A brake accelerator for drawing off air from the brake line of an air brake system for railway vehicles has a piston one side of which is subjected to air pressure in the brake line and the other side is subjected to a control pressure in an expansion chamber connected to the brake line through a throttle opening. A first valve is in a connection between the brake line and a pressure accumulation chamber connected to the atmosphere through a second throttle opening. The first valve is actuated by the first piston when the control pressure exerted on the first piston is predominant. A second valve opens subsequently to the first valve and is located in a connection leading from the expansion chamber through a throttle opening to the atmosphere. The second valve is actuated by a second piston loaded by the pressure in the pressure accumulation chamber in the direction to open the second valve against the force of a spring urging the second valve into its closed position.

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).

A vent valve device having a pair of diaphragm-type piston members forming a pilot chamber therebetween. The one piston controls a vent valve via which brake pipe pressure is vented locally, while the other piston controls a pilot valve a control venting of the pilot chamber. A breather choke between the pilot chamber on one side of the other piston and a control chamber on the opposite side establishes a predetermined pressure differential thereacross only when brake pipe pressure supplied to the pilot chamber is reduced at an emergency rate to thereby actuate the other piston to a position opening the pilot valve. In addition, this other piston operates a cut-off valve to isolate the pilot chamber from brake pipe pressure so that the pilot valve quickly exhausts pilot chamber pressure. The one piston controlling the vent valve is in turn actuated by the exhaust of pilot chamber pressure to positively effect an unrestricted, local reduction of brake pipe pressure via the vent valve when this one piston is actuated.

An emergency vent valve including a piston responsive to the differential pressure between the brake pipe and a control volume to open a vent valve to vent the brake pipe to atmosphere and includes an exhaust valve responsive to the differential pressure between brake pipe and control volume to connect the control volume to atmosphere through a service check and when the vent valve is opened through a second blow-down choke of a lesser rate which limits the exhausting of the control chamber. A choke valve connected to the piston connects the blow-down choke in series with the service choke when the vent valve becomes fully open.

A vent valve made from a standard emergency brake valve portion. It includes an emergency portion body with an interface to be mated with the emergency portion interface of the pipe bracket. The body includes a casting with at least one cover and the casting including all the cast cavities and passages for an emergency portion. A vent valve selectively connects a first brake pipe port to a vent port on the body, A vent piston controls the vent valve and a discharge valve pneumatically controls the vent piston. An emergency piston is responsive to brake pipe pressure for controlling the discharge valve. The body does not include at least one of an in shot valve and an accelerated application valve.