SPRING- 4646159 - Caterpillar

Illustration 1 g01323346
Pressure compensators (A) The valve is shown with the compensator piston in hold. (B) The valve is shown with the compensator piston partially open. (C) The valve is shown with the compensator piston fully open. (1) Signal line to pump control valve (2) Load sensing boost from the hystat charge pump (3) Signal pressure passage (4) Piston for the flow compensator (5) Cross-drilled passage in the piston for the flow compensator (6) Control valve spool (7) Flow from implement pump (8) Feeder passage (9) Openings in the bottom of the piston for the flow compensator (10) Bridge passage (11) Check valveThe Proportional Priority Pressure Compensated System (PPPC) directs the pump discharge oil to each individual implement circuit in proportion to the movement of the implement control lever. The implement circuit with the highest working pressure provides the true load signal pressure during multiple implement functions.Pump oil flow is directed into chamber (7). When control valve (C) is activated, the pump flow is directed into feeder passage (8). The oil in the feeder passage pushes the piston for the flow compensator (4) upward. The pump oil flows through openings in the bottom of the piston for the flow compensator (9) to bridge passage (10). In order for the oil to get from feeder passage (8) to bridge passage (10), the pressure must be high enough to overcome the spring in check valve (11). From bridge passage (10), pump flow is directed around control valve spool (6) to the work port.When the piston for the flow compensator (4) is pushed up, the oil in feeder passage (8) is also directed through cross-drilled passage (5) to signal pressure passage (3). The flow of oil through cross-drilled passage (5) supplements the oil from hystat charge pump (2). The combined flow of oil is directed to the top of the pistons for the flow compensators of the other control valves and to pump control valve (1). Pump control valve (1) causes the pump to UPSTROKE in order to increase the flow.If a second control valve (B) is partially opened, the same basic steps happen. The pump flow is directed into feeder passage (12). The oil in the feeder passage pushes the piston for the flow compensator (14) upward. The pump oil flows through openings in the bottom of flow compensator piston (13) to bridge passage (15) in proportion to the movement of the implement control lever. The piston for the flow compensator (14) will not raise fully because of the signal pressure from control valve (C). The signal with the highest work port pressure regulates the flow through all activated control valves.