Threaded bottle cap

Claim 1

In combination with a bottle having a tubular neck formed with an external screwthread and terminating at an annular rim surface having an outside diameter, a cap comprising: a cup-shaped body generally centered on an axis and formed unitarily with an end wall generally perpendicular to the axis, an annular skirt projecting axially downward from the end wall, an internal screwthread in the skirt matable with the screwthread of the bottle neck, a flexible and thin annular web having an outer periphery joined to the skirt adjacent and spaced from the end wall and an inner periphery, a thick seal ring secured to the inner periphery of the web, the web and seal ring being dimensioned to engage the rim surface when the cap is threaded onto the neck, and an annular lip projecting axially downward from the end wall immediately adjacent the skirt radially outside the seal ring and engageable with the web only radially outward of the seal ring between the seal ring and the skirt, the lip having a diameter greater than the outside diameter of the rim surface, whereby when the neck is screwed fully into the cap its rim surface crushes the seal ring directly against the end wall and compresses the lip with the web; and an antitamper ring secured to a lower end of the skirt.