Hydraulic System

Location of Components
(1) Steer pump. (2) Control valve. (3) Control lever. (4) Cylinder. (5) Blade.

The leveling blade is an optional piece of equipment used on the CP-433B only. The blade is designed for heavy-duty leveling and backfilling. The maximum depth of a cut is 130 mm (5 in.).

Cylinder (4) and Blade (5)

Blade (5) is attached to the machine at the yoke with bushings. Cylinder (4) is secured in a frame, which is trunnion mounted to the front scraper. Rod end of cylinder (4) is attached to blade (5). When the cylinder rod retracts or extends, the blade is raised or lowered.

Steer pump (1)

Hydraulic oil for the leveling blade system comes from the secondary outlet of the steer pump (1).

Reference: For information on steer pump (1), see Steering System, Form No. KEBR2249.

Control valve (2)

Oil from steer pump (1) is routed to control valve (2), located under the operator's seat. The operator sets the position of the blade with control lever (3). The control lever is attached to control valve (2), which sends hydraulic oil to and from cylinder (4).

Control lever (3)

By moving control lever (3), the operator can move the blade UP, move the blade DOWN, HOLD the blade in a set position, or FLOAT the blade.

Control Valve

Control Valve in HOLD Position
(1) Relief valve. (2) Chamber. (3) Inlet port. (4) Chamber. (5) Spool. (6) Extend port. (7) Outlet port. (8) Retract port. (9) Spring. (10) Detent.

The control valve is a four-position, lever-operated directional valve. The control valve's purpose is to port hydraulic oil to the blade cylinder as directed by the operator.

The operator sets the position of the control valve by moving the control lever at the operator's station. The four positions are HOLD, UP, DOWN, and FLOAT.

Spool (5) is spring-centered in the HOLD position. The control valve contains an integral relief valve (1), and a detent (10) which will hold the spool in place when set in the FLOAT position.

Hydraulic oil from the steer pump enters the control valve at inlet port (3). Extend port (6) and retract port (8) are connected to the blade cylinder. Outlet port (7) is connected to a return line which leads through an oil cooler and hydraulic return filter, to the hydraulic oil tank.

Reference: For information on the oil cooler and hydraulic return filter, see Steering System, Form No. KEBR2249.

Control Valve Operation

Hold Position

Control Valve in HOLD Position
(1) Relief valve. (2) Chamber. (3) Inlet port. (4) Chamber. (5) Spool. (6) Extend port. (7) Outlet port. (8) Retract port. (9) Spring. (10) Detent.

When the control lever (at operator's station) is in the HOLD position, spring (9) keeps spool (5) in the center position shown. Hydraulic oil from the secondary outlet of the steer pump enters the control valve at inlet port (3). This oil is routed to chamber (2), chamber (4), and relief valve (1).

Oil at chambers (2) and (4) flows through slots in spool (5) to outlet port (7). Oil exits the control valve through outlet port (7). This return oil is routed to the hydraulic oil tank through an oil cooler and a hydraulic return filter.

Extend port (6) and retract port (8) are both blocked by spool (5). Oil is prevented from entering or exiting the blade cylinder. This holds the leveling blade in whatever position the operator has set it.

Up Position

Control Valve in UP Position
(1) Relief valve. (2) Chamber. (3) Inlet port. (4) Chamber. (5) Spool. (6) Extend port. (7) Outlet port. (8) Retract port. (9) Spring. (10) Detent.

When the operator pulls the control lever back to raise the blade, spool (5) moves to the left as shown. Spring (9) is compressed. Hydraulic oil from the steer pump enters the control valve at inlet port (3). This oil is routed to chamber (2), chamber (4), and relief valve (1).

Oil at chamber (2) is blocked. Oil at chamber (4) flows through slots in spool (5) to retract port (8). Oil exits the control valve at retract port (8), and is ported to the blade cylinder. The blade cylinder retracts, raising the blade.

Return oil from the blade cylinder enters the control valve at extend port (6). Return oil flows through slots in spool (5) to outlet port (7). Oil exits the control valve through outlet port (7), and is routed to the hydraulic oil tank through an oil cooler and a hydraulic return filter.

If the pressure in the line to the blade cylinder reaches approximately 8620 kPa (1250 psi), relief valve (1) will open. Oil from inlet port (3) will flow through relief valve to outlet port (7).

When the operator releases the control lever, spring (7) moves spool (5), and the control lever, to the HOLD position. Oil flow through retract port (8) and extend port (6) will be blocked. The blade cylinder will remain in the raised position until the operator moves the control lever again.

Down Position

Control Valve in DOWN Position
(1) Relief valve. (2) Chamber. (3) Inlet port. (4) Chamber. (5) Spool. (6) Extend port. (7) Outlet port. (8) Retract port. (9) Spring. (10) Detent.

When the operator pushes the control lever forward to lower the blade, spool (5) moves to the right as shown. Spring (9) is compressed. Hydraulic oil from the steer pump enters the control valve at inlet port (3). This oil is routed to chamber (2), chamber (4), and relief valve (1).

Oil at chamber (4) is blocked. Oil at chamber (2) flows through slots in spool (5) to extend port (6). Oil exits the control valve at extend port (6), and is ported to the blade cylinder. The blade cylinder extends, lowering the blade.

Return oil from the blade cylinder enters the control valve at retract port (8). Return oil flows through slots in spool (5) to outlet port (7). Oil exits the control valve through outlet port (7), and is routed to the hydraulic oil tank through an oil cooler and a hydraulic return filter.

If the pressure in the line to the blade cylinder reaches approximately 8620 kPa (1250 psi), relief valve (1) will open. Oil from inlet port (3) will flow through relief valve to outlet port (7).

When the operator releases the control lever, spring (9) moves spool (5), and the control lever, to the HOLD position. Oil flow through extend port (6) and retract port (8) will be blocked. The blade cylinder will remain in the lowered position until the operator moves the control lever again.

Float Position

Control Valve in FLOAT Position
(1) Relief valve. (2) Chamber. (3) Inlet port. (4) Chamber. (5) Spool. (6) Extend port. (7) Outlet port. (8) Retract port. (9) Spring. (10) Detent.

When the operator pushes the control lever past the DOWN position to the detent, the leveling blade is in the FLOAT position. Spool (5) moves to the extreme right as shown. Spring (9) is compressed. Hydraulic oil from the steer pump enters the control valve at inlet port (3). This oil is routed to chamber (2), chamber (4), and relief valve (1).

Oil at chamber (2) is blocked. Oil at chamber (4) flows through slots in spool (5) to outlet port (7). Oil exits the control valve through outlet port (7), and is routed to the hydraulic oil tank through an oil cooler and a hydraulic return filter.

Extend port (6) and retract port (8) are also open to outlet port (7). This means there is no high-pressure oil going to either side of the blade cylinder. The leveling blade rests on the ground, due to its weight, and is free to "float" over the terrain.

Detent (10) will keep the control valve in the FLOAT position until the operator pulls the control lever back to a different position.

Cylinder

Cylinder Components
(1) Extend port. (2) Chamber. (3) Piston. (4) Chamber. (5) Retract port. (6) Rod end.

The blade cylinder is a double-acting hydraulic cylinder, used to raise and lower the leveling blade. The cylinder is secured inside a frame assembly, which is trunnion mounted to the front scraper of the machine. The rod end (6) of the cylinder is attached to the blade.

When the control lever (at operator's station) is in the HOLD position, hydraulic oil in chamber (2) and chamber (4) is trapped in the cylinder by the control valve. Piston (3) is prevented from moving. Rod end (6) holds the blade in position.

When the operator moves the control lever to the UP position, hydraulic oil from the control valve enters the cylinder at retract port (5). Piston (3) and rod end (6) retract, raising the blade off the ground. As piston (3) retracts, return oil exits the cylinder through extend port (1). This oil is routed through the control valve to the hydraulic oil tank.

When the operator moves the control lever to the DOWN position, hydraulic oil from the control valve enters the cylinder at extend port (1). Piston (3) and rod end (6) extend, lowering the blade. As piston (3) extends, return oil exits the cylinder through retract port (5). This oil is routed through the control valve to the hydraulic oil tank.

When the operator moves the control lever to the FLOAT position, oil in both chambers (2) and (4) is open to the return line. The blade will rest on the ground. Piston (3) and rod end (6) will retract and extend as the blade moves up and down with the terrain.