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| Illustration 1 | g02995877 |
Main control valve location | |
The main control valve is located on the front frame of the machine. The main control valve controls the flow of high-pressure oil to the implement cylinders.
Tilt Function
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| Illustration 2 | g03001096 |
Main control valve (tilt valve spool in the TILT BACK position and lift valve spool in the HOLD position) (1) Chamber for pilot oil (2) Springs (3) Spring (4) Makeup valve for the rod end of tilt cylinder (5) Passage to the rod end of the tilt cylinder (6) Passage to the head end of the tilt cylinder (7) Passage (8) Spring (9) Check valve for the tilt circuit (10) Inlet passage for implement pump oil (11) Tilt valve spool (12) Chamber for pilot oil (13) Passage (14) Passage (15) Outlet passage to the hydraulic tank (16) Lift valve spool | |
Oil from the implement pump flows through inlet passage (10) to tilt valve spool (11). On machines with an auxiliary control valve, pump oil flows to the auxiliary valve spool before the oil flows to the main control valve. Tilt valve spool (11) is spring centered. The tilt valve spool is controlled by pilot pressure oil. The tilt valve spool has an open center.
HOLD Position
Springs (2) keep tilt valve spool (11) in the HOLD position when there is no pilot pressure oil in chambers (1) and (12). Spool movement is controlled by pilot pressure oil in chambers (1) and (12) .
When tilt valve spool (11) is in the HOLD position, implement pump oil flows from inlet passage (10) to passage (14). The oil then flows through outlet passage (15) to the hydraulic tank. The position of the tilt valve spool prevents the flow of oil to passages (5) and (6). The tilt valve spool blocks the oil in both ends preventing the tilt cylinder from moving.
TILT BACK Position
When the joystick control lever is moved to the TILT BACK position, pilot oil flows to chamber (1). Tilt valve spool (11) moves to the right. Oil flows from inlet passage (10) to check valve (9) .
Check valve (9) does not open until oil pressure becomes greater than the combined force of spring (8) and oil pressure in passage (7). When the check valve opens, oil flows through passage (7) and out of passage (6) to the head end of the tilt cylinder. The bucket tilts back.
Oil from the rod end of the tilt cylinder flows in through passage (5). Oil from passage (5) flows around tilt valve spool (11) and through passage (13). The oil then flows around lift valve spool (16) and through outlet passage (15) to the hydraulic tank. Oil from rod end of tilt cylinder bypasses the lift circuit preventing simultaneous operation of tilting back the bucket and raising lift arms.
Note: When tilt valve spool (11) moves fully to the right, implement pump oil will not flow to lift valve spool (16). The lift circuit will not operate.
DUMP Position
When the joystick control lever is moved to the DUMP position, pilot oil flows to chamber (12). Tilt valve spool (11) moves to the left. Oil then flows from inlet passage (10) to check valve (9) .
Check valve (9) remains closed until oil pressure becomes greater than the combined force of spring (8) and oil pressure in passage (7). When check valve opens, oil flows through passage (7) and out of passage (5) to rod end of tilt cylinder causing the bucket to dump.
Oil from the head end of the tilt cylinder flows through passage (6). Oil from passage (6) flows around tilt valve spool (11) and through passage (13). Oil flows around lift valve spool (16) and through outlet passage (15) to hydraulic tank. The oil from the head end of tilt cylinder bypasses lift circuit preventing simultaneous operation of dumping the bucket and raising lift arms.
If the tilt cylinder retracts too fast, the implement pump cannot supply enough oil flow to the rod end of the tilt cylinder. The oil pressure then decreases in passage (5). This causes makeup valve (4) to move against spring (3) allowing the addition of return line oil to implement pump oil. Damage from cavitation (vacuum) in the hydraulic system is prevented.
Note: When tilt valve spool (11) is moved fully to the left, implement pump oil will not flow to lift valve spool (16). The lift circuit will not operate.
Lift Function
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| Illustration 3 | g02998284 |
Main control valve (tilt valve spool in the HOLD position and lift valve spool in the RAISE position) (10) Inlet passage for implement pump oil (11) Tilt valve spool (13) Passage (14) Passage (15) Outlet passage to the hydraulic tank (16) Lift valve spool (17) Chamber for pilot oil (18) Springs (19) Makeup valve for the rod end of the lift cylinders (20) Vent passage to the pilot valve (oil manifold) (21) Spring (22) Passage to the rod end of the lift cylinders (23) Passage to the head end of the lift cylinders (24) Passage (25) Check valve for the lift circuit (26) Spring (27) Chamber | |
Oil from the implement pump flows through inlet passage (10) and around tilt valve spool (11) before the oil reaches lift valve spool (16). On machines with an auxiliary control valve, pump oil flows to the auxiliary valve spool before the oil flows to the main control valve. Lift valve spool (16) is spring centered. The lift valve spool is controlled by pilot pressure oil. The lift valve spool has an open center.
HOLD Position
Springs (18) keep lift valve spool (16) in the HOLD position when there is no pilot pressure oil in chambers (17) and (27). Spool movement is controlled by pilot pressure oil in chambers (17) and (27) .
When lift valve spool (16) is in the HOLD position, implement pump oil flows from inlet passage (10) to passage (14). The oil then flows through outlet passage (15) to the hydraulic tank. The position of the lift valve spool prevents the flow of oil to passages (22) and (23). The lift valve spool blocks the oil in both ends of lift cylinder preventing the lift cylinder from moving.
RAISE Position
When the joystick control lever is moved to the RAISE position, pilot oil flows to chamber (17). This causes lift valve spool (16) to move to the right. Oil from the implement pump flows into inlet passage (10). The oil then flows through passage (14) to check valve (25) .
Check valve (25) remains closed until oil pressure becomes greater than the combined force of spring (26) and oil pressure in passage (24). When check valve (25) opens, oil flows through passage (24) and out of passage (23) to the head end of the lift cylinders. The lift arms raise.
Oil from the rod end of the lift cylinders flows through passage (22), and around lift valve spool (16). The oil then flows through passage (13) and passage (15) to the hydraulic tank.
LOWER Position
When the joystick control lever is moved to the LOWER position, pilot oil flows to chamber (27). Lift valve spool (16) moves to the left. Oil from the implement pump flows from inlet passage (10), through passage (14), and to check valve (25) .
Check valve (25) remains closed until oil pressure becomes greater than the combined force of spring (26) and oil pressure in passage (24). When check valve (25) opens, oil flows through passage (24) and passage (22) to the rod end of the lift cylinders. The lift arms lower.
Oil from the head end of the lift cylinders flows through passage (23), and around lift valve spool (16). The oil then flows through outlet passage (15) to the hydraulic tank.
Should the lift cylinder rod retract too fast, the implement pump cannot supply enough oil flow to the rod end of the lift cylinder. The pressure then decreases in passage (22). This causes makeup valve (19) to move against spring (21) allowing the addition of return line oil to implement pump oil. Damage from cavitation (vacuum) in the hydraulic system is prevented.
FLOAT Position
When joystick control lever is moved to FLOAT position, pilot oil flows to chamber (27) and lift valve spool (16) moves to the left. Oil from the pilot valve (oil manifold) opens vent passage (20) allowing makeup valve (19) to open.
Implement oil pressure keeps makeup valve (19) open. The oil from passage (24) and the oil in passage (22) flow through passage (13). The oil then flows through outlet passage (15) to the hydraulic tank.
The lift cylinders can move freely in either direction according to the force on the bucket. As the lift cylinder moves, excess oil from the lift cylinders flows to passage (15). The oil then flows to the hydraulic tank.
Auxiliary Function
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| Illustration 4 | g03001036 |
Auxiliary control valve (auxiliary valve spool in the HOLD position and main control valve spools in the HOLD position) (11) Tilt valve spool (15) Outlet passage to the hydraulic tank (16) Lift valve spool (28) Chamber for pilot oil (29) Springs (30) Auxiliary valve spool (31) Passage (32) Spring (33) Check valve for the auxiliary circuit (34) Inlet passage for implement pump oil (35) Chamber for pilot oil (36) Passage to the drain (37) Passage to the head end of the auxiliary cylinders (38) Passage to the rod end of the auxiliary cylinders (39) Passage for implement pump oil | |
The auxiliary control valve is added for machines with auxiliary attachments. The auxiliary control valve bolts to the main control valve. Auxiliary valve spool (30) controls the operation of an auxiliary attachment such as an ejector bucket. The auxiliary control valve is ahead of the main control valve in the implement hydraulic circuit.
Oil from the implement pump flows through inlet passage (34) to auxiliary valve spool (30). The auxiliary valve spool is spring centered. The auxiliary valve spool is controlled by pilot pressure oil. The auxiliary valve spool has an open center.
HOLD Position
Springs (29) keep the auxiliary valve spool in the HOLD position when there is no pilot pressure oil in chambers (28) and (35). Spool movement is controlled by pilot pressure oil in chambers (28) and (35) .
When auxiliary valve spool (30) is in the HOLD position, implement pump oil flows from inlet passage (34) to passage (39). Oil from passage (39) then flows around the tilt valve spool and the lift valve spool. The oil then flows through outlet passage (15) to the hydraulic tank.
The position of the auxiliary valve spool prevents the flow of oil to passages (37) and (38). This blocks the oil in both ends of the auxiliary cylinders. The auxiliary cylinders will not move.
RETRACT Position
When the auxiliary control lever is moved to the RETRACT position, pilot oil is sent to chamber (28). Auxiliary valve spool (30) moves to the right. Implement pump oil flows from inlet passage (34) to check valve (33) .
Check valve (33) Remains closed until oil pressure becomes greater than the combined force of spring (32) and oil pressure in passage (31). When check valve (33) opens, oil flows through passage (31) and out of passage (38) to the rod end of the auxiliary cylinders. The auxiliary cylinder rods retract.
Oil from the head end of the auxiliary cylinders flows through passage (37), and around auxiliary valve spool (30). The oil then flows through passage (36), and through outlet passage (15) to the hydraulic tank.
Note: When auxiliary valve spool (30) is moved fully in RETRACT position, oil will not flow to tilt control spool or lift control spool. The tilt cylinder and the lift cylinders will not operate.
EJECT Position
When the auxiliary control lever is moved to the EJECT position, pilot oil is sent to chamber (35). Auxiliary valve spool (30) moves to the left. Implement pump oil flows from inlet passage (34) to check valve (33) .
Check valve (33) does not open until the oil pressure becomes greater than the force of spring (32) and the oil pressure in passage (31). When check valve (33) opens, oil flows through passage (31) and out of passage (37) to the head end of auxiliary cylinder. The auxiliary cylinder rods extend.
Oil from the rod end of the auxiliary cylinder flows in through passage (38), and around auxiliary valve spool (30). The oil then flows through passage (39), and through outlet passage (15) to the hydraulic tank.
Note: When auxiliary valve spool (30) is moved fully to EJECT position, the following will occur. Pressure oil from rod end of auxiliary cylinders will be available to tilt control spool and lift control spool. The tilt circuit and the lift circuit will operate more slowly than normal.