Collapsible Last with String Attachment for Footwear Upper
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Solution Overview
Problem
Existing methods of string lasting in footwear production are mechanically complex, labor-intensive, and difficult to automate, leading to inefficiencies in production time, cost, and fit quality, especially in the toe and heel regions.
Innovation Solution
A method involving a collapsible last with means for attaching strings, which are extended to tension the upper, providing a uniform form-fitting tension for improved fit and allowing for automation, using an elastic upper that is larger when collapsed and smaller when extended, and incorporating a bridge for enhanced connection between sides in concave regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional string lasting methods are used, then the upper can be lasted to the last, but the process is mechanically complex and requires careful manipulation of lasting strings
Solution Approach 1:
The last is divided into two separable parts: a removable first part and a stationary second part. This segmentation allows the complex manipulation of strings to be replaced by simple insertion and removal actions, dramatically simplifying the manufacturing process while reducing mechanical complexity
Solution Approach 2:
The first part of the last is completely removed from the upper after the upper is stretched over it. This extraction eliminates the need for complex string manipulation mechanisms, as the lasting effect is achieved purely through the stretching action during insertion
2Reliability
If board lasting is used, then the resulting shoe is stable and durable, but it is heavy and requires skilled labor
Solution Approach 1:
The heavy board component is completely removed from the footwear structure. The stability and durability are maintained through the proper lasting of the upper to the last and subsequent bonding to the sole, without requiring the additional weight of a board
Solution Approach 2:
Instead of using a heavy board throughout the entire footwear structure, the invention applies strength and stability locally through the lasted upper itself, which is formed to fit precisely to the last and bonded to the sole where needed
3Weight of moving object
If an upper is sewn to an insole sheet using a Strobel sewing machine, then the shoe is more lightweight, but the process requires at least three steps and cannot be automated easily
Solution Approach 1:
The stretching and lasting operations are merged into a single action: inserting the first part of the last into the upper causes the upper to stretch and conform to the last in one continuous motion, eliminating the need for separate pre-forming, sewing, and lasting steps
Solution Approach 2:
The upper itself performs the lasting function by stretching over the first part of the last during insertion. The material's elastic properties enable it to self-form to the last shape without requiring external sewing or complex lasting mechanisms
4Ease of operation
If collapsible lasts are used, then the last can be removed easily from the upper, but they are not used in a dynamic manner to facilitate the lasting operation itself
Solution Approach 1:
The last transitions from a static tool to a dynamic component that actively facilitates lasting. The first part is inserted into the upper in a specific orientation and then rotated 180 degrees, dynamically shaping the upper as it is stretched over the last during the rotation process
Solution Approach 2:
The first part of the last is pre-positioned in a specific orientation within the upper before the lasting action begins. This preliminary placement ensures that the upper is properly aligned and stretched as the rotation occurs, facilitating efficient lasting
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 simplifies and automates the string lasting process, improving the fit and reducing production time and cost, enabling faster, more cost-effective production of lightweight footwear with better fit and breathability.
Implementation Method 1
The upper may be made of elastic material and may be larger than the last when the last is collapsed but smaller than the last when the last is extended
Data Source
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AI summary
The present invention concerns a method (10) of lasting an upper (14) for an article of footwear, comprising: (a) providing a last (11), wherein the last (11) comprises at least two parts (11a, 11b) that can be moved relative to each other such as to allow the last (11) to be collapsed along a substantially longitudinal direction, wherein the last (11) comprises at least one means (12) for attaching a string (13) configured to hold the string (13) in a collapsed and in an extended state of the last (11); (b) providing an upper (14); (c) inserting the collapsed last (11) into the upper (14); (d) attaching the upper (14) to the means (12) for attaching a string (13) using at least one string (13); and (e) extending the last (11), wherein step (d) is performed before step (e).