Hot-fill container having movable ribs for accommodating vacuum forces

A sidewall portion of a plastic container adapted for vacuum absorption, said sidewall portion comprising:

• a plurality of equidistantly spaced horizontal ribs arranged substantially perpendicular to a longitudinal axis of the container and separated by horizontal lands, a cross section of at least one of the horizontal ribs taken parallel to the longitudinal axis being defined by an upper wall, a lower wall, and an inner curved wall that extends between the upper and lower walls, the inner curved wall being curved along an innermost radius, the at least one of the horizontal ribs transitioning to one of the horizontal lands along an upper outer radius, the at least one of the horizontal ribs transitioninq to another of the horizontal lands along a lower outer radius, a sum of the upper and lower radii being at least 0.14 inches and at most 0.28 inches, the at least one of the horizontal ribs defining an acute angle that is variable according to vacuum forces generated within the container and loads directed parallel to the longitudinal axis to thereby accommodate the vacuum forces and the loads directed parallel to the longitudinal axis.

A method of making a blow-molded plastic container comprising:

• disposing a preform in a mold cavity;
• and
• blowing said preform against a mold surface of said mold cavity to form an upper portion, a sidewall portion and a base portion, said sidewall portion integrally formed with and extending between said upper portion and said base portion, said base portion closing off an end of the container, said sidewall portion defined in part by a plurality of horizontal ribs arranged substantially perpendicular to a longitudinal axis of the container, at least one of the horizontal ribs disposed longitudinally between an upper land and a lower land, a cross section of the at least one of the horizontal ribs taken parallel to the longitudinal axis being defined by an upper wall, a lower wall, and an inner curved wall that extends between the upper and lower walls, the inner curved wall being curved along an innermost radius, the at least one of the horizontal ribs transitioning to the upper land along an upper outer radius, the at least one of the horizontal ribs transitioning to the lower land along a lower outer radius, a sum of the upper and lower radii being at least 0.14 inches and at most 0.28 inches, the at least one of the horizontal ribs defining an acute angle that is variable according to vacuum forces generated within the container to thereby accommodate the vacuum forces.