Left Turn Position

TM-5-3805-258-24-1 Loader Scoop Type DED 4x4 Articulated Frame Steer 2 1/2 Cubic Yard Bucket (CCE) Airborne/Airmobile Manual
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TM 5-3805-258-24-1 S T E E R I N G S Y S T EM A M P L I F I E D S T E E R I N G S Y S T EM S Y S T E M S O P E R A T I O N If an outside force keeps the machine from turn- ing, the pressure in outlet (6) will increase. This pressure increase is also felt against the pilot valve and flow control valve. The pressure against flow control valve (18) causes it to move to the left. This lets more oil flow to the cylinders. If the pressure goes above the relief valve setting, the pilot valve will open. Return oil from the cylinders enters outlet (4). It flows into return passage (13) and then through out- let (5). STEERING CONTROL VALVE WITH RELIEF VALVE OPEN 11. Orifice. 16. Bell resolver velve. 17. Passege. 18. Flow control valve. 19. Pilot valve (relief valve). When the pilot valve opens, oil flows through pas- sage (17) and past the pilot valve. The flow of oil past orifice (11) causes a lower pressure in the chamber for the flow control spring. This lets the pressure of the oil in inlet passage (15) move flow control valve (18). Oil from inlet (15) can flow through the holes in the flow control valve, which now works as a dump valve. This releases the extra pressure from the cir- cuit. When the outside force is gone and the pressure is reduced, the flow control valve and pilot valve return to their normal positions. Left Turn Position The control valve operation for a left turn is similar to that for a right turn. Pilot oil enters inlet passage (10) and moves the spool to the right. Pump oil from inlet (15) flows through the slots in spool (12) to outlet (4). This oil flows to the head end of the right steering cylinder and to the rod end of the left steer- ing cylinder. The pressure of this oil moves the cy- linder rods and the machine turns to the left. When the valve spool is in the left turn position, the pressure of the oil to the cylinders is felt through passage (14) and across the ball resolver valve. This same pressure is felt through passage (17) and at pilot valve (19). The remainder of the relief valve operation is the same for the LEFT TURN position and the RIGHT TURN position. NEUTRALIZER VALVE NEUTRALIZER VALVE IN CLOSED POSITION 1. Striker (Stud Assembly). 2. Inlet. 3. Ball check valve. 4. Outlet. 5. Stem. 6. Srxina. The neutralizer valve stops the flow of pilot oil to the steering control valve at the end of a complete turn. This stops the steering action before the ma- chine turns against the frame stops. The pilot oil that flows from the hand metering unit (HMU) to the steering control valve must first pass through the right or left neutralizer valve. The oil from the HMU goes into the valve through inlet (2). The oil flows around stem (5) and through outlet (4) to the steering control valve. When the machine is at the end of a complete right turn, striker (1) comes in contact with stem (5) of the right neutralizer valve. It moves the stem until pilot oil can not flow from inlet (2) to outlet (4). This stops the flow of oil across the metering orifices in the main control spool. The steering valve spool will then re- turn to NEUTRAL, and the steering action of the machine stops. Before steering action can start back to the left, oil must flow from the return end of the steering valve spool through the right neutralizer valve. Since stem (5) has the oil stopped, the return oil from the end of the spool must flow past ball check valve (3). This lets the steering valve spool move and the steering action starts, As the machine moves to the left a small amount, striker (1) will move away from the stem. This lets the pilot oil flow around the stem again, and the ball check valve closes. 3-66

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