WO2008040541A1

WO2008040541A1 - An insole for footwear with a reinforced structure

Info

Publication number: WO2008040541A1
Application number: PCT/EP2007/008613
Authority: WO
Inventors: Leo Sartor; Mario Callegari
Original assignee: Novation S.P.A.
Priority date: 2006-10-06
Filing date: 2007-10-04
Publication date: 2008-04-10
Also published as: ITPD20060372A1

Abstract

An insole (1) for footwear with a reinforced structure comprises at least one filler layer (10) of soft material to which at least one reinforcing layer (11) is joined. These layers are positioned at least in a rear portion (2) of the insole and extend between opposing peripheral areas (6) adjacent to the edges (7) of the rear insole portion, passing through a median area (8) of the rear portion. The reinforcing layer comprises corresponding lateral portions (12a, 12b) extending over a first main surface (4) of the filler layer in the peripheral areas and a central portion (13), joined to the lateral portions and extending over a second opposing main surface (5) of the filler layer in the median area (8).

Description

AN INSOLE FOR FOOTWEAR WITH A REINFORCED STRUCTURE

DESCRIPTION Technical field

The present invention relates to an insole for footwear, with a reinforced structure, according to the characteristics disclosed in the preamble of the principal claim. It also relates to a method of producing an insole for footwear. Prior art In the technical field in question, there is a known way of producing insoles from soft material which can provide the insoles with characteristics of comfort and adaptability to the foot, with reinforcing elements of substantially rigid material inserted into the insoles. The most representative example of these reinforcing elements is what is known as a shank, in the form of a thin plate, normally made of metal, inserted into the rear of the insole along its longitudinal axis in order to prevent undesired bending of the insole.

However, the provision of a shank increases the weight of the insole and requires additional manufacturing operations, and is also relatively ineffective in the prevention of any twisting of the insole along its longitudinal axis. In insoles intended for use in sports footwear, there is also a known way of inserting, or externally applying, additional reinforcing plates shaped to provide adequate support for the foot arch. An insole of the type described above can be used as an insole on to which an upper is fitted, by bonding or stitching, and therefore the insole is preferably chemically compatible with the adhesives normally used or suitable for stitching operations.

Examples of soft material typically used in the production of the aforementioned insoles are thermoplastic polymers based on polyethylene or its copolymers, such as EVA (ethylene vinyl acetate), which may or may not be expanded.

In the more specific field of safety footwear, there is a known way of using insoles with puncture-proof properties, having a multi-layer structure and comprising a plurality of superimposed layers of different materials. In particular, there is a known way of producing insoles having one or more layers of a soft material, alternating with one or more layers of relatively rigid material which can also provide the insole with the necessary properties of resistance to puncture by sharp objects. An example of a rigid material used for this purpose is a metal sheet. However, sheets of this type make it difficult to establish a correct relationship between the flexibility characteristics of the front portion of the insole and the rigidity characteristics of the rear portion. Description of the invention

The problem tackled by the present invention is that of providing an insole for footwear with a reinforced structure, which is structurally and functionally designed to overcome the limitations described above with reference to the cited prior art.

Within the ambit of this problem, one object of the invention is to provide an insole structured in such a way that its rear part has not only a high degree of comfort, but also excellent mechanical properties to correctly support the foot and ensure good durability. In particular, it is desirable that this new insole should resist twisting along its longitudinal axis and should show a different bending resistance between the rear part (which is substantially rigid) and the front part (which is flexible, so as not to impede the movement of the foot during walking). Another object of the invention is to provide an insole whose overall weight and production costs are better than, or at least comparable with, those of conventionally produced insoles.

Another object of the invention which is no less important is that of providing an insole suitable for use as an insole on to which an upper can be fitted.

This problem is resolved and these objects are achieved by the present invention with an insole made in accordance with the following claims. Brief description of the drawings The characteristics and advantages of the invention will be made clearer by the following detailed description of a preferred example of embodiment thereof, illustrated, for the purposes of guidance and without restrictive intent, with reference to the attached drawings, in which :

- Figure 1 is a schematic view in perspective from above of an insole for footwear made according to the present invention; - Figure 2 is a perspective view from below of the insole of Figure 1;

- Figure 3 is a view on an enlarged scale of a cross section of the insole of Figure 1, taken along the line III-III;

- Figure 4 is an exploded view of the insole of Figure 1 in one step of its production; - Figure 5 is a perspective view from above of a variant embodiment of the insole of Figure 1. Preferred embodiment of the invention

With initial reference to Figures 1 to 4, the number 1 indicates the whole of an insole for footwear with a reinforced structure, made according to the present invention.

The insole 1 has a conventional profile in plan view, enabling it to be inserted into footwear of a conventional type, and thus it has a rear portion 2 and a front portion 3 which are easily identifiable and which are positioned sequentially along a longitudinal axis X which is generally curved. First and second opposite main surfaces 4 and 5 are also formed on the insole 1. Peripheral areas 6, immediately adjacent to an edge 7 of the insole 1, and a median area 8, spaced apart from the edge 7, are also formed on both the main surfaces 4 and 5. The insole 1 conveniently has a multi-layer structure with a substantially constant thickness, comprising a filler layer 10, made from soft material, to which a reinforcing layer 11, made from a relatively rigid material, is joined in the way detailed below.

In the present context, the terms "soft" and "rigid" are correctly interpreted in relation to their capacity to undergo deformation, thus adapting to the shape of a person's foot bearing on the insole, and/or to bend as a result of the normal walking movement.

Preferably, the filler layer 10 is made from polyethylene-based polymer or its copolymers, such as EVA, or is made from compressed felt. On the other hand, the reinforcing layer 11 is preferably made from composite material based on fibre-reinforced polymer. More preferably, the reinforcing layer 11 is made from continuous glass fibre impregnated with epoxy resin. This composite material is also of the high fibre content type, with a proportion of 50% to 70% by weight.

The reinforcing layer 11 preferably has a constant thickness and can be formed by a single layer or can be formed by a plurality of superimposed sub-layers.

To assist its joining to the reinforcing layer 11, the filler layer 10 is preferably covered with a thin layer of non-woven fabric (not shown in the drawings). The reinforcing layer 11 extends over the rear portion 2 of the insole 1 so as to cover the entire extension of the latter, but, according to a first aspect of the present invention, it has a pair of lateral portions, indicated by 12a and 12b, appearing on one side of the filler layer 10 in the peripheral areas 6 of the first main surface 4, together with a central portion 13 appearing on the opposite side of the filler layer 10, in the median area 8 of the second main surface 5.

In greater detail, the lateral portions 12a and 12b are joined to the central portion 13 by respective connecting portions 14a and 14b which extend through the filler layer 10 and which are substantially perpendicular to the plane defined by the main surfaces 4 and 5.

Since the reinforcing layer 11 preferably extends over the whole rear portion 2, the lateral portions 12a and 12b and the connecting portions 14a and 14b are also joined together at the longitudinal end of the rear portion 2, by means of corresponding connecting portions, of which only one, numbered 12c, is shown in the drawings. Thus the filler layer 10 is positioned in the peripheral areas 6 on one side of the reinforcing layer 11, while it is positioned in the median area 8 on the opposite side. However, it should be noted that the overall thickness of the insole 1 remains uniform throughout, having no substantial discontinuity. The particular configuration of the reinforcing layer 11 described above, which is shown in more detail in Figure 3, enables the rear portion 2 of the insole 1 to have greater resistance to bending and increased resistance to twisting about the longitudinal axis X. These advantageous features are also determined by the ratio between the corresponding transverse dimensions (with respect to the longitudinal axis X) of the lateral portions 12a and 12b and of the central portion 13 of the reinforcing layer 11. It has been found that the best results are obtained when the central portion 13 extends symmetrically along the axis X and its transverse dimension (indicated by A in Figure 3) is in the range from 30% to 60% of the overall transverse dimension of the insole 1 (indicated by B in Figure 3). This means that each of the peripheral areas 6 extends transversely for approximately 5 - 15 mm.

Tests conducted by the applicant have demonstrated that the aforesaid configuration makes it possible to obtain the same levels of bending and twisting resistance in a similar insole in which the reinforcing layer is practically twice as thick, but in which this layer is simply superimposed on and coplanar with the filler layer.

In view of the high cost of composite material, this saving in terms of materials will clearly have a favourable effect on the overall cost of the insole. A further benefit provided by the insole 1 is that the reinforcing layer 11 is not present in the peripheral areas 6 of the second main surface 5, but the filler layer 10 is present. This enables the insole 1 to be used as a conventional insole on to which the upper can be fitted, in which the upper can be easily bonded to the peripheral areas 6 of the second main surface 5.

In the preferred embodiment of the invention described herein, the reinforcing layer 11 is not limited to the rear portion 2, but also extends to the front portion 3, in the same way as that described with respect to the rear portion 2. Thus the lateral portions 12a and 12b of the reinforcing layer 11 appear on the first main surface 4 in the peripheral areas 6, while the central portion 13 appears on the second main surface 5 in the median area 8. In this case also, the lateral portions and the central portion are joined together by corresponding connecting portions extending through the thickness of the insole 1.

The difference from the configuration provided for the rear portion 2 lies in the fact that, in the front portion 3, the reinforcing layer 11 has parts with differential flexibility, in order not to impede the natural walking movement. This property is also advantageously determined by the configuration of the lateral portions 12a and 12b and of the central portion 13. As shown clearly in Figure 1, the lateral portions 12a and 12b do not run parallel to the edge 7 as in the fear portion 2, but have a generally curved shape, with a first and a second pair of indentations, indicated by 15a, 15b and 16a, 16b respectively, extending from the peripheral areas 6 towards the median area 8. Thus a high degree of flexibility of the insole 1 is obtained in the direction indicated by each pair of indentations 15a, b and 16a, b. It should be noted that this makes it possible to predetermine the areas of the insole around which the front portion 3 bends. In a variant embodiment of the insole according to the invention, shown in Figure 5, where identical details are indicated by the same reference numerals, the configuration of the reinforcing layer 11 is of a different type. In this case, the filler layer 10 appearing on the first main surface 4 (which is symmetrical with respect to the appearance of the reinforcing layer 11 on the second main surface 5) is in the shape of a fork, with two branches 17a and 17b extending in a diverging way from the rear portion 2, with an island 18 emerging between them.

This configuration is particularly useful in cases in which the insole 1 is intended for footwear in which the walking movement is not required (such as sports footwear for skating) and the main requirement is for rigidity of the insole, even in the front portion 3.

The insole 1 described above is preferably made by the following method, which is also shown schematically in Figure 4.

The first step is to prepare a filler layer 10, covered with a thin layer of non- woven fabric, and already shaped according to the final shape of the insole in plan view. A median area of this filler layer is removed, by punching for example, in such a way that the through hole formed in the filler layer 10 has the desired configuration which the central portion of the reinforcing layer 11 is intended to have. Thus a first intermediate product 20, formed by the peripheral areas 6 and a central through hole 21, and a second intermediate product 22, corresponding to the median area 8, are produced from the filler layer 10. At this point, the reinforcing layer 11 is applied to the first main surface 4 of the intermediate product 20, bearing on the peripheral areas and extending over the hole 21. The reinforcing layer 11 is made from composite material in which the epoxy resin has not yet been cross-linked, and which is therefore still deformable.

The second intermediate product 22 is then replaced in its original location, namely the hole 21, from the side of the first main surface 4. Thus the reinforcing layer 11, interposed between the intermediate products 22 and 20, is deformed in such a way that its central portion enters the hole 21 and appears on the opposite side, on the second main surface 5. Finally, the insole 1 formed in this way is subjected to a hot pressing treatment, to cross-link the epoxy resin and consolidate the whole structure into a single piece.

The production method is rapid and economical, and therefore the production of the whole insole, although using more costly materials, has an overall cost which is entirely comparable with conventional insoles of soft material reinforced with metal shanks. Although the example described above relates to an insole comprising only one filler layer and one reinforcing layer, it is equally preferable for the insole to comprise further layers in addition to these layers. The further layers can be joined in a simple superimposed arrangement, and can be made from the same materials as those used for the layers 10 and 11 or from different materials, without departing from the scope of the present invention.

Thus the present invention resolves the problem of the prior art identified above, while also offering numerous other benefits.

Claims

1. An insole for footwear with a reinforced structure, comprising at least one filler layer (10) of soft material which is joined to at least one reinforcing layer (11), the said layers being positioned at least in a rear portion (2) of the said insole (1) and extending between opposing peripheral areas (6) adjacent to the edges (7) of the said rear insole portion, passing through a median area (8) of the said rear portion, characterized in that the said reinforcing layer comprises corresponding lateral portions (12a, 12b) extending over a first main surface (4) of the said filler layer in the said peripheral areas and a central portion

(13), joined to the said lateral portions and extending over a second opposite main surface (5) of the said filler layer in the said median area.

2. An insole according to Claim 1, in which the said central portion (13) of the said reinforcing layer (11) is joined to the lateral portions ( 12a,

12b) adjacent to it, by corresponding connecting portions (14a, 14b) extending in a direction substantially perpendicular to a plane defined by the said main surfaces (4,5) of the filler layer.

3. An insole according to Claim 1 or 2, in which the said reinforcing layer extends over the whole rear portion of the said insole.

4. An insole according to one or more of the preceding claims, in which the said reinforcing layer has a substantially constant thickness.

5. An insole according to one or more of the preceding claims, in which the said reinforcing layer is formed by a polymer matrix reinforced with fibres.

6. An insole according to Claim 5, in which the said reinforcing layer comprises from 50% to 70% of continuous glass fibre impregnated with epoxy resin.

7. An insole according to one or more of the preceding claims, in which the said central portion (13) of the said reinforcing layer is substantially symmetrical about the longitudinal axis (x) of the said insole and extends transversely over a distance ranging from 30% to 60% of the transverse dimension of the rear portion of the insole.

8. An insole according to one or more of the preceding claims, in which the said filler layer of soft material is provided on one side with the said reinforcing layer in the said lateral areas and on the opposite side with the said reinforcing layer in the said central area, in such a way that the combination of the said filler and reinforcing layers is made to have a thickness without discontinuities.

9. An insole according to one or more of the preceding claims, in which the said filler layer is based on polyethylene or pressed felt.

10. An insole according to one or more of the preceding claims, in which the said filler layer (10) is covered, at least on the side facing the said reinforcing layer, with a layer of non-woven fabric.

11. An insole according to one or more of the preceding claims, in which the said filler layer (10) and the said reinforcing layer (11) also extend into a front portion (3) of the said insole between opposing peripheral areas (6) adjacent to the edges of the said front insole portion, passing through a median area (8) of the said front portion (3), the said reinforcing layer comprising corresponding lateral portions extending over the said first main surface of the filler layer, in the said peripheral areas, and a central portion extending over the said second opposite main surface of the filler layer, in the said median area.

12. An insole according to Claim 11, in which, in the said front portion, the 5 said central portion of the said reinforcing layer is joined to the lateral portions adjacent to it, by corresponding connecting portions extending in a direction substantially perpendicular to a plane defined by the said main surfaces.

13. An insole according to Claim 11 or 12, in which, in the said fronto portion, the said reinforcing layer has parts with differential flexibility.

14. An insole according to Claim 13, in which the said parts with differential flexibility are defined by the configuration of the said central portion (13) and of the said lateral portions (12a, 12b) of the reinforcing layer, in which there is provided at least one pair of correspondings indentations (15a, 15b, 16a, 16b) extending symmetrically from the said peripheral areas (6) towards the said median area (8).

15. An insole according to either or both of Claims 11 and 12, in which, in the said front portion, the said central portion (13) of the said reinforcing layer is shaped in such a way as to appear on the saido second main surface in a forklike shape, with a pair of branches (17a,

17b) extending in a diverging way from the said rear portion.

16. A method for manufacturing an insole for footwear with a reinforced structure, comprising the steps of:

- providing a filler layer of soft material having the final configuration of5 at least one rear portion of the said insole, - removing a median area of the said filler layer, at least in the said rear portion of the said insole, so as to form an intermediate product with a central through hole surrounded by peripheral areas of the said filler layer, - applying to a main surface of the said intermediate product a stratiform reinforcing layer, bearing on the said peripheral areas and extending over the said central through hole,

- repositioning the said median area of filler layer in the said central through hole from the side of the said reinforcing layer, the said reinforcing layer being pressed and deformed in such a way that it has corresponding lateral portions on the said first main surface in the said peripheral areas and a central portion extending over a second opposite main surface of the said insole in the said median area.

17. A method according to Claim 16, in which the said reinforcing layer is formed by a polymer matrix reinforced with fibres and the said polymer matrix is in a non-cross-linked state and a step of cross-linking the said reinforcing layer is provided after the aforesaid final step, to give this layer its final mechanical properties and bind it to the said filler layer.

18. A method according to Claim 17, in which the said cross-linking step is executed by hot pressing the said reinforcing layer and the said filler layer.