An anti-skid insert

Technical Field

The present invention relates to an anti-skid insert, a method for producing such an insert and a method for producing a product equipped with such an insert.

In particular, the anti-skid insert according to the present invention aims to define an anti-skid surface on a product, for example a tyre, a wheel, a sole for shoes or boots or the like.

To improve the adhesion of tyres on slippery ground and in the presence of water, snow and ice, the use of special mixtures is currently known, as well as the production of treads equipped with relatively complex tread patterns. Although the adhesion of tyres has improved over the years reaching a good level, it can definitely be increased further, especially in reference to more slippery ground and road surfaces, such as in the event of icy road surfaces.

Soles for shoes or boots are also made with special mixtures and with accentuated and complex tread patterns to improve their adhesion to slippery surfaces. This type of product is also open to notable improvements.

The object of the present invention is to offer a particularly effective anti- skid insert, which allows the anti-skid properties of numerous products to be improved without requiring substantial modifications to the production processes currently used.

Characteristics and advantages of the present invention will more fully emerge from the following detailed description of an embodiment of said invention, as illustrated in a non-limiting example in the accompanying drawings, in which:

Figure 1 shows a schematic view of the insert according to the present invention;

Figures 2 and 3 show two sectional views of two embodiments of the insert of figure 1 ;

Figures 4 and 5 show two examples of the use of the insert according to the present invention, for increasing the adhesion of the tread of a tyre;

- Figure 5a shows a schematic view of a tyre equipped with the insert according to the present invention;

Figure 6 shows a sectional view of the insert of Figure 4;

Figure 7 shows an enlargement of the insert according to the present invention, in a further embodiment.

The anti-skid insert according to the present invention comprises a first layer (1 ) of anti-skid material, preferably of very rough material. In an advantageous embodiment, the first layer (1 ) comprises powder and/or granules (G) of corundum or a similar material in terms of hardness. The thickness of the first layer ( ), and the degree of roughness and/or the size of the grains may vary according to the use of the insert.

The first layer (1 ) has a front side (F), which exposes the anti-skid material to the outside, and a rear side (R), which has a substantially uniform surface.

Preferably, but not necessarily, the first layer (1 ) may be provided with a plurality of through holes (11 ), distributed in a pre-fixed or random arrangement.

The number, shape and size of the through holes (1 1 ), as well as their distribution, may vary in relation to the requirement and use of the insert. The through holes ( 1 ) can perform a degassing function and/or promote the anchorage of the insert, as will be clarified better below. The through holes (11 ) may also comprise micro holes, particularly useful for allowing controlled gas permeability.

A second layer (2), comprising thermo-adhesive material is applied on one rear side of the first layer (1 ). Such second layer (2) may be crossed by through holes (11 ), or not be crossed by through holes (11). In the first case the second layer (2) is applied to the rear surface (R) of the first layer (1 ) before the through holes (11 ) are made. In the second case the second layer (2) is applied to the rear surface (R) of the first layer (1 ) after the through holes (11 ) are made. The second layer (2) has the function of providing a very solid and stable coupling of the anti-skid insert to a product, as will be described below.

Advantageously, but not necessarily, between the first layer (1 ) and the second layer (2) a layer of primer (not shown) may be interposed. Such layer of primer performs the function of increasing the adhesion between the first layer (1 ) and the second layer (2). Preferably the layer of primer comprises an elastic material, able to absorb shocks and vibrations of the first layer (1 ). By way of non-limiting example, the layer of primer comprises a thermo-resistant polyurethane resin, with a catalyst. The layer of primer may be replaced by a Corona treatment.

Between the first layer (1 ) and the second layer (2) an intermediate layer (21 ) may be arranged, preferably made of rubbery material. In particular, the intermediate layer (21 ) may be made of rubbery resin. Such rubbery resin is of the thermo-resistant type, i.e. it melts at temperatures of over 150 °C. The intermediate layer (21 ) may be applied to the first layer (1 ) before the application of the second layer (2), and however before the through holes (11 ) are made. To increase the elasticity and shock absorbing effect due to the intermediate layer (21 ), the intermediate layer (21 ) may be equipped with micro bubbles distributed within its mass. Such micro bubbles may be obtained, in the event of a rubbery resin, by energetically mixing or suddenly heating the resin after adding the catalyst and prior to application on the first layer (1 ).

In order to increase the strength of the coupling between the first layer (1 ) and the intermediate layer (21 ), the rear surface (R) of the first layer (1 ), i.e. the surface on which the intermediate layer (21 ) must be applied, may be subjected to a Corona treatment.

It is also possible to arrange a third layer (3) also comprising a thermo- adhesive material, applied on the second layer (2), after the through holes (11 ) are made. The third layer (3) allows the strength and stability of the anti-skid insert to be increased further.

Advantageously, the first layer (1 ), on the outer side, can be coated with a binding layer (LS) that covers and firmly stabilises the grains of corundum. Advantageously, the first layer (1 ) may be coated with a layer of non-stick material (4), for example silicone. The non-stick layer (4) may be applied by spraying or spreading, onto the front side (F) of the first layer (1 ). The function of the non-stick layer (4) is to prevent water or dirt adhering to the first layer (1 ). The non-stick layer (4) completely covers the granules or grains of corundum.

In the preferred embodiment, in which the first layer (1 ) comprises granules or grains of corundum, the non-stick layer (4) covers at least partially the projecting parts of the corundum granules.

As an alternative to the non-stick layer (4), the insert according to the present invention may be provided with a coating layer (5), applied to the first layer (1). In particular, the coating layer (5) can be applied to the external surface of the first layer (1 ). Preferably, the coating layer (5) has a thickness such as to fill the depressions between the corundum granules and leaving the tops of the corundum granules uncovered. In a preferred embodiment of the insert, the coating layer (5) is made of a rubbery resin, and can potentially be provided with micro bubbles, in the ways already described in relation to the intermediate layer (21 ). To promote the adhesion of the coating layer (5), the external surface of the first layer (1 ) can first be subjected to a Corona treatment.

Advantageously, prior to the application of the coating layer (5), the first layer (1 ) and the further layers potentially already applied thereto can be subjected to one or more deformation steps, in particular bending and/or flexing. These deformation steps aim to produce localised microfractures in the first layer (1 ), in particular in the zones interposed between the granules or grains of corundum. The microfractures produced between the corundum granules are subsequently re-joined by the coating layer (5), which penetrates into the fractures themselves. This allows the flexibility and elasticity of the first layer (1 ) to be increased. The deformation of the first layer (1 ) may be obtained in various ways, for example, by making the first layer (1 ) and any layers already applied thereto, slide in contact with one or more cylinders at a prefixed radius of curvature.

The anti-skid insert according to the present invention can be obtained according to two preferred, but not exclusive, production methods.

In general, the application of the various layers preferably envisages each layer being applied onto an already solidified layer, i.e. each layer being applied after the solidification of the previous layer, or the layer onto which it is applied.

Each layer can be applied in various known ways, for example, by spreading, spraying or immersion. By using solvent-free resins, the various layers can be applied or spread by extrusion.

The solidification of each layer can take place naturally in the air or can be accelerated by exposure to UV rays, forced heating by means of hot air. A first method for producing the insert according to the present invention envisages the following steps.

The first layer (1 ) of anti-skid material, in the preferred embodiment in which it comprises corundum granules, can be produced in the known way and is not described in detail.

After providing the first layer (1 ) of anti-skid material, it is possible to make a plurality of through holes (11 ) through the first layer (1 ) itself.

Subsequently it is possible to arrange a second layer (2) of thermo- adhesive material on one rear side of the first layer (1 ). In that case, the second layer (2) is not crossed by the through holes (11 ), if present.

Alternatively, it is possible to arrange the second layer (2) of thermo- adhesive material on the rear side (R) of the first layer (1 ) before the through holes (11 ) are made. In this case, also the second layer is crossed by the through holes (11 ).

Before the application of the second layer (2) it is possible to apply, onto the rear side (R) of the first layer (1 ), an intermediate layer (21 ), preferably of rubbery material. In particular, the intermediate layer (21 ) may be made of rubbery resin. The intermediate layer (21 ) may be applied to the first layer (1 ) before the application of the second layer (2), and in any case before the through holes (1 ) are made.

Before the application of the intermediate layer (21 ) it is also possible to subject the rear side (R) of the first layer (1 ) to a Corona treatment.

Subsequently it is possible to apply a third layer (3) of thermo-adhesive material to the second layer (2). The third layer (3) is not crossed by the through holes (11 ).

As already mentioned, to prevent water or dirt sticking to the first layer (1 ), it is possible to provide a coating step of the first layer (1 ) with a non-stick material, for example silicone.

A coating layer (5) can be applied to the first layer ( ) as an alternative to the non-stick layer. In particular, the coating layer (5) can be applied to the external surface of the first layer (1 ). In the preferred embodiment of the insert, the coating layer (5) fills the depressions between the corundum grains, leaving the tops of the grains themselves uncovered as already specified above.

Advantageously, prior to the application of the coating layer (5), the first layer (1 ) and the further layers potentially already applied thereto can be subjected to one or more deformation steps, in particular bending and/or flexing.

Before the application of the coating layer (5), the first layer (1 ) on its own outer surface, can be subjected to a Corona treatment, in order to increase the strength of the coupling with the coating layer (5).

A second method for producing the insert according to the present invention envisages the following steps.

Onto a supporting layer (B), intended to be subsequently removed from the anti-skid insert and made for example of polyester, the second layer

(2) of thermo-adhesive material is spread. Subsequently, onto the second layer (2) a first base binding layer (L) can be applied. Onto such a binding layer (L) an abrasive layer (A) of powder or granules of abrasive material is applied, for example corundum, so that the particles or grains of corundum are at least partially incorporated into the binding layer (L). The first binding layer (L) and the layer of abrasive material form the first layer (1 ). Following the solidification of the first binding layer (L), a second binding layer (LS) can be applied onto the layer of abrasive material.

Before the application of the binding layer (L), the intermediate layer (21 ), preferably made of rubbery resin, can be applied to the second layer (2). Onto such intermediate layer (21 ) the first binding layer is subsequently applied. To promote the adhesion of the first binding layer (L), the intermediate layer (21 ) can be first subjected to a Corona treatment.

Following the solidification of the first binding layer (L), and potentially of the second binding layer (LS), a coating layer (5) can be applied to the first layer (1 ). In the preferred embodiment of the insert, the coating layer (5) is applied to the second binding layer (LS). The coating layer (5) fills at least partially the depressions between the corundum grains, leaving the tops of the grains projecting.

Prior to the application of the coating layer (5), the first layer (1 ) and the further layers potentially already applied thereto can be subjected to one or more deformation steps, in particular bending and/or flexing.

At the end of the steps performed, all or part of those described above, the anti-skid insert can be subjected to a boring step for making through holes and/or micro holes (11 ).

The supporting layer (B) can be removed from the anti-skid insert before or after the boring step.

The anti-skid insert can be used for producing a product equipped with an anti-skid surface (S). For example, the insert can be used for improving the adhesion of the tread of a tyre, as shown in figures 4 and 5, or a sole or the like. For that purpose, the anti-skid insert can be arranged within a mould, into which a material intended for forming the product can also be introduced. The insert (10) is located within the die so as to be arranged at the antiskid surface (S).

The anti-skid insert can be used for example for making very high adhesion tyres. In that case one or more inserts (10) according to the present invention may be placed on the uncured tyre (i.e. before it has undergone the vulcanisation process), in such a position as to be substantially located on the tyre's tread.

As is known, the production of a tyre substantially envisages forming the casing and applying the tread strip onto the casing. Subsequently the casing and the tread strip applied thereto are subjected to vulcanisation. For producing a very high adhesion tyre, one or more inserts (10) according to the present invention are applied to the tyre strip before the vulcanisation process. Advantageously it is possible to produce a tread strip already provided with one or more inserts (10) according to the present invention. Such tread strip can be wound around the casing in the ways currently used by tyre manufacturers.

The inserts (10) can be in the form of plugs (figure 4) or in the form of rings that circumferentially surround the tread (figure 5). In the preferred embodiment of the tyre an insert (10) is provided of sufficient dimensions to completely cover the tread of the tyre and at least a part of the shoulder. To increase the strength of the coupling between the tread strip and the insert or inserts (10), the third layer (3) made of thermo-adhesive material can be directly applied to the tread strip, instead of onto the second layer

(2). In particular, it is possible to provide a tread strip already provided with a layer of thermo-adhesive material. The insert (10) in this case, shall be placed within the mould so that the second layer (2) is at the thermo- adhesive layer on the tread strip.

Subsequently, it is possible to perform the vulcanisation process that leads to the formation of the tyre. The raised tread patterns in the vulcanisation mould are impressed onto the tyre tread, also affecting the insert or inserts

(10) applied onto the tread.

During the vulcanisation process, the mixture penetrates into the through holes (11 ), if present, forming cylindrical portions (P) that prevent movements of the insert (10) with respect to the tread. The second layer

(2) and the third layer (3), if present, closely adhere to the mixture due to the effect of the temperature of the vulcanisation process. In particular, the thermo-adhesive material melts together with the rubber, coupling itself thereto permanently and unremovably. Furthermore, the cylindrical portions (P) drag a portion of the second layer (2) and/or of the third layer

(3) into the through holes (11 ) and are consequently covered in the thermo-adhesive material interposed between them and the through holes

(11 ) increasing the strength and stability of the anchoring between the insert (10) and the mixture. The coating of the cylindrical portions (P) takes place particularly in the embodiment of the insert (10) in which the third layer (3) applied in advance onto the tread strip is present.

The application of a thermo-adhesive layer, the third layer (3), onto the tread strip implies numerous advantages. Firstly, the solvent present in the thermo-adhesive material is coupled and adheres very strongly to the mixture that forms the tread. The second layer (2), adhering to the third layer (3), is coupled unremovably to the tyre tread. Furthermore, the thermo-adhesive layer applied onto the tread strip hinders, at least locally, the evaporation of the plasticisers contained in the mixture. Consequently, the tyre maintains its elasticity characteristics longer than traditional tyres. The number and size of the through holes (1 1 ), if present, determine the ratio on the anti-skid surface (S) between the surface of the first layer (1 ) that emerges on the anti-skid surface (S) and the surface made of rubber or another material used for the production of the product. Larger or more numerous through holes (11 ), in the event of a tyre, increase the rubber surface present on the tread.

The use of the insert (10) as described above is possible in every vulcanisation process, for the production of products other than tyres. A particularly advantageous use is for the production of soles for shoes. One or more inserts (10) can be positioned within the mould, so as to be located in pre-established positions on the tread of the sole.

In general, the insert (10) can be used in all processes in which a product is made by melting and moulding a material. The material in the molten state can in fact penetrate into the through holes (11 ), and can firmly adhere to the second layer (2) and/or the third layer (3) due to the effect of the temperature of the molten material. For example, one or more inserts (10) may be arranged in a mould into which a plastic material in the molten state is subsequently injected. Upon the solidification of the plastic material, the inserts (10) are perfectly anchored to the product, in the pre- established position for creating the anti-skid surface (S) within the mould. In these ways, the use of the insert (10) according to the present invention is particularly advantageous in the production of ski boots, wherein one or more inserts (10) can be placed in the mould at the sole of the boot.

The insert according to the present invention provides important advantages.

Above all, it guarantees very high adhesion to the sole also in very hazardous conditions, for example, in the presence of ice or slippery substances.

Furthermore, the insert has notable resistance to abrasion. A tyre equipped with inserts according to the present invention has a decisively longer life with respect to a traditional tyre. In this way, the consumption of rubber and the production of dust resulting from the degradation of the rubber are reduced.

A tyre equipped with inserts according to the present invention also has much lower rolling friction with respect to the tyres currently available. The insert can also be used effectively without particular complexity, in normal vulcanisation or injection moulding processes.