Pirelli Coordinamento Pneumatici S.p.a.

Marco Cipparrone

Omero Noferi

Gurdev Orjela

Guido Riva

Metal cord for use in reinforcing fabric for articles made from rubber, such as pneumatic tires, conveyor belts, flexible tubes, and similar, comprising a plurality of such metal cords orientated parallel to each other in a single direction and in which each cord comprises metal wires wound spirally around each other, wherein at least one of the wires of the cord consists of a shape memory material. During the phase of incorporation of the cords into the elastomeric material, the shape memory wire tends to recover the shape memorized initially and, by means of the force generated during this recovery, transmits by friction to the surrounding wires forces tending to shorten the pitch of the cord with spacing of each wire from the next, resulting in good penetration of elastomeric material between the wires. The closure of the cord is maintained in the subsequent heat cycles, owing to the memory degradation characteristics imparted to the wire. The invention is particularly suitable for fabrics forming belt layers and casing plies in pneumatic tires.

Shape memory cords for reinforcing articles made from elastomeric material

A cord comprising at least a first pair and a second pair of wires (,) of different diameter randomly disposed in transverse cross section thereof, is obtained by arranging in a nacelle (,) of a double-twisting laying machine, a twister (,) operating upstream of a preformer (,). The twister (,), rotating in a direction opposite to that of the impeller (,) and at a speed which is twice that of the impeller, neutralizes the internal torsional stresses induced in the wires (,) by effect of the double twisting carried out upon the action of the impeller itself. Thus, a better control of the preforming operation executed on the wires (,) disposed parallel in respectively coplanar axes is enabled. The obtained cord (,), within each laying pitch and only under a traction condition involving a load not exceeding 5 kg, has at least one right cross section in which at least one wire (,) is spaced apart from at least one of the adjacent wires so as to facilitate the rubberizing step, by enabling access of the blend to the cross section and penetration thereof along the cord axis. The cord is preferably used as a reinforcing element for the belt structure.

Process and apparatus for the manufacture of reinforcing metallic cord for elastomer-matrix composite articles

A metal cord for reinforcing articles made from elastomeric material comprises a plurality of metal wires wound spirally around each other. At least one of the metal wires is formed from a shape memory material, has capacities of recovering a previously memorized shape, and is deformed from the memorized shape. The shape memory wire of the cord has the recovery capacities substantially active in a first heat cycle and degraded to at least a significant predetermined extent after the first heat cycle. One or more such metal cords may be incorporated in pneumatic tires, reinforcing fabric, and other articles, including by means of processes described herein.

Pneumatic tire comprising reinforcing metal wire cords with at least one shape memory wire and method of making same

A cord comprising at least a first pair and a second pair of wires (2a, 2b) of different diameter randomly disposed in transverse cross section thereof, is obtained by arranging in a nacelle (7) of a double-twisting laying machine, a twister (16) operating upstream of a preformer (15). The twister (16), rotating in a direction opposite to that of the impeller (5) and at a speed which is twice that of the impeller, neutralizes the internal torsional stresses induced in the wires (2a, 2b) by effect of the double twisting carried out upon the action of the impeller itself. Thus, a better control of the preforming operation executed on the wires (2a, 2b) disposed parallel in respectively coplanar axes is enabled. The obtained cord (1), within each laying pitch and only under a traction condition involving a load not exceeding 5 kg, has at least one right cross section in which at least one wire (2a, 2b) is spaced apart from at least one of the adjacent wires so as to facilitate the rubberizing step, by enabling access of the blend to the cross section and penetration thereof along the cord axis. The cord is preferably used as a reinforcing element for the belt structure.

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Fiesole, Italy

Marco Cipparrone