2 GTH-4016SR • GTH-4018SR
Part No. 57.4400.9203
March 2010
Section 2 • Specification
SPECIFICATION
REV A
temperatures.
This filter package, which is flanged directly on the
top side of the tank, is provided with a electrical
pressure switch
(12)
indicating when the filter
cartridge is clogged and then has to be replaced.
The maximum pressure on the brake circuit line is
controlled by the pressure relief valve
(13)
which is
set to 180 bar.
The mechanical shutoff valve
(14)
when closed,
allows the pressure relief valve setting pressure
can be checked and adjusted as necessary.
In the normal machine working conditions this
shutoff valve must be placed in its fully open
position.
The hydrostatic pump
(2)
hydraulically powers the
Rexroth hydrostatic motor closed loop, piston bent
axis type
(15)
, model A6VM80 which transforms
the hydraulic power (pressure*flow rate) of the oil
contained in the hydrostatic transmission closed
loop circuit into mechanical power (torque*rotational
speed) to be used for the machine displacement.
The low pressure line, which is part of the
hydrostatic transmission, is also used to cool the
hydrostatic pump a motor through a drain case line
routed between the pump and the motor and finally
connected to the tank where the warm oil is finally
sent.
This drain case flow rate is controlled by the check
valve
(16)
having a cracking pressure of 2.5 bar.
When the pressure in the drain case line exceeds
2.5 bar, the flow rate in excess can be directly
discharged to the tank so preventing any damage
at the pump and motor sealing gaskets.
The hydrostatic motor is directly flanged on a
Carraro two-speed gear box
(17)
installed on the
central part of the undercarriage.
The speed shifting phase is activated by the
hydraulic actuator
(18)
, which is part of the gearbox
itself, and controlled by the 4 ways/3 positions
electrical selector valve
(19)
.
This selector valve is powered by the low pressure
generated by the hydrostatic transmission charge
pump.
The gearbox is mechanically linked, through two
distinct drive shafts, to the front axle
(20)
and to the
rear axle
(21)
, both manufactured by Carraro, so
transmitting to the wheels the torque generated by
the hydrostatic motor.
The front axle, provided with an embedded steering
cylinder
(22)
and articulation, is rigidly secured
on the front area of the undercarriage whilst the
rear axle, provided with an embedded steering
cylinder
(23)
and articulation, is floating around its
pivoting axle in most of the machine displacement
conditions.
The floating condition of the rear axle is controlled
by the single effect right and left rear axle pivoting
cylinders
(24)
and
(25)
which, when the rear axle
is floating, are completely free to extend/retract
exchanging oil between their piston chambers
and giving a negligible resistance to the rear axle
floating movement.
The free flow between the two cylinder is allowed
by the two 2 ways/2 positions electrical rear axle
pivoting lockout valves
(26)
which are energized
when the rear axle is floating free.
These valves are directly embedded in the cylinder
body and, when not energized, close the line
between the two cylinders piston chamber so
locking the floating movement of the rear axle.
The two air bleeding valves
(27)
, embedded one
for each cylinder, are used to eliminate air from the
cylinders after the first machine installation or in
occasion of maintenance operations.
The oil used to fill the rear axle pivoting cylinders
is provided by the low pressure line, powered by
the hydrostatic transmission charge pump, and is
controlled through the rear axle lockout cylinders
control valve
(28)
.
The scope of this valve is to provide a free flow of
oil when this is requested by the rear axle pivoting
cylinders (check valve opens) and to prevent any
pressure surges and peaks on the low pressure
line when the quantity of oil in the rear axle pivoting
cylinders is in excess (damping effect due to the
calibrated restrictor).
The machine open circuits are linked to the tank
through the heat exchanger
(29)
which cools the oil
before it is filtered through the special filter package
(11)
already described.
