Energy absorbers

Railroad vehicle end-of-car cushioning means comprising an energy absorber including a cylinder which is open at one end and closed at the other end;

• a hollow plunger which is located slidably within the cylinder, said hollow plunger having end walls and an aperture in the end wall that is nearer to the closed end of the cylinder and said hollow plunger being closed at its other end wall;
• the aperture being at one end of a liquid containing chamber within the plunger;
• resilient means operable to oppose movement of the plunger into the cylinder and thereby to provide a recoil force;
• an annular piston head slidable in the liquid containing chamber and mounted at one end of a tube which projects from the closed end of the cylinder through a surrounding cylinder space and the aperture within which it is a sliding fit, the annular piston head having a central aperture in communication with a longitudinally extending passage formed by the interior of the tube, there being a plurality of radially extending apertures formed at axially spaced intervals along the tube, each aperture placing the interior of the tube in communication with one of the surrounding cylinder space and the chamber;
• and including a plurality of normally-closed valves operable to open to permit flow through them from the annular portion of the chamber that is formed between the annular piston head and the end wall of the hollow plunger in which the aperture is formed to the remainder of that chamber when a predetermined pressure is established in that annular chamber portion, each said normally-closed valve being mounted in a structure which comprises said annular piston head and tube, and having an inlet which communicates via respective conduit means in said structure with a respective one of a plurality of ports which are formed in the outer surface of the tube at axially-spaced intervals along the tube such that they are progressively cut-off from communication with the annular chamber portion during extension of the energy absorber.