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.
The acceleration apparatus for connection with a pilot operated compressed-air brake comprises a tap-off valve which vents the main air line or conduit at the beginning of the braking procedure. This tap-off valve is opened by an actuator or actuating mechanism via a disengageable intermediary member. By employing a rotationally symmetrical plunger or push rod which is pivoted into the operative position thereof by a spring and deflected by an interrupter piston, the construction of the disengageable intermediary member can be substantially simplified. The plunger or push rod possesses at the one end thereof a cam or pin and a substantially conical surface.
