Abstract: A valve arrangement for amplifying the effect of the application or removal of atmospheric pressure upon a fluid pressure responsive actuator element such as a pneumatic cylinder or bellows comprising superposed chambers one connected to the atmosphere and the other to a source of vacuum and intermediately of them a chamber connected to the fluid pressure responsive actuator element and forming actually the beginning of a conduit leading to the actuator element. The middle chamber may selectively be set to communicate with one or the other of the two outer chambers through aligned openings in the walls that separate these chambers from the middle chamber and that may alternately be closed by a common stopper which can be moved to close one or the other of the openings so that either atmospheric air or a vacuum is applied through this middle chamber to the actuator element.