The present invention generally relates to a multilayer composite sole with an insulating core (insole).

More particularly, the sole or insole according to the invention allows to obtain an outstanding rigidity of the product, also ensuring an effective thermal insulation.

In preferred embodiments, the sole or insole according to the present invention is configured to make breathable any type of footwear, as said sole reduces the sweat of the foot and allows the exchange of air, temperature and humidity between the inside and the outside of the footwear.

The use of said sole allows to obtain a great comfort for the user and, at the same time, to make more resistant, soft and flexible footwear, with respect to known similar products.

Moreover, said sole can be used with any type of uppers and may include the heel in correspondence of a rear end.

Currently, many footwear are known which use mechanical systems, normally made on the sole, in order to allow a recycle of the air inside the shoe during a normal walking.

Among said systems, a first type of aeration devices to be counted is a device having a series of small holes on the insole and on the outsole of a shoe, on the side of the tread and in correspondence of the foot areas with the highest concentration of sweat glands (excluding the heel).

In this case, a breathable and waterproof membrane is also inserted inside the sole and below a perforated insole.

However, the use of a shoe fitted with an air circulation system of this type tends, during the time, to weaken the sole and real lacerations may be generated on said sole starting from the holes, thus leading to an unavoidable breakage of the waterproof membrane and to the undesired entry of water into the footwear.

The holes which are performed on the tread of the sole also allow the passage of dust and other debris that may be present on the soil, and said dust may also partly or completely block the holes themselves, thus decreasing the air passage through said holes and reducing the breathable capacity of the system.

A second type of known devices, which allow the air recirculation inside of a shoe provides the use of a pump with a double-valve one-way system, which is placed in a recess of the sole placed near the area of the heel. Said pumping system draws the air inside the shoe (which has a perforated insole) and discharges said air outside through an open hole provided in correspondence of one side of the sole.

The use of a shoe equipped with said second type of devices, however, can break the casing of the pumping system, which also has a complex structure with many elements at risk of breakage, such as, for example, the wrapping membrane of the pump, which is of a reduced thickness, the fastening means of the one-way valves connected to the casing and said one-way valves, with an immediate loss of their original functionality.

Moreover, the inlet and outlet holes for the air passage, even if they are arranged laterally on the shoe, are still subjected to be blocked because they are open to the outside of the sole but very close to the ground.

According to a third type of conventional air recirculation devices, use is made of a series of rubber micro-valves, located in the sole, which, with the pressure of the foot, are able to discharge the air contained inside the shoe through a perforated insole.

Even in this case, however, the micro-valves can be blocked, with an immediate loss of their functionality, especially if the footwear is used on dusty grounds, since said valves are placed in direct contact with the ground.

There are also footwear which have a perforated insole and in which the whole area of the sole is hollowed and shaped as an "igloo", so as to increase the comfort.

This system allows, through a pumping function, a partial recycle of the internal air, which, however, cannot be discharged outside.

In any case, in all said systems, the structure of the sole is weakened towards the outside by the presence of holes and/or cavities, thus resulting in a reduction of efficiency of the footwear and in a fast damage of the shoe, with a serious and quick loss of value of said footwear.

Furthermore, the conventional aeration devices are extremely complex and breakable during their operation and in any case do not guarantee a total comfort of the foot, especially if applied to light footwear, such as sandals, flip flops, clogs, etc.

In the light of the above mentioned requirements, therefore, an object of the present invention is to obviate the above-mentioned technical drawbacks and, specifically, to provide a multilayer composite sole (insole) with high comfort level for footwear, which allows to obtain a high thermal insulation, safeguarding, at the same time, the integrity of the sole and of the whole shoe during the time and ensuring a suitable comfort to the foot of the user even for long times.

Another object of the present invention is to provide a multilayer composite sole, which is used for any type of footwear and, in particular, for sports shoes.

Another object of the present invention is to provide a multilayer composite sole which can be manufactured at a low cost with respect to the advantages which are achieved.

A further object of the present invention is to provide a multilayer composite sole, which allows to obtain an extremely comfortable and flexible footwear, especially during the walking phase, while maintaining an extremely rigid and safe structure and ensuring a high thermal insulation.

The above mentioned objects and other features, which will become more clear in the following, are achieved by a multilayer composite sole according to the enclosed claim 1 ; other detailed technical features are also described in the other claims.

Advantageously, the multilayer composite structure of the sole according to the present invention has an insulating core and is formed in one piece by means of a single injection mold and preferably made of synthetic plastic material.

The sole or insole according to the invention is realized by exploiting the superposition of different layers of carbon or other aramid, para-aramid or meta-aramid synthetic materials, or synthetic technical fabrics configured to be thermoformed.

Furthermore, the sole or insole is designed so as to contain in its central part a synthetic material with insulating properties, consisting of a very homogeneous polymeric foam with having a closed-cell, thermoplastic and thermally stable structure.

The use of stacked fabrics which have fibers directed and oriented at different angles allows to obtain a greater stiffness of the product, with respect to the prior art, also ensuring a high thermal insulation.

Further characteristics and advantages of the multilayer composite sole according to the present invention, will be more clear from the following description, which refers to a preferred embodiment of the sole and from the enclosed drawing (fig. 1), which shows a schematic longitudinal section view of said sole or insole, which is the object of the present invention.

With reference to the above mentioned figure, the multilayer sole or insole according to the invention has a central insulating core and is made with the superposition of different layers having different thickness of carbon or other aramid, para-aramid or meta-aramid synthetic materials, or technical synthetic fabrics configured to be thermoformed.

In particular, according to preferred embodiments of the present invention, the sole or insole has in its central part a first layer 10 made of a synthetic material having insulating features, such as the so-called Airex material (which is constituted by a very homogeneous polymeric and non- deformable foam, with a closed cell, thermoplastic and thermally stable structure), having a thickness of approximately 3mm.

According to preferred embodiments, said first layer 10 made of synthetic material has a thickness D1 of about 1 mm in correspondence of the heel T of the shoe and a thickness D2 of about 4 mm in correspondence of the toe P of the shoe.

A second layer 20 made of synthetic material with insulating features, such as the so-called Airex material, and having the same features of the first layer 10 and a reduced surface, so as to fill the lower bas-relief of the insole, may be placed below the first layer 10 of synthetic material.

In preferred embodiments, said second layer 20 of synthetic material has a uniform thickness D3 of about 2 mm on the whole length of the sole.

Two respective carbon layers 30 having a thickness preferably equal to 0.3 mm and with a direction of the fibers having an angle of 90° with respect to the longitudinal direction of the sole are also placed above and below said central layers 10, 20 made of synthetic material; said carbon layers 30 are respectively coupled to additional carbon layers 40 having a thickness preferably equal to 0.3 mm and with a direction of the fibers having an angle of ±45° with respect to the longitudinal direction of the sole.

Additional end upper and lower layers of the sole, indicated with 50 in the enclosed figure 1 , are also preferably made of carbon, with a thickness of 0.3 mm and with a direction of the fibers having an angle of 0° with respect to the longitudinal direction of the sole.

According to preferred embodiments of the invention, said end layers 50 also have a surface view treatment of the so-called "Peel Ply" type.

According to the invention, the carbon layers can also be replaced with layers made of aramid, para-aramid or meta-aramid synthetic materials, or technical synthetic fabrics suitable for being thermoformed.

In practice it has been observed that the invention thus described solves the problems noted in known types of multilayer composite soles and, in particular, of footwear soles.

In particular, the invention provides the use of stacked fabrics, which have fibers oriented at different angles, so as to obtain a greater stiffness of the product, with respect to the solutions, thus achieving, at the same time, a relevant and effective thermal insulation of the structure.

Finally, the invention thus conceived is susceptible to numerous modifications and variants, all falling within the inventive idea of the attached claims; moreover, all the technical details may be replaced with other elements which are technically equivalent.

In particular, the structure can have a different number of layers, also ensuring said characteristics of stiffness and thermal insulation.

Finally, the materials employed, so long as compatible with the specific use, as well as the dimensions, may be any according to requirements and according to the state of the art.

Where the features and techniques mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly said reference signs do not have any limiting effect on the interpretation of each element identified by way of example by said reference signs.