Method of making a blown bottle having a ribbed interior surface

In a method of making a blown plastic container having integral reinforcing ribs on its interior wall surface, the steps of:

• 1. enclosing a blowable plastic parison within a pre-form mold cavity defined by mold wall surfaces having concave grooves therein;
• 2. expanding the blowable parison against the pre-form cavity wall surfaces and forming a blown pre-form having an outer wall surface pattern of outwardly directed bulbous projections formed by expansion of portions of the parison into the concave grooves;
• 3. enclosing the blown pre-form within a final blow mold cavity defined by smooth wall surfaces for forming a smooth outer configuration on the container;
• and
• 4. expanding the pre-form against the smooth final blow cavity wall surfaces (a) to form a final article having smooth exterior surfaces and (b) to convert the outwardly directed pre-form projections into concave portions separated by convex reinforcing ribs at the interior wall surface of the container.

In a method of forming a blown thermoplastic container having a region of both structural- and material-reinforcement, comprising the steps of:

• 1. enclosing a blowable plastic parison having a substantially uniform wall thickness within a pre-blow mold cavity defined by a mold wall surface including at least one region having a plurality of grooves;
• 2. inflating the blowable plastic parison against the pre-blow mold wall surface and forming a pre-form having a region of outwardly directed bulbous ribs formed by expansion of portions of the parison in the grooved pre-blow cavity region;
• 3. enclosing the pre-form within a final blow mold cavity defined by substantially smooth mold wall surfaces conforming to the outer configuration of a container;
• and
• 4. in a single blowing operation (a) inflating the pre-form into contact with the wall surfaces of the final blow mold, (b) stretching the ribbed portion of the pre-form to a lesser extent than the other expanded portions, (c) flattening the bulbous ribs to form a smooth outer wall configuration on the container, and (d) forming reinforcing ribs on the internal wall surface of the container.

In a method of forming a blown thermoplastic container having a reinforced region of both structural- and material-reinforcement, comprising the steps of:

• 1. enclosing a blowable plastic parison having a substantially uniform wall thickness within a pre-blow mold cavity defined by mold wall surfaces including a region having a plurality of concave grooves;
• 2. inflating the blowable plastic parison against the pre-blow mold wall surfaces and forming a pre-form having (a) a major wall with a thickness less than the thickness of the original blowable parison and (b) a plurality of integral, outwardly directed bulbous ribs having a thickness less than that of said major wall;
• 3. enclosing the pre-form within a final blow mold cavity defined in part by substantially smooth mold wall surfaces in the region corresponding to the bulbous ribs on the pre-form;
• and
• 4. in a single blowing operation (a) inflating and expanding the pre-form into contact with the mold surfaces of the final blow mold, (b) stretching the major wall of the pre-form to a greater extent than the ribbed portion, (c) flattening the bulbous ribs to form a smooth outer wall configuration on the container, and (d) forming two reinforcing ribs on the internal wall surface of the container from each previously existing bulbous rib.