Abstract: Apparatus is disclosed for heating thermoplastic parisons to a substantially uniform temperature across their wall thickness prior to a blow molding operation. The parisons are rotated about their longitudinal axes while being conveyed adjacent a thermal conditioning means, which includes vertically spaced radiant heating elements and a gaseous cooling source. The heating elements radiate infra-red rays having a wave length to penetrate and heat the full thickness of the parison wall; whereas the gaseous cooling source directs a stream of air onto the surface of the parison facing the heating elements to prevent the parison surface from being overheated. Additionally, each of the heating elements may be individually regulated so that the parisons can be differentially heated along their axes to control the wall thickness of the final blown articles.

Abstract: A method are disclosed for heating thermoplastic parisons to a substantially uniform temperature across their wall thickness prior to a blow molding operation. In the method, the parisons are rotated about their longitudinal axes while being conveyed adjacent a thermal conditioning means, which includes vertically spaced radiant heating elements and a gaseous cooling source. The heating elements radiate infra-red rays having a wave length to penetrate and heat the full thickness of the parison wall; whereas the gaseous cooling source directs a stream of air onto the surface of the parison facing the heating elements to prevent the parison surface from being overheated. Additionally, each of the heating elements may be individually regulated so that the parisons can be differentially heated along their axes to control the wall thickness of the final blown articles.