Reverse Shoe Last Design for Secure Outsole Sewing
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Solution Overview
Problem
The GOOD YEAR REVERSE technology in footwear manufacturing faces issues such as the inability to sew an outsole under the midsole due to insufficient space, leading to a glued anti-slip bottom that is aesthetically unpleasing and unreliable, and irreversible deformation of the upper at the toe during the assembly process.
Innovation Solution
Designing a new reverse shoe last with a thinner and more pointed configuration and a straight shoe last with a tapered end, along with a midsole featuring a channel that increases in distance from the perimeter edge from the shank to the toe, allowing for sufficient space to sew an outsole and preventing deformation of the upper.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional reverse shoe last is used in the GOOD YEAR REVERSE process, then the upper can be assembled in reverse position, but the toe of the upper undergoes irreversible deformation due to stress concentration
Solution Approach 1:
The reverse shoe last is designed with a localized modification at the toe end, transitioning from a conventional cylindrical shape to a conical shape with gradually decreasing diameter. This local quality change distributes the stress evenly during reverse assembly, preventing the stress concentration that causes toe deformation while maintaining the overall reverse assembly process.
2Ease of manufacture
If the channel on the midsole is positioned at a constant distance from the perimeter edge, then the manufacturing process is simplified, but there is insufficient space to sew an outsole under the midsole
Solution Approach 1:
The channel positioning transitions from a static, constant-distance configuration to a dynamic, variable-distance configuration. The channel distance from the perimeter edge increases progressively from the heel to the toe, creating additional space at the toe region for outsole sewing operations while maintaining simplified manufacturing through a systematic gradient rather than complex variable positioning.
3Ease of manufacture
If a glued anti-slip bottom is used instead of sewing, then the outsole can be attached, but the aesthetic appeal and reliability are compromised
Solution Approach 1:
The variable-distance channel configuration creates an intermediate space between the midsole perimeter edge and the channel that serves as a dedicated sewing channel. This intermediary space allows proper insertion of sewing needles and threads, enabling reliable mechanical attachment of the outsole with visible stitching that enhances both reliability and aesthetic appeal.
Data Source
Figure 1~2C
Figure 1A~1B
Figure 2D
AI summary
Method of designing and manufacturing a reverse shoe last (1) and a straight shoe last (2) used for manufacturing an article of footwear by means of a process that provides for fixing an upper (4) disposed in reverse position on the reverse shoe last (1) to the midsole; said method firstly providing for designing a shape and/or size of a foot suitable for wearing the footwear to be manufactured and secondly for designing and making a reverse shoe last (1) and for designing and making a straight shoe last (2) suitable for being inserted inside the upper (4) when the upper (4) has been turned and disposed in straight position; the peculiarity of the method according to the invention is that the reverse shoe last (1) is designed and made with a length (u1) higher than the length (u2) of the straight shoe last (2).