S Y S T E M S O P E R A T I O NTM 5-3805-258-24-1S T E E R I N G S Y S T E MA M P L I F I E D S T E E R I N G S Y S T E MSTEERING CONTROL VALVENeutral PositionSTEERING CONTROL VALVE IN NEUTRAL1. Metering orifices.9. Inlet(from right15. Inlet(from steering2. Paaaage.neutralizer valve).3. Paasage.pump section).10. Inlet(from left16. Sail resolvervalve.4. Outlet for left turn.neutralizer valve).17. Paasage.5. Outlet to tank.11. Orifice.1S. Flow control valve.6. Outlet for rightturn.12. spool.19. Pilot valve(relief7. Metering orifices.13. Return paaaage.valve).S. Spring.14. Paaaage.The flow of pilot oil to either end of valve spool(12) is stopped when; (a) rotation of steering wheel isstopped, or (b) the neutralizer valve stops the flowafter a complete turn has been made. With no pilotoil flow against either end of the valve spool, spring(8) will keep the spool in its NEUTRAL postion.When the steering control valve is in its NEU-TRAL position, the oil from the steering pump sec-tion is stopped by the valve spool. The pressure in-creases in inlet passage (15). This pressure increasemoves flow control valve (18). The flow control valvemoves until oil can flow through it to outlet (5).In the NEUTRAL position, the valve spool alsoblocks (stops) the oil in the lines to the cylinders. Thisholds the machine in the turned position where thesteering wheel was stopped.The pressure of the oil in blocked outlet (4) or(6) is felt through ball resolver valve (16) andagainst pilot valve (19). If an outside force tries toturn the machine when the valve spool is in theNEUTRAL position, the increase in pressure inoutlet (4) or (6) will open pilot valve (19). The pres-sure in the lines will not go higher than the reliefvalve setting [17 200 ± 340 kPa (2500 ± 50 psi)].When the pilot flow to one end of the spool stops,part of the oil on that end of the spool must beremoved before the valve spool can return to theNEUTRAL position. To do this, part of the oil ispushed, by the force of spring (8), to the opposite endof the spool. The spool can then move to its neutralposition.As an example, a left turn is made and pilot oilflows through inlet (10). The pressure of the oil frominlet (10) causes spool (12) to move to the right.When the pilot flow stem, part of the oil from theleft end of the spool must be removed so that the spoolcan move to the NEUTRAL position. The force ofspring (8) causes the spool to move to the left. As the3-64
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