450F Backhoe Loader Hydraulic and Steering System Control Valve (Extendable Stick) (Mechanically Operated) Caterpillar

The extendable stick control valve is located next to the stick control valve. In the HOLD position, spring (1) keeps spool (2) in the centered position. Oil from the pump flows from passage (3) into chamber (4). In the HOLD position, spool (2) blocks the flow of oil. Check valve (5) will maintain pressure in the line in order to avoid cylinder drift. Refer to this Systems Operation, "Load Check Valve" for more information.

RETRACT Position

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Illustration 2	g02178563
RETRACT position for the extendable stick valve (1) Port to the head side of the cylinder (2) Chamber for signal oil (3) Compensator spool (4) Chamber (5) Port to the rod end of the cylinder (6) Passage (7) Makeup and Relief valve (8) Signal oil passage (9) Spring (10) Check valve (11) Passage (12) Passage (13) Passage (14) Passage (15) Pump passage (16) Chamber (17) Spool (18) Spring (19) Passage (20) Makeup and Relief valve (21) Passage (22) Resolver Network (23) Spring Chamber

When you move the spool (17) to the left, the spring (18) is compressed toward the left. Oil from the pump flows from passage (15) into chamber (16). The oil flows around spool (17) into passage (13). As the oil flows into passage (13), the oil acts against the compensator spool (3). As the oil pressure increases, the spring of compensator (3) compresses and the compensator spool (3) moves up.

The oil flows around the compensator spool (3) into passage (12). Oil from passage (12) then enters the signal oil passage (8). The signal oil goes from the signal oil passage (8) into the resolver network (22). If this circuit is the only active circuit, or if this circuit has a work port pressure that is higher than the other circuits that are active, the oil pressure from this circuit will flow to the chamber for signal oil (2). The pump actuator will receive a signal in order to control the output from the pump. Refer to this Systems Operation, "Signal Network Resolver" for more information. The oil pressure in the chamber for signal oil (2) and the pressure of the compensator spring (3) balances oil pressure in passage (13) .

When the oil enters passage (12), oil on the left side of passage is blocked by spool (17). On the right side of passage (12), the oil flows around spool (17) into passage (11). As the oil flows into passage (11), the oil pressure increases. The oil enters the check valve (10). When pressure overcomes the force of spring (9) and the pressure in spring chamber (23), the check valve (10) moves to the right. Refer to this Systems Operation, "Load Check Valve" for more information. Oil flows through the check valve (10) into the makeup and relief valve (7). The oil flows from the makeup and relief valve (7) to passage (6). Refer to this Systems Operation, "Makeup and Relief Valve" for more information. The oil then flows through port (5) to the rod end of the cylinder. This will retract the cylinder. This returns the stick to the RETRACT position.

Return oil flows from the head end of the cylinder through port (1). The oil goes from port (1) into passage (21). The oil moves from passage (21) past the makeup and relief valve (20) into passage (19). The oil flows around spool (17) into passage (14) back to the tank.

EXTEND Position

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Illustration 3	g02178564
EXTEND position for the extendable stick valve (1) Port to the head side of the cylinder (2) Chamber for signal oil (3) Compensator spool (4) Chamber (5) Port to the rod end of the cylinder (6) Passage (7) Makeup and Relief valve (8) Signal oil passage (9) Spring (10) Check valve (11) Passage (12) Passage (13) Passage (14) Passage (15) Pump passage (16) Chamber (17) Spool (18) Spring (19) Passage (20) Makeup and Relief valve (21) Passage (22) Resolver Network (23) Spring Chamber

When you move the spool (17) to the right, the spring (18) is compressed toward the right. The pump sends oil into passage (15). The oil travels from passage (15) to chamber (16). The oil flows around spool (17) into passage (13). When the oil flows into passage (13) the oil acts against compensator spool (3). As the oil pressure increases, the spring of the compensator spool (3) compress and the compensator spool (3) moves up.

The oil flows around the compensator spool (3) into passage (12). Some of the oil that flows into passage (12) enters the signal oil passage (8). The signal oil goes from the signal oil passage (8) into the resolver network (22). If this circuit is the only active circuit, or if this circuit has a work port pressure that is higher than the other circuits that are active, the oil pressure from this circuit will flow to the chamber for signal oil (2). The pump actuator will receive a signal in order to control the output from the pump. Refer to this Systems Operation, "Signal Network Resolver" for more information. The oil pressure in the chamber for signal oil (2) and the pressure of the compensator spring (3) balances oil pressure in passage (13) .

When the oil enters passage (12) the oil on the right side of the passage is blocked by spool (17). On the left side of passage (12), the oil flows around spool (17) into passage (19). The oil moves from passage (19) past the makeup and relief valve (20) into passage (21). Refer to this Systems Operation, "Makeup and Relief Valve" for more information. The oil in passage (21) then flows through port (1) to the head end of the cylinder. This will extend the cylinder. This will return the stick to the EXTEND position.

Return oil flows from the rod end of the cylinder through port (5) into passage (6). The oil flows from passage (6) past the makeup and relief valve (7) into check valve (10). When the oil pressure overcomes the force of the spring (9) and the pressure in spring chamber (23), the check valve will move to the right. Refer to this Systems Operation, "Load Check Valve" for more information. Oil flows through the check valve (10) to passage (11). The oil flows around spool (17) into passage (14) back to the tank.