Mechanical central buffer coupling

An air valve, for a Scharfenberg type mechanical central buffer coupling arrangement for a rail vehicle having a coupling which is used to form a connection with a cooperating coupling of an adjacent rail vehicle upon movement of the couplings from an uncoupled to a coupled position, and in which arrangement a rail brake influencing main air conduit is provided for connection to a coupling lock in a brake actuator coupling lock for operating the brake of the rail vehicle, such coupling lock having a controlled pneumatic valve for opening the coupling lock, such that said air valve is adapted to be mounted on an end plate of the corresponding coupling and connected with the main air conduit and the pneumatic valve to control the brake actuator coupling lock whereby in the case of an unintentional severing of the connection of the central buffer coupling with that of the adjacent rail vehicle said air valve will actuate the brake of the rail vehicle by venting the main air conduit so as to cause the brake to operate automatically,

• said air valve comprising
• a cylinder having a first end and a second end and a wall defining an interior, and being arranged at its first end on a coupling end plate having an end plate opening,
• an inlet in the cylinder wall adapted for connection with such main air conduit and an outlet in the cylinder wall remote from the inlet for venting air,
• a guide movable in the cylinder and having a first end provided with a ram portion extending into the end plate opening and movable from an extended ram position protruding from the exterior of the end plate, which corresponds to the uncoupled position of the central buffer coupling, to a retracted ram position not protruding therefrom, which corresponds to the coupled position of the central buffer coupling, and having a second end provided with a reception recess,
• a piston movable in the cylinder and movable relative to the guide and having a stem portion extending into and displaceable in the reception recess and a head portion forming an air chamber with the cylinder interior, the piston being movable relative to the air chamber from an extended position in which its stem portion is closer to the cylinder first end to a retracted position in which its stem portion is farther from the cylinder first end, and
• means in the guide defining a closeable vent flow path for flow communicating the cylinder wall inlet with the cylinder wall outlet through the reception recess and arranged
• such that in the coupled position of the central buffer coupling in which the ram portion is in retracted position, the guide extends into blocking relation with the cylinder inlet so as to keep the vent flow path closed, and in the uncoupled position of the central buffer coupling in which the ram portion is in extended position the guide is positioned out of blocking relation with the cylinder inlet while the piston is in its extended position and extends into the reception recess and into blocking relation with the vent flow path so as to keep the vent flow path closed, and
• such that upon unintentional severing of the connection of the central buffer coupling, the ram portion moves to its extended position and the guide moves out of blocking relation with the cylinder inlet while the piston remains in its retracted position and is out of blocking relation with the vent flow path so as to open the vent flow path for venting air entering the cylinder inlet from the main air conduit through the vent flow path and the cylinder outlet to the exterior of the air valve.