The stick lowering control valve is on the rod end of the stick cylinder.
The stick lowering control valve has two functions:
- The stick lowering control valve prevents the stick from falling if a hydraulic supply line fails or if a supply tube to the stick cylinder fails.
- The stick lowering control valve allows the operator to manually lower the stick when the engine is shut down.
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| Illustration 1 | g06615253 |
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Partial schematic (STICK OUT) (1) Stick cylinder (2) Port to stick cylinder rod end (3) Stick lowering control valve (4) Port to main control valve (supply oil) (5) Drain port (6) Port to main control valve (pilot oil) (7) Pressure port (8) Stick cylinder head end pressure (9) Stick 2 cylinder extend solenoid (10) Main control valve (11) Stick 2 control valve (12) Stick 1 control valve (13) Stick cylinder rod end pressure (14) Stick 1 cylinder extend solenoid (15) Pilot pump (16) Pilot and drain manifold (17) Hydraulic tank (18) Pump 2 (19) Pump 1 | |
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| Illustration 2 | g06615256 |
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Stick Lowering Control Valve (2) Port to stick cylinder rod end (3) Stick lowering control valve (4) Port to main control valve (supply oil) (5) Drain port (6) Port to main control valve (pilot oil) (7) Pressure port | |
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| Illustration 3 | g06615254 |
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Stick out operation (2) Port to stick cylinder rod end (3) Stick lowering control valve (4) Port to main control valve (supply oil) (5) Drain port (6) Port to main control valve (pilot oil) (7) Pressure port (20) Passage (21) Relief valve (22) Passage (23) Passage (24) Orifice (25) Filter (26) Orifice (27) Passage (28) Passage (29) Valve (30) Spring (31) Check valve (32) Orifice (33) Passage | |
When the operator moves the joystick to the STICK OUT position, the pump oil flows from main control valve (10) through a line to port (4) of stick lowering control valve (3).
The pump oil flows into passage (28) and the pressure of the pump oil causes valve (29) to shift against spring (30). The pump oil flows through passage (28), valve (29), and passage (33) to port (2) to the stick cylinder rod end. The rod of stick cylinder (1) will retract to perform a STICK OUT.
When the joystick is returned to the NEUTRAL position, stick cylinder (1) is held in the OUT position. Valve (29) prevents the oil in the rod end of the stick cylinder (1) from flowing out.
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| Illustration 4 | g06615645 |
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Stick in operation (2) Port to stick cylinder rod end (3) Stick lowering control valve (4) Port to main control valve (supply oil) (5) Drain port (6) Port to main control valve (pilot oil) (7) Pressure port (20) Passage (21) Relief valve (22) Passage (23) Passage (24) Orifice (25) Filter (26) Orifice (27) Passage (28) Passage (29) Valve (30) Spring (31) Check valve (32) Orifice (33) Passage | |
When the operator moves the joystick to the STICK IN position, pump oil flows from main control valve (10) through lines that are ported to the head end of stick cylinder (1).
Simultaneously, pilot oil is provided to port (6) of stick lowering control valve (3). The pilot oil at port (6) will cause valve (29) to shift. Valve (29) will move against spring (30).
The oil in the rod end of stick cylinder (1) begins to flow to port (2) of stick lowering control valve (3). The oil then flows through passage (33), valve (29), passage (28), and to port (4). From port (4), the oil will flow through a line to main control valve (10). The head of stick cylinder (1) extends and the stick lowers.
When the joystick is returned to the NEUTRAL position, the loss of pilot oil pressure will allow spring (30) to shift valve (29) to close. Oil in the rod end of stick cylinder (1) is trapped and stick cylinder are held in position.
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| Illustration 5 | g06615694 |
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Manual stick lowering operation (2) Port to stick cylinder rod end (3) Stick lowering control valve (4) Port to main control valve (supply oil) (5) Drain port (6) Port to main control valve (pilot oil) (7) Pressure port (20) Passage (21) Relief valve (22) Passage (23) Passage (24) Orifice (25) Filter (26) Orifice (27) Passage (28) Passage (29) Valve (30) Spring (31) Check valve (32) Orifice (33) Passage | |
If a manual lower is desired, line relief valve (21) is adjusted to allow oil to flow from port (2) through the return passage and port (5) to the hydraulic tank. This return oil allows the stick to slowly lower.
Reference: For information on the location of the manual lower valve, see Operation and Maintenance Manual, "Equipment Lowering with Engine Stopped".