Patent Description:
Ice grip devices, also known as stud pins, are used to improve the traction of winter tires on icy roads and generally comprise a body embedded in a tread portion of the tire and a pin that protrudes from the tread portion to scrape ice. The interaction between the pin and road surface may lead to premature wear of both the road surface and the device and may also cause the device to shift within the tread portion. Shifting of the device within the tread portion may impair traction performance or even cause the device to fall out. One way to prevent shifting of the device is to reduce the size of the recess in the tread portion for receiving the device, which provides a tight fit between the device and the tread portion. However, an overly tight fit makes it difficult to install the device.

Accordingly, there remains a need for an improved ice grip device in view of these challenges.

An ice grip device in accordance with the preamble of claim <NUM> is known from <CIT> and <CIT>. Related ice grip devices are known from <CIT> and <CIT> (document according to Article <NUM>(<NUM>) EPC).

A first aspect provides an ice grip device having a body configured to be received in a recess provided in the tread portion of a tire and a pin connected to the body; the body comprises a top flange connected to the pin, a shaft and a bottom flange arranged adjacent to one another along a longitudinal axis, each having a cross-sectional area perpendicular to the longitudinal axis; the cross-sectional area of the shaft is smaller than the cross-sectional area of the top flange and the bottom flange, respectively; the bottom flange includes a main portion centered on the longitudinal axis and a single tail portion that extends radially outwardly from the main portion with respect to the longitudinal axis.

The bottom flange of the device therefore comprises a single tail portion that forms an extended tail, i.e. a single eccentric feature with respect to the longitudinal axis. When the device is inserted into a substantially cylindrical recess provided in the tread portion of a tire, the tail portion of the bottom flange stretches the recess at a single location, which prevents the device from rotating or shifting and improves the transmission of forces from the device to the tire, and thus improves traction performance.

Further features and advantages of the device are described in the dependent claims and in the following description. In the following, the expressions "radial" and "perpendicular" are defined relative to the longitudinal axis.

By providing the tail portion at only the bottom flange, the device is not substantially larger than other devices, and the installation of the device is not impaired. This is particularly the case in one embodiment in which the tail portion has a tail width that is smaller than or equal to a cross-sectional width of the shaft.

In one embodiment, a boundary line centered on the longitudinal axis, e.g. a circular boundary line, encloses the main portion of the bottom flange, and the tail portion extends at least <NUM>, preferably at least <NUM> in the radial direction beyond the boundary line. Some or all of an outer contour of the main portion may lie on the boundary line as long as the tail portion extends radially outside of the boundary line. Where the main portion and the tail portion are integrally formed, the boundary line is imaginary. However a visible boundary line where the main portion and tail portion are joined is also possible.

In the inventive ice grip device, the bottom flange includes first and second projections that form a Y-shape with the tail portion. The projections form additional edges and recesses along the periphery of the bottom flange. At least one of the projections and the tail portion may have a curved edge, but they may also have a straight edge. When the device is installed into the tread portion, tread rubber is pushed into the recesses while the additional edges of the projections bite into the rubber to prevent shifting or rotation of the device. The recesses may be formed as arc-shaped recesses that curve inward towards the longitudinal axis. In other embodiments not forming part of the present invention, in which the bottom flange does not have a Y-shape, one or more such aforementioned arc-shaped recesses may be formed at the bottom flange to accommodate tread rubber and prevent the device from shifting or rotating to improve traction performance.

The cross-sectional shape of the top flange may have various shapes. For example, the cross-section may have a substantially rectangular or a substantially trapezoidal shape.

Alternatively, the cross-section may have a substantially triangular shape. The triangular shape be rotationally symmetric by <NUM>° about the longitudinal axis. Optionally, one of the edges of the substantially triangular shape may face towards the tail portion and extend substantially in parallel to a tail edge of the edge portion. Therefore, the top flange is widest towards the tail portion, which further helps to suppress shifting and rotation of the device after installation.

Regardless of the cross-sectional shape of the top flange, the side edges of the top flange may comprise one or more, preferably two or more arc-shaped recesses that curve inward toward the longitudinal axis. When the device is installed in the tread portion, the edges formed at each end of the arc-shaped recess bite into the surrounding tread rubber while tread rubber is pushed into the recess to prevent shifting or rotation of the device.

A further optional feature to prevent shifting and rotation of the device is to provide the bottom flange with a chamfered surface that extends at an angle, for example <NUM>° to <NUM>°, relative to a body bottom surface that is substantially perpendicular to the longitudinal axis. The sharp edge formed by the chamfered surface exerts an additional force on the tread rubber to improve retention of the device.

When a tire provided with ice grip devices travels along a road surface, the body portion of the device may protrude slightly from the tread portion, which causes the front edge of the top flange to contact the road surface and results in premature wear of the device. In order to counteract this effect, the top flange may have a taper that extends at an angle of <NUM>° to <NUM>° relative to the body top surface, which extends substantially perpendicular to the longitudinal axis, to lower the front edge of the top flange.

In another embodiment, the pin comprises an angled surface that extends at an angle relative to a substantially perpendicular body top surface and a pin top surface extending substantially parallel to the body top surface; the angled surface and the pin top surface join to form a scraping edge.

Providing such an angled surface lowers a front edge of the pin, which is the first part of the pin to make contact with the road surface. The lowered front edge suppresses premature breakage of the pin, which improves performance in the so-called overrun test and reduces damage to the road surface. At the same time, the scraping edge makes contact with the icy road surface to improve traction. This aspect can be combined with the first aspect and its embodiments to improve the traction performance of ice grip devices.

An angle of the angled surface may be <NUM>° to <NUM>° relative to the body top surface. A height of the angled surface along the longitudinal axis of the device may be greater than <NUM> in less than or equal to <NUM>. The angled surface may have a length corresponding to <NUM> to <NUM> times the length of the pin from the front edge to the rear edge. The front edge of the pin is preferable formed by the angled surface, while the rear edge of the pin is formed by the pin top surface.

The pin comprises a convex rear edge that curves away from the longitudinal axis. This shape adds bulk to the shape of the pin, which increases its robustness. This effect is particularly pronounced in combination with a shape in which the pin comprises at least two contact points connected by a connecting arc that curves towards the longitudinal axis.

In a further embodiment, a top surface of the pin is curved to form a dome shape.

The dome shape lowers the front edge of the pin to provide the same effect as the angled surface and the scraping edge in an alternative manner. The lowered front edge of the pin makes contact with the ground later than the front edge of a pin whose entire surface is perpendicular to the longitudinal axis of the device. The dome-shaped pin may also be combined with a bottom flange having an extended tail portion to enhance traction performance.

For both the dome shaped pin and the pin having an angled surface and a scraping edge, a front edge of the pin may comprise at least two contact points connected by a connecting arc that curves towards the longitudinal axis. The contact points of the pin dig into the icy road surface to improve traction performance. When the front edge is located on the angled surface of the pin, premature wear and breakage of the contact points can be suppressed.

A further aspect is a pneumatic tire having a tread portion provided with one or more recesses and an ice grip device installed in each recess. The pneumatic tire has a rotational direction, and the tail portion of at least one or more of the installed device extends along the rotational direction. "Extending along" refers to a configuration in which the tail portion is aligned with the rotational direction, i.e. points towards or opposite to the rotational direction. Installing the devices with the tail portions pointing opposite to the rotational direction enables the tail portions to particularly resist rotation about the tire axial direction.

In one embodiment, the tread portion comprises two shoulder portions at each edge of the tread portion in a tire axial direction and a middle portion arranged between the shoulder portions. The devices installed in at least one of the shoulder portions have a different orientation to the devices installed in the middle portion. Having devices whose tail portions are oriented in different directions may help the tire to execute other movements, such as turning, on icy surfaces. For example, the respective tail portions of the devices installed in said at least one shoulder portion extend at an angle of <NUM>°, <NUM>° or <NUM>° relative to the tail portions of the devices installed in the middle portion.

In particular, the tail portions of the installed devices extend opposite to the rotational direction, but the tail portions of some or even all the installed devices can also extend in the rotational direction.

Further details and advantages of the device will be explained in reference to the following description and to the drawing.

<FIG> show a first embodiment of an advanced ice grip device or stud pin <NUM>, which comprises a body <NUM> configured to be received in a corresponding recess provided in the tread portion of a tire and a pin <NUM> connected to the body <NUM>. The stud pin <NUM> extends along a longitudinal axis Z. The expressions "radial", "radially", "perpendicular" or "perpendicularly" are defined relative to the longitudinal axis Z.

In particular, <FIG> shows that the body <NUM> comprises a top flange <NUM> and a bottom flange <NUM> that are connected by a neck or shaft <NUM>, which has a smaller cross-sectional area than either the top flange <NUM> or the bottom flange <NUM>. The pin <NUM> is connected to the top flange <NUM> and is arranged at the opposite end of the stud pin <NUM> from the bottom flange <NUM>. The various parts of the stud pin <NUM> can be formed as separate parts, e.g. of different materials, that are joined during manufacturing.

The bottom flange <NUM> comprises a main portion <NUM> arranged along the longitudinal axis Z and a tail portion <NUM> that protrudes from the main portion <NUM> in a radial direction. The tail portion <NUM> therefore forms an extended tail and gives the body <NUM> a boot-like shape. When the stud pin <NUM> is installed into the tread portion of a tire, the tail portion <NUM>, which forms the toes of the boot-like shape, digs into the tread rubber surrounding the stud pin <NUM> to prevent the stud pin <NUM> from shifting, e.g. tipping forwards or backwards, or from rotating about the longitudinal axis Z.

As shown in <FIG>, the main portion <NUM> of the bottom flange <NUM> is centered on the longitudinal axis Z and is encircled by an imaginary circular boundary line <NUM> that is also centered on the longitudinal axis Z. Part of an outer contour <NUM> of the bottom flange <NUM> overlaps with the boundary line <NUM>. The boundary line <NUM> need not necessarily have a circular shape as long as the shape is centered on the longitudinal axis Z. The bottom flange <NUM> has first and second projections 28a, 28b that form a Y-shape with the tail portion <NUM>. The outer contour <NUM> of the bottom flange <NUM> also forms arc-shaped recesses 30a relative to the boundary line <NUM>. The outer contour <NUM> forms an edge at the end of each arc-shaped recess 30a that digs into surrounding tread rubber and pushes the tread rubber into the recess 30a.

The tail portion <NUM> forms an eccentric feature that extends radially outward from the main portion <NUM>. A radial length T of the tail portion <NUM> from the boundary line <NUM> to a rounded tail edge <NUM> is at least <NUM>, preferably at least <NUM>. Alternatively, as shown in <FIG>, the tail edge <NUM> may be formed substantially straight across. As shown by the side view of the stud pin <NUM> in <FIG>, the tail portion <NUM> does not substantially increase the overall size of the stud pin <NUM>, which would make installation more difficult. A tail width W<NUM> of the tail portion <NUM> is smaller than or equal to a cross-sectional width W<NUM> of the shaft <NUM> (see <FIG>). This size relationship ensures that the tail portion <NUM> of the bottom flange <NUM> is not overly large with respect to the body <NUM> of the stud pin <NUM>. Although <FIG> shows a substantially cylindrical shaft <NUM>, the same relationship of widths would apply to a shaft <NUM> with a different cross-sectional shape.

The bottom flange <NUM> has a chamfered surface <NUM> that extends at an angle of <NUM>° to <NUM>° relative to a substantially perpendicular bottom surface <NUM> of the body <NUM>. The chamfered surface <NUM> forms a sharp knife edge that digs into the tread rubber surrounding the stud pin <NUM> to improve retention of the stud pin <NUM>.

<FIG> shows an enlarged view of the top flange <NUM> and pin <NUM> in <FIG>. The pin <NUM> comprises an angled surface <NUM> that extends at an angle α of <NUM>° to <NUM>° relative to a perpendicular top surface <NUM> of the body <NUM> and has a height h of <NUM> to <NUM> along the longitudinal axis Z. The pin <NUM> also has a substantially perpendicular top surface <NUM> that connects to the angled surface <NUM> at a straight scraping edge <NUM>. Due to the angled surface <NUM>, the front edge <NUM> of the pin <NUM> is lowered in comparison to a front edge <NUM>' for which the pin <NUM> has no angled surface <NUM>. When the stud pin <NUM> is installed in a tread portion, and the tire travels across a road surface, the lowered front edge <NUM> makes contact with the ground later than the front edge <NUM>'. The delayed contact with the ground surface suppresses breakage and wear of the pin <NUM> along the front edge <NUM> and increases the durability of the stud pin <NUM>.

Similarly, the top flange <NUM> comprises a taper <NUM> that extends at an angle β of <NUM>° to <NUM>° relative to the body top surface <NUM>. The taper <NUM> replaces a sharp corner the top flange <NUM> that may come into contact with the road surface as the body <NUM> protrudes slightly beyond the surface of the tread portion of the tire.

<FIG> shows an enlarged top view and a schematic side view of the pin <NUM> in <FIG>. The front edge <NUM> of the pin forms three contact points <NUM> that are connected by two connecting arcs <NUM> that curve inwards toward the longitudinal axis Z. The connecting arcs <NUM> cause the contact points <NUM> to protrude outwards and scrape along icy road surfaces to increase traction performance. To compensate for the loss of volume of the pin <NUM> that results from the connecting arcs <NUM>, a rear edge <NUM> of the pin <NUM> has a convex shape that curves away from the longitudinal axis Z.

<FIG> shows an enlarged top view and a schematic side view of another pin <NUM>' whose front edge <NUM> has only two contact points <NUM> that are connected by a single connecting arc <NUM>. While the rear edge <NUM> of the pin <NUM> in <FIG> has a convex rounded shape, the rear edge <NUM> of the pin <NUM>' in <FIG> forms a trapezoidal shape. In both cases the purpose of the rear edge <NUM> that protrudes away from the longitudinal axis Z is to increase the durability of the pin <NUM>, <NUM>'.

As shown in the schematic side views in <FIG>, a length L<NUM> of the angled surface <NUM> is <NUM> to <NUM> times the length L<NUM> from a front edge <NUM> to a rear edge <NUM> of the pin <NUM>.

<FIG> shows an enlarged top view and a schematic side view of a further pin <NUM>" that includes a domed top surface <NUM>' instead of an angled surface <NUM> as in the pins <NUM>, <NUM>' of <FIG>. The domed top surface <NUM>' has a suitable radius of curvature R that results in a lowered front edge <NUM> of the pin in a similar manner to the angled surface <NUM>, as shown by the dashed horizontal line in <FIG>. The top view in <FIG> shows that the pin <NUM>" has a total of six sides to form a substantially hexagonal shape that is robust and simple to manufacture. Although the pin <NUM>" is shown with six sides, it is also possible to realize a similar shape with four sides in which the side edges curve outwards.

<FIG> shows the substantially triangular shape 16b of the top flange <NUM> in <FIG> in more detail. The triangular shape 16b is arranged so that the bottom edge of the triangular shape 16b extends in parallel to the tail edge <NUM> of the tail portion <NUM>. Since the top flange <NUM> is wider towards the tail portion <NUM>, the stud pin <NUM> is able to withstand rotation and shifting in the tire tread portion. In order to make it easier to install the stud pin <NUM> in a tire tread, a front edge <NUM> of the top flange <NUM> is formed substantially straight across. As an alternative, <FIG> shows a similar top flange <NUM> having a rotational symmetry of <NUM>° about the longitudinal axis Z, so that the front edge <NUM> of the top flange <NUM> is curved.

<FIG> and <FIG> both also show that the top flange <NUM> is provided with arc-shaped recesses 30b, whose edges dig into the surrounding tread rubber and push the tread rubber into the arc-shaped recesses 30b and additionally prevent the stud pin <NUM> from shifting or rotating.

The shape of the top flange <NUM> shown in <FIG> can be combined with the various pins <NUM>', <NUM>" shown in <FIG>, as illustrated in <FIG> as well as with the shape of the top flange <NUM> shown in <FIG> (further embodiments not illustrated). Additionally or alternatively, the shape of the top flange <NUM> can be modified. For example, <FIG> shows a stud pin <NUM>' with a top flange <NUM>' that has a substantially trapezoidal shape formed by straight front and rear edges <NUM>, <NUM> that are connected by curved side edges <NUM>. The rear edge <NUM> is substantially shorter than the front edge <NUM>, which makes the installation of the stud pin <NUM>" easier.

<FIG> shows that a top flange <NUM>" with a substantially rectangular cross-sectional shape, with a rear edge <NUM> of that extend in parallel to the tail edge <NUM> of the tail portion <NUM>. The rear edge <NUM> is longer than the side edges <NUM> of the top flange <NUM>" to help the stud pin <NUM>" maintain its orientation in the tread portion. The pin <NUM>' of stud pin <NUM>" is also different from the previous figures, but the bottom flange <NUM> has the same shape as in <FIG>. The rectangular top flange <NUM>" of <FIG> can also be combined with the pins <NUM>, <NUM>" shown in <FIG>, respectively.

<FIG> shows a schematic view of a tread portion <NUM> of a winter tire that includes a middle portion <NUM> provided between two shoulder portions <NUM>, indicated by dashed lines, and has a rotational direction R indicated by an arrow. It is noted that the tread portion <NUM> is not drawn to scale and may include any suitable configuration of grooves and tread blocks.

Claim 1:
An ice grip device (<NUM>; <NUM>'; <NUM>") comprises a body (<NUM>) configured to be received in a recess provided in the tread portion of a tire and a pin (<NUM>; <NUM>'; <NUM>") connected to the body (<NUM>),
wherein the body (<NUM>) comprises a top flange (<NUM>; <NUM>'; <NUM>") connected to the pin (<NUM>; <NUM>'; <NUM>"), a shaft (<NUM>) and a bottom flange (<NUM>) arranged adjacent to one another along a longitudinal axis (Z), each having a cross-sectional area perpendicular to the longitudinal axis (Z),
wherein the cross-sectional area of the shaft (<NUM>) is smaller than the cross-sectional area of the top flange (<NUM>; <NUM>'; <NUM>") and the bottom flange (<NUM>), respectively,
wherein the bottom flange (<NUM>) includes a main portion (<NUM>) centered on the longitudinal axis (Z) and a single tail portion (<NUM>) that extends radially outwardly from the main portion (<NUM>) with respect to the longitudinal axis (Z),
characterized in that
the bottom flange (<NUM>) further comprises first and second projections (28a, 28b) that form a Y-shape with the tail portion (<NUM>), in particular with at least one of the first and second projections (28a, 28b) and the tail portion (<NUM>) having a curved edge (<NUM>).