EP4638151A1

EP4638151A1 - Studded tyre for vehicle wheels

Info

Publication number: EP4638151A1
Application number: EP23837768.3A
Authority: EP
Inventors: Diego Ettore Speziari; Giovanni Casarotto; Riccardo Guerra
Original assignee: Pirelli SpA; Pirelli Tyre SpA
Current assignee: Pirelli and C SpA; Pirelli Tyre SpA
Priority date: 2022-12-21
Filing date: 2023-12-11
Publication date: 2025-10-29
Also published as: WO2024134351A1; CN120359130A

Abstract

A studded tyre comprises a tread band (2), on which there are defined a plurality of blocks (5) and a plurality of studs (9) which are arranged on at least some of said blocks. On each block (5) on which a stud (9) is provided there is defined a protuberance (10) which is spaced apart from said stud and which extends continuously around said stud (9) over an angular extent greater than or equal to 270°. The protuberance (10) is delimited at its opposite sides by an internal channel (20) and by an external channel (30), which are both continuous.

Description

STUDDED TYRE FOR VEHICLE WHEELS

The present invention relates to a studded tyre for vehicle wheels.

A tyre generally comprises a carcass structure which is formed toroidally about a rotation axis and which includes at least one carcass ply which has terminal flaps which engage in respective annular anchoring structures, known as bead cores.

In a radially external position with respect to the carcass structure, there is provided a belt structure comprising, in the case of tyres for cars, at least two radially superimposed strips of rubberized fabric provided with reinforcement cords, which are usually made of metal and which are arranged in each strip in a mutually parallel manner but cross-wise with respect to the cords of the adjacent strip, preferably symmetrically with respect to the equatorial plane of the tyre.

Preferably, the belt structure further also comprises in a radially external position, at least at the ends of the belt strips below, a third layer of textile or metal cords which are arranged circumferentially (at 0 degrees). In tyres of the tubeless type, there is further present a radially internal layer called a "liner" which has characteristics of impermeability in order to allow the air-tightness for the tyre itself.

In a radially external position with respect to the belt structure, there is applied a tread band which is made of elastomer material and on which there is defined a tread surface which is intended for contact with the road surface.

The tyres, in order to obtain adequate road grip on a wet road surface, have a tread band which is provided with grooves of various formations and geometries which delimit tread band portions which are intended for contact with the ground, called blocks.

The main function of the grooves is to allow the discharge of the water present between the surface of the tyre and the road surface during mutual contact, preventing the hydrostatic pressure resulting from the impact of the water against the advancing tyre from being able to cause even partial lifting of the tyre off the road surface and the consequent loss of control of the vehicle.

The overall configuration of the tread band defined by the assembly of grooves and blocks constitutes the tread pattern.

The tread pattern is typically formed by the successive and continuous repetition along the entire circumferential development of the tread band of the same basic module.

In the case of winter tyres, there are formed on the blocks of the tread band small notches, called "sipes", which extend from the tread surface of the tyre towards the interior of the block. The function of the sipes is to provide additional grip elements in the case of travel on a snow-bound surface and to retain a specific quantity of snow, thereby improving the grip with respect to the road surface.

Furthermore, in some winter tyres there are provided on the tread band studs which, thanks to a portion thereof which projects from the tread surface (pin), improves the gripping characteristics of the tyre on the ice-bound road surface.

The term "equatorial plane" of the tyre is intended to be an axial centre plane which is perpendicular to the rotation axis of the tyre.

The term "circumferential" direction is intended to be a direction which is generally directed in the rotation direction of the tyre or which, at most, is slightly inclined (at most by approximately 5°) with respect to the rotation direction of the tyre.

The term "axial" direction is intended to be a direction which is substantially parallel with the rotation axis of the tyre or which is, at most, slightly inclined (at most by approximately 5°) with respect to this rotation axis of the tyre. The axial direction is generally perpendicular to the circumferential direction.

The term "tread surface" is intended to be the radially external surface portion of the tread band which is intended to come into contact with the road surface when the tyre is caused to roll.

The term "groove" is intended to be a recess which is formed in a tread band portion and which has a width greater than or equal to 1.5 mm and a depth greater than 3 mm.

The term "block" is intended to be a tread band portion which is delimited by grooves or by a lateral edge of the tread band and the radially external surface of which is intended for contact with the road surface when the tyre is caused to roll.

The term "sipe" is intended to be a recess which is formed in a tread band portion and which has a width less than 1.5 mm, preferably less than or equal to 1 mm.

The term "height" of a tread band region, such as a block or a portion thereof, is intended to be the radial dimension of this tread band region. Therefore, a first region has a lower height than a second region when the first region has a distance from the rotation axis of the tyre which is less than the second region.

The term "channel" is intended understood to be a recess which is formed in a block. In other words, a channel is a block region having a height lower than the height of an adjacent block region which delimits the channel. Preferably, a channel has a height less than the height of the tread surface. Preferably, a channel has a main longitudinal dimension. Preferably, a channel has a depth less than 3 mm.

A channel is "continuous" or "extends continuously" when inside the channel there are block portions (reliefs) having a height greater than or equal to the block region adjacent to the channel. In other words, a channel is continuous when it is substantially free from obstructions. Preferably, any reliefs which are present inside a continuous channel have a depth less than or equal to half of the depth of the channel. Preferably, any reliefs present inside a continuous channel have a depth of at least 0.2 mm.

The term "protuberance" is intended to be a block portion which rises with respect to the block zone immediately adjacent. In other words, a protuberance is a block region having a height greater than the height of an adjacent block region which delimits the protuberance. Preferably, a protuberance has a main longitudinal dimension. Preferably, a protuberance is delimited laterally by walls which are inclined with respect to the block region which is adjacent thereto at an angle greater than 60°, more preferably of approximately 90°.

A protuberance is "continuous" or "extends continuously" when it does not have interruptions, that is to say, when the height thereof always remains greater than the adjacent block region.

The term "width" of a groove, a protuberance, a channel or a portion thereof is intended to be the dimension parallel with the tread surface and perpendicular to the main longitudinal extent of the groove, protuberance, channel or portion thereof.

The width of a channel, groove or a portion thereof is intended to be measured at a depth equal to approximately half of the total depth of the recess or the portion thereof.

If the width of the groove, protuberance or channel varies along the longitudinal development thereof, the mean width, the value of which is obtained as the mean of different width values which are suitably weighted in accordance with the relative longitudinal extents, is considered. For example, if a groove has a width of 5 mm over 80% of the longitudinal extent thereof and a width of 3 mm for the remaining 20%, the mean value of the width to be considered will be equal to 5 x 0.8 + 3 x 0.2 = 4.6 mm.

A channel or a group of channels which communicate with each other is "closed" when the contour of the channel or the group of communicating channels remains confined at the radially external surface of the block or, in other words, when this channel or group of communicating channels is not open at a flank of the block. The term "tread pattern" is intended to be the overall configuration of the tread band as defined by the assembly of the grooves and blocks which are delimited thereby. In accordance with the configuration of the tread, there may be defined on a tyre a preferential rolling direction. In this case, the tyre is referred to as being of the "directional" type and it is configured to be mounted on the vehicle so that the tyre, during travel of the vehicle in a forward direction, is rotated in the preferential rolling direction.

The term "footprint area" is intended to be the portion of tread band which is instantaneously in contact with the road surface during the rotation of the tyre. Under real conditions, the footprint area is a function of different parameters, including the inflation pressure of the tyre, the load to which it is subjected, the road surface and the driving conditions, for which reference values can, however, be defined.

The Applicant has observed that, during travel of a studded tyre on an ice-bound road surface, the stud may carry out an action of eroding the ice with a resultant production of powdered ice.

In particular, the Applicant has observed that the powdered ice tends to accumulate in the immediate vicinity of the stud, but thereby reducing the projecting portion of stud which can cut into the road surface.

In fact, the stud portion which projects from the tread surface may be, partially or completely, embedded in the powdered ice which has accumulated around the stud. Clearly, this situation makes the gripping action of the stud on the road surface very ineffective or completely ineffective and is therefore highly undesirable.

Naturally, the action of erosion of the ice-bound road surface and the resultant production of powdered ice is more pronounced when the tyre is slithering on the road surface, as may occur in the case of abrupt acceleration or sharp braking or rapid steering.

The Applicant has observed that there are known solutions which provide for forming around the stud a recess which is suitable for collecting a specific quantity of powdered ice with the intention of limiting the effects of accumulating powdered ice around the stud.

WO 2018202341, US 2019/0135047, JP 62723393 describe respective solutions for studded tyres, in which one or more recesses, which are formed in various manners and where powdered ice can be collected, are formed around the studs.

However, the Applicant has verified that the provision of collecting recesses for the powder was not by itself sufficient to solve this problem and has therefore considered that it was necessary not only to form around the stud suitable regions which are suitable for accumulating the powdered ice eroded by the stud, but also to provide for expelling the powdered ice which is accumulated in these regions so as to release space for receiving any additional powdered ice which is eroded subsequently by the stud.

Therefore, the Applicant has found that, by proving around the stud a protuberance which extends continuously around the stud over an angular extent which is sufficiently extensive and which is delimited laterally by respective channels which also extend continuously, there is conferred on the protuberance a high level of deformability which, particularly during the steps of entrance into and exit from the footprint area, produces a contraction and expansion movement of the channels which are adjacent thereto, which promotes the discharge of the powdered ice which may have accumulated therein.

In particular, in a first aspect thereof, the invention relates to a studded tyre comprising a tread band, on which there are defined a plurality of blocks and a plurality of studs which are arranged on at least some of said blocks.

Preferably, on each of the blocks on which a stud is provided there is defined a protuberance.

Preferably, said protuberance is spaced apart from said stud.

Preferably, said protuberance extends around said stud over an angular extent greater than or equal to 270°.

Preferably, said protuberance extends continuously around said stud.

Preferably, said protuberance is delimited at its individual opposite sides by an internal channel and by an external channel.

Preferably, said internal channel is continuous.

Preferably, said external channel is continuous.

The Applicant has verified that, as a result of this configuration of the region surrounding the stud, any powdered ice which is eroded by the stud can be initially collected in the two channels which delimit the protuberance and subsequently expelled from the channels as a result of the deformation of the protuberance which contracts and dilates the two channels during the rolling movement of the tyre.

In fact, as a result of the peculiar shape thereof, the protuberance has a high level of deformability in the event of external stresses, for example, at entering into the footprint area, so as to become bent towards one of the two channels which flank it, reducing the section thereof and, at the same time, widening the section of the other channel.

Upon leaving the footprint area, the protuberance which is unloaded in terms of the pressure of the vehicle, resiliently returns to the original configuration thereof together with the two channels adjacent thereto, bringing about a pulse which tends to expel any powdered ice which is present in the channels.

This advantageously allows the accumulation of powdered ice, which would tend, once the channels are filled, to cover the protruding portion of the stud, limiting the efficiency thereof, to be avoided or at least reduced.

The studs can thereby maintain, during travel on ice-bound surfaces, a greater efficiency of grip and provide the studded tyre with better performance levels in terms of road-holding both during the traction phase (both accelerating and braking) and when driving round bends.

The present invention, in the above-mentioned aspect, may have at least one of the additional preferred features indicated below.

In some embodiments, said protuberance is completely delimited along the entire perimeter thereof by said internal channel, by said external channel and by two auxiliary channels which connect said internal channel to said external channel.

In some embodiments, said internal channel, said external channel and said auxiliary channels generally have a closed contour.

In some embodiments, said protuberance extends between a first end and a second end which is spaced apart from said first end.

The protuberance thereby extends along an open line.

Preferably, the protuberance extends along a line without any branches.

The protuberance is thereby more deformable.

In some embodiments, said auxiliary channels connect said internal channel to said external channel in the region of said first end and said second end, respectively.

In some embodiments, each of said auxiliary channels has a width less than said internal channel and said external channel.

In some embodiments, said protuberance extends around said stud in a symmetrical manner with respect to an axis of symmetry which passes through said stud.

Preferably, said internal channel extends around said stud in a symmetrical manner with respect to said axis of symmetry.

Preferably, said external channel extends around said stud in a symmetrical manner with respect to said axis of symmetry.

In some embodiments, said first end and said second end of said protuberance have a distance between 3 mm and 8 mm, preferably between 4 mm and 6 mm, more preferably of approximately 5 mm.

In some embodiments, said internal channel extends into an opening which is defined between said first end and said second end of said protuberance.

In this manner, there is defined between the two ends of the protuberance a more extensive region which is intended for collecting the powdered ice. As a result of the relatively small distance between the two ends of the protuberance, furthermore, the region corresponding to this opening is also subjected to contractions and expansions which are caused by the deformations of the protuberance, particularly the deformations in the region of the ends thereof.

Preferably, said internal channel is connected to a tread surface portion of said block by means of a chamfer in the region of said opening.

The discharge of the powdered ice from the opening region is thereby promoted.

In some embodiments, said internal channel, except for the portion in the region of the opening, has a width between 0.5 mm and 1.5 mm, preferably of approximately 1 mm.

Preferably, said internal channel, except for the portion in the region of the opening, has a substantially constant width.

In some embodiments, said external channel has a width between 0.5 mm and 1.5 mm, preferably of approximately 1 mm.

Preferably, said external channel has a substantially constant width.

In some embodiments, said protuberance, said internal channel and said external channel, over a fraction of at least 80% of the respective longitudinal extents thereof, have a substantially mutually identical width.

In some embodiments, the protuberance extends continuously around the stud over an angular extent greater than or equal to 300°.

In some embodiments, the protuberance has a width between 0.5 mm and 1.5 mm, preferably of approximately 1 mm.

Preferably, the protuberance has a substantially constant width along the longitudinal development thereof.

In this manner, the characteristics of deformability and mechanical strength of the protuberance are optimized.

In some embodiments, the distance of said protuberance from said stud is variable along the longitudinal development of the protuberance and is preferably between 1.5 mm and 4 mm. In some embodiments, said protuberance is substantially coplanar with a portion of tread surface of said block adjacent to said external channel at the side opposite said protuberance.

In this manner, the protuberance has the same height as the tread surface of the block, as a result of which it comes into contact with the road surface under the same conditions as the block. In fact, an excessively projecting protuberance from the tread surface could be worn prematurely while an excessively lowered protuberance with respect to the tread surface could be insufficiently deformed when it moves into the footprint area.

In some embodiments, said protuberance comprises a first substantially rectilinear portion. Preferably, said first portion terminates as said first end.

In some embodiments, said protuberance comprises a second substantially rectilinear portion. Preferably, said second portion terminates as said second end.

In some embodiments, said first portion and said second portion extend from said first end and from said second end, respectively, so as to diverge from each other.

In some embodiments, said first portion and said second portion are inclined with respect to said axis of symmetry at an angle between 10° and 30°, preferably at an angle between 15° and 20°.

In some embodiments, said protuberance comprises a curvilinear portion which extends in an intermediate position between said first end and said second end. Preferably, said curvilinear portion connects said first portion to said second portion. Preferably, said curvilinear portion is a circumferential arc, more preferably it is a circumferential arc which is concentric with said stud.

In some embodiments, said curvilinear portion extends around said stud over an angular extent between 90° and 180°, preferably between 120° and 170°.

In some embodiments, said internal channel is lowered with respect to a portion of tread surface of said block by a height between 0.2 mm and 1.5 mm, preferably approximately 0.5 mm.

In some embodiments, said external channel is lowered with respect to a portion of tread surface of said block by a height between 0.2 mm and 1.5 mm, preferably approximately 0.5 mm.

In this manner, the internal channel and the external channel define a volume sufficient to collect the powdered ice but without substantially reducing the capacity for retaining the stud inside the individual seat.

In some embodiments, said internal channel is separated from said stud by an island, in which there is formed a seat for receiving said stud.

Preferably, said internal channel completely surrounds said island.

In some embodiments, said island is substantially coplanar with a portion of tread surface of said block adjacent to said external channel at the side opposite said protuberance.

In some embodiments, said island is substantially coplanar with said protuberance.

In this manner, the island has the same height as the tread surface of the block and/or the protuberance.

In some embodiments, said island is partially delimited by walls which are parallel with said protuberance.

Preferably, said island separates said block from said internal channel by a distance of at least 1 mm.

The capacity for retaining the stud inside the individual seat is thereby preserved. In some embodiments, a preferential rolling direction is defined on said tread band. In some embodiments, said first end and said second end of said protuberance are positioned downstream of said stud with respect to said preferential rolling direction. In this manner, the opening defined between the end of the protuberance is also downstream of the stud, providing a greater volume for the powdered ice produced in a potential braking operation.

In some embodiments, said axis of symmetry of said protuberance is inclined with respect to a circumferential direction which is defined on said tread band at an angle between 0° and 30°.

In some embodiments, there is defined on said tread band an equatorial plane which divides said tread band into a first region of tread band and a second region of tread band.

In some embodiments, for each stud which is positioned on said tread band said axis of symmetry of said protuberance is inclined so that said first end and said second end are directed towards said equatorial plane.

Preferably, for each stud which is positioned on said first region of tread band said axis of symmetry of said protuberance is parallel with a first direction which is inclined with respect to said equatorial plane at an angle between 0° and 30°.

Preferably, for each stud which is positioned on said second region of tread band said axis of symmetry of said protuberance is parallel with a second direction which is inclined with respect to said equatorial plane at an angle between 0° and 30°.

Preferably, said first direction and said second direction are symmetrical with respect to said equatorial plane.

The features and advantages of the invention will be better appreciated from the detailed description of a preferred embodiment thereof, which is illustrated by way of non-limiting example with reference to the appended drawings, in which:

- Figure 1 is a schematic view of a representative tread band portion of a studded tyre for vehicle wheels constructed according to the present invention;

- Figure 2 is a schematic, perspective view, drawn to an enlarged scale, of a portion of a block of the tyre of Figure 1, and

- Figure 3 is a schematic plan view of the block of Figure 2.

With reference to the appended Figures, there is generally designated 1 a studded tyre for vehicle wheels constructed according to the present invention.

The studded tyre 1 comprises a tyre structure which is conventional per se and which is not illustrated in the appended Figures and a tread band 2, on which there is defined a tread surface 3 which is arranged in a radially external position with respect to the tread band 2 and which is intended for contact with a road surface.

The tyre 1 has a conventional, generically toroidal shape which develops about a rotation axis, defining on the tread surface 3 an axial direction which is parallel with the rotation axis and which is passed through by an equatorial plane X which is perpendicular to the rotation axis and which defines on the tread surface 3 a circumferential direction which is parallel therewith.

The equatorial plane X subdivides the tread band 2 into a first tread band region 7 and a second tread band region 8 with equal widths. There are formed on the tread band 2 a plurality of grooves which are all designated 4 and which at least partially delimit a plurality of blocks 5.

The configuration of the grooves 4 and the blocks 5 generally define the tread pattern of the tyre 1 which, in the preferred case described here, is a tyre of the directional type, in which there is defined a preferential rolling direction of the tyre which is denoted in Figure 1 with the arrow F.

Each block 5 has a radially external surface 6 which belongs to the tread surface 3, on which a plurality of sipes 5a are preferably formed.

Some blocks 5 are provided with one or more studs 9 which are configured to provide effective gripping edges for travel on ice-bound road surfaces and which are received in respective seats 36 in accordance with methods which are conventional per se.

Each stud 9 which is made from metal material comprises a base which is embedded inside the tread band 2, a head which is radially external with respect to the base and a gripping extension piece 9a which extends radially from the head of the stud so as to project from the tread surface 3.

There is provided around each stud 9 on the block 5 a clearance area which is substantially circular and which is centred on the stud 9 (indicated with broken lines in Figure 1), with a diameter of approximately from 15 to 20 mm, wherein any sipes 5a are interrupted.

A protuberance 10, which is spaced apart from the stud 9 and which extends continuously around the stud 9 over an angular extent greater than or equal to 270°, for example, approximately 310°, is defined on the block 5 inside the clearance area. The protuberance 10 extends along a longitudinal development line between a first end 11 and a second end 12 which are spaced apart from each other by approximately 5 mm.

The protuberance 10 is delimited at its opposite sides by an internal channel 20 and by an external channel 30.

Both the internal channel 20 and the external channel 30 are continuous and, in particular, have a substantially constant depth of approximately 0.5 mm with respect to the tread band portion 6 and which is identical for both channels.

In the region of the first end 11 and the second end 12, the internal channel 20 and external channel 30 are connected to each other by auxiliary channels 21 having identical depths and widths which are smaller with respect to the internal channel 20 and external channel 30.

Therefore, the protuberance is completely surrounded along the entire perimeter thereof by the internal channel 20, external channel 30 and the two auxiliary channels 21.

The internal channel 20, external channel 30 and the two auxiliary channels 21 therefore define a block portion with a lowered height with respect to the tread surface portion 6 and generally have a closed contour.

The protuberance 10, except for the portions in the region of the first end 11 and the second end 12, has a substantially constant width between 0.5 mm and 1.5 mm, for example, of approximately 1 mm, and is substantially coplanar with the tread surface portion 6 adjacent to the external channel 30 at the opposite side to the protuberance 10.

The protuberance 10 extends around the stud 9 symmetrically with respect to an axis of symmetry M which passes through the stud 9 and comprises a first portion 13, which is substantially rectilinear and terminates with the first end 11, a second portion 14 which is also substantially rectilinear and terminates with the second end 12, and a curvilinear portion 15 which connects the first portion 13 to the second portion 14.

The first portion 13 and the second portion 14 extend from the first end 11 and the second end 12, respectively, so as to diverge from each other, with an inclination of approximately 18° with respect to the axis of symmetry M.

The curvilinear portion 15 is a circumferential arc which is concentric with the stud 9 (in Figure 3, the centre axis of the stud is defined with the centre 0 of the seat 36 thereof) and extends around the stud 9 over an angular extent between 90° and 180°, for example, of approximately 140°.

The internal channel 20 is separated from the stud 9 by an island 35, in which the seat 36 for receiving the stud 9 is formed. The island 35 is further substantially coplanar with the tread surface portion 6 adjacent to the external channel 30 at the side opposite the protuberance 10.

The internal channel 20 therefore completely surrounds the island 35, but remaining spaced apart from the seat 36 by at least 1 mm.

The internal channel 20 has a constant width between 0.5 mm and 1.5 mm, for example, of approximately 1 mm in the portion between the island 35 and the protuberance 10.

The internal channel 20 further comprises a portion with a greater width, in the region of an opening 25 which is defined between the first end 11 and the second end 12 of the protuberance 10.

Similarly, the external channel 30 also has a constant width between 0.5 mm and 1.5 mm, for example, of approximately 1 mm in the portion between the tread surface portion 6 and the protuberance 10.

Therefore, it will be noted that the internal channel 20, the external channel 30 and the protuberance 10 substantially have the same width over a main portion (greater than 80%) of the respective longitudinal extent thereof.

The internal channel 20, in the region of the opening 25, and the auxiliary channels 21 and the terminal portion of the external channel 30 in the region of the first end 11 and the second end 12 of the protuberance 10, are connected to the tread surface portion 6 of the block 5 by means of a chamfer 26.

Each stud 9 with the respective protuberance 10 and the respective internal and external channels 20, 30 is arranged on the different blocks 5 of the tread band 2 in such a manner that the first end 11 and the second end 12 of the protuberance 10 are positioned downstream of the stud 9 with respect to the preferential rolling direction F.

In particular, in each stud positioned in the first region 7 of tread band, the respective axis of symmetry M of the protuberance 10 is inclined so that the first end 11 and the second end 12 of the protuberance 10 are directed towards the equatorial plane X and, furthermore, this axis of symmetry M is substantially parallel with a first direction A which is inclined with respect to the equatorial plane X by an angle less than 30°, for example, approximately 15°.

Similarly, in each stud positioned in the second region 8 of tread band, the respective axis of symmetry M of the protuberance 10 is inclined so that the first end 11 and the second end 12 of the protuberance 10 are directed towards the equatorial plane X and, furthermore, this axis of symmetry M is substantially parallel with a second direction B which is symmetrical with respect to the first direction A and which is inclined with respect to the equatorial plane X by an angle less than 30°, for example, approximately 15°.

During travel of the vehicle, any powdered ice which is eroded by the stud 9 is initially collected in the internal channel 20, external channel 30 and auxiliary channels 21. However, when the block with the stud enters a footprint area, the protuberance becomes deformed as a result of the particular configuration 10 thereof, becoming bent towards the internal channel 20 or towards the external channel 30, reducing the section thereof and, at the same time, widening the section of the other channel. When leaving the footprint area, the protuberance 10 tends to resiliently return into the original configuration thereof, bringing about a pulse which expels the powdered ice which has accumulated in the channels.

Therefore, the present invention solves the problem set out above with reference to the cited prior art, at the same time providing a number of other advantages, including the fact of making the studded tyre 1 aesthetically pleasing and recognizable, particularly in the region of the studs 9 which are identified by the particular formation of the protuberance 10 and the internal and external channels 20 and 30.

Naturally, in order to comply with specific and contingent application requirements, a person skilled in the art may apply to the above-described invention additional modifications and variants which are still included within the scope of protection as defined by the appended claims.

Claims

1. A studded tyre comprising a tread band (2), on which there are defined a plurality of blocks (5) and a plurality of studs (9) which are arranged on at least some of said blocks, wherein on each of said blocks (5) on which a stud is provided there is defined a protuberance (10) which is spaced apart from said stud and which extends continuously around said stud over an angular extent greater than or equal to 270°, said protuberance (10) being delimited at its opposite sides by an internal channel (20) and by an external channel (30), which are both continuous.

2. A tyre according to claim 1, wherein said protuberance (10) extends between a first end (11) and a second end (12) which is spaced apart from said first end (12) by a distance between 3 mm and 8 mm.

3. A tyre according to claim 1 or 2, wherein said protuberance (10) is completely delimited along the entire perimeter thereof by said internal channel (20), by said external channel (30) and by two auxiliary channels (21) which connect said internal channel (20) to said external channel (30).

4. A tyre according to claim 3 when dependent on claim 2, wherein said auxiliary channels (21) connect said internal channel (20) to said external channel (30) in the region of said first end (11) and said second end (12), respectively.

5. A tyre according to any one of the preceding claims, wherein said protuberance (10) extends around said stud (9) in a symmetrical manner with respect to an axis of symmetry (M) which passes through said stud (9).

6. A tyre according to any one of the preceding claims, wherein said protuberance (10) is coplanar with a portion of tread surface (6) of said block (5) adjacent to said external channel (30) at the side opposite said protuberance (10).

7. A tyre according to any one of claims 2 to 6, wherein said protuberance (10) comprises a first rectilinear portion (13) and a second rectilinear portion (14), said first portion (13) and said second portion (14) extending from said first end (11) and from said second end (12), respectively, so as to diverge from each other.

8. A tyre according to claim 7, wherein said protuberance (10) comprises a curvilinear portion (15) which connects said first portion (13) to said second portion (14) of said protuberance (10), said curvilinear portion (15) being a circumferential arc which is concentric with said stud (9).

9. A tyre according to any one of the preceding claims, wherein said internal channel (20) and said external channel (30) are lowered with respect to a portion of tread surface (6) of said block (5) by a height between 0.2 mm and 1.5 mm.

10. A tyre according to any one of the preceding claims, wherein said internal channel (20) is separated from said stud (9) by an island (35), in which there is formed a seat (36) for receiving said stud (9), said island (35) being coplanar with a portion of tread surface (6) of said block (5) adjacent to said external channel (30) at the side opposite said protuberance (10).

11. A tyre according to any one of the preceding claims, wherein said protuberance (10), said internal channel (20) and said external channel (30), over a fraction of at least 80% of the respective longitudinal extents thereof, have a mutually identical width.

12. A tyre according to any one of claims 2 to 11, wherein there is defined on said tread band (2) a preferential rolling direction (F) and said first end (11) and said second end (12) of said protuberance (10) are positioned downstream of said stud (9) with respect to said preferential rolling direction (F).

13. A tyre according to any one of claims 5 to 12, wherein said axis of symmetry (M) of said protuberance (10) is inclined with respect to a circumferential direction (X) which is defined on said tread band (2) at an angle between 0° and 30°.

14. A tyre according to any one of claims 5 to 13, wherein there is defined on said tread band (2) an equatorial plane (X) which divides said tread band into a first region (7) of tread band and a second region (8) of tread band, and wherein for each stud (9) which is positioned on said tread band (2) said axis of symmetry (M) of said protuberance (10) is inclined so that said first end (11) and said second end (12) are directed towards said equatorial plane (X).

15. A tyre according to any one of claims 5 to 14, wherein for each stud (9) which is positioned on said first region (7) of tread band said axis of symmetry (M) of said protuberance (10) is parallel with a first direction (A) which is inclined with respect to said equatorial plane (X) at an angle between 0° and 30°, for each stud (9) which is positioned on said second region (8) of tread band said axis of symmetry (M) of said protuberance (10) is parallel with a second direction (B) which is inclined with respect to said equatorial plane (X) at an angle between 0° and 30° and symmetrical to said first direction (A) with respect to said equatorial plane (X).