| 摘要 |
<p>1372254 Pneumatic tyres MICHELIN & CIE 29 Sept 1971 [30 Sept 1970] 45436/71 Heading B7C An unused or retreaded pneumatic tyre has a tread made of a vulcanized mixture based on an elastomer, e.g. rubber, the elastomer being oriented in a direction parallel to the groundengaging surface of the tread and not at right angles to the circumferential direction, e.g. the circumferential direction. The orientation of the elastomer is produced by stretching the unvulcanized tread prior to or during its being wrapped around the tyre carcass during manufacture of the tyre, the stretching being effected at least in the wrapping direction and producing an extension in the wrapping direction of 75-600%. The tread may comprise a plurality of layers of the mixture each 0À1-5 mm. thick, the layers being produced either by superimposing a plurality of sheets of the mixture on the tyre carcass or by wrapping a number of convolutions of a single sheet of the mixture around the carcass. Alternatively the tread may be made from a prefabricated member of profiled cross-section and in this case the extension to which the unvulcanized tread is subjected may be greater than that desired in the finished tyre and may exceed the elastic limit. A tread of layered construction in which the elastomer is oriented in the circumferential or wrapped direction may be produced on the apparatus shown in Fig. 1, wherein a tyre carcass 1 mounted on a wheel 2 is driven at a constant circumferential speed VI by a motor 3 regulated by a feeler 4, and tread strip 10 is drawn from a supply rool 15 through a compensator 19, which allows the roll 15 to continue to supply between successive tread applications, to driving rollers 20, 21, 22 which drive the tread strips 10 at a constant speed V 0 lower than the speed V 1 of the carcass, the strip thus being stretched by an amount proportional to the ratio V 1 /V 0 at the instant of its application to the carcass. Knives 24 are provided for cutting the strip 10 and there is a spool 18 which receives fabric or polyethylene sheet interleaving the strip 10 on the spool 15.</p> |
