PLATE 2831116 - Caterpillar

Illustration 6 g00669176
Shock reducing valve (28) Shock reducing valve (29) Solenoid valve (30) Flow control valve (38) Port (39) Port (40) Passage (42) Drain port (43) Pressure reducing valve (44) Passage (45) Passage (46) Passage (48) Passage (50) Passage (51) Secondary pressure chamber (52) Drain (circuit) (53) Check valve (54) Passage (57) Passage (58) Orifice (61) Passage (62) Passage (63) PassageWhen the boom control lever is operated in the BOOM RAISE position, oil from pilot control valve (19) flows in the following manner:
Oil flows to port (39) through passage (46) in solenoid (29) and through passages (61), (62), and (63) .
Oil reaches the boom control valve through line (24). The boom is raised at high speed just before the end of the stroke. At this time, solenoid valve (29) of shock reducing valve (28) is not energized. The solenoid valve is in the NEUTRAL position.
When the boom is in the BOOM LOWER position, return oil from the boom control valve flows into the hydraulic tank via passages (63) and (61) and check valve (53) from port (39) .
Illustration 7 g00669548
Shock reducing valve in energized state (28) Shock reducing valve (29) Solenoid valve (30) Flow control valve (38) Port (39) Port (40) Passage (42) Drain port (43) Pressure reducing valve (44) Passage (45) Passage (46) Passage (48) Passage (50) Passage (51) Secondary pressure chamber (52) Drain circuit (53) Check valve (54) Passage (55) Oil pressure chamber (56) Oil pressure chamber (57) Passage (58) Orifice (61) Passage (62) Passage (63) Passage (64) Spool (65) Plunger (66) Setscrew (67) Passage (68) PassageDuring the boom raise, the sensor that is located at the foot of the boom is activated just before the end of the piston stroke. Oil from pilot control valve (19) flows in the following manner:
Oil flows from port (38) into passages (45) and (44) of pressure reducing valve (43) .
After reaching passage (44), the oil enters secondary pressure chamber (51) through passage (50) of spool (64). The oil moves the spool to the left.
When spool (64) moves to the left, oil flows from passage (68) to passage (67). Oil in passage (44) flows into drain port (42) through passage (50), circuit (52), and solenoid valve (29). When the oil pressure is reduced, spool (64) returns to the right by the force of the spring.
When the spool returns to the right, oil is supplied to secondary pressure chamber (51) again from passage (44). Spool (64) is balanced in a constant position, and the pressure of the pressure reducing valve is maintained at 1180 kPa (170 psi).
After the pressure in passage (54) is reduced by pressure reducing valve (43), the pressure is reduced further through the action of flowing through orifice (58) and passage (57). Oil in passage (62) can flow abruptly. This causes a large pressure difference between the pressure in oil chamber (55) and the pressure in oil chamber (56) .
Oil in passage (62) is sent to boom I control valve (19) through passage (63), passage (39), and pilot line (24).