Compression molded footwear and methods of manufacture

Abstract

An article of footwear having an upper, which includes a first foam layer having a first surface and a second surface remote from the first surface, a second foam layer having a first surface and a second surface remote from the first surface, and a middle layer having a first surface and a second surface remote from the first surface. The first surface of the middle layer is affixed to the second surface of the first foam layer, and the second surface of the middle layer is affixed to the first surface of the second foam layer. The upper defines at least a portion of a foot receiving cavity for the article of footwear.

Description

BACKGROUND OF THE INVENTION [0001] The present invention relates generally to articles of footwear and, more particularly, to articles of footwear having multilayer molded uppers. [0002] Typically, many types of footwear are made by what is known as a cut and sew method, in which individual pieces of material are cut out and sewn together to form the three dimensional (“3-D”) shape of a footwear upper. In such a process, individual pieces of material are cut out according to a pattern, in which individual pieces are designated to form specified portions of the shoe upper. When the pieces are cut out, they are typically marked according to the portion of the upper which they are intended to form. The individual pieces are bonded, stitched and then lasted, giving the shoe the necessary 3-D shape. Other portions of the shoe may then be attached to the upper, such as an outsole, midsole, footbed, etc. [0003] Such a method requires a large number of steps, each requiring a skilled person...

AI Technical Summary

Benefits of technology

[0019] In a preferred embodiment the first foam layer, second foam layer and middle layer are integrally formed by compression molding. Additionally, the step of integrally forming may include adhesively affixing the middle layer between the first foam layer and the second foam layer. The adhesive used in the step of integrally forming is preferably heat activated. In a further embodiment, the middle layer is formed of a textile material defining a plurality of open portions such that the step of compression molding forces the first foam layer and the second foam layer into mutual contact within the open portions so as provide tensile strength to the layered material.

Problems solved by technology

Such a method requires a large number of steps, each requiring a skilled person for completion thereof.

This increases the overall manufacturing cost and can lead to throughput problems arising from bottlenecks in one step of the process.

For example, the absence of the person responsible for one step in the process can shut down an entire production line of footwear.

Furthermore, the use of such complicated individual pieces leads to a product that is more difficult to design, requiring the design of both the individual pieces and how the pieces will fit together to form the shape of the shoe upper.

This further contributes to increased costs of the finished product, and increases lead time when designing the shoe.

However, the injection molding method presents significant additional problems.

Specifically, the complicated molds necessary to form the 3-D shape of a shoe upper increase costs and lead time due to the time required to manufacture these molds.

If not controlled, creep can result in continued expansion of the polymer.

This causes the shoe upper to stretch, which affects the fit quality of the shoe.

Additionally, because the majority of the shoe upper is formed in a single process step, there are no available intermediate steps that can control factory defects in the upper of the shoe.

Such defects typically arise due to the difficulty in controlling the expansion of foam after injection into the mold, particularly during cooling.

In order to control such defects, tolerances within the molds need to be widened, which can lead to overall fit problems with the finished product.

However, this method does not alleviate the expense required by complex 3-D molds or the increased product lead time associated therewith.

Limitations in such a process arise, particularly from the materials, namely TPU, that are used in the 3-D compression molding.

Such materials are often somewhat thick or dense, resulting in shoe uppers that are too rigid or inflexible for practical purposes of footwear.

The relative weight of TPU can also make it less desirable for use in a shoe upper.

Additionally, footwear made from material including TPU retains heat and can make the foot hot, causing discomfort to the wearer.

Additionally, it is difficult to mold a 3-D shape from a single sheet of material having both thermoplastic and fabric materials, fabric not being thermoplastic.

This causes difficulty in molding the complex 3-D shape of the shoe upper because thermoplastic and non-thermoplastic materials conform to the mold differently.

The use of non-thermoformable materials can cause problems in the overall integrity of the product or the reliability of the process, leading to increased factory defects from the difficulty to control the molding process.

Additionally, compression molding of a 3-D form from a flat substrate of material can lead to thinning of certain layers of the material during formation because the material must stretch to conform to the mold.

This can weaken the overall material or diminish the foot protective properties of the materials used to form the upper.

It also limits the ability of the shoe to be formed with decorative or protective features on the shoe upper.

Stretching can also make it difficult to control the overall compression of the foam, which is desirous in compression molding because compression helps to bond the layers of material together.

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