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| Illustration 1 | g02175516 |
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(1) Piston chamber
(2) Piston (3) Spring (4) Passage (5) Port (6) Passage (7) Shaft (8) Piston (9) Barrel (10) Separator (11) Friction plate (12) Housing (13) Orifice (14) Reducing valve (15) Orifice | |
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| Illustration 2 | g03409165 |
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Travel motor (partial schematic) (1) Piston chamber (2) Piston (3) Spring (4) Passage (5) Port (6) Passage (14) Reducing valve (15) Orifice (16) Brake valve | |
Pump oil is supplied to the travel motor. The parking brake is released and the motor starts rotating. When no pump oil is supplied to the motor, the motor stops and the parking brake engages.
In the parking brake section of the travel motor, separator plates (10) are splined to housing (12). Friction plates (11) are splined to barrel (9).
When no pump oil is supplied to the travel motor, piston (2) is pushed to the left by the force of springs (3). The oil in piston chamber (1) now flows through passage (4). The oil flows back through orifice (13) and port (5) to the travel motor brake valve. Travel motor brake valve (16) returns the oil back to the motor case through passage (6). Friction plates (11) and separator plates (10) are held together against housing (12) by spring (3). The rotation of the motor stops as the parking brake is engaged.
Orifice (13) restricts return oil flow from piston chamber (1). The restriction of the oil flow delays the application of the parking brake. If the return oil was not restricted by orifice (13), the parking brake would be applied too early. Earlier wear and/or damage to the machine could result if the machine stayed in motion.
Prior to the operation of the travel motor, a portion of the pressure oil goes to port (5). The oil then flows through passages (4) to piston chamber (1). Piston (2) moves to the right against the force of spring (3). The load which compresses plates (10) and friction plates (11) is released. Barrel (9) and shaft (7) now turn.
After the piston has retracted, pressure increases in passage (4) and piston chamber (1) until reducing valve (14) opens. Supply pressure from port (5) is then reduced by the flow through orifice (13), reducing valve (14), and orifice (15). Applying lower pressure to the brake increases seal life and applying lower pressure allows air to be purged from the system.