Deep-Inset Base Plastic Container Molding

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Solution Overview

Problem

The reheat stretch blow molding process struggles to manufacture plastic containers with deep inset bases, often resulting in extreme stretching, thinning, crimping, or folding of the container wall in the base area, making it difficult to produce containers with a deep inset base effectively.

Innovation Solution

A method involving molding a container blank with a standing ring and a base projection portion, where the base projection is displaced upwardly relative to the standing ring while the container is still pressurized, allowing for the formation of a deep inset base without unwanted deformities, using a specific mold assembly and process in the reheat stretch blow molding process.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Shape

If the reheat stretch blow molding process is used to manufacture containers with deep inset bases, then the container can have a deep inset base for stackability and vacuum panel placement, but the container wall in the base area experiences extreme stretching, thinning, crimping, or folding

Engineering Contradiction:

Improvedeep inset base shapeVSAvoidcontainer wall deformity

Core Design Contradiction:

ShapeVSManufacturing precision

Solution Approach 1:

The mold cavity is designed with a push-up area that forms a base projection portion extending downwardly during the molding process. This preliminary formation of the base projection in the container blank allows the deep inset base to be created before the stretching operation, preventing wall deformities during the subsequent base inversion process

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention inverts the conventional approach by forming the base projection downwardly in the container blank, then inverting this projection upwardly to create the deep inset base. This reverse sequence of operations allows the base to be formed in a controlled manner without causing wall stretching or deformities

Inventive Principle:

Principle #13The other way round (Inversion)

2Shape

If conventional blow molding is used to form a deep inset base, then the base shape can be achieved, but the container wall thickness is significantly reduced and deformities occur

Engineering Contradiction:

Improveinset base configurationVSAvoidcontainer wall thickness

Core Design Contradiction:

ShapeVSStrength

Solution Approach 1:

The mold cavity includes a push-up area that preliminarily forms the base projection portion with adequate material thickness before the container is removed from the mold. This ensures the wall thickness is maintained at acceptable levels before the inversion operation

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The invention changes the timing and sequence of the forming operations. The base projection is formed during the initial molding while the material is still hot and formable, then inverted while maintaining controlled parameters to prevent excessive thinning

Inventive Principle:

Principle #35Parameter changes

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This method enables the production of plastic containers with a deep inset base, preventing unwanted deformities and allowing for optimal material distribution, which enhances stackability and accommodates volumetric shrinkage, while minimizing material costs through lightweight design.

Implementation Method 1

The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape of the container

Methodology Applied

Scientific EffectThermal expansion: Thermal Expansion

Implementation Method 2

The preform is longitudinally stretched and subsequently inflated within a mold cavity

Methodology Applied

Scientific EffectElastic deformation: Deformation

Implementation Method 3

The polymer solidifies after contacting the cooler surface of the mold

Methodology Applied

Scientific EffectCooling: Cooling

Implementation Method 4

The polymer solidifies after contacting the cooler surface of the mold

Methodology Applied

Scientific EffectPhase change: Phase Change

Implementation Method 5

relatively displacing the base projection portion upwardly with respect to the standing ring until the base projection portion is positioned above the standing ring

Methodology Applied

Scientific EffectPressure: Pressure Increase

Implementation Method 6

displaced upwardly with respect to the standing ring while the container is still pressurized

Methodology Applied

Scientific EffectElastic deformation: Deformation

Data Source

PatentUS8636944B2Method of making plastic container having a deep-inset base

Publication Date: 2014.01.28 CO2 PAC

AI summary

A method of plastic container having a deep inset base of the type that has a standing ring for supporting the container on a flat surface includes steps of molding a container blank having a standing ring and a base projection portion that is formed beneath the standing ring and relatively displacing the base projection portion upwardly with respect to the standing ring until the base projection portion is positioned above the standing ring. An improved plastic container having a deep inset base is also disclosed.