 | |
| Illustration 1 | g03816004 |
Under Operator Platform (1) Propel pump | |
Propel pump (1) is located under the operator platform. This pump is driven by the engine. The platform must be raised to access to this component.
Propel pump (1) is a piston-type pump with variable displacement. The pump housing contains two rotating groups. The rotating groups are face-to-face. The rotating group closest to the engine provides flow to the axle motor. The second rotating group provides flow to the drum motor.
A cable connects the propel lever to a bracket that controls the displacement control lever for the drum rotating group. This bracket is connected by a tie rod to a similar bracket which controls the displacement control lever for the axle rotating group.
The displacement control lever on each rotating group provides input to the displacement control valve in the rotating group. The position of the displacement control valve controls the servo piston. The servo piston for each rotating group controls the angle of the swashplate in the rotating group.
 | |
| Illustration 2 | g03816007 |
Propel Pump Graphic (2) Port "M14" (3) Neutral start switch (4) Port "MB" (5) Port "X7" (6) Port "MC" (7) Port "M14" (8) Port "MD" (9) Port "MA" (10) Port "AM3" (11) Charge relief valve (12) Interlock solenoid (13) Port "M5" (14) Port "L2" (15) Four crossover relief valves (16) Port "M3" (17) Port "L3" (18) Port "M5" (19) Port "C" (20) Port "D" (21) Port "A" (22) Port "B" (23) Port "E" (24) Port "M4" (25) Port "L1" (26) Port "M4" | |
Each port in the pump housing is identified by a numeric or an alpha-numeric designation that is cast into the housing next to the port.
The port configuration for the axle rotating group and the port configuration of the drum rotating group differ slightly. The function of each port on the two rotating groups is as follows:
Port "A" (21) - This port is a system port. Port "A" is the reverse pressure port for the axle drive system.
Port "B" (22) - This port is a system port. Port "B" is the forward pressure port for the axle drive system.
Port "C" (19) - This port is a system port. Port "C" is the reverse pressure port for the drum drive system.
Port "D" (20) - This port is a system port. Port "D" is the forward pressure port for the drum drive system.
Port "E" (23) - This port is the charge inlet port. Filtered charge oil is directed into port "E".
Port "L1" (25) - This port is a case drain port. Port "L1" is plugged.
Port "L2" (14) - This port is a case drain port. Case drain oil from the propel pump flows to the cooler bypass valve at port "L2". When case drain pressure exceeds 170 kPa (25 psi), the bypass valve opens. When the bypass valve is open, case drain oil is sent directly to tank.
Port "L3" (17) - This port is the main case drain port. Case drain oil from the propel pump flows to the oil cooler through port "L3". Most case drain oil from the pump flows through this port.
Port "MA" (9) - This port is a gauge port for axle reverse pressure. A hose connects port "MA" on the pump to port "MB" on the test manifold.
Port "MB" (4) - This port is a gauge port for axle forward pressure. A hose connects port "MB" on the pump to port "MA" on the test manifold.
Port "MC" (6) - This port is a gauge port for drum reverse pressure. A hose connects port "MC" on the pump to port "MD" on the test manifold.
Port "MD" (8) - This port is a gauge port for drum forward pressure. A hose connects port "MD" on the pump to port "MC" on the test manifold.
Port "M3" (16) - This port is a charge pressure port. Port "M3" is plugged.
Port "AM3" (10) - This port is a charge pressure port. Port "AM3" is plugged.
Port "M4" (24) and (26) - Each rotating group in the pump is equipped with a port labeled "M4". These ports are located on opposite sides of the pump housing. Each of these ports is plugged. The pressure on one side of the servo piston can be measured at port "M4". Port "M4" (24) on the shaft end of the propel pump can be used to measure reverse servo pressure for the axle rotating group. Port "M4" (26) on the capped end of the pump can be used to measure reverse servo pressure for the drum rotating group.
Port "M5" (13) and (18) - Each rotating group in the pump is equipped with a port labeled "M5". These ports are located on opposite sides of the pump housing. Each of these ports is plugged. The pressure on one side of the servo piston can be measured at port "M5". Port "M5" (13) on the shaft end of the propel pump can be used to measure forward servo pressure for the axle rotating group. Port "M5" (18) on the capped end of the pump can be used to measure forward servo pressure for the drum rotating group.
Port "M14" (2) and (7) - Each rotating group in the pump is equipped with a port labeled "M14" These ports are located on the direction control valves. Each of these ports is plugged. Case drain pressure can be measured at port "M14".
Port "X7" (5) - This port is the brake release port. When interlock solenoid (12) is energized, charge oil is directed out port "X7" into the drum brake piston. Brake release pressure is set at 1420 kPa (206 psi).
Neutral start switch (3) is located on top of the axle rotating group. The neutral start switch is activated by the position of the displacement control lever.
When the propel lever is in the NEUTRAL position, neutral start switch (3) is closed. When the propel lever is in the FORWARD position, the neutral switch is open. When the propel lever is in the REVERSE position, the neutral start switch is open.
The pump housing is equipped with charge relief valve (11). This valve is mechanically adjustable. The charge relief valve in the propel pump maintains charge pressure at 2500 ± 200 kPa (363 ± 29 psi). This valve also regulates case drain flow through the pump.
Interlock solenoid (12) is located on the propel pump. The parking brake switch controls this solenoid. When the parking brake is engaged, this solenoid is not energized. When the parking brake is released, the interlock solenoid is energized.
When interlock solenoid (12) is energized, charge oil is available at the direction control valve in each rotating group. When the solenoid is not energized, charge oil is blocked. In this case, the direction control valves and the parking brake are open to case drain. Under these conditions, the rotating group in each pump is at zero angle, and the parking brake is engaged. The interlock solenoid provides a drain passage for the oil in the parking brake piston.
Each rotating group of the propel pump is equipped with two makeup and relief valves. The relief section of the valves limits the pressure in the circuit to 35 500 ± 1500 kPa (5149 ± 218 psi). The makeup section of the valves allows charge oil to flow into the low-pressure circuit in order to replenish the oil lost to internal leakage.
The function of each makeup and relief valve is as follows:
Makeup and relief valve for port "A" (21) - This valve controls the pressure in the reverse loop of the axle circuit.
Makeup and relief valve for port "B" (22) - This valve controls the pressure in the forward loop of the axle circuit.
Makeup and relief valve for port "C" (19) - This valve controls the pressure in the reverse loop of the drum circuit.
Makeup and relief valve for port "D" (20) - This valve controls the pressure in the forward loop of the drum circuit.
 | |
| Illustration 3 | g03816011 |
Propel Pump Cross Section (27) Servo piston (28) Feedback link (29) Displacement control valve (axle) (30) Displacement control valve (drum) (31) Feedback link (32) Swashplate (33) Input shaft (34) Piston (35) Slipper pad (36) Rotating group (37) Rotating group (38) Slipper pad (39) Piston (40) Swashplate (41) Servo piston | |
Engine rotation turns pump input shaft (33), which then rotates two rotating groups (36) and (37). The rotating groups contain a piston and barrel assembly. Pistons (34) and (39) rotate with the barrel assembly. Slipper pads (35) and (38) allow the pistons to follow the angle of swashplates (32) and (40). The rotating groups only generate flow when the respective swashplate is not at zero angle.
When the propel lever is moved into the FORWARD position, a mechanical connection moves displacement control valve (29) and (30) on the pump. When this movement occurs, charge oil flows across the control valve spools and into the chamber on the forward side of each servo piston. The control valve spools direct the oil into the chamber on the reverse side of servo pistons (27) and (41).
The pressure differential between the two sides of servo piston (27) and (41) causes the pistons to move. This action tilts swashplate (32) and (40), and the piston displacement in the rotating groups changes. As the swashplates move, feedback link (28) and (31) moves the control spool back to neutral through an internal feedback spring. In this case, the servo pistons are prevented from tilting the corresponding swashplate too far by blocking the charge oil supply.
As input shaft (33) rotates, slipper pads (35) and (38) in rotating group (36) and (37) follow the angle of the corresponding swashplate. This action causes pistons (34) and (39) to move in and out of the barrel assembly. As the pistons move out, oil in the reverse circuit is drawn into the piston chamber. As the pistons move in, oil in the piston chamber is forced out of the forward port.
As the load on the propel system increases, increased pressure in the system moves swashplate (32) and (40) toward the neutral position. This movement causes feedback link (28) and (31) to reposition the control spools in order to send additional charge oil into the servo pistons. Increased pressure in servo piston (27) and (41) maintains the position of the swashplates in order to maintain supply flow from each rotating group.