초록 ▼

A method for blow molding containers and the like articles from thermoplastic parisons. The parisons are heated in two stages, i.e., in a pre-heating oven to a uniform temperature less than the blow molding temperature and by infra red radiation to a final blow molding temperature which, preferably,

A method for blow molding containers and the like articles from thermoplastic parisons. The parisons are heated in two stages, i.e., in a pre-heating oven to a uniform temperature less than the blow molding temperature and by infra red radiation to a final blow molding temperature which, preferably, is non-uniform along the length of the parison. The non-uniform heating is accomplished by moving the parison axially through an annular infra red radiator at varying rates of speed. Since the degree of heating is directly proportional to the time of exposure to the radiation, a variable temperature profile can be imparted to the parison by means of a simple speed program. Such a variable temperature profile results in controlled wall thickness distribution during blow molding, and the final container is of enhanced strength and of lower weight.

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