Threaded plastic bottle cap

Claim 1

In a bottle cap for use with a bottle having a threaded neck opening into the bottle, said cap being constructed of flexible plastic material and having a top wall, a cylindrical side wall depending from the top wall and a thread on the inner surface of the side wall for cooperating with the thread on the neck of the bottle, the improvement comprising: (a) a first annular sealing flange extending downwardly from said top wall for engagement with the wall surface of the bottle neck adjacent its opening into the bottle; (b) a second annular sealing flange extending downwardly from said top wall outwardly of said first sealing flange for engagement with the top surface of the bottle neck, said second sealing flange normally having a generally triangular cross-sectional shape with inner and outer side walls extending downwardly from the top wall of the cap in a direction tapering toward each other and with the inner wall including an uppermost wall portion extending toward the side wall of the cap and a lowermost wall portion extending axially of the side wall of the cap until intersecting with the outer wall of the flange, said lowermost wall portion having an internal diameter slightly less than the outer diameter of the neck of said bottle and defining, with the adjacent portion of the outer side wall, a lower flange tip; (c) said first and second sealing flanges being spaced from each other to seal against the cooperating surfaces of the bottle neck at spaced locations; and (d) said lower flange tip of the second flange being of sufficient flexibility to bend radially inwardly as it engages the top surface of the bottle neck.