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| Illustration 1 | g00818971 |
Priority valve (1) Adjusting screw for priority margin pressure (2) Spring for priority margin pressure (3) Priority control spool (4) Sleeve (5) Pilot control piston (6) Amplifier piston | |
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| Illustration 2 | g00548484 |
(7) Priority valve (8) Priority drain valve (9) Solenoid valve for priority actuation | |
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| Illustration 3 | g00704481 |
(2) Signal limiter valve (7) Priority valve (8) Priority drain valve (10) Control valve for auxiliary attachment | |
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| Illustration 4 | g00704396 |
(7) Priority valve (9) Solenoid valve for priority actuation (10) Control valve for auxiliary attachment (11) Line for priority pilot oil (13) Main control valve | |
Priority valve (7) is located on main control valve (13) between the main implements and auxiliary function valve (10) that needs to be prioritized. An auxiliary function is prioritized when the function receives a hydraulic oil flow that is constant regardless of other implement operations.
Priority valve (7) consists of the following main components:
Priority control spool (3) - The priority control spool controls the connections between the following signals:the load sensing signal from the main functions, the signal for load sensing priority from the prioritized function and the pump signal.
Adjusting screw for priority margin pressure (1) - The adjusting screw sets the point for regulation for the control spool.
Note: The priority margin pressure is set to a range of 1450 to 2200 kPa (210 to 319 psi). One full revolution of adjustment screw (2) changes the priority margin pressure by approximately 140 kPa (20 psi).
Note: The priority margin pressure must always be lower than the margin pressure that is set at the main pump regulator. If the priority margin pressure is set higher than the margin pressure for the main pump, pump pressure (P) will not overcome the force of the load sensing priority pressure plus the priority margin pressure. Consequently, the priority control spool will remain in the lower position and all implements will respond very slowly.
Note: The priority margin pressure setting is the minimum allowable value for the margin pressure at the auxiliary function that is being prioritized.
Amplifier piston (6) - When the amplifier piston is actuated by pilot pressure, priority valve (7) is disabled. The signal for load sensing priority is connected to the load sensing signal for the main pump and no priority is given to auxiliary function valve (10) .
Note: The prioritized function is enabled if pilot oil pressure drops below 900 kPa (130 psi). The prioritized function is disabled if pilot pressure is above 3000 kPa (435 psi).
Drain valve (8) - Drain valve (8) drains load sensing signal pressure oil that is produced by the prioritized function. The drain is set to 0.7 L/min (0.20 US gpm).
Priority Valve in the ON Position and Prioritized Implement with Low Pressure
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| Illustration 5 | g00575125 |
(1) Adjusting screw for priority margin pressure (2) Spring for priority margin pressure (3) Priority control spool (4) Sleeve (5) Pilot control piston (6) Amplifier piston (7) Priority valve (8) Priority drain valve (9) Solenoid valve for priority actuation (10) Control valve for auxiliary attachment (11) Line for priority pilot oil (13) Main control valve | |
Solenoid valve (9) is not energized and the pressure oil at the back of amplifier piston (6) is drained to the tank. Priority valve (7) is in a metering position. When the attachment that is prioritized receives the oil flow that is required, priority valve (7) will remain in the position for metering.
When the main hydraulic pump reaches the maximum flow rate and the implements that are not prioritized require more flow, the main load sensing signal will reduce the flow to the prioritized function (10). The compensator valve of prioritized function (10) will begin to close and the flow to the prioritized function will be reduced. The priority margin pressure is decreased. Control spool (3) of priority valve (7) is shifted in the downward direction, which compensates for the decrease in the priority margin pressure. When control spool (3) is shifted downward, the load sensing priority pressure is decreased. The combination of main pump pressure "P" and load sensing pressure "LS" that is sent to the implement compensator valves reduces the pressure oil to the implements. The priority margin pressure and the required flow at the prioritized function are returned to the initial values. The oil flow to the prioritized attachment remains constant.
Priority Valve OFF
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| Illustration 6 | g00548485 |
(1) Adjusting screw for priority margin pressure (2) Spring for priority margin pressure (3) Priority control spool (4) Sleeve (5) Pilot control piston (6) Amplifier piston (7) Priority valve (8) Priority drain valve (9) Solenoid valve for priority actuation (10) Control valve for auxiliary attachment (11) Line for priority pilot oil (13) Main control valve | |
Switch (12) energizes solenoid valve (9) which sends pilot pressure to amplifier piston (6) of priority valve (7). Priority control spool (3) is shifted upward. The signal for load sensing priority is connected to the line for the main load sensing signal for the main control valve (13). The signal for load sensing priority is disabled and the prioritized function is disabled.
When pilot manifold solenoid (9) is energized, the pilot pressure oil pushes amplifier piston (6). Amplifier piston (6) pushes up on pilot control piston (5) in order to turn off the priority function. To turn off the priority function, the pressure on the pilot control piston must overcome the spring pressure that is forcing control piston (3) upward against control spring (2). The pilot oil pressure and the main pump pressure cause control piston (3) to be forced upward against control spring (2). This opens priority valve (7) to full flow and this allows no significant change in the load sensing pressure. With no significant change in the load sensing pressure, all implement operating pressures are equal.