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| Illustration 1 | g00952541 |
Swing hydraulic system | |
The swing drive is equipped with a multi-disc parking brake. The parking brake is applied by spring force and released by pressurized pilot oil.
When the left hand pilot valve is actuated, the pressurized pilot oil is sent to one end of the swing control valve in order to activate the swing function. Swing pilot oil passes through the resolver valve in the swing control valve before splitting in two directions. The first direction is to the solenoid valve for the swing signal. When the operating parameters are correct, the machine control module will energize the solenoid valve for the swing signal. When the solenoid valve is energized, the swing pilot oil flows to the dual pressure relief valve. The dual pressure relief valve increases the pressure setting. The second path goes to the regulator control valve for the swing pump. The second pressure is called positive flow control pressure. The positive flow control pressure upstrokes the swing piston pump. Swing pilot pressure opens the pressure switch for the swing parking brake which signals the machine control module to check the ladder position switches. If the ladder position switches are in the UP position, the ladder position switches are closed and the machine control module will energize the swing parking brake solenoid valve. The swing parking brake solenoid valve directs the pressurized oil in the pilot system in order to release the swing parking brakes.
When the right hand pilot valve is actuated, the pressurized pilot oil is sent to one end of the front control valve or the rear control valve. The pilot oil will activate a function for an implement, travel, or bucket bottom dump. The pilot oil will also pressurize the implement pressure switch or the pressure switch for travel and bottom dump. The pressure switches signal the machine control module to check the ladder position switches. If the ladder position switches are in the UP position, the ladder position switches are closed and the machine control module will energize the swing parking brake solenoid valve. The swing parking brake solenoid valve directs the pressurized oil in the pilot system in order to release the swing parking brakes.
The machine control module signals the Engine Control Module (ECM) that the swing function, travel function, or implement function has been requested. The ECM will increase the engine speed to the throttle dial setting when the engine speed is at the setting for the automatic engine speed control (AESC) of 1350 rpm.
Note: If the ladder is in the DOWN position, the circuit for the ladder position switch is open and the machine control module will not energize the swing parking brake solenoid valve. When the swing parking brake solenoid valve remains de-energized the swing parking brakes remain engaged.
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| Illustration 2 | g00577072 |
Swing parking brake | |
When the swing pilot controls, stick pilot controls, boom pilot controls, or bucket pilot controls are in the NEUTRAL position, the swing parking brake is applied. Pilot oil to the ports is blocked and the brakes are applied. The friction discs are splined to the input shaft. The friction plates are splined to the swing brake housing. The springs for the swing parking brake will force the brake piston in an upward direction, which forces the friction plates and the friction discs together. Forcing the friction plates and the friction discs together applies a holding torque to the input shaft.