HOSE AS 1764774 - Caterpillar

Boom Lower - Long Reach Front
Illustration 2 g03807085
Long Reach Hydraulic Partial Schematic for Boom LOWER (1) Right joystick (boom) (2) Left joystick (stick) (3) Boom cylinders (4) Stick cylinder (5) Boom DOWN control pressure sensor (8) Pressure reducing valve for boom priority (9) Proportional reducing valve (Boom DOWN) (10) Proportional reducing valve (Stick IN) (13) Boom 1 control valve (14) Boom 2 control valve (15) Main relief valve (16) Drive pump (17) Idler pump (18) Pilot pump (19) Hydraulic tank (20) Pilot manifold (21) Boom regeneration valve (22) Pilot line (23) Proportional solenoid valve for boom regeneration valve (24) Boom drift reduction valve (25) Center bypass passage (26) Parallel feeder passage (27) Valve (28) Pilot line (29) Passage (30) Drain line (31) Valve (32) Passage (33) Check valveDuring a BOOM LOWER operation, the oil delivery from only drive pump (16) is supplied to boom cylinders (3) through boom I control valve (13) . Boom I control valve (13) operates alone. Boom II control valve (14) is not operational in the BOOM LOWER operation.The BOOM LOWER operation contains a regeneration circuit. When the joystick for the boom is moved to the BOOM LOWER position, control valve (13) and boom regeneration valve (21) are operational in the boom hydraulic circuit. The return oil flow from the head end of boom cylinders (3) flows through boom regeneration valve (21) to the rod end of the boom cylinders. The boom regeneration valve is described later in this section.When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (1) flows through pilot line (22) . The pilot oil flow then divides into three flow paths. Part of the pilot oil flows through proportional reducing valve (9) to boom I control valve (13) . Part of the pilot oil flows through the proportional solenoid valve for boom regeneration valve (23) to boom regeneration valve (21) . The remainder of the pilot oil flows through to boom drift reduction valve (24) .Since the pilot oil pressure has caused the spool in boom I control valve (13) to shift, the oil delivery from the drive pump that flows through center bypass passage (25) is restricted by the orifice in boom I control valve (13) . The negative flow control pressure in negative flow control line decreases. The drive pump upstrokes because of the negative flow control operation.ReferenceFor more information concerning the negative flow control operation, refer to Systems Operation, "Negative Flow Control System".The pilot oil shifts the spool in boom I control valve (13) . The oil delivery from the drive pump in parallel feeder passage (26) flows through boom I control valve (13) . The oil delivery from the drive pump then flows to the rod end of boom cylinders (3) .The return oil from the head end of boom cylinders (3) flows into boom drift reduction valve (24) . Since valve (27) is shifted by the pilot pressure from pilot line (28) , passage (29) is