The machine, similar in principle to Odigboh’s impact
melon (Citrullus vulgaris) sheller (Fig. 1), consists of a feed
hopper, pod shelling unit separation unit and power unit.
Figure 2 shows the assembly details of the machine. The
conical shaped hopper is mounted on the tool frame and is
held in place by a hopper support frame. The base is
connected directly to the shelling unit. A nut flow control
device is located between the hopper and the shelling
chamber. The shelling unit consists of a 410mmdiameter by
150mmheight cylindrical shell made from 5mmsteel sheet,
whose inner surface serves as the cracking surface, and an
impeller of 370 mm diameter made of 25 by 50 mm rectangular steel pipe similar to that described by Dicken
(1961) as shown in Fig. 3. These impellers were divided into
three groups: A – impeller slots positioned at 45 to the
tangent at the slots outlet (forward facing) represented with
subscript F; B – radially positioned impeller slots (at 90 to
tangent at the slots outlet) repre- sented with subscript R; and
C – impeller slots positioned at 135 to the tangent at the
slots outle (backward facing) represented with subscript B. Each group has impellers with eight, four and two slots. The
cylindrical shell is covered with a transparent plastic cover
400mmdiameter of 4mmthickness with a concentric opening
(80mmdiameter) at the center (pods inlet). The impeller
is concentrically positioned within the cylindrical shell and
horizontally mounted on a vertical shaft to give a clearance
that is greater than the size of the seed with cracking surface.
Figure 4 shows the impeller mounted in operational
position. This impeller is driven by a vertical shaft powered
by a 0.5 hPa 1920 r.p.m. electric motor through a system of
belt and pulley. The separation unit comprises the transition
channel (through which the mixture of seed and broken pods
from the shelling chamber flows into the separation
compartment), the separating chamber (where the seed and
pods are separated by air current), the inner funnel shapped
wire mesh for seeds collection, and the axial fan mounted
directly on the electric motor, which is powered by the electric
motor to supply the air stream required for winnowing.
At the upper part of the separating unit is the shells outlet. In between the separating compartment and the shells outlet is
a transparent cylindrical plastic column to observe the shells
upward movement. These components are assembled and
mounted on a rectangular tool frame that gives the machine
a compact design and a sturdy outlook.