Patent GB-1388618-A (GB)
Title: Pneumatic tyres
IPC: B60C9/04
Filed: 1972-03-08
Abstract: 1388618 Pneumatic tyres MICHELIN & CIE (COMPAGNIE GENERALE DES ETABS MICHELIN) 8 March 1972 [8 March 1971 14 Jan 1972] 10870/72 Heading B7C A pneumatic tyre has a carcass including a pair of superposed plies 12, 14 of parallel cords which extend from one bead of the tyre to the other and form a network of substantially parallelogram shaped meshes as shown in Fig. 4, the sides of each mesh making with the circumferential direction different acute angles (i.e. angles #90 degrees) α and #, both α and # varying as a function of distance from the tyre axis so as first to increase and then to decrease, the angle α being at all points on the tyre larger than the angle # and varying between any two points at different distances from the tyre axis more than does the angle #. The ratio R = sin α/sin # may be substantially constant over part or all of the tyre carcass and may be in the range 2-5. Examples are given in the Specification of the values at various points on the tyre of the angles a and # and the angles γ and 180-γ between adjacent sides of the meshes, and in one embodiment the angle a varies between 24À5 and 90 degrees, the angle # between 7À5 and 18À5 degrees, and the angle γ between 32 and 148 degrees. In both the bead regions and the crown region of the tyre the angles a and # may add up to less than 90 degrees, with the angles a and # lying in the same one of four imaginary quadrants defined by the circumferential direction and a direction at right angles thereto in the bead regions and lying in adjacent ones of such quadrants in the crown region. Formulµ are given in the Specification which relate the angle γ in the bead regions and the crown region to the ratio R, and the value of the angle γ in the bead regions added to the value of the angle γ in the crown region may be about 180 degrees. The areas of the meshes may be approximately equal in the bead and crown regions. The ply cords making the angle # may be of polyamide and may be disposed radially outwardly of the ply cords making the angle a which may be of rayon or non-elastic steel. A layer 13 of elastomer with a modulus of elasticity at 100% elongation between 200 and 500 g./mm.<SP>2</SP> may be interposed between the plies 12, 14 whose cords make the angles a and #. The tyre may have a breaker assembly comprising two plies 20, 22 of cords cross-laid at angles of 22 and 19 degrees respectively, the plies 20, 22 being separated by a layer 21 of elastomer 19 and the breaker assembly being superposed on a layer 19 of elastomer on the carcass crown. The beads of the tyre may be reinforced with bead wires 15, filler strips 16 and flipper strips 17 and the tyre may be provided with an air-impermeable liner 11. The tread 24 of the tyre may be separated from the breaker assembly by a layer 23 of elastomer. In manufacturing the tyre the carcass plies 12, 14 are cross-laid on a cylindrical building drum with their cords at numerically different angles, e.g. 13 and 45 degrees, bead wires are laid on the plies, the plies are turned up about the bead wires to form beads, and the assembly is then shaped to toroidal form whilst leaving the beads free to rotate about the drum axis thereby causing the ply cords to form a network of the type described above.