Attachment Tilt And Slave Circuit Description - JLG sky trak mmv Service Manual

9.8.28 Attachment Tilt and Slave Circuit
Description
System pressure is applied in the attachment tilt and
slave cylinder circuit (see page 9.44 and page 9.46) from
the attachment tilt section of the main control valve.
Fluid flow is directed to either side of the attachment tilt
and slave cylinder pistons by shifting of the spool valve in
the attachment tilt section of the main control valve as-
sembly. The spool valve is shifted by pilot pressure pro-
vided from the pilot select manifold, actuated by joystick
control and electrical solenoids.
The attachment tilt joystick functions are dependent on
the position of the attachment tilt mode switch in either
Mode 2A or Mode 2B.
a. Mode 2A
When the top of the attachment tilt mode
switch is depressed (Mode 2A) (1),
press and hold the top right button (2) on
the joystick (3). As the mode is activated
the corresponding lights will illuminate
on the logic panel (4).
Attachment Tilt Up..... move handle BACKWARD
Attachment Tilt Down .. move handle FORWARD
Boom Extend.................move handle to the right
Boom Retract .................. move handle to the left
OS0671
3
Model MMV Rev. 12/04
1. DOWN Position (Mode 2A) (See page 9.44)
MT3780
valve in the main control valve is shifted so system pres-
sure is directed to the rod end of the attachment tilt cylin-
der and the slave cylinders.
The extension of the slave cylinders is fixed by the posi-
tion of the boom so that only the attachment tilt cylinder is
retracted to tilt the attachment downward. The pilot pres-
sure opens the counterbalance valve. The open counter-
balance valve allows return oil from the base of the
attachment tilt cylinder to flow to ports of the attachment
tilt section of the main control valve, to the return filter and
ultimately to the reservoir.
If system pressure reaches 3500 ±100 psi (241 ±7 bar)
1
the main relief will open and allow hydraulic oil to return
to the return filter and to the reservoir. In any case, if the
return filter becomes restricted, hydraulic oil will bypass
the filter when the pressure reaches 25 psi (1,7 bar).
2. UP Position (Mode 2A) (See page 9.46)
OM0670
MT3790
in the main control valve is shifted so system pressure is
directed to the base end of the attachment tilt cylinder and
the slave cylinders.
If system pressure reaches 3500 ±100 psi (241 ±7 bar)
the main relief will open, allowing hydraulic oil to flow to
the return filter and to the reservoir. If the return filter be-
comes restricted, hydraulic oil will bypass the filter when
the pressure reaches 25 psi (1,7 bar).
Return oil from the rod side of the attachment tilt cylinder
is directed back to the attachment tilt section of the main
control valve through the spool valve, to the return filter
4
and to the reservoir. If the return filter becomes restricted,
hydraulic oil will bypass the filter when the pressure
reaches 25 psi (1,7 bar).
2
OM0680
Hydraulic System
With the attachment tilt switch in Mode 2A (top
depressed) (1), the right button on the joystick
pressed and held and the joystick moved FOR-
WARD, the attachment tilts DOWN. The spool
With the attachment tilt switch in Mode 2A (top
depressed) (1), the right button on the joystick
pressed and held and the joystick moved BACK-
WARD, the attachment tilts UP. The spool valve
9.79