Hollow Article Bonding via Low-Pressure Injection
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Solution Overview
Problem
Current injection molding methods for forming hollow articles face challenges in efficiently joining molded shells without causing inward deflection, particularly due to high injection pressures, which can lead to defects and reduced production efficiency.
Innovation Solution
A method involving the use of a third molding material with a lower injection pressure, potentially mixed with gases like nitrogen, to bond molded shells together, reducing the risk of deflection and enhancing the joining process by using a bead to secure the shells along their peripheral edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If high injection pressure is used to join molded shells, then joining strength is improved, but inward deflection of shells occurs
Solution Approach 1:
The patent changes the injection pressure parameter from high to low (at least 3.5 bar lower than first injection pressure) to prevent shell deflection while maintaining effective joining through alternative mechanisms such as bead formation and peripheral edge bonding
2Manufacturing precision
If low injection pressure is used to avoid shell deflection, then manufacturing precision is improved, but joining strength may be insufficient
Solution Approach 1:
The patent segments the joining process into two distinct stages: first forming molded shells at high pressure, then joining them at low pressure. This segmentation allows each stage to operate under optimal pressure conditions without compromising the other
Solution Approach 2:
The patent performs preliminary action by forming the molded shells with their peripheral edges prepared for joining before the actual joining process. The shells are positioned and held in place prior to low-pressure injection, ensuring proper alignment and preventing deflection during joining
3Device complexity
If conventional joining methods are used, then joining process is simple, but production efficiency is reduced
Solution Approach 1:
The patent enables continuous production by allowing low-pressure joining to occur without requiring complete cooling or interruption of the molding cycle. The process maintains continuous useful action through seamless transition between forming and joining operations
Solution Approach 2:
The patent applies dynamics by using a two-stage pressure approach where injection pressure is dynamically adjusted: high pressure for shell formation, then low pressure for joining. This dynamic pressure control optimizes both shell integrity and joining effectiveness
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 approach effectively avoids inward deflection of the shells during bonding, improving the quality and efficiency of the hollow article formation process by allowing for lower pressure injection and potentially reducing material usage and production time.
Implementation Method 1
injecting a third molding material into the third cavity at a third injection pressure to join together the first and second shells along the first and second peripheral edges to form the hollow article
Implementation Method 2
The third molding material comprises a gas that is mixed into the third molding material prior to injecting the third molding material into the third mold cavity
Data Source
AI summary
A method of forming a hollow article includes injecting a first molding material into a first mold cavity at a first injection pressure to form a first molded shell and injecting a second molding material into a second mold cavity at a second injection pressure to form a second molded shell. The first molded shell has a first peripheral edge, and the second molded shell has a second peripheral edge. The method includes positioning the first shell and second shell into facing relation with the first and second peripheral edges in a third cavity, and injecting a third molding material into the third cavity at a third injection pressure to bond together the first and second shells along the first and second peripheral edges to form the hollow article. The third injection pressure is less than the first injection pressure by at least about 3.5 bar.