Belt drum and tire building machine

The utility model discloses a belted drum which is used for forming a tread component, the tread component comprises a belted layer and a tread layer, the belted drum can rotate to be attached to the belted layer and the tread layer in sequence, the width of the tread layer is larger than that of the belted layer, and the belted drum comprises a drum shaft component and a belt shaft component, the drum tile assembly is mounted on the radial outer side of the drum shaft and comprises a plurality of drum tiles, and the drum tiles can move in the radial direction relative to the drum shaft; a supporting unit is arranged on one of the plurality of drum tiles, the supporting unit comprises a plurality of groups of supporting blocks, each group of supporting blocks comprises two supporting blocks which are symmetrically arranged along the width center surface of the belt drum, and at least one group of supporting blocks which are positioned on the axial outer side of a belt layer and the radial inner side of a trea