- Underground Articulated Truck:
- AD30 (S/N: CXR1-UP)
Illustration 26 shows the pilot control actuators referenced incorrectly. Replace the existing information with the information that follows.
Control Valve (Hoist)
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| Illustration 1 | g01062980 |
Hoist control valve in the HOLD position (1) Pilot control actuator (raise) (2) Valve body (3) Port (brake oil cooling) (4) Relief valve (brake oil cooler) (5) Tank port (6) Pilot control actuator (lower) (7) Lowering control valve (stopped engine) (8) Raise port (9) Lower port (10) Relief valve (hoist lower) (11) Pump port (12) Relief valve (13) Stem | |
Note: The position and operation of the ejector control valve is similar to the hoist control valve on standard AD30 Underground Articulated Trucks.
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| Illustration 2 | g01062731 |
The position of stem (13) is determined by the magnitude of the pilot pressure within pilot control actuators (1) and (6). This pilot pressure, which acts on the stem, is controlled by the solenoids which are part of the pilot control actuators. The solenoids are connected to the hoist control, which is in the cab, via the ECM. The stem has four positions.
HOLD Position
When the engine is shut off, the pilot pressure within pilot control actuators (1) and (6) is zero. The stem is centered to the HOLD position by the springs which are inside of the pilot control actuators.
When the hoist control is moved to the HOLD position and the engine is running, equal pilot pressure within the pilot control actuators moves the stem to the HOLD position. Oil flows from pump port (11) to port (3). All other ports are blocked by the stem.
RAISE Position
When the hoist control is moved to the RAISE position, the Power Train /Chassis ECM sends a current to pilot control actuator (1), which is proportional to the displacement of the hoist control. Pilot control actuator (1) is energized. The pilot pressure within pilot control actuator (1) is relieved and the stem is moved to the RAISE position by the pilot pressure within pilot control actuator (6). The stem is moved fully to the left. Oil flows from pump port (11) to the piston sides of the hoist cylinders from raise port (8). Oil flows from the rod sides of the hoist cylinders to lower port (9). This oil flows from lower port (9) to port (3). The hoist cylinders extend and the body is raised.
LOWER Position
When the hoist control is moved to the LOWER position, the Power Train /Chassis ECM sends a current to pilot control actuator (6), which is proportional to the displacement of the hoist control. Pilot control actuator (6) is energized. The pilot pressure within pilot control actuator (6) is relieved and the stem is moved to the LOWER position by the pilot pressure within pilot control actuator (1). The stem is moved fully to the right. Oil flows from pump port (11) to the rod sides of the hoist cylinders from lower port (9). Oil flows from the piston sides of the hoist cylinders to raise port (8). This oil flows from raise port (8) to tank port (5). The hoist cylinders retract and the body is lowered.
FLOAT Position
When the hoist control is moved to the FLOAT position, pilot control actuator (6) is partially energized. The pilot pressure within pilot control actuator (6) is partially relieved and the stem is moved to the FLOAT position by the pilot pressure within pilot control actuator (1). The stem is moved partially to the right. Oil flows from pump port (11) to port (3). Raise port (8) is connected to the tank. Lower port (9) is connected to the brake cooling system.
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| Illustration 3 | g00945877 |
Relief Valve
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| Illustration 4 | g00945876 |
The hoist control is in the HOLD, LOWER, or FLOAT position. (1) Relief valve (2) Piston (3) Spring (4) Port | |
Relief valve (1) is a two-stage relief valve with two relief settings.
When the body is being lowered, the relief setting of the relief valve is determined by spring (3) .
When the body is being raised, pressure in the line to the piston side of the hoist cylinders is transmitted to port (4). This moves piston (2) against spring (3) which increases the relief setting of the relief valve.
Reference: For information about testing and adjusting the line relief valves, refer to the Service Manual module for Testing and Adjusting, "Relief Valve (Main) - Test and Adjust" for the machine that is being serviced.
Lowering Control Valve (Stopped Engine)
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| Illustration 5 | g01034732 |
(1) Lowering control valve (stopped engine) (2) Plunger (3) Piston (4) Hole (5) Port | |
Lowering control valve (1) can be used to connect the raise port to the tank port of the hoist control valve. This is required in order to lower the body when the engine is not operational.
Plunger (2) is unscrewed from the lowering control valve. Pressure at port (5) moves piston (3) to the right. This connects port (5), which is connected to the raise port of the hoist control valve, to holes (4) which are connected to the hydraulic tank.
Relief Valve (Hoist Lower)
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| Illustration 6 | g00942961 |
(1) Locking nut (2) Spring (3) Poppet (4) Seat (5) Adjusting screw (6) Washer (7) Tank passage (8) Inlet | |
When the oil pressure at the inlet of the main control valve is less than the relief valve setting, the force of spring (2) holds poppet (3) onto seat (4). Hydraulic oil will not flow to the hydraulic tank.
As the oil pressure at inlet (8) exceeds the relief valve setting, the oil pressure overcomes the force of spring (2). Poppet (3) will move off seat (4). The oil then flows through tank passage (7) and into the hydraulic tank.
Reference: For information about testing and adjusting the line relief valves, refer to the Service Manual module for Testing and Adjusting, "Relief Valve (Hoist Lower) - Test and Adjust" for the machine that is being serviced.