GB927401A - Improvements relating to pneumatic tyres - Google Patents

Abstract

927,401. Pneumatic tyres. DUNLOP RUBBER CO. Ltd. Oct. 19, 1959 [Nov. 10, 1958], No. 35961/58. Class 144 (1). [Also in Group V] A pneumatic tyre incorporating a rigid breaker 17 of steel cord layers is built by first forming a tread band 18 around the breaker 17 on the surface of a former 1 so that the band has the same diameter as that desired for the shoulder regions of the finished tyre, restraining at least the shoulder regions 20 of the tread band to that diameter, as by a restraining ring 7, turning the edge portions 21 of the band radially inwardly, as by shaping rings 12, removing the former 1, and then expanding a built carcass 22 coaxially within the shaped tread band to adhere at its crown portion to the underside of the tread band crown and edge portions. As shown, the former 1 is of segmented collapsible form and the restraining ring 7 also comprises three or more segments and has an inner peripheral tread moulding surface. The ring 7 tapers on each side from a central portion 8, 9 to provide inclined outer peripheries 10 which terminate in chamfered edge portions 11. The shaping rings 12 each comprise inner peripheral surfaces 13, 14 complementary to the surfaces 10, 11 of the restraining ring 7, the surface 14 connecting into a shoulder shaping surface 15 which extends radially inwardly to a convex-section surface 16 converging toward the edges of the former 1. In use, with the restraining ring segments loosely assembly around the tread band 18 on the former 1, the shaping rings 12 are simultaneously moved axially inwardly to cam the segments radially inwardly and thereby consolidate the tread band, the surfaces 15, 16 of the shaping rings eventually pressing the edges of the tread band against the convex and concave shoulder shaping surfaces 3, 4 at each side edge of the former. The approach movement of the rings 12 is limited by engagement of their surfaces 14 with the edges 11 of the restraining ring. After removal of the former 1, expansion of the carcase 22 into adherence with the shaped tread band, Fig. 3, is effected so that the tread band crown is expanded into complete engagement with the mould surface of the restraining ring 7. The shaping rings 12 are then removed and the consolidation of the tread edges to the carcase is effected by rolling prior to positioning the tyre and ring 7 into a mould which has surfaces complementary to the surfaces 10, 11 of the ring 7. In an alternative construction the restraining mould ring 7 is replaced by a plain cylindrical restraining ring. Specification 907,692 is referred to.