Tire building drum with a turn-up mechanism

A tire building drum for building a tire having tire components of rubber, including two beads, the tire building drum comprising:

• a drum shaft;
• two bead holders arranged around the drum shaft, the bead holders being mutually spaced apart in the axial direction of the drum shaft to support the tire components at the location of the beads, first portions of the tire components being situated between the two bead holders and being configured to be radially expanded;
• a turn-up mechanism configured to turn-up second portions of the tire components situated outside of the bead holders around the beads against the expanded first portions of the tire components to form the tire, the turn-up mechanism comprising
• a respective group of arms arranged on each side of the drum shaft outside of the bead holders,
• the arms of each group being coupled to the drum shaft via a respective axially moveable arm support at a first end,
• the arms extending from the arm support of the respective group of arms towards the bead holders in radial planes equally distributed about the drum shaft,
• the arms being tiltable in said radial planes about a coupling part with the arm support of the respective group of arms between a low position and a high position,
• each group of arms comprising primary arms and secondary arms interposed between the primary arms,
• the primary arms and the secondary arms, at a second end opposite to the first end, being provided with primary pressing devices and secondary pressing devices, respectively, configured to exert a pressing force onto the tire components during the turning-up, the primary pressing devices being in a leading position,
• the secondary arms being provided with pneumatic drives configured to displace the secondary pressing devices from an axially trailing position with respect to the axial position of the primary pressing devices in the leading position towards the same axial position as the primary pressing devices in the leading position,
• wherein the secondary pressing devices are configured to be moved from the trailing position into the leading position when the primary arms are tilted from low positions into high positions,
• during the tilting of the primary arms from the low positions to the high positions, the primary pressing devices are configured to diverge with respect to each other in the circumferential direction of the drum shaft, and
• the pneumatic drives are configured to displace the secondary pressing devices from the trailing position to the leading position when the space consumed by the individual secondary pressing devices in the circumferential direction of the drum shaft is less than the smallest space between two directly subsequent primary pressing devices in the same circumferential direction.