Concave Gate Preform for Blow-Molded Containers
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Solution Overview
Problem
The existing preform designs for injection blow-molded plastic containers face challenges in achieving high mechanical rigidity of the bottom base while minimizing material weight in the gate portion, which affects manufacturing costs and the efficiency of the two-stages process.
Innovation Solution
A preform design featuring a concave gate sub-portion with a specific profile, allowing for higher stretch ratios and reduced material weight without compromising mechanical properties, and an injection mold stack geometry adapted to produce this concave sub-portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the weight of material in the gate portion is increased to improve bottom base mechanical rigidity, then the mechanical rigidity of the bottom base is improved, but the preform becomes more difficult to stretch and reheat, and manufacturing cost increases
Solution Approach 1:
The gate portion is designed with a concave outer face creating a specific geometry that concentrates material in the central zone while maintaining local thickness variations. This local quality distribution allows the central area to have sufficient material for rigidity while the peripheral areas remain thinner for easier stretching and reheating.
Solution Approach 2:
The concave outer face of the gate portion introduces a specific curvature profile that optimizes material flow and distribution during injection molding. This curved geometry facilitates more uniform stretching during the blow-molding process and improves heat distribution during reheating, addressing both rigidity and manufacturability requirements.
2Strength
If the weight of material in the gate portion is increased to improve bottom base mechanical rigidity, then the wall thickness in the bottom base is increased, but the manufacturing cost of the preform increases
Solution Approach 1:
The concave gate portion design creates localized material concentration exactly where needed for structural integrity (central zone), while allowing material reduction in non-critical areas. This optimized local quality distribution achieves the required mechanical rigidity with minimal overall material consumption.
Solution Approach 2:
The specific geometric parameters of the concave outer face (curvature radius, depth, and profile) are optimized to achieve the desired balance between material usage and mechanical performance. By carefully controlling these parameters, the design achieves cost-effective material utilization while meeting rigidity requirements.
3Ease of manufacture
If a convex gate portion with hemispherical shape is used, then the preform structure is simple and widely used, but the stretching efficiency and reheating performance are suboptimal
Solution Approach 1:
While maintaining the spherical inspiration of conventional designs, the outer face is inverted to a concave profile. This curvature modification fundamentally improves stretching efficiency by creating more uniform stress distribution during blow-molding and enhances reheating performance through improved heat penetration characteristics, while remaining compatible with standard manufacturing processes.
Solution Approach 2:
The conventional convex outer face is inverted to a concave profile. This inversion fundamentally changes the material flow and stress distribution patterns during subsequent processing, leading to improved stretching efficiency and reheating performance while maintaining compatibility with existing manufacturing infrastructure.
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
Enables higher stretch ratios for the bottom base of the container, improving mechanical rigidity while reducing material usage and manufacturing costs, and facilitating easier stretching and reheating in both one-stage and two-stages processes.
Implementation Method 1
a thermoplastic material is injected in a mould in order to form a preform
Implementation Method 2
the preform is biaxially stretched in a mould in order to form a rigid hollow container
Implementation Method 3
a reheating of the preform is performed before the stretch-blow molding operation
Data Source
Figure 1
Figure 2
Figure 3~4
AI summary
The preform (P) is suitable for subsequent blow-molding and comprises a neck portion (1) terminated by a pouring opening (10), a gate portion (3) forming a closed bottom end, and a body portion (2) extending between said gate portion (3) and said neck portion (1). Said gate portion (3) comprises a closed bottom end sub-portion (31) and a concave gate sub-portion (32). The closed bottom end sub- portion (31) comprises a bottom part (311) terminated by a central vestige (310) and having a convex outer face (311 b). The concave gate sub-portion (32) extends from said bottom part (311) towards the body portion (2), and the outer face (32b) of said concave gate sub- portion (32) is concave. An injection mold stack (4) for making the preform (P), processes for making the preform (P) and the container, and a blow-molded container are also disclosed.