Train holding apparatus with means for relieving the load imposed

Abstract

The piston rod of at least one hydraulic cylinder is axially connected to a pivot pin about which the car holding arm of a car holding device rotates in a vertical plane to engage the couplings between railroad cars. In the case of a single hydraulic cylinder, the inner chamber of the cylinder, located closest to the car holding arm, is connected to the outer chamber on the other side of the piston by a conduit. When hydraulic cylinders are connected to each pivot pin of the car holding arm, the inner chambers of the two cylinders are interconnected by a conduit as are the two outer chambers. When flow through the conduits is blocked by a solenoid valve, movement of the car holding arm in the direction parallel to the track is resisted and the arm holds the train in position. When the solenoid valve is open, the load imposed by the train on the car holding arm causes the hydraulic fluid to flow between the interconnected chambers and the arm moves parallel to the track until the load is relieved so that the arm can be raised out of engagement with the train under no-load conditions. A pump can be selectively connected to the conduit to transfer hydraulic fluid between chambers to recenter the raised arm or to position it precisely prior to reengagement with the train.