- Load Haul Dump:
- R2900G (S/N: JLK865-UP)
The hydraulic schematic for the main hydraulic system has incorrect information. Replace the information with the following information.
Main Hydraulic System
S/N: JLK865-UP
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| Illustration 1 | g01515694 |
Schematic for the hydraulic system (1) Main control valve (2) Line relief valve for rod end of tilt cylinder (3) Line relief valve for head end of tilt cylinder (4) Pressure tap for rod end of tilt cylinder (5) Tilt cylinder (6) Lift cylinders (7) Ride control accumulator (8) Ride control diverter valve (9) Pressure tap for head end of tilt cylinder (10) Lift circuit relief valve (11) Ride control relief valve (12) Implement and steering solenoid valve (13) Ride control solenoid valve (14) Main relief valve (15) Parking brake solenoid valves (16) Parking brake oil pressure switch (17) Pressure tap for the parking brake circuit (18) Check valve (19) Lift arm positioner valve (20) Float sequence valve (21) Line circuit remote control (22) Selector and pressure control valve (23) Line to parking brakes (24) Line from steering circuit (25) Pilot control valve (26) Brake accumulator charging valve (27) Breaker relief valve (28) Check valve (29) Portable hydraulic pump quick connect coupler (30) Line to brake accumulator (31) Pilot and braking pump (32) Steering pump (33) Implement pump (34) Hydraulic filters (35) Hydraulic tank (36) Pilot relief valve (37) Pilot system pressure tap (38) Pilot oil filter (39) Check valve (40) Portable hydraulic pump quick connect coupler | |
Tilt Circuit
Line relief valves (2) and (3) protect tilt cylinder (5) from external shocks. When the pressure in the tilt cylinder exceeds the setting of either line relief valve, the line relief valves open to relieve the excess pressure to hydraulic tank (35) .
TILT BACK Operation
When the engine is running with the joystick control lever in the HOLD position, pilot and braking pump (31) takes oil from hydraulic tank (35) and sends oil through check valve (39) to brake accumulator charging valve (26). Brake accumulator charging valve (26) divides pump flow between the brake accumulator circuit and the pilot circuit. Oil flows from brake accumulator charging valve (26) to pilot oil filter (38) then flows to pilot relief valve (36). Pilot oil relief valve (36) maintains the pilot system at a constant pressure. The pilot oil then flows through check valve (28) to selector and pressure control valve (22), implement and steering solenoid valve (12) and pilot control valve (25). The valve stems in pilot control valve (25) stop the flow of oil through the valve in the HOLD position. Excess oil flows from pilot relief valve (36) and returns to hydraulic tank (35) .
Implement pump (33) sends oil to main relief valve (14) which controls the maximum pressure in the implement oil system.
With both valve spools of main control valve (1) in their HOLD positions oil flows through the main control valve, through hydraulic filters (34) to hydraulic tank (35). If the hydraulic filters becomes full of foreign material (debris), the filter bypass valve (in the filter group) will open and let the return oil flow directly into the hydraulic tank.
When the joystick control lever is moved to the TILT BACK position, pilot control valve (25) tilt back stem moves to the TILT BACK position. Pilot oil is now free to flow through pilot control valve (25) to the tilt back end of the tilt control valve spool. This causes the tilt control valve spool to move. The pilot oil at the dump end of the tilt control valve spool flows back to pilot control valve (25), through the pilot valve dump stem to hydraulic tank (35) .
The movement of the tilt control valve spool stops the flow of oil through main control valve (1). Implement pump pressure increases and opens the load check valve. The oil from implement pump (33) now flows to the head end of tilt cylinder (5) and causes the cylinder rod to extend. The Z-bar linkage causes the bucket to tilt back. The movement of the cylinder piston and rod pushes the oil out of the rod end of tilt cylinder (5). This oil flows into main control valve (1) and returns to hydraulic tank (35) .
When released, the joystick control lever and the dump stem returns to the HOLD position causing the flow of pilot oil to be stopped. The springs on the tilt control valve spool move the valve spool back to the HOLD position. The pilot oil at the tilt back end of the tilt control valve spool flows back to pilot control valve (25), through the tilt back stem and returns to hydraulic tank (35) .
The implement oil in tilt cylinder (5) is held by the tilt control valve spool and movement of the cylinder piston and rod stops. The bucket will stay at that angle until the joystick control lever is moved again.
DUMP Operation
When the joystick control lever is moved to the DUMP position, pilot control valve (25) dump stem moves to the DUMP position. Pilot oil is now free to flow through pilot control valve (25) to the dump end of the tilt control valve spool. This causes the tilt control valve spool to move. The pilot oil at the tilt back end of the tilt control valve spool flows back to the tilt back stem of pilot control valve (25) and returns to hydraulic tank (35) .
The movement of the tilt control valve spool stops the flow of oil through main control valve (1). Implement pump pressure increases and opens the load check valve. The oil from implement pump (33) now flows to the rod end of tilt cylinder (5) and causes the cylinder rod to retract. The Z-bar linkage causes the bucket to dump.
The movement of the cylinder piston and rod pushes the oil out of the head end of the tilt cylinder. This oil flows into main control valve (1) and returns to hydraulic tank (35) .
When released, the joystick control lever and the dump stem returns to the HOLD position causing the flow of pilot oil to be stopped. The springs on the tilt control valve spool move the valve spool back to the HOLD position. The pilot oil at the dump end of the tilt control valve spool flows back to the dump stem in pilot control valve (25) and returns to hydraulic tank (35) .
The implement oil in tilt cylinder (5) is held by the tilt control valve spool and movement of the cylinder piston and rod stops. The bucket is held in the DUMP position until the joystick control lever is moved again.
DUMP Operation with engine off
When the lift arms are raised, the bucket can be dumped with the engine off. The pilot oil supply comes from the head end of the lift cylinders. This oil flows through check valve (18) to selector and pressure control valve (22) which decreases the pressure of the oil to pilot oil pressure. The oil flows to implement and steering solenoid valve (12) and then to pilot control valve (25). When the joystick control lever is moved to the DUMP position, the oil flows to the tilt control valve spool and moves it to the DUMP position. The head end of tilt cylinder (5) is now open to hydraulic tank (35). The make-up valve in main control valve (1) opens so that the rod end of tilt cylinder (5) is also open to hydraulic tank (35). The weight of the bucket causes the bucket to dump.
Note: When the engine is off and the lift arms are raised, the lift arms can also be lowered.
Lift Circuit
Lift circuit relief valve (10) protects lift cylinders (6) from external shocks when the lift control valve spool is in the HOLD position. When the pressure in lift cylinders (6) exceeds the setting of lift circuit relief valve (10), the relief valve opens, permitting movement of the lift cylinders and allowing high pressure oil to return to hydraulic tank (35). This prevents damage to the machine components.
RAISE Operation
When the engine is running with the joystick control lever in the HOLD position, pilot and braking pump (31) takes oil from hydraulic tank (35) and sends it through check valve (39) to brake accumulator charging valve (26). Brake accumulator charging valve (26) divides pump flow between the brake accumulator circuit and the pilot circuit. Oil flows from brake accumulator charging valve (26) to pilot oil filter (38) then flows to pilot relief valve (36). Pilot oil relief valve (36) reduces the pilot and braking pump oil to the specified pilot pressure. The pilot oil then flows through check valve (28), to selector and pressure control valve (22), implement and steering solenoid valve (12) and pilot control valve (25). The valve stems in pilot control valve (25) stop the flow of oil through the valve in the HOLD position. Excess oil flows from pilot relief valve (36) and returns to hydraulic tank (35) .
With both the control valve spools of main control valve (1) in the HOLD position oil flows through the main control valve, through hydraulic filters (34) and returns to hydraulic tank (35). If the oil filters become full of foreign material (debris), the filter bypass valve (in the filter group) will open and let the return oil go directly into the hydraulic tank.
When the joystick control lever is moved to the RAISE position, the lift stem in pilot control valve (25) moves to the RAISE position. Pilot oil is now free to flow through pilot control valve (25) to the raise end of the lift control valve spool. This causes the lift control valve spool to move. The pilot oil at the lower end of the lift control valve spool flows back to the lower stem in pilot control valve (25) and returns to hydraulic tank (35) .
The movement of the lift control valve spool stops the flow of oil through main control valve (1). The implement pump pressure increases and opens the load check valve in main control valve (1). The oil from implement pump (33) now flows to the head end of lift cylinders (6) and causes the cylinder rods to extend. The lift arms cause the bucket to lift.
The movement of the cylinder pistons and rods pushes the oil out of the rod end of the lift cylinders. This oil flows into main control valve (1) and returns to hydraulic tank (35) .
When released, the joystick control lever and the dump stem returns to the HOLD position causing the flow of pilot oil to be stopped. The springs on the lift control valve spool moves the valve spool to the HOLD position. The pilot oil at the lift end of the lift control valve spool flows back through pilot control valve (25) and returns to hydraulic tank (35). The implement oil in lift cylinders (6) is held by the lift control valve spool and movement of the cylinder pistons and rods stops. The lift arms and bucket are held until the joystick control lever is moved again.
LOWER Operation
When the joystick control lever is moved to the LOWER position, pilot control valve (25) lower stem moves to the LOWER position. Pilot oil is now free to flow through pilot control valve (25) to the lower end of the lift control valve spool. This causes the lift control valve spool to move. The pilot oil at the raise end of the lift control valve spool flows back to pilot control valve (25) lift stem and returns to hydraulic tank (35) .
The movement of the lift control valve spool stops the flow of oil through main control valve (1). Implement pump (33) pressure increases and opens the load check valve. The oil from implement pump (33) now flows to the rod end of lift cylinders (6) and causes the cylinder rods to retract. The lift arms cause the bucket to lower. The movement of the cylinder pistons and rods pushes the oil out of the head end of the lift cylinders. This oil flows into main control valve (1) and returns to hydraulic tank (35) .
When released, the joystick control lever and the lower stem returns to the HOLD position. The flow of pilot oil through pilot control valve (25) is stopped. The springs on the lift control valve spool move the valve spool back to the HOLD position. The pilot oil at the lower end of the lift control valve spool flows back to pilot control valve (25) and returns to hydraulic tank (35). The implement oil in lift cylinders (6) is held by the lift control valve spool and movement of the cylinder pistons and rods stops. The bucket is held in the lowered position until the joystick control lever is moved again.
FLOAT Operation
When the joystick control lever is moved to the FLOAT position, pilot control valve (25) lower stem moves to the FLOAT position. The flow of oil to the lift control valve spool is the same as in the LOWER position. The extra movement of the lower stem allows greater pilot pump oil pressure into the line to the lift control valve spool. This pressure is also felt in float sequence valve (20). This pressure moves the spool in float sequence valve (20), which allows oil in the spring chamber of the make-up valve in main control valve (1) to vent (drain) to hydraulic tank (35). This permits the make-up valve to open and lets implement oil flow directly to hydraulic tank (35). The head end and rod end of lift cylinders (6) are also open to hydraulic tank (35). Outside forces on the bucket will control the movement of the lift cylinder pistons and rods.
When the joystick control lever is released it will return to the HOLD position.
LOWER Operation with engine off
The bucket can be lowered with the engine off. The pilot oil supply comes from the head end of the lift cylinders. This oil flows through check valve (18) to selector and pressure control valve (22) which decreases the pressure of the oil to pilot oil pressure. The oil flows to implement and steering solenoid valve (12) and then flows to pilot control valve (25). When the joystick control lever is moved through the LOWER position and on to the FLOAT position, the lower stem moves to FLOAT position. Pilot oil flows to the lift control valve spool and moves it to the (LOWER) position. The head end of lift cylinders (6) is now open to hydraulic tank (35). The make-up valve in main control valve (1) opens so that the rod ends of lift cylinders (6) are also open to hydraulic tank (35). The weight of the bucket and lift arms causes the bucket to lower to the ground.
Note: When the engine is off and the lift arms are raised, the bucket can also be dumped.