Abstract: A railway car vent valve device having a bleed valve that is selectively operable to disable the vent valve device during a single car test procedure in which the service stability of the car control valve is checked. The bleed valve is automatically reset when the car brake pipe pressure drops below a predetermined value, such as occurs when the single car test apparatus is disconnected from the car brake pipe following completion of the single car test procedure.

Abstract: The usual brake cylinder in a conventional freight car brake apparatus is replaced by a novel cylinder that embodies a pair of pistons and a spring of sufficient strength to effect a hand brake application. Conventional brake applications and releases are effected accordingly as the usual brake control valve effects the supply of fluid under pressure to and the release thereof from one of the two pistons which are connected to a common piston rod through which force is transmitted to brake applying brake shoes. The second piston is subjected on one side to the force of the spring and on the other side selectively to brake pipe pressure or pressure in a hand brake release reservoir that is charged from the brake pipe to a higher pressure by an air-driven air booster operated by air from the brake pipe. Thus, the spring is enabled to effect a hand brake application in the absence of fluid under pressure acting on the other side of the second piston.