HOLD Position
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| Illustration 1 | g00853133 |
HOLD Position for the Tilt Valve (1) Makeup and line relief valve for the rod end, (2) Spool, (3) Passage to tank, (4) Signal passage, (5) Chamber, (6) Port to rod end of cylinder, (7) Flow control valve, (8) Passage, (9) Pump passage, (10) Slots, (11) Passage, (12) Spring, (13) Port to head end of cylinder, (14) Chamber, (15) Pump signal hole, (16) Signal passage, (17) Passage to tank, (18) Makeup and line relief valve for the head end, (19) Spring, (20) Primary resolver, (21) secondary resolver, (22) Magnetic detent assembly, (23) Passage from previous valve, (24) Passage to the next valve, (25) Control spool signal passage, (26) Pump signal hole, (27) Relief valve, (A) Pump oil, (B) Return oil and (C) Blocked oil | |
The tilt control valve is mounted between the lift control valve and the end cover for the loader control valve section that is standard. If the machine is equipped with an optional auxiliary circuit, the tilt control valve is mounted between the auxiliary control valve and the lift control valve.
In the HOLD position, spool (2) is centered by spring (19). Passages (6) and (13) are blocked by spool (2). Passage (4) is open to the tank through passage (3). Passage (16) is connected to the tank through passage (17). The return to the tank passage is common in all control valves.
Chamber (14) is connected to the primary resolver (20). Chamber (14) is open to the tank through passage (4) and (17) which is connected to the primary resolver (20) in the HOLD position.
The oil from the pump enters the passage (9). Passage (9) is common in all sections of the valves and the passage has no outlet. Oil flows into passage (8) through openings in flow control valve (7). The oil then flows into chamber (5) .
Pressure in chamber (5) rises and the pressure acts against flow control valve (7). The pressure overcomes the force of the spring (12) and the pressure causes flow control valve (7) to move down. As flow control valve (7) moves down, oil flows from passage (9) into passage (11). The oil in passage (11) is blocked by spool (2) until the operator moves the control lever.
As the flow control valve (7) moves down, the metering slots (10) begin to close. The oil that flows from passage (9) to passage (11) is restricted. Oil is now metered through slot (10) in order to maintain pressure in chamber (5) and passage (11) .
TILT BACK Position
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| Illustration 2 | g00853134 |
TILT BACK Position for the Tilt Valve (1) Makeup and line relief valve for the rod end, (2) Spool, (3) Passage to tank, (4) Signal passage, (5) Chamber, (6) Port to rod end of cylinder, (7) Flow control valve, (8) Passage, (9) Pump passage, (10) Slots, (11) Passage, (12) Spring, (13) Port to head end of cylinder, (14) Chamber, (15) Pump signal hole, (16) Signal passage, (17) Passage to tank, (18) Makeup and line relief valve for the head end, (19) Spring, (20) Primary resolver, (21) secondary resolver, (22) Magnetic detent assembly, (23) Passage from previous valve, (24) Passage to the next valve, (25) Control spool signal passage, (26) Pump signal hole, (27) Relief valve, (A) Pump oil, (B) Return oil and (C) Blocked oil | |
When the tilt control is moved to the TILT BACK position, spool (2) moves up.
For a given amount of lever movement, spool (2) will move a proportional distance.
As spool (2) starts to move, pump oil in passage (11) initially flows into hole (15) through passage (25). The oil flows out of hole (26) into port (13) and signal passage (16). The advance signal passage (25) allows signal pressure to be sent back to the pump in order to upstroke the pump. This will provide a better response to the demand of the work tool.
As the spool continues to move up, the pump oil in passage (11) flows around spool (2) into port (13). 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 (13). The oil in signal passage (16) flows to the primary resolver (20) and into chamber (14) .
The oil in the primary resolver (20) flows to the secondary resolver (21) and to the pump. This causes the pump to increase flow.
Flow control valve (7) compares the oil in chamber (5) to the signal pressure in chamber (14) and spring (12). Flow control valve (7) moves in order to provide the required oil flow to passage (11). Spool (2) controls the amount of flow that is desired.
As pump flow increases, flow control valve (7) moves in order to allow more oil to flow past spool (2) to the head ends of the tilt cylinders. The oil causes the rods to extend. When the rods extend, the rods cause the bucket to tilt back.
As the tilt cylinder extends, oil from the rod end of the cylinder flows from port (6), through passage (4) and into the passage to the tank (3) .
When the operator releases the control lever, spring (19) will return spool (2) to the HOLD position.
Magnetic detent assembly (22) is an electrical part of the system for the bucket positioner. As the bucket moves to the DUMP position the switch that is mounted on the tilt linkage closes. When the switch closes, current flows to the magnet that is part of magnetic detent assembly (22) .
When the operator moves the control valve to the full TILT BACK position, the magnet holds spool (2) in the TILT BACK position. The switch on the tilt linkage opens as the bucket moves to a preset angle. The switch opens in the TILT BACK position.
When the switch opens, current flow to magnetic detent assembly (22) stops. Spring (19) moves the spool downward to the HOLD position, when the magnet is no longer holding spool (2) in the TILT BACK position. This maintains the bucket in position in order to dig.
The system for the bucket positioner allows the operator to move the joystick to the full TILT BACK position after dumping the bucket and the bucket will automatically return to a preset dig position even when the joystick is released.
The pump compensator valve adjusts the pump flow and the pump compensator valve controls the system pressure.
If the pump supply pressure becomes less than the requirements for the work port, the flow control valve (7) will move upward in order to prevent drift.
Relief valve (27) will drain signal pressure in chamber (14) to the tank when the signal pressure becomes too high. Flow control valve (7) will limit the flow of oil to the cylinders when heavy loads and obstructions are encountered.
Refer to Systems Operation, "Makeup and Relief Valve" for the operation of valve (18) .
DUMP Position
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| Illustration 3 | g00853135 |
DUMP Position for the Tilt Valve (1) Makeup and line relief valve for the rod end, (2) Spool, (3) Passage to tank, (4) Signal passage, (5) Chamber, (6) Port to rod end of cylinder, (7) Flow control valve, (8) Passage, (9) Pump passage, (10) Slots, (11) Passage, (12) Spring, (13) Port to head end of cylinder, (14) Chamber, (15) Pump signal hole, (16) Signal passage, (17) Passage to tank, (18) Makeup and line relief valve for the head end, (19) Spring, (20) Primary resolver, (21) secondary resolver, (22) Magnetic detent assembly, (23) Passage from previous valve, (24) Passage to the next valve, (25) Control spool signal passage, (26) Pump signal hole, (27) Relief valve, (A) Pump oil, (B) Return oil and (C) Blocked oil | |
When you move the tilt control lever to the DUMP position, spool (2) moves down.
For a given amount of lever movement, spool (2) will move a proportional distance.
As spool (2) moves down, the pump oil in passage (11) flows around spool (2) into port (6). Oil in signal passage (4) is blocked from entering the passage to the tank (3). Oil in signal passage (3) senses the pressure in port (6). The oil in signal passage (3) flows to the primary resolver (20) and into chamber (14) .
The oil in the primary resolver (17) flows to the secondary resolver (19) and to the pump. This causes the pump to increase flow.
Flow control valve (7) compares the oil in chamber (5) to the signal pressure in chamber (14) and spring (12). Flow control valve (7) moves in order to provide the required oil flow to passage (11). Spool (2) controls the amount of flow that is desired.
As pump flow increases, flow control valve (7) moves in order to allow more oil to flow past spool (2) to the rod ends of the tilt cylinder. The oil causes the rod to retract. When the rod retracts, the rod causes the bucket to dump.
As the rod retracts, oil in the head end of the cylinder flows from port (13), through passage (16) and into the passage to the tank (17).
When the operator releases the control lever, spring (19) will return spool (2) to the HOLD position.
Relief valve (27) will drain signal pressure in chamber (14) to the tank when the signal pressure becomes too high. Flow control valve (7) will limit flow to the cylinders when heavy loads and obstructions are encountered.
Refer to Systems Operation, "Makeup and Relief Valve" for the operation of valve (1) .