Control valve for air brake - has brake fluid and pressure pistons movable together or separately

摘要

The control valve for an air brake has a command piston (20) for the fluid pressure for braking and a separate piston (13) to control fluid flow. The latter is movable together or separately. Each has a seat for a two seat valve to cooperate with a common valve gate. The pressure control piston has two annular stop shoulders (19,33) to prevent the two pistons touching and to (18') engage a reaction piston. The latter can have an annular surface in a cylindrical extension to the pressure piston.