HOSE AS 1538372 - Caterpillar

Pilot oil from the pilot control valves flows through pilot lines to the ports on the right side of main control valve (3) in order to perform the opposite operation.The following example is given for the BOOM LOWER operation and the BOOM RAISE operation. Machine operations for a stick operation, bucket operation, travel operation, and swing operation are accomplished in the same manner as the boom operation.When the joystick for the boom is moved to the BOOM RAISE position, pilot oil from pilot control valve (2) flows through pilot line (21) to boom I control valve (33) and boom II control valve (34). The pilot pressure shifts boom I control valve (33) and boom II control valve (34). The oil delivery from drive pump (19) flows to the head end of the boom cylinders in order to perform the BOOM RAISE operation.When the joystick for the boom is moved to the BOOM LOWER position, pilot oil from pilot control valve (2) flows through pilot line (29) to boom I control valve (33). The pilot pressure shifts boom I control valve (33). The BOOM LOWER operation is now performed.For more information concerning the operation of the boom, refer to Systems Operation, "Boom Hydraulic System".Pressure Switch Circuits
Pressure switches (42) and (43) are connected to travel pilot control valve (28). Pressure switch (9) is connected to pilot control valve (1) and pilot control valve (2). When all of the joysticks and/or travel levers/pedals are in the NEUTRAL position, the pilot oil pressure to the pressure switches is low. Pressure switches (42), (43), and (9) are OFF. Machine ECM (59) recognizes the OFF condition of all of the pressure switches. The AEC system is activated in order to lower the engine rpm.If any of the joysticks and/or travel levers/pedals are moved from the NEUTRAL position, the increased pilot oil pressure is sent to the pressure switches. If pressure switch (42), (43), and/or (9) is ON, machine ECM (59) activates the AEC system in order to increase the engine rpm.If both travel levers/pedals and either one of the joysticks are moved from the NEUTRAL position simultaneously, pilot oil pressure will cause pressure switches (42), (43), and (9) to be in the ON position. An electrical signal is sent to machine ECM (59). Machine ECM (59) energizes straight travel solenoid (54). Pilot pressure now activates straight travel control valve (37).Straight travel control valve (37) provides hydraulic oil flow to travel control valves (36) and (35) from drive pump (19). Idler pump (25) supplies all oil delivery to the remaining valves within main control valve (3).If the machine is equipped with a straight travel pedal, there will be a separate pressure switch that sends a signal to machine ECM (59). A signal is sent to machine ECM (59) in order to energize straight travel solenoid (54) when the straight travel pedal is moved from the NEUTRAL position.For more information concerning the operation of the straight travel control valve, refer to Systems Operation, "Control Valve (Straight