Tire tread comprising undulating grooves

Abstract

A tread (1) for a heavy-duty vehicle tyre, having a tread surface (10) and an undulating groove (2) formed therein, having, when new, external cavities (21) open onto the tread surface (10) and internal cavities (22) entirely situated there-beneath when new, these cavities (22) connected to cavities (21) by linking cavities (23), each external cavity (21) intersecting the tread surface (10) along a corner edge contour delimiting an opening (210) having two end regions (A1, A2) and a surface area Se measured on the tread surface (10). In each end region (A1, A2) at least one thin blade (41, 42) of rubbery material is formed which is secured to at least one of the walls delimiting the undulating groove to reduce the surface area of the opening (210) of each external cavity (21) viewed from the tread surface (10) when new.

Claims

1. A tread for a heavy-duty vehicle tire, this tread comprising a tread surface intended to come into contact with a road surface during running and, opening onto this tread surface, at least one groove undulating in the thickness of the tread, each undulating groove having, when new, external cavities that are open onto the tread surface and internal cavities that are entirely situated beneath the tread surface when new, these internal cavities being connected to the external cavities by linking cavities, each external cavity being delimited by lateral walls placed facing one another and meeting at a bottom, the innermost points of this bottom being situated at a distance Pce from the tread surface when new, each external cavity intersecting the tread surface along a corner edge contour having a maximum length Ls measured in the main direction of the undulating groove, this corner edge contour delimiting an opening of elongate form having first and second end regions and having a total surface area Se measured on the tread surface, the bottom of each external cavity having a maximum length Lf, wherein in each of the first and second end regions in the direction of the flow of fluid inside said groove of each external cavity, a pair of thin blades of rubbery material are formed, so as to form: a first opposing pair of thin blades, each having a shape of a disc portion, arranged at the first end region, each blade of the first opposing pair being secured to an opposing one of the lateral walls and directly opposite the other blade of the first opposing pair, and a second opposing pair of thin blades, each having a shape of a disc portion, arranged at the second end region, each blade of the second opposing pair being secured to an opposing one of the lateral walls and directly opposite the other blade of the second opposing pair, the first and second opposing pairs of thin blades being configured to delimit the undulating groove so as to reduce an open surface area of the opening of each external cavity viewed from the tread surface when new.

2. The tire tread according to claim 1, wherein each thin blade has a thickness at most equal to 3 mm.

3. The tire tread according to claim 1, wherein the thin blades cover at least 20% of the total surface area Se of each opening of the external cavities on the tread surface when new.

4. The tire tread according to claim 1, wherein, when the length of the bottom Lf of the external cavities is smaller than the maximum length Ls of the opening of the external cavities, the length of each thin blade is at least equal to half the difference between the maximum length Ls of the opening of the external cavities and the length of the bottom Lf.

5. The tire tread according to claim 1, wherein the undulating groove is a longitudinal groove.

6. The tire tread according to claim 1, wherein the thin blades are radially offset towards the inside of the tread so as to retain a certain level of effectiveness at least up to partial wear of the tread, this partial wear being chosen so as to be at most equal to 50% of the depth Pce of the external cavities.

7. The tire tread according to claim 6, wherein each thin blade has a variable thickness so as to ensure greater flexibility of the thin blade while ensuring good mechanical integrity when new.

8. The tire comprising a tread according to claim 1, wherein the tire is configured for fitting to a heavy-duty vehicle.

9. The tire according to claim 8, wherein the tire is configured to have a preferential direction of rotation and wherein the thin blades at the two ends (A1, A2) of each opening are geometrically different, with respect to their respective surface areas for covering said opening.

Description

DETAILED DESCRIPTION OF THE FIGURES

(1) FIG. 1 shows a view in cross section of a first variant of an undulating groove formed in a tread according to the invention;

(2) FIG. 2 shows a surface view of the tread shown in FIG. 1;

(3) FIG. 3 shows in cross section a second variant of an undulating groove according to the invention.

DESCRIPTION OF THE FIGURES

(4) In order to make the figures easier to understand, identical reference signs have been used to describe variants of the invention where these reference signs refer to elements of the same kind, whether in terms of structure or of function.

(5) FIG. 1 shows, in cross section in a plane perpendicular to the axis of rotation of a tire of size 315/70R22.5, a part of a tread 1 comprising an undulating groove 2, this undulating groove 2 extending in the circumferential direction of the tire. In combination with this FIG. 1, FIG. 2 shows a partial view of the tread surface 10 of the tread 1. The section plane of FIG. 1 corresponds to the plane of the longitudinal sipe 3.

(6) This undulating groove 2 comprises a plurality of external cavities 21 and a plurality of internal cavities 22, these external and internal cavities being disposed in alternation in the main direction of the undulating groove 2, that is to say in the direction of the flow of fluid inside said groove (in the case described, this direction corresponds to the circumferential direction).

(7) Each external cavity 21 opens, when new, onto the tread surface 10 of the tread 1, this tread surface 10 corresponding to the surface of the tread that is intended to come into contact with the road surface during running.

(8) Each internal cavity 22 is in the form of a channel moulded entirely beneath the tread surface 10 when new and is intended to open onto the tread surface after predetermined partial wear of the tread 1.

(9) Linking cavities 23 are formed between the external cavities 21 and the internal cavities 22 so as to ensure continuity of flow in the undulating groove 2 when new, specifically up to partial wear of the tread corresponding substantially to the disappearance of the external cavities.

(10) Moreover, a sipe 3 is formed between the tread surface 10 when new and the linking cavities 23 and the internal cavities 22, this sipe 3 being designed to close at least partially when entering the contact patch in contact with the road surface. This is not the case in the example shown here, but each corner edge formed on the tread surface by this sipe 3 may have, as is known, a chamfer which disappears after partial wear.

(11) Each external cavity 21 is delimited by lateral walls 211, 212 that are disposed facing one another and distant from one another by an appropriate distance for there to be no contact between these lateral walls 211, 212 when entering the contact patch in contact with the road surface. These lateral walls 211, 212 are connected to one another by a bottom 213, the points of this bottom 213 that are innermost in the external cavity 21 being situated at a distance Pce from the tread surface 10 when new.

(12) The corner edges formed by the lateral walls 211, 212 of the external cavity 21 on the tread surface 10 delimit an opening 210 of elongate form having two ends in the direction of the flow of fluid inside said groove, respectively denoted A1 and A2. At each of these ends a linking cavity 23 starts which is recessed into the tread so as to connect the external cavity 21 to internal cavities 22.

(13) The opening 210 of each external cavity 21 has a maximum length Ls determined by the farthest-apart points on the tread surface when new and a maximum bottom length Lf measured on the bottom 213 of said external cavity. In the present example, the maximum length Ls of the opening 210 is greater than the length Lf of the bottom 213.

(14) In this first described variant it is seen that two thin blades 41, 42 have been moulded at each end A1 and A2 of the opening 210 of each external cavity 21. These thin blades 41, 42 in this case have one and the same thickness equal to 2 mm and a maximum length Lm measured in the main direction of the external cavity 21 (direction connecting A1 to A2). This length Lm is in this case equal to 15 mm and is appropriate for partially covering the bottom 213 of the external cavity 21 and therefore covering the opening of the linking cavity 23. In this example, the length of the opening of the external cavities is equal to 55 mm, the depth Pce is equal to 6 mm, the length of the linking cavities equal to 10 mm and that of the internal cavities 55 mm.

(15) In the present variant, each thin blade 41, 42 is secured to the lateral walls 211, 212 delimiting the external cavity 21 and is formed so as to be level with the tread surface 10 when new.

(16) FIG. 2, showing the same tread variant, makes it possible to see the tread surface 10 when new onto which there open external cavities 21 which are extended into the tread by linking cavities and internal cavities. The total surface area Se of the opening 210 which comprises both the substantially rectangular open part and the parts covered by the four thin blades 41, 42 is equally clearly visible in this FIG. 2. The contour of the surface Se follows the visible corner edges of the lateral walls 211 and 212 and the dotted lines correspond to the extension thereof (hidden by the thin blades) towards the ends A1, A2 of the external cavity.

(17) The surface geometry of the thin blades 41, 42 formed at each end region A1, A2 of the external cavities 21 is also seen in this FIG. 2. This surface geometry is in this case substantially triangular and the set of the four thin blades which are formed on one and the same opening 210 covers a surface area equal in this case to 200 mm.sup.2, i.e. approximately 36% of the total surface area Se of the opening 210 delimited by the corner edge contour of the external cavity 21 on the tread surface 10 when new as explained above.

(18) By virtue of this arrangement, it is possible to reduce the contact noise resulting from the corner edge contour of each external cavity entering and leaving the contact patch in contact with a road surface during running when the tire is in the new state.

(19) To ensure that this technical effect has a certain level of durability, it is advantageous to offset the thin blades partially or completely closing the openings of each external cavity on the tread surface towards the inside of the tread.

(20) The second variant described with the aid of FIG. 3 shows the case of thin blades realized inside the tread at a non-zero distance from the tread surface when new.

(21) In FIG. 3 a second variant of an undulating groove 2 according to the invention is seen, viewed in cross section. In this variant again using the elements of the first variant, namely the presence at each end of the opening of each external cavity 21 of two thin blades, each thin blade 42 is offset relative to the tread surface 10 when new by a distance corresponding substantially to one third of the depth Pce of the external cavity 21. In this FIG. 3 a single thin blade 42 is visible but there is actually another thin blade in combination with said thin blade 42 as shown in FIGS. 1 and 2.

(22) To realize this offset, each thin blade 42 starts both on one of the walls delimiting the external cavity 21 and also on the wall delimiting the linking cavity 23. By virtue of its appropriate stiffness, each thin blade 41, 42 at least partially closes the opening 210 of each external cavity 21 which is favourable as regards the generation of noise during running on a dry road. Moreover, the suitable flexibility of each blade 41, 42 allows liquid to flow over the entire opening 210 of the external cavities 21 without excessively obstructing the linking cavities 23. In this example, the length Lm of the thin blades is adapted so that said thin blades are not constrained by possible contact thereof with the wall of the external cavity or of the linking cavity during bending under the effect of the circulation of a liquid in the groove 2.

(23) In a variant not shown here, each thin blade may have a non-uniform thickness; in particular, it may be advisable for the thickness to be at a maximum at the points of connection to the walls. This variation in thickness may be combined with one or other of the variants described above. As has already been stated, the blades may be appropriate for substantially, i.e. completely or virtually completely, closing the opening of each cavity.

(24) Of course, the invention is not limited to the examples described and depicted and various modifications may be made thereto without departing from the scope as defined by the claims.

(25) The scope of protection of the invention is not limited to the examples given hereinabove. The invention is embodied in each novel characteristic and each combination of characteristics, which includes every combination of any features which are stated in the claims, even if this feature or combination of features is not explicitly stated in the examples.