GB879368A - Improvements in pneumatic tyres - Google Patents

Abstract

879,368. Building pneumatic tyres. DUNLOP RUBBER CO. Ltd. Feb. 19, 1958 [March 6, 1957], No. 7371/57. Classes 144 (1) and 144 (2). In the " turn-over " method of building pneumatic tyres wherein a parallel cord ply 5 of cord fabric is transferred from an auxiliary drum 2, having an inflatable annular bag 3 coaxially supported thereon, to a building drum 1 by first inflating the bag 3 to force the outer surface of the ply 5 against a cylindrical cage 4 coaxially surrounding the auxiliary drum 2 and then effecting relative axial movement of the drum 1 and the cage 4 to transfer the ply 5 to the drum 1, the ply 5 is held firmly to the surface of the drum 1 as it is transferred thereto, and the drum 1 and cage 4 are relatively rotated during transfer so that the transferred ply has a cord angle which varies as desired across its axial width. As shown, a ply 5 with a cord angle of 70 degrees, Fig. 10, is laid on the auxiliary drum 2 with an end 5a turned down over the drum shoulder to be clamped thereagainst by the building drum 1, Fig. 4. On transfer of the ply, Fig. 5, the ply 5 is adhered to the building drum surface either by means of a layer of uncured rubber pre-laid on the drum surface, or by a suction effect, the drum in this case having a perforated surface communicating with an interior suction chamber. During the axial transfer movement of the cage 4, the drum 1 is braked against rotation, and the cage 4 is caused to rotate, for certain portions of its axial travel, in one or other direction by a cam mechanism (not shown) to produce the desired path of the cords across the ply such as shown in Fig. 11. In Figs. 10 and 11, a ply having an original uniform cord angle of 70 degrees is transferred to the drum 1 with cord angles of 90 degrees at the sidewall regions 7a, 7b and 60 degrees in the tread region. Where successive plies are cross laid, the rotations of the cage are effected in opposite directions respectively. Plies of any initial cord angle may be used to achieve any desired resultant cord path, and the apparatus may be used to make tyres of the form described in Specification 879,367. Specification 854,214 also is referred to.