Service brake accelerator for indirect compressed-air brakes on railway vehicles

A service brake accelerator for indirect brakes on railway vehicles, having

• a reference pressure chamber connected via a nozzle to the main airpipe;
• a control piston loaded by the pressure in the main airpipe against the pressure in the reference pressure chamber;
• a shutoff valve which can be closed by the control piston in the case of predominant action by the pressure in the reference pressure chamber, and which is in a connection from the main airpipe to a piston chamber acted upon by an auxiliary pressure;
• an outlet valve system which can be opened by the control piston in the case of predominant action by the pressure in the reference pressure chamber, and is in throttled connections from the main airpipe and from the piston chamber to atmosphere;
• and
• an air vent valve controlled by a valve piston and in a connection throttled via a further nozzle, from the reference pressure chamber to the atmosphere, where:
• the valve piston in the closing direction of the air vent valve is loaded by the force of a spring and the pressure in the piston chamber against the pressure in the reference pressure chamber, which with the air vent valve closed acts only upon a partial area;
• and where:
• the control piston, the shutoff valve and the outlet valve system are arranged coaxially and the shutoff valve and the outlet valve system can be actuated by means of a valve stem connected to the control piston, characterized in that:
• the outlet valve system comprises a first outlet valve (31, 32) between the main airpipe (1) and the atmosphere, and
• a spatially separate second outlet valve (38, 42) between the piston chamber (40) and the atmosphere;
• that
• the shutoff valve (29,31) having a closing stroke (a) which is at most equal to an opening stroke of the first outlet valve (31, 32) beginning from a rest position and with reference to the control piston (16), the second outlet valve (38,42) having an opening stroke (b) which is greater than the opening stroke of the first outlet valve (31,32);
• the valve piston (22) is disposed coaxially with the control piston (16) and at the side thereof where said valve piston is acted upon by pressure in the piston chamber (40) and is engageable against an end of the valve stem (27).