COMPONENT OPERATION / Control Valve

Hydraulic Circuit

Main Circuit

The main circuit contains a parallel circuit, which enables combined operations.

The main circuit (between the pump and the cylinder) is provided with the main relief valve. The main relief valve prevents the pressure in main circuit from increasing over the set pressure when the spool is in operation (or when the control lever is in operation).

The overload relief valves are provided in the bucket circuit and the auxiliary (coupler) circuit (between the control valve and the cylinder). The overload relief valve prevents circuit pressure developed by external loads in the front attachment circuit from increasing over the set pressure when the spool is in neutral (when the control lever is neutral).

The make-up valve is provided in the lift arm lower circuit (between the control valve and the cylinder). When pressure in the lift arm lower circuit decreases, the make-up valve draws oil from the hydraulic oil tank and prevents cavitation.

COMPONENT OPERATION / Control Valve

COMPONENT OPERATION / Control Valve

Operation

When bucket is in neutral

• Bucket spool (1) blocks cylinder port A1 (rod side) and port B1 (bottom side) when the loader control lever is in neutral (N) position.

Pressure oil from main circuit (2) is routed to drain circuit (4) and the hydraulic oil tank through neutral circuit (3). Consequently, the bucket cylinder rod is kept at this position.

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When bucket tilts

Operation:

COMPONENT OPERATION / Control Valve

1. Bucket spool (1) moves to the right (illustrated below) when the loader control lever is in the TILT position.

2. Pressure oil from main circuit (2) is routed to the bucket cylinder bottom side from port B1 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the bucket cylinder rod side is routed to drain circuit (4) and the hydraulic oil tank through port A1.

4. Consequently, the bucket cylinder rod is extended so that the bucket tilts.

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COMPONENT OPERATION / Control Valve

When bucket dumps

Operation:

1. Bucket spool (1) moves to the left (illustrated below) when the loader control lever is in the DUMP position

2. Pressure oil from main circuit (2) is routed to the bucket cylinder rod side from port A1 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the bucket cylinder bottom side is routed to drain circuit (4) and the hydraulic oil tank through port B1.

4. Consequently, the bucket cylinder rod is retracted so that the bucket dumps.

COMPONENT OPERATION / Control Valve

When lift arm is in neutral

• Lift arm spool (1) blocks cylinder port A2 (rod side) and port B2 (bottom side) when the loader control lever is in the neutral (N) position. Pressure oil from main circuit (2) is routed to drain circuit (4) and the hydraulic oil tank through neutral circuit (3). Consequently, the lift arm cylinder is kept in that position.

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When lift arm raises

Operation:

COMPONENT OPERATION / Control Valve

1. Lift arm spool (1) moves to the right (illustrated below) when the loader control lever is in the RAISE position.

2. Pressure oil from main circuit (2) is routed to the lift arm cylinder bottom side from port B2 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the lift arm cylinder rod side is routed to drain circuit (4) and the hydraulic oil tank through port A2.

4. Consequently, the lift arm cylinder rod is extended so that the lift arm raises.

COMPONENT OPERATION / Control Valve

When lift arm lowers

Operation:

1. Lift arm spool (1) moves to the left (illustrated below) when the loader control lever is in the LOWER position.

2. Pressure oil from main circuit (2) is routed to the lift arm cylinder rod side from port A2 through load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the lift arm cylinder bottom side is routed to drain circuit (4) and the hydraulic oil tank through port B2.

4. Consequently, the lift arm cylinder rod is retracted so that the lift arm lowers.

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When lift arm floats

Operation:

COMPONENT OPERATION / Control Valve

• Lift arm spool (1) moves to the left (illustrated below) when the loader control lever is in the FLOAT position.

• Pressure oil from main circuit (2) is routed to drain circuit (4) and the hydraulic oil tank through neutral circuit (3). In addition, port A2 and port A1 are connected to drain circuit (4) so that pressure oil is also routed to the lift arm cylinder bottom and rod sides.

• Therefore, pressure oil in the lift arm cylinder bottom and rod sides are routed to drain circuit (4) and the hydraulic oil tank through port A2 and port A1.

• Consequently, the lift arm cylinder rod is extend or retracted freely by the external force.

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COMPONENT OPERATION / Control Valve

When coupler pin is locked

Operation:

1. Bucket spool (1) moves to the right (illustrated below) when the auxiliary control lever is in the INSTALLATION position.

2. Pressure oil from main circuit (2) is routed to the coupler cylinder bottom side through port B3 and load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the coupler cylinder rod side is routed to drain circuit (4) and the hydraulic oil tank through port A3.

4. Consequently, the coupler cylinder rod is extended so that the coupler pin is inserted into the pin hole of the bucket.

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COMPONENT OPERATION / Control Valve

When coupler pin is unlocked

Operation:

1. Auxiliary spool (1) moves to the left (illustrated below) when the auxiliary control lever is in the REMOVAL position.

2. Pressure oil from main circuit (2) is routed to the coupler cylinder rod side through port A3 and load check valve (5) as neutral circuit (3) is blocked.

3. Therefore, pressure oil in the coupler cylinder bottom side is routed to drain circuit (4) and the hydraulic oil tank through port B3.

4. Consequently, the coupler cylinder rod is retracted so that the coupler pin comes out from the pin hole of the bucket. T4FGE-03-02-010

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