8
2.2.1
Hydraulic system
-
Control circuit:
oil supplied by a gear pump is delivered to an electro-hydraulically controlled,
power-assisted distributor. This distributor in this configuartion controls all arm
operations and functions.
Arm movement speed is controlled by a 2-axis joystick, which is powered by a low-
pressure circuit (20 bar). The grip features different buttons which serve to operate
ON/OFF solenoids which in turn operate some of the controls.
The pressure signal sent by the joystick at the distributor inlet is of the proportional
type, thus making for smoother arm movement.
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Power circuit
In this instance the hydraulic system powering the flail hedge mower rotor is of the
closed-circuit hydrostatic type with
axial piston pump and motor
.
Unlike the open circuit, in which oil flow is broken by the tank, in the closed circuit
the oil flow is continuous because the outlet from the pump goes directly to the
motor and the outlet from the motor goes straight back to the pump.
Closed circuits offer many operational advantages:
-
they can stop undamaged under full load with a minimum loss of power
-
they accurately maintain a pre-set speed in the presence of resistive or
overwhelming loads
-
their output is good, even when subjected to rather demanding duty cycles
-
they can operate in two directions at controlled speed, without any major
interference from external loads
-
when the control is disengaged, the flail holder shaft remains still
-
their response time is faster than any other type of transmission
WARNING:
Frequent checking of the suction filter is recommended. Remember that the
life of hydrostatic transmission strongly depends on the degree of filtering of
the circulating oil!!
