A spring brake actuator for a vehicle, in particular parking or emergency brake actuator for use in a commercial vehicle

A spring brake actuator (1) for a vehicle, in particular a parking or emergency brake actuator, for use in a commercial vehicle, the spring brake actuator (1) comprising:

• a cylinder housing (2) having a cylinder housing base (5) and a spring seat (7) disposed on the base,
• a spring brake piston (9) located in the said cylinder housing (5) for applying a braking force,
• a compression spring (11) arranged between the spring seat (7) and the spring brake piston (9), the compression spring providing a spring bias to push the spring brake piston (9) away from the base (5) and the spring seat (7),
• wherein the cylinder housing (2) is divided into a spring chamber (12) and a pressure chamber (14), the compression spring (11) being arranged in the spring chamber (12) and the pressure chamber (14) being supplied with pressurized fluid,
• wherein the cylinder housing (2) includes an elastically deformable diaphragm (15) disposed within the cylinder housing, the diaphragm having an annular flange (17) which is sealingly mounted to the cylinder housing (2) and an inner periphery (18) which is sealingly mounted to the spring brake piston (9) such that the pressure chamber (14) is fluid-tightly isolated from the spring chamber (12).