Hydraulic hand brake for pressure medium actuated brakes of railway vehicles

Claim 1

A hydraulic hand brake for a fluid pressure actuated brake on a railway vehicle having a brake cylinder and a brake piston slidable therein, and comprising a second cylinder coaxially mounted on the brake cylinder, an inner cylindrical portion in said second cylinder and a second piston slidable in said inner cylindrical portion, a threaded rod extending from said second piston engageable with said brake piston when said second piston is displaced in the braking direction, said rod having a reversible thread thereon and a nut on said thread, said nut having a first coupling surface on a first side thereof away from said brake piston, a coupling ring securely connected to said second cylinder and having a second coupling surface engageable with said nut first coupling surface to lock said nut against rotation, a spring urging said nut in the direction to engage lockingly said coupling surfaces, a first thrust bearing on said first side of said nut and a control piston having a portion thereof directly engageable with said first thrust bearing to disengage said first and second coupling surfaces when said control piston is subjected to a hydraulic pressure so that said nut is free to rotate.