Patent ID: 7314146

Claim:
A neck structure in combination with a closure, the neck structure defining a neck opening, a cylindrical sealing surface surrounding said neck opening, and a substantially cylindrical external neck surface, and the closure comprising a cap formed of resilient material having a top, a downwardly extending skirt portion depending from said top, an annual plug depending from an underside of said top, one or more buttresses spaced radially inwardly of said annular plug which merge with both said annular plug and with the underside of said top, and one or more ribs formed on an internal surface of said downwardly extending skirt portion, the annular plug and said one or more ribs being arranged concentrically and dimensioned such that, upon application of the cap to the neck structure, the annular plug projects into the neck opening and engages the cylindrical sealing surface and said one or more ribs engage said substantially cylindrical external neck surface, the annular plug being adapted to flex away from the cylindrical sealing surface pulled by said one or more buttresses upon the build up of excess pressure within the closure whereupon circumferentially spaced ends of each rib define therebetween a path for the venting of fluid to relieve said excess pressure.