Process and apparatus for manufacturing pneumatic tyres for vehicle wheels

An apparatus for building a tyre for vehicle wheels, comprising:

• a shaping drum comprising:
• first and second half drums;
• a first support, operatively associated with the first half-drum and a second support operatively associated with the second half-drum, each support carrying a plurality of turning-up levers having free ends positioned close to its respective half drum;
• a threaded shaft for axially moving the two supports and the two half-drums in mutually approached or mutually spaced relationship and for lifting the free ends of said turning-up levers through rotation of the threaded shaft;
• and
• two mechanical locking and unlocking devices each interposed between one of the half-drums and its associated support and being configured either in an unlocked position, in which the associated support is movable relative to its half-drum, or in a locked position, in which the associated support is fixed relative to its half-drum, wherein each mechanical locking and unlocking device comprises:
• a plurality of guide rods each having a first end integral with a respective one of the half-drums and a second end slidably coupled to the support, associated with the respective one of the half-drums, and
• a retaining unit mounted on the support, associated with the respective one of the half-drums, comprising a flange with openings for the second ends of the guide rods and actuators for moving the flange between an engaged position and a disengaged position, wherein in the engaged position the mechanical locking and unlocking device is in the locked position and the second ends of the guide rods are locked on its associated support in first portions of the openings to provide only stiff mechanical elements in mutual contact between the respective half-drum and its associated support, and in the disengaged position the mechanical locking and unlocking device is in the unlocked position and the second ends of the guide rods slide through their associated support in second portions of the openings.