.3 Cup feed mechanism

d) Cell feed mechanism - It is a mechanism in which seeds are collected and delivered by a series of equally spaced cells on the periphery of a circular plate or wheel.
e) Brush feed mechanism - It is a mechanism in which a rotating brush regulates the flow of seed from the hopper. A number of bullock drawn planters in the country have Brush feed mechanism.
f) Auger feed mechanism - It is a distributing mechanism, consisting of an auger which causes a substance to flow evenly in the field, through an aperture at the base or on the side of the hopper. Many of the fertilizer drills on the country have got Auger feed mechanism.
g) Picker wheel mechanism - It is a mechanism in which a vertical plate is provided with radially projected arms, which drop the large seeds like potato in furrows with the help of suitable jaws.
h) Star wheel mechanism - It is a feed mechanism which consists of a toothed wheel, rotating in a horizontal plane and conveying the fertilizer through a feed gate below the Star wheel.