GB1418800A - Two-stage blow-moulding process for the production of hollow mouldings from thermoplastic materials - Google Patents

Abstract

1418800 Blow-moulding G MEHNERT 19 Nov 1973 [18 Nov 1972 30 Oct 1973] 53638/73 Heading B5A In a blow-moulding process where an extruded tube is blow-moulded to form a preform in a preliminary mould and the preform is then blow-moulded in a final blow-mould to form the finished article, both blow-moulding stages are effected by only one blowing mandrel. As shown in Fig. 1, a preliminary mould is reciprocable between extrusion station I and first blowing station II and a blowing assembly 9 is rotatable to transfer mandrels 14, 16 between station II and final blowing station III, where there is a stationary final blow-mould 2. A tubular extrudate 3 is continuously extruded from nozzle 5 into mould 1 and severed by knife 12 while a finished moulding 8 cools in mould 2. Mould 1 moves in the direction of arrow a to station II and extrudate 3 is blown therein by mandrel 14 to preform (7) while article 8 drops from opened mould 2 on retraction of mandrel (16). Mould 1 then opens and returns to station I to receive further extrudate while assembly 9 rotates to place preform (7) on mandrel 14 at station III where it is finally blow-moulded in final mould 2. Alternatively (Figs. 4-6, not shown), both blow-moulds are movable and a single, stationary blowing mandrel is used. In a further alternative, the preliminary blow-mould is stationary, extrudate being fed thereto by grippers or by rotating the extruder. A plurality of final moulds may be used per preliminary mould and more than one preliminary mould may be used. A further chilling "mould" and chilling and/or ejection stations may be incorporated.