MLRS Attachment System. The MLRS attachment function is controlled by the electric joystick and the MLRS
control valve. Hydraulic oil flow from the axial piston pump supplies oil pressure and flow for MLRS control valve pilot and
function operations. A load sensing line from the MLRS control valve to the piston pump adjusts the pump output. Pilot
shuttles in each valve section, allow the pressure of the function with the greatest load to be sensed by the pump. As the
load of the MLRS control valve changes, the position of the swash plate angle changes in the piston pump.
When the electric joystick is in the center position, all solenoids of the MLRS control valve are de-energized and centering
springs keep the control valve spools in the center (hold) position.
By moving the electric joystick forward, the top left solenoid is energized. The solenoid allows pilot oil to flow through the
solenoid and push the spool in the top section towards the right of the machine. The main flow of hydraulic oil goes
through the top section, pilots open a load check poppet and allows oil to flow from the work port to the MLRS attachment
cylinder. Oil enters the left (rod end) port of the cylinder. The oil pilots open the counterbalance valve on the head end of
the cylinder, allowing oil to flow from the head end of the cylinder. The cylinder retracts, lowering the MLRS attachment.
Oil from the cylinder enters the work port of the top section of MLRS control valve and is directed to the return circuit
where it is sent to the hydraulic reservoir through the hydraulic filter.
The load compensating check valve moves up and down as the load and pump pressure change. If the load increases,
the pressure in the work port increases and pushes on the spring side of the load compensating check valve to block oil
passage to the work port. At this short instance, the load compensating check valve is operating as a load hold check
valve. Increased work port pressure is also sent to the piston pump through the sensing line. The pump output pressure
increases sufficiently to maintain the 400 psi (2758 kPa) pressure differential. The increase in pump pressure is now
sensed at the smaller end of the load compensating check valve and the valve moves up allowing oil flow to the work port
If the electric joystick is moved rearward, the top right solenoid is energized. The oil flow through top section of the MLRS
control valve is similar to the retract function but the oil flow to the cylinder is reversed. Oil pressure unseats the ball check
in the counterbalance valve on the head end and forces the rod out of the cylinder. The cylinder extends and raises the
The maximum pressure in all the circuits of the MLRS control valve is controlled by the maximum discharge of the pump
which is 3000 psi (20685 kPa).
Carriage Tilt System. The carriage tilt function is also controlled by the electric joystick and the MLRS control
valve. Hydraulic oil from the piston pump flows through the control valve the same as for the above MLRS attachment
Move the electric joystick to the left and the second from the top right solenoid is energized. The solenoid allows pilot oil to
flow through the solenoid and push the spool in the second section towards the left of the machine. Oil flows through the
second section, pilots open a load compensating