Image Number 6 for United States Patent #6651834.
A stopper for a bottle includes a resilient outer body having an axial bore, a rigid inner body disposed within the bore, and a valve actuator moveably disposed within an axial opening of the inner body. A lower flange portion of the outer body extends radially across the bore to an axial aperture having a sealing surface. The valve actuator has an upper operator portion connected to a lower valve body portion by a longitudinally extending shaft portion. The valve body portion is sealingly engageable with the sealing surface of the orifice to close the orifice. A vacuum in the bottle acts on a bottom biasing surface of the lower flange portion to bias the lower flange portion and the valve actuator downward into the bottle neck in opposition to a resilience force such that an indicator on the shaft portion proximate to the operator portion is withdrawn within the opening of the inner body when the vacuum is greater than a predetermined value and the indicator is visible above the inner body when the vacuum is less than the predetermined value.