Sole with improved damping effect

Abstract

The present invention describes a sole having a non-linear damping characteristic and a unique rebound effect, the structural design of which facilitates maximum weight reduction and maximum ease of use.

Description

TECHNICAL FIELD

[0001] The present invention is applicable to semi-finished products used in footwear production and related technology; more precisely, the present invention describes the lower part of the shoe in contact with the ground, i.e. the sole, also known as the outsole. BACKGROUND

[0002] Footwear is a highly diversified leather product in terms of shape, use and style. Today, especially thanks to the use of new materials and new technologies in the production process, there are thousands of styles, which offer the consumer a very wide choice on the market.

[0003] Some common footwear types can be distinguished, however, the boundaries of this distinction are increasingly difficult to define:

[0004] a. One type of footwear is classic footwear made of natural materials, which reproduces past style patterns, which are still almost made today with handcraft techniques, which give the finished product a high value and uniqueness,

[0005] b. Another type of footwear is technical footwear designed specifically for sports activities, including competitive sports. These shoes benefit from the technological innovations brought about by the use of synthetic materials and advanced assembly processes, which focus on obtaining features that are all aimed at improving sports performance and providing adequate protection to the foot. This category includes footwear for running, acceleration, tennis, hiking, up to specific products for sports such as cycling, motorcycling, skiing, climbing, etc.

[0006] c. Another type of footwear is footwear that combines some of the features of the previous one, i.e. technical performance, with improved comfort, all in line with the requirements of the fashion of the moment. These footwear have a casual, young appearance, with distinctive features given by a refined and unique appearance, but in some designs also do not give up the re-elaboration of the classic styles of the first category mentioned above.

[0007] Therefore, the footwear that can be attributed to the third category mentioned above have a design origin that always focuses on technical performance, such as comfort, correct support to the foot when walking, high air permeability and exchange of air inside and outside, use of materials with antibacterial and bactericidal properties, increased flexibility, etc.

[0008] In the footwear of the third category mentioned above, such as shoes for competitive use, the use of cutting-edge material technologies and construction methods optimized for mass production is predominant, and, as already emphasized in point c of paragraph 002, some technical improvements derived from competitive use can be shared to the benefit of the ordinary user.

[0009] Shoes can be divided into some main parts, for example:

[0010] a. an upper 10, which covers and houses the foot in the upper and downward parts, having an opening at the instep 11 which can be opened and closed, allowing it to be worn.

[0011] b. a sole 12, associated with the upper 13, forming the outer edge and support of the foot at the bottom of the shoe. In the lower section of the sole, the sole surface is in contact with the ground through the tread 14, which is a process or layer designed to improve grip and adhesion.

[0012] There are also further reinforcing and decorative elements, such as insoles, for increased comfort; linings associated with the upper (also inside the shoe); decorative piping, etc.

[0013] Obviously, the foot releases varying forces in the direction approximately perpendicular to the ground when walking, therefore all those technical improvements aimed at improving the pleasure or technical performance of walking mainly act on the sole.

[0014] In general, soles thus constructed are mainly the result of injection and molding manufacturing processes of synthetic materials capable of combining unique elastic and rebound factors that cannot be replicated with natural materials such as leather and its derivatives.

[0015] The current state of the art offers a huge difference of substances such as polyurethane (PU), PVC, EVA (ethylene-vinyl acetate), each with unique mechanical characteristics. For example, EVA is a cross-linkable polymer that swells and creates a semi-finished product that is extremely light, flexible, without shape memory when subjected to sufficient temperatures inside the mold. While EVA is not recyclable except as an inert filler added to other materials, thermoplastic polyurethane can be reused by melting and molding, thus having a great advantage.

[0016] These materials are enhanced by appropriate formulation variations of some of their mechanical characteristics, by the geometry of the sole and by the solutions designed inside the sole, enhancing the use of these materials, thus creating a semi-finished product that allows to combine a unique aesthetic appearance and a series of characteristics that highlight its functionality.

[0017] For example, the patent US2022248804A1 of Nike describes a synthetic material sole in which a special cushioning element, called "barrier layer", is inserted and combined in a closed volume also filled with a liquid or gas. This cushioning element is located in the mid / front area of the sole, for managing the pressure coming from the foot. The sole thus constructed undoubtedly has great advantages, but also significant complexities in the construction process.

[0018] Patent WO2016191109A1 describes a sole in which a resilient layer works internally through openings formed in various sizes and scales to vary the elastic effect of this resilient layer. This is an interesting but extremely complex solution, as synthetic soles are usually produced through injection and molding, which forces the process of the invention to be within the technical limits of a layout that allows the sole to be easily removed from the mold.

[0019] Nike’s publication US2022378150A1 describes a sole whose shock-absorbing element is made up of a series of mutually facing recesses and protrusions that, when they come into contact, produce a cushioning effect. This layout includes closed chambers also filled with a liquid; in this case, the layout described is also very effective, but it is complex to implement.

[0020] Reebok’s patent US7966749B2 describes an element that can be inserted into a sole, which is made up of two closed chambers connected by a corrugated channel. Inside the two chambers there is air, which can pass from the first chamber to the second and vice versa, creating a shock-absorbing element. Again, this is a highly effective but extremely complex system.

[0021] Adidas’s patent US9930928B2 describes a sole that includes two spatial areas using two materials, the first being a free-moving foamed material, the second area of more compact material penetrates the first and obstructs it, thus creating a controlled shock-absorbing effect. The solution described is again extremely complex and limits the cost-effectiveness of the invention.

[0022] Newton Running’s publication WO2023122761A1 describes a sole in which there are two mutually facing layers. The two layers are worked with a sinusoidal undulation and are coupled by inserting a thin membrane. When subjected to a compression force, the two layers penetrate each other, the membrane creates a progressive resistance, stores energy and releases it as a rebound force opposite to the compression force to the foot. This solution is powerful, but it has problems of construction complexity and low economic efficiency.

[0023] Mitsunobu’s publication US2020305541A1 describes a sole made up of different layers, i.e. different coupled soles. The first sole has a plurality of protrusions on the side that comes into contact with the foot, the outsole has a plurality of protrusions on the surface that comes into contact with the ground, while the intermediate sole between the two has great rigidity. The combination of protrusions between the different sole layers produces a shock-absorbing effect. However, this solution is complex and produces a floating effect that is not always comfortable when walking, so this solution needs to be improved.

[0024] The patent US6026593 of New Balance describes a shock-absorbing element designed to be inserted into the sole. The shock-absorbing element is composed of a plurality of closed tubular elements. This solution can cause a significant floating effect and presents a certain structural complexity.

[0025] The aim of the present invention is to overcome the problems of the prior art, creating a sole in synthetic material in which:

[0026] a. the sole must be produced through an injection and moulding process, therefore it must not have a layout which prevents it from being removed from the mould mentioned above, or a layout which makes the above operation particularly difficult,

[0027] b. the sole must be composed of a minimum number of superimposed layers, preferably of a single layer, in order to reduce production costs,

[0028] c. the sole must contain a small number of semi-finished products inside it, the purpose of which is also to absorb the shock due to walking,

[0029] d. the sole must also be made of synthetic materials of different origin but in such a way as to maintain its comfort characteristics unaffected,

[0030] e. the sole must have unique shock-absorbing and rebounding characteristics, while avoiding the floating effect, said effect being due to the linear capacity to absorb the forces generated during walking,

[0031] f. the sole must be particularly light in order to be able to assemble a shoe which is comfortable to use. SUMMARY

[0032] The present invention describes a sole with non-linear shock-absorbing characteristics and a unique rebounding effect, the structural design of which is advantageous for maximum weight reduction and maximum ease of use.

[0033] Advantages of the invention

[0034] The present invention has the following advantages:

[0035] a. unlike many other cushioning and rebounding systems integrated in the sole, the present invention - i.e. the sole - allows the creation of non-linear elastic characteristics, which weaken with the push of the foot.

[0036] b. unlike many other cushioning and rebounding systems integrated in the sole, the present invention provides a shock-absorbing function in different degrees of intensity in specific areas of the surface, without the need for excessive technical complexity.

[0037] c. unlike many other cushioning and rebounding systems integrated in the sole, the technical elements which allow the increase of the rebounding effect in the present invention have a small surface area and light weight.

[0038] d.The present invention - i.e. the sole - can be produced without the use of technical elements that increase the rebound effect, without losing its non-linear shock-absorbing characteristics.

[0039] e.When technical elements that increase the rebound effect are placed in the present invention, no additional work is required for their positioning on the sole.

[0040] f.The present invention - i.e. the sole - can be made of a single synthetic material, with different elastic and rebound characteristics obtained through processing. BRIEF DESCRIPTION OF DRAWINGS

[0041] The list of enclosed drawings, together with the document of the present application, serves to illustrate the characteristics of the invention and highlights the application variants in the description. More specifically, it comprises:

[0042] Figure 1

[0043] Figure 1 shows a sole, according to the prior art, combined with an upper,

[0044] Figure 1a

[0045] Figure 1a shows a top view and a cross-sectional view of a sole according to the present invention,

[0046] Figure 1b

[0047] Figure 1b shows another embodiment of the central area of a sole according to the present invention, Figure 2

[0048] Figure 2 shows a top view of a sole according to the present invention, in which the peripheral cracks and the transverse cracks can be seen,

[0049] Figure 2a

[0050] Figure 2a shows another embodiment of the peripheral cracks according to the present invention, Figure 3

[0051] Figure 3 shows the movement of the central area of a sole according to the present invention when subjected to the forces generated by walking,

[0052] Figure 4

[0053] Figure 4 shows the non-linear characteristics of the increased elastic factor according to the present invention, Figure 5

[0054] Figure 5 shows a longitudinal cross-sectional view of a sole according to the present invention,

[0055] Figure 6

[0056] Figure 6 A cross-sectional view of a sole according to the present application is shown, in which additional elements are applied to improve the rebound effect,

[0057] Figure 7

[0058] Figure 7 A top view of a sole according to the present application is shown, in which the elements that improve the rebound effect are evident,

[0059] Figure 7a

[0060] Figure 7a A top view of a sole in another embodiment of the inventive concept is shown, in which the elements that improve the rebound effect are evident,

[0061] Figure 8

[0062] Figure 8 A cross-sectional view of a sole according to the present application is shown, in which the crack is partially filled with an elastic polymer according to the inventive concept,

[0063] Figure 9

[0064] Figure 9 A side cross-sectional view of a sole according to the present application is shown in the walking phase, Figure 10

[0065] Figure 10 A top view of a sole according to the present application is shown with an inserted elastic cushioning element,

[0066] Figure 11

[0067] Figure 11 A detail of the height of the elastic cushioning element is shown. DETAILED DESCRIPTION

[0068] The description of the various methods of implementation of the present application is only for illustrative purposes, therefore, all the obvious modifications made by a person skilled in the art within the field of application of the present application will not limit the terms used to protect the patent itself.

[0069] The devices described in the present application relate to other solutions already present in the state of the art, which are used to correctly implement the present application in the selected technical field.

[0070] In this text, unless specifically indicated, the reference to a single technical element can also refer to a plurality of identical elements within the scope of the present application.

[0071] In this text, the term "sole" refers to the improved sole.

[0072] According to an embodiment of the present application, a shoe sole made of synthetic material is designed, which is made by means of the known injection molding process by means of a mold. The sole can also be manufactured by means of a mold casting technique, if deemed feasible and in compliance with other factors, even non-technical ones.

[0073] According to an embodiment of the present application, the synthetic material that constitutes the sole can be selected from the materials known in the state of the art, such as EVA (Ethylene Vinyl Acetate), Polyurethane (PU), TR, etc.: the choice will depend on the desired damping effect, which will be adjusted by the special shape of the sole described herein.

[0074] According to an embodiment of the present application, the particular process that provides the improved damping effect and the improved "rebound" effect (i.e. the rebound effect) of the sole is applicable to any sole produced by injection / molding or casting / molding; therefore, in the attached figures, the aesthetics of the sole shown can be easily modified according to production needs.

[0075] According to an embodiment of the present application, the structure of the sole in the central area 10a is different from the structure in the peripheral area 11a. Figure 1a In the attached figures, the cross-section Z-Z' profile of the sole is shown, which is equipped with a tread 15a that, along a vertical axis, rises perimetrically to its upper outer edge 12a together with the wall 14a, then it descends 13a until it encounters the central area 10a. The central area of the sole is the area that is most subject to the downward thrust of the foot and is also the one that participates in the damping function during walking.

[0076] According to an embodiment of the present application, the central area of the sole has intrinsic elastic properties, which come from the material with which the sole is made, as described in paragraph 0044. However, in the state of the art, the use of elastic materials to make shoe soles can generate, during walking, an undesirable phenomenon, the floating effect, which makes the positioning of the foot on the ground feel not exact.

[0077] While this floating effect can be sought to improve the comfort of the shoe, i.e. the ability to absorb the vibrations during walking, it makes it impossible to consider the ground as a stable reference to operate the foot on it with the thrusts and movements required for walking, running or sports.

[0078] Therefore, the floating effect can cause orientation disorders, balance instability; in general, this happens in all those shoes in which the sole has a high damping effect.

[0079] It is known in the prior art that the forces acting on the sole from the foot during walking are differently distributed on different areas of the same sole: in particular, the heel 18a and the tip 17a are pressure areas of support and thrust forces which allow walking in a rapid alternation.

[0080] Furthermore, in the support of the heel, the area subjected to thrust towards the ground is smaller than that generated when the foot is parallel to the ground, so the deformation to which the sole is subjected is significantly higher. The same applies to the thrust generated towards the top part of the sole during the forefoot walk.

[0081] As these movements generate great forces and thrusts on small areas of the sole, i.e. on the area of the tip 17a of the foot and on the rear area of the heel 18a, the final result is that it is easier to generate the floating effect.

[0082] In order to inhibit and control the floating effect, according to an embodiment of the present application, a continuous peripheral slit 16a is suitably designed on the inner perimeter of the sole, which has the function of separating the central area 10a thus formed from the peripheral areas 12a, 13a, 14a, i.e. the areas consisting of the elevation of the tread along the vertical axis, its edges and the descending profile, which remain joined to each other thanks to the lower part of the sole, i.e. the lower part of the tread 15a.

[0083] According to a further embodiment of the present application, the central area 10b of the sole can be conveniently added to the tread area 11b in a subsequent processing phase, as shown in Figure 1b while respecting the construction criteria declared in paragraph 0051 of the present application, i.e. the central area of the sole is separated from the peripheral areas 12b, 13b, 14b by a peripheral slit.

[0084] According to an embodiment of the present application, the generation of the central area of the sole is not in contact with the edges of the sole, which amplifies the softness and elasticity effect during walking, since the yielding of this area of the sole is enhanced by its own deformation, which develops freely along the empty space formed by the peripheral slit.

[0085] According to an embodiment of the present application, the elastic properties are defined as "enhanced" and do not have linear characteristics, since once the peripheral slit area 30 is filled by the application of the vertical forces 33 generated during walking, the material constituting the central area of the sole comes into contact with the edges 31, 32 of the sole, thus preventing the sole from further expanding and eliminating the floating effect of the sole, limiting the elasticity of the sole, triggering a non-linear damping phenomenon.

[0086] According to an embodiment of the present application, it is generated:

[0087] a. first of all, the enhanced elastic properties generated by the central area of the sole during walking, which freely expands laterally in the peripheral slit.

[0088] b. secondly, the interruption of the damping effect, which interrupts the linear progression 40 of the damping effect, i.e. the non-linear damping effect.

[0089] According to an embodiment of the present application, the non-linearity of the enhancement of the elastic factor depends on the width of the peripheral slit, however, as mentioned in paragraphs 0050, 0051 and 0052, the progression of the thrust generated by walking and the areas subjected to this stress are not constant; therefore, the peripheral slit of the sole will also be advantageously designed with different widths depending on its extension along the internal perimeter of the sole.

[0090] According to a further embodiment of the present application, and thanks to the other technical features that will be disclosed in the subsequent part of the present description, it is also possible to provide a slit layout with a constant width along the entire internal perimeter of the sole. This will also depend on the technical elastic properties required during the design phase of the sole, the materials used and other construction factors.

[0091] With Figure 2 reference, the following areas of the sole 20 are identified in the present description:

[0092] a. top end area 21, from the front vertex of the sole to the section line A-A’.

[0093] b. forefoot area, from the section line A-A’ of the sole to the section line B-B’.

[0094] c. fore-intermediate area 22, from the section line B-B’ to the section line C-C’.

[0095] d. central area 23, from the section line C-C’ to the section line D-D’.

[0096] e. rear-intermediate area 24, from the section line D-D’ to the section line E-E’.

[0097] f. rear area 25, also called heel area, from the section line E-E’ to the rear vertex of the sole.

[0098] According to an embodiment of the present application, for each area of the sole, the peripheral slit presents variable values, depending on the fact that, according to the thrust generated at the time of walking, the enhancement of the elasticity must be more or less inhibited by the damping factor; here an example of variation of the thickness of the peripheral slit is provided:

[0099] a. the top end area, which is subjected to great stresses and must provide an excellent sensation of support and precision of the foot push, for which the damping element of the enhancement of the elasticity is quickly activated by the peripheral slit limited in width 201a to 3 mm to limit the floating effect.

[0100] b. The forefoot region of the sole is designed to have a higher enhanced elastic factor than the top region, so that the width 26 of the peripheral slit increases from 3 mm to 4 mm along the portion of the area delimited by the section lines A-A' / B-B'.

[0101] c. The forefoot region of the forefoot region is designed to have a higher enhanced elastic factor than the forefoot region, so that the width 27 of the peripheral slit increases from 4 mm to 5 mm along the portion of the area delimited by the section lines B-B' / C-C'.

[0102] d. The central region is designed to have a higher enhanced elastic factor than the forefoot region of the forefoot region, so that the width 270 of the peripheral slit increases from 5 mm to 6 mm along the portion of the area delimited by the section lines C-C' / D-D'.

[0103] e. The rear intermediate region is designed to have a lower enhanced elastic factor than the central region of the sole, so that the width 271 of the peripheral slit decreases from 6 mm to 3 mm along the portion of the area delimited by the section lines D-D' / E-E'.

[0104] f. The heel region must provide good support, so the enhanced elastic damping element is quickly active by limiting the peripheral slit to a width 272 of 3 mm (similar to the top region) in order to limit the floating effect.

[0105] According to an embodiment of the present application, thanks to the peripheral slit with variable thickness, a damping factor of the enhanced elastic element is generated, i.e. a factor weighted by the force acting on it and by the area involved by the walk, compared to the sole of the prior art. Therefore, the enhanced elastic factor loses its linear characteristic, i.e. the proportional relationship with the force, since it is inhibited by the contact between the edge of the central region 10a of the sole and the peripheral regions 12a, 13a, 14a of the sole.

[0106] According to a further embodiment of the present application, a net variation of the width of the peripheral slit can be implemented, instead of the progressive variation shown in paragraphs 0059 and Figure 2 Details are observed Figure 2a , for example in section B, the variation of the width of the peripheral slit from the previous stage 21c to the next stage 22c is implemented by a sudden increase of the aforementioned stage 20c or by a step, which does not impair any of the advantages of the present application disclosed in the previous paragraphs. Therefore it can be obtained that, within the extent of each individual region of the sections A / A', B / B', C / C', D / D', E / E', the width of the peripheral slit remains constant.

[0107] According to an embodiment of the present application, in order to further vary the elasticity of the material used to produce the sole, the central region 10a of the sole can be further processed by making transverse grooves with different sections and lengths.Figure 2 An example of the number of groove groups that can be made in the central area of the sole is shown, i.e.:

[0108] a. a first group of three slits 28, 29, 20a, extending from the forefoot area to the fore-mid area, with a thickness of 2 mm.

[0109] b. a second group of three slits 21a, 22a, 23a, extending from the fore-mid area to the central area, with a thickness of 4 mm.

[0110] c. a third group of three slits 24a, 25a, 26a, extending from the central area to the rear-mid area, with a thickness of 4 mm, except for the slit 24a, located in the central area of the sole, which has a thickness of 6 mm.

[0111] d. a fourth group of three slits 27a, 28a, 29a, extending from the rear-mid area to the heel area, with a thickness of 2 mm.

[0112] According to an embodiment of the present application, the groove groups allow adapting the various materials used to construct the sole to the various applications of each type of footwear. In fact, by making the grooves described in paragraph 0062, it is possible to increase the degree of enhanced elasticity of the materials used to manufacture the sole, while maintaining the high damping factor generated by the contact of the internal areas of the sole with the respective edges.

[0113] Figure 5 A longitudinal section of a sole is shown, with an example of a group of slits 50 as described in paragraph 0062.

[0114] As described herein, the sole is preferably manufactured by injecting the synthetic material into a mold, more precisely by means of injection molding or even casting. As is known, the production cost of the mold is very high, and therefore the sole manufacturing companies also wish to optimize the production process in terms of economic parameters; obviously, it is more advantageous from an economic point of view to use a single material. Thanks to the peripheral slits of the sole and the transverse group of slits in the central area, the sole according to the concept of the present application can be manufactured using the same material, with different elastic properties and different damping properties. Moreover, with regard to the transverse group of slits in the central area of the sole, it is also possible to adopt a single slit, or even, in some cases, a single slit that forms part of a single group suitably positioned.

[0115] According to another embodiment of the present application, a technique is designed that, when applied to the sole, allows changing the "rebound" properties, i.e. the rebound properties of the elastic elements inherent to the material used to construct the sole, while also changing the overall performance of the sole during use, such as walking, running, jumping, etc.

[0116] The technology developed avoids producing "n" molds for "n" elastic and rebound characteristics, but rather adapts additional characteristics through a limited number of sole models, distinguished by the number of groups of cracks or by the width of the peripheral cracks. Moreover, this technology according to the inventive idea allows reducing the types of synthetic material used for manufacturing the sole, since it is possible to limit or increase the elastic and rebound characteristics of a single material.

[0117] According to what has been described in the text of the present invention, the technical features of the sole that affect the performance it provides during use are:

[0118] a. the material with which the sole is manufactured,

[0119] b. the degree of the peripheral cracks according to the invention,

[0120] c. the number and size of the groups of transversal cracks in the central area of the sole according to the invention.

[0121] According to a further embodiment of the invention, on the basis of the above-mentioned factors, two further factors are added, namely:

[0122] a. the insertion of additional elastic means in the sole,

[0123] b. the partial or total filling of the cracks, including the peripheral cracks and the cracks of the individual groups, with a polymer that hardens when subjected to mechanical stress.

[0124] According to a further embodiment of the invention, an elastic means made of metal (for example tempered steel) or of a synthetic material without shape memory (for example carbon or composite material) is designed, which is inserted in the space formed by the peripheral cracks according to the invention.

[0125] According to a further embodiment of the invention, the elastic means 64 is "C"-shaped, or staple-shaped, as can be seen from Figure 6 the cross section 60 of the sole in the middle, in which the vertex of the 90° folded portion 61 of the elastic means is further twisted by 180° to form a hook 62, thus thickening the top end portion. The size of the elastic means allows it to be inserted in the inner edge of the peripheral cracks in a transversal position, thus overlapping the central portion of the sole 63, thus creating an additional support surface for the foot that will react to the vertical forces generated by walking, with an enhanced rebound effect due to the presence of the elastic means.

[0126] According to a further embodiment of the invention, the number of elastic means that can be inserted in the sole depends on the amount of rebound that is desired to be obtained; in fact, the elastic means are designed without mechanical memory, so that once subjected to the vertical forces from walking, they bend and react with an upward thrust that is added to the thrust of the material with which the sole is manufactured.

[0127] According to a further embodiment of the present application, the hook-shaped portion of the top end area of the 90° folded portion of the elastic means fits tightly in the peripheral split, allowing its stability when in contact with the sole itself during the construction thereof.

[0128] According to a further embodiment of the present application, the elastic means do not affect the non-linear damping factor of the enhanced elasticity of the sole, since they limit the volume of the peripheral split in a negligible manner; however, surprisingly, they increase said property, since the above-mentioned means have a limited bending capacity along the area of the portion bent by 90°, or they make the material in the portion outside the peripheral split of the sole more rigid.

[0129] In Figure 7 In the top view of Figure 1, there is a series of four elastic means 70, 71, 72, 73 inserted in the sole 74, suitably distributed between the top end area and the heel of the sole.

[0130] According to a further embodiment of the present application, the elastic means inserted in the sole to improve the effect of rebound or bounce, can protrude, by means of suitable different shapes, the portion of the horizontal surface of the central area of the sole delimited by the peripheral split, these shapes deriving from the need to increase or reduce the effect of rebound. For example, asymmetric shapes 70a, 71a can be created to vary the performance through the internal area 73a or the external area 74a of the sole, or to vary its shape 72a by creating support areas with uneven surfaces that will interact with the rebound function.

[0131] According to a further embodiment of the present application, both the peripheral split of the sole and the split group of the central area provide a well-defined internal volume, which can be filled in whole or in part with an expanded elastic polymer or with a material that tends to be fluid, and in which the speed of the force applied immediately makes the structure rigid, thus passing from a fluid state to a solid / semi-solid state.

[0132] These substances, known in the state of the art, if subjected to a gradual force that weakens over time, tend to remain soft and / or fluid, thus not varying the performance of the structure that contains them. However, if they are suddenly subjected to a force in a very short time, they become rigid, providing the properties of protection, obstruction, structure, etc.

[0133] According to a further embodiment of the present application, one or more of the crack areas 80, 81 of the sole, including the peripheral cracks of the sole and the cracks of the group of cracks inside the central area, can be filled with the elastic polymers described above, which react to the high and sudden thrusts during walking or running in a manner proportional to the speed of the walk or run, stiffening the sole structure in the selected areas, or changing the elastic characteristics and the floating effect. However, if the intensity of the thrusts is small and more evenly distributed over time, for example in the case of repeated slow walking, the stiffening effect of the structure of the elastic polymers will be minimal.

[0134] Surprisingly, the presence of the group of transverse cracks can provide the sole with additional technical performance, thanks to the design of devices that can be inserted inside the group of transverse cracks. In fact, all the solutions described so far in this description have focused on the rebound effect and the enhanced elastic characteristics, aspects that concern the forces released vertically with respect to the ground.

[0135] According to a further embodiment of the present application, it is therefore also possible to modulate the tendency of the sole to bend more or less easily in the transverse direction 90, or to make its bending ability dependent on more or less accentuated walking movements, thus making this bending ability programmable.

[0136] According to a further embodiment of the present application, this is possible thanks to the design of an elastic cushioning element 100 without shape memory, which is structured from a sheet of synthetic or metallic material, in the shape of a double ogive with two opposite concave side walls 101, 102, thus creating an internal opening 103. In the presence of a compression force 104 orthogonal to the two opposite side walls, the elastic cushioning element has a compression 105 and therefore the ability to exert an opposite repulsion force 106.

[0137] According to a further embodiment of the present application, the elastic cushioning element is inserted inside one or more of the grooves of the group of transverse grooves, with the side walls of the elastic cushioning element in contact with the side walls 112 of the grooves. The elastic cushioning element is subjected to cyclic compression generated by the walking movements, since the group of transverse grooves will tend to cyclically close and open 91 as a result of the bending of the sole. The forces that will be released onto the elastic cushioning element will therefore more or less oppose them.

[0138] According to a further embodiment of the present application, in addition, when the sole is no longer in cyclic contact with the ground, it is subjected to the modulation of the thrust of the elastic cushioning element, which will facilitate the stretching of the sole along the longitudinal axis.

[0139] According to a further embodiment of the present application, the elastic cushioning element can also be made with a suitable height 110 - "h", or with a height less than the depth 111 - "hi" of the cracks of the group of transverse cracks of the sole, if necessary, to avoid affecting the compression of the above-mentioned areas during walking.

[0140] Therefore, according to the above description and the embodiments of the present application, the technical features that affect the performance of the sole depend on a set of integrated factors, namely:

[0141] a. The material with which the sole is made.

[0142] b. The peripheral cracks generated according to the present application.

[0143] c. The number and size of the set of transverse cracks in the central area of the sole according to the present application.

[0144] d. The insertion in the sole of one or more elastic means according to the present application.

[0145] e. The filling of the set of transverse cracks and of the peripheral cracks according to the present application with an elastic polymer.

[0146] f. The insertion of one or more elastic cushioning elements within the set of transverse cracks.

[0147] Inventive Example

[0148] None.

[0149] Industrial Applicability of the Invention

[0150] The present application is applicable to any type of footwear, even styles not designed for specific and highly specialized sports activities, to make synthetic soles with improved comfort characteristics.

[0151] References in the Invention

[0152] The list of references is as follows: None.

[0153] Patent Literature PTL1: US2022248804A1 PTL2: WO2016191109A1 PTL3: US7966749B2 PLT4: US9930928B2 PTL5: WO2023122761A1 PTL6: US2020305541A1 PTL7: US6026593 Non-Patent Literature NPL1: None.

Claims

1. Sole for footwear made of synthetic material using an injection / moulding or cast moulding process, characterised in that, The tread (15a) in contact with the ground rises in the vertical direction with the wall (14a) on the periphery to the upper outer edge (12a) and the central area (10a), said sole being composed of a tip area (21), a forefoot area (200a), a fore-intermediate area (22), a central area (23), a rear-intermediate area (24) and a heel area (25), wherein: a. the central area of the sole is delimited by a peripheral slit (16a) extending along the entire inner periphery of the sole, said peripheral slit separating said central area (10a) from said upper outer edge (12a) and said wall (14a), said central area being connected to said sole through said tread area, said central area also being added to the sole (10b) inside said tread area (11b), b. said peripheral slit has a variable thickness around said entire inner periphery of said sole, c. in said central area of said sole, one or more groups of transversal slits are arranged between said tip area (200a) and said heel area (25), said transversal slits differing in thickness and length, said groups can also consist of a single slit.

2. Sole according to claim 1, wherein said peripheral slit has a variable width along said entire inner periphery of said sole, characterized in that: a. a tip area arranged with a width (201a) of the peripheral slit of 3 mm, b. a forefoot area delimited by the section lines A-A’ / B-B’ with a width (26) of the peripheral slit increasing from 3 mm to 4 mm, c. a fore-intermediate area delimited by the section lines B-B’ / C-C’ with a width (27) of the peripheral slit increasing from 4 mm to 5 mm, d. a central area delimited by the section lines C-C’ / D-D’ with a width (270) of the peripheral slit increasing from 5 mm to 6 mm, e. a rear-intermediate area delimited by the section lines D-D’ / E-E’ with a width (271) of the peripheral slit decreasing from 6 mm to 3 mm, f. a heel area arranged with a width (272) of the peripheral slit of 3 mm.

3. Sole according to claim 1, wherein in said central area of said sole four groups of transversal slits are arranged, characterized by the following dimensions: a. a first group of three slits (28, 29, 20a) extending from said forefoot area (220a) to said fore-intermediate area (22), said slits being characterized by a thickness of 2 mm, b. a second group of three slits (21a, 22a, 23a) extending from said fore-intermediate area to said central area, characterized by a thickness of 4 mm, c. a third group of three slits (24a, 25a, 26a) extending from said central area to said rear-intermediate area, characterized by a thickness of 4 mm, except for the slit located in said central area of said sole, which has a thickness of 6 mm, d. a fourth group of three slits (27a, 28a, 29a) extending from said rear-intermediate area to said heel area, characterized by a thickness of 2 mm.

4. Sole according to claim 1, wherein the elastic factor loses its linear and progressive characteristics when subjected to a force along the vertical axis (33) such that the central area expands until it comes into contact with the upper outer edge (12a) and the wall (14a) of the sole.

5. Sole according to claim 1, wherein one or more elastic devices for increasing the rebound effect are arranged on the central area (10a); said elastic devices comprise: a. metallic materials and / or synthetic materials without shape memory, b. a "C" profile (64) in which the vertex of the 90° folded portion (61) is further twisted 180° to form a hook (62) such that the top end section is thickened, c. the shape of the horizontal section of the elastic device, which lies on the horizontal surface of the central area of the sole, can also be of the asymmetric type (70a, 71a).

6. Sole according to claim 5, wherein the vertex of the 90° folded portion of the elastic device is inserted into the peripheral slit of the sole with the transverse orientation with respect to the sole (63).

7. Sole according to claims 1 and 5, wherein the peripheral slit is partially or totally filled with expanded elastomeric polymer.

8. Sole according to claims 1 and 5, wherein one or more slits of the group of transverse slits are partially or totally filled with expanded elastomeric polymer.

9. Sole according to claims 1 and 5, wherein the peripheral slit and the slits of the group of transverse slits are partially or totally filled with expanded elastomeric polymer.

10. Sole according to claim 1, wherein the variation in the width of the peripheral slit occurs near the mutual intersection of the cross-sectional areas A / A', B / B', C / C', D / D', E / E' and remains constant within the extent of each cross-sectional area.

11. Sole according to claim 1, wherein the peripheral slit has a constant width along the entire inner perimeter of the sole.

12. Sole according to claim 1, one or more elastic cushioning elements (100) are inserted into one or more transverse slits belonging to the group of transverse slits, said elastic cushioning elements are made of a sheet of synthetic or metallic material, without shape memory, in the shape of a double pointed roof with two opposite concave side walls (101, 102) forming an internal opening (103), said elastic cushioning elements are further characterized by a height "h" (110) which is less than the depth "hi" (111) of the transverse slit belonging to the group of transverse slits.

13. Sole according to claim 1, wherein the elastic cushioning elements are inserted into the transverse slits with their side walls in contact with the side walls (112) of the transverse slits.

14. Sole according to claims 1 and 5, wherein the elastic effect, the rebound effect and the overall dynamic performance are determined by: a. the material from which the sole is made, b. the peripheral slit, c. the number of the group of transverse slits, d. the insertion of one or more elastic devices in the sole. e. filling of said peripheral cracks and said set of transversal cracks with an elastic polymer, f. insertion of one or more elastic cushioning elements within said set of transversal cracks.

15. A shoe manufactured with the sole of claim 1.

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