Molded Foam Rib Structure for Void-Free Corner Filling
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Solution Overview
Problem
Molded foams, such as car seat cushions, often have voids at external corners due to the projecting steps in the mold, which prevent complete filling by expanding polyurethane, leading to air entrapment and defects.
Innovation Solution
Incorporating small ribs at external corners and thin plate-like ribs in the molded foam, with corresponding mold recesses and grooves to allow the expanding resin to fill these areas, ensuring no voids and facilitating backboard attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If a projecting step is used in the mold to form a recessed step in the molded foam, then the molded foam can engage with a backboard, but air becomes trapped at the external corner and voids are formed
Solution Approach 1:
The projecting step in the mold is divided into two portions: a first portion that extends along the parting line and a second portion that protrudes from the first portion. This segmentation allows the expanding polyurethane to flow around both portions and fill the external corner completely, preventing air entrapment while still forming the necessary recessed step for backboard engagement.
Solution Approach 2:
The projecting step is designed with a three-dimensional structure that extends in multiple directions - along the parting line and perpendicular to it. This dimensional approach creates pathways for the expanding resin to access and fill the external corner region, eliminating voids while maintaining the functional recessed step geometry.
2Ease of manufacture
If the mold is simplified for easy manufacture, then production efficiency increases, but voids form at external corners due to incomplete filling
Solution Approach 1:
The mold's projecting step is pre-configured with specific geometric features (extending along the parting line and protruding portions) that proactively guide the expanding polyurethane flow to ensure complete filling of external corners before the molding process completes, preventing void formation from the outset.
Solution Approach 2:
The geometry of the projecting step is optimized with specific dimensional parameters - the extension along the parting line and the protrusion distance - that create ideal flow pathways for the expanding resin, ensuring reliable void-free filling while maintaining mold manufacturing simplicity.
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 ensures void-free molded foams by allowing the resin to fill corners completely, preventing air entrapment and enabling smooth backboard attachment without hindrance.
Implementation Method 1
The lids 3 and 4 are closed to the bowl 2 before polyurethane reaction by heating
Data Source
AI summary
A molded foam containing no voids and a mold for forming such a molded foam are provided. A molded foam 5 has an external corner 5a where a small rib 10 is formed and a recessed step 7 where thin plate-like ribs 11 are formed. The rib 10 has a triangular cross-sectional shape in a direction perpendicular to the longitudinal direction of the recessed step 7. The rib 10 is tapered from the base to an end thereof in a direction in which the rib 10 protrudes. The ribs 11 are arranged at intervals in the longitudinal direction of the recessed step 7.