Document 57.4402.8200 - 1
st
Edition 03/2007
INDEX
v
GYRO 4020 - 4518
INTRODUCTION
discharge valve when the pump flow is not used for the
boom movements, and of 5 modules.
Four of these modules control specific functions of the
telescopic boom (lifting/lowering, attachment holding
frame rotation, extension/retraction, attachment lock/
unlock) and the fifth module controls the rotation of the
turntable of the machine.
In the head there is a pressure relief valve set to 300
bar which, acting on the line of the “load sensing” signal,
limits the maximum pressure at the inlet of the main
valve through such 3-way compensator.
On the main inlet head of the main valve, there is the pilot
line head which includes an inlet safety filter, a pressure
relief valve acting on the pilot line, and a safety solenoid
valve which, when de-excited, discharges the input pilot
pressure, thus preventing the main valve from working.
This solenoid valve is used as a “dead man” control and
is activated by the relevant button on the joysticks in the
driving cab.
The pilot head delivers oil at pressure to the 5 pilot
modules of the main valve. These modules operate the
relevant main sliders in relation to the command signal
they receive from the joysticks via the control unit.
Module 1 of the main valve controls the telescopic
boom lifting cylinder (
12
). This cylinder has one single-
acting compensation valve (
13
) with safety function.
The control module of element 2 of the main valve is
the electro-proportional type with electrical feed-back
and integrated electronics. The 1,5-lt. accumulator
prefilled at 35 bar (
14
) and located on the line of the
differential chamber of the lifting cylinder (
12
), allows
for damping the boom swings when the same boom is
moved down.
Module 2 of the main valve controls the boom telescopes
extension cylinder (
15
). This cylinder is equipped with
a double-acting compensation valve (
16
) with safety
function. The control module of this element of the main
valve is the electro-proportional type with electrical
feed-back and integrated electronics.
Module 3 of the main valve controls the cylinder
operating the attachment holding plate of the telescopic
boom (
17
). This cylinder is equipped with a double-
acting compensation valve (
18
) with safety function.
Paralleled to this cylinder we find the fork levelling
cylinder (
19
) (or balancing cylinder) equipped with a
special double-acting compensation valve (
20
). Inside
this valve, the one-way valves are installed in a reverse
manner with respect to the normal position to avoid
the pressurisation of the cylinder when the rotation
command of the attachment holding plate is operated.
Again inside this valve, there are other two one-way
valves set to 5 bar with anti-cavitation function (
21
).
These valves are used to deliver oil, sucked from the
low pressure line coming from the pressure relief valve
(
11
), to the fork levelling compensation circuit, when such