Patent ID: 6199671
Filing Date: 2001-03-13
Classification: B61K,F16F

Abstract:
A wagon retarder comprising:a) a cylinder defining a cavity between first and second end walls;b) a piston rod extending axially through one of the end walls;c) a piston assembly including a piston carried on the piston rod and mounted to slide axially within the cylinder so as to divide the cavity into first and second working chambers arranged to contain damping fluid;d) first passage means extending through the piston assembly and communicating between the first and second working chambers;e) first spring valve means for at least partly closing the first passage means in the event of the axial velocity of the piston relative to the cylinder in a first axial direction exceeding a predetermined value, andf) at least one permanently open restricted orifice being defined in the first valve means and communicating between the first and second working chambers via the first passage means on closure of the first valve means,the restricted orifice being restricted relative to the first passage means so as to limit the flow of damping fluid between the first and second working chambers and to set up a pressure differential therebetween to apply a predetermined damping force, with the dimensions of the restricted orifice being determined in accordance with the desired force-displacement profile of the wagon retarder, wherein the first spring valve means includes a first valve plate and first biasing means for biasing the valve plate into an open position whilst the axial velocity of the piston relative to the cylinder in the first axial direction is less than the predetermined value, with the restricted orifice extending through the valve plate and communicating directly with the first passage means when the valve plate is closed.