EP4719785A1 - Tyre - Google Patents

Abstract

A tyre (1) comprising a tread band (2) with a plurality of three- dimensional sipes (10) defined on each block (8). Each sipe (10) separates the block (8) into a first and a second portion (11, 12) respectively comprising a first and a second surface (13, 14) extended at least partially along a first and a second reference plane (X, X') incident to the tread surface (3). Between said first and second portion (11, 12), a plurality of couplings is provided, comprising: • - at least one protrusion (15) formed on the first surface (13) and extended from the first reference plane (X) towards the second portion (12) of the block (8) up to a portion of maximum protrusion lying on a third reference plane (Y), • - at least one recess (16) formed on the second surface (14) and extended from the second reference plane (X') away from the first portion of the block (11) up to a portion of maximum recess lying on a fourth reference plane (Y'), where the third and fourth reference planes (Y, Y') are spaced by a first distance (L1) from the first and second reference planes (X, X').

Description

Tyre

Description

The present invention concerns a tyre.

More specifically, the invention relates to a tyre equipped with a tread whose blocks comprise, advantageously, sipes created to improve performance levels on dry and wet surfaces, without impacting the grip characteristics on surfaces with snowy or icy ground, both when the tyre is new and subsequently.

Prior art

In a typical configuration, a tyre generally comprises a carcass structure, toroidally shaped around an axis of rotation, on which are applied, in a radially outer position, a belt structure and, in further superposition, a tread band, made of elastomeric material, on which a tread surface intended for contact with the road surface is defined.

On the tread band, a plurality of grooves with circumferential and/or transverse progression is typically defined, delimiting a corresponding plurality of blocks that, collectively, define the tyre's tread pattern.

The characteristics of the tread band, and in particular the quantity and configuration of the grooves and blocks provided on the tread surface, mainly determine the tyre's performance in terms of road behavior, especially concerning the possible different conditions of the road surface itself.

To improve the grip of a tyre on snowy ground, small cuts, called "sipes," can also be made on the blocks of the tread band, extending from the tyre's tread surface into the block. The function of the sipes is to offer additional gripping elements on the snowy ground and to retain a certain amount of snow, thereby improving the adherence with the snowy road surface.

However, the presence of cuts on the blocks of the tread band can reduce the tyre's performance when the road surface is free of snow, whether it is dry or wet, due to the decreased ability of the blocks to adequately resist shear stresses during acceleration, braking, or cornering. In this sense, it is known that, on dry road surfaces, the tyre configuration that gives the best performance results is one with a tread having a completely smooth surface to provide a larger contact zone with the ground and greater stiffness when subjected to tangential forces, which are typical of phases involving acceleration, braking, or cornering.

However, the presence of grooves in the tread pattern is indispensable when there is a wet road surface because it allows for rapid discharge of water that may be present on it, thus preventing the dangerous phenomenon of hydroplaning with the consequent lifting of the tyre.

Therefore, a tyre that is suitable for traveling under all the previously described road conditions is necessary, balancing the opposing requirements concerning its configuration, so that the arrangement of grooves on the tread band and sipes on the thus defined blocks is optimized based on usage needs.

This need is particularly evident in those countries where winters are characterized by sporadic or occasional snowfalls. In this case, the use of winter tyres is recommended over summer ones because the composition of the polymeric material that makes up the tread is more suitable for harsh winter temperatures, despite a large part of the journeys taking place on roads that are not covered in snow, but simply dry or wet.

It is necessary to specify that, with the term "groove," an indentation made on the tread surface is meant, having at least a portion with a width of at least 1.5 mm. Preferably, such a groove has a minimum depth of about 5 mm.

With the term "sipe," on the other hand, an indentation made in a portion of the tread band is meant, having a width ranging from about 0.1 mm to 1.5 mm.

Each sipe separates the block on which it is made into two block portions having respective mutually facing surfaces. Such surfaces are extended at least partially along a respective "reference plane" intersecting the tread surface and coinciding with the respective surface, net of any protrusions and recesses.

A sipe is "three-dimensional" when at least one of the mutually facing surfaces of the block portions presents at least one protrusion and/or at least one recess that deviates from the respective reference plane by a variable distance along the depth of the sipe.

If a recess is located in correspondence with and acts to accommodate at least part of a protrusion, the three-dimensional sipe forms a male-female coupling.

In this way, a relative movement of the two block portions along a direction parallel to the reference plane is hindered by the interference between the two block portions at the protrusion and recess.

A sipe is defined as "simple" when there are no protrusions and/or recesses on the mutually facing surfaces of the block portions, or there are protrusions or recesses that deviate from the reference plane by a constant distance along the depth of the sipe.

In this way, the mutually facing surfaces of the block portions do not interfere with each other in case of a relative movement along a direction parallel to the reference plane.

The term "chamfer" means that the transition portion that is created between a radially extended block surface made by the sipe and the tread surface portion corresponding to the block forms a surface rather than an edge.

For example, the transition portion can be an inclined surface.

In other words, the edge that would structurally be created due to the presence of the sipe, as a transition portion between the radially extended block surface and the block surface arranged on the tread, is eliminated/chamfered and replaced by a surface.

In this way, the radially extended block surface moves away from the relative reference plane up to the tread surface portion corresponding to the block, forming the chamfer.

A "substantially flat" connecting surface indicates a surface that is flat for at least 50% of its extension.

A tyre is defined as "directional" when it is configured to have a preferential rolling direction, typically coinciding with the direction of rotation of the tyre when mounted on a vehicle moving forward.

On the tread surface of a directional tyre, an "advance direction" is identified, tangential to the tread surface and directed in the preferential rolling direction of the tyre.

A tyre is defined as "asymmetric" when it is configured to have a design on one side of the tread different from that on the opposite side.

The term "equatorial plane" of the tyre refers to a plane perpendicular to the axis of rotation of the tyre.

The terms "radial" and "axial" and the expressions "radially inner/outer" and "axially inner/outer" are used with reference to the axis of rotation of the tyre, while the terms "circumferential" and "circumferentially" are used with reference to the direction of the annular development of the tyre, that is, to the rolling direction of the tyre, which corresponds to a direction lying on a plane coincident with or parallel to the equatorial plane of the tyre.

In particular:

The expression "radial direction" is used to indicate a direction substantially perpendicular to the axis of rotation of the tyre;

The expression "axial direction" or "transverse direction" is intended to indicate a direction parallel to the axis of rotation of the tyre, or inclined with respect to such axis by an angle less than or equal to 45°;

The expression "circumferential direction" or "longitudinal direction" is used to indicate a direction parallel to the rolling direction of the tyre, or inclined with respect to the rolling direction by an angle less than 45°.

The term "effective width" referring to the tread band means the width of the radially outermost portion of the tread band (from edge to edge) intended for contact with the ground.

With "central zone" of the tread band is meant a region of the tread surface centered on the equatorial plane of the tyre and extended for a measure up to 60% of the effective width of the tread band.

With "shoulder zone" are identified the regions of the tread surface extended from the axially opposed ends of the tread band to the central region symmetrically with respect to the equatorial plane of the tyre. An example of a tyre whose blocks are affected by three-dimensional sipes is described in the international patent application WO2017212399, in the name of the same Applicant.

Summary of the invention

The Applicant has first verified that the provision of sipes of a three-dimensional type on the blocks increases their rigidity, compared to the case where only simpletype sipes are provided on the blocks, when the said blocks are subjected to shear stresses, improving the performance of the tyre on both dry and wet surfaces, during braking as well as traction and cornering.

In particular, the Applicant has observed that the rigidity of a block increases with the increase in interference between the portions of the block and therefore with the increase in size and number of protrusions carved on their respective surfaces.

At the same time, however, the Applicant has verified that such an increase in block rigidity, due to the provision of three-dimensional sipes, may correspond to a lesser mutual mobility of the adjacent block portions, with a consequent decrease in effectiveness in retaining snow and therefore in performance on snowy surfaces, due to the tyre-snow friction, which is notoriously very low and is the main cause of tyre slipping and, consequently, of the entire vehicle slipping.

Furthermore, the Applicant has verified that the current tread designs, which comprise three-dimensional sipes, do not take into account the fact that the tyre's performance, in all the above-described conditions, must be maintained over time, and therefore, not only when the tyre is new but also during its wear.

Indeed, the geometry of the three-dimensional sipes currently used, particularly due to the presence of sharp edges at protrusions/recesses, which are mechanically the main points of cracking and/or fracture of the tyre, along with the stresses they must endure in use due to the interference between the portions of the block on which they are provided, do not guarantee that the tyre's performance will be maintained acceptably over time, leading the user to replace it frequently, even if it is not yet at the end of its life.

In fact, over time, the tread tends to wear out due to the abrasion that occurs with the rolling of the tyre on the road surface, becoming increasingly smooth, decreasing performance, particularly on snowy and wet surfaces.

In this context, the Applicant felt the need to devise a tread design capable of improving the tyre's performance throughout its life, on snowy surfaces as well as overall on dry or wet surfaces, while maintaining an acceptable level of safety.

The Applicant perceived that this objective could be achieved by creating three- dimensional sipes that extend between a relative top portion, located at the tread surface, and a relative base, located at the base of the block, where the base of the sipe turns out to be misaligned, or rather, lying on parallel reference planes and, therefore, different from those on which the top portion lies.

More specifically, each sipe, being of the three-dimensional type, comprises, between the relative top portion and the relative base, a portion of maximum protrusion and maximum recess lying on their respective parallel reference planes to those on which the base of the sipe lies, so that the reference planes on which the base of the sipe lies are included between the reference planes on which the top portion lies and those on which the portion of maximum protrusion and maximum recess lies.

In this way, the Applicant believes that a substantially trapezoidal shape/structure is created between the facing surfaces of the blocks, to increase the interlocking of snow inside the sipe.

Advantageously, the more snow that is trapped in the sipes of the tyre, the greater will be the friction between the tyre, filled with snow, and the snow on the road surface, since the snow-snow friction, as in the described case, is greater than the tyresnow friction.

Furthermore, each sipe comprising a plurality of adjacent trapezoidal shapes/structures has an overall symmetrical trend and, at the respective base, is substantially zigzag, so that, during the tyre wear process, as described above, the three-dimensional shape of the sipe and its characteristic trend continue to be present even in depth (at the base), ensuring that the snow can continue to interlock inside over time, maintaining the tyre's performance.

In particular, in a first aspect, the invention relates to a tyre comprising a tread band on which a tread surface is defined in a radially outer position to said tyre.

Preferably, the said tread band includes a plurality of grooves and a plurality of blocks delimited by at least a first pair of grooves of said plurality of grooves. Preferably, the grooves of said first pair of grooves are mostly arranged in a longitudinal direction on the block.

In other preferred embodiments, said plurality of blocks is also delimited by a second pair of grooves of said plurality of grooves.

Preferably, the grooves of said second pair of grooves are typically arranged in a transverse direction on said block.

Generally, preferably, said tread band includes a plurality of sipes extended transversely on the plurality of blocks. Preferably, said plurality of sipes is substantially parallel to the respective second pair of grooves of said plurality of grooves.

Said plurality of sipes is preferably open on said tread band. Preferably, the plurality of sipes has a sipe width. Preferably, the sipe width is greater than or equal to 0.1 mm. Preferably, the sipe width is less than or equal to 1.5 mm.

Even more preferably, the sipe width is between 0.1 mm and 1.5 mm, extremes included.

Preferably, each sipe separates said at least one block into a first block portion comprising a first surface and a second block portion comprising a second surface.

Said first surface preferably extends along a first reference plane intersecting the tread surface.

Preferably, said second surface extends along a second reference plane intersecting the said tread surface.

Preferably, the second surface faces the first surface.

In a further preferred embodiment, the said block comprises at least a first sipe and a second sipe, as described above, substantially parallel to each other.

In another embodiment, at least one of said first surface and said second surface diverges from its respective reference plane up to the said tread surface, creating a chamfer.

Preferably, the chamfer has, at the said tread surface, a chamfer width of a larger size compared to the said sipe width.

Generally, regardless of the embodiment under examination, said three- dimensional sipes carved on said at least one block extend on the tread surface along substantially parallel directions and divide said at least one block into portions having a substantially equal circumferential size to each other.

In this way, each block presents mechanical characteristics (in particular resistance to shear stresses) that are substantially homogeneous corresponding to the different portions into which it is divided by the three-dimensional sipes.

Preferably, between said first block portion and the said second block portion, a plurality of couplings is provided.

Even more preferably, such a plurality of couplings is of the male-female type. Preferably, the couplings between said first block portion and said second block portion are formed by at least one protrusion formed on said first surface and extending from the said first reference plane towards the said second block portion up to a portion of maximum protrusion lying on a third reference plane, and by at least one recess formed on the said second surface and extending from the said second reference plane away from the said first block portion up to a portion of maximum recess lying on a fourth reference plane.

Preferably, said portion of maximum protrusion and the said portion of maximum recess are located at a radially inner level with respect to the said tread surface.

Preferably, said level is not greater than 40% of the depth of the said sipe.

Preferably, a depth of said level, starting from the said tread surface, is greater than 2 mm.

Even more preferably, a depth of said level, starting from the said tread surface, is less than 4 mm.

Most preferably, a depth of the said level is greater than 2 mm and less than 4 mm, extremes included, starting from said tread surface.

Preferably, said third and fourth reference planes are spaced by a first distance respectively from the first and the second reference plane.

Preferably, the first distance is greater than or equal to three times said sipe width.

Preferably, the first distance is less than or equal to six times said sipe width.

Even more preferably, the first distance is greater than three times and less than six times the said sipe width.

Preferably, the first distance is greater than or equal to 1 mm. Preferably, the first distance is less than or equal to 3 mm.

Even more preferably, the first distance is between 1 mm and 3 mm, extremes included.

Preferably, the sipe extends to a base located radially internally with respect to said portion of maximum protrusion and said portion of maximum recess.

Said base advantageously lies on a respective fifth and sixth reference plane.

Preferably, the fifth and sixth reference planes are respectively included between said first and second reference plane and said third and fourth reference plane. Preferably, the first and second reference plane and the fifth and sixth reference plane are respectively spaced by a second distance smaller than the first distance.

Advantageously, the fact that the reference planes on which the base of the sipe lies (fifth and sixth reference plane) are misaligned compared to those on which the first and second surface of the sipe lie (first and second reference plane) in a radially external position with respect to the protrusion and the recess, as well as compared to the planes on which the portion of maximum protrusion and maximum recess of each sipe lie (third and fourth reference plane), ensures that a tread design is created capable of improving the performance of the tyre, throughout its life, on any type of road surface, with an acceptable level of safety.

Preferably, said second distance is greater than or equal to two times the said sipe width. Even more preferably, the second distance is less than or equal to five times the said sipe width.

Most preferably, the second distance is greater than two times and less than five times the said sipe width. Furthermore, the sipe preferably comprises a top portion located in a radially external position with respect to said at least one protrusion and said at least one recess. Preferably, the top portion of said sipe lies on said first and second reference plane.

Preferably, the depth of said top portion is greater than 1 mm.

More preferably, the depth of said top portion is less than 3 mm.

Even more preferably, the depth of said top portion is less than 3 mm and greater than 1 mm, extremes included.

The above-mentioned characteristics, alone or in combination with each other, define a configuration of the protrusions that advantageously does not excessively weaken the block portion on which the recesses are created, despite the protrusions being positioned near the tread surface.

Moreover, such a configuration of the protrusions allows for easier extraction of the tyre from the vulcanization mold.

In preferred but not limiting embodiments, said at least one protrusion and said at least one recess comprise, in the portion of maximum protrusion and the corresponding portion of maximum recess, a respective edge, lying on said third and fourth reference planes which extends substantially parallel to said first and second reference planes.

Preferably, said edge is radially positioned between said base and said top portion of said sipe. Preferably, the extension of said edge is greater than 1 mm.

Preferably, the extension of said edge is less than 3 mm. Even more preferably, the extension of said edge is between 1 mm and 3 mm, extremes included.

The present invention, in the aforementioned aspect, may present at least one of the preferred characteristics indicated below, considered individually or in combination with each other.

According to a preferred embodiment, said at least one protrusion and said at least one recess have a substantially prismatic configuration with a quadrilateral base.

Advantageously, the aforementioned configuration is such that it increases the interlocking of snow inside the sipe. Preferably, in the aforementioned embodiment, said at least one protrusion and said at least one recess are connected, respectively, to said first and second reference planes through respective lateral connecting surfaces.

In preferred but not limiting embodiments, such lateral connecting surfaces are substantially flat.

Preferably, said lateral connecting surfaces are located corresponding to two opposite sides respectively of said at least one protrusion and said at least one recess.

Preferably, said lateral connecting surfaces extend, for a longitudinal section of said sipe, for a length greater than 1 mm.

Even more preferably, said lateral connecting surfaces extend, for a longitudinal section of said sipe, for a length less than 3 mm.

More preferably, said lateral connecting surfaces extend, for a longitudinal section of said sipe, for a length between 1 mm and 3 mm, extremes included.

In preferred but not limiting embodiments, said lateral connecting surfaces are inclined, respectively, from said at least one protrusion and from said at least one recess to said first and second reference planes, by a first and a second angle with respect to a direction perpendicular to said first reference plane.

Preferably, said first and second angles are substantially equal. More specifically, preferably, said first angle and/or said second angle are less than 90°.

Preferably, said first angle and/or said second angle are greater than 30°. Even more preferably, said first angle and/or said second angle are between 30° and 90°, extremes included.

For example, said first angle and/or said second angle are 33°.

Preferably, said at least one protrusion and said at least one recess are connected respectively from said third and fourth reference planes to said first and second reference planes through a respective first radial connecting surface.

Preferably, said at least one protrusion and said at least one recess are connected respectively from said third and fourth reference planes to said fifth and sixth reference planes, through a respective second radial connecting surface.

Preferably, said first radial connecting surface is positioned radially above said edge.

Furthermore, said second radial connecting surface is positioned, preferably, radially below said edge.

Advantageously, said first radial connecting surface connects to said first reference plane at said top portion of said sipe.

Preferably, said second radial connecting surface connects to said fifth and sixth reference planes at said base of said sipe.

Even more preferably, said first radial connecting surface is inclined at a third angle with respect to a direction parallel to said first and second reference planes.

Preferably, said second radial connecting surface is inclined at a fourth angle with respect to a direction parallel to said first and second reference planes.

Preferably, said fourth angle is less than said third angle.

Preferably, said third angle is greater than 30°.

More preferably, said third angle is less than 90°.

Even more preferably, said third angle is between 30° and 90°, extremes included.

For example, said third angle is 60°.

Advantageously, the amplitude of said third angle may depend on the depth of said sipe.

Preferably, said fourth angle is greater than 5°.

More preferably, said fourth angle is less than 35°.

Even more preferably, said fourth angle is between 5° and 35°, extremes included. For example, said fourth angle is 8°.

Advantageously, the amplitude of said fourth angle depends on the depth of said sipe.

Advantageously, preferably, said sipe comprises at least two protrusions and respective at least two recesses adjacent to each other, each comprising respective lateral connecting surfaces, connected to a separation portion lying on said first and second reference planes.

Preferably, said at least two protrusions each comprise a respective edge, and said separation portion has an extension in a direction parallel to said first and second reference planes substantially equal to the extension of said respective edge.

Preferably, said respective at least two recesses each comprise a respective edge, and said separation portion has an extension in a direction parallel to said first and second reference planes substantially equal to the extension of said respective edge.

Advantageously, preferably, said base generally has a zigzag pattern. In the described embodiment, such a pattern is obtained by juxtaposing a plurality of protrusions of substantially trapezoidal shape with an overall symmetrical pattern.

Advantageously, such a pattern extending deep into the sipe is such that during the wear process of the tyre, this characteristic pattern of the sipe, which optimizes the interlocking of snow inside it, continues to be present, even deep within the sipe, maintaining the performance of the tyre over time.

Preferably, said at least one protrusion and said at least one recess have, respectively, an overall extension in a direction parallel to said first and second reference planes greater than 3 mm.

Preferably, said at least one protrusion and said at least one recess have, respectively, an overall extension in a direction parallel to said first and second reference planes less than 7 mm.

Furthermore, preferably, said at least one protrusion and said at least one recess have, respectively, an overall extension in a direction parallel to said first and second reference planes between 3 mm and 7 mm, extremes included.

Preferably, a pitch between two protrusions and between two recesses of said plurality of pairings is greater than 4 mm.

Preferably, a pitch between two protrusions and between two recesses of said plurality of pairings is less than 9 mm.

Preferably, a pitch between two protrusions and between two recesses of said plurality of pairings is greater than 4 mm and less than 9 mm, extremes included.

In preferred but not limiting embodiments, said tyre is of the directional type when said first surface does not include recesses and said second surface does not include protrusions. In further preferred but not limiting embodiments, said tyre is of the asymmetric type.

In particular, preferably, the tyre is of the asymmetric type in the case where the sipe is not of the three-dimensional type or, alternatively, in the case where also said first surface includes recesses and said second surface includes protrusions. Brief description of the figures. The characteristics and advantages of the invention will be more apparent from the detailed description of a preferred embodiment thereof, illustrated by way of non-limiting example, with reference to the attached drawings in which:

- Figure 1A shows a plan development of a portion of the tread band of a tyre according to the present invention;

- Figure IB shows a cross-sectional view of the portion of the tread band of Figure 1A, in which the blocks comprising the three-dimensional sipes are visible, according to an embodiment of the present invention;

- Figure 2 shows an enlarged perspective view of a portion of a sipe, according to an embodiment of the present invention;

- Figure 3A is a longitudinal sectional view, at various depths, in an enlarged scale, of the sipe portion of Figure 2;

- Figure 3B is an enlarged cross-sectional view along line A-A of the sipe of Figure 3A, highlighting the reference planes and angles related to the recess of said sipe;

- Figure 3C is an enlarged cross-sectional view along line A-A of the sipe of Figure 3A, highlighting the reference planes and angles related to the protrusion of said sipe;

- Figure 3D is an enlarged cross-sectional view along line B-B of the sipe in Figure 3 A;

- Figure 4A is a front perspective view of a sipe, according to an embodiment of the present invention, obtained on a block;

- Figure 4B is a rear perspective view of the sipe of Figure 4A;

- Figure 4C is a bottom view of the sipe of Figure 4A.

Detailed Description

Referring to the enclosed figures, 1 overall indicates a tyre made in accordance with the present invention.

The tyre 1 includes a tyre structure, conventional in itself and not shown in the attached figures, as well as a tread band 2, positioned radially outside the tyre 1 and on which a tread surface 3 is defined.

As visible in figure 1A, the portion of the tread band 2 specifically intended to come into contact with the road surface is axially extended to define an effective width L, and is connected at its axially opposed ends to the sides 4 of the tyre 1.

Within the effective width L of the tread band, a central zone C of the tread band 2 is also identified, symmetrically extended around an equatorial plane P of the tyre, two intermediate zones 5, adjacent to the central zone C and arranged in an axially symmetrical manner to the same, and two shoulder zones 6, adjacent, respectively, to the two intermediate zones 5 and arranged in an axially symmetrical manner with respect to the same two intermediate zones 5.

As visible in figures 1A and IB, a plurality of grooves, indicated with the numerical references 7A, 7B, are created on the tread band 2.

Advantageously, the aforementioned plurality of grooves includes at least a first pair of grooves 7A.

Preferably, the aforementioned first pair of grooves 7A is mostly arranged substantially in a longitudinal direction on said tyre 1.

In further preferred but not limiting embodiments, the direction in which at least one groove of said first pair of grooves 7A on said block defines an angle with respect to the equatorial plane P of the tyre 1.

Advantageously, the aforementioned angle between the equatorial plane and at least one of said first pair of grooves 7A is greater than 5° and less than 50°.

More specifically, in a first embodiment of the tyre 1, according to the present invention, the aforementioned first pair of grooves 7A delimits a plurality of blocks 8, arranged in succession along a circumferential development of the tread band 2.

In other preferred embodiments, said plurality of blocks 8 is also delimited by a second pair of grooves 7B of said plurality of grooves 7A, 7B.

The set of blocks 8 and the plurality of grooves 7A, 7B, as described above, defines the tread pattern of the tyre 1.

On the plurality of blocks 8, a plurality of three-dimensional sipes 10 is formed. Advantageously, the aforementioned plurality of three-dimensional sipes 10 extends transversely across the aforementioned plurality of blocks 8.

Advantageously, the aforementioned plurality of sipes 10 is open on the tread surface 3.

Furthermore advantageously, the aforementioned plurality of sipes 10 has a sipe width W, as visible, only by way of example, in figures 2 and 3D.

Preferably, the sipe width W is greater than or equal to 0.1 mm. Preferably, the sipe width W is less than or equal to 1.5 mm.

Even more preferably, the sipe width W is between 0.1 mm and 1.5 mm, inclusive. In further embodiments, each plurality of sipes 10 is substantially parallel to a respective second pair of grooves 7B.

In a further embodiment, not visible in the figures, a block 8 comprises a first and a second sipe 10, of said plurality of sipes 10, substantially parallel to each other.

Generally, each sipe 10, as visible in particular in figures 3A-3D, separates the respective block 8 into a first and a second block portion, respectively indicated by the numerical references 11 and 12.

More specifically, the first and second block portions 11, 12 have, respectively, a first surface 13 and a second surface 14.

Advantageously, the second surface 14 faces the first surface 13. For greater clarity, as visible for example in figure 3C, the first surface 13 is extended along a first reference plane indicated with X which plane is incident to the tread surface 3.

Similarly, as visible in figure 3B, the second surface 14 is extended along a second reference plane X' incident to the tread surface 3. In a further embodiment, not shown in the figures, at least one of the first surface 13 and the second surface 14 deviates from the respective reference plane X, X' up to the tread surface 3, creating at least one chamfer.

Preferably, said chamfer has, at the tread surface 3, a chamfer width W1 of a dimension larger than said sipe width W.

Advantageously, this chamfer creates a substantially "funnel" shape/structure that serves as an invitation for the snow that, during the rolling of the tyre 1, inserts itself inside it, getting stuck.

Regardless of the embodiment under examination, between said first portion 11 of block 8 and said second portion 12 of block 8, a plurality of couplings is provided.

Even more preferably, this plurality of couplings is of the male-female type.

As visible in figures 3A-3D, the plurality of couplings between said first portion 11 of block 8 and said second portion 12 of block 8 are formed by at least one protrusion 15 formed on said first surface 13 and extended from said first reference plane X towards said second portion 12 of block 8 up to a portion of maximum protrusion lying on a third reference plane Y, and by at least one recess 16 formed on said second surface 14 and extended from said second reference plane X' away from said first portion 11 of portion 8 up to a portion of maximum recess lying on a fourth reference plane Y'.

Preferably, as more visible in figures 4A and 4B, the plurality of couplings provided between the first portion 11 of block 8 and the second portion 12 of block 8 are formed by protrusions 15 obtained on the first surface 13 and by corresponding recesses 16 obtained on the second surface 14.

In a more preferred manner, as visible in figure 4B, all the protrusions 15 of the sipe 10 are obtained on the first surface 13, so that the second surface 14 is devoid of protrusions, and in an equally preferred manner, as visible in figure 4A, all the recesses

16 are obtained on the second surface 14, so that the first surface 13 is devoid of recesses.

According to the embodiment under examination, the tyre 1 is of the directional type when the first surface 13 does not include recesses 16 and the second surface 14 does not include protrusions 15.

In the preferred embodiment and as illustrated here, the portion of maximum protrusion and maximum recess are obtained, respectively, in the first surface 13 and the second surface 14 at a radially internal level with respect to the tread surface 3. Preferably, the aforementioned level is not higher than 40% of the depth of the sipe 10.

Preferably, a depth of said level, starting from said tread surface 3, is greater than 2 mm.

Even more preferably, a depth of said level, starting from said tread surface 3, is less than 4 mm. Most preferably, a depth of said level is greater than 2 mm and less than 4 mm, extremes included, starting from said tread surface 3. It is understood that the recesses 16 obtained on the second surface 14 have a shape similar and corresponding to the protrusions 15.

Based on what has just been said, generally and, in particular, where not explicitly described, what will be described in relation to the protrusions 15 is to be considered valid and analogous for the description of the recesses 16.

As visible in figures 2 and 3A, 3C, said third and fourth reference planes Y, Y' are spaced by a first distance LI respectively from the first and second reference planes X, X'. Preferably, the first distance LI is greater than or equal to three times the sipe width W.

More preferably, the first distance LI is less than or equal to six times the sipe width W.

Even more preferably, the first distance is greater than three times and less than six times the sipe width W.

Preferably, the first distance LI is greater than or equal to 1 mm. More preferably, the first distance LI is less than or equal to 3 mm.

Even more preferably, the first distance LI is between 1 mm and 3 mm, extremes included.

As visible in more detail in figures 4A and 4C, the sipe 10 extends to a base 101 located radially internally with respect to said portion of maximum protrusion and said portion of maximum recess.

The aforementioned base 101 lies, advantageously, on a respective fifth and sixth reference plane Z, Z'. Preferably, the fifth and sixth reference planes Z, Z' are respectively included between said first and second reference planes X, X' and said third and fourth reference planes Y, Y'.

As seen in figures 3A-3C, the first and second reference planes X, X' and the fifth and sixth reference planes Z, Z' are respectively spaced by a second distance L2 less than the first distance LI. Advantageously, this type of configuration in which the base of the sipe is offset with respect to the first and second surface of the sipe in a radially external position with respect to the protrusion and the relative recess, as well as with respect to the portion of maximum protrusion and maximum recess of each sipe, makes it possible to create a tread pattern capable of improving the performance of the tyre, throughout its life, on any type of road surface, including snow and wet, with an acceptable level of safety.

Preferably, the aforementioned second distance L2 is greater than or equal to two times the sipe width W.

Even more preferably, the second distance L2 is less than or equal to five times the sipe width W.

Most preferably, the second distance L2 is greater than two times and less than five times the sipe width W.

Furthermore, as visible in figures 3B and 3C, the sipe 10 preferably includes a top portion 100 located radially outside of said at least one protrusion 15 and said at least one recess 16.

Preferably, the top portion 100 of said sipe 10 lies on said first and second reference planes X, X'.

Advantageously, the base 101 lies on the respective fifth and sixth reference planes Z, Z' and the top portion 100 of the sipe 10 lie on the respective first and second reference planes X, X' in such a way as to be substantially offset from each other, advantageously increasing the snow-locking effect inside the sipe 10.

Preferably, a depth of said top portion 100 is greater than 1 mm.

More preferably, a depth of said top portion 100 is less than 3 mm.

Even more preferably, a depth of said top portion 100 is between 1 mm and 3 mm, extremes included.

Advantageously, said at least one protrusion 15 and said at least one recess 16 include, in the portion of maximum protrusion and in the relative portion of maximum recess, a respective edge 20, lying on said third and fourth reference planes Y, Y' and extending substantially parallel to the first and second reference planes X, X'.

As visible in figures 2, 3B and 3C, said edge 20 is radially positioned between said base 100 and said top portion 101 of said sipe 10.

Preferably, the extension of said edge 20 is greater than 1 mm.

Preferably, the extension of said edge 20 is less than 3 mm.

Even more preferably, the extension of said edge 20 is between 1 mm and 3 mm, extremes included.

According to a preferred embodiment, said at least one protrusion 15 and said at least one recess 16 have a substantially prismatic shape with a quadrilateral base.

Advantageously, the aforementioned shape is such as to increase the snowlocking inside the sipe.

With reference to figures 2, 3A, 4A-4B, in this shape, advantageously, said at least one protrusion 15 and said at least one recess 16 are connected, respectively, to said first and second reference planes X, X' through respective lateral connecting surfaces 21, 21'.

In preferred, but not limiting embodiments, these lateral connecting surfaces are substantially flat.

Preferably, these lateral connecting surfaces 21, 21' are located at two opposite sides respectively of said at least one protrusion 15 and said at least one recess 16 (figure 3A).

These lateral connecting surfaces 21, 21' extend, for a longitudinal section of said sipe 10, for a stretch greater than 1 mm.

Even more preferably, these lateral connecting surfaces 21, 21' extend, for a longitudinal section of said sipe 10, for a stretch less than 3 mm.

Most preferably, these lateral connecting surfaces 21, 21' extend, for a longitudinal section of said sipe 10, for a stretch between 1 mm and 3 mm, extremes included.

As visible in figure 3A, these lateral connecting surfaces 21, 21' are inclined, respectively, from said at least one protrusion 15 and said at least one recess 16 to said first and second reference planes X, X', by a first and a second angle a, o' with respect to a direction perpendicular to said first reference plane X.

Preferably, said first angle a and said second angle o' are substantially equal. In more detail, preferably, said first angle a and/or said second angle o' are less than 90°.

Preferably, said first angle a and/or said second angle o' are greater than 30°.

Most preferably, said first angle a and/or said second angle o' are between 30° and 90°, extremes included. For example, said first angle a and/or said second angle o' are 33°.

Advantageously, said at least one protrusion 15 and said at least one recess 16 are connected respectively from said third and fourth reference planes Y, Y' to said first and second reference planes X, X' through a respective first radial connecting surface 22 (figures 2, 3B-3C and 4A-4B).

Also advantageously, said at least one protrusion 15 and said at least one recess 16 are connected respectively from said third and fourth reference planes Y, Y' to said fifth and sixth reference planes Z, Z', through a respective second radial connecting surface 22 (figures 2, 3B-3C and 4A-4B).

Preferably, said first radial connecting surface 22 is arranged radially above said edge 20.

Also, said second radial connecting surface 22' is preferably arranged radially below said edge 20.

Advantageously, always with reference to the aforementioned figures, said first radial connecting surface 22 connects to said first reference plane X at said top portion 100 of said sipe 10. Said second radial connecting surface 22' connects to said fifth and sixth reference planes Z, Z' at said base 101 of said sipe 10.

Advantageously, with reference to figures 3B, 3C, said first radial connecting surface 22 is inclined by a third angle with respect to a direction parallel to said first and second reference planes X, X'.

Still with reference to the aforementioned figures, said second radial connecting surface 22' is inclined by a fourth angle y with respect to a direction parallel to said first and second reference planes X, X'.

Preferably, said fourth angle y is less than said third angle 0.

More preferably, said third angle 0 is greater than 30°. Even more preferably, said third angle 0 is less than 90°.

Even more preferably, said third angle 0 is between 30° and 90°, extremes included.

For example, said third angle 0 is 60°.

Advantageously, the amplitude of the aforementioned third angle 0 can depend on the depth of said sipe 10.

More preferably, said fourth angle y is greater than 5°. Even more preferably, said fourth angle y is less than 35°.

Even more preferably, said fourth angle y is between 5° and 35°, extremes included.

For example, said fourth angle y is 8°.

Advantageously, the amplitude of the aforementioned fourth angle y can depend on the depth of said sipe 10.

Advantageously, said sipe 10 includes at least two protrusions 15 and respective at least two recesses 16 adjacent to each other (figures 2, 3A, 4A-4C), each comprising respective lateral connecting surfaces 21, 21', connected to a separation portion 23 lying on said first and second reference planes X, X'. Said at least two protrusions 15 each include a respective edge 20 and said separation portion 23 has an extension in a direction parallel to said first and second reference planes X, X' substantially equal to the extension of said respective edge 20.

Said respective at least two recesses 16 each include a respective edge 20 and said separation portion 23 has an extension in a direction parallel to said first and second reference planes X, X' substantially equal to the extension of said respective edge 20.

Advantageously, as particularly visible in figure 4C, said base 101 generally has a substantially zigzag course.

In the described embodiment, this course is obtained by a plurality of adjacent trapezoidal shapes/structures having a generally symmetrical course.

Advantageously, the aforementioned course deep into the sipe 10 is such that during the wear process of the tyre 1, this characteristic course of the sipe 10, which increases the snow-locking inside it, continues to be present, even in depth, maintaining the performance of the tyre 1 over time.

Advantageously, said at least one protrusion 15 and said at least one recess 16 have, respectively, an overall extension in a direction parallel to said first and second reference planes X, X' greater than 3 mm.

Preferably, said at least one protrusion 15 and said at least one recess 16 have, respectively, an overall extension in a direction parallel to said first and second reference planes X, X' less than 7 mm.

Even more preferably, said at least one protrusion 15 and said at least one recess 16 have, respectively, an overall extension in a direction parallel to said first and second reference planes included between 3 mm and 7 mm, extremes included. Advantageously, a pitch between two protrusions 15 and between two recesses 16 of said plurality of couplings is greater than 4 mm.

Preferably, a pitch between two protrusions 15 and between two recesses 16 of said plurality of couplings is less than 10 mm. Even more preferably, a pitch between two protrusions 15 and between two recesses 16 of said plurality of couplings is greater than 4 mm and less than 10 mm, extremes included.

Finally, in a further embodiment, not shown in the figures, the tyre 1 is of the asymmetric type in the case where the first surface 13 includes recesses 16 and the second surface 14 includes protrusions 15.

The invention as conceived and illustrated here is susceptible to numerous modifications and variations, all falling within the scope of the inventive concept.

Furthermore, all details can be replaced by other technically equivalent elements. Where the characteristics and techniques mentioned in any claim are followed by reference signs, these reference signs have been attached for the sole purpose of increasing the intelligibility of the claims and, consequently, such reference signs have no limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

1. Tyre (1) comprising a tread band (2) on which, in a radially outward position of said tyre (1), is defined a tread surface (3), said tread band (2) comprising

- a plurality of grooves (7A);

- a plurality of blocks (8) delimited by at least a first pair of grooves (7A);

- a plurality of three-dimensional sipes (10) formed on each block (8) of said plurality of blocks; wherein, each sipe (10) of three-dimensional type of said plurality of sipes (10) is open on said tread surface (3), separates said block (8) into a first portion (11) comprising a first surface (13) extending at least partially along a first reference plane (X) incident upon said tread surface (3), and a second portion (12) comprising a second surface (14) extending at least partially along a second reference plane (X') incident upon said tread surface (3), wherein between said first portion (11) and said second portion (12) of said block (8) there is provided a plurality of couplings comprising

- at least one protuberance (15) formed on said first surface (13) and extended from said first reference plane (X) towards said second portion (12) of said block (8) up to a portion of maximum protuberance lying on a third reference plane (Y)

- at least one recess (16) formed on said second surface (14), extending from said second reference plane (X') away from said first portion (11) of block (8) up to a portion of maximum recess lying on a fourth reference plane (Y') said third and fourth reference planes (Y, Y') being spaced by a first distance (LI) from said first and second reference planes (X, X') respectively, wherein said portion of maximum protuberance of said at least one protuberance (15) and said portion of maximum recess of said at least one recess (16) are respectively positioned at an height radially inward with respect to said tread surface (3), and wherein said sipe (10) extend to a base (101), said base (101) being positioned radially inwardly with respect to said portion of maximum protuberance and said portion of maximum recess, said base (101) lying on a respective fifth and sixth reference plane (Z, Z') respectively included between said first and second reference planes (X, X') and said third and fourth reference planes (Y, Y'), so that said first and second reference planes (X, X') and said fifth and sixth reference planes (Z, Z') are respectively spaced by a second distance (L2) smaller than said first distance (LI).

2. Tyre (1) as in the previous claim, characterized in that said sipe (10) has a sipe width (W) between 0.1 mm and 1.5 mm.

3. Tyre (1), as in the previous claim, characterized in that said first distance (LI) is greater than or equal to three times and less than or equal to six times with respect to said sipe width (W).

4. Tyre (1) as in claim 2 or 3, characterized in that said second distance (L2) is greater than or equal to two times and less than or equal to five times said sipe width (W).

5. Tyre (1) as to at least one of the preceding claims, characterized in that said sipe (10) comprises a top portion (100) positioned radially outward from said at least one protuberance (15) and said at least one recess (16), wherein said top portion (100) of said sipe (10) lies on said first and second reference planes (X, X').

6. Tyre (1) as in the previous claim, characterized in that a depth of said top portion (100) is greater than 1 mm and less than 3 mm.

7. Tyre (1) as in claim 1, characterized in that said height is not more than 40% of a depth of said sipe (10).

8. Tyre (1) as in the previous claim, characterized in that a depth of said height is greater than 2 mm and less than 4 mm from said tread surface (3).

9. Tyre (1) as to at least one of the preceding claims, characterized in that said at least one protuberance (15) and said at least one recess (16) comprise, respectively, in said portion of said maximum protuberance and of said maximum recess, a respective block edge (20) lying on said third and fourth reference planes (Y, Y') and extending substantially parallel to said first and second reference planes (X, X').

10. Tyre (1) according to the preceding claim, characterized in that the extension of said block edge (20) is greater than 1 mm and less than 3 mm.

11. Tyre (1) according to at least one of the preceding claims, characterized in that said at least one protuberance (15) and said at least one recess (16) have a substantially prismatic conformation with a quadrilateral base and are connected, respectively, to said first and second reference planes (X, X'), by means of respective lateral connecting surfaces (21, 21').

12. Tyre (1) as in the preceding claim, characterized in that said lateral connecting surfaces (21, 21') are placed at two opposite sides respectively of said at least one protuberance (15) and of said at least one recess (16).

13. Tyre (1) as to at least one of claims 11-12, characterized in that said lateral connecting surfaces (21, 21') extend, in a longitudinal section of said sipe (10), for a tract greater than 1 mm and less than 3 mm.

14. Tyre (1) as to at least one of claims 11-13, characterized in that said lateral connecting surfaces (21, 21') are inclined from said at least one protuberance (15) and from said at least one recess (16) to said first and second reference planes (X, X'), respectively, by a first and second angle (a, o') with respect to a direction perpendicular to said first reference plane (X).

15. Tyre (1) as in the previous claim, characterized in that said first and/or said second angle (a, o') is/are between approximately 30° and 90°.

16. Tyre (1) according to at least one of the preceding claims, characterized in that said at least one protuberance (15) and said at least one recess (16) are respectively connected from said third and fourth reference planes (Y, Y') to said first and second reference planes (X, X') by means of a respective first radial connecting surface (22) and, from said third and fourth reference planes (Y, Y') to said fifth and sixth reference planes (Z, Z'), by means of a respective second radial connecting surface (22¹).

17. Tyre (1) as in the previous claim, characterized in that said first radial connecting surface (22) is arranged radially upwards with respect to said block edge (20) and said second radial connecting surface (22') is arranged radially downwards with respect to said block edge (20).

18. Tyre (1) as to at least one of claims 16 or 17, characterized in that said first radial connecting surface (22) connects to said first reference plane (X) at said top portion (100) of said sipe (10).

19. Tyre (1) as to at least one of claims 16 or 17, characterized in that said second radial connecting surface (22') connects to said fifth and sixth reference planes (Z, Z') at said base (101) of said sipe (10).

20. Tyre (1) as to at least one of claims 16-19 characterized in that said first radial connecting surface (22) is inclined by a third angle ( ) and said second radial connecting surface (22') is inclined by a fourth angle (y) with respect to a direction parallel to said first and second reference planes (X, X'), wherein said fourth angle (y) is smaller than said third angle (3).

21. Tyre (1) as in the previous claim, characterized in that said third angle (3) is greater than 30° and smaller than 90° and said fourth angle (y) is greater than 5° and smaller than 35°.

22. Tyre (1) as at least one of claims 11-14, characterized in that said sipe comprises at least two protuberances (15) and respective at least two recesses (16) adjacent to each other, each comprising respective lateral connecting surfaces (21, 21'), connected to a separation portion (23) lying on said first and second reference planes (X, X').

23. Tyre (1) as in the previous claim, characterized in that said at least two protuberances (15) and respective said at least two recesses (16) each comprise a respective block edge (20) and said separation portion (23) has an extension in a direction parallel to said first and second reference planes (X, X') substantially equal to the extension of said respective block edge (20).

24. Tyre (1) as in the previous claim, characterized in that said base (101) has an overall zigzag course.

25. Tyre (1) according to at least one of the preceding claims, characterized in that said at least one protuberance (15) and said at least one recess (16) have, respectively, a total extension in the direction parallel to said first and second reference planes (X, X') greater than 3 mm and less than 7 mm.

26. Tyre (1) as in claim 1, characterized in that a pitch between two protuberances (15) and between two recesses (16) of said plurality of couplings is greater than 4 mm and less than 9 mm.

27. Tyre (1) as to at least one of the preceding claims, characterized in that said plurality of blocks (8) is also delimited by a second pair of (7B) grooves of said plurality of grooves (7A, 7B), wherein each of said plurality of sipes (10) is substantially parallel to a respective second pair of grooves (7B)

28. Tyre (1) as to at least one of the preceding claims, characterized in that at least one of said first surface (13) and said second surface (14) deviates from the respective reference plane (X, X') up to said tread surface (3), creating at least one chamfer having, at said tread surface (3), a chamfer width of a dimension greater than said sipe width (W).

29. Tyre (1) as at least one of the preceding claims, characterized in that said tyre (1) is of the directional type, said first surface (13) does not comprise recesses

(16) and said second surface does not comprise protuberances (15).