Bottle stopper for evacuation pump

A stopper for evacuating and maintaining a vacuum, comprising:

• a hollow casing having a lower tubular section and an upper cylindrical section with a transparent wall;
• a resilient sleeve mounted on said lower section of the casing and forming a valve seat thereon, said seat having a dome-shaped geometry pointing upward with an aperture facing the lower section of the casing;
• a plunger slidably inserted in the casing, said plunger including a lower shaft with a tip adapted to mesh with the aperture in the valve seat to form a seal and an upper flange housed in said upper cylindrical section of the casing;
• and
• an opening in said upper cylindrical section of the casing for connection with an evacuating pump;
• wherein the sleeve includes exterior resilient ribs for sealed retention of the stopper in a bottle, said ribs having respective diameters;
• and
• wherein the plunger is movable between an upper position, where the tip is removed from the valve seat and the flange is visible through said transparent wall, and a lower position, where the tip is connected to the valve seat to form a seal and the valve seat is resiliently drawn downward toward the bottle and where said upper flange buts against the casing to form an additional seal.