Footwear Midsole with Density-Zoned Recesses
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Solution Overview
Problem
Athletic footwear soles often face challenges in achieving optimal resiliency and traction while maintaining a lightweight design, as traditional materials can suffer from compression set and increased weight due to lower density foams.
Innovation Solution
A midsole structure with strategically placed recesses of varying density, where higher density foam is used in pressure zones to enhance resiliency without increasing overall weight, and the recesses are spaced according to foot pressure maps to optimize cushioning and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If lower density foam is used in the midsole, then the overall weight of the midsole is reduced, but the resiliency and compression resistance deteriorate
Solution Approach 1:
The midsole is designed with non-uniform density distribution, featuring a higher density outer skin layer and a lower density inner core layer. This local quality differentiation allows the outer layer to provide structural support and compression resistance while the inner layer reduces overall weight, resolving the contradiction between weight reduction and resiliency maintenance.
Solution Approach 2:
The midsole combines two different foam densities into a single composite structure. The outer skin uses higher density foam for durability and compression resistance, while the inner core uses lower density foam for weight reduction. This composite material approach enables the midsole to achieve both lightweight design and reliable performance simultaneously.
2Reliability
If higher density foam is used throughout the midsole, then resiliency and compression resistance are improved, but the overall weight increases
Solution Approach 1:
Instead of uniformly increasing density throughout the midsole, the invention applies higher density only to the outer skin layer where structural support is most needed. The inner core maintains lower density to minimize weight, thus improving resiliency without proportionally increasing overall weight.
Solution Approach 2:
The midsole is segmented into distinct density zones: an outer skin layer with higher density and an inner core layer with lower density. This segmentation allows each region to be optimized for its specific function - the outer layer for compression resistance and the inner layer for weight reduction - resolving the weight-resiliency contradiction.
3Ease of manufacture
If uniform density foam is used in the midsole, then manufacturing is simplified, but performance in different pressure zones is suboptimal
Solution Approach 1:
The midsole employs different density levels in different regions - higher density in the outer skin and lower density in the inner core. This local quality variation optimizes performance for different functional requirements while remaining manufacturable through techniques like two-shot molding or co-molding processes.
Data Source
AI summary
A sole structure for an article of footwear includes a midsole having a first side with a first surface and a second side with a second surface. The first side has recesses extending toward the second side without extending to the second surface. A thickness of the midsole between the second side and a deepest extent of each of the recesses may be substantially uniform. Spacing of the recesses may correspond to a foot pressure map. The midsole may be a foam material that has a first density in a first portion along the first surface and a second density less than the first density in a second portion adjacent the first portion. A method of forming the midsole includes providing such recesses in the midsole such as by molding the midsole, and controlling a temperature of mold tools to achieve the first density in the first portion.