Method and apparatus for manufacturing pneumatic tyres

Abstract

A green pneumatic tyre is built on a rigid toroidal support externally having a forming surface of a conformation corresponding to the inner shape of a tyre. The green tyre engaged on the expandable toroidal support is introduced into a vulcanisation mould and submitted to a vulcanisation cycle. During vulcanisation, axial moving apart of side portions of the toroidal support is caused so as to press the beads and sidewalls of the tyre against the vulcanisation mould.

1 - 51 . (canceled) 
     
     
         52 . An apparatus for manufacturing pneumatic tyres, each tyre comprising a crown region extending between side regions axially spaced apart from each other and each carrying a respective bead at a radially internal position, comprising:
 at least one toroidal support having an outer forming surface of a conformation corresponding to an inner shape of a built tyre and provided with axially opposite side portions;   devices for building a green pneumatic tyre on the toroidal support;   at least one vulcanisation mould set to engage the green tyre disposed on the toroidal support;   devices for curing the tyre enclosed in the vulcanisation mould; and   devices for axially moving apart said side portions of the toroidal support at the side regions of the tyre enclosed in the vulcanisation mould.   
     
     
         53 . The apparatus as claimed in  claim 52 , wherein the toroidal support comprises a plurality of circumferential sectors removably engaged in circumferential mutual alignment relationship. 
     
     
         54 . The apparatus as claimed in  claim 53 , wherein said devices for axially moving apart said side portions comprise for each circumferential sector, at least one pair of stop struts, each strut being divided into two portions adapted to enable an axial movement of said side portions. 
     
     
         55 . The apparatus as claimed in  claim 52 , wherein the forming surface is obtained on a shaped wall confining at least one circumferential cavity in the toroidal support. 
     
     
         56 . The apparatus as claimed in  claim 55 , wherein said shaped wall substantially extends along a U-shaped outline in a diametral section plane of the toroidal support. 
     
     
         57 . The apparatus as claimed in  claim 55 , wherein said axially opposite side portions of the shaped wall are movable in an axial direction. 
     
     
         58 . The apparatus as claimed in  claim 52 , wherein said vulcanisation mould further comprises stop seats set to act against said side portions of the toroidal support in a maximum axial spacing apart condition. 
     
     
         59 . The apparatus as claimed in  claim 52 , wherein said devices for axially moving apart the side portions act between a rest condition and an axially spread apart condition, in which the side portions are mutually spaced apart relative to the rest condition by a stroke between about 0.1 mm and about 0.5 mm, measurable at respective bead seats arranged in correspondence with each bead of the tyre. 
     
     
         60 . The apparatus as claimed in  claim 54 , wherein said stop struts have abutment surfaces axially acting against respective locating seats to stop axial approaching movements between said side portions. 
     
     
         61 . The apparatus as claimed in  claim 60 , wherein said abutment surfaces and locating seats, in the absence of stresses on the toroidal support, are disposed at such a distance as to stop said axial approaching movements upon reaching of an axial contraction stroke between about 0.01 mm and about 0.15 mm. 
     
     
         62 . The apparatus as claimed in  claim 61 , wherein said axial contraction stroke is less than about 0.1 mm. 
     
     
         63 . The apparatus as claimed in  claim 52 , wherein the vulcanisation mould is movable between an open condition and a closed condition which defines a moulding cavity having a shape corresponding to the outer conformation of a cured tyre, 
     
     
         64 . The apparatus as claimed in  claim 52 , wherein said devices for vulcanisation of the tyre comprise a feeding circuit opening into the vulcanisation mould to feed a vulcanisation fluid into the toroidal support. 
     
     
         65 . The apparatus as claimed in  claim 52 , wherein control devices operate on the feeding circuit to supply vulcanisation fluid to a first pressure value, over a predetermined period of time, and subsequently supply vulcanisation fluid to a second pressure value higher than the first pressure value. 
     
     
         66 . The apparatus as claimed in  claim 65 , wherein the first pressure value is between about 7 and about 17 bars. 
     
     
         67 . The apparatus as claimed in  claim 65 , wherein the second pressure value is between about 20 bars and about 30 bars. 
     
     
         68 . The apparatus as claimed in  claim 65 , wherein said feeding circuit further comprises at least one auxiliary feeding circuit to admit a counter-pressure fluid into the vulcanisation mould to generate a first pressure gradient, so as to press the radially internal surface of the tyre against a radially external surface of the toroidal support concurrently with admission of the vulcanisation fluid to said first pressure value, and to evacuate said counter-pressure fluid to generate a second pressure gradient, so as to press a radially external surface of the tyre against a radially internal surface of a moulding cavity concurrently with admission of the vulcanisation fluid to said second pressure value. 
     
     
         69 . The apparatus as claimed in  claim 52 , wherein said devices for building a green tyre on the toroidal support comprise a plurality of building stations distributed along a building line, each building station being set to form one component of the green tyre directly on said toroidal support. 
     
     
         70 . The apparatus as claimed in  claim 69 , wherein the building stations distributed along the building line each operate on a respective green tyre being processed carried by a respective toroidal support sequentially transferred from a building station to the next one by means of robotized arms. 
     
     
         71 . A toroidal support for building pneumatic tyres, each pneumatic tyre comprising a crown region extending between side regions axially spaced apart from each other and each carrying a respective bead at a radially internal position, said toroidal support comprising:
 an outer forming surface of a conformation corresponding to the inner shape of a built tyre and having axially opposite side portions; and   devices for axially moving apart said side portions at the side regions of said built tyre.   
     
     
         72 . The toroidal support as claimed in  claim 71 , comprising a plurality of circumferential sectors removably in engagement in circumferential mutual alignment relationship. 
     
     
         73 . The toroidal support as claimed in  claim 72 , wherein said devices for axially moving apart said side portions comprise for each circumferential sector, at least one pair of stop struts, each stop strut being divided into two portions adapted to allow an axial movement of said side portions. 
     
     
         74 . The toroidal support as claimed in  claim 71 , wherein the forming surface is obtained on a shaped wall confining at least one circumferential cavity in the toroidal support. 
     
     
         75 . The toroidal support as claimed in  claim 74 , wherein said shaped wall substantially extends along a U-shaped outline in a diametral section plane of the toroidal support. 
     
     
         76 . The toroidal support as claimed in  claim 74 , wherein said axially opposite side portions of the shaped wall are movable in an axial direction. 
     
     
         77 . The toroidal support as claimed in  claim 71 , wherein said devices for axially moving apart the side portions act between a rest condition and an axially spread apart condition, in which the side portions are mutually spaced apart relative to the rest condition by a stroke between about 0.1 mm and about 0.5 mm, measurable at respective bead seats arranged in correspondence with each bead of the tyre built on said toroidal support. 
     
     
         78 . The toroidal support as claimed in  claim 73 , wherein said stop struts have abutment surfaces axially acting against respective locating seats to stop axial approaching movements between said side portions. 
     
     
         79 . The toroidal support as claimed in  claim 78 , wherein said abutment surfaces and locating seats, in the absence of stresses on the toroidal support, are disposed at such a distance as to stop said axial approaching movements upon reaching of an axial contraction stroke between about 0.01 mm and about 0.15 mm. 
     
     
         80 . The toroidal support as claimed in  claim 79 , wherein said axial contraction stroke is less than about 0.1 mm.