Vehicle wheel tyre

Abstract

A tyre (1) comprising a plurality of blocks (5, 6) defined on a tread band (2) and at least one first sipe (10; 20). The first sipe (10; 20) extends along a first longitudinal direction (A) and comprises a first linear portion (11) extending substantially along the first longitudinal direction (A), a single-wave portion (12) extending continuously with the first linear portion (11), and a second linear portion (13) extending continuously with the single-wave portion (12). The single-wave portion (12) comprises: a first segment (14) inclined and extending from the first linear portion (11) to the first crest portion (15); a second segment (16) inclined and extending from the first crest portion (15) to an opposite second crest portion (17); and a third segment (18) inclined and extending from the second crest portion (17) to the second linear portion (13). The second segment (16) of the single-wave portion (12) is inclined at an angle relative to the first longitudinal direction (A) that is greater than the angles of the first segment (14) and the third segment (18) relative to the first longitudinal direction.

Description

Technical Field

[0001] The invention relates to a tyre for vehicle wheels, in particular a winter tyre. Background Art

[0002] The tyre generally comprises a carcass structure shaped toroidally around an axis of rotation, comprising at least one carcass ply, the end edges of which are engaged in respective annular anchoring structures, called bead cores.

[0003] A belt structure is arranged in a radially external position relative to the carcass structure, which, in the case of a tire for a vehicle, comprises at least two radially superimposed rubberized fabric strips, which are provided with reinforcing cords, which are usually made of metal and are arranged parallel to each other in each strip, but crossed with respect to the cords of adjacent strips, preferably symmetrically arranged with respect to the equatorial plane of the tire.

[0004] Preferably, the belt structure also comprises, in a radially external position, at least on the ends of the underlying belt strips, a third layer of textile or metal cords, arranged in the circumferential direction (at 0 degrees). In tubeless type tyres, there is also a radially internal layer called "liner", which has an impermeability in order to obtain airtightness in the tyre itself.

[0005] In a radially outer position with respect to the belt structure there is applied a tread band made of elastomeric material and defining thereon a tread surface intended to come into contact with the road surface.

[0006] In order to obtain sufficient road grip also on wet roads, the tyre has a tread band provided with grooves of different shapes and geometries, the main purpose of which is to allow the drainage of water present between the tyre surface and the road surface during their mutual contact.

[0007] The grooves generally define a plurality of blocks on the tread band, each block comprising a radially outer surface intended to come into contact with the road surface and thus forming part of the tread surface of the tyre. Each block is also at least partially delimited by one or more walls defined by the grooves surrounding the walls.

[0008] In some cases, the wall of the block or a portion thereof is connected to the tread surface of the block by means of a chamfer, which is generally formed by a plane appropriately inclined relative to the wall and the tread surface and defines the edge of the block.

[0009] In the case of winter tires, the blocks of the tread band are generally formed with small recesses, called "sipes", which extend from the tread surface of the tire towards the inside of the blocks. The function of the sipes is to provide additional gripping elements in the case of driving on snowy roads and to retain a certain amount of snow, thereby improving the grip relative to the road surface. The sipes can have a variety of configurations that differ from each other, for example, the sipes can have a straight or curved or wavy development.

[0010] The term "circumferential" direction means a direction pointing substantially in the direction of rotation of the tyre or in any case a direction slightly inclined (at most about 5°) relative to the direction of rotation of the tyre.

[0011] The term "axial" direction means a direction substantially parallel to the axis of rotation of the tyre or, at most, slightly inclined (up to about 5°) relative to this axis of rotation of the tyre. The axial direction is generally perpendicular to the circumferential direction.

[0012] The term "radial" direction refers to a direction intersecting the axis of rotation of the tire perpendicularly or, at most, a direction slightly inclined (for example, at most about 5°) relative to the direction perpendicular to the axis of rotation of the tire.

[0013] The term "equatorial plane" of the tire means the axial centerline plane perpendicular to the tire's axis of rotation.

[0014] The term "groove" means a recess formed in the tread band portion and extending along a main longitudinal direction, having a width greater than or equal to 1.5 mm. Preferably, the depth of the groove is at least 3 mm.

[0015] The term "sipe" means a recess formed in a tread band portion and extending along a main longitudinal direction, said recess having a width less than 1.5 mm.

[0016] The “longitudinal extension direction” of the sipe is defined by the linear development of the sipe in the region of the radially outer surface of the block.

[0017] The term "block" means the portion of the tread band intended to come into contact with the road surface, delimited over its entire circumference by one or more grooves and, where applicable, by the axial ends of the tread band.

[0018] Thus, a block may be considered both as a portion of the tread band having a closed outline defined by three or more grooves, and as a circumferential rib defined by a pair of grooves extending circumferentially around the tread band.

[0019] A "central block" is defined as a block not bounded by the axial ends of the tread band, whereas a block partially bounded by one of the axial ends of the tread band is defined as a "shoulder block".

[0020] The term "wall" of a block refers to the surface that extends generally from the bottom of the grooves that delimit the block towards the tread surface portion of the block.

[0021] The term "edge" of a block refers to the area of ​​the block connecting the wall of the block to the tread surface portion of the block.

[0022] If the wall intersects the tread surface portion directly, the edge may be formed by a corner, or the edge may be formed by a connecting surface connecting the wall to the tread surface portion, which is defined as a "chamfer".

[0023] Two or more linear distances, such as, for example, two or more distances between sipes or between sipe elements, have "substantially equal" lengths when the respective lengths do not differ from each other by more than 10% of a maximum length.

[0024] Two or more directions or two or more elements extending in corresponding directions (such as, for example, two or more sipes or parts thereof) are "substantially parallel" when they are inclined relative to each other at an angle of less than 10°, preferably less than 5°.

[0025] The inclination of the first direction relative to the second direction, for example the inclination of the direction of the sipe portion relative to the longitudinal extension direction of the sipe, is defined by the acute angle formed by the first direction and the second direction. As a special example, when the first direction is perpendicular to the second direction, the inclination is 90°.

[0026] Two or more directions or two or more elements extending in respective directions (such as, for example, two or more sipes or portions thereof) are inclined in a "consistent manner" relative to another direction if, when considered on a Cartesian plane containing the two or more directions and whose abscissa axis is parallel to the other direction, the tendency of the two or more directions is increasing for all of them or decreasing for all of them. For example, two different portions of the sipe extending in the longitudinal direction of the sipe are inclined in a consistent manner relative to the longitudinal direction of the sipe if, when considered on a Cartesian plane whose abscissa axis is parallel to the longitudinal direction of the sipe, the tendency of the two different portions of the sipe extending in the longitudinal direction of the sipe to extend in the respective direction both increases or both decreases.

[0027] Thus, two or more directions or two or more elements extending along corresponding directions (such as, for example, two or more sipes or portions thereof) are inclined in an "inconsistent manner" if their tendency, when considered on this Cartesian plane, is to increase for one or more of the directions and to decrease for one or more other of the directions.

[0028] The term "peak portion" defined on a sipe or a portion thereof refers to the maximum area or minimum area defined on a linear cross-section of the sipe or the portion when considering a linear cross-section on a Cartesian plane, the abscissa axis of which is positioned in the longitudinal extension direction of the sipe.

[0029] Two sipe portions spaced apart from one another are "substantially aligned" when their longitudinal directions, at least in the region of their respective two ends facing each other, are as follows:

[0030] - Alignment; or,

[0031] - if the respective longitudinal directions incident with respect to one another, said longitudinal directions are inclined by an angle of less than 10°, preferably less than 5°, or

[0032] If the respective longitudinal directions are parallel to one another, said longitudinal directions are offset by a value less than 1.5 mm.

[0033] Two sipes are “consecutive” when they are arranged one after the other on the tread surface of a block, taking into account a direction perpendicular to the longitudinal development direction of at least one of the two sipes.

[0034] The term "single wave portion" of the sipe refers to the section of the linear trend of the sipe at the radially outer surface of the block, which has a first wave peak and a second wave peak, which are consecutive and opposite in direction relative to the longitudinal development of the sipe itself.

[0035] The sipes formed on the block divide the block into two block parts having respective mutually facing surfaces.

[0036] The sipe is defined as "compound" when at least one of the mutually facing surfaces of the block portions has at least one projection and another of these surfaces has a corresponding recess capable of at least partially receiving this projection. In other words, the corresponding projections in a plane perpendicular to the radial direction of the two block portions separated by the sipe are at least partially overlapping in the region of the projection and the corresponding recess.

[0037] In this way, a relative movement of the two block parts in the radial direction is hindered due to the interference between the two block parts in the region of the projections and recesses.

[0038] Compound sipes are also referred to in the art as "three-dimensional" sipes.

[0039] The sipe is defined as being of “simple type” when there are no elevations and / or recesses on the mutually facing surfaces of the block portions which interfere with each other during the relative movement of the two block portions in radial direction.

[0040] Examples of sipes configured in various ways are described in, for example, EP 3375639, US 5198047, US 2021 / 0107319, EP 3867081A1, JP 6946658, JP 2018020689, US 3799231, US 20030029537, US 2005 / 0150581, EP 0598300, US 5327953 and US 5591280. Summary of the invention

[0041] The Applicant has observed that the performance level of the tire on snowy roads depends to a certain extent on the number and extent of the sipes formed on the blocks, so that for the same tread pattern, blocks formed with a plurality of sipes can provide better snow performance.

[0042] However, the Applicant has also observed that the presence of the sipes weakens the structure of the block, making it less rigid and therefore reducing its ability to withstand external stresses, in particular tangential stresses.

[0043] Due to this weakening, during braking, acceleration or cornering, the block may deform in a relevant way, causing it to be partially lifted from the road surface, thereby reducing the contact area between the block and the road surface and thus also causing a reduction in the total friction force exerted by the tire on the road surface.

[0044] The Applicant has demonstrated that the causes of the weakening of the block consist in that the sipes subdivide the block into two parts which, in the region of the sipes, are able to slide relative to one another.

[0045] In particular, the Applicant has observed that this sliding occurs in a direction parallel to the separation surface of the two parts, so that the sliding can always be considered as the synthesis of movements in two main directions defined on the separation surface: a direction extending perpendicular to the tread surface from the bottom of the sipe (substantially coinciding with the radial direction of the tread band) and a second direction parallel to the longitudinal extension direction of the sipe.

[0046] The Applicant has demonstrated that it is possible to increase the resistance of the blocks in the region of the sipes by preventing or limiting the possibility of mutual sliding along these two main directions to the greatest possible extent.

[0047] The Applicant has observed that a sipe of the composite type having a profile provided with protuberances and corresponding recesses is able to resist mutual sliding of the block portions, in particular along the first direction defined above. However, providing a profile of this type is not always sufficient to effectively resist sliding behaviour along the aforementioned second direction (parallel to the longitudinal development direction of the sipe), in particular in the area of ​​the tread surface.

[0048] The Applicant has therefore observed that, in order to resist this type of sliding, it is generally known to configure the sipes to have an undulating linear development, for example in a zigzag manner.

[0049] The Applicant has also observed that, in order to obtain a sufficiently effective resistance action, the linear development of the wave must extend over a large part of the longitudinal extension of the sipe, providing a plurality of waves having a substantially symmetrical form.

[0050] However, the Applicant has found that the resistance to tangential sliding of the block parts provided by this configuration is not always effective.

[0051] The Applicant has therefore recognised the need to provide a sipe which is particularly configured so as to make the resistance to the sliding of the block portion more effective in the longitudinal extension direction of the sipe, without having to use an undulating tendency with a large number of undulations. In order to comply with this requirement, the Applicant has realised that the above resistance can be made more effective by giving the sipe a specific configuration, in particular in the area of ​​the undulations.

[0052] Finally, the Applicant has discovered a sipe comprising a first linear portion and a second linear portion, the first linear portion and the second linear portion being straight or slightly curved, and between which a single wave portion is interposed, the single wave portion in turn comprising:

[0053] a first segment which is inclined relative to the longitudinal direction of the sipe from a first linear portion to a first wave crest,

[0054] a second section which is inclined relative to the longitudinal direction of the sipe and which extends from the first wave crest to the second wave crest, and

[0055] a third section which is inclined with respect to the longitudinal direction and which extends from the second wave crest to the second linear portion,

[0056] The second segment is more inclined relative to the longitudinal direction than the first segment and the third segment, so that the longitudinal sliding of the block parts separated by the sipes can be effectively resisted even when the number of wavy parts is reduced.

[0057] In particular, in a first aspect thereof, the invention relates to a tyre comprising a tread band and a tread surface, said tread surface being radially external with respect to said tread band.

[0058] Preferably, a plurality of blocks are defined on said tread band.

[0059] Preferably, at least one first sipe is formed on each of the plurality of blocks, and the first sipe is open at the tread surface.

[0060] Preferably, said first incision is open at said tread surface so as to define a first longitudinal extension direction of said first incision.

[0061] Preferably, said first incision comprises a first linear portion extending substantially along said first longitudinal direction.

[0062] Preferably, the first linear portion is a straight line or a curve with a minimum curvature radius of not less than 20 mm.

[0063] Preferably, the first sipe includes a single wave portion extending continuously with the first linear portion.

[0064] Preferably, the first sipe includes a second linear portion extending continuously with the single wave portion.

[0065] Preferably, the second linear portion is a straight line or a curve with a minimum curvature radius of not less than 20 mm.

[0066] Preferably, said single wave portion comprises a first segment which is inclined relative to said first longitudinal direction.

[0067] Preferably, the first segment extends from the first linear portion to a first wave crest of the single wave portion.

[0068] Preferably, the single wave portion comprises a second segment inclined relative to the longitudinal direction.

[0069] Preferably, the second segment extends from the first wave peak to a second wave peak of the single wave portion.

[0070] Preferably, the second wave peak portion is defined on a side opposite to the first wave peak portion with respect to the first longitudinal direction.

[0071] Preferably, the single wave portion comprises a third segment which is inclined relative to the first longitudinal direction.

[0072] Preferably, the third segment extends from the second wave crest portion to the second linear portion.

[0073] Preferably, the second segment is inclined at an angle relative to the first longitudinal direction that is greater than the angles at which the first segment and the third segment are inclined relative to the first longitudinal direction.

[0074] The applicant believes that, due to this special configuration, even if the number of wavy portions is greatly reduced, for example, there are only one or two wavy portions in the entire sipe pattern, it is possible to effectively resist the sliding behavior of the block parts separated by the sipe pattern, thereby allowing a harder block to be obtained under the same other conditions and the block can provide better behavior on dry and icy roads.

[0075] The present invention in the above aspects may have at least one of the following additional preferred features.

[0076] In some embodiments, the first segment of the single wave portion is inclined at an angle between 20° and 45°, more preferably at an angle of about 24°, relative to the first longitudinal direction.

[0077] In some embodiments, the third segment of the single wave portion is inclined at an angle between 20° and 45°, more preferably at an angle of about 24°, relative to the first longitudinal direction.

[0078] Preferably, the first segment and the third segment of the single wave portion are inclined relative to each other in a consistent manner.

[0079] Preferably, the second segment of the single wave portion is tilted in a non-uniform manner relative to the first segment and the third segment of the single wave portion.

[0080] In some embodiments, the first segment and the third segment of the single wave portion are substantially parallel to each other.

[0081] In some embodiments, the second segment of the single wave portion is inclined at an angle between 60° and 90°, more preferably at an angle of about 80°, relative to the first longitudinal direction.

[0082] In some embodiments, the length of the first segment of the single wave portion is substantially the same as the length of the third segment of the single wave portion.

[0083] Preferably, the length of the first segment and the third segment is between 1.5 mm and 3 mm, more preferably about 2 mm.

[0084] In some embodiments, the distance between the first wave crest and the first longitudinal direction is substantially the same as the distance between the second wave crest and the first longitudinal direction. Preferably, the distance is between 0.5 mm and 1.5 mm, more preferably about 1 mm.

[0085] In some embodiments, the length of the second linear portion is at least 50% greater, preferably at least 100% greater, and more preferably at least 200% greater relative to the length of the first linear portion.

[0086] In this way, the single wave portion of the first sipe is greatly offset from the center relative to the first and second portions, allowing it to be positioned near the edge of the block, where it can perform its role of reinforcing the block in an even more effective manner.

[0087] In some embodiments, the first longitudinal extension direction of the first incision intersects the first edge and the second edge of the block.

[0088] Preferably, the first linear portion extends towards the first edge.

[0089] Preferably, the second linear portion extends towards the second edge.

[0090] Preferably, the distance between the single wave portion and the first edge measured along the first longitudinal direction is between 5% and 40%, more preferably between 25% and 35%, of the distance between the first edge and the second edge measured along the first longitudinal direction.

[0091] In this way, the single wave portion of the sipe is positioned near the edge of the block, where it can perform its role of reinforcing the block in a more effective manner.

[0092] Preferably, a distance from the single wave portion to the second edge measured along the first longitudinal direction is at least twice a distance from the single wave portion to the first edge measured along the first longitudinal direction.

[0093] It may be noted that the distance of the single wave portion from the first edge or from the second edge, respectively, is measured from the center point of the single wave portion at the first edge and at the second edge, respectively.

[0094] In some embodiments, the first linear portion is open at the first edge of the block.

[0095] Preferably, the length of the first linear portion is between 2 mm and 5 mm.

[0096] Preferably, the depth of the first incision in the region of the first linear portion is smaller than the depth of the first incision in the region of the single wave portion.

[0097] In this way, the reinforcing effect of the block in the region of the first linear portion is advantageously increased.

[0098] In some embodiments, the second linear portion is open at the second edge of the block.

[0099] Preferably, the length of the second linear portion is between 4 mm and 25 mm.

[0100] Preferably, said second linear portion is substantially aligned with said first linear portion along said first longitudinal direction.

[0101] In some embodiments, the first sipe includes only a single wave portion.

[0102] In some embodiments, a plurality of sipes are further formed on the block, and the plurality of sipes are configured similarly to the at least one first sipe.

[0103] In some specific embodiments, a second sipe extending along a second longitudinal direction is further formed on the block.

[0104] Preferably, said second incision is consecutive to said first incision.

[0105] Preferably, said second incision is similar to said first incision.

[0106] It may be noted that a second incision is considered similar to a first incision when the same main element is present in the second incision, ie a single wave portion interposed between the first and second linear portions, albeit with different dimensions.

[0107] In particular, the second sipe preferably comprises:

[0108] - a first linear portion extending substantially along said second longitudinal direction,

[0109] - a single wave portion extending continuously with said first linear portion, and

[0110] - a second linear portion extending continuously with said single wave portion.

[0111] Preferably, the first linear portion and the second linear portion of the second sipe are straight lines or curves with a minimum curvature radius of not less than 20 mm.

[0112] Furthermore, the single wave portion of the second sipe preferably comprises:

[0113] a first section, said first section being inclined with respect to said second longitudinal direction and extending from said first linear portion up to a first crest of said second sipe,

[0114] a second segment inclined with respect to the second longitudinal direction and extending from the first wave peak of the second sipe to a second wave peak defined on a side opposite to the first wave peak with respect to the second longitudinal direction, and

[0115] - a third section inclined with respect to said second longitudinal direction and extending from said second wave crest of the second incision as far as said second linear portion of the second incision.

[0116] Preferably, the second segment of the second incision is inclined relative to the second longitudinal direction at an angle greater than the angles at which the first segment and the third segment of the second incision are inclined relative to the second longitudinal direction.

[0117] Preferably, the second sipe has only one single wave portion.

[0118] In some embodiments, the first longitudinal direction of the first incision and the second longitudinal direction of the second incision intersect the first edge and the second edge of the block.

[0119] Preferably, the first linear portion of said first incision is open at said first edge of said block.

[0120] Preferably, the distance between the single wave portion of the first incision pattern and the first edge measured along the first longitudinal direction of the first incision pattern is between 5% and 40%, more preferably between 25% and 35%, of the distance between the first edge and the second edge measured along the first longitudinal direction of the first incision pattern.

[0121] Preferably, said first linear portion of said second incision is open at said second edge of said block.

[0122] Preferably, the distance between the single wave portion of the second incision pattern and the second edge measured along the second longitudinal direction of the second incision pattern is between 5% and 40%, more preferably between 25% and 35%, of the distance between the second edge and the first edge measured along the second longitudinal direction of the second incision pattern.

[0123] In this way, the single wave portion of the first incision and the single wave portion of the second incision are positioned near opposite edges of the block, thereby applying their reinforcing effect to both sides of the block in order to obtain sufficient homogeneity of behavior.

[0124] Preferably, the first longitudinal direction of the first incision and the second longitudinal direction of the second incision are substantially parallel to each other.

[0125] Preferably, the first peak portion of the first incision closer to the first edge and the first peak portion of the second incision closer to the second edge are laterally offset on the same side relative to the first longitudinal direction of the first incision and the second longitudinal direction of the second incision, respectively.

[0126] In other words, the first, second and third segments of the first incision are inclined in a non-uniform manner with respect to the first or second longitudinal direction relative to the first, second and third segments of the second incision, respectively.

[0127] In this way, the second segments of the first and second sipes, which are intended to provide maximum resistance to longitudinal sliding of the block portion, are inclined in an inconsistent manner relative to each other so as to make the rigidity of the block essentially homogeneous when the block is subjected to a tangential stress parallel to and opposite to the first or second longitudinal direction.

[0128] In some embodiments, at least three sipes are formed in succession to each other on the block, and the at least three sipes are formed alternately and successively by one of the first sipes and one of the second sipes.

[0129] In some embodiments, a central block is formed on said tread band, said central block being delimited only by one or more grooves.

[0130] In some embodiments, each central block of said tread band comprises at least one of said first sipes.

[0131] Preferably, all the incisions formed on the central block of said tread band having a length greater than a minimum predetermined value are either one of said first incisions or one of said second incisions and more preferably have only one single wave portion.

[0132] Preferably, the minimum predetermined value is between 5 mm and 15 mm, for example, about 10 mm.

[0133] In this way, the sipe extends far enough to be able to have a configuration in which a single wave portion is interposed between two linear portions of suitable size.

[0134] In some embodiments, two single wave portions are defined on the first incision pattern and are separated from each other by the second linear portion.

[0135] In some embodiments, shoulder blocks are formed on said tread band, said shoulder blocks being partially delimited by axial ends of said tread band.

[0136] Preferably, the first sipe having two single wave portions defined thereon is formed on the shoulder block.

[0137] More preferably, each of the sipes formed on the shoulder blocks is one of the first sipes having two single wave portions which are spaced apart from each other by the second linear portion.

[0138] In some embodiments, the at least one sipe is compound. BRIEF DESCRIPTION OF THE DRAWINGS

[0139] The characteristics and advantages of the present invention will be better understood from the detailed description of a number of preferred embodiments shown by way of non-limiting examples with reference to the accompanying drawings, in which:

[0140] - Figure 1 is a schematic front view of a tread band portion of a tire for a vehicle wheel manufactured in accordance with the present invention;

[0141] - Figure 2 is Figure 1 A schematic front view, drawn on an enlarged scale, of a sipe pattern formed on a block of a tire. DETAILED DESCRIPTION

[0142] With reference to the accompanying drawings, there is indicated generally at 1 a tyre for vehicle wheels (not shown in its entirety) made in accordance with the invention.

[0143] The tyre 1 has a conventional generally toroidal shape, extending about an axis of rotation and defining an axial direction Y of the tyre, through which passes an equatorial plane X perpendicular to the axis of rotation.

[0144] The tyre 1 comprises a tread band 2 on which is defined a tread surface 3, arranged in a radially outer position relative to the tread band 2 and intended to come into contact with a road surface.

[0145] For example, the nominal section width of the tire 1 is about 205 mm and the rim diameter is 16 inches.

[0146] The tread band 2 still defines a central region extending circumferentially and symmetrically around the equatorial plane X and a pair of shoulder regions, which extend to corresponding axial ends of the tread band 2 at opposite axial sides of the central region.

[0147] A plurality of grooves are formed on the tread band 2, which are all marked 4 and which delimit a corresponding plurality of central blocks 5 formed in a central region of the tread band 2 and a plurality of shoulder blocks 6 formed in a shoulder region of the tread band 2, the shoulder blocks being delimited by the axial end 2a of the tread band 2 in their axially outer region.

[0148] In the embodiment described here, the grooves 4 have a depth between 3 mm and 9 mm and a width between 2.5 mm and 9.5 mm.

[0149] For example, Figure 1 One central block 5 and one shoulder block 6 are schematically shown, it being understood that the same considerations apply analogously to all other central blocks and all other shoulder blocks 6 formed in the tread band 2 .

[0150] The central block 5 is defined by: a tread surface portion 3, which is defined on the radially outer surface of the central block and is intended to come into contact with the road surface; a first edge 8 and a second edge 9 opposite to the first edge 8, which connect the tread surface portion 3 of the central block 5 to the wall of the corresponding groove 4.

[0151] The first edge 8 and the second edge 9 together delimit the tread surface portion 3 of the central block 5 and may be fully or partially chamfered.

[0152] A plurality of first sipes 10 and a plurality of second sipes 10 a are formed on each central block 5 in an alternating manner.

[0153] The first incisions 10 extend along respective first longitudinal directions A, while the second incisions 10a extend along respective second longitudinal directions B. All first longitudinal directions A and second longitudinal directions B are substantially parallel to each other.

[0154] In the illustrated embodiment of the central block 5 , the first longitudinal direction A and the second longitudinal direction B are inclined by about 60° relative to the equatorial plane X, but these directions can have a different inclination and can be parallel to the axial direction Y.

[0155] The first blocks 10 and the second blocks 10a are formed on the central block 5 in an alternating manner and are preferably equidistant, for example, with a spacing of between about 5 mm and about 6 mm.

[0156] The first incision 10 and the second incision 10a are arranged one after the other and have a similar structure, as will be better explained in detail below.

[0157] from Figure 2 As can be better seen in FIG. 5 , each first sipe 10 extends along the first longitudinal direction A in a manner straddling the central block 5 so as to be open at the first edge 8 and the second edge 9 .

[0158] Each first sipe 10 includes a first linear portion 11 open at the first edge 8 , a single wave portion 12 extending continuously with the first linear portion 11 , and a second linear portion 13 extending continuously with the single wave portion 12 and open at the second edge 9 .

[0159] Both the first linear portion 11 and the second linear portion 13 are substantially straight and aligned along the first longitudinal direction A.

[0160] The length of the second linear portion 13 may be greater than that of the first linear portion 11 , preferably, it is at least 50% greater than the first linear portion 11 , more preferably at least 100% greater, even more preferably at least 200% greater.

[0161] The length of the first linear portion 11 is between 2 mm and 5 mm, and the length of the second linear portion 13 is between 4 mm and 25 mm.

[0162] The single wave portion 12 includes:

[0163] a first substantially rectilinear segment 14 which extends from the first linear portion 11 up to the first wave crest 15 and is inclined relative to the first longitudinal direction A;

[0164] a substantially rectilinear second segment 16 extending from the first wave crest 15 as far as a second wave crest 17 defined on a side opposite to the first wave crest 15 with respect to the first longitudinal direction A; and

[0165] a substantially rectilinear third section 18 which extends from the second wave crest 17 to the second linear portion 13 and which is inclined relative to the first longitudinal direction A.

[0166] The first segment 14 and the third segment 18 are substantially parallel to each other and are inclined by about 30° with respect to the first longitudinal direction A. Furthermore, the first segment 14 and the third segment 18 have substantially equal lengths of about 2 mm.

[0167] In a manner that is not consistent with the first section 14 and the third section 18 relative to the first longitudinal direction A, the second section 16 is inclined by approximately 80° relative to the first longitudinal direction A.

[0168] The first wave crest 15 and the second wave crest 17 each have substantially the same distance from the first longitudinal direction A, which is equal to about 1 mm.

[0169] Thus, the single wave portion 12 is substantially symmetrical about the point at which the second segment 16 intersects the first longitudinal direction A defined by the first linear portion 11 and the second linear portion 13 .

[0170] Each first incision 10 has a width of about 0.5 mm and a variable depth between 3 mm (at its end regions, in particular at the first linear portion 11 ) to about 7 mm (at the single wave portion 12 and the central region of the first incision 10 ).

[0171] Each first incision 10 is also preferably of compound type, having along its radial section one or more protrusions and corresponding recesses which hinder free sliding in the radial direction of the parts of the central block 5 separated by this first incision 10 .

[0172] As mentioned above, the second incisions 10a are similar to the first incisions 10. In fact, in each second incision 10a, a first linear portion 11 can be identified, which is followed by a single wave portion 12 and thus by a second linear portion 13 which is longer than the first linear portion 11.

[0173] Each second incision 10a differs from any first incision 10 in that, in the second incision 10a, the first linear portion 11 is open at the second edge 9 (as well as at the first edge 8), and the second linear portion 13 is open at the first edge 8 (as well as at the second edge 9).

[0174] Since the first incisions 10 and the second incisions 10a are arranged in an alternating manner, the single wave portions 12 of both the first incisions 10 and the second incisions 10a are positioned in an alternating manner near the first edge 8 and the second edge 9 so as to reinforce these edges of the central block 5 in a substantially homogeneous manner.

[0175] Furthermore, the first wave peak 15 of each first incision 10 and the first wave peak 15 of each second incision 10a are laterally offset on the same side with respect to the respective longitudinal directions A and B.

[0176] Such a configuration may be obtained by configuring the sipes 10 and 10a in such a way that the first segment 14, the second segment 16 and the third segment 18 of the first sipe 10 are inclined relative to the first longitudinal direction A in a manner that is inconsistent with the first segment 14, the second segment 16 and the third segment 18 of the second sipe 10a.

[0177] Preferably, all the sipes formed on the central block 5 are first sipes 10 or second sipes 10a, provided that the total length thereof is greater than a minimum value of about 10 mm.

[0178] In the case where a sipe with a smaller size is provided on the central block 5, as Figure 1In the case of the corner regions shown (here the sipes are referenced 19), the sipes may have different configurations, for example a straight configuration or a wavy configuration with a single wave crest.

[0179] A plurality of third sipes 20 are formed on the shoulder block 6 , and extend parallel to each other along respective third longitudinal extension directions A′, which are substantially different from the first A and second B longitudinal directions.

[0180] The third incision 20 is similar to the first incision 10 and the second incision 10a formed on the central block 5, but unlike the first incision 10 and the second incision 10a having only one single wave portion 12, the third incision 20 has two single wave portions. In fact, each third incision 20 can be regarded as a first incision 10 having two single wave portions.

[0181] Therefore, each third sipe pattern 20 includes: a first linear portion 21, which is open at the first edge 7 of the shoulder block 6; a first single wave portion 22, which extends continuously with the first linear portion 21; a second linear portion 23, which extends continuously with the first single wave portion 22; a second single wave portion 24, which extends continuously with the second linear portion 23; and a third linear portion 25, which extends continuously with the second single wave portion 24 until the axial end 2a of the tread band 2.

[0182] It may be noted that the third linear portion 25 may be considered as a first linear portion of the second single wave portion 24 , the second linear portion 23 being common to both single wave portions 22 and 24 .

[0183] The single wave portions 22 and 24 of the sipe 20 are completely similar to the single wave portion 12 described in detail above with reference to the first and second sipes 10 and 10a.

[0184] The Applicant has verified that central blocks 5 and shoulder blocks 6 provided with a plurality of sipes as described above provide the best resistance to tangential stresses directed in the direction of longitudinal development, thus improving the performance level on icy and dry roads.

[0185] Of course, in order to meet specific and accidental application requirements, those skilled in the art may make additional modifications and variations to the above invention, and these modifications and variations are still included in the protection scope defined by the attached claims.

[0186] For example, the number of first sipes and / or second sipes present on the central block may be different from the above number, and there may also be sipes with different configurations or sipes with multiple single wave portions on the central block, for example, the third sipe in the shoulder block described herein.

Claims

1. A tire (1) comprising a tread band (2), a tread surface (3) located radially outward relative to the tread band, a plurality of blocks (5, 6) defined on the tread band (2) and at least one first sipe (10; 20), wherein the first sipe pattern (10; 20) being open at the tread surface (3) so as to define a first longitudinal extension direction (A) of the first sipe (15), wherein the first sipe comprises: - a first linear portion (11) extending substantially along said first longitudinal direction (A), - a single wave portion (12) extending continuously with the first linear portion (11), and - a second linear portion (13) extending continuously with the single-wave portion (12), The first linear portion (11) and the second linear portion (13) are straight lines or curves with a minimum curvature radius of not less than 20 mm. Wherein, the single wave part (12) comprises: a first section (14) which is inclined relative to the first longitudinal direction (A) and which extends from the first linear portion (11) to a first wave crest (15), a second section (16) which is inclined relative to the first longitudinal direction (A) and extends from the first wave crest (15) to a second wave crest (17) which is defined on the side opposite to the first wave crest (15) relative to the first longitudinal direction (A), and a third section (18) which is inclined relative to the first longitudinal direction (A) and extends from the second wave crest (17) to the second linear portion (13), And wherein the angle at which the second segment (16) is inclined relative to the first longitudinal direction (A) is greater than the angle at which the first segment (14) and the third segment (18) are inclined relative to the first longitudinal direction.

2. The tire (1) according to claim 1, wherein: The first segment (14) and the third segment (18) of the single wave portion (12) are inclined at an angle between 20° and 45° relative to the first longitudinal direction (A).

3. The tire (1) according to claim 1 or 2, wherein: The second segment (16) of the single wave portion (12) is inclined at an angle between 60° and 90° relative to the first longitudinal direction (A).

4. Tyre (1) according to any one of the preceding claims, wherein: The first segment (14) and the third segment (18) of the single wave portion (12) are substantially parallel.

5. Tyre (1) according to any one of the preceding claims, wherein: The length of the first segment (14) of the single wave portion (12) is substantially the same as the length of the third segment (18) of the single wave portion (12).

6. Tyre (1) according to any one of the preceding claims, wherein: The distance between the first wave crest portion (15) and the first longitudinal direction (A) is substantially the same as the distance between the second wave crest portion (17) and the first longitudinal direction (A).

7. Tyre (1) according to any one of the preceding claims, wherein: The length of the second linear portion (13) is at least 50% greater than the length of the first linear portion (11).

8. The tire (1) according to claim 7, wherein: The length of the second linear portion (13) is at least 100% greater than the length of the first linear portion (11).

9. The tyre (1) according to claim 8, wherein: The length of the second linear portion (13) is at least 200% greater than the length of the first linear portion (11).

10. Tyre (1) according to any one of the preceding claims, wherein: The first longitudinal extension direction (A) of the first sipe pattern (10) intersects the first edge (8) and the second edge (9) of the block, the first linear portion (11) extends toward the first edge (8), the second linear portion (13) extends toward the second edge (9), and wherein the distance between the single wave portion (12) and the first edge (8) measured along the first longitudinal direction (A) is between 5% and 40% of the distance between the first edge (8) and the second edge (9) measured along the first longitudinal direction (A).

11. The tyre (1) according to claim 10, wherein: The distance between the single wave portion (12) and the second edge (9) measured along the first longitudinal direction (A) is at least twice the distance between the single wave portion (12) and the first edge (8) measured along the first longitudinal direction (A).

12. Tyre (1) according to claim 10 or 11, wherein: The first linear portion (11) is open at the first edge (8) of the block (5).

13. Tyre (1) according to any one of the preceding claims, wherein: The first linear portion (11) has a length between 2 mm and 5 mm.

14. Tyre (1) according to any one of the preceding claims, wherein: The depth of the first sipe (10) in the region of the first linear portion (11) is smaller than the depth of the first sipe (10) in the region of the single wave portion (12).

15. Tyre (1) according to any one of claims 10 to 14, wherein: The second linear portion (13) is open at the second edge (9) of the block (5).

16. Tyre (1) according to any one of the preceding claims, wherein: The second linear portion (13) has a length between 4 mm and 25 mm.

17. Tyre (1) according to any one of the preceding claims, wherein: The second linear portion (13) is substantially aligned with the first linear portion (11) along the first longitudinal direction (A).

18. Tyre (1) according to any one of the preceding claims, wherein: The first sipe (10) comprises only a single wave portion (12).

19. Tyre (1) according to any one of the preceding claims, wherein: A second sipe (10a) extending along a second longitudinal direction (B) is also formed on the block (5), the second sipe being consecutive to the first sipe (10) and having: - a first linear portion (11) extending substantially along said second longitudinal direction (B), - a single wave portion (12) extending continuously with said first linear portion (11), and - a second linear portion (13) extending continuously with the single-wave portion (12), The first linear portion (11) and the second linear portion (13) are straight lines or curves with a minimum curvature radius of not less than 20 mm.

20. Tyre (1) according to claim 19, wherein: The first incision and the second incision each have only one single wave portion (12).

21. Tyre (1) according to claim 20, wherein: The first longitudinal direction (A) of the first sipe (10) and the second longitudinal direction (B) of the second sipe (10a) intersect the first edge (8) and the second edge (9) of the block (5), and wherein: - said first linear portion (11) of said first sipe (10) is open at said first edge (8) of said block, - the distance between the single wave portion (12) of the first sipe (10) and the first edge (8), measured along the first longitudinal direction (A) of the first sipe, is between 5% and 40% of the distance between the first edge (8) and the second edge (9), measured along the first longitudinal direction of the first sipe (10), - said first linear portion (11) of said second sipe (10a) is open at said second edge (9) of said block (5), and - the distance between the single wave portion (12) of the second sipe (10a) and the second edge (9) measured along the second longitudinal direction (B) of the second sipe (10a) is between 5% and 40% of the distance between the second edge (9) and the first edge (8) measured along the second longitudinal direction (B) of the second sipe (10a).

22. Tyre (1) according to claim 21, wherein: The first longitudinal direction (A) of the first incision (10a) and the second longitudinal direction (B) of the second incision (10a) are substantially parallel to each other.

23. Tyre (1) according to any one of claims 19 to 22, wherein: The first wave peak portion (15) of the first sipe (10) closer to the first edge (8) and the first wave peak portion (15) of the second sipe (10a) closer to the second edge (9) are laterally offset on the same side relative to the first longitudinal direction (A) of the first sipe and the second longitudinal direction (B) of the second sipe (10a), respectively.

24. Tyre (1) according to any one of claims 19 to 23, wherein: At least three sipes are formed successively on the block (5), and the at least three sipes are formed alternately and successively by one of the first sipes (10) and one of the second sipes (10a).

25. Tyre (1) according to any one of the preceding claims, wherein: Central blocks (5) are formed on said tread band (2), said central blocks being delimited only by one or more grooves (4), each central block (5) comprising at least one of said first sipes (10).

26. Tyre (1) according to claim 25, wherein: All sipes formed on the central block (5) of the tread band (2) and having a length greater than a minimum predetermined value are either one of the first sipes (10) or one of the second sipes (10a) and have only one single wave portion (12).

27. Tyre (1) according to any one of the preceding claims, wherein: A shoulder block (6) is formed on the tread band (2), the shoulder block being partially defined by an axial end (2a) of the tread band, and wherein each sipe (20) formed on the shoulder block (6) is one of the first sipes having two single wave portions (22, 24) separated from each other by the second linear portion (23).

Images