GB1480647A - Process for producing hollow articles by injection and blow moulding - Google Patents

Abstract

1480647 Injection-blow-moulding; temperature control UNILEVER Ltd 30 July. 1974 [1 Aug 1973] 33554/74 Heading B5A In an injection-blow-moulding process, the preform is formed by injection-moulding in the thermoplastic temperature range, cooled to the thermoelastic temperature range, expanded in an intermediate blow-mould where the desired temperature profile in the preform is obtained by locally differential heat exchange between the expanded preform and the mould walls, blow-moulded with that temperature profile in a final blow-mould and cooled to set. A plurality of intermediate blow-moulds may be used to effect heat exchange in a number of successive steps and the pressure in the preform may be released between each step. As shown in Fig. 1, a turret 1 carries four radially disposed mandrels 2-5 and is indexed between stations where the cores are engaged with injection mould 6, first and second intermediate blowmoulds 9, 10 and a final blow-mould 11. In the embodiment of Fig. 2 (not shown), mandrels (23) are mounted on both faces of and parallel to the axis of the rotary turret (21) for co-operation with moulds (e.g. 17, 18) on platens (16). Different zones of the intermediate blow-moulds are maintained at different temperatures by means of materials of different thermal coefficients, heating elements of different numbers, density or temperatures, ducts for fluids at different temperatures or induction heating of different zones. The moulding material may be p.v.c.