Pneumatic tire building drum

A building drum for building a first-stage, steel-reinforced, radial monoply, pneumatic tire carcass, whereby two carcass-bead-defining annular metallic cores are secured to the opposite end portions, respectively, of a cylindrically-oriented carcass-monoply, said drum comprising a circumferential array of drum-forming segments, guide means supporting said segments for radial displacement to and from contracted and expanded dispositions, shifting means for displacing said segments radially between said contracted and expanded dispositions, each of said segments having the same axial extent and terminating at each end in a respective flange projecting radially inwardly, each of said flanges having a respective recess exposed radially outwardly, corresponding ones of said recesses which are at the same segment end defining cooperatively with one another at each such segment end a radially outwardly exposed annular bead-seat, said segments when in a fully contracted disposition presenting a substantially cylindrical outer carcass-ply support-surface having an outer diameter which is less than the inner diameter of any carcass-bead-defining annular metallic core to be thereby operated upon, said bead-seats each having an inner diameter which is less than said outer diameter of said outer carcass-ply support-surface, said bead-seats each being entirely rigid and, thereby, having a depth-to-width ratio that does not vary with the expansion and contraction of said segments, said guide means including an axially extending hub portion, a pair of axially spaced, but radially extending, annular plates affixed to said hub portion, and means for defining a radial array of equidistantly spaced slots arranged on each of said annular plates, each of said segments including a respective radially extending leg affixed thereto at one leg end portion and movably confined at the other leg end portion in a respective one of said slots, and a cylindrical member affixed to and bridging said annular plates, said shifting means including an annular inflatable bladder interposed between said cylindrical member and said circumferential array of drum-forming segments, each of said segments including an arcuate shield presenting a concave surface which is engageable with said bladder, said shields overlapping one another throughout the complete displacement of said segments to and from said contracted and expanded dispositions and, thereby, preventing portions of said bladder from squeezing radially outwardly between said segments.