SELECTOR VALVE FOR A PRESSURE CONTROL DEVICE IN A RAILWAY VEHICLE AIR BRAKE SYSTEM

摘要

A pressure control valve for the compressed air brakes of a railway vehicle includes a triple pressure control valve with a constant pressure chamber, a selector valve and a selector reservoir. Upon the occurrence of pressure reductions in the main brake line for service braking, the selector valve remains at rest. When stronger pressure reductions in the main brake line occur, the selector valve evacuates the selector reservoir which lags in relation to the main brake line pressure as result of the force exerted by a pre-stressed spring until a specific minimum pressure is attained by a retention valve. In a subsequent brake release, the selector valve will produce a pressure balance between the constant pressure chamber and the selector reservoir to facilitate the brake release process and a balancing or proportioning of the pressure control valve at an optionally reduced normal pressure head in the main brake line. The selector valve includes a piston retained in a middle position by a spring buffer and by two valves positioned on both sides of the piston and spring loaded in their respective closing directions. On one side, the piston is loaded by the main brake line pressure and on the other side by the pressure in the selector reservoir.