Tire mold having a plurality of blocks defining a matrix with venting gaps between the blocks

A mold of the centripetal type for curing raw tire carcasses for vehicles, comprising

• two axially opposite sidewall portions, substantially corresponding to the sidewalls of said tire, axially and reciprocally displaceable with respect to each other,
• a central annular portion, interposed between said sidewall portions, substantially corresponding to the tread portion of said tire, said annular portion having a plurality of sectors circumferentially disposed around the axis of said mold and provided with air evacuation holes,
• said sections being mounted to be radially displaceable toward and away from said axis, said sections carrying on their radially inner surfaces a plurality of blocks forming are relief rib matrix for molding a corresponding tread design disposed in at least two flanked circumferential rows with each of said blocks being separated from adjacent blocks substantially along its entire contour by clearances acting as venting gaps connected to said air evacuation holes in the secondary body, the width of said clearances being determined by the rheometric characteristics of the mixed raw material and by the molding conditions, in such a way that at the curing temperature the clearance is wide enough to permit air trapped within the mold to escape, but to prevent elastomeric material from being extruded therethrough so as to avoid burrs on the surface of the cured tire said blocks being further separated from the sector that contains them by clearances also acting as venting gaps and connected to said air evacuation holes in the sector body.