PLATE-COVER 2654859 - Caterpillar

Illustration 1 g00875499
Signal duplication valve (3) Passage (oil flow to hydraulic tank) (11) Passage (pump delivery pressure) (12) Passage (load sensing signal pressure) (14) Passage (true load signal pressure) (24) Center manifold (25) Passage (oil flow to hydraulic tank) (26) Passage (load sensing signal pressure) (27) Passage (pump delivery pressure) (28) Passage (center chamber) (29) Signal duplication valve spool (30) Chamber (PD) Pump delivery pressure (PL) True load signal pressureThe true load signal pressure in passage (14) pushes on the right end of signal duplication valve spool (29) . Signal duplication valve spool (29) moves to the left. When signal duplication valve spool (29) moves to the left, chamber (28) opens to the pump delivery pressure (PD) in passage (11) and passage (25) closes. Pump delivery pressure enters the signal duplication valve and pressure passes through the orifices from the center chamber (28) into passage (26) in the signal duplication valve spool (29) . Pump delivery pressure pressurizes the passage (26) of the signal duplication valve spool and chamber (30) of the signal duplication valve. The pressure on the left end of signal duplication valve spool (29) is load sensing signal pressure (12) . The load sensing signal pressure moves the signal duplication valve spool (29) to the right. When the signal duplication valve spool (29) moves to the right, the passage for pump delivery pressure (11) partially closes and the drain passage (3) partially opens. Load sensing signal pressure on the left end of signal duplication valve spool (29) is reduced. True load signal pressure on the right end moves signal duplication valve spool (29) to the left until the true load signal pressure (14) and the load sensing signal pressure (12) are equal. Load sensing signal pressure (12) is sent from chamber (30) into the load sensing network.