One boom cylinder is used to RAISE and LOWER the boom. When the boom cylinder rod EXTENDS, the boom LOWERS. When the boom cylinder rod RETRACTS, the boom RAISES.
The hydraulic pump supplies oil to the main control valve. The oil flows to the various valve spools through center bypass passage and parallel feeder passages for use upon activation. The oil also flows to the pilot pressure reducing valve. The valve reduces the pressure of the oil for use in the pilot circuit. The pilot oil flows to hydraulic activation solenoid. When the hydraulic activation solenoid is energized, pilot oil flows to the control solenoids.
When the operator uses the joystick to move the boom, an input signal is sent to the Machine Electronic Control Module (ECM). The ECM determines the direction and speed of the boom cylinder in proportion to the movement of the joystick. The ECM sends an output signal to the boom cylinder solenoids. Pilot pressure in the main control valve is now allowed to flow through the boom cylinder solenoids. Pilot oil pressure is used by the solenoids to control the movement of the boom control valve in the main control valve. The boom control valve spool, in turn, controls the flow of the high-pressure oil to the boom cylinder.
Components of the boom system include:
- Boom control valve
- Variable angle boom (VAB) control valve (if equipped)
- Power offset boom (POB) control valve (if equipped)
- Swing boom control valve (if equipped)
- Boom lowering check valve
- Boom lowering control valve
- Boom cylinder
Note: Refer to the appropriate sections in this manual for more information.