Patent GB-703973-A (GB)
Title: Improvements in method of making pneumatic tyres
IPC: B29C48/12
Filed: 1952-05-23
Abstract: 703,973. Building tyres. UNITED STATES RUBBER CO. May 23, 1952 [June 21, 1951], No. 13087/52. Class 144(1) [Also in Group V] Pneumatic tyres are formed by first moulding an annular preform of the tread or tread and side wall portions and then uniting the preform to a tyre carcass by heat and pressure. Side wall and tread stock 13, 14 are extruded from a die 12 and cut longitudinally and transversely by knives 16, 21, respectively. The lengths of stock are then spliced together, as by cementing, to form annular preforms. The preforms are then applied to core surfaces 29, 30. The preforms may be slightly smaller in diameter than the core so that they have to be stretched on to the core, and if they are not at a temperature of e.g. 200F from the extrusion step, they are heated to this temperature. The preforms are moulded under heat and pressure between mould halves 24, 25. Cooling fluid is then circulated through passages 36, 37 until the temperature is e.g. 150F, and the mould halves opened. To ensure that the moulded preforms stick to the mould halves, the core surfaces are made of polished chromium. The mould surfaces are preferably made of unpolished chromium. A shaped tyre carcass 40 containing a curing bag 41 is then placed between the mould halves. The mould halves are then closed, Fig. 7, and the bag 41 inflated through an opening 42. To avoid trapping air between the carcass and the tread, the mould is almost closed, and then the bag is inflated to expel any air, before the mould is finally closed. The mould is then opened and the tyre assembly placed in a conventional vulcanizer having two mould halves with a tread design to form the finished tyre. In a modification, Figs. 11 to 14, (not shown), the tread portion of the tyre is first formed by using a suitable core which is then replaced by a core as in Fig. 4 and the side wall portion is moulded on to the tread portion, and both portions moulded on to the tyre carcass as previously described. In a further modification, Figs. 15 to 19, (not shown), the side wall portion is first moulded and then united to the tyre carcass. The tread portion is then moulded and united to the combined side wall portion and carcass. In another modification, Figs. 20 to 25, (not shown), the tread portion is first formed, then the side wall portion is formed on a core which has a surface such that this portion sticks to the core when the mould is opened. The core with the side wall portion is then disposed in the first mould carrying the tread portion and the two portions united. The portions are then united to a tyre carcass as previously described. In another modification, Figs. 26 to 28, (not shown), the tread portion is first moulded and a tyre carcass having formed on it the side wall portion is then placed in the mould and the whole united. In another modification, Figs. 29 to 31, (not shown), the tyre is formed as in the last modification, except that part of the side wall portion is formed with the tread portion and part is formed on the carcass. In a final modification, Fig. 32, rubber is injected through an orifice 113, a chamber 112, and a series of passages 111 into a cavity 110 to form the tread projections of the tyre. A carcass having formed thereon a side wall portion is then united to the tread portion as previously described..