Tire tread with directional design

Abstract

A tread having a plurality of grooves formed on each half of the tread on each side of a midplane X-X, each opening axially to the outside and extending axially towards the midplane X-X so that the plurality of grooves forms a first pattern in the overall shape of a V pointing in a groove direction Xr. The tread includes a plurality of sipes. From a certain degree of wear onwards, all or some of the sipes become enlarged forming cavities extending in an oblique direction forming a second pattern in the overall shape of a V pointing in a cavity direction Xc. Each of these cavities opens into just one of the grooves of the tread, the plurality of grooves forming, at this level of wear, the same first pattern.

Claims

1. A tread comprising: a plurality of grooves which are formed on each half of the tread on each side of a midplane X-X, each of these grooves opening axially to the outside and extending axially towards the midplane X-X so that the plurality of grooves forms on the tread a first pattern in the overall shape of a V pointing in a groove direction Xr, a plurality of sipes wherein from a certain tread wear onwards, all or some of the sipes of this tread become enlarged in order to form cavities, wherein these cavities extend in an oblique direction, forming a second pattern in the overall shape of a V pointing in a cavity direction Xc, wherein each of these cavities opens into just one of the grooves of the tread, the plurality of grooves forming, at this level of wear, the same first pattern, and wherein the grooves have a predetermined curvature on the tread surface of the tread, each groove delimiting a first wall of material on the inside of the curvature and a second wall of material opposite the first wall of material, wherein the cavity direction Xc is identical to the groove direction Xr, and wherein each cavity extends between the first wall of a first groove and the second wall of a second groove adjacent to the first groove, this cavity opening onto the first wall of the first groove and not opening onto the second wall of the second groove.

2. The tread according to claim 1, wherein the cavity delimits a wall respectively facing the first wall of the first groove or the second wall of the second groove, the shape of this wall on the tread surface being parallel respectively to the curvature of the first wall or parallel to the curvature of the second wall.

3. The tread according to claim 1, wherein the cavity comprises a principal part of width wp and an intermediate part of width wi less than the width wp of the principal part, this intermediate part connecting the principal part of the cavity to a groove.

4. The tread according to claim 3, wherein the width wi of the intermediate part of the cavity decreases progressively from the principal part of this cavity towards the groove.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other features and advantages of the invention will become apparent from the description which follows, given by way of non-limiting example with reference to the attached drawings in which:

(2) FIG. 1 schematically depicts a tread surface of a tread according to an embodiment of the invention, in the new state;

(3) FIG. 2 depicts an enlarged view of part of the tread of FIG. 1 in the worn state;

(4) FIG. 3 depicts a partial view of a tread surface according to a third embodiment;

(5) FIG. 4 depicts a partial view of a tread surface according to a fourth embodiment;

(6) FIG. 5 depicts a partial view of a tread surface according to a fifth embodiment.

(7) In the description which will follow, elements which are substantially identical or similar will be denoted by identical references.

DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

(8) FIG. 1 schematically depicts a tread surface of a tread 1 in the new state. It is this tread surface that will come into contact with a road surface when a tire which comprises this tread is being driven on.

(9) In more detail, the tread 1 comprises a plurality of grooves 3a, 3b formed on each half of the tread on either side of a midplane X-X. Each of these grooves opens axially to the outside, namely towards the shoulder parts of the tire (which have not been depicted here) and extend axially towards the midplane X-X with a predetermined curvature. These grooves 3a, 3b form on the tread a first pattern in the overall shape of a V pointing in a groove direction Xr. More specifically, each groove delimits a first wall of material 9a, 9b on the inside of the curvature of the groove and a second wall of material 11a, 11b opposite the first wall of material. The tread further comprises a plurality of sipes 5. Each of these sipes extends here between two adjacent grooves in an oblique direction.

(10) FIG. 2 shows the state of the tread 1 when this tread reaches a certain degree of wear, for example, when the degree of wear of the tread reaches 20%. At this level of wear, the sipes become enlarged to form cavities 7. Each of these cavities opens into just one of the grooves 3a, 3b. These cavities 7 form a second pattern on the surface of the tread. This second pattern has the overall shape of a V and points in a cavity direction Xc.

(11) In the embodiment illustrated in FIG. 2, the cavities 7 point in a direction Xc the opposite of the direction Xr of the grooves 3a, 3b and each cavity extends between the first wall 9a of a first groove 3a and the second wall of a second groove 3b adjacent to the first groove 3a. The cavity 7 opens then onto the second wall 11b of the second groove 3b but this cavity does not open onto the first wall 9a of the first groove 3a. Thus, a flow of water being removed from the cavity 7, referred to as a secondary flow Fs, will proceed in the same direction as a flow of water being removed from the grooves 3a, 3b and referred to as the main flow Fp.

(12) In another embodiment illustrated in FIG. 5, the cavities 7 point in a direction Xc parallel to the direction Xr of the grooves. These cavities 7 will therefore open onto the first wall 9a of the first groove 3a and these cavities 7 will not open onto the second wall 11b of the second groove 3b. Thus, the flows of water Fs being removed from the cavity 7 will proceed in the same direction as the flows of water Fp being removed from the grooves 3a, 3b.

(13) FIG. 2 shows an enlargement at one end of a cavity 7, this end not opening into one of the grooves 3a, 3b. The cavity 7 at this end delimits a wall 13 facing the first wall 9a of the first groove. This wall has a shape on the tread surface of the tread which here is parallel to the curvature C of the first wall 9a. It will be noted that it is possible to measure the distances d1, d2, d3 between the first wall 9a and three points on the wall 13 which are respectively distributed at the ends of the wall 13 and the centre of this wall. The term parallel means that if the differences between the distances d1, d2, d3 are measured, the greatest of these differences needs to be less than 10% of the smallest distance d1, d2, d3.

(14) The design that is mentioned hereinabove may also be applied to the walls 13 of the cavities 7 of FIG. 5.

(15) FIG. 3 is an alternative form of embodiment of the cavity 7 in which this cavity comprises a principal part 15 of width wp and an intermediate part 17 connecting the principal part 15 of this cavity to a groove. This intermediate part is depicted here in the form of a sipe.

(16) FIG. 4 is another alternative form of embodiment of the cavity 7 in which the intermediate part decreases progressively from the principal part of this cavity towards the groove.

(17) The invention is not restricted to the examples described and depicted and various modifications can be made thereto without departing from its scope.

(18) Thus, the principal direction in which the sipes extend is, as may be seen in FIG. 1, parallel overall to the direction in which the cavities that extend these sipes extend, as can be seen in FIG. 2. In other embodiments, it is possible for the principal direction in which the sipes extend to be angularly offset with respect to the principal direction in which the cavities extend.

(19) Furthermore, the cavities are shown in the figures to have a rectangular overall shape. As an alternative, the cavity along its length has different shapes, such as curved shapes.