Double diaphragm spring brake actuator (DDSB) for Disc Brake
Double diaphragm cylinders are combined cylinders. The front section is dedicated to the service brake and the rear section to the spring brake. The front section is always a diaphragm type. In the rear section, the powerful spring is compressed during normal vehicle operation (driving). When parked, the pressure holding the spring in position is released. The spring then acts directly on the brake.