Patent ID: 7740040

Claim:
A shaping drum for a tire blank comprising bottom zones formed of a circular reinforcement ring, the drum movable in rotation about an axis XX′ and comprising bead-holding means ( 2 a , 2 b ) mounted opposite one another on a central spindle ( 1 ), each of the bead-holding means comprising: a support ( 5 a , 5 b ) mounted to be axially movable relative to the spindle ( 1 ); an assembly of return segments ( 9 a , 9 b ) distributed circumferentially around the axis XX′, which are movable radially while guided by and between two circular rings ( 6 a , 7 a , 6 b , 7 b ) fixed on the support ( 5 a , 5 b ), and comprising a bead-receiving seat ( 10 a , 10 b ); and a turn-up membrane ( 12 a , 12 b ) that can slide over the bead-receiving seat, anchored in an airtight manner by its two ends ( 121 a , 122 a , 121 b , 122 b ) on the radially outer circumference of the circular rings ( 6 a , 7 a , 6 b , 7 b ) and anchored mechanically by appropriate means ( 14 a , 14 b ) on the return segments ( 9 a , 9 b ) along a circumferential anchoring line ( 90 a ), wherein the section of the bead-receiving seat ( 10 a , 10 b ) is of essentially circular shape with a developed length L 1 , and the circumferential anchoring line of the turn-up membrane ( 12 a , 12 b ) on the return segments ( 9 a , 9 b ) is axially offset towards the centre of the drum by a length L 2 relative to the bead-receiving seat ( 10 a , 10 b ), the length L 2 being between 0.7 and 2 times the length L 1 .