ALARM 4761847 - Caterpillar

Illustration 1 g02641698
Tamper Hydraulic System (OFF) (1) Displacement piston (2) Bias spring (3) Feedback spring (4) Check valve (5) Flushing control spool (6) Pressure compensator spool (7) Displacement control spool (8) Tamper solenoid (9) Tamper pump (10) From port "1" hydraulic tank (11) Displacement piston cavity (12) To hydraulic tank (13) To port "P" of oil distribution manifoldWhen the engine is not operating, bias spring (2) forces the swashplate in tamper pump (9) to maximum angle. When the engine is started, the pump begins to produce flow. Supply oil is sent to displacement control spool (7), to pressure compensator spool (6), and to flushing control spool (5) which are inside the pump. Supply oil is also sent out port "B" of the pump to port "P" of oil distribution manifold (13) .When the tamper is OFF, tamper solenoid (8) is not energized. In this situation, supply oil flows across displacement control spool (7) and divides into two branches. One branch directs oil into displacement piston cavity (11), and the other branch directs oil to the chamber at the end of the displacement control spool.As the pressure in displacement piston cavity (11) increases, displacement piston (1) moves the swashplate in the pump toward minimum angle. At the same time. the pressure in the chamber at the end of displacement control spool (7) causes the spool to shift. This shift opens a passage for some supply oil to flow across the displacement control spool and into the pump case.At this point, pressure in displacement piston cavity (11) decreases, and bias spring (2) causes displacement piston (1) to increase the angle of the swashplate. Movement of the displacement piston causes feedback spring (3) to exert a greater force against displacement control spool (7). This movement closes the passage to the case drain, and more supply oil is forced into the displacement piston cavity. Eventually, the pump reaches equilibrium, and the pump produces enough flow to make up for system leakage. In this case, the pump does not produce enough flow to overcome the restriction of the tamper motors, and the motors do not operate.When the tamper is not operating, the force from the spring which acts on flushing control spool (5) is greater than the force from the oil pressure which acts against the spool in opposition to the spring. In this case, the flushing control spool allows some supply oil to flow into the pump case. This flow helps cool the pump.
Illustration 2 g02641700
Tamper Hydraulic System (ON)When the tamper system is operating, tamper solenoid (8) is energized. The tamper solenoid moves displacement control spool (7) into a position that is proportional to the input signal to the tamper solenoid.Tamper solenoid (8) uses displacement control spool (7) to control the oil pressure in displacement piston cavity (11) : the greater the input signal to the tamper solenoid, the less pressure in the displacement piston cavity. Therefore, a greater input signal results in a greater swashplate angle, and greater flow from the pump.When the