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G761 SERIES SERVOVALVES
The G761 Series flow control
servovalves are throttle valves
for 3- and preferably 4-way
applications. They are a high
performance, two-stage design
that covers the range of rated
flows from 1 to 16.5 gpm at
1000 psi valve drop. The
output stage is a closed center,
four-way, sliding spool. The pilot
stage is a symmetrical double nozzle
and flapper, driven by a
double air gap, dry torque
motor. Mechanical feedback of
the spool position is provided
by a cantilever spring. The valve
design is simple and rugged for
dependable, long life operation.
These valves are suitable for
electrohydraulic position,
speed, pressure or force control
systems with high dynamic
response requirements.
Principle of operation
An electrical command signal
(flow rate set point) is applied
to the torque motor coils and
creates a magnetic force, which
acts on the ends of the pilot
stage armature. This causes a
deflection of armature/flapper
assembly within the flexure
tube. Deflection of the flapper
restricts fluid flow through one
nozzle, which is carried through
to one spool end, displacing
the spool.
Movement of the spool opens
the supply pressure port (P) to
one control port while simultaneously
opening the tank port
(T) to the other control port.
The spool motion also applies
a force to the cantilever spring,
creating a restoring torque on
the armature/flapper assembly.
Once the restoring torque
becomes equal to the torque
from the magnetic forces, the
armature/flapper assembly
moves back to the neutral
position, and the spool is held
open in a state of equilibrium
until the command signal
changes to a new level.
In summary, the spool position
is proportional to the input
current. With constant pressure
drop across the valve, flow to
the load is proportional to the
spool position.
VALVE FEATURES
2-stage design with dry torque motor
Low friction double nozzle pilot stage
High spool control forces
High dynamics
Rugged, long-life design
High resolution, low hysteresis
Completely set-up at the factory
Optional fifth port for separate pilot supply
Field replaceable first stage disc filter
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