METHOD OF REGULATING PROCESS OF MOULDING HOLLOW ARTICLES FROM THERMOPLASTIC MATERIAL

1453468 Injection-blow-moulding UNILEVER Ltd 13 Dec 1973 [14 Dec 1972 (2)] 57723/73 Heading B5A In an injection-blow-moulding process, the elapsed time for a working cycle is measured and compared with a predetermined constant time and a subsequent working cycle is begun at the end of the elapsed time or the predetermined time, whichever is the longer. As shown in Fig. 1, a rotor 1 carries four mandrels 2, 3, 4, 5. In any one position, one mandrel is enclosed in injection mould 6 while the opposite mandrel with an injection moulded preform thereon is enclosed in a blow-mould 12, 13. The injection cylinder 7 has a nozzle 9 contacting mould 6, cylinder 7 having a heater band 10 and mould 6 having a cooling band 11. Upon ejection of a finished article from blow mould 12/13, switch 14 is closed, signalling the end of a cycle to device 16, which also receives a signal from timer 20 at the end of the predetermined time. When both signals have been received, device 16 actuates controller 18 to turn rotor 1 through 90 degrees for a further cycle, and also restarts timer 20. Switch 14 and timer 20 are also connected to regulator 22 so as to increase and reduce the power applied to heater band 10 and cooling band 11 respectively when the elapsed time is longer than the predetermined time.