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| Illustration 1 | g00467341 |
Three-way pilot control valve (A) Pilot port (B) Pilot port (C) Pilot port (D) Drain port (1) Adjustment screw (2) Valve spring (3) Valve (4) Valve spool (5) Valve spool (6) Passage (7) Passage (8) Passage (9) Passage | |
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| Illustration 2 | g00467570 |
Location of three-way pilot control valve (10) Three-way pilot control valve | |
Three-way pilot control valve (10) controls the pilot signal to the two-way pilot control valve. Both valves are part of the boom and hook control valve which is located below the floorplate in the operator's compartment. A signal that is sent from valve (10) opens the two-way pilot control valve. This allows the pump pressure to flow to the hook control valve.
A pilot signal from a pilot control valve enters port (A) . The pressure from this signal pushes on spools (4) and (5) . When the pressure is great enough to overcome spring (2) , spools (4) and (5) move upward against valve (3) .
The movement of spools (4) and (5) cause passage (6) to open to passage (9) . This produces a direct path from port (B) to port (C) .
Port (B) receives a pilot signal from the pump pressure. Port (C) is connected to a passage to the two-way control valve. The signal enters port (B) and the oil travels through passages (6) and (9) . The oil exits port (C) and the signal travels to the two-way control valve. This signal causes the two-way control valve to shift and a path from the pump pressure to the hook control valve is opened.
When the signal in port (A) is removed, spools (4) and (5) move downward. Passage (6) is blocked and port (C) is opened to passage (8) . Passage (8) allows the oil from port (C) to drain to port (D) . This allows the two-way pilot control valve to close and the pump pressure is blocked.