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| Illustration 1 | g01507884 |
(1) Spring (2) Load sensing port (3) Excess flow port (4) Inlet port (5) Spool (6) Controlled flow port | |
The steering pump is connected to the priority valve through inlet port (4) . Controlled flow port (6) is the port to the steering metering unit. Excess flow port (3) sends oil to the implement valve. Spring (1) moves spool (5) when there is no pressure in the system. The oil is free to flow to the steering metering unit in this position. The oil is blocked by spool (5) from going to excess flow port (3) and to the implement valve.
As the system becomes pressurized, oil flows around spool (5) to the passage in controlled flow port (6) . The oil then flows to the bottom of spool (5) . When the steering wheel is not turned, pressure in controlled flow port (6) increases. As the pressure on the bottom of spool (5) becomes sufficient to overcome spring (1) , spool (5) moves up. Spool (5) moves to a position in order to maintain a pressure in controlled flow port (6) to the steering metering unit as long as the steering is not active.
The steering metering unit supplies oil to the left steering cylinder and to the right steering cylinder. As the signal from the steering system combines with the force of spring (1) the spool (5) moves down for increased flow to the steering metering unit through controlled flow port (6) . As spool (5) moves down the flow to the implement valve is restricted. Restricting the plow to the implement valve allows the steering system to have priority over the implement system.
Oil flows through controlled flow port (6) to the steering metering unit. The oil is sent from the steering metering unit to steering cylinders. Return oil is sent back through the steering metering unit.
Signal pressure on spool (5) is limited by the steering load sensing pressure, which causes the priority valve to balance pressure at port (6) . Signal pressure on spool (5) is limited by the steering load sensing pressure, which causes the priority valve to limit pressure at port (6) .