Center deck assembly for tire building drum

A center deck assembly for a tire building drum, the tire building drum being rotatably mounted on a central drive shaft and including a center section, the center deck assembly being disposed in the center section of the drum, the center deck assembly comprising:

• a hub seating on and being secured to the central drive shaft, the hub cooperating with a frame to form a cylinder;
• a piston extending circumferentially in the tire building drum about the hub, the piston seating in the cylinder and being contained in the cylinder;
• a plurality of segment bars being disposed about the circumference of the center deck assembly;
• the piston being operably connected to the segment bars by a plurality of linkages, wherein each of the linkages comprises a scissor-lever mechanism, each of the linkages including a radially inward link and a radially outward link that are pivotally interconnected;
• and
• a roller disposed on each linkage at the pivotal interconnection between the radially inward link and the radially outward link, wherein the roller engages a bearing surface formed on an axially outward surface of the piston, in which the bearing surface is formed with a conical shape that angles axially inwardly as it extends radially outwardly.