Dual-Density Footwear Midsole via Multi-Material Injection Molding

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Solution Overview

Problem

Conventional midsole manufacturing methods are limited in creating dual density midsoles with varying performance characteristics, as they rely on single material polymer foams and lack the ability to efficiently integrate materials with different densities and hardnesses.

Innovation Solution

A method involving a multi-step mold assembly process where different materials are injected and processed at varying temperatures and pressures to form midsoles with distinct density and hardness regions, allowing for the creation of midsoles with tailored performance characteristics by using a first material for one portion and a second material with different hardness for another portion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a single material polymer foam is used for the midsole, then the manufacturing process is simple, but the ability to provide varying densities and performance characteristics in different regions is limited

Engineering Contradiction:

Improvemanufacturing process simplicityVSAvoidperformance characteristics variation

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The midsole is divided into multiple regions with different densities by using a multi-cavity mold assembly where each cavity receives a different material formulation. This segmentation allows each region to have tailored performance characteristics while maintaining a unified manufacturing process

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention uses composite material formulations with varying polymer compositions, fillers, and plasticizers injected into different mold cavities to create regions with distinct density and performance properties within the same midsole structure

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If multiple materials with different densities are integrated into the midsole, then performance characteristics can be tailored for specific activities, but the manufacturing process complexity increases

Engineering Contradiction:

Improveperformance characteristics customizationVSAvoidmanufacturing process complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple material injection operations are merged into a single multi-cavity mold assembly that can be filled simultaneously or in a controlled sequence, integrating what would otherwise be separate manufacturing steps into one unified process

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The multi-cavity mold assembly serves multiple functions: it acts as both the forming tool and the distribution system for different materials, while also providing the structural framework for creating the dual-density midsole configuration

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Ease of manufacture

If conventional single-material polymer foam is used, then manufacturing is straightforward, but the midsole cannot provide optimized ground reaction force attenuation and stability in different regions

Engineering Contradiction:

Improvemanufacturing simplicityVSAvoidground reaction force attenuation

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

Different regions of the midsole are assigned different material properties with specific density ranges optimized for their functional requirements: softer materials in areas requiring shock absorption and firmer materials in areas requiring stability and support

Inventive Principle:

Principle #3Local quality

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

Enables the production of midsoles with specific performance characteristics in different regions, enhancing the midsole's ability to attenuate ground reaction forces and provide stability, while allowing for customization based on intended activity.

Implementation Method 1

injecting a first material into a first recess and a second recess in the first mold member to form first and second portions of a midsole preform while the first mold member is maintained at a temperature below an ambient temperature

Methodology Applied

Scientific EffectCooling: Cooling

Implementation Method 2

subjecting the second material and the first and second portions in the second mold assembly to heat to form a midsole preform

Methodology Applied

Scientific EffectHeating: Heating

Implementation Method 3

subjecting the midsole preform in the third mold assembly to heat and pressure to form a midsole

Methodology Applied

Scientific EffectHeating: Heating

Data Source

PatentUS8906280B2Method of manufacturing sole assembly for article of footwear

Publication Date: 2014.12.09 NIKE INC

AI summary

A method of forming a midsole includes the steps of placing a first mold member and a second mold member in contact with one another, injecting a first material into the first mold member to form first and second portions of a midsole preform, positioning the first and second portions in a third mold member of a second mold assembly; placing a second material in the third mold member; placing the third mold member and a fourth mold member in contact with one another, subjecting the second material and the first and second portions to heat to form a midsole preform, placing the midsole preform in a fifth mold member, placing the fifth mold member and a sixth mold member in contact with one another; and subjecting the midsole preform to heat and pressure to form a midsole.