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| Illustration 1 | g00300639 |
Cab (1) Pilot control valve (stick and swing) (2) Pilot control valve (boom and grapple) | |
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| Illustration 2 | g00368764 |
Main control valve compartment (top view from front of machine) (3) Stick II (4) Boom I (5) Grapple (6) Right travel (7) Left travel (8) Swing (9) Stick I (10) Boom II | |
When joystick (1) and/or joystick (2) are operated, the pilot control valves send pilot pump oil through the pilot lines to pilot ports at the main control valve in order to shift the spools in the main control valve. Pilot oil that enters the control valves from the top causes the machine operations in Table 1. Pilot oil that enters the control valves from the bottom causes the machine operations in Table 2.
| Reference | Control Valve | Machine Operation (Top) |
| (3) | Stick II | Drain (1) |
| (4) | Boom I | BOOM RAISE |
| (5) | Grapple | GRAPPLE CLOSE |
| (6) | Right travel | REVERSE RIGHT TRAVEL |
| (7) | Left travel | REVERSE LEFT TRAVEL |
| (8) | Swing | SWING RIGHT |
| (9) | Stick I | STICK IN |
| (10) | Boom II | BOOM RAISE |
| ( 1 ) | No pilot oil goes to top of control valve. |
| Reference | Control Valve | Machine Operation (Bottom) |
| (3) | Stick II | STICK OUT |
| (4) | Boom I | BOOM LOWER |
| (5) | Grapple | GRAPPLE OPEN |
| (6) | Right travel | FORWARD RIGHT TRAVEL |
| (7) | Left travel | FORWARD LEFT TRAVEL |
| (8) | Swing | SWING LEFT |
| (9) | Stick I | STICK OUT |
| (10) | Boom II | BOOM UP limiter |
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| Illustration 3 | g00824776 |
Pilot control valve (implement and swing) (11) Spool (12) Passage (13) Return passage (14) Spring (15) Spring (16) Seat (17) Rod (18) Plate (19) Rod (20) Spring (21) Seat (22) Spring (23) Spring (24) Return chamber (25) Passage (26) Spool (27) Port (28) Port | |
When the pilot control lever is moved to the right side, plate (18) tilts to the right side. Plate (18) pushes down on rod (19). Seat (21) pushes against the force of metering spring (22) and spring (23). The force of metering spring (22) shifts spool (26). Passage (25) opens. The oil flows through passage (25) and port (27) to the main control valve. The oil pressure shifts the stem of the main control valve. This enables the implement operation or swing operation.
The oil at the opposite end of the stem flows back through port (28). The oil next flows through return passage (13) and into return chamber (24). The oil then flows back to the tank.
When rod (17) is not forced down, return passage (13) is open and passage (12) is blocked.
The control levers will return to the NEUTRAL position due to the force of spring (23) and spring (14) .
When the pilot control lever is moved to the left, plate (18) tilts to the left. Plate (18) pushes down on rod (17). Seat (16) pushes against the force of metering spring (15) and spring (14). Metering spring (15) forces spool (11) to move down. Movement of spool (11) controls the amount of pilot oil that flows through passage (12). The pilot oil flows through passage (12) to the main control valves.
The pilot oil that flows to the main control valves changes proportionally to the travel distance of the pilot control lever. Movement of the stem of the main control valve causes a change in the oil flow to the cylinders and/or motors. Fine movement of the pilot control lever allows fine control of the operation of the cylinders and/or motors.
When the control lever is moved a little, spring (22) controls spool (26). The change in the pilot pressure is small and fine control of the machine is accomplished. When the control lever is moved a lot, the bottom of rod (19) begins to contact spring (20), springs (22), springs (23) and spool (26). A large rate of change in the pilot pressure allows a large change in control.