EP4684682A1

EP4684682A1 - Footwear sole

Info

Publication number: EP4684682A1
Application number: EP25190378.7A
Authority: EP
Inventors: Giuseppe SANTONI
Original assignee: Santoni SpA
Current assignee: Santoni SpA
Priority date: 2024-07-23
Filing date: 2025-07-18
Publication date: 2026-01-28

Abstract

Sole (1) molded from low-density ethylene vinyl acetate (EVA) in such a way that said sole (1) has a density of less than 0.4 g/cm<sup>3</sup> and a hardness of less than 40 Shore A, wherein said sole (1) comprises a heel (2), a central part (3) at a plantar arch and a front part (4), and said heel (2) has an external lateral surface (20) and an embossing (9) made in said external lateral surface (20) of the heel; said embossing (9) having protrusions (90) that protrude from said external lateral surface (20) of the heel.

Description

The present invention relates to a footwear sole.
Ethyl vinyl acetate (EVA) soles are widely used in the footwear industry because EVA provides a good compromise between mechanical strength, comfort, and lightness of the sole.
Hereinafter in this description, Shore A indicates the hardness of the sole measured according to ISO 868 using a ball instrument in a minimum time of 15 seconds.
Generally speaking, the EVA soles of the prior art use medium-density EVA. Therefore, these soles have a hardness of approximately 50 Shore A. Such a hardness value of the sole has been studied and selected precisely to achieve a good compromise between mechanical resistance, comfort, and lightness of the sole. Such a type of sole, i.e., a sole with a hardness of approximately 50 Shore A, is described in US2021/076774 . In particular, US2021/076774 describes a sole made of a polymer foam material, such as thermoplastic polyurethane (TPU) foam, Phylon, Phylite, or EVA, with a material hardness of between 40 and 60 Shore A.
More and more often, the footwear market requires lighter, softer, and more comfortable soles.
However, if low-density EVA is used to make a sole in order to make a sole with a density of less than 0.4 g/cm³ and a hardness of less than 40 Shore A, such soles are impaired by several drawbacks.
In fact, very soft soles tend to wrinkle, especially in the heel area, which is the part of the sole with the highest thickness and also the area subject to the greatest stress or load during walking. In fact, when walking, the shoe first comes into contact with the ground with the heel of the sole, whereon the heel of the foot rests. Then, the external arch of the foot rests on an external lateral part of the sole. Therefore, the pressure is greater on the heel of the sole, where the wrinkles are formed.
Such wrinkles are plastic wrinkles, meaning that, once they are formed, they remain permanently, as they are not subject to natural elastic recovery.
Fig. 1 shows a sole (100) made of low-density EVA with a hardness of 30 Shore A. The sole (100) has a heel (102) which is the part of the sole with the highest thickness.
After carrying out compression tests that simulate the weight of an average user during walking, a plurality of wrinkles (G) was formed in the heel area (102).
As shown in Fig. 1, the wrinkles (G) are clearly visible to the naked eye, negatively affecting the aesthetic appearance of the footwear provided with such a type of sole.
The purpose of the present invention is to eliminate the drawbacks of the prior art by providing a footwear sole that is particularly soft, light, and comfortable and at the same time is not subject to wrinkling.
These objectives are achieved in accordance with the invention with the characteristics of the attached independent claims.
Advantageous embodiments of the invention appear from the dependent claims.
Further features of the invention will become clearer from the detailed description below, which refers to a purely exemplary and therefore non-limiting embodiment illustrated in the accompanying drawings, wherein:

Fig. 1 is a perspective view of a sole according to the prior art with wrinkles in the heel;
Fig. 2 is a perspective view of a sole according to the invention;
Fig. 3 is a perspective rear view of the sole of Fig. 2;
Fig. 4 is a perspective front view of the sole of Fig. 2;
Fig. 5 is a bottom view of the sole of Fig. 2; and
and Fig. 6 is a photograph illustrating a heel portion of a sole according to the invention;
Fig. 7 is a front view of an embossed portion of the heel of the sole according to the invention; and
Fig. 8 is a sectional view taken along the horizontal sectional plane VIII-VIII of Fig. 7.

With the aid of Figures 2 to 8, a sole according to the invention, which is comprehensively indicated with reference numeral 1, is described.
The sole (1) is made of low-density EVA by means of molding in a mold for footwear soles wherein the EVA polymer crosslinks.
The sole (1) has a density of less than 0.4 g/cm³, preferably comprised between 0.28 and 0.38 g/cm³, more preferably 0.33 g/cm³, and a hardness lower than 40 Shore A, preferably comprised between 25 and 35 Shore A, more preferably equal to 30 Shore A.
The sole (1) has a heel (2), a central part (3) in correspondence with the arch of the foot, and a front part (4). The heel (2) is the part of the sole with the highest thickness.
The front part (4) of the sole has a thickness (S4).
With reference to Figs. 2 and 5, the central part (3) of the sole has a variable thickness with a minimum thickness (S3) in the areas of the internal plantar arch (31) and of the external plantar arch (32). Such a minimum thickness (S3) gradually increases towards a median area (33) of the central part and towards the front part (4) of the sole, where the thickness of the central part (3) is joined with the thickness (S4) of the front part (4) of the sole.
The heel (2) has a thickness (S2) greater than twice the thickness (S4) of the front part of the sole. In fact, the heel (2) forms a step with respect to the central part (3) of the sole. Generally speaking, the ratio between the thickness (S2) of the heel and the thickness (S4) of the front part of the sole is comprised between 2.5 and 4.
The sole (1) has an upper edge (5) that protrudes upwards, surrounding the perimeter of the sole, so as to define a recessed seat (6) suitable for accommodating a midsole. The upper edge (5) also serves to assemble the upper on the sole.
The heel (2) is provided with lightening apertures (7) open at the top. When seen in a plan view, each lightening aperture (7) has a quadrilateral shape with a strip of material (70) arranged a diagonal of the quadrilateral. The strip of material (70) acts as stiffening rib to prevent an excessive deformation of the heel (2) of the sole in correspondence with the lightening apertures (7).
In the front part (4) of the sole, there may be at least one slotted aperture (8) that extends transversely.
The heel (2) has a U-shaped external lateral surface (20). According to the invention, the external lateral surface (20) of the heel has a knurled surface finish obtained by means of embossing (9). The embossing (9) comprises a plurality of protrusions (90) protruding outwardly from the external lateral surface (20) of the heel.
Advantageously, each protrusion (90) has a pyramid shape with the base of the pyramid on the external lateral surface (20) of the heel. Preferably, each protrusion (90) has a pyramid shape with square or rhomboidal base, so that the embossing (9) forms a diamond-type texture.
With reference to Figs. 7 and 8, each protrusion (90) has a height (H) of 0.5-1 mm and a diagonal (D) of the base of 1-2 mm.
The protrusions (90) are aligned in rows along a diagonal of the base with a pitch (P) of 1-2 mm. The rows of protrusions (90) are alternately staggered.
With reference to Fig. 3, the embossing (9) is made in a median part with respect to the height of the external lateral surface (20) of the heel, i.e., the external lateral surface (20) of the heel has a lower strip (21) without protrusions under the embossing (9) and an upper strip (22) without protrusions above the embossing (9).
The lower strip (21) of the lateral surface of the heel is smooth. The upper strip (22) of the lateral surface of the heel has no protrusions similar to those of the embossing, but has a rough, dotted surface that creates a sand effect.
In view of the above, the embossing (9) of the external lateral surface of the heel is interrupted at a short distance from a lower edge of the heel, leaving a perimeter band consisting of the smooth lower strip (21) without protrusions and with constant height, imitating a typical top lift.
It should be noted that the protrusions (90) are made in such a way not to affect the aesthetic appearance of the sole. Therefore, the protrusions (90) are made in such a way to be virtually imperceptible, so that the entire external lateral surface (20) of the heel (2) appears to be substantially smooth at a first glance.
With reference to Fig. 2, the embossing (9) extends for a height (H9) in the external lateral surface (20) of the heel. The ratio between the height (H9) of the embossing and the thickness (S) of the heel is 0.4-0.8.
The embossing (9) provided on the external lateral surface (20) of the heel prevents wrinkles from forming in the heel. Several tests carried out on the sole (1), simulating the weight of a person during walking, have shown that no wrinkles are generated in the heel (2) thanks to the embossing (9).
The front part (4) of the sole has an external lateral edge (40) in the shape of a "U." Advantageously, the sole (1) may comprise a second embossing (109) made on the external lateral edge (40) of the front part of the sole. The second embossing (109) of the front part of the sole has a structure identical to the embossing (9) of the heel. Therefore, also the second embossing (109) comprises protrusions (90) identical to those of the embossing (9) of the heel.
The second embossing (9) extends only in a front part of the external lateral edge (40) of the front part of the sole.
With reference to Fig. 5, the central part (3) of the sole has a first lateral edge (30a) extending at the external plantar arch (32) and a second lateral edge (30b) extending at the internal plantar arch (31). The first lateral edge (30a) and the second lateral edge (30b) of the central part of the sole do not have any protrusions similar to the protrusions of the embossing, but have a rough, dotted surface that creates a sand effect. In fact, the central part (3) of the sole is the part of the sole subject to the least pressure during walking. Therefore, in such a case, the rough surface of the first and second lateral edge (30a, 30b) of the central part is sufficient to prevent wrinkles in the central part.
Numerous modifications can be made to the present embodiment of the invention, which are within the reach of a person skilled in the art and fall in any case within the scope of the invention as disclosed by the attached claims.

Claims

Sole (1) molded from low-density ethylene vinyl acetate (EVA) in such a way that said sole (1) has a density of less than 0.4 g/cm³ and a hardness of less than 40 Shore A, wherein said sole (1) comprises a heel (2), a central part (3) at a plantar arch and a front part (4), and said heel (2) has an external lateral surface (20) and an embossing (9) made in said external lateral surface (20) of the heel; said embossing (9) having protrusions (90) that protrude from said external lateral surface (20) of the heel.
The sole (1) according to claim 1, wherein the heel (2) is the part of the sole with the highest thickness.
The sole (1) according to claim 1 or 2, wherein each protrusion (90) of the embossing has a pyramid shape with a base of the pyramid on the external lateral surface (20) of the heel.
The sole (1) according to claim 3, wherein each protrusion (90) of the embossing has the shape of a pyramid with square or rhomboidal base.
The sole (1) according to claim 4, wherein each protrusion (90) of the embossing has a height (H) of 0.5-1 mm and a diagonal (D) of the base of 1-2 mm.
The sole (1) according to any of claims 3 to 5, wherein the protrusions (90) of the embossing are aligned in horizontal rows along a diagonal of the base and the rows of protrusions (90) are alternately staggered.
The sole (1) according to claim 6, wherein the protrusions (90) of a row are arranged with a pitch (P) of 1-2 mm.
The sole (1) according to any of claims 3 to 7, wherein the embossing (9) is made in a median part with respect to the height of the external lateral surface (20) of the heel, so that the external lateral surface (20) of the heel has a lower strip (21) without protrusions under the embossing (9), and an upper strip (22) without protrusions above the embossing (9).
The sole (1) according to claim 8, wherein the lower strip (21) and the upper strip (22) of the external lateral surface of the heel do not have any protrusions similar to those of the embossing (9), the lower strip (21) is smooth and the upper strip (22) is rough and dotted.
The sole (1) according to any of the preceding claims, wherein the front part (4) of the sole has an external lateral edge (40) and a second embossing (109) made on the external lateral edge (40) of the front part of the sole; said second embossing (109) having protrusions (90) that protrude from said external lateral edge (40) of the front part of the sole.
The sole (1) according to any of the preceding claims, wherein the central part (3) of the sole has a first lateral edge (30a) extending at an external plantar arch (32) and a second lateral edge (30b) extending at an internal plantar arch (31); wherein the first lateral edge (30a) and the second lateral edge (30b) of the central part of the sole have a rough dotted surface.