Abstract: An improved rotary valve is provided with a bellows surrounding a bent shaft to create a hermetic seal and thereby prevent fluid loss from the interior of the valve body. The shaft is provided within a seal assembly housing, and has a lower end axis offset from the valve stem axis, and an upper end axis offset from the lower end axis. The bellows is fixedly secured at its upper end to the seal assembly housing and at its lower end to an end cap to prevent fluid within the cavity from passing out the seal assembly housing. An epicyclic gearing assembly is provided within the cavity and mechanically interconnects the lower end of the shaft to the valve stem. An actuator may be provided for connection with the upper end of the shaft for rotating the shaft. The activating device of the present invention may be used for rotating various members mounted within an enclosure with sealing the enclosure from the environment.