Attachment Circuit with Diverter Valve
An attachment circuit with a diverter valve is used on machines that have both a multipurpose bucket and a ripper. The oil flow is the same path in the attachment circuit except that the diverter valve is added. The diverter valve is added between the third valve spool and the attachment cylinders.
Multipurpose Bucket Operation
When the diverter valve control lever is moved to the MULTIPURPOSE BUCKET position, the selector spool of the diverter valve opens passages to the multipurpose bucket cylinders. Oil flows to the multipurpose bucket cylinders and the passages to the ripper cylinders close. The multipurpose bucket can now be operated by moving the pilot control lever.
Ripper Operation
When the diverter valve control lever is moved to the RIPPER CONTROL position, the selector spool of the diverter valve opens passages to the ripper cylinders. Oil flows to the ripper cylinders and the passages to the multipurpose bucket cylinders close. The ripper can now be operated by moving the pilot control lever.
Third Valve Operation
Implement Hydraulic System (Colored Schematic)
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| Illustration 1 | g01014841 |
Attachment Circuit Third valve spool (10) is in the OPEN or RAISE positions. Tilt valve spool (15) is in the HOLD position. Lift valve spool (21) is in the HOLD position. (1) Line to Pilot Pump (2) Line from Pilot Relief Valve (3) Line from Pilot Pump (4) Hydraulic Oil Cooler (5) Pressure Reducing Valve (6) Implement Pump (7) Pressure Tap (8) Load Check Valve (9) Main Relief Valve (10) Third Valve Spool (11) Diverter Valve (12) Ripper Cylinders (13) Multipurpose Bucket Cylinders (14) Load Check Valve (15) Tilt Valve Spool (16) Dual Setting Relief Valve (17) Tilt Cylinders (18) Load Check Valve (19) Lift Cylinders (20) Vented Makeup Valve (21) Lift Valve Spool (22) Shuttle Valve (23) Pilot Control Valve (Lift Cylinders) (24) Float Valve (25) Pilot Control Valve (Tilt Cylinders) (26) Breaker Relief Valve (27) Hydraulic Oil Tank (28) Pilot Control Valve (Ripper and Bucket Cylinders) (29) Check Valve (FF) Activated Components (GG) Tank Pressure (JJ) High Pressure (PP) Pilot Pressure (SS) Trapped Oil | |
Third valve spool (10) has three positions. The positions are OPEN, HOLD, and CLOSE for the multipurpose bucket. The positions are RAISE, HOLD, and LOWER for the ripper.
Third Valve HOLD Position
When the engine is running with the pilot control valves in the HOLD position, the pilot pump (not shown) sends pilot oil to pressure reducing valve (5). The pressure reducing valve limits the pressure of the pilot oil that flows to the pilot control valves.
Oil flow from implement pump (6) flows through third valve spool (10) before reaching tilt valve spool (15) and lift valve spool (21). The movement of third valve spool (10) is controlled by pilot pressure oil from pilot control valve (28) .
The valve stems in the pilot control valves stop the flow of pilot oil when the pilot control lever is in the HOLD position. The oil from the pilot pump flows through the pilot relief valve (not shown). The oil is then directed back to hydraulic oil tank (27) .
At the same time, implement pump (6) sends oil to main relief valve (9) which controls the maximum pressure in the attachment circuit. The oil then flows to third valve spool (10). The oil flows through third valve spool (10) to tilt valve spool (15). Oil flows through tilt valve spool (15) to lift valve spool (21). If all three valve spools are in the HOLD position, the oil flows back to the hydraulic oil cooler (4) and through the filters in hydraulic oil tank (27) .
When third valve spool (10) is in the HOLD position, third valve spool (10) traps the oil between third valve spool (10) and diverter valve (11). The oil that is trapped in the attachment cylinders keeps the cylinders from moving.
Third Valve OPEN and RAISE Position
When the pilot control lever is moved to the OPEN position or to the RAISE position, pilot oil from pilot control valve (28) flows to third valve spool (10). This causes third valve spool (10) to move to the OPEN or RAISE position.
The movement of third valve spool (10) diverts pump oil to load check valve (8). The pressure at implement pump (6) increases. Load check valve (8) opens when the pump pressure becomes greater than the sum of the force of the spring in load check valve (8) and the rod end pressure of the attachment cylinders. When the load check valve opens, the oil from implement pump (6) flows through third valve spool (10) to diverter valve (11). The oil can then flow to the attachment cylinders. This causes the cylinder pistons and rods to retract.
The movement of the cylinder pistons and rods pushes oil out of the head ends of the attachment cylinders. The oil flows through diverter valve (11) to third valve spool (10). The oil flows to hydraulic oil cooler (4) to the filters in hydraulic oil tank (27) .
When third valve spool (10) is in the full OPEN or in the full RAISE position, pressurized oil is blocked from flowing to tilt valve spool (15) and lift valve spool (21). The lift circuit and the tilt circuit are now inoperable.
There are no detents on pilot control valve (28). When the pilot control lever is released, the lever moves to the HOLD position. The flow of pilot oil through pilot control valve (28) is stopped. The centering springs move third valve spool (10) back to the HOLD position. The oil in the attachment cylinders is blocked by third valve spool (10). Therefore, movement of the cylinders is stopped until the lever for the pilot control valve is moved again.
Cutaway View of Third Valve
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| Illustration 2 | g01042374 |
Third valve spool (10) is in the OPEN position or RAISE position. (8) Load Check Valve (10) Third Valve Spool (A) Chamber for Pilot Oil (B) Passage for Supply Oil (C) Spring (D) Inlet for Supply Oil from Implement Pump (E) Chamber for Pilot Oil (F) Centering Springs (G) Outlet to Lift and Tilt Valve Spools (H) Passage to Rod End (J) Passage to Head End (K) Passage to Hydraulic Oil Cooler (FF) Activated Components (GG) Tank pressure (JJ) High pressure (PP) Pilot pressure | |
Third valve spool (10) has three positions. The positions are OPEN, HOLD, and CLOSE for the multipurpose bucket. The positions are RAISE, HOLD, and LOWER for the ripper.
Third Valve HOLD Position
When the engine is running with the pilot control valves in the HOLD position, the pilot pump (not shown) sends pilot oil to the pressure reducing valve. The pressure reducing valve controls the pressure in the pilot system.
Oil flow from the implement pump flows through inlet (D) to third valve spool (10) before reaching the tilt valve spool and the lift valve spool. The movement of third valve spool (10) is controlled by pilot pressure oil from the pilot control valve. Pilot oil is sent to chamber (A) or chamber (E) .
The valve stems in the pilot control valves stop the flow of oil when the pilot control lever is in the HOLD position. The oil from the pilot pump flows through the pilot relief valve (not shown) and to the hydraulic oil tank.
At the same time, the implement pump sends oil to the main relief valve which controls the maximum pressure in the attachment circuit. The oil then flows to third valve spool (10) through inlet (D) from the implement pump. Centering springs (F) keep third valve spool (10) in the HOLD position when there is no pilot pressure oil in chamber (A) or chamber (E). The oil flows through third valve spool (10) to outlet (G) to the tilt valve spool and the lift valve spool. If all three valve spools are in the HOLD position, the oil flows back to the hydraulic oil cooler and through the filters in the hydraulic oil tank.
When third valve spool (10) is in the HOLD position, third valve spool (10) holds the oil in passage (H) and in passage (J). The oil that is trapped in the attachment cylinders keeps the cylinders from moving.
Third Valve OPEN and RAISE Position
When the pilot control lever is moved to the OPEN position or to the RAISE position, pilot oil from the pilot control valve flows to chamber (A) of third valve spool (10). This causes third valve spool (10) to move to the OPEN or RAISE position.
The movement of third valve spool (10) diverts pump oil to load check valve (8). The pressure at the implement pump increases. Load check valve (8) opens when the pump pressure becomes greater than the sum of the force of spring (C) and the rod end pressure of the attachment cylinders. When the load check valve opens, the oil from the implement pump flows through third valve spool (10) and out through passage (H) to the optional diverter valve and to the rod ends of the attachment cylinders. This causes the cylinder pistons and rods to retract.
The movement of the cylinder pistons and rods pushes oil out of the head ends of the attachment cylinders. The oil flows through the diverter valve and to passage (J). The oil then flows through third valve spool (10), through passage (K), to the hydraulic oil cooler, and then to the filters in the hydraulic oil tank.
When third valve spool (10) is in the full OPEN or in the full RAISE position, pressure oil is blocked from flowing to the tilt valve spool and the lift valve spool. The lift circuit and the tilt circuit are now inoperable.
There are no detents on the pilot control valve for third valve spool (10). When the pilot control lever is released, the lever moves to the HOLD position. The flow of pilot oil through the pilot control valve is stopped. Centering springs (F) move third valve spool (10) back to the HOLD position. The oil in the attachment cylinders is blocked by third valve spool (10). Therefore, movement of the cylinders is stopped until the lever for the pilot control valve is moved again.
Lower or Close Operation
When the pilot control valve is moved to the CLOSE position or to the LOWER position, pilot oil flows to chamber (E). This causes third valve spool (10) to move to the CLOSE or LOWER position.
The movement of third valve spool (10) blocks the oil from flowing to passage (G) from inlet (D). The pressure at the implement pump increases. Load check valve (8) opens when the pump pressure becomes greater than the sum of the force of spring (C) and the pressure of the oil at the head end of the attachment cylinders. When the load check valve opens, the oil from the implement pump flows through third valve spool (10), through passage (J) to the optional diverter valve, and to the head ends of attachment cylinders. This causes the cylinder pistons and rods to extend.
The movement of the cylinder pistons and rods pushes oil out of the rod ends of the attachment cylinders. The oil flows through the diverter valve and passage (H) to third valve spool (10). Then, the oil flows through third valve spool (10) and through outlet (G) to the tilt valve spool and the lift valve spool. This allows simultaneous operation, as needed.
When the pilot control lever for the pilot control valve is released, the lever moves to the HOLD position. The flow of pilot oil through the pilot control valve is stopped. Centering springs (F) move third valve spool (10) back to the HOLD position. The oil in the attachment cylinders is blocked by third valve spool (10). Therefore, movement of the cylinders is stopped until the pilot control lever is moved again.
Load Check Valve
Load check valve (8) prevents reverse oil flow from the cylinders, which can cause cylinder drift. The load check valve opens when the inlet pressure becomes greater than the sum of the force of the spring and the pressure in the cylinders that are being moved.
For example, when third valve spool (10) is in the OPEN or RAISE position, pump oil opens load check valve (8) when the inlet pressure becomes greater than the sum of the force of spring (C) and the pressure in the rod end of the attachment cylinders. The oil flows through passage (B) through third valve spool (10). The oil then flows through passage (H) to the rod end of the attachment cylinders.
If the pressure at inlet (D) decreases, spring (C) and the pressure of the oil in the cylinders close load check valve (8). The oil is trapped in the attachment cylinders.
The oil that is trapped in the attachment cylinders will prevent any movement of the attachments.