Description May 2008
when the controls are not activated, and then to the tank.
When the mechanical lever controls are activated, the
movement of the main valve sliders chokes the oil flow,
thus producing the necessary pressure for the control
of the activated function. Each of the 6 sections of the
main valve control a specific function of the machine
(lifting/lowering, attachment holding plate rotation, boom
extension/ retraction, attachment locking/unlocking,
outriggers and chassis sway function).
In the head there is a pressure relief valve set at 270
bar also serving as a safety valve of the circuit which
directly acts on the main line of the hydraulic oil. Again
in the input head of the main valve there is a solenoid
valve discharging the main flow which activates the
movements of the main valve only when its solenoid
is energised. When such solenoid is not energised all
the flow from the pump is discharged. In this specific
version of the machine, this solenoid valve is mainly
used to stop some movements of the machine when
the stability limits are reached, and also to completely
deactivate such functions when the relevant selector in
the driving place is turned to the "road" position.
By moving the main lever in the driving place to one
side, section 1 of the main valve directly delivers oil
to the oil-dynamic block (37) consisting of a 6-way/2
position electrical switch block and 3 pressure relief
valves. Two of these valves, calibrated at 295 bar,
are mounted on the lines controlling the rotation of the
attachment holding frame; the third one, set at 200 bar,
is installed on the extension line of the telescopic boom
lifting cylinder.
When the coil of the electrical switch block is not
energised, the oil coming from section 1 of the main
valve is sent to the extension cylinders (21) and (22 only
for GTH-4013 SX) of the telescopic boom, connected in
series with each other. Cylinder (21), which activates
the second telescope of the boom, is equipped with
a double-acting compensation valve serving also as
a safety valve, while cylinder (22), which activates
the third telescope of the boom, is equipped with a
singleacting compensation valve again serving also
as a safety valve. This pressure relief valve set at 200
bar and fitted to the oil-dynamic block (37), reduces
the maximum load during the boom extension phase in
those work areas where the electronic moment limiting
system cannot detect overload conditions with respect
to the admissible load chart of the machine.
When the coil of the electrical switch block is energised
by the activation of the pushbutton placed at the top of
the main lever in the cab, oil is sent to the attachment
holding frame cylinder (19) of the telescopic boom. This
cylinder is equipped with a double-acting compensation
valve serving also as a safety valve.
Parallel to this cylinder, there is the fork levelling
compensation cylinder (20) (also called balancing
cylinder) which is equipped with a special double-acting
compensation valve. Inside this valve, the one-way
valves are mounted in reversed manner with respect
to the normal position to avoid the pressurisation of the
cylinder when the rotation control of the attachment
holding frame is activated. Again inside this valve, there
are other two one-way valves (36), set at 5 bar, serving
as anti-cavitation check valves. These valves deliver
oil, taken from the low-pressure line of the transmission
pump (2), to the fork levelling compensation circuit
when needed.
The two pressure relief valves set at 295 bar and mounted
in the oil-dynamic block (37), protect the automatic fork
levelling circuit during the boom lifting/lowering phases
and in all cases of overload on the attachment holding
frame (for instance, in the case of use of the bucket).
Section 2 of the main valve (16) controls the telescopic
boom lifting cylinder (17) through the longitudinal
displacement of the main lever placed in the driving
cab. This cylinder has one single-acting compensation
valve with safety function.
Section 3 of the main valve controls the chassis sway
cylinder (31) mounted on the right side of the machine
and equipped with a double-acting compensation
valve serving also as a safety valve, through the lateral
displacement of the special lever installed in the driving
place.
Section 4 of the main valve controls the left outrigger
cylinder (29) equipped with double-acting compensation
valve serving also as a safety valve, through the
longitudinal displacement of the special lever placed in
the driving cab.
Section 5 of the main valve controls the right outrigger
cylinder (30) equipped with double-acting compensation
valve serving also as a safety valve, through the
longitudinal displacement of the special lever placed in
the driving cab.
Section 6 of the control valve controls the attachment
locking cylinder (23) through the lateral displacement
of the special lever placed in the driving place. This
cylinder has a double one-way valve with hydraulic
release and safety function.
On the feeding lines of this cylinder, there are two quickfit
connectors (24) for the connection of the hydraulic lines
to those optional attachments necessitating hydraulic
power for their operation (ex. hydraulic winch and
maintenance jib, mixing bucket, etc.). In the model
dealt with in this manual, this function is optional. All
the sections of the main valve (16) are equipped with a
micro-switch which senses and transmits a special ON/
OFF signal when the relevant slider is activated. Such
signals are used by the operating logic of the system
protecting the machine in case of loss of stability (LMI).
The SAFIM S6 servo-assisted braking system with
pedal (25) receives oil from pump (4) and uses this oil
to pressurise a hydraulic accumulator (39) connected to
DESCRIZIONE
Document 57.4403.4200
GTH-4013 SX GTH-4017 SX
vi
Courtesy of Crane.Market