Blue Bird Vision 2021, Руководство водителя

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R O U T I N E O P E R A T I O N R O U T I N E O P E R A T I O N
Parking Brakes (With Air Brakes)
On Blue Bird buses, the parking brake function is provided not by the air pressure, but by
coil springs incorporated within the rear wheel brake actuation chambers. When the park-
ing brake valve on the dash is pulled outward, air pressure is vented from the rear brake
actuators, allowing the springs to engage the rear brakes and locking the rear wheels.
When the parking brake valve is pushed in, it allows the air pressure in the rear brake ac-
tuators to overcome the spring pressure, thereby releasing the rear spring brakes.
Although the parking brake control is an air valve, it is not air pressure which applies
the parking brake, but the absence of air. The parking brake is applied by mechanical
springs which are released (caged) when the air system pressure is sufficient for normal
brakes operation. Pushing in the parking brake valve to release the parking brake does not
release air pressure, it applies it to cage the spring brakes. This is why the parking brake
button automatically “pops out” if you try to release the parking brake before sufficient air
pressure has built up.
If for any reason the air reserve in both the primary and secondary circuits drops below
a safe minimum, the spring brakes automatically engage and apply braking at the rear
wheels. If this occurs enroute, the Driver should call for professional service assistance.
Provisions are made for a qualified service technician to mechanically release the spring
brakes to allow the bus to be towed for repair.
Pull to apply parking brakes. Push to release. The parking
brake valve does not apply air brakes. It applies air to release
the mechanical spring brakes.
The park brake valve cannot release the spring brakes until
sufficient air is in the system for normal service air brakes
operation. If it is pushed in before system pressure is present,
it will automatically “pop out.”