Abstract: In an oscillating valve in which a slide plate is subjected to a swinging movement between an opening position in which it is clear of a flow passage and a closing position in which it is inserted in the flow path, and, in its closing position, is applied against a sealing surface by a sealing force to block the flow path, a single drive device is provided to produce both the swinging movement and the sealing force and the sealing force is produced by moving the slide plate perpendicular to the sealing surface only after the slide plate has reached the closing position associated with its swinging movement.