COMPONENT OPERTATION / Control Valve Pilot Control Circuit Pressure oil (indicated with numbers) from the pilot valve acts on the spool in control valve in order to move the spool. In the following operations, pressure oil moves the spool and acts on the valves as follows. During auxiliary operation, pressure oil moves the auxiliary spool and shifts the bypass shut-out valve in 4-spool section. (Optional) The air bleed circuit is located on the upper section of control valve and bleeds any air trapped inside auto- matically.
External Pilot Pressure Circuit As the boom 1 spool is shifted during boom lower operation, pressure oil from the pilot pump acts on the boom anti-drift valve and releases the lock of boom anti-drift valve. As the arm 1 spool is shifted during arm roll-in operation, pressure oil from the pilot pump acts on the arm anti-drift valve and releases the lock of arm anti-drift valve. Pressure in the main relief valve is increased by pilot pressure from solenoid valve (SG) The boom overload relief control valve is shifted by pilot pressure from solenoid valve unit (SC). The boom flow rate control valve is shifted by pilot pressure from solenoid valve unit (SF).
The flow combiner valve is shifted by pilot pres- sure from the flow combiner valve control spool in signal control valve. The arm flow rate control valve is shifted by pilot pressure from the arm flow rate control valve control spool in signal control valve. T3-3-18