Tham khảo tài liệu 'advanced vehicle technology episode 3 part 7', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Fig. Tractor three line brake system the tractor s rear axle to reduce the risk of jackknifing during an emergency application. Parking circuit Fig. Applying the hand brake lever opens the hand brake valve so that pressurized air flows to the rear axle parking line chambers within the double diaphragm actuators to apply the brakes. At the same time the mechanical parking linkage locks the brake shoes in the applied position and then releases the air from the parking actuator chambers. This parking brake is therefore mechanical with air assistance. Trailer three line brake system Fig. All trailer air braking systems have their own reservoir which is supplied through the emergency line from the tractor s service reservoir. Service line circuit Fig. When applying the brakes air pressure from the tractor s relay valve signals the emergency relay valve to open and supply air pressure from the trailer s own reservoir to the trailer s service line brake actuator chambers relative to that applied to the tractor brakes. The Fig. Trailer three line brake system 512 object of the separate reservoir and relay valve installed on the trailer is to speed up the application and release of the trailer brakes which are at some distance from the driver s foot control valve. Should there be a reduction in emergency line pressure below some predetermined minimum the emergency relay valve will sense this condition and will automatically apply the trailer service brakes. Secondary line circuit Fig. The secondary braking system of the trailer is controlled by the hand control valve mounted in front of the driver. Moving the hand control valve lever towards the applied position delivers a graduable air pressure via the secondary lines to the secondary chamber within each double diaphragm actuator. A quick release valve incorporated at the junction between the trailer s front and rear brakes speeds up the exhausting of the secondary chambers and .
