Process and plant for building tyres for vehicle wheels

A process for building tyres comprising:

• positioning, in a shaping station, a toroidal forming drum within a carcass sleeve comprising at least one carcass ply associated with a pair of beads;
• wherein after positioning in the shaping station, the carcass sleeve is engaged by one or more gripping elements operating axially and/or radially inside the beads;
• shaping the carcass sleeve toroidally by radial expansion of the forming drum from a first, radially contracted, operating condition, up to a second,
• radially expanded, operating condition forming an expanded forming drum, the expanded forming drum having a toroidal shape corresponding to an inner shape of the shaped carcass sleeve;
• wherein during shaping by radial expansion of the forming drum, the one or more gripping elements disengage the beads after a radially outer portion of the forming drum has abutted against the carcass sleeve;
• imposing a controlled tension to the carcass sleeve by the expanded forming drum at the second, radially expanded, operating condition after the end of the shaping and causing the beads, due to the controlled tension, to act in axial thrust relation against respective axially outer circumferential portions of an abutment surface carried by the expanded forming drum;
• removing the forming drum carrying the shaped carcass sleeve from the shaping station;
• and
• applying sidewall portions externally on the shaped carcass sleeve carried by the expanded forming drum;
• wherein the sidewall portions are applied by wrapping at least one elongated continuous element made of elastomeric material according to circumferential turns against axially opposite lateral portions of the carcass sleeve in proximity to the beads, while the forming drum rotates and moves to distribute the circumferential turns according to a predefined scheme;
• wherein wrapping of the elongated continuous element takes place with the aid of an applicator roller exerting a thrust action on the carcass sleeve;
• further comprising maintaining the controlled tension to the carcass sleeve by the expanded forming drum at the second, radially expanded, operating condition after the end of the shaping and causing the beads, due to the controlled tension, to maintain their axial thrust action against the expanded forming drum after the end of shaping, wherein during the application of said sidewall portions, entire axially inner surfaces of said beads are in axial thrust relation against the respective axially outer circumferential portions of the abutment surface, while the beads oppose the thrust action exerted by the applicator roller in proximity to radially inner edges of the forming drum.