Patent ID: 7451689
Filing Date: 2008-11-18
Classification: B60T

Abstract:
1. A combined service brake and spring brake cylinder for a vehicle brake system, comprising: a housing common to both the service brake and the spring brake cylinders; a spring brake piston and a service brake piston, the spring and the service brake pistons being guided within the housing; at least one preloaded spring for loading the spring brake piston, the preloaded spring having a larger outer diameter than the service brake piston; wherein the spring brake piston is an annular piston having a piston rod, at least part of the piston rod being configured as a piston tube surrounding the service brake piston and forming a radially outer running and sealing surface for the service brake piston; wherein the piston tube of the spring brake piston carries, on a side facing away from the spring brake piston, an axially displaceable bottom; a pressure chamber of the service brake cylinder formed between the axially displaceable bottom and the service brake piston; wherein the axially displaceable bottom is formed of a flexible diaphragm, with an exception of a radially outer annular portion fastened to the piston tube and capable of butting against the service brake piston, which is supportable on a bottom of the housing when the service brake pressure chamber is pressurized.