GB1462683A - Pneumatic tyres and methods of manufacture thereof - Google Patents

Abstract

1462683 Pneumatic tyre treads INDUSTRIE PIRELLI SpA 23 Jan 1974 [23 Jan 1973] 02862/74 Heading B7C A pneumatic tyre comprises a radial carcass 1, and a breaker 4, and a tread 5 having a plurality of ribs or, as shown, blocks 6 each with at least one radial projection 9 on its radially outer surface which has a height h of 2-5 mm, the projections 9 and at least the outer surfaces of the ribs or blocks 6 being formed from an elastomeric compound 11 containing filaments 12 having a length of 2-10 mm and a modulus of elasticity at least 50 times higher than that of the elastomeric mixture forming the remainder of the compound 11, and the filaments 12 being oriented in a substantially radial direction in the projections 9 and adjacent the side walls 7 of the ribs or blocks 6. The tyre is particularly intended for use on icy or snowy ground. The projections 9, may, as shown, be of radially outwardly tapering frusto-conical shape, having a base diameter a of 3-7 mm and a tip diameter b of 1-4 mm. The filaments 12 may be of metal, e.g. steel, and may have a diameter of 0À15-0À30 mm and form 10-50% by weight of the total weight of the compound 11 including the filaments. Alternatively the filaments may be of polyamide, e.g. nylon. The filaments may protrude by 0À2-0À4 mm from the radially outer surface of the projections 9. The projections 9 and the outer regions only of the ribs or blocks may be formed from the compound 11 with filaments, the remainder of the tyre tread being formed from a different compound 10, suitable formulations for the compounds 10, 11 being given in the Specification. In making the tyre elastomer and other ingredients are mixed with the filaments 12 to form the compound 11, the compound 11 is extruded or calendered to produce an elongate strip in which the majority of filaments are parallel to the longitudinal axis of the strip, the strip is applied to the tyre so that the filaments extend circumferentially, and the tyre is then cured in a mould, the flowing of the compound 11 during moulding causing the filaments to become oriented in a substantially radial direction in the projections and adjacent the sidewalls of the ribs or blocks.