Polyester container for hot fill liquids

A PET container formed by blow molding and adapted to be filled with liquid at an elevated temperature above room temperature, said container comprising an upper portion defining a sealable closure, a sidewall portion, and

• a base portion closing the bottom of the container and formed integral with said sidewall portion, said base portion having a generally flat outer support ring at the lower end of said sidewall portion that is substantially concentric with said sidewall portion, a dome formed integral with said outer ring and extending upwardly into said container and terminating in a central disc portion that is also substantially concentric with said sidewall portion, said dome also including an annular wall extending between said disc portion and said outer ring, a portion of said annular wall being subject to deformation by virtue of the presence therein of unrelaxed retractive stresses resulting from blow molding and the heating effect of the filling liquid at said elevated temperature, said annular wall being shaped to resist deformation by said stresses by reducing the area of said dome in which said stresses may be formed by providing a series of alternately arranged radially upwardly sloping and radially downwardly sloping portions in said annular wall which provide said annular wall with a serpentine appearance extending radially from said disc portion along said dome down to said outer ring when viewed in radial cross section, said upwardly and downwardly sloping portions thereafter forming at least one inwardly concave reinforcing ring and at least one inwardly convex reinforcing ring being substantially concentrically positioned around said central disc portion to thereby reinforce the ability of said annular wall to resist deformation during filling of the container with liquid at said elevated temperature.