A service brake accelerator for indirect compressed-air brakes on railway vehicles includes a control piston which is loaded by the pressure in the main airpipe against the pressure in a reference pressure chamber and which controls a shutoff valve between the main airpipe and a piston chamber, a first outlet valve for the main airpipe and a second outlet valve for the piston chamber. Through appropriate dimensioning of the valve strokes (a,b), upon movement of the control piston out of its rest position the shutoff valve is closed first, and simultaneously or later the first outlet valve is opened and only subsequently the second outlet valve is opened. A valve piston arranged coaxially with the control piston is loaded by the pressure in the piston chamber and the force of a spring. On its other side, the valve piston is acted upon by the reference pressure over a partial area, but with the air vent valve open it is acted upon by the reference pressure over its entire area. When the piston chamber is vented, and after opening of the air vent valve, the valve piston rests against a valve stem connected to the control piston, thereby equalizing changes in loading with respect to the control piston.
A freight brake control valve device in which the emergency piston is arranged to operate a pair of slide valves having lost motion therebetween to provide a continuous, local reduction in the brake pipe pressure in response to initial actuation of the emergency piston when a service rate of brake pipe pressure reduction is made, in order to quickly propagate a brake pipe pressure reduction wave along the train and accordingly provide an accelerated application of the train brakes. This accelerated application function in response to a service rate of brake pipe pressure reduction is achieved during movement of the emergency piston toward emergency position, during which movement, the quick-action chamber "breathing" function also occurs, the latter being presently incorporated in the emergency piston slide valve to stabilize the emergency piston following initial actuation thereof, so as to prevent further actuation of the emergency piston to emergency position.
A control valve having, in a series with a first inlet valve of a quick brake volume, two different rates of flow restrictions operable as a function of the position of the piston. The first flow rate of one first restriction is insufficient to cause the piston to a braking position for applying a minimum service application for first range of piston positions which would generally be produced by the mechanical vibration. The second restriction has a greater flow and will accelerate the piston to a braking position for a second range of piston positions which will be produced by the reduction of the brake pipe pressure on one face of the piston. By providing two flow rates, the valve becomes insensitive to mechanically produced forces while maintaining the reaction time of the valve to fluidically produced reduction of brake pipe pressure.
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 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.
A microprocessor based electro-pneumatic locomotive brake control system in which a brake application is obtained automatically on the locomotive consist and train only in response to a loss of power at the lead or controlling locomotive microprocessor, and not in response to a loss of power at a trail or non-controlling locomotive microprocessor. The brake control system provides for releasing such a fail-safe brake application at the locomotive independently of the train brakes.
