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| Illustration 1 | g03872640 |
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Components of the Service Brake Group (1) Reaction plate (2) Separator plates (nine) (3) Chamber (4) Springs (six) (5) Friction discs (nine) (6) Hub (7) Piston | |
The service brakes are positioned at all four of the interfaces between the spindles and axle housings. The heat from the friction of the service brakes is removed by the oil in the compartment for the service brakes.
Reaction plate (1) is fastened between the spindle and the axle housing. Reaction plate (1) does not turn. The splines on the outside circumference of separator plates (2) engage with the splines positioned on the inside of reaction plate (1).
There are splines on the outside circumference of hub (6). These splines engage with the splines on the inside circumference of friction discs (5). This engagement causes hub (6) and friction discs (5) to turn together.
Oil pressure flows from the service brake control valve into chamber (3) when a brake pedal is pushed. The oil pressure in chamber (3) pushes piston (7) against separator plates (2) and against friction discs (5). This oil pressure creates friction between separator plates (2) and friction discs (5). Separator plates (2) are held stationary by reaction plate (1) and by friction discs (5), which turn with the rotation of the axle shafts. This friction causes the wheels to turn at a slower rate or to stop.
Friction discs (5) have grooves which allow cooling oil to pass between separator plates (2) and friction discs (5). These grooves allow oil to flow in either the activated position or the released position. If the depth of the grooves in the friction discs is adequate, the cooling oil constantly flows between friction discs (5) and separator plates (2). This flow still occurs when the service brake is applied.
The oil from chamber (3) flows back to the service brake control valve, and to the hydraulic tank when the service brake pedal is released. Springs (4) pull piston (7) away from separator plates (2). The flow of oil between separator plates (2) and friction discs (5) also assists the release of the service brake.