DESCRIPTION OF MAIN COMPONENTS OF AIR BRAKE
DESCRIPTION OF MAIN COMPONENTS OF AIR BRAKE
A-9 AUTOMATIC BRAKE VALVE
DESCRIPTION
A – 9 Automatic brake valve is a self – lapping brake valve capable of graduating the application or release of locomotive and train brakes. It has five positions : Release, minimum reduction, fun service over reduction and emergency.
The brake valve consists of a self – lapping regulating portion and a vent valve. The self lapping regulating portion actuated by carn dog, controls brake pipe pressure from Release to over production. The vent valve actuated by specials Cam dog in the emergency position of the brake valve handle vents the brake pipe pressure to the atmosphere at an emergency rate.
OPERATION
CHARGING
In the “Release Position” of the handle, regulating cam dog will hold the inlet and exhaust valve unit in normal release position, the regulating spring will cause the double ban valve assembly to be seated at the exhaust and unseated at the inlet. Main reservoir air supplied through port 30 in the pipe brackets passes through the open inlet valve to port 5. This air also Passes through a restricted hole, in front of diaphragm,. When the pressure on the face of the diaphragm is sufficient to overcome the force exerted by the Regulating spring, the diaphragm moves to allow the inlet valve spring to seat the double ban valve assembly at the inlet. The brake valve will resume a Lap position.
APPLICATION
When the brake valve handle is moved in to the ‘minimum reduction position’ service application zone, or fun service position the regulation cam Dog will pen nit the inlet valve to be moved away from the diaphragm by the Exhaust valve spring. The inlet valve assembly will carry the double ball valve assembly with it. Exhaust valve will be unseated, allowing brake pipe to air flow to flow to exhaust at a service rate. The pressure action on the diaphragm will be reduced and the regulating valve spring will move the diaphragm towards the inlet valve. When the forces acting on the two sides of the diaphragm assembly are equalized, the double ball valve assembly will be seated at exhaust, causing the brake valve to assume a lap position.
RELEASE
When the brake valve handle is removed towards Release position after application, the regulating cam dog will move the inlet valve assembly towards the diaphragm assembly. This will cause the inlet valve to open M.R Pressure will flow through the open inlet to port 5 and also on to the face of the diaphragm will move against the regulating spring. When the forces acting on two sides of the diaphragm have equalized, the double ball valve assembly again seat at the inlet valve and the brake valve will assume a lap position.
EMERGENCY
When the brake valve handle is moved to emergency position the brake valve will have passed through the service application zone performing service operations, the special carn dog on the cam shaft actuates the vent valve, allowing the brake pipe air to vent to atmosphere at an emergency rate.
QUICK RELEASE POSITION
` The Quick release position of the independent brake valve Provides a means of releasing an automatic brake application on the locomotive with out affecting the automatic brake application on the train brakes.
The quick release feature is actuated by release by release valve carn on the brake valve handle shaft. When the brake handle is placed in the quick Release position, the release valve earn positions the release valve to connect vacuum control reservoir (port 7) to vacuum brake pipe (port 1). Since the automatic brake application is effect on the locomotive, the vacuum in the control reservoir of the control valve will be greater then that of vacuum break pipe the vacuum in the control reservoir will be permitted to equalize with the brake pipe. This will cause the 28VB control valve to assume a release position and sub subsequently cause the release of the break cylinder pressure on the locomotive. The equalizing of vacuum control reservoir and vacuum, brake pipe will have no effect on V-A – 1A Control valve, and so the train brakes will remain applied.