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| Illustration 1 | g00412723 |
The steering quad check valve is located on the lower left side of the non-engine end frame, and near the articulated hitch.
The steering quad check valve consists of four check valves inside a manifold. Two of the check valves have a lower cracking pressure. These check valves are in-line with the flow of oil from the pilot control valve. One check valve with lower cracking pressure is for left turns. One check valve with lower cracking pressure is for right turns.
The other two check valves have a higher cracking pressure. These check valves are positioned in a reverse direction. These check valves only unseat when the return pilot oil pressure exceeds a preset value. One check valve with higher cracking pressure is for left turns. One check valve with higher cracking pressure is for right turns.
LEFT TURN Position
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| Illustration 2 | g00495422 |
Schematic of the Check Valve (Steering Quad Check) and Associated Components in the LEFT TURN Position (1) Signal line (2) Left steering cylinder (3) Right steering cylinder (4) Return line to the hydraulic oil tank (5) Manifold (orifice and screen) (6) Screen (7) Orifice (8) Steering control valve (9) Pilot oil line for left turns. (10) Check valve (steering quad check) (11) Check valve with a higher cracking pressure (12) Left neutralizer valve (13) Check valve with a lower cracking pressure (14) Pilot oil line for right turns (15) Pilot oil line to the hydraulic oil tank (16) Directional spool (17) Hydraulic oil line from the steering pump (18) Secondary pilot pressure line (AA) Pressure tap for checking pilot pressure for left turns at the steering control valve (BB) Pressure tap for checking pilot pressure for right turns at the steering control valve | |
When you turn the steering wheel counterclockwise in order to make a left turn, pilot oil flows from the pilot control valve. The pilot oil flows through pilot oil line for left turns (9), and then through check valve (13). The oil then flows through left neutralizer valve (12) .
From neutralizer valve (12), the oil flows to a pilot oil chamber in one end of directional spool (16). The pressure of the pilot oil causes directional spool (16) to move left. Any excess pilot oil flows through screen (6) and orifice (7) in manifold (5). The excess pilot oil then flows back to the hydraulic oil tank through return line (4) .
When the steering wheel is returned from the LEFT TURN position to the NEUTRAL position, pilot oil flow through pilot oil line (9) will stop. This will cause check valve (13) to close.
The oil between directional spool (16) and check valve (13) will return to the hydraulic oil tank through screen (6) and orifice (7). Screen (6) and orifice (7) are inside manifold (5) .
Orifice (7) dampens the movement of directional spool (16) as directional spool (16) returns to the Neutral position. The flow of oil through orifice (7) allows directional spool (16) to smoothly return to the NEUTRAL position.
If either screen (6) or orifice (7) becomes plugged, pilot oil will flow through check valve (11) when the oil pressure exceeds the cracking pressure of check valve (11). The oil will then flow though the pilot control valve before the oil returns to the hydraulic tank. As the oil is vented to the tank, directional spool (16) will return to the neutral position.
RIGHT TURN Position
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| Illustration 3 | g00495443 |
Schematic of the Check Valve (Steering Quad Check) and Associated Components in the RIGHT TURN Position (1) Signal line (2) Left steering cylinder (3) Right steering cylinder (4) Return line to the hydraulic oil tank (5) Manifold (orifice and screen) (8) Steering control valve (9) Pilot oil line for left turns (10) Check valve (steering quad check) (14) Pilot oil line for right turns (15) Pilot oil line to the hydraulic oil tank (16) Directional spool (17) Hydraulic oil line from the steering pump (18) Secondary pilot pressure line (19) Orifice (20) Screen (21) Check valve with a lower cracking pressure (22) Check valve with a higher cracking pressure (23) Right neutralizer valve (AA) Pressure tap for checking pilot pressure for left turns at the steering control valve (BB) Pressure tap for checking pilot pressure for right turns at the steering control valve | |
Steering quad check valve (10) functions in a similar manner when you turn the steering wheel clockwise in order to make a right turn.
When a right turn is made, the pilot oil flows through low pressure check valve (21). The oil then flows through right neutralizer valve (23), and then to the pilot oil chamber for right turns in steering control valve (8) .
The pressure of the pilot oil in the chamber for right turns overcomes the force of the centering spring for directional spool (16). This causes directional spool (16) to move to the right. Any excess pilot oil flows through screen (20) and orifice (19) in manifold (5). The pilot oil then flows back to the hydraulic oil tank through return line (4) .
When the steering wheel is returned from the RIGHT TURN position to the NEUTRAL position, the pilot oil flow through pilot oil line (14) will stop. This will cause check valve (21) to close.
The oil between directional spool (16) and check valve (21) will return to the hydraulic oil tank through screen (20) and orifice (19). Screen (20) and orifice (19) are inside manifold (5). Orifice (19) dampens the movement of directional spool (16) as directional spool (16) returns to the NEUTRAL position.
The flow of oil through orifice (19) allows directional spool (16) to smoothly return to the NEUTRAL position.
If either screen (20) or orifice (19) becomes plugged, the pilot oil will flow through check valve (22) when the oil pressure exceeds the cracking pressure of check valve (22). The oil will then flow through the pilot control valve before the oil returns to the hydraulic tank. As the oil is vented to the hydraulic tank, directional spool (16) will return to the NEUTRAL position.