BRACKET AS 3577840 - Caterpillar

When the lift control lever is moved to the fast LOWER position, the position sensor for the tilt control lever sends a pulse width modulated signal (PWM) to the implement electronic control module (ECM). The implement ECM analyzes this signal and the signals from the tilt linkage position sensor and from the lift linkage position sensor. The implement ECM then sends a signal that energizes the solenoid for (12) pilot control actuator on the main control valve (left). The implement ECM also sends a signal that energizes the solenoid for the pilot control actuator (15) on the main control valve (right). The signals may be of different proportions.The solenoid valves in pilot control actuator (12, 15) will shift. The pilot oil at the end of both stems (19, 22) is released to hydraulic tank (48). This reduces the pilot pressure at the end of the stems (19, 22). The combination of the spring force and the oil pressure on stems (19, 22) will shift the stems to the LOWER position.The oil from fixed displacement piston pump (40) flows around stem 19 in the main control valve (left) to the rod end of lift cylinders (1). Also, the oil from variable displacement piston pump (46) flows around stem (22) in the main control valve (right) to the rod end of lift cylinders (1) .The oil from the head end of lift cylinders (1) flows around stems (19, 22) to the hydraulic tank. The flow of return oil through each stem is proportional to the flow of supply oil that is flowing through each stem.The desired speed of the lift cylinders determines the difference in oil flow between the fixed displacement piston pump (40) and variable displacement piston pump (46). A slower speed will cause a larger difference in oil flow than a faster speed.Float Position
Illustration 6 g01056922
Hydraulic System Operation (1) Lift cylinders (2) Tilt cylinder (3) Pressure reducing valve (4) Shuttle valve (5) Rod end line relief valve for the lift cylinders (6) Head end line relief valve for the lift cylinders (7) Rod end line relief valve for the tilt cylinder (8) Head end line relief valve for the tilt cylinder (9) Relief valve for the fixed displacement piston pump (10) Backup relief valve for the variable displacement piston pump (11) Head end line relief valve for the tilt cylinder (12) Pilot control actuator (LOWER) (13) Pilot control actuator (TILT BACK) (14) Pilot control actuator (TILT BACK) (15) Pilot control actuator (LOWER) (16) Ride control Accumulators (17) Solenoid valve (hydraulic lockout) (18) Ride control valve (19) Lift stem (left) (20) Tilt stem (left) (21) Tilt stem (right) (22) Lift stem (right) (23) Float sequence valve (24) Float check valve (25) Float check valve (26) Solenoid valve (variable displacement piston pump) (27) Pilot control actuator (RAISE) (28) Pilot control actuator (DUMP) (29) Pilot control actuator (DUMP) (30) Pilot control actuator (RAISE) (31) Pilot relief valve (32) Pilot oil filter (33) High pressure screen (If equipped) (34) High pressure screen