Tread Comprising A Long Tread Bar Having A Plurality Of Cut-Outs

Abstract

Tread for a tire, having an elongate block (3) extending in a circumferential direction and having a contact surface (5) intended to come into contact with the ground, a first and a second lateral wall delimiting said contact surface (5), the elongate block having a plurality of cuts that each have a first and a second end, the cuts (n, n+1) longitudinally following one another on the contact surface (5) such that, when one cut (n) reaches its second end, another cut (n+1) starts, at one and the same circumferential level on the elongate block (3). Moreover, all or some of the sipes (n, n+1) have at least one narrowing protrusion protruding from a wall of the cut.

Claims

1. Tread for a tire, the tread comprising at least one elongate block of rubbery material of width W and length L, where L>>W, said elongate block extending in a circumferential direction when the tread is mounted on the tire, each said elongate block having a contact surface, adapted to come into contact with the ground, and a first lateral wall and a second lateral wall delimiting said contact surface, said elongate block having a plurality of N successive oblique cuts that each have a first end and a second end, at least one of the first end and the second end opening onto the first lateral wall or second lateral wall, wherein the oblique cuts longitudinally follow one another on said contact surface such that at least one of the first and second ends of one of the oblique cuts is at the same circumferential level on said elongate block as one of the first and second ends of another of said oblique cuts, and wherein all or some of the oblique cuts have at least one narrowing protrusion protruding from a wall of the cut.

2. The tread according to claim 1, wherein the narrowing protrusion extends up to the contact surface.

3. The tread according to claim 1, wherein the cut narrows over at least 20% of the height of said cut.

4. The tread according to claim 1, wherein the cut narrows over at least 20% of the surface of the wall from which the protrusion protrudes.

5. The tread according to claim 1, wherein the wall of the cut opposite the protrusion is inclined.

6. The tread according to claim 1, wherein the narrowing is formed by two facing protrusions that protrude from opposite walls of the cut.

7. The tread according to claim 1, wherein the width of the protrusion decreases away from the wall from which said protrusion protrudes.

8. The tread according to claim 1, wherein the cut is wholly or partially chamfered at the surface of the tread.

9. The tread according to claim 1, wherein the width of the cut at the narrowing is less than or equal to 0.7 mm.

10. The tread according to claim 1, wherein the width of the cut at the narrowing is between 0.3 mm and 0.5 mm.

11. The tread according to claim 1, wherein the cuts are sipes.

12. The tread according to claim 1, wherein the cuts are grooves.

13. A tire comprising a tread according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Further features and advantages of the invention will become apparent from the following description, given by way of non-limiting example, with reference to the attached drawings, in which:

[0059] FIG. 1 schematically shows a partial view of a tread according to a first exemplary embodiment of the invention;

[0060] FIGS. 2 to 5 illustrate examples of profiles in the depth of the tread of a sipe according to the invention;

[0061] FIGS. 6 to 8 illustrate examples of grooves according to the invention.

DETAILED DESCRIPTION

[0062] In the following description, elements which are substantially identical or similar will be denoted by identical references.

[0063] FIG. 1 shows a partial view of a tread 1 of a tire according to a first embodiment of the invention.

[0064] The tread 1 comprises at least one block 3 of rubbery material. The block 3 is delimited here by two grooves 4, which have been shaded grey in FIG. 1 to make the invention easier to understand. More specifically, the block 3 has a width W and a length L, this length L being very much greater than the width W. The expression very much greater means that the length L is at least equal to 5 times the width W. In this way, when the tread 1 is mounted on a tire, the block 3 looks like a strip extending in a circumferential direction X. This strip may extend all around the circumference of the tire. In a variant, this strip extends around only part of this circumference.

[0065] In addition, the block 3 has a contact surface 5 intended to come into contact with the ground, and a first lateral wall 7 and a second lateral wall 9 delimiting this contact surface 5.

[0066] Moreover, the block 3 has a plurality of sipes n, n+1 opening onto the contact surface 5. The sipes n, n+1 extend in an oblique direction, opening onto the first lateral wall 7 with their respective first ends E1, E3 and onto the second lateral wall 9 by way of their respective second ends E2, E4.

[0067] The sipes n, n+1 of the block 3 are in this case oriented in the same direction, that is to say the sipes extend from the first lateral wall 7 towards the second lateral wall 9 in a direction that is positive in X and Y. These sipes are distributed over the contact surface 5 of the block 3 in such a way that when one sipe n reaches the second lateral wall 9, another sipe n+1 starts from the first lateral wall 7, substantially at the same level on the block 3.

[0068] The expression at the same level x on the block means a determined circumferential position x on this block. In addition, substantially means that there may be a slight offset between the circumferential position of the sipes n, n+1. This offset is limited, however. It is preferably less than 5% of the spacing between the two sipes n, n+1 delimiting the sub-block 8. In order to assess whether or not such an offset is present, use is made of the idea of a neutral axis associated with each sipe.

[0069] Moreover, each sipe n, n+1 has a narrowing protrusion which narrows the distance between the walls of the sipes. In particular, the narrowing starts from a certain depth.

[0070] FIG. 2 illustrates a cross-sectional view on the axis A-A in FIG. 1 illustrating the profile in the depth of the tread of a sipe n according to a first exemplary embodiment. In this exemplary embodiment, the sipe n has, at a depth P of the tread, a narrowing protrusion 10 protruding from a wall 11 of the sipe n.

[0071] FIG. 3 is a variant in which the narrowing of the sipe is formed by two facing protrusions 100, 101. Each protrusion 100, 101 protrudes from a wall 110, 111 of the sipe n1.

[0072] FIG. 4 is another variant, in which the wall 1100 of the cut n2 opposite the protrusion 1000 is inclined. It will also be noted that the protrusion 1000 protruding from the opposite wall 1001 has a wall 1002 adjacent to the inclined walls 1100 and parallel thereto.

[0073] FIG. 5 is another variant, in which the sipe n3 has a chamfer at the surface of the tread.

[0074] It will be noted that in the example in FIG. 2 the protrusion 10 has a fixed width, while in the examples in FIGS. 3, 4 and 5 the width w1 of the protrusions 100, 101; 1000; 10000 decreases away from the wall from which each protrusion protrudes.

[0075] FIG. 6 illustrates an example of two grooves n4, n4+1 according to the invention which follow one another on the tread 5. The groove n+4 has a first end E41 and a second end E42 and the groove n4+1 has a first end E43 and a second end E44. The ends E42 and E43 are adjacent to one another on the tread.

[0076] In particular, the upper end A of the lower wall of the groove n4 is aligned, at the level x1 in the circumferential direction X, with the lower end B of the lower wall 32 of the groove n4+1. Furthermore, the upper end C of the upper wall 31 of the groove n4 is aligned, at the level x2 in the circumferential direction X, with the lower end D of the upper wall 33 of the groove n4+1.

[0077] In addition, each of the grooves n4, n4+1 has a narrowing protrusion 20, 21 protruding from a wall 30, 31 of the groove n4, n4+1.

[0078] FIG. 7 is a variant in which the narrowing of each groove n5 is formed by two facing protrusions 200, 201. Each protrusion 200, 201 protrudes from a wall 210, 211 of the groove n5.

[0079] It will be noted that in the examples in FIGS. 6 and 7, the narrowing protrusions 20; 200, 201 are at a certain depth in the contact surface 5 of the tread.

[0080] FIG. 8 illustrates another variant, in which the narrowing protrusion 2000 of the groove n6 extends up to the contact surface 5 of the tread.

[0081] It will also be noted that for the examples in FIGS. 6 to 8, the narrowing along the length of the grooves n4, n5, n6 is partial, in this case in a central portion.

[0082] In a variant that is not illustrated, the lengths of the cuts n, n+1 are shorter. The ends E2, E4 are then separated by a distance D. This distance D has a transverse component at least equal to 10% of the width W of the elongate block.

[0083] In a variant that is not illustrated, the elongate block has a series of oblique sipes n, n+1 that open onto the first lateral wall 7 and extend as far as ends E2, E4 of sipes that do not open onto the lateral walls 7, 9. The ends E2, E4 are in this case located on a median plane of the tread.

[0084] The sipes n, n+1 are distributed over the contact surface 5 such that when the cut n reaches its cut end E2, another cut n+1 starts from the first lateral wall 7, substantially at the same circumferential level x on the elongate block 3.

[0085] Thus, when the sipes n, n+1 are projected in the circumferential direction X, sipes are not superimposed in this circumferential direction X. This limits the variation in the void ratio in the elongate block 3 in this circumferential direction.

[0086] It will also be noted that, since the sipes n, n+1 do not pass through the elongate block 3, good overall stiffness of the elongate block 3 is ensured.

[0087] In a variant that is not illustrated, the cut n does not open into the second lateral wall 9 and the cut n+1 opens onto the second lateral wall 9 such that the elongate block 3 is formed by a plurality of sub-blocks.

[0088] According to one non-limiting embodiment, at least one cut has a maximum depth of between 50% and 100% of the height of the first and/or second lateral wall 7, 9. This depth is measured from the contact surface 5.

[0089] According to one variant, at least one cut has a maximum depth of between 80% and 95% of the height of the first and/or second lateral wall 7, 9.

[0090] The invention is not limited to the examples described and shown and various modifications can be made thereto without departing from its scope.