Perforated Last for Footwear Midsole Gas Venting
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Solution Overview
Problem
The existing methods for forming shoe midsoles often result in the formation of macro bubbles, air traps, and voids due to off-gassing during the injection and curing of foaming materials, leading to undesirable blemishes on the midsole surface and affecting the durability and aesthetic appeal of the shoe.
Innovation Solution
A perforated last is used in conjunction with a mold, allowing gases to vent through perforations that fluidly couple the interior of the mold cavity with the surrounding atmosphere, reducing the likelihood of macro bubbles and voids by equalizing pressure and assisting gas evacuation, either through atmospheric venting or a vacuum source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional methods are used to form the midsole, then the manufacturing process is simple, but macro bubbles, air traps, and voids are formed due to off-gassing during injection and curing
Solution Approach 1:
The mold cavity is divided into multiple zones with different pressure characteristics. The first region maintains positive pressure to prevent void formation, while the second region allows negative pressure to vent gases. This segmentation resolves the contradiction by addressing gas venting needs in different locations without requiring a completely complex mold structure.
Solution Approach 2:
The invention changes the pressure parameters within the mold cavity during the injection and curing process. By creating regions of positive and negative pressure, the system effectively manages off-gassing while maintaining a relatively simple overall mold structure, thus improving surface quality without excessive complexity.
2Manufacturing precision
If gases are vented during midsole formation, then macro bubbles and voids are reduced, but additional venting mechanisms increase device complexity
Solution Approach 1:
The venting function is merged into the existing mold cavity structure rather than adding separate venting components. The second region of the mold cavity naturally facilitates gas evacuation through its pressure characteristics, combining venting with the basic molding function and avoiding additional complexity.
Solution Approach 2:
The invention uses pressure differentials as an intermediary mechanism to facilitate gas venting. By creating negative pressure in the second region, gases are naturally drawn out without requiring active venting components, thus improving surface quality while maintaining simplicity.
3Strength
If the midsole is formed directly onto the upper, then attachment quality is improved, but off-gassing causes cosmetic defects on the midsole surface
Solution Approach 1:
The mold cavity is segmented into regions that serve different functions: the first region ensures strong attachment by maintaining positive pressure and preventing void formation at the interface with the upper, while the second region manages gas venting to prevent cosmetic defects. This segmentation allows simultaneous optimization of both attachment quality and surface quality.
4Productivity
If excess material is present during midsole formation, then the midsole can be formed, but additional trimming is required increasing manufacturing time and cost
Solution Approach 1:
By changing the pressure parameters in the mold cavity, the invention enables precise control of material flow and gas evacuation. This results in complete filling of the mold cavity without excess material, eliminating the need for trimming operations and improving manufacturing efficiency while reducing material waste.
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 enhances the quality of the midsole by minimizing cosmetic defects, improving the attachment of the midsole to the upper, and reducing manufacturing costs by eliminating excess material trimming, thereby increasing production efficiency and aesthetic appeal.
Implementation Method 1
The perforated last may allow gases generated during a chemical reaction to form the midsole to be vented
Implementation Method 2
reducing the likelihood of macro bubbles and voids by equalizing pressure and assisting gas evacuation
Implementation Method 3
gases generated during a chemical reaction to form the midsole
Data Source
AI summary
Methods and systems are provided for forming an article of footwear. In one example, forming the article of footwear includes using a perforated last during molding of a midsole of the article of footwear. The midsole may be attached to a seam of the upper of the article footwear to secure the midsole to the upper.