Piston for multi-stage operation

摘要

A piston is disclosed which is particularly adapted for multi-stage operation in a combined air and spring-loaded brake cylinder. The piston is formed of a resilient or elastic material such as spring steel, a synthetic resin or hard rubber and has a central portion of a reduced wall strength with respect to the surrounding peripheral portion of the piston. The central portion is thus capable of elastic deformation when subjected to a force exceeding a predetermined level. The reduced strength relationship of the central portion may be achieved by a reduced wall thickness, or by the use of radially extending slots. The piston thus has a differential deformability when a pressure is applied thereto such that the entire piston can be shifted as a unit until abutting a stop structure on the housing of the brake cylinder. The central portion of the piston can then be additionally displaced if an increased pressure or force is applied to the central portion.