Parking brake mechanism for railway vehicle

The invention provides a parking brake mechanism for a railway vehicle. The parking brake mechanism comprises a cylinder block, a cylinder cover, a piston, a screw and a pressing spring, wherein a rotational ratchet wheel cylinder is installed in the cylinder cover, the top of the ratchet wheel cylinder is provided with a single-way ratchet wheel, the lower end of the screw is connected with a stretching rod, the center of the piston is provided with a rotation-preventing sleeve, a rotation-prevention bush which is matched with the screw through a feather key is fixed inside the rotation-preventing sleeve, a rotational sleeve nut is sleeved on the outside of the rotation-preventing sleeve, the sleeve nut and the rotation-preventing sleeve are locked in the axial direction, the inner side of the sleeve nut is in thread fit with the screw, and the outer side of the sleeve nut is matched with the ratchet wheel cylinder through a feather key. According to the parking brake mechanism, a traditional parking braking