A combined service
brake and
parking brake cylinder (1) for actuating a service
brake and a
parking brake has a spring-loaded
parking brake cylinder (2) with a housing (4) which is cylindrical at least in sections, a spring-loaded parking
brake piston (21) and at least one accumulator spring (22) which loads the parking brake
piston (21) in an actuating direction of the parking brake, wherein the parking brake
piston (21) is displaceably guided on a radially inner circumferential surface of the parking brake cylinder (2), and the parking brake piston (21) and the housing (4) delimit a parking brake chamber (23) which can be ventilated by a parking
brake pressure, a service brake cylinder (3) and a service brake piston (31), wherein the service brake cylinder (3) and the service brake piston (31) delimit a service brake chamber (33) which can be acted upon and vented by a service
brake pressure, a
piston rod (5) coupled to the parking brake piston (21) and the service brake piston (31), wherein the service brake cylinder (3), viewed radially, is arranged inside the parking brake cylinder (2), wherein the housing (4) of the parking brake cylinder (2) is closed at a first end face by a cover (6) provided with an opening (61), into which a first end portion (53) of the
piston rod (5) projects, wherein an annular seal (7) is arranged between an outer circumference (51) of the
piston rod (5) and an inner circumference of the opening (61) of the cover (6, wherein the seal (7) has a first sealing segment (71) which is designed as an annular lip which rests on an outer end face (62) of the cover (6), preferably on an outer end face of a sleeve (8) of the cover (6), and functions as a pressure
relief valve to allow pressurized air to escape into the environment.