Preform, a mold stack for producing the preform, and a preform handling apparatus for handling the preform
A preform suitable for subsequent blow-molding into a final-shaped container comprises: a neck portion; a base portion; and a body portion extending between the neck portion and the base portion; the body portion being defined between an inner surface having a circular transverse cross-sectional shape and an outer surface also having a circular transverse cross-sectional shape, the inner and outer surfaces being non-concentric, such that a wall thickness of the body portion varies circumferentially around the preform. A preform handling apparatus for retrieving a preform from a mold comprises a take-off device having a preform carrier and a take-off device alignment mechanism for maintaining the preform carrier in alignment with a contact surface of a body portion of the preform regardless of any offset between a longitudinal axis of a cylindrical outer surface of the body portion and a longitudinal axis of a cylindrical inner surface of the body portion.
1. A preform comprising:
a neck portion;
a base portion; and
a body portion extending between the neck portion and the base portion;
the body portion being defined between an inner surface having a circular transverse cross-sectional shape and an outer surface also having a circular transverse cross-sectional shape, the inner and outer surfaces having respective longitudinal axes that are offset from one another along substantially the entire length of the body portion, such that a wall thickness of the body portion varies circumferentially around the preform;
wherein the base portion is defined between an inner end surface and an outer end surface that extend from the inner surface of the body portion and the outer surface of the body portion, respectively, coaxially therewith, wherein a base thickness of the base portion varies circumferentially around the preform within a region of the base portion defined by the circumference of the inner surface of the body portion,
wherein the longitudinal axis of the inner surface of the body portion is offset from the longitudinal axis of the outer surface of the body portion by an offset amount that is one-half of a difference in wall thickness between a thickest wall of the body portion of the preform and a thinnest wall of the body portion of the preform.
2. The preform of claim 1 , wherein the wall thickness comprises a first wall thickness at a first point of a plurality of points around a circumference of the body portion and a second wall thickness at a second point of the plurality of points around the circumference of the body portion.
3. The preform of claim 2 , wherein the first wall thickness and the second wall thickness are selected based on blow-molding considerations for the first point and the second point respectively.
4. The preform of claim 3 , wherein the first wall thickness is larger than the second wall thickness where a travel distance of the first point during a blow-molding process will be longer than a travel distance of the second point during the blow-molding process.
5. The preform of claim 1 , wherein the base portion has one of a substantially hemispherical or conical shape that terminates in a vestige portion.