| 摘要 |
<p>An elastic envelope or cover for enclosing a combination of a tyre carcass and a prefabricated tread hoop for retread vulcanisation, where the toroidal cover has a 'U' cross-section of non-uniform wall thickness, being relatively thick along the region in contact with the tread zone. Also describes an extrusion die with an adjustable offset and assymetric conical mandrel for extrusion of a profile of suitably varying wall thickness which can be slit longitudinally and then transversely for making such envelopes. Alternatively the envelope may be extruded as a flat or 'U' profile which is relatively thick along its central zone. Used for supporting tread/carcass combinations involving casing in autoclaves at e.g. 98-148 degrees C with the carcasses pressurised to higher pressures than the pressures in the surrounding over chamber. The greater strength and tear resistance of the thicker envelope wall alongside the enclosed tread prolongs the life of the cover against damage caused by repeated fitting and stripping.</p> |
