PULLEY 1157465 - Caterpillar

Oil from Pump to Implement Valve, Armed, All HOLD
Illustration 3 g03597436
Implement pump control ARMED (1) Loading relief valve (2) Loading manifold (3) Loading control valve (4) Return to tank (5) From port "LS1" of implement control valve (6) Flow compensator spool (7) Implement pump solenoid (8) Brake accumulator (9) Pressure reducing valve (10) Rear differential lock (11) Rear differential lock solenoid (12) Needle valve (13) Pump unloading valve (14) To port "P" of brake manifold (15) Return from other systems (16) Attachment load sensing solenoid (17) Implement pump (18) Bias piston (19) Actuator piston (20) Pressure compensator spool (21) To port "LX" of implement control valve (22) To port "P" of implement control valve (23) Loading enable valve (24) Implement resolverWhen the system is armed, implement pump solenoid (7) is energized, and the load sensing signal from port "LS1" of implement manifold (5) for implement pump (17) is no longer open to the return line. In this situation, a load sensing signal is sent to flow compensator spool (6) in the implement pump. The combined force from the load sensing signal and the margin spring cause the flow compensator spool to shift against the force which is created by the pump supply pressure. This shift decreases the pressure in the piston chamber of large actuator (19), and the angle of the swashplate increases.Pump supply oil charges brake accumulator (8). This action causes load sensing signal (5) to increase. The increased load sensing signal causes the pump to produce more flow.As the pressure in brake accumulator (8) increases, the pressure which acts against pump unloading valve (13) increases. When the pressure acting against the pump unloading valve overcomes the force of the pump unloading valve spring, the spool of the valve shifts. This shift directs some of the pump supply oil into the return line. In this case, the pressure in the brake accumulator seats the check valve, and the load sensing pressure decreases.The combined action of pump unloading valve (13) and flow compensator valve (6) maintains the pump output pressure between approximately 10,335 - 20,670 kPa (1500 - 3000 psi) when no implements require flow. This feature ensues that brake accumulator (8) remains charged with oil.If an implement is operated, the highest load sensing signal from the implement manifold is directed into port "LS VLV" of the middle manifold. The load-sensing signal is sent to pressure compensator spool (20) .Refer to System Operation, "Main Hydraulic System" for additional information about the implement operation.When the system is armed the hydraulic oil flows to port "P" of loading manifold (2). When the hydraulic oil is below 40° C (104° F), the solenoid on loading control valve (3) is energized. Hydraulic oil is sent to loading relief valve (1) from the loading control valve. The combined force from the loading control valve flow and the loading relief valve spring cause the loading relief valve to shift.When the system is armed and the solenoid of loading enable valve (23) is energized, hydraulic oil