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| Illustration 1 | g06381349 |
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Travel motor (1) Head (2) Barrel (3) Piston (4) Retainer (5) Displacement change valve piston (6) Displacement change valve (7) Displacement change valve spring (8) Drive shaft (9) Timing plate (10) Brake spring (11) Brake Piston (12) Friction plate (13) Separator plate (14) Parking brake (15) Swashplate | |
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| Illustration 2 | g06613636 |
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Travel motor (partial schematic) (6) Displacement change valve (14) Parking brake (15) Swashplate (16) Motor rotary group (17) Counterbalance valve (18) Crossover relief valves (19) Port (20) Port (21) Port (22) Port | |
The travel motors convert hydraulic energy into rotating action. Oil from the pump enters the travel motor through head (1). Oil travels in one direction to release parking brake (14). The oil is also routed through timing plate (9) into barrel (2).
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| Illustration 3 | g06305942 |
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Typical example (1) Head (2) Barrel (9) Timing plate (21) Port | |
Timing plate (9) is held stationary with head (1). The timing plate has ports that align with ports (21) and (22). The oil enters the pistons that are aligned with the ports in the timing plate and head. The oil pushes pistons (3), and the pushing force is converted into rotation around angled swashplate (15). Drive shaft (8) is splined to barrel (2), and the rotation of the barrel turns drive shaft (8). As the barrel rotates, the oil in the pistons that are aligned with the ports in the timing plate flows out of the head.
Swashplate (15) can be positioned at different angles to change the displacement of the motor which results in a change in speed. The displacement is controlled by the travel speed switch in the cab. When the switch is in low speed, no pilot oil will be sent to displacement change valve (6) to change the swashplate angle. The swashplate angle is at the steepest angle with the switch in low speed. With the swashplate angle at the steepest angle, displacement is at the maximum and the motor produces low speed and high torque.
When the switch is in high speed, pilot oil will be sent through port (19) to the displacement change valve. The valve shifts allowing a path for pump oil to flow to displacement change valve piston (5). The oil pressure forces the displacement change valve piston to shift the angle of the swashplate to the minimum angle. With the swashplate angle at the minimum angle, displacement is at the minimum and the motor produces high speed and low torque.
The flow of the oil from the pump depends on the direction of travel. The oil flow from the pump flows into the travel motor through port (21) or port (22). Pump oil returns to tank through the opposite port. For forward travel, the oil flows into the travel motor through port (22).
Case drain oil returns to the hydraulic tank through drain port (20).
Crossover relief valves (18) protect the travel motor by releasing the high-pressure oil. The crossover relief valves also provide makeup oil from the outlet side of the travel motor to the inlet side of the travel motor. This makeup oil prevents a vacuum condition in the travel motor.