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| Illustration 1 | g03320977 |
(1) Main control valve (2) Main relief valve (3) Front pump (4) Rear pump (5) Pilot gear pump (6) Swing drive (7) Swing brake (8) Swing motor (9) Hydraulic tank (10) Hydraulic return filter (11) Oil sampling port (12) Hydraulic oil refill pump and motor (13) Stabilizer valve (14) Swivel (15) Thermal bypass valve (16) Hydraulic oil cooler (17) Pilot filter (18) Pilot shutoff manifold (19) Grapple rotator motor (20) Pilot valve (right joystick) (Boom/ Grapple Open/ Close) (21) Pilot valve (Swing) (22) Pilot valve (left joystick) (Stick/ Grapple Rotate) (23) Flow control valve | |
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| Illustration 2 | g03258385 |
Activated Hydraulic Lockout Control Solenoid (24) Seat Switch | |
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| Illustration 3 | g03329035 |
(25) Pilot Enable Button activated. Green light Off. | |
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| Illustration 4 | g03319294 |
View of pilot hydraulic components. Parts removed for clarity. (18) Pilot shutoff manifold (20) Pilot valve (right joystick) (STICK/ROTATOR) (21) Pilot valve (foot pedal) (SWING) (22) Pilot valve (left joystick) (BOOM/GRAPPLE) (24) Seat Switch (26) Swing Rocker Pedal | |
The pilot hydraulic system is located under the upper frame of machine. The components are mounted to the upper frame of the machine.
The pilot hydraulic system uses the following components:
- Main Control Valve
- Pilot Gear Pump
- Pilot Filter
- Flow Control Valve
- Thermal Bypass Valve
- Swing Drive (spring-applied brake and swing motor)
- Foot Pedal Valve
- Pilot Shutoff Manifold
- Stabilizer Valve
- Pilot Joystick Control
- Pilot oil accumulator
The pilot hydraulic system contains the main control valve, pilot gear pump (5), pilot filter (17), and the pilot shut-off manifold (18). The system also contains a flow control valve (23), two joysticks (20,22), and one swing pedal controller (21) .
The pilot hydraulic system supplies oil to the main pumps (3,4), the main control valve (1), the swing brake (7), and stabilizer valve (13). In a negative-control system, the main pump is brought off stroke by an increase in oil pressure through the main valve. At start-up, this oil pressure build-up would overload the starter. For this reason, the main pump is destroked at start-up by the fixed-displacement pilot pump. Pressure is regulated by a relief valve at the pump outlet. The pilot hydraulic system also controls various solenoid-operated valves that are activated by electric switches.
In order for the pilot system to operate, the hydraulic lockout solenoid must be deactivated and the pilot enable button (25) on the control panel, activated. To deactivate the hydraulic lockout solenoid, the left-hand armrest must be in the Lowered position. See Illustration 2. Once the left-hand armrest is in the Lowered position, activate the pilot enable button (25) on the control panel (green light OFF). When these conditions are met, the pilot shut-off solenoid valve is open and the pilot system is pressurized. When the left-hand armrest is in the Raised position, the hydraulic lockout control is activated and pilot functions will stop. The swing parking brake (7) is released whenever the left-hand armrest is lowered and the pilot enable button is activated.
The pilot filter is located between the pilot gear pump and the pilot shut-off manifold. The filter (17) has a 275 kPa (40 psi) bypass valve and an electric filter clog indicator.
The control valves of the loader are actuated by pilot signals from hand and foot-operated controllers. Pilot supply pressure and pilot drain oil are routed through a dual-chambered manifold located beneath the cab. Pressure and return lines lead from the pressure and return chambers of this manifold to the hand and foot controllers. The left joystick actuates the main boom up/down and grapple open/close. The right joystick actuates stick and grapple rotate. The rocker pedal (26) actuates the swing motor.
Pilot Shutoff Manifold
Oil flow into the pilot supply system is controlled by the pilot shut-off manifold (18). From the pump, pilot supply oil flow is directed to the normally closed hydraulic lockout solenoid of the pilot shut-off manifold. The hydraulic lockout control solenoid is activated by an electric seat switch (24) attached to the lower left arm rest. See Illustrations 2 and 3. When the arm rest is raised up, the hydraulic lockout solenoid is open and the valve is closed. This forces the pilot oil to dump back to the reservoir through the pilot relief. When the arm rest is lowered and the pilot enable button pressed, the seat switch is closed. This action energizes the solenoid to open the shut-off valve and pressurize the pilot system. Pilot pressure is checked through a test port on the pilot shut-off manifold or at the pilot pump.
Joystick Controls
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| Illustration 5 | g03319118 |
(27) Disc (28) Plunger (29) Spool | |
The joystick is a hydraulic proportional controller. A pivoting handle tilts a disc (27) which depresses one or another of the four plungers protruding from the top of the valve block. Each plunger (28) is connected to a spring-loaded valve spool (29). As the control is moved over different ports, the valve spool pressurizes the port. The left joystick actuates the main boom up/down and grapple open/close. The right joystick actuates stick and grapple rotate.
Swing Pilot Valve
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| Illustration 6 | g03320717 |
(30) Top Plate (31) Spool | |
The swing controller is a hydraulic proportional control valve. A rocker pedal (26), which pivots from the center, is bolted to the top portion of the controller, which protrudes beneath the cab floor. The pivoting top plate (30) presses against the spring-loaded valve spool (31), releasing pilot oil flow to one, or the other pilot ports.