MODULAR HYDRAULICS
iVTInternational.com June 2019
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FIGURE 1: The automotive
industry is used to modular
and standardized design of
non-visible components. MEB
is Volkswagen’s proposed
new modular platform for
electric vehicles
FIGURE 2: Example of
a compact valve block in
modular design: A Hawe
‘mooring block’ for combine
harvesters
FIGURE 3: The modular
proportional directional
spool valve PSL allows
for a flexible design of the
hydraulic system. This is also
true for the MMI – from hand
lever to on-board electronics
– and bus integration
reduced to a minimum, the ‘one size
fits all’ approach must be avoided
because all vehicles have their
specific requirements.
Block design: Thinking in modules
In hydraulics, the modular principle
is quite easy to adapt. Instead of
different blocks to which the valves
are added, a basic block is defined
which can be complemented by
additional blocks for optional
functions. In this way, complexity is
reduced. When the engineers, at the
same time, aim to keep the area of
the hydraulic block(s) within defined
dimensions, installation is easier
because the same mounting points
can be used irrespective of hydraulic
options. External piping can also be
reduced which may in turn lead to
less leakage risk (figure 2).
For Hawe, modular design has
been practice for more than 30 years
with the proportional directional
spool valve type PSL (figure 3). It is
used, for instance, as a control block
in concrete pumps or for controlling
lifting platforms. In this valve
program, different sizes can be
combined in a valve bank. A hand
lever, the electro-hydraulic control
(joystick) and other special forms
can also be combined as actuation
within a valve bank or actuation with
on-board electronics via CANbus.
At Bauma 2019 in Munich, Hawe
Hydraulik presented a completely
new combination of PSL CAN and
CAN Lite actuations in a single
valve assembly. This possibility
fulfills the customer demand that
the fully equipped CAN actuation
version with spool position feedback
is only necessary for certain
functions with very high demands
on precision and repeatability. If the
OEM only wants to use the extreme
time-saving operation set-up thanks
to the taught-in start values and very
convenient connection with only
one connector per control block, he
can now do so with the new version
PSL CAN Lite. Thanks to the ideal
selection, the OEM can influence
the price/ performance ratio itself.
Alternative: Sandwich plate design
As an alternative, there are modular
manifolds in sandwich plate design
on offer – like the new RS20
platform from Bosch Rexroth. It
allows, so its designers say, futureproof
integration of various functions
without compromise in operating life
or robustness (figure 4).
With this platform, Bosch
Rexroth marks the transition from
the mono block to the flexible
sandwich plate design. With a
maximum flow of 300 l/min per
section, it achieves an even lower
pressure loss compared to its mono
block predecessors M7 20 and M6
22. At the same time, the sandwich
plate design allows any combination
of small and large valve sections. As
a result, the specific flow can be
provided for each actuator in mobile
machines, and the manufacturers of
vehicles can match the sections to
ensure that their requirements are
optimally met.
The sandwich-plate platform is
ideal for use as a main control valve
for 13-17 ton mobile and tracked
excavators as well as 20-50 ton wheel
loaders and bulldozers. Further
areas of application include material
handling, mobile cranes, forklifts
and drilling machines. The number
and arrangement of the functional
slices, even those of different sizes
and with different control
technology, make it possible to
control various applications flexibly
at all times. And functions which
previously had to be installed
separately can now be integrated
into the main control valve. These
include a stabilization modules,
bypass priority modules and an antidrift
valve. The pump and return
channels pass through the entire
manifold without diversions or
constrictions, so flexibility and
variety are increased by the
possibility of combining manifolds
and functions.
Freedom of design
At Bauma Munich, Linde
Hydraulics has presented a concept
called VW18M3-02 which also
combines flexibility with modular
design: a triple monoblock in NG 18
which can be complemented by
sandwich sections with the nominal
sizes 14 and 18. For the control of,
for example, an excavator, a
maximum of 12 sections can be
combined for controlling driving
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/iVTInternational.com