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US 4,034,036 AGranted
Parison control in longitudinal stretch
AssigneeConsupak, Inc.
InventorJohn Jerome Farrell
Life of this patent
Estimating the term…
Abstract
An injection molded parison is positioned in a mold cavity having a high length to diameter ratio and being provided with means along the length of the cavity to selectively and alternatively exert positive pressure as an air cushion, or negative pressure as a vacuum, on portions of the parison as the parison is expanded through the length of the cavity. The thickness of the expanding parison is thus controlled so that in subsequent expansion in the blow mold, the finished hollow article will have the desired wall thickness.
Claims7
A method for controlling the thickness of a parison comprising:
- providing a fluid on the inside of the parison to expand the parison in the longitudinal direction while exerting a vacuum on a first portion of the outside of the parison to hold that first portion from further longitudinal extension and exerting a fluid cushion on another portion of the outside of the parison to permit longitudinal extension of that another portion so as to control the thickness of the parison as it undergoes longitudinal expansion prior to blow molding.
Dependencies are inferred from the claim text.