GB922463A - Improvements relating to the manufacture of pneumatic tyres - Google Patents

Abstract

922,463. Shaping tyre carcasses. DUNLOP RUBBER CO. Ltd. Aug. 25, 1959 [Sept. 3, 1958], No. 28244/58. Class 144 (1). A float band pneumatic tyre carcass 6 is shaped by moving its beads 8 axially towards each other whilst radially expanding the carcass between the beads, the radial expansion being constrained initially only to the crown portion 9 and the constraint gradually eased as expansion proceeds to permit the region of expansion to increase towards the beads. As shown, the beads 8 are seated in angle-section rings 1 at the ends of an inflatable cylindrical rubber diaphragm 4, and a pair of constraining rings 11 surround the carcass for respectively opposed axial displacement relative to the radial plane of symmetry of the carcass. Each ring 11 has an inner periphery 12, slightly larger in diameter than the beads 8 and rings 1, which joins via a convex constraining surface 16, into a concave carcase shaping surface 15. The surface 15 terminates in a radial surface 14 leading to the outer periphery 13 of the ring 11, the surfaces 14 of the two rings abutting in their closed initial constraining position, Fig. 1, and the peripheries 13 being recessed at 19 to define, in the shaping position of the rings 11, Fig. 5, a locating recess for an inextensible annular breaker 20. In operation, the rings 11 are moved apart simultaneously with the mutual approach of the bead supporting rings 1, during inflation and radial expansion of the diaphragm 4, the carcass 6 engaging the surfaces 16 of the rings 11 and expanding only therebetween. To reduce friction, air jets 18 extend through the rings 11 to the surfaces 16. After final shaping of the carcase, Fig. 5, the breaker 20 is located in the recesses 19, and a tread strip 21 is centred thereon, by means of markings on the peripheries 13 of the rings 11. The rings 11 are then withdrawn to permit consolidation of the breaker and tread on to the carcass. The rings I and 11 are rotatable about their common axis to facilitate location and consolidation of the breaker and tread strips. To facilitate rolling of the beads 8 on the rings 1 during shaping, each ring may carry an inflatable bead-seating tube 22, Fig. 6, which may serve also to seal the beads to the rings and thus permit the diaphragm 4 to be omitted.