The slewing motor is equipped with a parking brake, which can make the upper slewing device immobile when lifting heavy objects on a slope, and it can also prevent the upper slewing device from rotating by itself due to inertia when walking. This parking brake is a structural type in which a wet disc brake holds the motor's rotating shaft. It is a normally closed type, that is, when it is not in motion, it always holds the shaft and brakes by spring force.
As long as any one of the excavator rotation or the working device is operated, the oil return in the logic signal circuit of the main control valve cannot lead to the oil tank, and the logic pressure rises. As soon as the logic pressure rises, the hydraulic timer is switched, and the pilot pressure oil passes through the valve to release the parking brake, so the swing action can be performed, and the operating device will not exert excessive force on the swing motor parking brake when the work device is operating.
When the joystick is returned from the working position to the neutral position, the oil return in the logic signal circuit of the main control valve can be connected to the fuel tank, and the logic pressure will drop immediately. As soon as the logic pressure drops, the hydraulic timer is switched back to cut off the oil supply circuit of the pilot pump, so that the oil in the parking brake cavity is slowly returned to the oil tank through throttling, and the parking brake is re-applied after about 5 seconds.
