Improvements in or relating to inner tubes for pneumatic tires and methods of, and mold for, forming said inner tube

摘要

528,758. Moulding inner tubes for pneumatic tyres. FIRESTONE TYRE & RUBBER CO., Ltd. May 4, 1939, No. 13360. Convention date, May 17, 1938. [Class 87 (ii)] [Also in Group XXIX] An inner tube for pneumatic tyres has a valve stem integrally cast therewith. As shown, an annular mould 11 and core 12 together form a semi-tubular cavity 13, for producing one half of the tube. The core has a pouring sprue 16 and vents 17, and it is formed with flanges 14 which rest on the mould. A valve stem cavity 19 is formed in the mould and in this cavity a valve body 21 is supported by a rod 22, entering the core, and a clamping plate 23. The mould is filled with liquid latex through the sprue 16 and the mould is then heated to coagulate the latex. In a modification the core 12 is dispersed with and the mould filled with latex, a film being then coagulated on the mould and the remainder poured off. Two moulds, each containing a half tube, are placed together, compressed air or steam is forced in through the valve stem, and the tube is vulcanized by heat. The half-tubes are provided with thickened rims 30 so that reinforced inner and outer circumferential junctions are formed between the halves.