Boom Raise (High Speed)
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| Illustration 1 | g03559940 |
Hydraulic schematic for BOOM RAISE (high speed) (1) Boom cylinders (2) Line (oil flow from boom cylinder rod end) (3) Line (oil flow to boom cylinder head end) (4) Pilot control valve (bucket and boom) (5) Pilot line (6) Pressure reducing valve for boom priority (7) Return line (8) Pilot line (9) Port (10) Pilot line (11) Port (12) Check valve (13) Boom II control valve (14) Spring (15) Parallel feeder passage (16) Return passage (17) Line (18) Main control valve (19) Pilot line (20) Parallel feeder passage (21) Load check valve (22) Return passage (23) Boom I control valve (24) Boom regeneration valve (25) Spring (26) Port (27) Passage (28) Valve (29) Boom drift reduction valve (30) Drive pump (31) Pilot pump (32) Idler pump | |
A BOOM RAISE operation at high speed is accomplished when the oil delivery from both drive pump (30) and idler pump (32) is supplied to the head end of boom cylinders (1) . Boom I control valve (23) and boom II control valve (13) operate during the high speed operation. A BOOM RAISE operation at low speed is accomplished when the oil delivery from only idler pump (32) is supplied to the head end of boom cylinders (1) . During the low speed operation, boom I control valve (23) operates alone.
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| Illustration 2 | g02142273 |
Main control valve compartment (13) Boom II control valve (23) Boom I control valve | |
The oil delivery from drive pump (30) flows through parallel feeder passage (20) in main control valve (18) to boom I control valve (23) . The oil delivery from idler pump (32) flows through parallel feeder passage (15) in main control valve (18) to boom II control valve (13) .
When the joystick for the boom is moved to the full BOOM RAISE position, the pilot oil flows from pilot control valve (bucket and boom) (4) through pilot line (8) . The pilot oil flow then divides into two flow paths. Part of the pilot oil flows through pilot line (10) to port (11) of main control valve (18) . The remainder of the pilot oil flows through pilot line (19) to port (26) of the main control valve.
A portion of the oil in pilot line (19) also flows through pilot line (5) to the pressure reducing valve for boom priority (6) . During a combined operation of BOOM RAISE and STICK IN, the pilot oil flow to the pressure reducing valve for boom priority (6) causes the boom circuit to receive oil flow priority. This action allows the boom to raise at a high speed.
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| Illustration 3 | g02142295 |
Control valve BOOM RAISE (boom I) (20) Parallel feeder passage (21) Load check valve (22) Return passage (25) Spring (26) Port (33) Passage (34) Passage (35) Port (36) Spool (37) Passage (38) Passage | |
The pilot oil flow from port (26) moves spool (36) in main control valve (18) downward against the force of spring (25) . The drive pump oil in parallel feeder passage (20) flows through load check valve (21) , and passages (34) and (37) . The oil then flows through port (35) to boom drift reduction valve (29) . The drive pump oil shifts valve (28) left. The oil then flows through line (3) to the head end of boom cylinders (1) .
ReferenceFor more information regarding the boom drift reduction valve, refer to Systems Operation, "Boom Drift Reduction Valve".
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| Illustration 4 | g02380618 |
Control valve BOOM RAISE (boom II) (9) Port (11) Port (12) Check valve (15) Parallel feeder passage (39) Passage (40) Spool (41) Passage (42) Spring | |
The pilot oil in port (11) in main control valve (18) moves spool (40) downward against the force of spring (14) . Idler pump oil from parallel feeder passage (15) now flows through passage (39) , passage (41) , check valve (12) and flows out of port (9) to line (17) . The oil then combines with the drive pump oil in boom drift reduction valve (29) . The combined pump oil flows to the head end of boom cylinders (1) .
Return oil from the rod end of boom cylinders (1) flows through line (2) to boom I control valve (23) . The oil then flows to return passage (22) and to return line (7) back to the hydraulic tank.
The pilot oil flow from port (26) shifts spool (36) of boom I control valve (23) against the force of spring (25) . The oil delivery from the drive pump in parallel feeder passage (20) flows through load check valve (21) , passage (34) , passage (37) and port (35) to boom drift reduction valve (29) . The oil delivery from the drive pump shifts valve (28) in boom drift reduction valve (29) left. The oil delivery from the drive pump then flows through line (3) to the head end of boom cylinders (1) .
ReferenceFor more information on the boom drift reduction valve, refer to Systems Operation, "Boom Drift Reduction Valve".
Boom Raise (Low Speed)
When the joystick for the boom is moved less than half of the travel distance for BOOM RAISE, low pilot oil pressure is supplied to boom I control valve (23) and boom II control valve (13) .
When the boom is raised at a low speed, boom I control valve (23) opens and boom II control valve (13) remains closed. The force of spring (25) in boom I control valve (23) is less than the force of spring (14) in boom II control valve (13) . Because of the low pilot oil pressure, boom I control valve (23) will open and boom II control valve (13) will remain closed.
The oil delivery from drive pump (30) now flows to the head end of boom cylinders (1) . Without the oil delivery from idler pump (32) , the cylinder rod movement slows down when the boom is raised. The low speed operation of the boom is performed.
Boom Priority
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| Illustration 5 | g03559942 |
Hydraulic schematic for BOOM RAISE and STICK IN (1) Boom cylinders (4) Pilot control valve (bucket and boom) (6) Pressure reducing valve for boom priority (43) Stick II control valve (44) Pilot control valve (stick and swing) | |
During combined operations of BOOM RAISE and STICK IN, the pilot oil pressure from the pilot control valve for the boom (4) activates the pressure reducing valve for boom priority (6) . Pressure reducing valve for boom priority (6) causes oil flow priority to the head end of the boom cylinders (1) during this combined hydraulic operation.
When the joystick for the stick is moved to the STICK IN position, a portion of the pilot oil from the pilot control valve for the stick (46) flows through the pressure reducing valve for the boom priority (6) to the stick II control valve (43) . As the joystick for the boom is moved farther from the NEUTRAL position during a BOOM RAISE operation, pilot oil pressure from the pilot control valve for the boom (4) increases. This gradual increase in pilot oil pressure causes the spool in the pressure reducing valve for the boom priority (6) to shift gradually.
A portion of the pilot oil that flows to stick II control valve (43) from the pilot control valve for the stick (44) is routed to the hydraulic tank. The pilot oil pressure that acts on stick II control valve (43) decreases. Stick II control valve (43) shifts toward the NEUTRAL position. The amount of oil flow from the main pumps to the stick hydraulic circuit decreases. This action causes a greater portion of the oil flow from the main pumps to flow to the head end of the boom cylinders (1) .
Since the pilot oil pressure from the pilot control valve for the boom (4) directly corresponds to the amount of movement or position of the joystick a gradual change to boom priority occurs. Thus, boom priority is controlled by the position of the joystick for the boom and boom priority automatically activates when the joystick reaches a certain position during a BOOM RAISE operation.
Boom Lower
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| Illustration 6 | g03559943 |
Hydraulic schematic for BOOM LOWER (1) Boom cylinders (2) Line (oil flow from boom cylinder rod end) (3) Line (oil flow to boom cylinder head end) (4) Pilot control valve (bucket and boom) (5) Drain line (6) Spool (boom regeneration valve) (7) Valve (8) Boom drift reduction valve (9) Drain line (10) Passage (11) Center bypass passage (12) Parallel feeder passage (13) Load check valve (14) Return passage (15) Control valve (boom I) (16) Orifice (17) Boom regeneration valve (18) Control valve (stick II) (19) Line (20) Port (21) Pilot line (23) Drive pump (24) Idler pump (25) Pilot pump | |
Introduction
When the boom is lowered, oil from drive pump (23) is supplied to boom cylinders (1) through control valve (15) .
The BOOM LOWER operation contains a regeneration circuit. When the joystick for the boom is moved to the BOOM LOWER position, orifice (16) in boom I control valve (15) and boom regeneration valve (17) are operational in the boom hydraulic circuit. The return oil flow from the head end of boom cylinders (1) flows through boom regeneration valve (8) to the rod end of the boom cylinders. The boom regeneration valve is described later in this section.
Boom Lower
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| Illustration 7 | g02143198 |
Control valve BOOM LOWER (boom I) (12) Parallel feeder passage (13) Load check valve (14) Return passage (16) Orifice (20) Port (26) Port (27) Port (28) Spool (29) Passage (30) Passage (31) Spring | |
The pilot oil flow from port (20) shifts spool (28) in boom I control valve (15) against the force of spring (31) . The oil delivery from the drive pump in parallel feeder passage (12) flows through load check valve (13) , passage (30) and port (26) . The oil delivery from the drive pump then flows through line (2) to the rod end of boom cylinders (1) .
The return oil from the head end of boom cylinders (1) flows through line (3) into boom drift reduction valve (8) . Since valve (6) is shifted by the pilot pressure from pilot line (21) , valve (7) is open to the return circuit.
A portion of the return oil flows into port (26) of boom I control valve (15) . The return oil flow is restricted by orifice (16) . The return oil pressure increases. Most of the return oil flows through boom regeneration valve (17) . The return oil is now supplied to the rod end of the boom cylinders through line (2) .
ReferenceFor more information regarding the boom drift reduction valve, refer to Systems Operation, "Boom Drift Reduction Valve".
Boom Regeneration Valve
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| Illustration 8 | g02144700 |
Top view of main control valve | |
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| Illustration 9 | g02144695 |
Boom regeneration valve (slow boom down) (32) Pilot port (33) Passage (34) Check valve (35) Spool (boom regeneration valve) (36) Passage | |
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| Illustration 10 | g02145202 |
Boom regeneration valve (fast boom down) (32) Pilot port (33) Passage (34) Check valve (35) Spool (boom regeneration valve) (36) Passage | |
The boom hydraulic circuit contains a regeneration circuit. The regeneration circuit allows the return oil from the head end of the boom cylinders to be supplied to the rod end of the boom cylinders during the BOOM LOWER operation.
When the joystick for the boom is moved to the BOOM LOWER position, pilot oil flow from the pilot control valve enters pilot port (32) . Spool (35) in the boom regeneration valve shifts downward. The return oil from the head end of the boom cylinders flows through passage (36) and through the throttling slots on the spool for the boom regeneration valve to check valve (34) . Check valve (34) opens and the return oil flows through passage (33) . The return oil from the head end of the boom cylinders in passage (33) combines with the oil delivery from the drive pump. This combined oil now flows to the rod end of the boom cylinders.
The oil delivery from only the drive pump is used for the BOOM LOWER operation. Since the boom regeneration valve supplies return oil from the head end to the rod end of the boom cylinders, more efficient use of the oil delivery from the drive pump is achieved during a BOOM LOWER operation.