Tire bead for a heavy civil engineering vehicle

摘要

A technique for improving the durability of the beads of a radial tire for a heavy vehicle of the civil engineering type, by reducing the rate of spread of cracks initiated at the turned-back end of carcass reinforcement and the spread through the coating, edge-binding and filler polymer materials. A transition element (25), made of a transition polymer material, is at least partially in contact, on its axially external face, with the edge-binding polymer material (22) and, on its axially internal face, with a filler polymer material (23b), the radially external (E25) and radially internal (I25) ends of the transition element are respectively radially on the outside of and radially on the inside of the end of the turned-back portion of carcass reinforcement, and the elastic modulus at 10% elongation of the transition polymer material is somewhere between the respective elastic moduli at 10% elongation of the edge-binding polymer material and of the filler polymer material with which the transition element is in contact.

主权项

1. A tire for a heavy vehicle of the civil engineering type, comprising:
two beads configured to come into contact with a rim; a carcass reinforcement consisting of one carcass reinforcement layer made up of metal reinforcing elements coated in a coating polymer material, said carcass reinforcement layer comprising a main portion which, in each of said two beads, is wound from the inside towards the outside of the tire, around a bead wire core to form a turned-back portion of carcass reinforcement, said turned-back portion comprising an end covered by an edge-binding element made of an edge-binding polymer material; and a filler element in each of said two beads, said filler element extending said bead wire core radially outwards, said filler element having, in any meridian plane, a substantially triangular cross section and being made of at least one filler polymer material, said at least one filler polymer material being in contact with said edge-binding element and having an elastic modulus at 10% elongation that is less than the elastic modulus at 10% elongation of said edge-binding polymer material, wherein a transition element, made of a transition polymer material, is at least partially in contact, on its axially external face, with said edge-binding polymer material and, on its axially internal face, with a filler polymer material, wherein the radially external and radially internal ends of said transition element are respectively radially on the outside of and radially on the inside of said end of said turned-back portion of carcass reinforcement, and wherein the elastic modulus at 10% elongation of said transition polymer material is somewhere between the respective elastic moduli at 10% elongation of said edge-binding polymer material and of said filler polymer material with which said transition element is in contact.