TREAD WITH CHANNELS ON THE EDGES OF SAME

Abstract

The tread has circumferential grooves delimiting intermediate and edge parts and formed so as to be present at least until a tread wear limit is reached. The tread also having a tread surface with at least one tread wear indicator formed in a circumferential groove. The tread comprising on its edge regions a plurality of transverse cuts that have depths suited to be present down to the tread wear limit. Each transverse cut is formed of a first part opening onto the tread surface when new and extending towards the inside of the tread by a void part forming a channel of mean width greater than a mean width of the groove. The channel forms a new transverse groove after a predetermined amount of part wear. A cross section of each channel increases when progressing along the cut axially from the inside towards the outside of the tread.

Claims

1. A tread (1) for a tire, said tread having a tread wear limit signalled by at least one tread wear indicator and comprising at least two grooves (2, 3) of circumferential overall orientation delimiting intermediate parts (4) and edge parts (5), said edge parts (5) axially delimiting said tread (1), said grooves of circumferential overall orientation being formed so as to be present at least until said tread wear limit is reached, said tread comprising a tread surface (10) when new, said tread surface having an external transverse profile (7) obtained as the intersection of said tread surface with a plane containing the axis of rotation of said tire tyre, said transverse profile generating a reduction in the thickness of wearable material on said edge parts (5) of said tread, said tread comprising at least one tread wear indicator formed in a circumferential groove (2, 3) to indicate said tread wear limit for said tread during running, said tread comprising on its said edge regions (5) a plurality of cuts (6) of transverse overall orientation and opening onto a lateral part of said tread, each of said transverse cuts having a depth suited to being present down to the tread wear limit, each of said cuts (6) of transverse overall orientation being formed of a first part (61) opening onto the tread surface (10) when new, said first part (61) having a mean width and being extended towards an inside of said tread by a void part forming a channel (63) of mean width greater than the mean width of said first part (61), said channel (63) being intended to form a new transverse groove after a predetermined amount of part wear, each channel (63) having a cross section, said cross section being measured between the bottom of this channel (63) and at least a height equal to the height of the tread wear indicator and increasing when progressing along said cut (6) axially from said inside of said tread towards an outside of said tread.

2. The tread (1) for a tire as set forth in to claim 1, wherein said cut (6) formed by said first part (61) extended by said channel (63) has a total cross section when new which is constant over an entire length of said cut (6).

3. The tread for a as set forth in claim 1, wherein said cut (6) formed by said first part (61) extended by said channel (63) has a total cross section when new which increases when progressing along said cut (6) axially from said inside of said tread towards said outside of said tread.

4. The tread for a tire as set forth in claim 1, wherein a maximum depth of each cut (6) formed on said edge regions (5) is equal to a maximum depth of said grooves (2, 3) of circumferential overall orientation.

5. The tread for a tire as set forth in claim 1, wherein said first part (61) of each transverse cut (6) formed on said edge regions (5) is formed by a sipe of which the delimiting walls are able to come into contact with one another as they enter the contact patch.

6. The tread for a tire as set forth in claim 1, wherein each transverse cut (6) formed on said edge regions (5) comprises an intermediate part (62) making a progressive connection between said first part (61) that opens onto said tread surface (10) when new, and wherein said channel (63) extends said first part (61) inwards.

7. The tread for a tire as set forth in claim 1, wherein said transverse cuts (6) formed on said edge regions (5) open into said circumferential grooves (2, 3).

Description

BRIEF DESCRIPTION OF THE FIGURES

[0037] FIG. 1 depicts a partial plan view of a surface of a tread;

[0038] FIG. 2 depicts a perspective view of an edge region of the tread shown in FIG. 1;

[0039] FIG. 3 shows a view in section on I-I of FIG. 1; and

[0040] FIG. 4 shows a view in section on II-II of FIG. 1.

DETAILED DESCRIPTION OF THE ENABLING EMBODIMENT

[0041] FIG. 1 depicts a partial plan view of a tread surface 10 of a tread 1. This FIG. 1 partially depicts a tread 1 intended to equip a tire of a passenger vehicle. This tread 1 comprises four circumferential grooves 2, 3 all having the same depth equal to 8 mm. Tread wear indicators are moulded into the bottom of at least one of these grooves. The depth of these grooves 2, 3 is such that, when tread wear reaches the tread wear limit set by the national regulations (the moulded tread wear indicators come into contact with the tread surface), these grooves have not completely disappeared and there is still the possibility of draining away any water that might be present on a roadway.

[0042] The two circumferential grooves 2 closest to the equatorial plane (indicated by a line XX in FIG. 1) have a mean width equal to 10 mm while the other two grooves 3 have a mean width equal to 8 mm.

[0043] These four grooves delimit three intermediate rows 4 and two edge rows 5 axially delimiting the tread 1. The intermediate rows 4 are provided with a plurality of oblique sipes 41 that close when they enter the contact patch.

[0044] On this tread and, more specifically, in the circumferential grooves, several tread wear indicators 8 are moulded all around the tread in order to allow the user easily to gauge the level of tire wear and assure himself that his tires have not yet reached the tread wear limit set by legislation. In this particular instance, the tread wear indicators 8 form a relief in the bottom of the grooves of a height equal to 1.6 mm. Accordingly, when the external surface of these indicators 8 comes into contact with the roadway, there is still enough depth in the circumferential grooves to ensure safe driving. At that moment, it of course becomes necessary for the user to replace this worn tire with a new tire.

[0045] Each edge row 5 comprises a plurality of transverse cuts 6, each transverse cut 6 opening onto the tread surface 10 and into a circumferential groove 3. Each transverse cut 6 in this particular instance comprises a groove 61 opening onto the tread surface 10 when new, this groove 61 being extended by an intermediate connecting part 62 of a width that can vary in the depth of the tread, this intermediate connecting part 62 ending in a channel 63, the width of which is greater than the width of the groove 61.

[0046] Given the external transverse profile of the tread when new (this profile 7 is visible in FIG. 2 which depicts a partial perspective view of an edge region 5) and given the internal reinforcing structure of a tire, it is clear that the wearable thickness at the edge of the tread is significantly reduced especially with increasing axial distance away from the equatorial midplane. If the performance of the tread 1 is to be maintained, notably in the edge regions 5 thereof, it is advantageous to construct the transverse cuts 6 in these regions according to the disclosure, namely by contriving for the cross section of each channel 63 to increase when progressing axially from the inside of the tire outwards, notably by increasing the mean width thereof.

[0047] Thus, following wear corresponding to the tread wear limit, the volume available for drainage in the transverse cuts (reduced to the channels) is not reduced when progressing towards the outside, but rather is increased in this particular instance.

[0048] FIG. 3 shows a view in section on I-I of FIG. 1. In this FIG. 3, it may be seen that a transverse cut 6 is formed of a groove 61 of constant width equal to 2.5 mm, extended towards the inside by a channel 63 of maximum width L1 equal to 5.5 mm, the groove 61 being connected to the channel 63 by an intermediate connecting part 62 having a width that can vary and is suited to connecting the groove 61 to the channel 63. The distance between the tread surface 10 when new and the bottom of the channel 63 is denoted P1 whereas the distance between the external surface of the tread wear indicator TW identified by the dotted line and the bottom of the channel is denoted H.

[0049] The cross section of the channel 63 remaining beyond the tread wear limit represents 9 mm.sup.2. The total cross section of the cut when new is equal to 25 mm.sup.2.

[0050] FIG. 4 shows a view in section on II-II of FIG. 1. The position of this section is situated axially on the outside of the position of the section shown in FIG. 3.

[0051] The distance between the tread surface 10 when new and the bottom of the channel 63 in this plane of section is denoted P2 whereas the distance between the external surface of the tread wear indicator TW identified by the dotted line and the bottom of the channel is denoted H.

[0052] In this FIG. 4, it may be seen that, in this plane of section, the transverse cut 6 has a cross section equal to what it had for the position corresponding to the section shown in FIG. 3, whereas the width of the groove 61 opening onto the tread surface when new has increased and is equal to 4.5 mm and the width L2 of the channel 63 remaining beyond the tread wear limit TW has increased in comparison with the width L1 of the channel considered in FIG. 3 so that the cross section of the channel remaining beyond the tread wear limit TW in this plane of section II-II is greater than it was in the plane of section I-I of FIG. 3.

[0053] In this plane of section, the cross section of channel remaining beyond the tread wear limit is equal to 12 mm.sup.2 (the maximum width of the channel is equal to 7.5 mm).

[0054] In an alternative form that has not been shown here, the width of each groove opening onto the tread surface when new remains constant over the entire length of the transverse cut, only the width of the channel extending each groove varying by increasing.

[0055] In another alternative form that has not been depicted, the first part of the cut is formed of a sipe of which the walls are able to come at least partially into contact with one another in the contact patch. The walls of this sipe may of course be provided with means, such as reliefs, that collaborate with one another to limit relative movement.

[0056] Of course, the disclosure is not restricted to the examples described or depicted and various modifications can be made thereto without departing from the scope defined by the claims.