Overmold Direct Attach Sole Bonding
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Solution Overview
Problem
Traditional methods of attaching a bottom unit to an article of footwear using adhesives increase manufacturing costs and quality concerns due to the need for primers and potential bond failures between materials of different compositions.
Innovation Solution
A direct attach method where a midsole core and upper are over molded with a shell, using fluid-like state materials that transition to a cured state to physically bond the components without adhesives, leveraging different materials for the core and shell to enhance bonding and reduce manufacturing complexities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If adhesive bonding is used to join upper and bottom unit, then bond between materials is achieved, but manufacturing costs increase and quality concerns arise
Solution Approach 1:
The patent extracts and eliminates the adhesive bonding step from the manufacturing process. Instead of using adhesives to join the upper and bottom unit, the invention uses direct mechanical attachment methods such as stitching, bonding through shared mold cavities, or integrated construction where the upper is formed directly over the bottom unit, thereby removing the source of manufacturing complexity and quality issues associated with adhesive application
Solution Approach 2:
The invention merges the upper and bottom unit construction into a more integrated process. By using shared mold cavities during formation or direct attachment methods, the upper and bottom unit are joined in a single operational step rather than through separate adhesive application and curing processes, simplifying the overall manufacturing process
2Strength
If adhesive bonding is used to join upper and bottom unit, then bond between materials is achieved, but manufacturing time and costs increase
Solution Approach 1:
The patent applies preliminary action by pre-forming attachment features such as stitching channels, bonding surfaces, or integrated mold cavities before the final assembly of the upper and bottom unit. This allows the attachment process to occur simultaneously with or immediately upon assembly, eliminating the separate adhesive application and curing time that would otherwise extend manufacturing cycles
Solution Approach 2:
By removing the adhesive bonding step entirely and replacing it with direct mechanical attachment or integrated formation processes, the patent eliminates the time-consuming adhesive application, spreading, and curing operations, thereby significantly improving manufacturing efficiency and productivity
3Strength
If adhesive bonding is used to join upper and bottom unit, then bond between materials is achieved, but bond failures may occur between materials of different compositions
Solution Approach 1:
The patent extracts and eliminates the adhesive layer from the bonding interface between the upper and bottom unit. By using direct mechanical attachment methods such as stitching through both components, bonding through shared mold cavities that create integrated structures, or direct friction-based attachment, the invention removes the intermediate adhesive that is susceptible to failure when joining materials of different compositions with incompatible surface properties
Solution Approach 2:
The invention applies local quality by creating attachment features specifically adapted to the local material properties at the bonding interface. For example, stitching channels are positioned and sized to accommodate the specific thickness and material characteristics of both the upper and bottom unit at each location, ensuring reliable mechanical interlocking that is independent of material composition compatibility issues that plague adhesive bonding
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 method reduces manufacturing costs and quality concerns by eliminating the need for adhesives and primers, providing a strong and durable bond between the midsole core and upper, while allowing for the use of materials with different characteristics, thus improving the overall construction of the footwear.
Implementation Method 1
A direct attach method where a midsole core and upper are over molded with a shell, using fluid-like state materials that transition to a cured state to physically bond the components without adhesives
Data Source
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AI summary
Joining a bottom unit, such as an athletic shoe sole, with an upper is achieved with an over molding process. A midsole core may be formed with a direct attach to an underfoot portion of the upper. The forming of the midsole core may be achieved with open cast molding or injection molding, for example. A shell may encapsulate the midsole core and also mechanically engage with the upper to further join the bottom unit with the upper. The shell and the midsole core may be formed from an elastomeric polymer such as polyurethane, thermoplastic polyurethane, ethyl-vinyl acetate, and/or silicone-based materials.