Patent GB-743336-A (GB)
Title: Improvements in or relating to tire bead ledge construction
IPC: B29D30/06
Filed: 1952-11-11
Abstract: 743,336. Moulding tubeless tyres. FIRESTONE TIRE & RUBBER CO. Nov. 11, 1952 [May 2, 1952], No. 28368/52. Class 87 (2). A method of forming a contour on. the lateral inside surface of tyre head comprises: (i) forming a ring-receiving recess in each of the lateral sides of the base of a curing bag (ii)' assembling two composite moulding rings by vulcanizing flexible tapered outer rings to the peripheral surface of rigid inner rings (iii) inserting the curing bag in the tyre (iv positioning a composite moulding ring in each of the ring- receiving recesses of. the curing bag with its flexible ring extending axially outwards (v) placing the tyre containthe bag and rings in a vulcanizing mould (vi) applying pressure against the inside walls of the curing bag and heat to the mould to form said contour. The tubeless kind of tyre to which the invention relates is shown in Fig. 12, where the beads 43, 44 of the diaphragm 45 seat behind ledges 18 in the tyre cover, and it is to the moulding of these ledges that the invention is directed. The Specification first describes the building up of the cover into the composite form, shown in Fig. 4, which comprises a layer 2 of rubbery compound adapted to seal punctures in the finished tyre, an inter-liner or inner ply 3 of non-porous rubbery material, e.g. butyl rubber, a strip 4 of rubbery material from which a ledge 18 is eventually to be formed, fabric plies 5, 6, a bead assembly 7, fabric plies 8, 9, a nylon fabric chafer strip 10, a rubbery abrasion strip 17 and the sidewall and tread assembly 11, 1 being the removable drum on which the cover is built. The tyre is shaped in a bagging machine, then removed and radial inward pressure is applied to the top of the tread to spread the beads outwards. Moulding rings 14, Fig. 6, are then slipped between the beads and the curing bag 12, which is recessed to accommodate the rings. Each ring, Fig. 5, comprises a rigid inner portion 15 in the hooked part 19 of which the required ledge is to be moulded and, banded to the portion 15, an extension 16 of flexible rubbery material. The assembly is placed in a vulcanizer, Fig. 6, wherein steam or hot water is forced under pressure into the curing bag and the moulding rings 14 are pressed against the rubber of the tyre bead, the rubbery inner ply being pressed by the flexible portions 16 which do not penetrate it and chafe the fabric. The tyre may be vulcanized in a machine as shown in Fig. 9, using a curing diaphragm 23 which is clamped between members 24, 25 at one end of a piston rod 22 and members 26, 27 at the. other end. A moulding ring 31 is placed between the uncured tyre 28 and the member 27, on which the ring rests, and another moulding ring 32, of smaller inside diameter, is placed between the tyre 28 and the member 24, on which it also rests. As the upper mould section 20 is lowered to meet the lower mould section 21 the piston rod 22 is retracted, causing the curing diaphragm 23 to distend and press the uncured tyre against the mould. Steam is circulated in cavities in the upper and lower sections 20, 21 and internal gas or water pressure is supplied to the diaphragm 23. During the curing the moulding rings 31, 32 are pressed into the soft hot rubber of the tyre bead, forming the desired ledge.