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| Illustration 1 | g06371655 |
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Parking brake (Final Drive) (1) Passage from the brake pilot valve (2) Brake piston (3) Springs (4) Coupling (5) Plates (6) Spindle housing (7) Friction discs (8) Plate (9) Retaining ring | |
The parking brake consists of the following components: brake piston (2), springs (3), friction discs (7), and plates (5).
In the parking brake, the plates are splined to the coupling (4). The friction discs are splined to spindle housing (6).
When a travel lever is moved, the oil from the pump flows to the inlet port of the travel motor.
The brake pilot valve shifts allowing oil to flow through an internal passage of the motor head to the passage (1) in the spindle housing. The oil flows through the passage to the piston chamber. The oil pressure in the piston chamber overcomes the force of the springs. The brake piston moves to the left. The spring force that is holding the brake piston against the plates and friction discs is released. The parking brake is disengaged.
At the same time, oil from the pump flows through a passage and a check valve in the motor head. The oil then flows to the travel motor. The parking brake is disengaged before the travel motor starts to rotate. The output shaft of the travel motor directs power to the gear within in the final drive.
When the travel lever is returned to the NEUTRAL position, the oil from the pump is blocked at the travel control valve in the main control valve. The motor head regulates the stopping of the travel motor. The travel motor is gradually slowed to a stop.
The brake pilot valve shifts to the closed position. The force of the oil pressure on the brake piston is lower than the force of the springs. The brake piston is pushed slowly to the right by the force of the springs. The oil in the piston chamber now flows through the passage from the brake pilot valve through an internal passage to the brake pilot valve. The oil flows through a passage in the brake pilot valve and into the motor case drain line. The friction discs and plates are forced together by the brake piston. The force of the springs holds the brake piston against the friction discs (7) and plates. The friction discs are splined to the spindle housing. The plates are splined to the coupling. When the plates and friction discs are forced together, the parking brake is engaged. The travel motor stops rotating before the parking brake engages.
The parking brake is delayed in order to give the machine time to stop. Earlier wear and/or damage to the machine could result if the machine stayed in motion.