Tire building drum

Abstract

A tire building drum having a plurality of alternating wide and narrow drum segments bearing shells matable to form a cylindrical tire-building surface includes a shaft and concentric hub rotatable relative one another to expand and collapse the drum. In a preferred embodiment, blocks coupled to each respective segment via springs are mounted for bidirectional radial movement in rotationally-fixed relation to the shaft. Links nestable when the drum is collapsed connect the blocks with the hub to drive the blocks radially and function as over-center toggles stabilizing the drum when expanded. Variable-engagement slides associated with the blocks most effectively resist non-radial forces exerted by the links when their relative magnitude is greatest. Dimensional stability and precision of the drum are facilitated by radial and angular stops which are not subject to sliding wear. Pins of different lengths coupling the wide and narrow drum segments to the blocks cooperate with the springs to retract the narrow drum segments first and by a greater distance when collapsing the drum. The springs also cooperate with the radial stops by taking up relative movement between the blocks and drum segments to prevent expansion of the drum at any point during transition to its collapsed condition.