CA3151745A1 - Anti-skid stud for a vehicle tyre - Google Patents

Abstract

The invention relates to an anti-skid stud (10) for a vehicle tyre (1), comprising a study body, the anti-skid stud body comprising a bottom flange (14) at the lower end of the stud body, and a stem (13) extending away from the bottom flange. The anti-skid stud (10) comprises a stud pad (20), the stud pad comprising an inner surface (25) and an outer surface (26), and the thickness (t20) of the stud pad being between 0.4 mm and 3 mm, the stud pad (20) being arranged at least partly below said bottom flange (14), and the area of the inner surface (25) of the stud pad (20) being at least 10% of the bottom surface of the bottom flange of the anti-skid stud, the stud pad (20) of the anti-skid stud comprising or being made of a polymer material, which polymer material is arranged to soften at warm tempera-tures so that the ShA hardness of the stud pad is not greater than 55 at an ambient temperature of +22 C, and to harden at cold temperatures so that the ShA hardness of the stud pad is at least 70 at an ambient temperature of ¨25 C. The invention further relates to a studded pneumatic tyre for a vehicle, and the use of a polymer material in an anti-skid stud for a vehicle tyre.

Description

I
ANTI-SKID STUD FOR A VEHICLE TYRE
Field of the invention The present invention relates to an anti-skid stud for a vehicle tyre. The invention also relates to a vehicle tyre equipped with anti-skid studs, particularly a pneumatic tyre for a vehicle.
Technical background In the field of tyres for vehicles, it is known to install anti-skid studs in winter tyres developed particularly for snowy and icy roads, to improve road holding.
The function of the studs is to bite into ice and thereby to form a mechanical bond between the ground surface and the tyre, particularly for situations in which a suffi-cient result is not provided merely by the rubber of the tyre and the pattern formed in it. An anti-skid stud typically comprises a body of the anti-skid stud and a tip of the anti-skid stud. The tip of the anti-skid stud, or a part of it, is intended to be in contact with the ground surface.
Summary of the invention It is an aim of the invention to provide a novel type of an anti-skid stud. It is another aim of the invention to provide a vehicle tyre equipped with such anti-skid studs.
The anti-skid stud for a vehicle tyre as well as a vehicle tyre according to the inven-tion are characterized in what will be defined in the independent claims.
Advanta-geous embodiments are presented in the dependent claims.
With the anti-skid stud presented herein, it is possible to achieve an anti-skid stud which wears the driving surface to a lesser extent but which may have suitable road-holding properties in spite of its reduced wearing effect on the driving surface.
The anti-skid stud comprises a body comprising a stem and a bottom flange. The diameter of the bottom flange is suitably larger than the diameter of the stem of the anti-skid stud. Furthermore, the anti-skid stud comprises a stud pad, placed at least partly below the bottom flange of said anti-skid stud. Said body is preferably made of metal, but other suitable materials may be used as well. Typically, the anti-skid Date Recue/Date Received 2022-03-09

2 stud also comprises a tip of the anti-skid stud, which may consist of, for example, hard metal or ceramic, but other suitable materials may be used as well.
Thanks to the novel solution, in which the anti-skid stud comprises a stud pad, wear of the driving surface may be substantially reduced in comparison with an anti-skid stud without a stud pad. The stud pad is preferably placed, at least primarily, below the bottom flange of the anti-skid stud.
In an example, the stud pad of the anti-skid stud may be in direct contact with the bottom flange of the anti-skid stud, whereby, for example, no separate adhesive layer is provided between the stud pad and the bottom flange. This example may be particularly advantageous if the stud pad is attached to the vehicle tyre already at the stage of vulcanization.
Preferably, for example an adhesive layer is provided between the stud pad and the bottom flange. Thus, the installation of the anti-skid stud may be easier, the stud pad being attached to the bottom flange by means of the adhesive layer. Thanks to the adhesive layer, the anti-skid stud can be installed as one piece in the tyre; in other words, the stud pad and the body of the anti-skid stud do not need to be attached one by one to the tyre. Furthermore, wear of the stud pad may be reduced if the stud pad and the bottom flange are glued together, because a movement of the stud pad in relation to the bottom flange can thus be prevented.
Preferably, the stud pad is placed at least partly, preferably at least primarily, below the body, preferably the bottom flange, of the anti-skid stud. By means of the stud pad placed at least partly below the body of the anti-skid stud, it is possible to have an effective impact on certain properties of the anti-skid stud and the tyre.
Thus, the stud pad may substantially improve, for example, the road-holding properties of the tyre on an icy driving surface.
Thus, the anti-skid stud for a vehicle tyre comprises an anti-skid stud body, which anti-skid stud body comprises a bottom flange at the bottom end of the stud body, and a stem extending from the bottom flange. Furthermore, the anti-skid stud com-prises a stud pad of the anti-skid stud, having a suitable thickness between 0.4 mm and 3 mm. The stud pad is suitably placed at least partly below said bottom flange.
The stud pad comprises, and is preferably made of, a polymer material whose hard-ness is substantially dependent on the ambient temperature.
Date Recue/Date Received 2022-03-09

3 Preferably, the stud pad is made of a polymer material, which polymer material is configured to soften at warm ambient temperatures so that the ShA hardness of the stud pad is not greater than 55 when the ambient temperature is +22 C, and to stiffen at cold temperatures so that the ShA hardness of the stud pad is at least 60 when the ambient temperature is ¨25 C. Furthermore, in an embodiment, the ShA
hardness of the stud pad is preferably not greater than 95 when the ambient tem-perature is ¨25 C. Hardening of the stud pad under cold conditions provides the anti-skid stud with a better support and thereby provides the tyre with better road-holding properties. In other words, hardening of the stud pad may increase the stud force of the anti-skid stud, because the anti-skid stud thus cannot substantially pen-etrate into the tyre, whereby the penetration of the stud into the ice is greater and the road-holding of the tyre can be significantly better. Under warm conditions, the stud pad may substantially soften, whereby the softening stud pad may allow the penetration of the stud body into the tyre, whereby it can reduce the stud force and the dynamic stud impact, and can thereby reduce the wear of the road.
In an embodiment, the ShA hardness of the anti-skid stud is not greater than 38 and preferably not greater than 30 when the ambient temperature is 40 C. Thus, the ShA hardness of the stud pad of the anti-skid stud may be preferably at least 70, more preferably at least 80, and most preferably at least 88 when the ambient tem-perature is ¨25 C. Such an anti-skid stud may have particularly good properties in view of varying ambient temperatures. The greater the difference in hardness of the stud pad at different temperatures, the greater the effect of the stud pad on the road holding of the tyre in cold weather and on road wear in warm weather.
In an embodiment, the ShA hardness of the stud pad of the anti-skid stud is between 40 and 55 when the ambient temperature is 25 C, and/or the ShA hardness of the stud pad of the anti-skid stud is between 60 and 75 when the ambient temperature is ¨25 C. Thus, the effects of the stud pad may be particularly advantageous for both cold and warm conditions.
In this application, the thickness of the stud pad refers to the thickness of the stud pad when the anti-skid stud is in rest position, that is, when the anti-skid stud is not subjected to external forces, such as pressure caused by the driving surface.
The thickness of the stud pad may be at least 0.4 mm, more preferably at least 0.7 mm and most preferably at least 0.9 mm. Furthermore, the thickness of the stud Date Recue/Date Received 2022-03-09

4 pad may be not greater than 3 mm, preferably not greater than 2.5 mm, more pref-erably not greater than 2.0 mm, and most preferably not greater than 1.5 mm.
By applying a stud pad having said thickness, the road-holding properties of the anti-skid stud in relation to the wear of the driving surface may be particularly suitable.
Furthermore, the manufacture of the vehicle tyre may be more efficient compared with a stud pad having a different thickness. The stud pad of the presented thickness may be sufficiently compressible to reduce wear of the driving surface, as well as make the tip of the anti-skid stud protrude from the tyre to a sufficient extent to pro-vide the tyre with good road holding on an icy driving surface. Moreover, installing a stud pad thicker than that presented may be challenging, and manufacturing a stud pad thinner than that presented may be particularly challenging.
The area of the inner surface of the stud pad, i.e. the surface substantially facing the bottom flange, is at least 10%, preferably at least 30%, more preferably at least 50%, and most preferably at least 80% of the bottom area of the bottom flange of the anti-skid stud. Furthermore, the area of the inner surface of the stud pad may be not greater than 120%, suitably not greater than 110%, preferably not greater than 100%, more preferably not greater than 90%, and most preferably not greater than 80% of the bottom area of the bottom flange of the anti-skid stud. The area of the inner surface of the stud pad may be, for example, between 30% and 90% of the bottom area of the bottom flange of the anti-skid stud. The control of the road-holding properties of the tyre may be substantially improved by using a stud pad having said size in relation to the area of the bottom flange.
The area of the outer surface of the stud pad may be at least 10%, preferably at least 30%, more preferably at least 50%, and most preferably at least 70% of the bottom area of the bottom flange of the anti-skid stud. Furthermore, the area of the outer surface of the stud pad may be not greater than 120%, suitably not greater than 110%, preferably not greater than 100%, more preferably not greater than 90%, and most preferably not greater than 80% of the bottom area of the bottom flange of the anti-skid stud. The area of the outer surface of the stud pad may be, for example, between 30% and 90% of the bottom area of the bottom flange of the anti-skid stud. Control of the road-holding properties of the tyre can be substantially improved and wear of the road surface can be substantially decreased by using a stud pad having the said size in relation to the area of the bottom flange.
The stud pad of the anti-skid stud covers suitably at least 10%, preferably at least 25%, more preferably at least 40%, and most preferably at least 55% of the bottom Date Recue/Date Received 2022-03-09

5 surface of the bottom flange of the anti-skid stud. Moreover, the stud pad covers suitably not more than 100%, preferably not more than 90%, more preferably not more than 80%, and most preferably not more than 70% of the bottom surface of the bottom flange. The stud pad may cover, for example, 30% to 80% of the bottom area of the bottom flange. In such a case, the advantages of the stud pad may be more pronounced. An advantage of this embodiment may be, for example, more precise controllability of the properties of the anti-skid stud. For example, the control of the road-holding properties of the tyre may be substantially improved by using a stud pad covering said proportion of the bottom area of the bottom flange.
Further-more, the advantages of the stud pad may become more pronounced so that road wear at warm temperatures may be significantly reduced when the stud pad covers said proportion of the bottom area of the bottom flange.
In an embodiment, the outer surface of the stud pad of the anti-skid stud is placed below the bottom flange of the anti-skid stud. Preferably, the inner surface of the stud pad of the anti-skid stud is placed below the bottom flange of the anti-skid stud.
Thus, the properties of the anti-skid stud may be more predictable.
Preferably, the shape of the bottom of the stud pad may be at least substantially symmetrical. Thus, the stud pad may be so designed that the stud pad can be divided into two equal parts which are at least substantially mirror images of each other. The mirror images may differ from each other by, for example, a feature hav-ing a relatively minor impact on the properties of the stud pad, for example a protru-sion or notch facilitating installation. The effect of the substantially symmetrical anti-skid stud on the properties of the tyre can be deduced more precisely than before already during the manufacture of the anti-skid stud.
The shape of the bottom of the stud pad may be selected, for example, from the list below:
- circle, - ellipse, - shape of the bottom flange of the anti-skid stud, - triangle, - rectangle, - pentagon, - Polygon, and - ribbon, such as a ring-shaped ribbon.
Date Recue/Date Received 2022-03-09

6 Instead of these, it is also possible to use another shape in a stud pad. The ribbon shape is preferably the shape of an endless loop.
In an embodiment, the shape of a stud pad may be said ribbon so that the stud pad preferably forms an endless loop. Thus, in road contact, the stud pad can be more efficiently compressed into the hollow center, and the damping effect of the stud pad can be improved. The air space in the center of the stud pad can provide the stud pad material with space for deformation and facilitate the retraction of the stud when in contact with the driving surface, reducing the stud force, the dynamic impact, and road wear.
Preferably, the shape of the stud pad is circular and/or conforms to the shape of the bottom flange. Such a shape of the stud pad may facilitate the installation of the anti-skid stud. Said shape may be particularly advantageous with orientable studs, i.e. studs which are installed in a given orientation. In an example, the stud pad shape conforming to the shape of the bottom flange is ribbon-like. A stud pad in the shape of an endless loop may be easier to install and align compared to a ribbon-like shape which is not the shape of an endless loop.
A stud pad may comprise an opening in the stud pad. Alternatively or in addition, the stud pad may comprise a concave point. The opening and/or the concave point in the stud pad are suitably placed on the inner surface and/or the outer surface, preferably in the middle, or substantially in the middle, of the inner surface and/or the outer surface of the stud pad. Preferably, the opening and/or the concave point in the stud pad are arranged on the inner surface of the stud pad. Thanks to the opening and/or the concave point of the stud pad, expansion of the stud pad may be more controllable. The opening and/or the concave point in the stud pad may provide the stud pad with space to expand, whereby the properties of the anti-skid stud may be more controllable at various temperatures. In road contact, a stud pad with an opening and/or a concave point may be compressed more efficiently, thanks to the hollow center, whereby the damping effect of the stud pad may be improved.
The opening and/or the concave point in the stud pad may facilitate the retraction of the stud in the contact, and reduce the stud force, the dynamic impact, and road wear.
In addition or alternatively, the stud pad may have a guiding feature, such as a notch and/or a protrusion, at one or more points, such as one or more edge points.
Said guiding feature, such as a protrusion or a notch, facilitates the arrangement of the Date Recue/Date Received 2022-03-09

7 stud pad in a desired orientation, for example in relation to the shape of the bottom flange. This may facilitate the manufacture and/or installation of the anti-skid stud.
The anti-skid stud with a stud pad may have various advantages. The anti-skid stud with the stud pad can dampen a dynamic impact and stud force compared with an anti-skid stud without a stud pad, when the anti-skid stud is not needed to secure traction. Thus, harmful noise caused by the tyre can be substantially reduced.
Fur-thermore, road wear caused by the tyre can be substantially reduced. Moreover, an anti-skid stud with a stud pad can reinforce the dynamic impact and stud force of the anti-skid stud when the ambient temperature falls below the freezing point so that the anti-skid stud provides a sufficient stud force to improve the traction of the tyre to an appropriate level.
In an embodiment, the stud pad of the anti-skid stud is made of a polymer material whose hardness is modified according to forces effective on the stud pad so that the road holding of the anti-skid stud is improved when the forces effective on the stud pad are changed, for example upon braking or accelerating.
Preferably, at an ambient temperature above 0 C, the stud pad is an elastic piece capable of resuming its original shape after compression. Preferably, the stud pad is made, or at least primarily made, of an elastomer material capable of resuming its original shape after compression, at an ambient temperature above 0 C.
This may substantially reduce road wear when the ambient temperature is high enough that no ice is formed on road surfaces; moreover, the stud pad having resumed its original thickness may improve the road holding properties of the anti-skid stud at temperatures below the freezing point.
In an embodiment, the stud pad contains - at least 10 phr of styrene butadiene rubber (SBR), and/or - at lest 10 phr of natural rubber (caoutchuc), and/or - at least 10 phr of polybutadiene rubber.
In addition or alternatively, the stud pad may comprise - at least 5 phr of resin, preferably 5 to 60 phr of resin, and/or - at least 20 phr, preferably 20 to 50 phr of at least one reinforcement which is preferably selected from carbon black reinforcement and silica rein-forcement.
The properties of the stud pad may thus be easier to control.
Date Recue/Date Received 2022-03-09

8 In an embodiment, the stud pad is a rubber spacer to be placed below the bottom flange of an anti-skid stud and changing its hardness according to the temperature.
Such a solution may be particularly cost efficient.
A notch may be provided at the bottom of the stud body, the notch forming an air space between the bottom flange of the anti-skid stud and the stud pad. Said notch may provide the stud pad with space to expand, whereby the properties of the anti-skid stud can be more controllable at different temperatures. This property may be particularly advantageous in a case where the stud pad does not comprise an open-ing, a hollow, or a corresponding shape on its inner surface.
The stud pad can be attached to the bottom flange of the anti-skid stud by gluing, for example. Thus, the anti-skid stud may comprise an adhesive layer, at least in some points, between the stud pad and the bottom flange of the anti-skid stud.
If the anti-skid stud comprises said adhesive layer, the adhesive layer may be continuous, or it may comprise gaps and/or pores.
A studded air-filled tyre for a vehicle may comprise a tyre tread, with anti-skid studs attached to the tread.
The anti-skid stud presented in this application may have, for example, the advantage that the road-holding properties of the anti-skid stud are adjusted accord-ing to the temperature so that the road-holding properties of the anti-skid stud can be significantly less pronounced when the driving surfaces are unfrozen than when the driving surfaces are snowy and/or icy. Thanks to this, the best road-holding properties of the anti-skid stud can be provided when the road-holding properties of the anti-skid stud are needed, that is, on an icy and snowy surface, whereas the road holding properties of the anti-skid stud can be substantially less pronounced on an unfrozen driving surface, to reduce wear of the driving surface. Thus, the effect and the road-holding properties of the anti-skid stud according to the solution can be particularly good when the winter tyre is used under icy conditions, whereas under warm conditions, the anti-skid stud according to the solution can protect driv-ing surfaces and reduce wear of the pavement of the driving surface.
Furthermore, when driving under warm conditions, the noise caused by the anti-skid stud may be at a lower than normal level.
Date Recue/Date Received 2022-03-09

9 The novel solution also has the advantage that existing tyre moulds can be used for manufacturing tyres with the novel anti-skid studs. This may improve the cost effi-ciency of tyre manufacture as well as be a solution of particular environmental friend-liness.
Brief description of the drawings In the following, the invention will be described in more detail with reference to the appended drawings, in which Fig. la shows the structure of an anti-skid stud in a side view;
Fig. 2b shows the structure of an anti-skid stud in a cross-sectional view in the longitudinal direction;
Figs. 2a to 2d show various advantageous shapes of outer and inner surfaces of a stud pad for an anti-skid stud;
Fig. 3a shows a photograph of an anti-skid stud with a stud pad;
Fig. 3b shows a vehicle tyre in a perspective view;
Figs. 4a and 4b illustrate the operation of the anti-skid stud in principle views;
Figs. 5a to 5f show shapes of a stud pad for an anti-skid stud according to some examples, in cross-sectional views in the longitudinal direction; and Fig. 6 illustrates the hardness of a stud pad according to an example, as a function of temperature.
The figures are conceptual figures intended to help to understand the invention. The figures are not necessarily in scale.
Detailed description of some embodiments In this application, the following reference numerals will be used:
1 tyre,

10 anti-skid stud,

11 tip of the anti-skid stud,

12 blind hole in the anti-skid stud,

13 stem of the anti-skid stud,

14 bottom flange of the anti-skid stud, 20 stud pad of the anti-skid stud, t20 thickness of the stud pad, Date Recue/Date Received 2022-03-09 21 guiding feature of the stud pad, 22 opening in the stud pad, 23 concave point in the stud pad, 24 ribbon-like shape of the stud pad, 25 inner surface of the stud pad, and 26 outer surface of the stud pad.
In this application, the unit phr (parts per hundred rubber) is used, which is known to a person skilled in the art.
Figure la shows a reduced side view of an anti-skid stud 10 comprising a stud pad of the anti-skid stud. Figure lb shows a reduced cross-sectional view of an anti-skid stud.

15 The body of the anti-skid stud comprises a bottom flange 14 and a stem 13 extend-ing away from the bottom flange 14. Furthermore, the anti-skid stud typically com-prises an anti-skid stud tip 11 fastened to the body. The tip 11 of the anti-skid stud may be made of a material different from said body of the anti-skid stud. The tip of the anti-skid stud may be made of, for example, hard metal or hard ceramic.
The tip 20 of the anti-skid stud may be partly placed within the body of the anti-skid stud and protrude from its outer end.
The anti-skid stud 10 comprises a bottom flange 14 of the anti-skid stud 10 and a stud pad 20 arranged to be placed in the bottom section of a hole for an anti-skid stud in a tyre 1 for a vehicle.
The body of the anti-skid stud 10 can be made according to a technique of prior art, for example by cold working of the shape from a circular wire preform which can be forced to a desired shape in a number of different steps. A hard metal tip, if used, can be made, for example, by compressing a preform from hard metal powder together with a binder, and by sintering it at a high temperature. The hard metal tip typically has a wedge-like shape, and the body of the anti-skid stud typically com-prises a blind hole 12 having a shape matching with the tip 11 of the anti-skid stud.
Such an anti-skid stud is assembled, for example, by pressing the hard metal tip into the anti-skid stud body, whereby a strong cotter joint is formed between them.
In this context, hard metal refers to, among other things, hard metal according to prior art. Hard metal is typically a wear resistant metal composite material that may Date Recue/Date Received 2022-03-09 contain tungsten as a carbide compound, and the binding component is usually cobalt. The compounds may also contain titanium carbide, tantalum carbide, molyb-denum carbide, or vanadium carbide. Various ceramic based materials with strength and wear properties corresponding to those of hard metal, or particularly wear resistant polymers, can also be classified as materials that can be parallelled with hard metal in this context. The anti-skid stud comprising a stud pad may be particu-larly suitable for use with such a tip of an anti-skid stud that is made of a hard metal or ceramic based material.
The stud pad 20 has an inner surface 25 and an outer surface 26. The inner surface 25 of the stud pad is arranged, or intended to be arranged, at least partly in the direction of the bottom flange of the anti-skid stud. The outer surface 26 of the stud pad is arranged, or intended to be arranged, substantially in the direction of the center of the tyre 1.
Figures 2a to 2d show some example embodiments of a stud pad for an anti-skid stud. The stud pad may have, for example, an inner surface 25 and/or an outer surface 26 according to the examples 2a to 2d. These illustrated shapes represent some possible shapes of a stud pad. The shape of the stud pad may also deviate substantially from the examples shown in the figures.
In an embodiment, the shape of the inner and/or outer surface of the stud pad is a circle, an ellipse, a polygon, an o-ring, a triangle, a square, a rectangle, or substan-tially the shape of the bottom flange of the anti-skid stud, but other shapes of a stud pad for an anti-skid stud may be used as well.
The stud pad of the anti-skid stud has a thickness t20 (shown e.g. in Figs. lb and 5a to 5f), referring to the dimension of the stud pad in the depth direction.
The stud pad may comprise, for example, concave points, which is why the thickness of the stud pad may vary in different parts of the stud pad. In this application, the thickness t20 of the stud pad refers to the thickness of the stud pad at a location below the bottom flange of the anti-skid stud where the stud pad has the greatest measurable thickness.
The shape of the stud pad for an anti-skid stud is preferably symmetrical, or at least substantially symmetrical. This means that the stud pad is preferably so designed that the stud pad can be divided into two equal parts so that both parts are substan-tially mirror images with respect to each other. This may substantially improve the Date Recue/Date Received 2022-03-09 functionality of the anti-skid stud during use, as well as predictability of the function-ality during use.
In an embodiment, the stud pad is asymmetrical; that is, it is not divisible into two equal parts so that both parts would be substantially mirror images with respect to each other.
Preferably, the stud pad has a shape conforming, or substantially conforming, to the shape of the bottom flange. The shape conforming to the shape of the bottom flange may be ribbon-like (shown in Figs. 2b and 2d) or substantially solid (shown in Fig. 2c).
If the stud pad has a ribbon-like shape, said ribbon-like shape is preferably the shape of an endless loop. A ribbon-like shape of the stud pad, which is the shape of an endless loop, is shown in Figs. 2b and 2d. Thanks to the hollow space in the middle, the stud pad in the shape of an endless loop can be compressed more effi-ciently when in contact with the road, whereby the damping effect of the stud pad may be greater. The air space in the center of the stud pad can provide the stud pad material with a space for deformation and facilitate the retraction of the stud when in contact, reducing the stud force, the dynamic impact and the road wear.
The stud pad may have a stud pad opening 22 on the inner surface 25 of the stud pad. The opening of the stud pad is preferably arranged in the center of the stud pad. The opening 22 of the stud pad is preferably left below the bottom flange of the anti-skid stud. Placed on the inner surface of the stud pad, this stud pad opening 22 can form an air space below the bottom flange of the anti-skid stud. Said air space may enhance the predictability of the functionality of the stud pad upon expansion of the stud pad and allow more efficient compression of the stud pad at warm weather and thereby reduce road wear and harmful noise.
Alternatively or in addition, a concave point 23, such as a hollow, may be provided on the inner surface 25 of the stud pad. Preferably, the concave point 23 in the stud pad is placed substantially at the center of the stud pad. The concave point 23 in the stud pad is preferably left below the bottom flange of the anti-skid stud.
This concave point 23 in the stud pad, placed on the inner surface of the stud pad, can form an air space between the bottom flange of the anti-skid stud and the stud pad of the anti-skid stud. The concave point in the stud pad may allow more efficient Date Recue/Date Received 2022-03-09 compression of the stud pad at warm weather and thereby reduce road wear and noise.
In an embodiment, an opening 22 and/or a concave point 23 is provided on the outer surface 26 of the stud pad, preferably placed substantially at the center of the stud pad. The opening and/or the concave point 23 of the stud pad can allow expansion of the stud pad in an advantageous way.
Also, a stud pad in a shape conforming to the shape of the bottom flange may have an opening 22 and/or a concave point 23 on the outer surface and/or the inner sur-face, preferably placed substantially at the center of the stud pad.
Instead of or in addition to one or more openings and/or concave points in the stud pad, the bottom of the bottom flange of the anti-skid stud may be provided with a notch which forms an air space between the bottom flange of the anti-skid stud and the stud pad, or makes the air space formed by the stud pad larger.
In addition to or instead of the above-mentioned features placed substantially at the center of the stud pad, the stud pad may comprise a guiding feature 21, such as a notch and/or a protrusion, at one or more edge locations. An example of a stud pad with a guiding feature 21 is shown in Figs. 2b and 2c. Figure 2b shows a guiding feature 21 which is a protrusion. Figure 2c shows a guiding feature 21 which is a notch. The stud pad may comprise one or more guiding features 21. The guiding feature is suitably arranged so that the stud pad is orientable in a specific position with respect to the position of the bottom flange. Thus, the orientation of the stud pad in relation to the body of the anti-skid stud, particularly its bottom flange, may be substantially facilitated.
As presented in this application, most of the stud pad of the anti-skid stud is prefer-ably placed below the bottom of the bottom flange of the anti-skid stud.
Preferably, the entire stud pad of the anti-skid stud is placed below the bottom of the bottom flange of the anti-skid stud.
The size of the stud pad, for example the circumference of a ribbon-like stud pad, is suitably defined so that the stud pad is suitable for use in connection with the bottom flange of the respective anti-skid stud.
Date Recue/Date Received 2022-03-09 The diameter of the bottom flange of the anti-skid stud may be, for example, between 6.5 and 9 mm. Thus, in an advantageous embodiment, the diameter of the stud pad (measured at a point giving the greatest measurement) could be, for example, between 5.2 and 7.2 mm.
The bottom area of the stud pad is at least 10%, preferably at least 30%, more preferably at least 50%, yet more preferably at least 70%, and most preferably at least 80% of the bottom area of the bottom flange of the anti-skid stud.
Moreover, the bottom area of the stud pad of the anti-skid stud is suitably not greater than 120%, preferably not greater than 110%, more preferably not greater than 100%, and most preferably not greater than 90% of the bottom area of the bottom flange of the anti-skid stud. This may substantially facilitate the installation of the anti-skid stud with the stud pad. Furthermore, the control of the road holding properties of the anti-skid stud may be improved. In addition, the stud pad with the size in question may efficiently reduce wear of the driving surface.
Figures 5a to 5f show some example shapes of a stud pad for an anti-skid stud, in cross-sectional views in the longitudinal direction. Figures 5a to 5f show the inner surface of the stud pad, the outer surface of the stud pad, and the thickness of the stud pad according to the examples.
The thickness of the stud pad is measured at the thickest point of the stud pad in the longitudinal direction of the anti-skid stud, preferably below the bottom flange of the anti-skid stud. In an embodiment, the thickness t20 of the stud pad may be at least 0.7 mm, more preferably at least 0.8 mm and most preferably at least 0.9 mm.
Moreover, in this embodiment, the thickness of the stud pad may be not greater than 2.5 mm, more preferably not greater than 2 mm and most preferably not greater than 1.5 mm. Thus, the control of the road holding properties of the anti-skid stud can be substantially improved at cold weather, and moreover, the wear of the driving surface at warm weather can be substantially reduced.
The total length of the anti-skid stud, including the stud pad, may be, for example, between 9 mm and 15 mm. For example, for cars, the total length of the anti-skid stud may be e.g. between 9 and 12 mm. The length of the anti-skid stud in relation to the size of the stud pad can influence the properties of the anti-skid stud and the tyre.
Date Recue/Date Received 2022-03-09 The bottom flange of the anti-skid stud, together with the stud pad, can substantially determine the stud force of the anti-skid stud with respect to the driving surface.
When the outdoor temperature is above the freezing point, the stud pad of the anti-skid stud may be of a relatively soft, elastic material, allowing the anti-skid stud to retract deeper into the hole for the anti-skid stud. Thus, the anti-skid stud can also wear the driving surface to a lesser extent. Moreover, noise caused by the tyre can be substantially reduced.
When the outdoor temperature decreases so that ice or snow may build up on the road, the material of the stud pad of the anti-skid stud can substantially harden, whereby the anti-skid stud can bite into the driving surface more efficiently, improv-ing the road holding of the tyre.
Figures 4a and 4b illustrate the operation of the anti-skid stud in principle views.
Figure 4a shows a situation in which the stud pad of the anti-skid stud has hardened so that the stud protrudes from the surface of the tyre. Figure 4b, in turn, shows a situation in which the stud pad of the anti-skid stud behaves like a soft elastic mate-rial, allowing the stud to retract deeper into the tyre.
In this application, the term hardness (ShA) refers to material hardness which can be determined according to the standard ASTM D2240.
Preferably, said stud pad of the anti-skid stud is made of a polymer material, which polymer material is configured to soften at warm temperatures so that the ShA
hard-ness of the stud pad is not greater than 55 at an ambient temperature of +22 C, and to harden at cold temperatures so that the ShA hardness of the stud pad is at least 60 at an ambient temperature of ¨25 C. Furthermore, in an embodiment, the ShA
hardness of the stud pad is preferably not greater than 95 at an ambient temperature of ¨25 C. The greater hardness of the stud pad at freezing temperatures can sub-stantially increase the stud force and thereby improve the road holding of the tyre on ice.
The ShA hardness of the stud pad is at least 60, preferably at least 70, more pref-erably at least 75, and most preferably at least 80 at an ambient temperature of ¨
25 C. Furthermore, the ShA hardness of the stud pad is not greater than 55, pref-erably not greater than 50, and most preferably not greater than 45 at an ambient temperature of +22 C. A softer stud pad material may substantially increase the Date Recue/Date Received 2022-03-09

16 retraction of the stud into the tyre at warmer temperatures and thereby reduce road wear and noise.
According to an advantageous example, the ShA hardness of the stud pad for an anti-skid stud is at least 60, preferably at least 65, more preferably at least 70 and most preferably at least 75 at an ambient temperature of ¨5 C. Furthermore, the ShA hardness of the stud pad is thus not greater than 100, preferably not greater than 95 and most preferably not greater than 90 at an ambient temperature of ¨5 C.
Thus, the advantages of the stud pad can be manifest as soon as the temperature falls below the freezing point.
According to an embodiment, the ShA hardness of the stud pad is between 45 and 89, preferably between 50 and 80, and most preferably at least 60 at an ambient temperature of 0 C. Thus, at a temperature around 0 C, the hardness may be par-ticularly suitable for the stud pad.
The stud pad is made, at least in part, of a polymer material whose hardness is substantially dependent on the ambient temperature. In an embodiment, the poly-mer material of the stud pad is vulcanized so that sulphur is used as a vulcanization agent.
The stud pad may comprise, comprise primarily, or consist of a polymer material whose glass transition temperature (Tg) may at least ¨40 C, such as at least ¨30 C, preferably at least ¨20 C, more preferably at least ¨15 C, or at least ¨10 C, and most preferably at least ¨5 C. Furthermore, the glass transition temperature of the polymer material may not greater than 40 C, such as not greater than 30 C, prefer-ably not greater than 20 C, more preferably not greater than 15 C, or not greater than 10 C, and most preferably not greater than 5 C. Thus, the hardening of the stud pad may take place at a point optimal in view of road wear and road holding. If the glass transition temperature is arranged close to 0 C, the hardening of the stud pad may take place at a point optimal in view of road wear and road holding.
In an embodiment, the stud pad may comprise at least 10 phr of styrene butadiene rubber (SBR). The content of styrene butadiene rubber may be at least 10 phr, pref-erably at least 20 phr, more preferably at least 30 phr, and most preferably at least phr, calculated from the stud pad of the anti-skid stud. Furthermore, the stud pad may comprise not more than 100 phr of styrene butadiene rubber. By using SBR, Date Recue/Date Received 2022-03-09

17 the glass transition temperature can be more easily set as desired in view of the implementation of the anti-skid stud.
If styrene butadiene rubber (SBR) is applied, it may be solution-polymerized styrene butadiene rubber (SSBR). Thus, the solution-polymerized styrene butadiene rubber (SSBR) has a vinyl content of preferably at least 30%, more preferably at least 35%
and most preferably at least 40%. Furthermore, the vinyl content of the styrene butadiene rubber (SSBR) is thus preferably not greater than 70%, more preferably not greater than 65% and most preferably not greater than 60%. Moreover, the styrene content of the styrene butadiene rubber (SSBR) produced is preferably between 30 and 40%. Thus, the glass transition temperature of the polymer can be particularly suitable for the stud pad material, and hardening can take place at a moment determined more precisely in advance.
The stud pad may contain resin. The amount of resin, if used, may be at least 5 phr of resin, preferably at least 10 phr of resin, more preferably at least 15 phr of resin, and most preferably at least 20 phr of resin. Furthermore, the stud pad of the anti-skid stud may contain not more than 70 phr of resin, preferably not more than 60 phr of resin, more preferably not more than 50 phr of resin, and most preferably not more than 40 phr of resin. By applying resin, the glass transition temperature of the stud pad material can be raised by a predetermined level so that the hardening of the stud pad can be implemented within a predetermined temperature range.
The stud pad may contain a reinforcement. The amount of reinforcement, if used, may be at least 20 phr of reinforcement, preferably at least 25 phr of reinforcement, more preferably at least 30 phr of reinforcement, and most preferably at least 35 phr of reinforcement. Furthermore, the stud pad of the anti-skid stud may contain equal to or less than 50 phr of reinforcement, preferably equal to or less than 45 phr of reinforcement, more preferably equal to or less than 40 phr of reinforcement, and most preferably equal to or less than 35 phr of reinforcement. The reinforcement may contain or consist of carbon black reinforcement and/or silica reinforcement.
The reinforcement can be used to increase the strength of the stud pad material, whereby the strength of the stud pad can be improved. Furthermore, the reinforce-ment can be used to influence the ShA hardness of the stud pad so that the hard-ness of the stud pad can be more easily optimized to a desired level.
Date Recue/Date Received 2022-03-09

18 Figure 6 shows an example of the change in hardness of the stud pad for an anti-skid stud as the temperature is changed. In this advantageous example, the hard-ness of the stud pad is adjusted so that the stud pad is hardened when the ambient temperature is below the freezing point.
Figure 3 shows a vehicle tyre which comprises a tread intended to be in rolling con-tact with a surface and equipped with anti-skid studs. The vehicle tyre 1 may be, for example, a pneumatic tyre for a vehicle.
Anti-skid studs according to the invention can be fastened to the vehicle tyre by embedding a stud pad of an anti-skid stud and the bottom flange and the stem of an anti-skid stud into a hole formed in the vehicle tyre, which hole may be called a hole for an anti-skid stud. Thus, the stud pad and the bottom flange of the anti-skid stud are preferably placed in the bottom area of the hole for the anti-skid stud, and the stem extends from it outwards, towards the surface of the tyre.
The stud pad can be fastened to the bottom flange of the anti-skid stud, for example by gluing, before the anti-skid stud is attached to the vehicle tyre.
Alternatively, the stud pad can be placed in the hole made in the vehicle tyre before the body of the anti-skid stud is inserted in said hole.
A method for manufacturing a vehicle tyre may comprise, for example, the following steps:
¨ providing o a body of an anti-skid stud, comprising a bottom flange, o a stud pad having a thickness between 0.4 mm and 3 mm and comprising polymer material which is arranged to soften at warm temperatures and to harden at cold temperatures so that the ShA hardness of the stud pad of the anti-skid stud is at least 70 at an ambient temperature of ¨25 C, and the ShA hardness of the stud pad is not greater than 55 at an ambient temperature of +22 C, and o a vehicle tyre comprising a tyre body and a rubber tread provided with an anti-skid stud hole for an anti-skid stud, ¨ fastening the stud pad of the anti-skid stud, the area of the inner surface (25) of the stud pad (20) being at least 10% of the bottom surface of the bottom flange of the anti-skid stud, to the lower surface of the bottom flange, for example by gluing, and Date Recue/Date Received 2022-03-09

19 ¨ fastening the anti-skid stud to the anti-skid stud hole provided in the vehicle tyre.
By this method, the anti-skid stud can be installed in the tyre in a particularly efficient way.
The stud pad can be fastened to the lower surface of the bottom flange preferably by gluing, but other suitable solutions are possible as well.
The invention and its different embodiments are not limited to the above presented examples of the embodiments. The presented single features may be present in a solution according to the invention irrespective of the other presented single fea-tures. The expressions describing the presence of the features included in the claims are open in such a way that presenting the characteristics does not exclude such characteristics from the solution which are not presented in the independent or dependent claims.
Date Recue/Date Received 2022-03-09

Claims (17)

Claims:

1. An anti-skid stud (10) for a vehicle tyre (1), comprising - a stud body, the anti-skid stud body comprising o a bottom flange (14) at the lower end of the stud body, and o a stem (13) extending away from the bottom flange, characterized in that the anti-skid stud (10) comprises a stud pad (20), the stud pad comprising an inner surface (25) and an outer surface (26), the thickness (t20) of the stud pad being between 0.4 mm and 3 mm, wherein the stud pad (20) is placed at least partly below said bottom flange (14), and the area of the inner surface (25) of the stud pad (20) is at least 10% determined of the bottom surface of the bottom flange of the anti-skid stud, which stud pad (20) comprises or is made of a polymer material, which poly-mer material is arranged to soften at warm temperatures so that the ShA
hardness of the stud pad is not greater than 55 at an ambient temperature of +22 C, and to harden at cold temperatures so that the ShA hardness of the stud pad is at least 70 at an ambient temperature of ¨25 C.

2. The anti-skid stud for a tyre according to claim 1, wherein - the ShA hardness of the stud pad is at least 60, preferably at least 70, at an ambient temperature of ¨5 C, and/or - the ShA hardness of the stud pad is not greater than 95, preferably not greater than 90, at an ambient temperature of ¨5 C.

3. The anti-skid stud for a tyre according to any of the preceding claims, wherein - the ShA hardness of the stud pad is between 40 and 55 at an ambient temperature of 25 C, and/or - the ShA hardness of the stud pad is between 70 and 90 at an ambient temperature of ¨25 C.

4. The anti-skid stud for a tyre according to any of the preceding claims, wherein the area of the inner surface (25) of the stud pad (20) is between 20% and 120%, more preferably between 30% and 90%, of the bottom surface of the flange of the anti-skid stud.
Date Recue/Date Received 2022-03-09

5. The anti-skid stud for a tyre according to any of the preceding claims, wherein the outer surface (26) of the stud pad (20) is placed below the bottom flange of the anti-skid stud.

6. The anti-skid stud for a tyre according to any of the preceding claims, wherein the shape of the stud pad (20) is symmetrical, or at least substantially symmet-rical, wherein the stud pad (20) can be divided into two equal parts so that said parts are substantially mirror images with respect to each other.

7. The anti-skid stud for a tyre according to any of the preceding claims, wherein the thickness (t20) of the stud pad (20) is at least 0.9 mm and not greater than 2.5 mm.

8. The anti-skid stud for a tyre according to any of the preceding claims, wherein the stud pad comprises an opening (22) in the stud pad.

9. The anti-skid stud for a tyre according to any of the preceding claims, wherein the stud pad comprises a concave point (23) in the stud pad.

10. The anti-skid stud for a tyre according to any of the preceding claims, wherein the anti-skid stud (10) comprises an adhesive layer arranged between the stud pad and the bottom flange.

11. The anti-skid stud for a tyre according to any of the preceding claims, wherein the glass transition temperature (Tg) of said polymer material is arranged between ¨40 C and +40 C, more preferably between ¨20 C and +20 C, and most preferably between ¨5 C and +5 C.

12. The anti-skid stud for a tyre according to any of the preceding claims, wherein the stud pad comprises - at least 10 phr of styrene butadiene rubber (SBR), and/or - at least 10 phr of natural rubber (caoutchouc), and/or - at least 10 phr of polybutadiene rubber.

13. The anti-skid stud for a tyre according to claim 12, wherein the stud pad com-prises solution-polymerized styrene butadiene rubber (SSBR) having a vinyl content between 30% and 60% and a styrene content between 30% and 40%.
Date Recue/Date Received 2022-03-09

14.
The anti-skid stud for a tyre according to any of the preceding claims, wherein the stud pad comprises - at least 5 phr of resin, preferably 5 to 60 phr of resin, and/or - at least 20 phr, preferably 20 to 50 phr of at least one reinforcement which is preferably selected from carbon black reinforcement and silica rein-forcement.

15. A studded pneumatic tyre for a vehicle, comprising a tyre tread equipped with anti-skid studs according to any of the preceding claims 1 to 14.

16. A studded pneumatic tyre for a vehicle, comprising a tread of the tyre, the tread being provided with anti-skid studs which anti-skid studs comprise - an anti-skid stud body, which anti-skid stud body comprises a bottom flange (14) at the lower end of the stud body, and a stem (13) extending away from the bottom flange, characterized in that the anti-skid stud comprises a stud pad (20), having a thickness (t20) between 0.4 mm and 3 mm, wherein the stud pad is arranged at least partly below said bottom flange (14), and the area of the inner surface (25) of the stud pad (20) is at least 10% of the bottom area of the bottom flange of the anti-skid stud, and that the stud pad (20) is made of a polymer material, which polymer material is configured to soften at warm temperatures so that the ShA hard-ness of the stud pad is not greater than 55 at an ambient temperature of +22 C, and to harden at cold temperatures so that the ShA hardness of the stud pad is at least 70 at an ambient temperature of ¨25 C.

17. Use of a polymer material in a stud pad of an anti-skid stud in a tyre for a vehicle, characterized in that the polymer material is configured to soften at warm temper-atures so that the ShA hardness of the stud pad is not greater than 55 at an ambient temperature of +22 C, and to harden at cold temperatures so that the ShA
hardness of the stud pad is at least 70 at an ambient temperature of ¨25 C.
Date Recue/Date Received 2022-03-09