718,832. Pneumatic tyres. GENERAL TIRE & RUBBER CO. April 7, 1952, No. 8836/52. Class 144(1) [Also in Group V] A flat tyre band is formed by first moulding a seamless annular rubber tread band D in a mould C and then replacing, the inner core of the mould with an expansible mandrel F on which is supported a pre-formed annular carcase band E of rubberized plies, the mandrel when positioned in the mould then being expanded to expand the carcase band E radially into contact with the tread band D and thereby stitch the two bands together. Fig. 2 shows a mould C comprising an outer mould member 17, the inner face 45 of which defines the contour of the tread band periphery, secured at one end to a conical end member 23 which, with a conically faced disc member 28 clamped between the outer mould member 17 and its end member 23, defines a conical annular tapering feed passage 32 for plastic rubber fed thereto under pressure via a conduit 13. The annular feed passage 32 leads via circumferentially arranged holes 33 in a flange 29 of the disc member 28, into an annular mould cavity 44. An inner mould member 42, the outer surface 43 of which is substantially cylindrical to define with the outer mould member 17 the annular moulding cavity 44 of tread band section, is removably supported coaxially within the outer member 17 on an axial bar 35 removably screwed into a central boss 39 of the disc member 28, the inner end 48 of the mould member 42 being slidably received over the disc member boss 39. When in operative position, an annular groove 59 in the outer surface of the inner mould member 42 is radially aligned with a fixed shearing ring 20 to provide an arcuate continuation of the feed passage 32 leading into the mould cavity, the end corner of the mould member 42 sliding against the inner edge of the shearing ring 20 on withdrawal of the inner mould member 42 to effect shearing of the moulded tread from the feed rubber. To facilitate withdrawal of inner member 42, its surface is smoothly polished or plated and may be slightly tapered, there being a corresponding taper of the outer mould surface 45. In this way the moulded tread band is left adhering to the outer mould member 17 ready for the positioning therewithin of a pre-formed carcase band E Fig. 7 which is carried on an expansible F. The mandrel F is removably supported on the bar 35 in the same way as was the inner mould member 42 and comprises a cylindrical body 70 with end bead-supporting flanges 80, 81 defining an annular space 76 in which is housed an inflatable annular air bag 77. When the mandrel F is correctly located within the mould 17 the bag 77 is inflated as in Fig. 8 to expand the carcase band E radially against the tread band F and thereby stitch them together. Subsequent deflation of the bag 77 allows the carcase band E to contract radially towards its original diameter thereby causing radial contraction of the tread band away from the outer mould surface ready for withdrawal from the mould. The tire band so formed comprises carcase and tread bands which are respectively under slight circumferential tension and compression. An alternative arrangement is shown in Fig. 11 wherein a vertically movable ram-operated outer mould member 108 containing an annular slug of rubber stock S is telescoped over a fixed inner mould member 124 to force the rubber to flow into the annular mould cavity of tread-section formed between the two members. The outer mould member comprises a flanged cylindrical body 108 secured to a base ring 107 and housing a removable liner 111 the inner face of which is shaped to define the outer surface of the mould cavity. The inner mould member 124 comprises a fixed cylindrical body, the outer surface of which is of highly polished metal or plastic such as chromium or polytetrafluoroethylene and defines the inner surface of the mould cavity, slidably. housing a locating sleeve 128 the lower end 132 of which is flanged to form a pressure ring and provide a continuation of the outer surface of the cylindrical body 124. As the two mould parts 108, 124 are telescoped a sealing ring 138 recessed into the pressure ring 132 engages around a guide cylinder 136 fixed to the base ring 107 to locate the two mould parts coaxially, the cylinder 136 sliding within the locating sleeve 128. Fig. 12 shows the moulding action as the slug S of rubber is placed under pressure, the surface 147 of the pressure ring 132 defining, with a surface 146 on the outer mould body flange, a progressively narrowing gate. The locating sleeve 128 is so bolted to the fixed cylindrical body 124 that on initial return movement of the outer mould member 108, the sleeve 128 follows with it for a short distance, Fig. 14, holding the end of the moulded tread T clamped in position while the inner mould body 124 is freed therefrom. Subsequent return movement of the mould part 108 withdraws the tread T from off the inner mould body 124, the tread adhering to the liner 111 which may in turn be withdrawn from the mould part 108. Fig. 16 shows an expansible mandrel 154 lowered into and located coaxially within the liner 111 which is supported on a locating ring 150, a pre-formed annular carcase band B being supported over an expansible diaphragm 158 carried by the mandrel 154. Expansion and deflation of the diaphragm effects the stitching of the tread and carcase bands and the subsequent release of the tire band so formed from the liner 111. In an alternative procedure the carcase band and mandrel may be located in the liner 111 with the latter in situ in the outer mould part 108.