GB812908A - Improvements in and relating to methods and apparatus for use in the remoulding of pneumatic tyres - Google Patents

Abstract

812,908. Remoulding tyres. BARWELL RUBBER CO. Ltd., BARWELL, J. H., and LANHAM, D. J. Sept. 12, 1955 [Sept. 22, 1954], No. 27434/54. Class 87(2). Pneumatic tyres are remoulded by the direct application to a prepared tyre carcass of camelback strip in hot, tacky condition, as it emerges from the extrusion head of a press which produces the strip. The tyre 25 which is to be re-treaded is slipped over two parallel horizontal rollers 26 and the end 62 of extruded strip rubber 23, in the tacky plastic condition in which it issues from the extrusion machine 21, is applied to the tyre, which is rotated to wind on the strip. The extruded strip is conveyed from the die over horizontal rollers 27 which are spaced apart so that the strip may be festooned, as at 63, to allow for differences between the speeds of extruding the strip and of applying it to the tyre. A second, parallel row of rollers is positioned on which extruded strip, which is not to be applied directly to a tyre may be festooned and allowed to cool. The extrusion die head 36 is fitted on the end of a cylinder 35, Fig. 4, in which works the head 34 of the extrusion ram. The ram also comprises a hollow sleeve 33 inside which is a piston rod 44 and into which extends the cylinder 46 in which the piston 45, mounted on the rod 44, is reciprocable. The cylinder 45 is fixed to the end plate 47 of a larger cylinder 32, through the other end of which the sleeve 33 passes with suitable packing. The die head 36 may be swung open about a hinge 38 ; when closed it is held by a pivoted locking arm 39, Fig. 6. Milled rubber containing compounding ingredients and a vulcanizing agent is softened, by heating it in a steam or water heated chamber, and placed in the open cylinder 35, the extrusion ram being retracted. A choke is then inserted to ensure an even flow of material over the whole die area. The choke comprises two plates 52, 53 spaced by bars 54, 55 and shaped pieces 56, Fig. 8, and cut away at 58, 59, to provide flow channels for the rubber which is also deflected by bars 61 on the front face of the plate 53. Arcuate rim plates 57 are an easy fit in the extrusion cylinders 35. The extrusion cylinder 35 and die-carrying head 36 are jacketed at 48, 49 for steam or water heating. With the rubber charge inserted the die head is closed and locked by the arm 39 and hydraulic pressure is applied to the piston 45 to bring the extrusion ram rapidly into contact with the material, when the hydraulic pressure is diverted to the ram itself to effect the extrusion. The thickness of the extruded strip may be controlled by varying the hydraulic pressure on the ram, and a thickness indication may be associated with the die head. The choke may have alternative forms. The dies may be interchangeable.