| 摘要 |
1460297 Treading or retreading tyres KENTREDDER Ltd 9 Sept 1974 [7 Sept 1973 22 Nov 1973] 42208/73 and 54243/73 Heading B5A [Also in Division B7] A method of applying a tread band or lug to a tyre carcass comprises in either order the two steps of placing a pre-vulcanised tread band or lug on the carcass and shortening at least the ground engaging surface of the band or lug in a direction parallel to the longitudinal axis of the band or lug by exerting a compressive stress in that surface in that direction, the compressive stress being maintained while the band or lug is bonded to the carcass, wherein the steps are such that in the final assembly the ground engaging surface of the band or lug is compressed along its length with respect to its initial non- compressed state and has maintained therein a compressive stress. In one method a lug or an arcuate portion of a tread band having a radius of curvature r<SP>1</SP> is applied to a carcass portion 10 having a larger radius of curvature r. Four such arcuate portions may extend over the whole circumference of the carcass, and each portion or lug preferably includes an inextensible reinforcement along or adjacent its carcass engaging surface. In a further method, a preformed annular tread band and a carcass having an external diameter smaller than the internal diameter of the band are each coated with a bonding agent (e.g. unvulcanized rubber) and the band is applied to the carcass, with a layer of cushion rubber therebetween, by means of pressure applied to the band by an inflatable bag or a clamp. Alternatively the band may be applied to an inextensible breaker of smaller external diameter than the internal diameter of the band prior to application to the carcass. In another method, the annular tread band is formed in one mould and transferred to a smaller mould 21 and the carcass is applied to the tread band in the smaller mould. Alternatively the two moulds may be replaced by a single radially adjustable mould. Pins 8 are placed at the illustrated positions prior to application of the tread band and again prior to the application of the carcass. The presence of the pins is stated to prevent the formation of a large crinkle in each of the tread band and carcass (Fig. 3 not shown). |
