Packaging Bag Reinforcing Member Sagging Prevention
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Solution Overview
Problem
Conventional packaging bags with reinforcing members suffer from reduced impact resistance and aesthetic degradation due to sagging or warping of the upper and side outer edges during thermoplastic resin injection, which compromises the reinforcing member's effectiveness and appearance.
Innovation Solution
A packaging bag design featuring thermoplastic resin-made reinforcing members with strategically placed windows at the outer edges, where the molds have projections to hold the edges in place and prevent sagging, ensuring uniform thickness and improved impact resistance without increasing costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the upper outer edge and side outer edges of the bag body are greatly projected into the recesses of the molds, then the reinforcing member is increased in width and impact resistance is improved, but the upper outer edge or side outer edge of the bag body tends to sag or warp inside the recesses, causing difference in thickness and degraded appearance
Solution Approach 1:
The mold is designed with a support structure (bump or ridge) that preliminarily supports the bag body edge during the injection molding process. This preliminary support prevents sagging and warping before the thermoplastic resin is injected, ensuring uniform thickness and preventing appearance degradation while still allowing the edge to be greatly projected for improved impact resistance
2Strength
If the upper outer edge and side outer edges of the bag body are greatly projected into the recesses of the molds, then the reinforcing member is increased in width and impact resistance is improved, but the upper outer edge or side outer edge of the bag body may warp by heat and flow of injected thermoplastic resin
Solution Approach 1:
The mold support structure is positioned to hold the bag body edge in place before thermoplastic resin injection. This preliminary positioning prevents the edge from warping due to heat and resin flow during the molding process, maintaining shape stability while enabling greater projection width for improved impact resistance
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 solution enhances the impact resistance and maintains the appearance of the packaging bag by preventing sagging and warping of the reinforcing members, thereby improving their structural integrity without increasing material usage or costs.
Implementation Method 1
injecting melted or softened thermoplastic resin to fill the cavity of the thus clamped molds in order to form the reinforcing member at the outer edge of the bag body
Data Source
AI summary
A packaging bag is provided with a bag body and thermoplastic resin-made reinforcing members provided at the outer edge of the bag body. A window is provided in each reinforcing member. In forming the packaging bag, the bag body is placed between a pair of molds respectively having recesses to clamp these two molds so that a corresponding pair of the recesses are opposed to each other. Thereafter, in order to form the reinforcing members at the outer edge of the bag body, melted or softened thermoplastic resin is injected to fill cavities formed by the recesses of the thus clamped molds. Each of the cavities of the molds is formed so as to coincide with an outer shape of the corresponding reinforcing member. A projection extends from the bottom face of each recess at a part of the cavity corresponding to a part of each reinforcing member on which the window is provided. The outer edge of the bag body placed between the two molds is placed inside the cavities in a state of being held between the two projections.