Production Practices and Quality Assessment of Food Crops. Vol. 1

Fruit and Vegetables Harvesting Systems 269
Figure 6. Tomato harvester. (a) Cutting unit, (b) elevating chain, (c) shaker, (d) selection band, (e)
loading conveyor, (f) shaker unit.
applied accelerations for fruit detachment are in the order of 10–60 g’s (times the
acceleration of gravity) (see also Table 2)
n.g (m/s 2 ) = F d (N)/m (kg) (III.1.6.4–3)
This relationship means that only those products with a relatively high mass and
relatively low detachment force are easy to detach by vibration, as is the case with
the present tomato varieties. In general, fruits are easy to detach by shaking if n
is between 1 and 10 (Moser, 1984). Inertial application of vibratory energy for
detachment results from accelerating the plant commodity with a suitable machine
device to attain a pattern of vibration and a frequency which are suitable for that
commodity. In this sense it has to be designated as ‘the only non-contact’ principle
for detachment of fruits (Ortiz-Cañavate and Hernanz, 1989). In the case of
tree fruits (see further ahead) the necessary acceleration has to be applied in the
lowest-force abscission point of the fruit, and that is difficult for small fruits.
These considerations can be applied to other vegetable crops where shaking could
be a good solution for detachment.
The rest of the functions and units of tomato harvesters combine complementary
operations, and manual or automatic optical VIS (visible, color) sensors
or NIR (near-infrared) sensors for color grading and for soil clod separation,
respectively.
Threshing: This separation procedure uses a rotating drum to remove peas (also
some beans) from their pods in pea harvesters. Similarly to one of the effects used