Patent Description:
The present invention relates, moreover, to a method for manufacturing such an outsole.

As is known, whenever a person rests a foot on the ground during a walking or running movement, an impact is created on the shoe and more precisely on the outsole itself.

The way in which the footwear is made may influence the ways in which said impact is perceived by the user.

In order to assess the effect of the impacts on the body of the user of the footwear during a walking or running movement, generally accelerometers or inertial sensors are used, these being intended to be applied directly onto the user's body, in particular in the region of the lower limbs.

The behaviour of the outsole subject to impacts may be analysed instead by measuring what proportion of the impact energy is returned by the material of the outsole. This characteristic is commonly defined as being the "resilience" and allows the various materials which can be used to manufacture an outsole to be classified depending on their response to the impacts acting on them.

It is clear that footwear users may have different physical structures and different foot sizes and that, for this reason, the various models of footwear are produced in a certain number of sizes.

However, if it is known that a variation in the size of outsole from <NUM> to <NUM>, measured using the French system, corresponds to an increase in its length of about <NUM> and an increase in its width of about <NUM>, there is only a minimal increase in the thickness of said outsole.

Furthermore, it is also known that there exists a certain correlation between the foot size and the weight of a user (c. in this connection the report "<NPL>).

As a direct consequence, an outsole with a thickness of about <NUM> may not represent the ideal solution in terms of impact response both for a user weighing <NUM> and for a user weighing <NUM>.

The outsole necessarily constitutes a compromise solution and consequently at least one of the two users will not have an outsole which is best suited to his/her needs.

The object of the present invention is therefore to overcome at least partially the drawbacks mentioned above with reference to the prior art. <CIT> discloses an outsole according to the preamble of claim <NUM>.

In particular, a first aim of the present invention is to provide an outsole for footwear which is able to provide a uniform response when subjected to different impact loads.

A further aim of the present invention is to provide an outsole for footwear which has a uniform response to different impact loads irrespective as to the size of the user and/or the use.

Yet another aim of the present invention is to provide an outsole for footwear which is able to provide a uniform response when subjected to different impact loads and which has a simplified structure.

Finally, an aim of the present invention is to provide a method which facilitates the manufacturing of said outsole.

The object and aims indicated above are achieved by an outsole according to that claimed in Claim <NUM> and by a method according to that claimed in Claim <NUM>.

The characteristic features and the further advantages of the invention will emerge from the description hereinbelow of an example of embodiment, provided by way of a non-limiting illustration, with reference to the accompanying drawings in which:.

With reference to the attached figures, an outsole according to the present invention is indicated overall by the reference number <NUM>.

In the continuation of the present description, "front" will be used to identify the part of the outsole, or of its single components, which during use is relatively closer to the toe of the foot, while "rear" will be used to identify the part of the outsole, or of its single components, which during use is relatively closer to the heel.

In a similar manner "top" will be used to identify the part of the outsole, or of its single components, which during use is relatively further from the ground, while "bottom" will be used to identify the part of the outsole, or of its single components, which during use is relatively closer to the ground.

As shown in <FIG>, the outsole <NUM> is intended to be joined to an upper <NUM> in order to form the footwear <NUM>. The upper <NUM> may be made using the usual materials such as leather, imitation leather and/or fabric.

The footwear <NUM>, in turn, may be walking, sports or safety footwear.

In this latter case, preferably, the footwear <NUM> is provided, at the toe, with a rigid protection tip and, in some cases, with an anti-perforation layer arranged in the region of the outsole <NUM>.

The outsole <NUM> extends along a toe-to-heel direction X and comprises a tread <NUM> arranged on the bottom surface of a midsole <NUM>.

The tread <NUM> and the midsole <NUM> are elastic structural elements.

Preferably, they are made using a polyurethane material. By way of example, the tread <NUM> may be made using a compact polyurethane material, i.e. with a density greater than <NUM>/dm<NUM>, while the midsole <NUM> may be made using an expanded polyurethane material, i.e. with a density less than <NUM>/dm<NUM>, preferably less than <NUM> - <NUM>/dm<NUM>.

Alternatively, the tread <NUM> may be made using a thermoplastic polyurethane material, commonly called TPU, or a vulcanized rubber, while the midsole <NUM> may be made of ethylene vinyl acetate (EVA) or using known supercritical expanded compounds based on polyamide, polyethylene or polyolefin.

As shown in <FIG>, the midsole <NUM> has a heel portion <NUM> with at least one through-opening <NUM> which extends transversely with respect to the toe-to-heel direction X. In other words, the through-opening <NUM> crosses from one side to the other the side surfaces of the midsole <NUM>.

The direction along which the through-opening <NUM> extends is indicated by the letter Y in <FIG>.

This through-opening <NUM> does not have a ventilation function. As will become clear from the description below, it has the function, in combination with other technical features of the outsole, of ensuring a uniform response of the outsole to impacts.

Preferably, the heel portion <NUM> of the midsole <NUM> is provided with two through-openings <NUM> as can be seen from <FIG>. However, different embodiments of the outsole <NUM> may have a greater number of through-openings <NUM>. Advantageously, in the case of more than one opening <NUM>, these openings are formed in the heel portion <NUM> of the midsole <NUM> so as to be substantially parallel to each other.

The heel portion <NUM> of the midsole <NUM> is moreover provided with a slit <NUM> which extends along the toe-to-heel direction X and which intercepts each through-opening <NUM>, dividing it up into two parts 8a, 8b (see <FIG>). Preferably, the slit <NUM> is provided in a central part of the heel portion <NUM> (see <FIG> and <FIG>).

The slit <NUM> is open at the front and is delimited by a side wall <NUM> which extends downwards from a base portion <NUM> of the slit <NUM>.

As clearly shown in <FIG>, in accordance with the invention, the tread <NUM> comprises a portion <NUM> which extends inside the slit <NUM> so as to cover solely the side wall <NUM>, leaving the base portion <NUM> exposed.

Advantageously, the portion <NUM> of the tread <NUM> is provided with at least two holes <NUM> (see <FIG>) which are designed to match the holes 20a, 20b defined at the intersection between the two parts 8a,8b, into which each opening <NUM> is divided, and the slit <NUM>.

In this way, although the tread <NUM> extends inside the slit, each opening <NUM> remains a through-opening.

Preferably, the tread <NUM> has a uniform thickness. Said thickness, excluding any reliefs present on the bottom surface, is preferably between <NUM> and <NUM>. Consequently, the portion <NUM> of the tread which extends inside the slit <NUM> has preferably the same thickness as the tread portion provided on the bottom surface of the midsole <NUM>.

As shown in the attached figures, preferably the slit <NUM> has a profile, measured along the toe-to-heel direction X, which is V-shaped, wherein opposite portions of the side wall <NUM> diverge slightly, extending towards the front opening.

Alternatively, according to another embodiment not shown in the attached figures, the slit <NUM> has a profile <NUM>, measured along the toe-to-heel direction X, which is U-shaped, wherein the opposite portions of the side wall <NUM> run substantially parallel to each other towards the front opening.

Preferably, in both embodiments, i.e. V-shaped slit or U-shaped slit, the profile of the slit encloses an area of between <NUM><NUM> and <NUM><NUM>.

In the case of a V-shaped slit, the front opening of the slit has preferably a width of between <NUM> and <NUM>, while the portion opposite the front opening, in other words the portion which defines the base of the V, has a width of between <NUM> and <NUM>.

In the case of a U-shaped slit, the slit has a width, calculated along the direction Y, which is substantially constant and between <NUM> and <NUM>.

With reference to the opening or the through-openings <NUM> formed in the heel portion <NUM> of the midsole <NUM>, they advantageously have a circular form.

In an alternative embodiment, these through-openings <NUM> may have a quadrilateral - preferably square - cross-section.

As mentioned, the slit <NUM> crosses each opening <NUM>, dividing it into two separate parts 8a, 8b.

Each of these parts 8a, 8b has preferably a length, calculated along the direction Y, of between <NUM> and <NUM>, even more preferably between <NUM> and <NUM>. The thickness of these parts, in turn, is preferably between <NUM> and <NUM>, even more preferably between <NUM> and <NUM>.

The combination of the through-openings <NUM>, of the slit <NUM> and of the tread portion <NUM>, which lines the side walls <NUM> of the slit <NUM>, leaving exposed the corresponding base portion <NUM>, influences the behaviour of the outsole <NUM> in response to any impacts acting on it.

In <FIG> the arrow F indicates in schematic form the impact energy applied to the heel portion <NUM> of the midsole <NUM>. This impact energy depends on the weight of the user and the speed with which the outsole hits the ground.

Experimental tests carried out by the applicant of the present application on the outsole according to the invention have shown how the moment an impact energy is applied in the direction indicated by the arrow F, firstly there is a deformation of the material forming the midsole <NUM>, this being followed, if the impact energy increases, by the deformation of the through-openings <NUM>. In order to highlight this deformation, in <FIG> the through-openings <NUM> have been coloured black so as to show how their cross-section has been subjected to a vertical crushing force.

A similar effect may be noted when viewing from below the heel portion of the outsole (see <FIG>).

Above a certain level of impact energy, in fact, the heel portion of the outsole tends to expand outwards. This expansion affects firstly solely the heel portion in the vicinity of the front opening of the slit <NUM>, since it is surrounded by a smaller quantity of material. This deformation is indicated schematically in <FIG> by the arrows T.

Thereafter, when the impact energy increases, there is an expansion of the heel portion also in the region of the narrowest portion of the slit <NUM>. This expansion is indicated schematically in <FIG> by the arrows S.

The lateral expansion of the heel is allowed by the fact that the tread portion <NUM> does not line the base portion <NUM> of the slit. The tread <NUM>, therefore, while being stably fixed to the midsole <NUM>, does not oppose the elastic deformation of the material of the midsole <NUM>.

The deformation of the through-openings <NUM> (see <FIG>) together with the lateral expansion of the heel portion of the outsole (see <FIG>), which is favoured by the configuration of the slit <NUM> and by the specific arrangement of the tread <NUM> inside said slit <NUM>, allow the outsole to store a greater quantity of impact energy compared to the known solutions, so as to be able to return it in such a way as to obtain a more uniform response of the outsole to impacts acting on it.

The behaviour of the outsole described above in qualitative terms was also confirmed by the numerical measurement of the quantity of energy which the outsole according to the invention is able to return following an impact.

In such tests a pendulum device <NUM>, schematically shown in <FIG>, was used.

The pendulum <NUM> consists of an arm <NUM> having a first end rotatably fastened to a support <NUM>. A hammer <NUM> is fixed to the opposite free end. The outsole <NUM> to be tested is fixed to a support <NUM> which extends vertically from the base <NUM> of the pendulum.

The outsole is fixed to the support so as to maintain therefore a vertical position.

The test carried out by means of the pendulum <NUM> consists in raising the arm <NUM> so that it defines with the vertical axis passing through the support <NUM> a first angle "a".

Then the arm <NUM> is left free so that the hammer <NUM> is able to strike the outsole (the impact in <FIG> is indicated schematically by means of the broken line I) and to rebound into a new position - indicated by means of broken lines in <FIG> - which is measured by means of a second angle "b".

On a theoretical level, if all the impact energy were to be returned by the outsole, the second angle "b" would be equal to the first angle "a".

In reality, the second angle "b" is always less than the first angle "a". By determining the ratio between the first angle "a" and the second angle "b" and multiplying the result by <NUM> it is possible to determine the percentage of energy which is returned by the outsole.

The impact energy applied to the outsole to be tested depends on the weight of the hammer <NUM> and the first angle "a", i.e. the starting angle. By varying these parameters it is possible to set different values for the impact energy, so as to simulate various users and different modes of use (walking or running).

In particular, during the tests carried out with the pendulum <NUM>, the impact energy applied to the outsole was varied between 2J and 12J with intervals of <NUM>.

The results obtained are shown in the graph of <FIG> where the x axis shows the impact energy value measured in joules applied to the outsole and the y axis shows the percentage of energy returned by the outsole.

In particular, the continuous line N relates to the tests carried out on the outsole according to the invention, while the broken line O relates to the same tests, but carried out on a polyurethane outsole without the through-holes <NUM>, the slit <NUM> and the tread arrangement on the side wall of the slit.

From the graph it can be seen how in both cases the quantity of energy returned by the outsole diminishes with an increase in the impact energy. However, whereas in an outsole of the conventional type there is reduction in the amount of energy absorbed equal to about <NUM>% over the range 2J to 12J, in an outsole according to the invention, said reduction is equal to about half said amount.

For easier understanding, in the graph of <FIG>, the reduction in return of the impact energy received is schematically indicated by the arrow K, in the case of a conventional outsole, and by the arrow L, in the case of the outsole according to the invention.

The tests carried out show how the outsole according to the invention is able to provide a more uniform response to different energy impacts, for example generated by users with a different body structure and/or by a different use of the footwear.

In other words, different users will perceive the same response of the outsole to impacts of varying intensity, unlike that which occurs with conventional outsoles.

As already mentioned, the present invention also relates to a method for manufacturing the outsole <NUM> described above.

Said method comprises the following steps:.

The method according to the invention is characterized in that it comprises a step f) of providing an insert <NUM> of elastomer material intended to be placed between the base <NUM> and the first lid <NUM> during moulding of the tread <NUM> inside the first mould cavity <NUM> in order to form a seal which prevents the moulding material from flowing into the base portion <NUM> of the slit <NUM>.

Said insert <NUM> is intended to be compressed when the base <NUM> and first lid <NUM> are put in close proximity to each other. Advantageously, the insert <NUM> prevents the material of the tread from covering the base portion <NUM> of the slit <NUM> and prevents moulding burrs from forming in this base portion <NUM>. Said moulding burrs, in fact, would be difficult to remove.

Advantageously, said insert <NUM> is fixed to the bottom surface of the first lid <NUM> so as to face the top of a projection <NUM> of the base <NUM> intended to form the slit <NUM>.

Preferably, the insert <NUM> is made using an elastomer material which belongs to the family of silicones.

The moulding of the tread and the midsole is carried out preferably by means of an injection moulding process. For example, by means of the injection of polyurethane or EVA-based mixtures.

Alternatively, the tread may be made by means of compression-moulding of vulcanized rubber.

In order to prevent air bubbles from remaining trapped inside the tread <NUM>, the base <NUM> and first lid <NUM> are designed to leave, once they have been put in close proximity to each other, a perimetral slit <NUM> which extends outside the first mould cavity <NUM>.

The so-called moulding burr 4a will form in the region of this slit <NUM>, once the tread <NUM> has been moulded.

Similarly, the base <NUM> and second lid <NUM> are designed to leave, once put in close proximity to each other, a perimetral slit which extends outside the second mould cavity <NUM>.

In the region of this slit, once moulding of the midsole <NUM> has been carried out, a further moulding burr 6a will form, said burr being intended to be superimposed on the previously formed moulding burr 4a.

Both moulding burrs 4a, 6a will be removed at the end of the moulding operations.

Advantageously, the first lid <NUM> may also be provided with seats <NUM> designed to receive the movable pistons <NUM>. These pistons <NUM> are movable inside said seats <NUM> so as to move between a first configuration, where they are outside the seats <NUM>, and a second configuration, where they are inserted inside the seats <NUM> so as to abut against the sides of the projection <NUM>.

The tread moulding step c) is advantageously carried out with the movable pistons <NUM> in the second configuration, i.e. inserted inside the seats <NUM>.

The pistons <NUM> have the function of forming the holes <NUM> in the portion <NUM> of the tread <NUM>. Said holes <NUM> match the holes <NUM> defined by the openings <NUM> in the region of the slit <NUM>.

Advantageously, inserts <NUM> made of elastomer material, preferably silicone material, are provided along the sides of the projection <NUM> aligned with the pistons <NUM>.

During the tread moulding step c), the movable pistons <NUM> in the second configuration are brought into abutment against these inserts <NUM>.

In this way it is ensured that moulding burrs, which are also difficult to remove, do not form in the region of the holes <NUM>.

Advantageously, the second lid <NUM>, as shown in <FIG>, may comprise a pair of half-rings <NUM>, divided along a longitudinal plane and intended to abut against the sides of a closing element <NUM>, the bottom surface of which is shaped according to the inner profile of the outsole. The seats <NUM> housing the movable pistons <NUM> inside the second lid <NUM> are preferably formed in the half-rings <NUM>.

In this embodiment,. the step c) of moulding the tread and the step e) of moulding the midsole are carried out by means of an injection moulding process.

Preferably, the closing element <NUM> may consist of an aluminium last onto which the upper <NUM> of the footwear <NUM> may be advantageously fitted.

In this way, the moulding of the midsole, and consequently of the outsole <NUM>, may be carried out by means of a direct injection process onto the upper.

Alternatively, the mould <NUM> may comprise two different bases. A first base intended to be coupled with the first lid <NUM> in order to form the first mould cavity <NUM> and the second base intended to be coupled with the second lid <NUM> in order to form the second mould cavity <NUM>.

In this case, the inserts <NUM> are arranged in the region of the first base and the second base.

In this embodiment, the step c) of moulding the tread is carried out using the first base and the first lid, while the step e) of moulding the midsole is carried out using the second base and the second lid, after loading the tread made during the moulding step c) inside the second base.

In this way the method for manufacturing the outsole is carried out in two separate steps which involve the use of two different moulds.

Alternatively, the tread <NUM> may be made using the first base and the first lid, while the midsole <NUM> may be made using the second base and the second lid. Thereafter, the outsole may be completed by manually assembling together tread and midsole using a gluing process.

The advantages which may be achieved with the outsole and the method according to the invention are therefore clear from the above description.

The provision of the slit <NUM>, the openings <NUM> and the tread <NUM>, intended to leave the base portion of the slit <NUM> exposed, results in an outsole which is able to provide a uniform response when subjected to different impact loads.

In particular, the outsole according to the invention, irrespective as to the use which is made thereof or the physical structure of the user, is able to store the impact energy and return it in a uniform manner.

In this way, different users will be guaranteed the same degree of cushioning in a substantially uniform manner.

Claim 1:
Outsole (<NUM>) for footwear (<NUM>) extending along a toe-to-heel direction (X) and comprising a tread (<NUM>) arranged on a bottom surface of a midsole (<NUM>), said midsole (<NUM>) having a heel portion (<NUM>) with at least one through-opening (<NUM>) which extends transversely with respect to said toe-to-heel direction (X); said heel portion (<NUM>) being provided with a slit (<NUM>) which extends along the toe-to-heel direction (X), intercepting said at least one through-opening (<NUM>) so as to divide it into two parts (8a, 8b); said slit (<NUM>) being open at the front and being delimited by a side wall (<NUM>) which extends downwards from a base portion (<NUM>), said outsole (<NUM>) being characterized in that the tread (<NUM>) comprises a portion (<NUM>) which extends inside said slit (<NUM>), so as to cover solely the side wall (<NUM>) leaving exposed the base portion (<NUM>) of the slit (<NUM>), wherein said portion (<NUM>) of the tread (<NUM>) is provided with at least two holes (<NUM>) which are designed to match the holes (20a, 20b) defined at the intersection between the two parts (8a, 8b), into which said at least one opening (<NUM>) is divided, and the slit (<NUM>), so that, although the tread (<NUM>) extends inside the slit (<NUM>), each said at least one opening (<NUM>) remains a through-opening.