Heat-Set PET Container With Movable Pushup Base
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Solution Overview
Problem
PET containers used for hot fill applications face challenges in resisting fill pressures, absorbing vacuum pressures, and maintaining shape due to their lightweight material, which makes it difficult to create functional designs that can withstand top loading forces and maintain shape during the hot fill process.
Innovation Solution
A heat-set container design with a base portion featuring a central pushup portion that is moveable in response to internal vacuum pressure, along with a mold system for forming this design, which includes a plurality of contact surfaces and a central pushup portion that extends toward the finish, optimizing the container's size and shape to resist pressures and maintain shape.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If PET containers are made lighter in material weight, then container cost and environmental impact are improved, but the ability to resist fill pressures, absorb vacuum pressures, and withstand top loading forces deteriorates
Solution Approach 1:
The base portion is divided into multiple functional segments: a plurality of contact surfaces for supporting the container, and a central pushup portion that is moveable in response to internal vacuum pressure. This segmentation allows each part to perform its specific function efficiently, enabling the container to withstand pressures and maintain shape with less material.
Solution Approach 2:
The central pushup portion is designed to be moveable rather than fixed, allowing it to dynamically respond to internal vacuum pressure by decreasing the volume. This dynamic response enables the container to absorb vacuum pressures effectively while using lighter material, as the pushup portion actively compensates for pressure changes rather than relying on rigid structural support.
2Reliability
If the container volume is decreased during cooling phase, then vacuum pressure is absorbed effectively, but the container shape and volume must be restored to maintain functionality
Solution Approach 1:
The central pushup portion is designed to move in response to internal vacuum pressure, dynamically decreasing the volume during the cooling phase to absorb vacuum pressures. This dynamic movement allows the container to reliably handle pressure changes while maintaining its functional shape when not under vacuum.
Solution Approach 2:
The base portion geometry is specifically designed to resist expansion under pressure before it occurs, and the central pushup portion is pre-configured to move in response to vacuum pressure. This preliminary design ensures the container maintains its shape and volume characteristics while effectively absorbing vacuum pressures during the cooling phase.
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
The container design effectively resists expansion under pressure, maintains shape, and shrinks back to its original volume during the cooling phase, addressing the challenges of lightweight PET containers by enhancing structural integrity and vacuum response while minimizing weight.
Implementation Method 1
The central pushup portion is moveable in response to internal vacuum pressure to decrease the volume
Implementation Method 2
thermal processing involves heating the material (either amorphous or semi-crystalline) to promote crystal growth
Implementation Method 3
The thermal processing of an oriented PET container, which is known as heat setting, typically includes blow molding a PET preform against a mold heated to a temperature of approximately 250° F.-350° F. (approximately 121° C.-177° C.), and holding the blown container against the heated mold for approximately two (2) to five (5) seconds
Implementation Method 4
Mechanical processing involves orienting the amorphous material to achieve strain hardening. This processing commonly involves stretching an injection molded PET preform along a longitudinal axis and expanding the PET preform along a transverse or radial axis
Data Source
AI summary
A heat-set container that defines a longitudinal axis is disclosed that includes a finish and a sidewall portion extending from the finish. The container also includes a base portion extending from the sidewall portion and enclosing said sidewall portion to form a volume therein for retaining a commodity. The base portion has a plurality of contact surfaces for supporting the container. The plurality of contact surfaces are spaced away from each other about the longitudinal axis. Also, the container includes a central pushup portion disposed in the base portion and extending generally toward the finish. The central pushup portion is substantially centered on the longitudinal axis, and the central pushup portion is moveable in response to internal vacuum pressure to decrease the volume.