Winnowing

Winnowing

1. 15. Winnowing RVG

2. RVG

3. RVG

4. RVG

5. RVG

6. RVG

7. A

ESA
ㆍ

6

SEED
: a RVG

9. Winnowing Fans

When the natural wind velocity is not adequate,
artificial means are used to create a sufficiently
strong air blast.

Winnowing fans either manually operated or
mechanically operated, are mostly used.
Manually, operated fans of various types are
available for use in India.

Most often, the hand operated or pedal ‘operated
winnowing fans are used by farmers.

In either case, the fan blades create a sicady blast of
air at the front side of the fan.

10. Various type of hand operated and pedal operated
winnowing fans are being manufactured by many
firms in India .

The number of blades on their impellers is either
three or four. The diameter of the impellers varies
from about 0.90 to 1.25 m.

Mostly, the blades are made of mild steel sheet and
their frames are made of either wood or welded steel
or a combination of the two.

In order to increase the rotational speed, various
driving mechanisms are employed, namely sprocket
and chain, V-belt pulleys and single or double
reduction gears.

All these fans are without casing around the impeller
and they are expected to be operated in the speed
range of 200-350 rpm.

11. Pedal Cum Power Operated Seed Cleaner Grader

Blades

Fig. 24. Winnowing fan

RVG

14. Winnower

The winnower consists of wooden or angle iron frame,
housing, blower, feed hopper, feed and purity adjustment

mechanisms, grain outlet, immature grain outlet, chaff

and dust outlets and blower hand wheel with gears and
pulley arrangement .

Walls of the feed hopper taper towards inside from all
sidés and ensures gravity flow.

Flow of the mixture is regulated by the feed rate
adjustment mechanism, which makes the mixture to fall
as a thin stream perpendicular to the air current, is
essentially a gate obstructing the flow below the feed
hopper.

Blower consists of four curved blades mounted
horizontally on a shaft with two ball bearings.

RVG

15. The sieve is placed in front of the fan at the lower end of the
winnower.

A set of sieves are supplied with machine to suit the different
sizes of grains.

These sieves have holes of 12,8, 6, 4, 3 and 2 mm diameter.

The sieve is reciprocated by an eccentric roller which gets its
motion from the axle of the blower.

The reciprocating action of the sieve permits the grains and
dirt particles to fall down, while the straw is blown out.

16. ・ Working of Winnower

“和 As the mixture falls into the air current, the
E

lighter materials and chaff are blown through
the opening for chaff and husk outlet by the air
blast, while the good grains being heavier fall
0 below and guided out by the gram
outlet.

Proper rpm of the blower and feed rate are
essential for efficient winnowing of the grains
from the other lighter fractions.

17. Volet
réglant
le débit

Trémie contenant

Ventilateur = 모비
les grains á vanner

Balles

et
oo menues
= e = pailles

RVG Bielle

Epis ou

Bons grains ee

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