Mechanical Technology — January 2015
25
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Hydraulic and pneumatic systems
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B
osch Rexroth, distributed
in southern Africa by the
Hytec Group of Companies,
has optimised its EHC-8
electro-hydraulic hitch control in order
to replicate the same precise regulation
of power and positioning for the lifting
and lowering of towed agricultural
ploughs in Asia as has been delivered
to European and North American
markets.
In the transatlantic environments
for which it was principally designed,
the EHC-8 enhances agricultural ap-
plications through a greater control of
implement depth, which increases the
accuracy of tillage, turning soils gently
and uniformly for improved yields. The
same levels of project satisfaction were
not, however, originally replicated out-
side of these regions due to the vastly
different climactic and terrain condi-
tions and yields, necessitating Bosch
Rexroth to modify and re-engineer
certain core components and mechani-
cal designs that comprised the EHC-8
control to meet the specific needs of
Asia’s agricultural markets.
The first step of tailoring such a
solution, was a detailed analysis of the
operating conditions. Many regions are
affected by monsoon climates, high
rainfall and high humidity conditions
in which excessively saturated land
poses unique challenges to the use of
mechanically-propelled implements.
The winter months endured by these
regions, conversely, present hot, dry and
This article reports on the customisation by Bosch Rexroth of its
Eurocentric EHC-8 electro-hydraulic hitch control solution to suit
the Indian agricultural market with its rugged and more variable
ground conditions.
Optimised hitch control for Indian ploughs
The saturated, muddy sludge that can characterise Asia’s arable land presents unique
performance challenges for electrical and mechanical components.
The modified components used in the EHC-8 electro-hydraulic hitch control, including the angular
sensor and redesigned control panel.
dusty conditions, extending the loading
demands on equipment components.
Designed for extremes
In optimising the hitch control for
operation in these conditions, two com-
ponents in particular required modifica-
tions: the angular sensor and the control
panel. The control panel was optimised
for enhanced rough terrain capability
through the application of a protective
film, while increased brightness offered
greater visibility under intense sunlight.
The control panel was installed into the
operator armrest to provide maximum
ergonomic operability for improved
productivity and operator safety.
Another modification required to
enhance the hitch’s viability in these
conditions was resistance to leaks. The
IP 67 protection code adhered to in
European environments was not suited
to the dusty conditions experienced in
Asia, requiring a modified sensor and
the separation of electrical components
from the mechanical space.
The controller software also had to
be adapted, shifting from the European
lower linkage to upper linkage control.
Because this configuration only requires
one power regulation sensor instead of
two, Bosch Rexroth was also able to
reduce production costs.
The company reduced costs in
several other areas as well. Because
the plastics used in the construction
are sourced locally, sourcing them is
cheaper, in addition to being more tol-
erant of the local conditions, offering a
slightly more durable service life. Local
manufacturers are also producing the
EHR5 hydraulic valve, which regulates
the flow of hydraulic fluid to the cylin-
ders for greater precision of movement
control for the lifting unit.
Further research and development is
planned for the hitch control beyond the
commencement of mass production in
the first quarter of 2015, including the
implementation of a power measure-
ment sensor tailored to local power
ranges.
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