PUMP 0777183 - Caterpillar

Illustration 1 g00567909
(1) Load control valve for the loader lift circuit (if equipped), (2) Lift cylinder and (3) Lift armsTwo load control valves (if equipped) for the lift circuit are used. The control valves are used in order to hold the lift arms in place in case of a hose failure in the loader lift circuit.One load control valve for the lift circuit is located on each lift cylinder.
Illustration 2 g00839321
(1) Line to the rod end of the loader lift cylinder, (2) Line to the head end of the loader lift cylinder, (3) Shutoff valve, (4) Line to the control valve, (5) Line to the control valve, (6) Check valve, (7) Check valve, (8) Relief valve and (9) Relief valveThe operator moves the control for the loader in order to move the lift arms to the RAISE position. The oil flows from the control valve to line (4). The oil flows past check valve (6) and the oil flows into the head end of the loader lift cylinder. The oil in the rod end of the cylinder flows through check valve (7) and through the orifice. This causes the rod to extend. As the rod extends this causes the loader lift arms to raise.The operator moves the control for the loader in order to move the lift arms to the LOWER position. The oil flows from the control valve to lines (5). The oil is blocked at check valve (7). The oil flows to the relief valve (8) and the oil flows to the orifice. As the pressure rises the valve opens and the valve sends oil to the rod end of lift cylinder (1). The pressure in the line to the control valve (5) also acts as a signal to open the relief valve (9) at the head end. When the relief valve opens, the oil in the head end of the cylinder flows back to the tank. This causes the rod to retract. As the rod retracts, the loader lift arms lower.In the HOLD position, check valve (6), relief valve (8) and shutoff valve (3) cause the oil to be blocked in the head end of the cylinder. This will prevent the loader lift arms from falling in case of a hose failure in the loader lift circuit.Move the control for the loader to the FLOAT position. Lock valve (3) opens in order to allow the oil in line (2) to flow back to the tank.Shutoff valve (3) opens under any of the following conditions:
The loader control is placed in the FLOAT position.
The ride control (If equipped) is activated.
The dead engine lower switch (If equipped) is activated.If there is a loss of hydraulic power, refer to the Operation and Maintenance Manual for the proper procedure to lower the implements.