EVA Shoe Sole Mechanical Insertion Without Adhesives
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Solution Overview
Problem
EVA materials used in shoe soles and other products face issues with mechanical resistance and adhesive detachment due to environmental factors, making it difficult to attach components securely without using unsatisfactory and cumbersome adhesives, and preventing the use of threaded connections with harder materials.
Innovation Solution
A semi-finished product is created using an EVA-based compound with an expanding additive, allowing for the insertion of additional portions, such as rubber, TPU, or metal inserts, while the EVA is still warm and expanded, ensuring a secure mechanical connection without adhesives by utilizing the expansion and cooling shrinkage for a stable fit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adhesives are used to attach components to EVA semi-finished product, then components can be attached, but the adhesion is lost due to elasticity and environmental factors leading to detachment
Solution Approach 1:
The patent replaces the chemical adhesion mechanism with a mechanical interlocking mechanism. The insert is inserted into a cavity in the EVA semi-finished product, and the cavity is designed with features (such as ribs, protrusions, or friction-fit geometries) that mechanically secure the insert in place, eliminating reliance on adhesives that degrade over time.
Solution Approach 2:
The patent utilizes temperature parameter changes to facilitate the attachment process. The EVA material is heated to a temperature where it becomes more flexible and easier to manipulate, allowing the insert to be inserted into the cavity. Upon cooling, the EVA returns to its original shape, creating a secure mechanical fit without adhesives.
2Strength
If threaded seats are made in EVA to couple screws, then mechanical connections can be established, but the seat is soon damaged by the screw due to insufficient mechanical resistance
Solution Approach 1:
The patent separates the functional requirements into different components: the EVA semi-finished product provides the structural body, while separate inserts made of more rigid materials (such as metal, thermoplastic, or rubber) provide the mechanical fastening features. This segmentation allows each component to be optimized for its specific function without compromising the other.
Solution Approach 2:
The patent creates a composite structure by combining EVA material with inserts of different materials (metal, thermoplastic, rubber). The insert is inserted into a cavity in the EVA, creating a multi-material composite product that leverages the elasticity of EVA and the mechanical strength of the insert material to achieve durable connections.
3Ease of manufacture
If multiple portions are attached using adhesives, then components can be assembled, but the process becomes cumbersome and production efficiency decreases
Solution Approach 1:
The patent merges the attachment process with the molding process itself. The cavity for the insert is formed as an integral part of the EVA semi-finished product during molding, eliminating the need for separate attachment steps. This integration streamlines production and improves efficiency by reducing the number of discrete operations required.
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 allows for the creation of EVA products with enhanced mechanical properties and secure attachment of inserts, improving durability and allowing for connections with rigid elements, while eliminating the need for adhesives and enhancing eco-sustainability.
Implementation Method 1
molding an EVA-based compound containing an expanding additive with the temperature and made so as to define an insertion seat
Implementation Method 2
as long as the semi-finished product is still hot, easily manipulated, therefore the at least one further portion is made prior to the first portion. After the first portion has cooled, the at least one further portion is no longer separable from the first
Data Source
Figure 1
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AI summary
Method for manufacturing a shoe sole (S) comprising a step of hot molding a first portion (1) made of EVA (ethylene vinyl acetate) comprising an interlocking seat (H) and a subsequent phase of insertion by force, while the first portion is hot and expanded, of a second portion (2) in the seat, wherein the second portion has a complementary shape with the seat.