Abstract: The electropneumatic control system for the pressure in the main air pipe (37) of compressed air brakes of rail cars is provided with one inlet and one outlet solenoid valve (3 and 4) to control the pressure in a control chamber (26) of a relay valve (19). The inlet solenoid valve (3) and the relay valve (19) are supplied with compressed air from a main reservoir pipe (34). The relay valve controlled by the pressure in the control chamber (26) against the pressure in the main air pipe (37) controls the compressed air lead-in and lead-out for the main air pipe (37). To avoid the undesired response of the relay valve (19) to pressure changes elsewhere in the main air pipe (37), the two sides of the piston (20) of the relay valve (19) are closed without any throttling by way of the secondary valve parts (13 or 14) of the two solenoid valves (3 and 4) in the unactuated state of the control system (2).

Abstract: 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 selector 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.