Heat-Shrinkable Knitted Shoe Upper for Precise Last Conformity
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Solution Overview
Problem
Existing shoe manufacturing methods fail to consistently conform the upper to the shape of the last, leading to gaps that can cause discomfort and reduced foot retention, especially on the lateral side, requiring additional stuffing to address these issues.
Innovation Solution
A shoe upper composed of two layers of knitted fabric, where one layer has yarns with heat shrinkability and a higher fusion point, allowing for precise shaping to conform to the last through controlled heat application, ensuring a snug fit without the need for additional filling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the upper is shaped with conventional materials and methods, then the shaping process is simple, but the upper cannot conform precisely to the shape of the last, creating gaps that reduce foot retention
Solution Approach 1:
The upper is constructed from composite knitted fabric incorporating multiple types of yarns with different properties: heat-shrinkable yarns for dimensional control, fusible yarns for bonding, and elastic yarns for flexibility. This composite structure enables precise conformity to the last shape while maintaining wearability
Solution Approach 2:
The shaping process utilizes thermal parameter changes by heating the upper to trigger heat shrinkage of specific yarns and fusion of bonding yarns. This temperature-dependent transformation allows the upper to transition from a loose state to a tightly conforming state, achieving high manufacturing precision
2Reliability
If stuffing is added to fill gaps in the upper, then foot retention improves, but the wearing comfort deteriorates
Solution Approach 1:
The mechanical stuffing system is replaced with a thermal-forming system. By applying heat, the upper material itself undergoes shrinkage and fusion to eliminate gaps, achieving reliable foot retention through material transformation rather than mechanical filling. This eliminates discomfort caused by stuffing while maintaining secure fit
3Manufacturing precision
If the upper material has high heat shrinkage rate, then the upper conforms easily to the last shape, but the material may lose structural integrity
Solution Approach 1:
Different regions of the upper contain different yarn compositions tailored to local requirements. Areas requiring high conformity have higher concentrations of heat-shrinkable yarns, while areas requiring strength have more fusible and elastic yarns. This localized material differentiation achieves both easy conforming and structural integrity
Solution Approach 2:
The multi-component yarn composite provides both heat shrinkage capability and structural strength. The synergistic combination of heat-shrinkable polyester, fusible polyamide, and elastic spandex yarns creates a material that can undergo significant thermal transformation while maintaining cohesive structure and tensile strength
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 enables the shoe upper to be easily molded to the last's shape, enhancing foot retention and comfort by eliminating gaps and providing a better fit, thus improving the overall wearing experience.
Implementation Method 1
the first yarns have a heat shrinkability
Implementation Method 2
the second yarns have a higher fusion point than that of the first yarns
Data Source
AI summary
A shoe including: an upper that includes a first layer made of knitted fabric and a second layer made of knitted fabric arranged inside the first layer, wherein at least one of the first layer and the second layer includes first yarns and second yarns as yarns for forming the knitted fabric, wherein the first yarns have a heat shrinkability, wherein the second yarns have a higher fusion point than that of the first yarns, and wherein the at least one of the first layer and the second layer including the first yarns and the second yarns has a higher heat shrinkage rate in a width direction than in a longitudinal direction.