Shoe Sole with Improved Shock Absorbing Effect

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This invention applies to semi-finished products and connected technologies used in the production of footwear; more precisely, this Invention describes the shoe lower portion in contact with the ground called sole, also called outer sole.

Footwear is a highly diversified leather goods item in terms of shape, use and declination. Today, there are thousands of models especially thanks to the use of new materials and new technologies in the production processes, which allow the consumer to have an extremely wide offer on the market.

It is possible to differentiate some general types of footwear, however said distinction has boundary lines whose tracing is increasingly difficult:

Footwear that can be classified in the third category above therefore has a design origin that always remains attentive to technical performance such as comfort, correct support for the foot during walking, a high breathability factor and gas exchange between the inside and outside, use of materials with antifungal and germicidal characteristics, improved flexibility, etc.

Footwear in the third category above, such as those intended for competitive use, mainly uses cutting-edge material technologies and construction processes that are optimized for large production quantities and, as already highlighted in paragraph 002, point c), can share some technical refinements deriving from competitive use for the benefit of the general user.

A shoe can be separated into some macro-parts, for example:

There are further reinforcement and finishing elements such as the internal sole, to increase comfort, the linings coupled to the upper—also internal to the shoe—finishing welts etc.

It is obvious that the foot during walking releases variable forces in directions mostly orthogonal to the ground, so it is the sole that is most affected by all those technical improvements aimed at improving the pleasure or technical performance of walking.

In general, the soles thus constructed are mainly the result of manufacturing processes through injection and molding of synthetic materials, which can combine unique elasticity and resilience factors that cannot be reproduced with natural materials, such as leather and its derivatives.

Prior Art today offers a large differentiation of substances such as Polyurethane (PU), PVC, EVA (Ethylene Vinyl Acetate) etc. and each of them has peculiar mechanical characteristics. EVA, for example, is a cross-linkable polymer which, when subjected to an adequate temperature inside a mould, expands and produces an extremely light, flexible semi-finished product with no shape memory. While EVA is not easily recyclable, except in its inert filler added to another material, Thermoplastic Polyurethane can instead be reused through fusion and moulding, thus proving extremely advantageous.

The use of these materials, with the appropriate formulation variations to enhance some of their mechanical characteristics, is enhanced by the geometric shape of the sole and by the solutions that are designed inside it, thus creating a semi-finished product that allows combining both a peculiar aesthetic aspect and a series of characteristics that highlight its functionality.

Nike™'s patent US2022248804A1 describes, for example, a sole in synthetic material in which a peculiar cushioning element, called a “barrier layer”, is inserted and incorporated inside a closed volume, also filled with liquids or gases. This cushioning element is located in the central/front area of the sole and manages the pressure forces coming from the foot. The sole, constructed in this way, presents unquestionably great advantages but also a significant complexity in the construction process.

Patent WO2016191109A1 describes a sole in which an elastic layer is worked inside through openings created in various sizes and dimensions, in order to modify the elastic effect of the aforementioned layer. This is an interesting but extremely complicated solution, since synthetic soles are generally produced by injection and mould, thus forcing the inventive process within the technical limits of a layout that allows easy extraction of the sole from the mould.

Publication US2022378150A1 by Nike™ describes a sole in which the shock-absorbing element consists by a series of recesses and lobes facing each other that when in contact create a cushion effect. This layout includes closed chambers also filled with liquids; in this case, too, the layout described is very efficient but complicated to implement.

Reebok™'s patent U.S. Pat. No. 7,966,749B2 describes an element that can be inserted inside a sole, composed of two closed chambers connected by a corrugated channel. The presence of air inside the two chambers, air that can pass from the first chamber to the second and vice versa, creates a shock-absorbing element. Again, this is a highly efficient but extremely complicated system.

Adidas™'s patent U.S. Pat. No. 9,930,928B2 describes a sole that includes two regions of space in which two types of materials are used, a first type of expanded materials that are free to move, and a second region of more compact materials that penetrates the first region causing it to block, thus creating a controlled shock-absorbing effect. The described solution is once again extremely complex and limits the cost-effectiveness of the Invention.

Newton Running Company™ publication WO2023122761A1 describes a sole in which there are two layers facing each other. The two layers are worked using sinusoidal undulations and are coupled by the interposition of a membrane. The presence of a compressive force causes the two layers to penetrate and the membrane creates a progressive resistance, storing the energy that will be released to the foot as a rebound force, opposed to the compression force. This solution is highly functional but has construction complications and economic inefficiency.

Mizuno™'s publication US2020305541A1 describes a sole made up of different layers, therefore different coupled soles. A first sole has a plurality of protrusions on the side in contact with the foot, the outer sole has a plurality of protrusions on the surface in contact with the ground, and an intermediate sole between the two has a great rigidity. The combination of the protrusions between the layers of the different soles creates a shock-absorbing effect. This solution, however, is complex and furthermore is proven to create a floating effect during walking that is not always pleasant, and for this reason this solution can be improved.

New Balance™ Patent U.S. Pat. No. 6,026,593 describes a shock-absorbing element designed to be inserted into the sole of a shoe. The shock-absorbing element consists of several closed tubular elements. This solution can trigger an evident floating effect and presents a certain structural complexity.

The aim of this Invention is to overcome the criticality in the Prior Art to create a sole for shoes made of synthetic materials in which:

The Invention describes a shoe sole featuring a non-linear shock-absorbing feature and a unique rebound effect, favoring a layout designed for weight maximum containment and maximum ease of use.

This Invention offers the following advantages:

a. unlike many other cushioning and rebound systems integrated into a shoe sole, the Invention—i.e. the sole—allows for the creation of a non-linear elastic characteristic, which regresses as the foot pushes,

The description of the various methods for implementing this Invention is outlined for illustration purposes, therefore all possible modifications of an obvious nature in its field of application, when carried out by industry operators, will not limit the terms for protecting the patent itself.

The device described in this Invention is related to further solutions already known in the Prior Art which are used for the correct implementation in the chosen technical field.

In this text, the reference to a single technical element can also refer to a plurality of the same within the scope of the Invention, unless specifically indicated.

In the present text, the term “Sole” refers to the improved sole.

According to the embodiment of the Invention, is designed a sole for footwear in synthetic material, obtained by the already known injection processes on a mould. The Sole can also be made by a casting technique on a mould, when deemed feasible and consistent with additional factors, even of a non-technological nature.

According to the embodiment of the Invention, the synthetic material that constitutes the sole can be chosen from those already known in the State of the Art, for example EVA (Ethylene Vinyl Acetate), Polyurethane (PU), TR etc.: the choice will depend on the quantity of the desired shock-absorbing effect, an effect that will then be modulated by the peculiar shape of the sole as disclosed in this text.

According to the embodiment of the Invention, the specific processes that provide the Sole with an improved shock-absorbing effect and an improved “rebound” effect—i.e. a rebound effect—are applicable to any sole produced by injection/mould or casting/mould; for this reason, in the drawing table, the aesthetics of the sole shown therein can conveniently be modified according to production needs.

According to the embodiment of the Invention, the Sole presents a differentiation of its structure in the central area () compared to the peripheral area ().shows how the cross-section profile of the sole (Z-Z′) equipped with its tread () which rises peripherally with a wall along a vertical axis () up to its upper outer edge () to descend again () until it meets a central area (). The central area of the sole is the one that is most subjected to the downward thrust given by the foot, and is the one involved in producing the shock-absorbing functions during walking.

According to the embodiment of the Invention, the central area of the sole is equipped with an intrinsic elasticity characteristic deriving from the materials of which the Sole is made, as described in paragraph 0044. In the Prior Art, however, the use of elastic materials for the manufacturing of footwear soles can create an unwanted phenomenon during walking, namely a floating effect that makes the sensation of the positioning of the foot on the ground uncertain.

The said floating effect, if can be sought to increase the degree of comfort of the shoe, namely the ability to absorb shocks during walking, however it does not make it possible to perceive the ground as a stable reference on which to operate the necessary thrusts and movements of the foot for walking, running or practicing sports.

The floating effect can therefore create disorientation, precarious balance; in general it occurs on all those footwear equipped with a high shock-absorbing effect of the sole.

In the Prior Art it is known that the forces acting from the foot towards the sole during walking are distributed differently on the various areas of the same sole: in particular the heel () and the tip of the foot () are the areas of pressure of the support and thrust forces, which in rapid alternation allow walking.

Furthermore, during the support of the heel, the area subjected to a thrust towards the ground is smaller than the area that is created when the foot is parallel to the ground, so the deformation that the sole undergoes is decidedly higher. The same reasoning can be applied to the thrust that the forefoot generates during walking towards the sole in its apical part.

Since these movements generate great forces and thrusts on small surface areas of the sole, namely the apical area of the sole () and the posterior area of the heel (), the final result is a greater tendency for the floating effect to arise.

In order to contain and control the floating effect, and according to the embodiment of the Invention, a continuous perimetral crack is appropriately designed on the internal perimeter of the sole () whose effect is to separate the central area thus formed () from the peripheral area (,,), i.e. the area composed of the elevation of the tread along the vertical axis, its edge and the descending profile, keeping the two areas mutually united thanks to the lower portion of the sole, i.e. that of the tread ().

According to a further embodiment of the Invention, the central area of the sole () can conveniently be added in a subsequent processing phase to the tread area () as disclosed in, while respecting the construction criteria of the present Invention as declared in 0051, i.e. the central area of the sole is separated from the peripheral area (,,) by the presence of the perimetral cracking.

According to the embodiment of the Invention, the creation of a central area of the sole not in contact with the edge of the same amplifies the effect of softness and elasticity during walking, as the yielding of this area of the sole is enhanced by its own deformation, a deformation that develops freely along the empty space created by the perimetral cracking.

According to the embodiment of the Invention, the elasticity characteristic is defined as “enhanced” and has not a linear character, since once the area of the perimetral crack () has been filled by the application of the vertical forces that develop during walking (), the material forming part of the central area of the sole comes into contact with the edge of the sole (,) which stops its expansion and deprives the sole of the floating effect, limiting its elasticity, triggering a non-linear damping phenomenon.

According to the embodiment of the Invention, what is created is:

According to the embodiment of the Invention, the non-linearity of the enhanced elasticity factor depends on the width of the perimeter crack, however—as disclosed in paragraphs 0050, 0051 and 0052—the progression of the thrust forces generated by walking and the areas subjected to such stresses are not constant; for this reason, the perimetral crack of the sole will also be advantageously designed with variable widths depending on its development along the internal perimeter of the sole.

According to a further embodiment of the Invention, and by virtue of further technical characteristics that will be disclosed in the continuation of this Description, it is also possible to provide a layout of the crack with constant width along the entire internal perimeter of the sole. This will also depend on the technical elasticity performances required during the design phase of the Sole, on the materials used and on further construction factors.

Havingas a reference, the following areas of the sole () are identified in the present exposition:

According to the embodiment of the Invention, for each area of the sole the perimetral cracking assumes a variable value depending on the fact that the increased elasticity must be contrasted more or less by the damping factor, depending on the thrusts that arise during walking; an example of variable thickness of the perimeter cracking is provided here: