Tread Having Hidden Cavities

Abstract

Tread (1) for a heavy-duty vehicle tire having a total thickness corresponding to the thickness of material to be worn away during running, this tread having, in the new state, a tread surface (10) intended to come into contact with a roadway when running, this tread (1) comprising at least one hidden cavity (2) intended to form a new groove opening onto the tread surface after a predetermined amount of partial wear, this hidden cavity (2) comprising two opposite lateral walls (21, 22) connected together by a bottom (23) radially towards the inside and by a crown part (24) radially towards the outside, the tread according to invention being characterized in that the crown part (24) of the hidden cavity is provided with a plurality of fine ribs (25) extending radially towards the inside of the hidden cavity (2) from the crown part (24) delimiting the hidden cavity.

Claims

1. A tread for a heavy-duty vehicle tire having a total thickness corresponding to the thickness of material to be worn away during running, the tread having, in the new state, a tread surface adapted to come into contact with a roadway when running, the tread comprising at least one hidden cavity configured to form a new groove opening onto the tread surface after a predetermined amount of partial wear, said hidden cavity comprising two opposite lateral walls connected together by a bottom radially towards the inside and by a crown part radially towards the outside, wherein the crown part of the hidden cavity has a plurality of fine ribs, the height of which extends radially towards the inside of the hidden cavity from the crown part delimiting the hidden cavity.

2. The tread according to claim 1, wherein said fine ribs extend in a direction that makes an angle at least equal to 40 degrees with the main direction of the cavity, the main direction of a cavity corresponding to the direction of flow of a liquid inside this cavity when it is open onto the tread surface.

3. The tread according to claim 1, wherein the fine ribs formed on the crown part delimiting the hidden cavity have a maximum height at least equal to 1 mm and at most equal to 5 mm.

4. The tread according to claim 1, wherein the fine ribs formed on the crown part delimiting the hidden cavity are oriented at an angle close or equal to 90 degrees to the main direction of the hidden cavity, the main direction of a cavity corresponding to the direction of flow of a liquid inside this cavity when it is open onto the tread surface.

5. The tread according to claim 1, wherein the hidden cavity is continued radially as far as the tread surface in the new state by a sipe (4).

6. The tread according to claim 5, wherein the upper part of the hidden cavity comprises, on each side of the sipe, a flat face inclined at an angle greater than zero and at most equal to 45 degrees, said angle being measured with respect to a direction parallel to the transverse direction.

7. The tread according to claim 1, wherein the fine ribs continue on a part of at least one of the lateral walls delimiting the hidden cavity.

8. The tread according to claim 7, wherein the height over which these fine ribs extend along at least one of the lateral walls is at least equal to 1.5 mm.

9. The tread according to claim 8, wherein the height over which these fine ribs extend along at least one of the lateral walls is at most equal to 3 mm.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0030] FIG. 1 shows a partial view of the edge of a tread comprising a plurality of channels formed entirely beneath the tread surface in the new state, these channels being oriented transversely, i.e. parallel to the axis of rotation of the tire provided with this tread;

[0031] FIG. 2 shows a cross section on a plane containing the axis of rotation and the line of which is indicated by the line II-II in FIG. 1;

[0032] FIG. 3 shows a variant of a hidden channel according to the invention that is continued towards the tread surface by a sipe and comprises a plurality of fine ribs formed on the upper part of the hidden channel;

[0033] FIG. 4 shows a variant of the invention applied to a wavy groove having a succession of parts that are open onto the tread surface in the new state and hidden parts.

DESCRIPTION OF THE FIGURES

[0034] The examples described below relate to heavy-duty vehicle tires of size 315/70R22.5. They can be transposed easily to heavy-duty vehicle tires of different sizes.

[0035] The first variant illustrating the invention is shown in FIG. 1 and relates to a tread 1 of a tire for a heavy-duty vehicle, this tread 1 having, in the new state, a tread surface 10 intended to come into contact with a roadway. This tread 1 comprises hidden channels 2 under the tread surface 10 that are intended, after the tread has been partially worn away, to form new grooves that open onto the tread surface. In the present case, these hidden channels 2 are oriented transversely, that is to say in a direction corresponding to the transverse or axial direction of a tire provided with this tread. The transverse direction is coincident with the axis of rotation of the tire.

[0036] As can be seen in FIG. 1, these hidden channels 2 open towards the outside at the lateral edges of the tread 1. Each hidden channel 2 comprises two opposite lateral walls 21, 22, the distance between these lateral walls defining the width Lc of the channel. These lateral walls 21 and 22 are connected together by a channel bottom 23 in the innermost part of the tread and by a crown part 24 in the part closest to the tread surface 10.

[0037] Located on each of the channels 2 and on the crown part 24 are a plurality of fine ribs 25 with a maximum height t equal to 4 mm, these fine ribs 25 being oriented perpendicularly with respect to the main direction of the channels 2. In the present case, the main direction of the channels corresponds to the transverse or axial direction on the tread, the latter direction corresponding to the direction perpendicular to the plane of FIG. 1.

[0038] Each channel 2 is situated beneath the tread surface 10 of the tread 1 at a distance Hs equal, in the present case, to 5 mm and has a total height Hc equal, in the case of the example, to 8 mm. The thickness of tread material to be worn away corresponds substantially to the sum of the heights Hs and Hc. The width Lc of the hidden channel 2 is equal to 6 mm.

[0039] FIG. 2 shows a cross section of the tread shown in FIG. 1 made in a radial section plane, that is to say a plane containing the axis of rotation of the tire. It is apparent in this section plane that the upper wall delimiting the hidden cavity 2 comprises a plurality of fine ribs with a maximum height t equal, in the example described, to 2 mm, these fine ribs being disposed regularly at a spacing P. These fine ribs have a maximum width equal to 1.5 mm The distance P between the fine ribs is between one and five times the maximum width Lc of the hidden cavity 2.

[0040] The fine ribs are oriented perpendicularly to the plane of FIG. 2, that is to say perpendicularly to the main direction of the hidden cavity 2 (the latter being indicated by the direction AA in FIG. 2).

[0041] In a variant that is not shown here, the fine ribs may be oriented obliquely so as to form an angle less than 90 degrees. Preferably, this angle is at least equal to 45 degrees.

[0042] FIG. 3 shows a variant of the invention in which a channel 2 is continued towards the tread surface 10 by a sipe 4. In this variant, the crown part 24 of the channel 2 is subdivided on either side of the sipe 4 into two crown parts 241, 242. Each of these crown parts 241, 242 is inclined at an angle G equal to 15 degrees in the example, so as to form an angle of 150 degrees therebetween. Also formed on each of these crown parts 241, 242 are a plurality of transversely oriented fine ribs 25. These fine ribs 25 make an angle of 90 degrees with the main direction of the hidden cavity corresponding to the direction perpendicular to the plane of FIG. 3. These fine ribs 25 continue over a height h along the lateral faces 21, 22 delimiting the cavity 2. In the present case, this height h is equal to 2 mm.

[0043] The combination of the presence of a plurality of fine ribs 25 and the inclination G of the crown parts 241, 242 is particularly effective on the wearing surface before the formation of new grooves that open onto the tread surface.

[0044] The third variant, shown in FIG. 4, relates to a tread 1 for a heavy-duty vehicle tire of size 315/70R22.5.

[0045] This tread has, in its thickness, at least one groove referred to as wavy, this wavy groove 3 having an alternation of groove parts 31 that open onto the tread surface 10 in the new state and hidden cavities 32 that are intended to open onto the tread surface after a predetermined amount of wear in order to form new grooves. These open groove parts 31 and hidden cavity parts 32 are connected together by connecting parts 33 that ensure continuity of the flow of fluids in the wavy groove in the new state, this flow taking place in the main direction of the groove. This type of wavy groove is described in the patent EP2483087-B1, to which reference is made in particular for the figures contained in this cited patent.

[0046] The maximum width of the hidden cavity 32 is equal to 5 mm and its height is equal to 6 mm.

[0047] In order to make it easier to mould and demould this wavy groove 3, a sipe 4 is also formed that extends between each hidden cavity 32 and each connecting part 33 for connecting to the tread surface 10 in the new state. The sipe 4 has a width equal to 0.6 mm and is delimited by walls that are able to come into at least partial contact with one other under use conditions.

[0048] Each hidden part 32 comprises two opposite lateral walls, these lateral walls being connected together by a lower part forming the bottom radially on the inside and by an upper part radially on the outside. The upper part is divided into two parts that are continued by walls delimiting the sipe 4.

[0049] In order to improve the wearing surface radially above the hidden cavities and thus to achieve more regular wear over the entire tread surface, a plurality of fine ribs 35 are formed on the upper part of each hidden cavity, said fine ribs 35 being oriented in the present case so as to make an angle of 90 degrees with the main direction of the groove 3, this main direction corresponding to the direction of the flow of water in the groove 3 when running in wet weather.

[0050] These fine ribs 35 continue over a small height h (equal here to 1.5 mm) on the walls delimiting each hidden cavity 32 widthwise. These fine ribs 35 are disposed parallel to one another at a spacing equal to 6 mm.

[0051] After the tread has been partially worn away, and before the hidden cavity becomes a groove open onto the tread surface of the tread, the addition of material associated with the presence of these fine ribs causes localized stiffening in the vicinity of the cavity, making it possible to ensure more a more regular wearing surface.

[0052] The examples described are not intended to limit the invention and various modifications can be made thereto by a person skilled in the art without departing from the scope of the invention as defined in the claims.