Method of increasing the wall thickness of a bottom structure of a blown plastic material container

摘要

This disclosure relates to an unexpected increase in the strength of a bottle bottom of the champagne type by the addition of ribs internally of the preform when the preform is axially stretched prior to the blowing thereof within the blow mold. Most particularly, by adding internal ribs to the interior surface of the bottom defining portion of the preform, the preform has the bottom forming portion unduly strengthened against shrinkage in wall thickness when the preform is axially lengthened through the use of a stretch rod. The net result is that the stretching of the preform and the thinning of the wall is held to a minimum in the bottom forming portion of the preform and is transferred primarily to the body forming portion of the preform where lesser wall thickness does not unduly detract from the strength of the bottle.