A brake accelerator is operable sequentially upon each successive braking stage over the service application range of brake line pressure reductions and is employed with a single release brake control valve of an indirectly acting compressed air brake for railway vehicles. The control valve has a service brake portion and an emergency brake portion provided with a emergency brake piston one side of which is subjected to brake line pressure and the other side is subjected to auxiliary chamber pressure . The accelerator has a main piston which operates an inlet valve to connect the accelerator to the brake line. The main piston which is also subjected on one side to brake line pressure and the other side to auxiliary chamber pressure is moved to a service position upon an application of the brakes to open the inlet valve and connect a control piston with the brake line such that the control piston is subjected on both sides to brake line pressure. The control piston is repeatedly moved between two positions such that quantities of air are cyclically withdrawn from the brake line and the auxiliary chamber to maintain the pressure relationship existing on both sides of the main piston during the service application. The drawing off of air from the auxiliary chamber by the control piston is carried out separately and independently from venting of the auxiliary chamber by the emergency brake piston.
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.
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.
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).
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).
A microprocessor-based, electropneumatic brake control system for a locomotive having a pneumatic back-up control valve which includes a quick release valve for maintaining a release condition of the control valve during dynamic braking. An arrangement is provided to prevent the control valve from applying during a trainline-initiated emergency application prior to the dynamic brake becoming ineffective following dynamic brake knockout, in order to avoid the possibility of a wheel skid.
