An accelerator for control valves, particularly for triple pressure control valves (3) of pneumatic brake systems of rail vehicles, having a pick-up accelerator (30) and a transfer chamber (40) as well as a service brake accelerator (52), the service brake accelerator (52) having a reference pressure chamber (55) which is connected to the transfer chamber (40) of the pick-up accelerator, the transfer chamber having a bleeder nozzle which is not open at all times. As a result, the service brake accelerator (52) is activated only during braking operations, while the reference pressure chamber (55) is protected from filling strokes, the volumes which are in continuous connection with the air main (1) are reduced, and the air consumption is lowered, especially during brake release operations. Service brake accelerators (52) of any desired construction may be used, especially, however, service brake accelerators which, during pressure reductions within the air main (1), draw off pulsating pressurized air from the latter.

A fluid brake control system for a railway train has control valves of the ABD type that have service valves that are modified to provide continuous quick service, thus eliminating the need for special accelerated application valves as currently used in ABDW control valves.

A service brake accelerator having a line chamber (3) connected to the main air supply line (1) and a reference pressure chamber (6) connected to the line chamber via a nozzle (7). The line chamber is separated from the reference pressure chamber by a diaphragm piston (5) which is biased by a spring (10) against a valve seat (9) projecting into the reference pressure chamber and restricting a nozzle opening (23) to the inner chamber (24) of a second valve seat (20). A second diaphragm piston (17) is biased against this second valve seat by a spring (21). The space (16) surrounding the second valve seat can be connected, partly throttled, via a nozzle (14), to the line chamber by way of a shut-off valve (12, 13) which opens laterally of the reference pressure chamber upon overbalancing pressure upon the first diaphragm piston; this space is always open to atmosphere via a further nozzle (25). The accelerator operates cyclically and has a safe, stable neutral position between its work cycles and rest position.

A continual type quick service valve adapted to be independently mounted on a railway car to provide local, supplemental venting of the car brake pipe pressure, as long as the brake pipe pressure continues to be reduced externally. This quick service venting of the brake pipe pressure is achieved utilizing a single piston actuated exhaust valve that is either cyclically-operated between open and closed states or is held open continuously depending upon the degree of brake application in effect. By selective tuning, the open duration of the exhaust valve can be made to exceed the duration the exhaust valve is closed during each cycle of operation or to remain open for the duration of the external brake pipe pressure reduction to achieve high operating efficiency.

A pulsating brake accelerating device for an indirectly operating air brake for rail vehicles has a pulsator (12), which is attached to the brake pipe (BP) via a jet (23). The pulsator (12) forms a mixed pressure from two pressures. One of the pressures is formed by the pressure of the brake pipe (BP) via a jet (23) and the other pressure is formed by pressure from a control chamber (QAC) via another jet. At every braking level the pulsator (12) drains mixed pressure pulses off into the atmosphere, while at the same time the brake pipe pressure and the control chamber pressure is lowered via the mixed pressure pulsator (12). The mixed pressure can consist of two valves (14, 15). The control element (4) of the brake accelerator unit can be the emergency brake piston, which monitors several valves, one of which is the pulsator-excitation valve (8).