Method and apparatus for manufacturing pneumatic tyres

摘要

A green tire disposed on a toroidal support is introduced into a vulcanization mold. The mold is closed through axial approaching of a pair of sidewall plates acting against the sidewalls of the tire. Circumferential sectors set to operate against the tire tread band are maintained spaced apart from the tread band itself during admission of a working fluid designed to press the tire against the toroidal support. Subsequently, the sectors are centripetally approached for penetration into the tread band concurrently with a step of full molding and vulcanization of the tire carried out through admission of steam under pressure into the tire itself.

主权项

1. A tyre manufacturing apparatus, comprising:
a toroidal support having an outer surface conformal to the shape of the inner surface of a tyre under working, the tyre under working comprising a tread band provided with a radially external surface; arranging devices configured to arrange the tyre on the toroidal support; a vulcanisation mould having a pair of axially opposite sidewall plates and a moulding cavity circumscribed by centripetally-approachable circumferential sectors carrying forming ridges facing a geometric axis at a radial center of the moulding cavity; a casing having a base portion and a closing portion each carrying one of the sidewall plates and movable relative to each other between an open condition at which the base portion and the closing portion are mutually spaced apart to enable introduction of the tyre into the mould, and a closed position, at which the base portion and the closing portion abut against each other, for closing the tyre into the moulding cavity; first pressing devices configured to press the tyre enclosed in the moulding cavity against the outer surface of the toroidal support; first heat administering devices configured to administer heat to the inner surface of the tyre pressed against the toroidal support; second pressing devices configured to press the radially external surface of the tread band of the tyre against a radially internal surface of the moulding cavity; driving devices configured to be activated subsequently to closure of the tyre into the moulding cavity to cause translation of the circumferential sectors between a first work condition at which the forming ridges are radially spaced apart from the radially external surface of the tread band of the tyre enclosed in the moulding cavity, and a second work condition at which the forming ridges penetrate at least partly into the radially external surface of the tread band, wherein the driving devices comprise a sector-carrying ring having a cone-shaped surface slidably engaging said circumferential sectors to cause translation of the sectors between said first and second work conditions following an axial movement of the sector-carrying ring, the driving devices further comprising control rods which slide through the casing under the actuation of fluid-operated actuators that are fastened to the casing and operate on the controls rods through idler arms pivotably mounted on the casing to achieve the axial movement of the sector-carrying ring; and second heat administering devices configured to administer heat to the tyre penetrated by the forming ridges of the circumferential sectors; wherein said driving devices are configured to keep the circumferential sectors at the first work condition during operation of said first pressing devices and first heat administering devices, and keep the circumferential sectors at the second work condition during operation of said second pressing devices and second heat administering devices; wherein the circumferential sectors are radially closer to the geometric axis of the moulding cavity in the second work condition than in the first work condition; and wherein one of the sidewall plates is configured to move so that the circumferential sectors slide against the cone-shaped surface and thereby cause radial moving apart of the circumferential sectors while the casing is brought in the open condition.