ACTUATOR GP-HYDRAULIC 3829226 - Caterpillar

Illustration 2 g02697276
Pilot hydraulic system
(1) Main control valve
(3) Line
(4) Pilot control valve (joystick)
(5) Pilot control valve (joystick)
(7) Line
(8) Line
(10) Pilot control manifold
(11) Pressure reducing valve
(13) Accumulator
(14) Hydraulic lockout solenoid valve Pilot Oil Circuit
The oil delivery from gear pump (15) provides the oil flow to the pilot hydraulic system.The pilot circuit pressure is limited by reducing valve (11).The pilot hydraulic circuit performs the following main functions:
Enable the load sensing control circuit in the main control valve to control pump output flow.
Provide pilot oil pressure to the control valves for swing, stick, boom and bucket circuits in order to perform machine operations.Note: Each pilot circuit performs one of the functions above.The pilot circuit is classified into the following circuits:
Pilot control valve circuits
Main control valve circuits
Load sensing control valve circuitPilot Control Valve Circuits
Oil from gear pump (15) flows to pilot control valve (10). The oil then flows through pressure reducing valve (11) and check valve (12) to accumulator (13).When the hydraulic lockout control is shifted to the UNLOCKED position, the machine energizes the hydraulic lockout solenoid valve (14). The pilot oil then flows from pilot control valve (10) to line (9), line (7) and line (8) to joystick (4) and joystick (5).When the joysticks and/or travel levers/pedals are moved, the pilot oil flows to main control valve (1) in order to control the swing, stick, boom and bucket circuits.Main Control Valve Circuits
Pilot oil from the joysticks flows through pilot lines to the ports on the top and bottom of the main control valve. Each operation is controlled by a pilot input from either the top, or the bottom of the main control valve.When the hydraulic lockout control is shifted to the UNLOCKED position, the machine energizes the hydraulic lockout solenoid valve (14). The pilot oil then flows from pilot control valve (10) to line (3) and then to port (PIL) of main control valve (1). Pilot oil then shifts load sensing control valve (2) in order to activate the load sensing circuit.Reference: For more information concerning the operation of the load sensing circuit, refer to Systems Operation, "Main Control Valve".
Illustration 3 g02697277
Main control valve ports
(Pa1) Swing
(Pb1) Swing
(Pa3) Stick
(Pb3) Stick
(Pa4) Boom
(Pb4) Boom
(Pa5) Bucket
(Pb5) Bucket
(PIL) Pilot (load sensing control valve) When joystick (4) and/or joystick (5) are operated, pilot oil flows through pilot lines to pilot ports at the main control valve. The pilot oil shifts the spools in the main control valve. Refer to Illustration 3 and Table 1 for the location of the pilot lines and machine operations.
Table 1
Pilot line Control Valve Machine Operation
(Pa1) Swing control valve SWING LEFT
(Pb1) SWING RIGHT
(Pa3) Stick control valve STICK IN
(Pb3) STICK OUT
(Pa4) Boom control valve BOOM DOWN
(Pb4) BOOM RAISE
(Pa5) Bucket control valve BUCKET CLOSE
(Pb5) BUCKET OPEN The following example is given for the BOOM LOWER operation and the BOOM RAISE operation. Machine operations for a swing operation, stick operation and bucket operation are accomplished in the same manner as the boom operation.When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from