The stick lowering control valve has two functions:
- A check valve prevents the stick from falling if a hydraulic supply line or a supply tube to the stick cylinder fails.
- A manual valve allows the operator to manually lower the stick when the engine is shut down.
Note: The stick lowering control valve is supplied only when there is a boom lowering control valve.
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| Illustration 1 | g02165033 |
Simplified Hydraulic Schematic (1) Drain line for pilot system (2) Drain line for pilot system (3) Pilot line (4) Solenoid valve (5) Spool valve (6) Check valve (7) Spool valve (8) Relief valve (9) Manual valve for stick lowering (10) Return line (11) Supply line to rod end of stick cylinder (12) Check valve (13) Supply line to head end of stick cylinder (14) Stick cylinder (15) Stick lowering control valve | |
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| Illustration 2 | g02164453 |
Stick lowering control valve STICK IN (2) Drain line for pilot system (3) Pilot line (5) Spool valve (6) Check valve (7) Spool valve (8) Relief valve (9) Manual valve for stick lowering (10) Return line (11) Supply line from main control valve (12) Check valve (16) Port to rod end of stick cylinder | |
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| Illustration 3 | g02170775 |
Stick cylinder lines (2) Drain line for pilot system (3) Pilot line (8) Relief valve (10) Return line (11) Supply line to rod end of stick cylinder (15) Stick lowering control valve | |
Stick Out Operation
Refer to Systems Operation, "Main Control Valve - Operation" for an explanation of the operation of the stick control valve.
When the joystick for the stick is moved to the STICK OUT position, an electrical signal is sent to the machine ECM. The machine ECM sends an electrical signal to the proportional solenoid valve to shift the spool in the stick control valve. Pump oil flows through the stick control valve and into the rod end of stick cylinder (14) .
The oil in the head end of the stick cylinder flows through line (13) and back to the hydraulic tank through the stick control valve.
When the joystick for the stick is moved to the NEUTRAL position, the stick is held in the OUT position. Check valve (12) prevents the oil in the rod end of the stick cylinder from flowing out of the stick cylinder.
Stick In Operation
When the joystick for the stick is moved to the STICK IN position, an electrical signal is sent to the machine ECM. The machine ECM sends an electrical signal to the proportional solenoid valve to shift the spool in the stick control valve. Pump oil flows into the head end of the stick cylinder (14) .
The oil in the rod end of the stick cylinder (14) flows into stick lowering control valve (15). Solenoid valve (4) is energized when the STICK IN operation is initiated. Pilot oil flows from solenoid valve (4) through line (3). The pilot oil shifts valve (5) and valve (7). System oil drains from the spring chamber in check valve (6) through valve (7). The system oil drains from valve (7) through line (2) to the hydraulic tank. The oil from the rod end of the stick cylinder flows through check valve (6), valve (5), and line (11) to the stick control valve. The oil passes through the stick control valve and flows to the hydraulic tank.
Relief Operation of the Cylinder Head End
When the stick is pushed downward by an outside force the oil pressure in the rod end of the stick cylinder increases. The oil pressure is sensed at the relief valve (14) in the stick lowering control valve (15). When the relief valve opens, the oil flows back to the hydraulic tank.
Manual Stick Lower Operation
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| Illustration 4 | g02165273 |
Manual valve for stick lowering (17) Locknut (18) Piston (19) Ball | |
This function is used to manually lower the stick when the engine is shut down and pilot oil pressure is not supplied for stick lowering.
When locknut (17) and piston (18) are loosened, oil flows from the rod end of the cylinder to valve (9). The oil flows through valve (9) and through line (10) to the hydraulic tank.