HOLD Position
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| Illustration 1 | g00875333 |
HOLD position for the stick valve (1) Head end line relief valve, (2) Spool, (3) Chamber for pilot oil, (4) Spring, (5) Passage to tank, (6) Signal passage, (7) Chamber, (8) Load check valve, (9) Passage, (10) Pump passage, (11) Hole, (12) Passage, (13) Hole, (14) Spring, (15) Chamber, (16) Signal passage, (17) Passage to tank, (18) Signal line to the next valve, (19) Secondary resolver, (20) Signal line from the previous valve, (21) Primary resolver, (22) Chamber for pilot oil, (23) Spring, (24) Rod end line relief valve, (25) Port to rod end, (26) Passage, (27) Stick cylinder, (28) Check valve, (29) Passage, (30) Port to head end, (31) Pilot passage, (32) Chamber, (33) Piston, (34) Ball check valve, (35) Chamber, (A) Pump oil, (B) Return oil, (C) Blocked oil and (D) Pilot oil | |
The control valve for the stick is located between the control valve for the bucket and the control valve for the extendable stick.
Pilot oil in chamber (3) and chamber (22) is vented back to the tank through the pilot valve in the HOLD position.
In the HOLD position, spool (2) blocks pressure oil in passage (12) from flowing to passages (26) and (29). Spool (2) is centered by springs (4) and (23) .
Supply oil flows into the valve through passage (10). Passage (10) is common in all sections of the valves and the passage has no outlet. Oil flows into passage (9) through hole (11) in load check valve (8). The oil then flows into chamber (7) .
Pressure in chamber (7) rises and the pressure acts against load check valve (8). When the pressure overcomes the force of the spring (14) and the pressure in chamber (15), the pressure causes load check valve (8) to move to the left.
As the load check valve (8) moves to the left, oil flows from passage (10) into passage (12). The oil in passage (12) is blocked by spool (2) until the operator moves the control lever.
The oil in passage (12) enters hole (13). The oil flows into chamber (15). The combination of oil in chamber (15) and the spring (14) cause the load check valve (8) to move to the right. Load check valve (8) blocks oil from entering passage (12).
Passage (6) is open to the tank through passage (5). Passage (16) is open to the tank through passage (17). The return to the tank passage is common in all control valves.
The check valve (28) blocks the oil in port (25). The spool (2) blocks the oil in port (30) .
STICK OUT Position
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| Illustration 2 | g00875334 |
STICK OUT position for the stick valve (1) Head end line relief valve, (2) Spool, (3) Chamber for pilot oil, (4) Spring, (5) Passage to tank, (6) Signal passage, (7) Chamber, (8) Load check valve, (9) Passage, (10) Pump passage, (11) Hole, (12) Passage, (13) Hole, (14) Spring, (15) Chamber, (16) Signal passage, (17) Passage to tank, (18) Signal line to the next valve, (19) Secondary resolver, (20) Signal line from the previous valve, (21) Primary resolver, (22) Chamber for pilot oil, (23) Spring, (24) Rod end line relief valve, (25) Port to rod end, (26) Passage, (27) Stick cylinder, (28) Check valve, (29) Passage, (30) Port to head end, (31) Pilot passage, (32) Chamber, (33) Piston, (34) Ball check valve, (35) Chamber, (A) Pump oil, (B) Return oil, (C) Blocked oil and (D) Pilot oil | |
When the operator places the joystick into the STICK OUT position, pilot oil flows into chamber (22). The pilot oil in chamber (22) compresses spring (4). This allows the spool (2) to move to the right.
For a given amount of lever movement, spool (2) will move a proportional amount because of the pilot oil that is sent into chamber (22) .
Pump oil from passage (12) flows around spool (2) and into passage (26). Oil in signal passage (16) is blocked from entering the passage to the tank (17). Oil in signal passage (16) senses the pressure in port (26). The oil in signal passage (16) flows to the primary resolver (21) .
The oil in the primary resolver (21) flows to the secondary resolver (19) and to the pump. This causes the pump to increase flow.
Load check valve (8) compares the pressure in chamber (7) to the signal pressure in chamber (15) and spring (14). When the pressure in chamber (7) is greater than the pressure in chamber (15) and force of spring (14) combined, load check valve (8) will move down and oil will be directed to chamber (26). Spool (2) controls the amount of flow into passage (26) that is desired.
As the pressure in passage (26) rises, the pressure opens check valve (28). Check valve (28) allows oil to flow into the port for the rod end of the stick cylinder (25). This will cause the rod of the stick cylinder to retract and the stick will move out.
As the rod retracts, oil flows from the head end of the cylinder through port (30), into passage (29), past the spool (2) and into passage (6). Then, the oil flows into passage (5) to the hydraulic tank.
If the pump supply pressure becomes less than the requirements for the work port, the load check valve (8) will move to the right in order to prevent stick cylinder drift. Check valve (28) also prevents the stick cylinder from drifting. Check valve (28) opens when pump supply pressure enters passage (26) or pilot pressure enters passage (31) .
When the operator releases the control lever, spring (3) moves the spool (2) to the HOLD position.
Refer to Systems Operation, "Makeup and Relief Valve" for the operation of relief valve (24) .
STICK IN Position
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| Illustration 3 | g00875335 |
STICK IN position for the stick valve (1) Head end line relief valve, (2) Spool, (3) Chamber for pilot oil, (4) Spring, (5) Passage to tank, (6) Signal passage, (7) Chamber, (8) Load check valve, (9) Passage, (10) Pump passage, (11) Hole, (12) Passage, (13) Hole, (14) Spring, (15) Chamber, (16) Signal passage, (17) Passage to tank, (18) Signal line to the next valve, (19) Secondary resolver, (20) Signal line from the previous valve, (21) Primary resolver, (22) Chamber for pilot oil, (23) Spring, (24) Rod end line relief valve, (25) Port to rod end, (26) Passage, (27) Stick cylinder, (28) Check valve, (29) Passage, (30) Port to head end, (31) Pilot passage, (32) Chamber, (33) Piston, (34) Ball check valve, (35) Chamber, (A) Pump oil, (B) Return oil, (C) Blocked oil and (D) Pilot oil | |
When the operator places the joystick into the STICK IN position, pilot oil flows into chamber (3). The pilot oil in chamber (3) compresses spring (23). This allows the spool (2) to move to the left.
For a given amount of lever movement, spool (2) will move a proportional amount because of the pilot oil that is sent into chamber (3) .
Pilot oil flows through passage (31) and into chamber (32). The pressure in chamber (32) will move piston (33) downward. Ball check valve (34) will unseat when piston (33) moves downward. The trapped oil in chamber (35) will be vented to the tank and check valve (28) will open. When check valve (28) opens, oil will flow from the rod end of the cylinder to tank when the rod extends.
Pump oil from passage (12) flows around spool (2) and into passage (29). Oil in signal passage (6) is blocked from entering the passage to the tank (5). Oil in signal passage (6) senses the pressure in port (29). The oil in signal passage (6) flows to the primary resolver (21) .
The oil in the primary resolver (21) flows to the secondary resolver (19) and to the pump. This causes the pump to increase flow.
Load check valve (8) compares the pressure in chamber (7) to the signal pressure in chamber (15) and spring (14). When the pressure in chamber (7) is greater than the pressure in chamber (15) and force of spring (14) combined, load check valve (8) will move down and oil will be directed to chamber (29). Spool (2) controls the amount of flow into passage (29) that is desired.
As pump flow increases, more oil flows past spool (2) to passage (29) for the head end of the stick cylinder. The rod of the stick cylinder will extend and the stick will move in.
As the rod extends, oil flows from the rod end of the cylinder through port (25), past the check valve (28) and into passage (26). Then, the oil flows through passage (6) and into passage (5) to the hydraulic tank.
When the operator releases the control lever, spring (23) and spring (4) move the spool (2) to the HOLD position.
Refer to Systems Operation, "Makeup and Relief Valve" for the operation of valve (1) .