Abstract: A closure device for drinking from a liquid container (2) is sealingly mounted with a bottom part (3) of a main body thereof extending into an opening of the container. A top part (4) has a circular-arc portion with a groove (6) therein. Liquid-emitting and air-admitting bore holes (10, 11) are positioned in a base of the groove. A pivotally movable cap (14) is mounted on the top part covering the groove. When the cap is pivoted, it causes a flexible hose (12) mounted in the liquid-emitting bore hole to bend and thereby closes it. At the same time, the bent hose closes the air-admitting opening.