Manufacture of pneumatic tires

A method for the manufacture of a pneumatic tire having parts including beads, sidewalls and a tread portion reinforced by means of a breaker assembly, comprising the following steps:

• a. working curable but uncured rubber to an extent sufficient to destroy its nerve but not to start the rubber on to a curing cycle;
• b. preassembling a breaker assembly for the tread portion of the tire and positioning it in an annular mould cavity for the tread portion of the tire;
• c. forming the tire in three parts from said worked uncured rubber by forcing said rubber into annular mould cavities including the mould cavity for the tread portion of the tire in which said breaker assembly has been preassembled, and mould cavities for the sidewall and bead on each side of the tire, at least the sidewall and bead moulds each being provided with gas-tight locking spures to assist in maintaining a formed tire in a desired part of each of the latter moulds when the latter moulds are opened;
• d. opening the moulds for the tire parts, at least the moulds for the sidewalls being opened in a pressurized atmosphere such that gas under pressure flows between parts of the moulds for the sidewalls and is prevented by the gas-tight locking sprues from passing around one side of each of the formed tire sidewalls whereby the tire sidewalls are retained in desired parts of the sidewall moulds;
• e. reassembling the moulds for the tire parts into a tire mould to bring the tire parts into joining contact;
• and
• f. joining the parts of the tire under head and gas pressure.