Double-Layer Sole Molding with Sequential Supercritical Injection

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Solution Overview

Problem

Existing injection molding methods struggle to efficiently produce double-layer soles with different materials or colors using a supercritical injection molding process, as conventional methods are not adaptable to simultaneous injections of multiple materials.

Innovation Solution

A supercritical molding method involving a series of operations including preparing, first and second injecting, and opening operations to form a double-layer sole structure by injecting and expanding materials in high-pressure and vacuum conditions within a mold system, allowing for different materials or colors to be integrated efficiently.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional injection method is used with composite mold and heating operation, then two different materials can be injected simultaneously, but the method cannot be adapted to supercritical injection molding process

Engineering Contradiction:

Improveadaptability to supercritical injection molding processVSAvoidmanufacturing process complexity

Core Design Contradiction:

Adaptability or versatilityVSEase of manufacture

Solution Approach 1:

The injection process is divided into two separate sequential operations: first injecting the midsole material, then injecting the outsole material. This segmentation allows each material to be processed independently under supercritical conditions, making the process adaptable to supercritical injection molding while maintaining the ability to use different materials.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The midsole is formed first as a preliminary structure before the outsole is injected. The partition mold is removed after midsole formation, preparing the mold cavity for the second injection. This preliminary action enables the sequential injection process to work effectively with supercritical materials.

Inventive Principle:

Principle #10Preliminary action

2Extent of automation

If manual sole-grinding and sole-cementing operations are conducted, then midsole and outsole can be joined, but assembling demand cannot be mechanically automated

Engineering Contradiction:

Improvemechanical automation of assemblyVSAvoidmanufacturing process complexity

Core Design Contradiction:

Extent of automationVSEase of manufacture

Solution Approach 1:

The molding and joining operations are merged into a single injection process. The partition mold creates a interface between midsole and outsole materials during injection, and the direct contact and pressure during the second injection automatically join the two materials, eliminating separate grinding and cementing steps and enabling full mechanical automation.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The partition mold acts as an intermediary tool that facilitates the joining of two different materials during the injection process. It creates the necessary interface and contact conditions between midsole and outsole materials, enabling automatic joining without manual intervention.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Strength

If rubber material is used for sole, then good support force and durability are achieved, but shock-absorbing ability and elasticity are poor

Engineering Contradiction:

Improvesupport force and durabilityVSAvoidground reaction forces delivered to feet

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The sole is constructed as a composite structure with midsole and outsole made of different materials. The outsole uses rubber for durability and support, while the midsole uses a softer material with better shock-absorbing properties. This composite approach combines the advantages of different materials to achieve both strength and comfort.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

Different regions of the sole have different material properties optimized for their specific functions. The outsole region has hard, durable material for ground contact and support, while the midsole region has softer, more elastic material for shock absorption. This local differentiation of material quality resolves the contradiction between support and comfort.

Inventive Principle:

Principle #3Local quality

Data Source

PatentEP4644084A1A supercritical molding method for manufacturing a double-layer sole structure

Publication Date: 2025.11.05 HSU YI-HAO

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AI summary

A supercritical molding method (3) includes a first injecting operation (32) executed by covering a lower mold (411) with a partition mold (412) and then injecting a first injection material (M1) to form a first semi-finished sole (51), a first opening operation (33) executed by separating the partition mold (412) from the lower mold (411) and cutting a first surplus material (511) off the first semi-finished sole (51) to form a first sole (5A), a second injecting operation (34) executed by covering the lower mold (411) with an upper mold (413) and then injecting a second injection material (M2) to form a second semi-finished sole (52), and a second opening operation (35) executed by separating the upper mold (413) from the lower mold (411) and cutting a second surplus material (521) off the second semi-finished sole (52) to form a second sole (5B) joined to the first sole (5A). Accordingly, a double-layer sole structure (5) having the first sole (5A) and the second sole (5B) is quickly manufactured.