This invention relates to the molding of tires. In particular, it pertains to the molding of a tire comprising two beads of special shape, requiring an undercut molding of a portion in the axially and radially inner zone of the bead. Reference is made here to a zone undercut in relation to the relative motion between the tire and the molding parts normally used to mold the axially outer surface of the side and bead of a tire.
In the prior art, means are known for accomplishing the undercut molding of a portion on a tire bead. For example, U.S. Pat. No. 5,129,802 proposes using two counter-molding rings for the axially and radially inner portion of the bead, said rings being continuous. In such a case, the counter-molding rings must be introduced into the interior of the tire. For this, it is necessary to deform the raw blank of a tire by ovalizing at least one of the beads, so that the said bead can be made to pass beyond the counter-molding ring. Rings for molding the radially and axially inner portion of a bead have also been described in connection with so-called membrane-less vulcanizing presses. See, for example, U.S. Pat. No. 4,236,883, which discloses such rings, in this instance made in several segments circumferentially adjacent in molding position. The patent cited above describes a mechanism occupying integrally the inner volume of the press, so that the necessary movements can be imparted to the several ring segments in order for said segments to accommodate a closing or opening movement in sequence. By a "movement in sequence" is meant that, from a configuration in which the mold is open, the segments do not all go to their molding position at the same time. A first group is brought to its final molding position, then the segments of a second group are inserted between segments of the first group to make a continuous ring.