Method for depositing a piece of band-like elastomeric element on a forming support in a process for building a tyre for vehicle wheels

A method for depositing a piece of band-like elastomeric element on a forming support in a process for building a tyre for vehicle wheels, comprising:

• providing a reference image acquired in a previous calibration process in which a template of a known length of the band-like elastomeric element was used;
• feeding a piece of band-like elastomeric element having a predetermined nominal length towards said forming support along a predetermined feeding direction;
• measuring an actual length of said piece of band-like elastomeric element along said feeding direction via the following steps:
• a) detecting a first instant of passage of a head end of said piece of band-like elastomeric element;
• b) determining a second instant of passage of a tail end of said piece of band-like elastomeric element as a function of said first instant of passage, said nominal length and a speed of movement of the band-like elastomeric element;
• c) acquiring a single image of the tail end at the second instant determined in step b);
• and
• d) calculating the actual length of said piece of band-like elastomeric element based on the detection of said first instant and second instant;
• wherein calculating the actual length of said piece of band-like elastomeric element comprises:
• comparing the single image with the reference image;
• and
• determining the actual length of said piece of band-like elastomeric element based on a comparison between said single image and said reference image,
• if said actual length is lower than or equal to a circumferential length of a deposition surface defined on the forming support, depositing said piece of band-like elastomeric element on said deposition surface while said forming support rotates about a rotation axis thereof;
• if said actual length is lower than said circumferential length of said deposition surface, then:
• i) obtaining from an adaptive correlation table a pressing force that corresponds to the actual length;
• and
• ii) during the deposition of said piece of band-like elastomeric element on said deposition surface pressing said piece of band-like elastomeric element on said deposition surface with said pressing force, thereby stretching said piece so that, at the end of the deposition of said piece, a corrected actual length of said piece that substantially coincides with said circumferential length of said deposition surface is obtained.