Patent GB-702311-A (GB)
Title: Improvements in moulding method and apparatus, e.g., for use in moulding tyres and inner tubes
IPC: B29C48/09
Filed: 1952-03-31
Abstract: 702,311. Injection - moulding pneumatic tyres, inner tubes &c. UNITED STATES RUBBER CO. March 31, 1952 [May 18, 1951], No. 8110/52. Class 87 (2). Annular articles are formed by injecting plastic material into a mould casting defined by two mould surfaces. In order to carry the plastic material from the point of injection around the mould, one of the moulding surfaces is rotated with respect to the other, and the others mould surface is lubricated. As applied to the moulding of an inner tube, Figs. 1 and 3, the operator, with the mould halves 10, 11 in an open position, inserts a valve stem assembly 100 having an inner rod 101 to prevent the rubber from clogging the air hole in the valve. A hub assembly 15 having arms 13, 14 carrying the mould halves is then rotated by a motor 137 to bring the mould opposite a rubber extruder 18 to which a core 19 is fixed.. The extruder and core are heated by passing fluid through internal passages 60, 61, 62, and the mould halves are heated by passing fluid through'pipes 150, 151, 145, 146 and 72, 73, 160, 161 to spaces 63 in the mould halves. When the mould halves are in correct register with the core, the moulds are closed by operating a valve 114 to cause movement of a piston rod 108 pivotally connected at 109 to the arm 13. The registration of the moulds is controlled by a brake 139. Rubber is then fed into the mould by the screw 54 of the extruder, at the same time the mould halves are rotated about a vertical axis, by means of pinions 82, 83 which engage gear teeth 80, 81 on the mould halves, to cause the rubber to be carried around the mould cavities by the frictional engagement of the rubber with the mould walls. This distribution of the rubber is facilitated by continuously introducing a lubricant, e.g. paraffin oil, through passages 91, 93 and 92, 94, Fig. 5, to the surface of the core. As the mould halves complete a revolution the rubber is sheared off at the extrusion orifices 57, 58, and the piston rod 108 is actuated to separate the mould halves, the moulded inner tube halves remaining in the mould cavities. The motor 137 is then actuated to rotate the mould halves away from the extruder, and bring the next empty mould halves into position. The piston rod 108 then closes the mould halves to unite the edges of the two inner tube halves. Fig. 6, excess stock being squeezed out between lips 44.45, and as this stock is uncured it may be used again. The rod 101 is replaced by the normal valve stem, and an air hose is applied to the stem to provide a suitable air pressure inside the tube during. vulcanization.. After vulcanization, the mould is opened and the tube removed. As applied .to the moulding of tyres, Fig. 13, mould halves 200, 201 are brought opposite and closed over a core fixed to an extruder 215, Fig. 7. The core is of such a form as to provide two mould cavities each of such a shape as to form one-half of the central tyre tread. Rubber is injected from the extruder 215 into the mould and simultaneously the mould halves are rotated about a vertical axis by a driving mechanism 215a. The mould halves are then opened, the mould rotated by means of arms 202. 203 to a position opposite an extruder 216 to which a core is attached to form mould. cavities corresponding to the side walls of a tyre. The extruder 216 is then operated to form the side walls, simultaneously with the rotation of the mould halves about their vertical axis by driving mechanism 216a. After extrusion, the mould halves are separated and the moulds rotated away from the extruder. A previously prepared tyre carcass 24, Fig. 13, on a curing bag 242 is inserted in the lower mould half, and the mould halves closed. The tyre assembly is then vulcanized in the normal way as the mould rotates away from the extruders, and further moulds are brought up to the extruders. The flow of heating fluid to the mould and bag is controlled by valves 245. Fluid may be exhausted from the bag by compressed air. As applied to making tyre flaps, Figs. 14 and 17, an outer mould member is moved over an inner mould member 251 attached to an extruder 250 by means of a cylinder 256, to form a mould cavity 257. Rubber is extruded through a passageway 263 into the mould cavity and, simultaneously, the outer mould is rotated by means of interengaging teeth 264, 265 and lubricant is supplied through pipes 268, 269. The outer mould is then moved back and the tyre flap ejected through the opening 271 by compressed air. In a modification of this apparatus (Figs. 18 and 19. not shown) comprising two extruders and an inner member having two slots each corresponding to each of the extruders, one extruder forms the tread portion and the other the side wall portion of a tyre. In a further modification, Fig. 20, a tyre is built on a drum 366, a turn table 350 is rotated to bring the drum into the position previously occupied by the drum 367, i.e. opposite an extruder 380. The extruder has a head assembly comprising a lower fixed half 390, Fig. 22, and a pivoted upper half 391. When the drum, which has been raised to allow it to be moved, is opposite the extruder, it is lowered on to the lower half 390 of the extruder, and the top half of the extruder is lowered about it, to form a mould cavity 399 corresponding to the tyre side wall portion. Rubber is then extruded into the mould and simultaneously the drum 367 is rotated by a drive 373, and lubricant is introduced through a pipe 403. After completion of the extrusion operation, the drum is moved to a position opposite an extruder 405, where a similar operation is performed to mould the tread portion of the tyre. The completed tyre is then removed at the initial position of the drum 366.